| Author | Title | Year | Journal/Proceedings | Reftype | DOI/URL |
|---|---|---|---|---|---|
| Ababou, R. and Gelhar, L.W. | A High-Resolution Finite Difference Simulator for 3D Unsaturated Flow in Heterogeneous Media | 1988 | Vol. 35Computational Methods in Water Resources Vol. L Modeling Surface and Sub-Surface Flows, Proceedings of the VII International Conference, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA, pp. 173-178 |
incollection | URL |
| Abstract: The nonlinear equation of three-dimensional unsaturated flow is solved by a finite difference method for large single realizations of random field coefficients, based on a stochastic approach of field heterogeneity. The most difficult case considered for solution is a transient strip-source infiltration in a large domain discretized into 300.000 grid points, with a spatially random unsaturated conductivity curve. Numerical issues are briefly discussed, along with simulation results. | |||||
BibTeX:
@incollection{Ababou1988,
author = {Ababou, R. and Gelhar, L. W.},
title = {A High-Resolution Finite Difference Simulator for 3D Unsaturated Flow in Heterogeneous Media},
booktitle = {Computational Methods in Water Resources Vol. L Modeling Surface and Sub-Surface Flows, Proceedings of the VII International Conference, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA},
publisher = {Elsevier},
year = {1988},
volume = {35},
pages = {173--178},
url = {http://www.sciencedirect.com/science/article/pii/S0167564808703344}
}
|
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| Ababou, R., Sagar, B. and Wittmeyer, G. | Testing procedures for spatially distributed flow models | 1992 | Advances in Water Resources Vol. 15(3)Validation of Geo-hydrological Models, pp. 181-198 |
article | URL |
| Abstract: Methods for testing, verifying, and validating predictive models of variably saturated groundwater flow are discussed. Specific procedures are introduced for measuring model complexity, assessing model consistency, and testing model validity. The discussion addresses numerical formulation, verification of internal consistency, benchmarking, groundtruth testing, performance measures, parameter estimation, hypothesis testing, and probabilistic induction. Verification of models includes tests of internal consistency and accuracy, like mass conservation and sensitivity to mesh size. Verification of codes also involves comparing results from the numerical model to analytical solutions, which are, however, limited in scope, and comparison with other numerical codes or ‘benchmarking’. These aspects are illustrated using available three-dimensional codes developed by the authors. Recognizing the diversity of spatially distributed modeling approaches, we also propose measures of model complexity and of the amount of information inherent in model predictions. One of these measures is the spatial degree of freedom, a function of material and boundary heterogeneities in the model. Another one is the quantity of information or entropy, which depends also on precision. Several aspects of ‘groundtruth’ model validation using data from laboratory and field tests are discussed. Logical inference is used to distinguish model validation from refutation. Recognizing that full validation is not possible in practice, we formulate performance criteria to define the ‘degree of validation’. Concepts and methods based on inductive calculus, Bayesian hypothesis testing, and maximum likelihood, are analyzed in some detail as alternative model validation strategies. Several examples of model testing are also discussed. | |||||
BibTeX:
@article{Ababou1992,
author = {Ababou, Rachid and Sagar, Budhi and Wittmeyer, Gordon},
title = {Testing procedures for spatially distributed flow models},
booktitle = {Validation of Geo-hydrological Models},
journal = {Advances in Water Resources},
year = {1992},
volume = {15},
number = {3},
pages = {181--198},
url = {http://www.sciencedirect.com/science/article/pii/030917089290023U}
}
|
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| Abdel-Salam, A. and Chrysikopoulos, C.V. | Analysis of a model for contaminant transport in fractured media in the presence of colloids | 1995 | Journal of Hydrology Vol. 165(1-4), pp. 261-281 |
article | URL |
| Abstract: A mathematical model has been developed to study the cotransport of contaminants with colloids in saturated rock fractures. The contaminant is assumed to decay, and sorb on to fracture surfaces and on to colloidal particles, as well as to diffuse into the rock matrix; whereas, colloids are envisioned to deposit irreversibly on to fracture surfaces without penetration into the rock matrix. The governing one-dimensional equations describing the contaminant and the colloid transport in the fracture, colloid deposition on to fracture surfaces, and contaminant diffusion into the rock matrix are coupled. This coupling is accomplished by assuming that the amount of contaminant mass captured by colloidal particles in solution and the amount captured by deposited colloids on fracture surfaces are described by modified Freundlich reversible equilibrium sorption relationships, and that mass transport by diffusion into the rock matrix is a first-order process. The contaminant sorption on to fracture surfaces is described by a linear equilibrium sorption isotherm, while the deposition of colloids is incorporated into the model as a first-order process. The resulting coupled contaminant transport non-linear equation is solved numerically with the fully implicit finite difference method. The constant concentration as well as the constant flux boundary conditions have been considered. The impact of the presence of colloids on contaminant transport is examined. According to model simulations the results show that, depending on the conditions of the physical system considered, colloids can increase or decrease the mobility of contaminants. | |||||
BibTeX:
@article{Abdel-Salam1995,
author = {Abdel-Salam, Assem and Chrysikopoulos, Constantinos V.},
title = {Analysis of a model for contaminant transport in fractured media in the presence of colloids},
journal = {Journal of Hydrology},
year = {1995},
volume = {165},
number = {1-4},
pages = {261--281},
url = {http://www.sciencedirect.com/science/article/pii/002216949402557R}
}
|
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| Abidi, S. | Detection of diethylnitrosamine in nitrite-rich water following treatment with rhodamine flow tracers | 1982 | Water Research Vol. 16(2), pp. 199-204 |
article | URL |
| Abstract: Extremely carcinogenic diethylnitrosamine (DENA) was found to form in up to 75% yield from the reaction of nitrite with the two commonly used water tracing dyes. Rhodamine B and Rhodamine WT, DENA was detected at trace levels (0.13–7.02 μg −1) in river water samples after treatment with the dye and nitrite. Analysis of these chemically treated environmental water samples required extensive separation techniques prior to acquisition of reliable analytical data using highly sensitive instruments for detection. The occurrence of DENA in nitrite-rich water treated with Rhodamines may pose a health hazard to general populations. | |||||
BibTeX:
@article{Abidi1982,
author = {Abidi, S.L.},
title = {Detection of diethylnitrosamine in nitrite-rich water following treatment with rhodamine flow tracers},
journal = {Water Research},
year = {1982},
volume = {16},
number = {2},
pages = {199--204},
url = {http://www.sciencedirect.com/science/article/pii/0043135482901117}
}
|
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| Acharya, R., van Dijke, M., Sorbie, K., Van der Zee, S. and Leijnse, A. | Quantification of longitudinal dispersion by upscaling Brownian motion of tracer displacement in a 3D pore-scale network model | 2007 | Advances in Water Resources Vol. 30(2)Pore-scale Modeling Computational Methods in Water Resources 2004 International Conference, pp. 199-213 |
article | URL |
| Abstract: We present a 3D network model with particle tracking to upscale 3D Brownian motion of non-reactive tracer particles subjected to a velocity field in the network bonds, representing both local diffusion and convection. At the intersections of the bonds (nodes) various jump conditions are implemented. Within the bonds, two different velocity profiles are used. At the network scale the longitudinal dispersion of the particles is quantified through the coefficient DL, for which we evaluate a number of methods already known in the literature. Additionally, we introduce a new method for derivation of DL based on the first-arrival times distribution (FTD). To validate our particle tracking method, we simulate Taylor’s classical experiments in a single tube. Subsequently, we carry out network simulations for a wide range of the characteristic Péclet number Peℓ to assess the various methods for obtaining DL. Using the new method, additional simulations have been carried out to evaluate the choice of nodal jump conditions and velocity profile, in combination with varying network heterogeneity. In general, we conclude that the presented network model with particle tracking is a robust tool to obtain the macroscopic longitudinal dispersion coefficient. The new method to determine DL from the FTD statistics works for the full range of Peℓ, provided that for large Peℓ a sufficiently large number of particles is used. Nodal jump conditions should include molecular diffusion and allow jumps in the upstream direction, and a parabolic velocity profile in the tubes must be implemented. Then, good agreement with experimental evidence is found for the full range of Peℓ, including increased DL for increased porous medium heterogeneity. | |||||
BibTeX:
@article{Acharya2007,
author = {Acharya, R.C. and van Dijke, M.I.J. and Sorbie, K.S. and Van der Zee, S.E.A.T.M. and Leijnse, A.},
title = {Quantification of longitudinal dispersion by upscaling Brownian motion of tracer displacement in a 3D pore-scale network model},
booktitle = {Pore-scale Modeling Computational Methods in Water Resources 2004 International Conference},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {2},
pages = {199--213},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806000194}
}
|
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| Adams, E.E. and Gelhar, L.W. | Field study of dispersion in a heterogeneous aquifer: 2. Spatial moments analysis | 1992 | Water Resources Research Vol. 28(12), pp. 3293-3307 |
article | URL |
| Abstract: Analysis is performed of a 20-month natural gradient tracer study in the saturated zone of a highly heterogeneous aquifer. Graphical presentation of concentration distributions versus time and spatial moments analysis reveal dramatically non-Gaussian behavior and a systematic mass loss. Implications of the mass loss on plume moments is analyzed through sensitivity studies. The moments data are interpreted by applying two simple models: (1) pure advection from a continuous source, and (2) advection plus dispersion in a converging nonuniform flow field. A longitudinal dispersivity of 5–10 m is estimated from the latter model and is somewhat larger than the value of about 1.5 m calculated by Rehfeldt et al. (this issue) using the stochastic theory of Gelhar and Axness (1983) based on independent measurements of the spatial variation of hydraulic conductivity. The dispersivity of 5–10 m is an order of magnitude larger than values measured at recently studied field sites (Borden and Cape Cod) with less heterogeneity, but an order of magnitude lower than would be computed from the moments data if the flow is presumed to be uniform. | |||||
BibTeX:
@article{Adams1992a,
author = {Adams, E. Eric and Gelhar, Lynn W.},
title = {Field study of dispersion in a heterogeneous aquifer: 2. Spatial moments analysis},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1992},
volume = {28},
number = {12},
pages = {3293--3307},
url = {http://dx.doi.org/10.1029/92WR01757}
}
|
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| Adams, R. and Parkin, G. | Development of a coupled surface-groundwater-pipe network model for the sustainable management of karstic groundwater | 2002 | Environmental Geology Vol. 42(5), pp. 513-517 |
article | URL |
| Abstract: This paper considers the hydrogeological simulation of groundwater movement in karstic regions using a hydrological modelling system (SHETRAN) which has been adapted for modelling flow in karstic aquifers. Flow and transport through karstic aquifers remains poorly understood, yet quantitative hydrogeological models are essential for developing and implementing groundwater protection policies. The new model has been developed and used within the STALAGMITE (Sustainable Management of Groundwater in Karstic Environments) project, funded by the European Commission. The SHETRAN model is physically based insofar as most of the parameters have some physical meaning. The SHETRAN model represents all of the key processes in the hydrological cycle, including subsurface flow in the saturated and unsaturated zones, surface flow over the ground surface and in channels, rainfall interception by vegetation canopies, evapotranspiration, snow-pack development and snowmelt. The modifications made to SHETRAN to simulate karstic aquifers are (1) the coupling of a pipe network model to a variably saturated, three-dimensional groundwater component (the VSS-NET component), to simulate flow under pressure in saturated conduits; (2) the coupling of surface water features (e.g. sinking streams or "ponors", and spring discharges) to the conduit system; (3) the addition of a preferential "bypass" flow mechanism to represent vertical infiltration through a high-conductivity epikarst zone. Lastly, a forward particle tracking routine has been developed to trace the path of hypothetical particles with matrix and pipe flow to springs or other discharge points. This component allows the definition of groundwater protection zones around a source for areas of the catchment (watershed) which are vulnerable to pollution from non-point sources (agriculture and forestry). | |||||
BibTeX:
@article{Adams2002,
author = {Adams, R. and Parkin, G.},
title = {Development of a coupled surface-groundwater-pipe network model for the sustainable management of karstic groundwater},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2002},
volume = {42},
number = {5},
pages = {513--517},
url = {http://dx.doi.org/10.1007/s00254-001-0513-8}
}
|
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| Adar, E., Rosenthal, E., Issar, A. and Batelaan, O. | Quantitative assessment of the flow pattern in the southern Arava Valley (Israel) by environmental tracers and a mixing cell model | 1992 | Journal of Hydrology Vol. 136(1-4), pp. 333-352 |
article | URL |
| Abstract: This paper demonstrates the implementation of a novel mathematical model to quantify subsurface inflows from various sources into the arid alluvial basin of the southern Arava Valley divided between Israel and Jordan. The model is based on spatial distribution of environmental tracers and is aimed for use on basins with complex hydrogeological structure and/or with scarce physical hydrologic information. However, a sufficient qualified number of wells and springs are required to allow water sampling for chemical and isotopic analyses. Environmental tracers are used in a multivariable cluster analysis to define potential sources of recharge, and also to delimit homogeneous mixing compartments within the modeled aquifer. Six mixing cells were identified based on 13 constituents. A quantitative assessment of 11 significant subsurface inflows was obtained. Results revealed that the total recharge into the southern Arava basin is around 12.52 × 106m3year−1. The major source of inflow into the alluvial aquifer is from the Nubian sandstone aquifer which comprises 65–75% of the total recharge. Only 19–24% of the recharge, but the most important source of fresh water, originates over the eastern Jordanian mountains and alluvial fans. | |||||
BibTeX:
@article{Adar1992,
author = {Adar, E.M. and Rosenthal, E. and Issar, A.S. and Batelaan, O.},
title = {Quantitative assessment of the flow pattern in the southern Arava Valley (Israel) by environmental tracers and a mixing cell model},
journal = {Journal of Hydrology},
year = {1992},
volume = {136},
number = {1-4},
pages = {333--352},
url = {http://www.sciencedirect.com/science/article/pii/002216949290017P}
}
|
|||||
| Adell, J.A. and Alzer, H. | Inequalities for the median of the gamma distribution | 2009 | Journal of Computational and Applied Mathematics Vol. 232(2), pp. 481-495 |
article | URL |
| Abstract: We provide several new inequalities involving λ n , the median of the gamma distribution of order n + 1 with parameter 1. Among others, we present sharp upper and lower bounds for the arithmetic mean of λ 1 , λ 2 , … , λ n . For all integers n ⩾ 1 we have α n + 7 6 + n 2 + 8 405 H n n < 1 n ∑ k = 1 n λ k ⩽ β n + 7 6 + n 2 + 8 405 H n n with the best possible constants α = ∑ k = 1 ∞ ( λ k − k − 2 3 − 8 405 k ) = − 0.0150 … and β = λ 1 − 683 405 = − 0.0080 … . Here, H n denotes the n th harmonic number. | |||||
BibTeX:
@article{Adell2009,
author = {Adell, José A. and Alzer, Horst},
title = {Inequalities for the median of the gamma distribution},
journal = {Journal of Computational and Applied Mathematics},
year = {2009},
volume = {232},
number = {2},
pages = {481--495},
url = {http://www.sciencedirect.com/science/article/pii/S0377042709003811}
}
|
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| Adeniyi, O.D., Abdulkareem, A.S., Odigure, J.O., Aweh, E.A. and Nwokoro, U.T. | Mathematical Modeling and Simulation of a Non-Ideal Plug Flow Reactor in a Saponification Pilot Plant | 2003 | Assumption University of Thailand Journal of Technology Vol. 7(2), pp. 65-74 |
article | |
| Abstract: This paper proposes a mathematical model for the operation of a non- ideal plug flow reactor in a saponification pilot plant of a typical process industry in Lagos, Nigeria. The residence time distribution (RTD) analysis technique involving tracer experiments was used. The model also gives a prediction of the number of ideal continuous stirred tank reactors (CSTR) that could represent the non-ideal plug flow reactor (PFR) in question. Simulated results reveals that 8.18 number of ideal stirred tanks in series would represent the non-ideal plug flow reactor under study. | |||||
BibTeX:
@article{Adeniyi2003,
author = {Adeniyi, O. D. and Abdulkareem, A. S. and Odigure, J. O. and Aweh, E. A. and Nwokoro, U. T.},
title = {Mathematical Modeling and Simulation of a Non-Ideal Plug Flow Reactor in a Saponification Pilot Plant},
journal = {Assumption University of Thailand Journal of Technology},
publisher = {Assumption University Hua Mak},
year = {2003},
volume = {7},
number = {2},
pages = {65--74}
}
|
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| Adeosun, J.T. and Lawal, A. | Residence-time distribution as a measure of mixing in T-junction and multilaminated/elongational flow micromixers | 2010 | Chemical Engineering Science Vol. 65(5), pp. 1865-1874 |
article | URL |
| Abstract: The ineffective mixing in microchannel mixers or reactors, primarily due to the laminar flow behavior in such microfluidic devices, has become an issue of significant interest to many researchers working in the field of microreaction engineering and related disciplines. The present study describes the numerical and experimental investigation of mixing performance in a proposed multilaminated/elongational flow micromixer (herein referred to as MEFM-4) and a standard T-junction micromixer (TjM). These two micromixers that employ different mixing enhancement strategies were fabricated from silicon using micro-electromechanical systems (MEMS) technology. Computational fluid dynamics (CFD) approach was first used to establish the experimental platform for the mixing study. Tracer experiment utilizing UV–vis absorption spectroscopy detection technique was used to obtain the required concentration data for residence-time distribution (RTD) analysis. The RTD and its coefficient of variation (CoV) were used for indirect characterization of flow and mixing behavior in the micromixers. Using this measure, the proposed MEFM-4, as expected, exhibits a better mixing performance (with its narrower RTD and lower CoV values) than the standard TjM. The comparison of results from the CFD simulation and the experiment shows very good agreement, especially in the low Reynolds number flow regime (Re<29). In combination with matching experiment and advanced microfabrication techniques, CFD simulation is a powerful tool for effective design and evaluation of simple to complex microfluidic devices for useful applications in chemical analysis and synthesis. | |||||
BibTeX:
@article{Adeosun2010,
author = {Adeosun, John T. and Lawal, Adeniyi},
title = {Residence-time distribution as a measure of mixing in T-junction and multilaminated/elongational flow micromixers},
journal = {Chemical Engineering Science},
year = {2010},
volume = {65},
number = {5},
pages = {1865--1874},
url = {http://www.sciencedirect.com/science/article/pii/S0009250909008392}
}
|
|||||
| Adeosun, J.T. and Lawal, A. | Numerical and experimental studies of mixing characteristics in a T-junction microchannel using residence-time distribution | 2009 | Chemical Engineering Science Vol. 64(10), pp. 2422-2432 |
article | URL |
| Abstract: The mixing behavior in laminar flow in microchannels is investigated using numerical and experimental approaches. The concept of residence-time distribution (RTD) was applied to indirectly characterize flow and mixing in a T-junction microchannel chosen as a model microchannel mixer/reactor. The residence-time distribution used in this study, although a well-known method for characterizing mixing behavior in conventional macro mixers/reactors, is still a novel measure for the characterization of mixing in microchannels. The standard T-junction microchannel and one of its modifications were studied for their mixing characteristics by performing computational fluid dynamics (CFD) simulations of pulse tracer experiments. Experimentally, RTD measure in conjunction with a UV–vis absorption spectroscopy detection technique was used to characterize flow and mixing quality in the microchannels studied. The moments of the RTD and coefficient of variation were used to quantify the mixing behavior. Two flow models, namely the well-known axial dispersion model (ADM) and a semi-empirical model (SEM), were used to obtain model descriptions for the RTD of the microchannel. As expected, the SEM fits better the experimental data than the ADM since the SEM with its characteristic asymmetric distribution predicts better the strong laminar flow behavior in the microchannels than the ADM. The results from the simulations and experiments are in very good agreement thus establishing the validity of the mathematical model and the associated solution algorithm implemented in the CFD simulations. The CFD code in conjunction with the RTD measure can then be used as a predictive tool in the design, evaluation, and optimization of microscale flow systems. | |||||
BibTeX:
@article{Adeosun2009,
author = {Adeosun, John T. and Lawal, Adeniyi},
title = {Numerical and experimental studies of mixing characteristics in a T-junction microchannel using residence-time distribution},
journal = {Chemical Engineering Science},
year = {2009},
volume = {64},
number = {10},
pages = {2422--2432},
url = {http://www.sciencedirect.com/science/article/pii/S0009250909001195}
}
|
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| Adinolfi Falcone, R., Falgiani, A., Parisse, B., Petitta, M., Spizzico, M. and Tallini, M. | Chemical and isotopic (δ18O‰, δ2H‰, δ13C‰, 222Rn) multi-tracing for groundwater conceptual model of carbonate aquifer (Gran Sasso INFN underground laboratory – central Italy) | 2008 | Journal of Hydrology Vol. 357(3-4), pp. 368-388 |
article | URL |
| Abstract: A hydrochemical and isotope study was conducted on the drainage waters of an underground laboratory, located inside the Gran Sasso massif (central Italy). The study was expected to improve the conceptual model of groundwater circulation at the base of an over 1000-thick unsaturated zone in the Gran Sasso partitioned karst aquifer. This lithostratigraphically and tectonically complex aquifer is typical of Africa–Europe thrust-and-fold collision belt in the Mediterranean area. | |||||
BibTeX:
@article{AdinolfiFalcone2008,
author = {Adinolfi Falcone, Raffaele and Falgiani, Antonella and Parisse, Barbara and Petitta, Marco and Spizzico, Michele and Tallini, Marco},
title = {Chemical and isotopic (δ18O‰, δ2H‰, δ13C‰, 222Rn) multi-tracing for groundwater conceptual model of carbonate aquifer (Gran Sasso INFN underground laboratory – central Italy)},
journal = {Journal of Hydrology},
year = {2008},
volume = {357},
number = {3-4},
pages = {368--388},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408002552}
}
|
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| Ahfir, N.-D., Wang, H.Q., Benamar, A., Alem, A., Massei, N. and Dupont, J.-P. | Transport and deposition of suspended particles in saturated porous media: hydrodynamic effect | 2007 | Hydrogeology Journal Vol. 15(4), pp. 659-668 |
article | URL |
| Abstract: A laboratory study was undertaken to determine the transport and deposition rate of suspended particles in columns of saturated porous media (gravel and glass beads), where the porous media were subjected to steady-state flow. Silt particles with a mode of 14 μm diameter (used as the suspended particles) and fluorescein (as the conservative tracer) were injected into the columns in short pulses. The breakthrough curves were competently described with the analytical solution of a convection–dispersion equation with a first-order deposition rate. The experiments were performed using different flow rates. The suspended particle size distribution, the porous media, and the flow rates themselves were the main factors retained in this study to investigate the mechanisms governing the transport and deposition kinetics in detail. The results showed the existence of a flow rate, beyond which suspended particles travel faster than the conservative tracer. A decrease of the deposition rate of suspended particles beyond a critical flow velocity was also observed. Such behaviour led to consideration of the couple hydrodynamic-gravity forces at high flow rates. As the hydrodynamic force increases, particle deposition rates are reduced due to the effect of hydrodynamic forces inhibiting the deposition. | |||||
BibTeX:
@article{Ahfir2007,
author = {Ahfir, Nasre-Dine and Wang, Hua Qing and Benamar, Ahmed and Alem, Adbellah and Massei, Nicolas and Dupont, Jean-Paul},
title = {Transport and deposition of suspended particles in saturated porous media: hydrodynamic effect},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2007},
volume = {15},
number = {4},
pages = {659--668},
url = {http://dx.doi.org/10.1007/s10040-006-0131-3}
}
|
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| Ahmad, F., Schnitker, S.P. and Newell, C.J. | Remediation of RDX- and HMX-contaminated groundwater using organic mulch permeable reactive barriers | 2007 | Journal of Contaminant Hydrology Vol. 90(1-2), pp. 1-20 |
article | URL |
| Abstract: Organic mulch is a complex organic material that is typically populated with its own consortium of microorganisms. The organisms in mulch breakdown complex organics to soluble carbon, which can then be used by these and other microorganisms as an electron donor for treating RDX and HMX via reductive pathways. A bench-scale treatability study with organic mulch was conducted for the treatment of RDX- and HMX-contaminated groundwater obtained from a plume at the Pueblo Chemical Depot (PCD) in Pueblo, Colorado. The site-specific cleanup criteria of 0.55 ppb RDX and 602 ppb HMX were used as the logical goals of the study. Column flow-through tests were run to steady-state at the average site seepage velocity, using a 70%:30% (vol.:vol.) mulch:pea gravel packing to approach the formation's permeability. Significant results included: (1) Complete removal of 90 ppb influent RDX and 8 ppb influent HMX in steady-state mulch column effluent; (2) pseudo-first-order steady-state kinetic rate constant, k, of 0.20 to 0.27 h− 1 based on RDX data, using triplicate parallel column runs; (3) accumulation of reduced RDX intermediates in the steady-state column effluent at less than 2% of the influent RDX mass; (4) no binding of RDX to the column fill material; and (5) no leaching of RDX, HMX or reduction intermediates from the column fill material. The results of the bench-scale study will be used to design and implement a pilot-scale organic mulch/pea gravel permeable reactive barrier (PRB) at the site. | |||||
BibTeX:
@article{Ahmad2007,
author = {Ahmad, Farrukh and Schnitker, Stephen P. and Newell, Charles J.},
title = {Remediation of RDX- and HMX-contaminated groundwater using organic mulch permeable reactive barriers},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {90},
number = {1-2},
pages = {1--20},
url = {http://www.sciencedirect.com/science/article/pii/S0169772206001707}
}
|
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| Ahnert, M., Kuehn, V. and Krebs, P. | Temperature as an alternative tracer for the determination of the mixing characteristics in wastewater treatment plants | 2010 | Water Research Vol. 44(6), pp. 1765-1776 |
article | URL |
| Abstract: The hydraulic characteristics, i.e. the residence time distributions, of wastewater treatment plant reactors are usually determined using conventional tracers. This paper aims to present an alternative approach based on wastewater temperature. The step in temperature change, e.g. from stormwater events with cold rainwater, is used as a tracer signal. The method was verified using lab- and pilot-scale tests that showed very good agreement of the time series estimated both with conventional and temperature tracer methods. Results from lab-scale tests exhibit a zone with a minor water exchange of about 10% of the volume of all reactors, while the respective zone in the pilot-scale tests was estimated at about 30% of the total volume. The short-circuit flow was more than 50% of the inflow resulting from gaps between the walls inside the reactor cascade. An application example shows the importance of reliable residence time distribution underlying activated sludge modelling and the uncertainty associated with neglecting the determination of appropriate flow-through characteristics. | |||||
BibTeX:
@article{Ahnert2010,
author = {Ahnert, Markus and Kuehn, Volker and Krebs, Peter},
title = {Temperature as an alternative tracer for the determination of the mixing characteristics in wastewater treatment plants},
journal = {Water Research},
year = {2010},
volume = {44},
number = {6},
pages = {1765--1776},
url = {http://www.sciencedirect.com/science/article/pii/S0043135409008021}
}
|
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| Akdağ, S., Bagiorgas, H. and Mihalakakou, G. | Use of two-component Weibull mixtures in the analysis of wind speed in the Eastern Mediterranean | 2010 | Applied Energy Vol. 87(8), pp. 2566-2573 |
article | URL |
| Abstract: The statistical characteristics of wind speed data recorded at nine buoys, located in Ionian and Aegean Sea (Eastern Mediterranean) are analyzed in this paper, in order to present a more accurate method for estimation of wind speed characteristics, according to the suitability of the probability distribution functions (pdf). This article has focussed on wind regimes that present nearly zero percentages of null wind speeds. The selected distributions for examination are the typical two-parameter Weibull wind speed distribution (W-pdf) and the two-component mixture Weibull distribution (WW-pdf), involving five parameters (two shape parameters, two scale parameters, and one proportionality parameter). | |||||
BibTeX:
@article{Akdag2010,
author = {Akdağ, S.A. and Bagiorgas, H.S. and Mihalakakou, G.},
title = {Use of two-component Weibull mixtures in the analysis of wind speed in the Eastern Mediterranean},
journal = {Applied Energy},
year = {2010},
volume = {87},
number = {8},
pages = {2566--2573},
url = {http://www.sciencedirect.com/science/article/pii/S030626191000067X}
}
|
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| Aksoy, H. | Use of Gamma Distribution in Hydrological Analysis | 2000 | Turkish Journal of Engineering and Environmental Sciences Vol. 24(6), pp. 419-428 |
article | URL |
| Abstract: In this study, amounts of daily rainfall and the ascension curve of the hydrograph are investigated. In both cases, the 2-parameter gamma distribution is used. The distribution is fitted to the amounts of daily rainfall and to the differences between the flows of successive days on the ascension curve of the hydrograph. The shape and scale parameters of the distribution, in both cases, are estimated in a monthly time interval. A 30-year daily rainfall series and a 35-year daily runoff series are used for the application. It may be seen that the distribution fits very well to the rainfall data and also that the ascension curve of the hydrograph can easily be represented by the distribution. | |||||
BibTeX:
@article{Aksoy2000,
author = {Aksoy, Hafzullah},
title = {Use of Gamma Distribution in Hydrological Analysis},
journal = {Turkish Journal of Engineering and Environmental Sciences},
year = {2000},
volume = {24},
number = {6},
pages = {419--428},
url = {http://mistug.tubitak.gov.tr/bdyim/abs2.php?dergi=muh&rak=9909-13}
}
|
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| Akyol, N.H., Yolcubal, I. and Yüksel, D.I. | Sorption and transport of trichloroethylene in caliche soil | 2011 | Chemosphere Vol. 82(6), pp. 809-816 |
article | URL |
| Abstract: Sorption of TCE to the caliche soil exhibited linear isotherm at the high TCE concentrations (Co = 122–1300 mg L−1) but Freundlich isotherm at the low concentration range (1–122 mg L−1). Sorption strength of the carbonate fraction of the soil was about 100-fold lower than the sorption strength of soil organic matter (SOM) in the caliche soil, indicating weak affinity of TCE for the carbonate fraction of the soil. Desorption of TCE from the caliche soil was initially rapid (7.6 × 10−4 s−1), then continued at a 100-fold slower rate (7.7 × 10−6 s−1). Predominant calcium carbonate fraction of the soil (96%) was responsible for the fast desorption of TCE while the SOM fraction (0.97%) controlled the rate-limited desorption of TCE. Transport of TCE in the caliche soil was moderately retarded with respect to the water (R = 1.75–2.95). Flow interruption tests in the column experiments indicated that the rate-limited desorption of TCE controlled the non-ideal transport of TCE in the soil. Modeling studies showed that both linear and non-linear nonequilibrium transport models provided reasonably good match to the TCE breakthrough curves (r2 = 0.95–0.98). Non-linear sorption had a negligible impact on both the breakthrough curve shape and the values of sorption kinetics parameters at the high TCE concentration (Co = 1300 mg L−1). However, rate-limited sorption/desorption processes dominated at this concentration. For the low TCE concentration case (110 mg L−1), in addition to the rate-limited sorption/desorption, contribution of the non-linear sorption to the values of sorption kinetics became fairly noticeable. | |||||
BibTeX:
@article{Akyol2011,
author = {Akyol, Nihat Hakan and Yolcubal, Irfan and Yüksel, Derya Imer},
title = {Sorption and transport of trichloroethylene in caliche soil},
journal = {Chemosphere},
year = {2011},
volume = {82},
number = {6},
pages = {809--816},
url = {http://www.sciencedirect.com/science/article/pii/S0045653510013226}
}
|
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| Al-Abry, S.M., Rao, L.N. and Feroz, S. | Residence Time Distribution Studies in Miniature Pipes | 2011 | Journal of Chemical, Biological and Physical Sciences Vol. 1(2), pp. 363-377 |
article | |
| Abstract: The research work is focused on the residence time distribution (RTD) studies in small pipes using pulse input technique. The extent of dispersion is expressed in terms of dispersion coefficient (DL). RTD studies are carried out by tracer analysis and DL is estimated using axial dispersion model. Laminar flow in short pipes follow pure convection model but the experimental data in the present study is found to be in good agreement with axial dispersion model. The variance and dispersion coefficients are estimated and the effects of flow and geometric parameter on dispersion coefficients are studied. In scope of present study, the dispersion coefficient is found to increase with an increase in velocity and length of tube but the effect of pipe diameter on dispersion coefficient is found to be marginal. | |||||
BibTeX:
@article{Al-Abry2011,
author = {Al-Abry, Suleiman Mohammed and Rao, L. Nageswara and Feroz, Shaik},
title = {Residence Time Distribution Studies in Miniature Pipes},
journal = {Journal of Chemical, Biological and Physical Sciences},
year = {2011},
volume = {1},
number = {2},
pages = {363--377}
}
|
|||||
| Albert, I. and Mafart, P. | A modified Weibull model for bacterial inactivation | 2005 | International Journal of Food Microbiology Vol. 100(1-3)The Fourth International Conference on Predictive Modelling in Foods, pp. 197-211 |
article | URL |
| Abstract: In this paper, a modified Weibull model is proposed to fit microbial survival curves. This model can incorporate shoulder and/or tailing phenomena if they are encountered. We aim to obtain an accurate fit of the “primary” modelling of the bacterial inactivation and to provide a useful and meaningful model for biologists and food industry. A δ parameter close to the classical concept of the D value, established for sterilisation processes, is used in the model. The specific parameterisation of the Weibull model is evaluated for the parameter of interest δ. The goodness-of-fit of the model is compared to the one produced by the model proposed by Geeraerd et al., [Geeraerd, A.H., Herremans, C.H., Van Impe, J.F., 2000. Structural model requirements to describe microbial inactivation during a mild heat treatment. Int. J. Food Microbiol. 59, 185-209.] on experimental data. As our model provides good fits for the different types of survival curves analysed, further research can focus on the development of suitable secondary model types. In this respect, it is interesting to note that the δ parameter is close to the D concept. | |||||
BibTeX:
@article{Albert2005,
author = {Albert, I. and Mafart, P.},
title = {A modified Weibull model for bacterial inactivation},
booktitle = {The Fourth International Conference on Predictive Modelling in Foods},
journal = {International Journal of Food Microbiology},
year = {2005},
volume = {100},
number = {1-3},
pages = {197--211},
url = {http://www.sciencedirect.com/science/article/pii/S0168160504004751}
}
|
|||||
| Al-Charideh, A. | Environmental isotope study of groundwater discharge from the large karst springs in West Syria: a case study of Figeh and Al-sin springs | 2011 | Environmental Earth Sciences Vol. 63(1), pp. 1-10 |
article | URL |
| Abstract: Environmental isotopes (δ 18 O, δD and 3 H) in precipitation and groundwater were integrated for the description of groundwater discharge from the large karst springs of Figeh and Al-sin located in West Syria. The two springs are considered as the most important springs in this Middle East country due to their huge discharge. The δ 18 O values are −8.91 and −6.49‰ for Figeh and Al-sin, respectively. The regression line for both precipitation and groundwater is described by the equation: δD = 7.9δ 18 O + 19.7, which shows no evaporation during precipitation and suggests that the groundwater is mainly from direct infiltration of precipitation. The altitude gradients in the precipitation were estimated to be −0.23‰/100 m for δ 18 O. The main recharge areas are 2,100 and 750 m.a.s.l., for Figeh and Al-sin springs, respectively. The tritium concentrations in groundwater are low and very close to the rainfall values of 4.5 and 3.5 TU for Bloudan and Kadmous meteoric stations, respectively. Adopting a model with exponential time distribution, the main residence time of groundwater in Figeh and Al-sin springs was evaluated to be 50–60 years. A value of around 3.9 and 4.2 billion m 3 was obtained for Figeh and Al-sin, respectively, as the maximum groundwater reservoir size. | |||||
BibTeX:
@article{Al-Charideh2011,
author = {Al-Charideh, A.},
title = {Environmental isotope study of groundwater discharge from the large karst springs in West Syria: a case study of Figeh and Al-sin springs},
journal = {Environmental Earth Sciences},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {63},
number = {1},
pages = {1--10},
url = {http://dx.doi.org/10.1007/s12665-010-0660-x}
}
|
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| Alcocer, D.J.R., Vallejos, G.G. and Champagne, P. | Assessment of the plug flow and dead volume ratios in a sub-surface horizontal-flow packed-bed reactor as a representative model of a sub-surface horizontal constructed wetland | 2012 | Ecological Engineering Vol. 40(0), pp. 18-26 |
article | URL |
| Abstract: The aim of this study was to assess the influence of design parameters on the plug flow and dead volume ratios in a sub-surface horizontal-flow packed-bed reactor (HPBR), as a representative model of a sub-surface horizontal-flow constructed wetland (SSHFCW), to provide a further understanding of SSHFCW, and to assist in the design and application of these systems on a larger scale. Design parameters included the aspect ratio, the size of the porous media and the loading rate of the HPBR. Integral parameters, such as plug flow, dead volume and short-circuiting ratios, were determined using tracer tests and the Wolf–Resnick empirical flow model. The experiment was conducted in three packed-bed reactors with volumes of 192 L and different length-to-width aspect ratios (1:1, 1.5:1 and 3:1). Each packed-bed reactor received three different controlled influent hydraulic loading rates (0.3 L/min, 0.6 L/min, and 1.5 L/min), and the size of the porous media was varied in the individual beds, using three nominal diameters (4.7 mm, 9.2 mm and 12.7 mm). Results showed that the aspect ratio had the greatest effect on the hydraulic behaviour of the system. An increase in the aspect ratio resulted in a experimental retention time that was closer to the theoretical retention time, and exhibited higher plug flow and lower dead volume ratios compared to an ideal plug flow system operated under similar conditions. An increase in loading rate negatively affected the plug flow portion in the system by increasing dispersion. The retention time increased, making it more similar to ideal plug flow and reducing the dead volume ratio. Finally, it was demonstrated that a decrease in the nominal diameter increased dispersion and reduced the plug flow ratio; however, the retention times obtained were closer to those of the ideal plug flow system. It was concluded that a constructed sub-surface flow wetland design should incorporate a combination of higher aspect ratios, higher loading rate and finer porous media to induce a hydraulic behaviour closer to an ideal plug flow system. | |||||
BibTeX:
@article{Alcocer2012,
author = {Alcocer, David Jafet Rodríguez and Vallejos, Germán Giácoman and Champagne, Pascale},
title = {Assessment of the plug flow and dead volume ratios in a sub-surface horizontal-flow packed-bed reactor as a representative model of a sub-surface horizontal constructed wetland},
journal = {Ecological Engineering},
year = {2012},
volume = {40},
number = {0},
pages = {18--26},
url = {http://www.sciencedirect.com/science/article/pii/S0925857411003399}
}
|
|||||
| Alexander, G.N. | The use of gamma distribution in estimating regulated output from storages [BibTeX] |
1962 | Transactions of the Institution of Engineers, Australia, Civil Engineering Vol. 4(1), pp. 29-34 |
article | |
BibTeX:
@article{Alexander1962,
author = {Alexander, G. N.},
title = {The use of gamma distribution in estimating regulated output from storages},
journal = {Transactions of the Institution of Engineers, Australia, Civil Engineering},
year = {1962},
volume = {4},
number = {1},
pages = {29--34}
}
|
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| Alfreider, A., Loferer-Krössbacher, M. and Psenner, R. | Influence of artificial groundwater lakes on the abundance and activity of bacteria in adjacent subsurface systems | 2001 | Limnologica - Ecology and Management of Inland Waters Vol. 31(4), pp. 249-255 |
article | URL |
| Abstract: Bacterial abundances and activity, estimated by 4′,6-diamidino-2-phenylindole staining (DAPI) and the reduction of 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT), were investigated in two oligotrophic artificial groundwater lakes and the surrounding aquifers. To evaluate the effect of lake water on groundwater downstream, samples were taken from wells at different distances from the lakes, and the total number of bacteria and the number of active bacteria in these samples were compared with samples collected upstream. In addition, sterilized sandy sediments were exposed in groundwater wells to measure the number and activity of bacteria attached to particles. At one of the study sites, where the lake sediments were disturbed by dredging, total bacterial abundance and the number of respiring bacteria in the groundwater aquifer was clearly influenced by the lake water. The average bacterial abundances decreased from 2.6 ± 1.9 × 105 cells ml−1 in the well closest to the lake (S2) to 2.9 ± 3.8 × 104 cells ml−1 in the most distant one (S4), which was equivalent to cell numbers in the upstream well. The number of respiring bacteria showed a similar tendency with 1.3 ± 2.7 × 104 active cells ml−1 in S2 and 1.9 ± 1.5 × 103 active cells ml−1 in S4. At the second study site, which was not influenced by dredging, bacteria in the downstream wells seemed not to be affected by the lake water. The number and activity of bacteria, which colonized exposed sediments, were not significantly different in the upstream and downstream wells, indicating a minor influence of lake water on this habitat. Our results suggest that gravel-pit lakes may influence the free living bacterial assemblages in nearshore groundwater systems, but do not visibly affect numbers and activity of bacteria attached to the surface of aquifer sediments. | |||||
BibTeX:
@article{Alfreider2001,
author = {Alfreider, Albin and Loferer-Krössbacher, Maria and Psenner, Roland},
title = {Influence of artificial groundwater lakes on the abundance and activity of bacteria in adjacent subsurface systems},
journal = {Limnologica - Ecology and Management of Inland Waters},
year = {2001},
volume = {31},
number = {4},
pages = {249--255},
url = {http://www.sciencedirect.com/science/article/pii/S007595110180027X}
}
|
|||||
| Alkhaddar, R., Higgins, P., Phipps, D. and Andoh, R. | Residence time distribution of a model hydrodynamic vortex separator | 2001 | Urban Water Vol. 3(1–2), pp. 17-24 |
article | URL |
| Abstract: This study investigates the macromixing within a hydrodynamic vortex separator (HDVS). The device is a scale model of a prototype unit and is operated with zero baseflow. The device under investigation is typically used for the removal of settleable and colloidal solids. The macromixing is investigated by conducting tracer experiments from which the residence time distribution (RTD) is obtained and interpreted to characterise the mixing regime within the HDVS. The method of moments and non-linear regression are used to obtain various RTD functions and flow-model parameters to aid in the characterisation of the device's mixing regime and the degree of any non-ideal flow behaviour. The axial dispersion model (ADM) and tanks-in-series model (TISM) are used in this study. The RTD imperfectly approximates a plug-flow distribution but, the device has some amount of dispersion and is equal to approximately 2–3 perfectly stirred tanks in series. The ADM seems to give a closer representation of the experimental curves compared to the TISM. The sludge hopper appears to be acting as a stagnant zone. | |||||
BibTeX:
@article{Alkhaddar2001,
author = {Alkhaddar, R.M and Higgins, P.R and Phipps, D.A and Andoh, R.Y.G},
title = {Residence time distribution of a model hydrodynamic vortex separator},
journal = {Urban Water},
year = {2001},
volume = {3},
number = {1–2},
pages = {17--24},
url = {http://www.sciencedirect.com/science/article/pii/S1462075801000152}
}
|
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| Allaire, G., Brizzi, R., Mikelić, A. and Piatnitski, A. | Two-scale expansion with drift approach to the Taylor dispersion for reactive transport through porous media | 2010 | Chemical Engineering Science Vol. 65(7)International Symposium on Mathematics in Chemical Kinetics and Engineering, pp. 2292-2300 |
article | URL |
| Abstract: In this work we study reactive flows through porous media. We suppose dominant Péclet's number, dominant Damköhler's number and general linear reactions at the pore boundaries. Our goal is to obtain the dispersion tensor and the upscaled model. We introduce the multiple scale expansions with drift for the problem and use this technique to upscale the reactive flow equations. Our result is illustrated with numerical simulations for the dispersion tensor. | |||||
BibTeX:
@article{Allaire2010,
author = {Allaire, Grégoire and Brizzi, Robert and Mikelić, Andro and Piatnitski, Andrey},
title = {Two-scale expansion with drift approach to the Taylor dispersion for reactive transport through porous media},
booktitle = {International Symposium on Mathematics in Chemical Kinetics and Engineering},
journal = {Chemical Engineering Science},
year = {2010},
volume = {65},
number = {7},
pages = {2292--2300},
url = {http://www.sciencedirect.com/science/article/pii/S0009250909006034}
}
|
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| Al-Rawashdeh, M., Cantu-Perez, A., Ziegenbalg, D., Löb, P., Gavriilidis, A., Hessel, V. and Schönfeld, F. | Microstructure-based intensification of a falling film microreactor through optimal film setting with realistic profiles and in-channel induced mixing | 2012 | Chemical Engineering Journal Vol. 179(0), pp. 318-329 |
article | URL |
| Abstract: The high liquid based specific interfacial area, up to ∼20,000 m2/m3, of falling film microreactors renders them to be ideally suited to carry out fast exothermic and mass transfer limited reactions. To understand the role of and control this interfacial area, it is important to account for realistic liquid film profiles. Here, we vary the liquid film profile or its velocity profile by two different means – through the (external) shape of a plain microchannel and through in-channel structures within the microchannel (staggered herringbone grooves (SHG) on the microchannel bottom). The variations in the liquid films are evaluated via two computational fluid dynamic (CFD) models. First is the pseudo 3-D which explicitly accounts for the liquid film thicknesses, flow velocities, species transport and reactions. Here, the pseudo 3-D model is used to investigate (1) the effects of five microchannel shapes and (2) three microchannel cross section dimensions; to account for a scale-out through both numbering-up and smart increase in dimensions. The model reaction used is the absorption of CO2 in aqueous NaOH solution. It is found that the mass transfer into the liquid and the reaction conversion depend on the velocity profile and flow pattern. Second CFD model is the full 3-D which is used to evaluate the liquid film in the presence of SHG. The simulations from the full 3-D model indicate that: (1) residence time distribution is narrowed by five times compared to plain microchannels and (2) the penetration depths of particles seeded at the gas/liquid interface are 1.7 times larger in the presence of SHG. Furthermore the effect of SHG on penetration depth is more pronounced at higher flow rates. This is experimentally exploited by increasing the liquid throughput by more than a factor of two while keeping the same reaction conversion, using the SHG microchannels. | |||||
BibTeX:
@article{Al-Rawashdeh2012a,
author = {Al-Rawashdeh, Ma’moun and Cantu-Perez, Alberto and Ziegenbalg, Dirk and Löb, Patrick and Gavriilidis, Asterios and Hessel, Volker and Schönfeld, Friedhelm},
title = {Microstructure-based intensification of a falling film microreactor through optimal film setting with realistic profiles and in-channel induced mixing},
journal = {Chemical Engineering Journal},
year = {2012},
volume = {179},
number = {0},
pages = {318--329},
url = {http://www.sciencedirect.com/science/article/pii/S1385894711013933}
}
|
|||||
| Al-Saleh, J.A. and Agarwal, S.K. | Finite mixture of gamma distributions: A conjugate prior | 2007 | Computational Statistics & Data Analysis Vol. 51(9), pp. 4369-4378 |
article | URL |
| Abstract: A finite mixture of gamma distributions [Finite mixture of certain distributions. Comm. Statist. Theory Methods 31(12), 2123–2137] is used as a conjugate prior, which gives a nice form of posterior distribution. This class of conjugate priors offers a more flexible class of priors than the class of gamma prior distributions. The usefulness of a mixture gamma-type prior and the posterior of uncertain parameters λ for the Poisson distribution are illustrated by using Markov Chain Monte Carlo (MCMC), Gibbs sampling approach, on hierarchical models. Using the generalized hypergeometric function, the method to approximate maximum likelihood estimators for the parameters of Agarwal and Al-Saleh [Generalized gamma type distribution and its hazard rate function. Comm. Statist. Theory Methods 30(2), 309–318] generalized gamma-type distribution is also suggested. | |||||
BibTeX:
@article{Al-Saleh2007,
author = {Al-Saleh, Jamal A. and Agarwal, Satish K.},
title = {Finite mixture of gamma distributions: A conjugate prior},
journal = {Computational Statistics & Data Analysis},
year = {2007},
volume = {51},
number = {9},
pages = {4369--4378},
url = {http://www.sciencedirect.com/science/article/pii/S0167947306001952}
}
|
|||||
| Al-Saleh, J.A. and Agarwal, S.K. | Extended Weibull type distribution and finite mixture of distributions | 2006 | Statistical Methodology Vol. 3(3), pp. 224-233 |
article | URL |
| Abstract: An extended form of Weibull distribution is suggested which has two shape parameters ( m and δ ). Introduction of another shape parameter δ helps to express the extended Weibull distribution not only as an exact form of a mixture of distributions under certain conditions, but also provides extra flexibility to the density function over positive range. The shape of density function of the extended Weibull type distribution for various values of the parameters is shown which may be of some interest to Bayesians. Certain statistical properties such as hazard rate function, mean residual function, r th moment are defined explicitly. The proposed extended Weibull distribution is used to derive an exact form of two, three and k -component mixture of distributions. With the help of a real data set, the usefulness of mixture Weibull type distribution is illustrated by using Markov Chain Monte Carlo (MCMC), Gibbs sampling approach. | |||||
BibTeX:
@article{Al-Saleh2006,
author = {Al-Saleh, Jamal A. and Agarwal, Satish K.},
title = {Extended Weibull type distribution and finite mixture of distributions},
journal = {Statistical Methodology},
year = {2006},
volume = {3},
number = {3},
pages = {224--233},
url = {http://www.sciencedirect.com/science/article/pii/S1572312705000754}
}
|
|||||
| Alvord, H. and Kadlec, R. | Atrazine fate and transport in the Des Plaines Wetlands | 1996 | Ecological Modelling Vol. 90(1), pp. 97-107 |
article | URL |
| Abstract: Atrazine fate and transport in three constructed pond and island wetlands in north east Illinois, USA, were studied in the field (1991) and modeled. The wetlands received pumped inflow from the Des Plaines River. The nominal residence time was about eight days for two, but was longer for the third. | |||||
BibTeX:
@article{Alvord1996,
author = {Alvord, H.H. and Kadlec, R.H.},
title = {Atrazine fate and transport in the Des Plaines Wetlands},
journal = {Ecological Modelling},
year = {1996},
volume = {90},
number = {1},
pages = {97--107},
url = {http://www.sciencedirect.com/science/article/pii/0304380095001506}
}
|
|||||
| Alvord, H. and Kadlec, R. | The interaction of atrazine with wetland sorbents | 1995 | Ecological Engineering Vol. 5(4), pp. 469-479 |
article | URL |
| Abstract: Atrazine equilibrium sorption data for sediments, litter, peat, root mat, and soil from three Midwestern USA wetlands fit the Freundlich isotherm model, Cs = K Cwn. Water atrazine concentrations were in the μg/dm3 range. Sorbent analyses recovered most of the atrazine not found in the water. Data errors in sorbent atrazine concentrations were much larger than those in water concentrations. Maximum likelihood and logarithmic regression methods gave similar parameter estimates. | |||||
BibTeX:
@article{Alvord1995,
author = {Alvord, H.H. and Kadlec, R.H.},
title = {The interaction of atrazine with wetland sorbents},
journal = {Ecological Engineering},
year = {1995},
volume = {5},
number = {4},
pages = {469--479},
url = {http://www.sciencedirect.com/science/article/pii/0925857495000364}
}
|
|||||
| Alzaid, A. and Sultan, K. | Discriminating between gamma and lognormal distributions with applications | 2009 | Journal of King Saud University - Science Vol. 21(2), pp. 99-108 |
article | URL |
| Abstract: In this paper, we discuss the use of the coefficient of skewness as a goodness-of-fit test to distinguish between the gamma and lognormal distributions. We also show the limitations of this idea. Next, we use the moments of order statistics from gamma distribution to adjust the correlation goodness-of-fit test. In addition, we calculate the power of the test based on some other alterative distributions including the lognormal distribution. Further, we show some numerical illustration. Finally, we apply the procedure developed in the paper to some real data sets. | |||||
BibTeX:
@article{Alzaid2009,
author = {Alzaid, A. and Sultan, K.S.},
title = {Discriminating between gamma and lognormal distributions with applications},
journal = {Journal of King Saud University - Science},
year = {2009},
volume = {21},
number = {2},
pages = {99--108},
url = {http://www.sciencedirect.com/science/article/pii/S1018364709000056}
}
|
|||||
| Amaziane, B., Pankratov, L. and Piatnitski, A. | Nonlinear flow through double porosity media in variable exponent Sobolev spaces | 2009 | Nonlinear Analysis: Real World Applications Vol. 10(4), pp. 2521-2530 |
article | URL |
| Abstract: We studied the asymptotic behavior of the solution of a nonlinear parabolic equation with nonstandard growth in a ε -periodic fractured medium, where ε is the parameter that characterizes the scale of the microstructure tending to zero. We consider a double porosity type model describing the flow of a compressible fluid in a heterogeneous anisotropic porous medium obeying the nonlinear Darcy law. We assume that the permeability ratio of matrix blocks to fractures is of order ε p ε ( x ) , where p ε is a continuous positive function. We obtained the convergence of the solution and a macroscopic model of the problem was constructed using the notion of two-scale convergence combined with the variational homogenization method in the framework of Sobolev spaces with variable exponents. | |||||
BibTeX:
@article{Amaziane2009,
author = {Amaziane, B. and Pankratov, L. and Piatnitski, A.},
title = {Nonlinear flow through double porosity media in variable exponent Sobolev spaces},
journal = {Nonlinear Analysis: Real World Applications},
year = {2009},
volume = {10},
number = {4},
pages = {2521--2530},
url = {http://www.sciencedirect.com/science/article/pii/S1468121808001429}
}
|
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| Amin, I.E. and Campana, M.E. | A general lumped parameter model for the interpretation of tracer data and transit time calculation in hydrologic systems | 1996 | Journal of Hydrology Vol. 179(1-4), pp. 1-21 |
article | URL |
| Abstract: We present a general lumped parameter mathematical model for hydrologic tracer data interpretation and mean transit time calculation in hydrologic systems. The model takes the form of the three-parameter gamma distribution and accounts for different mixing types: perfect mixing; no mixing (piston flow); partial mixing (dispersive mixing, or the type between perfect mixing and no mixing); and various combinations of the above types. In these combinations, the different mixing types simulated by the model conceptually represent reservoirs in series. We introduce the mixing efficiency to characterize the extent or degree of natural mixing in hydrologic systems. This parameter equals zero for piston flow (no mixing), unity for perfect mixing, and a value in between these two extremes for partial mixing. The general model simulates the combination of perfect mixing, partial mixing, and piston flow. Six other models that simulate one or two of these mixing types can be obtained as special cases from the general model. Therefore, seven models are introduced in this effort. Of these, four (including the general model) are new, and three are currently existing in the field of tracer hydrology. The three existing models are the perfect mixing model, piston flow model, and the perfect-piston flow model which simulates the combination of perfect mixing and piston flow. The new models are the perfect-partial-piston flow model (the general model), perfect-partial mixing model, partial-piston flow model, and partial mixing model. | |||||
BibTeX:
@article{Amin1996,
author = {Amin, Isam E. and Campana, Michael E.},
title = {A general lumped parameter model for the interpretation of tracer data and transit time calculation in hydrologic systems},
journal = {Journal of Hydrology},
year = {1996},
volume = {179},
number = {1-4},
pages = {1--21},
url = {http://www.sciencedirect.com/science/article/pii/0022169495028803}
}
|
|||||
| Anderson, M.P. and Woessner, W.W. | Applied Groundwater Modeling: Simulation of Flow and Advective Transport [BibTeX] |
1992 | , pp. - | book | |
BibTeX:
@book{Anderson1992,
author = {Anderson, Mary P. and Woessner, William W.},
title = {Applied Groundwater Modeling: Simulation of Flow and Advective Transport},
publisher = {Academic Press Inc.},
year = {1992},
pages = {--}
}
|
|||||
| Andreo, B., Goldscheider, N., Vadillo, I., Vías, J.M., Neukum, C., Sinreich, M., Jiménez, P., Brechenmacher, J., Carrasco, F., Hötzl, H., Perles, M.J. and Zwahlen, F. | Karst groundwater protection: First application of a Pan-European Approach to vulnerability, hazard and risk mapping in the Sierra de Líbar (Southern Spain) | 2006 | Science of The Total Environment Vol. 357(1-3), pp. 54-73 |
article | URL |
| Abstract: The European COST action 620 proposed a comprehensive approach to karst groundwater protection, comprising methods of intrinsic and specific vulnerability mapping, validation of vulnerability maps, hazard and risk mapping. This paper presents the first application of all components of this Pan-European Approach to the Sierra de Líbar, a karst hydrogeology system in Andalusia, Spain. The intrinsic vulnerability maps take into account the hydrogeological characteristics of the area but are independent from specific contaminant properties. Two specific vulnerability maps were prepared for faecal coliforms and BTEX. These maps take into account the specific properties of these two groups of contaminants and their interaction with the karst hydrogeological system. The vulnerability assessment was validated by means of tracing tests, hydrological, hydrochemical and isotope methods. The hazard map shows the localization of potential contamination sources resulting from human activities, and evaluates those according to their dangerousness. The risk of groundwater contamination depends on the hazards and the vulnerability of the aquifer system. The risk map for the Sierra de Líbar was thus created by overlaying the hazard and vulnerability maps. | |||||
BibTeX:
@article{Andreo2006,
author = {Andreo, Bartolomé and Goldscheider, Nico and Vadillo, Iñaki and Vías, Jesús María and Neukum, Christoph and Sinreich, Michael and Jiménez, Pablo and Brechenmacher, Julia and Carrasco, Francisco and Hötzl, Heinz and Perles, María Jesús and Zwahlen, François},
title = {Karst groundwater protection: First application of a Pan-European Approach to vulnerability, hazard and risk mapping in the Sierra de Líbar (Southern Spain)},
journal = {Science of The Total Environment},
year = {2006},
volume = {357},
number = {1-3},
pages = {54--73},
url = {http://www.sciencedirect.com/science/article/pii/S0048969705003761}
}
|
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| Andreo, B., Liñán, C., Carrasco, F., Jiménez de Cisneros, C., Caballero, F. and Mudry, J. | Influence of rainfall quantity on the isotopic composition (18O and 2H) of water in mountainous areas. Application for groundwater research in the Yunquera-Nieves karst aquifers (S Spain) | 2004 | Applied Geochemistry Vol. 19(4), pp. 561-574 |
article | URL |
| Abstract: The isotopic composition (18O and 2H) of rainwater and groundwater was determined in the Yunquera-Nieves hydrogeological unit, a karstic massif in S Spain with complex orography and hydrogeology. The aims were to identify: (1) the source of the water, (2) the main factors determining the isotopic content, (3) the catchment area of the springs and (4) the aquifer behaviour. The isotopic content of the sampled waters is of mixed Atlantic–Mediterranean origin and is opposite to the quantity of rainwater distribution, both in space and time. Spatially, water is isotopically less depleted toward the eastern sector, where rainwater quantity is lower (which is locally affected by the orography): thus, it is possible to differentiate the catchment areas of the main springs. Aquifer recharge is produced by winter precipitation, when rainfall water is isotopically more negative and evaporation is lower. The decrease in rainfall quantity during the study period provoked an increase in δ18O and δ2H values, both in rainwater and in groundwater. The recorded variations of the isotopic content of the rainfall are rapidly evident in the spring waters, which demonstrates a well developed karst network inside the carbonate aquifers, and thus the existence of conduit flow systems. | |||||
BibTeX:
@article{Andreo2004,
author = {Andreo, B. and Liñán, C. and Carrasco, F. and Jiménez de Cisneros, C. and Caballero, F. and Mudry, J.},
title = {Influence of rainfall quantity on the isotopic composition (18O and 2H) of water in mountainous areas. Application for groundwater research in the Yunquera-Nieves karst aquifers (S Spain)},
journal = {Applied Geochemistry},
year = {2004},
volume = {19},
number = {4},
pages = {561--574},
url = {http://www.sciencedirect.com/science/article/pii/S0883292703001641}
}
|
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| Angulo-Jaramillo, R., Vandervaere, J.-P., Roulier, S., Thony, J.-L., Gaudet, J.-P. and Vauclin, M. | Field measurement of soil surface hydraulic properties by disc and ring infiltrometers: A review and recent developments | 2000 | Soil and Tillage Research Vol. 55(1-2), pp. 1-29 |
article | URL |
| Abstract: Soil management influences physical properties and mainly the soil hydraulic functions. Their measurement becomes one of the research preferences in this branch of applied soil science. Tension disc and pressure ring infiltrometers have become very popular devices for the in situ estimates of soil surface hydraulic properties. Their use for measuring solute–water transfer parameters of soils is now well established too. A number of publications testify that both devices have been extensively used all around the world for different purposes. In this review, a short introduction is devoted to the background theory and some examples are given to show how the theory can be used to determine hydraulic conductivity and sorptivity from measured cumulative infiltration. The methods of analysis of cumulative infiltration are based either on quasi-analytical solutions of the flow equation for homogeneous soil profile or on inverse parameter estimation techniques from the numerical solution of flow equation whether the soil profile is homogeneous or not. The disc infiltrometer has also been shown as a suitable device for inferring parameters describing the water-borne transport of chemicals through near saturated soils. Associated with conservative tracers, it has been recognized as a promising tool for the determination of both hydraulic and solute transport properties as well as for other parameters such as mobile/immobile water content fraction or exchange coefficient. An emphasis is put here on some published studies performed in different soils and environmental conditions focusing on heterogeneous soil profiles (crusted soils) or structured cultivated soils (aggregated soils), either when local water transport process is studied or when field spatial variability is investigated. Some new research studies such as water–solute transfer in structured or swelling–shrinking soils and multi-interactive solute transport are emerging. A number of challenges still remain unresolved for both theory and practice for tension and pressure infiltrometers. They include questions on how to consider and characterize saturated–unsaturated preferential flow or preferential transport process (including hydrodynamic instabilities) induced by biological activity (e.g. capillary macropores, earthworm holes or root channels) by specific pedagogical conditions (e.g. cracking, crusting) and by soil management practices (i.e. conservation tillage). | |||||
BibTeX:
@article{Angulo-Jaramillo2000,
author = {Angulo-Jaramillo, Rafael and Vandervaere, Jean-Pierre and Roulier, Stéphanie and Thony, Jean-Louis and Gaudet, Jean-Paul and Vauclin, Michel},
title = {Field measurement of soil surface hydraulic properties by disc and ring infiltrometers: A review and recent developments},
journal = {Soil and Tillage Research},
year = {2000},
volume = {55},
number = {1-2},
pages = {1--29},
url = {http://www.sciencedirect.com/science/article/pii/S0167198700000982}
}
|
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| Ani, E.-C., Wallis, S., Kraslawski, A. and Agachi, P.S. | Development, calibration and evaluation of two mathematical models for pollutant transport in a small river | 2009 | Environmental Modelling & Software Vol. 24(10), pp. 1139-1152 |
article | URL |
| Abstract: The present research has two main objectives (1) to build two models for concentration prediction in a stream subject to a pollutant release and (2) to investigate options for estimating the parameters of the models. The models rely on the fundamental advection–dispersion equation and were developed, calibrated and evaluated using tracer data from experiments conducted in the Murray Burn in Edinburgh, UK. During the evaluation by comparison against field data both models were able to predict the main features of the observations at the first three monitoring sites, but results at the final site were less good. | |||||
BibTeX:
@article{Ani2009,
author = {Ani, Elisabeta-Cristina and Wallis, Steve and Kraslawski, Andrzej and Agachi, Paul Serban},
title = {Development, calibration and evaluation of two mathematical models for pollutant transport in a small river},
journal = {Environmental Modelling & Software},
year = {2009},
volume = {24},
number = {10},
pages = {1139--1152},
url = {http://www.sciencedirect.com/science/article/pii/S1364815209000838}
}
|
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| Antizar-Ladislao, B., Lopez-Real, J. and Beck, A.J. | In-vessel composting-bioremediation of aged coal tar soil: effect of temperature and soil/green waste amendment ratio | 2005 | Environment International Vol. 31(2)Recent Advances in Bioremediation, pp. 173-178 |
article | URL |
| Abstract: The biodegradation of 16 United States Environmental Protection Agency (USEPA)-listed polycyclic aromatic hydrocarbons (PAHs) present in contaminated soil from a manufactured gas plant site was investigated using laboratory-scale in-vessel composting–bioremediation reactors over 8 weeks. The influence of temperature (T, 38, 55, and 70 °C) and soil/green waste ratio (S:GW, 0.6:1, 0.7:1, 0.8:1, and 0.9:1) was investigated. A comparative study using a temperature profile during in-vessel composting–bioremediation to meet current regulatory requirements was also investigated. Temperature and amendment ratio were found to be important operating parameters for PAH removal for in-vessel composting–bioremediation of aged coal tar-contaminated soil. After 8 weeks of continuous treatment, the highest removal of 16 USEPA PAHs was observed at T=38 °C and S:GW=0.8:1 (75.2%). Lower removal of 16 USEPA PAHs was observed for temperature profile treatment (60.8%). We recommend that when conventional composting processes using temperature profiles to meet regulatory requirements for pathogen control need to be used, these should start with a prolonged mesophilic stage (6 weeks in this investigation) followed by thermophilic, cooling, and maturation stages. | |||||
BibTeX:
@article{Antizar-Ladislao2005,
author = {Antizar-Ladislao, Blanca and Lopez-Real, Joe and Beck, Angus J.},
title = {In-vessel composting-bioremediation of aged coal tar soil: effect of temperature and soil/green waste amendment ratio},
booktitle = {Recent Advances in Bioremediation},
journal = {Environment International},
year = {2005},
volume = {31},
number = {2},
pages = {173--178},
url = {http://www.sciencedirect.com/science/article/pii/S016041200400162X}
}
|
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| Anwar, S. and Sukop, M.C. | Lattice Boltzmann Models for Flow and Transport in Saturated Karst | 2009 | Ground Water Vol. 47(3), pp. 401-413 |
article | URL |
| Abstract: Flow and transport simulation in karst aquifers remains a significant challenge for the ground water modeling community. Darcy’s law–based models cannot simulate the inertial flows characteristic of many karst aquifers. Eddies in these flows can strongly affect solute transport. The simple two-region conduit/matrix paradigm is inadequate for many purposes because it considers only a capacitance rather than a physical domain. Relatively new lattice Boltzmann methods (LBMs) are capable of solving inertial flows and associated solute transport in geometrically complex domains involving karst conduits and heterogeneous matrix rock. LBMs for flow and transport in heterogeneous porous media, which are needed to make the models applicable to large-scale problems, are still under development. Here we explore aspects of these future LBMs, present simple examples illustrating some of the processes that can be simulated, and compare the results with available analytical solutions. Simulations are contrived to mimic simple capacitance-based two-region models involving conduit (mobile) and matrix (immobile) regions and are compared against the analytical solution. There is a high correlation between LBM simulations and the analytical solution for two different mobile region fractions. In more realistic conduit/matrix simulation, the breakthrough curve showed classic features and the two-region model fit slightly better than the advection-dispersion equation (ADE). An LBM-based anisotropic dispersion solver is applied to simulate breakthrough curves from a heterogeneous porous medium, which fit the ADE solution. Finally, breakthrough from a karst-like system consisting of a conduit with inertial regime flow in a heterogeneous aquifer is compared with the advection-dispersion and two-region analytical solutions. | |||||
BibTeX:
@article{Anwar2009,
author = {Anwar, Shadab and Sukop, Michael C.},
title = {Lattice Boltzmann Models for Flow and Transport in Saturated Karst},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2009},
volume = {47},
number = {3},
pages = {401--413},
url = {http://dx.doi.org/10.1111/j.1745-6584.2008.00514.x}
}
|
|||||
| Aquilina, L., Ladouche, B., Doerfliger, N., Seidel, J., Bakalowicz, M., Dupuy, C. and Le Strat, P. | Origin, evolution and residence time of saline thermal fluids (Balaruc springs, southern France): implications for fluid transfer across the continental shelf | 2002 | Chemical Geology Vol. 192(1-2), pp. 1-21 |
article | URL |
| Abstract: Thermal fluids in the Balaruc-les-Bains peninsula, on the northeastern edge of the Thau lagoon (southern France), supply the third largest spa in France. These thermal fluids interact with karst water in the Upper Jurassic aquifer composed of limestone and dolomite, forming two massifs to the east and north of the lagoon. These calcareous formations extend under the western end of the Thau lagoon. Geochemical and isotope analyses were carried out in 1996 and 1998 on the thermal wells of the Balaruc-les-Bains peninsula to determine the origin of the thermal fluids and their interaction with subsurface karst water. | |||||
BibTeX:
@article{Aquilina2002,
author = {Aquilina, L. and Ladouche, B. and Doerfliger, N. and Seidel, J.L. and Bakalowicz, M. and Dupuy, C. and Le Strat, P.},
title = {Origin, evolution and residence time of saline thermal fluids (Balaruc springs, southern France): implications for fluid transfer across the continental shelf},
journal = {Chemical Geology},
year = {2002},
volume = {192},
number = {1-2},
pages = {1--21},
url = {http://www.sciencedirect.com/science/article/pii/S0009254102001602}
}
|
|||||
| Arey, J.S. and Gschwend, P.M. | A physical–chemical screening model for anticipating widespread contamination of community water supply wells by gasoline constituents | 2005 | Journal of Contaminant Hydrology Vol. 76(1-2), pp. 109-138 |
article | URL |
| Abstract: Continuing modifications of fuels like gasoline should include evaluations of the proposed constituents for their potential to damage environmental resources such as subsurface water supplies. Consequently, we developed a screening model to estimate well water concentrations and transport times for gasoline components migrating from underground fuel tank (UFT) releases to typical at-risk community water supply wells. Representative fuel release volumes and hydrogeologic characteristics were used to parameterize the transport calculation. Subsurface degradation processes were neglected in the model in order to make risk-conservative assessments. The model was tailored to individual compounds based on their abundances in gasoline, gasoline–water partition coefficients (Kgw), and organic matter–water partition coefficients (Kom). Transport calculations were conducted for 20 polar and 4 nonpolar compounds found in gasoline, including methyl tert-butyl ether (MTBE) and other ether oxygenates, ethanol, methanol, and some aromatic hydrocarbons. With no calibration, the screening model successfully captured the reported magnitude of MTBE contamination of at-risk community supply wells. Such screening indicates that other oxygenates would cause similar widespread problems unless they were biodegradable. Stochastic analysis of field parameter variability concluded that community supply well contamination estimates had order-of-magnitude reliability. This indicated that such pre-manufacturing analyses may reasonably anticipate widespread environmental problems and/or inspire focused investigations into chemical properties (e.g., biodegradability) before industrial adoption of new fuel formulations. | |||||
BibTeX:
@article{Arey2005,
author = {Arey, J. Samuel and Gschwend, Philip M.},
title = {A physical–chemical screening model for anticipating widespread contamination of community water supply wells by gasoline constituents},
journal = {Journal of Contaminant Hydrology},
year = {2005},
volume = {76},
number = {1-2},
pages = {109--138},
url = {http://www.sciencedirect.com/science/article/pii/S0169772204001482}
}
|
|||||
| Arfib, B., De Marsily, G. and Ganoulis, J. | Locating the Zone of Saline Intrusion in a Coastal Karst Aquifer Using Springflow Data | 2007 | Ground Water Vol. 45(1), pp. 28-35 |
article | URL |
| Abstract: Coastal fresh water aquifers are an increasingly desirable resource. In a karstic aquifer, sea water intrusion occurs as a salt water wedge, like in porous media. However, preferential flow conduits may alter the spatial and temporal distribution of the salt water. This is typically the case when the outlet of the aquifer is a brackish spring. This paper shows that salinity and flow rate variations at a spring, where salinity is inversely proportional to discharge, can help to understand the hydrodynamic functioning of the aquifer and to locate the fresh water–sea water mixing zone deep inside the aquifer. The volume of water-filled conduit between the sea water intrusion zone and the spring outlet is calculated by the integral over time of the flow rate during the time lag between the flow rate increase and the salinity decrease as measured at the spring. In the example of the spring at Almyros of Heraklio (Crete, Greece), this time lag is variable, depending on the discharge, but the volume of water-filled conduit appears to be constant, which shows that the processes of salt water intrusion and mixing in the conduit are constant throughout the year. The distance between the spring and the zone where sea water enters the conduit is estimated and provides an indication of the position where only fresh water is present in the conduit. | |||||
BibTeX:
@article{Arfib2007,
author = {Arfib, Bruno and De Marsily, Ghislain and Ganoulis, Jacques},
title = {Locating the Zone of Saline Intrusion in a Coastal Karst Aquifer Using Springflow Data},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2007},
volume = {45},
number = {1},
pages = {28--35},
url = {http://dx.doi.org/10.1111/j.1745-6584.2006.00252.x}
}
|
|||||
| Armstrong, P., Cobb, C., Cobb, B., Stewart-Wright, J. and Byl, T. | Characterization of Bacteria and Geochemistry of Springs in Nashville, Tennessee | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 69 | inproceedings | URL |
| Abstract: The objective of the project was to evaluate the water quality of four limestone bedrock springs in an urban environment during a severe drought in the summer of 2007. Three of the springs were discovered on the Tennessee State University (TSU) campus in Nashville, TN in May, 2007. Two are located near a poultry research facility and a third near the TSU athletic center. An additional spring flowing from a cave in the Charlotte Park neighborhood of west Nashville (Carlos Cave) was also included in the study. The two TSU springs behind the poultry barns were sampled approximately every week from June through September, 2007. The cave and TSU athletic center springs were sampled less frequently. Water quality parameters included temperature, specific conductance, and dissolved oxygen, pH, sulfate, nitrogen, E. coli, and bacteria Biological Activity Reaction Tests (BART). Continuous water-quality monitoring devices were installed at two of the springs to measure changes associated with different weather patterns. Water temperatures were very stable, ranging from 16oC in June to 19oC in September. Sulfate concentrations were consistently higher in the spring water than the receiving surface waters, suggesting that surface vegetation may have removed the sulfate. Conversely, nitrogen levels were lower in the spring water (<10 mg/L) than the surface waters, suggesting denitrification by bacteria in the subsurface. Fecal bacteria levels fluctuated randomly with no discernable correlation to weather pattern. BART tests confirmed the presence of denitrifying, iron-reducing, sulfur-reducing, and slime-producing bacteria at each of the springs. Spring discharges decreased at all sites as the drought continued but never decreased below 10 gallons per minute. The data showed that each spring had unique water quality characteristics reflective of the different hydrologic recharge areas that replenish them. | |||||
BibTeX:
@inproceedings{Armstrong2008,
author = {Armstrong, Patrice and Cobb, Carlton and Cobb, Brandon and Stewart-Wright, Jennifer and Byl, Tom},
title = {Characterization of Bacteria and Geochemistry of Springs in Nashville, Tennessee},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U. S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {69},
url = {http://pubs.usgs.gov/sir/2008/5023/24armstrong.htm}
}
|
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| Arnold, B.C., Castillo, E. and María Sarabia, J. | Variations on the classical multivariate normal theme | 2007 | Journal of Statistical Planning and Inference Vol. 137(11)Special Issue: In Celebration of the Centennial of The Birth of Samarendra Nath Roy (1906-1964), pp. 3249-3260 |
article | URL |
| Abstract: Description is provided of a variety of flexible models that include the classical multivariate normal as a special case. Special emphasis is placed on models constructed by conditional specification, hidden truncation and contour specification. | |||||
BibTeX:
@article{Arnold2007,
author = {Arnold, Barry C. and Castillo, Enrique and María Sarabia, José},
title = {Variations on the classical multivariate normal theme},
booktitle = {Special Issue: In Celebration of the Centennial of The Birth of Samarendra Nath Roy (1906-1964)},
journal = {Journal of Statistical Planning and Inference},
year = {2007},
volume = {137},
number = {11},
pages = {3249--3260},
url = {http://www.sciencedirect.com/science/article/pii/S0378375807000948}
}
|
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| Arratia, P., Lacombe, J., Shinbrot, T. and Muzzio, F. | Segregated regions in continuous laminar stirred tank reactors | 2004 | Chemical Engineering Science Vol. 59(7), pp. 1481-1490 |
article | URL |
| Abstract: Using visualization techniques, including acid/base reactions and UV fluorescence, we provide experimental evidence of segregated regions (islands) during mixing of viscous Newtonian fluids under laminar flow conditions in continuous stirred tank reactors (CSTRs). The effect of inlet/outlet stream position and Reynolds number on the dynamics of the mixing processes is examined. Numerical experiments in 3-D map were able to capture the main features of the CSTR flow by perturbing a Batch system using an imposed axial flow. Asymmetric flow patterns produced by off-center positioning of inlet and outlet pipes cause a reduction in size of the segregated region, enlarging the chaotic region and leading to more efficient mixing. Under dynamic inlet flow conditions, the laminar steady flow is perturbed, giving rise to an asymmetric flow pattern that is able to destroy toroidal segregated regions. Counter-intuitively, higher agitation speed (higher Re) did not enhance overall mixing efficiency. Faster agitation stabilized the toroidal regions, making it harder to destroy them. In addition, dynamic mixing protocols are investigated to enhance mixing performance. We demonstrate that time-dependent pumping and stirring protocols are able to efficiently destroy long-lasting toroidal regions. | |||||
BibTeX:
@article{Arratia2004,
author = {Arratia, P.E. and Lacombe, J.P. and Shinbrot, T. and Muzzio, F.J.},
title = {Segregated regions in continuous laminar stirred tank reactors},
journal = {Chemical Engineering Science},
year = {2004},
volume = {59},
number = {7},
pages = {1481--1490},
url = {http://www.sciencedirect.com/science/article/pii/S0009250903005451}
}
|
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| Asadolahi, A.N., Gupta, R., Fletcher, D.F. and Haynes, B.S. | CFD approaches for the simulation of hydrodynamics and heat transfer in Taylor flow | 2011 | Chemical Engineering Science Vol. 66(22), pp. 5575-5584 |
article | URL |
| Abstract: Previous studies on heat and mass transfer in the Taylor flow regime in microchannels have shown the transport (heat/mass) rates to be dependent on the length of the liquid slug. In order to understand the effect of slug length on transport rates and to have a one-to-one comparison with experimental data, a computational approach is required to simulate flows with liquid slugs and bubbles of controlled lengths. | |||||
BibTeX:
@article{Asadolahi2011,
author = {Asadolahi, Azadeh N. and Gupta, Raghvendra and Fletcher, David F. and Haynes, Brian S.},
title = {CFD approaches for the simulation of hydrodynamics and heat transfer in Taylor flow},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {22},
pages = {5575--5584},
url = {http://www.sciencedirect.com/science/article/pii/S0009250911005185}
}
|
|||||
| Athanasios, L. | Flood frequency estimation by a derived distribution procedure | 2002 | Journal of Hydrology Vol. 255(1-4), pp. 69-89 |
article | URL |
| Abstract: An event rainfall-runoff simulation procedure based on the method of derived distributions is proposed for the estimation of flood frequency for ungauged watersheds. The procedure uses a stochastic rainfall generation model and a rainfall-runoff watershed model. The results of previous research on rainfall characteristics and watershed response are incorporated into the two models. These rainfall characteristics are storm depth, storm duration, space and time distribution. The simplified watershed model, used in the procedure, has previously been tested and given good simulation of the watershed response. Some of the rainfall and watershed model parameters are stochastic in nature and are assumed to follow various probability distributions. Monte Carlo simulation is used for the generation of the various parameter values and simulation of the flood hydrographs. After 5000 realizations, the frequency of the hourly and daily peak flow and the flood volume is estimated. The proposed procedure is applied to eight coastal British Columbia watersheds and the results compare well with the observed data and with the Extreme Value type I (EVI or Gumbel) fitted probability distribution. The method is easy to apply, requires limited regional data and is shown to be reliable for small and medium forested watersheds with areas ranging from 10 to 600 km2. Sensitivity analysis shows that the procedure is stable and is not sensitive to the number of realizations. It is suggested that, given an appropriate adjustment of the rainfall generation model and testing and validation, the procedure could be used in areas with climates other than that of coastal British Columbia. | |||||
BibTeX:
@article{Athanasios2002,
author = {Athanasios, Loukas},
title = {Flood frequency estimation by a derived distribution procedure},
journal = {Journal of Hydrology},
year = {2002},
volume = {255},
number = {1-4},
pages = {69--89},
url = {http://www.sciencedirect.com/science/article/pii/S0022169401005054}
}
|
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| Attarakih, M.M., Bart, H.-J. and Faqir, N.M. | Numerical solution of the spatially distributed population balance equation describing the hydrodynamics of interacting liquid–liquid dispersions | 2004 | Chemical Engineering Science Vol. 59(12), pp. 2567-2592 |
article | URL |
| Abstract: In liquid–liquid contacting equipment such as completely mixed and differential contactors, droplet population balance based modeling is now being used to describe the complex hydrodynamic behavior of the dispersed phase. For the hydrodynamics of these interacting dispersions this model accounts for droplet breakage, droplet coalescence, axial dispersion, exit and entry events. The resulting population balance equations are integro-partial differential equations (IPDE) that rarely have an analytical solution, especially when they show spatial dependency, and hence numerical solutions are sought in general. To do this, these IPDEs are projected onto a system of convective dominant partial differential equations by discretizing the droplet diameter (internal coordinate). This is accomplished by generalizing the fixed-pivot (GFP) technique of Kumar and Ramkrishna (Chem. Eng. Sci. 51 (1996a) 1311) handling any two integral properties of the population number density for continuous flow systems by treating the inlet feed distribution as a source term. Moreover, the GFD technique has the advantage of being free of repeated or double integral evaluation resulting from the weighted residual approaches such as the Galerkin's method. This allows the time-dependent breakage and coalescence functions to be easily handled without appreciable increase in the computational time. The resulting system of PDEs is spatially discretized in conservative form using a simplified first order upwind scheme as well as first- and second-order non-oscillatory central differencing schemes. This spatial discretization avoids the characteristic decomposition of the convective flux based on the approximate Riemann solvers and the operator splitting technique required by classical upwind schemes. The time variable is discretized using an implicit strongly stable approach that is formulated by careful lagging of the non-linear parts of the convective and source terms. The algorithm is tested against analytical solutions of the simplified population balance equation for a differential liquid–liquid extraction column through four case studies. In all these case studies the discrete models converge successfully to the available analytical solutions and to solutions on relatively fine grids when the analytical solution is not available. Realization of the algorithm is accomplished by comparing its predictions to experimental steady-state hydrodynamic data of a laboratory scale rotating disc contactor of 0.15 m diameter. Practically, the combined algorithm is found fast enough for the computation of the transient and steady-state hydrodynamic behavior of the continuously and spatially distributed interacting liquid–liquid dispersions. | |||||
BibTeX:
@article{Attarakih2004,
author = {Attarakih, Menwer M. and Bart, Hans-Jörg and Faqir, Naim M.},
title = {Numerical solution of the spatially distributed population balance equation describing the hydrodynamics of interacting liquid–liquid dispersions},
journal = {Chemical Engineering Science},
year = {2004},
volume = {59},
number = {12},
pages = {2567--2592},
url = {http://www.sciencedirect.com/science/article/pii/S0009250904001484}
}
|
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| Attinger, S., Dimitrova, J. and Kinzelbach, W. | Homogenization of the transport behavior of nonlinearly adsorbing pollutants in physically and chemically heterogeneous aquifers | 2009 | Advances in Water Resources Vol. 32(5)Dispersion in Porous Media, pp. 767-777 |
article | URL |
| Abstract: This paper addresses the question of how spatial variability in the hydraulic and chemical properties of groundwater systems affects the transport and sorption behavior of pollutants at the field scale. In this paper, we limit our investigations on pollutants that adsorb according to an equilibrium controlled nonlinear Freundlich sorption isotherm. The new contribution of this paper is take into account not only spatially variable Freundlich distribution coefficients K S but spatially variable Freundlich nonlinearity parameters p as well. Using a homogenization theory approach, we shortly review the impact of spatially variable hydraulic properties on the transport and extend the theory to spatially variable chemical properties. We show that spatially variable Freundlich exponents cause a very different field scale transport and sorption behavior than spatial variations in the distribution coefficients only since in the first case field scale Freundlich parameters and field scale dispersion coefficients become concentration dependent. In particular, field scale retardation is much larger than small-scale retardation. | |||||
BibTeX:
@article{Attinger2009,
author = {Attinger, Sabine and Dimitrova, Jiva and Kinzelbach, Wolfgang},
title = {Homogenization of the transport behavior of nonlinearly adsorbing pollutants in physically and chemically heterogeneous aquifers},
booktitle = {Dispersion in Porous Media},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {5},
pages = {767--777},
url = {http://www.sciencedirect.com/science/article/pii/S030917080900013X}
}
|
|||||
| Aubin, J., Prat, L., Xuereb, C. and Gourdon, C. | Effect of microchannel aspect ratio on residence time distributions and the axial dispersion coefficient | 2009 | Chemical Engineering and Processing: Process Intensification Vol. 48(1), pp. 554-559 |
article | URL |
| Abstract: The effect of microchannel aspect ratio (channel depth/channel width) on residence time distributions and the axial dispersion coefficient have been investigated for Newtonian and shear-thinning non-Newtonian flow using computational fluid dynamics. The results reveal that for a fixed cross-sectional area and throughput, there is a narrowing of the residence time distribution as the aspect ratio decreases. This is quantified by an axial dispersion coefficient that increases rapidly for aspect ratios less than 0.3 and then tends towards an asymptote as the aspect ratio goes to 1. The results also show that the axial dispersion coefficient is related linearly to the Reynolds number when either the aspect ratio or the mean fluid velocity is varied. However, the fluid Péclet number is a linear function of the Reynolds number only when the aspect ratio (and therefore hydraulic diameter) is varied. Globally, the results indicate that microchannels should be designed with low aspect ratios (≤0.3) for reduced axial dispersion. | |||||
BibTeX:
@article{Aubin2009,
author = {Aubin, J. and Prat, L. and Xuereb, C. and Gourdon, C.},
title = {Effect of microchannel aspect ratio on residence time distributions and the axial dispersion coefficient},
journal = {Chemical Engineering and Processing: Process Intensification},
year = {2009},
volume = {48},
number = {1},
pages = {554--559},
url = {http://www.sciencedirect.com/science/article/pii/S0255270108001773}
}
|
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| Avgousti, M. and Beris, A.N. | Viscoelastic Taylor-Couette Flow: Bifurcation Analysis in the Presence of Symmetries | 1993 | Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences Vol. 443(1917), pp. 17-37 |
article | DOI URL |
| Abstract: The morphogenesis of secondary vortices is investigated for the axisymmetric flow of a viscoelastic fluid, confined between two independently rotating, infinitely long cylinders, in the region near the onset of instability of the purely azimuthal Couette flow. The Oldroyd-B constitutive equation is used to model viscoelasticity. Three characteristic regions in the parameter space, corresponding to three distinct solution families have been investigated where the onset of instability is due primarily to inertia, both inertia and elasticity, and exclusively elasticity, respectively. The secondary flow corresponds to a steady Taylor vortex in the first case, but to a time-periodic one when elasticity becomes important (Hopf bifurcation). Degenerate Hopf bifurcation theory in the presence of symmetries (O(2) $times $ S$^1$) has been used to show the existence of two different time-periodic solution families, each following either one of two possible patterns, the rotating wave or the standing wave. Through a computer-aided nonlinear analysis, all of the steady and time-periodic bifurcating solutions are shown to be supercritical, implying that one and only one is stable. These results are consistent with the conclusions of time-dependent numerical simulations which have demonstrated an exchange of stabilities from the rotating to the standing wave pattern emerging after the bifurcation, as the elasticity of the fluid increases. | |||||
BibTeX:
@article{Avgousti1993,
author = {Avgousti, Marios and Beris, Antony N.},
title = {Viscoelastic Taylor-Couette Flow: Bifurcation Analysis in the Presence of Symmetries},
journal = {Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences},
year = {1993},
volume = {443},
number = {1917},
pages = {17--37},
url = {http://rspa.royalsocietypublishing.org/content/443/1917/17.abstract},
doi = {http://dx.doi.org/10.1098/rspa.1993.0129}
}
|
|||||
| Ayraud, V., Aquilina, L., Labasque, T., Pauwels, H., Molenat, J., Pierson-Wickmann, A.-C., Durand, V., Bour, O., Tarits, C., Le Corre, P., Fourre, E., Merot, P. and Davy, P. | Compartmentalization of physical and chemical properties in hard-rock aquifers deduced from chemical and groundwater age analyses | 2008 | Applied Geochemistry Vol. 23(9), pp. 2686-2707 |
article | URL |
| Abstract: Using groundwater age determination done through CFC analysis and geochemical data obtained from seven sites in Brittany (France), a hydrogeochemical model for hard-rock aquifers is presented. According to the geological structure, three zones can be defined: the weathered layer, about 30 m thick; the weathered-fissured layer (fractured rock with a high density of fissures induced by weathering), which represents a transition zone between the weathered zone and the lower fractured zone; and the unweathered part of the aquifer. (1) The weathered layer (alterites) is often considered as a porous medium and is the only part frequently used in hard-rock aquifers. Recent apparent ages (0–10 a) are observed in the groundwater fluctuation zone in a thin layer, which is from 1–2 m-thick in the lower parts and 10–15 m-thick in the upper parts of the catchments. Below this thin layer, the groundwater apparent age is high (between 10 and 25 a) and is unexpectedly homogeneous at the regional scale. This groundwater apparent age contrast, which also corresponds to a Cl− concentration contrast, is attributed to rapid lateral transfers in the fluctuation zone which limit water transfer to the underlying weathered zone. Groundwater chemistry is characterized by NO 3 - and Cl− concentrations related to land uses (high in agricultural areas, low in preserved ones). (2) At the interface between the weathered and the weathered-fissured layers a strong biogeochemical reactivity is observed. Autotrophic denitrification is enhanced by a higher availability of sulfides. (3) Under this interface, in the weathered-fissured layer and the underlying fractured deep part of the aquifer, groundwater apparent age is clearly correlated to depth. The vertical groundwater velocity is estimated to be 3 m/a, whatever be the site, which seems to indicate a regional topographic control on groundwater circulation in the deep part of the aquifer. In this deep part, groundwater chemistry is modified by water–rock interaction processes as indicated by Ca and Na concentrations, and a slight sea-water contribution (from 0.1% to 0.65%) in the sites close to the seacoast. One site inland shows a saline and old end-member. The global hydrogeochemical scheme is modified when the aquifer is pumped at a high rate in the fissured-weathered layer and/or the fractured layer. The increase in water velocity leads to a homogeneous groundwater apparent age, whatever be the depth in the weathered-fissured and fractured layers. | |||||
BibTeX:
@article{Ayraud2008,
author = {Ayraud, Virginie and Aquilina, Luc and Labasque, Thierry and Pauwels, Hélène and Molenat, Jérôme and Pierson-Wickmann, Anne-Catherine and Durand, Véronique and Bour, Olivier and Tarits, Corinne and Le Corre, Pierre and Fourre, Elise and Merot, Philippe and Davy, Philippe},
title = {Compartmentalization of physical and chemical properties in hard-rock aquifers deduced from chemical and groundwater age analyses},
journal = {Applied Geochemistry},
year = {2008},
volume = {23},
number = {9},
pages = {2686--2707},
url = {http://www.sciencedirect.com/science/article/pii/S0883292708002230}
}
|
|||||
| Baedke, S.J. and Krothe, N.C. | Derivation of effective hydraulic parameters of a Karst Aquifer from discharge hydrograph analysis | 2001 | Water Resources Research Vol. 37(1), pp. 13-19 |
article | URL |
| Abstract: In well-developed karst terrains, three or more distinct portions of the karst continuum can be identified from hydrographs of springs issuing from the karst aquifer. Hydrographs from two karst springs within the same drainage basin at the Crane Naval Surface Warfare Center, Indiana, have been analyzed, and ratios of transmissivity and specific yield (T/Sy) have been established for the conduit and diffuse flow systems. These ratios have been compared with values of T derived from aquifer tests, so that independent values of Sy can be calculated for the diffuse system. Similarly, if the value of Sy is assumed to be 1.0 for a pure conduit, then independent values of T can be calculated for this end-member of the karst continuum. The values of T and Sy derived from this study are similar to values obtained from a dye trace of the conduit-dominated flow system and of values derived from aquifer tests of the diffuse flow system. Values of T for the conduit system of these springs may need to be established at a local scale, while the values for the diffuse flow system may be applicable at a regional scale. A hydrograph separation using isotopic data suggests that the intermediate-flow system represents a mix of water from the conduit and diffuse flow systems. If this portion of the hydrograph is a truly mixing phenomena, ratios of T/Sy cannot be determined from the hydrograph analysis presented herein. However, if instead, the intermediate-flow system represents water released from a third reservoir (such as small fractures), ratios of T/Sy can be established for the intermediate-flow system. | |||||
BibTeX:
@article{Baedke2001,
author = {Baedke, S. J. and Krothe, N. C.},
title = {Derivation of effective hydraulic parameters of a Karst Aquifer from discharge hydrograph analysis},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2001},
volume = {37},
number = {1},
pages = {13--19},
url = {http://dx.doi.org/10.1029/2000WR900247}
}
|
|||||
| Baeumer, B., Benson, D. and Meerschaert, M. | Advection and dispersion in time and space | 2005 | Physica A: Statistical Mechanics and its Applications Vol. 350(2-4), pp. 245-262 |
article | URL |
| Abstract: Previous work showed how moving particles that rest along their trajectory lead to time-nonlocal advection–dispersion equations. If the waiting times have infinite mean, the model equation contains a fractional time derivative of order between 0 and 1. In this article, we develop a new advection–dispersion equation with an additional fractional time derivative of order between 1 and 2. Solutions to the equation are obtained by subordination. The form of the time derivative is related to the probability distribution of particle waiting times and the subordinator is given as the first passage time density of the waiting time process which is computed explicitly. | |||||
BibTeX:
@article{Baeumer2005,
author = {Baeumer, B. and Benson, D.A. and Meerschaert, M.M.},
title = {Advection and dispersion in time and space},
journal = {Physica A: Statistical Mechanics and its Applications},
year = {2005},
volume = {350},
number = {2-4},
pages = {245--262},
url = {http://www.sciencedirect.com/science/article/pii/S0378437104014141}
}
|
|||||
| Baheri, H. and Meysami, P. | Feasibility of fungi bioaugmentation in composting a flare pit soil | 2002 | Journal of Hazardous Materials Vol. 89(2-3), pp. 279-286 |
article | URL |
| Abstract: The feasibility of fungi bioaugmentation in composting of a flare pit soil was studied in lab-scale composters. The preliminary screening tests, using a range of bulking agents and white rot fungi strains, were conducted to determine, best strain and bulking agent for the main experiments. The initial total petroleum hydrocarbon (TPH) of the flare pit soil was found to be 16%. The effect of moisture and bulking agent content and the fungi application on biodegradation of hydrocarbons were then evaluated based on a fractional factorial design over a 3-months period. Analysis of the TPH content of the soil after 98 days (using gravimetric method) showed an average of 29% reduction in most jars. Furthermore, gas chromatograph (GC) analysis of the oil extract from the samples showed 70–99% reduction in the peak area of the selected hydrocarbons. However, statistical analysis of the results did not show any significant effect due to the fungi application or the change in the moisture content (30–50% range). The results showed that the change in the bulking agent content was marginally significant for the hydrocarbon loss. | |||||
BibTeX:
@article{Baheri2002,
author = {Baheri, H and Meysami, P},
title = {Feasibility of fungi bioaugmentation in composting a flare pit soil},
journal = {Journal of Hazardous Materials},
year = {2002},
volume = {89},
number = {2--3},
pages = {279--286},
url = {http://www.sciencedirect.com/science/article/pii/S0304389401003181}
}
|
|||||
| Bai, M. and Roegiers, J.-C. | Triple-porosity analysis of solute transport | 1997 | Journal of Contaminant Hydrology Vol. 28(3), pp. 247-266 |
article | URL |
| Abstract: As an extension to the traditional dual-porosity approach, a triple-porosity model is presented to study the solute transport in heterogeneous porous media where the transport processes are distinctly different between macropores, mesopores and micropores. The distinctions in terms of conductance and storage in the respective pore domain are characterized by the fact that: (a) macropores are primary flow paths where both dispersion and convection are prevalent; (b) mesopores are intermediate flow paths where convection becomes dominant and (c) micropores are supplemental flow paths and mass storage spaces where only diffusive flow is manifested. In cascading coupling, the solute interchange between micropores and mesopores is maintained by assuming micropore diffusion as internal sources (sinks) attached to mesopore skins. A comprehensive solute exchange between macropores and mesopores is preserved. A mathematical model is constructed in accordance with the physical conceptualization. The coupled partial differential equations are solved in a one-dimensional geometry using Laplace transform, and the subsequent coupled ordinary differential equations are circumvented via the method of differential operators. Semi-analytical solutions are obtained. | |||||
BibTeX:
@article{Bai1997,
author = {Bai, M. and Roegiers, J.-C.},
title = {Triple-porosity analysis of solute transport},
journal = {Journal of Contaminant Hydrology},
year = {1997},
volume = {28},
number = {3},
pages = {247--266},
url = {http://www.sciencedirect.com/science/article/pii/S0169772296000861}
}
|
|||||
| Baillie, R.T. | Long memory processes and fractional integration in econometrics | 1996 | Journal of Econometrics Vol. 73(1), pp. 5-59 |
article | URL |
| Abstract: This paper provides a survey and review of the major econometric work on long memory processes, fractional integration, and their applications in economics and finance. Some of the definitions of long memory are reviewed, together with previous work in other disciplines. Section 3 describes the population characteristics of various long memory processes in the mean, including ARFIMA. Section 4 is concerned with estimation and examines semiparametric procedures in both the frequency and time domain, and also the properties of various regression based and maximum likelihood techniques. Long memory volatility processes are discussed in Section 5, while Section 6 discusses applications in economics and finance. The paper also has a concluding section. | |||||
BibTeX:
@article{Baillie1996,
author = {Baillie, Richard T.},
title = {Long memory processes and fractional integration in econometrics},
journal = {Journal of Econometrics},
year = {1996},
volume = {73},
number = {1},
pages = {5--59},
url = {http://www.sciencedirect.com/science/article/pii/0304407695017321}
}
|
|||||
| Bailly-Comte, V., Jourde, H. and Pistre, S. | Conceptualization and classification of groundwater–surface water hydrodynamic interactions in karst watersheds: Case of the karst watershed of the Coulazou River (Southern France) | 2009 | Journal of Hydrology Vol. 376(3-4), pp. 456-462 |
article | URL |
| Abstract: Over the last two decades, groundwater systems and surface water bodies are being more and more considered as a same entity which constitutes a single resource within the hydrologic system; understanding groundwater surface water (GW–SW) interactions is necessary to effectively manage the water resources. Concepts, methods of analysis and classifications of these hydrodynamic interactions have thus been developed, mostly in case of porous aquifer. Today, GW–SW interactions are still often poorly understood in many watersheds, particularly in the case of complex aquifers like karst aquifers. | |||||
BibTeX:
@article{Bailly-Comte2009,
author = {Bailly-Comte, V. and Jourde, H. and Pistre, S.},
title = {Conceptualization and classification of groundwater–surface water hydrodynamic interactions in karst watersheds: Case of the karst watershed of the Coulazou River (Southern France)},
journal = {Journal of Hydrology},
year = {2009},
volume = {376},
number = {3-4},
pages = {456--462},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409004557}
}
|
|||||
| Bailly-Comte, V., Jourde, H., Roesch, A., Pistre, S. and Batiot-Guilhe, C. | Time series analyses for Karst/River interactions assessment: Case of the Coulazou river (southern France) | 2008 | Journal of Hydrology Vol. 349(1-2), pp. 98-114 |
article | URL |
| Abstract: In many karst systems throughout the world, numerous karst features facilitate the exchange of water between the surface, the vadose zone and the saturated zone of the aquifer. These interactions play actually a prominent role in the ground and surface waters circulation. This study aims at assessing Karst/River interactions by the way of flood hydrograph analysis and new tools for time series analysis in this field of research. | |||||
BibTeX:
@article{Bailly-Comte2008,
author = {Bailly-Comte, V. and Jourde, H. and Roesch, A. and Pistre, S. and Batiot-Guilhe, C.},
title = {Time series analyses for Karst/River interactions assessment: Case of the Coulazou river (southern France)},
journal = {Journal of Hydrology},
year = {2008},
volume = {349},
number = {1-2},
pages = {98--114},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407006403}
}
|
|||||
| Bailly-Comte, V., Martin, J.B., Jourde, H., Screaton, E.J., Pistre, S. and Langston, A. | Water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams | 2010 | Journal of Hydrology Vol. 386(1-4), pp. 55-66 |
article | URL |
| Abstract: Karst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes (matrix and fractures). For more than a century, various approaches have used flood recession curves, which integrate all hydrodynamic processes in a karst aquifer, to infer physical properties of the movement and storage of groundwater. These investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves. | |||||
BibTeX:
@article{Bailly-Comte2010,
author = {Bailly-Comte, Vincent and Martin, Jonathan B. and Jourde, Hervé and Screaton, Elizabeth J. and Pistre, Séverin and Langston, Abigail},
title = {Water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams},
journal = {Journal of Hydrology},
year = {2010},
volume = {386},
number = {1-4},
pages = {55--66},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410001319}
}
|
|||||
| Bailly-Comte, V., Martin, J.B. and Screaton, E.J. | Time variant cross correlation to assess residence time of water and implication for hydraulics of a sink-rise karst system | 2011 | Water Resources Research Vol. 47(5), pp. W05547- |
article | URL |
| Abstract: Transport rates and residence time in the subsurface are critical parameters for understanding water-rock interactions for efficient contaminant remediation. This paper presents a methodology for assessing flow and transit time of water through hydrological systems, with specific applications to karst systems and implication for hydraulics of a conduit system surrounded by a porous and permeable intergranular matrix. A time variant cross-correlation function analysis is applied to bivariate time series that characterize mass transfer, assuming a stationary system using sliding windows of various sizes. We apply the method to 1 year long temperature records in the Santa Fe River (north central Florida) measured at (1) the River Sink, where all the incoming surface water drains into a sinkhole, (2) Sweetwater Lake, where the river resurges into a 500 m long karst window, and (3) the River Rise, where the water discharges from a first-magnitude karst spring. Results are compared with those obtained using specific conductivity. Estimated residence time ranges from less than 1 day during floods to more than 15 days during base flow within the 8000 m flow path between the River Sink and the River Rise. Results are used to characterize geometric, hydraulic, and hydrodynamic properties of this sink-rise system with strong matrix-conduit interactions. These properties are critical to the chemical and physical behavior of surface water–groundwater mixing. Our results also have direct implications for sampling strategies and hydrograph separation of many karst systems with different degrees and types of matrix porosity and permeability. | |||||
BibTeX:
@article{Bailly-Comte2011,
author = {Bailly-Comte, V. and Martin, Jonathan B. and Screaton, E. J.},
title = {Time variant cross correlation to assess residence time of water and implication for hydraulics of a sink-rise karst system},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2011},
volume = {47},
number = {5},
pages = {W05547--},
url = {http://dx.doi.org/10.1029/2010WR009613}
}
|
|||||
| Bajracharya, K. and Barry, D. | MCMFIT: Efficient optimal fitting of a generalized nonlinear advection-dispersion model to experimental data | 1995 | Computers & Geosciences Vol. 21(1), pp. 61-76 |
article | URL |
| Abstract: The use of standard numerical schemes to solve nonlinear advective-dispersive equations for the estimation of parameters is CPU-time consuming and hence not desirable for routine use. An efficient scheme using a novel mixing cell approach has been used to estimate parameter values by nonlinear least-squares fitting for nonlinear adsorption of a single solute species coupled with one-dimensional transport. A problem with gradient methods of nonlinear least-squares fitting is that they are prone to determine best-fit parameters corresponding to local minima rather than the global minimum. As is well known, this problem can be avoided by judicious selection of the starting values. The present code, MCMFIT, includes a random search of the parameter space in order to determine a suitable set of initial parameter values. The program also includes the option of selecting user-defined initial parameter values because of possible physical considerations. These values then are passed to the nonlinear least-squares fitting program to obtain the optimal parameter values. Penalty functions have been employed to maintain user-imposed constraints on the parameter values. MCMFIT is capable of handling linear, Freundlich, Langmuir, and S-curve adsorption isotherms. The use of MCMFIT is demonstrated with the use of synthetic as well as laboratory and field data. | |||||
BibTeX:
@article{Bajracharya1995,
author = {Bajracharya, K. and Barry, D.A.},
title = {MCMFIT: Efficient optimal fitting of a generalized nonlinear advection-dispersion model to experimental data},
journal = {Computers & Geosciences},
year = {1995},
volume = {21},
number = {1},
pages = {61--76},
url = {http://www.sciencedirect.com/science/article/pii/0098300494000608}
}
|
|||||
| Bakalowicz, M. | Karst groundwater: a challenge for new resources | 2005 | Hydrogeology Journal Vol. 13(1), pp. 148-160 |
article | URL |
| Abstract: Karst aquifers have complex and original characteristics which make them very different from other aquifers: high heterogeneity created and organised by groundwater flow; large voids, high flow velocities up to several hundreds of m/h, high flow rate springs up to some tens of m 3 /s. Different conceptual models, known from the literature, attempt to take into account all these particularities. The study methods used in classical hydrogeology—bore hole, pumping test and distributed models—are generally invalid and unsuccessful in karst aquifers, because the results cannot be extended to the whole aquifer nor to some parts, as is done in non-karst aquifers. Presently, karst hydrogeologists use a specific investigation methodology (described here), which is comparable to that used in surface hydrology. | |||||
BibTeX:
@article{Bakalowicz2005,
author = {Bakalowicz, Michel},
title = {Karst groundwater: a challenge for new resources},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2005},
volume = {13},
number = {1},
pages = {148--160},
note = {From the issue entitled "The Future of Hydrogeology"},
url = {http://dx.doi.org/10.1007/s10040-004-0402-9}
}
|
|||||
| Balakrishnan, S., Roy, A., Ierapetritou, M.G., Flach, G.P. and Georgopoulos, P.G. | A comparative assessment of efficient uncertainty analysis techniques for environmental fate and transport models: application to the FACT model | 2005 | Journal of Hydrology Vol. 307(1-4), pp. 204-218 |
article | URL |
| Abstract: This work presents a comparative assessment of efficient uncertainty modeling techniques, including Stochastic Response Surface Method (SRSM) and High Dimensional Model Representation (HDMR). This assessment considers improvement achieved with respect to conventional techniques of modeling uncertainty (Monte Carlo). Given that traditional methods for characterizing uncertainty are very computationally demanding, when they are applied in conjunction with complex environmental fate and transport models, this study aims to assess how accurately these efficient (and hence viable) techniques for uncertainty propagation can capture complex model output uncertainty. As a part of this effort, the efficacy of HDMR, which has primarily been used in the past as a model reduction tool, is also demonstrated for uncertainty analysis. The application chosen to highlight the accuracy of these new techniques is the steady state analysis of the groundwater flow in the Savannah River Site General Separations Area (GSA) using the subsurface Flow And Contaminant Transport (FACT) code. Uncertain inputs included three-dimensional hydraulic conductivity fields, and a two-dimensional recharge rate field. The output variables under consideration were the simulated stream baseflows and hydraulic head values. Results show that the uncertainty analysis outcomes obtained using SRSM and HDMR are practically indistinguishable from those obtained using the conventional Monte Carlo method, while requiring orders of magnitude fewer model simulations. | |||||
BibTeX:
@article{Balakrishnan2005,
author = {Balakrishnan, Suhrid and Roy, Amit and Ierapetritou, Marianthi G. and Flach, Gregory P. and Georgopoulos, Panos G.},
title = {A comparative assessment of efficient uncertainty analysis techniques for environmental fate and transport models: application to the FACT model},
journal = {Journal of Hydrology},
year = {2005},
volume = {307},
number = {1-4},
pages = {204--218},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404004998}
}
|
|||||
| Balanda, K.P. and MacGillivray, H.L. | Kurtosis: A Critical Review | 1988 | The American Statistician Vol. 42(2), pp. 111-119 |
article | URL |
| Abstract: We critically review the development of the concept of kurtosis. We conclude that it is best to define kurtosis vaguely as the location- and scale-free movement of probability mass from the shoulders of a distribution into its center and tails and to recognize that it can be formalized in many ways. These formalizations are best expressed in terms of location- and scale-free partial orderings on distributions and the measures that preserve them. The role of scale- matching techniques and placement of shoulders in the formalizations that have appeared in the literature are emphasized. | |||||
BibTeX:
@article{Balanda1988,
author = {Balanda, Kevin P. and MacGillivray, H. L.},
title = {Kurtosis: A Critical Review},
journal = {The American Statistician},
publisher = {American Statistical Association},
year = {1988},
volume = {42},
number = {2},
pages = {111--119},
url = {http://www.jstor.org/stable/2684482}
}
|
|||||
| Balasubramanian, V., Jayaraman, G. and Iyengar, S. | Effect of secondary flows on contaminant dispersion with weak boundary absorption | 1997 | Applied Mathematical Modelling Vol. 21(5), pp. 275-285 |
article | URL |
| Abstract: The present analysis brings out the interaction of curvature and a weak wall absorption parameter on the dispersion process using Taylor analysis. A perturbation series solution has been obtained to find the values of the effective dispersion coefficient. The constraints imposed by the perturbation techniques have been removed using a numerical scheme based on spectral method. Results are found to be applicable for a time at which the Taylor dispersion model holds. It has been observed that in the interphase transport of reactive contaminants the effective dispersion coefficient is significantly different from that of Taylor due to the wall absorption parameter. The results corresponding to the straight tube are verified with the published results, and those obtained from the perturbation and spectral techniques are found to be comparable. The restriction of the present analysis is confined to the effect of weak wall absorption under laminar flow conditions. This restriction needs to be relaxed. For moderate or large values of the absorption parameter a generalized dispersion model has to be resorted to. | |||||
BibTeX:
@article{Balasubramanian1997,
author = {Balasubramanian, Vidhya and Jayaraman, Girija and Iyengar, S.R.K.},
title = {Effect of secondary flows on contaminant dispersion with weak boundary absorption},
journal = {Applied Mathematical Modelling},
year = {1997},
volume = {21},
number = {5},
pages = {275--285},
url = {http://www.sciencedirect.com/science/article/pii/S0307904X97000152}
}
|
|||||
| Baldi, P. and Nasr, R. | When is Chemical Similarity Significant? The Statistical Distribution of Chemical Similarity Scores and Its Extreme Values | 2010 | Journal of Chemical Information and Modeling Vol. 50(7)Journal of Chemical Information and Modeling, pp. 1205-1222 |
article | URL |
| Abstract: As repositories of chemical molecules continue to expand and become more open, it becomes increasingly important to develop tools to search them efficiently and assess the statistical significance of chemical similarity scores. Here, we develop a general framework for understanding, modeling, predicting, and approximating the distribution of chemical similarity scores and its extreme values in large databases. The framework can be applied to different chemical representations and similarity measures but is demonstrated here using the most common binary fingerprints with the Tanimoto similarity measure. After introducing several probabilistic models of fingerprints, including the Conditional Gaussian Uniform model, we show that the distribution of Tanimoto scores can be approximated by the distribution of the ratio of two correlated Normal random variables associated with the corresponding unions and intersections. This remains true also when the distribution of similarity scores is conditioned on the size of the query molecules to derive more fine-grained results and improve chemical retrieval. The corresponding extreme value distributions for the maximum scores are approximated by Weibull distributions. From these various distributions and their analytical forms, Z-scores, E-values, and p-values are derived to assess the significance of similarity scores. In addition, the framework also allows one to predict the value of standard chemical retrieval metrics, such as sensitivity and specificity at fixed thresholds, or receiver operating characteristic (ROC) curves at multiple thresholds, and to detect outliers in the form of atypical molecules. Numerous and diverse experiments that have been performed, in part with large sets of molecules from the ChemDB, show remarkable agreement between theory and empirical results. As repositories of chemical molecules continue to expand and become more open, it becomes increasingly important to develop tools to search them efficiently and assess the statistical significance of chemical similarity scores. Here, we develop a general framework for understanding, modeling, predicting, and approximating the distribution of chemical similarity scores and its extreme values in large databases. The framework can be applied to different chemical representations and similarity measures but is demonstrated here using the most common binary fingerprints with the Tanimoto similarity measure. After introducing several probabilistic models of fingerprints, including the Conditional Gaussian Uniform model, we show that the distribution of Tanimoto scores can be approximated by the distribution of the ratio of two correlated Normal random variables associated with the corresponding unions and intersections. This remains true also when the distribution of similarity scores is conditioned on the size of the query molecules to derive more fine-grained results and improve chemical retrieval. The corresponding extreme value distributions for the maximum scores are approximated by Weibull distributions. From these various distributions and their analytical forms, Z-scores, E-values, and p-values are derived to assess the significance of similarity scores. In addition, the framework also allows one to predict the value of standard chemical retrieval metrics, such as sensitivity and specificity at fixed thresholds, or receiver operating characteristic (ROC) curves at multiple thresholds, and to detect outliers in the form of atypical molecules. Numerous and diverse experiments that have been performed, in part with large sets of molecules from the ChemDB, show remarkable agreement between theory and empirical results. |
|||||
BibTeX:
@article{Baldi2010,
author = {Baldi, Pierre and Nasr, Ramzi},
title = {When is Chemical Similarity Significant? The Statistical Distribution of Chemical Similarity Scores and Its Extreme Values},
booktitle = {Journal of Chemical Information and Modeling},
journal = {Journal of Chemical Information and Modeling},
publisher = {American Chemical Society},
year = {2010},
volume = {50},
number = {7},
pages = {1205--1222},
url = {http://dx.doi.org/10.1021/ci100010v}
}
|
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| Baldwin, B., Peacock, A., Park, M., Ogles, D., Istok, J., McKinley, J., Resch, C. and White, D. | Multilevel Samplers as Microcosms to Assess Microbial Response to Biostimulation | 2008 | Ground Water Vol. 46(2), pp. 295-304 |
article | URL |
| Abstract: Passive multilevel samplers (MLS) containing a solid matrix for microbial colonization were used as in situ microcosms in conjunction with a push-pull biostimulation experiment designed to promote biological U(VI) and Tc(VII) reduction. MLS were deployed at 24 elevations in the injection well and two downgradient wells to investigate the spatial variability in microbial community composition and growth prior to and following biostimulation. The microbial community was characterized by real-time quantitative polymerase chain reaction (Q-PCR) quantification of bacteria, NO3−-reducing bacteria (nirS and nirK), δ-proteobacteria, Geobacter sp., and methanogens (mcrA). Pretest cell densities were low overall but varied substantially with significantly greater bacterial populations detected at circumneutral pH (t-test, α= 0.05), suggesting carbon substrate and low pH limitations of microbial activity. Although pretest cell densities were low, denitrifying bacteria were dominant members of the microbial community. Biostimulation with an ethanol-amended ground water resulted in concurrent NO3− and Tc(VII) reduction, followed by U(VI) reduction. Q-PCR analysis of MLS revealed significant (1 to 2 orders of magnitude, Mann–Whitney U-test, α= 0.05) increases in cell densities of bacteria, denitrifiers, δ-proteobacteria, Geobacter sp., and methanogens in response to biostimulation. Traditionally, characterization of sediment samples has been used to investigate the microbial community response to biostimulation; however, collection of sediment samples is expensive and not conducive to deep aquifers or temporal studies. The results presented demonstrate that push-pull tests with passive MLS provide an inexpensive approach to determine the effect of biostimulation on contaminant concentrations, geochemical conditions, and the microbial community composition and function. | |||||
BibTeX:
@article{Baldwin2008,
author = {Baldwin, B.R. and Peacock, A.D. and Park, M. and Ogles, D.M. and Istok, J.D. and McKinley, J.P. and Resch, C.T. and White, D.C.},
title = {Multilevel Samplers as Microcosms to Assess Microbial Response to Biostimulation},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2008},
volume = {46},
number = {2},
pages = {295--304},
url = {http://dx.doi.org/10.1111/j.1745-6584.2007.00411.x}
}
|
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| Bandstra, J.Z., Ross, D.E., Brantley, S.L. and Burgos, W.D. | Compendium and synthesis of bacterial manganese reduction rates | 2011 | Geochimica et Cosmochimica Acta Vol. 75(2), pp. 337-351 |
article | URL |
| Abstract: We have compiled time-series concentration data for the biological reduction of manganese(III/IV) published between 1985 and 2004 and fit these data with a simple hyperbolic rate expression or, when appropriate, one of its limiting forms. The compiled data and rate constants are available in Electronic Annex EA-1. The zero- and first-order rate constants appear to follow a log–normal distribution that could be used, for example, in predictive modeling of Mn-oxide reduction in a reactive transport scenario. We have also included details of the experimental procedures used to generate each time-series data-set in our compilation. These meta-data—mostly pertaining to the type and concentration of micro-organism, electron donor, and electron acceptor—enable us to examine the rate data for trends. We have computed a number of rudimentary, mono-variate statistics on the compiled data with the hope of stimulating both more detailed statistical analyses of the data and new experiments to fill gaps in the existing data-set. We have also analyzed the data with parametric models based on the log–normal distribution and rate equations that are hyperbolic in the concentration of cells and Mn available for reduction. This parametric analysis allows us to provide best estimates of zero- and first-order rate constants both ignoring and accounting for the meta-data. | |||||
BibTeX:
@article{Bandstra2011,
author = {Bandstra, Joel Z. and Ross, Daniel E. and Brantley, Susan L. and Burgos, William D.},
title = {Compendium and synthesis of bacterial manganese reduction rates},
journal = {Geochimica et Cosmochimica Acta},
year = {2011},
volume = {75},
number = {2},
pages = {337--351},
url = {http://www.sciencedirect.com/science/article/pii/S0016703710005752}
}
|
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| Barfield, B., Felton, G., Stevens, E. and McCann, M. | A simple model of karst spring flow using modified NRCS procedures | 2004 | Journal of Hydrology Vol. 287(1-4), pp. 34-48 |
article | URL |
| Abstract: A simple model of spring flow in a karst watershed with numerous sinkholes is presented. The watershed is divided into subwatersheds and runoff volume calculated using the NRCS curve number procedure with corrections for actual antecedent moisture conditions using the 5-day antecedent rainfall volume as a parameter. The peak discharge for each subwatershed is calculated with the TR-55 unit discharge equations with time of concentration corrected for the flow through the epikarst and routed exponentially to the spring, using a calibration coefficient. Total discharge at the spring is calculated by summing attenuated peaks from each subwatershed, using a weighting factor based on the predicted arrival time for each peak flow. The model was calibrated on long-term flow data collected at the spring. The calibrated model was then evaluated on four storms measured subsequent to the calibration. The results were acceptable for all but one storm, but indicate the need for improved runoff volume calculation methods in karst watersheds. | |||||
BibTeX:
@article{Barfield2004,
author = {Barfield, B.J. and Felton, G.K. and Stevens, E.W. and McCann, M.},
title = {A simple model of karst spring flow using modified NRCS procedures},
journal = {Journal of Hydrology},
year = {2004},
volume = {287},
number = {1-4},
pages = {34--48},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403003962}
}
|
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| Barger, G.L. and Thom, H.C.S. | Evaluation of Drought Hazard [BibTeX] |
1949 | Agronomy Journal Vol. 41(11), pp. 519-526 |
article | URL |
BibTeX:
@article{Barger1962,
author = {Barger, Gerald L. and Thom, H. C. S.},
title = {Evaluation of Drought Hazard},
journal = {Agronomy Journal},
year = {1949},
volume = {41},
number = {11},
pages = {519--526},
url = {https://www.agronomy.org/publications/aj/abstracts/41/11/AJ0410110519}
}
|
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| Baringhaus, L. and Taherizadeh, F. | Empirical Hankel transforms and its applications to goodness-of-fit tests | 2010 | Journal of Multivariate Analysis Vol. 101(6), pp. 1445-1457 |
article | URL |
| Abstract: We introduce a special Hankel transform for probability distributions on the nonnegative half-line and discuss some of its properties. Due to the uniqueness of the transform we suggest an integral type test statistic based on the empirical Hankel transform to treat simple and composite hypotheses goodness-of-fit problems. The special case of exponential distributions is studied in detail. | |||||
BibTeX:
@article{Baringhaus2010,
author = {Baringhaus, Ludwig and Taherizadeh, Fatemeh},
title = {Empirical Hankel transforms and its applications to goodness-of-fit tests},
journal = {Journal of Multivariate Analysis},
year = {2010},
volume = {101},
number = {6},
pages = {1445--1457},
url = {http://www.sciencedirect.com/science/article/pii/S0047259X09002218}
}
|
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| de Barros, F., Mills, W. and Cotta, R. | Integral transform solution of a two-dimensional model for contaminant dispersion in rivers and channels with spatially variable coefficients | 2006 | Environmental Modelling & Software Vol. 21(5), pp. 699-709 |
article | URL |
| Abstract: The Generalized Integral Transform Technique (GITT) is employed to obtain numerical–analytical solutions for mathematical models that predict the dispersion of dissolved pollutants in rivers, streams and channels with either symmetric or asymmetric flow. The two-dimensional steady-state model presented allows for the use of variable coefficients represented by non-uniform velocity profiles and turbulent diffusion coefficients, in any general functional form. The proposed model is then applied to an example of biocides contamination downstream of thermohydroelectric power stations, originated from the cleaning of cooling water systems undergoing biofouling. | |||||
BibTeX:
@article{Barros2006,
author = {de Barros, F.P.J. and Mills, W.B. and Cotta, R.M.},
title = {Integral transform solution of a two-dimensional model for contaminant dispersion in rivers and channels with spatially variable coefficients},
journal = {Environmental Modelling & Software},
year = {2006},
volume = {21},
number = {5},
pages = {699--709},
url = {http://www.sciencedirect.com/science/article/pii/S1364815205000411}
}
|
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| Barry, D.A. and Sposito, G. | Analytical solution of a convection-dispersion model with time-dependent transport coefficients | 1989 | Water Resources Research Vol. 25(12), pp. 2407-2416 |
article | URL |
| Abstract: Mathematical studies of solute transport in porous media have often utilized “equivalent” models of the transport process to remove undesired variability in the transport coefficients at the space and time scales of direct interest. Both deterministic and stochastic approaches in this genre produce an “effective” convection-dispersion equation with time-dependent coefficients. This type of equation in one spatial dimension is investigated mathematically in the present paper. A closed-form solution of the solute transport equation is derived for a semi-infinite spatial domain with arbitrary initial and boundary flux conditions. It is shown that the solution reduces to well-known results for special forms of the time-dependent coefficients. In general, however, a Volterra integral equation of the second kind must be solved to evaluate the analytical solution of the transport equation. We present a stable and convergent numerical scheme, utilizing a trapezoidal quadrature rule, for the solution of the Volterra equation. The method of solution developed should be applicable to a broad variety of solute transport problems, including particularly those in heterogeneous porous media. | |||||
BibTeX:
@article{Barry1989,
author = {Barry, D. A. and Sposito, Garrison},
title = {Analytical solution of a convection-dispersion model with time-dependent transport coefficients},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1989},
volume = {25},
number = {12},
pages = {2407--2416},
url = {http://dx.doi.org/10.1029/WR025i012p02407}
}
|
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| Barry, D., Bajracharya, K. and Miller, C. | Alternative split-operator approach for solving chemical reaction/groundwater transport models | 1996 | Advances in Water Resources Vol. 19(5), pp. 261-275 |
article | URL |
| Abstract: Various schemes are available to solve coupled transport/reaction mathematical models, one of the most efficient and easy to apply being the two-step split-operator method in which the transport and reaction steps are performed separately. Operator splitting, however, does not solve exactly the fully coupled numerical model derived from the governing partial differential and algebraic equations describing the transport and reaction processes. An error, proportional to Δt (the time step used in the numerical solution) is introduced. Thus, small time steps must be used to ensure that accurate solutions result. An alternative scheme is presented, which iterates to the exact solution of the fully coupled numerical model. The new scheme enables accurate solutions to be calculated more efficiently than the two-step method, while maintaining separation of the transport and reaction steps in the calculations. As in the two-step method, the reaction calculations are performed node-wise throughout the computation grid. However, because the scheme relies on LU factorisation of the coefficient matrix in the transport equation solution, the reaction calculations must be performed in sequence, the sequence order being determined by the ordering of the nodes in the grid. Also, because LU factorisation is used, the scheme is limited to solute transport problems for which LU factorisation is a practical solution method. | |||||
BibTeX:
@article{Barry1996,
author = {Barry, D.A. and Bajracharya, K. and Miller, C.T.},
title = {Alternative split-operator approach for solving chemical reaction/groundwater transport models},
journal = {Advances in Water Resources},
year = {1996},
volume = {19},
number = {5},
pages = {261--275},
url = {http://www.sciencedirect.com/science/article/pii/0309170896000024}
}
|
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| Barry, D., Prommer, H., Miller, C., Engesgaard, P., Brun, A. and Zheng, C. | Modelling the fate of oxidisable organic contaminants in groundwater | 2002 | Advances in Water Resources Vol. 25(8-12), pp. 945-983 |
article | URL |
| Abstract: Subsurface contamination by organic chemicals is a pervasive environmental problem, susceptible to remediation by natural or enhanced attenuation approaches or more highly engineered methods such as pump-and-treat, amongst others. Such remediation approaches, along with risk assessment or the pressing need to address complex scientific questions, have driven the development of integrated modelling tools that incorporate physical, biological and geochemical processes. | |||||
BibTeX:
@article{Barry2002,
author = {Barry, D.A. and Prommer, H. and Miller, C.T. and Engesgaard, P. and Brun, A. and Zheng, C.},
title = {Modelling the fate of oxidisable organic contaminants in groundwater},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {8-12},
pages = {945--983},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802000441}
}
|
|||||
| Barry, D., Prommer, H., Miller, C., Engesgaard, P., Brun, A. and Zheng, C. | Modelling the fate of oxidisable organic contaminants in groundwater | 2002 | Advances in Water Resources Vol. 25(8-12), pp. 945-983 |
article | URL |
| Abstract: Subsurface contamination by organic chemicals is a pervasive environmental problem, susceptible to remediation by natural or enhanced attenuation approaches or more highly engineered methods such as pump-and-treat, amongst others. Such remediation approaches, along with risk assessment or the pressing need to address complex scientific questions, have driven the development of integrated modelling tools that incorporate physical, biological and geochemical processes. | |||||
BibTeX:
@article{Barry2002a,
author = {Barry, D.A. and Prommer, H. and Miller, C.T. and Engesgaard, P. and Brun, A. and Zheng, C.},
title = {Modelling the fate of oxidisable organic contaminants in groundwater},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {8--12},
pages = {945--983},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802000441}
}
|
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| Barth, G. and Hill, M.C. | Numerical methods for improving sensitivity analysis and parameter estimation of virus transport simulated using sorptive–reactive processes | 2005 | Journal of Contaminant Hydrology Vol. 76(3-4), pp. 251-277 |
article | URL |
| Abstract: Using one- and two-dimensional homogeneous simulations, this paper addresses challenges associated with sensitivity analysis and parameter estimation for virus transport simulated using sorptive–reactive processes. Head, flow, and conservative- and virus-transport observations are considered. The paper examines the use of (1) observed-value weighting, (2) breakthrough-curve temporal moment observations, and (3) the significance of changes in the transport time-step size. The results suggest that (1) sensitivities using observed-value weighting are more susceptible to numerical solution variability, (2) temporal moments of the breakthrough curve are a more robust measure of sensitivity than individual conservative-transport observations, and (3) the transport-simulation time step size is more important than the inactivation rate in solution and about as important as at least two other parameters, reflecting the ease with which results can be influenced by numerical issues. The approach presented allows more accurate evaluation of the information provided by observations for estimation of parameters and generally improves the potential for reasonable parameter-estimation results. | |||||
BibTeX:
@article{Barth2005,
author = {Barth, Gilbert and Hill, Mary C.},
title = {Numerical methods for improving sensitivity analysis and parameter estimation of virus transport simulated using sorptive–reactive processes},
journal = {Journal of Contaminant Hydrology},
year = {2005},
volume = {76},
number = {3-4},
pages = {251--277},
url = {http://www.sciencedirect.com/science/article/pii/S0169772204001743}
}
|
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| Bartłomiej, R. | Carbonate aquifers with hydraulically non-active matrix: A case study from Poland | 2008 | Journal of Hydrology Vol. 355(1-4), pp. 202-213 |
article | URL |
| Abstract: The Devonian carbonate (karst) rocks of the Holy Cross Mountains (Góry Świętokrzyskie) in Poland, which constitute a major water supply for the region, are the subject of the presented study. Using standard laboratory methods, the matrix hydrogeological properties (open porosity, permeability and specific yield) of the limestones and dolomites were determined. The test results showed very low open porosities of the samples, as well as an extremely low permeability. The specific yield in all the cases was zero. There was a very slight correlation between the permeability (represented by the hydraulic conductivity) and the open porosity for limestones – and no correlation for dolomites. The measured parameters do not depend on the structure of the rock matrix (classified as pelite, sparite or crystalline) nor does the occurrence of fractures. Differences in open porosity (but not in hydraulic conductivity) were observed between the samples from different structural units. | |||||
BibTeX:
@article{Bartlomiej2008,
author = {Bartłomiej, Rzonca},
title = {Carbonate aquifers with hydraulically non-active matrix: A case study from Poland},
journal = {Journal of Hydrology},
year = {2008},
volume = {355},
number = {1-4},
pages = {202--213},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408001534}
}
|
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| Bassingthwaighte, J.B. | Physiology and theory of tracer washout techniques for the estimation of myocardial blood flow: Flow estimation from tracer washout | 1977 | Progress in Cardiovascular Diseases Vol. 20(3)The 39th Annual Binghamton Geomorphology Symposium: Fluvial Deposits and Environmental History: Geoarchaeology, Paleohydrology, and Adjustment to Environmental Change, pp. 165-189 |
article | URL |
| Abstract: The time course of washout of tracer from the myocardium provides an estimate of the flow per unit volume when the blood-tissue exchange is flow-limited. Methods of testing for the flow-limitation and for the absence of influences of low permeability or diffusion on the washout include the uses of paired or multiple tracers and the examination for similarity of the shapes of the residue function or washout curves at varied coronary blood flows. A conceptual framework for these studies is provided by a clearance-flow diagram for the myocardium where capillaries are long compared to radial intercapillary distances. This anatomic-physiologic framework coupled with a probabilistic, general analytical approach and with various experimental approaches to tracer studies of mass transport through the heart provides a general basis for methods of estimating myocardial blood flow in the whole organ and in its component regions. | |||||
BibTeX:
@article{Bassingthwaighte1977,
author = {Bassingthwaighte, James B.},
title = {Physiology and theory of tracer washout techniques for the estimation of myocardial blood flow: Flow estimation from tracer washout},
booktitle = {The 39th Annual Binghamton Geomorphology Symposium: Fluvial Deposits and Environmental History: Geoarchaeology, Paleohydrology, and Adjustment to Environmental Change},
journal = {Progress in Cardiovascular Diseases},
year = {1977},
volume = {20},
number = {3},
pages = {165--189},
url = {http://www.sciencedirect.com/science/article/pii/0033062077900196}
}
|
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| Basu, B., Tiwari, D., Kundu, D. and Prasad, R. | Is Weibull distribution the most appropriate statistical strength distribution for brittle materials? | 2009 | Ceramics International Vol. 35(1), pp. 237-246 |
article | URL |
| Abstract: Strength reliability, one of the critical factors restricting wider use of brittle materials in various structural applications, is commonly characterized by Weibull strength distribution function. In the present work, the detailed statistical analysis of the strength data is carried out using a larger class of probability models including Weibull, normal, log-normal, gamma and generalized exponential distributions. Our analysis is validated using the strength data, measured with a number of structural ceramic materials and a glass material. An important implication of the present study is that the gamma or log-normal distribution function, in contrast to Weibull distribution, may describe more appropriately, in certain cases, the experimentally measured strength data. | |||||
BibTeX:
@article{Basu2009,
author = {Basu, Bikramjit and Tiwari, Devesh and Kundu, Debasis and Prasad, Rajesh},
title = {Is Weibull distribution the most appropriate statistical strength distribution for brittle materials?},
journal = {Ceramics International},
year = {2009},
volume = {35},
number = {1},
pages = {237--246},
url = {http://www.sciencedirect.com/science/article/pii/S0272884207003665}
}
|
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| Basu, N.B., Fure, A.D. and Jawitz, J.W. | Simplified contaminant source depletion models as analogs of multiphase simulators | 2008 | Journal of Contaminant Hydrology Vol. 97(3-4), pp. 87-99 |
article | URL |
| Abstract: Four simplified dense non-aqueous phase liquid (DNAPL) source depletion models recently introduced in the literature are evaluated for the prediction of long-term effects of source depletion under natural gradient flow. These models are simple in form (a power function equation is an example) but are shown here to serve as mathematical analogs to complex multiphase flow and transport simulators. The spill and subsequent dissolution of DNAPLs was simulated in domains having different hydrologic characteristics (variance of the log conductivity field = 0.2, 1 and 3) using the multiphase flow and transport simulator UTCHEM. The dissolution profiles were fitted using four analytical models: the equilibrium streamtube model (ESM), the advection dispersion model (ADM), the power law model (PLM) and the Damkohler number model (DaM). All four models, though very different in their conceptualization, include two basic parameters that describe the mean DNAPL mass and the joint variability in the velocity and DNAPL distributions. The variability parameter was observed to be strongly correlated with the variance of the log conductivity field in the ESM and ADM but weakly correlated in the PLM and DaM. The DaM also includes a third parameter that describes the effect of rate-limited dissolution, but here this parameter was held constant as the numerical simulations were found to be insensitive to local-scale mass transfer. All four models were able to emulate the characteristics of the dissolution profiles generated from the complex numerical simulator, but the one-parameter PLM fits were the poorest, especially for the low heterogeneity case. | |||||
BibTeX:
@article{Basu2008,
author = {Basu, Nandita B. and Fure, Adrian D. and Jawitz, James W.},
title = {Simplified contaminant source depletion models as analogs of multiphase simulators},
journal = {Journal of Contaminant Hydrology},
year = {2008},
volume = {97},
number = {3-4},
pages = {87--99},
url = {http://www.sciencedirect.com/science/article/pii/S0169772208000089}
}
|
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| Bateman, H. and of Technology Bateman Manuscript Project, C.I. | Tables of integral transforms: Based, in part, on notes left by Harry Bateman [BibTeX] |
1954 | , pp. - | book | |
BibTeX:
@book{Bateman1954c,
author = {Bateman, Harry and California Institute of Technology Bateman Manuscript Project},
title = {Tables of integral transforms: Based, in part, on notes left by Harry Bateman},
publisher = {McGraw-Hill},
year = {1954},
pages = {--},
note = {Two volumes prepared at the California Institute of Technology under contract no. N6onr-244, task order XIV, with the Office of Naval Research. Project designation number: NR043-045}
}
|
|||||
| Bateman, H. and of Technology, C.I. | Tables of integral transforms [BibTeX] |
1954 | Vol. 1, pp. - |
book | |
BibTeX:
@book{Bateman1954a,
author = {Bateman, Harry and California Institute of Technology},
title = {Tables of integral transforms},
publisher = {McGraw-Hill},
year = {1954},
volume = {1},
pages = {--},
note = {Volume 1 of 2}
}
|
|||||
| Bateman, H. and of Technology, C.I. | Tables of integral transforms [BibTeX] |
1954 | Vol. 2, pp. - |
book | |
BibTeX:
@book{Bateman1954b,
author = {Bateman, Harry and California Institute of Technology},
title = {Tables of integral transforms},
publisher = {McGraw-Hill},
year = {1954},
volume = {2},
pages = {--},
note = {Volume 2 of 2}
}
|
|||||
| van Baten, J.M., Ellenberger, J. and Krishna, R. | Radial and axial dispersion of the liquid phase within a KATAPAK-S® structure: experiments vs. CFD simulations | 2001 | Chemical Engineering Science Vol. 56(3)16th International Conference on Chemical Reactor Engineering, pp. 813-821 |
article | URL |
| Abstract: The radial, and axial, liquid-phase dispersion within the catalytically packed criss-crossing sandwich structures of KATAPAK-S has been studied experimentally with the use of computational fluid dynamics (CFD). The KATAPAK-S structure has excellent radial dispersion characteristics. The radial dispersion coefficient in such structures is about one order of magnitude higher than that for conventional packed (trickle) beds. The CFD simulations of the radial dispersion are in good agreement with experiments. At high-liquid loads, there is liquid flow outside the wire gauze envelopes, leading to enhanced axial dispersion. The axial dispersion coefficient of the liquid phase of KATAPAK-S is of the same order of magnitude as the radial dispersion coefficient. | |||||
BibTeX:
@article{Baten2001,
author = {van Baten, J. M and Ellenberger, J. and Krishna, R.},
title = {Radial and axial dispersion of the liquid phase within a KATAPAK-S® structure: experiments vs. CFD simulations},
booktitle = {16th International Conference on Chemical Reactor Engineering},
journal = {Chemical Engineering Science},
year = {2001},
volume = {56},
number = {3},
pages = {813--821},
url = {http://www.sciencedirect.com/science/article/pii/S0009250900002931}
}
|
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| Batlle, F., Carrera, J. and Ayora, C. | A comparison of lagrangian and eulerian formulations for reactive transport modelling | 2002 | Vol. 47Computational Methods in Water Resources Proceedings of the XIVth International Conference on Computational Methods in Water Resources (CMWR XIV), Delft, The Netherlands, pp. 571-578 |
incollection | URL |
| Abstract: Some ground water transport phenomena display sharp-edged fronts, specially when dealing with chemical reactions, such as oxidation processes. Eulerian formulations often fail to reproduce this kind of discontinuities due to numerical diffusion or instabilities. Lagrangian formulations overcome these difficulties, but introduce new ones, specially when dealing with transient flow and chemical reactions, each acting at a different rate. We propose a set of flexible lagrangian formulations that can override these issues. They are based on different approximations of the material derivative and the integration along the flow path. Those formulations have been implemented on a finite element code and some tests were performed in order to evaluate their performance. | |||||
BibTeX:
@incollection{Batlle2002,
author = {Batlle, F. and Carrera, J. and Ayora, C.},
title = {A comparison of lagrangian and eulerian formulations for reactive transport modelling},
booktitle = {Computational Methods in Water Resources Proceedings of the XIVth International Conference on Computational Methods in Water Resources (CMWR XIV), Delft, The Netherlands},
publisher = {Elsevier},
year = {2002},
volume = {47},
pages = {571--578},
url = {http://www.sciencedirect.com/science/article/pii/S0167564802801101}
}
|
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| Battaglia, A., Fox, P. and Pohland, F. | Calculation of residence time distribution from tracer recycle experiments | 1993 | Water Research Vol. 27(2), pp. 337-341 |
article | URL |
| Abstract: This note develops a procedure that can be used to calculate the single pass residence time distribution in a reactor system, such as a landfill, operated with recycle, from pulse tracer studies. An equation relating the effluent tracer concentration and residence time distribution (“E curve”) is derived, and a numerical technique to solve such an equation is presented and applied to data obtained from experiments on a laboratory-scale reactor. The significance of the procedure developed to biological reactors is discussed. | |||||
BibTeX:
@article{Battaglia1993,
author = {Battaglia, A. and Fox, P. and Pohland, F.G.},
title = {Calculation of residence time distribution from tracer recycle experiments},
journal = {Water Research},
year = {1993},
volume = {27},
number = {2},
pages = {337--341},
url = {http://www.sciencedirect.com/science/article/pii/004313549390093W}
}
|
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| Bauer, R.D., Maloszewski, P., Zhang, Y., Meckenstock, R.U. and Griebler, C. | Mixing-controlled biodegradation in a toluene plume — Results from two-dimensional laboratory experiments | 2008 | Journal of Contaminant Hydrology Vol. 96(1-4), pp. 150-168 |
article | URL |
| Abstract: Various abiotic and biotic processes such as sorption, dilution, and degradation are known to affect the fate of organic contaminants, such as petroleum hydrocarbons in saturated porous media. Reactive transport modeling of such plumes indicates that the biodegradation of organic pollutants is, in many cases, controlled by mixing and therefore occurs locally at the plume's fringes, where electron donors and electron-acceptors mix. Herein, we aim to test whether this hypothesis can be verified by experimental results obtained from aerobic and anaerobic degradation experiments in two-dimensional sediment microcosms. Toluene was selected as a model compound for oxidizable contaminants. The two-dimensional microcosm was filled with quartz sand and operated under controlled flow conditions simulating a contaminant plume in otherwise uncontaminated groundwater. Aerobic degradation of toluene by Pseudomonas putida mt-2 reduced a continuous 8.7 mg L− 1 toluene concentration by 35% over a transport distance of 78 cm in 15.5 h. In comparison, under similar conditions Aromatoleum aromaticum strain EbN1 degraded 98% of the toluene infiltrated using nitrate (68.5 ± 6.2 mg L− 1) as electron acceptor. A major part of the biodegradation activity was located at the plume fringes and the slope of the electron-acceptor gradient was steeper during periods of active biodegradation. The distribution of toluene and the significant overlap of nitrate at the plume's fringe indicate that biokinetic and/or microscale transport processes may constitute additional limiting factors. Experimental data is corroborated with results from a reactive transport model using double Monod kinetics. The outcome of the study shows that in order to simulate degradation in contaminant plumes, detailed data sets are required to test the applicability of models. These will have to deal with the incorporation of existing parameters coding for substrate conversion kinetics and microbial growth. | |||||
BibTeX:
@article{Bauer2008,
author = {Bauer, Robert D. and Maloszewski, Piotr and Zhang, Yanchun and Meckenstock, Rainer U. and Griebler, Christian},
title = {Mixing-controlled biodegradation in a toluene plume — Results from two-dimensional laboratory experiments},
journal = {Journal of Contaminant Hydrology},
year = {2008},
volume = {96},
number = {1-4},
pages = {150--168},
url = {http://www.sciencedirect.com/science/article/pii/S0169772207001283}
}
|
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| Bauget, F. and Fourar, M. | Non-Fickian dispersion in a single fracture | 2008 | Journal of Contaminant Hydrology Vol. 100(3-4), pp. 137-148 |
article | URL |
| Abstract: Solute transport in fractured rocks is of major interest in many applications, from the petroleum industry to ground water management. This work focuses on the dispersion process in a transparent replica of a real single fracture. The fracture exhibits strong changes in heterogeneity, with the first half very heterogeneous and the second half fairly homogeneous. Three models have been used to interpret the tracer experiments: the classical advection-dispersion equation (ADE), the continuous time random walk (CTRW), and the stratified model. The main goals were to test these models and to study possible correlations between fitting parameters and heterogeneities. As expected, the solution derived from the ADE equation appears to be unable to model long-time tailing behavior. On the other hand, the results confirm the CTRW robustness and the coefficient β seems well correlated to heterogeneities. Finally, the stratified model is also able to describe non-Fickian dispersion. The parameters defined by this model are correlated to the heterogeneities of the fracture. | |||||
BibTeX:
@article{Bauget2008,
author = {Bauget, F. and Fourar, M.},
title = {Non-Fickian dispersion in a single fracture},
journal = {Journal of Contaminant Hydrology},
year = {2008},
volume = {100},
number = {3-4},
pages = {137--148},
url = {http://www.sciencedirect.com/science/article/pii/S0169772208000909}
}
|
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| Bayani Cardenas, M., Wilson, J.L. and Haggerty, R. | Residence time of bedform-driven hyporheic exchange | 2008 | Advances in Water Resources Vol. 31(10), pp. 1382-1386 |
article | URL |
| Abstract: Biogeochemical and ecological transformations in hyporheic zones are dependent on the timing of hyporheic exchange. We show through linked modeling of open channel turbulent flow, groundwater flow, and solute transport that the residence time distributions of solutes advected by hyporheic flow induced by current–bedform interaction follow power-laws. This tailing behavior of solutes exiting the sediments is explained by the presence of multiple path lengths coupled with very large variability in Darcy flow velocity, both occurring without heterogeneity in sediment permeability. Hyporheic exchange through bedforms will result in short-time fractal scaling of stream water chemistry. | |||||
BibTeX:
@article{Cardenas2008,
author = {Bayani Cardenas, M. and Wilson, John L. and Haggerty, Roy},
title = {Residence time of bedform-driven hyporheic exchange},
journal = {Advances in Water Resources},
year = {2008},
volume = {31},
number = {10},
pages = {1382--1386},
url = {http://www.sciencedirect.com/science/article/pii/S0309170808001231}
}
|
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| Bayari, S. | TRACER: an EXCEL workbook to calculate mean residence time in groundwater by use of tracers CFC-11, CFC-12 and tritium | 2002 | Computers & Geosciences Vol. 28(5), pp. 621-630 |
article | URL |
| Abstract: An EXCEL workbook is presented for calculating the mean residence time of groundwater based on the environmental tracers, tritium, CFC-11 and CFC-12. The program TRACER is written in Visual Basic for Application language and uses piston, exponential, linear, exponential-piston and linear-piston flow types of lumped-parameter models. Input and output data are stored in worksheets and a graph of results that are best fitted to observations is drawn for visual evaluation. Recharge temperature and altitude are used to convert atmospheric partial pressures of CFC-11 and CFC-12 to dissolved concentrations to provide a direct comparison between the models’ output and observed data. The model can also be used to check whether an inferred flow type could be valid in the groundwater system being investigated. Other radioactive and gaseous environmental tracers and reactions such as, sorption and degradation can be included either as decay constant or with modifications in the program code. TRACER matches, satisfactorily, the results obtained from other softwares. | |||||
BibTeX:
@article{Bayari2002,
author = {Bayari, Serdar},
title = {TRACER: an EXCEL workbook to calculate mean residence time in groundwater by use of tracers CFC-11, CFC-12 and tritium},
journal = {Computers & Geosciences},
year = {2002},
volume = {28},
number = {5},
pages = {621--630},
url = {http://www.sciencedirect.com/science/article/pii/S0098300401000942}
}
|
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| Beach, T., Luzzadder-Beach, S., Dunning, N. and Cook, D. | Human and natural impacts on fluvial and karst depressions of the Maya Lowlands | 2008 | Geomorphology Vol. 101(1–2)The 39th Annual Binghamton Geomorphology Symposium: Fluvial Deposits and Environmental History: Geoarchaeology, Paleohydrology, and Adjustment to Environmental Change, pp. 308-331 |
article | URL |
| Abstract: This paper begins to differentiate the major drivers and chronology of erosion and aggradation in the fluvial and fluviokarst landscapes of the southern and central Maya Lowlands. We synthesize past research on erosion and aggradation and add new data from water, soils, radiocarbon dating, and archaeology to study the quantity, timing, and causes of aggradation in regional landscape depressions. Geomorphic findings come from many excavations across a landscape gradient from upland valleys, karst sinks, and fans into the coastal plain floodplains and depressions. Findings from water chemistry show that sources in the uplands have low quantities of dissolved ions but water in the coastal plains has high amounts of dissolved ions, often nearly saturated in calcium and sulfate. We found significant geomorphic complexity in the general trends in upland karst sinks. In a few instances, sediments preserve Late Pleistocene paleosols, buried 2–3 m, though many more have distinct middle to late Holocene paleosols, buried 1–2 m, after c. 2300 BP (Maya Early to Late Preclassic). From 2300–1100 BP (Late Preclassic to Classic Periods), the landscape aggraded from five main mechanisms: river flooding, climatic instability, accelerated erosion, ancient Maya landscape manipulation, and gypsum precipitation from a rise in a water table nearly saturated in calcium and sulfate ions. Evidence exists for two or three high magnitude floods, possibly driven by hurricanes. Moreover, lake-core and geophysical studies from the Petén Lakes region have shown high rates of deposition of silicate clays (‘Maya Clays’) starting and peaking during the Maya Preclassic and continuing to be high through the Late Classic. The main driver on upland karst depressions, the Petén lakes, upland valleys, and fans was accelerated soil erosion, but water table rise, probably driven by sea-level rise, was the main driver on the wetlands of the coastal plain because the aggraded sediments here are dominantly composed of gypsum, precipitated from the groundwater. This latter mechanism represents a little recognized mechanism of aggradation over a large region. These large scale environmental changes occurred during periods of intensive ancient Maya land use and climatic instability, both of which may have contributed to erosion by increasing runoff. Despite these geomorphic changes, ancient Maya farmers adapted in several key cases. | |||||
BibTeX:
@article{Beach2008a,
author = {Beach, Timothy and Luzzadder-Beach, Sheryl and Dunning, Nicholas and Cook, Duncan},
title = {Human and natural impacts on fluvial and karst depressions of the Maya Lowlands},
booktitle = {The 39th Annual Binghamton Geomorphology Symposium: Fluvial Deposits and Environmental History: Geoarchaeology, Paleohydrology, and Adjustment to Environmental Change},
journal = {Geomorphology},
year = {2008},
volume = {101},
number = {1–2},
pages = {308--331},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X0800216X}
}
|
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| Beach, T.M., Bradley, M.W., Painter, R. and Byl, T.D. | The Value of Single-Well Tracer Studies for Characterizing Karst Sites | 2008 | U. S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 99 | inproceedings | URL |
| Abstract: Water movement, contaminant migration and energy transfer in heterogeneous karst aquifers is challenging to describe quantitatively. Karst ground-water aquifers may be characterized by high velocity, turbulent flow within solution-enhanced fractures, conduits, or stratiform passageways. In other parts of the same aquifer, ground-water flow may be stagnant or very slow. Once a contaminant has entered a karst aquifer, it is often difficult to determine its precise flow-path or residence time in the bedrock. Attempts to characterize a karst site with traditional tracer tests may yield limited information, especially if the tracer cannot be detected at down-gradient monitoring sites. This project applied an integrated approach using local geology, data from fracture mapping, borehole geophysics, and hydraulic testing, as well as geochemical and single-well tracer tests to characterize aquifer hydraulic properties at several karst sites in Middle Tennessee. Two types of wells; existing wells with the characteristics of typical domestic-water wells, and wells constructed to meet project specifications were also evaluated. Single-well tracer studies were conducted by injecting a conservative salt tracer of known concentrations into several wells at known depths and measuring the decrease in tracer concentration with time. Changes in tracer concentration were then analyzed to provide information about aquifer advection and dispersion properties in the immediate proximity of the wells. Unfortunately, some of the wells used in this study were drilled approximately 25 years ago and proved to be less than ideal for single-well injection studies. The most difficult problem encountered involved wells characterized by long vertical sections with no bedrock openings for the tracer to enter the aquifer freely. These wells yielded very little useful information. For example, the mean residence time in the water column of bedrock wells with few openings was 65 hours or greater. Conversely, tracer injections in wells with good hydraulic communication with the bedrock aquifer provided useful data with mean residence times ranging from 14 to 45 hours. Single-well tracer studies conducted in properly designed wells provided valuable hydrologic information on the residence-time distribution and dispersion of the tracer in the vicinity of the injection wells. The information collected from single-well injection tests when combined with water chemistry and water level data can be useful for the design of remediation strategies at contaminated karst sites. | |||||
BibTeX:
@inproceedings{Beach2008,
author = {Beach, Tarra M. and Bradley, Michael W. and Painter, Roger and Byl, Thomas D.},
title = {The Value of Single-Well Tracer Studies for Characterizing Karst Sites},
booktitle = {U. S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U. S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {99},
url = {http://pubs.usgs.gov/sir/2008/5023/38beach.htm}
}
|
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| Beaulieu, M.-C., Dufour, J.-M. and Khalaf, L. | Asset-pricing anomalies and spanning: Multivariate and multifactor tests with heavy-tailed distributions | 2010 | Journal of Empirical Finance Vol. 17(4), pp. 763-782 |
article | URL |
| Abstract: In this paper we propose a multivariate regression based assessment of the multifactor model first developed by Fama and French (1993). We study mean-variance efficiency and spanning, as well as factor relevance. In particular, we assess the relative contribution of the factors in accounting for asset pricing anomalies. Our tests are motivated by a finite-sample distributional theory, invariant to portfolio repackaging, and achieve size control exactly conditioning on observed factors, in normal and non-normal contexts. We focus on the multivariate normal and Student-t distributions, in which case we rely on the simulation procedure proposed and applied in Beaulieu et al. (2007). We also assess, from a finite-sample and multivariate test perspective, the specification and fit of the model and error distributions considered. In its most general form, the model considered includes six factors: the market portfolio, size, the ratio of book equity to market equity as well as term structure variables (a term premium and a default premium) and momentum. Portfolio returns (coming from assets traded at NYSE, AMEX and NASDAQ) from Fama and French's data base are analyzed on monthly frequencies from 1961–2000. | |||||
BibTeX:
@article{Beaulieu2010,
author = {Beaulieu, Marie-Claude and Dufour, Jean-Marie and Khalaf, Lynda},
title = {Asset-pricing anomalies and spanning: Multivariate and multifactor tests with heavy-tailed distributions},
journal = {Journal of Empirical Finance},
year = {2010},
volume = {17},
number = {4},
pages = {763--782},
url = {http://www.sciencedirect.com/science/article/pii/S0927539810000162}
}
|
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| Beazley, M.J., Martinez, R.J., Webb, S.M., Sobecky, P.A. and Taillefert, M. | The effect of pH and natural microbial phosphatase activity on the speciation of uranium in subsurface soils | 2011 | Geochimica et Cosmochimica Acta Vol. 75(19), pp. 5648-5663 |
article | URL |
| Abstract: The biomineralization of U(VI) phosphate as a result of microbial phosphatase activity is a promising new bioremediation approach to immobilize uranium in both aerobic and anaerobic conditions. In contrast to reduced uranium minerals such as uraninite, uranium phosphate precipitates are not susceptible to changes in oxidation conditions and may represent a long-term sink for uranium in contaminated environments. So far, the biomineralization of U(VI) phosphate has been demonstrated with pure cultures only. In this study, two uranium contaminated soils from the Department of Energy Oak Ridge Field Research Center (ORFRC) were amended with glycerol phosphate as model organophosphate source in small flow-through columns under aerobic conditions to determine whether natural phosphatase activity of indigenous soil bacteria was able to promote the precipitation of uranium(VI) at pH 5.5 and 7.0. High concentrations of phosphate (1–3 mM) were detected in the effluent of these columns at both pH compared to control columns amended with U(VI) only, suggesting that phosphatase-liberating microorganisms were readily stimulated by the organophosphate substrate. Net phosphate production rates were higher in the low pH soil (0.73 ± 0.17 mM d−1) compared to the circumneutral pH soil (0.43 ± 0.31 mM d−1), suggesting that non-specific acid phosphatase activity was expressed constitutively in these soils. A sequential solid-phase extraction scheme and X-ray absorption spectroscopy measurements were combined to demonstrate that U(VI) was primarily precipitated as uranyl phosphate minerals at low pH, whereas it was mainly adsorbed to iron oxides and partially precipitated as uranyl phosphate at circumneutral pH. These findings suggest that, in the presence of organophosphates, microbial phosphatase activity can contribute to uranium immobilization in both low and circumneutral pH soils through the formation of stable uranyl phosphate minerals. | |||||
BibTeX:
@article{Beazley2011,
author = {Beazley, Melanie J. and Martinez, Robert J. and Webb, Samuel M. and Sobecky, Patricia A. and Taillefert, Martial},
title = {The effect of pH and natural microbial phosphatase activity on the speciation of uranium in subsurface soils},
journal = {Geochimica et Cosmochimica Acta},
year = {2011},
volume = {75},
number = {19},
pages = {5648--5663},
url = {http://www.sciencedirect.com/science/article/pii/S0016703711003930}
}
|
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| Beddingfield, M., Ahmed, K., Painter, R. and Byl, T.D. | Desorption Isotherms for Toluene and Karstic Materials and Implications for Transport in Karst Aquifers | 2005 | U. S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160, pp. 188 | inproceedings | URL |
| Abstract: Karst aquifers dominated by conduit flow are extremely vulnerable to fuel contamination such as from leaky underground storage tanks or spills. Direct flow paths through fractures and sinkholes often allow contaminants to move rapidly into the conduit system. Not much is known about how the fuel will interact with the carbonate rock in the conduit system. The objective of this research was to bridge this information gap by measuring sorption and desorption of fuels to karst materials. The first phase of this study involved the dissolution and desorption processes. Initial experiments (n=5) used karst bedrock fragments of known size soaked in toluene for 24 hours. Then the sterile toluene-soaked rocks were placed in sterile distilled water. The concentration of toluene dissolved in the water was measured over increasing time periods. These data were used to derive a first-order exponential rate of desorption [Cw(t)=Ciekt]. The empirical value for k was 0.8958. The toluene concentration in the water reached a maximum carrying capacity in approximately 3 weeks. The second phase of this project involved sorption studies using limestone frag- ments of known size and water containing a known concentration of dissolved toluene. The empirical value for the sorption k was 1.006. These results show that sorption is faster than desorption and have implications for designing a model that predicts the fate and transport of fuels in karst aquifers. | |||||
BibTeX:
@inproceedings{Beddingfield2005,
author = {Beddingfield, Mario and Ahmed, Khalid and Painter, Roger and Byl, T. D.},
title = {Desorption Isotherms for Toluene and Karstic Materials and Implications for Transport in Karst Aquifers},
booktitle = {U. S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160},
publisher = {U. S. Geological Survey Karst Interest Group},
year = {2005},
pages = {188},
url = {pubs.usgs.gov/sir/2005/5160/index.html}
}
|
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| Beddows, P.A., Smart, P.L., Whitaker, F.F. and Smith, S.L. | Decoupled fresh–saline groundwater circulation of a coastal carbonate aquifer: Spatial patterns of temperature and specific electrical conductivity | 2007 | Journal of Hydrology Vol. 346(1-2), pp. 18-32 |
article | URL |
| Abstract: The coastal carbonate aquifer of the eastern Yucatan Peninsula discharges groundwaters to the Caribbean Sea. Temperature and specific electrical conductance (SEC) are used as natural tracers to gain new insight into the fresh and saline groundwater circulation along an 80 km section of the Caribbean coastline. The aquifer is density stratified, with a cooler freshwater lens overlying a warmer saline water zone. Non-conduit sites generally have lower temperatures and SEC in the freshwater lens than conduit sites. In conduits <1 km from the coast, there is a very rapid increase in both fresh water temperature and SEC indicating very active mixing with the underlying warm saline water. Further inland, the rates of change of SEC and temperature are lower, and conduit morphology and network geometry are important controls on salinisation along the conduit flow paths. Turbulent mixing is enhanced by flow around obstacles where the conduit spans the mixing zone (sites 1–4 km inland), but mixing is limited where the conduit is entirely filled with fresh water (sites >4 km inland). Within the shallow saline water zone, temperature decreases exponentially with distance from the coast, with near equilibrium with the fresh waters reached at ∼10 km inland, a distance coincident with the known limit of conduit development. This pattern is indicative of the progressive cooling of warm seawater moving inland from the coast, a flow direction opposite to that of both the conventional freshwater flow entrainment and geothermal convection models of coastal aquifer circulation. | |||||
BibTeX:
@article{Beddows2007,
author = {Beddows, Patricia A. and Smart, Peter L. and Whitaker, Fiona F. and Smith, Samantha L.},
title = {Decoupled fresh–saline groundwater circulation of a coastal carbonate aquifer: Spatial patterns of temperature and specific electrical conductivity},
journal = {Journal of Hydrology},
year = {2007},
volume = {346},
number = {1-2},
pages = {18--32},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407004593}
}
|
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| Behin, J. and Aghajari, M. | Influence of water level on oil–water separation by residence time distribution curves investigations | 2008 | Separation and Purification Technology Vol. 64(1), pp. 48-55 |
article | URL |
| Abstract: The separation of crude oil and water mixtures is an important process in the oil and chemical industries. This work studied the flow behavior of crude oil and water in a pilot scale oil–water separator. This gravity separator (diameter of 1.2 m and length of 5.2 m) was operated by Drood oil of the Iranian Offshore Oil Company (IOOC) located in Kharg Island (Iran). The residence time distribution (RTD) curves were acquired in this separator by radioactive tracer (131I) injection. Experimental results showed that the separator operational performance increased with the water level in the vessel. Perfect mixing tanks-in-series (with a dead zone) have been used to describe the liquid behavior, and the experimental results were in good agreement with this model. Increasing the water level in the vessel from 0.5 m to 0.9 m increases the number of mixing tanks-in-series of both organic and aqueous phases, from 9.0 to 9.1 and from 8 to 8.3, respectively. The dead volume of the organic phase path decreased with water level, but this trend was reversed for the aqueous phase path. Less than 3% of the volume of the separator is active. The separator’s optimum efficiency occurred when the water level in the separator was about 0.7 m. | |||||
BibTeX:
@article{Behin2008,
author = {Behin, J. and Aghajari, M.},
title = {Influence of water level on oil–water separation by residence time distribution curves investigations},
journal = {Separation and Purification Technology},
year = {2008},
volume = {64},
number = {1},
pages = {48--55},
url = {http://www.sciencedirect.com/science/article/pii/S1383586608003092}
}
|
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| Behrens, H., Beims, U., Dieter, H., Dietze, G., Eikmann, T., Grummt, T., Hanisch, H., Henseling, H., Käß, W., Kerndorff, H., Leibundgut, C., Müller-Wegener, U., Rönnefahrt, I., Scharenberg, B., Schleyer, R., Schloz, W. and Tilkes, F. | Toxicological and ecotoxicological assessment of water tracers | 2001 | Hydrogeology Journal Vol. 9(3), pp. 321-325 |
article | URL |
| Abstract: Uncertainties regarding possible negative effects on the environment or on human health of authorizing tracing experiments in groundwater and surface waters led to the establishment of a Working Group at the German Federal Environmental Agency (Umweltbundesamt – UBA) for conducting a toxicological and ecotoxicological assessment. A total of 17 water tracers was assessed by the Working Group on the basis of the results of toxicological tests, the available literature, and the group's expert knowledge. In the future, tracers that pose a risk to the environment or to human health should no longer be used. Nevertheless, there are a number of tracers that could be used in hydrogeological and hydrological investigations for water-pollution-control purposes with no adverse environmental impact. | |||||
BibTeX:
@article{Behrens2001,
author = {Behrens, H. and Beims, U. and Dieter, H. and Dietze, G. and Eikmann, T. and Grummt, T. and Hanisch, H. and Henseling, H. and Käß, W. and Kerndorff, H. and Leibundgut, C. and Müller-Wegener, U. and Rönnefahrt, I. and Scharenberg, B. and Schleyer, R. and Schloz, W. and Tilkes, F.},
title = {Toxicological and ecotoxicological assessment of water tracers},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2001},
volume = {9},
number = {3},
pages = {321--325},
url = {http://dx.doi.org/10.1007/s100400100126}
}
|
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| Beirlant, J., de Wet, T. and Goegebeur, Y. | A goodness-of-fit statistic for Pareto-type behaviour | 2006 | Journal of Computational and Applied Mathematics Vol. 186(1)Special Issue: Jef Teugels, pp. 99-116 |
article | URL |
| Abstract: The fit of a statistical model can be visually assessed by inspection of a quantile–quantile or QQ plot. For the strict Pareto distribution, since log-transformed Pareto random variables are exponentially distributed, it is natural to consider an exponential quantile plot based on the log-transformed data. In case the data originate from a Pareto-type distribution, the Pareto quantile plot will be linear but only in some of the largest observations. In this paper we modify the Jackson statistic, originally proposed as a goodness-of-fit statistic for testing exponentiality, in such a way that it measures the linearity of the k largest observations on the Pareto quantile plot. Further, by taking the second-order tail behaviour of a Pareto-type model into account we construct a bias-corrected Jackson statistic. For both statistics the limiting distribution is derived. Next to these asymptotic results we also evaluate the small sample behaviour on the basis of a simulation study. The method is illustrated on two practical case studies. | |||||
BibTeX:
@article{Beirlant2006,
author = {Beirlant, Jan and de Wet, Tertius and Goegebeur, Yuri},
title = {A goodness-of-fit statistic for Pareto-type behaviour},
booktitle = {Special Issue: Jef Teugels},
journal = {Journal of Computational and Applied Mathematics},
year = {2006},
volume = {186},
number = {1},
pages = {99--116},
url = {http://www.sciencedirect.com/science/article/pii/S0377042705001913}
}
|
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| Bekins, B.A., Godsy, E.M. and Goerlitz, D.F. | Modeling steady-state methanogenic degradation of phenols in groundwater | 1993 | Journal of Contaminant Hydrology Vol. 14(3–4), pp. 279-294 |
article | URL |
| Abstract: Field and microcosm observations of methanogenic phenolic compound degradation indicate that Monod kinetics governs the substrate disappearance but overestimates the observed biomass. In this paper we present modeling results from an ongoing multidisciplinary study of methanogenic biodegradation of phenolic compounds in a sand and gravel aquifer contaminated by chemicals and wastes used in wood treatment. Field disappearance rates of four phenols match those determined in batch microcosm studies previously performed by E.M. Godsy and coworkers. The degradation process appears to be at steady-state because even after a sustained influx over several decades, the contaminants still are disappearing in transport downgradient. The existence of a steady-state degradation profile of each substrate together with a low biomass density in the aquifer indicate that the bacteria population is exhibiting no net growth. This may be due to the oligotrophic nature of the biomass population in which utilization and growth are approximately independent of concentration for most of the concentration range. Thus a constant growth rate should exist over much of the contaminated area which may in turn be balanced by an unusually high decay or maintenance rate due to hostile conditions or predation. | |||||
BibTeX:
@article{Bekins1993,
author = {Bekins, Barbara A. and Godsy, E. Michael and Goerlitz, Donald F.},
title = {Modeling steady-state methanogenic degradation of phenols in groundwater},
journal = {Journal of Contaminant Hydrology},
year = {1993},
volume = {14},
number = {3–4},
pages = {279--294},
url = {http://www.sciencedirect.com/science/article/pii/016977229390029R}
}
|
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| Bekins, B.A., Warren, E. and Godsy, E.M. | A Comparison of Zero-Order, First-Order, and Monod Biotransformation Models | 1998 | Ground Water Vol. 36(2), pp. 261-268 |
article | URL |
| Abstract: Under some conditions, a first-order kinetic model is a poor representation of biodegradation in contaminated aquifers. Although it is well known that the assumption of first-order kinetics is valid only when substrate concentration, S, is much less than the half-saturation constant, K s, this assumption is often made without verification of this condition. We present a formal error analysis showing that the relative error in the first-order approximation is S/Ks and in the zero-order approximation the error is Ks/S. We then examine the problems that arise when the first-order approximation is used outside the range for which it is valid. A series of numerical simulations comparing results of first- and zero-order rate approximations to Monod kinetics for a real data set illustrates that if concentrations observed in the field are higher than Ks, it may be better to model degradation using a zero-order rate expression. Compared with Monod kinetics, extrapolation of a first-order rate to lower concentrations under-predicts the biotransformation potential, while extrapolation to higher concentrations may grossly over-predict the transformation rate. A summary of solubilities and Monod parameters for aerobic benzene, toluene, and xylene (BTX) degradation shows that the a priori assumption of first-order degradation kinetics at sites contaminated with these compounds is not valid. In particular, out of six published values of Ks for toluene, only one is greater than 2 mg/L, indicating that when toluene is present in concentrations greater than about a part per million, the assumption of first-order kinetics may be invalid. Finally, we apply an existing analytical solution for steady-state one-dimensional advective transport with Monod degradation kinetics to a field data set. | |||||
BibTeX:
@article{Bekins1998,
author = {Bekins, Barbara A. and Warren, Ean and Godsy, E. Michael},
title = {A Comparison of Zero-Order, First-Order, and Monod Biotransformation Models},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {1998},
volume = {36},
number = {2},
pages = {261--268},
url = {http://dx.doi.org/10.1111/j.1745-6584.1998.tb01091.x}
}
|
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| Bencala, K.E. and Walters, R.A. | Simulation of solute transport in a mountain pool-and-riffle stream: A transient storage model | 1983 | Water Resources Research Vol. 19(3), pp. 718-724 |
article | URL |
| Abstract: The physical characteristics of mountain streams differ from the uniform and conceptually well- defined open channels for which the analysis of solute transport has been oriented in the past and is now well understood. These physical conditions significantly influence solute transport behavior, as demonstrated by a transient storage model simulation of solute transport in a very small (0.0125 m3s−1) mountain pool-and-riffle stream. The application is to a carefully controlled and intensively monitored chloride injection experiment. The data from the experiment are not explained by the standard convection-dispersion mechanisms alone. A transient storage model, which couples dead zones with the one-dimensional convection-dispersion equation, simulates the general characteristics of the solute transport behavior and a set of simulation parameters were determined that yield an adequate fit to the data. However, considerable uncertainty remains in determining physically realistic values of these parameters. The values of the simulation parameters used are compared to values used by other authors for other streams. The comparison supports, at least qualitatively, the determined parameter values. | |||||
BibTeX:
@article{Bencala1983,
author = {Bencala, Kenneth E. and Walters, Roy A.},
title = {Simulation of solute transport in a mountain pool-and-riffle stream: A transient storage model},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1983},
volume = {19},
number = {3},
pages = {718--724},
url = {http://dx.doi.org/10.1029/WR019i003p00718}
}
|
|||||
| Benson, D.A. and Meerschaert, M.M. | A simple and efficient random walk solution of multi-rate mobile/immobile mass transport equations | 2009 | Advances in Water Resources Vol. 32(4), pp. 532-539 |
article | URL |
| Abstract: We extend the particle-tracking method to simulate general multi-rate mass transfer (MRMT) equations. Previous methods for single-rate equations used two-state Markov chains and found that the time a particle spends in the mobile state between waiting time epochs is random and exponentially distributed. Using Bochner’s subordination technique for Markov processes, we find that the random mobile times are still exponential for the stochastic process that corresponds to the MRMT equations. The random times in the immobile phase have a distribution that is directly related to the memory function of the MRMT equation. This connection allows us to interpret the MRMT memory function as the rate at which particles of a certain age, measured by residence time in the immobile zone, exit to become mobile once again. Because the exact distributions of mobile and immobile times are known from the MRMT equations, they can be simulated very simply and efficiently using random walks. | |||||
BibTeX:
@article{Benson2009,
author = {Benson, David A. and Meerschaert, Mark M.},
title = {A simple and efficient random walk solution of multi-rate mobile/immobile mass transport equations},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {4},
pages = {532--539},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809000128}
}
|
|||||
| Berglund, S., Kautsky, U., Lindborg, T. and Selroos, J.-O. | Integration of hydrological and ecological modelling for the assessment of a nuclear waste repository | 2009 | Hydrogeology Journal Vol. 17(1), pp. 95-113 |
article | URL |
| Abstract: The Swedish Nuclear Fuel and Waste Management Co. (SKB) is currently investigating two sites in Sweden as potential locations for underground disposal of spent nuclear fuel. The site investigations cover geology, chemistry, hydrology and ecology, among several other disciplines. Strong emphasis is put on the characterisation of properties and processes affecting the water-born transport and retention of radionuclides along potential flow paths from repository depth (ca. 500 m below ground) to ground surface, and the dispersal and accumulation of the radionuclides in the surface system. The modelling performed to support the site descriptions and the safety assessments utilises a wide range of hydrological modelling tools. These include tools primarily developed for modelling groundwater flow in fractured rock, and modelling tools that handle surface and subsurface flows, water uptake in vegetation and the interactions with the atmosphere. The couplings between the hydrogeology, the near surface hydrology and the surface ecosystems are especially important in this integrated modelling. This paper highlights some ecohydrological aspects of this coupled modelling and provides example results from site descriptive and safety assessment modelling. | |||||
BibTeX:
@article{Berglund2009,
author = {Berglund, Sten and Kautsky, Ulrik and Lindborg, Tobias and Selroos, Jan-Olof},
title = {Integration of hydrological and ecological modelling for the assessment of a nuclear waste repository},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {95--113},
url = {http://dx.doi.org/10.1007/s10040-008-0399-6}
}
|
|||||
| Berkowitz, B. | Characterizing flow and transport in fractured geological media: A review | 2002 | Advances in Water Resources Vol. 25(8-12), pp. 861-884 |
article | URL |
| Abstract: We analyze measurements, conceptual pictures, and mathematical models of flow and transport phenomena in fractured rock systems. Fractures and fracture networks are key conduits for migration of hydrothermal fluids, water and contaminants in groundwater systems, and oil and gas in petroleum reservoirs. Fractures are also the principal pathways, through otherwise impermeable or low permeability rocks, for radioactive and toxic industrial wastes which may escape from underground storage repositories. We consider issues relating to (i) geometrical characterization of fractures and fracture networks, (ii) water flow, (iii) transport of conservative and reactive solutes, and (iv) two-phase flow and transport. We examine the underlying physical factors that control flow and transport behaviors, and discuss the currently inadequate integration of conceptual pictures, models and data. We also emphasize the intrinsic uncertainty associated with measurements, which are often interpreted non-uniquely by models. Throughout the review, we point out key, unresolved problems, and formalize them as open questions for future research. | |||||
BibTeX:
@article{Berkowitz2002,
author = {Berkowitz, Brian},
title = {Characterizing flow and transport in fractured geological media: A review},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {8-12},
pages = {861--884},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802000428}
}
|
|||||
| Berkowitz, B., Cortis, A., Dentz, M. and Scher, H. | Modeling non-Fickian transport in geological formations as a continuous time random walk | 2006 | Reviews of Geophysics Vol. 44(2), pp. RG2003- |
article | URL |
| Abstract: Non-Fickian (or anomalous) transport of contaminants has been observed at field and laboratory scales in a wide variety of porous and fractured geological formations. Over many years a basic challenge to the hydrology community has been to develop a theoretical framework that quantitatively accounts for this widespread phenomenon. Recently, continuous time random walk (CTRW) formulations have been demonstrated to provide general and effective means to quantify non-Fickian transport. We introduce and develop the CTRW framework from its conceptual picture of transport through its mathematical development to applications relevant to laboratory- and field-scale systems. The CTRW approach contrasts with ones used extensively on the basis of the advection-dispersion equation and use of upscaling, volume averaging, and homogenization. We examine the underlying assumptions, scope, and differences of these approaches, as well as stochastic formulations, relative to CTRW. We argue why these methods have not been successful in fitting actual measurements. The CTRW has now been developed within the framework of partial differential equations and has been generalized to apply to nonstationary domains and interactions with immobile states (matrix effects). We survey models based on multirate mass transfer (mobile-immobile) and fractional derivatives and show their connection as subsets within the CTRW framework. | |||||
BibTeX:
@article{Berkowitz2006,
author = {Berkowitz, Brian and Cortis, Andrea and Dentz, Marco and Scher, Harvey},
title = {Modeling non-Fickian transport in geological formations as a continuous time random walk},
journal = {Reviews of Geophysics},
publisher = {American Geophysical Union (AGU)},
year = {2006},
volume = {44},
number = {2},
pages = {RG2003--},
url = {http://dx.doi.org/10.1029/2005RG000178}
}
|
|||||
| Berthiaux, H., Espitalier, F., Kiefer, J.C., Niel, M. and Mizonov, V.E. | A markov chain model to describe the residence time distribution in a stirred bead mill [BibTeX] |
2001 | Vol. 10Handbook of Conveying and Handling of Particulate Solids, pp. 685-691 |
incollection | URL |
BibTeX:
@incollection{Berthiaux2001,
author = {Berthiaux, H. and Espitalier, F. and Kiefer, J. C. and Niel, M. and Mizonov, V. E.},
title = {A markov chain model to describe the residence time distribution in a stirred bead mill},
booktitle = {Handbook of Conveying and Handling of Particulate Solids},
publisher = {Elsevier Science B. V.},
year = {2001},
volume = {10},
pages = {685--691},
url = {http://www.sciencedirect.com/science/article/pii/S0167378501800701}
}
|
|||||
| Bertrand–Krajewski, J.-L., Barraud, S. and Bardin, J.-P. | Uncertainties, performance indicators and decision aid applied to stormwater facilities | 2002 | Urban Water Vol. 4(2), pp. 163-179 |
article | URL |
| Abstract: Performance indicators play an increasing role in the design and the operation of urban drainage systems. However, uncertainties linked to both calculation of performance indicators and their use in decision-aid tools and methods have been rarely accounted for. Two case studies concerning stormwater facilities are presented in this paper. The first one concerns the effect of sampling and analytical uncertainties on the evaluation of a single performance indicator defined as the annual interception efficiency of a stormwater storage and settling tank. The second one is related to the effect of modelling uncertainties on the evaluation of several performance indicators and on their impact as regards the choice of maintenance strategy of a stormwater infiltration tank. Both cases show that uncertainties are very significant and shall be accounted for in the calculation and the use of performance indicators. | |||||
BibTeX:
@article{Bertrand–Krajewski2002,
author = {Bertrand–Krajewski, J.-L. and Barraud, S. and Bardin, J.-P.},
title = {Uncertainties, performance indicators and decision aid applied to stormwater facilities},
journal = {Urban Water},
year = {2002},
volume = {4},
number = {2},
pages = {163--179},
url = {http://www.sciencedirect.com/science/article/pii/S146207580200016X}
}
|
|||||
| Best, D. and Rayner, J. | Chi-squared components for tests of fit and improved models for the grouped exponential distribution | 2007 | Computational Statistics & Data Analysis Vol. 51(8), pp. 3946-3954 |
article | URL |
| Abstract: We consider testing for an exponential distribution with unspecified rate parameter when it is only possible to observe the counts in groups with boundaries specified before sighting the data. On the basis of a size and power study we recommend that tests of fit for the exponential distribution be based on the Anderson–Darling statistic and the SW 2 statistic recommended by Gulati and Neus [(2001). Goodness-of-fit statistics for the exponential distribution when the data are grouped. In: Huber-Carol, C., Balakrishnan, N., Nikulin, M.S., Mesbah, M., (Eds.), Goodness-of-Fit Tests and Validity of Models. Birkhauser, Boston, pp. 113–123 (Chapter 9)]. We also suggest that inference based on one of these be complemented by examination of the components of the X 2 statistic. We illustrate how to use these components to give improved models. | |||||
BibTeX:
@article{Best2007,
author = {Best, D.J. and Rayner, J.C.W.},
title = {Chi-squared components for tests of fit and improved models for the grouped exponential distribution},
journal = {Computational Statistics & Data Analysis},
year = {2007},
volume = {51},
number = {8},
pages = {3946--3954},
url = {http://www.sciencedirect.com/science/article/pii/S0167947306000855}
}
|
|||||
| Bester, K. and Schäfer, D. | Activated soil filters (bio filters) for the elimination of xenobiotics (micro-pollutants) from storm- and waste waters | 2009 | Water Research Vol. 43(10), pp. 2639-2646 |
article | URL |
| Abstract: A technical scale (0.12 m3) activated soil filter (bio filter) has been used to eliminate diverse xenobiotics (organic micro-pollutants) such as organophosphate flame retardants, and -plasticisers, musk fragrances, DEHP, benzothiazoles and triclosan from water. Model experiments to treat combined sewer overflow, storm water and a post treatment of waste water were performed in controlled laboratory experiments. The indicator compounds were typical for waste water. Diverse chemical compound groups and a wide spectrum from the lipophilic (pKow = 5.9) to the hydrophilic (pKow = 2.6) were included. The system consisted of a layer with high organic content (with vegetation to prevent clogging), a sand filter and a gravel drainage layer. The organic layer was spiked with activated sludge to enhance biomass and biodegradation potential. Usually the elimination rates varied from 64% to 99%, with only one compound reaching as little as 17%. For a technical suitability assessment it was calculated how long these filters would be stable in eliminating organic compounds from water. The estimated operating times for such systems was found to be about 100 years for a stack height of 2 m a year in regard to most compounds in this study. | |||||
BibTeX:
@article{Bester2009,
author = {Bester, Kai and Schäfer, Daniel},
title = {Activated soil filters (bio filters) for the elimination of xenobiotics (micro-pollutants) from storm- and waste waters},
journal = {Water Research},
year = {2009},
volume = {43},
number = {10},
pages = {2639--2646},
url = {http://www.sciencedirect.com/science/article/pii/S0043135409001857}
}
|
|||||
| Beven, K.J. | Preferential flows and travel time distributions: defining adequate hypothesis tests for hydrological process models | 2010 | Hydrological Processes Vol. 24(12), pp. 1537-1547 |
article | URL |
| Abstract: This introduction to the second annual review issue of Hydrological Processes tries to put the collection of papers on preferential flows and travel time distributions into a more general context of testing models as hypotheses about how catchment systems function. It is suggested that, because of the possibilities of non-stationary and epistemic errors in both data and models, such tests could be carried out within a rejectionist limits-of-acceptability framework. The principles and difficulties of hypothesis testing within these particular research areas are discussed. An important point to take from this discussion is that the use of a formal testing framework, and the consequent rejection of models as hypotheses after allowing for uncertainties in the data, is the starting point for developing better theories and data sets. | |||||
BibTeX:
@article{Beven2010,
author = {Beven, Keith J.},
title = {Preferential flows and travel time distributions: defining adequate hypothesis tests for hydrological process models},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {12},
pages = {1537--1547},
url = {http://dx.doi.org/10.1002/hyp.7718}
}
|
|||||
| van Beynen, P., Niedzielski, M., Bialkowska-Jelinska, E., Alsharif, K. and Matusick, J. | Comparative study of specific groundwater vulnerability of a karst aquifer in central Florida | 2012 | Applied Geography Vol. 32(2), pp. 868-877 |
article | URL |
| Abstract: The Floridan aquifer system (FAS) is known to be one of the most productive aquifer systems in the USA. With the FAS being a karst aquifer, it presents unique challenges to land use planners because of inherent vulnerabilities to contamination through direct connections between the aquifer and the surface. In this study a new Geographic Information Systems (GIS) -based index, the Karst Aquifer Vulnerability Index (KAVI), incorporates geologic layers used in intrinsic groundwater vulnerability models (GVMs) plus an epikarst layer specific to karst, with land use coverages to create a specific groundwater vulnerability model. The KAVI model was compared to another specific vulnerability model, the Susceptibility Index (SI). Tabulation of the percentage areas of vulnerability classes reveals major differences between the two models with SI suggesting greater vulnerability for the study area than KAVI. Validation of these two models found that KAVI vulnerability levels best reproduced spatially varying concentrations of nitrate in the aquifer. Sensitivity analysis, the application of a variation index and measuring the effective weights for each parameter included in KAVI confirmed the importance of closed depressions but also aquifer hydraulic conductivity. The inclusion of land use was justified; however, effective weight analysis determined its assigned weight was too high as used in the initial calculation of KAVI. | |||||
BibTeX:
@article{Beynen2012,
author = {van Beynen, P.E. and Niedzielski, M.A. and Bialkowska-Jelinska, E. and Alsharif, K. and Matusick, J.},
title = {Comparative study of specific groundwater vulnerability of a karst aquifer in central Florida},
journal = {Applied Geography},
year = {2012},
volume = {32},
number = {2},
pages = {868--877},
url = {http://www.sciencedirect.com/science/article/pii/S0143622811001743}
}
|
|||||
| Bhattacharya, R. | Multiscale Diffusion Processes with Periodic Coefficients and an Application to Solute Transport in Porous Media | 1999 | The Annals of Applied Probability Vol. 9(4), pp. 951-1020 |
article | URL |
| Abstract: Consider diffusions on $mathbb R^k, k > 1$, governed by the Itô equation dX(t) = b(X(t)) + β(X(t)/a)dt + σ dB(t), where b, β are periodic with the same period and are divergence free, σ is nonsingular and a is a large integer. Two distinct Gaussian phases occur as time progresses. The initial phase is exhibited over times 1 ≪ t ≪ a2/3. Under a geometric condition on the velocity field β, the final Gaussian phase occurs for times t ≫ a2(log a)2, and the dispersion grows quadratically with a. Under a complementary condition, the final phase shows up at times t ≫ a4(log a)2, or t ≫ a2 log a under additional conditions, with no unbounded growth in dispersion as a function of scale. Examples show the existence of non-Gaussian intermediate phases. These probabilisitic results are applied to analyze a multiscale Fokker-Planck equation governing solute transport in periodic porous media. In case b, β are not divergence free, some insight is provided by the analysis of one-dimensional multiscale diffusions with periodic coefficients. | |||||
BibTeX:
@article{Bhattacharya1999,
author = {Bhattacharya, Rabi},
title = {Multiscale Diffusion Processes with Periodic Coefficients and an Application to Solute Transport in Porous Media},
journal = {The Annals of Applied Probability},
publisher = {Institute of Mathematical Statistics},
year = {1999},
volume = {9},
number = {4},
pages = {951--1020},
url = {http://www.jstor.org/stable/2667140}
}
|
|||||
| Bhunya, P., Berndtsson, R., Ojha, C. and Mishra, S. | Suitability of Gamma, Chi-square, Weibull, and Beta distributions as synthetic unit hydrographs | 2007 | Journal of Hydrology Vol. 334(1-2), pp. 28-38 |
article | URL |
| Abstract: Most available methods for synthetic unit hydrograph (SUH) derivation involve manual, subjective fitting of a hydrograph through a few data points. Because of this tedious procedure, the generated unit hydrograph is often left unadjusted for unit runoff volume. During recent decades, use of probability distribution functions (pdfs) in developing SUH has received much attention because of its similarity with unit hydrograph properties. In this study, the potential of four popular pdfs, i.e., two-parameter Gamma, three-parameter Beta, two-parameter Weibull, and one-parameter Chi-square distribution to derive SUH have been explored. Simple formulae are derived using analytical and numerical schemes to compute the distribution parameters, and their validity is checked with simulation of field data. The Gamma and Chi-square distributions behave analogously, and the Beta distribution approximates a Gamma distribution in a limiting case. Application to field data shows that the Beta and Weibull distributions are more flexible in hydrograph prediction than the Gamma, Chi-square, Gray [Gray, D.M., 1961. Synthetic hydrographs for small drainage areas. In: Proceedings of the ASCE, 87, HY4, pp. 33–54], SCS [SCS, 1957. Use of Storm and Watershed Characteristics in Synthetic Hydrograph Analysis and Application: V. Mockus. US Dept. of Agriculture, Soil Conservation Service, Washington, DC], and Snyder [Synder, F.F., 1938. Synthetic unit hydrographs. Trans. Am. Geophys. Union 19, 447–454] methods. A sensitivity analysis of pdf parameters on peak flow estimates of an UH indicated that Gamma and Chi-square distributions overestimate the peak flow value, for any overestimation in its parameter estimates. However, for the Beta and Weibull distributions a reverse trend was observed. Both were found to behave similarly at higher α (ratio of time to base and time to peak of UH) values. Further, an analogous triangular hydrograph approach was used to express the mean and variance of the UH in terms of time base and time to peak of the UH. This enabled a simple parameter estimation equation involving only time base and time to peak of the UH. Although the validity of this equation could not be evaluated with a proper amount of data, the results give an indication of the relationship between pdf and statistical properties of the UH to be further elaborated in future research. | |||||
BibTeX:
@article{Bhunya2007,
author = {Bhunya, P.K. and Berndtsson, R. and Ojha, C.S.P. and Mishra, S.K.},
title = {Suitability of Gamma, Chi-square, Weibull, and Beta distributions as synthetic unit hydrographs},
journal = {Journal of Hydrology},
year = {2007},
volume = {334},
number = {1--2},
pages = {28--38},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406005075}
}
|
|||||
| Bhunya, P.K., Mishra, S.K. and Berndtsson, R. | Simplified Two-Parameter Gamma Distribution for Derivation of Synthetic Unit Hydrograph | 2003 | Journal of Hydrologic Engineering Vol. 8(4), pp. 226-230 |
article | URL |
| Abstract: Several methods for synthetic unit hydrographs are available in the literature. Most of them involve manual, subjective fitting of a hydrograph through few data points. Because it is difficult, the generated unit hydrograph is often left unadjusted for unit runoff volume. To circumvent this problem, a simplified version of the existing two-parameter gamma distribution is introduced to derive a synthetic hydrograph more conveniently and accurately than the popular Gray, Soil Conservation Service, and Synder methods. The revised version incorporates the approximate, but accurate, empirical relations developed for the estimation of β and λ (factors governing the shape of the dimensionless unit hydrograph) from the Nash parameter n (=number of reservoirs). The Marquardt algorithm was used to develop the nonlinear relationships. The applicability of the simplified version is tested on both text and field data. | |||||
BibTeX:
@article{Bhunya2003,
author = {Bhunya, P. K. and Mishra, S. K. and Berndtsson, Ronny},
title = {Simplified Two-Parameter Gamma Distribution for Derivation of Synthetic Unit Hydrograph},
journal = {Journal of Hydrologic Engineering},
publisher = {American Society of Civil Engineers (ASCE)},
year = {2003},
volume = {8},
number = {4},
pages = {226--230},
url = {http://dx.doi.org/10.1061/(ASCE)1084-0699(2003)8:4(226)}
}
|
|||||
| Birk, S., Geyer, T., Liedl, R. and Sauter, M. | Process-based interpretation of tracer tests in carbonate aquifers | 2005 | Ground Water Vol. 43(3), pp. 381-388 |
article | URL |
| Abstract: A tracer test in a carbonate aquifer is analyzed using the method of moments and two analytical advection-dispersion models (ADMs) as well as a numerical model. The numerical model is a coupled continuum-pipe flow and transport model that accounts for two different flow components in karstified carbonate aquifers, i.e., rapid and often turbulent conduit flow and Darcian flow in the fissured porous rock. All techniques employed provide reasonable fits to the tracer breakthrough curve (TBC) measured at a spring. The resulting parameter estimates are compared to investigate how each conceptual model of flow and transport processes that forms the basis of the analyses affects the interpretation of the tracer test. Numerical modeling results suggest that the method of moments and the analytical ADMs tend to overestimate the conduit volume because part of the water discharged at the spring is wrongly attributed to the conduit system if flow in the fissured porous rock is ignored. In addition, numerical modeling suggests that mixing of the two flow components accounts for part of the dispersion apparent in the measured TBC, while the remaining part can be attributed to Taylor dispersion. These processes, however, cannot reasonably explain the tail of the TBC. Instead, retention in immobile-fluid regions as included in a nonequilibrium ADM provides a possible explanation. | |||||
BibTeX:
@article{Birk2005,
author = {Birk, Steffen and Geyer, Tobias and Liedl, Rudolf and Sauter, Martin},
title = {Process-based interpretation of tracer tests in carbonate aquifers},
journal = {Ground Water},
publisher = {Blackwell Science Inc},
year = {2005},
volume = {43},
number = {3},
pages = {381--388},
url = {http://dx.doi.org/10.1111/j.1745-6584.2005.0033.x}
}
|
|||||
| Birk, S. and Hergarten, S. | Early recession behaviour of spring hydrographs | 2010 | Journal of Hydrology Vol. 387(1-2), pp. 24-32 |
article | URL |
| Abstract: The long-term flow recession of many springs can be approximated by an exponential function. However, the early recession often exhibits a different behaviour. The exponential recession function represents a long-term approximation of analytical solutions of the flow equation of fissured matrix blocks draining toward a fixed-head boundary. Thus, early deviations from the exponential behaviour potentially originate from the inappropriateness of this approximation at short times. We therefore examine the properties of the exact analytical solutions and make comparisons with field data. If hydraulic heads are initially constant within the matrix blocks the flow recession exhibits a power-law decrease at short times. Both from steady-state initial conditions and after finite recharge pulses the early flow recession follows a power law, too, if discharge is appropriately shifted and rescaled. If the catchment is composed of multiple blocks drained by highly conductive conduits the recession behaviour of the spring is identical to that of the individual blocks if the blocks are of the same size. The recession curves of the published hydrograph of Cheddar spring (Great Britain) are found to be in good agreement with this model if reasonable initial conditions are assumed. A brief look at recession curves from other springs suggests that the model might be applicable to most of them, too. The model also provides satisfactory fits to the flow recession of the Gallusquelle (Germany). However, the observed power-law exponent differs from that predicted by the analytical model. A consistent interpretation of the shape of several recession curves from this spring is provided by a more general fractal approach, which assumes that the catchment is composed of blocks of strongly different sizes. | |||||
BibTeX:
@article{Birk2010,
author = {Birk, Steffen and Hergarten, Stefan},
title = {Early recession behaviour of spring hydrographs},
journal = {Journal of Hydrology},
year = {2010},
volume = {387},
number = {1-2},
pages = {24--32},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410001526}
}
|
|||||
| Birk, S., Liedl, R. and Sauter, M. | Karst Spring Responses Examined by Process-Based Modeling | 2006 | Ground Water Vol. 44(6), pp. 832-836 |
article | URL |
| Abstract: Ground water in karst terrains is highly vulnerable to contamination due to the rapid transport of contaminants through the highly conductive conduit system. For contamination risk assessment purposes, information about hydraulic and geometric characteristics of the conduits and their hydraulic interaction with the fissured porous rock is an important prerequisite. The relationship between aquifer characteristics and short-term responses to recharge events of both spring discharge and physicochemical parameters of the discharged water was examined using a process-based flow and transport model. In the respective software, a pipe-network model, representing fast conduit flow, is coupled to MODFLOW, which simulates flow in the fissured porous rock. This hybrid flow model was extended to include modules simulating heat and reactive solute transport in conduits. The application of this modeling tool demonstrates that variations of physicochemical parameters, such as solute concentration and water temperature, depend to a large extent on the intensity and duration of recharge events and provide information about the structure and geometry of the conduit system as well as about the interaction between conduits and fissured porous rock. Moreover, the responses of solute concentration and temperature of spring discharge appear to reflect different processes, thus complementing each other in the aquifer characterization. | |||||
BibTeX:
@article{Birk2006,
author = {Birk, Steffen and Liedl, Rudolf and Sauter, Martin},
title = {Karst Spring Responses Examined by Process-Based Modeling},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2006},
volume = {44},
number = {6},
pages = {832--836},
url = {http://dx.doi.org/10.1111/j.1745-6584.2006.00175.x}
}
|
|||||
| Birk, S., Liedl, R. and Sauter, M. | Identification of localised recharge and conduit flow by combined analysis of hydraulic and physico-chemical spring responses (Urenbrunnen, SW-Germany) | 2004 | Journal of Hydrology Vol. 286(1-4), pp. 179-193 |
article | URL |
| Abstract: Karst aquifers are highly vulnerable to contamination due to the rapid transport of pollutants in conduit systems. Effective strategies for the management and protection of karst aquifers, therefore, require an adequate hydrogeological characterisation of the conduit systems. In particular, the identification and characterisation of conduits transmitting rapid, localised recharge to springs is of great interest for vulnerability assessments. In this work, it is demonstrated that localised recharge and conduit flow in a karst aquifer (Urenbrunnen catchment, southwest Germany) can be characterised by jointly analysing the hydraulic and physico-chemical responses of a spring to recharge events. Conduit volumes are estimated by evaluating time lags between increases in spring discharge and associated changes in the electrical conductivity and temperature of the discharged water. These estimates are confirmed by the results of a combined tracer and recharge test. Variations in electrical conductivity are also shown to assist in the quantification of the fast recharge component associated with short-term recharge pulses. However, spectral analysis of temperature fluctuations reveals that highly mineralised surface waters locally infiltrate into the aquifer during the winter and spring without causing significant electrical conductivity variations in the spring water. Hence, the most consistent conceptual model is obtained by a combined analysis of both physico-chemical parameters. | |||||
BibTeX:
@article{Birk2004,
author = {Birk, Steffen and Liedl, Rudolf and Sauter, Martin},
title = {Identification of localised recharge and conduit flow by combined analysis of hydraulic and physico-chemical spring responses (Urenbrunnen, SW-Germany)},
journal = {Journal of Hydrology},
year = {2004},
volume = {286},
number = {1-4},
pages = {179--193},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403003779}
}
|
|||||
| Birkel, C., Dunn, S.M., Tetzlaff, D. and Soulsby, C. | Assessing the value of high-resolution isotope tracer data in the stepwise development of a lumped conceptual rainfall–runoff model | 2010 | Hydrological Processes Vol. 24(16), pp. 2335-2348 |
article | URL |
| Abstract: A study was undertaken in a small agricultural catchment in north east Scotland with the objective of assessing the value of high-resolution isotope data for integration within a lumped, conceptual hydrological model to improve calibration and aid evaluation. Daily samples of precipitation and stream flow, collected over a year, were analysed for deuterium using new laser spectroscopy technology. The utility of such high-resolution isotope data was evaluated in relation to the associated uncertainty which was contextualized in relation to uncertainties over hydrometric data and the influence of different sampling resolutions. The simulations were evaluated against model and data errors using auxiliary stream deuterium time series in addition to discharge. The lumped conceptual catchment isotope model (CIM) was developed and adequately reflects flow dynamics and deuterium peaks, but a simple assumption of ‘good mixing’ is not able to fully reproduce the daily stream deuterium dynamic. Using auxiliary data for model evaluation, however, significantly constrained acceptable behavioural parameter sets and therefore reduces the model's degree of freedom. The data indicate that isotopic variability in the stream response is not adequately captured using weekly tracer data. The input resolution of precipitation deuterium concentrations, which were much more variable, proved to be crucial. This approach has provided further assessment of the value of tracers in hydrological modelling, demonstrating their usefulness in terms of model conceptualization, development and calibration, which outweighs the additional uncertainty. | |||||
BibTeX:
@article{Birkel2010,
author = {Birkel, C. and Dunn, S. M. and Tetzlaff, D. and Soulsby, C.},
title = {Assessing the value of high-resolution isotope tracer data in the stepwise development of a lumped conceptual rainfall–runoff model},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {16},
pages = {2335--2348},
url = {http://dx.doi.org/10.1002/hyp.7763}
}
|
|||||
| Birkel, C., Soulsby, C. and Tetzlaff, D. | Modelling catchment-scale water storage dynamics: reconciling dynamic storage with tracer-inferred passive storage | 2011 | Hydrological Processes Vol. 25(25), pp. 3924-3936 |
article | URL |
| Abstract: We investigate the storage–discharge relationships of two nested (3·6 and 30·4 km2) upland catchments using rainfall–runoff models: (1) a nonlinear discharge sensitivity function and (2) a tracer-constrained process-based conceptual model. Both approaches explicitly acknowledge that water storage is neither time nor space invariant and this provided insight into the respective scaling relationships. Both modelling approaches consistently demonstrated small seasonal storage fluctuations consistent with the wet, cool Scottish climate: the smaller catchment exhibited a greater average dynamic storage (ca 55 mm) compared to the larger scale (ca 40 mm). However, there are differences in simulated storage quantities and ranges inferred from both models, which can largely be explained by model uncertainties and model assumptions. In contrast to the dynamic (active) storage indicated by the rainfall-runoff models, input-output relationships of δ18O in both catchments were used to estimate the passive storage available for mixing and tracer damping in streams. This showed that catchment storage is an order of magnitude greater (ranging from 500 to 900 mm) than the dynamic storage estimated by both models, though again, storage estimates were greater for the smaller catchment. The passive storage inferred for mixing indicates that discussion of dynamic storage revealed by water balance considerations masks a much larger catchment storage which may in turn determine sensitivity to environmental change. | |||||
BibTeX:
@article{Birkel2011,
author = {Birkel, Christian and Soulsby, Chris and Tetzlaff, Doerthe},
title = {Modelling catchment-scale water storage dynamics: reconciling dynamic storage with tracer-inferred passive storage},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {2011},
volume = {25},
number = {25},
pages = {3924--3936},
url = {http://dx.doi.org/10.1002/hyp.8201}
}
|
|||||
| Birkel, C., Soulsby, C., Tetzlaff, D., Dunn, S. and Spezia, L. | High-frequency storm event isotope sampling reveals time-variant transit time distributions and influence of diurnal cycles | 2012 | Hydrological Processes Vol. 26(2), pp. 308-316 |
article | URL |
| Abstract: High-frequency sampling of stable water isotopes in precipitation and stream water during winter and summer storm events was carried out in a 2·3 km2 lowland agricultural catchment. During peak flows of monitored events, the responses of δ2H and δ18O were comparable and inferred the dominance (ca 70%) of ‘old’ pre-event water. Transit Time Distribution (TTD) inferred by a gamma function were fitted (Nash–Sutcliffe = 0·8) and were also similar for δ2H and δ18O. However, the shape (α) and scaling (β) parameters were markedly different for summer and winter events. Consequently, when antecedent wetness was high, mean transit times were in the order of days; when drier, they increased to months. Moreover, while the responses of δ2H and δ18O exhibited similar gradual recovery to pre-event conditions during winter hydrograph recessions, they differed dramatically on summer recessions. Time series analysis showed that δ2H isotope content was correlated with the diurnal cycle of air temperature, suggesting an evaporative fractionation pattern which could be reproduced by a temperature-based first-order autoregressive model. The heavier δ18O isotope showed no evidence for such diurnal variability. The study highlights the utility of high-frequency stable isotope sampling to explore the time-variant nature of TTDs. Furthermore, it shows that the time of sampling in a diurnal cycle may have crucial significance for interpreting stream isotope signatures, particularly δ2H. | |||||
BibTeX:
@article{Birkel2012,
author = {Birkel, Christian and Soulsby, Chris and Tetzlaff, Doerthe and Dunn, Sarah and Spezia, Luigi},
title = {High-frequency storm event isotope sampling reveals time-variant transit time distributions and influence of diurnal cycles},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2012},
volume = {26},
number = {2},
pages = {308--316},
url = {http://dx.doi.org/10.1002/hyp.8210}
}
|
|||||
| Bischoff, K.B. and Levenspiel, O. | Fluid dispersion—generalization and comparison of mathematical models—II comparison of models | 1962 | Chemical Engineering Science Vol. 17(4), pp. 257-264 |
article | URL |
| Abstract: Part I of this paper discussed methods for experimentally finding dispersion coefficients for each of the two important classes of dispersion models. We treated the models as if they were completely separate. Now these models are interrelated and are also related to the more general models which do not assume plug flow and constant values for dispersion coefficients. However, in some cases certain conditions must be satisfied for the relationships between models to hold. The purpose of this paper is to consider these interrelationships and restrictions, thus justifying the use of the simpler models in place of the more cumbersome ones. | |||||
BibTeX:
@article{Bischoff1962,
author = {Bischoff, K. B. and Levenspiel, Octave},
title = {Fluid dispersion—generalization and comparison of mathematical models—II comparison of models},
journal = {Chemical Engineering Science},
year = {1962},
volume = {17},
number = {4},
pages = {257--264},
url = {http://www.sciencedirect.com/science/article/pii/0009250962850040}
}
|
|||||
| Bischoff, K.B. and Levenspiel, O. | Fluid dispersion-generalization and comparison of mathematical models—I generalization of models | 1962 | Chemical Engineering Science Vol. 17(4), pp. 245-255 |
article | URL |
| Abstract: Many models have been used to characterize dispersion of fluids in flowing systems. Some account for both transverse and longitudinal dispersion, while others account for longitudinal dispersion alone. In addition, the variety of experimental tracer methods used to find the parameters of the models makes the resultant analyses seemingly unrelated. | |||||
BibTeX:
@article{Bischoff1962a,
author = {Bischoff, K. B. and Levenspiel, Octave},
title = {Fluid dispersion-generalization and comparison of mathematical models—I generalization of models},
journal = {Chemical Engineering Science},
year = {1962},
volume = {17},
number = {4},
pages = {245--255},
url = {http://www.sciencedirect.com/science/article/pii/0009250962850039}
}
|
|||||
| Bishop, J.W., Montañez, I.P., Gulbranson, E.L. and Brenckle, P.L. | The onset of mid-Carboniferous glacio-eustasy: Sedimentologic and diagenetic constraints, Arrow Canyon, Nevada | 2009 | Palaeogeography, Palaeoclimatology, Palaeoecology Vol. 276(1-4), pp. 217-243 |
article | URL |
| Abstract: The Devonian–Permian Late Paleozoic Ice Age (LPIA) has been considered the longest-lived and most widespread ice age of the past half billion years. However, it is increasingly clear that the LPIA consisted of several discreet icehouse times punctuated by warmer periods of glacial minima. This paper documents the timing and dynamics of a transition between two climate modes: from the greenhouse that characterized most of the Visean (Osagean and Meramecian) to the icehouse that characterized the late Visean and Serpukhovian (Chesterian). This transition is archived in the stratigraphy and early diagenetic history of an equatorial ramp exposed in the Arrow Canyon Range, southeastern Nevada. | |||||
BibTeX:
@article{Bishop2009,
author = {Bishop, James W. and Montañez, Isabel P. and Gulbranson, Erik L. and Brenckle, Paul L.},
title = {The onset of mid-Carboniferous glacio-eustasy: Sedimentologic and diagenetic constraints, Arrow Canyon, Nevada},
journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},
year = {2009},
volume = {276},
number = {1-4},
pages = {217--243},
url = {http://www.sciencedirect.com/science/article/pii/S0031018209000492}
}
|
|||||
| Bishop, K., Seibert, J., Nyberg, L. and Rodhe, A. | Water storage in a till catchment. II: Implications of transmissivity feedback for flow paths and turnover times | 2011 | Hydrological Processes Vol. 25(25), pp. 3950-3959 |
article | URL |
| Abstract: This paper explores the flow paths and turnover times within a catchment characterized by the transmissivity feedback mechanism where there is a strong increase in the saturated hydraulic conductivity towards the soil surface and precipitation inputs saturate progressively more superficial layers of the soil profile. The analysis is facilitated by the correlation between catchment water storage and groundwater levels, which made it possible to model the daily spatial distribution of water storage, both vertically in different soil horizons and horizontally across a 6300-m2 till catchment. Soil properties and episodic precipitation input dynamics, combined with the influence of topographic features, concentrate flow in the horizontal, vertical, and temporal dimensions. Within the soil profile, there was a vertical concentration of lateral flow to superficial soil horizons (upper 30 cm of the soil), where much of the annual flow occurred during runoff episodes. Overland flow from a limited portion of the catchment can contribute to peak flows but is not a necessary condition for runoff episodes. The spatial concentration of flow, and the episodic nature of runoff events, resulted in a strong and spatially structured differentiation of local flow velocities within the catchment. There were large differences in the time spent by the laterally flowing water at different depths, with turnover times of lateral flow across a 1-m-wide soil pedon ranging from under 1 h at 10- to 20-cm depth to a month at 70- to 80-cm depth. In many regards, the hydrology of this catchment appears typical of the hydrology in till soils, which are widespread in Fenno-Scandia. | |||||
BibTeX:
@article{Bishop2011,
author = {Bishop, Kevin and Seibert, Jan and Nyberg, Lars and Rodhe, Allan},
title = {Water storage in a till catchment. II: Implications of transmissivity feedback for flow paths and turnover times},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {2011},
volume = {25},
number = {25},
pages = {3950--3959},
url = {http://dx.doi.org/10.1002/hyp.8355}
}
|
|||||
| Blöcher, G. and Zimmermann, G. | Settle3D—A numerical generator for artificial porous media | 2008 | Computers & Geosciences Vol. 34(12), pp. 1827-1842 |
article | URL |
| Abstract: Reservoir rocks, regardless of what kind (oil-, gas- or water-bearing), are classified by their specific properties. Most rock properties, such as storage, permeability, electric conductivity, heat capacity and so on are determined by laboratory experiments and field tests under different external conditions. Besides temperature, pressure and chemical reactions, also the geometry of the pore space as well as porosity control the specific behaviour of a rock. In most experiments, heterogeneous deformation of the pore space, changes in porosity and inner surface or closing of micro-cracks or pore-throats, cannot be observed directly. To study the dynamic processes behind these changes, we developed the sedimentary tool “Settle3D”. With this software it is possible to generate different clastic rocks in a discrete way, which means that each grain inside this rock can be handled separately. The resulting porous medium can be directly used as import structure for different mechanical, hydraulic and thermal simulations. So the structural information of rocks can be linked to the petrophysical behaviour of porous media. To address these questions, we will present the development as well as the possibilities of “Settle3D”. These include the generation of various 3D grainpacks, handling of input parameters (such as grain size distribution of different materials), sedimentary processes via direct collision procedures and an analysis of the final pore space geometry. | |||||
BibTeX:
@article{Bloecher2008,
author = {Blöcher, G. and Zimmermann, G.},
title = {Settle3D—A numerical generator for artificial porous media},
journal = {Computers & Geosciences},
year = {2008},
volume = {34},
number = {12},
pages = {1827--1842},
url = {http://www.sciencedirect.com/science/article/pii/S0098300408000745}
}
|
|||||
| Bobeck, P. | Henry Darcy in his own words | 2006 | Hydrogeology Journal Vol. 14(6), pp. 998-1004 |
article | URL |
| Abstract: A recently published English translation of the Les Fontaines publiques de la ville de Dijon 1 provides access to Henry Darcy's own words on the importance of water for public sanitation and on questions engineers face in building water supply systems. Written near the end of Darcy's life, the book is a compendium of the water knowledge he had gained over decades and his opinions on these topics reveal his personality. In the 1840s, Darcy built a water supply system to provide water to 120 street fountains for domestic purposes, street washing and firefighting. Surrounded by poverty, Darcy insisted on free water for the poor and on sharing the spring water with towns located along the aqueduct that brought it to Dijon. In the preface to the book, Darcy introduces his experiment on water flow through sand with the modest words “to my knowledge, no one has experimentally demonstrated the laws of water flow through sand.” This article provides a sampling of the book's insights into the personality of this remarkable man. | |||||
BibTeX:
@article{Bobeck2006,
author = {Bobeck, Patricia},
title = {Henry Darcy in his own words},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {6},
pages = {998--1004},
url = {http://dx.doi.org/10.1007/s10040-005-0013-0}
}
|
|||||
| Bobée, B. and Ashkar, F. | The Gamma Family and Derived Distributions Applied in Hydrology [BibTeX] |
1991 | , pp. - | book | |
BibTeX:
@book{Bobée1991,
author = {Bobée, Bernard and Ashkar, Fahim},
title = {The Gamma Family and Derived Distributions Applied in Hydrology},
publisher = {Water Resources Publications},
year = {1991},
pages = {--}
}
|
|||||
| Bolster, C.H., Mills, A.L., Hornberger, G.M. and Herman, J.S. | Effect of surface coatings, grain size, and ionic strength on the maximum attainable coverage of bacteria on sand surfaces | 2001 | Journal of Contaminant Hydrology Vol. 50(3-4), pp. 287-305 |
article | URL |
| Abstract: The injection of bacteria in the subsurface has been identified as a potential method for in situ cleanup of contaminated aquifers. For high bacterial loadings, the presence of previously deposited bacteria can result in decreased deposition rates—a phenomenon known as blocking. Miscible displacement experiments were performed on short sand columns (∼5 cm) to determine how bacterial deposition on positively charged metal-oxyhydroxide-coated sands is affected by the presence of previously deposited bacteria. Approximately 8 pore volumes of a radiolabeled bacterial suspension at a concentration of ∼1×109 cells ml−1 were introduced into the columns followed by a 2-pore-volume flush of cell-free buffer. It was found that the presence of Al- and Fe-coated sand increased both deposition rates and maximum fractional surface coverage of bacteria on the sediment surfaces. The effect of grain size on maximum bacterial retention capacity, however, was not significant. Decreasing ionic strength from 10−1 to 10−2 M KCl resulted in noticeable decreases in sticking efficiency (α) and maximum surface coverage (θmax) for clean silica sand—results consistent with DLVO theory. In columns containing positively charged Al- and Fe-coated sands, however, changes in α and θmax due to decreasing ionic strength were minimal. These findings demonstrate the importance of geochemical controls on the maximum bacterial retention capacity of sands. | |||||
BibTeX:
@article{Bolster2001,
author = {Bolster, Carl H and Mills, Aaron L and Hornberger, George M and Herman, Janet S},
title = {Effect of surface coatings, grain size, and ionic strength on the maximum attainable coverage of bacteria on sand surfaces},
journal = {Journal of Contaminant Hydrology},
year = {2001},
volume = {50},
number = {3-4},
pages = {287--305},
url = {http://www.sciencedirect.com/science/article/pii/S0169772201001061}
}
|
|||||
| Bolster, D., de Anna, P., Benson, D.A. and Tartakovsky, A.M. | Incomplete mixing and reactions with fractional dispersion | 2012 | Advances in Water Resources Vol. 37(0), pp. 86-93 |
article | URL |
| Abstract: A common barrier to accurately predicting the fate of reactive contaminants is accurately describing the role of incomplete mixing. In this paper we develop a stochastic analytical framework for an irreversible kinetic bimolecular reaction in a system with anomalous transport, governed by the fractional advection–dispersion equation (fADE). The classical well-mixed (thermodynamic) solution dictates that the concentration of reactants after an initial transient decreases proportional to t−1. As the system becomes less and less well-mixed, the rate of reaction decreases relative to the thermodynamic solution, at late times scaling with t−1/(2α) instead of t−1, where 1 < α ⩽ 2 is the fractional order of the dispersion term in the fADE. The time at which this transition takes place is derived, giving an indication of the range of validity of the classical (well-mixed) equation. We verify these analytic results using particle-based simulations of random walks and reactions. | |||||
BibTeX:
@article{Bolster2012,
author = {Bolster, Diogo and de Anna, Pietro and Benson, David A. and Tartakovsky, Alexandre M.},
title = {Incomplete mixing and reactions with fractional dispersion},
journal = {Advances in Water Resources},
year = {2012},
volume = {37},
number = {0},
pages = {86--93},
url = {http://www.sciencedirect.com/science/article/pii/S030917081100217X}
}
|
|||||
| Boluda-Botella, N., León, V., Cases, V., Gomis, V. and Prats, D. | Fate of linear alkylbenzene sulfonate in agricultural soil columns during inflow of surfactant pulses | 2010 | Journal of Hydrology Vol. 395(3-4), pp. 141-152 |
article | URL |
| Abstract: The transport and reaction processes of linear alkylbenzene sulfonate (LAS) were characterised in columns of agricultural soil with a constant inflow of irrigation water. A pulse input of commercial LAS was performed with different mixtures of soil and sea sand (0/100%, 25/75% and 50/50%) and a continuous water flow of approximately 0.5 mL/min. LAS homologue retention was favoured at a higher soil rate, due mainly to higher clay and organic matter contents. C10LAS and C11LAS were less retained in soil columns, and were eluted faster and in higher proportion through soil columns than other homologues. C12LAS and C13LAS showed stronger interactions with soil due to their higher sorption capacity, and a lower proportion was eluted than the lightest homologues. In general, sorption of LAS was reversible and significant fractions were desorbed when the LAS input ceased and they were transported to deeper layers in the soil column, especially for short-chain homologues. Longer LAS homologues were eluted from soil columns, but required an elution of >10 pore-volumes. When there was biodegradation in the soil column, >25% of LAS could be removed, reducing percolation to deeper layers. | |||||
BibTeX:
@article{Boluda-Botella2010,
author = {Boluda-Botella, N. and León, V.M. and Cases, V. and Gomis, V. and Prats, D.},
title = {Fate of linear alkylbenzene sulfonate in agricultural soil columns during inflow of surfactant pulses},
journal = {Journal of Hydrology},
year = {2010},
volume = {395},
number = {3-4},
pages = {141--152},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410006153}
}
|
|||||
| Bombach, P., Richnow, H., Kästner, M. and Fischer, A. | Current approaches for the assessment of in situ biodegradation | 2010 | Applied Microbiology and Biotechnology Vol. 86(3), pp. 839-852 |
article | URL |
| Abstract: Considering the high costs and technical difficulties associated with conventional remediation strategies, in situ biodegradation has become a promising approach for cleaning up contaminated aquifers. To verify if in situ biodegradation of organic contaminants is taking place at a contaminated site and to determine if these processes are efficient enough to replace conventional cleanup technologies, a comprehensive characterization of site-specific biodegradation processes is essential. In recent years, several strategies including geochemical analyses, microbial and molecular methods, tracer tests, metabolite analysis, compound-specific isotope analysis, and in situ microcosms have been developed to investigate the relevance of biodegradation processes for cleaning up contaminated aquifers. In this review, we outline current approaches for the assessment of in situ biodegradation and discuss their potential and limitations. We also discuss the benefits of research strategies combining complementary methods to gain a more comprehensive understanding of the complex hydrogeological and microbial interactions governing contaminant biodegradation in the field. | |||||
BibTeX:
@article{Bombach2010,
author = {Bombach, Petra and Richnow, Hans and Kästner, Matthias and Fischer, Anko},
title = {Current approaches for the assessment of in situ biodegradation},
journal = {Applied Microbiology and Biotechnology},
publisher = {Springer Berlin / Heidelberg},
year = {2010},
volume = {86},
number = {3},
pages = {839--852},
url = {http://dx.doi.org/10.1007/s00253-010-2461-2}
}
|
|||||
| Bonacci, O., Pipan, T. and Culver, D. | A framework for karst ecohydrology | 2009 | Environmental Geology Vol. 56(5), pp. 891-900 |
article | URL |
| Abstract: Ecohydrology can be defined as the science of integrating hydrological and biological processes over varied spatial and temporal scales. There exists in karst a strong and direct interaction between the circulation and storage of groundwater and surface water. These fluxes in turn affect the spatial distribution of organisms in these habitats. Because of the fact that the appearance, storage and circulation of water in karstified areas is significantly different from other more homogenous and isotropic terrains, karst ecohydrology should develop original methods and approaches. At the same time, traditional approaches are also very useful. Large karst underground geomorphological patterns occur in many sizes and varieties, ranging from a few meters long or deep to very large, the deepest being deeper than 1 km and longer than hundreds of kilometres. In this article, special attention is paid to ecohydrological functions of karst underground features (caves, pits, conduits, etc.), which play a crucial dual role in (1) hydrology and hydrogeology of water circulation and storage and (2) ecology of many rare and endangered species. Differences in morphology, hydrology, hydrogeology and climate have resulted in a range of different environments, which provide the opportunity for the coexistence of different species. The role of the epikarst and vadose zones, as well as caves in ecohydrological processes, is discussed. The importance of the flood factor in karst ecology is analysed. The aim of this article is to move forward the discussion among different disciplines to promote and develop a conceptual framework for karst ecohydrology. | |||||
BibTeX:
@article{Bonacci2009,
author = {Bonacci, Ognjen and Pipan, Tanja and Culver, David},
title = {A framework for karst ecohydrology},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {56},
number = {5},
pages = {891--900},
url = {http://dx.doi.org/10.1007/s00254-008-1189-0}
}
|
|||||
| Bonacci, O. and Z̆ivaljević, R. | Hydrological explanation of the flow in karst: example of the Crnojevića spring | 1993 | Journal of Hydrology Vol. 146(0), pp. 405-419 |
article | URL |
| Abstract: This paper deals with various methods of solving the complex problems of the hydrological transformation of rainfall into runoff in karst terrains. As an example of a typical karst catchment, the Crnojevića spring, located in deep Dinaric karst, is used to illustrate, explain and solve several hydrological problems in karst. The introduction deals with the geographical, geological and meteorological factors which conditioned a specific system of surface and underground flows, typical for karst terrains. The paper also explains some basic activities related to the identification of such a system. Special attention has been paid to the karst terrain of the Cetinje polje and its flooding, which occurred in February 1986. This flood initiated numerous intensive investigations which made it possible to define the catchment area of Crnojevića spring and the volume of the underground karst reservoir. | |||||
BibTeX:
@article{Bonacci1993,
author = {Bonacci, Ognjen and Z̆ivaljević, Ratomir},
title = {Hydrological explanation of the flow in karst: example of the Crnojevića spring},
journal = {Journal of Hydrology},
year = {1993},
volume = {146},
number = {0},
pages = {405--419},
url = {http://www.sciencedirect.com/science/article/pii/002216949390287J}
}
|
|||||
| Bonilla, F.A., Kleinfelter, N. and Cushman, J.H. | Microfluidic aspects of adhesive microbial dynamics: A numerical exploration of flow-cell geometry, Brownian dynamics, and sticky boundaries | 2007 | Advances in Water Resources Vol. 30(6-7)Biological processes in porous media: From the pore scale to the field, pp. 1680-1695 |
article | URL |
| Abstract: Bacterial adhesion and motility are studied at the pore scale by focusing on two interrelated aspects of transport: wall attachment/detachment (reversible sorption) and the role of convection and pore geometry on adhesion. Motility is also examined through use of Brownian dynamics. Bacteria motility and reversible attachment/detachment are incorporated with a numerical laminar flow solver. Since individual bacteria are modeled, the results apply to low concentrations/coverage. Pore geometries consistent with a microflow cell of variable cross sectional area are used. This exploratory modeling work precedes an ongoing microflow cell experimental study and more detailed Lévy particle models. Adsorption reactions occurring over different time scales are modeled as multimodal distributions with power law tails. Computations show the relative magnitude of bacterial motility to advection controls the average number of collisions against solid walls. Variable cross section in pore geometry changes hydrodynamic conditions for deposition (e.g., variable shear stress). In regions of reduced cross sectional area, the ratio of bacteria motility to average velocity is smaller and results in less collisions and reduced retardation. Additionally, reduced cross sectional area increases both wall shear stress and vorticity which should be considered in adhesive models. While the shear forces acting on a particle deposited at the wall work on a spatial scale of the microbe’s size, adhesive forces may be confined to tens of nanometers. Multimodal adhesion causes the first passage time distributions to have long tails. | |||||
BibTeX:
@article{Bonilla2007,
author = {Bonilla, F. Alejandro and Kleinfelter, Natalie and Cushman, John H.},
title = {Microfluidic aspects of adhesive microbial dynamics: A numerical exploration of flow-cell geometry, Brownian dynamics, and sticky boundaries},
booktitle = {Biological processes in porous media: From the pore scale to the field},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {6-7},
pages = {1680--1695},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001436}
}
|
|||||
| Borghi, A., Renard, P. and Jenni, S. | A pseudo-genetic stochastic model to generate karstic networks | 2012 | Journal of Hydrology Vol. 414-415(0), pp. 516-529 |
article | URL |
| Abstract: In this paper, we present a methodology for the stochastic simulation of 3D karstic conduits accounting for conceptual knowledge about the speleogenesis processes and accounting for a wide variety of field measurements. | |||||
BibTeX:
@article{Borghi2012,
author = {Borghi, Andrea and Renard, Philippe and Jenni, Sandra},
title = {A pseudo-genetic stochastic model to generate karstic networks},
journal = {Journal of Hydrology},
year = {2012},
volume = {414-415},
number = {0},
pages = {516--529},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411008171}
}
|
|||||
| Borghi, A., Renard, P. and Jenni, S. | A pseudo-genetic stochastic model to generate karstic networks | 2012 | Journal of Hydrology Vol. 414--415(0), pp. 516-529 |
article | URL |
| Abstract: In this paper, we present a methodology for the stochastic simulation of 3D karstic conduits accounting for conceptual knowledge about the speleogenesis processes and accounting for a wide variety of field measurements. | |||||
BibTeX:
@article{Borghi2012a,
author = {Borghi, Andrea and Renard, Philippe and Jenni, Sandra},
title = {A pseudo-genetic stochastic model to generate karstic networks},
journal = {Journal of Hydrology},
year = {2012},
volume = {414--415},
number = {0},
pages = {516--529},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411008171}
}
|
|||||
| Bork, J., Berkhoff, S., Bork, S. and Hahn, H. | Using subsurface metazoan fauna to indicate groundwater–surface water interactions in the Nakdong River floodplain, South Korea | 2009 | Hydrogeology Journal Vol. 17(1), pp. 61-75 |
article | URL |
| Abstract: Hydrological interactions between surface water and groundwater (GW) can be described using hydrochemical and biological methods. Surface water–groundwater interactions and their effects on groundwater invertebrate communities were studied in the Nakdong River floodplain in South Korea. Furthermore, the GW-Fauna-Index, a promising new index for assessing the strength of surface-water influence on groundwater, was tested. The influence of surface water on groundwater decreased with increasing depth and distance from the river. While hydrochemistry prevailingly reflected the origin of the waters in the study area (i.e. whether alluvial or from adjacent rock), faunal communities seemed to display an affinity to surface-water intrusion. Fauna reacted quickly to changes in hydrology, and temporal changes in faunal community structure were significantly linked to the hydrological situation in the floodplain. The metazoan faunal community and the GW-Fauna-Index allow a distinction between surface and subsurface waters with varying degrees of exchange. The results indicate that hydrological conditions are reflected by faunal assemblages on a high spatiotemporal resolution, and that surface-water intrusion can be estimated using the GW-Fauna-Index. | |||||
BibTeX:
@article{Bork2009,
author = {Bork, Jörg and Berkhoff, Sven and Bork, Sabine and Hahn, Hans},
title = {Using subsurface metazoan fauna to indicate groundwater–surface water interactions in the Nakdong River floodplain, South Korea},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {61--75},
url = {http://dx.doi.org/10.1007/s10040-008-0374-2}
}
|
|||||
| Bošković, D. and Loebbecke, S. | Modelling of the residence time distribution in micromixers | 2008 | Chemical Engineering Journal Vol. 135, Supplement 1(0)Microreaction Technology IMRET 9: Proceedings of the Ninth International Conference on Microreaction Technology IMRET9 Special Issue, pp. S138-S146 |
article | URL |
| Abstract: A technique for the measurement of the residence time distribution (RTD) in microfluidic devices is presented. The measurements were performed by an input–response technique monitoring a dye tracer concentration spectroscopically at the inlet and outlet of a microfluidic device. The measurement setup ensures the interchangeability of microfluidic devices and thus allows characterising of many different devices containing diverse mixing structures and microchannel geometries. | |||||
BibTeX:
@article{Boskovic2008,
author = {Bošković, D. and Loebbecke, S.},
title = {Modelling of the residence time distribution in micromixers},
booktitle = {Microreaction Technology IMRET 9: Proceedings of the Ninth International Conference on Microreaction Technology IMRET9 Special Issue},
journal = {Chemical Engineering Journal},
year = {2008},
volume = {135, Supplement 1},
number = {0},
pages = {S138--S146},
url = {http://www.sciencedirect.com/science/article/pii/S1385894707005153}
}
|
|||||
| Bosma, W.J.P., Marinussen, M.P. and van der Zee, S.E. | Simulation and areal interpolation of reactive solute transport | 1994 | Geoderma Vol. 62(1-3), pp. 217-231 |
article | URL |
| Abstract: Reactive solute transport in a spatially variable field is studied. Adsorption is assumed to be described by the nonlinear modified Freundlich isotherm with an adsorption coefficient that depends on pH and organic matter content. Assuming spatial variation of pH and organic carbon content, a chemically heterogeneous field is simulated by the generation of a random field of the Freundlich adsorption coefficient. A three-dimensional reference transport calculation is performed with the complete heterogeneous field as input. The effect of the sequence of calculations and interpolations, and of the size of the data set are examined. A CI (calculations before interpolations) and an IC (interpolation followed by calculations) procedure are defined. Attention is focused on the prediction of average solute breakthrough and on the prediction of concentrations at specific locations. The results show that the optimal procedure and data set size depend on the quantity of interest. For the prediction of average behaviour, a smaller data set is sufficient compared with the prediction of concentrations at specific locations. For the calculation of the average solute breakthrough a more efficient IC procedure can be used in combination with the smaller data set. If the concentrations at specific locations in the field are requested, the size of the data set is more significant. However, for relatively small data sets a CI procedure performs better than an IC procedure. | |||||
BibTeX:
@article{Bosma1994,
author = {Bosma, Willem Jan P. and Marinussen, Mari P.J.C. and van der Zee, Sjoerd E.A.T.M.},
title = {Simulation and areal interpolation of reactive solute transport},
journal = {Geoderma},
year = {1994},
volume = {62},
number = {1-3},
pages = {217--231},
url = {http://www.sciencedirect.com/science/article/pii/001670619490037X}
}
|
|||||
| Bothe, D., Lojewski, A. and Warnecke, H.-J. | Fully resolved numerical simulation of reactive mixing in a T-shaped micromixer using parabolized species equations | 2011 | Chemical Engineering Science Vol. 66(24)Novel Gas Conversion Symposium- Lyon 2010, C1-C4 Catalytic Processes for the Production of Chemicals and Fuels, pp. 6424-6440 |
article | URL |
| Abstract: This paper introduces and exploits a hybrid numerical approach for fully resolved numerical simulations of reactive mixing in T-shaped microreactors and thereby enables a computational analysis of how chemical reactions interact with convective and diffusive transport. The approach exploits the fast redirection of the flow inside the mixing channel, resulting in a flow field with positive axial flow component everywhere after a short entry zone. This allows handling the axial flow direction as a pseudo-time variable, so that the evolution of the concentration profile can be computed consecutively on successive cross sections, following the main axial flow direction. With this approach the finest length scales, given by the Batchelor length scale, can be resolved for such a reactive mixing process inside a T-microreactor at stationary flow conditions. This allows for a detailed analysis of the mixing state as well as important characteristics of the reactive mixing process like yield and selectivity. The concrete numerical simulations yield local diffusion times inside the reactor, reveal the influence of the strength of the secondary flow on the progress of the chemical reaction and show how local selectivities result from the species transport. | |||||
BibTeX:
@article{Bothe2011,
author = {Bothe, Dieter and Lojewski, Alexander and Warnecke, Hans-Joachim},
title = {Fully resolved numerical simulation of reactive mixing in a T-shaped micromixer using parabolized species equations},
booktitle = {Novel Gas Conversion Symposium- Lyon 2010, C1-C4 Catalytic Processes for the Production of Chemicals and Fuels},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {24},
pages = {6424--6440},
url = {http://www.sciencedirect.com/science/article/pii/S0009250911006142}
}
|
|||||
| Bottacin-Busolin, A., Marion, A., Musner, T., Tregnaghi, M. and Zaramella, M. | Evidence of distinct contaminant transport patterns in rivers using tracer tests and a multiple domain retention model | 2011 | Advances in Water Resources Vol. 34(6), pp. 737-746 |
article | URL |
| Abstract: Solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges with distinct retention zones. Surface and hyporheic retention processes can be accounted for separately in solute transport models with multiple storage compartments. In the simplest two component model, short term storage can be associated to in-channel transient retention, e.g. produced by riparian vegetation or surface dead zones, and the long-term storage can be associated to hyporheic exchange. The STIR (Solute Transport In Rivers) multiple domain transport model is applied here to tracer test data from three very different Mediterranean streams with distinctive characteristics in terms of flow discharge, vegetation and substrate material. The model is used with an exponential residence time distribution (RTD) to represent surface storage processes and two distinct modeling closures are tested to simulate hyporheic retention: a second exponential RTD and a power-law distribution approximating a known solution for bedform-induced hyporheic exchange. Each stream shows distinct retention patterns characterized by different timescales of the storage time distribution. Both modeling closures lead to very good approximations of the observed breakthrough curves in the two rivers with permeable bed exposed to the flow, where hyporheic flows are expected to occur. In the one case where the occurrence of hyporheic flows is inhibited by bottom vegetation, only the two exponential RTD model is acceptable and the time scales of the two components are of the same magnitude. The significant finding of this work is the recognition of a strong signature of the river properties on tracer data and the evidence of the ability of multiple-component models to describe individual stream responses. This evidence may open a new perspective in river contamination studies, where rivers could possibly be classified based on their ability to trap and release pollutants. | |||||
BibTeX:
@article{Bottacin-Busolin2011,
author = {Bottacin-Busolin, Andrea and Marion, Andrea and Musner, Tommaso and Tregnaghi, Matteo and Zaramella, Mattia},
title = {Evidence of distinct contaminant transport patterns in rivers using tracer tests and a multiple domain retention model},
journal = {Advances in Water Resources},
year = {2011},
volume = {34},
number = {6},
pages = {737--746},
url = {http://www.sciencedirect.com/science/article/pii/S0309170811000546}
}
|
|||||
| Bouchard, D., Wood, A., Campbell, M., Nkedi-Kizza, P. and Rao, P. | Sorption nonequilibrium during solute transport | 1988 | Journal of Contaminant Hydrology Vol. 2(3), pp. 209-223 |
article | URL |
| Abstract: The effects of pore-water velocity, solute hydrophobicity, and sorbent organic-carbon content on sorption nonequilibrium during solute transport were evaluated. Nonequilibrium transport was observed to increase with pore-water velocity, solute hydrophobicity, and sorbent organic-carbon content. Nonequilibrium transport of neutral organic compounds was not detected with low organic-carbon (TOC = 0.33 g kg−1) aquifer material, but was detected on higher organic sorbents from the unsaturated zone (TOC = 2.6 g kg−1) and the soil surface (TOC = 6.9 g kg−1). For solute-sorbent combinations yielding retardation factors > 2, nonequilibrium during transport was observed. After experimentally accounting for slow solute diffusion in the aqueous phase and isotherm nonlinearity as potential contributors to nonequilibrium solute transport, sorption nonequilibrium was attributed to slow solute diffusion within the organic-carbon matrix. | |||||
BibTeX:
@article{Bouchard1988,
author = {Bouchard, D.C and Wood, A.L and Campbell, M.L and Nkedi-Kizza, P and Rao, P.S.C},
title = {Sorption nonequilibrium during solute transport},
journal = {Journal of Contaminant Hydrology},
year = {1988},
volume = {2},
number = {3},
pages = {209--223},
url = {http://www.sciencedirect.com/science/article/pii/0169772288900228}
}
|
|||||
| Boucot, A. and Gray, J. | A critique of Phanerozoic climatic models involving changes in the CO2 content of the atmosphere | 2001 | Earth-Science Reviews Vol. 56(1-4), pp. 1-159 |
article | URL |
| Abstract: Critical consideration of varied Phanerozoic climatic models, and comparison of them against Phanerozoic global climatic gradients revealed by a compilation of Cambrian through Miocene climatically sensitive sediments (evaporites, coals, tillites, lateritic soils, bauxites, calcretes, etc.) suggests that the previously postulated climatic models do not satisfactorily account for the geological information. Nor do many climatic conclusions based on botanical data stand up very well when examined critically. Although this account does not deal directly with global biogeographic information, another powerful source of climatic information, we have tried to incorporate such data into our thinking wherever possible, particularly in the earlier Paleozoic. In view of the excellent correlation between CO2 present in Antarctic ice cores, going back some hundreds of thousands of years, and global climatic gradient, one wonders whether or not the commonly postulated Phanerozoic connection between atmospheric CO2 and global climatic gradient is more coincidence than cause and effect. | |||||
BibTeX:
@article{Boucot2001,
author = {Boucot, A.J. and Gray, Jane},
title = {A critique of Phanerozoic climatic models involving changes in the CO2 content of the atmosphere},
journal = {Earth-Science Reviews},
year = {2001},
volume = {56},
number = {1-4},
pages = {1--159},
url = {http://www.sciencedirect.com/science/article/pii/S0012825201000666}
}
|
|||||
| Boufadel, M.C., Xia, Y. and Li, H. | Modeling solute transport and transient seepage in a laboratory beach under tidal influence | 2011 | Environmental Modelling & Software Vol. 26(7), pp. 899-912 |
article | URL |
| Abstract: This paper explored numerical techniques to simulate the movement of an applied tracer plume in a laboratory beach subjected to tide. The MARUN model (Boufadel et al., 1999) was used. The movement of the tracer plume in the beach and the development of a transient seepage on the beach surface were modeled. By calibrating the results of the numerical model against the observed data, the laboratory beach was found to have two different zones: a top layer (thickness 9–17 cm) with a saturated hydraulic conductivity, K0, of 0.2 cm/s and a lower layer with a K0 of 0.12 cm/s. The simulations revealed that the plume moved seaward during falling tides and downward during rising tides, which is consistent with previous studies. It was also observed that the plume developed a tail that extended in the landward direction, and a freshwater pool became entrapped between the main plume and its extended tail. | |||||
BibTeX:
@article{Boufadel2011,
author = {Boufadel, Michel C. and Xia, Yuqiang and Li, Hailong},
title = {Modeling solute transport and transient seepage in a laboratory beach under tidal influence},
journal = {Environmental Modelling & Software},
year = {2011},
volume = {26},
number = {7},
pages = {899--912},
url = {http://www.sciencedirect.com/science/article/pii/S1364815211000326}
}
|
|||||
| Bouguila, N., Almakadmeh, K. and Boutemedjet, S. | A finite mixture model for simultaneous high-dimensional clustering, localized feature selection and outlier rejection | 2012 | Expert Systems with Applications Vol. 39(7), pp. 6641-6656 |
article | URL |
| Abstract: Model-based approaches and in particular finite mixture models are widely used for data clustering which is a crucial step in several applications of practical importance. Indeed, many pattern recognition, computer vision and image processing applications can be approached as feature space clustering problems. For complex high-dimensional data, however, the use of these approaches presents several challenges such as the presence of many irrelevant features which may affect the speed and also compromise the accuracy of the used learning algorithm. Another problem is the presence of outliers which potentially influence the resulting model’s parameters. For this purpose, we propose and discuss an algorithm that partitions a given data set without a priori information about the number of clusters, the saliency of the features or the number of outliers. We illustrate the performance of our approach using different applications involving synthetic data, real data and objects shape clustering. | |||||
BibTeX:
@article{Bouguila2012,
author = {Bouguila, Nizar and Almakadmeh, Khaled and Boutemedjet, Sabri},
title = {A finite mixture model for simultaneous high-dimensional clustering, localized feature selection and outlier rejection},
journal = {Expert Systems with Applications},
year = {2012},
volume = {39},
number = {7},
pages = {6641--6656},
url = {http://www.sciencedirect.com/science/article/pii/S095741741101709X}
}
|
|||||
| Boyce, G. | The social relevance of ethics education in a global(ising) era: From individual dilemmas to systemic crises | 2008 | Critical Perspectives on Accounting Vol. 19(2)Chinese Learning, pp. 255-290 |
article | URL |
| Abstract: Ethics in accounting and business education must be considered in the contemporary context of neoliberal economic globalisation. Official responses to corporate scandals have included new laws and regulations, and some have argued that these scandals illustrate the need for change at an individual level, but this paper argues that the problem is manifested at a system level and that greater attention must be paid to the wider economic and social system within which individuals operate. | |||||
BibTeX:
@article{Boyce2008,
author = {Boyce, Gordon},
title = {The social relevance of ethics education in a global(ising) era: From individual dilemmas to systemic crises},
booktitle = {Chinese Learning},
journal = {Critical Perspectives on Accounting},
year = {2008},
volume = {19},
number = {2},
pages = {255--290},
url = {http://www.sciencedirect.com/science/article/pii/S1045235406001079}
}
|
|||||
| Boyce, G. | Critical accounting education: teaching and learning outside the circle | 2004 | Critical Perspectives on Accounting Vol. 15(4-5)A Critical Response to Managerialism in the Academy, pp. 565-586 |
article | URL |
| Abstract: The development of the corporate university is an element in the suite of “economically rational” public policy changes promulgated in recent decades. Working from a position that the practice of accounting is centrally implicated in these changes, it is contended in this paper that accounting, and accounting education, can in fact play a part in challenging these positions. Extant accounting research is sufficiently well-developed such that we are aware of the conflicts and contradictions both within accounting and flowing from the practice of the discipline, yet the effect of this body of knowledge on the content of teaching and learning within the accounting classroom remains limited. By and large, accounting education continues to be constrained within narrowly defined, but mis-conceived, disciplinary boundaries, focusing on the techniques and “skills” of accounting practice. | |||||
BibTeX:
@article{Boyce2004,
author = {Boyce, Gordon},
title = {Critical accounting education: teaching and learning outside the circle},
booktitle = {A Critical Response to Managerialism in the Academy},
journal = {Critical Perspectives on Accounting},
year = {2004},
volume = {15},
number = {4-5},
pages = {565--586},
url = {http://www.sciencedirect.com/science/article/pii/S1045235403000479}
}
|
|||||
| Brander, L., Brouwer, R. and Wagtendonk, A. | Economic valuation of regulating services provided by wetlands in agricultural landscapes: A meta-analysis | 2013 | Ecological Engineering Vol. 56(0)Bringing Together Science and Policy to Protect and Enhance Wetland Ecosystem Services in Agricultur, pp. 89-96 |
article | URL |
| Abstract: This paper presents a meta-analysis of the economic valuation literature on ecosystem services provided by wetlands in agricultural landscapes. We focus on the value of three regulating services, namely flood control, water supply and nutrient recycling. We construct a database containing 66 value estimates, mainly for wetlands in the US and Europe but also a substantial number in developing countries. Values are standardised to USD per hectare per year. The mean (median) values are found to be 6923 (427) USD/ha/yr for flood control; 3389 (57) USD/ha/yr for water supply; and 5788 (243) USD/ha/yr for nutrient recycling. The values of these services are highly variable across individual wetland sites due to, amongst other factors, differences in wetland type, size, the scarcity or abundance of other wetlands in the surrounding landscape, and the socio-economic characteristics of the beneficiaries of these services. We include explanatory variables in the meta-analysis to account for these influences on estimated wetland values. GIS is used to quantify potentially important spatial variables. The meta-regression is used to produce a value function for wetland regulating services, which can be used to transfer values to other wetland sites while controlling for site and context specific characteristics. An illustrative value transfer exercise is conducted to estimate global values for wetland regulating services in agricultural landscapes. | |||||
BibTeX:
@article{Brander2013,
author = {Brander, Luke and Brouwer, Roy and Wagtendonk, Alfred},
title = {Economic valuation of regulating services provided by wetlands in agricultural landscapes: A meta-analysis},
booktitle = {Bringing Together Science and Policy to Protect and Enhance Wetland Ecosystem Services in Agricultur},
journal = {Ecological Engineering},
year = {2013},
volume = {56},
number = {0},
pages = {89--96},
url = {http://www.sciencedirect.com/science/article/pii/S0925857412004661}
}
|
|||||
| Brawn, D. and Upton, G. | Estimation of an atmospheric gamma drop size distribution using disdrometer data | 2008 | Atmospheric Research Vol. 87(1), pp. 66-79 |
article | URL |
| Abstract: Atmospheric raindrop size distributions are believed to be often well approximated by gamma distributions. However, since disdrometers cannot measure the numbers of very small drops, the parameters of these distributions must be estimated from information concerning a truncated form of the distribution. Although simple formulae connect the moments of an untruncated gamma distribution, when these formulae are applied to a truncated distribution they give parameter estimates that are both biased and imprecise. In this paper we present a new method that, while utilising relations between moments, also takes account of the truncation. The resulting estimates are simple functions of the observed data. Using simulated data, and also using data from impact and optical disdrometers, the new method is compared with four moment-based methods. The results show the new method to be very reliable, giving estimates that are nearly unbiased and that are much less variable than those obtained using the moment methods. | |||||
BibTeX:
@article{Brawn2008,
author = {Brawn, Dan and Upton, Graham},
title = {Estimation of an atmospheric gamma drop size distribution using disdrometer data},
journal = {Atmospheric Research},
year = {2008},
volume = {87},
number = {1},
pages = {66--79},
url = {http://www.sciencedirect.com/science/article/pii/S0169809507001238}
}
|
|||||
| Brezonik, P.L. and Stadelmann, T.H. | Analysis and predictive models of stormwater runoff volumes, loads, and pollutant concentrations from watersheds in the Twin Cities metropolitan area, Minnesota, USA | 2002 | Water Research Vol. 36(7), pp. 1743-1757 |
article | URL |
| Abstract: Urban nonpoint source pollution is a significant contributor to water quality degradation. Watershed planners need to be able to estimate nonpoint source loads to lakes and streams if they are to plan effective management strategies. To meet this need for the twin cities metropolitan area, a large database of urban and suburban runoff data was compiled. Stormwater runoff loads and concentrations of 10 common constituents (six N and P forms, TSS, VSS, COD, Pb) were characterized, and effects of season and land use were analyzed. Relationships between runoff variables and storm and watershed characteristics were examined. The best regression equation to predict runoff volume for rain events was based on rainfall amount, drainage area, and percent impervious area (R2=0.78). Median event-mean concentrations (EMCs) tended to be higher in snowmelt runoff than in rainfall runoff, and significant seasonal differences were found in yields (kg/ha) and EMCs for most constituents. Simple correlations between explanatory variables and stormwater loads and EMCs were weak. Rainfall amount and intensity and drainage area were the most important variables in multiple linear regression models to predict event loads, but uncertainty was high in models developed with the pooled data set. The most accurate models for EMCs generally were found when sites were grouped according to common land use and size. | |||||
BibTeX:
@article{Brezonik2002,
author = {Brezonik, Patrick L and Stadelmann, Teresa H},
title = {Analysis and predictive models of stormwater runoff volumes, loads, and pollutant concentrations from watersheds in the Twin Cities metropolitan area, Minnesota, USA},
journal = {Water Research},
year = {2002},
volume = {36},
number = {7},
pages = {1743--1757},
url = {http://www.sciencedirect.com/science/article/pii/S004313540100375X}
}
|
|||||
| Bridges, T.C. and Haan, C.T. | Reliability of Precipitation Probabilities Estimated From the Gamma Distribution | 1972 | Monthly Weather Review Vol. 100(8), pp. 607-611 |
article | URL |
| Abstract: A technique is developed for evaluating the reliability of precipitation estimates determined by using the gamma distribution. Tables are presented showing the probabilities of errors of various magnitudes in precipitation estimates as a function of record length for selected cases. | |||||
BibTeX:
@article{Bridges1972,
author = {Bridges, T. C. and Haan, C. T.},
title = {Reliability of Precipitation Probabilities Estimated From the Gamma Distribution},
journal = {Monthly Weather Review},
publisher = {American Meteorological Society},
year = {1972},
volume = {100},
number = {8},
pages = {607--611},
url = {http://dx.doi.org/10.1175/1520-0493(1972)100<0607:ROPPEF>2.3.CO;2}
}
|
|||||
| Briens, C., Margaritis, A. and Wild, G. | A new stochastic model and measurement errors in residence time distributions of multiphase reactors | 1995 | Chemical Engineering Science Vol. 50(2), pp. 279-287 |
article | URL |
| Abstract: Residence time distributions are required for modeling, design and optimization of chemical and biochemical multiphase reactors. Most models either cannot discriminate between true backmixing and a spread in fluid velocity or they require a large number of empirical parameters. A new stochastic model can make this discrimination with only three parameters. Extensive calculations demonstrated that most tracer experiments performed with “open” boundary conditions yield residence time distributions which are even more erroneous than previously thought. | |||||
BibTeX:
@article{Briens1995,
author = {Briens, C.L. and Margaritis, A. and Wild, G.},
title = {A new stochastic model and measurement errors in residence time distributions of multiphase reactors},
journal = {Chemical Engineering Science},
year = {1995},
volume = {50},
number = {2},
pages = {279--287},
url = {http://www.sciencedirect.com/science/article/pii/000925099400240R}
}
|
|||||
| Brooks, M.C. and Wise, W.R. | Quantifying uncertainty due to random errors for moment analyses of breakthrough curves | 2005 | Journal of Hydrology Vol. 303(1-4), pp. 165-175 |
article | URL |
| Abstract: The uncertainty in moments calculated from breakthrough curves (BTCs) is investigated as a function of random measurement errors in the data used to define the BTCs. The method presented assumes moments are calculated by numerical integration using the trapezoidal rule, and is theoretically applicable to moments of any order. Moreover, the method is applicable to either temporal or volumetric moments, and in the latter case, explicitly accounts for errors in volume measurements. The complexity of the calculations for the zeroth moment is comparable to that associated with the typical propagation-of-errors formula based on a Taylor series expansion. However, the formulae for higher moments are substantially more complex than the typical propagation-of-errors formula. For the zeroth and normalized first moments, moment uncertainties are more sensitive to random errors in concentration measurements compared to random errors in volume measurements. The robust nature of moment calculations is exemplified by the fact that relative uncertainty in moments is less than the relative error in volume and concentration measurements. Furthermore, moment uncertainty decreases as more data points are collected to define the BTC. For a BTC (based upon the solution to the one-dimensional advective-dispersion equation with a Peclet number of 10) with 100 data points, the zeroth moment and normalized first moment coefficient of variations are approximately 6 and 2%, respectively, for concentration coefficient of variation equal to 25% over a range of volume errors. | |||||
BibTeX:
@article{Brooks2005,
author = {Brooks, Michael C. and Wise, William R.},
title = {Quantifying uncertainty due to random errors for moment analyses of breakthrough curves},
journal = {Journal of Hydrology},
year = {2005},
volume = {303},
number = {1-4},
pages = {165--175},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404003968}
}
|
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| Brovelli, A., Carranza-Diaz, O., Rossi, L. and Barry, D. | Design methodology accounting for the effects of porous medium heterogeneity on hydraulic residence time and biodegradation in horizontal subsurface flow constructed wetlands | 2011 | Ecological Engineering Vol. 37(5)Advances in pollutant removal processes and fate in natural and constructed wetlands, pp. 758-770 |
article | URL |
| Abstract: Horizontal flow constructed wetlands are engineered systems capable of eliminating a wide range of pollutants from the aquatic environment. Nevertheless, poor hydrodynamic behavior is commonly found resulting in preferential pathways and variations in both (i) the hydraulic residence time distribution (HRTD) and, consequently, (ii) the wetland's treatment efficiency. The aim of this work was to outline a methodology for wetland design that accounts for the effect of heterogeneous hydraulic properties of the porous substrate on the HRTD and treatment efficiency. Biodegradation of benzene was used to illustrate the influence of hydraulic conductivity heterogeneity on wetland efficiency. Random, spatially correlated hydraulic conductivity fields following a log-normal distribution were generated and then introduced in a subsurface flow numerical model. The results showed that the variance of the distribution and the correlation length in the longitudinal direction are key indicators of the extent of heterogeneity. A reduction of the mean hydraulic residence time was observed as the extent of heterogeneity increased, while the HRTD became broader with increased skewness. At the same time, substrate heterogeneity induced preferential flow paths within the wetland bed resulting in variations of the benzene treatment efficiency. Further to this it was observed that the distribution of biomass within the porous bed became heterogeneous, rising questions on the representativeness of sampling. It was concluded that traditional methods for wetland design based on assumptions such as a homogeneous porous medium and plug flow are not reliable. The alternative design methodology presented here is based on the incorporation of heterogeneity directly during the design phase. The same methodology can also be used to optimize existing systems, where the HRTD has been characterized with tracer experiments. | |||||
BibTeX:
@article{Brovelli2011,
author = {Brovelli, A. and Carranza-Diaz, O. and Rossi, L. and Barry, D.A.},
title = {Design methodology accounting for the effects of porous medium heterogeneity on hydraulic residence time and biodegradation in horizontal subsurface flow constructed wetlands},
booktitle = {Advances in pollutant removal processes and fate in natural and constructed wetlands},
journal = {Ecological Engineering},
year = {2011},
volume = {37},
number = {5},
pages = {758--770},
url = {http://www.sciencedirect.com/science/article/pii/S0925857410001382}
}
|
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| Bruderer-Weng, C., Cowie, P., Bernabé, Y. and Main, I. | Relating flow channelling to tracer dispersion in heterogeneous networks | 2004 | Advances in Water Resources Vol. 27(8), pp. 843-855 |
article | URL |
| Abstract: Flow channelling is a well-documented phenomenon in heterogeneous porous media and is widely recognised to have a substantial effect on solute transport. The goal of this study is to quantify flow channelling in heterogeneous, two-dimensional, pipe networks and to investigate its relation with dispersion. We explored the effect of pore size heterogeneity and correlation length by, respectively, varying the normalised standard deviation of the pipe diameter distribution and imposing an exponential variogram to their spatial distribution. By solving the flow equations, we obtained a complete description of the volumetric flow and pressure gradient fields in each network realisation. Both fields displayed lineations but their preferential directions were roughly perpendicular to each other. We estimated their multifractal dimension spectra and showed that the correlation dimension was a reliable quantitative indicator of flow channelling. We then simulated solute dispersion in these networks using a previously published method. We observed that flow channelling corresponded to an increase of the asymptotic dispersion coefficient and a lengthening of the pre-asymptotic period. We conclude at the existence of a strong, but not exactly one-to-one, relation between the asymptotic longitudinal dispersion coefficients and the correlation dimension of the flow field. | |||||
BibTeX:
@article{Bruderer-Weng2004,
author = {Bruderer-Weng, Céline and Cowie, Patience and Bernabé, Yves and Main, Ian},
title = {Relating flow channelling to tracer dispersion in heterogeneous networks},
journal = {Advances in Water Resources},
year = {2004},
volume = {27},
number = {8},
pages = {843--855},
url = {http://www.sciencedirect.com/science/article/pii/S030917080400079X}
}
|
|||||
| Brusseau, M.L. | Non-ideal transport of reactive solutes in heterogeneous porous media: 3. model testing and data analysis using calibration versus prediction | 1998 | Journal of Hydrology Vol. 209(1-4), pp. 147-165 |
article | DOI URL |
| Abstract: The transport of reactive solutes is often influenced by multiple factors and processes. Complex mathematical models accounting for these multiple factors and processes are required to simulate accurately the transport of reactive solutes. There are numerous concerns and constraints associated with the application of mathematical models to the transport of reactive solutes, especially for field-scale problems. The specific issue of using calibration (fitting a model to measured data) for model evaluation and data analysis was examined in this paper. Selected laboratory data, as well as the results of the well-known Borden natural-gradient field experiment were used as case studies to illustrate the potential pitfalls of using model calibration for the analysis of reactive solute transport. It is shown that erroneous parameter values can be obtained from calibration if all significant transport factors are not properly represented. Perhaps of greater significance, the (mis)use of calibration can lead to a mistaken belief that the model accurately represents the physical system and, hence, result in a misinterpretation of the factors controlling solute transport. | |||||
BibTeX:
@article{Brusseau1998,
author = {Brusseau, Mark L.},
title = {Non-ideal transport of reactive solutes in heterogeneous porous media: 3. model testing and data analysis using calibration versus prediction},
journal = {Journal of Hydrology},
year = {1998},
volume = {209},
number = {1-4},
pages = {147--165},
url = {http://www.sciencedirect.com/science/article/pii/S0022169498001218},
doi = {http://dx.doi.org/10.1016/S0022-1694(98)00121-8}
}
|
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| Brusseau, M.L. | The effect of nonlinear sorption on transformation of contaminants during transport in porous media | 1995 | Journal of Contaminant Hydrology Vol. 17(4), pp. 277-291 |
article | URL |
| Abstract: The transport of contaminants through porous media is influenced by several processes, two of the most important being sorption and transformation. Several mathematical models have been developed to investigate the effects of sorption and transformation on contaminant transport. Almost all of these models are based on the assumption of linear sorption. However, it is well known that sorption of reactive contaminants is often nonlinear. A mathematical model that describes the transport of solute undergoing nonlinear, rate-limited sorption and first-order transformation is used to investigate the effect of coupled transformation and non-linear sorption on contaminant transport. Results of the analyses show that a model based on linear sorption cannot provide an accurate simulation of the transformation and transport of nonlinearly sorbing solutes when n is less than ∼0.9. In addition, the relative impact of non-linear sorption on solute transport is mediated by the magnitude of transformation. The nondimensional time required for a specified fraction of solute mass to be transformed during transport is influenced by nonlinear sorption. These examples illustrate the intriguing effects that coupled processes can have on contaminant transport and which may be important for many contaminants of interest. | |||||
BibTeX:
@article{Brusseau1995,
author = {Brusseau, Mark L.},
title = {The effect of nonlinear sorption on transformation of contaminants during transport in porous media},
journal = {Journal of Contaminant Hydrology},
year = {1995},
volume = {17},
number = {4},
pages = {277--291},
url = {http://www.sciencedirect.com/science/article/pii/016977229400041F}
}
|
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| Brusseau, M.L. and Srivastava, R. | Nonideal transport of reactive solutes in heterogeneous porous media 2. Quantitative analysis of the Borden natural-gradient field experiment | 1997 | Journal of Contaminant Hydrology Vol. 28(1-2), pp. 115-155 |
article | DOI URL |
| Abstract: Field experiments constitute an integral component of research on transport and fate of contaminants in the subsurface. One of the most well known of the few field experiments performed with reactive solutes is the natural-gradient experiment conducted at the Borden site during 1982 to 1984. A major finding of the experiment was that the transport of the reactive, organic compounds was nonideal. First, the velocities of the centers of mass of the plumes decreased with time, which was reflected in a temporal increase in effective retardation. Second, the longitudinal spreading observed for the organic solutes was about three times larger than that of the nonreactive tracers for an equivalent travel distance. Third, the breakthrough curves measured at selected monitoring points exhibited greater asymmetry compared to the nonreactive tracers. The cause(s) of the nonideal transport observed for the organic solutes has remained unexplained, despite a number of attempts. We have used a multi-scale, multi-factor mathematical model to successfully predict the displacement and spreading behavior of the tetrachloroethene and tetrachloromethane plumes. Based on our analyses, we conclude that a near-field trend of increasing sorption capacity was a primary cause of the deceleration of the centers of mass of the organic-solute plumes. The coupled effects of nonlinear sorption and enhanced spreading caused by spatially variable hydraulic conductivity and spatially variable sorption also influenced plume displacement. In addition, it is possible that the combination of spatially variable hydraulic conductivity and sorption contributed directly to plume deceleration. However, a magnitude of sorption variability larger than has been measured to date is required for this contribution to be significant. The combined spatial variability of hydraulic conductivity and sorption, and a potential negative cross correlation between them, appears to have been the major cause of the enhanced longitudinal spreading observed for the organic-solute plumes in comparison to the nonreactive-solute plumes. However, nonlinear sorption, the spatial trend of increasing sorption capacity, and rate-limited sorption/mass transfer also influenced spreading behavior. In total, it is evident that the transport of the organic compounds during the Borden natural-gradient field experiment was influenced by several interacting factors and coupled processes, and that accurate prediction of the observed behavior requires the use of a mathematical model that accounts for this complexity. | |||||
BibTeX:
@article{Brusseau1997,
author = {Brusseau, Mark L. and Srivastava, Rajesh},
title = {Nonideal transport of reactive solutes in heterogeneous porous media 2. Quantitative analysis of the Borden natural-gradient field experiment},
journal = {Journal of Contaminant Hydrology},
year = {1997},
volume = {28},
number = {1-2},
pages = {115--155},
url = {http://www.sciencedirect.com/science/article/pii/S0169772297000363},
doi = {http://dx.doi.org/10.1016/S0169-7722(97)00036-3}
}
|
|||||
| Buckley, R., Loyalka, S. and Williams, M. | Numerical studies of solute transport in a fractured medium subject to near- and non-equilibrium mass transfer | 1995 | Annals of Nuclear Energy Vol. 22(7), pp. 453-469 |
article | URL |
| Abstract: Numerical investigations of solute transport in a fractured medium consisting of a plane fracture surrounded by a rock matrix are conducted. The transport in the liquids is described by advection-diffusion equations, while the boundary interactions within the rock matrix are modeled by use of isotherms. Near-equilibrium and non-equilibrium conditions are considered, and computations are carried out for a wide range of rock matrix and interaction parameters. We find that if the solute travel time is much greater than the time constant governing the rate of adsorption-desorption occurring in the rock matrix, near-equilibrium conditions may be assumed. However, if the travel time is comparable to the time constant, then the non-equilibrium considerations are important. | |||||
BibTeX:
@article{Buckley1995,
author = {Buckley, R.L. and Loyalka, S.K. and Williams, M.M.R.},
title = {Numerical studies of solute transport in a fractured medium subject to near- and non-equilibrium mass transfer},
journal = {Annals of Nuclear Energy},
year = {1995},
volume = {22},
number = {7},
pages = {453--469},
url = {http://www.sciencedirect.com/science/article/pii/030645499400072M}
}
|
|||||
| Burnett, W., Aggarwal, P., Aureli, A., Bokuniewicz, H., Cable, J., Charette, M., Kontar, E., Krupa, S., Kulkarni, K., Loveless, A., Moore, W., Oberdorfer, J., Oliveira, J., Ozyurt, N., Povinec, P., Privitera, A., Rajar, R., Ramessur, R., Scholten, J., Stieglitz, T., Taniguchi, M. and Turner, J. | Quantifying submarine groundwater discharge in the coastal zone via multiple methods | 2006 | Science of The Total Environment Vol. 367(2-3), pp. 498-543 |
article | URL |
| Abstract: Submarine groundwater discharge (SGD) is now recognized as an important pathway between land and sea. As such, this flow may contribute to the biogeochemical and other marine budgets of near-shore waters. These discharges typically display significant spatial and temporal variability making assessments difficult. Groundwater seepage is patchy, diffuse, temporally variable, and may involve multiple aquifers. Thus, the measurement of its magnitude and associated chemical fluxes is a challenging enterprise. | |||||
BibTeX:
@article{Burnett2006,
author = {Burnett, W.C. and Aggarwal, P.K. and Aureli, A. and Bokuniewicz, H. and Cable, J.E. and Charette, M.A. and Kontar, E. and Krupa, S. and Kulkarni, K.M. and Loveless, A. and Moore, W.S. and Oberdorfer, J.A. and Oliveira, J. and Ozyurt, N. and Povinec, P. and Privitera, A.M.G. and Rajar, R. and Ramessur, R.T. and Scholten, J. and Stieglitz, T. and Taniguchi, M. and Turner, J.V.},
title = {Quantifying submarine groundwater discharge in the coastal zone via multiple methods},
journal = {Science of The Total Environment},
year = {2006},
volume = {367},
number = {2-3},
pages = {498--543},
url = {http://www.sciencedirect.com/science/article/pii/S0048969706003445}
}
|
|||||
| Burns, D., Vitvar, T., McDonnell, J., Hassett, J., Duncan, J. and Kendall, C. | Effects of suburban development on runoff generation in the Croton River basin, New York, USA | 2005 | Journal of Hydrology Vol. 311(1-4), pp. 266-281 |
article | URL |
| Abstract: The effects of impervious area, septic leach-field effluent, and a riparian wetland on runoff generation were studied in three small (0.38–0.56 km2) headwater catchments that represent a range of suburban development (high density residential, medium density residential, and undeveloped) within the Croton River basin, 70 km north of New York City. Precipitation, stream discharge, and groundwater levels were monitored at 10–30 min intervals for 1 year, and stream water and groundwater samples were collected biweekly for δ18O, NO3−, and SO42− analysis for more than 2 years during an overlapping period in 2000–2002. Data from 27 storms confirmed that peak magnitudes increased and recession time decreased with increasing development, but lags in peak arrival and peak discharge/mean discharge were greatest in the medium density residential catchment, which contains a wetland in which storm runoff is retained before entering the stream. Baseflow during a dry period from Aug. 2001–Feb. 2002 was greatest in the high-density residential catchment, presumably from the discharge of septic effluent through the shallow groundwater system and into the stream. In contrast, moderate flows during a wet period from Mar.–Aug. 2002 were greatest in the undeveloped catchment, possibly as a result of greater subsurface storage or greater hydraulic conductivity at this site. The mean residence time of baseflow was about 30 weeks at all three catchments, indicating that human influence was insufficient to greatly affect the groundwater recharge and discharge properties that determine catchment residence time. These results suggest that while suburban development and its associated impervious surfaces and storm drains accelerate the transport of storm runoff into streams, the combined effects of remnant natural landscape features such as wetlands and human alterations such as deep groundwater supply and septic systems can change the expected effects of human development on storm runoff and groundwater recharge. | |||||
BibTeX:
@article{Burns2005,
author = {Burns, Douglas and Vitvar, Tomas and McDonnell, Jeffrey and Hassett, James and Duncan, Jonathan and Kendall, Carol},
title = {Effects of suburban development on runoff generation in the Croton River basin, New York, USA},
journal = {Journal of Hydrology},
year = {2005},
volume = {311},
number = {1--4},
pages = {266--281},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405000703}
}
|
|||||
| Burton, A., Kilsby, C., Fowler, H., Cowpertwait, P. and O'Connell, P. | RainSim: A spatial–temporal stochastic rainfall modelling system | 2008 | Environmental Modelling & Software Vol. 23(12), pp. 1356-1369 |
article | URL |
| Abstract: RainSim V3 is a robust and well tested stochastic rainfall field generator used successfully in a broad range of climates and end-user applications. Rainfall fields or multi-site time series can be sampled from a spatial–temporal Neyman–Scott rectangular pulses process: storm events occur as a temporal Poisson process; each triggers raincell generation using a stationary spatial Poisson process; raincells are clustered in time lagging the storm event; each raincell contributes rainfall uniformly across its circular extent and throughout its lifetime; raincell lag, duration, radius and intensity are random variables; orographic effects are accounted for by non-uniform scaling of the rainfall field. Robust and efficient numerical optimization schemes for model calibration are identified following the evaluation of five schemes with optional log-transformation of the parameters. The log-parameter Shuffled Complex Evolution (lnSCE) algorithm with a convergence criterion is chosen for single site applications and an effort limited restarted lnSCE algorithm is selected for spatial applications. The new objective function is described and shown to improve model calibration. Linear and quadratic expressions are identified which can reduce the bias between the fitted and simulated probabilities of both dry hours and dry days as used in calibration. Exact fitting of mean rainfall statistics is also implemented and demonstrated. An application to the Dommel catchment on the Netherlands/Belgian border illustrates the ability of the improved model to match observed statistics and extremes. | |||||
BibTeX:
@article{Burton2008,
author = {Burton, A. and Kilsby, C.G. and Fowler, H.J. and Cowpertwait, P.S.P. and O'Connell, P.E.},
title = {RainSim: A spatial–temporal stochastic rainfall modelling system},
journal = {Environmental Modelling & Software},
year = {2008},
volume = {23},
number = {12},
pages = {1356--1369},
url = {http://www.sciencedirect.com/science/article/pii/S1364815208000613}
}
|
|||||
| Bury, K.V. | Statistical Distributions in Engineering [BibTeX] |
1999 | , pp. - | book | |
BibTeX:
@book{Bury1999,
author = {Bury, Karl V.},
title = {Statistical Distributions in Engineering},
publisher = {Cambridge University Press},
year = {1999},
pages = {--}
}
|
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| Butscher, C., Auckenthaler, A., Scheidler, S. and Huggenberger, P. | Validation of a Numerical Indicator of Microbial Contamination for Karst Springs | 2011 | Ground Water Vol. 49(1), pp. 66-76 |
article | URL |
| Abstract: Rapid changes in spring water quality in karst areas due to rapid recharge of bacterially contaminated water are a major concern for drinking water suppliers and users. The main objective of this study was to use field experiments with fecal indicators to verify the vulnerability of a karst spring to pathogens, as determined by using a numerical modeling approach. The groundwater modeling was based on linear storage models that can be used to simulate karst water flow. The vulnerability of the karst groundwater is estimated using such models to calculate criteria that influence the likelihood of spring water being affected by microbial contamination. Specifically, the temporal variation in the vulnerability, depending on rainfall events and overall recharge conditions, can be assessed and quantified using the dynamic vulnerability index (DVI). DVI corresponds to the ratio of conduit to diffuse flow contributions to spring discharge. To evaluate model performance with respect to predicted vulnerability, samples from a spring were analyzed for Escherichia coli, enterococci, Clostridium perfringens, and heterotrophic plate count bacteria during and after several rainfall events. DVI was shown to be an indication of the risk of fecal contamination of spring water with sufficient accuracy to be used in drinking water management. We conclude that numerical models are a useful tool for evaluating the vulnerability of karst systems to pathogens under varying recharge conditions | |||||
BibTeX:
@article{Butscher2011,
author = {Butscher, Christoph and Auckenthaler, Adrian and Scheidler, Stefan and Huggenberger, Peter},
title = {Validation of a Numerical Indicator of Microbial Contamination for Karst Springs},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {2011},
volume = {49},
number = {1},
pages = {66--76},
url = {http://dx.doi.org/10.1111/j.1745-6584.2010.00687.x}
}
|
|||||
| Butscher, C. and Huggenberger, P. | Enhanced vulnerability assessment in karst areas by combining mapping with modeling approaches | 2009 | Science of The Total Environment Vol. 407(3), pp. 1153-1163 |
article | URL |
| Abstract: The objective of this work is to facilitate a sustainable regional planning of water resources in karst areas by providing a conceptual framework for an integrative vulnerability assessment. A combined mapping and modeling approach is proposed, taking into account both spatial and temporal aspects of karst groundwater vulnerability. The conceptual framework comprises the delineation of recharge areas, vulnerability mapping, numerical flow and transport modeling and the integration of information into a combined vulnerability map and time series. The approach is illustrated at a field site in northwest Switzerland (Gempen plateau). The results show that the combination of vulnerability mapping and numerical modeling allows the vulnerability distribution, both in the recharge and discharge areas, to be identified, and at the same time, the time dependence of karst groundwater vulnerability to be assessed. The combined vulnerability map and time series provide a quantitative basis for drinking water management and for regional planning. | |||||
BibTeX:
@article{Butscher2009,
author = {Butscher, Christoph and Huggenberger, Peter},
title = {Enhanced vulnerability assessment in karst areas by combining mapping with modeling approaches},
journal = {Science of The Total Environment},
year = {2009},
volume = {407},
number = {3},
pages = {1153--1163},
url = {http://www.sciencedirect.com/science/article/pii/S0048969708010097}
}
|
|||||
| Butscher, C. and Huggenberger, P. | Implications for karst hydrology from 3D geological modeling using the aquifer base gradient approach | 2007 | Journal of Hydrology Vol. 342(1–2), pp. 184-198 |
article | URL |
| Abstract: Summary We use the gradient of the aquifer base to investigate the hydrology of mature, shallow karst systems. We first present a 3D geological model of the Gempen plateau (NW Switzerland) that reveals the geometry of aquifers and aquitards and their displacement at faults, then transfer the 3D geological model to a hydrological model. The transformation is based on a conceptual karst model approximating subsurface flow in mature, shallow karst systems to open surface flow on the top of the uppermost aquitard or aquifer base. The gradient of this surface is expected to mainly influence regional groundwater flow patterns. We use the hydrological model to delineate spring catchment areas. The discharge areas and corresponding catchment areas of the model are compared with the occurrence of springs in the study area and with hydraulic links confirmed by tracer tests. We also describe the way in which the hydrological model contributes to identifying flow processes. The proposed aquifer base gradient approach enhances vulnerability assessment in mature, shallow karst regions by (1) localizing catchment areas as a precondition of source protection strategies and (2) indicating dominant flow processes associated with individual springs. | |||||
BibTeX:
@article{Butscher2007,
author = {Butscher, Christoph and Huggenberger, Peter},
title = {Implications for karst hydrology from 3D geological modeling using the aquifer base gradient approach},
journal = {Journal of Hydrology},
year = {2007},
volume = {342},
number = {1–2},
pages = {184--198},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407003204}
}
|
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| Byl, T., Ray, K., Walden, C., Watson, V. and Painter, R. | The Role of Free-Living and Attached Bacteria in Processing Contamination in Karst Aquifers | 2008 | U. S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 68 | inproceedings | URL |
| Abstract: In karst aquifers, biodegradation can be accomplished both by surface-attached and free-living bacteria. Biodegradation by attached bacteria is dependent upon and limited by the relatively low surface area to volume ratio (SA/V) of karst aquifers. Biodegradation due to free-living bacteria, however, is not limited by SA/V, but by residence time. The objective of this research was to determine if free-living karst bacteria contributed as much to the removal of ammonia (NH3) as attached, indigenous karst bacteria. These results were compared with the results of a toluene biodegradation study conducted using the same set up (Painter and others, 2005 KIG). The experimental setup included flow-through karst microcosms with high and low SA/V ratios. The low SA/V ratio system consisted of three 1-L cylinders connected together with non-stick tubing. The high SA/V ratio karst system was similar except the cylinders were packed with glass beads to increase the SA/V ratio by approximately 500%. Microscopic examination confirmed that bacteria colonized the interior surfaces of the lab karst systems. Fresh spring water containing between 10,000 and 20,000 indigenous karst bacteria was continuously pumped through each system. A known quantity of NH3 was added as a food source and measured at the exit port. Flow rates were similar and residence time differences were compensated for with the residence-time distribution (RTD) formula described by King and others (2005). First-order NH3-biotransformation rate constants were 0.17 day-1 for the low SA/V system and 0.27 day-1 for the high SA/V system. In the previous toluene study, the first-order rate constants were 0.014 hour-1 for the low SA/V system and 0.016 hour-1 for the high SA/V ratio system leading Painter (2005) to conclude that free-living bacteria contribute as much to toluene biodegradation processes as attached bacteria in karst aquifers. This study suggests that this is not the case with respect to NH3 biotransformation in karst systems. | |||||
BibTeX:
@inproceedings{Byl2008,
author = {Byl, Tom and Ray, Kelly and Walden, Chad and Watson, Valetta and Painter, Roger},
title = {The Role of Free-Living and Attached Bacteria in Processing Contamination in Karst Aquifers},
booktitle = {U. S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U. S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {68},
url = {http://pubs.usgs.gov/sir/2008/5023/23byl.htm}
}
|
|||||
| Byl, T.D. and Painter, R. | Microbial Adaptations to Karst Aquifers with Contaminants [BibTeX] |
2009 | Proceedings of American Water Resources Association (AWRA) Annual Water Resources Conference, Seattle, WA, USA, 9-12 November 2009 | inproceedings | |
BibTeX:
@inproceedings{Byl2009,
author = {Byl, T. D. and Painter, R.},
title = {Microbial Adaptations to Karst Aquifers with Contaminants},
booktitle = {Proceedings of American Water Resources Association (AWRA) Annual Water Resources Conference, Seattle, WA, USA, 9-12 November 2009},
year = {2009}
}
|
|||||
| Byl, T.D. and Painter, R. | Microbial Adaptations to Karst Aquifers with Contaminants | 2009 | Proceedings of the 19th Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 15 - 17, 2009, pp. 2C-9-2C-12 | inproceedings | |
| Abstract: There is a lack of studies examining biodegradation in karst aquifers, which may be due to the widespread perception that contaminants are rapidly flushed out of karst aquifers. Also, there is reports in the scientific literature about the quantity or types of bacteria that inhabit karst aquifers. The objective of this project was to address these two issues. In highly developed and well- connected conduit systems, the rate of contaminant migration is expected to be much faster than the rate of biodegradation. Field (1993) states that remediation techniques such as ground-water extraction or bioremediation are impractical in karst aquifers dominated by conduit flow; however, he also states that the belief that contaminants are rapidly flushed out of karst aquifers is a popular misconception. Large volumes of water may be trapped in fractures along bedding planes and other features isolated from active ground-water flowpaths in karst aquifers (Wolfe and others, 1997). In areas isolated from the major ground-water flowpaths, contaminant migration may possibly be slow enough that biodegradation could reduce contaminant mass if favorable microorganisms, food sources, and geochemical conditions are present (Byl and Williams, 2000; Byl and others, 2001). The capacity for biodegradation processes in a karst setting was evaluated at sites in Tennessee and Kentucky. The potential for biodegradation of trichloroethylene (TCE) was studied in a karst aquifer at Lewisburg, Tennessee. This site was selected because of the presence of TCE degradation by- products in the karst aquifer, available site hydrologic and chlorinated-ethene information. Additional chemical, biological and hydrological data were gathered to evaluate if the occurrence of TCE degradation by-products in the karst aquifer was the result of biodegradation in the aquifer or simply transport into the aquifer. Geochemical analysis established that sulfate- reducing conditions, essential for reductive dechlorination of chlorinated solvents, existed in parts of the contaminated karst aquifer. Geochemical conditions in other areas of the aquifer fluctuated between anaerobic and aerobic conditions and contained compounds associated with cometabolism, such as ethane, methane, ammonia and dissolved oxygen. A large, diverse bacteria population inhabits the contaminated aquifer. Bacteria known to biodegrade TCE and other chlorinated solvents, such as sulfate-reducers, methanotrophs, and ammonia-oxidizers, were identified from karst-aquifer water using the RNA-hybridization technique. Results from microcosms using raw karst-aquifer water found that aerobic cometabolism and anaerobic reductive dechlorination degradation processes were possible when appropriate conditions were established in the microcosms. The chemical and biological results provide circumstantial evidence that several biodegradation processes are potentially active in the karst aquifer. Additional site hydrologic information was developed to determine if appropriate conditions persisted long enough in the karst aquifer for these biodegradation processes to be significant. Continuous monitoring devices placed in four wells during the spring of 1998 documented a dual phase ground-water flow system within the karst aquifer. Dynamic areas were present within the karst aquifer where active flow occurred, as well as, stable areas in the karst aquifer that were isolated from active flow. The pH, specific conductance, low dissolved oxygen levels and low oxidation-reduction potentials changed very little in the stable areas isolated from active flow. The stable areas in the karst aquifer had geochemical conditions and bacteria conducive to reductive dechlorination of chlorinated ethenes. The dynamic areas of the karst aquifer associated with active flow fluctuated between anaerobic and aerobic conditions in response to rain events. Associated with this dynamic environment were bacteria and geochemical conditions conducive to cometabolism. In summary, multiple lines of evidence developed from biological, chemical and hydrological data demonstrate that a variety of biodegradation processes were active in this karst aquifer. A second karst-aquifer site contaminated with jet fuel was also investigated. The site is located at an airfield in southern Kentucky. Ground-water samples were collected for bacteria and geochemical analysis from several contaminated monitoring wells in an unconsolidated regolith and karst aquifer that had varying concentrations of dissolved fuel. Bacteria counts ranged from approximately 700,000 bacteria per milliliter to 1.2 million depending on the well and sample collection time. These bacteria counts were derived using two methods, direct counts and BART growth tests, and the results of the two tests were within 20 percent of each other. These numbers are much greater than previously reported when tryptic soy agar was used to quantify heterotrophic bacteria in the same wells (Byl and others, 2001). Bacteria from the fuel- contaminated part of the karst aquifer had a 5% lighter buoyant density and a wider range of sizes than the bacteria from the non-contaminated well. Additionally, bacteria isolated from fuel- contaminated ground-water samples readily grew with dissolved gasoline as the only source of food. Static microcosms (n=3) set up using aerated raw karst water spiked with benzene at 1 mg/L established a biodegradation rate of 50% loss (T1/2) in 3 days. Sterile control microcosms had less than 10% benzene loss over the same time period. Additional field evidence that biodegradation was taking place in the aquifer was established by measuring geochemical indicators. The wells with screens intersecting non-contaminated sections of the aquifer had greater dissolved oxygen concentrations (generally above 2 milligrams per liter) than those intersecting more contaminated sections (dissolved oxygen less than 0.1 milligrams per liter). Also, where the oxygen concentrations were diminished, geochemical evidence indicated that anaerobic processes were active. This evidence includes elevated levels of ammonia, sulfide and ferrous iron in the fuel-contaminated ground-water samples. Based on these results, biodegradation of fuel constituents in the karst aquifer is indicated, and therefore, natural attenuation should not be disregarded because of preconceptions about low microbial activity in karst aquifers. The third set of experiments reported here considers whether free-living bacteria or attached bacteria were responsible for biodegradation processes in karst. In karst aquifers, biodegradation can be accomplished both by surface-attached and free-living bacteria. Biodegradation by attached bacteria is dependent upon and limited by the relatively low surface area to volume ratio (SA/V) of karst aquifers. Biodegradation due to free-living bacteria, however, is not limited by SA/V, but by residence time. The objective of this research was to determine if free-living karst bacteria contributed as much to the removal of ammonia (NH3) as attached, indigenous karst bacteria. These results were compared with the results of a toluene biodegradation study conducted using the same set up (Painter and others, 2005 KIG). The experimental setup included flow-through karst microcosms with high and low SA/V ratios. The low SA/V ratio system consisted of three 1-L cylinders connected together with non-stick tubing. The high SA/V ratio karst system was similar except the cylinders were packed with glass beads to increase the SA/V ratio by approximately 500%. Microscopic examination confirmed that bacteria colonized the interior surfaces of the lab karst systems. Fresh spring water containing between 10,000 and 20,000 indigenous karst bacteria was continuously pumped through each system. A known quantity of NH3 was added as a food source and measured at the exit port. Flow rates were similar and residence time differences were compensated for with the residence-time distribution (RTD) formula described by King and others (2005). First-order NH3-biotransformation rate constants were 0.17 day-1 for the low SA/V system and 0.27 day-1 for the high SA/V system. In the previous toluene study, the first-order rate constants were 0.014 hour-1 for the low SA/V system and 0.016 hour-1 for the high SA/V ratio system leading Painter (2005) to conclude that free-living bacteria contribute as much to toluene biodegradation processes as attached bacteria in karst aquifers. This study suggests that this is not the case with respect to NH3 biotransformation in karst systems. |
|||||
BibTeX:
@inproceedings{Byl2009b,
author = {Byl, Tom D. and Painter, Roger},
title = {Microbial Adaptations to Karst Aquifers with Contaminants},
booktitle = {Proceedings of the 19th Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 15 - 17, 2009},
year = {2009},
pages = {2C-9--2C-12}
}
|
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| Byl, T.D. and Williams, S.D. | Biodegradation of Chlorinated Ethenes at a Karst Site in Middle Tennessee, U.S. Geological Survey Water-Resources Investigations Report 99-4285 | 2000 | techreport | URL | |
| Abstract: This report presents results of field and laboratory investigations examining the biodegradation of chlorinated ethenes in a karst aquifer contaminated with trichloroethylene (TCE). The study site, located in Middle Tennessee, was selected because of the presence of TCE degradation byproducts in the karst aquifer and available site hydrologic and chlorinated-ethene information. Additional chemical, biological, and hydrologic data were gathered to evaluate whether the occurrence of TCE degradation byproducts in the karst aquifer was the result of biodegradation within the aquifer or simply transport into the aquifer. Geochemical analysis established that sulfate-reducing conditions, essential for reductive dechlorination of chlorinated solvents, existed in parts of the contaminated karst aquifer. Other areas of the aquifer fluctuated between anaerobic and aerobic conditions and contained compounds associated with cometabolism, such as ethane, methane, ammonia, and dissolved oxygen. A large, diverse bacteria population inhabits the contaminated aquifer. Bacteria known to biodegrade TCE and other chlorinated solvents, such as sulfate-reducers, methanotrophs, and ammonia-oxidizers, were identified from karst-aquifer water using the RNA-hybridization technique. Results from microcosms using raw karst-aquifer water found that aerobic cometabolism and anaerobic reductive-dechlorination degradation processes were possible when appropriate conditions were established in the microcosms. These chemical and biological results provide circumstantial evidence that several biodegradation processes are active in the aquifer. Additional site hydrologic information was developed to determine if appropriate conditions persist long enough in the karst aquifer for these biodegradation processes to be significant. Continuous monitoring devices placed in four wells during the spring of 1998 indicated that pH, specific conductance, dissolved oxygen, and oxidation-reduction potentials changed very little in areas isolated from active ground-water flow paths. These stable areas in the karst aquifer had geochemical conditions and bacteria conducive to reductive dechlorination of chlorinated ethenes. Other areas of the karst aquifer were associated with active ground-water flow paths and fluctuated between anaerobic and aerobic conditions in response to rain events. Associated with this dynamic environment were bacteria and geochemical conditions conducive to cometabolism. In summary, multiple lines of evidence developed from chemical, biological, and hydrologic data demonstrate that a variety of biodegradation processes are active in this karst aquifer. | |||||
BibTeX:
@techreport{Byl2000,
author = {Byl, Tom D. and Williams, Shannon D.},
title = {Biodegradation of Chlorinated Ethenes at a Karst Site in Middle Tennessee, U.S. Geological Survey Water-Resources Investigations Report 99-4285},
year = {2000},
url = {http://pubs.usgs.gov/wri/wri994285/}
}
|
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| Cai, J.-l., Zhou, Z.-f. and Huang, Y. | Laboratory experiments on solute transport in a partial transfixion single fracture | 2011 | Journal of Hydrodynamics, Ser. B Vol. 23(5), pp. 570-579 |
article | URL |
| Abstract: In the study of solute transport in rough single fracture, the contact area is an important factor. The single fracture is defined as two categories in this article: the full transfixion single fracture and the partial transfixion single fracture. The purpose of this article is to research how the contact area affects the solute transport in partial transfixion single fracture. The contact area is generalized as square blocks with three sizes, and contact rate is variable, a series of experiments for solute transport were conducted in a simulation model which can simulate the two types of fractures in the laboratory. Based on the analysis of the breakthrough curves and the experiment phenomena, it is concluded that the difference of breakthrough curves of various contact rates is evident and increases with the increase of contact rate, the relative error curves reflect the difference of block sizes, and the maximum errors increase from smaller than 0.2 to about 0.8 with the increase of contact rate. These phenomena are also explained qualitatively in this article. It is concluded that the contact area strongly affects solute transport, and the research of channels formed by contact area is useful to further understand the rule of solute transport in partial transfixion single fracture. | |||||
BibTeX:
@article{Cai2011,
author = {Cai, Jin-long and Zhou, Zhi-fang and Huang, Yong},
title = {Laboratory experiments on solute transport in a partial transfixion single fracture},
journal = {Journal of Hydrodynamics, Ser. B},
year = {2011},
volume = {23},
number = {5},
pages = {570--579},
url = {http://www.sciencedirect.com/science/article/pii/S1001605810601515}
}
|
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| Cai, Q.-Y., Mo, C.-H., Wu, Q.-T., Zeng, Q.-Y., Katsoyiannis, A. and Férard, J.-F. | Bioremediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated sewage sludge by different composting processes | 2007 | Journal of Hazardous Materials Vol. 142(1-2), pp. 535-542 |
article | URL |
| Abstract: The efficiency of four different composting processes to bioremediate polycyclic aromatic hydrocarbons (PAHs)-contaminated sewage sludge was investigated. Prior to composting, sewage sludge coming from the Datansha wastewater treatment plant, Guangzhou, China, was mixed with rice straw to obtain a C/N ratio of 13:1. After 56 days of composting, the total concentrations of 16 PAHs (ΣPAHs) ranged from 1.8 to 10.2 mg kg−1 dry weight, decreasing in order of inoculated-manual turned compost (IMTC) > manual turned compost (MTC) > continuous aerated compost (CAC) > intermittent aerated compost (IAC), exhibiting removal rates of 64%, 70%, 85% and 94%, respectively. Individual PAHs were generally removed in similar rates. IAC treatment showed a higher removal rate of high molecular weight PAHs and carcinogenic PAHs comparing to the other composting processes. | |||||
BibTeX:
@article{Cai2007,
author = {Cai, Quan-Ying and Mo, Ce-Hui and Wu, Qi-Tang and Zeng, Qiao-Yun and Katsoyiannis, Athanasios and Férard, Jean-François},
title = {Bioremediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated sewage sludge by different composting processes},
journal = {Journal of Hazardous Materials},
year = {2007},
volume = {142},
number = {1--2},
pages = {535--542},
url = {http://www.sciencedirect.com/science/article/pii/S0304389406010041}
}
|
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| Cai, Z., Thomson, N.R., Wilson, R.D. and Oswald, S.E. | A lumped parameter approach to model the treatment of organic contaminants by a granular iron filled fracture | 2006 | Advances in Water Resources Vol. 29(4), pp. 624-638 |
article | URL |
| Abstract: Zero-valent iron permeable reactive barriers (Fe0-PRBs) have been widely used in unconsolidated media to treat certain dissolved phase organic contaminants, but little attention has been given to their application in fractured porous media. In principle, it is possible to create a Fe0-PRB in a fractured porous medium by injecting an iron slurry mixture into the fracture network. This emplacement method likely results in a complicated system of incompletely iron filled fractures. To aid in the design and performance assessment of such complex systems, representative models must be used that capture the essence of the controlling processes; however, existing models cannot directly account for the complex processes dominating treatment in a partly iron-filled fracture at the required spatial scale. As a first step to address this need, we have developed a modelling approach for an idealized single partly iron filled fracture wherein the physical and chemical processes are represented by a first-order lumped rate parameter. The performance of the developed lumped rate parameter model was examined over a range of conditions by comparing simulation results to those produced by a more comprehensive analytical solution and a numerical model. While some deviations were observed, the lumped parameter model was shown to be valid for a range of iron grain sizes, iron layer thicknesses, open fracture apertures, flow velocities, and reaction rate coefficients. We also demonstrated that the developed lumped parameter approach can represent situations where the system is initially contaminated, and can be used to optimize the thickness of the iron layer. The advantage of this first-order lumped rate parameter model is that it can be used directly in existing discrete fracture models without modifications to their computational framework, and hence will make it possible to approximate the field-scale treatment performance of Fe0-PRBs in fractured porous media. | |||||
BibTeX:
@article{Cai2006,
author = {Cai, Zuansi and Thomson, Neil R. and Wilson, Ryan D. and Oswald, Sascha E.},
title = {A lumped parameter approach to model the treatment of organic contaminants by a granular iron filled fracture},
journal = {Advances in Water Resources},
year = {2006},
volume = {29},
number = {4},
pages = {624--638},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805001764}
}
|
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| Camponelli, K.M., Lev, S.M., Snodgrass, J.W., Landa, E.R. and Casey, R.E. | Chemical fractionation of Cu and Zn in stormwater, roadway dust and stormwater pond sediments | 2010 | Environmental Pollution Vol. 158(6)Advances of air pollution science: from forest decline to multiple-stress effects on forest ecosystem services, pp. 2143-2149 |
article | URL |
| Abstract: This study evaluated the chemical fractionation of Cu and Zn from source to deposition in a stormwater system. Cu and Zn concentrations and chemical fractionation were determined for roadway dust, roadway runoff and pond sediments. Stormwater Cu and Zn concentrations were used to generate cumulative frequency distributions to characterize potential exposure to pond-dwelling organisms. Dissolved stormwater Zn exceeded USEPA acute and chronic water quality criteria in approximately 20% of storm samples and 20% of the storm duration sampled. Dissolved Cu exceeded the previously published chronic criterion in 75% of storm samples and duration and exceeded the acute criterion in 45% of samples and duration. The majority of sediment Cu (92–98%) occurred in the most recalcitrant phase, suggesting low bioavailability; Zn was substantially more available (39–62% recalcitrant). Most sediment concentrations for Cu and Zn exceeded published threshold effect concentrations and Zn often exceeded probable effect concentrations in surface sediments. | |||||
BibTeX:
@article{Camponelli2010,
author = {Camponelli, Kimberly M. and Lev, Steven M. and Snodgrass, Joel W. and Landa, Edward R. and Casey, Ryan E.},
title = {Chemical fractionation of Cu and Zn in stormwater, roadway dust and stormwater pond sediments},
booktitle = {Advances of air pollution science: from forest decline to multiple-stress effects on forest ecosystem services},
journal = {Environmental Pollution},
year = {2010},
volume = {158},
number = {6},
pages = {2143--2149},
url = {http://www.sciencedirect.com/science/article/pii/S0269749110000850}
}
|
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| Campos, J. | Modeling the Yield–Evaporation–Spill in the Reservoir Storage Process: The Regulation Triangle Diagram | 2010 | Water Resources Management Vol. 24(13), pp. 3487-3511 |
article | URL |
| Abstract: From the dimensionless reservoir water budget equation, a graphical method to model the yield–spill–evaporation loss trade-off in the reservoir storage process was built. The reservoir inflows were transformed into three parts that sum to the total mean inflow for long-term operation: evaporation, spill and yield. A regulation triangle diagram (RTD) has been proposed to provide a better understanding of the reservoir storage process as a function of reservoir capacity, hydrological river regime, evaporation and reservoir morphology. The inflows were assumed to be serially uncorrelated and to originate from a Gamma probability distribution function. The diagrams were developed using the Monte Carlo method, while the graphics were developed for intermittent rivers with a coefficient of variation of annual inflows that ranges from 0.6 to 1.6. In the model, the reservoir is a single over-year system, and the values are referenced to the steady state conditions. | |||||
BibTeX:
@article{Campos2010,
author = {Campos, José},
title = {Modeling the Yield–Evaporation–Spill in the Reservoir Storage Process: The Regulation Triangle Diagram},
journal = {Water Resources Management},
publisher = {Springer Netherlands},
year = {2010},
volume = {24},
number = {13},
pages = {3487--3511},
url = {http://dx.doi.org/10.1007/s11269-010-9616-x}
}
|
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| Cantu-Perez, A., Barrass, S. and Gavriilidis, A. | Residence time distributions in microchannels: Comparison between channels with herringbone structures and a rectangular channel | 2010 | Chemical Engineering Journal Vol. 160(3)10th International Conference on Microreaction Technology, pp. 834-844 |
article | URL |
| Abstract: Residence time distributions (RTD) have been determined numerically and experimentally for channels with and without herringbone structures. Computational fluid dynamics (CFD) and particle tracking with random walk diffusion were employed for the numerical calculation of the RTD. The axial dispersion exchanging mass with a stagnant zone model was shown to fit the particle tracking data for the channels with staggered herringbone structures. This model provides a simpler method for RTD characterisation. Experimental RTD measurements were performed by monitoring the concentration of a tracer dye by means of a LED-photodiode system. For all cases, the calculations agreed well with experiments. The results show that for low Peclet numbers (Pe < 102) the use of herringbone structures does not have an impact on the RTD, however at high Peclet numbers (Pe > 102), channels with herringbone structures exhibit a narrower RTD than a plain channel of the same dimensions. Thus, at high Pe, inclusion of herringbones to the bottom floor of rectangular channels allows the increase in channel dimensions without adverse effect on the RTD behaviour or reaction performance. | |||||
BibTeX:
@article{Cantu-Perez2010,
author = {Cantu-Perez, Alberto and Barrass, Simon and Gavriilidis, Asterios},
title = {Residence time distributions in microchannels: Comparison between channels with herringbone structures and a rectangular channel},
booktitle = {10th International Conference on Microreaction Technology},
journal = {Chemical Engineering Journal},
year = {2010},
volume = {160},
number = {3},
pages = {834--844},
url = {http://www.sciencedirect.com/science/article/pii/S1385894709005191}
}
|
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| Cantu-Perez, A., Bi, S., Barrass, S., Wood, M. and Gavriilidis, A. | Residence time distribution studies in microstructured plate reactors | 2011 | Applied Thermal Engineering Vol. 31(5)MNF 2009 Special Issue, pp. 634-639 |
article | URL |
| Abstract: Residence time distributions (RTDs) have been investigated experimentally for reactors with straight and zig-zag channels. The channels are formed by microstructured plates placed on top of each other and containing obstacles and holes to allow flow in 3 dimensions. Experimental RTD measurements were performed by monitoring the concentration of a tracer dye by means of a LED-photodiode system. The RTD was obtained for five different flowrates and four geometries containing straight and zig-zag channels. It was found that the zig-zag channel configuration gives a narrower distribution as compared to the straight channel ones. Secondary flows were thought to be present in the zig-zag channel even at small Reynolds numbers. Furthermore, as the flowrate increased, the variance of the distribution of all geometries increased. The RTD for a single rectangular cross section channel (with no 3-dimensional flow) was found to have the largest variance from all reactors investigated due to its largest hydraulic diameter. However, its variance was not far from those of microstructured reactors and this was attributed to its small aspect ratio (shallow, wide channel). The RTDs of all microstructured reactors, and in particular the zig-zag geometry, were less sensitive to flowrate increase than the RTDs of the rectangular channel, for the range of flowrates investigated. | |||||
BibTeX:
@article{Cantu-Perez2011,
author = {Cantu-Perez, Alberto and Bi, Shuang and Barrass, Simon and Wood, Mark and Gavriilidis, Asterios},
title = {Residence time distribution studies in microstructured plate reactors},
booktitle = {MNF 2009 Special Issue},
journal = {Applied Thermal Engineering},
year = {2011},
volume = {31},
number = {5},
pages = {634--639},
url = {http://www.sciencedirect.com/science/article/pii/S1359431110001870}
}
|
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| Cao, R. and González-Manteiga, W. | Goodness-of-fit tests for conditional models under censoring and truncation | 2008 | Journal of Econometrics Vol. 143(1)Specification testing, pp. 166-190 |
article | URL |
| Abstract: The problem of specification tests for conditional models is studied when the data are subject to left truncation and right censoring. A general method is applied to derive tests for the polynomial regression, the proportional hazards, the additive risks and the proportional odds models. Bootstrap versions to approximate the critical values of the test are introduced and proved to work both from a theoretical viewpoint as well as in a small simulation study. | |||||
BibTeX:
@article{Cao2008,
author = {Cao, Ricardo and González-Manteiga, Wenceslao},
title = {Goodness-of-fit tests for conditional models under censoring and truncation},
booktitle = {Specification testing},
journal = {Journal of Econometrics},
year = {2008},
volume = {143},
number = {1},
pages = {166--190},
url = {http://www.sciencedirect.com/science/article/pii/S0304407607001662}
}
|
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| Capela, I., Bilé, M.J., Silva, F., Nadais, H., Prates, A. and Arroja, L. | Hydrodynamic behaviour of a full-scale anaerobic contact reactor using residence time distribution technique | 2009 | Journal of Chemical Technology and Biotechnology Vol. 84(5), pp. 716-724 |
article | URL |
| Abstract: BACKGROUND: The knowledge of the fluid pattern of full-scale anaerobic reactors is of fundamental importance for the optimisation of biological processes. High solids concentrations often lead to inefficient mixing conditions, which may reduce treatment capacity due to heterogeneity within the biomass. RESULTS: The hydrodynamic characteristics of a full-scale anaerobic contact reactor treating evaporator condensate from a sulphite pulp mill were investigated. The methodology applied was based on the residence time distribution (RTD) technique using lithium as a tracer. Different non-ideal hydraulic flow models were tested and the best model fitting RTD data was the Gamma distribution model with by-pass. It was concluded that the full-scale bioreactor presents a good degree of mixing with about 22% of non-effective volume due to the presence of high amounts of inorganic materials. CONCLUSION: As a result of this study it was possible to both improve the full-scale bioreactor performance and decrease the running costs by changes in the plant operation strategies which allowed reduction of the huge amount of inorganic materials contributing to the non-effective volume. The methodology is simple and results from a unique RTD experiment and confirms the importance of considering mixing characteristics when assessing complex full-scale treatment processes. | |||||
BibTeX:
@article{Capela2009,
author = {Capela, Isabel and Bilé, Maria João and Silva, Flávio and Nadais, Helena and Prates, António and Arroja, Luís},
title = {Hydrodynamic behaviour of a full-scale anaerobic contact reactor using residence time distribution technique},
journal = {Journal of Chemical Technology and Biotechnology},
publisher = {John Wiley & Sons, Ltd.},
year = {2009},
volume = {84},
number = {5},
pages = {716--724},
url = {http://dx.doi.org/10.1002/jctb.2104}
}
|
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| Capell, R., Tetzlaff, D., Hartley, A.J. and Soulsby, C. | Linking metrics of hydrological function and transit times to landscape controls in a heterogeneous mesoscale catchment | 2012 | Hydrological Processes Vol. 26(3), pp. 405-420 |
article | URL |
| Abstract: Long-term river flow data and one year of isotopic tracer data in a nested 749 km2 catchment were analysed conjunctively to evaluate the relationships between hydrometric statistics, transit times, and catchment characteristics. The catchment comprised two distinct geomorphic provinces; upland headwaters draining glaciated landscapes underlain by crystalline geology and lowland headwaters draining a major regional sandstone aquifer. In the uplands, flow regimes were ‘flashy’ with high runoff coefficients for storm hydrographs, steep recession curves and strong nonlinearity in event responses. In the lowlands, runoff coefficients were low, recessions less steep, and event responses more linear. Flow data from the catchment outfall showing damping of these extremes, but was most strongly influenced by the upland headwaters where precipitation was highest. The damping of variability in stable water isotopes between precipitation inputs and streamflow outputs reflected this; with upland tributaries least damped and lowland tributaries most damped. Attempts to quantify the mean transit times of the sampling points met with mixed success; partly reflecting the short run (1 year) of data, but mainly as a result of the marked damping in lowland sites. As a consequence, MTT estimates can only be said to be in the order of a few years in upland sites, but are probably decadal or greater in lowland tributaries. Again, the catchment outfall averages these extremes, but is more similar to the upland headwaters. Despite the difficulties in quantifying MTTs, it is clear that they, like the hydrological response, primarily reflect the dominant control of catchment soil cover, which in turn is determined by geology and glacial history. | |||||
BibTeX:
@article{Capell2012,
author = {Capell, R. and Tetzlaff, D. and Hartley, A. J. and Soulsby, C.},
title = {Linking metrics of hydrological function and transit times to landscape controls in a heterogeneous mesoscale catchment},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {2012},
volume = {26},
number = {3},
pages = {405--420},
url = {http://dx.doi.org/10.1002/hyp.8139}
}
|
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| Carew, A. and Mitchell, C. | Teaching sustainability as a contested concept: capitalizing on variation in engineering educators' conceptions of environmental, social and economic sustainability | 2008 | Journal of Cleaner Production Vol. 16(1), pp. 105-115 |
article | URL |
| Abstract: This study documents variation in engineering academics conceptions of sustainability. We investigated how a group of Australian engineering academics described environmental, social and economic sustainability, and identified a broad range of actions that participating academics associated with achieving sustainability. The study suggested marked variation in the actions that participating academics viewed as coherent with sustainable engineering practice, and therefore, potentially marked variations in the sustainability actions academics might advocate to their undergraduate students. Rather than framing this variation as problematic for teaching and learning sustainable engineering, we suggest that such variation in conception of sustainability, and explicit contestation of this variation in the engineering classroom, offers opportunities to enrich undergraduate sustainability learning and teaching. We develop this argument by using some generic environmental, economic, and social theoretical frameworks to characterize the differences according to the values and assumptions that may underpin the observed variation. Validated frameworks are useful to move beyond discussions based on ‘opinion’, because they provide a framework for critical reflection by engineering students and academics about the values and assumptions that inform engineering practice generally and sustainable engineering practice, particularly. | |||||
BibTeX:
@article{Carew2008a,
author = {Carew, A.L. and Mitchell, C.A.},
title = {Teaching sustainability as a contested concept: capitalizing on variation in engineering educators' conceptions of environmental, social and economic sustainability},
journal = {Journal of Cleaner Production},
year = {2008},
volume = {16},
number = {1},
pages = {105--115},
url = {http://www.sciencedirect.com/science/article/pii/S0959652606004173}
}
|
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| Carleton, J., Grizzard, T., Godrej, A. and Post, H. | Factors affecting the performance of stormwater treatment wetlands | 2001 | Water Research Vol. 35(6), pp. 1552-1562 |
article | URL |
| Abstract: Data from 35 studies on 49 wetland systems used to treat stormwater runoff or runoff-impacted surface waters were examined and compared in order to identify any obvious trends that may aid future stormwater treatment wetland design efforts. Despite the intermittent nature of hydrologic and pollutant inputs from stormwater runoff, our analysis demonstrates that steady-state first-order plug-flow models commonly used to analyze wastewater treatment wetlands can be adapted for use with stormwater wetlands. Long-term pollutant removals are analyzed as functions of long-term mean hydraulic loading rate and nominal detention time. First-order removal rate constants for total phosphorus, ammonia, and nitrate generated in this fashion are demonstrated to be similar to values reported in the literature for wastewater treatment wetlands. Constituent removals are also demonstrated via regression analyses to be functions of the ratio of wetland area to watershed area. Resulting equations between these variables can be used as preliminary design tools in the absence of more site-specific details, with the understanding that they should be employed cautiously. | |||||
BibTeX:
@article{Carleton2001,
author = {Carleton, J.N and Grizzard, T.J and Godrej, A.N and Post, H.E},
title = {Factors affecting the performance of stormwater treatment wetlands},
journal = {Water Research},
year = {2001},
volume = {35},
number = {6},
pages = {1552--1562},
url = {http://www.sciencedirect.com/science/article/pii/S0043135400004164}
}
|
|||||
| Carleton, J.N. | Modeling Approaches for Treatment Wetlands | 2009 | School: University of Maryland, College Park | phdthesis | URL |
| Abstract: Although treatment wetlands can reduce pollutant loads, reliably predicting their performance remains a challenge because removal processes are often complex, spatially heterogeneous, and incompletely understood. Although initially popular for characterizing wetland performance, plug flow reactor models are problematic because their parameters exhibit correlation with hydraulic loading. One-dimensional advective-dispersive-reactive (ADE) models are also inadequate because longitudinal dispersion in wetlands is often non-Fickian as a result of steep velocity gradients. Models that make use of residence time distributions have shown promise in improving performance characterization, particularly when interdependencies of stream-tube scale velocities and reaction rate coefficients are considered (the "DND" approach). However this approach is limited to steady-state conditions, and to an assumption that transverse mixing is nil. This dissertation investigates three aspects of wetland modeling and is organized in a journal paper format. The first paper describes development of a DND model which accommodates non-steady-state conditions. The model processes flow and inlet concentration time series, and calculates as output effluent concentration time series. A version of the code allows optimization of model parameters by minimization of summed squared deviations between predicted and measured effluent concentrations. In example comparisons, model results compare favorably with measured data. The second paper develops an analytical solution to a two-dimensional advective-dispersive-reactive equation, in which all flux terms are expressed as power functions of the transverse dimension. For uniform inlet concentration this idealized heterogeneity model is similar to a DND model, but with the inclusion of transverse diffusion. An example is used to illustrate the beneficial impact that transverse mixing has on reactor performance. The third paper describes development of a model based upon a stochastic interpretation of the ADE. The solution technique that is employed results in a bicontinuum model that for steady-state conditions becomes a weighted sum of two exponential decline functions. For low and intermediate degrees of mixing, model results nicely match those of the corresponding idealized heterogeneity model, and for high mixing they match results of the corresponding one-dimensional ADE. Comparisons against data suggest the bicontinuum model may represent wetland performance better than the DND model in some but not all cases. | |||||
BibTeX:
@phdthesis{Carleton2009b,
author = {Carleton, James Nagle},
title = {Modeling Approaches for Treatment Wetlands},
school = {University of Maryland, College Park},
year = {2009},
url = {http://drum.lib.umd.edu/handle/1903/9585}
}
|
|||||
| Carleton, J.N. | Damköhler number distributions and constituent removal in treatment wetlands | 2002 | Ecological Engineering Vol. 19(4), pp. 233-248 |
article | URL |
| Abstract: Using hypothetical wetland simulations and data from the literature, Kadlec [Eco. Eng. 15 (2000) 105] recently demonstrated that plug-flow models commonly used to quantify treatment wetland performance fail to describe conditions other than those under which calibration data are collected. Parameters of these models (removal rate constants (k) and background concentrations (C*)) demonstrate apparent dependence on inlet concentration and hydraulic loading rate which is not alleviated by including dispersion to address non-ideal flow. The phenomenon can be understood as resulting from an interdependence between k and local flow velocity, due to the functional dependence of each on drag-inducing surfaces (and attached biofilms) associated with submerged vegetation and litter. This paper presents a simple method, based on theoretical considerations, for determining C* using inlet–outlet data, independent of the degree of mixing or the nature of the removal processes. This paper also expands upon the hypothetical multi-channel example to suggest a modeling approach in which a wetland is treated conceptually as an ensemble of parallel, non-interacting stream tubes in plug-flow, characterized by a continuous distribution of Damköhler numbers. The Damköhler number distribution (DND) can be estimated from the residence time distribution (RTD) under the assumption of uniform flow path length. For such a wetland, under steady state conditions and with constant inlet concentration, the fraction of a removable pollutant remaining as a function of normalized distance from inlet to outlet is given by the Laplace transform of the DND. Similarly, the DND can be derived from the inverse Laplace transform of the normalized concentration versus normalized distance curve. Given both an RTD and a DND, it is possible to investigate the relationship between k and residence time, and the mechanistic nature of the removal process. Employing these concepts makes it possible to generate an expression for normalized concentration as a function of fractional distance that is unaffected by changes in inlet concentration, and inherently takes into account changes in hydraulic loading rate. | |||||
BibTeX:
@article{Carleton2002,
author = {Carleton, James N},
title = {Damköhler number distributions and constituent removal in treatment wetlands},
journal = {Ecological Engineering},
year = {2002},
volume = {19},
number = {4},
pages = {233--248},
url = {http://www.sciencedirect.com/science/article/pii/S0925857402000940}
}
|
|||||
| Carleton, J.N., Grizzard, T.J., Godrej, A.N., Post, H.E., Lampe, L. and Kenel, P.P. | Performance of a Constructed Wetlands in Treating Urban Stormwater Runoff | 2000 | Water Environment Research Vol. 72(3), pp. 295-304 |
article | URL |
| Abstract: An investigation was conducted on the pollutant removal performance of a constructed wetlands treating stormwater runoff from a residential townhome complex in northern Virginia. Constituent event mean concentrations for 33 runoff events between April 1996 and May 1997 were measured based on flow-weighted composite samples collected at the facility's inlet and outlet. With the results from a limited number of grab samples representing ungauged overland drainage from an adjacent wooded area, estimated removals were positive for most constituents and typically exceeded those obtained at a nearby companion wetland study site, consistent with expectations based on the relative ratios of wetland area to drainage area at the two sites. Median load removals of all constituents were greater for a subset of 22 storms that had inflow volumes less than the maximum volume of the marsh. Orthophosphate phosphorus and ammonia removals were significantly better during spring of 1996 than spring of 1997. Lysimeter data suggest a possible explanation for this, which is development of anaerobic conditions in the shallow sediments in 1997. Outlet concentrations of oxidized nitrogen were consistently lower in base flow than in storm samples, suggesting that removal of this constituent occurred primarily between, rather than during, storm events. | |||||
BibTeX:
@article{Carleton2000,
author = {Carleton, James N. and Grizzard, Thomas J. and Godrej, Adil N. and Post, Harold E. and Lampe, Les and Kenel, Pamela P.},
title = {Performance of a Constructed Wetlands in Treating Urban Stormwater Runoff},
journal = {Water Environment Research},
year = {2000},
volume = {72},
number = {3},
pages = {295--304},
url = {http://dx.doi.org/10.2175/106143000X137518}
}
|
|||||
| Carleton, J.N. and Montas, H.J. | An analysis of performance models for free water surface wetlands | 2010 | Water Research Vol. 44(12), pp. 3595-3606 |
article | URL |
| Abstract: Although treatment wetlands are intended to attenuate pollutants, reliably predicting their performance remains a challenge because removal processes are often complex, spatially heterogeneous, and incompletely understood. Although initially popular for characterizing wetland performance, plug flow reactor models are problematic because their parameters exhibit correlation with hydraulic loading. One-dimensional advective-dispersive-reactive models may also be inadequate when longitudinal dispersion is non-Fickian as a result of pronounced transverse gradients in velocity (preferential flow). Models that make use of residence time distributions have shown promise in improving wetland performance characterization, however their applicability may be limited by certain inherent assumptions, e.g. that transverse mixing is nil. A recently-developed bicontinuum (mobile–mobile) model that addresses some of these weaknesses may hold promise for improving wetland performance modeling, however this model has yet to be tested against real-world wetland data. This paper examines the state of the science of free water surface wetland hydrodynamics and transport modeling, discusses the strengths and weaknesses of various steady state models, and compares them to each other in terms of each model’s ability to represent data sets from monitored wetlands. | |||||
BibTeX:
@article{Carleton2010,
author = {Carleton, James N. and Montas, Hubert J.},
title = {An analysis of performance models for free water surface wetlands},
journal = {Water Research},
year = {2010},
volume = {44},
number = {12},
pages = {3595--3606},
url = {http://www.sciencedirect.com/science/article/pii/S0043135410002484}
}
|
|||||
| Carleton, J.N. and Montas, H.J. | Reactive transport in stratified flow fields with idealized heterogeneity | 2009 | Advances in Water Resources Vol. 32(6), pp. 906-915 |
article | URL |
| Abstract: A two-dimensional equation governing the steady state spatial concentration distribution of a reactive constituent within a heterogeneous advective–dispersive flow field is solved analytically. The solution which is developed for the case of a single point source can be generalized to represent analogous situations with any number of separate point sources. A limiting case of special interest has a line source of constant concentration spanning the domain’s upstream boundary. The work has relevance for improving understanding of reactive transport within various kinds of advection-dominated natural or engineered environments including rivers and streams, and bioreactors such as treatment wetlands. Simulations are used to examine quantitatively the impact that transverse dispersion (deviations from purely stochastic-convective flow) can have on mean concentration decline in the direction of flow. Results support the contention that transverse mixing serves to enhance the overall rate of reaction in such systems. | |||||
BibTeX:
@article{Carleton2009,
author = {Carleton, James N. and Montas, Hubert J.},
title = {Reactive transport in stratified flow fields with idealized heterogeneity},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {6},
pages = {906--915},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809000426}
}
|
|||||
| Carleton, J.N. and Montas, H.J. | Stochastic modeling of reactive transport in wetlands | 2009 | Advances in Water Resources Vol. 32(11), pp. 1615-1631 |
article | URL |
| Abstract: This study describes the development of a general model for reaction in and performance of spatially heterogeneous bioreactors such as treatment wetlands. The modeled domain possesses local-scale velocities, reaction rates and transverse dispersion coefficients that are functions of an underlying heterogeneity variate representing one or more controlling biophysical attributes, for example, reactive surface area (submerged plant) density. Reaction rate coefficients are treated as related to local velocities in an inverse square fashion via their mutual dependence upon the variate. The study focuses on the solution for the steady-state case with constant inlet concentration. Results compare well with exact solutions developed for laterally-bounded systems in which the heterogeneity is represented explicitly. Employing the bicontinuum analogue of a second-order model, an expression for an effective longitudinal dispersion coefficient as a function of travel distance is developed using the method of moments. The result provides insights into the behavior of concentration as transverse mixing drives the system asymptotically toward Fickian longitudinal dispersion. The model may represent an improvement over other approaches for characterizing treatment wetland performance because it accounts for evolving shear flow dispersion, and because parameters are few in number, physically based, and invariant with mean velocity. | |||||
BibTeX:
@article{Carleton2009a,
author = {Carleton, James N. and Montas, Hubert J.},
title = {Stochastic modeling of reactive transport in wetlands},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {11},
pages = {1615--1631},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809001353}
}
|
|||||
| Carleton, J.N. and Montas, H.J. | A modeling approach for mixing and reaction in wetlands with continuously varying flow | 2007 | Ecological Engineering Vol. 29(1), pp. 33-44 |
article | URL |
| Abstract: Prior investigations have examined steady-state flow in surface flow treatment wetlands, with mixing modeled as advection-dominated, and reaction calculated using flow-weighted averages over collections of stream tubes with different velocities. This work extends these concepts to non-steady flow conditions and temporally varying inlet concentrations. The essential construct that makes the approach feasible is definition of a set of reference (steady) state conditions under which the residence time distribution (RTD) and stream-tube specific rate constants are defined. Residence time in any stream tube under non-steady flow is treated as a linear function of its reference-condition residence time, and the overall wetland retention time under both mean and varying flow regimes. Outlet concentration is found by convolution of the reaction term with a varying inlet concentration function. For real-world flow and concentration data collected at discrete points in time, integration for outlet concentration is approximated using linear interpolation to generate inlet concentrations and velocities at intermediate points in time. The approach is examined using data from the literature. Vegetation density and depth distributions are seen as central in determining mixing and treatment performance. | |||||
BibTeX:
@article{Carleton2007,
author = {Carleton, James N. and Montas, Hubert J.},
title = {A modeling approach for mixing and reaction in wetlands with continuously varying flow},
journal = {Ecological Engineering},
year = {2007},
volume = {29},
number = {1},
pages = {33--44},
url = {http://www.sciencedirect.com/science/article/pii/S0925857406001510}
}
|
|||||
| Carlson, A.E. and Barnes, D.L. | Movement of trichloroethene in a discontinuous permafrost zone | 2011 | Journal of Contaminant Hydrology Vol. 124(1-4), pp. 1-13 |
article | URL |
| Abstract: At a site with discontinuous permafrost in Fairbanks, Alaska, releases of trichloroethene (TCE), an industrial solvent, have caused contamination of the groundwater. The objective of this study was to investigate the relationship between the migration pathway of the TCE groundwater plume and the distribution of the discontinuous permafrost at the site. The TCE plume configuration is substantially different than what regional hydrology trends would predict. Using GIS, we conducted a geostatistical analysis of field data collected during soil-boring installations and groundwater monitoring well sampling. With the analysis results, we constructed maps of the permafrost-table elevation (top of permafrost) and of the groundwater gradients and TCE concentrations from multiyear groundwater sampling events. The plume concentrations and groundwater gradients were overlain on the permafrost map to correlate permafrost locations with groundwater movement and the spatial distribution of TCE moving with groundwater. Correlation of the overlay maps revealed converging and diverging groundwater flow in response to the permafrost-table distribution, the absence of groundwater contamination in areas with a high permafrost-table elevation, and channeling of contaminants and water between areas of permafrost. In addition, we measured groundwater elevations in nested wells to quantify vertical gradients affecting TCE migration. At one set of nested wells down gradient from an area of permafrost we measured an upward vertical gradient indicating recharge of groundwater from the subpermafrost region of the aquifer causing dilution of the plume. The study indicates that the variable distribution of the permafrost is affecting the way groundwater and TCE move through the aquifer. Consequently, changes to the permafrost configuration due to thawing would likely affect both groundwater movement and TCE migration, and areas that were contaminant-free may become susceptible to contamination. | |||||
BibTeX:
@article{Carlson2011,
author = {Carlson, Andrea E. and Barnes, David L.},
title = {Movement of trichloroethene in a discontinuous permafrost zone},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {124},
number = {1-4},
pages = {1--13},
url = {http://www.sciencedirect.com/science/article/pii/S016977221000135X}
}
|
|||||
| Carpenter, N. and Roberts, E. | Mass Transport and Residence Time Characteristics of an Oscillatory Flow Electrochemical Reactor | 1999 | Chemical Engineering Research and Design Vol. 77(3)Process and Product Development, pp. 212-217 |
article | URL |
| Abstract: The mass transport and residence time characteristics of a parallel-plate oscillatory flow reactor have been investigated by studying the reduction of ferricyanide under an array of experimental conditions, including variations in oscillation frequency, oscillation amplitude, net flow rate and flow geometry. Under certain conditions, oscillatory flow has been found to give enhancement of mass transport rates in excess of an order of magnitude. The residence time distribution (RTD) response to the injection of an electrochemical tracer has been determined, and results are compared with that predicted by the axial dispersion model. | |||||
BibTeX:
@article{Carpenter1999,
author = {Carpenter, N.G. and Roberts, E.P.L.},
title = {Mass Transport and Residence Time Characteristics of an Oscillatory Flow Electrochemical Reactor},
booktitle = {Process and Product Development},
journal = {Chemical Engineering Research and Design},
year = {1999},
volume = {77},
number = {3},
pages = {212--217},
url = {http://www.sciencedirect.com/science/article/pii/S0263876299717788}
}
|
|||||
| Carrera, J. | An overview of uncertainties in modelling groundwater solute transport | 1993 | Journal of Contaminant Hydrology Vol. 13(1-4)Chemistry and Migration of Actinides and Fission Products, pp. 23-48 |
article | URL |
| Abstract: Model predictions are uncertain because of uncertainties on future and/or anthropogenic stresses, parameter values and conceptual models. The first two groups of problems can be addressed through rather systematic methods (scenario analysis, error transmission techniques, automatic calibration algorithms, etc.). However, conceptual uncertainties are rarely given adequate attention. The objective of this paper is to synthesize conceptual difficulties associated with transport. These include: (1) processes that are significant at small scales may not be relevant at large scales; (2) inversely, new processes (e.g., dispersion) emerge in response to increase in scale and the way to represent them may depend on the assumed model structure; (3) the observed shapes of both breakthrough curves and pollutant plumes are not well represented by the classical transport equation; (4) porosities and dispersivities derived from field tracer tests often exhibit a directional dependence; etc. Though not directly related to solute transport, scale effects on hydraulic conductivity may also affect solute transport modelling. When these anomalies are examined, it is concluded that they are directly or indirectly caused by heterogeneity. Current approaches for dealing with heterogeneity can be divided into stochastic and deterministic. Stochastic methods have been successful in explaining qualitatively some anomalies of solute transport, but they appear to be far from reaching a stage at which they can be used routinely for solving realistic field problems. On the other hand, when applied with care, deterministic methods have been successfully used in actual problems. Yet, it can be argued that they fail to account for small-scale variability of concentrations so that they would become ineffective when dealing with nonlinear processes, such as chemical reactions. Relevance of on-going research for overcoming these difficulties is discussed. | |||||
BibTeX:
@article{Carrera1993,
author = {Carrera, Jesús},
title = {An overview of uncertainties in modelling groundwater solute transport},
booktitle = {Chemistry and Migration of Actinides and Fission Products},
journal = {Journal of Contaminant Hydrology},
year = {1993},
volume = {13},
number = {1-4},
pages = {23--48},
url = {http://www.sciencedirect.com/science/article/pii/016977229390049X}
}
|
|||||
| Carrera, J., Mousavi, S.F., Usunoff, E.J., Sánchez-Vila, X. and Galarza, G. | A discussion on validation of hydrogeological models | 1993 | Reliability Engineering & System Safety Vol. 42(2-3), pp. 201-216 |
article | URL |
| Abstract: Groundwater flow and solute transport are often driven by heterogeneities that elude easy identification. It is also difficult to select and describe the physico-chemical processes controlling solute behavior. As a result, definition of a conceptual model involves numerous assumptions both on the selection of processes and on the representation of their spatial variability. Even if a unique conceptual model could be identified, estimation of its parameters may be highly uncertain. Using a calibrated model for making groundwater predictions involves three types of uncertainties: those associated with the correctness of the conceptual model, which may arise during model construction or during prediction; those related to the accuracy of model parameters; and those corresponding to uncertainties in future stresses. In this context, validating a numerical model by comparing its predictions with actual measurements may not be sufficient for evaluting whether or not it provides a good representation of ‘reality’. Predictions will be close to measurements, regardless of model validity, if these are taken from experiments that stress well-calibrated model modes. On the other hand, predictions will be far from measurements when model parameters are very uncertain, even if the model is indeed a very good representation of the real system. Hence, we contend that ‘classical’ validation of hydrogeological models is not possible. Rather, models should be viewed as theories about the real system. This can be proven wrong, but they cannot be proven right. In this sense, we propose to follow a rigorous modeling approach in which different sources of uncertainty are explicitly recognized. The application of one such approach is illustrated by modeling a laboratory uranium tracer test performed on fresh granite, which was used as Test Case 1b in INTRAVAL. | |||||
BibTeX:
@article{Carrera1993a,
author = {Carrera, Jesús and Mousavi, Sayed F. and Usunoff, Eduardo J. and Sánchez-Vila, Xavier and Galarza, Germán},
title = {A discussion on validation of hydrogeological models},
journal = {Reliability Engineering & System Safety},
year = {1993},
volume = {42},
number = {2-3},
pages = {201--216},
url = {http://www.sciencedirect.com/science/article/pii/095183209390089H}
}
|
|||||
| Carretier, E., Wyart, Y., Guichardon, P., Badens, E., Boutin, O., Vallejos, J.-C. and Charbit, G. | New insight into micromixing in supercritical CO2 using a chemical method | 2006 | The Journal of Supercritical Fluids Vol. 38(3), pp. 332-338 |
article | URL |
| Abstract: Competing reactions have been studied in order to characterize micromixing efficiency in supercritical medium. A new chemical reaction test has been developed because the current systems involving ionic species are not suitable for a supercritical medium (CO2). The system is based on two competitive reactions: the esterification of phenylacetic acid by ethyl alcohol using paratoluenesulfonic acid monohydrate as a catalyst and the neutralization of paratoluenesulfonic acid monohydrate by tributylamin. | |||||
BibTeX:
@article{Carretier2006,
author = {Carretier, E. and Wyart, Y. and Guichardon, P. and Badens, E. and Boutin, O. and Vallejos, J.-C. and Charbit, G.},
title = {New insight into micromixing in supercritical CO2 using a chemical method},
journal = {The Journal of Supercritical Fluids},
year = {2006},
volume = {38},
number = {3},
pages = {332--338},
url = {http://www.sciencedirect.com/science/article/pii/S0896844605002512}
}
|
|||||
| Carroll, R.W., Pohll, G.M., Earman, S. and Hershey, R.L. | A comparison of groundwater fluxes computed with MODFLOW and a mixing model using deuterium: Application to the eastern Nevada Test Site and vicinity | 2008 | Journal of Hydrology Vol. 361(3-4), pp. 371-385 |
article | URL |
| Abstract: The primary objective of this study was to verify groundwater flows in the vicinity of the eastern Nevada Test Site (NTS) computed with a hydraulically defined flow model against groundwater δD values computed by a steady-state mixing model. The United States Geological Survey’s Death Valley regional flow model (DVRFM) is a transient, three-dimensional, groundwater model that uses the public domain, finite-difference code MODFLOW. The mixing model (Discrete-State Compartment Model-Shuffled Complex Evolution, or DSCM-SCE) is a recently developed code that is able to autocalibrate groundwater fluxes (both magnitude and direction) to best match observed tracer concentrations in groundwater. To compare modeling approaches, DVRFM boundary conditions and cell-to-cell interactions were implemented into a previously developed 15-cell DSCM-SCE δD model of the eastern NTS. Analysis of δD and δ18Ο data conducted throughout the model domain suggests recharge and mixing are the dominant mechanisms for groundwater isotopic enrichment in the downgradient direction. Therefore, evaporation, at least at the regional scale, was ignored. Model results showed that DVRFM boundary fluxes and cell outflow volumes reproduced observed groundwater δD values in nine of the 11 hydrographic basins that contained deuterium data. The remaining four modeled basins did not have any deuterium data, however, modeling results closely matched estimated δD for two of these basins. The isotope mixing model independently verified that most of the hydraulically defined groundwater flows simulated by MODFLOW are reasonable. Optimization of the DSCM-SCE was then done by adjusting groundwater fluxes between cells to improve predicted groundwater δD values. This significantly lowered the weighted root-mean-squared error and helped to identify several basins where DVRFM–simulated boundary conditions and groundwater fluxes should be reexamined. Overall, the two modeling approaches complemented each other, such that the isotope mixing model verified the hydraulically based groundwater flow model and refined groundwater flux estimates to better understand the physical system. | |||||
BibTeX:
@article{Carroll2008,
author = {Carroll, Rosemary W.H. and Pohll, Greg M. and Earman, Sam and Hershey, Ronald L.},
title = {A comparison of groundwater fluxes computed with MODFLOW and a mixing model using deuterium: Application to the eastern Nevada Test Site and vicinity},
journal = {Journal of Hydrology},
year = {2008},
volume = {361},
number = {3-4},
pages = {371--385},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408004101}
}
|
|||||
| Carroll, R.W.H., Pohll, G.M., Earman, S. and Hershey, R.L. | Global optimization of a deuterium calibrated, discrete-state compartment model (DSCM): Application to the eastern Nevada Test Site | 2007 | Journal of Hydrology Vol. 345(3-4), pp. 237-253 |
article | URL |
| Abstract: As part of a larger study to estimate groundwater recharge volumes in the area of the eastern Nevada Test Site (NTS), [Campana, M.E., 1975. Finite-state models of transport phenomena in hydrologic systems, PhD Dissertation: University of Arizona, Tucson] Discrete-state compartment model (DSCM) was re-coded to simulate steady-state groundwater concentrations of a conservative tracer. It was then dynamically linked with the shuffled complex evolution (SCE) optimization algorithm [Duan, Q., Soroosh, S., Gupta, V., 1992. Effective and efficient global optimization for conceptual rainfall-runoff models. Water Resources Research 28(4), 1015–1031] in which both flow direction and magnitude were adjusted to minimize errors in predicted tracer concentrations. Code validation on a simple four-celled model showed the algorithm consistent in model predictions and capable of reproducing expected cell outflows with relatively little error. The DSCM–SCE code was then applied to a 15-basin (cell) eastern NTS model developed for the DSCM. Auto-calibration of the NTS model was run given two modeling scenarios, (a) assuming known groundwater flow directions and solving only for magnitudes and, (b) solving for groundwater flow directions and magnitudes. The SCE is a fairly robust algorithm, unlike simulated annealing or modified Gauss–Newton approaches. The DSCM–SCE improves upon its original counterpart by being more user-friendly and by auto-calibrating complex models in minutes to hours. While the DSCM–SCE can provide numerical support to a working hypothesis, it can not definitively define a flow system based solely on δD values given few hydrogeologic constraints on boundary conditions and cell-to-cell interactions. | |||||
BibTeX:
@article{Carroll2007,
author = {Carroll, Rosemary W. H. and Pohll, Greg M. and Earman, Sam and Hershey, Ronald L.},
title = {Global optimization of a deuterium calibrated, discrete-state compartment model (DSCM): Application to the eastern Nevada Test Site},
journal = {Journal of Hydrology},
year = {2007},
volume = {345},
number = {3-4},
pages = {237--253},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407004568}
}
|
|||||
| Carty, A., Scholz, M., Heal, K., Gouriveau, F. and Mustafa, A. | The universal design, operation and maintenance guidelines for farm constructed wetlands (FCW) in temperate climates | 2008 | Bioresource Technology Vol. 99(15), pp. 6780-6792 |
article | URL |
| Abstract: This paper comprises the scientific justification for the Farm Constructed Wetland (FCW) Design Manual for Northern Ireland and Scotland. Moreover, this document addresses an international audience interested in applying wetland systems in the wider agricultural context. Farm constructed wetlands combine farm wastewater (predominantly farmyard runoff) treatment with landscape and biodiversity enhancements, and are a specific application and class of integrated constructed wetlands (ICW), which have wider applications in the treatment of other wastewater types such as domestic sewage. The aim of this review paper is to propose guidelines highlighting the rationale for FCW, including key water quality management and regulatory issues, important physical and biochemical wetland treatment processes, assessment techniques for characterizing potential FCW sites and discharge options to water bodies. The paper discusses universal design, construction, planting, maintenance and operation issues relevant specifically for FCW in a temperate climate, but highlights also catchment-specific requirements to protect the environment. | |||||
BibTeX:
@article{Carty2008,
author = {Carty, Aila and Scholz, Miklas and Heal, Kate and Gouriveau, Fabrice and Mustafa, Atif},
title = {The universal design, operation and maintenance guidelines for farm constructed wetlands (FCW) in temperate climates},
journal = {Bioresource Technology},
year = {2008},
volume = {99},
number = {15},
pages = {6780--6792},
url = {http://www.sciencedirect.com/science/article/pii/S0960852408000837}
}
|
|||||
| Case, M.W., Williams, R., Yeatts, K., Chen, F.-L., Scott, J., Svendsen, E. and Devlin, R.B. | Evaluation of a direct personal coarse particulate matter monitor | 2008 | Atmospheric Environment Vol. 42(19), pp. 4446-4452 |
article | URL |
| Abstract: One aspect of the North Carolina Adult Asthma and Environment study (NCAAES) was to evaluate personal exposures to coarse particulate matter (PM10−2.5) and their associated variability. As part of this, we examined the ability of a community-based monitor to act as a surrogate for an individual's true exposure to this size fraction in linked health effect studies. To assess personal exposures to various particulate matter (PM) size fractions, a personal PM monitor was evaluated. This monitor featured a multi-stage cascade impactor that allowed for the simultaneous collection of PM10−2.5 and PM2.5 size fractions. The monitor was evaluated for collocated bias and comparability with a dichotomous (dichot) sampler (device for dividing aerosol PM population into two size fractions during sampling) at an outdoor monitoring site. Results of this evaluation indicated that the prototype was capable of agreement within ±20% of that provided by the reference methodology as well as 20% daily precision for PM10−2.5 mass measurements. | |||||
BibTeX:
@article{Case2008,
author = {Case, Martin W. and Williams, Ron and Yeatts, Karin and Chen, Fu-Lin and Scott, James and Svendsen, Erik and Devlin, Robert B.},
title = {Evaluation of a direct personal coarse particulate matter monitor},
journal = {Atmospheric Environment},
year = {2008},
volume = {42},
number = {19},
pages = {4446--4452},
url = {http://www.sciencedirect.com/science/article/pii/S1352231008001283}
}
|
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| Castelain, C., Berger, D., Legentilhomme, P., Mokrani, A. and Peerhossaini, H. | Experimental and numerical characterisation of mixing in a steady spatially chaotic flow by means of residence time distribution measurements | 2000 | International Journal of Heat and Mass Transfer Vol. 43(19), pp. 3687-3700 |
article | URL |
| Abstract: This work describes an experimental study and a numerical simulation of residence time distributions (RTD) in a spatially chaotic three-dimensional flow. The experimental system is made up of a succession of bends in which centrifugal force generates a pair of streamwise Dean roll-cells. Fluid particle trajectories become chaotic through geometrical perturbation obtained by rotating the curvature plane of each bend ±90° with respect to the neighbouring ones. Different numbers of bends, ranging from 3 to 33, were tested. RTD is experimentally obtained by using a two-measurement-point conductimetric method, the concentration of the injected tracer being determined both at the inlet and at the outlet of the chaotic mixer. The experimental RTD is modelled by a plug flow with axial dispersion volume exchanging mass with a stagnant zone. RTD experiments were conducted for Reynolds numbers between 30 and 13,000. Péclet number based on the diameter of the pipe PeD=W̄DDax increases with Reynolds number, whatever the number of bends in the system. This reduction in axial dispersion is due to the secondary Dean flow and the chaotic trajectories. Globally, the flowing fraction increases with Reynolds number, whatever the number of bends, to reach a maximum value between 90 and 100%. For Reynolds numbers between 50 and 200, the flowing fraction increases with the number of bends. The stagnant zone models fluid particles located close to the tube wall. The pathlines become progressively chaotic in small zones in the cross section and then spread across the flow as the number of bends is increased, allowing more trapped particles to move towards the tube centre. In order to characterise more completely the efficiency of the device, a criterion is proposed that takes into account both the mixing characteristics and the pressure drop. The RTD for low Reynolds numbers has also been obtained numerically using a flow model based on Dean’s asymptotic perturbation solutions of the mean flow in a curved pipe. At the end of each bend, the velocity field is rotated by ±90° before entering the next bend. The RTD is calculated by following the trajectories of 250,000 ‘numerical’ particles along the device. Numerical results are in good agreement with experiments in the same Reynolds number range. | |||||
BibTeX:
@article{Castelain2000,
author = {Castelain, C. and Berger, D. and Legentilhomme, P. and Mokrani, A. and Peerhossaini, H.},
title = {Experimental and numerical characterisation of mixing in a steady spatially chaotic flow by means of residence time distribution measurements},
journal = {International Journal of Heat and Mass Transfer},
year = {2000},
volume = {43},
number = {19},
pages = {3687--3700},
url = {http://www.sciencedirect.com/science/article/pii/S0017931099003634}
}
|
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| Castelain, C. and Legentilhomme, P. | Residence time distribution of a purely viscous non-Newtonian fluid in helically coiled or spatially chaotic flows | 2006 | Chemical Engineering Journal Vol. 120(3), pp. 181-191 |
article | URL |
| Abstract: This work is dedicated to an experimental study of residence time distributions (RTD) of a pseudoplastic fluid in different configurations of helically coiled or chaotic systems. The experimental system is made up of a succession of bends in which centrifugal force generates a pair of streamwise Dean cells. Fluid particle trajectories become chaotic through a geometrical perturbation obtained by rotating the curvature plane of each bend of ±90° with respect to the neighboring ones (alternated or twisted curved ducts). Different numbers of bends, ranging from 3 to 33, were tested. RTD is experimentally obtained by using a two-measurement-point conductimetric method, the concentration of the injected tracer being determined both at the inlet and at the outlet of the device. The experimental RTD is modeled by a plug flow with axial dispersion volume exchanging mass with a stagnant zone. RTD experiments were conducted for generalized Reynolds numbers varying from 30 to 270. The Péclet number based on the diameter of the pipe is found to increase with the Reynolds number whatever the number of bends in the system. This reduction in axial dispersion is due to both the secondary Dean flow and the chaotic trajectories. Globally, the flowing fraction, which is one of the characteristic parameters of the model, increases with the Reynolds number, whatever the number of bends, to reach a maximum value ranging from 90% to 100%. For Reynolds numbers less than 200, the flowing fraction increases with the number of bends. The stagnant zone models fluid particles located close to the tube wall. The pathlines become progressively chaotic in small zones in the cross section and then spread across the flow as the number of bends is increased, allowing more trapped particles to move towards the tube center. Results have been compared with those previously obtained using Newtonian fluids. The values of the Péclet number are greater for the pseudoplastic fluid, the local change of apparent viscosity affecting the secondary flow. For pseudoplastic fluids, the apparent viscosity is lower near the wall and higher at the center of the cross section. The maximum axial velocity is flattened as the flow behavior index is reduced, inducing a decrease of the secondary flow in the central part of the pipe and an acceleration of it near the wall, which reduces the axial dispersion. These results are encouraging for the use of this system as continuous mixer for complex fluids in laminar regime, particularly for small Reynolds numbers. | |||||
BibTeX:
@article{Castelain2006,
author = {Castelain, C. and Legentilhomme, P.},
title = {Residence time distribution of a purely viscous non-Newtonian fluid in helically coiled or spatially chaotic flows},
journal = {Chemical Engineering Journal},
year = {2006},
volume = {120},
number = {3},
pages = {181--191},
url = {http://www.sciencedirect.com/science/article/pii/S1385894706001574}
}
|
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| Čermáková, J., Scargiali, F., Siyakatshana, N., Kudrna, V., Brucato, A. and Machoň, V. | Axial dispersion model for solid flow in liquid suspension in system of two mixers in total recycle | 2006 | Chemical Engineering Journal Vol. 117(2), pp. 101-107 |
article | URL |
| Abstract: The measurement of residence time distribution of solid particles in solid–liquid suspension is experimentally difficult. However, the twin system approach is particularly suited for the assessment of particle RTD in flow systems as it allows overcoming some of the usual difficulties generally encountered in this kind of measurement. Twin system consists of two vessels and external piping in total recycle. Experimental results from this system can be evaluated using Z-transforms to derive particle RTD for subsequent testing of alternative flow models. Recently, the axial dispersion model was applied using the “advection diffusion equation” (sometimes called the “diffusion with bulk flow equation”) derived thereof, which was solved numerically. This contribution presents an analytical solution of analogous equations, which enables direct and precise evaluations of this problem. | |||||
BibTeX:
@article{Cermakova2006,
author = {Čermáková, J. and Scargiali, F. and Siyakatshana, N. and Kudrna, V. and Brucato, A. and Machoň, V.},
title = {Axial dispersion model for solid flow in liquid suspension in system of two mixers in total recycle},
journal = {Chemical Engineering Journal},
year = {2006},
volume = {117},
number = {2},
pages = {101--107},
url = {http://www.sciencedirect.com/science/article/pii/S138589470500361X}
}
|
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| Cevza Melek, K.-A. | Analytical solutions for contaminant transport in streams | 2008 | Journal of Hydrology Vol. 348(3-4), pp. 524-534 |
article | URL |
| Abstract: The importance of the effect of surface/ground water interactions on contaminant transport in streams and rivers has been greatly recognized in the last two decades. Bencala and Walters (1983) [Bencala, K.E., Walters, R.A., 1983. Simulation of solute transport in a mountain pool-and-riffle stream – a transient storage model. Water Resources Research 19 (3), 718–724.] developed a mathematical model for the transient storage zone to represent the movement of solute from main streams into stagnant zones and back to the main stream. This model calculates the concentrations of a main channel and a storage zone and the transient storage is represented by the mass exchange due to the concentration difference between the stream and the storage zone. Later, Kazezyılmaz-Alhan and Medina (2006) [Kazezyılmaz-Alhan, C.M., Medina Jr., M.A., 2006. Stream solute transport incorporating hyporheic zone processes. Journal of Hydrology 329 (1–2), 26–38.] made several improvements to this transient storage model by incorporating advection and dispersion into the hyporheic zone and representing the mass transport between the channel and hyporheic zone by mass flux terms. In this study, analytical solutions are derived for both transient storage models for the cases of continuous and finite injections of a tracer. The analytical solutions provide the researchers with computational speed in obtaining results for contaminant transport problems, and a means to check the validity of the numerical models. The analytical solutions are compared to the numerical solutions for hypothetical problems. Comparison of results shows that the numerical and analytical solutions are in very good agreement. | |||||
BibTeX:
@article{CevzaMelek2008,
author = {Cevza Melek, Kazezyılmaz-Alhan},
title = {Analytical solutions for contaminant transport in streams},
journal = {Journal of Hydrology},
year = {2008},
volume = {348},
number = {3-4},
pages = {524--534},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407006130}
}
|
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| Chakraborty, S. and Balakotaiah, V. | Low-dimensional models for describing mixing effects in laminar flow tubular reactors | 2002 | Chemical Engineering Science Vol. 57(13), pp. 2545-2564 |
article | URL |
| Abstract: The Liapunov–Schmidt (LS) technique of bifurcation theory is used to average the convective-diffusion equation in the transverse direction and obtain low-dimensional two-mode models that describe mixing effects in laminar flow tubular reactors. For the isothermal case, these models are described by a pair of equations involving two modes, namely, the spatially averaged (〈C〉) and the mixing-cup (Cm) concentration vectors. The first equation traces the evolution of Cm with residence time, while the second is a local balance equation that describes local mixing as an exchange between the reaction scale (represented by 〈C〉) and the convection scale (represented by Cm) in terms of the local mixing time. The LS method also shows that such low-dimensional description is possible only if the local Damköhler number (ratio of local mixing time to reaction time) satisfies the convergence criteria of being less than 0.858. It is shown that the two-mode models have the same accuracy as the infinite (radial) mode convection model, within the range of validity of the latter. The two-mode models for homogeneous reactors have many similarities with the classical two-phase models for heterogeneous catalytic reactors, with the transfer coefficient concept (between surface and mixing cup concentrations, CS and Cm, respectively) being replaced by that of an exchange coefficient (between 〈C〉 and Cm). Examples are presented to illustrate the usefulness of the two-mode models in predicting the effects of non-identical local mixing times, non-uniform reactant feeding and non-linear kinetics on conversion and yields of products for single and multiple reactions in laminar flow tubular reactors. | |||||
BibTeX:
@article{Chakraborty2002,
author = {Chakraborty, Saikat and Balakotaiah, Vemuri},
title = {Low-dimensional models for describing mixing effects in laminar flow tubular reactors},
journal = {Chemical Engineering Science},
year = {2002},
volume = {57},
number = {13},
pages = {2545--2564},
url = {http://www.sciencedirect.com/science/article/pii/S000925090200129X}
}
|
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| Chang, C.-M. and Kemblowski, M.W. | The impact of finite flow domain size on the statistical properties of the flow system in heterogeneous porous media | 2003 | Journal of Hydrology Vol. 278(1-4), pp. 121-130 |
article | URL |
| Abstract: A modified covariance function of log hydraulic conductivity, accounting for a finite field size, is derived to assess the impact of finite flow domain size on the statistical properties of the flow system in heterogeneous porous media, such as the uncertainty of a large-scale mean model (variation of head fluctuations) and the effective hydraulic conductivity. This development is accomplished by applying a perturbation approximation and spectral representation to a steady three-dimensional flow field of finite extent. Closed-form expressions in a statistically isotropic porous medium indicate that the finite flow domain size has a direct effect on the head variance and the effective hydraulic conductivity. The comparison of the presented formulation for effective hydraulic conductivity is made with existing results. | |||||
BibTeX:
@article{Chang2003,
author = {Chang, Ching-Min and Kemblowski, Mariush W.},
title = {The impact of finite flow domain size on the statistical properties of the flow system in heterogeneous porous media},
journal = {Journal of Hydrology},
year = {2003},
volume = {278},
number = {1-4},
pages = {121--130},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403001379}
}
|
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| Chapelle, F.H. | Bioremediation of Petroleum Hydrocarbon-Contaminated Ground Water: The Perspectives of History and Hydrology | 1999 | Ground Water Vol. 37(1), pp. 122-132 |
article | URL |
| Abstract: Bioremediation, the use of microbial degradation processes to detoxify environmental contamination, was first applied to petroleum hydrocarbon-contaminated ground water systems in the early 1970s. Since that time, these technologies have evolved in some ways that were clearly anticipated by early investigators, and in other ways that were not foreseen. The expectation that adding oxidants and nutrients to contaminated aquifers would enhance biodegradation, for example, has been born out by subsequent experience. Many of the technologies now in common use such as air sparging, hydrogen peroxide addition, nitrate addition, and bioslurping, are conceptually similar to the first bioremediation systems put into operation. More unexpected, however, were the considerable technical problems associated with delivering oxidants and nutrients to heterogeneous ground water systems. Experience has shown that the success of engineered bioremediation systems depends largely on how effectively directions and rates of ground water flow can be controlled, and thus how efficiently oxidants and nutrients can be delivered to contaminated aquifer sediments. The early expectation that injecting laboratory-selected or genetically engineered cultures of hydrocarbon-degrading bacteria into aquifers would be a useful bioremediation technology has not been born out by subsequent experience. Rather, it appears that petroleum hydrocarbon-degrading bacteria are ubiquitous in ground water systems and that bacterial addition is usually unnecessary. Perhaps the technology that was least anticipated by early investigators was the development of intrinsic bioremediation. Experience has shown that natural attenuation mechanisms - biodegradation, dilution, and sorption - limit the migration of contaminants to some degree in all ground water systems. Intrinsic bioremediation is the deliberate use of natural attenuation processes to treat contaminated ground water to specified concentration levels at predetermined points in the aquifer. In current practice, intrinsic bioremediation of petroleum hydrocarbons requires a systematic assessment to show that ambient natural attenuation mechanisms are efficient enough to meet regulatory requirements and a monitoring program to verify that performance requirements are met in the future. | |||||
BibTeX:
@article{Chapelle1999,
author = {Chapelle, Francis H.},
title = {Bioremediation of Petroleum Hydrocarbon-Contaminated Ground Water: The Perspectives of History and Hydrology},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {1999},
volume = {37},
number = {1},
pages = {122--132},
url = {http://dx.doi.org/10.1111/j.1745-6584.1999.tb00965.x}
}
|
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| Chatelier, M., Ruelleu, S., Bour, O., Porel, G. and Delay, F. | Combined fluid temperature and flow logging for the characterization of hydraulic structure in a fractured karst aquifer | 2011 | Journal of Hydrology Vol. 400(3-4), pp. 377-386 |
article | URL |
| Abstract: Fractured karst aquifers are well known to conceal channeled flow where a few productive-water bearing conduits comprise a relatively small volume within the flow system. This study investigates the ability of combined water temperature measurements and flow logs in wells to reveal the structure of these channeled flows. Temperature and flow logs discussed in this study were performed under various hydrodynamic conditions from ambient flow to radial forced flow at the large scale. Both techniques complement each other since flow logs measure local flow velocities in wells whereas water column temperature profiles delineate inflow depths. For example, temperatures indicate the origin of water (e.g., shallow versus deep) which is not indicated by flow logs. On the other hand, complex temperature profiles due to the interception by a well of several productive layers are better explained when local flow directions are provided by flow logs. The results indicate hydrodynamic conditions affecting the connections between different water-bearing bodies. Pumping the monitored well at a low rate will capture a short-term and local effect related to the convergence of flow into the well bore. When pumping at high discharge rates in a distant well, temperatures and flow logs will capture the long-term re-adjustment of hydraulic heads over a wide portion of the aquifer. In the end, the association of temperature and flow logs reveals a handy and cost-effective tool, well suited to delineate the complex structure of flow in fractured karst aquifers. Knowing this structure would probably improve the ability to design proper scenarios of water resources exploitation and management in complex aquifers. | |||||
BibTeX:
@article{Chatelier2011,
author = {Chatelier, Marion and Ruelleu, Sébastien and Bour, Olivier and Porel, Gilles and Delay, Frederick},
title = {Combined fluid temperature and flow logging for the characterization of hydraulic structure in a fractured karst aquifer},
journal = {Journal of Hydrology},
year = {2011},
volume = {400},
number = {3-4},
pages = {377--386},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411000850}
}
|
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| Che, Z., Wong, T.N. and Nguyen, N.-T. | An analytical model for plug flow in microcapillaries with circular cross section | 2011 | International Journal of Heat and Fluid Flow Vol. 32(5), pp. 1005-1013 |
article | URL |
| Abstract: Plug flow in microcapillaries or microchannels offers significant advantages for the development of microfluidic applications and recently triggers many interests and studies. Recirculation is formed within liquid plugs due to the presence of interfaces. This paper presents an analytical model to investigate the recirculation flow and the flow resistance in microcapillaries with circular cross section. A fourth order partial differential equation is used to model the Stokes flow within the liquid plug. The results of the flow field show that the flow pattern is affected by the plug length. The flow resistance is determined through the force balance of the liquid plug. The comparison of the flow field and the flow resistance from the analytical model and the experiments shows good agreement. | |||||
BibTeX:
@article{Che2011,
author = {Che, Zhizhao and Wong, Teck Neng and Nguyen, Nam-Trung},
title = {An analytical model for plug flow in microcapillaries with circular cross section},
journal = {International Journal of Heat and Fluid Flow},
year = {2011},
volume = {32},
number = {5},
pages = {1005--1013},
url = {http://www.sciencedirect.com/science/article/pii/S0142727X11000981}
}
|
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| Chen, D.J. and MacQuarrie, K.T. | Numerical simulation of organic carbon, nitrate, and nitrogen isotope behavior during denitrification in a riparian zone | 2004 | Journal of Hydrology Vol. 293(1-4), pp. 235-254 |
article | URL |
| Abstract: Riparian zones have been investigated in order to determine the processes that control the removal of agriculturally derived nitrate from groundwater; however, many gaps exist in our understanding of the functioning of riparian zones as regulators of nitrate fluxes in shallow groundwater. In this study, a reactive-transport model is applied to simulate organic carbon, nitrate, and nitrogen isotope behavior during denitrification in a river riparian zone. The model includes the reactive-transport processes presented by MacQuarrie and Sudicky [J. Contam. Hydrol. 47 (2001) 53], but has been extended to compute nitrogen isotope fractionation during biogeochemical reactions. Numerical simulation results have been compared to field data from a well-characterized river riparian aquifer and the comparison shows that the model captures the essential reactive-transport processes for major reactive species, including δ15N. A surficial peat zone is the main source of dissolved organic carbon (DOC), and the supply of this DOC to underlying sands and gravels by hydrodynamic processes controls the denitrification of upland nitrate flowing into the riparian zone. The model results support the previously proposed conceptual models for denitrification in riparian aquifers in that enriched δ15N, declining DOC, and declining groundwater NO3−–N concentrations all occur within a relatively thin (1.5 m) zone. The simulated isotope enrichment factors for selected locations within the model domain range from −2% to −8‰, and it is noted that these values are significantly lower than the value specified in the model input. This suggests that it would be very difficult to derive accurate isotopic enrichment factors from a limited number of piezometers in such riparian aquifers. Numerical sensitivity analyses show that denitrification can occur at depths as great as 4 m below the ground surface, but the overall nitrate mass removal capacity of the riparian zone will decrease as the groundwater flow system becomes thicker. | |||||
BibTeX:
@article{Chen2004,
author = {Chen, David J.Z. and MacQuarrie, Kerry T.B.},
title = {Numerical simulation of organic carbon, nitrate, and nitrogen isotope behavior during denitrification in a riparian zone},
journal = {Journal of Hydrology},
year = {2004},
volume = {293},
number = {1-4},
pages = {235--254},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404000861}
}
|
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| Chen, G., Zeng, L. and Wu, Z. | An ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow | 2010 | Ecological Modelling Vol. 221(24), pp. 2927-2937 |
article | URL |
| Abstract: As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under environmental dispersion. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of contaminant cloud in the wetland channel flow, critical length and duration of the contaminant cloud with concentration beyond given environmental standard level are concretely illustrated for typical pollutant constituents in wastewater emission. Under the same emission intensity and environmental standard, the duration of contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect. | |||||
BibTeX:
@article{Chen2010,
author = {Chen, G.Q. and Zeng, L. and Wu, Z.},
title = {An ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow},
journal = {Ecological Modelling},
year = {2010},
volume = {221},
number = {24},
pages = {2927--2937},
url = {http://www.sciencedirect.com/science/article/pii/S0304380010004138}
}
|
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| Chen, J.-S., Chen, J.-T., Liu, C.-W., Liang, C.-P. and Lin, C.-W. | Analytical solutions to two-dimensional advection–dispersion equation in cylindrical coordinates in finite domain subject to first- and third-type inlet boundary conditions | 2011 | Journal of Hydrology Vol. 405(3–4), pp. 522-531 |
article | URL |
| Abstract: This study presents exact analytical solutions to the two-dimensional advection–dispersion equation in cylindrical coordinates in finite domain subject to the first- and third-type inlet boundary conditions. The second kind finite Hankel transform and the generalized integral transform technique are adopted to solve the two-dimensional advection–dispersion equation in cylindrical coordinates and its associated initial and boundary conditions. The developed analytical solutions are compared with the solutions for semi-infinite domain subject to the first- and third-type inlet boundary conditions available in literature to illustrate the impacts of the exit boundary conditions. Results show that significant discrepancies between the breakthrough curves obtained from analytical solutions for the finite domain and infinite domain for small Peclet number. Numerical evaluations of the developed analytical solutions for finite domain are computationally intensive because that the convergences of the series progress slowly for medium Peclet number. The developed solutions should be especially useful for testing numerical model simulated solutions for the finite domain subject to first- and third-type inlet boundary conditions. | |||||
BibTeX:
@article{Chen2011a,
author = {Chen, Jui-Sheng and Chen, Juan-Tse and Liu, Chen-Wuing and Liang, Ching-Ping and Lin, Chien-Wen},
title = {Analytical solutions to two-dimensional advection–dispersion equation in cylindrical coordinates in finite domain subject to first- and third-type inlet boundary conditions},
journal = {Journal of Hydrology},
year = {2011},
volume = {405},
number = {3–4},
pages = {522--531},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411003878}
}
|
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| Chen, J.-S., Lai, K.-H., Liu, C.-W. and Ni, C.-F. | A novel method for analytically solving multi-species advective–dispersive transport equations sequentially coupled with first-order decay reactions | 2012 | Journal of Hydrology Vol. 420–421(0), pp. 191-204 |
article | URL |
| Abstract: Analytical solutions for coupled multi-species solute transport problems are difficult to derive and relatively few in subsurface hydrology. Decomposition strategy such as linear transform format or matrix diagonalization method which decomposes the set of coupled advective–dispersive transport equations into a system of independent differential equations have been widely used to derive the analytical solution for coupled multi-species solute transport problem. These decomposition techniques are generally limited to derive the analytical solution for an infinite or a semi-infinite domain. In this study, we present a novel method for analytically solving multi-species advective–dispersive transport equations sequentially coupled by first-order decay reactions. The method first performs Laplace transform with respect to time and the generalized integral transform technique with respect to the spatial coordinate to convert the set of partial differential equations into a system of algebraic equations. Subsequently, the system of algebraic equations is solved using simple algebraic manipulation, thus the concentrations in the transformed domain for each species can be independently obtained. Ultimately, the concentrations in the original domain for all species are obtained by successive application of Laplace and the corresponding generalized integral transform inversions. A coupled four-species transport problem in a finite domain is used to demonstrate the robustness of the proposed method for deriving the analytical solutions associated with sequentially coupled multi-species solute transport problem. The developed analytical solution is tested by comparing their results against those generated with the corresponding numerical solutions. Results show perfect agreements between the analytical and numerical solutions. Moreover, the developed analytical solution is compared with the analytical solutions for a semi-infinite domain available in literature to illustrate the impacts of the exit boundary conditions on coupled multi-species transport. It is observed that significant discrepancies exist between two solutions for small Peclet numbers, whereas two solutions deviate negligibly each other for medium Peclet numbers. | |||||
BibTeX:
@article{Chen2012a,
author = {Chen, Jui-Sheng and Lai, Keng-Hsin and Liu, Chen-Wuing and Ni, Chuen-Fa},
title = {A novel method for analytically solving multi-species advective–dispersive transport equations sequentially coupled with first-order decay reactions},
journal = {Journal of Hydrology},
year = {2012},
volume = {420–421},
number = {0},
pages = {191--204},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411008730}
}
|
|||||
| Chen, J.-S., Liu, Y.-H., Liang, C.-P., Liu, C.-W. and Lin, C.-W. | Exact analytical solutions for two-dimensional advection–dispersion equation in cylindrical coordinates subject to third-type inlet boundary condition | 2011 | Advances in Water Resources Vol. 34(3), pp. 365-374 |
article | URL |
| Abstract: Exact analytical solutions for two-dimensional advection–dispersion equation (ADE) in cylindrical coordinates subject to the third-type inlet boundary condition are presented in this study. The finite Hankel transform technique in combination with the Laplace transform method is adopted to solve the two-dimensional ADE in cylindrical coordinates. Solutions are derived for both continuous input and instantaneous slug input. The developed analytical solutions are compared with the solutions for first-type inlet boundary condition to illustrate the influence of the inlet condition on the two-dimensional solute transport in a porous medium system with a radial geometry. Results show significant discrepancies between the breakthrough curves obtained from analytical solutions for the first-type and third-type inlet boundary conditions for large longitudinal dispersion coefficients. The developed solutions conserve the solute mass and are efficient tools for simultaneous determination of the longitudinal and transverse dispersion coefficients from a laboratory-scale radial column experiment or an in situ infiltration test with a tracer. | |||||
BibTeX:
@article{Chen2011,
author = {Chen, Jui-Sheng and Liu, Yiu-Hsuan and Liang, Ching-Ping and Liu, Chen-Wuing and Lin, Chien-Wen},
title = {Exact analytical solutions for two-dimensional advection–dispersion equation in cylindrical coordinates subject to third-type inlet boundary condition},
journal = {Advances in Water Resources},
year = {2011},
volume = {34},
number = {3},
pages = {365--374},
url = {http://www.sciencedirect.com/science/article/pii/S030917081000237X}
}
|
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| Chen, Q., Liu, J., Ho, K.C. and Yang, Z. | Development of a relative risk model for evaluating ecological risk of water environment in the Haihe River Basin estuary area | 2012 | Science of The Total Environment Vol. 420(0), pp. 79-89 |
article | URL |
| Abstract: Ecological risk assessment for water environment is significant to water resource management of basin. Effective environmental management and systems restoration such as the Haihe River Basin require holistic understanding of the relative importance of various stressor-related impacts throughout the basin. As an effective technical tool for evaluating the ecological risk, relative risk model (RRM) was applied in regional scale successfully. In this study, the risk transfer from upstream of basin was considered and the RRM was developed through introducing the source–stressor–habitat exposure filter (SSH), the endpoint–habitat exposure filter (EH) and the stressor–endpoint effect filter (SE) to reflect the meaning of exposure and effect more explicit. Water environment which includes water quality, water quantity and aquatic ecosystems was selected as the assessment endpoints. We created a conceptual model which depicting potential and effect pathways from source to stressor to habitat to endpoint. The Haihe River Basin estuary (HRBE) was selected as the model case. The results showed that there were two low risk regions, one medium risk region and two high risk regions in the HRBE. The results also indicated that urbanization was the biggest source, the second was shipping and the third was industry, their risk scores are 5.65, 4.71 and 3.68 respectively. Furthermore, habitat destruction was the largest stressor with the risk scores (2.66), the second was oxygen consuming organic pollutants (1.75) and the third was pathogens (1.75). So these three stressors were the main influencing factors of the ecological pressure in the study area. For habitats, open waters (9.59) and intertidal mudflat were enduring the bigger pressure and should be taken considerable attention. Ecological service values damaged (30.54) and biodiversity decreased were facing the biggest risk pressure. | |||||
BibTeX:
@article{Chen2012,
author = {Chen, Qiuying and Liu, Jingling and Ho, Kin Chung and Yang, Zhifeng},
title = {Development of a relative risk model for evaluating ecological risk of water environment in the Haihe River Basin estuary area},
journal = {Science of The Total Environment},
year = {2012},
volume = {420},
number = {0},
pages = {79--89},
url = {http://www.sciencedirect.com/science/article/pii/S0048969711010783}
}
|
|||||
| Chen, S.X. and Gao, J. | An adaptive empirical likelihood test for parametric time series regression models | 2007 | Journal of Econometrics Vol. 141(2), pp. 950-972 |
article | URL |
| Abstract: We propose an adaptive empirical likelihood (EL) test for a parametric regression model against a class of alternatives for weakly dependent time series observations. The test is formulated by maximizing a standardized version of the EL statistic over a set of smoothing bandwidths. It is demonstrated that the proposed test is able to distinguish the null hypothesis from a series of local alternatives at an optimal rate. | |||||
BibTeX:
@article{Chen2007,
author = {Chen, Song Xi and Gao, Jiti},
title = {An adaptive empirical likelihood test for parametric time series regression models},
journal = {Journal of Econometrics},
year = {2007},
volume = {141},
number = {2},
pages = {950--972},
url = {http://www.sciencedirect.com/science/article/pii/S0304407606002533}
}
|
|||||
| Chen, Z., Chen, G., Chen, B., Zhou, J., Yang, Z. and Zhou, Y. | Net ecosystem services value of wetland: Environmental economic account | 2009 | Communications in Nonlinear Science and Numerical Simulation Vol. 14(6), pp. 2837-2843 |
article | URL |
| Abstract: For decision making in terms of environmental economics for wetland construction, restoration and preservation, net ecosystem services values of constructed, human-interfered and natural wetlands are explored in the present work as a comparative study. The ecosystem services values of a pilot constructed wetland in Beijing, China in different discount rates and time horizons are accounted and compared with those of the natural wetlands all over the world as a mean and of a typical human-interfered wetland in Wenzhou, China. Results show that in both finite and infinite time horizons considered, the constructed wetland has the largest net services value in a reasonable discount rate. | |||||
BibTeX:
@article{Chen2009,
author = {Chen, Z.M. and Chen, G.Q. and Chen, B. and Zhou, J.B. and Yang, Z.F. and Zhou, Y.},
title = {Net ecosystem services value of wetland: Environmental economic account},
journal = {Communications in Nonlinear Science and Numerical Simulation},
year = {2009},
volume = {14},
number = {6},
pages = {2837--2843},
url = {http://www.sciencedirect.com/science/article/pii/S1007570408001512}
}
|
|||||
| Chen-Charpentier, B.M., Dimitrov, D.T. and Kojouharov, H.V. | Numerical simulation of multi-species biofilms in porous media for different kinetics | 2009 | Mathematics and Computers in Simulation Vol. 79(6)Applied and Computational MathematicsSelected Papers of the Sixth PanAmerican WorkshopJuly 23-28, 2006, Huatulco-Oaxaca, Mexico, pp. 1846-1861 |
article | URL |
| Abstract: There are bacteria that can form strong biofilms in porous media. These biofilms can be used as biobarriers to restrict the flow of pollutants. For certain contaminants, a second species of bacteria that can actually react with the contaminants can be added to the biobarrier to actually degrade the pollutants. We propose some mathematical models for the formation of these reacting biobarriers under different hypotheses, and numerically solve the resulting equations for the flow, transport and reactions. Qualitative comparisons with some experimental results are also given. | |||||
BibTeX:
@article{Chen-Charpentier2009,
author = {Chen-Charpentier, Benito M. and Dimitrov, Dobromir T. and Kojouharov, Hristo V.},
title = {Numerical simulation of multi-species biofilms in porous media for different kinetics},
booktitle = {Applied and Computational MathematicsSelected Papers of the Sixth PanAmerican WorkshopJuly 23-28, 2006, Huatulco-Oaxaca, Mexico},
journal = {Mathematics and Computers in Simulation},
year = {2009},
volume = {79},
number = {6},
pages = {1846--1861},
url = {http://www.sciencedirect.com/science/article/pii/S037847540700153X}
}
|
|||||
| Chen-Charpentier, B.M. and Kojouharov, H.V. | Mathematical modeling of bioremediation of trichloroethylene in aquifers | 2008 | Computers & Mathematics with Applications Vol. 56(3)Mathematical Models in Life Sciences & Engineering, pp. 645-656 |
article | URL |
| Abstract: Trichloroethylene (TCE) is a very common contaminant of groundwater. It is used as an industrial solvent and is frequently poured into the soil. There exist bacteria that can degrade TCE. In contrast with most cases of bioremediation, the bacteria that degrade TCE do not use it as a carbon source. Instead the bacteria produce an enzyme to metabolize methane. This enzyme can degrade other organics including TCE. In this paper we model in situ bioremediation of TCE in an aquifer by using two species of bacteria: one that forms biobarriers to restrict the movement of TCE and the second one to reduce TCE. The model includes flow of water, transport of TCE and the nutrients, bacterial growth and degradation of TCE. Nonstandard numerical methods are used to discretize the equations. Some results are presented. | |||||
BibTeX:
@article{Chen-Charpentier2008,
author = {Chen-Charpentier, Benito M. and Kojouharov, Hristo V.},
title = {Mathematical modeling of bioremediation of trichloroethylene in aquifers},
booktitle = {Mathematical Models in Life Sciences & Engineering},
journal = {Computers & Mathematics with Applications},
year = {2008},
volume = {56},
number = {3},
pages = {645--656},
url = {http://www.sciencedirect.com/science/article/pii/S0898122108000552}
}
|
|||||
| Cheng, J.M. and Chen, C.X. | An integrated linear/non-linear flow model for the conduit-fissure-pore media in the karst triple void aquifer system | 2005 | Environmental Geology Vol. 47(2), pp. 163-174 |
article | URL |
| Abstract: Most karstic aquifer media may be characterized as the triple-void media with highly-varied hydraulic properties, including matrix pore, fissure and conduit, in which liner flow may co-exist with non-linear flow. In this paper, an attempt is made to couple linear flow with non-linear flow in a single unified flow governing equations by introducing the concept of equivalent hydraulic conductivity (EHC) and deriving a general Darcy’s law for various flow. The expression of EHC in the karst conduit and fissure are also derived. The procedures of numerical implementation are demonstrated via an ideal model and a case study of karst aquifer system in the Beishan Ore Formation area, Guangxi Autonomous Region, China. | |||||
BibTeX:
@article{Cheng2005,
author = {Cheng, J. M. and Chen, C. X.},
title = {An integrated linear/non-linear flow model for the conduit-fissure-pore media in the karst triple void aquifer system},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2005},
volume = {47},
number = {2},
pages = {163--174},
url = {http://dx.doi.org/10.1007/s00254-004-1128-7}
}
|
|||||
| Cheng, K.-S., Hou, J.-C., Liou, J.-J., Wu, Y.-C. and Chiang, J.-L. | Stochastic simulation of bivariate gamma distribution: a frequency-factor based approach | 2011 | Stochastic Environmental Research and Risk Assessment Vol. 25(2), pp. 107-122 |
article | URL |
| Abstract: A frequency-factor based approach for stochastic simulation of bivariate gamma distribution is proposed. The approach involves generation of bivariate normal samples with a correlation coefficient consistent with the correlation coefficient of the corresponding bivariate gamma samples. Then the bivariate normal samples are transformed to bivariate gamma samples using the well-known general equation of hydrological frequency analysis. We demonstrate that the proposed bivariate gamma simulation approach is capable of generating random sample pairs which not only have the desired marginal densities of component random variables but also their correlation coefficient. Scatter plots of simulated bivariate sample pairs also exhibit appropriate linear patterns (dependence structure) that are commonly observed in environmental and hydrological applications. Caution should also be exercised when specifying combinations of coefficients of skewness and the correlation coefficient for bivariate gamma simulation. | |||||
BibTeX:
@article{Cheng2011,
author = {Cheng, Ke-Sheng and Hou, Ju-Chen and Liou, Jun-Jih and Wu, Yii-Chen and Chiang, Jie-Lun},
title = {Stochastic simulation of bivariate gamma distribution: a frequency-factor based approach},
journal = {Stochastic Environmental Research and Risk Assessment},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {25},
number = {2},
pages = {107--122},
url = {http://dx.doi.org/10.1007/s00477-010-0427-7}
}
|
|||||
| Chin, D.A. | An assessment of first-order stochastic dispersion theories in porous media | 1997 | Journal of Hydrology Vol. 199(1-2), pp. 53-73 |
article | URL |
| Abstract: Random realizations of three-dimensional exponentially correlated hydraulic conductivity fields are used in a finite-difference numerical flow model to calculate the mean and covariance of the corresponding Lagrangian-velocity fields. The dispersivity of the porous medium is then determined from the Lagrangian-velocity statistics using the Taylor definition. This estimation procedure is exact, except for numerical errors, and the results are used to assess the accuracy of various first-order dispersion theories in both isotropic and anisotropic porous media. The results show that the Dagan theory is by far the most robust in both isotropic and anisotropic media, producing accurate values of the principal dispersivity components for σy as high as 1.0, In the case of anisotropic media where the flow is at an angle to the principal axis of hydraulic conductivity, it is shown that the dispersivity tensor is rotated away from the flow direction in the non-Fickian phase, but eventually coincides with the flow direction in the Fickian phase. | |||||
BibTeX:
@article{Chin1997,
author = {Chin, David A.},
title = {An assessment of first-order stochastic dispersion theories in porous media},
journal = {Journal of Hydrology},
year = {1997},
volume = {199},
number = {1-2},
pages = {53--73},
url = {http://www.sciencedirect.com/science/article/pii/S0022169496033045}
}
|
|||||
| Chin-Shang, L. | Using local linear kernel smoothers to test the lack of fit of nonlinear regression models | 2005 | Statistical Methodology Vol. 2(4), pp. 267-284 |
article | URL |
| Abstract: Herein, we propose a data-driven test that assesses the lack of fit of nonlinear regression models. The comparison of local linear kernel and parametric fits is the basis of this test, and specific boundary-corrected kernels are not needed at the boundary when local linear fitting is used. Under the parametric null model, the asymptotically optimal bandwidth can be used for bandwidth selection. This selection method leads to the data-driven test that has a limiting normal distribution under the null hypothesis and is consistent against any fixed alternative. The finite-sample property of the proposed data-driven test is illustrated, and the power of the test is compared with that of some existing tests via simulation studies. We illustrate the practicality of the proposed test by using two data sets. | |||||
BibTeX:
@article{Chin-Shang2005,
author = {Chin-Shang, Li},
title = {Using local linear kernel smoothers to test the lack of fit of nonlinear regression models},
journal = {Statistical Methodology},
year = {2005},
volume = {2},
number = {4},
pages = {267--284},
url = {http://www.sciencedirect.com/science/article/pii/S1572312705000341}
}
|
|||||
| Cho, H.C., Kim, K.H., Lee, H. and Kim, D.J. | Study of residence time distribution and mill hold-up for a continuous centrifugal mill with various G/D ratios in a dry-grinding environment | 2011 | Minerals Engineering Vol. 24(1), pp. 77-81 |
article | URL |
| Abstract: It is important to determine the residence time distribution (RTD) of a mill in order to predict the performance of the mill. In this study, the residence time distribution of a continuous centrifugal mill was measured experimentally by using aluminum powder as a tracer in a dry-grinding environment. Aluminum powder was placed into the continuous centrifugal mill chamber as a pulse under a steady-state condition, and then, the discharge time and proportional concentration of the tracer was measured using a metal detector at various G/D ratios and feed rates. During the measurement procedure, the mill product was collected and analyzed with regard to the size distribution to investigate the relationship between the mill product and the characteristics of RTD. In addition, the mill hold-up data was also analyzed after measurement. These test results can be used to predict the mill product size distribution in combination with a kinetic grinding model. | |||||
BibTeX:
@article{Cho2011,
author = {Cho, Hee Chan and Kim, Kwan Ho and Lee, Hoon and Kim, Dong Jun},
title = {Study of residence time distribution and mill hold-up for a continuous centrifugal mill with various G/D ratios in a dry-grinding environment},
journal = {Minerals Engineering},
year = {2011},
volume = {24},
number = {1},
pages = {77--81},
url = {http://www.sciencedirect.com/science/article/pii/S0892687510003006}
}
|
|||||
| Cho, H.C., Kim, K.H., Lee, H. and Kim, D.J. | Study of residence time distribution and mill hold-up for a continuous centrifugal mill with various G/D ratios in a dry-grinding environment | 2011 | Minerals Engineering Vol. 24(1), pp. 77-81 |
article | URL |
| Abstract: It is important to determine the residence time distribution (RTD) of a mill in order to predict the performance of the mill. In this study, the residence time distribution of a continuous centrifugal mill was measured experimentally by using aluminum powder as a tracer in a dry-grinding environment. Aluminum powder was placed into the continuous centrifugal mill chamber as a pulse under a steady-state condition, and then, the discharge time and proportional concentration of the tracer was measured using a metal detector at various G/D ratios and feed rates. During the measurement procedure, the mill product was collected and analyzed with regard to the size distribution to investigate the relationship between the mill product and the characteristics of RTD. In addition, the mill hold-up data was also analyzed after measurement. These test results can be used to predict the mill product size distribution in combination with a kinetic grinding model. | |||||
BibTeX:
@article{Cho2011a,
author = {Cho, Hee Chan and Kim, Kwan Ho and Lee, Hoon and Kim, Dong Jun},
title = {Study of residence time distribution and mill hold-up for a continuous centrifugal mill with various G/D ratios in a dry-grinding environment},
journal = {Minerals Engineering},
year = {2011},
volume = {24},
number = {1},
pages = {77--81},
url = {http://www.sciencedirect.com/science/article/pii/S0892687510003006}
}
|
|||||
| Choi, E., Cheema, T. and Islam, M. | A new dual-porosity/dual-permeability model with non-Darcian flow through fractures | 1997 | Journal of Petroleum Science and Engineering Vol. 17(3-4), pp. 331-344 |
article | URL |
| Abstract: The presence of fractures is associated with high oil or water productivity as well as high contaminant vulnerability. Consequently, it is important to develop a technique for properly modeling fractured formations. The recent dual-porosity/dual-permeability approach uses Darcian flow through both matrix and fractures. Unfortunately, Darcian flow applies to creeping flow only. It is well known that the fluid velocity through fractures is often too high for the flow to be Darcian. This paper reports results of a new formulation which uses the Forchheimer equation to describe fluid flow through fractures and couples this equation with Darcy's law in order to describe flow through the matrix. Results are compared with those of the conventional Darcian dual-porosity/dual-permeability formulation. Results show a considerable difference between the two models. However, the discrepancy between the two models is less for a given range of parameters. Results of a series of numerical runs are presented in order to show the behavior of the new model for a range of different flow parameters, such as matrix permeability, fracture width, and fracture spacing. The scaling up problem of fluid flow is considered with a series of numerical runs for a field scale. Results show that the flow prediction is consistent only if the fracture width is not scaled up using the conventional approach. Finally, steady-state results are compared with field observations and a good agreement between the two is observed. | |||||
BibTeX:
@article{Choi1997,
author = {Choi, E.S. and Cheema, T. and Islam, M.R.},
title = {A new dual-porosity/dual-permeability model with non-Darcian flow through fractures},
journal = {Journal of Petroleum Science and Engineering},
year = {1997},
volume = {17},
number = {3-4},
pages = {331--344},
url = {http://www.sciencedirect.com/science/article/pii/S0920410596000502}
}
|
|||||
| Choi, N.-C., Kim, D.-J. and Kim, S.-B. | Quantification of bacterial mass recovery as a function of pore-water velocity and ionic strength | 2007 | Research in Microbiology Vol. 158(1), pp. 70-78 |
article | URL |
| Abstract: Transport of bacteria in aquifer systems plays an important role in bioaugmentation, which relies upon successful bacterial delivery to a target area. In the present study, we conducted a set of laboratory column experiments under various conditions of pore-water velocity (υω) and ionic strength (IS) of culture medium for Pseudomonas aeruginosa, known to be a benzene-degrading bacteria, in order to investigate their relationship to mass recovery in saturated quartz sands. The column experiments revealed that both peak concentrations and mass recoveries of bacteria were lower than those of a conservative tracer KCl when deionized water was used as leaching water for all ranges of pore-water velocity (0.18-6.23 cm/min). Thus, the parameter responsible for transport of P. aeruginosa was only the deposition coefficient. Bacterial cells could not be attached to the mineral surfaces by predominance of electrostatic charge or repulsive forces over hydrophobicity or attractive forces due to the very low ionic strength (≈0 mM) of deionized water. The loss of bacterial mass was attributed to the deposition in the crevice formed on the quartz surfaces, as evidenced by SEM images. For a given pore-water velocity, the ionic strength markedly influenced bacterial deposition, showing decreased peak concentrations and mass recoveries with increasing ionic strength of column leaching water. An optimum range of υω and IS for achieving bacterial mass recovery higher than 70% in the studied quartz sand was found such that: (i) at low IS (≈0 mM), a pore-water velocity higher than 0.30 cm/min, and (ii) at pore-water velocity of 0.52 cm/min, an IS lower than 290 mM, were required, respectively. | |||||
BibTeX:
@article{Choi2007,
author = {Choi, Nag-Choul and Kim, Dong-Ju and Kim, Song-Bae},
title = {Quantification of bacterial mass recovery as a function of pore-water velocity and ionic strength},
journal = {Research in Microbiology},
year = {2007},
volume = {158},
number = {1},
pages = {70--78},
url = {http://www.sciencedirect.com/science/article/pii/S0923250806002087}
}
|
|||||
| Chou, C.-W. and Huang, W.-J. | A note on characterizations of the bivariate gamma distribution | 2005 | Journal of Statistical Planning and Inference Vol. 128(1), pp. 259-269 |
article | URL |
| Abstract: Given two independent non-degenerate positive random variables X and Y, Lukacs (1955) proved that X/(X+Y) and X+Y are independent if and only if X and Y are gammally distributed with the same scale parameter. | |||||
BibTeX:
@article{Chou2005,
author = {Chou, Chao-Wei and Huang, Wen-Jang},
title = {A note on characterizations of the bivariate gamma distribution},
journal = {Journal of Statistical Planning and Inference},
year = {2005},
volume = {128},
number = {1},
pages = {259--269},
url = {http://www.sciencedirect.com/science/article/pii/S0378375803003276}
}
|
|||||
| Chrysikopoulos, C.V. | Effective parameters for flow in saturated heterogeneous porous media | 1995 | Journal of Hydrology Vol. 170(1-4), pp. 181-197 |
article | URL |
| Abstract: Effective parameters for flow in saturated porous media are obtained via Taylor-Aris-Brenner moment analysis considering both periodic as well as stationary porous medium properties. It is assumed that a slug is instantaneously introduced into an unbounded, anisotropic porous medium having a compressible matrix, and that the correlation length of the local hydraulic conductivity and specific storage fluctuations is smaller than the correlation length of hydraulic head fluctuations (gradually varying flow). It is shown that the effective specific storage is equal to its volume average. The effective hydraulic conductivity is derived by a small-perturbation analysis and it is shown to consist of its volume average and of a second term which accounts for the ‘small’ local conductivity fluctuations. | |||||
BibTeX:
@article{Chrysikopoulos1995,
author = {Chrysikopoulos, Constantinos V.},
title = {Effective parameters for flow in saturated heterogeneous porous media},
journal = {Journal of Hydrology},
year = {1995},
volume = {170},
number = {1-4},
pages = {181--197},
url = {http://www.sciencedirect.com/science/article/pii/0022169494026752}
}
|
|||||
| Church, T.M. | Biogeochemical factors influencing the residence time of microconstituents in a large tidal estuary, Delaware Bay | 1986 | Marine Chemistry Vol. 18(2-4)VIII International Symposium on the Chemistry of the Mediterranean, pp. 393-406 |
article | URL |
| Abstract: Generally the large tidal estuaries of the eastern United States, such as Delaware Bay, are characterized by rather high suspended particle concentrations at the landward end and high biological activity at the seaward end. As such, these estuaries can be conceptualized as geochemical and biochemical “reactors” for those processes controlling the transmission of trace elements from fresh to the coastal shelf waters. The efficiency of these reaction processes relative to estuarine flushing will control the residence times of microconstituents in such estuaries. | |||||
BibTeX:
@article{Church1986,
author = {Church, Thomas M.},
title = {Biogeochemical factors influencing the residence time of microconstituents in a large tidal estuary, Delaware Bay},
booktitle = {VIII International Symposium on the Chemistry of the Mediterranean},
journal = {Marine Chemistry},
year = {1986},
volume = {18},
number = {2--4},
pages = {393--406},
url = {http://www.sciencedirect.com/science/article/pii/0304420386900204}
}
|
|||||
| Chwastiak, M. and Young, J.J. | Silences in Annual Reports | 2003 | Critical Perspectives on Accounting Vol. 14(5), pp. 533-552 |
article | URL |
| Abstract: In this paper, we show how annual reports rely upon the silencing of injustices in order to make profit appear to be an unproblematic measure of success. In particular, we examine the ways in which corporations silence the negative impact of their activities upon the earth, the hell of war and the beauty of peace, the spiritual, human and social impoverishment arising from excessive consumption, and the dehumanization of workers. Only by breaking silence and counter-posing corporate values with alternatives can we hope to free humankind from the limitations of profit maximization and promote a world in which peace, happiness, respect for diversity, etc. take precedence to capital accumulation. | |||||
BibTeX:
@article{Chwastiak2003a,
author = {Chwastiak, Michele and Young, Joni J},
title = {Silences in Annual Reports},
journal = {Critical Perspectives on Accounting},
year = {2003},
volume = {14},
number = {5},
pages = {533--552},
url = {http://www.sciencedirect.com/science/article/pii/S1045235402001624}
}
|
|||||
| Cirpka, O.A., Frind, E.O. and Helmig, R. | Numerical simulation of biodegradation controlled by transverse mixing | 1999 | Journal of Contaminant Hydrology Vol. 40(2), pp. 159-182 |
article | URL |
| Abstract: Microbial activity in aquifers is controlled by the mixing between the reacting substrates. Conventional modelling methods that are commonly used to analyze reactive transport of organics in heterogeneous systems may give erroneous results because mixing is often over-represented in the model. This effect will be strongest when the reaction is controlled by transverse dispersion as in the case of aerobic degradation of waste-water introduced into an aquifer by an injection well. We show that fictitious transverse mixing can be created by a numerical model based on rectangular grids, and that this problem can be controlled by formulating the problem in streamline-oriented coordinates. In both model formulations, nonlinear high-resolution techniques minimizing the amount of artificial diffusion were applied, so that fictitious mixing is exclusively due to grid-orientation effects. Additionally it is shown that applying dispersivity values based on the second spatial moment transverse to the direction of flow leads to an overestimation of mixing. The fictitious degradation produced by model-dependent transverse dispersion caused the modelled plume to degrade much faster, and therefore appear much shorter, than the actual plume. Thus, the choice of appropriate dispersivity values as well as the control of artificial transverse diffusion is crucial when modelling mixing-controlled reactive transport. | |||||
BibTeX:
@article{Cirpka1999,
author = {Cirpka, Olaf A. and Frind, Emil O. and Helmig, Rainer},
title = {Numerical simulation of biodegradation controlled by transverse mixing},
journal = {Journal of Contaminant Hydrology},
year = {1999},
volume = {40},
number = {2},
pages = {159--182},
url = {http://www.sciencedirect.com/science/article/pii/S0169772299000443}
}
|
|||||
| Claret, C. and Boulton, A. | Integrating hydraulic conductivity with biogeochemical gradients and microbial activity along river–groundwater exchange zones in a subtropical stream | 2009 | Hydrogeology Journal Vol. 17(1), pp. 151-160 |
article | URL |
| Abstract: The pervious lateral bars (parafluvial zone) and beds (hyporheic zone), where stream water and groundwater exchange, are dynamic sites of hydrological and biological retention. The significance of these biogeochemical ‘hotspots’ to stream and groundwater metabolism is largely controlled by filtration capacity, defined as the extent to which subsurface flowpaths and matrix hydraulic conductivity modify water characteristics. Where hydraulic conductivity is high, gradients in biogeochemistry and microbial activity along subsurface flowpaths were hypothesized to be less marked than where hydraulic conductivity is low. This hypothesis was tested in two riffles and gravel bars in an Australian subtropical stream. At one site, gradients in chemical and microbial variables along flowpaths were associated with reduced hydraulic conductivity, longer water residence time and reduced filtration capacity compared with the second site where filtration capacity was greater and longitudinal biogeochemical trends were dampened. These results imply that factors affecting the sediment matrix in this subtropical stream can alter filtration capacity, interstitial microbial activity and biogeochemical gradients along subsurface flowpaths. This hydroecological approach also indicates potential for a simple field technique to estimate filtration capacity and predict the prevailing hyporheic gradients in microbial activity and biogeochemical processing efficiency, with significant implications for stream ecosystem function. | |||||
BibTeX:
@article{Claret2009,
author = {Claret, Cécile and Boulton, Andrew},
title = {Integrating hydraulic conductivity with biogeochemical gradients and microbial activity along river–groundwater exchange zones in a subtropical stream},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {151--160},
url = {http://dx.doi.org/10.1007/s10040-008-0373-3}
}
|
|||||
| Claudel, S., Leclerc, J., Tétar, L., Lintz, H. and Bernard, A. | Recent extensions of the residence time distribution concept: unsteady state conditions and hydrodynamic model developments | 2000 | Brazilian Journal of Chemical Engineering Vol. 17(4-7), pp. 947-954 |
article | URL |
| Abstract: Two recent extensions of the residence time distribution concept are developed. The first one concerns the use of this method under transient conditions, a concept theoretically treated but rarely confirm by relevant experiments. In the present work, two experimental set-ups have been used to verify some limits of the concept. The second extension is devoted to the development of hydrodynamic models. Up to now, the hydrodynamics of the process are either determined by simple models (mixing cells in series, plug flow reactor with axial dispersion) or by the complex calculation of the velocity profile obtained via the Navier-Stokes equations. An alternative is to develop a hydrodynamic model by use of a complex network of interconnected elementary reactors. Such models should be simple enough to be derived easily and sufficiently complex to give a good representation of the behavior of the process. | |||||
BibTeX:
@article{Claudel2000,
author = {Claudel, S. and Leclerc, J.P. and Tétar, L. and Lintz, H.G. and Bernard, A.},
title = {Recent extensions of the residence time distribution concept: unsteady state conditions and hydrodynamic model developments},
journal = {Brazilian Journal of Chemical Engineering},
publisher = {scielo},
year = {2000},
volume = {17},
number = {4--7},
pages = {947--954},
url = {http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322000000400059}
}
|
|||||
| Cobb, C., Johnson, J., Cobb, B., Armstrong, P., Sharpe, L. and Byl, T. | Wetland Removal of Nutrients and Pollution from a Mixed Sewer and Karst Spring System in Nashville, Tennessee | 2008 | U. S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U. S. Geological Survey Scientific Investigations Report 2008-5023, pp. 73 | inproceedings | URL |
| Abstract: Wetlands have been shown to attenuate suspended sediments and agricultural pollution in rural areas but little work has been conducted regarding the benefits of the wetlands in mitigating urban non-point source pollution (NPS). The objective of this project was to determine if an 80 acre natural wetland located down gradient of bedrock springs, parking lots, city streets and leaky sewer systems in Nashville, Tennessee helped to mitigate urban NPS runoff. Sampling points were selected by reconnaissance during rainfall events to determine general flow paths. Water samples were collected at these sampling points during base-flow and rain runoff events. Water-quality monitors were also placed in the springs and along the flow path during the 12 month period of study. Water samples were analyzed within 48 hours for turbidity, specific conductance, pH, and volatile organic compounds (VOC). Additional analyses were performed for sulfate (SO4), nitrate (NO3) ammonia (NH3) and chemical oxygen demand (COD). It was found that runoff from parking lots and roads during winter storms had relatively high VOC levels (62 µg/L benzene, 132 µg/L toluene, 106 µg/L xylenes, and a number of unidentified compounds). Water samples collected downstream of the wetland, however, had VOC concentrations below detection levels. Water samples collected at the most downstream site also had significantly lower levels of turbidity (90% lower), NH3 (99% lower), COD (95% lower), NO3 (90% lower), and SO4 (63% lower) on average for the year. The results indicated that routing water through the urban wetland resulted in significant water-quality improvements during the study period. | |||||
BibTeX:
@inproceedings{Cobb2008,
author = {Cobb, Carlton and Johnson, Jameka and Cobb, Brandon and Armstrong, Patrice and Sharpe, Lonnie and Byl, Tom},
title = {Wetland Removal of Nutrients and Pollution from a Mixed Sewer and Karst Spring System in Nashville, Tennessee},
booktitle = {U. S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U. S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U. S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {73},
url = {http://pubs.usgs.gov/sir/2008/5023/28cobb.htm}
}
|
|||||
| Cogan, J.J. and Morris, P. | The development of civics values: an overview | 2001 | International Journal of Educational Research Vol. 35(1), pp. 1-9 |
article | URL |
| Abstract: This chapter lays out the research questions that guided the study and the methods used to conduct the study. The study was conducted in 17 secondary schools in six countries: Australia, Hong Kong, Japan, Taiwan, Thailand, and the United States. The first research question related to the school's policies with respect to civics education. The second question inquired into the nature and extent of the curriculum activities that were provided for the purpose of promoting civics education. The third question asked how key stakeholders perceived the nature and impact of the implemented curriculum. The fourth question concerned the similarities and differences across schools within each society with regard to each of the first three questions. Interviews and observations provided the primary data used to address the questions. | |||||
BibTeX:
@article{Cogan2001,
author = {Cogan, John J. and Morris, Paul},
title = {The development of civics values: an overview},
journal = {International Journal of Educational Research},
year = {2001},
volume = {35},
number = {1},
pages = {1--9},
url = {http://www.sciencedirect.com/science/article/pii/S0883035501000027}
}
|
|||||
| Cohen, M.J. and Brown, M.T. | A model examining hierarchical wetland networks for watershed stormwater management | 2007 | Ecological Modelling Vol. 201(2), pp. 179-193 |
article | URL |
| Abstract: There is increasing awareness that solutions to degraded quality and excessive quantity of stormwater and resulting impacts on downstream water bodies may require a watershed approach to management rather that the incremental approach that is now common. Examination of low-relief watersheds characteristic of the southeastern coastal plain reveals common hierarchical patterns of surface water convergence that may be emulated in developed watersheds to enhance the efficacy of peak-flow attenuation and pollutant removal. A dynamic systems model was developed to compare stormwater management using a hierarchical network of treatment wetlands with the standard incremental approach wherein treatment systems are designed considering only site-level effluent criteria. The model simulates watershed hydrology, suspended sediment transport and phosphorus removal and transformation. Results indicate that watershed planning of stormwater collection and treatment systems using hierarchical networks can greatly enhance overall effectiveness (annual retention improvements of 31% for flow, 36% for sediment and 27% for phosphorus) with respect to an equal area of uniformly sized wetlands. Further, network proportions can be adjusted to specific runoff characteristics. Distinct roles were observed for each wetland size class: small headwater wetlands effectively removed sediment, medium-sized mid-reach wetlands retained phosphorus, while large wetlands primarily stored and attenuated long-period hydrologic flows. | |||||
BibTeX:
@article{Cohen2007,
author = {Cohen, Matthew J. and Brown, Mark T.},
title = {A model examining hierarchical wetland networks for watershed stormwater management},
journal = {Ecological Modelling},
year = {2007},
volume = {201},
number = {2},
pages = {179--193},
url = {http://www.sciencedirect.com/science/article/pii/S0304380006004200}
}
|
|||||
| Collins, K.A., Lawrence, T.J., Stander, E.K., Jontos, R.J., Kaushal, S.S., Newcomer, T.A., Grimm, N.B. and Cole Ekberg, M.L. | Opportunities and challenges for managing nitrogen in urban stormwater: A review and synthesis | 2010 | Ecological Engineering Vol. 36(11)Managing Denitrification in Human Dominated Landscapes, pp. 1507-1519 |
article | URL |
| Abstract: Although nitrogen (N) is prevalent in urban stormwater, regulation of this pollutant has occurred only more recently. This paper reviews the concerns over N in urban stormwater, mechanisms and design enhancements for N uptake and denitrification through various stormwater control measures (SCMs), and presents opportunities to integrate this current knowledge into the regulatory framework. A survey of personnel directly involved in various aspects of US state and territory NPDES programs revealed that the top three pollutants of concern were total suspended solids (TSS), pathogens and bacteria, and total phosphorus (TP). Surprisingly, nitrate (NO3−) was of little concern among the survey respondents, with 3.9% giving it the highest level of concern, 2.0% ranking it second, and 6.0% ranking it third. When asked which strategies were currently used in their geographic area for stormwater management, the most common results were wet ponds and dry ponds. At the same time, wet ponds and dry ponds were recognized as less effective practices to manage stormwater. | |||||
BibTeX:
@article{Collins2010,
author = {Collins, Kelly A. and Lawrence, Timothy J. and Stander, Emilie K. and Jontos, Robert J. and Kaushal, Sujay S. and Newcomer, Tamara A. and Grimm, Nancy B. and Cole Ekberg, Marci L.},
title = {Opportunities and challenges for managing nitrogen in urban stormwater: A review and synthesis},
booktitle = {Managing Denitrification in Human Dominated Landscapes},
journal = {Ecological Engineering},
year = {2010},
volume = {36},
number = {11},
pages = {1507--1519},
url = {http://www.sciencedirect.com/science/article/pii/S0925857410000935}
}
|
|||||
| Colombo, J.C., Cabello, M. and Arambarri, A.M. | Biodegradation of aliphatic and aromatic hydrocarbons by natural soil microflora and pure cultures of imperfect and lignolitic fungi | 1996 | Environmental Pollution Vol. 94(3), pp. 355-362 |
article | URL |
| Abstract: The biodegradation of aliphatic and aromatic hydrocarbons by natural soil microflora and seven fungi species, including imperfect strains and higher level lignolitic species, is compared in a 90-day laboratory experiment using a natural, not-fertilized soil contaminated with 10% crude oil. The natural microbial soil assemblage isolated from an urban forest area was unable to significantly degrade crude oil, whereas pure fungi cultures effectively reduced the residues by 26–35% in 90 days. Normal alkanes were almost completely degraded in the first 15 days, whereas aromatic compounds (phenanthrene and methylphenanthrenes) exhibited slower kinetics. Aspergillus terreus and Fusarium solani, isolated from oil-polluted areas, produced the more efficient attack of aliphatic and aromatic hydrocarbons, respectively. Overall, imperfect fungi isolated from polluted soils showed a somewhat higher efficiency, but the performance of unadapted, indigenous, lignolitic fungi was comparable, and all three species, Pleurotus ostreatus, Trametes villosus and Coriolopsis rigida, effectively degraded aliphatic and aromatic components. The simultaneous, multivariate analysis of 22 parameters allowed the elucidation of a clear reactivity trend of the oil components during biodegradation: lower molecular weight n-alkanes > phenanthrene > 3-2-methylphenanthrenes > intermediate chain length n-alkanes > longer chain length n-alkanes > isoprenoids ≈9-1-methylphenanthrenes. Irrespective of the individual degrading capacities, all fungi species tested seem to follow this decomposition sequence. | |||||
BibTeX:
@article{Colombo1996,
author = {Colombo, Juan C. and Cabello, Marta and Arambarri, Angélica M.},
title = {Biodegradation of aliphatic and aromatic hydrocarbons by natural soil microflora and pure cultures of imperfect and lignolitic fungi},
journal = {Environmental Pollution},
year = {1996},
volume = {94},
number = {3},
pages = {355--362},
url = {http://www.sciencedirect.com/science/article/pii/S0269749196000449}
}
|
|||||
| Compant, S., Clément, C. and Sessitsch, A. | Plant growth-promoting bacteria in the rhizo- and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization | 2010 | Soil Biology and Biochemistry Vol. 42(5), pp. 669-678 |
article | URL |
| Abstract: In both managed and natural ecosystems, beneficial plant-associated bacteria play a key role in supporting and/or increasing plant health and growth. Plant growth-promoting bacteria (PGPB) can be applied in agricultural production or for the phytoremediation of pollutants. However, because of their capacity to confer plant beneficial effects, efficient colonization of the plant environment is of utmost importance. The majority of plant-associated bacteria derives from the soil environment. They may migrate to the rhizosphere and subsequently the rhizoplane of their hosts before they are able to show beneficial effects. Some rhizoplane colonizing bacteria can also penetrate plant roots, and some strains may move to aerial plant parts, with a decreasing bacterial density in comparison to rhizosphere or root colonizing populations. A better understanding on colonization processes has been obtained mostly by microscopic visualisation as well as by analysing the characteristics of mutants carrying disfunctional genes potentially involved in colonization. In this review we describe the individual steps of plant colonization and survey the known mechanisms responsible for rhizosphere and endophytic competence. The understanding of colonization processes is important to better predict how bacteria interact with plants and whether they are likely to establish themselves in the plant environment after field application as biofertilisers or biocontrol agents. | |||||
BibTeX:
@article{Compant2010,
author = {Compant, Stéphane and Clément, Christophe and Sessitsch, Angela},
title = {Plant growth-promoting bacteria in the rhizo- and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization},
journal = {Soil Biology and Biochemistry},
year = {2010},
volume = {42},
number = {5},
pages = {669--678},
url = {http://www.sciencedirect.com/science/article/pii/S0038071709004398}
}
|
|||||
| Conerly, M.D. and Webster, J.T. | MINQE for the One-Way Classification | 1987 | Technometrics Vol. 29(2), pp. 229-236 |
article | DOI URL |
| Abstract: The minimum norm quadratic estimator (MINQE), without the condition of unbiasedness, is given for the effect variance of a one-way classification. The computational form is relatively simple with no iteration necessary, and the prior weight is given as a function of the harmonic mean of the numbers of readings per classification. A comparison is made of the mean squared error (MSE) of MINQE and the estimators of Swallow and Monahan (1984) for the layouts of that article. The MSE of MINQE is shown to be smaller than the MSE of these estimators when the effect variance is greater than the error variance. A discussion is also given illustrating a desirable property of a smaller MSE even in the presence of nontrivial bias. The minimum norm quadratic estimator (MINQE), without the condition of unbiasedness, is given for the effect variance of a one-way classification. The computational form is relatively simple with no iteration necessary, and the prior weight is given as a function of the harmonic mean of the numbers of readings per classification. A comparison is made of the mean squared error (MSE) of MINQE and the estimators of Swallow and Monahan (1984) for the layouts of that article. The MSE of MINQE is shown to be smaller than the MSE of these estimators when the effect variance is greater than the error variance. A discussion is also given illustrating a desirable property of a smaller MSE even in the presence of nontrivial bias. |
|||||
BibTeX:
@article{Conerly1987,
author = {Conerly, M. D. and Webster, J. T.},
title = {MINQE for the One-Way Classification},
journal = {Technometrics},
publisher = {Taylor & Francis},
year = {1987},
volume = {29},
number = {2},
pages = {229--236},
url = {http://amstat.tandfonline.com/doi/abs/10.1080/00401706.1987.10488214},
doi = {http://dx.doi.org/10.1080/00401706.1987.10488214}
}
|
|||||
| Constantino, M. | Biodegradation of wastewater nitrogen compounds in fractures: Laboratory tests and field observations | 2007 | Journal of Contaminant Hydrology Vol. 92(3-4), pp. 230-254 |
article | URL |
| Abstract: Throughout several coastal regions in the Mediterranean where rainfalls rarely exceed 650 mm per year municipal treated wastewater can be conveniently reused for soil irrigation. Where the coastal aquifer supplies large populations with freshwater in such area, an assessment of ground water quality around spreading sites is needed. In this study, the efficacy of natural filtration on nitrogen degradation in wastewater spreads on the soil covering the Salento (Southern Italy) fractured limestone was quantified by using laboratory tests and field measurements. In the laboratory, effluent from municipal wastewater treatment plants was filtered through a package of fractures made by several slabs of limestone. An analysis of wastewater constituent concentrations over time allowed the decay rates and constants for nitrogen transformation during natural filtration to be estimated in both aerated and non-aerated (i.e., saturated) soil fractures. A simulation code, based on biodegradation decay constants defined in the laboratory experiments, was then used to quantify the total inorganic nitrogen removal from wastewater injected in an aquifer in the Salento region (Nardò). Here the water sampled in two monitoring wells at 320 m and 500 m from the wastewater injection site and downgradient with respect to groundwater flow was used to verify the laboratory nitrification and denitrification rates. | |||||
BibTeX:
@article{Constantino2007,
author = {Constantino, Masciopinto},
title = {Biodegradation of wastewater nitrogen compounds in fractures: Laboratory tests and field observations},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {92},
number = {3-4},
pages = {230--254},
url = {http://www.sciencedirect.com/science/article/pii/S016977220700006X}
}
|
|||||
| Cook, P., Love, A., Robinson, N. and Simmons, C. | Groundwater ages in fractured rock aquifers | 2005 | Journal of Hydrology Vol. 308(1-4), pp. 284-301 |
article | URL |
| Abstract: In fractured porous media, matrix diffusion processes mean that groundwater ages obtained with environmental tracers usually do not reflect the hydraulic age of the water. The distribution of groundwater ages within these heterogeneous systems will be related to the groundwater velocity within the fractures, but also to the size of the fractures and the geometry of the fracture network, and to the hydraulic properties of the aquifer matrix. In this paper, we present analytical and numerical simulations of environmental tracer concentrations in fractured rock aquifers to examine the effect of changes in aquifer parameters on the tracer distributions. In particular, we show that where horizontal fractures are strongly vertically connected, then it may be reasonable to use one-dimensional models of flow and transport through vertical fractures to represent flow through aquifers containing both horizontal and vertical fractures. The presence of large numbers of horizontal fractures will not cause flow to depart significantly from the one-dimensional approximation. Where a smaller number of horizontal fractures are present, then abrupt decreases in the vertical water velocity can occur, as water is intercepted and diverted laterally. Measurements of 14C, 3H, 36Cl, and chlorofluorocarbons within nested piezometers from the Clare Valley, South Australia, display a number of the features apparent in the generic simulations. The use of a number of different tracers appears to allow some fracture and matrix parameters to be constrained more tightly than might previously have been thought possible. | |||||
BibTeX:
@article{Cook2005,
author = {Cook, P.G. and Love, A.J. and Robinson, N.I. and Simmons, C.T.},
title = {Groundwater ages in fractured rock aquifers},
journal = {Journal of Hydrology},
year = {2005},
volume = {308},
number = {1-4},
pages = {284--301},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404005360}
}
|
|||||
| Cooper, A.H., Farrant, A.R. and Price, S.J. | The use of karst geomorphology for planning, hazard avoidance and development in Great Britain | 2011 | Geomorphology Vol. 134(1–2)Geomorphology and Natural Hazards in Karst Areas, pp. 118-131 |
article | URL |
| Abstract: Within Great Britain five main types of karstic rocks – dolomite, limestone, chalk, gypsum and salt – are present. Each presents a different type and severity of karstic geohazard which are related to the rock solubility and geological setting. Typical karstic features associated with these rocks have been databased by the British Geological Survey (BGS) with records of sinkholes, cave entrances, stream sinks, resurgences and building damage; data for more than half of the country has been gathered. BGS has manipulated digital map data, for bedrock and superficial deposits, with digital elevation slope models, superficial deposit thickness models, the karst data and expertly interpreted areas, to generate a derived dataset assessing the likelihood of subsidence due to karst collapse. This dataset is informed and verified by the karst database and marketed as part of the BGS GeoSure suite. It is currently used by environmental regulators, the insurance and construction industries, and the BGS semi-automated enquiry system. The database and derived datasets can be further combined and manipulated using GIS to provide other datasets that deal with specific problems. Sustainable drainage systems, some of which use soak-aways into the ground, are being encouraged in Great Britain, but in karst areas they can cause ground stability problems. Similarly, open loop ground source heat or cooling pump systems may induce subsidence if installed in certain types of karstic environments such as in chalk with overlying sand deposits. Groundwater abstraction also has the potential to trigger subsidence in karst areas. GIS manipulation of the karst information is allowing Great Britain to be zoned into areas suitable, or unsuitable, for such uses; it has the potential to become part of a suite of planning management tools for local and National Government to assess the long term sustainable use of the ground. | |||||
BibTeX:
@article{Cooper2011,
author = {Cooper, Anthony H. and Farrant, Andrew R. and Price, Simon J.},
title = {The use of karst geomorphology for planning, hazard avoidance and development in Great Britain},
booktitle = {Geomorphology and Natural Hazards in Karst Areas},
journal = {Geomorphology},
year = {2011},
volume = {134},
number = {1–2},
pages = {118--131},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X1100287X}
}
|
|||||
| Cooper, J. and Lemckert, C. | Extreme sea level rise and adaptation options for coastal resort cities: A qualitative assessment from the Gold Coast, Australia | Ocean & Coastal Management(0), pp. - | article | URL | |
| Abstract: The Gold Coast, Australia is a coastal resort city whose urban environment has evolved through a series of human interventions on the natural shoreline. Such cities rely on a perceived high quality environment which in turn is reliant on continuing maintenance (e.g. beach nourishment, inlet dredging, drainage). Climate change consequently holds particular challenges for coastal resort cities. Sea-level rise impacts are likely to be manifest in increased frequency of flooding and beach erosion episodes. Here we consider adaptation options for the city under various future sea-level rise (SLR) scenarios at the high end of current predictions for the next century (+1m, +2m and +5m) with the proviso that the beach and waterways must be preserved to enable the city to continue to exist as a resort. | |||||
BibTeX:
@article{Cooper,
author = {Cooper, J.A.G. and Lemckert, C.},
title = {Extreme sea level rise and adaptation options for coastal resort cities: A qualitative assessment from the Gold Coast, Australia},
journal = {Ocean & Coastal Management},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0964569112000701?v=s5}
}
|
|||||
| Coppola, A., Comegna, V., Basile, A., Lamaddalena, N. and Severino, G. | Darcian preferential water flow and solute transport through bimodal porous systems: Experiments and modelling | 2009 | Journal of Contaminant Hydrology Vol. 104(1-4)Preferential Flow, pp. 74-83 |
article | URL |
| Abstract: Soils often exhibit a variety of small-scale heterogeneities such as inter-aggregate pores and voids which partition flow into separate regions. In this paper a methodological approach is discussed for characterizing the hydrological behaviour of a heterogeneous clayey–sandy soil in the presence of structural inter-aggregate pores. For the clay soil examined, it was demonstrated that, coupling the transfer function approach for analyzing BTCs and water retention data obtained with different methods from laboratory studies captures the bimodal geometry of the porous system along with the related existence of fast and slow flow paths. To be effectively and reliably applied this approach requires that the predominant effects of the soil hydrological behaviour near saturation be supported by accurate experimental data of both breakthrough curves (BTCs) and hydraulic functions for high water content values. This would allow the separation of flow phases and hence accurate identification of the processes and related parameters. | |||||
BibTeX:
@article{Coppola2009,
author = {Coppola, Antonio and Comegna, Vincenzo and Basile, Angelo and Lamaddalena, Nicola and Severino, Gerardo},
title = {Darcian preferential water flow and solute transport through bimodal porous systems: Experiments and modelling},
booktitle = {Preferential Flow},
journal = {Journal of Contaminant Hydrology},
year = {2009},
volume = {104},
number = {1-4},
pages = {74--83},
url = {http://www.sciencedirect.com/science/article/pii/S0169772208001733}
}
|
|||||
| Copty, N.K., Trinchero, P. and Sanchez-Vila, X. | Inferring spatial distribution of the radially integrated transmissivity from pumping tests in heterogeneous confined aquifers | 2011 | Water Resources Research Vol. 47(5), pp. W05526- |
article | URL |
| Abstract: Hydrologists routinely analyze pumping test data using conventional interpretation methods that are based on the assumption of homogeneity and that, consequently, yield single estimates of representative flow parameters. However, natural subsurface formations are intrinsically heterogeneous, and hence, the flow parameters influencing the drawdown vary as the cone of depression expands in time. In this paper a novel procedure for the analysis of pumping tests in heterogeneous confined aquifers is developed. We assume that a given heterogeneous aquifer can be represented by a homogeneous system whose flow parameters evolve in time as the pumping test progresses. At any point in time, the interpreted flow parameters are estimated using the ratio of the drawdown and its derivative observed at that particular time. The procedure is repeated for all times, yielding time-dependent estimates of transmissivity Ti(t) and storativity, Si(t). Based on the analysis of the sensitivity of drawdown to inhomogeneities in the T field, the time-dependent interpreted transmissivity values are found to be a good estimate of Tg(r), the geometric mean of the transmissivity values encompassed within a progressively increasing radius r from the well. The procedure is illustrated for Gaussian heterogeneous fields with ln(T) variances up to a value of 2. The impact of the separation distance between the pumping well and observation point on data interpretation is discussed. The results show that information about the spatial variability of the transmissivity field can be inferred from time-drawdown data collected at a single observation point. | |||||
BibTeX:
@article{Copty2011a,
author = {Copty, Nadim K. and Trinchero, Paolo and Sanchez-Vila, Xavier},
title = {Inferring spatial distribution of the radially integrated transmissivity from pumping tests in heterogeneous confined aquifers},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2011},
volume = {47},
number = {5},
pages = {W05526--},
url = {http://dx.doi.org/10.1029/2010WR009877}
}
|
|||||
| Corburn, J. | Community knowledge in environmental health science: co-producing policy expertise | 2007 | Environmental Science & Policy Vol. 10(2), pp. 150-161 |
article | URL |
| Abstract: As lay publics demand a greater role in the environmental and health decision-making that impacts their lives, policy makers are being forced to find new ways of understanding and incorporating the expertise of professionals with the contextual intelligence that community residents possess. This paper highlights how co-producing science policy, where technical issues are not divorced from their social setting and a plurality of participants engage in everything from problem setting to decision-making, can contribute to more scientifically legitimate and publicly accountable decisions. Through a detailed case study utilizing participant observation, ethnographic field work, semi-structured interviews, and reviews of original documents, this paper highlights how residents in a low income, Latino immigrant neighborhood in New York City organized their knowledge to participate in and significantly alter a U.S. Environmental Protection Agency exposure assessment. This paper reveals both the contributions and limits of local knowledge in environmental health governance and how the co-production framework can contribute to more technically credible science and democratically accountable policy. | |||||
BibTeX:
@article{Corburn2007,
author = {Corburn, Jason},
title = {Community knowledge in environmental health science: co-producing policy expertise},
journal = {Environmental Science & Policy},
year = {2007},
volume = {10},
number = {2},
pages = {150--161},
url = {http://www.sciencedirect.com/science/article/pii/S1462901106001158}
}
|
|||||
| Cornaton, F. and Perrochet, P. | Reply to “Comment on groundwater age, life expectancy and transit time distributions in advective–dispersive systems: 1. Generalized reservoir theory” by Timothy R. Ginn [BibTeX] |
2007 | Advances in Water Resources Vol. 30(4), pp. 1058-1059 |
article | URL |
BibTeX:
@article{Cornaton2007,
author = {Cornaton, F. and Perrochet, P.},
title = {Reply to “Comment on groundwater age, life expectancy and transit time distributions in advective–dispersive systems: 1. Generalized reservoir theory” by Timothy R. Ginn},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {4},
pages = {1058--1059},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001734}
}
|
|||||
| Cornaton, F. and Perrochet, P. | Groundwater age, life expectancy and transit time distributions in advective–dispersive systems: 1. Generalized reservoir theory | 2006 | Advances in Water Resources Vol. 29(9), pp. 1267-1291 |
article | URL |
| Abstract: We present a methodology for determining resslervoir groundwater age and transit time probability distributions in a deterministic manner, considering advective–dispersive transport in steady velocity fields. In a first step, we propose to model the statistical distribution of groundwater age at aquifer scale by means of the classical advection–dispersion equation for a conservative and non-reactive tracer, associated to proper boundary conditions. The evaluated function corresponds to the density of probability of the random variable age, age being defined as the time elapsed since the water particles entered the aquifer. An adjoint backward model is introduced to characterize the life expectancy distribution, life expectancy being the time remaining before leaving the aquifer. By convolution of these two distributions, groundwater transit time distributions, from inlet to outlet, are fully defined for the entire aquifer domain. In a second step, an accurate and efficient method is introduced to simulate the transit time distribution at discharge zones. By applying the reservoir theory to advective–dispersive aquifer systems, we demonstrate that the discharge zone transit time distribution can be evaluated if the internal age probability distribution is known. The reservoir theory also applies to internal life expectancy probabilities yielding the recharge zone life expectancy distribution. Internal groundwater volumes are finally identified with respect to age and transit time. One- and two-dimensional theoretical examples are presented to illustrate the proposed mathematical models, and make inferences on the effect of aquifer structure and macro-dispersion on the distributions of age, life expectancy and transit time. | |||||
BibTeX:
@article{Cornaton2006a,
author = {Cornaton, F. and Perrochet, P.},
title = {Groundwater age, life expectancy and transit time distributions in advective–dispersive systems: 1. Generalized reservoir theory},
journal = {Advances in Water Resources},
year = {2006},
volume = {29},
number = {9},
pages = {1267--1291},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805002472}
}
|
|||||
| Cornaton, F. and Perrochet, P. | Groundwater age, life expectancy and transit time distributions in advective–dispersive systems; 2. Reservoir theory for sub-drainage basins | 2006 | Advances in Water Resources Vol. 29(9), pp. 1292-1305 |
article | URL |
| Abstract: Groundwater age and life expectancy probability density functions (pdf) have been defined, and solved in a general three-dimensional context by means of forward and backward advection–dispersion equations [Cornaton F, Perrochet P. Groundwater age, life expectancy and transit time distributions in advective–dispersive systems; 1. Generalized reservoir theory. Adv Water Res (xxxx)]. The discharge and recharge zones transit time pdfs were then derived by applying the reservoir theory (RT) to the global system, thus considering as ensemble the union of all inlet boundaries on one hand, and the union of all outlet boundaries on the other hand. The main advantages in using the RT to calculate the transit time pdf is that the outlet boundary geometry does not represent a computational limiting factor (e.g. outlets of small sizes), since the methodology is based on the integration over the entire domain of each age, or life expectancy, occurrence. In the present paper, we extend the applicability of the RT to sub-drainage basins of groundwater reservoirs by treating the reservoir flow systems as compartments which transfer the water fluxes to a particular discharge zone, and inside which mixing and dispersion processes can take place. Drainage basins are defined by the field of probability of exit at outlet. In this way, we make the RT applicable to each sub-drainage system of an aquifer of arbitrary complexity and configuration. The case of the well-head protection problem is taken as illustrative example, and sensitivity analysis of the effect of pore velocity variations on the simulated ages is carried out. | |||||
BibTeX:
@article{Cornaton2006b,
author = {Cornaton, F. and Perrochet, P.},
title = {Groundwater age, life expectancy and transit time distributions in advective–dispersive systems; 2. Reservoir theory for sub-drainage basins},
journal = {Advances in Water Resources},
year = {2006},
volume = {29},
number = {9},
pages = {1292--1305},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805002484}
}
|
|||||
| Coronado, M., Ramírez, J. and Samaniego, F. | New Considerations on Analytical Solutions Employed in Tracer Flow Modeling | 2004 | Transport in Porous Media Vol. 54(2), pp. 221-237 |
article | URL |
| Abstract: A methodology commonly used to obtain analytical and semi-analytical solutions to describe spike and finite-step tracer injection tests is discussed. In these cases, solutions to the diffusion–convection equation are derived from the solution of a different problem, namely the continuous injection of a tracer. Within this procedure, spike injection results from the time derivative of this solution, and finite-step injection from the superposition of two solutions shifted in time. In this paper we show that although this methodology is mathematically correct, attention should be paid to the properties of the solutions. Their boundary conditions may not represent physically acceptable situations, since these conditions are inherited from a different problem. The application of the methodology to a simple one-dimensional case of a tracer pulse diffusing in a homogeneous, semi-infinite reservoir shows serious problems regarding boundary conditions and mass conservation. These problems has not probably been found before since tracer breakthrough curves are not very sensitive to them. However, the problems clearly show up when the tracer distribution in space is analyzed. We conclude that the traditional methodology should not be employed. Equations should be solved imposing the specific boundary and initial conditions corresponding to the original system under consideration. | |||||
BibTeX:
@article{Coronado2004,
author = {Coronado, Manuel and Ramírez, Jetzabeth and Samaniego, Fernando},
title = {New Considerations on Analytical Solutions Employed in Tracer Flow Modeling},
journal = {Transport in Porous Media},
publisher = {Springer Netherlands},
year = {2004},
volume = {54},
number = {2},
pages = {221--237},
url = {http://dx.doi.org/10.1023/A:1026335905169}
}
|
|||||
| Coronado, M. and Ramírez-Sabag, J. | A New Analytical Formulation for Interwell Finite-Step Tracer Injection Tests in Reservoirs | 2005 | Transport in Porous Media Vol. 60(3), pp. 339-351 |
article | URL |
| Abstract: Analytical models to describe tracer transport in reservoirs commonly set conditions either on the tracer concentration or the tracer flow at the injection border. Here a different formulation based on tracer sources is presented. This approach avoids some of the physical inconsistencies that can be found when setting conditions on the tracer concentration. The case of a tracer injected as a finite-step in an infinite one-dimensional homogeneous reservoir with a uniform flow is considered. The solution is analytically obtained. The results are confronted against the two common boundary cases. The new approach predicts slightly delayed and broader pulses. The tracer breakthrough curves differences can be large for small Peclet numbers. These differences weakly reduce by increasing the injection period. The new approach contains tracer injection elements that can make it suitable to describe real conditions found in reservoir tracer tests. | |||||
BibTeX:
@article{Coronado2005,
author = {Coronado, Manuel and Ramírez-Sabag, Jetzabeth},
title = {A New Analytical Formulation for Interwell Finite-Step Tracer Injection Tests in Reservoirs},
journal = {Transport in Porous Media},
publisher = {Springer Netherlands},
year = {2005},
volume = {60},
number = {3},
pages = {339--351},
url = {http://dx.doi.org/10.1007/s11242-004-6747-7}
}
|
|||||
| Cortis, A. and Berkowitz, B. | Anomalous Transport in "Classical" Soil and Sand Columns | 2004 | Soil Science Society of America Journal Vol. 68(5), pp. 1539-1548 |
article | URL |
| Abstract: We re-examine—in light of recent theoretical developments—classical experiments on dispersion of a passive tracer in fully and partially saturated porous columns. We find that the dispersion breakthrough curves (BTCs) exhibit anomalous (non-Fickian) early arrival times and late time tailing, which can be explained by the Continuous Time Random Walk (CTRW) theory. The CTRW framework includes as a special case the classical advection-dispersion equation (ADE) for Fickian transport. We argue that existing measurements and interpretations of dispersion should be carefully reconsidered in the framework of these advances in conceptual understanding and quantification. | |||||
BibTeX:
@article{Cortis2004,
author = {Cortis, Andrea and Berkowitz, Brian},
title = {Anomalous Transport in "Classical" Soil and Sand Columns},
journal = {Soil Science Society of America Journal},
year = {2004},
volume = {68},
number = {5},
pages = {1539--1548},
url = {https://www.agronomy.org/publications/sssaj/abstracts/68/5/1539}
}
|
|||||
| Cortis, A. and Berkowitz, B. | Anomalous Transport in "Classical" Soil and Sand Columns | 2004 | Soil Science Society of America Journal Vol. 68(5), pp. 1539-1548 |
article | DOI URL |
| Abstract: We re-examine—in light of recent theoretical developments—classical experiments on dispersion of a passive tracer in fully and partially saturated porous columns. We find that the dispersion breakthrough curves (BTCs) exhibit anomalous (non-Fickian) early arrival times and late time tailing, which can be explained by the Continuous Time Random Walk (CTRW) theory. The CTRW framework includes as a special case the classical advection-dispersion equation (ADE) for Fickian transport. We argue that existing measurements and interpretations of dispersion should be carefully reconsidered in the framework of these advances in conceptual understanding and quantification. | |||||
BibTeX:
@article{Cortis2004a,
author = {Cortis, Andrea and Berkowitz, Brian},
title = {Anomalous Transport in "Classical" Soil and Sand Columns},
journal = {Soil Science Society of America Journal},
year = {2004},
volume = {68},
number = {5},
pages = {1539--1548},
url = {https://www.agronomy.org/publications/sssaj/abstracts/68/5/1539},
doi = {http://dx.doi.org/10.2136/sssaj2004.1539}
}
|
|||||
| Cory, D.C. and Rahman, T. | Environmental justice and enforcement of the safe drinking water act: The Arizona arsenic experience | 2009 | Ecological Economics Vol. 68(6)Eco-efficiency: From technical optimisation to reflective sustainability analysis, pp. 1825-1837 |
article | URL |
| Abstract: Environmental justice is concerned with the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies. A wide variety of empirical studies have concluded that disparate-impact discrimination does in fact exist since minority and low-income communities are at disproportionate risk for environmental harm. In this paper we examine these issues in the context of enforcing the safe drinking water act (SDWA). Specifically, we focus on the association between race, income, and hazardous levels of arsenic concentration and analyze the broad equity implications of implementing the new arsenic regulation by examining the relationship between community-level exposure to arsenic and socioeconomic and demographic characteristics of the population in Arizona. The results provide no support for the contention that continued selective implementation and enforcement of the revised SDWA arsenic standard is likely to disadvantage minority or low-income groups disproportionately in Arizona. | |||||
BibTeX:
@article{Cory2009a,
author = {Cory, Dennis C. and Rahman, Tauhidur},
title = {Environmental justice and enforcement of the safe drinking water act: The Arizona arsenic experience},
booktitle = {Eco-efficiency: From technical optimisation to reflective sustainability analysis},
journal = {Ecological Economics},
year = {2009},
volume = {68},
number = {6},
pages = {1825--1837},
url = {http://www.sciencedirect.com/science/article/pii/S0921800908005302}
}
|
|||||
| Courty, P.-E., Buée, M., Diedhiou, A.G., Frey-Klett, P., Le Tacon, F., Rineau, F., Turpault, M.-P., Uroz, S. and Garbaye, J. | The role of ectomycorrhizal communities in forest ecosystem processes: New perspectives and emerging concepts | 2010 | Soil Biology and Biochemistry Vol. 42(5), pp. 679-698 |
article | URL |
| Abstract: The fungal symbionts forming ectomycorrhizas, as well as their associated bacteria, benefit forest trees in a number of ways although the most important is enhancing soil nutrient mobilization and uptake. This is reciprocated by the allocation of carbohydrates by the tree to the fungus through the root interface, making the relationship a mutualistic association. Many field observations suggest that ectomycorrhizal fungi contribute to a number of key ecosystem functions such as carbon cycling, nutrient mobilization from soil organic matter, nutrient mobilization from soil minerals, and linking trees through common mycorrhizal networks. Until now, it has been very difficult to study trees and their fungal associates in forest ecosystems and most of the work on ECM functioning has been done in laboratory or nursery conditions. In this review with discuss the possibility of working at another scale, in forest settings. Numerous new techniques are emerging that makes possible the in situ study of the functional diversity of ectomycorrhizal communities. This approach should help to integrate developing research on the functional ecology of ectomycorrhizas and their associated bacteria with the potential implications of such research for managing the effects of climate change on forests. | |||||
BibTeX:
@article{Courty2010,
author = {Courty, Pierre-Emmanuel and Buée, Marc and Diedhiou, Abdala Gamby and Frey-Klett, Pascale and Le Tacon, François and Rineau, François and Turpault, Marie-Pierre and Uroz, Stéphane and Garbaye, Jean},
title = {The role of ectomycorrhizal communities in forest ecosystem processes: New perspectives and emerging concepts},
journal = {Soil Biology and Biochemistry},
year = {2010},
volume = {42},
number = {5},
pages = {679--698},
url = {http://www.sciencedirect.com/science/article/pii/S0038071709004696}
}
|
|||||
| Covington, M.D., Luhmann, A.J., Wicks, C.M. and Saar, M.O. | Process length scales and longitudinal damping in karst conduits | 2012 | Journal of Geophysical Research Vol. 117(F1), pp. F01025- |
article | URL |
| Abstract: Simple mathematical models often allow an intuitive grasp of the function of physical systems. We develop a mathematical framework to investigate reactive or dissipative transport processes within karst conduits. Specifically, we note that for processes that occur within a characteristic timescale, advection along the conduit produces a characteristic process length scale. We calculate characteristic length scales for the propagation of thermal and electrical conductivity signals along karst conduits. These process lengths provide a quantitative connection between karst conduit geometry and the signals observed at a karst spring. We show that water input from the porous/fractured matrix is also characterized by a length scale and derive an approximation that accounts for the influence of matrix flow on the transmission of signals through the aquifer. The single conduit model is then extended to account for conduits with changing geometries and conduit flow networks, demonstrating how these concepts can be applied in more realistic conduit geometries. We introduce a recharge density function, ϕR, which determines the capability of an aquifer to damp a given signal, and cast previous explanations of spring variability within this framework. Process lengths are a general feature of karst conduits and surface streams, and we conclude with a discussion of other potential applications of this conceptual and mathematical framework. | |||||
BibTeX:
@article{Covington2012,
author = {Covington, M. D. and Luhmann, A. J. and Wicks, C. M. and Saar, M. O.},
title = {Process length scales and longitudinal damping in karst conduits},
journal = {Journal of Geophysical Research},
publisher = {American Geophysical Union (AGU)},
year = {2012},
volume = {117},
number = {F1},
pages = {F01025--},
note = {Journal of Geophysical Research-Earth Surface},
url = {http://dx.doi.org/10.1029/2011JF002212}
}
|
|||||
| Cox, B. | A review of currently available in-stream water-quality models and their applicability for simulating dissolved oxygen in lowland rivers | 2003 | Science of The Total Environment Vol. 314-316(0)Land Ocean Interaction: processes, functioning and environmental management:a UK perspective, pp. 335-377 |
article | URL |
| Abstract: In this paper, a review is undertaken of the major models currently in use for describing water quality in freshwater river systems. The number of existing models is large because the various studies of water quality in rivers around the world have often resulted in the construction of new ‘bespoke’ models designed for the particular situation of that study. However, it is worth considering models that are already available, since an existing model, suitable for the purposes of the study, will save a great deal of work and may already have been established within regulatory and legal frameworks. The models chosen here are SIMCAT, TOMCAT, QUAL2E, QUASAR, MIKE-11 and ISIS, and the potential for each model is examined in relation to the issue of simulating dissolved oxygen (DO) in lowland rivers. These models have been developed for particular purposes and this review shows that no one model can provide all of the functionality required. Furthermore, all of the models contain assumptions and limitations that need to be understood if meaningful interpretations of the model simulations are to be made. The work is concluded with the view that it is unfair to set one model against another in terms of broad applicability, but that a model of intermediate complexity, such as QUASAR, is generally well suited to simulate DO in river systems. | |||||
BibTeX:
@article{Cox2003,
author = {Cox, B.A.},
title = {A review of currently available in-stream water-quality models and their applicability for simulating dissolved oxygen in lowland rivers},
booktitle = {Land Ocean Interaction: processes, functioning and environmental management:a UK perspective},
journal = {Science of The Total Environment},
year = {2003},
volume = {314-316},
number = {0},
pages = {335--377},
url = {http://www.sciencedirect.com/science/article/pii/S0048969703000639}
}
|
|||||
| Crandall, C.A., Kauffman, L.J. and Katz, B.G. | Simulations of Ground-Water Flow and Particle Pathline Analysis in the Contributing Recharge Area of a Public-Supply Well in Temple Terrace, Tampa Bay Region, Florida | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 92 | inproceedings | URL |
| Abstract: Shallow ground water in the north-central Tampa Bay region is affected by nitrate concentrations above background concentrations (the detection level (<0.06 milligrams per liter as Nitrogen (mg/L-N)) and detectable concentrations of volatile organic compounds and pesticides as a result of ground-water development and intensive urban land use. The region relies primarily on ground water for drinking water supplies. Sustainability of ground-water quality for public supply requires monitoring and understanding of the mechanisms controlling the vulnerability of public-supply wells to contamination. One representative public-supply well was selected based on the detection of a variety of chemical constituents for intensive study to evaluate the dominant processes affecting the vulnerability of public-supply wells in the Upper Floridan aquifer in the City of Temple Terrace near Tampa, Florida. A ground-water flow model was calibrated and used to determine the area contributing recharge to the selected public-supply well. A network of 28 monitoring wells was installed, and water and sediment samples were collected within the area contributing recharge to support a detailed analysis of physical and chemical conditions and processes affecting the water chemistry. Samples from the monitoring-well network indicated that nitrate concentrations, derived primarily from residential/commercial fertilizer use and atmospheric deposition, were highest (median 2.4 mg/L as N and maximum 6.11 mg/L as N) in shallow ground water from the surficial aquifer system and lowest (less than the detection level) in water from the Upper Floridan aquifer. Dissolved gas analysis indicated that denitrification had occurred near the interface of the surficial aquifer system and the intermediate confining unit, within the intermediate confining unit, and in the Upper Floridan aquifer because of reducing conditions. Simulations also indicated that the rapid movement of water from the surficial aquifer system to the selected public-supply well with high pumping rates, allows nitrate to reach the selected public-supply well in concentrations that resemble those of the overlying surficial aquifer system. Recharge water is most likely traveling through karst features such as sinkholes and conduits that bypass the denitrifying zones. Estimated advective travel times resulting from particle tracking from the time of recharge until discharge at the public supply well ranged from a few hours to 127 years, with a median of 13 years; nearly 45 percent of the particle ages reached the well within 10 years or less. Water from the surficial aquifer system with higher concentrations of nitrate and detectable volatile organic compounds and pesticides, is expected to continue moving to the selected public-supply well. Land-use and the proportion of young affected water contributing to the well is likely to remain relatively constant over time. The calculated nitrate concentration in the selected well indicates a lag of 1 to 10 years between peak concentrations of non-point source contaminants in recharge water and arrival at the well. | |||||
BibTeX:
@inproceedings{Crandall2008,
author = {Crandall, Christy A. and Kauffman, Leon J. and Katz, Brian G.},
title = {Simulations of Ground-Water Flow and Particle Pathline Analysis in the Contributing Recharge Area of a Public-Supply Well in Temple Terrace, Tampa Bay Region, Florida},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {92},
url = {http://pubs.usgs.gov/sir/2008/5023/36crandall.htm}
}
|
|||||
| Criddle, C.S., McCarty, P.L., Elliott, M.C. and Barker, J.F. | Reduction of hexachloroethane to tetrachloroethylene in groundwater | 1986 | Journal of Contaminant Hydrology Vol. 1(1-2)Transport and Transformations of Organic Contaminants, pp. 133-142 |
article | URL |
| Abstract: At the Canadian Forces Base, Borden, hexachloroethane (HCE) that was introduced into an unconfined sand aquifer disappeared rapidly, with a half-life of about 40 days. Laboratory-scale studies, initiated to help assess the fate of HCE, indicated that it is reductively biotransformed to tetrachloroethylene (PCE) both by aerobic cultures of wastewater microflora and by microcosms containing unhomogenized Borden aquifer material. The results also indicate that the agents involved in the aquifer transformation of HCE to PCE are not homogeneously distributed in the aquifer material. | |||||
BibTeX:
@article{Criddle1986,
author = {Criddle, Craig S. and McCarty, Perry L. and Elliott, M. Claire and Barker, James F.},
title = {Reduction of hexachloroethane to tetrachloroethylene in groundwater},
booktitle = {Transport and Transformations of Organic Contaminants},
journal = {Journal of Contaminant Hydrology},
year = {1986},
volume = {1},
number = {1-2},
pages = {133--142},
url = {http://www.sciencedirect.com/science/article/pii/0169772286900124}
}
|
|||||
| Crofton, F.S. | Educating for sustainability: opportunities in undergraduate engineering | 2000 | Journal of Cleaner Production Vol. 8(5), pp. 397-405 |
article | URL |
| Abstract: Awareness of the complex and interrelated environmental, economic and social problems in our world is increasing; the sustainability debate no longer focuses on whether changes are necessary but on what kind of changes are needed and how they can be carried out. Engineers are increasingly looked to for sustainable solutions yet find themselves less than adequately prepared to provide answers. Education is consistently identified as one of the key strategies for facilitating sustainable development; the required shift in the thinking, values and actions of individuals and institutions calls for efforts to make sustainability concerns a central theme of all education. This paper examines ways to better prepare engineers for the challenges of sustainable development and to increase the effectiveness of their solutions. | |||||
BibTeX:
@article{Crofton2000,
author = {Crofton, Fiona S.},
title = {Educating for sustainability: opportunities in undergraduate engineering},
journal = {Journal of Cleaner Production},
year = {2000},
volume = {8},
number = {5},
pages = {397--405},
url = {http://www.sciencedirect.com/science/article/pii/S0959652600000433}
}
|
|||||
| Crohn, D.M., Ruud, N.C., Decruyenaere, J.G. and Carlon, D.B. | Goodness-of-Fit Test for Modeling Tracer Breakthrough Curves in Wetlands | 2005 | Journal of Environmental Engineering Vol. 131(2), pp. 242-251 |
article | URL |
| Abstract: Wetland transport models generally either assume plug flow (with or without dispersion) or conceptualize the wetland as a series of continuously stirred tank reactors (CSTRs). To evaluate the CSTR approach, we present a goodness-of-fit test suitable for evaluating breakthrough curves from tracer experiments. The test, which makes use of confidence intervals associated with the multivariate normal distribution, can be used to test the fit of the breakthrough curve model, but requires sampling across a transect rather than from a single point. To test the CSTR assumption, we conducted a pair of two-dimensional tracer experiments within a 9.9 ha wetland constructed to receive effluent from a wastewater treatment plant in San Jacinto, Calif. The wetland operates with five parabolic inlets and a single large parabolic outlet to encourage lateral uniformity. In both experiments tritium oxide (HTO) was used as the tracer. Rhodamine WT dye was also included in the second experiment. Tracer samples were collected along transects installed perpendicular to the direction of flow. Analysis of the results indicates satisfactory lateral mixing and no significant short-circuiting. Rhodamine WT dye performed similarly to HTO when detectable but was too dilute to be observed at the outlet. When tracer movement was modeled as a series of continuously stirred reaction vessels, the parameter associated with the integer number of vessels increased from 2 at the first transect to 8 at the outlet. At each transect, the model was checked with a new goodness-of-fit test. At the α = 0.05 confidence level, all fitted models were rejected, suggesting that while the CSTR assumption may usefully approximate transport processes, it is not statistically valid for this wetland. | |||||
BibTeX:
@article{Crohn2005,
author = {Crohn, David M. and Ruud, Nels C. and Decruyenaere, Joseph G. and Carlon, David B.},
title = {Goodness-of-Fit Test for Modeling Tracer Breakthrough Curves in Wetlands},
journal = {Journal of Environmental Engineering},
publisher = {American Society of Civil Engineers (ASCE)},
year = {2005},
volume = {131},
number = {2},
pages = {242--251},
url = {http://dx.doi.org/10.1061/(ASCE)0733-9372(2005)131:2(242)}
}
|
|||||
| Cruz Jr., F., Karmann, I., Magdaleno, G., Coichev, N. and Viana Jr., O. | Influence of hydrological and climatic parameters on spatial-temporal variability of fluorescence intensity and DOC of karst percolation waters in the Santana Cave System, Southeastern Brazil | 2005 | Journal of Hydrology Vol. 302(1-4), pp. 1-12 |
article | URL |
| Abstract: Fluorescence intensity (FI) and organic carbon concentration of groundwater percolating through soil and rock into the Santana Cave were monitored at eight different cave sites between 2000 and 2002 to investigate their relationships to climatic parameters, stalactite discharge and thickness of rock overlying the cave. FI values, compared among sampling sites, are inversely proportional to depth and directly proportional to discharge; in contrast, dissolved organic matter (DOC) shows no significant spatial variability. Time-series analysis demonstrated similarities in DOC trends of different waters, but no correlation was observed with FI trends. Combined evaluation of DOC of infiltration waters, rainfall data and chemical parameters of Fe, O2, pH, Eh in soil solution indicate that peaks in DOC content coincide with more reduced conditions in the soil and have a lag time of 2–3 months after heavy showers. Variation of FI throughout the year occurs at all sampling sites but only higher drip discharge and rimstone pool waters were correlatable to rainfall events. FI of lower discharge sampling sites shows similar trends, but no relationship between drip discharge and rainfall variation was observed. Ranges and means of FI for all drip waters were significantly higher in the 2001–2002 period than in the preceding 2000–2001 period, which correlates with a 5.5 °C increase in mean austral winter temperatures in 2001. Hence, FI variations of karst waters that form carbonate speleothems under a humid subtropical climate may provide a useful proxy in paleoenvironmental reconstruction. | |||||
BibTeX:
@article{CruzJr.2005,
author = {Cruz Jr., F.W. and Karmann, I. and Magdaleno, G.B. and Coichev, N. and Viana Jr., O.},
title = {Influence of hydrological and climatic parameters on spatial-temporal variability of fluorescence intensity and DOC of karst percolation waters in the Santana Cave System, Southeastern Brazil},
journal = {Journal of Hydrology},
year = {2005},
volume = {302},
number = {1-4},
pages = {1--12},
url = {http://www.sciencedirect.com/science/article/pii/S002216940400294X}
}
|
|||||
| Cuesta, C. and Pop, I. | Numerical schemes for a pseudo-parabolic Burgers equation: Discontinuous data and long-time behaviour | 2009 | Journal of Computational and Applied Mathematics Vol. 224(1), pp. 269-283 |
article | URL |
| Abstract: We consider a simplified model for vertical non-stationary groundwater flow, which includes dynamic capillary pressure effects. Specifically, we consider a viscous Burgers-type equation that is extended with a third-order term containing mixed derivatives in space and time. We analyse the one-dimensional boundary value problem and investigate numerically its long-time behaviour. The numerical schemes discussed here take into account possible discontinuities of the solution. | |||||
BibTeX:
@article{Cuesta2009,
author = {Cuesta, C.M. and Pop, I.S.},
title = {Numerical schemes for a pseudo-parabolic Burgers equation: Discontinuous data and long-time behaviour},
journal = {Journal of Computational and Applied Mathematics},
year = {2009},
volume = {224},
number = {1},
pages = {269--283},
url = {http://www.sciencedirect.com/science/article/pii/S0377042708002070}
}
|
|||||
| Cunningham, J.A. and Fadel, Z.J. | Contaminant degradation in physically and chemically heterogeneous aquifers | 2007 | Journal of Contaminant Hydrology Vol. 94(3-4), pp. 293-304 |
article | URL |
| Abstract: This paper examines the importance of the correlation between hydraulic conductivity (K) and degradation rate constant (k) during the transport of reactive contaminants in heterogeneous aquifers. We simulated reactive transport in an ensemble of two-dimensional heterogeneous aquifers. Two sets of transport simulations were conducted: one in which a perfect positive correlation was assumed between ln(K) and ln(k), and one in which a perfect negative correlation was assumed. We found that the sign of the correlation has important consequences for the contaminant transport. Qualitatively, a negative correlation leads to significantly more pronounced “fingering” of the contaminant plume than does a positive correlation, with potentially important consequences for downgradient receptors. Quantitatively, the expected behavior (as quantified by the contaminant mass remaining in the aquifer) is statistically different between the positive and negative cases: on average, more contaminant mass persists when K and k are negatively correlated. Also, the negative correlation leads to more variability between realizations of the ensemble, whereas a positive correlation induces relatively little variability between realizations. We discuss the implications of these findings for the management of contaminated aquifers. | |||||
BibTeX:
@article{Cunningham2007,
author = {Cunningham, Jeffrey A. and Fadel, Ziad J.},
title = {Contaminant degradation in physically and chemically heterogeneous aquifers},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {94},
number = {3-4},
pages = {293--304},
url = {http://www.sciencedirect.com/science/article/pii/S0169772207000873}
}
|
|||||
| Cvetkovic, V., Dagan, G. and Cheng, H. | Contaminant Transport in Aquifers with Spatially Variable Hydraulic and Sorption Properties | 1998 | Proceedings: Mathematical, Physical and Engineering Sciences Vol. 454(1976), pp. 2173-2207 |
article | URL |
| Abstract: We consider migration of contaminants in groundwater and wish to characterize transport globally using spatial and temporal moments. The specific problem addressed in this work is how to simultaneously account for the spatial variability of the hydraulic conductivity, K, and of one or several sorption parameters, P. The Lagrangian framework for reactive transport in aquifers of Cvetkovic and Dagan is extended to incorporate the spatial variability in sorption parameters. For arbitrary sorption reactions, the general result can be used for simplified Monte Carlo simulations, where a three-dimensional advection-sorption problem is reduced to a three-dimensional advection and one-dimensional advection-sorption problem. The first two spatial moments characterize the spatial extent of a contaminant plume and are derived for ergodic transport, for cases of continuous and pulse injection. Expressions for the first three temporal moments which characterize field-scale contaminant discharge are derived for linear sorption reactions. All the derived expressions for the global transport quantities are given in terms of Lagrangian statistics of the fluid velocity and the sorption parameter(s) random fields. Analytical solutions are provided for a few sorption models which are most frequent in applications: nonlinear equilibrium sorption and linear non-equilibrium sorption. Analytical results are given in terms of Lagrangian statistics of the 'reaction flow path', μ , which integrates the sorption parameter along an advection flow path with time as the integration variable. Lagrangian statistics of μ are related to the Eulerian statistics of the hydraulic conductivity, K, and the sorption parameter, P, analytically and using Monte Carlo particle-tracking simulations. The derived analytical expressions are robust for the considered range of variabilities when compared to simulation results. For extraction of a contaminant subject to Langmuir sorption, the effect of spatial variability in the sorption capacity on the first two moments of the displacament front is supressed by the effect of nonlinearity. For linear non-equilibrium sorption, spatial variability in the forward rate coefficient has a more significant influence than in the backward rate on the first three temporal moments. | |||||
BibTeX:
@article{Cvetkovic1998,
author = {Cvetkovic, V. and Dagan, G. and Cheng, H.},
title = {Contaminant Transport in Aquifers with Spatially Variable Hydraulic and Sorption Properties},
journal = {Proceedings: Mathematical, Physical and Engineering Sciences},
publisher = {The Royal Society},
year = {1998},
volume = {454},
number = {1976},
pages = {2173--2207},
url = {http://www.jstor.org/stable/53213}
}
|
|||||
| Cvetkovic, V. and Molin, S. | Combining numerical simulations with time-domain random walk for pathogen risk assessment in groundwater | 2012 | Advances in Water Resources Vol. 36(0)Special Issue on Uncertainty Quantification and Risk Assessment, pp. 98-107 |
article | URL |
| Abstract: We present a methodology that combines numerical simulations of groundwater flow and advective transport in heterogeneous porous media with analytical retention models for computing the infection risk probability from pathogens in aquifers. The methodology is based on the analytical results presented in [1,2] for utilising the colloid filtration theory in a time-domain random walk framework. It is shown that in uniform flow, the results from the numerical simulations of advection yield comparable results as the analytical TDRW model for generating advection segments. It is shown that spatial variability of the attachment rate may be significant, however, it appears to affect risk in a different manner depending on if the flow is uniform or radially converging. In spite of the fact that numerous issues remain open regarding pathogen transport in aquifers on the field scale, the methodology presented here may be useful for screening purposes, and may also serve as a basis for future studies that would include greater complexity. | |||||
BibTeX:
@article{Cvetkovic2012,
author = {Cvetkovic, V. and Molin, S.},
title = {Combining numerical simulations with time-domain random walk for pathogen risk assessment in groundwater},
booktitle = {Special Issue on Uncertainty Quantification and Risk Assessment},
journal = {Advances in Water Resources},
year = {2012},
volume = {36},
number = {0},
pages = {98--107},
url = {http://www.sciencedirect.com/science/article/pii/S0309170811001205}
}
|
|||||
| Dagan, G. and Cvetkovic, V. | Reactive Transport and Immiscible Flow in Geological Media. I. General Theory | 1996 | Proceedings: Mathematical, Physical and Engineering Sciences Vol. 452(1945), pp. 285-301 |
article | URL |
| Abstract: Steady flow of incompressible fluids takes place in geological formations of spatially variable permeability. The permeability is regarded as a stationary random space function (RSF) of given statistical moments. The fluid carries reactive solutes and we consider, for illustration purposes, two types of reactions: nonlinear equilibrium sorption of a single species and mineral dissolution (linear kinetics). In addition, we analyse the nonlinear problem of horizontal flow of two immiscible fluids (the Buckley-Leverett flow). We consider injection at constant concentration in a semi-infinite domain at constant initial concentration and we neglect the effect of pore scale dispersion. The field-scale transport problem consists of characterizing an erratic plume, or displacement front, emanating from a given source area along distinct random flow paths. Reactive transport along three-dimensional flow paths is transformed to a one-dimensional Lagrangian-Eulerian domain (τ , t), where τ is the fluid residence time and t is the real time. Due to nonlinearity, discontinuities (shock waves) along a flow path may develop. Close form solutions are obtained for the expected values of the spatial and temporal moments of a nonlinearly reacting solute plume, or of two immiscible fluids. These results generalize the previous results for linearly reacting solute (Cvetkovic & Dagan 1994). The general results are illustrated and discussed in part II. | |||||
BibTeX:
@article{Dagan1996,
author = {Dagan, G. and Cvetkovic, V.},
title = {Reactive Transport and Immiscible Flow in Geological Media. I. General Theory},
journal = {Proceedings: Mathematical, Physical and Engineering Sciences},
publisher = {The Royal Society},
year = {1996},
volume = {452},
number = {1945},
pages = {285--301},
url = {http://www.jstor.org/stable/52878}
}
|
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| Daher, W., Pistre, S., Kneppers, A., Bakalowicz, M. and Najem, W. | Karst and artificial recharge: Theoretical and practical problems: A preliminary approach to artificial recharge assessment | 2011 | Journal of Hydrology Vol. 408(3-4), pp. 189-202 |
article | URL |
| Abstract: Managed Aquifer Recharge (MAR) is an emerging sustainable technique that has already generated successful results and is expected to solve many water resource problems, especially in semi-arid and arid zones. It is of great interest for karst aquifers that currently supply 20–25% of the world’s potable water, particularly in Mediterranean countries. However, the high heterogeneity in karst aquifers is too complex to be able to locate and describe them simply via field observations. Hence, as compared to projects in porous media, MAR is still marginal in karst aquifers. | |||||
BibTeX:
@article{Daher2011,
author = {Daher, Walid and Pistre, Séverin and Kneppers, Angeline and Bakalowicz, Michel and Najem, Wajdi},
title = {Karst and artificial recharge: Theoretical and practical problems: A preliminary approach to artificial recharge assessment},
journal = {Journal of Hydrology},
year = {2011},
volume = {408},
number = {3-4},
pages = {189--202},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411004598}
}
|
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| Dai, Y. and Wang, D.-g. | Numerical study on the purification performance of riverbank | 2007 | Journal of Hydrodynamics, Ser. B Vol. 19(5), pp. 643-652 |
article | URL |
| Abstract: During the rain time, the runoff infiltrates into the riverbank through the collecting gutter and slope surface. The city runoff is generally polluted by organic, oil, heavy metal particulates, etc. The pollutants moving with the water through the riverbank experience advection, dispersion, diffusion, adsorption, biochemical reaction and plant uptaking processes. In this article, a mathematical model was developed to simulate the performance of pollutant removal of the riverbank. The model took those main mechanisms into account. The modified Richards equation was used in simulating flow field. The mass balance law was employed in deriving the equation for pollutant transport, where the diffusion and dispersion were described with the Fick-type law, the adsorption was macroscopically expressed as form isotherm, and the bio-chemical degradation process was assumed to follow the Monod kinetics. The NH3-N and TP were considered in the present model. The mathematical model was descritized with a finite element numerical model, which was applied to two types of model riverbanks. In the model test, the hydraulic loading was assumed to have the intermittent pattern simulating the storm runoff of certain return period, and the values of the rainfall runoff and concentrations of the NH3-N and TP were taken from the model test. The computed overall removal rates for the NH3-N and TP in 6 cases are in the range of 88%-98%, 87%-97%, respectively. The differences between the computed and tested overall removal rates for the NH3-N and TP are less than 5%. The time-varying oscillation pattern of the concentrations of the NH3-N and TP were rationally simulated, which shows that the model presented in this article can be used to assess the purification performance of the riverbank constructed with sand or soil. | |||||
BibTeX:
@article{Dai2007,
author = {Dai, Yu and Wang, De-guan},
title = {Numerical study on the purification performance of riverbank},
journal = {Journal of Hydrodynamics, Ser. B},
year = {2007},
volume = {19},
number = {5},
pages = {643--652},
url = {http://www.sciencedirect.com/science/article/pii/S1001605807601656}
}
|
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| Dai, Z., Wolfsberg, A., Reimus, P., Deng, H., Kwicklis, E., Ding, M., Ware, D. and Ye, M. | Identification of sorption processes and parameters for radionuclide transport in fractured rock | 2012 | Journal of Hydrology Vol. 414-415(0), pp. 220-230 |
article | URL |
| Abstract: Identification of chemical reaction processes in subsurface environments is a key issue for reactive transport modeling because simulating different processes requires developing different chemical–mathematical models. In this paper, two sorption processes (equilibrium and kinetics) are considered for modeling neptunium and uranium sorption in fractured rock. Based on different conceptualizations of the two processes occurring in fracture and/or matrix media, seven dual-porosity, multi-component reactive transport models are developed. The process models are identified with a stepwise strategy by using multi-tracer concentration data obtained from a series of transport experiments. In the first step, breakthrough data of a conservative tracer (tritium) obtained from four experiments are used to estimate the flow and non-reactive transport parameters (i.e., mean fluid residence time in fracture, fracture aperture, and matrix tortuosity) common to all the reactive transport models. In the second and third steps, by fixing the common non-reactive flow and transport parameters, the sorption parameters (retardation factor, sorption coefficient, and kinetic rate constant) of each model are estimated using the breakthrough data of reactive tracers, neptunium and uranium, respectively. Based on the inverse modeling results, the seven sorption-process models are discriminated using four model discrimination (or selection) criteria, Akaike information criterion (AIC), modified Akaike information criterion (AICc), Bayesian information criterion (BIC) and Kashyap information criterion (KIC). These criteria suggest the kinetic sorption process for modeling reactive transport of neptunium and uranium transport in both fracture and matrix. This conclusion is confirmed by two chemical criteria, the half reaction time and Damköhler number criterion. | |||||
BibTeX:
@article{Dai2012,
author = {Dai, Zhenxue and Wolfsberg, Andrew and Reimus, Paul and Deng, Hailin and Kwicklis, Edward and Ding, Mei and Ware, Doug and Ye, Ming},
title = {Identification of sorption processes and parameters for radionuclide transport in fractured rock},
journal = {Journal of Hydrology},
year = {2012},
volume = {414-415},
number = {0},
pages = {220--230},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411007591}
}
|
|||||
| Dai, Z., Wolfsberg, A., Reimus, P., Deng, H., Kwicklis, E., Ding, M., Ware, D. and Ye, M. | Identification of sorption processes and parameters for radionuclide transport in fractured rock | 2012 | Journal of Hydrology Vol. 414--415(0), pp. 220-230 |
article | URL |
| Abstract: Summary Identification of chemical reaction processes in subsurface environments is a key issue for reactive transport modeling because simulating different processes requires developing different chemical–mathematical models. In this paper, two sorption processes (equilibrium and kinetics) are considered for modeling neptunium and uranium sorption in fractured rock. Based on different conceptualizations of the two processes occurring in fracture and/or matrix media, seven dual-porosity, multi-component reactive transport models are developed. The process models are identified with a stepwise strategy by using multi-tracer concentration data obtained from a series of transport experiments. In the first step, breakthrough data of a conservative tracer (tritium) obtained from four experiments are used to estimate the flow and non-reactive transport parameters (i.e., mean fluid residence time in fracture, fracture aperture, and matrix tortuosity) common to all the reactive transport models. In the second and third steps, by fixing the common non-reactive flow and transport parameters, the sorption parameters (retardation factor, sorption coefficient, and kinetic rate constant) of each model are estimated using the breakthrough data of reactive tracers, neptunium and uranium, respectively. Based on the inverse modeling results, the seven sorption-process models are discriminated using four model discrimination (or selection) criteria, Akaike information criterion (AIC), modified Akaike information criterion (AICc), Bayesian information criterion (BIC) and Kashyap information criterion (KIC). These criteria suggest the kinetic sorption process for modeling reactive transport of neptunium and uranium transport in both fracture and matrix. This conclusion is confirmed by two chemical criteria, the half reaction time and Damköhler number criterion. | |||||
BibTeX:
@article{Dai2012a,
author = {Dai, Zhenxue and Wolfsberg, Andrew and Reimus, Paul and Deng, Hailin and Kwicklis, Edward and Ding, Mei and Ware, Doug and Ye, Ming},
title = {Identification of sorption processes and parameters for radionuclide transport in fractured rock},
journal = {Journal of Hydrology},
year = {2012},
volume = {414--415},
number = {0},
pages = {220--230},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411007591}
}
|
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| Daillant, O., Kirchner, G., Pigrée, G. and Porstendörfer, J. | Lichens as indicators of tritium and radiocarbon contamination | 2004 | Science of The Total Environment Vol. 323(1–3), pp. 253-262 |
article | URL |
| Abstract: Lichens were collected in France in the surroundings of a military nuclear facility in Burgundy, near the la Hague reprocessing plant and in an area away from any direct source of contamination. Organically bound tritium (OBT) has been analysed on 18 samples and radiocarbon on 11. It appeared that on the most contaminated spots, the OBT activity in lichens was higher than the background by a factor of 1000 and was still a factor 10–100 at a distance of 20 km from the source. Radiocarbon from la Hague could be traced by lichens. The slow metabolism of lichens makes them suitable for the follow-up of 3H and 14C, which have been incorporated by photosynthesis. | |||||
BibTeX:
@article{Daillant2004,
author = {Daillant, Olivier and Kirchner, Gerald and Pigrée, Gilbert and Porstendörfer, Justin},
title = {Lichens as indicators of tritium and radiocarbon contamination},
journal = {Science of The Total Environment},
year = {2004},
volume = {323},
number = {1–3},
pages = {253--262},
url = {http://www.sciencedirect.com/science/article/pii/S0048969703005813}
}
|
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| Danckwerts, P. | The effect of incomplete mixing on homogeneous reactions | 1958 | Chemical Engineering Science Vol. 8(1-2), pp. 93-102 |
article | URL |
| Abstract: The rate of a homogeneous reaction depends on rate of encounter between reactant molecules. When the reaction mixture consists of two reactant streams flowing into a continuous reactor, or of earlier and later parts of a single stream, the average rate of reaction is in general dependent on the degree of mixing on the molecular scale. It cannot generally be predicted simply from the distribution of residence times. | |||||
BibTeX:
@article{Danckwerts1958,
author = {Danckwerts, P.V.},
title = {The effect of incomplete mixing on homogeneous reactions},
journal = {Chemical Engineering Science},
year = {1958},
volume = {8},
number = {1-2},
pages = {93--102},
url = {http://www.sciencedirect.com/science/article/pii/0009250958800408}
}
|
|||||
| Danckwerts, P., Jenkins, J. and Place, G. | The distribution of residence-times in an industrial fluidised reactor | 1954 | Chemical Engineering Science Vol. 3(1), pp. 26-35 |
article | URL |
| Abstract: The distribution of residence-times of the gas flowing through a fluidised catalyst regenerator has been determined by using helium as a tracer. Only about 5% of the gas spends less than half, and about 5% more than twice, the mean residence-time in the regenerator. It appears that the flow through the fluidised bed itself is much closer to piston-flow than to complete mixing, the hold-back being less than 0·1. | |||||
BibTeX:
@article{Danckwerts1954,
author = {Danckwerts, P.V. and Jenkins, J.W. and Place, G.},
title = {The distribution of residence-times in an industrial fluidised reactor},
journal = {Chemical Engineering Science},
year = {1954},
volume = {3},
number = {1},
pages = {26--35},
url = {http://www.sciencedirect.com/science/article/pii/0009250954800042}
}
|
|||||
| Danckwerts, P.V. | Continuous flow systems: Distribution of residence times | 1953 | Chemical Engineering Science Vol. 2(1), pp. 1-13 |
article | URL |
| Abstract: When a fluid flows through a vessel at a constant rate, either “piston-flow” or perfect mixing is usually assumed. In practice many systems do not conform to either of these assumptions, so that calculations based on them may be inaccurate. It is explained how distribution-functions for residence-times can be defined and measured for actual systems. Open and packed tubes are discussed as systems about which predictions can be made. The use of the distribution-functions is illustrated by showing how they can be used to calculate the efficiencies of reactors and blenders. It is shown how models may be used to predict the distribution of residence-times in large systems. | |||||
BibTeX:
@article{Danckwerts1953,
author = {Danckwerts, P. V.},
title = {Continuous flow systems: Distribution of residence times},
journal = {Chemical Engineering Science},
year = {1953},
volume = {2},
number = {1},
pages = {1--13},
url = {http://www.sciencedirect.com/science/article/pii/0009250996818112}
}
|
|||||
| Danquigny, C., Ackerer, P. and Carlier, J. | Laboratory tracer tests on three-dimensional reconstructed heterogeneous porous media | 2004 | Journal of Hydrology Vol. 294(1-3)Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media, pp. 196-212 |
article | URL |
| Abstract: Tracer tests have been performed on a 3D tank of dimensions 560×100×100 cm3. These experiments at laboratory scale are used to define effective hydraulic conductivity and macrodispersivity. The tracer tests have been performed on two kinds of heterogeneous porous material: a channel structured medium, with channels crossing the whole tank, and a statistically correlated random structure. The statistically correlated field was first established by a sequential type generator with a prescribed exponential covariance. The theoretical random field is then modified according to the available sand hydraulic conductivities. The obtained LnK variance is 1.03 and the integral scale 23.1 cm. | |||||
BibTeX:
@article{Danquigny2004,
author = {Danquigny, C and Ackerer, P and Carlier, J.P},
title = {Laboratory tracer tests on three-dimensional reconstructed heterogeneous porous media},
booktitle = {Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media},
journal = {Journal of Hydrology},
year = {2004},
volume = {294},
number = {1-3},
pages = {196--212},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404001015}
}
|
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| Datta, G.S. | On symmetry of finite mixtures of normal distributions | 2007 | Journal of Statistical Planning and Inference Vol. 137(9), pp. 2993-2995 |
article | URL |
| Abstract: In this note we derive a necessary and sufficient condition for a distribution obtained by taking a finite mixture of multivariate normal distributions to be symmetric about zero. The result derived also holds for mixtures of symmetric stable distributions, including the Cauchy distribution. | |||||
BibTeX:
@article{Datta2007,
author = {Datta, Gauri Sankar},
title = {On symmetry of finite mixtures of normal distributions},
journal = {Journal of Statistical Planning and Inference},
year = {2007},
volume = {137},
number = {9},
pages = {2993--2995},
url = {http://www.sciencedirect.com/science/article/pii/S0378375807000614}
}
|
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| Daunizeau, J., Friston, K. and Kiebel, S. | Variational Bayesian identification and prediction of stochastic nonlinear dynamic causal models | 2009 | Physica D: Nonlinear Phenomena Vol. 238(21), pp. 2089-2118 |
article | URL |
| Abstract: In this paper, we describe a general variational Bayesian approach for approximate inference on nonlinear stochastic dynamic models. This scheme extends established approximate inference on hidden-states to cover: (i) nonlinear evolution and observation functions, (ii) unknown parameters and (precision) hyperparameters and (iii) model comparison and prediction under uncertainty. Model identification or inversion entails the estimation of the marginal likelihood or evidence of a model. This difficult integration problem can be finessed by optimising a free-energy bound on the evidence using results from variational calculus. This yields a deterministic update scheme that optimises an approximation to the posterior density on the unknown model variables. We derive such a variational Bayesian scheme in the context of nonlinear stochastic dynamic hierarchical models, for both model identification and time-series prediction. The computational complexity of the scheme is comparable to that of an extended Kalman filter, which is critical when inverting high dimensional models or long time-series. Using Monte-Carlo simulations, we assess the estimation efficiency of this variational Bayesian approach using three stochastic variants of chaotic dynamic systems. We also demonstrate the model comparison capabilities of the method, its self-consistency and its predictive power. | |||||
BibTeX:
@article{Daunizeau2009,
author = {Daunizeau, J. and Friston, K.J. and Kiebel, S.J.},
title = {Variational Bayesian identification and prediction of stochastic nonlinear dynamic causal models},
journal = {Physica D: Nonlinear Phenomena},
year = {2009},
volume = {238},
number = {21},
pages = {2089--2118},
url = {http://www.sciencedirect.com/science/article/pii/S0167278909002425}
}
|
|||||
| Davies, A.R. | Environmental justice as subtext or omission: Examining discourses of anti-incineration campaigning in Ireland | 2006 | Geoforum Vol. 37(5), pp. 708-724 |
article | URL |
| Abstract: The incineration of waste is a controversial issue marked by a history of opposition from community groups and environmentalists around the globe. Opponents, particularly in the USA, have frequently adopted a discourse of environmental justice to challenge the legitimacy of incineration. In line with these broad geographies of resistance recent proposals to introduce municipal solid waste incinerators in Ireland have sparked a series of opposition campaigns. However an examination of the discourses of resistance adopted by campaigners in one specific site of resistance, the Galway region on the west coast of Ireland, indicates that the vocabulary of environmental justice has not been publicly articulated. This paper investigates this absence of environmental justice in the language of opposition. The research reveals an interwoven set of contingent conditions that conspire to inhibit the adoption of environmental justice discourses in Ireland. However these conditions are not static and a combination of pressures, both within and beyond Ireland, are creating a dynamic context that could promote the emergence of environmental justice discourses in the future. | |||||
BibTeX:
@article{Davies2006,
author = {Davies, Anna R.},
title = {Environmental justice as subtext or omission: Examining discourses of anti-incineration campaigning in Ireland},
journal = {Geoforum},
year = {2006},
volume = {37},
number = {5},
pages = {708--724},
url = {http://www.sciencedirect.com/science/article/pii/S001671850600008X}
}
|
|||||
| Davit, Y., Debenest, G., Wood, B.D. and Quintard, M. | Modeling non-equilibrium mass transport in biologically reactive porous media | 2010 | Advances in Water Resources Vol. 33(9), pp. 1075-1093 |
article | URL |
| Abstract: We develop a one-equation non-equilibrium model to describe the Darcy-scale transport of a solute undergoing biodegradation in porous media. Most of the mathematical models that describe the macroscale transport in such systems have been developed intuitively on the basis of simple conceptual schemes. There are two problems with such a heuristic analysis. First, it is unclear how much information these models are able to capture; that is, it is not clear what the model's domain of validity is. Second, there is no obvious connection between the macroscale effective parameters and the microscopic processes and parameters. As an alternative, a number of upscaling techniques have been developed to derive the appropriate macroscale equations that are used to describe mass transport and reactions in multiphase media. These approaches have been adapted to the problem of biodegradation in porous media with biofilms, but most of the work has focused on systems that are restricted to small concentration gradients at the microscale. This assumption, referred to as the local mass equilibrium approximation, generally has constraints that are overly restrictive. In this article, we devise a model that does not require the assumption of local mass equilibrium to be valid. In this approach, one instead requires only that, at sufficiently long times, anomalous behaviors of the third and higher spatial moments can be neglected; this, in turn, implies that the macroscopic model is well represented by a convection–dispersion–reaction type equation. This strategy is very much in the spirit of the developments for Taylor dispersion presented by Aris (1956). On the basis of our numerical results, we carefully describe the domain of validity of the model and show that the time-asymptotic constraint may be adhered to even for systems that are not at local mass equilibrium. | |||||
BibTeX:
@article{Davit2010,
author = {Davit, Yohan and Debenest, Gérald and Wood, Brian D. and Quintard, Michel},
title = {Modeling non-equilibrium mass transport in biologically reactive porous media},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {9},
pages = {1075--1093},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810001259}
}
|
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| Dawson, C.N., Duijn, C.J.v. and Grundy, R.E. | Large Time Asymptotics in Contaminant Transport in Porous Media | 1996 | SIAM Journal on Applied Mathematics Vol. 56(4), pp. 965-993 |
article | URL |
| Abstract: In this paper we derive large time solutions of the partial differential equations modelling contaminant transport in porous media for initial data with bounded support. While the main emphasis is on two space dimensions, for the sake of completeness we give a brief summary of the corresponding results for one space dimension. The philosophy behind the paper is to compare the results of a formal asymptotic analysis of the governing equations as t → ∞ with numerical solutions of the complete initial value problem. The analytic results are obtained using the method of dominant balance which identifies the dominant terms in the model equations determining the behavior of the solution in the large time limit. These are found in terms of time scaled space similarity variables and the procedure results in a reduction of the number of independent variables in the original partial differential equation. This generates what we call a reduced equation, the solution of which depends crucially on the value of a parameter appearing in the problem. In some cases the reduced equation can be solved explicitly, while others have a particularly intractable structure which inhibits any analytic or numerical progress. However, we can extract a number of global and local properties of the solution, which enables us to form a reasonably complete picture of what the profiles look like. Extensive comparison with numerical solution of the original initial value problem provides convincing confirmation of our analytic solutions. In the final section of the paper, by way of motivation for the work, we give some results concerning the temporal behavior of certain moments of the two-dimensional profiles commonly used to compute physical parameter characteristics for contaminant transport in porous media. | |||||
BibTeX:
@article{Dawson1996,
author = {Dawson, C. N. and Duijn, C. J. van and Grundy, R. E.},
title = {Large Time Asymptotics in Contaminant Transport in Porous Media},
journal = {SIAM Journal on Applied Mathematics},
publisher = {Society for Industrial and Applied Mathematics},
year = {1996},
volume = {56},
number = {4},
pages = {965--993},
url = {http://www.jstor.org/stable/2102599}
}
|
|||||
| Day, T.J. | Longitudinal dispersion of fluid particles in mountain streams: 1. Theory and field evidence | 1977 | Journal of Hydrology (N. Z.) Vol. 16(1), pp. 7-25 |
article | URL |
| Abstract: The longitudinal dispersion of fluid particles in mountain streams was investigated in a series of 49 experiments. Mean properties of the dispersion process were studied over a maximum downstream distance of 2250 m, a mean velocity range of 0.32-1.57 m/s, and a mean flow width range of 2.7-21.8 m. It is conclusively shown that for distances of up to 800 mean channel widths in these steep, turbulent streams, the spread or standard deviation of an initially concentrated mass increases linearity with distance, and not as its square root as necessary for the application of conventional mixing models. Consequences of this linearity are an ever-increasing dispersion coefficient along the channel and a persistent asymmetrical concentration distribution. | |||||
BibTeX:
@article{Day1977a,
author = {Day, T. J.},
title = {Longitudinal dispersion of fluid particles in mountain streams: 1. Theory and field evidence},
journal = {Journal of Hydrology (N. Z.)},
year = {1977},
volume = {16},
number = {1},
pages = {7--25},
url = {http://www.hydrologynz.org.nz/journal.php?article_id=385}
}
|
|||||
| Day, T.J. | Longitudinal dispersion of fluid particles in mountain streams: 2. Similarity of the mean motion and its application | 1977 | Journal of Hydrology (N. Z.) Vol. 16(1), pp. 26-52 |
article | URL |
| Abstract: The mean longitudinal motion of fluid particles dispersing in mountain streams is shown, for distances up to 800 mean channel widths, to exhibit the characteristics of a self-similar process with constant velocity ratios and geometric form. Although the kinematic relations and the structure of the turbulent field are shown to be sensitive to the nature of the flow boundaries, and the geometry of the channel, similarity is shown to exist for flows in a wide range of steep gravel- and boulder-bed channels. A dimensionless time—concentration curve is developed and a method for prediction of the dispersion pattern. based upon the co-ordinates of this shape and the linearity of its scaling parameters, is presented. | |||||
BibTeX:
@article{Day1977b,
author = {Day, T. J.},
title = {Longitudinal dispersion of fluid particles in mountain streams: 2. Similarity of the mean motion and its application},
journal = {Journal of Hydrology (N. Z.)},
year = {1977},
volume = {16},
number = {1},
pages = {26--52},
url = {http://www.hydrologynz.org.nz/journal.php?article_id=386}
}
|
|||||
| Dayan, J. and Levenspiel, O. | Longitudinal dispersion in packed beds of porous adsorbing solids | 1968 | Chemical Engineering Science Vol. 23(11), pp. 1327-1334 |
article | URL |
| Abstract: The dispersion models developed by Turner and Aris for fluids flowing in packed beds of porous solids is here extended to packed beds of porous adsorbing solids. For the nonadsorbing systems it was found that molecular diffusion, convective flow in the bed channels, and holdup in pores are additive contributions to the overall dispersion coefficient. In adsorbing systems, however, it is here shown that pore holdup and adsorption are not simply additive contributions, but are combined in a complex fashion. | |||||
BibTeX:
@article{Dayan1968,
author = {Dayan, Joshua and Levenspiel, Octave},
title = {Longitudinal dispersion in packed beds of porous adsorbing solids},
journal = {Chemical Engineering Science},
year = {1968},
volume = {23},
number = {11},
pages = {1327--1334},
url = {http://www.sciencedirect.com/science/article/pii/0009250968890438}
}
|
|||||
| De Biase, C., Reger, D., Schmidt, A., Jechalke, S., Reiche, N., Martínez-Lavanchy, P.M., Rosell, M., Van Afferden, M., Maier, U., Oswald, S.E. and Thullner, M. | Treatment of volatile organic contaminants in a vertical flow filter: Relevance of different removal processes | 2011 | Ecological Engineering Vol. 37(9), pp. 1292-1303 |
article | URL |
| Abstract: Vertical flow filters and vertical flow constructed wetlands are established wastewater treatment systems and have also been proposed for the treatment of contaminated groundwater. This study investigates the removal processes of volatile organic compounds in a pilot-scale vertical flow filter. The filter is intermittently irrigated with contaminated groundwater containing benzene, MTBE and ammonium as the main contaminants. The system is characterized by unsaturated conditions and high contaminant removal efficiency. The aim of the present study is to evaluate the contribution of biodegradation and volatilization to the overall removal of benzene and MTBE. Tracer tests and flow rate measurements showed a highly transient flow and heterogeneous transport regime. Radon-222, naturally occurring in the treated groundwater, was used as a gas tracer and indicated a high volatilization potential. Radon-222 behavior was reproduced by numerical simulations and extrapolated for benzene and MTBE, and indicated these compounds also have a high volatilization potential. In contrast, passive sampler measurements on top of the filter detected only low benzene and MTBE concentrations. Biodegradation potential was evaluated by the analysis of catabolic genes involved in organic compound degradation and a quantitative estimation of biodegradation was derived from stable isotope fractionation analysis. Results suggest that despite the high volatilization potential, biodegradation is the predominant mass removal process in the filter system, which indicates that the volatilized fraction of the contaminants is still subject to subsequent biodegradation. In particular, the upper filter layer located between the injection tubes and the surface of the system might also contribute to biodegradation, and might play a crucial role in avoiding the emission of volatilized contaminants into the atmosphere. | |||||
BibTeX:
@article{DeBiase2011,
author = {De Biase, Cecilia and Reger, Daniel and Schmidt, Axel and Jechalke, Sven and Reiche, Nils and Martínez-Lavanchy, Paula M. and Rosell, Mònica and Van Afferden, Manfred and Maier, Uli and Oswald, Sascha E. and Thullner, Martin},
title = {Treatment of volatile organic contaminants in a vertical flow filter: Relevance of different removal processes},
journal = {Ecological Engineering},
year = {2011},
volume = {37},
number = {9},
pages = {1292--1303},
url = {http://www.sciencedirect.com/science/article/pii/S0925857411001194}
}
|
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| De Lucia, M., Lagneau, V., de Fouquet, C. and Bruno, R. | The influence of spatial variability on 2D reactive transport simulations | 2011 | Comptes Rendus Geoscience Vol. 343(6), pp. 406-416 |
article | URL |
| Abstract: In reactive transport simulations, the effects of the spatial variability of geological media are generally neglected. The impact of this variability is systematically examined here in 2D simulations, with a simple geometry and chemistry with a positive feedback: increase of porosity and of permeability during calcite dissolution. The results highlight the leading role in these conditions of: (i) the correlation length of porosity and of permeability; and (ii) the kinematic dispersivity, whose effects are dominant compared to those of variance and reaction kinetics. The impact of stochastic variability (between several random draws) is also significant, as it is of the same order of magnitude as the impact of the range and dispersivity. | |||||
BibTeX:
@article{DeLucia2011,
author = {De Lucia, Marco and Lagneau, Vincent and de Fouquet, Chantal and Bruno, Roberto},
title = {The influence of spatial variability on 2D reactive transport simulations},
journal = {Comptes Rendus Geoscience},
year = {2011},
volume = {343},
number = {6},
pages = {406--416},
url = {http://www.sciencedirect.com/science/article/pii/S1631071311000940}
}
|
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| De Smedt, F. | Analytical solution and analysis of solute transport in rivers affected by diffusive transfer in the hyporheic zone | 2007 | Journal of Hydrology Vol. 339(1-2), pp. 29-38 |
article | URL |
| Abstract: A model is presented for solute transport in rivers including transient storage in hyporheic zones. The model consists of an advection–dispersion equation for transport in the main channel with a sink term describing diffusive solute transfer to the hyporheic zone. This system of equations is solved analytically for instantaneous injection of a conservative tracer in an infinite uniform river reach with steady flow. The solution enables to estimate the temporal and spatial evolution of tracer concentrations downstream of the injection point with fewer parameters than any other model before. The solution is linked to a non-linear least squares optimisation algorithm to analyse breakthrough curves and estimate solute transport parameters. The model is applied to tracer experiments conducted in the Chillán River, Chile, which were previously analysed with a model including mass exchange between the river and a stagnant storage zone. The fit between observations and model results is good, except for some experiments where the tailing of the fitted curves is more pronounced than observed. Estimates of the water flow velocity are practically identical with previous findings, but the estimates of the cross-sectional area and the dispersion coefficient are markedly different. Estimated values for the diffusion coefficient in the hyporheic zone agree with values cited in literature and with the magnitude of chemical diffusion coefficients in porous media. | |||||
BibTeX:
@article{DeSmedt2007,
author = {De Smedt, F.},
title = {Analytical solution and analysis of solute transport in rivers affected by diffusive transfer in the hyporheic zone},
journal = {Journal of Hydrology},
year = {2007},
volume = {339},
number = {1-2},
pages = {29--38},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407000777}
}
|
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| De Smedt, F., Brevis, W. and Debels, P. | Analytical solution for solute transport resulting from instantaneous injection in streams with transient storage | 2005 | Journal of Hydrology Vol. 315(1-4), pp. 25-39 |
article | URL |
| Abstract: An analytical solution is presented for solute transport in rivers including the effects of transient storage. The traditional advection–dispersion equation for transport in the main channel is linked to a first order mass exchange term between the main channel and the transient storage zones. This system of equations is solved analytically for the case of an instantaneous injection of a tracer mass in a river with constant and uniform flow. The solution enables to estimate the temporal and spatial evolution of the tracer concentration downstream of the injection point. The correctness of the solution is verified by comparison with the numerical model OTIS (USGS). The solution is programmed in MATLAB and linked to a non-linear least squares optimisation algorithm to obtain an effective and reliable method to estimate solute transport parameters from observed breakthrough curves. The procedure is successfully applied to the Chillán River, Chile, where five tracer experiments were conducted. The observed concentration profiles vs. time at the different measuring locations are well reproduced by the model. In all cases the exchange of solute between the main flow channel and transient storage zones is markedly present. | |||||
BibTeX:
@article{DeSmedt2005,
author = {De Smedt, F. and Brevis, W. and Debels, P.},
title = {Analytical solution for solute transport resulting from instantaneous injection in streams with transient storage},
journal = {Journal of Hydrology},
year = {2005},
volume = {315},
number = {1-4},
pages = {25--39},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405001757}
}
|
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| De Waele, J., Gutiérrez, F., Parise, M. and Plan, L. | Geomorphology and natural hazards in karst areas: A review [BibTeX] |
2011 | Geomorphology Vol. 134(1-2)Geomorphology and Natural Hazards in Karst Areas, pp. 1-8 |
article | URL |
BibTeX:
@article{DeWaele2011,
author = {De Waele, Jo and Gutiérrez, Francisco and Parise, Mario and Plan, Lukas},
title = {Geomorphology and natural hazards in karst areas: A review},
booktitle = {Geomorphology and Natural Hazards in Karst Areas},
journal = {Geomorphology},
year = {2011},
volume = {134},
number = {1-2},
pages = {1--8},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X11003825}
}
|
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| De Waele, J., Martina, M.L., Sanna, L., Cabras, S. and Cossu, Q.A. | Flash flood hydrology in karstic terrain: Flumineddu Canyon, central-east Sardinia | 2010 | Geomorphology Vol. 120(3-4), pp. 162-173 |
article | URL |
| Abstract: In the last five winters (2004–2008) several exceptional meteorological events producing flash floods have been registered in central-east Sardinia. The first of these (December 2004) was the most severe and caused important geomorphic changes in the Riu Flumineddu watershed where the influence of human activity is limited. The hydrological characterisation of this flood is extremely difficult because of the lack of streamflow gauges and the relative paucity of meteorological stations in the region. Peak discharge of the fluviokarstic Riu Flumineddu Canyon has been estimated based on a distributed hydrological model (TOPKAPI) and on empirical methods based on geomorphic and sedimentological observations. The comparison between the results derived from these independent methods allows us to obtain the best possible estimate of peak discharge. Differences between modelled and measured peak flows can be attributed to water losses and/or gains along the river channel from interactions with the underground karst drainage network. | |||||
BibTeX:
@article{DeWaele2010,
author = {De Waele, Jo and Martina, Mario L.V. and Sanna, Laura and Cabras, Salvatore and Cossu, Q. Antonio},
title = {Flash flood hydrology in karstic terrain: Flumineddu Canyon, central-east Sardinia},
journal = {Geomorphology},
year = {2010},
volume = {120},
number = {3-4},
pages = {162--173},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X10001406}
}
|
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| De Wilde, J., Heynderickx, G.J., Vierendeels, J., Dick, E. and Marin, G.B. | An extension of the preconditioned advection upstream splitting method for 3D two-phase flow calculations in circulating fluidized beds | 2002 | Computers & Chemical Engineering Vol. 26(12), pp. 1677-1702 |
article | URL |
| Abstract: For the calculation of gas–solid flow in circulating fluidized beds, a Eulerian–Eulerian approach is taken. An integration scheme based on dual time stepping and a finite volume technique is developed and implemented in 3D. The inviscid part of the equations is treated following an extension of the preconditioned advection upstream splitting method (AUSMP) to two-phase flows. Calculations on an industrial size straight riser are performed. The influence of the inelasticity of particle–particle collisions on the stability of the flow is investigated. Further, the effects of a double abrupt side outlet configuration are shown. | |||||
BibTeX:
@article{DeWilde2002,
author = {De Wilde, Juray and Heynderickx, Geraldine J. and Vierendeels, Jan and Dick, Erik and Marin, Guy B.},
title = {An extension of the preconditioned advection upstream splitting method for 3D two-phase flow calculations in circulating fluidized beds},
journal = {Computers & Chemical Engineering},
year = {2002},
volume = {26},
number = {12},
pages = {1677--1702},
url = {http://www.sciencedirect.com/science/article/pii/S0098135402001576}
}
|
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| DeAngelis, D., Loreau, M., Neergaard, D., Mulholland, P. and Marzolf, E. | Modelling nutrient-periphyton dynamics in streams: the importance of transient storage zones | 1995 | Ecological Modelling Vol. 80(2–3), pp. 149-160 |
article | URL |
| Abstract: The dynamics of a nutrient-limited periphyton community in a segment of stream was modeled. The stream segment was assumed to consist of two zones, free-flowing water and a boundary zone of zero water flow, which acted as a transient storage zone for nutrients. Studies with a biologically unreactive tracer solute (sodium chloride) were used to obtain parameters for diffusion of solute into the transient storage zone. Two simple alternative functional responses representing nutrient-limited periphyton growth were formulated, one with only nutrient limitation on periphyton growth and one that additionally included density-dependent limitation of periphyton growth. | |||||
BibTeX:
@article{DeAngelis1995,
author = {DeAngelis, D.L. and Loreau, M. and Neergaard, D. and Mulholland, P.J. and Marzolf, E.R.},
title = {Modelling nutrient-periphyton dynamics in streams: the importance of transient storage zones},
journal = {Ecological Modelling},
year = {1995},
volume = {80},
number = {2–3},
pages = {149--160},
url = {http://www.sciencedirect.com/science/article/pii/030438009400066Q}
}
|
|||||
| DeBusk, T.A., Grace, K.A., Dierberg, F.E., Jackson, S.D., Chimney, M.J. and Gu, B. | An investigation of the limits of phosphorus removal in wetlands: a mesocosm study of a shallow periphyton-dominated treatment system | 2004 | Ecological Engineering Vol. 23(1), pp. 1-14 |
article | URL |
| Abstract: The performance of a mesocosm-scale experimental wetland system (9-cm deep raceways with a limerock substrate followed by a limerock filter) that received effluent from a treatment wetland in south Florida was monitored for 19 months. The raceways were operated at a constant hydraulic load of 11 cm per day, resulting in a nominal hydraulic retention time (HRT) of 0.8 days. The vegetation community that developed in these systems varied along the longitudinal phosphorus (P) gradient and became dominated by eutrophic periphyton at the inflow (Cladophora and Microspora) and oligotrophic taxa along the raceway's mid-regions and outflow (Schizothrix and Scytonema). The inflow total P (TP) concentration (mean = 18 μg P L−1) was reduced to a mean of 10 μg P L−1 at the raceway outflow and 8 μg P L−1 exiting the limerock filters. Total P removal for the entire system was 0.32 g m−2 per year, or 46% of the inflow TP load, and uptake rates (k values) were 24 and 32 m per year for the raceway and the raceway/limerock filter system, respectively. Most TP removal occurred within the first 3 m of the raceways at an HRT of 1.3 h. Both soluble reactive and particulate P were reduced to their analytical detection limits, while dissolved organic P was removed less efficiently. There was little evidence for a diel trend in P removal. Following a 1-week dry-out, the raceways exported P for only 24 h after rehydration, after which treatment performance quickly returned to pre-desiccation levels. Nutrient ratios suggest that the raceways were never N-limited and that P limitation increased with distance from the inflow ports. Accrued sediment had a high percentage of non-labile P (>70%). A number of operational and construction issues need to be resolved before this technology could be scaled up for use in conjunction with Everglades restoration. | |||||
BibTeX:
@article{DeBusk2004,
author = {DeBusk, Thomas A. and Grace, Kevin A. and Dierberg, Forrest E. and Jackson, Scott D. and Chimney, Michael J. and Gu, Binhe},
title = {An investigation of the limits of phosphorus removal in wetlands: a mesocosm study of a shallow periphyton-dominated treatment system},
journal = {Ecological Engineering},
year = {2004},
volume = {23},
number = {1},
pages = {1--14},
url = {http://www.sciencedirect.com/science/article/pii/S0925857404000795}
}
|
|||||
| DeBusk, T., Kharbanda, M., Jackson, S., Grace, K., Hileman, K. and Dierberg, F. | Water, vegetation and sediment gradients in submerged aquatic vegetation mesocosms used for low-level phosphorus removal | 2011 | Science of The Total Environment Vol. 409(23), pp. 5046-5056 |
article | URL |
| Abstract: Gradients in phosphorus (P) removal and storage were investigated over 6 years using mesocosms (each consisting of three tanks in series) containing submerged aquatic vegetation (SAV) grown on muck and limerock (LR) substrates. Mean inflow total P concentrations (TP) of 32 μg L−1 were reduced to 15 and 17 μg L−1 in the muck and LR mesocosms, respectively. Mesocosm P loading rates (mean = 1.75 g m−2 year−1) varied widely during the study and were not correlated with outflow TP, which instead varied seasonally with lowest monthly mean values in December and January. | |||||
BibTeX:
@article{DeBusk2011,
author = {DeBusk, T.A. and Kharbanda, M. and Jackson, S.D. and Grace, K.A. and Hileman, K. and Dierberg, F.E.},
title = {Water, vegetation and sediment gradients in submerged aquatic vegetation mesocosms used for low-level phosphorus removal},
journal = {Science of The Total Environment},
year = {2011},
volume = {409},
number = {23},
pages = {5046--5056},
url = {http://www.sciencedirect.com/science/article/pii/S0048969711009041}
}
|
|||||
| Deheuvels, P. and Martynov, G.V. | A Karhunen–Loeve decomposition of a Gaussian process generated by independent pairs of exponential random variables | 2008 | Journal of Functional Analysis Vol. 255(9)Special issue dedicated to Paul Malliavin, pp. 2363-2394 |
article | URL |
| Abstract: We obtain the explicit Karhunen–Loeve decomposition of a Gaussian process generated as the limit of an empirical process based upon independent pairs of exponential random variables. The orthogonal eigenfunctions of the covariance kernel have simple expressions in terms of Jacobi polynomials. Statistical applications, in extreme value and reliability theory, include a Cramér–von Mises test of bivariate independence, whose null distribution and critical values are tabulated. | |||||
BibTeX:
@article{Deheuvels2008,
author = {Deheuvels, Paul and Martynov, Guennadi V.},
title = {A Karhunen–Loeve decomposition of a Gaussian process generated by independent pairs of exponential random variables},
booktitle = {Special issue dedicated to Paul Malliavin},
journal = {Journal of Functional Analysis},
year = {2008},
volume = {255},
number = {9},
pages = {2363--2394},
url = {http://www.sciencedirect.com/science/article/pii/S0022123608002930}
}
|
|||||
| Deidda, R. and Puliga, M. | Sensitivity of goodness-of-fit statistics to rainfall data rounding off | 2006 | Physics and Chemistry of the Earth, Parts A/B/C Vol. 31(18)Time Series Analysis in Hydrology, pp. 1240-1251 |
article | URL |
| Abstract: An analysis based on the L-moments theory suggests of adopting the generalized Pareto distribution to interpret daily rainfall depths recorded by the rain-gauge network of the Hydrological Survey of the Sardinia Region. Nevertheless, a big problem, not yet completely resolved, arises in the estimation of a left-censoring threshold able to assure a good fitting of rainfall data with the generalized Pareto distribution. In order to detect an optimal threshold, keeping the largest possible number of data, we chose to apply a “failure-to-reject” method based on goodness-of-fit tests, as it was proposed by Choulakian and Stephens [Choulakian, V., Stephens, M.A., 2001. Goodness-of-fit tests for the generalized Pareto distribution. Technometrics 43, 478–484]. Unfortunately, the application of the test, using percentage points provided by Choulakian and Stephens (2001), did not succeed in detecting a useful threshold value in most analyzed time series. A deeper analysis revealed that these failures are mainly due to the presence of large quantities of rounding off values among sample data, affecting the distribution of goodness-of-fit statistics and leading to significant departures from percentage points expected for continuous random variables. A procedure based on Monte Carlo simulations is thus proposed to overcome these problems. | |||||
BibTeX:
@article{Deidda2006,
author = {Deidda, Roberto and Puliga, Michelangelo},
title = {Sensitivity of goodness-of-fit statistics to rainfall data rounding off},
booktitle = {Time Series Analysis in Hydrology},
journal = {Physics and Chemistry of the Earth, Parts A/B/C},
year = {2006},
volume = {31},
number = {18},
pages = {1240--1251},
url = {http://www.sciencedirect.com/science/article/pii/S1474706506002889}
}
|
|||||
| DeJong, J.T., Soga, K., Banwart, S.A., Whalley, W.R., Ginn, T.R., Nelson, D.C., Mortensen, B.M., Martinez, B.C. and Barkouki, T. | Soil engineering in vivo: harnessing natural biogeochemical systems for sustainable, multi-functional engineering solutions | 2011 | Journal of The Royal Society Interface Vol. 8(54), pp. 1-15 |
article | URL |
| Abstract: Carbon sequestration, infrastructure rehabilitation, brownfields clean-up, hazardous waste disposal, water resources protection and global warming—these twenty-first century challenges can neither be solved by the high-energy consumptive practices that hallmark industry today, nor by minor tweaking or optimization of these processes. A more radical, holistic approach is required to develop the sustainable solutions society needs. Most of the above challenges occur within, are supported on, are enabled by or grown from soil. Soil, contrary to conventional civil engineering thought, is a living system host to multiple simultaneous processes. It is proposed herein that ‘soil engineering in vivo’, wherein the natural capacity of soil as a living ecosystem is used to provide multiple solutions simultaneously, may provide new, innovative, sustainable solutions to some of these great challenges of the twenty-first century. This requires a multi-disciplinary perspective that embraces the science of biology, chemistry and physics and applies this knowledge to provide multi-functional civil and environmental engineering designs for the soil environment. For example, can native soil bacterial species moderate the carbonate cycle in soils to simultaneously solidify liquefiable soil, immobilize reactive heavy metals and sequester carbon—effectively providing civil engineering functionality while clarifying the ground water and removing carbon from the atmosphere? Exploration of these ideas has begun in earnest in recent years. This paper explores the potential, challenges and opportunities of this new field, and highlights one biogeochemical function of soil that has shown promise and is developing rapidly as a new technology. The example is used to propose a generalized approach in which the potential of this new field can be fully realized. | |||||
BibTeX:
@article{DeJong2011,
author = {DeJong, Jason T. and Soga, Kenichi and Banwart, Steven A. and Whalley, W. Richard and Ginn, Timothy R. and Nelson, Douglas C. and Mortensen, Brina M. and Martinez, Brian C. and Barkouki, Tammer},
title = {Soil engineering in vivo: harnessing natural biogeochemical systems for sustainable, multi-functional engineering solutions},
journal = {Journal of The Royal Society Interface},
year = {2011},
volume = {8},
number = {54},
pages = {1--15},
url = {http://rsif.royalsocietypublishing.org/content/8/54/1.abstract}
}
|
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| Dekker, T.J. and Abriola, L.M. | The influence of field-scale heterogeneity on the surfactant-enhanced remediation of entrapped nonaqueous phase liquids | 2000 | Journal of Contaminant Hydrology Vol. 42(2-4), pp. 219-251 |
article | URL |
| Abstract: Numerical simulation techniques are used to explore the surfactant-enhanced solubilization of a spill of tetrachloroethylene (PCE) entrapped in a heterogeneous, saturated sandy aquifer. A two-dimensional, multicomponent solubilization simulator is employed to simulate spill cleanup, utilizing ensembles of realizations of random, spatially correlated permeability fields. Flushing volumes required to remove the organic liquid and to reduce effluent concentrations to specified levels are used as measures of remediation effectiveness. Simulations illustrate the long-term persistence of nonaqueous phase liquid (NAPL) in low permeability regions and associated tailing of effluent organic concentrations. The tendency of the high concentration organic plumes to migrate downward under gravity forces is also demonstrated, and is shown to enhance migration of aqueous phase organic into regions of low permeability, causing substantially increased concentration tailing. Remediation efficiency is shown to be strongly dependent on spatial correlation structure and variance of the permeability distribution. Delivery of surfactant to low permeability regions is primarily controlled by transverse mixing processes. The influence of local mass transfer limitations on cleanup efficiency, although statistically significant, is found to be relatively minor for the contamination scenarios explored. | |||||
BibTeX:
@article{Dekker2000,
author = {Dekker, Timothy J. and Abriola, Linda M.},
title = {The influence of field-scale heterogeneity on the surfactant-enhanced remediation of entrapped nonaqueous phase liquids},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {42},
number = {2-4},
pages = {219--251},
url = {http://www.sciencedirect.com/science/article/pii/S0169772299000911}
}
|
|||||
| Delay, F., Kaczmaryk, A. and Ackerer, P. | Inversion of a Lagrangian time domain random walk (TDRW) approach to one-dimensional transport by derivation of the analytical sensitivities to parameters | 2008 | Advances in Water Resources Vol. 31(3), pp. 484-502 |
article | URL |
| Abstract: Lagrangian approaches are well suited to transport in contrasted media but have been considered irrelevant when inversion is envisioned. The randomness of results for the same transport scenario adds to the rough evaluation by perturbation of the sensitivities, yielding an inaccurate search of parameters. It is shown here how a Time Domain Random Walk (TDRW) method can be inverted by deriving the sensitivities analytically. The calculations are very rapid and provide a precise evaluation of the descent directions followed by a Gauss–Newton optimizer. The method handles advection–dispersion + retention by matrix diffusion or sorption with first-order kinetics and proves its worth in all cases. Since analytical sensitivities are available, calculations are rigorous and allow discussing the inversion feasibility, the accuracy of the sought parameters, according to the predominant mechanism involved in the transport scenario. | |||||
BibTeX:
@article{Delay2008,
author = {Delay, Frederick and Kaczmaryk, Anne and Ackerer, Philippe},
title = {Inversion of a Lagrangian time domain random walk (TDRW) approach to one-dimensional transport by derivation of the analytical sensitivities to parameters},
journal = {Advances in Water Resources},
year = {2008},
volume = {31},
number = {3},
pages = {484--502},
url = {http://www.sciencedirect.com/science/article/pii/S0309170807001637}
}
|
|||||
| Delgado, M.A. and Carlos Escanciano, J. | Nonparametric tests for conditional symmetry in dynamic models | 2007 | Journal of Econometrics Vol. 141(2), pp. 652-682 |
article | URL |
| Abstract: This article proposes omnibus tests for conditional symmetry around a parametric function in a dynamic context. Conditional moments may not exist or may depend on the explanatory variables. Test statistics are suitable functionals of the empirical process of residuals and explanatory variables, whose limiting distribution under the null is nonpivotal. The tests are implemented with the assistance of a bootstrap method, which is justified assuming very mild regularity conditions on the specification of the center of symmetry and the underlying serial dependence structure. Finite sample properties are examined by means of a Monte Carlo experiment. | |||||
BibTeX:
@article{Delgado2007,
author = {Delgado, Miguel A. and Carlos Escanciano, J.},
title = {Nonparametric tests for conditional symmetry in dynamic models},
journal = {Journal of Econometrics},
year = {2007},
volume = {141},
number = {2},
pages = {652--682},
url = {http://www.sciencedirect.com/science/article/pii/S0304407606002107}
}
|
|||||
| Delgado, M.A. and Stute, W. | Distribution-free specification tests of conditional models | 2008 | Journal of Econometrics Vol. 143(1)Specification testing, pp. 37-55 |
article | URL |
| Abstract: This article proposes a class of asymptotically distribution-free specification tests for parametric conditional distributions. These tests are based on a martingale transform of a proper sequential empirical process of conditionally transformed data. Standard continuous functionals of this martingale provide omnibus tests while linear combinations of the orthogonal components in its spectral representation form a basis for directional tests. Finally, Neyman-type smooth tests, a compromise between directional and omnibus tests, are discussed. As a special example we study in detail the construction of directional tests for the null hypothesis of conditional normality versus heteroskedastic contiguous alternatives. A small Monte Carlo study shows that our tests attain the nominal level already for small sample sizes. | |||||
BibTeX:
@article{Delgado2008,
author = {Delgado, Miguel A. and Stute, Winfried},
title = {Distribution-free specification tests of conditional models},
booktitle = {Specification testing},
journal = {Journal of Econometrics},
year = {2008},
volume = {143},
number = {1},
pages = {37--55},
url = {http://www.sciencedirect.com/science/article/pii/S0304407607001625}
}
|
|||||
| Delvigne, F., Destain, J. and Thonart, P. | Structured mixing model for stirred bioreactors: An extension to the stochastic approach | 2005 | Chemical Engineering Journal Vol. 113(1), pp. 1-12 |
article | URL |
| Abstract: The potentiality of a stochastic approach is examined in the case of a mixing model for stirred vessels. This model is interesting due to the probabilistic and discrete properties that can be used further to facilitate the implementation of a hydrodynamic model into complex reacting systems, such as those encountered in bioprocesses. Stochastic model performances are compared to well known deterministic compartment mixing models (CM). It appears that parameters coming from CM can be used in the stochastic approach and that they give equivalent results. A methodology is elaborated that simplifies the determination procedure of the adjustable parameters of the stochastic model. The most important parameter to determine is the time step of a simulation performed by the aim of the stochastic model. Indeed, the time step is not explicitly given by the model and a correlation is necessary to translate simulation intervals into real time increments. After an appropriate analysis of several mixing systems (single or multi-agitated), it appears that a simple correlation involving circulation time could be used to perform this translation. The correlation contains an adjustable parameter, which has been quantified for the operating conditions covered in the study. The circulation of micro-organisms was also simulated simply by using the transition matrix coming from the stochastic model, which shows the potentiality of this kind of model in the field of complex reacting systems, such as those encountered in bioprocesses. | |||||
BibTeX:
@article{Delvigne2005,
author = {Delvigne, F. and Destain, J. and Thonart, P.},
title = {Structured mixing model for stirred bioreactors: An extension to the stochastic approach},
journal = {Chemical Engineering Journal},
year = {2005},
volume = {113},
number = {1},
pages = {1--12},
url = {http://www.sciencedirect.com/science/article/pii/S1385894705002251}
}
|
|||||
| Deng, J., Ghidaoui, M., Gray, W. and Xu, K. | A Boltzmann-based mesoscopic model for contaminant transport in flow systems | 2001 | Advances in Water Resources Vol. 24(5), pp. 531-550 |
article | URL |
| Abstract: The objective of this paper is to demonstrate the formulation of a numerical model for mass transport based on the Bhatnagar–Gross–Krook (BGK) Boltzmann equation. To this end, the classical chemical transport equation is derived as the zeroth moment of the BGK Boltzmann differential equation. The relationship between the mass transport equation and the BGK Boltzmann equation allows an alternative approach to numerical modeling of mass transport, wherein mass fluxes are formulated indirectly from the zeroth moment of a difference model for the BGK Boltzmann equation rather than directly from the transport equation. In particular, a second-order numerical solution for the transport equation based on the discrete BGK Boltzmann equation is developed. The numerical discretization of the first-order BGK Boltzmann differential equation is straightforward and leads to diffusion effects being accounted for algebraically rather than through a second-order Fickian term. The resultant model satisfies the entropy condition, thus preventing the emergence of non-physically realizable solutions including oscillations in the vicinity of the front. Integration of the BGK Boltzmann difference equation into the particle velocity space provides the mass fluxes from the control volume and thus the difference equation for mass concentration. The difference model is a local approximation and thus may be easily included in a parallel model or in accounting for complex geometry. Numerical tests for a range of advection–diffusion transport problems, including one- and two-dimensional pure advection transport and advection–diffusion transport show the accuracy of the proposed model in comparison to analytical solutions and solutions obtained by other schemes. | |||||
BibTeX:
@article{Deng2001,
author = {Deng, J.Q. and Ghidaoui, M.S. and Gray, W.G. and Xu, K.},
title = {A Boltzmann-based mesoscopic model for contaminant transport in flow systems},
journal = {Advances in Water Resources},
year = {2001},
volume = {24},
number = {5},
pages = {531--550},
url = {http://www.sciencedirect.com/science/article/pii/S0309170800000440}
}
|
|||||
| Deng, Z., de Lima, J. and Singh, V. | Fractional Kinetic Model for First Flush of Stormwater Pollutants | 2005 | Journal of Environmental Engineering Vol. 131(2), pp. 232-241 |
article | URL |
| Abstract: By generalizing the urban ground as a fractal surface and revising the classical Fick’s formula as a law of dispersion with a fractional-order derivative, a fractional kinetic model is developed for simulation of the first flush phenomenon of urban stormwater pollutants. The model is comprised of (1) a fractional dispersion-advection equation (FADE); (2) the kinematic-wave overland flow equation; and (3) methods for numerical solution of the equations. A split-operator method is proposed for numerical solution of the FADE by means of a newly presented F.3 finite-difference scheme for fractional partial differential equations. The kinematic-wave overland flow equation is solved using the Lax–Wendroff explicit scheme. Under a constant rainstorm the hydrograph displays an initial rising limb followed by a constant flow discharge. The pollutograph exhibits a steep receding limb (the first flush), followed by a long stretched tail (heavy tail process). The agreement between simulated and measured dispersion characteristics is found to be good, demonstrating that the fractional kinetic model is capable of accurately predicting the characteristics of the first flush phenomenon. | |||||
BibTeX:
@article{Deng2005,
author = {Deng, Z. and de Lima, J. and Singh, V.},
title = {Fractional Kinetic Model for First Flush of Stormwater Pollutants},
journal = {Journal of Environmental Engineering},
publisher = {American Society of Civil Engineers},
year = {2005},
volume = {131},
number = {2},
pages = {232--241},
url = {http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9372%282005%29131%3A2%28232%29}
}
|
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| Deng, Z.-Q. and Jung, H.-S. | Scaling dispersion model for pollutant transport in rivers | 2009 | Environmental Modelling & Software Vol. 24(5), pp. 627-631 |
article | URL |
| Abstract: This communication presents a scale-dependent model, called Scaling Dispersion (SD) Model, for simulating solute dispersion and transport in rivers without using a user-specified residence time distribution function. The SD model consists of (1) the advection dispersion equation with a transient storage term which is characterized by a variable residence time, (2) a new method for estimation of the longitudinal Fickian dispersion coefficient involved in the model, and (3) a split-operator method for numerical solution of the equations involved in the model. Comparisons between the SD model and the most widely used transient storage model against tracer test data observed in three US rivers show that the SD model is capable of simulating different types of residence time distributions commonly observed in streams with an accuracy higher than or at least comparable with existing solute transport models, demonstrating the efficacy of the SD model. The SD model unifies the residence time distributions observed in natural rivers within a single modelling framework for the first time. The SD model provides an efficient and cost effective tool for predicting solute dispersion and transport in streams and rivers. | |||||
BibTeX:
@article{Deng2009,
author = {Deng, Zhi-Qiang and Jung, Hoon-Shin},
title = {Scaling dispersion model for pollutant transport in rivers},
journal = {Environmental Modelling & Software},
year = {2009},
volume = {24},
number = {5},
pages = {627--631},
url = {http://www.sciencedirect.com/science/article/pii/S1364815208001862}
}
|
|||||
| Deng, Z.-Q., Jung, H.-S. and Ghimire, B. | Effect of channel size on solute residence time distributions in rivers | 2010 | Advances in Water Resources Vol. 33(9), pp. 1118-1127 |
article | URL |
| Abstract: The effect of channel size on residence time distributions (RTDs) of solute in rivers is investigated in this paper using tracer test data and the variable residence time (VART) model. Specifically, the investigation focuses on the influence of shear dispersion and hyporheic exchange on the shape of solute RTD, and how these two transport processes prevail in larger and smaller streams, respectively, leading to distinct tails of RTD. Simulation results show that (1) RTDs are dispersion-dependent and thereby channel-size (scale) dependent. RTDs increasing longitudinal dispersion coefficient. Small streams with negligible dispersion coefficient may display various types of RTD from upward curving patterns to a straight line (power-law distributions) and further to downward curving lognormal distributions when plotted in log–log coordinates. Moderate-sized rivers are transitional in terms of RTDs and commonly exhibit lognormal and power-law RTDs; (2) the incorporation of water and solute losses/gains in the VART model can improve simulation results and make parameter values more reasonable; (3) the ratio of time to peak concentration to the minimum mean residence time is equal to the recovery ratio of tracer. The relation provides a simple method for determining the minimum mean residence time; and (4) the VART model is able to reproduce various RTDs observed in rivers with 3–4 fitting parameters while no user-specified RTD functions are needed. | |||||
BibTeX:
@article{Deng2010,
author = {Deng, Zhi-Qiang and Jung, Hoon-Shin and Ghimire, Bhuban},
title = {Effect of channel size on solute residence time distributions in rivers},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {9},
pages = {1118--1127},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810001284}
}
|
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| Dentz, M., Gouze, P. and Carrera, J. | Effective non-local reaction kinetics for transport in physically and chemically heterogeneous media | 2011 | Journal of Contaminant Hydrology Vol. 120-121(0)Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media, pp. 222-236 |
article | URL |
| Abstract: The correct characterization of the effective reactive transport dynamics is an important issue for modeling reactive transport on the Darcy scale, specifically in situations in which reactions are localized, that is when different reactions occur in different portions of the porous medium. Under such conditions the conventional approach of homogenizing only the porous medium chemistry is not appropriate. We consider here reactive transport in a porous medium that is characterized by mass transfer between a mobile and a distribution of immobile regions. Chemical and physical heterogeneities are reflected by distributions of kinetic reaction rate constants and residence times in the immobile zones. We derive an effective reactive transport equation for the mobile solute that is characterized by non-local physical mass transfer and reaction terms. Specifically, chemical heterogeneity is upscaled in terms of a reactive memory function that integrates both chemical and physical heterogeneity. Mass transfer limitations due to physical heterogeneity yield effective kinetic rate coefficients that can be much smaller than the volumetric average of the local scale coefficients. These results help to explain and quantify the often reported discrepancy between observed field reaction rate constants and the ones obtained under well mixed laboratory conditions. Furthermore, these results indicate that transport under physical and chemical heterogeneity cannot be upscaled separately. | |||||
BibTeX:
@article{Dentz2011,
author = {Dentz, Marco and Gouze, Philippe and Carrera, Jesús},
title = {Effective non-local reaction kinetics for transport in physically and chemically heterogeneous media},
booktitle = {Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {120-121},
number = {0},
pages = {222--236},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210000641}
}
|
|||||
| Dentz, M., Le Borgne, T., Englert, A. and Bijeljic, B. | Mixing, spreading and reaction in heterogeneous media: A brief review | 2011 | Journal of Contaminant Hydrology Vol. 120-121(0)Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media, pp. 1-17 |
article | URL |
| Abstract: Geological media exhibit heterogeneities in their hydraulic and chemical properties, which can lead to enhanced spreading and mixing of the transported species and induce an effective reaction behavior that is different from the one for a homogeneous medium. Chemical heterogeneities such as spatially varying adsorption properties and specific reactive surface areas can act directly on the chemical reaction dynamics and lead to different effective reaction laws. Physical heterogeneities affect mixing-limited chemical reactions in an indirect way by their impact on spreading and mixing of dissolved species. To understand and model large-scale reactive transport the interactions of these coupled processes need to be understood and quantified. This paper provides a brief review on approaches of non-reactive and reactive transport modeling in geological media. | |||||
BibTeX:
@article{Dentz2011a,
author = {Dentz, Marco and Le Borgne, Tanguy and Englert, Andreas and Bijeljic, Branko},
title = {Mixing, spreading and reaction in heterogeneous media: A brief review},
booktitle = {Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {120-121},
number = {0},
pages = {1--17},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210000495}
}
|
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| Desantes, J., Serrano, J., Arnau, F. and Piqueras, P. | Derivation of the method of characteristics for the fluid dynamic solution of flow advection along porous wall channels | 2012 | Applied Mathematical Modelling Vol. 36(7), pp. 3134-3152 |
article | URL |
| Abstract: This paper describes in detail a novel formulation of the method of characteristics for its application to solve one-dimensional compressible unsteady non-homentropic flow advected along porous wall channels. In particular, the method is implemented into a wall-flow monolith Diesel particulate filter model whose purpose is the pressure drop prediction. The flow inside the monolith channels is considered to be one-dimensional and the flow through the porous wall treated as a source term agree with the Darcy’s law. The flow dynamic behaviour at internal nodes of the channels is solved by means of shock capturing methods, whereas the end nodes, or boundary conditions, are solved applying the method of characteristics. The derived solution in this study of the Riemann variables and the entropy level includes the variation along the space–time plane due to cross-section area changes, friction and heat transfer as traditionally stated, but also takes into account the key influence on every line of the flow leaving or entering to the channels through the porous walls. | |||||
BibTeX:
@article{Desantes2012,
author = {Desantes, J.M. and Serrano, J.R. and Arnau, F.J. and Piqueras, P.},
title = {Derivation of the method of characteristics for the fluid dynamic solution of flow advection along porous wall channels},
journal = {Applied Mathematical Modelling},
year = {2012},
volume = {36},
number = {7},
pages = {3134--3152},
url = {http://www.sciencedirect.com/science/article/pii/S0307904X11006494}
}
|
|||||
| Desbois, G., Urai, J.L., Kukla, P.A., Konstanty, J. and Baerle, C. | High-resolution 3D fabric and porosity model in a tight gas sandstone reservoir:A new approach to investigate microstructures from mm- to nm-scale combining argon beam cross-sectioning and SEM imaging | 2011 | Journal of Petroleum Science and Engineering Vol. 78(2), pp. 243-257 |
article | URL |
| Abstract: The development of new technologies to enhance tight gas reservoir productivity could strongly benefit from a better resolution and imaging of the porosity. Numerous methods are available to characterize sandstone porosity. However, imaging of pore space at scales below 1 μm in tight gas sands remains difficult due to limits in resolution and sample preparation. We explored the use of high resolution SEM in combination with argon ion beam cross sectioning (BIB, Broad Ion Beam) to prepare smooth, and damage-free, true-2D surfaces of tight gas sandstone core samples from the Permian Rotliegend in Germany, to image porosity down to 10 nm. The quality of cross-sections allows measuring porosity at pore scale, and describing the bulk porosity by defining different regions with characteristic pore morphology and pore size distribution. Serial cross sectioning of samples produces a 3D model of the porous network. We present a model of fabric and porosity at 2 different scales: the scale of sand grains and the scale of the clay grains in the intergranular volume. | |||||
BibTeX:
@article{Desbois2011,
author = {Desbois, Guillaume and Urai, Janos L. and Kukla, Peter A. and Konstanty, Jan and Baerle, Claudia},
title = {High-resolution 3D fabric and porosity model in a tight gas sandstone reservoir:A new approach to investigate microstructures from mm- to nm-scale combining argon beam cross-sectioning and SEM imaging},
journal = {Journal of Petroleum Science and Engineering},
year = {2011},
volume = {78},
number = {2},
pages = {243--257},
url = {http://www.sciencedirect.com/science/article/pii/S0920410511001306}
}
|
|||||
| Desmarais, K. and Rojstaczer, S. | Inferring source waters from measurements of carbonate spring response to storms | 2002 | Journal of Hydrology Vol. 260(1-4), pp. 118-134 |
article | URL |
| Abstract: We infer information about the nature of groundwater flow within a karst aquifer from the physical and chemical response of a spring to storm events. The spring discharges from the Maynardville Limestone in Bear Creek Valley, Tennessee. Initially, spring discharge peaks approximately 1–2 h from the midpoint of summer storms. The initial peak is likely due to surface loading, which pressurizes the aquifer and results in water moving out of storage. All of the storms monitored exhibited recessions that follow a master recession curve very closely, indicating that storm response is fairly consistent and repeatable, independent of the time between storms and the configuration of the rain event itself. Electrical conductivity initially increases for 0.5–2.9 days (longer for smaller storms), the result of moving older water out of storage. This is followed by a 2.1–2.5 day decrease in conductivity, resulting from an increasing portion of low conductivity recharge water entering the spring. Stable carbon isotope data and the calcite saturation index of the spring water also support this conceptual model. Spring flow is likely controlled by displaced water from the aquifer rather than by direct recharge through the soil zone. | |||||
BibTeX:
@article{Desmarais2002,
author = {Desmarais, Kathryn and Rojstaczer, Stuart},
title = {Inferring source waters from measurements of carbonate spring response to storms},
journal = {Journal of Hydrology},
year = {2002},
volume = {260},
number = {1-4},
pages = {118--134},
url = {http://www.sciencedirect.com/science/article/pii/S0022169401006072}
}
|
|||||
| Desmet, G., Verelst, H. and Baron, G.V. | Transient and stationary axial dispersion in vortex array flows—I. Axial scan measurements and modeling of transient dispersion effects | 1997 | Chemical Engineering Science Vol. 52(14), pp. 2383-2401 |
article | URL |
| Abstract: Whereas conventional RTD experiments yield incomplete and potentially misleading information, the axial scan method is shown to be a powerful technique to analyze the transient dispersion effects in vortex array flows (VAFs). Applying different initial tracer distributions to a given vortex, and making axial scans of the spreading tracer distribution, allowed, for the first time, to quantify and classify the complete set of strongly different transient dispersion modes. As a model system, the laminar Couette-Taylor flow has been selected. By working under high viscosity conditions, the time scale of the different acting phenomena has been enlarged to such an extent that even the fastest dispersion events could be extensively studied and quantified. It is shown that in laminar VAFs effective axial dispersion coefficients can be obtained which vary over orders of magnitude, just by applying different initial tracer distributions to a given vortex. A first principles two-dimensional model (valid when the mixing along the streamlines occurs fast) with which all observed transient dispersion effects can be accurately represented is proposed. The insights obtained in the present study are especially useful for the development of VAF reactors for the treatment of strongly viscous fluids. | |||||
BibTeX:
@article{Desmet1997,
author = {Desmet, G. and Verelst, H. and Baron, G. V.},
title = {Transient and stationary axial dispersion in vortex array flows—I. Axial scan measurements and modeling of transient dispersion effects},
journal = {Chemical Engineering Science},
year = {1997},
volume = {52},
number = {14},
pages = {2383--2401},
url = {http://www.sciencedirect.com/science/article/pii/S0009250997000481}
}
|
|||||
| Dette, H. and Podolskij, M. | Testing the parametric form of the volatility in continuous time diffusion models—a stochastic process approach | 2008 | Journal of Econometrics Vol. 143(1)Specification testing, pp. 56-73 |
article | URL |
| Abstract: We present new tests for the form of the volatility function which are based on stochastic processes of the integrated volatility. We prove weak convergence of these processes to centered processes whose conditional distributions are Gaussian. In the case of testing for a constant volatility the limiting process are standard Brownian bridges. As a consequence an asymptotic distribution free test and bootstrap tests (for testing of a general parametric form) can easily be implemented. It is demonstrated that the new tests are more than the currently available procedures. The new approach is also demonstrated by means of a simulation study. | |||||
BibTeX:
@article{Dette2008,
author = {Dette, Holger and Podolskij, Mark},
title = {Testing the parametric form of the volatility in continuous time diffusion models—a stochastic process approach},
booktitle = {Specification testing},
journal = {Journal of Econometrics},
year = {2008},
volume = {143},
number = {1},
pages = {56--73},
url = {http://www.sciencedirect.com/science/article/pii/S0304407607001595}
}
|
|||||
| Di Fazio, A. and Vurro, M. | Experimental tests using Rhodamine Wt as tracer | 1994 | Advances in Water Resources Vol. 17(6), pp. 375-378 |
article | URL |
| Abstract: Tracer tests with fluorescent dyes have been commonly used to describe physical mechanisms and consequently to determine hydrodispersive parameters. The actual behaviour of these dyes is one of the central issues in the evaluation of tracer tests. In this paper we describe an experimental set-up designed to investigate the behaviour of Rhodamine Wt. A batch experiment was conducted using a standardized technique and equilibrium isotherms were interpolated. The column experiment was conducted using a cylindrical permeameter with the aim of minimizing dead volume and outlining only the sorption of the porous media. Inside the permeameter a constant-rate injection of a solution with both NaCl and Rhodamine Wt was performed and breakthrough curves have been obtained. The tests reveal a mild nonlinear sorption behaviour of Rhodamine Wt. The experimental tests have also pointed out the feasibility of the mathematical model used to calibrate the experimental data. | |||||
BibTeX:
@article{DiFazio1994,
author = {Di Fazio, A. and Vurro, M.},
title = {Experimental tests using Rhodamine Wt as tracer},
journal = {Advances in Water Resources},
year = {1994},
volume = {17},
number = {6},
pages = {375--378},
url = {http://www.sciencedirect.com/science/article/pii/0309170894900132}
}
|
|||||
| Dickinson, T.D. | Strengthening women's studies through applied activism: Theoretical, classroom, regional, and cross-border strategies for participating in change | 2005 | Women's Studies International Forum Vol. 28(2-3)Women in higher Education: Issues and challenges Women in higher Education SI, pp. 115-126 |
article | URL |
| Abstract: Synopsis Through activist scholarship Women's Studies has helped to support material and cultural change in the university and in social-change projects around the world. To strengthen Women's Studies social-change applications, this article stresses the importance of consciously integrating material and cultural knowledge and recognizing material feminism's historical, social relational, and local-to-global contributions. Applied activist knowledge in Women's Studies would be enhanced by more engagement in theoretical, classroom-based, and organizational work in regional and cross-border feminist social-change networks. Examples are drawn from the author's experiences teaching Women's Studies, her work in feminist theory construction in relation to historical analysis, and her activist research in U.S. urban areas, the U.S. Great Plains, and in regions of Nicaragua, Costa Rica, and Guatemala. Emphases are placed on the grounding of gendered and intersecting hierarchies within our historical, global society; the connection of social-change frameworks to an exploration of democratically defined women's and community needs; and the preparation of applied activists for the work of developing new, redistributive models of inclusive regional and global development. | |||||
BibTeX:
@article{Dickinson2005,
author = {Dickinson, Torry D.},
title = {Strengthening women's studies through applied activism: Theoretical, classroom, regional, and cross-border strategies for participating in change},
booktitle = {Women in higher Education: Issues and challenges Women in higher Education SI},
journal = {Women's Studies International Forum},
year = {2005},
volume = {28},
number = {2-3},
pages = {115--126},
url = {http://www.sciencedirect.com/science/article/pii/S0277539505000129}
}
|
|||||
| Diebolt, J., Garrido, M. and Trottier, C. | Improving extremal fit: a Bayesian regularization procedure | 2003 | Reliability Engineering & System Safety Vol. 82(1), pp. 21-31 |
article | URL |
| Abstract: In structural reliability, special attention is devoted to model distribution tails. The distributions are required to fit the upper observations and provide a picture of the tail above the maximal observation. Goodness-of-fit tests can be constructed to check this tail fit. Then what can we do with distributions having a good central fit and a bad extremal fit? We propose a regularization procedure. It is based on Bayesian tools and takes into account the opinion of experts. Predictive distributions are proposed as model distributions. We numerically investigate this method on normal, lognormal, exponential, gamma and Weibull distributions. | |||||
BibTeX:
@article{Diebolt2003,
author = {Diebolt, J. and Garrido, M. and Trottier, C.},
title = {Improving extremal fit: a Bayesian regularization procedure},
journal = {Reliability Engineering & System Safety},
year = {2003},
volume = {82},
number = {1},
pages = {21--31},
url = {http://www.sciencedirect.com/science/article/pii/S0951832003000966}
}
|
|||||
| Diehl, R., Toomey, R., Roland, V., Embry, I. and West, A. | Effectiveness of Stormwater Filters at Mammoth Cave National Park, Kentucky | 2012 | Proceedings of the 22nd Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 11 - 13, 2012, pp. P-29-P-36 | inproceedings | |
| Abstract: Due to the complexity of possible flow paths in karst aquifers, it is difficult to create a mathematical framework to model the flow of contaminants and other particles through the aquifer. The objective of this project was to apply both traditional methods of tracer interpretations and a new interpretative method to tracer data from a quantitative field tracer study at Mammoth Cave National Park. Generally, a tracer study is performed to qualitatively or quantitatively approximate the flow conditions. The quantitative results of the tracer experiment are displayed in the tracer breakthrough curve which represents the effluent tracer concentration over time. The breakthrough curve can be used to determine the residence time distribution (RTD) function. The RTD function numerically describes the time that particles have spent reacting in a system. This project focuses on the continued development and application of a new dye tracer interpretative method as compared to the traditional advection dispersion equation (ADE) method. The interpretive method is based on the gamma probability density function (PDF) where the tracer travel distance and linear velocity are assumed to be randomly distributed variables with gamma distributions. The gamma RTD function is derived from the individual distributions of tracer travel distance and linear velocity based on their relationship with time. The normalized forms of the gamma RTD and the advection dispersion equation RTD were compared with the normalized tracer RTD. The normalized gamma RTD function had a better fit than the advection dispersion equation RTD function with the tracer RTD function. This conclusion is based on the sum of the squares of the differences (SOSOD) between the normalized form of the gamma and the tracer RTD function versus the SOSOD between the normalized form of the advection dispersion equation and the tracer RTD function. | |||||
BibTeX:
@inproceedings{Diehl2012,
author = {Diehl, Roger and Toomey, Rick and Roland, Victor and Embry, Irucka and West, Ashley},
title = {Effectiveness of Stormwater Filters at Mammoth Cave National Park, Kentucky},
booktitle = {Proceedings of the 22nd Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 11 - 13, 2012},
year = {2012},
pages = {P-29--P-36},
note = {authors with acknowledgment to Byl, Tom and Trimboli, Shannon}
}
|
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| Dierberg, F., DeBusk, T., Jackson, S., Chimney, M. and Pietro, K. | Submerged aquatic vegetation-based treatment wetlands for removing phosphorus from agricultural runoff: response to hydraulic and nutrient loading | 2002 | Water Research Vol. 36(6), pp. 1409-1422 |
article | URL |
| Abstract: Submerged aquatic vegetation (SAV) communities exhibit phosphorus (P) removal mechanisms not found in wetlands dominated by emergent macrophytes. This includes direct assimilation of water column P by the plants and pH-mediated P coprecipitation with calcium carbonate (CaCO3). Recognizing that SAV might be employed to increase the performance of treatment wetlands, we investigated P removal in mesocosms (3.7 m2) stocked with a mixture of taxa common to the region: Najas guadalupensis, Ceratophyllum demersum, Chara spp. and Potamogeton illinoensis. Three sets of triplicate mesocosms received agricultural runoff from June 1998 to February 2000 at nominal hydraulic retention times (HRTs) of 1.5, 3.5 or 7.0 days. Mean total P (TP) loading rates were 19.7, 8.3 and 4.5 g/m2/yr. After eight months of operation, N. guadalupensis dominated the standing crop biomass and P storage, whereas C. demersum exhibited the highest tissue P content. Chara spp. was prominent only in the 7.0-day HRT treatments while P. illinoensis largely disappeared. Inflow soluble reactive phosphorus (SRP) (10–163 μg/L) was reduced consistently to near the detection limit (2 μg/L) in the 3.5- and 7.0-day HRT treatments, and to a mean of 9 μg/L in the 1.5-day HRT treatment. The mean inflow TP concentration (107 μg/L) was reduced to 52, 29 and 23 μg/L in the 1.5-, 3.5- and 7.0-day HRT treatments, respectively. Total P concentrations in new sediment (mean=641, 408 and 459 mg/kg in the 1.5-, 3.5-, and 7.0-day HRT mesocosms, respectively) were much higher than in the muck soil used to stock the mesocosms (236 mg/kg). The calcium content of new sediment was twice that of the muck soil (16.5% vs. 7.6%), demonstrating that CaCO3 production and, perhaps, coprecipitation of P occurred. We observed no nocturnal remobilization of SRP despite diel fluctuations in pH and dissolved oxygen. Mean outflow TP (21 μg/L) from a 147 ha SAV wetland (4-day nominal HRT) was similar to mean outflow TP in the 3.5-day and 7.0-day HRT treatments. The mesocosms adequately mimicked P removal and other important characteristics of the larger system and can be used to address research questions regarding treatment performance of full-scale SAV wetlands. Available data suggest that the incorporation of SAV communities into the stormwater treatment areas may benefit Everglades restoration. | |||||
BibTeX:
@article{Dierberg2002,
author = {Dierberg, F.E. and DeBusk, T.A. and Jackson, S.D. and Chimney, M.J. and Pietro, K.},
title = {Submerged aquatic vegetation-based treatment wetlands for removing phosphorus from agricultural runoff: response to hydraulic and nutrient loading},
journal = {Water Research},
year = {2002},
volume = {36},
number = {6},
pages = {1409--1422},
url = {http://www.sciencedirect.com/science/article/pii/S0043135401003542}
}
|
|||||
| Dierberg, F.E. and DeBusk, T.A. | Particulate phosphorus transformations in south Florida stormwater treatment areas used for Everglades protection | 2008 | Ecological Engineering Vol. 34(2), pp. 100-115 |
article | URL |
| Abstract: Six large treatment wetlands (352–6698 ha), designated Stormwater Treatment Areas (STAs), have been constructed to sequester phosphorus (P) in drainage waters before entering the Everglades. We performed oxic and anoxic laboratory incubations to assess the stability of P in suspended particles from inflow and outflow waters for selected flow-paths of STA-2, a “well-performing” wetland, and STA-1 West (W), an “under-performing” wetland. Particles were concentrated by filtration prior to incubation. STA-2 flow-paths exhibited a reduction in the particulate P (PP) concentration (e.g., 28 to 3–8 μg/L), as well as an increase in particle stability (i.e., reduced conversion of PP to soluble reactive P [SRP]) with passage through the wetland. By contrast, while the STA-1W flow-path exhibited a PP reduction of 68–46 μg/L under anoxic incubations, the particles exiting the wetland were more labile than those entering. For PP collected from both STAs, anoxic incubations produced higher conversion rates to SRP than did oxic conditions. This redox influence on SRP release was more pronounced for outflow PP from STA-1W than for PP exiting the STA-2 flow-paths. | |||||
BibTeX:
@article{Dierberg2008,
author = {Dierberg, Forrest E. and DeBusk, Thomas A.},
title = {Particulate phosphorus transformations in south Florida stormwater treatment areas used for Everglades protection},
journal = {Ecological Engineering},
year = {2008},
volume = {34},
number = {2},
pages = {100--115},
url = {http://www.sciencedirect.com/science/article/pii/S0925857408001407}
}
|
|||||
| Dierberg, F.E., DeBusk, T.A., Larson, N.R., Kharbanda, M.D., Chan, N. and Gabriel, M.C. | Effects of sulfate amendments on mineralization and phosphorus release from South Florida (USA) wetland soils under anaerobic conditions | 2011 | Soil Biology and Biochemistry Vol. 43(1), pp. 31-45 |
article | URL |
| Abstract: We investigated the potential effects of elevated water-column sulfate (SO4) levels on heterotrophic microbial respiration and net phosphorus (P) release for soils collected from impacted and unimpacted Everglades wetlands in south Florida. Soils from three sites, ranging from low P and low SO4 to high P and high SO4 environments, were examined under controlled laboratory conditions. The soils were subjected to anaerobic incubations to evaluate net P release and organic matter decomposition in response to SO4 amendments of 32 or 96 mg l−1 (0.33 and 1.0 mM). | |||||
BibTeX:
@article{Dierberg2011,
author = {Dierberg, Forrest E. and DeBusk, Thomas A. and Larson, Nichole R. and Kharbanda, Michelle D. and Chan, Nancy and Gabriel, Mark C.},
title = {Effects of sulfate amendments on mineralization and phosphorus release from South Florida (USA) wetland soils under anaerobic conditions},
journal = {Soil Biology and Biochemistry},
year = {2011},
volume = {43},
number = {1},
pages = {31--45},
url = {http://www.sciencedirect.com/science/article/pii/S0038071710003391}
}
|
|||||
| Dierberg, F.E., Juston, J.J., DeBusk, T.A., Pietro, K. and Gu, B. | Relationship between hydraulic efficiency and phosphorus removal in a submerged aquatic vegetation-dominated treatment wetland | 2005 | Ecological Engineering Vol. 25(1), pp. 9-23 |
article | URL |
| Abstract: A tracer study (Rhodamine-WT dye) was performed on a 147-ha submerged aquatic vegetation (SAV)-dominated free-water surface treatment wetland in south Florida that received agricultural drainage waters (ADW). Two dimensional, time series plots of the dye concentrations revealed that a disproportionate amount of tracer flowed along the eastern and western levees of the cell. The tracer response curve developed from the outflow data indicated a prominent short circuit, which conveyed 44% of the volumetric flow based on model analysis. This large fraction of flow bypassed the SAV community and exited the wetland with only partial treatment for total phosphorus (TP) removal. | |||||
BibTeX:
@article{Dierberg2005,
author = {Dierberg, Forrest E. and Juston, John J. and DeBusk, Thomas A. and Pietro, Kathy and Gu, Binhe},
title = {Relationship between hydraulic efficiency and phosphorus removal in a submerged aquatic vegetation-dominated treatment wetland},
journal = {Ecological Engineering},
year = {2005},
volume = {25},
number = {1},
pages = {9--23},
url = {http://www.sciencedirect.com/science/article/pii/S0925857405000042}
}
|
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| Diersch, H.-J. and Kolditz, O. | Variable-density flow and transport in porous media: approaches and challenges | 2002 | Advances in Water Resources Vol. 25(8-12), pp. 899-944 |
article | URL |
| Abstract: We review the state of the art in modeling of variable-density flow and transport in porous media, including conceptual models for convection systems, governing balance equations, phenomenological laws, constitutive relations for fluid density and viscosity, and numerical methods for solving the resulting nonlinear multifield problems. The discussion of numerical methods addresses strategies for solving the coupled spatio-temporal convection process, consistent velocity approximation, and error-based mesh adaptation techniques. As numerical models for those nonlinear systems must be carefully verified in appropriate tests, we discuss weaknesses and inconsistencies of current model-verification methods as well as benchmark solutions. We give examples of field-related applications to illustrate specific challenges of further research, where heterogeneities and large scales are important. | |||||
BibTeX:
@article{Diersch2002,
author = {Diersch, H.-J.G. and Kolditz, O.},
title = {Variable-density flow and transport in porous media: approaches and challenges},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {8--12},
pages = {899--944},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802000635}
}
|
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| Dillon, K.S., Corbett, D.R., Burnett, W.C. and Chanton, J.P. | The Use of Artificial Tracers to Determine Ground-Water Flow and the Fate of Nutrients in the Karst System Underlying the Florida Keys | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 177-178 | inproceedings | URL |
| Abstract: To determine the fate and movement of sewage derived contaminants and their possible interaction with surface waters in the Florida (USA) Keys, several types of experiments were conducted using SF6 as an artificial tracer. The first type of experiment examined fluid flow from septic tanks placed in Miami Oolite on Big Pine Key, where there is a shallow freshwater lens overlying saline ground waters. Here ground water transport rates were constrained to be between 0.11 to 1.87 m/hr, traveling in an easterly direction (Dillon et al., 1999). The second type of experiment took place on Key Largo where there is no freshwater lens and the matrix of the aquifer is solely the more porous Key Largo limestone (KLL). Here we injected the tracer into a shallow well, which was screened from 0.6 to 10 m. This allowed us to evaluate groundwater movement in the shallow upper portion of the aquifer, the area to which inputs by septic tanks occur. Groundwater transport rates in the Upper Keys were as great as 3.7 m/hr and were controlled by the Atlantic tide (Dillon et al., 1999). SF6 laden groundwater plumes moved back and forth due to tidal pumping. SF6 reached nearby surface waters within 8 hours. Our results indicate that wastewater injected into the shallow subsurface can travel rapidly and may reach marine surface waters within a few hours. Three dual tracer experiments were conducted on Long Key, Florida USA to examine the fate of waste water following sewage disposal in 10 to 30 m deep injection wells. This waste disposal practice introduces extraordinary amounts of nutrients into the ground waters of the Florida Keys. In three experiments, artificial ground water tracers, sulfur hexafluoride (SF6) and radioiodine (131I) were used to determine transport rates and directions of soluble non reactive substances injected into the saline ground waters underlying the Keys. Simultaneously, reactive tracers (bulk unlabeled phosphate, PO4, and nitrate, NO3, and radio-labeled phosphate (32PO4) were also added to determine the fate of nutrients in the subsurface. Two types of transport were observed: (1) rapid flow (0.20 - 2.20 m/hr) presumably due to the many conduits present in the limestone and (2) slow diffusive flow (< 0.003 - 0.14 m/hr) associated with the limestone's primary porosity (Dillon et al., 2000). Vertical flow was comparable to horizontal flow due to either the density driven buoyancy of the waste water plume or to preferential flow paths which allow upward advection or combination of both. These experiments showed that conservative artificial tracers injected into the subsurface reach surface waters in a matter of days and can remain in the immediate vicinity of the injection well for several months. At this low discharge site (2600 L/day) the reactive tracers' behaviors in the subsurface indicate that PO4 and NO3 are both partially removed from solution in the subsurface. Phosphate showed an initial rapid uptake followed by a slower removal, caused by adsorption-desorption reactions with the KLL (Corbett et al., 2000). Based on our observations, we estimate that approximately 95% of the PO4 injected into the subsurface could be removed in 20-50 hours. There was also evidence for some removal of nitrate from solution, most likely due to denitrification. Approximately 65% of the nitrate was removed over several days, suggesting denitrification rates between 2700 and 7000 mmoles m-3 hr-1. Collectively, our results from this site suggest that much of the nutrients injected into the subsurface are removed from solution and may not have a significant impact on surface waters. However, these experiments were conducted at a relatively small facility, while some facilities in the Keys inject as much as 750,000 L per day. Saturation of available adsorption sites and organic substrate availability may limit the efficiency of waste water nutrient removal under such conditions. To evaluate the fate of waste waster at a high volume injection well facility, another dual tracer study using 32PO4 and SF6 was conducted. During this study, rapid conduit flow as high as 7.9 m/day was observed. At this site, waste water rises rapidly after injection to 18-27 m due to the buoyancy of the low salinity waste water plume. It buoys upward until it meets an impermeable mud layer at about 5 m that overlies the KLL. The majority of the plume is then advected to the east due to the local hydraulic gradient that exists across this site. Initially, phosphate was rapidly adsorbed as observed at the Long Key site. After approximately 36 hours, however we began to see radio labeled PO4 returning to solution, indicating that phosphate is being desorbed from the KLL and slowly returning to solution. The KLL underlying this site seems to be acting as a phosphate buffered system. As a result, the PO4 concentrations 15 m from the injection well seem to be maintained at approximately 25µM. This is supported by column experiments (Elliot, 1999), which also show that adding low phosphate water to KLL that is saturated with PO4 will cause desorption of PO4 until an equilibrium value of approximately 25 µM is reached. Denitrification assays (Acetylene-block technique) suggest rates of denitrification as high as 3000 mmoles m-3 hr-1, comparable to estimates from the Long Key study. Seagrass and macroalgae samples collected from surface waters around the site indicate that isotopically heavy nitrogen, which is indicative of sewage derived nitrogen (McClelland et al., 1997), is being incorporated into the biomass of these primary producers. Macroalgae collected in a canal to the east of the disposal well showed a del 15N value of +13.55 per mil. Stable nitrogen isotopic samples of subsurface NO3 as well as N2/Ar samples have been collected and should provide a clearer picture of the fate of NO3 in the subsurface at this site. |
|||||
BibTeX:
@inproceedings{Dillon2001,
author = {Dillon, Kevin S. and Corbett, D. Reide and Burnett, William C. and Chanton, Jeffrey P.},
title = {The Use of Artificial Tracers to Determine Ground-Water Flow and the Fate of Nutrients in the Karst System Underlying the Florida Keys},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {177--178},
url = {http://water.usgs.gov/ogw/karst/kigconference/ksd_useofartificial.htm}
}
|
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| Din, G.U., Chughtai, I.R., Inayat, M.H. and Khan, I.H. | Axial dispersion, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column by radiotracer residence time distribution analysis | 2008 | Applied Radiation and Isotopes Vol. 66(12), pp. 1818-1824 |
article | URL |
| Abstract: Axial dispersion, holdup and slip velocity of dispersed phase have been investigated for a range of dispersed and continuous phase superficial velocities in a pulsed sieve plate extraction column using radiotracer residence time distribution (RTD) analysis. Axial dispersion model (ADM) was used to simulate the hydrodynamics of the system. It has been observed that increase in dispersed phase superficial velocity results in a decrease in its axial dispersion and increase in its slip velocity while its holdup increases till a maximum asymptotic value is achieved. An increase in superficial velocity of continuous phase increases the axial dispersion and holdup of dispersed phase until a maximum value is obtained, while slip velocity of dispersed phase is found to decrease in the beginning and then it increases with increase in superficial velocity of continuous phase. | |||||
BibTeX:
@article{Din2008,
author = {Din, Ghiyas Ud and Chughtai, Imran Rafiq and Inayat, Mansoor Hameed and Khan, Iqbal Hussain},
title = {Axial dispersion, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column by radiotracer residence time distribution analysis},
journal = {Applied Radiation and Isotopes},
year = {2008},
volume = {66},
number = {12},
pages = {1818--1824},
url = {http://www.sciencedirect.com/science/article/pii/S0969804308003692}
}
|
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| Divine, C.E. and McDonnell, J.J. | The future of applied tracers in hydrogeology [BibTeX] |
2005 | Hydrogeology Journal Vol. 13(1), pp. 255-258 |
article | URL |
BibTeX:
@article{Divine2005,
author = {Divine, Craig E. and McDonnell, Jeffrey J.},
title = {The future of applied tracers in hydrogeology},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2005},
volume = {13},
number = {1},
pages = {255--258},
url = {http://dx.doi.org/10.1007/s10040-004-0416-3}
}
|
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| Doctor, D.H., Weary, D.J., Epstein, J.B. and Orndorff, R.C. | A Karst Aquifer Map for the United States -- Is it possible? | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 34-36 | inproceedings | URL |
| Abstract: Is it possible to classify karst aquifers? This question is central to any attempt to construct a map of karst aquifers for the United States. To make such a map, one must assign spatial boundaries to karst aquifers that are defined by an encompassing set of classifying criteria. The classification paradigm used to make such a map should permit comparison of studies conducted in different regions of the nation and world, and facilitate knowledge transfer between karst regions. However, even attempting to classify different types of karst terrain presents obstacles (Veni, 2002; Weary, 2005). Criteria for establishing boundaries of karst aquifers may call for compromise in "transitional" areas ( Taylor, 2001). For example, does a karst aquifer end at a lithologic contact with less soluble rock? How does the definition of a karst aquifer differ from that of a fractured carbonate aquifer? What role does hypogenic speleogenesis play in regulating flow regimes and storage within a karst aquifer (Klimchouk, 2007)? What techniques does one employ when dye-tracing is not practicable for defining basin boundaries and establishing ground water transit time distribution in karst? An encompassing classification of karst aquifers is one based upon measurable parameters derived from discharge and chemistry at springs and wells within the context of known geologic controls on aquifer extent and speleogenetic development (White, 2003). Such a paradigm presents two main challenges: (1) establishing a conceptual model of karst aquifer development through construction of the geologic framework and speleogenetic history, and (2) determining quantitative indices of the hydrologic response of an aquifer to recharge events from records of flow and water chemistry, supplemented by targeted water tracing experiments and local well tests. The geologic framework provides the basic information on the physical constraints on water storage and movement in the aquifer, including its boundaries and internal structures that guide permeability development through solution. The geologic framework is built through detailed geologic mapping (1:24,000 scale or larger), supplemented by geophysical investigations (e.g., Orndorff and others, 2001; Kozar and others, 2008). The speleogenetic history provides the information on how the permeability structure has been integrated into a highly conductive flow network. The speleogenetic history is reconstructed through the study of caves throughout the geographic extent of the aquifer, their relations to the geologic framework, and what they reveal of former hydrogeologic regimes experienced by the aquifer (Palmer, 2007). Caves represent the greatest degree of integration of the high-transmissivity conduits within the aquifer flow system, thus the processes which lead to their development help to classify the aquifer. Together, the geologic framework and the speleogenetic history provide the conceptual model for the development of the karst. The broadest categories for karst aquifer classification are therefore determined by the conceptual model of karst development. Examples of such broad categories include epigenic (unconfined) versus hypogenic (confined) karst aquifer formation (Klimchouk, 2007; Ford and Williams, 2007), and eogenetic (diagenetically immature) versus telogenetic (diagenetically mature) rocks which host karst aquifers (Florea and Vacher, 2006). Spring flow records provide the most vital information for karst aquifer resource assessment. Working backwards from discharge may yield more fruitful and realistic aquifer assessment than attempting to work forward from site-specific porosity/permeability characterization and scaling up to the regional aquifer (Bredehoeft, 2007; Fleury and others, 2007). This is best achieved by determining diagnostic parameters of aquifer response to recharge from hydrograph and chemograph analysis. For example, multiple aquifer flow regimes can be identified through hydrograph recession analysis, and aquifer storage volumes drained by springs can be estimated by integrating across recession curves (Doctor and Alexander, 2005). Hydrograph recession analysis thus provides useful quantitative indices for karst aquifer classification, such as the base flow recession coefficient, α (day-1), and the ratio of dynamic phreatic storage volume to total annual volume discharged, or the "regulating power" of the aquifer system, k (dimensionless) (El-Hakim and Bakalowicz, 2007). While important for karst aquifer classification, quantitative indices derived from hydrograph recession analysis are insufficient for aquifer mapping. A necessary component is the water balance. The exercise of constructing a balanced water budget may reveal the presence of additional water sources or sinks across previously hypothesized aquifer boundaries, and provides a check on the storage capacity of the aquifer estimated from spring flow recession analysis for a particular basin of interest. A balanced water budget will require that the spatial extent for recharge of a particular ground water basin has been properly delineated, thus enabling a mapped representation of the karst aquifer on the land surface. Boundary refinement is best achieved through well-designed tracing experiments. For example, dye-tracing provides information on groundwater flowpaths and subsurface basin divides. In addition, dye-tracing provides quantitative information on the distribution of travel times within an aquifer. Where dye-tracing is impractical, tracing with natural environmental isotopes and chemistry may provide needed information, particularly in aquifers with a significant artesian component (e.g., Doctor, 2007). In summary, we suggest a classification paradigm for karst aquifers with two primary components: (1) an initial broad categorization based upon a conceptual model for karst development grounded in geologic and speleogenetic data, and (2) refinement within the initial category based upon quantitative indices of aquifer response to recharge from discharge records obtained at springs. Thus, long-term, high frequency hydrologic data are necessary for determining quantitative parameters for karst aquifer classification. However, karst aquifer classification ought not to be based solely upon the prevailing climatic factors of the broader aquifer region. Although climate is often the driving force for karst development, climate is dynamic and variable over time. Rather, the long-term aquifer response (centennial to millennial) to climatic forcing needs to be assessed independently of the short-term aquifer response (annual to decadal) to hydrologic factors that may be used for aquifer classification. In this way, comparisons among a single aquifer type existing under different climatic regimes may facilitate predictions of aquifer response to future climate change. |
|||||
BibTeX:
@inproceedings{Doctor2008,
author = {Doctor, Daniel H. and Weary, David J. and Epstein, Jack B. and Orndorff, Randall C.},
title = {A Karst Aquifer Map for the United States -- Is it possible?},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {34--36},
url = {http://pubs.usgs.gov/sir/2008/5023/08doctor.htm}
}
|
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| Dodds, W.K., Banks, M.K., Clenan, C.S., Rice, C.W., Sotomayor, D., Strauss, E.A. and Yu, W. | Biological properties of soil and subsurface sediments under abandoned pasture and cropland | 1996 | Soil Biology and Biochemistry Vol. 28(7), pp. 837-846 |
article | URL |
| Abstract: Little is known about the effects of most surface land-use practices on shallow subsurface microbial communities. We analyzed duplicate cores taken aseptically from up to 10 m depth from unconsolidated valley sediments (soils) beneath an abandoned pasture reverting to tall grass prairie and cropland. Both profiles had similar soil texture, with moderately higher silt under cropland and a slight decrease in clay with depth. Soluble organic C was about two times higher in the grassland site and dissolved O2 was about 8% lower compared with the cropland site. Water content and C-to-N ratios were greatest at the grassland surface but were less in the grassland than the cropland site within 2 m depth. In general, numbers of aerobic heterotrophic bacteria and protozoa decreased with depth until the saturated zone (4.3 m in grassland and 5.3 m in the cropland site). Bacterial numbers as determined by plate counts were about 10-fold less at the groundwater interface than in the surface soils at both sites. Direct microscopic counts of total bacteria were approximately the same in the surface soil and the sediments at the top of the water table at both sites. The top of the water table generally did not exhibit elevated microbial biomass or activity relative to deeper sediments. There was no significant relationship between protozoan numbers and microbial thymidine uptake at the cropland site, but a negative relationship was observed at the grassland site. The data suggest that cultivation may affect microbial biomass and activity in the subsurface, as well as community interactions between protozoa and bacteria. | |||||
BibTeX:
@article{Dodds1996,
author = {Dodds, Walter K. and Banks, Margaret K. and Clenan, Courtney S. and Rice, Charles W. and Sotomayor, David and Strauss, Eric A. and Yu, Wei},
title = {Biological properties of soil and subsurface sediments under abandoned pasture and cropland},
journal = {Soil Biology and Biochemistry},
year = {1996},
volume = {28},
number = {7},
pages = {837--846},
url = {http://www.sciencedirect.com/science/article/pii/0038071796000570}
}
|
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| Dodds, W.K., Randel, C.A. and Edler, C.C. | Microcosms for Aquifer Research: Application to Colonization of Various Sized Particles by Ground-Water Microorganisms | 1996 | Ground Water Vol. 34(4), pp. 756-759 |
article | URL |
| Abstract: Flow-through microcosms were constructed to conduct ecological experiments on aquifer organisms. The two 5-channel microcosms were simple to construct, were fed by an artesian spring, and maintained close to in situ temperature and O2 concentrations. They were used to test relative microbial colonization of three substrate sizes: silt (0.063 mm), sand (0.9 mm), and gravel (3 mm). After 96 days of incubation, O2 microelectrode measurements revealed the lowest O2 tension in the silt, the highest in the gravel, and intermediate values in the sand. Microbial activity (3[H]-thymidine incorporation) was greatest in the gravel, followed by sand and then silt. Denitrification was greatest in the silt, followed by sand and then gravel. Microbial activity may be greatest with the largest particle size because of increased water exchange through pores, and denitrification may be greatest with the smallest particle sizes because of the occurrence of anaerobic microzones. | |||||
BibTeX:
@article{Dodds1996a,
author = {Dodds, Walter K. and Randel, Clay A. and Edler, Christopher C.},
title = {Microcosms for Aquifer Research: Application to Colonization of Various Sized Particles by Ground-Water Microorganisms},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {1996},
volume = {34},
number = {4},
pages = {756--759},
url = {http://dx.doi.org/10.1111/j.1745-6584.1996.tb02065.x}
}
|
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| Doerr, S., Shakesby, R. and Walsh, R. | Soil water repellency: its causes, characteristics and hydro-geomorphological significance | 2000 | Earth-Science Reviews Vol. 51(1-4), pp. 33-65 |
article | URL |
| Abstract: Water repellency (hydrophobicity) of soils is a property with major repercussions for plant growth, surface and subsurface hydrology, and for soil erosion. Important advances have been made since the late 1980s in identifying the range of environments affected by water repellency, its characteristics and its hydro-geomorphological impacts. This review summarises earlier work, but focusses particularly on these recent advances and identifies remaining research gaps. | |||||
BibTeX:
@article{Doerr2000,
author = {Doerr, S.H. and Shakesby, R.A. and Walsh, R.P.D.},
title = {Soil water repellency: its causes, characteristics and hydro-geomorphological significance},
journal = {Earth-Science Reviews},
year = {2000},
volume = {51},
number = {1-4},
pages = {33--65},
url = {http://www.sciencedirect.com/science/article/pii/S0012825200000118}
}
|
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| Dörfliger, N., Fleury, P. and Ladouche, B. | Inverse Modeling Approach to Allogenic Karst System Characterization | 2009 | Ground Water Vol. 47(3), pp. 414-426 |
article | URL |
| Abstract: Allogenic karst systems function in a particular way that is influenced by the type of water infiltrating through river water losses, by karstification processes, and by water quality. Management of this system requires a good knowledge of its structure and functioning, for which a new methodology based on an inverse modeling approach appears to be well suited. This approach requires both spring and river inflow discharge measurements and a continuous record of chemical parameters in the river and at the spring. The inverse model calculates unit hydrographs and the impulse responses of fluxes from rainfall hydraulic head at the spring or rainfall flux data, the purpose of which is hydrograph separation. Hydrograph reconstruction is done using rainfall and river inflow data as model input and enables definition at each time step of the ratio of each component. Using chemical data, representing event and pre-event water, as input, it is possible to determine the origin of spring water (either fast flow through the epikarstic zone or slow flow through the saturated zone). This study made it possible to improve a conceptual model of allogenic karst system functioning. The methodology is used to study the Bas-Agly and the Cent Font karst systems, two allogenic karst systems in Southern France. | |||||
BibTeX:
@article{Doerfliger2009,
author = {Dörfliger, N. and Fleury, P. and Ladouche, B.},
title = {Inverse Modeling Approach to Allogenic Karst System Characterization},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2009},
volume = {47},
number = {3},
pages = {414--426},
url = {http://dx.doi.org/10.1111/j.1745-6584.2008.00517.x}
}
|
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| Dou, W. and Chung Jin, Y. | Analytical solution of the solute transport equation for the binary homovalent ion exchange in groundwater | 1996 | Journal of Hydrology Vol. 180(1-4), pp. 139-153 |
article | URL |
| Abstract: A binary homovalent ion exchange transport model governed by local chemical equilibrium is considered for a one-dimensional, steady flow in a homogeneous soil column. An analytical solution of the aqueous concentration distribution for the convex exchange is obtained by applying nonlinear shock wave theory. The main nonlinear feature is the breaking of fronts into shock waves. The corresponding mathematical theory is the method of characteristics with a special treatment of shock waves. The wave velocity and front thickness are also obtained to illustrate the front propagation and structure. The derivation of the solution presented may offer a wide range of application opportunities and may also provide a good approach for solving the binary heterovalent exchange transport model. | |||||
BibTeX:
@article{Dou1996,
author = {Dou, Wei and Chung Jin, Yee},
title = {Analytical solution of the solute transport equation for the binary homovalent ion exchange in groundwater},
journal = {Journal of Hydrology},
year = {1996},
volume = {180},
number = {1-4},
pages = {139--153},
url = {http://www.sciencedirect.com/science/article/pii/002216949502901X}
}
|
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| Doummar, J., Sauter, M. and Geyer, T. | Simulation of flow processes in a large scale karst system with an integrated catchment model (Mike She) – Identification of relevant parameters influencing spring discharge | 2012 | Journal of Hydrology Vol. 426–427(0), pp. 112-123 |
article | URL |
| Abstract: Summary In a complex environment such as karst systems, it is difficult to assess the relative contribution of the different components of the system to the hydrological system response, i.e. spring discharge. Not only is the saturated zone highly heterogeneous due to the presence of highly permeable conduits, but also the recharge processes. The latter are composed of rapid recharge components through shafts and solution channels and diffuse matrix infiltration, generating a highly complex, spatially and temporally variable input signal. The presented study reveals the importance of the compartments vegetation, soils, saturated zone and unsaturated zone. Therefore, the entire water cycle in the catchment area Gallusquelle spring (Southwest Germany) is modelled over a period of 10 years using the integrated hydrological modelling system Mike She by DHI (2007). Sensitivity analyses show that a few individual parameters, varied within physically plausible ranges, play an important role in reshaping the recessions and peaks of the recharge functions and consequently the spring discharge. Vegetation parameters especially the Leaf Area Index (LAI) and the root depth as well as empirical parameters in the relationship of Kristensen and Jensen highly influence evapotranspiration, transpiration to evaporation ratios and recharge respectively. In the unsaturated zone, the type of the soil (mainly the hydraulic conductivity at saturation in the water retention and hydraulic retention curves) has an effect on the infiltration/evapotranspiration and recharge functions. Additionally in the unsaturated karst, the saturated moisture content is considered as a highly indicative parameter as it significantly affects the peaks and recessions of the recharge curve. At the level of the saturated zone the hydraulic conductivity of the matrix and highly conductive zone representing the conduit are dominant parameters influencing the spring response. Other intermediate significant parameters appear to influence the characteristics of the spring response yet to a smaller extent, as for instance bypass and the parameters α in the Van Genuchten relation for soil moisture content curves. | |||||
BibTeX:
@article{Doummar2012,
author = {Doummar, Joanna and Sauter, Martin and Geyer, Tobias},
title = {Simulation of flow processes in a large scale karst system with an integrated catchment model (Mike She) – Identification of relevant parameters influencing spring discharge},
journal = {Journal of Hydrology},
year = {2012},
volume = {426–427},
number = {0},
pages = {112--123},
url = {http://www.sciencedirect.com/science/article/pii/S0022169412000649}
}
|
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| Dreiss, S.J. | Regional scale transport in a Karst Aquifer: 1. Component separation of spring flow hydrographs | 1989 | Water Resources Research Vol. 25(1), pp. 117-125 |
article | URL |
| Abstract: Large fluctuations in Ca and Mg concentrations occur in the discharge of karst springs in southeastern Missouri after major storm events. Rapid flow of relatively dilute, storm-derived water through solution conduits in the aquifer causes the fluctuations in chemistry. A cation balance for the discharge of one spring indicates that about 25% of the total spring flow is storm-derived water. These storm-derived contributions reach a maximum during the recession of storm responses in the spring flow hydrograph. At the peak of the responses, spring flow is composed primarily of prestorm water that has been displaced in the conduit system by the storm-derived water. The observed chemical fluctuations and hydrograph components differ from those observed in streamflow where the time of the maximum dilution usually coincides with the time of peak discharge. | |||||
BibTeX:
@article{Dreiss1989a,
author = {Dreiss, Shirley J.},
title = {Regional scale transport in a Karst Aquifer: 1. Component separation of spring flow hydrographs},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1989},
volume = {25},
number = {1},
pages = {117--125},
url = {http://dx.doi.org/10.1029/WR025i001p00117}
}
|
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| Dreiss, S.J. | Regional scale transport in a Karst Aquifer: 2. Linear systems and time moment analysis | 1989 | Water Resources Research Vol. 25(1), pp. 126-134 |
article | URL |
| Abstract: Travel time distributions of water or tracers in conduit-type karst aquifers can be found from linear systems analysis of either tracer test data or naturally occurring fluctuations in springflow chemistry. I use the chemical fluctuations at Maramec Spring, Missouri described in paper 1 (Dreiss, this issue) and results from a previous tracer test to derive a set of kernal functions that represent regional scale transport in the karst conduit network. A single kernel is sufficient to simulate the storm-derived component of Maramec springflow, suggesting that rapid transport in the conduit network is well-approximated by temporal stationarity. Time moment analysis of the kernels leads to several conclusions. The kernel for the tracer test exhibits a larger mean residence time and much smaller variance than the kernels derived from nonpoint source recharge. Thus the tracer travel distance appears to be longer than the mean travel distance of rapid recharge and much of the variance of nonpoint source kernels apparently results from the distribution of flow path lengths to the spring. By assuming an effective transport model and comparing the moments of the empirical tracer test kernel to the moments of the impulse response of the model, I compute an effective velocity between the tracer input point and Maramec Spring of 1.3 km/day and an effective dispersivity of 0.29 km. Because the time moments of the kernels and the effective transport parameters can be computed from readily measured springflow properties, they may prove to be a convenient means for studying and comparing regional scale transport in karst aquifers. | |||||
BibTeX:
@article{Dreiss1989b,
author = {Dreiss, Shirley J.},
title = {Regional scale transport in a Karst Aquifer: 2. Linear systems and time moment analysis},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1989},
volume = {25},
number = {1},
pages = {126--134},
url = {http://dx.doi.org/10.1029/WR025i001p00126}
}
|
|||||
| Dridi, L., Pollet, I., Razakarisoa, O. and Schäfer, G. | Characterisation of a DNAPL source zone in a porous aquifer using the Partitioning Interwell Tracer Test and an inverse modelling approach | 2009 | Journal of Contaminant Hydrology Vol. 107(1-2), pp. 22-44 |
article | URL |
| Abstract: In this paper, we discuss the results of a Partitioning Interwell Tracer Test (PITT) performed in a large scale experiment with a well-defined TCE spill, and present a novel combined analytical–numerical inverse modelling approach using measured concentration profiles within a TCE plume to predict the distribution of the DNAPL in a virtual vertical plane of the source. The proposed inverse modelling approach assumes local thermodynamic equilibrium of the distribution of TCE between the NAPL phase and the aqueous phase and no decay or sorption of the dissolved TCE concentrations downstream of the spill area. | |||||
BibTeX:
@article{Dridi2009,
author = {Dridi, Lotfi and Pollet, Ingrid and Razakarisoa, Olivier and Schäfer, Gerhard},
title = {Characterisation of a DNAPL source zone in a porous aquifer using the Partitioning Interwell Tracer Test and an inverse modelling approach},
journal = {Journal of Contaminant Hydrology},
year = {2009},
volume = {107},
number = {1-2},
pages = {22--44},
url = {http://www.sciencedirect.com/science/article/pii/S0169772209000461}
}
|
|||||
| Duah-Yentumi, S. and Kuwatsuka, S. | Effect of organic matter and chemical fertilizers on the degradation of benthiocarb and MCPA herbicides in the soil | 1980 | Soil Science and Plant Nutrition Vol. 26(4), pp. 541-549 |
article | |
| Abstract: The degradation of herbicides in soils amended with rice straw, compost and NPK chemical fertilizers was investigated in the laboratory under upland, oxidative-flooded (aerobic-flooded) and reductive-flooded (anaerobic-flooded) conditions using 14C-benthiocarb and 14C-MCPA labelled at the phenyl ring. Rice straw, compost and NPK amendments promoted the degradation of these herbicides under upland and oxidative-flooded conditions and large amounts of 14CO2 were evolved. Under reductive-flooded conditions, the degradation of the herbicides was remarkably slow and the various soil amendments had practically no effect on the degradation of the two herbicides. 4-Chlorobenzoic acid, desethylbenthiocarb, benthiocarb sulfoxide and 4-chlorobenzyl methyl sulfone were found to be the major degradation products of benthiocarb. Rice straw amendments appeared to increase the amount of benthiocarb sulfoxide but the amount of desethylbenthiocarb was reduced by both rice straw and compost, especially under upland conditions. 4-Chloro-2-methylphenol, which was the major degradation product of MCPA, was produced in relatively large amounts in the rice straw amendment under oxidative-flooded conditions and in the NPK amendment under upland conditions. |
|||||
BibTeX:
@article{Duah-Yentumi1980,
author = {Duah-Yentumi, Stephen and Kuwatsuka, Shozo},
title = {Effect of organic matter and chemical fertilizers on the degradation of benthiocarb and MCPA herbicides in the soil},
journal = {Soil Science and Plant Nutrition},
year = {1980},
volume = {26},
number = {4},
pages = {541--549}
}
|
|||||
| Ducci, D., De Masi, G. and Delli Priscoli, G. | Contamination risk of the Alburni Karst System (Southern Italy) | 2008 | Engineering Geology Vol. 99(3-4)Engineering and environmental problems in karst Natural and Anthropogenic Hazards in Karst Areas, pp. 109-120 |
article | URL |
| Abstract: The Alburni massif (1742m a.s.l.) stretches NW–SE, about 23km long and 9–10km wide, covering 246km2 with an average elevation of about 940m a.s.l. This massif, with more than 500 caves, is the most important karst area in southern Italy. The karst channel network is hierarchically organized: some channels feed a major spring (1m3/s) with a very short transit time while others communicate directly with the basal water table related to other springs (Q > 3m3/s). | |||||
BibTeX:
@article{Ducci2008,
author = {Ducci, Daniela and De Masi, Giuseppe and Delli Priscoli, Giuseppe},
title = {Contamination risk of the Alburni Karst System (Southern Italy)},
booktitle = {Engineering and environmental problems in karst Natural and Anthropogenic Hazards in Karst Areas},
journal = {Engineering Geology},
year = {2008},
volume = {99},
number = {3-4},
pages = {109--120},
url = {http://www.sciencedirect.com/science/article/pii/S0013795208000306}
}
|
|||||
| Duffy, C.J. and Gelhar, L.W. | A Frequency Domain Analysis of Groundwater Quality Fluctuations: Interpretation of Field Data | 1986 | Water Resources Research Vol. 22(7), pp. 1115-1128 |
article | URL |
| Abstract: Environmental tracer or pollution patterns in groundwater have been regarded as a qualitative means of studying complex or large-scale hydrogeologic systems. However, questions have arisen as to whether the “natural state” analog has quantitative value, such as for the estimation of transport or aquifer parameters. In this paper we demonstrate the application of spectral analysis and frequency domain methods to temporal tracer patterns for the physical interpretation of transient environmental tracers in a variety of hydrologic settings. Three case studies are examined where the source of environmental tracer is represented as a stochastic process. Process and parameter estimation is performed by comparison of the theoretical transfer function and phase spectrum. The most important result of this paper is that different source configurations (nonpoint, point, etc.) and different groundwater flow patterns produce unique frequency response characteristics for solutes within each system. It is this feature which allows us to make inference about the governing physical processes and parameters. | |||||
BibTeX:
@article{Duffy1986,
author = {Duffy, Christopher J. and Gelhar, Lynn W.},
title = {A Frequency Domain Analysis of Groundwater Quality Fluctuations: Interpretation of Field Data},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1986},
volume = {22},
number = {7},
pages = {1115--1128},
url = {http://dx.doi.org/10.1029/WR022i007p01115}
}
|
|||||
| Duffy, C.J. and Gelhar, L.W. | A Frequency Domain Approach to Water Quality Modeling in Groundwater: Theory | 1985 | Water Resources Research Vol. 21(8), pp. 1175-1184 |
article | URL |
| Abstract: A method for the analysis of complex temporal variations of environmental tracers or pollution time series in groundwater is examined using spectral analysis and linear filter theory for stationary stochastic processes. The interpretation of solute fluctuations subject to a time varying source is accomplished via frequency domain solutions to stochastic differential equations for three widely applied transport models: (1) a lumped parameter or linear reservoir model; (2) convective (advective) transport in a curvilinear flow field; and (3) convective-dispersive transport in a uniform flow field. Frequency domain solutions are presented in terms of the theoretical transfer function and phase spectra which describe the amplitude attenuation and phase lag between frequencies in the input and output. A comparison of the frequency response of the three models indicates that the unique filtering characteristics of each may provide a diagnostic tool for matching the appropriate theory to a sampled water quality “signal.” A procedure is suggested for parameter estimation which involves comparison of the theoretical and field estimated transfer function and phase spectra. | |||||
BibTeX:
@article{Duffy1985,
author = {Duffy, C. J. and Gelhar, L. W.},
title = {A Frequency Domain Approach to Water Quality Modeling in Groundwater: Theory},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1985},
volume = {21},
number = {8},
pages = {1175--1184},
url = {http://dx.doi.org/10.1029/WR021i008p01175}
}
|
|||||
| Duffy, C.J., Gelhar, L.W. and Wierenga, P.J. | Stochastic models in agricultural watersheds | 1984 | Journal of Hydrology Vol. 69(1–4), pp. 145-162 |
article | URL |
| Abstract: A stochastic time-series approach using spectral analysis theory is developed and applied to drainage analysis of an agricultural watershed, Rio Grande Valley, New Mexico, U.S.A. The spectral theory demonstrates that a linear reservoir model is a suitable approximation to the Dupuit aquifer over a wide range of frequencies. A first-order perturbation of the variables allows the system parameters to be evaluated from both the stochastic solution of the fluctuating or zero-mean process, and the temporal-mean or steady-state solution. Deep percolation is estimated by first assuming a “no storage” situation in which recharge is a constant fraction (leaching fraction) of applied water. A second approach to deep percolation incorporates a soil-moisture reservoir to simulate storage in the soil zone. The equations developed are useful for characterizing drainage systems which exhibit a statistically stationary response to rainfall and/or irrigation. | |||||
BibTeX:
@article{Duffy1984,
author = {Duffy, Christopher J. and Gelhar, Lynn W. and Wierenga, Peter J.},
title = {Stochastic models in agricultural watersheds},
journal = {Journal of Hydrology},
year = {1984},
volume = {69},
number = {1–4},
pages = {145--162},
url = {http://www.sciencedirect.com/science/article/pii/0022169484901604}
}
|
|||||
| Dufresne, D.P. and Drake, C.W. | Regional groundwater flow model construction and wellfield site selection in a karst area, Lake City, Florida | 1999 | Engineering Geology Vol. 52(1-2), pp. 129-139 |
article | URL |
| Abstract: The city of Lake City is in the process of expanding their water supply facilities by 45 420 m3 day−1 (12 MGD) to meet future demands. One portion of wellfield site selection addressed here includes analysis of ambient groundwater quality and its potential for contamination. This study also addresses the potential impacts of groundwater withdrawals to existing legal users, wetlands, surface waters and spring flows. A regional groundwater flow model (MODFLOW) was constructed using existing hydrogeologic data from state and federal agencies in order to simulate the existing hydrologic conditions of this karst area and to predict withdrawal impacts. The model was calibrated by matching potentiometric surface maps and spring flows to within reasonable ranges. Drawdowns in the Floridan and surficial aquifers predicted by the model show minimal impacts to existing legal users and only a 5% reduction in the flow at Ichetucknee Springs ca 21 km (13 miles) away. Due to the karstic nature of the Floridan aquifer here, the equivalent-porous-medium flow model constructed would not be appropriate for contaminant transport modeling. The groundwater flow model is, however, appropriate to represent hydraulic heads and recharge/discharge relationships on a regional scale. | |||||
BibTeX:
@article{Dufresne1999,
author = {Dufresne, Douglas P and Drake, Charles W},
title = {Regional groundwater flow model construction and wellfield site selection in a karst area, Lake City, Florida},
journal = {Engineering Geology},
year = {1999},
volume = {52},
number = {1-2},
pages = {129--139},
url = {http://www.sciencedirect.com/science/article/pii/S0013795298000660}
}
|
|||||
| Dunn, S.M., Birkel, C., Tetzlaff, D. and Soulsby, C. | Transit time distributions of a conceptual model: their characteristics and sensitivities | 2010 | Hydrological Processes Vol. 24(12), pp. 1719-1729 |
article | URL |
| Abstract: The internal behaviour of a conceptual hydrological and tracer transport model, STREAM, has been examined through generation of transit time distributions for the model. The model has been applied to a small sub-catchment of the Lunan Water in the east of Scotland where daily precipitation and stream water samples have been analysed for isotope content. Transit time distributions are generated by numerically tracking pulse inputs of tracer to the model and evaluating the simulated stream outputs. A set of baseline simulations was first established through calibration to time series of stream flow. A series of model experiments was then undertaken to assess the sensitivity of the simulated transit time distributions to different model parameterizations, flow paths and mixing assumptions. The results of the analysis show that the model transit time distributions do not conform to any simple statistical function and that their characteristics can be significantly altered depending on how the model is set up. The analysis provided valuable insight into the functioning of the model and could be usefully applied to other model codes. Comparison of the transit time distributions generated by conceptual models with data-based empirical evidence of distributions gives the potential to close the gap in understanding the physical explanation for why catchment systems behave as they do. | |||||
BibTeX:
@article{Dunn2010,
author = {Dunn, S. M. and Birkel, C. and Tetzlaff, D. and Soulsby, C.},
title = {Transit time distributions of a conceptual model: their characteristics and sensitivities},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {12},
pages = {1719--1729},
url = {http://dx.doi.org/10.1002/hyp.7560}
}
|
|||||
| Dupraz, C., Reid, R.P., Braissant, O., Decho, A.W., Norman, R.S. and Visscher, P.T. | Processes of carbonate precipitation in modern microbial mats | 2009 | Earth-Science Reviews Vol. 96(3)Microbial Mats in Earth's Fossil Record of Life: Geobiology, pp. 141-162 |
article | URL |
| Abstract: Microbial mats are ecosystems that arguably greatly affected the conditions of the biosphere on Earth through geological time. These laminated organosedimentary systems, which date back to > 3.4 Ga bp, are characterized by high metabolic rates, and coupled to this, rapid cycling of major elements on very small (mm-µm) scales. The activity of the mat communities has changed Earth's redox conditions (i.e. oxidation state) through oxygen and hydrogen production. Interpretation of fossil microbial mats and their potential role in alteration of the Earth's geochemical environment is challenging because these mats are generally not well preserved. | |||||
BibTeX:
@article{Dupraz2009,
author = {Dupraz, Christophe and Reid, R. Pamela and Braissant, Olivier and Decho, Alan W. and Norman, R. Sean and Visscher, Pieter T.},
title = {Processes of carbonate precipitation in modern microbial mats},
booktitle = {Microbial Mats in Earth's Fossil Record of Life: Geobiology},
journal = {Earth-Science Reviews},
year = {2009},
volume = {96},
number = {3},
pages = {141--162},
url = {http://www.sciencedirect.com/science/article/pii/S0012825208001190}
}
|
|||||
| Dutil, Y., Rousse, D.R., Salah, N.B., Lassue, S. and Zalewski, L. | A review on phase-change materials: Mathematical modeling and simulations | 2011 | Renewable and Sustainable Energy Reviews Vol. 15(1), pp. 112-130 |
article | URL |
| Abstract: Energy storage components improve the energy efficiency of systems by reducing the mismatch between supply and demand. For this purpose, phase-change materials are particularly attractive since they provide a high-energy storage density at a constant temperature which corresponds to the phase transition temperature of the material. Nevertheless, the incorporation of phase-change materials (PCMs) in a particular application calls for an analysis that will enable the researcher to optimize performances of systems. Due to the non-linear nature of the problem, numerical analysis is generally required to obtain appropriate solutions for the thermal behavior of systems. Therefore, a large amount of research has been carried out on PCMs behavior predictions. The review will present models based on the first law and on the second law of thermodynamics. It shows selected results for several configurations, from numerous authors so as to enable one to start his/her research with an exhaustive overview of the subject. This overview stresses the need to match experimental investigations with recent numerical analyses since in recent years, models mostly rely on other models in their validation stages. | |||||
BibTeX:
@article{Dutil2011,
author = {Dutil, Yvan and Rousse, Daniel R. and Salah, Nizar Ben and Lassue, Stéphane and Zalewski, Laurent},
title = {A review on phase-change materials: Mathematical modeling and simulations},
journal = {Renewable and Sustainable Energy Reviews},
year = {2011},
volume = {15},
number = {1},
pages = {112--130},
url = {http://www.sciencedirect.com/science/article/pii/S1364032110001589}
}
|
|||||
| Dzakpasu, M., Scholz, M., Harrington, R., Jordan, S.N. and McCarthy, V. | Characterising infiltration and contaminant migration beneath earthen-lined integrated constructed wetlands | 2012 | Ecological Engineering Vol. 41(0), pp. 41-51 |
article | URL |
| Abstract: The concept of integrated constructed wetlands (ICW) uses in situ soils to construct and line their cells. The integrity of soil materials, however, may provide a potential pathway for contaminants to flow into the subsoil. In this study, the rates of infiltration and contaminants loading occurring beneath a full-scale ICW treating domestic wastewater were evaluated over an 18-month period. The ICW is located at Glaslough in Co. Monaghan, Ireland. It consists of two sludge cells and a sequence of five shallow vegetated wetland cells. The ICW cells were lined with 500 mm thick local subsoil materials. Infiltration water was collected from zero-tension pan lysimeters, which were placed within the soil-liners of the first three ICW cells and analysed for water quality parameters such as chemical oxygen demand, ammonia-nitrogen, nitrate-nitrogen, and molybdate reactive phosphate. Infiltration rates were 4.3 × 10−9, 3.7 × 10−9 and 1.0 × 10−8 m s−1 from the first three ICW cells. The variation among locations was small. The apparent hydraulic conductivity of the soil liner, calculated with empirical water budgets, ranged between 3.5 × 10−9 and 9.8 × 10−9 m s−1across the cells. In the first two cells of the ICW, less than 0.5% of the influent contaminant loading to the cells was lost through infiltration to subsoil. Overall, the amount of infiltration and contaminant loading occurring beneath the ICW cells increased from the proximal cells to the distal one. Higher contaminant loading was recorded in the third cell, which received partially treated wastewater. This implies that each ICW cell has the potential to impact differently on the underlying groundwater and that the potential for groundwater contamination from ICW systems was minimal in the first ICW cells, when compared to the last one. | |||||
BibTeX:
@article{Dzakpasu2012,
author = {Dzakpasu, Mawuli and Scholz, Miklas and Harrington, Rory and Jordan, Siobhán N. and McCarthy, Valerie},
title = {Characterising infiltration and contaminant migration beneath earthen-lined integrated constructed wetlands},
journal = {Ecological Engineering},
year = {2012},
volume = {41},
number = {0},
pages = {41--51},
url = {http://www.sciencedirect.com/science/article/pii/S0925857412000328}
}
|
|||||
| Eaton, J.W., Bateman, D. and Hauberg, S. | GNU Octave Version 3.0.1 Manual: A High-Level Interactive Language For Numerical Computations [BibTeX] |
2009 | book | URL | |
BibTeX:
@book{Eaton2009,
author = {Eaton, John W. and Bateman, David and Hauberg, Soren},
title = {GNU Octave Version 3.0.1 Manual: A High-Level Interactive Language For Numerical Computations},
publisher = {Network Theory Limited},
year = {2009},
url = {http://www.octave.org}
}
|
|||||
| Eaton, J.W., Bateman, D. and Hauberg, S. | GNU Octave Manual Version 3 [BibTeX] |
2008 | book | URL | |
BibTeX:
@book{Eaton2008,
author = {Eaton, John W. and Bateman, David and Hauberg, Søren},
title = {GNU Octave Manual Version 3},
publisher = {Network Theory Limited},
year = {2008},
url = {http://www.octave.org}
}
|
|||||
| Eaton, T.T. | On the importance of geological heterogeneity for flow simulation | 2006 | Sedimentary Geology Vol. 184(3-4)Heterogeneity in Sedimentary Aquifers: Challenges for Characterization and Flow Modeling Geological Society of America Annual Meeting “GeoScience Horizons 2003”, pp. 187-201 |
article | URL |
| Abstract: Geological heterogeneity is recognized as a major control on reservoir production and constraint on many aspects of quantitative hydrogeology. Hydrogeologists and reservoir geologists need to characterize groundwater flow through many different types of geological media for different purposes. In this introductory paper, an updated perspective is provided on the current status of the long effort to understand the effect of geological heterogeneity on flow using numerical simulations. A summary is given of continuum vs. discrete paradigms, and zonal vs. geostatistical approaches, all of which are used to structure model domains. Using these methods and modern simulation tools, flow modelers now have greater opportunities to account for the increasingly detailed understanding of heterogeneous aquifer and reservoir systems. | |||||
BibTeX:
@article{Eaton2006,
author = {Eaton, Timothy T.},
title = {On the importance of geological heterogeneity for flow simulation},
booktitle = {Heterogeneity in Sedimentary Aquifers: Challenges for Characterization and Flow Modeling Geological Society of America Annual Meeting “GeoScience Horizons 2003”},
journal = {Sedimentary Geology},
year = {2006},
volume = {184},
number = {3-4},
pages = {187--201},
url = {http://www.sciencedirect.com/science/article/pii/S0037073805003714}
}
|
|||||
| Edmonds, C. | Improved groundwater vulnerability mapping for the karstic chalk aquifer of south east England | 2008 | Engineering Geology Vol. 99(3–4)Engineering and environmental problems in karst Natural and Anthropogenic Hazards in Karst Areas, pp. 95-108 |
article | URL |
| Abstract: The Cretaceous age Chalk of south east England forms an important aquifer. Within chalk the storage and transmission of groundwater is enhanced by subsurface karstic weathering. The case study presented in this paper demonstrates that current approaches to assessing groundwater vulnerability to pollution and delineating source protection zones are flawed, as they do not take proper account of the karstic nature of chalk. | |||||
BibTeX:
@article{Edmonds2008,
author = {Edmonds, Clive},
title = {Improved groundwater vulnerability mapping for the karstic chalk aquifer of south east England},
booktitle = {Engineering and environmental problems in karst Natural and Anthropogenic Hazards in Karst Areas},
journal = {Engineering Geology},
year = {2008},
volume = {99},
number = {3–4},
pages = {95--108},
url = {http://www.sciencedirect.com/science/article/pii/S001379520800029X}
}
|
|||||
| Einsiedl, F. | Flow system dynamics and water storage of a fissured-porous karst aquifer characterized by artificial and environmental tracers | 2005 | Journal of Hydrology Vol. 312(1-4), pp. 312-321 |
article | URL |
| Abstract: Concentration breakthrough curves obtained from a tracer test and time series of environmental tracers were analyzed to characterize slow and preferential water flow in a karst aquifer of the Franconian Alb, Germany. Tritium (3H) and chemical tracers (uranine, bromide, strontium) were measured during low flow conditions and a storm runoff event. The mean transit time of water along the conduits was determined using bromide. Environmental tracer data collected between 1969 and 2003 were modeled to estimate the mean transit time of 3H in the fissured-porous karst system (diffuse flow). The modelling approach was also used to estimate the water volume of the karst system and the conduits. The results suggest that the total water volume in the fissured-porous karst aquifer is in the range of 57×106 m3 and approximately 6% of the total water volume is stored in the soil zone and the epikarst. The water storage capacity of the conduits seems to be of minor importance. A mean transit time of bromide in the range of 14 h was calculated for the conduit flow. The fissures and the porous rock matrix have a calculated water saturated porosity of 5.5% and a mean transit time of approximately 62 years was calculated. Thus the porous rock matrix represents the major dilution and storage zone for pollutants in the karst system. | |||||
BibTeX:
@article{Einsiedl2005,
author = {Einsiedl, F.},
title = {Flow system dynamics and water storage of a fissured-porous karst aquifer characterized by artificial and environmental tracers},
journal = {Journal of Hydrology},
year = {2005},
volume = {312},
number = {1-4},
pages = {312--321},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405001010}
}
|
|||||
| Einsiedl, F., Maloszewski, P. and Stichler, W. | Multiple isotope approach to the determination of the natural attenuation potential of a high-alpine karst system [BibTeX] |
2009 | Journal of Hydrology Vol. 365(1-2), pp. 113-121 |
article | DOI URL |
BibTeX:
@article{Einsiedl2009,
author = {Einsiedl, Florian and Maloszewski, Piotr and Stichler, Willibald},
title = {Multiple isotope approach to the determination of the natural attenuation potential of a high-alpine karst system},
journal = {Journal of Hydrology},
year = {2009},
volume = {365},
number = {1-2},
pages = {113--121},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408005829},
doi = {http://dx.doi.org/10.1016/j.jhydrol.2008.11.042}
}
|
|||||
| Einsiedl, F., Radke, M. and Maloszewski, P. | Occurrence and transport of pharmaceuticals in a karst groundwater system affected by domestic wastewater treatment plants [BibTeX] |
2010 | Journal of Contaminant Hydrology Vol. 117(1-4), pp. 26-36 |
article | DOI URL |
BibTeX:
@article{Einsiedl2010,
author = {Einsiedl, Florian and Radke, Michael and Maloszewski, Piotr},
title = {Occurrence and transport of pharmaceuticals in a karst groundwater system affected by domestic wastewater treatment plants},
journal = {Journal of Contaminant Hydrology},
year = {2010},
volume = {117},
number = {1-4},
pages = {26--36},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210000550},
doi = {http://dx.doi.org/10.1016/j.jconhyd.2010.05.008}
}
|
|||||
| Eisenlohr, L., Bouzelboudjen, M., Király, L. and Rossier, Y. | Numerical versus statistical modelling of natural response of a karst hydrogeological system | 1997 | Journal of Hydrology Vol. 202(1-4), pp. 244-262 |
article | URL |
| Abstract: Structural and hydrodynamic characteristics of karst aquifers are mostly deduced from studies of global responses of karst springs (hydrographs, chemical or isotopic composition). In this case, global response is often used to make inferences with respect to infiltration and ground water flow processes as well as on the hydrodynamic parameters. Obviously, the direct verification of these inferences is very difficult. We have used an indirect method of verification, introducing well defined theoretical karst structures into a finite element model and then analysing the simulated global response according to the currently accepted interpretation schemes. As we know what we are introducing into the numeric model, the consistency of the interpretation may be checked immediately. The results obtained in the hydrogeological study of two karst basins in the Swiss Jura and from 2-D and 3-D numerical simulations show the difficulty of finding structural parameters and hydrodynamic behaviour from statistical methods alone, i.e. correlation analyses discharge–discharge and precipitation–discharge. In effect, our first results show that the form of the correlograms depends on several factors besides the structure of the karst aquifer: (i) on the form of the floods, in other words the contrast between quick flow and base flow, (ii) on the frequency of hydrological events during the period analysed and (iii) on the type of infiltration processes, in other words the ratio of diffuse infiltration to concentrated infiltration. Obviously, the variability of a karst hydrograph is a result of a combination of these factors. Distinction between them is not always possible on hydrographs, and therefore on correlations (discharge–discharge and precipitation–discharge). | |||||
BibTeX:
@article{Eisenlohr1997a,
author = {Eisenlohr, Laurent and Bouzelboudjen, Mahmoud and Király, László and Rossier, Yvan},
title = {Numerical versus statistical modelling of natural response of a karst hydrogeological system},
journal = {Journal of Hydrology},
year = {1997},
volume = {202},
number = {1-4},
pages = {244--262},
url = {http://www.sciencedirect.com/science/article/pii/S0022169497000693}
}
|
|||||
| Eisenlohr, L., Király, L., Bouzelboudjen, M. and Rossier, Y. | Numerical simulation as a tool for checking the interpretation of karst spring hydrographs | 1997 | Journal of Hydrology Vol. 193(1-4), pp. 306-315 |
article | URL |
| Abstract: A schematic representation of karst aquifers may be that of a high hydraulic conductivity channel network with kilometre-wide intervals, surrounded by a low hydraulic conductivity fractured limestone volume and connected to a local discharge area, the karst spring. The behaviour of the karst spring (hydrographs, chemical or isotopic composition, etc.) represents the global response of the karst aquifer to input events. | |||||
BibTeX:
@article{Eisenlohr1997,
author = {Eisenlohr, Laurent and Király, László and Bouzelboudjen, Mahmoud and Rossier, Yvan},
title = {Numerical simulation as a tool for checking the interpretation of karst spring hydrographs},
journal = {Journal of Hydrology},
year = {1997},
volume = {193},
number = {1-4},
pages = {306--315},
url = {http://www.sciencedirect.com/science/article/pii/S002216949603140X}
}
|
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| El-Hakim, M. and Bakalowicz, M. | Significance and origin of very large regulating power of some karst aquifers in the Middle East. Implication on karst aquifer classification | 2007 | Journal of Hydrology Vol. 333(2-4), pp. 329-339 |
article | URL |
| Abstract: Karst aquifers are the main groundwater resource in Lebanon as well as in most Mediterranean countries. Most of them are not exploited in a sustainable way, partly because their characteristics remain unknown. Karst aquifers are so complex that the assessment of their resource and their exploitable storage requires an analysis of their whole functioning, particularly by analysing the spring hydrograph. Among all various methods, the method proposed by Mangin aims to characterize at the same time the recharge conditions and the storage and recession of the saturated zone by analyzing the spring hydrograph. This method defines two parameters, the infiltration delay i, and the regulating power k which are the roots of a classification of karst systems. This classification makes the distinction between karst and porous aquifers considering the value of the regulating power. k is assumed to be lower than 0.5 in karst, and between 0.5 and 1 for all other aquifers, 1 being the upper limit. | |||||
BibTeX:
@article{El-Hakim2007,
author = {El-Hakim, Massaad and Bakalowicz, Michel},
title = {Significance and origin of very large regulating power of some karst aquifers in the Middle East. Implication on karst aquifer classification},
journal = {Journal of Hydrology},
year = {2007},
volume = {333},
number = {2-4},
pages = {329--339},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406004768}
}
|
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| El-Kadi, A.I. | Variability of infiltration under uncertainty in unsaturated zone parameters | 1987 | Journal of Hydrology Vol. 90(1-2), pp. 61-80 |
article | DOI URL |
| Abstract: A problem of special interest is the variability of infiltration caused by uncertainty in unsaturated zone parameters. The problem is studied here by solving a one-dimensional form of Richards' equation within a Monte Carlo analysis. Based on experimental data, cross-correlation between measurable soil properties — namely, the soil-water characteristic function and the hydraulic conductivity function — is defined. The unsaturated zone parameters can be estimated explicitly from the value of the saturated hydraulic conductivity. Also clarified are the effects of spatially varied parameters on the variability of point infiltration, water content, and time to the onset of ponding. The paper explores how both model sophistication and parameter cross-correlation affect modeling results. Analytical solutions can be used in the stochastic analysis if cross-correlation is considered. The inclusion of cross-correlation decreases the variability of output parameters without much effect on the mean values of these parameters. An effective value is defined for the saturated hydraulic conductivity that may characterize the heterogeneous soil. For a specified rainfall intensity, this value depends on the variability and autocorrelation structure of the saturated hydraulic conductivity. Neglecting variability may lead to unacceptable errors. | |||||
BibTeX:
@article{El-Kadi1987,
author = {El-Kadi, Aly I.},
title = {Variability of infiltration under uncertainty in unsaturated zone parameters},
journal = {Journal of Hydrology},
year = {1987},
volume = {90},
number = {1-2},
pages = {61--80},
url = {http://www.sciencedirect.com/science/article/pii/0022169487901739},
doi = {http://dx.doi.org/10.1016/0022-1694(87)90173-9}
}
|
|||||
| Emblanch, C., Zuppi, G., Mudry, J., Blavoux, B. and Batiot, C. | Carbon 13 of TDIC to quantify the role of the unsaturated zone: the example of the Vaucluse karst systems (Southeastern France) | 2003 | Journal of Hydrology Vol. 279(1-4), pp. 262-274 |
article | URL |
| Abstract: The total dissolved inorganic carbon (TDIC) and 13CTDIC have been used as chemical and isotopic tracers to evaluate the contribution of different water components discharging at the Fontaine de Vaucluse karst spring near Avignon. At the same time they have been used to separate its flood hydrograph. Waters flowing from unsaturated zone (UZ) and saturated zone (SZ) show similar concentration in TDIC. In UZ and SZ water rock interactions do not obey to the same kinetic. The mixing rate between water coming from the UZ characterised by a short residence time and water from the SZ with a longer residence time has been evaluated in the spring discharge. In a hydrodynamic system, which is rather complex as it is open to the soil CO2 in UZ and closed to the same CO2 in the SZ, 13CTDIC has excellent characteristics as an environmental tracer. | |||||
BibTeX:
@article{Emblanch2003,
author = {Emblanch, C and Zuppi, G.M and Mudry, J and Blavoux, B and Batiot, C},
title = {Carbon 13 of TDIC to quantify the role of the unsaturated zone: the example of the Vaucluse karst systems (Southeastern France)},
journal = {Journal of Hydrology},
year = {2003},
volume = {279},
number = {1-4},
pages = {262--274},
url = {http://www.sciencedirect.com/science/article/pii/S002216940300180X}
}
|
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| Embry, I. | Social Sustainability and the Pursuit of Design in Engineering [BibTeX] |
2011 | EWRI Environmental and Water Engineering Practice Vol. 1(1), pp. 5-5 |
article | |
BibTeX:
@article{Embry2011a,
author = {Embry, Irucka},
title = {Social Sustainability and the Pursuit of Design in Engineering},
journal = {EWRI Environmental and Water Engineering Practice},
year = {2011},
volume = {1},
number = {1},
pages = {5--5}
}
|
|||||
| Embry, I. and Painter, R. | Graphical Residence Time Distribution Model for Karst Systems Using MATLAB® and GNU Octave Derived from Independent Gamma Distributions of Tracer Travel Distance and Linear Velocity | 2011 | Proceedings of the 21st Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 13 - 15, 2011, pp. P-22-P-22 | inproceedings | |
| Abstract: The Residence Time Distribution (RTD) is the time that a particle will take to complete its path from the injection to the exit point in a closed system. Most RTD models have used the advection dispersion equation (ADE) for tracer breakthrough curves for karst systems. ADE solutions for tracer breakthrough curves exhibiting near plug flow behavior are usually Gaussian (normally distributed) in nature. This symmetric solution often predicts finite tracer concentrations at zero time and this is not often shown in tracer breakthrough curves, which frequently are characterized by relatively long upper tails. There are few quantitative tracer studies modeling karst systems that have tracer concentrations normally distributed about the mean residence time and few of these models graphically display this distribution. The objective of this project was to create an M-file language computer algorithm in MATLAB® Version 6.5.1 and GNU Octave Version 3.2.4 that combined both the numerical and visual aspects of karst tracer studies. This project used the transformed residence time distribution function using the independent gamma distributions of tracer travel distance and linear velocity. This algorithm computes the transformed RTD function from the time inputs and then displays the RTD function versus Time graph, the Tracer Concentration versus Time graph, and the graph of the tracer concentration normally distributed about the mean residence time. | |||||
BibTeX:
@inproceedings{Embry2011b,
author = {Embry, Irucka and Painter, Roger},
title = {Graphical Residence Time Distribution Model for Karst Systems Using MATLAB® and GNU Octave Derived from Independent Gamma Distributions of Tracer Travel Distance and Linear Velocity},
booktitle = {Proceedings of the 21st Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 13 - 15, 2011},
year = {2011},
pages = {P-22--P-22},
note = {authors with acknowledgments to Byl, Tom D.}
}
|
|||||
| Embry, I., Painter, R. and Byl, T.D. | Residence Time Distribution Model for Non-ideal Flow Derived from Independent Gamma Distributions of Tracer Travel Distance and Linear Velocity | 2011 | Abstract Book of the 32nd Annual Meeting in North America of the Society of Environmental Toxicology and Chemistry (SETAC), Boston, Massachusetts, USA, 13-17 November 2011, pp. 198-198 | inproceedings | |
| Abstract: The Residence Time Distribution (RTD) is the time that a particle will take to complete its path from the injection to the exit point in a closed system. Most RTD models have used the advection dispersion equation (ADE) for tracer breakthrough curves for karst systems. ADE solutions for tracer breakthrough curves exhibiting near plug flow behavior are usually Gaussian (normally distributed) in nature. This symmetric solution often predicts finite tracer concentrations at zero time and this is not often shown in tracer breakthrough curves, which frequently are characterized by relatively long upper tails. There are few quantitative tracer studies modeling karst systems that have tracer concentrations normally distributed about the mean residence time and few of these models graphically display this distribution. The objective of this project was to create an M-file language computer algorithm in MATLAB® Version 6.5.1 and GNU Octave Version 3.2.4 that combined both the numerical and visual aspects of karst tracer studies. This project used the transformed residence time distribution function using the independent gamma distributions of tracer travel distance and linear velocity. This algorithm computes the transformed RTD function from the time inputs and then displays the RTD function versus Time graph, the Tracer Concentration versus Time graph, and the graph of the tracer concentration normally distributed about the mean residence time. | |||||
BibTeX:
@inproceedings{Embry2011c,
author = {Embry, Irucka and Painter, Roger and Byl, Tom D.},
title = {Residence Time Distribution Model for Non-ideal Flow Derived from Independent Gamma Distributions of Tracer Travel Distance and Linear Velocity},
booktitle = {Abstract Book of the 32nd Annual Meeting in North America of the Society of Environmental Toxicology and Chemistry (SETAC), Boston, Massachusetts, USA, 13-17 November 2011},
year = {2011},
pages = {198--198},
note = {Navigating Environmental Challenges: Historical Lessons Guiding Future Directions is the theme of the meeting}
}
|
|||||
| Embry, I., Roland, V., Agbaje, O., Watson, V., Martin, M., Painter, R., Byl, T. and Sharpe, L. | Derivation of a Multiparameter Gamma Model for Analyzing the Residence-Time Distribution Function for Nonideal Flow Systems as an Alternative to the Advection-Dispersion Equation | 2013 | ISRN Chemical Engineering Vol. 2013 |
article | DOI URL |
| Abstract: A new residence-time distribution (RTD) function has been developed and applied to quantitative dye studies as an alternative to the traditional advection-dispersion equation (AdDE). The new method is based on a jointly combined four-parameter gamma probability density function (PDF). The gamma residence-time distribution (RTD) function and its first and second moments are derived from the individual two-parameter gamma distributions of randomly distributed variables, tracer travel distance, and linear velocity, which are based on their relationship with time. The gamma RTD function was used on a steady-state, nonideal system modeled as a plug-flow reactor (PFR) in the laboratory to validate the effectiveness of the model. The normalized forms of the gamma RTD and the advection-dispersion equation RTD were compared with the normalized tracer RTD. The normalized gamma RTD had a lower mean-absolute deviation (MAD) (0.16) than the normalized form of the advection-dispersion equation (0.26) when compared to the normalized tracer RTD. The gamma RTD function is tied back to the actual physical site due to its randomly distributed variables. The results validate using the gamma RTD as a suitable alternative to the advection-dispersion equation for quantitative tracer studies of non-ideal flow systems. | |||||
BibTeX:
@article{Embry2013a,
author = {Embry, Irucka and Roland, Victor and Agbaje, Oluropo and Watson, Valetta and Martin, Marquan and Painter, Roger and Byl, Tom and Sharpe, Lonnie},
title = {Derivation of a Multiparameter Gamma Model for Analyzing the Residence-Time Distribution Function for Nonideal Flow Systems as an Alternative to the Advection-Dispersion Equation},
journal = {ISRN Chemical Engineering},
year = {2013},
volume = {2013},
url = {http://www.hindawi.com/isrn/chemeng/2013/539209/},
doi = {http://dx.doi.org/10.1155/2013/539209}
}
|
|||||
| Embry, I., Roland, V., Painter, R., Toomey, R. and Sharpe, L. | Quantitative Dye Tracing – Development of a New Interpretative Method | 2012 | Proceedings of the 22nd Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 11 - 13, 2012, pp. 1C-6-1C-16 | inproceedings | |
| Abstract: Due to the complexity of possible flow paths in karst aquifers, it is difficult to create a mathematical framework to model the flow of contaminants and other particles through the aquifer. The objective of this project was to apply both traditional methods of tracer interpretations and a new interpretative method to tracer data from a quantitative field tracer study at Mammoth Cave National Park. Generally, a tracer study is performed to qualitatively or quantitatively approximate the flow conditions. The quantitative results of the tracer experiment are displayed in the tracer breakthrough curve which represents the effluent tracer concentration over time. The breakthrough curve can be used to determine the residence time distribution (RTD) function. The RTD function numerically describes the time that particles have spent reacting in a system. This project focuses on the continued development and application of a new dye tracer interpretative method as compared to the traditional advection dispersion equation (ADE) method. The interpretive method is based on the gamma probability density function (PDF) where the tracer travel distance and linear velocity are assumed to be randomly distributed variables with gamma distributions. The gamma RTD function is derived from the individual distributions of tracer travel distance and linear velocity based on their relationship with time. The normalized forms of the gamma RTD and the advection dispersion equation RTD were compared with the normalized tracer RTD. The normalized gamma RTD function had a better fit than the advection dispersion equation RTD function with the tracer RTD function. This conclusion is based on the sum of the squares of the differences (SOSOD) between the normalized form of the gamma and the tracer RTD function versus the SOSOD between the normalized form of the advection dispersion equation and the tracer RTD function. | |||||
BibTeX:
@inproceedings{Embry2012,
author = {Embry, Irucka and Roland, Victor and Painter, Roger and Toomey, Rick and Sharpe, Lonnie},
title = {Quantitative Dye Tracing – Development of a New Interpretative Method},
booktitle = {Proceedings of the 22nd Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 11 - 13, 2012},
year = {2012},
pages = {1C-6--1C-16},
note = {authors with special acknowledgment to Byl, Tom D.}
}
|
|||||
| Enfield, C.G., Wood, A.L., Espinoza, F.P., Brooks, M.C., Annable, M. and Rao, P. | Design of aquifer remediation systems: (1) Describing hydraulic structure and NAPL architecture using tracers | 2005 | Journal of Contaminant Hydrology Vol. 81(1-4), pp. 125-147 |
article | URL |
| Abstract: Aquifer heterogeneity (structure) and NAPL distribution (architecture) are described based on tracer data. An inverse modelling approach that estimates the hydraulic structure and NAPL architecture based on a Lagrangian stochastic model where the hydraulic structure is described by one or more populations of lognormally distributed travel times and the NAPL architecture is selected from eight possible assumed distributions. Optimization of the model parameters for each tested realization is based on the minimization of the sum of the square residuals between the log of measured tracer data and model predictions for the same temporal observation. For a given NAPL architecture the error is reduced with each added population. Model selection was based on a fitness which penalized models for increasing complexity. The technique is demonstrated under a range of hydrologic and contaminant settings using data from three small field-scale tracer tests: the first implementation at an LNAPL site using a line-drive flow pattern, the second at a DNAPL site with an inverted five-spot flow pattern, and the third at the same DNAPL site using a vertical circulation flow pattern. The Lagrangian model was capable of accurately duplicating experimentally derived tracer breakthrough curves, with a correlation coefficient of 0.97 or better. Furthermore, the model estimate of the NAPL volume is similar to the estimates based on moment analysis of field data. | |||||
BibTeX:
@article{Enfield2005,
author = {Enfield, Carl G. and Wood, A. Lynn and Espinoza, Felipe P. and Brooks, Michael C. and Annable, Michael and Rao, P.S.C.},
title = {Design of aquifer remediation systems: (1) Describing hydraulic structure and NAPL architecture using tracers},
journal = {Journal of Contaminant Hydrology},
year = {2005},
volume = {81},
number = {1-4},
pages = {125--147},
url = {http://www.sciencedirect.com/science/article/pii/S0169772205001427}
}
|
|||||
| Engel, A.S., Porter, M.L., Stern, L.A., Quinlan, S. and Bennett, P.C. | Bacterial diversity and ecosystem function of filamentous microbial mats from aphotic (cave) sulfidic springs dominated by chemolithoautotrophic “Epsilonproteobacteria” | 2004 | FEMS Microbiology Ecology Vol. 51(1), pp. 31-53 |
article | URL |
| Abstract: Filamentous microbial mats from three aphotic sulfidic springs in Lower Kane Cave, Wyoming, were assessed with regard to bacterial diversity, community structure, and ecosystem function using a 16S rDNA-based phylogenetic approach combined with elemental content and stable carbon isotope ratio analyses. The most prevalent mat morphotype consisted of white filament bundles, with low C:N ratios (3.5–5.4) and high sulfur content (16.1–51.2%). White filament bundles and two other mat morphotypes had organic carbon isotope values (mean δ13C = −34.7‰, 1σ = 3.6) consistent with chemolithoautotrophic carbon fixation from a dissolved inorganic carbon reservoir (cave water, mean δ13C = −7.4‰ for two springs, n = 8). Bacterial diversity was low overall in the clone libraries, and the most abundant taxonomic group was affiliated with the “Epsilonproteobacteria” (68%), with other bacterial sequences affiliated with Gammaproteobacteria (12.2%), Betaproteobacteria (11.7%), Deltaproteobacteria (0.8%), and the Acidobacterium (5.6%) and Bacteriodetes/Chlorobi (1.7%) divisions. Six distinct epsilonproteobacterial taxonomic groups were identified from the microbial mats. Epsilonproteobacterial and bacterial group abundances and community structure shifted from the spring orifices downstream, corresponding to changes in dissolved sulfide and oxygen concentrations and metabolic requirements of certain bacterial groups. Most of the clone sequences for epsilonproteobacterial groups were retrieved from areas with high sulfide and low oxygen concentrations, whereas Thiothrix spp. and Thiobacillus spp. had higher retrieved clone abundances where conditions of low sulfide and high oxygen concentrations were measured. Genetic and metabolic diversity among the “Epsilonproteobacteria” maximizes overall cave ecosystem function, and these organisms play a significant role in providing chemolithoautotrophic energy to the otherwise nutrient-poor cave habitat. Our results demonstrate that sulfur cycling supports subsurface ecosystems through chemolithoautotrophy and expand the evolutionary and ecological views of “Epsilonproteobacteria” in terrestrial habitats. | |||||
BibTeX:
@article{Engel2004,
author = {Engel, Annette Summers and Porter, Megan L. and Stern, Libby A. and Quinlan, Sarah and Bennett, Philip C.},
title = {Bacterial diversity and ecosystem function of filamentous microbial mats from aphotic (cave) sulfidic springs dominated by chemolithoautotrophic “Epsilonproteobacteria”},
journal = {FEMS Microbiology Ecology},
year = {2004},
volume = {51},
number = {1},
pages = {31--53},
url = {http://www.sciencedirect.com/science/article/pii/S0168649604002272}
}
|
|||||
| Epting, J., Huggenberger, P. and Glur, L. | Integrated investigations of karst phenomena in urban environments | 2009 | Engineering Geology Vol. 109(3-4), pp. 273-289 |
article | URL |
| Abstract: Theories that describe karst systems are often limited to conceptual models. However, engineering projects within complex karst systems demand the development of tools that allow site-specific descriptions of the hydrogeologic settings and calibrating the processes of karst evolution. | |||||
BibTeX:
@article{Epting2009,
author = {Epting, Jannis and Huggenberger, Peter and Glur, Lukas},
title = {Integrated investigations of karst phenomena in urban environments},
journal = {Engineering Geology},
year = {2009},
volume = {109},
number = {3-4},
pages = {273--289},
url = {http://www.sciencedirect.com/science/article/pii/S001379520900221X}
}
|
|||||
| Erel, E. and Ghosh, J.B. | Minimizing weighted mean absolute deviation of job completion times from their weighted mean | 2011 | Applied Mathematics and Computation Vol. 217(22), pp. 9340-9350 |
article | URL |
| Abstract: We address a single-machine scheduling problem where the objective is to minimize the weighted mean absolute deviation of job completion times from their weighted mean. This problem and its precursors aim to achieve the maximum admissible level of service equity. It has been shown earlier that the unweighted version of this problem is NP-hard in the ordinary sense. For that version, a pseudo-polynomial time dynamic program and a 2-approximate algorithm are available. However, not much (except for an important solution property) exists for the weighted version. In this paper, we establish the relationship between the optimal solution to the weighted problem and a related one in which the deviations are measured from the weighted median (rather than the mean) of the job completion times; this generalizes the 2-approximation result mentioned above. We proceed to give a pseudo-polynomial time dynamic program, establishing the ordinary NP-hardness of the problem in general. We then present a fully-polynomial time approximation scheme as well. Finally, we report the findings from a limited computational study on the heuristic solution of the general problem. Our results specialize easily to the unweighted case; they also lead to an approximation of the set of schedules that are efficient with respect to both the weighted mean absolute deviation and the weighted mean completion time. | |||||
BibTeX:
@article{Erel2011,
author = {Erel, Erdal and Ghosh, Jay B.},
title = {Minimizing weighted mean absolute deviation of job completion times from their weighted mean},
journal = {Applied Mathematics and Computation},
year = {2011},
volume = {217},
number = {22},
pages = {9340--9350},
url = {http://www.sciencedirect.com/science/article/pii/S0096300311005777}
}
|
|||||
| Essaid, H.I., Bekins, B.A., Godsy, E.M., Warren, E., Baedecker, M.J. and Cozzarelli, I.M. | Simulation of aerobic and anaerobic biodegradation processes at a crude oil spill site | 1995 | Water Resources Research Vol. 31(12), pp. 3309-3327 |
article | URL |
| Abstract: A two-dimensional, multispecies reactive solute transport model with sequential aerobic and anaerobic degradation processes was developed and tested. The model was used to study the field-scale solute transport and degradation processes at the Bemidji, Minnesota, crude oil spill site. The simulations included the biodegradation of volatile and nonvolatile fractions of dissolved organic carbon by aerobic processes, manganese and iron reduction, and methanogenesis. Model parameter estimates were constrained by published Monod kinetic parameters, theoretical yield estimates, and field biomass measurements. Despite the considerable uncertainty in the model parameter estimates, results of simulations reproduced the general features of the observed groundwater plume and the measured bacterial concentrations. In the simulation, 46% of the total dissolved organic carbon (TDOC) introduced into the aquifer was degraded. Aerobic degradation accounted for 40% of the TDOC degraded. Anaerobic processes accounted for the remaining 60% of degradation of TDOC: 5% by Mn reduction, 19% by Fe reduction, and 36% by methanogenesis. Thus anaerobic processes account for more than half of the removal of DOC at this site. | |||||
BibTeX:
@article{Essaid1995,
author = {Essaid, Hedeff I. and Bekins, Barbara A. and Godsy, E. Michael and Warren, Ean and Baedecker, Mary Jo and Cozzarelli, Isabelle M.},
title = {Simulation of aerobic and anaerobic biodegradation processes at a crude oil spill site},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1995},
volume = {31},
number = {12},
pages = {3309--3327},
url = {http://dx.doi.org/10.1029/95WR02567}
}
|
|||||
| Everts, C. and Kanwar, R. | Evaluation of Rhodamine WT as an adsorbed tracer in an agricultural soil | 1994 | Journal of Hydrology Vol. 153(1-4), pp. 53-70 |
article | URL |
| Abstract: Two column breakthrough tests and a series of 88 batch-equilibrium isotherms were conducted to quantify adsorption parameters for the fluorescent dye Rhodamine WT (Acid Red 388), in contact with a Nicollet loam soil. Results from batch-equilibrium isotherms performed at a 2:1 (water:soil) ratio showed that dye adsorption reached an equilibrium after 10 min on a shaker table. Regression equations were developed to predict distribution coefficients (Kd) for Rhodamine WT (RWT) adsorption to the soil based on soil organic carbon and the ionic strength of the RWT solution. A linear isotherm fitted the batchequilibrium data for RWT in the concentration range evaluated (25–8000 μg 1−1). | |||||
BibTeX:
@article{Everts1994,
author = {Everts, C.J. and Kanwar, R.S.},
title = {Evaluation of Rhodamine WT as an adsorbed tracer in an agricultural soil},
journal = {Journal of Hydrology},
year = {1994},
volume = {153},
number = {1-4},
pages = {53--70},
url = {http://www.sciencedirect.com/science/article/pii/0022169494901864}
}
|
|||||
| Evin, G., Merleau, J. and Perreault, L. | Two-component mixtures of normal, gamma, and Gumbel distributions for hydrological applications | 2011 | Water Resources Research Vol. 47(8), pp. W08525- |
article | URL |
| Abstract: Whether mixtures of distributions are employed as a flexible modeling device to estimate densities or are used to model data thought to arise from several populations, they provide an efficient tool to approximate a distribution. Indeed, mixtures of distributions can model multiple modes, different types of skewness, etc., but they can also be employed to classify observations from heterogeneous data sets. In this paper, we study mixtures of distributions with normal, gamma, and Gumbel components. Moving away from the standard normal setting, gamma mixtures are developed in order to model strictly positive hydrological data and Gumbel mixtures for extreme variates. Since the data analyzed can exhibit dependency through time, we treat both the independent and dependent cases, where the latter is modeled through a Markov process. A fairly unified approach is adopted for the different distributions and the problem is treated from the Bayesian perspective, which enables us to use marginal densities to automatically compare the adequacy of the different models for a given data set. This model-selection framework allows us to formally test the relevance of using mixture models by computing the marginal likelihoods of single distribution models and to verify the presence of a persistence in the time series by comparing independent and identically distributed (IID) and Markovian mixture models. | |||||
BibTeX:
@article{Evin2011,
author = {Evin, G. and Merleau, J. and Perreault, L.},
title = {Two-component mixtures of normal, gamma, and Gumbel distributions for hydrological applications},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2011},
volume = {47},
number = {8},
pages = {W08525--},
url = {http://dx.doi.org/10.1029/2010WR010266}
}
|
|||||
| Eykholt, G.R. and Li, L. | Fate and transport of species in a linear reaction network with different retardation coefficients | 2000 | Journal of Contaminant Hydrology Vol. 46(1-2), pp. 163-185 |
article | URL |
| Abstract: A response function approach is used to generate semi-analytical solutions to model the transport of species within a first-order reaction network. If the retardation coefficients of these species are not the same, product species will either be delayed or displaced forward relative to the reactants. A novel approach is used to simulate linear, kinetic response functions (KRFs) for species in plug flow, then to integrate with the conservative residence time density function (E-curve) to yield a residence time density for the reacted species. This kinetic E-curve can be used with linear operator methods such as convolution to yield the semi-analytical solution for nonuniform inputs, nonideal mixing, and complex reaction networks. Closed-form analytical solutions are presented for the linear response functions for straight, three-member reaction networks in plug flow. Only irreversible reactions are considered. Several examples with various mixing conditions are shown and compared to other analytical solutions. Although the approach is related to other transfer function models, the kinetic residence time density is a transfer function that is generated directly from the plug-flow response functions and the numerical evaluation of the E-curve. The advantage is that a wide variety of mixing conditions and reaction networks may be considered without the need to generate analytical transfer functions for each species and mixing condition. | |||||
BibTeX:
@article{Eykholt2000,
author = {Eykholt, Gerald R. and Li, Lin},
title = {Fate and transport of species in a linear reaction network with different retardation coefficients},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {46},
number = {1-2},
pages = {163--185},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200001133}
}
|
|||||
| Fairchild, I.J., Tuckwell, G.W., Baker, A. and Tooth, A.F. | Modelling of dripwater hydrology and hydrogeochemistry in a weakly karstified aquifer (Bath, UK): Implications for climate change studies | 2006 | Journal of Hydrology Vol. 321(1-4), pp. 213-231 |
article | URL |
| Abstract: A better knowledge of dripwater hydrology in karst systems is needed to understand the palaeoclimate implications of temporal variations in Mg/Ca and Sr/Ca of calcareous cave deposits. Quantitative modelling of drip hydrology and hydrochemistry was undertaken at a disused limestone mine (Brown's Folly Mine) in SW England overlain by 15 m of poorly karstified Jurassic limestones, with sub-vertical fracturing enhanced by proximity to an escarpment. Discharge was monitored at 15 sites intermittently from the beginning of 1996, and every 10–20 days from later 1996 to early 1998. Samples for hydrochemical parameters (pH, alkalinity, cations, anions, fluorescence) were taken corresponding to a sub-set of these data and supplemented by bedrock and soil sampling, limited continuously logged discharge, and soil water observations. Three sites, covering the range of discharge (approximately 1 μL s−1 to 1 ml s-1 maximum discharge) and hydrochemical behaviours, were studied in more detail. A quantitative flow model was constructed, based on two parallel unit hydrographs: responsive and relatively unresponsive to discharge events, respectively. The linear response and conservative mixing assumptions of the model were tested with hydrogeochemical data. | |||||
BibTeX:
@article{Fairchild2006,
author = {Fairchild, Ian J. and Tuckwell, George W. and Baker, Andy and Tooth, Anna F.},
title = {Modelling of dripwater hydrology and hydrogeochemistry in a weakly karstified aquifer (Bath, UK): Implications for climate change studies},
journal = {Journal of Hydrology},
year = {2006},
volume = {321},
number = {1-4},
pages = {213--231},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405003884}
}
|
|||||
| Falk, L. and Commenge, J.-M. | Performance comparison of micromixers | 2010 | Chemical Engineering Science Vol. 65(1)20th International Symposium in Chemical Reaction Engineering—Green Chemical Reaction Engineering for a Sustainable Future, pp. 405-411 |
article | URL |
| Abstract: The present paper proposes a detailed comparison of mixing efficiency of different mixers that have been characterized by the Villermaux/Dushman test reaction. Considering simple relations of mixing in laminar flow, it is shown how to obtain the theoretical mixing time and how to relate it with operating parameters as the Reynolds number of the flow and the specific power dissipation per mass unit of fluid. The comparison of the experimental and of the theoretical mixing times indicates that only a few percents of the total mechanical power transmitted to the fluid is effective for mixing. | |||||
BibTeX:
@article{Falk2010,
author = {Falk, L. and Commenge, J.-M.},
title = {Performance comparison of micromixers},
booktitle = {20th International Symposium in Chemical Reaction Engineering—Green Chemical Reaction Engineering for a Sustainable Future},
journal = {Chemical Engineering Science},
year = {2010},
volume = {65},
number = {1},
pages = {405--411},
url = {http://www.sciencedirect.com/science/article/pii/S0009250909003819}
}
|
|||||
| Falk, L. and Schaer, E. | A PDF modelling of precipitation reactors | 2001 | Chemical Engineering Science Vol. 56(7)Industrial Crystallisation, pp. 2445-2457 |
article | URL |
| Abstract: Efforts to model precipitation processes in chemical reactors need to combine fluid mechanics with precipitation processes description. The main difficulty is to consider together micromixing phenomena, which are known to play an important role, with complex reactions kinetics and particles size distribution in the flow. In the present study, a probability density function (PDF) method is presented to calculate the evolution of the particles size distribution. The main advantage of the method is to include a micromixing model based on a Lagrangian frame where chemical reactions are treated without modelling and which requires minimal computational resources. The micromixing model considered is the interaction and exchange with the mean (IEM). Precipitation reactions are nucleation, growth and aggregation. Because of the nature of the powerful numerical technique used, based on Monte-Carlo simulations, the method is able to produce, at any point in the flow, reactants concentration and supersaturation fields, and the particles size distribution field, by simple moments method. The main advantage of the method over traditional population balance solvers is its capability to treat multi-dimensional (e.g. size, crystal morphology, chemical properties, etc.) population balances just as efficiently as it treats high-dimensional PDF. The PDF code is coupled with the commercial CFD package FLUENT which is used for the turbulent calculation of the flow (classical k–ε turbulence model), where the presence of the solid phase is assumed not to affect the flow field. An example is presented in the case of silica particles aggregation. The influence of initial reactants concentration and hydrodynamics parameter are investigated. | |||||
BibTeX:
@article{Falk2001,
author = {Falk, L. and Schaer, E.},
title = {A PDF modelling of precipitation reactors},
booktitle = {Industrial Crystallisation},
journal = {Chemical Engineering Science},
year = {2001},
volume = {56},
number = {7},
pages = {2445--2457},
url = {http://www.sciencedirect.com/science/article/pii/S0009250900004474}
}
|
|||||
| Falk, M. | Asymptotic independence of median and MAD | 1997 | Statistics & Probability Letters Vol. 34(4), pp. 341-345 |
article | URL |
| Abstract: The asymptotic joint normality of the sample median and the median absolute deviation from the median (MAD) as robust counterparts of sample mean and standard deviation is established. This characterizes their asymptotic independence, paralleling the asymptotic independence of mean and standard deviation. Analogous results are established for the median and the interquartile range. | |||||
BibTeX:
@article{Falk1997,
author = {Falk, Michael},
title = {Asymptotic independence of median and MAD},
journal = {Statistics & Probability Letters},
year = {1997},
volume = {34},
number = {4},
pages = {341--345},
url = {http://www.sciencedirect.com/science/article/pii/S016771529600199X}
}
|
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| Fan, C., Chang, F.-C., Ko, C.-H., Sheu, Y.-S., Teng, C.-J. and Chang, T.-C. | Urban pollutant removal by a constructed riparian wetland before typhoon damage and after reconstruction | 2009 | Ecological Engineering Vol. 35(3), pp. 424-435 |
article | URL |
| Abstract: Flood damage as a result of an extreme weather event is always a potential threat to constructed riparian wetlands in subtropical regions, and such damage can significantly impair the pollutant-removing performance of these wetlands The present study compares the pollutant-removal performance of the Hsin-Hai Bridge constructed wetland in the Tan-shui River basin of metropolitan Taipei in September 2000 (before the system was inundated by flood as a result of Typhoon Aere’) and in mid-October 2004 (after reconstruction of the wetland). The study analyses biochemical oxygen demand (BOD), ammonia nitrogen (NH4-N), and total phosphorus (TP) of influents and effluents in each of several compartments and for the system as a whole before the typhoon and after reconstruction. The study finds that performance with respect to BOD and NH4-N was marginally reduced (with no statistical significance) after reconstruction, but that performance with respect to TP was markedly improved (with statistical significance) after reconstruction. The study provides possible explanations for these findings and concludes that wetlands can be successfully reconstructed after extreme flood damage. | |||||
BibTeX:
@article{Fan2009,
author = {Fan, Chihhao and Chang, Fang-Chih and Ko, Chun-Han and Sheu, Yiong-Shing and Teng, Chia-Ji and Chang, Tzi-Chin},
title = {Urban pollutant removal by a constructed riparian wetland before typhoon damage and after reconstruction},
journal = {Ecological Engineering},
year = {2009},
volume = {35},
number = {3},
pages = {424--435},
url = {http://www.sciencedirect.com/science/article/pii/S092585740800236X}
}
|
|||||
| Fan, L., Shen, B. and Chou, S. | Stochastic modeling of transient residence-time distributions during start-up | 1995 | Chemical Engineering Science Vol. 50(2), pp. 211-221 |
article | URL |
| Abstract: The theory of residence-time distribution, RTD theory in short, is a cornerstone of chemical engineering science and practice, in general, and that of chemical reactor analysis and design, in particular. The creation of the modern, systematic RTD theory has been attributed to Danckwerts. As evident from his liberal adoption of terminologies of probability and statistics, he was apparently well aware of the stochastic nature of the process that gives rise to a residence-time distribution. While Danckwerts steered the development of the RTD theory essentially along the path of deterministic physics, obviously, the description of RTD is better couched in the statistical or stochastic parlance. Stochastic modeling visualizes the fluid in a flow system as being composed of discrete entities. This visualization reveals a greater insight into the underlying mechanism than deterministic modeling, thereby facilitating our understanding of the flow and mixing characteristic of the system. In the present work, an attempt has been made to derive a unified mathematical model of the RTD during process start-up by rigorously resorting to the theories and methodologies of stochastic processes. Specifically, the expressions for RTDs of molecules, fluid particles or any flowing entities passing through continuous flow systems have been derived from the stochastic population balance of these molecules, particles or entities. The resultant expressions are applicable to both unsteady-state and steady-state flow conditions. | |||||
BibTeX:
@article{Fan1995,
author = {Fan, L.T. and Shen, B.C. and Chou, S.T.},
title = {Stochastic modeling of transient residence-time distributions during start-up},
journal = {Chemical Engineering Science},
year = {1995},
volume = {50},
number = {2},
pages = {211--221},
url = {http://www.sciencedirect.com/science/article/pii/000925099400224F}
}
|
|||||
| Faridi, F., Painter, R. and Byl, T. | Biodegradation of Toluene as It Continuously Enters a 5-Liter Laboratory Karst System | 2005 | U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160, pp. 191 | inproceedings | URL |
| Abstract: Contamination releases can occur as slow, long-term spills rather than as instantaneous spills. These continuous releases can result in a steady state of contaminants that can last months to years. Predicting the fate and transport of these contaminants in a karst aquifer is especially challenging because of the complex hydrogeology and uncertainties in residence time. The objective of this research was to adapt the residence- time distribution (RTD) biodegradation model, which was developed to predict the biotransformation of a single spill in a karst aquifer, for a continuous input of contaminants. Theoretically, the RTD for a karst system calculated from either a pulse- or a continuous-input tracer study would be identical, but mathemat- ical manipulation of the data for the two approaches is quite different. Determination of the RTD from a continuous input requires numerical differentiation of tracer response data as opposed to numerical integra- tion for the pulse approach. Three experimental runs were conducted involving the application of a contin- uous input: (1) rhodamine dye alone to establish RTDs for the systems, (2) sterile toluene (25 micrograms per liter) to quantify abiotic sorption, and (3) toluene with karst bacteria to quantify biodegradation. The three replicate karst systems were each 5 liters and had a continuous flow rate of 3.3 milliliters per minute. The difference between the RTD-based model prediction and the experimental toluene conversions was 17 percent. The continuous-input approach (numerical differentiation) had the tendency to magnify experi- mental and random errors in the tracer response data as compared to the pulse-input method (numerical inte- gration). | |||||
BibTeX:
@inproceedings{Faridi2005,
author = {Faridi, Fuzail and Painter, Roger and Byl, T.D.},
title = {Biodegradation of Toluene as It Continuously Enters a 5-Liter Laboratory Karst System},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2005},
pages = {191},
url = {pubs.usgs.gov/sir/2005/5160/index.html}
}
|
|||||
| Farooq, S. and Karimi, I. | Dispersed plug flow model for steady-state laminar flow in a tube with a first order sink at the wall | 2003 | Chemical Engineering Science Vol. 58(1), pp. 71-80 |
article | URL |
| Abstract: Steady state, laminar flow transport in a tube with a first order sink at the wall involves two dimensions—radial and axial. In this paper, a novel iterative technique has been proposed for reducing such a two-dimensional model to an equivalent one-dimensional dispersed plug flow model. The latter yields an analytical expression for the equivalent axial dispersion and a simple, closed form, but approximate, analytical solution of the original two-dimensional problem. The operating range in which this analytical solution is useful has been investigated for a system with mass transfer at the wall. | |||||
BibTeX:
@article{Farooq2003,
author = {Farooq, S and Karimi, I.A},
title = {Dispersed plug flow model for steady-state laminar flow in a tube with a first order sink at the wall},
journal = {Chemical Engineering Science},
year = {2003},
volume = {58},
number = {1},
pages = {71--80},
url = {http://www.sciencedirect.com/science/article/pii/S0009250902004335}
}
|
|||||
| Farthing, M.W., Kees, C.E., Russell, T.F. and Miller, C.T. | An ELLAM approximation for advective–dispersive transport with nonlinear sorption | 2006 | Advances in Water Resources Vol. 29(5), pp. 657-675 |
article | URL |
| Abstract: We consider an Eulerian–Lagrangian localized adjoint method (ELLAM) applied to nonlinear model equations governing solute transport and sorption in porous media. Solute transport in the aqueous phase is modeled by standard advection and hydrodynamic dispersion processes, while sorption is modeled with a nonlinear local-equilibrium model. We present our implementation of finite volume ELLAM (FV-ELLAM) and finite element (FE-ELLAM) discretizations to the reactive transport model and evaluate their performance for several test problems containing self-sharpening fronts. | |||||
BibTeX:
@article{Farthing2006,
author = {Farthing, Matthew W. and Kees, Christopher E. and Russell, Thomas F. and Miller, Cass T.},
title = {An ELLAM approximation for advective–dispersive transport with nonlinear sorption},
journal = {Advances in Water Resources},
year = {2006},
volume = {29},
number = {5},
pages = {657--675},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805001788}
}
|
|||||
| Faulkner, J., Hu, B.X., Kish, S. and Hua, F. | Laboratory analog and numerical study of groundwater flow and solute transport in a karst aquifer with conduit and matrix domains | 2009 | Journal of Contaminant Hydrology Vol. 110(1-2), pp. 34-44 |
article | URL |
| Abstract: New mathematical and laboratory methods have been developed for simulating groundwater flow and solute transport in karst aquifers having conduits imbedded in a porous medium, such as limestone. The Stokes equations are used to model the flow in the conduits and the Darcy equation is used for the flow in the matrix. The Beavers–Joseph interface boundary conditions are adopted to describe the flow exchange at the interface boundary between the two domains. A laboratory analog is used to simulate the conduit and matrix domains of a karst aquifer. The conduit domain is located at the bottom of the transparent plexiglas laboratory analog and glass beads occupy the remaining space to represent the matrix domain. Water flows into and out of the two domains separately and each has its own supply and outflow reservoirs. Water and solute are exchanged through an interface between the two domains. Pressure transducers located within the matrix and conduit domains of the analog provide data that is processed and stored in digital format. Dye tracing experiments are recorded using time-lapse imaging. The data and images produced are analyzed by a spatial analysis program. The experiments provide not only hydraulic head distribution but also capture solute front images and mass exchange measurements between the conduit and matrix domains. In the experiment, we measure and record pressures, and quantify flow rates and solute transport. The results present a plausible argument that laboratory analogs can characterize groundwater water flow, solute transport, and mass exchange between the conduit and matrix domains in a karst aquifer. The analog validates the predictions of a numerical model and demonstrates the need of laboratory analogs to provide verification of proposed theories and the calibration of mathematical models. | |||||
BibTeX:
@article{Faulkner2009,
author = {Faulkner, Jonathan and Hu, Bill X. and Kish, Stephen and Hua, Fei},
title = {Laboratory analog and numerical study of groundwater flow and solute transport in a karst aquifer with conduit and matrix domains},
journal = {Journal of Contaminant Hydrology},
year = {2009},
volume = {110},
number = {1-2},
pages = {34--44},
url = {http://www.sciencedirect.com/science/article/pii/S0169772209001107}
}
|
|||||
| Faunt, C., Belitz, K. and Hanson, R. | Development of a three-dimensional model of sedimentary texture in valley-fill deposits of Central Valley, California, USA | 2010 | Hydrogeology Journal Vol. 18(3), pp. 625-649 |
article | URL |
| Abstract: A three-dimensional (3D) texture model was developed to help characterize the aquifer system of Central Valley, California (USA), for a groundwater flow model. The 52,000-km 2 Central Valley aquifer system consists of heterogeneous valley-fill deposits. The texture model was developed by compiling and analyzing approximately 8,500 drillers’ logs, describing lithologies up to 950 m below land surface. The lithologic descriptions on the logs were simplified into a binary classification of coarse- and fine-grained. The percentage of coarse-grained sediment, or texture, was then computed for each 15-m depth interval. The model was developed by 3D kriging of the percentage of coarse-grained deposits onto a 1.6-km spatial grid at 15-m depth intervals from land surface down to 700 m below land surface. The texture model reflects the known regional, spatial, and vertical heterogeneity in the aquifer system. The texture model correlates to sediment source areas, independently mapped geomorphic provinces, and factors affecting the development of alluvial fans, thus demonstrating the utility of using tcdrillers’ logs as a source of lithologic information. The texture model is upscaled to a layered groundwater flow model for use in defining the hydraulic properties of the aquifer system. | |||||
BibTeX:
@article{Faunt2010,
author = {Faunt, Claudia and Belitz, Kenneth and Hanson, Randall},
title = {Development of a three-dimensional model of sedimentary texture in valley-fill deposits of Central Valley, California, USA},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2010},
volume = {18},
number = {3},
pages = {625--649},
url = {http://dx.doi.org/10.1007/s10040-009-0539-7}
}
|
|||||
| Felton, G.K. and Currens, J.C. | Peak flow rate and recession-curve characteristics of a karst spring in the Inner Bluegrass, central Kentucky | 1994 | Journal of Hydrology Vol. 162(1-2), pp. 99-118 |
article | URL |
| Abstract: The flow rate at the terminal spring of a 1929 ha karst ground-water catchment has been continuously monitored for 2 years, and 108 identifiable events were analyzed. The peak flow rates followed a beta frequency distribution with parameters α = 0.365 and γ = 1.135. Events were separated into high-flow and low-flow. High-flow events had characteristics attributable to pipe flow. Correlation and stepwise regression were used to develop peak flow rate prediction equations for the combined 108 events and for the 81 low-flow events. The portion of the recession curve identified as pipe flow was a watershed constant and time invariant. The base flow was seasonal, increasing in the winter to approximately 0.071 m3s−1 and decreasing in the summer to approximately 0.014 m3s−1. | |||||
BibTeX:
@article{Felton1994,
author = {Felton, Gary K. and Currens, James C.},
title = {Peak flow rate and recession-curve characteristics of a karst spring in the Inner Bluegrass, central Kentucky},
journal = {Journal of Hydrology},
year = {1994},
volume = {162},
number = {1-2},
pages = {99--118},
url = {http://www.sciencedirect.com/science/article/pii/002216949490006X}
}
|
|||||
| Fen, C.-S. and Abriola, L.M. | A comparison of mathematical model formulations for organic vapor transport in porous media | 2004 | Advances in Water Resources Vol. 27(10), pp. 1005-1016 |
article | URL |
| Abstract: Investigation of the behavior of volatile organic contamination in unsaturated soils requires a thorough understanding of vapor transport processes. This paper presents a modeling investigation of one-dimensional, transient, binary gas transport in open porous systems. Several model formulations, based on mass and molar balance equations and Fickian-type diffusion expressions are compared to predictions of the full set of the Dusty Gas model (DGM) equations. The DGM is also used to investigate the relative contributions of various mechanisms to predictions of transient transport behavior for a number of diffusing species and porous media. This research reveals that, in general, predictions of a molar-based advection-Fickian-type diffusion model agree more closely with DGM results than mass-based model predictions. A modified definition of tortuosity for use in Fickian-type diffusion models is proposed to reduce model discrepancies in low permeability media. Results also demonstrate that application of a mass-based coupled flow and transport model to non-equimolar species transport can lead to substantial errors in transport predictions, especially under transient conditions in diffusion-dominated systems, due to discrepancies between Darcy and mass average velocities. | |||||
BibTeX:
@article{Fen2004,
author = {Fen, Chiu-Shia and Abriola, Linda. M.},
title = {A comparison of mathematical model formulations for organic vapor transport in porous media},
journal = {Advances in Water Resources},
year = {2004},
volume = {27},
number = {10},
pages = {1005--1016},
url = {http://www.sciencedirect.com/science/article/pii/S0309170804001253}
}
|
|||||
| Feng, X., Kirchner, J.W. and Neal, C. | Measuring catchment-scale chemical retardation using spectral analysis of reactive and passive chemical tracer time series | 2004 | Journal of Hydrology Vol. 292(1–4), pp. 296-307 |
article | URL |
| Abstract: Catchment-scale chemical transport is jointly controlled by hydrological and chemical processes. Water may take a complex set of flowpaths underground toward the stream, carrying soluble substances with it. Some chemical constituents are non-reactive; these act as passive tracers, moving with the water. Other constituents react with the porous medium; concentrations of these reactive tracers reveal how porewaters chemically interact with the subsurface. Thus, passive and reactive chemical tracers are indispensable tools for understanding hydrological and chemical processes at whole-catchment scale. | |||||
BibTeX:
@article{Feng2004,
author = {Feng, Xiahong and Kirchner, James W. and Neal, Colin},
title = {Measuring catchment-scale chemical retardation using spectral analysis of reactive and passive chemical tracer time series},
journal = {Journal of Hydrology},
year = {2004},
volume = {292},
number = {1–4},
pages = {296--307},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404000551}
}
|
|||||
| Fernandes, M. and Grammig, J. | Nonparametric specification tests for conditional duration models | 2005 | Journal of Econometrics Vol. 127(1), pp. 35-68 |
article | URL |
| Abstract: This paper deals with the testing of autoregressive conditional duration (ACD) models by gauging the distance between the parametric density and hazard rate functions implied by the duration process and their non-parametric estimates. We derive the asymptotic justification using the functional delta method for fixed and gamma kernels, and then investigate the finite-sample properties through Monte Carlo simulations. Although our tests display some size distortion, bootstrapping suffices to correct the size without compromising their excellent power. We show the practical usefulness of such testing procedures for the estimation of intraday volatility patterns. | |||||
BibTeX:
@article{Fernandes2005,
author = {Fernandes, Marcelo and Grammig, Joachim},
title = {Nonparametric specification tests for conditional duration models},
journal = {Journal of Econometrics},
year = {2005},
volume = {127},
number = {1},
pages = {35--68},
url = {http://www.sciencedirect.com/science/article/pii/S030440760400137X}
}
|
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| Fernandez-Cortes, A., Calaforra, J. and Sanchez-Martos, F. | Spatiotemporal analysis of air conditions as a tool for the environmental management of a show cave (Cueva del Agua, Spain) | 2006 | Atmospheric Environment Vol. 40(38), pp. 7378-7394 |
article | URL |
| Abstract: We recorded the air temperature and carbon dioxide concentration within the Cueva del Agua, a cave in Spain, under natural conditions prior to the cave being opened to tourists. Geostatistical tools are useful techniques for characterizing microclimate parameters with the aim of adopting measures to ensure the conservation and sound environmental management of tourist caves. We modelled the spatial distribution of these microclimatic parameters over an annual cycle using iterative residual kriging, revealing the stratification of air related to the cave's topography. Replenishment of the cave air is activated by convective circulation that accompanies the development of inversions in the thermal gradient of the air. Comparison of the spatial distribution of each microclimatic parameter over time enables us to characterize the exchange of air between the cave interior and the outside, as well as identify potential areas that could be opened to tourists and determine suitable visiting schedules. | |||||
BibTeX:
@article{Fernandez-Cortes2006,
author = {Fernandez-Cortes, A. and Calaforra, J.M. and Sanchez-Martos, F.},
title = {Spatiotemporal analysis of air conditions as a tool for the environmental management of a show cave (Cueva del Agua, Spain)},
journal = {Atmospheric Environment},
year = {2006},
volume = {40},
number = {38},
pages = {7378--7394},
url = {http://www.sciencedirect.com/science/article/pii/S135223100600700X}
}
|
|||||
| Ferreira, J.S. and Costa, M. | Implicit formulation for advection–diffusion simulation based on particle distribution moments | 2007 | Applied Mathematical Modelling Vol. 31(3), pp. 404-416 |
article | URL |
| Abstract: This paper introduces an implicit method for advection–diffusion equations called Implicit DisPar, based on particle displacement moments applied to uniform grids. The present method tries to solve constraints associated with explicit methods also based on particle displacement methods, in which diffusivity-dominated situations can only be handled by considerably increasing the associated computational costs. In fact, a higher particle destination nodes number allows the use of higher diffusion coefficients for the transport simulation without instabilities. The average was evaluated by an analogy between the Fokker–Planck and the transport equations. The variance is considered to be Fickian. The particle displacement distribution is used to predict deterministic mass transfers between domain nodes. Mass conservation was guaranteed by the distribution concept. In the truncation error analysis, it was shown that the linear Implicit DisPar formulation does not have numerical error up to v − 1 order, if the first v particle moments are forced by the Gaussian moments. It was shown by theoretical tests for linear conditions that the model accuracy level is proportional to the number of particle destination nodes. | |||||
BibTeX:
@article{Ferreira2007,
author = {Ferreira, João Serpa and Costa, Manuel},
title = {Implicit formulation for advection–diffusion simulation based on particle distribution moments},
journal = {Applied Mathematical Modelling},
year = {2007},
volume = {31},
number = {3},
pages = {404--416},
url = {http://www.sciencedirect.com/science/article/pii/S0307904X05002416}
}
|
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| Fesch, C., Lehmann, P., Haderlein, S.B., Hinz, C., Schwarzenbach, R.P. and Flühler, H. | Effect of water content on solute transport in a porous medium containing reactive micro-aggregates | 1998 | Journal of Contaminant Hydrology Vol. 33(1-2), pp. 211-230 |
article | URL |
| Abstract: The water content of porous media may substantially affect the transport behaviour of conservative and sorbing solutes. Physical processes potentially involved include alterations of the flow velocities, flow patterns, or of accessible surface sites. We performed column experiments using a synthetic porous medium, in which a substantial part of the sorption sites was concentrated in regions within small grained aggregates that were accessible only by diffusion, a feature often found in natural soils and sediments. We investigated the transport of solutes exhibiting very different sorption characteristics under steady state conditions at different water contents of the porous medium. The tracers used were either nonreactive, partitioned into organic matter or sorbed specifically and nonlinearly to clay minerals. Hydrodynamic dispersion generally increased with decreasing water content, reflected by the breakthrough curves (BTCs) of conservative and only slightly sorbing tracers, which exhibited stronger spreading and early breakthrough of the fronts at lower water saturation. Nonlinear sorption and nonequilibrium mass transfer between the mobile region and the immobile water present within the aggregates dominated the BTCs of the strongly sorbing tracer at all degrees of water saturation, and, thus, rendered the effects of increased hydrodynamic dispersion negligible. Due to a relative increase in the ratio of sorption sites per water volume, the retardation of this tracer distinctly increased at low water contents of the porous medium. Solute transport of all tracers was successfully simulated with an advective–dispersive transport model that considered the respective sorption behaviour and retarded intra-aggregate diffusion as predominant processes. All parameter values of the model had been determined previously in independent experiments under completely saturated conditions. Our results demonstrate that a well parameterised transport model that was calibrated under completely saturated conditions was able to describe rate-limited advective-dispersive transport of reactive solutes also under unsaturated steady-state conditions. Enhanced relative retardation of strongly sorbing compounds under such conditions is likely to affect biological and chemical transformation processes of these compounds. | |||||
BibTeX:
@article{Fesch1998,
author = {Fesch, Claudia and Lehmann, Peter and Haderlein, Stefan B. and Hinz, Christoph and Schwarzenbach, René P. and Flühler, Hannes},
title = {Effect of water content on solute transport in a porous medium containing reactive micro-aggregates},
journal = {Journal of Contaminant Hydrology},
year = {1998},
volume = {33},
number = {1-2},
pages = {211--230},
url = {http://www.sciencedirect.com/science/article/pii/S0169772298000710}
}
|
|||||
| Fesch, C., Simon, W., Haderlein, S.B., Reichert*, P. and Schwarzenbach, R.P. | Nonlinear sorption and nonequilibrium solute transport in aggregated porous media: Experiments, process identification and modeling | 1998 | Journal of Contaminant Hydrology Vol. 31(3-4), pp. 373-407 |
article | URL |
| Abstract: The combined effects of nonlinear sorption, nonequilibrium mass transfer and the distribution of sorption sites on transport of organic contaminants has been examined in porous media containing aggregates of clay minerals and organic matter as sorbents. The major goal was to develop general concepts for describing, deterministically, the transport processes of solutes with different adsorption characteristics in such systems. Various sets of batch adsorption and miscible displacement experiments were performed covering a wide range of time scales and other experimental conditions. Using a multiple reactive tracer approach, independent information was obtained on the hydrodynamic properties of the columns, on the relative importance of the two different sorbents present, and on the accessibility and the distribution of these sorbents at the pore scale. The breakthrough curves (BTCs) of the nonlinearly sorbing tracer generally exhibited sharp fronts and excessive tailing, consistent with the Langmuir–Freundlich type adsorption at clays. The effect of nonequilibrium mass transfer was most evident from the tailing of the self-sharpened fronts of the BTCs and from the results of interrupted flow experiments. A two-region model, which incorporated nonlinear sorption and retarded intra-aggregate diffusion, successfully described the results of our entire set of miscible displacement data using a single set of parameter values. Our study demonstrates that although nonlinear sorption and nonequilibrium mass transfer may have very similar effects on solute BTCs, these processes can be distinguished from experimental data if experiments with different solutes, different flow rates and different input concentrations are evaluated simultaneously. It is shown that a very small volume fraction of immobile regions (<0.1% of total porosity), which is insignificant for the transport of conservative solutes, may strongly affect the transport of sorbing solutes if sorption sites are concentrated within these regions. In soils and aquifers, clay minerals and other reactive surfaces are often present in aggregates. Thus, the transport of solutes that strongly interact with such sites generally is very susceptible to rate-limited mass transfer processes while the transport of conservative tracers is poorly affected. | |||||
BibTeX:
@article{Fesch1998a,
author = {Fesch, Claudia and Simon, Werner and Haderlein, Stefan B and Reichert*, Peter and Schwarzenbach, René P},
title = {Nonlinear sorption and nonequilibrium solute transport in aggregated porous media: Experiments, process identification and modeling},
journal = {Journal of Contaminant Hydrology},
year = {1998},
volume = {31},
number = {3-4},
pages = {373--407},
url = {http://www.sciencedirect.com/science/article/pii/S0169772297000788}
}
|
|||||
| Field, M.S. | Karst hydrology and chemical contamination | 1993-1994 | Journal of Environmental Systems Vol. 22(1), pp. 1-26 |
article | URL |
| Abstract: Ground-water flow in karst aquifers is very different from flow in granular or fractured aquifers. Karst ground-water flow is often turbulent within discrete conduits that are convergent in their upper reaches and may be divergent in their very lower reaches, simulating the flow pattern of surface water streams that are dendritic or trellised but with discharge to one or more springs. Significant precipitation events tend to flood karst aquifers quickly, causing a rapid rise in the potentiometric surface that may flood older, higher levels which discharge to a different set of springs. The epikarstic zone in karst terranes stores and directs infiltrating water down discrete percolation points. Chemical contamination may be fed directly to a karst aquifer via overland flow to a sinkhole with little or no attenuation and may contaminate downgradient wells, springs, and sinkholes within a few hours or a few days. Contaminants may also become temporarily stored in the epikarstic zone for eventual release to the aquifer. Flood pulses may flush the contaminants to cause transiently higher levels of contamination in the aquifer and discharge points. The convergent nature of flow in karst aquifers may result in contaminants becoming concentrated in conduits. Once contaminants have reached the subsurface conduits, they are likely to be rapidly transported to spring outlets. Traditional aquifer remediation techniques for contaminated aquifers are less applicable to karst aquifers | |||||
BibTeX:
@article{Field1993,
author = {Field, Malcolm S.},
title = {Karst hydrology and chemical contamination},
journal = {Journal of Environmental Systems},
year = {1993-1994},
volume = {22},
number = {1},
pages = {1--26},
url = {http://baywood.metapress.com/openurl.asp?genre=article&id=doi:10.2190/X7MV-C93E-66GK-BFH7}
}
|
|||||
| Field, M.S. | Application of robust statistical methods to background tracer data characterized by outliers and left-censored data | 2011 | Water Research Vol. 45(10), pp. 3107-3118 |
article | URL |
| Abstract: Accurate analysis of tracer-breakthrough curves is dependent on the removal of measured background concentrations from the measured tracer recovery data. Background concentrations are commonly converted to a single mean background concentration that is subtracted from tracer recovery data. To obtain an improved estimate for the mean background concentration, a statically-robust procedure addressing left-censored data and possible outliers in background concentration data is presented. A maximum likelihood estimate and other robust methods coupled with outlier removal are applied. Application of statically-robust procedures to background concentrations results not only in better estimates for mean background concentration but also results in more accurate quantitative analyses of tracer-breakthrough curves when the mean background concentration is subtracted. | |||||
BibTeX:
@article{Field2011,
author = {Field, Malcolm S.},
title = {Application of robust statistical methods to background tracer data characterized by outliers and left-censored data},
journal = {Water Research},
year = {2011},
volume = {45},
number = {10},
pages = {3107--3118},
url = {http://www.sciencedirect.com/science/article/pii/S0043135411001291}
}
|
|||||
| Field, M.S. | Assessing Aquatic Ecotoxicological Risks Associated with Fluorescent Dyes Used for Water-Tracing Studies | 2005 | Environmental & Engineering Geoscience Vol. 11(4), pp. 295-308 |
article | DOI URL |
| Abstract: Hydrological tracer testing is the most reliable diagnostic technique available for identifying and quantifying hydrodispersive transport processes. As such, hydrologic tracing is an essential tool that is commonly used to establish flow trajectories, to understand solute-transport processes, and to develop human health and ecological risk assessments. Unfortunately, the use of anthropogenic materials to trace the flow of water may also impart another source of risk to human health and the environment. In general, attempts are usually made to deliberately release tracer agents at concentrations far below their recognized toxic levels. Ecotoxicologically safe levels for injection concentrations of fluorescent tracer agents are generally set at levels far below that which are necessary to maintain measurable downstream concentrations. Appropriate tracer test design is important, because incorrect tracer-mass estimates may result in the release of larger tracer masses than are necessary and that exceed expected environmental concentrations (EECs). To maintain tracer concentrations at or below accepted levels, optimal tracer-test design is essential and may be achieved using the Efficient Hydrologic Tracer-Test Design methodology. By applying an optimal tracer-test design, it is more likely that downstream tracer EECs will be maintained at or below accepted concentrations while maintaining sufficiently high downstream EECs necessary for positive tracer detection. | |||||
BibTeX:
@article{Field2005,
author = {Field, Malcolm S.},
title = {Assessing Aquatic Ecotoxicological Risks Associated with Fluorescent Dyes Used for Water-Tracing Studies},
journal = {Environmental & Engineering Geoscience},
year = {2005},
volume = {11},
number = {4},
pages = {295--308},
url = {http://eeg.geoscienceworld.org/content/11/4/295.abstract},
doi = {http://dx.doi.org/10.2113/11.4.295}
}
|
|||||
| Field, M.S. | A review of some tracer-test design equations for tracer-mass estimation and sample-collection frequency | 2003 | Environmental Geology Vol. 43(8), pp. 867-881 |
article | URL |
| Abstract: Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estimation equations have been developed over the past century. These 33 equations are reviewed here, 32 of which were evaluated using previously published tracer-test design examination parameters. Comparison of the results produced a wide range of estimated tracer mass, but no means is available by which one equation may be reasonably selected over the others. Each equation produces a simple approximation for tracer mass. Most of the equations are based primarily on estimates or measurements of discharge, transport distance, and suspected transport times. Although the basic field parameters commonly employed are appropriate for estimating tracer mass, the 33 equations are problematic in that they were all probably based on the original developers experience in a particular field area and not necessarily on measured hydraulic parameters or solute-transport theory. Suggested sampling frequencies are typically based primarily on probable transport distance, but with little regard to expected travel times. This too is problematic in that tracer sampling remains a haphazard process that tends to result in false negatives or data aliasing. Simulations from the recently developed efficient hydrologic tracer-test design methodology (EHTD) were compared with those obtained from 32 of the 33 published tracer-mass estimation equations and suggested sampling frequencies. EHTD applies functional relationships developed from hydrologic measurements in a solute-transport model to develop a preliminary tracer-breakthrough curve that has been shown to reasonably predict actual tracer-test results. | |||||
BibTeX:
@article{Field2003a,
author = {Field, Malcolm S.},
title = {A review of some tracer-test design equations for tracer-mass estimation and sample-collection frequency},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2003},
volume = {43},
number = {8},
pages = {867--881},
url = {http://dx.doi.org/10.1007/s00254-002-0708-7}
}
|
|||||
| Field, M.S. | Efficient hydrologic tracer-test design for tracer-mass estimation and sample-collection frequency. 2. Experimental results | 2002 | Environmental Geology Vol. 42(7), pp. 839-850 |
article | URL |
| Abstract: Effective tracer-test design requires that the likely results be predicted in advance of test initiation to ensure tracer-test success. EHTD-predicted breakthrough curves (BTCs) for various hydrological conditions were compared with measured BTCs obtained from actual tracer tests. The hydrological conditions for the tracer tests ranged from flowing streams to porous-media systems. Tracer tests evaluated included flowing streams tracer tests conducted in small and large surface-water streams, a karst solution conduit, and a glacial-meltwater stream and porous-media systems conducted as natural-gradient, forced-gradient, injection-withdrawal, and recirculation tracer tests. Comparisons between the actual tracer tests and the predicted results showed that tracer breakthrough, hydraulic characteristics, and sample-collection frequency may be forecasted sufficiently well in most instances as to facilitate good tracer-test design. Comparisons were generally improved by including tracer decay and/or retardation in the simulations. Inclusion of tracer decay in the simulations also tended to require an increase in set average tracer concentration to facilitate matching peak concentrations in the measured BTCs, however. Both nonreactive tracer and reactive tracer predictions produced recommended sample-collection frequencies that would adequately define the actual BTCs, but estimated tracer-mass estimates were less precise. | |||||
BibTeX:
@article{Field2002,
author = {Field, Malcolm S.},
title = {Efficient hydrologic tracer-test design for tracer-mass estimation and sample-collection frequency. 2. Experimental results},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2002},
volume = {42},
number = {7},
pages = {839--850},
url = {http://dx.doi.org/10.1007/s00254-002-0592-1}
}
|
|||||
| Field, M.S. | Efficient hydrologic tracer-test design for tracer-mass estimation and sample-collection frequency, 1. method development | 2002 | Environmental Geology Vol. 42(7), pp. 827-838 |
article | URL |
| Abstract: Hydrological tracer testing is the most reliable diagnostic technique available for the determination of basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed to facilitate the design of tracer tests by root determination of the one-dimensional advection-dispersion equation (ADE) using a preset average tracer concentration which provides a theoretical basis for an estimate of necessary tracer mass. The method uses basic measured field parameters (e.g., discharge, distance, cross-sectional area) that are combined in functional relationships that describe solute-transport processes related to flow velocity and time of travel. These initial estimates for time of travel and velocity are then applied to a hypothetical continuous stirred tank reactor (CSTR) as an analog for the hydrological-flow system to develop initial estimates for tracer concentration, tracer mass, and axial dispersion. Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be necessary for describing the predicted tracer-breakthrough curve (BTC). Inclusion of tracer retardation and decay cause a net increase in tracer-mass estimates so that the preset average tracer concentration will be maintained and there will be a consequent steepening of the BTC, but retardation also causes BTC spreading and a delay in tracer arrival. | |||||
BibTeX:
@article{Field2002a,
author = {Field, Malcolm S.},
title = {Efficient hydrologic tracer-test design for tracer-mass estimation and sample-collection frequency, 1. method development},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2002},
volume = {42},
number = {7},
pages = {827--838},
url = {http://dx.doi.org/10.1007/s00254-002-0591-2}
}
|
|||||
| Field, M.S. | The QTRACER2 Program for Tracer Break-through Curve Analysis For Tracer Tests in Karst Aquifers and Other Hydrologic Systems [BibTeX] |
2002 | , pp. 194-194 | manual | |
BibTeX:
@manual{Field2002b,
author = {Field, Malcolm S.},
title = {The QTRACER2 Program for Tracer Break-through Curve Analysis For Tracer Tests in Karst Aquifers and Other Hydrologic Systems},
year = {2002},
pages = {194--194},
note = {EPA/600/R-02/001}
}
|
|||||
| Field, M.S. | Risk assessment methodology for karst aquifers: (2) solute-transport modeling | 1997 | Environmental Monitoring and Assessment Vol. 47(1), pp. 23-37 |
article | URL |
| Abstract: Ground-water flow and solute-transport simulation modeling are major components of most exposure and risk assessments of contaminated aquifers. Model simulations provide information on the spatial and temporal distributions of contaminants in subsurface media but are difficult to apply to karst aquifers in which conduit flow is important. Ground-water flow and solute transport in karst conduits typically display rapid-flow velocities, turbulent-flow regimes, concentrated pollutant-mass discharge, and exhibit open-channel or closed-conduit flow. Conventional ground-water models, dependent on the applicability of Darcy`s law, are inappropriate when applied to karst aquifers because of the (1) nonapplicability of Darcian-flow parameters, (2) typically nonlaminar flow regime, and (3) inability to locate the karst conduits through which most flow and contaminant transport occurs. Surface-water flow and solute-transport models conditioned on a set of parameters determined empirically from quantitative ground-water tracing studies may be effectively used to render fate-and-transport values of contaminants in karst conduits. Hydraulic-flow and geometric parameters developed in a companion paper were used in the surface-water model, TOXI5, to simulate hypothetical slug and continuous-source releases of ethylbenzene in a karst conduit. TOXI5 simulation results showed considerable improvement for predicted ethylbenzene-transport rates and concentrations over qualitative tracing and analytical ground-water model results. Ethylbenzene concentrations predicted by TOXI5 simulations were evaluated in exposure and risk assessment models. | |||||
BibTeX:
@article{Field1997b,
author = {Field, Malcolm S.},
title = {Risk assessment methodology for karst aquifers: (2) solute-transport modeling},
journal = {Environmental Monitoring and Assessment},
publisher = {Springer Netherlands},
year = {1997},
volume = {47},
number = {1},
pages = {23--37},
url = {http://dx.doi.org/10.1023/A:1005782102565}
}
|
|||||
| Field, M.S. and Leij, F.J. | Solute transport in solution conduits exhibiting multi-peaked breakthrough curves | 2012 | Journal of Hydrology Vol. 440–441(0), pp. 26-35 |
article | URL |
| Abstract: Summary Solute transport in karst aquifers is primarily constrained to solution conduits where transport is rapid, turbulent, and relatively unrestrictive. Breakthrough curves generated from tracer tests are typically positively-skewed and may exhibit multiple peaks. In order to understand the circumstances under which multi-peaked positively skewed breakthrough curves occur, physical experiments utilizing single- and multiple-flow channels were conducted. Experiments also included waterfalls, short-term solute detention in pools, and flow obstructions. Results demonstrated that breakthrough curve skewness nearly always occurs to some degree but is magnified as immobile-flow regions are encountered. Multi-peaked breakthrough curves occurred when flow in the main channel became partially occluded from blockage in the main channel that forced divergence of solute into auxiliary channels and when waterfalls and detention in pools occurred. Currently, multi-peaked breakthrough curves are fitted by a multi-dispersion model in which a series of curves generated by the advection–dispersion equation are fitted to each measured peak by superimposing the measured breakthrough curve to obtain a combined model fit with a consequent set of estimated velocities and dispersions. In this paper, a dual-advection dispersion equation with first-order mass transfer between conduits was derived. The dual-advection dispersion equation was then applied to the multi-peaked breakthrough curves obtained from the physical experiments in order to obtain some insight into the operative solute-transport processes through the acquisition of a consequent set of velocities, dispersions, and related parameters. Successful application of the dual-advection, dispersion equation to a tracer test that exhibited dual peaks for a karst aquifer known to consist of two connected but mostly separate conduits confirmed the appropriateness of using a multi-dispersion type model when conditions warrant. | |||||
BibTeX:
@article{Field2012,
author = {Field, Malcolm S. and Leij, Feike J.},
title = {Solute transport in solution conduits exhibiting multi-peaked breakthrough curves},
journal = {Journal of Hydrology},
year = {2012},
volume = {440–441},
number = {0},
pages = {26--35},
url = {http://www.sciencedirect.com/science/article/pii/S0022169412002168}
}
|
|||||
| Field, M.S. and Mose, D.G. | Estimating subsurface fissure apertures in karst aquifers from equilibrium activities | 1998 | Environmental & Engineering Geoscience Vol. 4(2), pp. 145-159 |
article | URL |
| Abstract: 222 Rn activities were determined for the karst aquifer underlying Walkersville, Maryland, in an area of ground-water discharge from a single geological unit during the summer and fall seasons. Radon-222 equilibrium activities in karst ground waters can be employed in mass-balance models to estimate microfissure, macrofissure, and conduit aperture dimensions. This approach defines 222 Rn generation and loss in karst aquifers as a function of fissure apertures and the 238 U content of the rock. High 222 Rn activities occur in tight fissures and low 222 Rn activities occur in conduits. In the vadose zone, 222 Rn activities are low as a result of degassing, especially if flow is turbulent and activities are decoupled from the phreatic zone. In the phreatic zone, if recharge to fissures causes a reduction of residence time below that required for equilibrium ( nearly equal 26 days), 222 Rn activities fall. At springs and in the vadose zone, after a rainfall event, 222 Rn activities increase as waters with long residence and with high 222 Rn activities are expelled from fissure and fracture storage. Field data and selected literature values were used to test the model. Models used to predict median microfissure apertures for this karst aquifer yield aperture estimates ranging from 2.8 mu m to 9.2 mu m. Median macrofissure apertures ranged from 5.53 cm to 5.88 cm. Median conduit apertures ranged from 1.16 m to 1.24 m. Comparison of the models results with published data on karst aquifers and observations at the field site suggest that the predicted apertures are reasonable. | |||||
BibTeX:
@article{Field1998,
author = {Field, Malcolm S. and Mose, Douglas G.},
title = {Estimating subsurface fissure apertures in karst aquifers from equilibrium activities},
journal = {Environmental & Engineering Geoscience},
year = {1998},
volume = {4},
number = {2},
pages = {145--159},
url = {http://eeg.geoscienceworld.org/content/4/2/145.abstract}
}
|
|||||
| Field, M.S. and Nash, S.G. | Risk assessment methodology for karst aquifers: (1) estimating karst conduit-flow parameters | 1997 | Environmental Monitoring and Assessment Vol. 47(1), pp. 1-21 |
article | URL |
| Abstract: Quantitative ground-water tracing of conduit-dominated karst aquifers allows for reliable and practical interpretation of karst ground-water flow. Insights into the hydraulic geometry of the karst aquifer may be acquired that otherwise could not be obtained by such conventional methods as potentiometric-surface mapping and aquifer testing. Contamination of karst aquifers requires that a comprehensive tracer budget be performed so that karst conduit hydraulic-flow and geometric parameters be obtained. Acquisition of these parameters is necessary for estimating contaminant fate-and-transport. A FORTRAN computer program for estimating total tracer recovery from tracer-breakthrough curves is proposed as a standard method. Estimated hydraulic-flow parameters include mean residence time, mean flow velocity, longitudinal dispersivity, Peclet number, Reynolds number, and Froude number. Estimated geometric parameters include karst conduit sinuous distance, conduit volume, cross-sectional area, diameter, and hydraulic depth. These parameters may be used to (1) develop structural models of the aquifer, (2) improve aquifer resource management, (3) improve ground-water monitoring systems design, (4) improve aquifer remediation, and (5) assess contaminant fate-and-transport. A companion paper demonstrates the use of these hydraulic-flow and geometric parameters in a surface-water model for estimating contaminant fate-and-transport in a karst conduit. Two ground-water tracing studies demonstrate the utility of this program for reliable estimation of necessary karst conduit hydraulic-flow and geometric parameters. | |||||
BibTeX:
@article{Field1997a,
author = {Field, Malcolm S. and Nash, Stephen G.},
title = {Risk assessment methodology for karst aquifers: (1) estimating karst conduit-flow parameters},
journal = {Environmental Monitoring and Assessment},
publisher = {Springer Netherlands},
year = {1997},
volume = {47},
number = {1},
pages = {1--21},
url = {http://dx.doi.org/10.1023/A:1005753919403}
}
|
|||||
| Field, M.S. and Pinsky, P.F. | A two-region nonequilibrium model for solute transport in solution conduits in karstic aquifers | 2000 | Journal of Contaminant Hydrology Vol. 44(3-4), pp. 329-351 |
article | URL |
| Abstract: A two-region nonequilibrium model was used to calibrate initial solute-transport parameter estimates generated from tracer-breakthrough curves (TBCs) developed from tracer tests conducted in uni-axial solution conduits in karstic aquifers. Two-region nonequilibrium models account for partitioning of solute into mobile- and immobile-fluid regions to produce a more representative model fit to the strong tails associated with TBCs than do equilibrium models. The nonequilibrium model resulted in an increase in average flow velocities and a decrease in longitudinal dispersion coefficients over comparable estimates using an equilibrium model. Increases in velocity and decreases in dispersion were obtained at the expense of including parameters that describe solute partitioning and mass transfer rate for the mobile- and immobile-fluid regions. In addition, nonidentifiable sorption and mass transfer parameters for the immobile-fluid regions could only be described in terms of upper and lower bounds using readily determined identifiable ratios representing solute partitioning and system constraints based on known physical properties. The identifiable ratios and system constraints serve to minimize model nonuniqueness and renders the nonidentification problem trivial. | |||||
BibTeX:
@article{Field2000,
author = {Field, Malcolm S. and Pinsky, Paul F.},
title = {A two-region nonequilibrium model for solute transport in solution conduits in karstic aquifers},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {44},
number = {3-4},
pages = {329--351},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200000991}
}
|
|||||
| Fill, H.D. and Stedinger, J.R. | Homogeneity tests based upon Gumbel distribution and a critical appraisal of Dalrymple's test | 1995 | Journal of Hydrology Vol. 166(1-2), pp. 81-105 |
article | URL |
| Abstract: Homogeneity tests are an important component of many regional flood frequency analysis methods, particularly index flood methods. The index flood method was first suggested by Dalrymple, who also proposed a homogeneity test. Dalrymple's test has been widely used in hydrologic practice for more than 30 years. This paper analyzes the relative performance of Dalrymple's test, a normalized quantile test based upon L-moment parameter estimation (X-10 test), and a method of moment Cν test (MoM-Cν test). Dalrymple's original test is shown to be in error and a corrected version is developed. A Monte Carlo study compares the power of these three tests, after applying correction factors to the test statistics to achieve a 5% Type I error. The L-moment X-10 test was always more powerful then Dalrymple's test or the MoM-Cν test. Moreover, the X-10 test needs much less correction to achieve the specified Type I error. An analytical analysis of the power of the tests is consistent with the Monte Carlo results. The superior performance of the X-10 test is due to its L-moment estimation procedure, which yields a smaller sampling variance and a sampling distribution closer to normality than classical product moments. The relationship of the X-10 test with other L-moment based tests proposed by other workers is discussed. The original version of Dalrymple's test should not be used. | |||||
BibTeX:
@article{Fill1995,
author = {Fill, Heinz D. and Stedinger, Jery R.},
title = {Homogeneity tests based upon Gumbel distribution and a critical appraisal of Dalrymple's test},
journal = {Journal of Hydrology},
year = {1995},
volume = {166},
number = {1-2},
pages = {81--105},
url = {http://www.sciencedirect.com/science/article/pii/0022169494025997}
}
|
|||||
| Fillaudeau, L., Le-Nguyen, K. and André, C. | Influence of flow regime and thermal power on residence time distribution in tubular Joule Effect Heaters | 2009 | Journal of Food Engineering Vol. 95(3), pp. 489-498 |
article | URL |
| Abstract: To improve treatment homogeneity in tubular Joule Effect Heater (JEH), geometric modifications could be used even in laminar regime inducing flow perturbation and mixing.As a response variable, residence time distribution (RTD) is an important parameter and it has been commonly used in determining the performances of industrial heat exchangers.In present work, our objectives were (i) to investigate the impact of processing conditions (flow regime, heat flux) on RTD in an industrial JEH equipped with smooth and modified tubes, (ii) to contribute to the estimation of treatment homogeneity versus global energetic performances of heat exchanger and (iii) to validate a general reactor model.Analytical solution and systemic analysis of RTD signals were reported.The evolutions of mean reduced variance, β2 against efficiency number, Eff for smooth (β2 = 0.00129 · Eff − 0.0300, R2 = 0.992) and modified (β2 = 0.000547 ·  Eff − 0.0169, R2 = 0.979) tubes exhibited a similar and linear relationship.Under the conditions investigated (38 < Re < 10,000, 4 < Pr < 950 with Newtonian fluids), treatment homogeneity was significantly improved by modified geometry and strong interactions between heat transfer and hydrodynamics.A significant decrease in reduced variance under both laminar ( β ST 2 = 0.1054 · Exp - 0.00518 · P / ( ρ · Q ) , β MT 2 = 0.0661 · Exp - 0.00342 · P / ( ρ · Q ) ) and turbulent ( β ST 2 = 0.00624 · Exp - 0.00447 · P / ( ρ · Q ) , β MT 2 = 0.00108 · Exp - 0.00195 · P / ( ρ · Q ) ) regimes was observed versus heat energy.However geometric modification and heat treatment affected the residence time distribution and specifically reduced variance, β2 within same order of magnitude.Systemic analysis of experimental data enabled to evaluate two reactor models:Dispersed Plug Flow (DPF) and Plug Flow (PF) + 2 Continuous Stirred Tank Reactor (CSTR) with and without convolution and with 1 or 2 degrees of freedom.Second model could be considered as the most accurate model to predict RTD in JEH with an accurate degree of confidence for residence time and reduced variance estimation (τ = 0.995 · ts R2 = 0.64, error < 3% and β 2 = 0.3119 · β exp 2 0.73 R 2 = 0.98 ) and a simplified model with only 1 degree of freedom can be used. | |||||
BibTeX:
@article{Fillaudeau2009,
author = {Fillaudeau, L. and Le-Nguyen, K. and André, C.},
title = {Influence of flow regime and thermal power on residence time distribution in tubular Joule Effect Heaters},
journal = {Journal of Food Engineering},
year = {2009},
volume = {95},
number = {3},
pages = {489--498},
url = {http://www.sciencedirect.com/science/article/pii/S0260877409002866}
}
|
|||||
| Finley, J.B. and Drever, J.I. | Chemical mass balance and rates of mineral weathering in a high-elevation catchment, west glacier lake, wyoming [BibTeX] |
1997 | Hydrological Processes Vol. 11(7), pp. 745-764 |
article | URL |
BibTeX:
@article{Finley1997,
author = {Finley, Jim B. and Drever, James I.},
title = {Chemical mass balance and rates of mineral weathering in a high-elevation catchment, west glacier lake, wyoming},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {1997},
volume = {11},
number = {7},
pages = {745--764},
url = {http://dx.doi.org/10.1002/(SICI)1099-1085(199706)11:7<745::AID-HYP521>3.0.CO;2-E}
}
|
|||||
| Fiori, A., Berglund, S., Cvetkovic, V. and Dagan, G. | A first-order analysis of solute flux statistics in aquifers: The combined effect of pore-scale dispersion, sampling, and linear sorption kinetics | 2002 | Water Resources Research Vol. 38(8), pp. 1137- |
article | URL |
| Abstract: We consider steady groundwater flow of uniform mean in aquifers of random, spatially variable, hydraulic conductivity. Analytical expressions for the statistical moments of mass fluxes of sorbing solutes in presence of pore-scale dispersion are derived, where the reactive solutes undergo first-order sorption kinetics. The developments which lead to the analytical formulation of the solute flux are rigorous in the first-order analysis framework, and results obtained are valid for weakly heterogeneous formations. The methodology is exemplified for a two-dimensional aquifer, assuming that the source is of small transverse extent compared to the heterogeneity length scales. The examples show that pore-scale dispersion has a relatively small effect on the mean point flux, whereas the point flux variance shows much larger sensitivity to pore-scale dispersion. The variance first decreases as the reaction rate departs from the nonreactive limit, but for equilibrium reactions it is of the same order as for nonreactive solutes. The effect of averaging the solute flux over a finite sampling area is also investigated. It is found that for the expected area-averaged flux the mixing effect induced by sampling tends to supersede that caused by pore-scale dispersion. On the contrary, pore-scale dispersion may have a strong effect on the flux variance also when sampling effects are taken into account. | |||||
BibTeX:
@article{Fiori2002,
author = {Fiori, A. and Berglund, S. and Cvetkovic, V. and Dagan, G.},
title = {A first-order analysis of solute flux statistics in aquifers: The combined effect of pore-scale dispersion, sampling, and linear sorption kinetics},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2002},
volume = {38},
number = {8},
pages = {1137--},
url = {http://dx.doi.org/10.1029/2001WR000678}
}
|
|||||
| Fiorillo, F. | Tank-reservoir drainage as a simulation of the recession limb of karst spring hydrographs | 2011 | Hydrogeology Journal Vol. 19(5), pp. 1009-1019 |
article | URL |
| Abstract: Drainage of a cylindrical water-filled tank-reservoir has been analysed by different physical models, providing relative discharge-time equations. The process has been simulated (1) in a condition of free-flow discharge, where no energy is lost during the process, and (2) where friction forces and water viscosity take effect. Simulation (1) is considered to be a Torricelli reservoir, characterised by a linear decrease of discharge; (2) is based on Darcy’s law or on Poiseuille’s law, where discharge decreases exponentially with time, giving a straight line in the semilogarithm plot. For the Darcy’s law simulation, the tank tube was filled with sand. The cylindrical water-filled tank-reservoir drainage analysis has been applied to simulation of the actual shape of karst spring hydrographs. It has been determined that the recession coefficient, α , is proportional to a hydraulic constant, c , which represents the hydraulic characteristics during the baseflow recession, and α is inversely proportional to the product of the water-table area with the effective porosity. This product expresses the area of the aquifer filled by free-flowing water along the water table and can vary during the aquifer drainage. | |||||
BibTeX:
@article{Fiorillo2011,
author = {Fiorillo, Francesco},
title = {Tank-reservoir drainage as a simulation of the recession limb of karst spring hydrographs},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {19},
number = {5},
pages = {1009--1019},
url = {http://dx.doi.org/10.1007/s10040-011-0737-y}
}
|
|||||
| Fitzwater, R., Painter, R., Watson, V. and Byl, T. | Computer Program that Uses Residence-Time Distribution and First-Order Biodegradation to Predict BTEX Fate in Karst Aquifers | 2005 | U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160, pp. 189 | inproceedings | URL |
| Abstract: Approximately 40 percent of the United States east of the Mississippi River is underlain by karst aqui- fers. Karst ground-water systems are extremely vulnerable to contamination; however, the fate and transport of contaminants in karst areas are poorly understood because of the complex hydraulic characteristics of karst aquifers. Ground-water models developed using Darcy’s Law coupled to rates of biodegradation are useful for predicting the fate of fuels in unconsolidated aquifers, but have little utility in karst conduits. Con- ceptual models developed for karst aquifers have a consistent theme of non-ideal flow, storage, and active flow components. This research used a residence-time distribution (RTD) model approach that integrated residence times of contaminants isolated in storage areas with the residence time of contaminants moving through conduits coupled to a pseudo-first order rate of biodegradation. The microcosms consisted of four 1-liter chambers connected with small glass tubing. A peristaltic pump provided a consistent flow of karst water from a 10-gallon reservoir. First, a quantitative dye study was done to establish the residence-time distribution of the three systems. This was followed by a sterile toluene run to measure sorption of toluene to the microcosm systems. The third microcosm run incorporated karst bacteria and toluene. The removal of toluene predicted by the RTD-biodegradation model and the experiment were within 2 percent agreement (n=3). The RTD-biodegradation model was transformed into a user-friendly program that utilizes MS Excel® with Visual Basic interfaces. The input sheet of this prototype program requires site information, a biodegradation rate, and the results of a quantitative tracer study. The results, or output pages, provide res- idence-time distribution graphs and various statistical calculations. The output pages also report the calcu- lated amount of BTEX removed during transport through the karst aquifer based on RTD and biodegradation. Additional work is needed to incorporate dilution into the model. | |||||
BibTeX:
@inproceedings{Fitzwater2005,
author = {Fitzwater, Ryan and Painter, Roger and Watson, Valetta and Byl, T.D.},
title = {Computer Program that Uses Residence-Time Distribution and First-Order Biodegradation to Predict BTEX Fate in Karst Aquifers},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2005},
pages = {189},
url = {pubs.usgs.gov/sir/2005/5160/index.html}
}
|
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| Fleckenstein, J.H., Krause, S., Hannah, D.M. and Boano, F. | Groundwater-surface water interactions: New methods and models to improve understanding of processes and dynamics | 2010 | Advances in Water Resources Vol. 33(11)Special Issue on ground water-surface water interactions GW-SW Interactions, pp. 1291-1295 |
article | URL |
| Abstract: Interest in groundwater (GW)-surface water (SW) interactions has grown steadily over the last two decades. New regulations such as the EU Water Framework Directive (WFD) now call for a sustainable management of coupled ground- and surface water resources and linked ecosystems. Embracing this mandate requires new interdisciplinary research on GW-SW systems that addresses the linkages between hydrology, biogeochemistry and ecology at nested scales and specifically accounts for small-scale spatial and temporal patterns of GW-SW exchange. Methods to assess these patterns such as the use of natural tracers (e.g. heat) and integrated surface-subsurface numerical models have been refined and enhanced significantly in recent years and have improved our understanding of processes and dynamics. Numerical models are increasingly used to explore hypotheses and to develop new conceptual models of GW-SW interactions. New technologies like distributed temperature sensing (DTS) allow an assessment of process dynamics at unprecedented spatial and temporal resolution. These developments are reflected in the contributions to this Special Issue on GW-SW interactions. However, challenges remain in transferring process understanding across scales. | |||||
BibTeX:
@article{Fleckenstein2010,
author = {Fleckenstein, Jan H. and Krause, Stefan and Hannah, David M. and Boano, Fulvio},
title = {Groundwater-surface water interactions: New methods and models to improve understanding of processes and dynamics},
booktitle = {Special Issue on ground water-surface water interactions GW-SW Interactions},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {11},
pages = {1291--1295},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810001739}
}
|
|||||
| Fleury, P., Bakalowicz, M. and de Marsily, G. | Submarine springs and coastal karst aquifers: A review | 2007 | Journal of Hydrology Vol. 339(1-2), pp. 79-92 |
article | URL |
| Abstract: This article reports on current knowledge of coastal karst aquifers, in which conduit flow is dominant, and its aim is to characterise the functioning of these systems which are closely linked to the sea. First, earlier and recent studies of these aquifers are discussed. On the basis of their findings, it can be shown that two essential mechanisms are involved in the functioning of these systems, i.e., aquifer discharge through submarine springs and saline intrusion through conduits open to the sea. | |||||
BibTeX:
@article{Fleury2007,
author = {Fleury, Perrine and Bakalowicz, Michel and de Marsily, Ghislain},
title = {Submarine springs and coastal karst aquifers: A review},
journal = {Journal of Hydrology},
year = {2007},
volume = {339},
number = {1-2},
pages = {79--92},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407001874}
}
|
|||||
| Fleury, P., Ladouche, B., Conroux, Y., Jourde, H. and Dörfliger, N. | Modelling the hydrologic functions of a karst aquifer under active water management – The Lez spring | 2009 | Journal of Hydrology Vol. 365(3-4), pp. 235-243 |
article | URL |
| Abstract: A rainfall-discharge model is applied to an aquifer characterized by active groundwater management – the Lez karst aquifer in the South of France. Groundwater is withdrawn by pumping in the main drain, 400 m upstream from the main spring and 48 m below the aquifer overflow level. A reservoir model was developed to characterize the functioning of this aquifer. It is based on a conceptual model of the karst aquifer that takes into account flow through both the saturated zone and the unsaturated infiltration zone. Both rapid and slow flow in the infiltration zone and flow in the saturated zone are modelled. Since pumping withdraws groundwater from the main drain of the saturated zone, modules characterizing various pumping practices are taken into account in the saturated zone reservoir. The model simultaneously simulates spring discharge and water levels in the drain, which characterize the saturated zone of the karst. The groundwater reserves stored in the saturated zone can then be estimated. The model can be used for water management. Since runoff and overflow from the aquifer feeding the Lez River depend on the degree of saturation of the aquifer, the model could be used for the flood management. | |||||
BibTeX:
@article{Fleury2009,
author = {Fleury, P. and Ladouche, B. and Conroux, Y. and Jourde, H. and Dörfliger, N.},
title = {Modelling the hydrologic functions of a karst aquifer under active water management – The Lez spring},
journal = {Journal of Hydrology},
year = {2009},
volume = {365},
number = {3-4},
pages = {235--243},
url = {http://www.sciencedirect.com/science/article/pii/S002216940800588X}
}
|
|||||
| Fleury, P., Plagnes, V. and Bakalowicz, M. | Modelling of the functioning of karst aquifers with a reservoir model: Application to Fontaine de Vaucluse (South of France) | 2007 | Journal of Hydrology Vol. 345(1-2), pp. 38-49 |
article | URL |
| Abstract: This work deals with a rainfall-discharge model applied to a well known karst aquifer. A new approach is developed in order to minimize the fitting parameters: here, some of the model parameters do not result from a simple fitting, as it was the case with earlier models, i.e., some of them were assessed from the hydrograph analysis. The conceptual model of the functioning is based on a production function based on a simple calculation of effective rainfall and a transfer function consisting of two reservoirs. A slow discharge reservoir transfers the low flow and a rapid discharge reservoir feeds the high flow. The model has three fitted parameters plus one for its initialisation. Three parameters are deduced from the hydrograph analysis over the entire time series. For example, the recession coefficient of the slow discharge reservoir is determined from the hydrodynamic analysis of the recession [Mangin, A., 1975. Contribution à l’étude hydrodynamique des aquifères karstiques. 3ème partie. Constitution et fonctionnement des aquifères karstiques. Annales de Spéléologie, 30 (1), 210–124]. | |||||
BibTeX:
@article{Fleury2007a,
author = {Fleury, Perrine and Plagnes, Valérie and Bakalowicz, Michel},
title = {Modelling of the functioning of karst aquifers with a reservoir model: Application to Fontaine de Vaucluse (South of France)},
journal = {Journal of Hydrology},
year = {2007},
volume = {345},
number = {1-2},
pages = {38--49},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407004295}
}
|
|||||
| Florea, L.J. and Wicks, C.M. | Solute transport through laboratory-scale karstic aquifers | 2001 | Journal of Cave and Karst Studies Vol. 63(2), pp. 59-66 |
article | URL |
| Abstract: Laboratory-scale models of branchwork and of network karstic aquifers were constructed to provide data needed for calibration of numerical models. The distribution and connectedness of the conduits and sinkholes were scaled similarly to those found in nature; however, the porosity of models (2 and 3%) and the recharge rate (80 cm/hr) could not be scaled appropriately. Pulses of 1-M NaCl were injected sequentially at ten locations on both models to determine transport parameters using QTRACER. For all experiments, the Reynolds numbers were <150, the Peclet numbers were >6, and the Froude numbers were ~0. The flow regime was laminar and subcritical and advective processes dominated transport processes. The mean tracer transit times were significantly greater in the network model (29 s and 49 s) than in the branchwork model (17 s and 35 s) for injection locations that were proximal to (<10 cm) and distal from (10-20 cm) the spring. The lag times and times to peak concentration were highly variable and no systematic variation with distance from the spring could be discerned. The results can be used in calibration of numerical models of tracer transport through karstic aquifers. | |||||
BibTeX:
@article{Florea2001,
author = {Florea, Lee J. and Wicks, Carol M.},
title = {Solute transport through laboratory-scale karstic aquifers},
journal = {Journal of Cave and Karst Studies},
year = {2001},
volume = {63},
number = {2},
pages = {59--66},
url = {http://www.caves.org/pub/journal/JCKS/PDF/V63/v63n2-Florea.htm}
}
|
|||||
| Flukiger, F. and Bernard, D. | A new numerical model for pore scale dissolution of calcite due to CO2 saturated water flow in 3D realistic geometry: Principles and first results | 2009 | Chemical Geology Vol. 265(1-2)CO2 geological storage: Integrating geochemical, hydrodynamical, mechanical and biological processes from the pore to the reservoir scale, pp. 171-180 |
article | URL |
| Abstract: A fully coupled reactive transport model at pore-scale has been developed using finite volumes in order to improve the comprehension of reactive flow-through experiments by CO2-saturated water. Six constituents (H+, OH−, HCO3−, Ca2+, CO2⁎ and CO32−) are considered for reactive transport through the 3D pore network geometry of a limestone sample assumed to be of pure calcite. Three speciation reactions at equilibrium (giving three mass action relations) are involved in the bulk of the fluid phase, the electro-neutrality of the solution is imposed (giving one relation), and two transport equations are solved to compute the concentrations of the six constituents with space and time. Fick's law models diffusion and different diffusion coefficients are used for the different constituents. Calcite dissolution rate at the fluid–mineral interface is written as a function of the activities of all the constituents appearing in the dissolution reactions. The pressure and velocity fields of the one-phase solution circulating through the sample are computed solving Stokes equations. For negative times the circulating solution is in equilibrium with the rock sample, and at t = 0 a disequilibrium is introduced (increase of CO2 pressure and/or decrease of Ca2+ concentration). Then, the non-linear system of equations representing the reactive transport is solved until steady state. Applications on realistic 3D geometry (defined from real media images obtained by X-ray computed micro-tomography) illustrate the possibilities offered by this model. The behaviour of an effective reaction rate has been examined for samples having different geometry, showing that, at the pore scale, calcite dissolution is mainly influenced by the mean pore fluid velocity. | |||||
BibTeX:
@article{Flukiger2009,
author = {Flukiger, F. and Bernard, D.},
title = {A new numerical model for pore scale dissolution of calcite due to CO2 saturated water flow in 3D realistic geometry: Principles and first results},
booktitle = {CO2 geological storage: Integrating geochemical, hydrodynamical, mechanical and biological processes from the pore to the reservoir scale},
journal = {Chemical Geology},
year = {2009},
volume = {265},
number = {1-2},
pages = {171--180},
url = {http://www.sciencedirect.com/science/article/pii/S0009254109002277}
}
|
|||||
| Flynn, R., Cornaton, F., Hunkeler, D. and Rossi, P. | Bacteriophage transport through a fining-upwards sedimentary sequence: laboratory experiments and simulation | 2004 | Journal of Contaminant Hydrology Vol. 74(1-4), pp. 231-252 |
article | URL |
| Abstract: A column containing four concentric layers of progressively finer-grained glass beads (graded column) was used to study the transport of the bacteriophage T7 in water flowing parallel to layering through a fining-upwards (FU) sedimentary structure. By passing a pulse of T7, and a conservative solute tracer upwards through a column packed with a single bead size (uniform column), the capacity of each bead type to attenuate the bacteriophage was determined. Solute and bacteriophage responses were modelled using an analytical solution to the advection–dispersion equation, with first-order kinetic deposition simulating bacteriophage attenuation. Resulting deposition constants for different flow velocities indicated that filtration theory-determined values differed from experimentally determined values by less than 10%. In contrast, the responses of solute and bacteriophage tracers passing upwards through graded columns could not be reproduced with a single analytical solution. However, a flux-weighted summation of four one-dimensional advective–dispersive analytical terms approximated solute breakthrough curves. The prolonged tailing observed in the resulting curve resembled that typically generated from field-based tracer test data, reflecting the potential importance of textural heterogeneity in the transport of dissolved substances in groundwater. Moreover, bacteriophage deposition terms, determined from filtration theory, reproduced the T7 breakthrough curve once desorption and inactivation on grain surfaces were incorporated. To evaluate the effect of FU sequences on mass transport processes in more detail, bacteriophage passage through sequences resembling those sampled from a FU bed in a fluvioglacial gravel pit were carried out using an analogous approach to that employed in the laboratory. Both solute and bacteriophage breakthrough responses resembled those generated from field-based test data and in the graded column experiments. Comparisons with the results of simulations using averaged hydraulic conductivities show that simulations employing averaged parameters overestimate bacteriophage travel times and underestimate masses recovered and peak concentrations. | |||||
BibTeX:
@article{Flynn2004,
author = {Flynn, Raymond and Cornaton, Fabien and Hunkeler, Daniel and Rossi, Pierre},
title = {Bacteriophage transport through a fining-upwards sedimentary sequence: laboratory experiments and simulation},
journal = {Journal of Contaminant Hydrology},
year = {2004},
volume = {74},
number = {1-4},
pages = {231--252},
url = {http://www.sciencedirect.com/science/article/pii/S0169772204000427}
}
|
|||||
| Flynn, R.M. and Sinreich, M. | Characterisation of virus transport and attenuation in epikarst using short pulse and prolonged injection multi-tracer testing | 2010 | Water Research Vol. 44(4)Transport and Fate of Colloids and Microbes in Granular Aqueous Environments, pp. 1138-1149 |
article | URL |
| Abstract: Attenuation processes controlling virus fate and transport in the vadose zone of karstified systems can strongly influence groundwater quality. This research compares the breakthrough of two bacteriophage tracers (H40/1 and T7), with contrasting properties, at subsurface monitoring points following application onto an overlying composite sequence of thin organic soil and weathered limestone (epikarst). Short pulse multi-tracer test results revealed that T7 (Source concentration, Co = 1.8 × 106 pfu/mL) and H40/1 (Co = 5.9 × 106 pfu/mL) could reach sampling points 10 m below ground less than 30 min after tracer application. Contrasting deposition rates, determined from simulated tracer responses, reflected the potential of the ground to differentially attenuate viruses. Prolonged application of both T7 (Co = 2.3 × 104 pfu/mL) and H40/1 (Co = 1.3 × 105 pfu/mL) over a five hour period during a subsequent test, in which ionic strength levels observed at monitoring points rose consistently, corresponded to a rapid rise in T7 levels, followed by a gradual decline before the end of tracer injection; this reflected reaction-limited deposition in the system. T7's response contrasted with that of H40/1, whose concentration remained constant over a three hour period before declining dramatically prior to the end of tracer injection. Subsequent application of lower ionic strength tracer-free flush water generated a rapid rise in H40/1 levels and a more gradual release of T7. Results highlight the benefits of employing prolonged injection multi-tracer tests for identifying processes not apparent from conventional short pulse tests. Study findings demonstrate that despite rapid transport rates, the epikarst is capable of physicochemical filtration of viruses and their remobilization, depending on virus type and hydrochemical conditions. | |||||
BibTeX:
@article{Flynn2010,
author = {Flynn, Raymond M. and Sinreich, Michael},
title = {Characterisation of virus transport and attenuation in epikarst using short pulse and prolonged injection multi-tracer testing},
booktitle = {Transport and Fate of Colloids and Microbes in Granular Aqueous Environments},
journal = {Water Research},
year = {2010},
volume = {44},
number = {4},
pages = {1138--1149},
url = {http://www.sciencedirect.com/science/article/pii/S0043135409007775}
}
|
|||||
| Fogler, H.S. | Elements of chemical reaction engineering [BibTeX] |
1999 | , pp. - | book | |
BibTeX:
@book{Fogler1999,
author = {Fogler, H. Scott},
title = {Elements of chemical reaction engineering},
publisher = {Prentice Hall PTR},
year = {1999},
pages = {--},
edition = {Third}
}
|
|||||
| Foley, A., Cachandt, G., Franklin, J., Willmore, F. and Atkinson, T. | Tracer tests and the structure of permeability in the Corallian limestone aquifer of northern England, UK | 2012 | Hydrogeology Journal, pp. 1-16 | article | URL |
| Abstract: The Corallian limestone of northern England (UK) is widely exploited for water supplies and exhibits the karstic phenomena of sinking rivers, conduit development and groundwater velocities of several kilometres per day. To test a number of model-derived source protection zones and elucidate contaminant transport mechanisms in the aquifer, three tracer tests were conducted from a set of swallow-holes draining the River Derwent toward public water supply wells in the eastern part of the aquifer. Tracers used included: Enterobacter cloacae ( bacteriophage), Photine C (optical brightener), sodium fluorescein (fluorescent dye) and sulphur hexafluoride (dissolved gas), the varying properties of which make them suitable analogues for different types of potential contaminant. Observed tracer transport times and arrival patterns indicate that tracer transport occurs through karstic channels embedded in a network of primary fissures which exert control over tracer concentrations once initial tracer plumes have passed. A dipole flow system is observed between the swallow-holes and the closest abstraction well, whilst previously modelled source protection zones do not accurately reflect either groundwater velocity or those areas of the aquifer supplying the wells. These findings imply that managing such aquifers for potential contamination should rely upon empirical tracer evidence for source-protection zone modelling. | |||||
BibTeX:
@article{Foley2012,
author = {Foley, Aidan and Cachandt, Gerd and Franklin, Janine and Willmore, Fergus and Atkinson, Tim},
title = {Tracer tests and the structure of permeability in the Corallian limestone aquifer of northern England, UK},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2012},
pages = {1--16},
url = {http://dx.doi.org/10.1007/s10040-012-0830-x}
}
|
|||||
| Fomin, S.A., Chugunov, V.A. and Hashida, T. | Non-Fickian mass transport in fractured porous media | 2011 | Advances in Water Resources Vol. 34(2), pp. 205-214 |
article | URL |
| Abstract: The paper provides an introduction to fundamental concepts of mathematical modeling of mass transport in fractured porous heterogeneous rocks. Keeping aside many important factors that can affect mass transport in subsurface, our main concern is the multi-scale character of the rock formation, which is constituted by porous domains dissected by the network of fractures. Taking into account the well-documented fact that porous rocks can be considered as a fractal medium and assuming that sizes of pores vary significantly (i.e. have different characteristic scales), the fractional-order differential equations that model the anomalous diffusive mass transport in such type of domains are derived and justified analytically. Analytical solutions of some particular problems of anomalous diffusion in the fractal media of various geometries are obtained. Extending this approach to more complex situation when diffusion is accompanied by advection, solute transport in a fractured porous medium is modeled by the advection–dispersion equation with fractional time derivative. In the case of confined fractured porous aquifer, accounting for anomalous non-Fickian diffusion in the surrounding rock mass, the adopted approach leads to introduction of an additional fractional time derivative in the equation for solute transport. The closed-form solutions for concentrations in the aquifer and surrounding rocks are obtained for the arbitrary time-dependent source of contamination located in the inlet of the aquifer. Based on these solutions, different regimes of contamination of the aquifers with different physical properties can be readily modeled and analyzed. | |||||
BibTeX:
@article{Fomin2011,
author = {Fomin, Sergei A. and Chugunov, Vladimir A. and Hashida, Toshiyuki},
title = {Non-Fickian mass transport in fractured porous media},
journal = {Advances in Water Resources},
year = {2011},
volume = {34},
number = {2},
pages = {205--214},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810001971}
}
|
|||||
| Fomin, S., Chugunov, V. and Hashida, T. | Application of Fractional Differential Equations for Modeling the Anomalous Diffusion of Contaminant from Fracture into Porous Rock Matrix with Bordering Alteration Zone | 2010 | Transport in Porous Media Vol. 81(2), pp. 187-205 |
article | URL |
| Abstract: Solute diffusion from a fracture into a porous rock with an altered zone bordering the fracture is modeled by a system of two diffusion equations (one for the altered zone and another for the intact porous matrix) with different coefficients of effective diffusivity. Since experimental studies of diffusion into rock samples with altered zones indicate that mathematical models of diffusion based on Fick’s law do not adequately describe the concentration field in a sample, fractional order diffusion equations are chosen in this study for modeling the anomalous mass transport in the rocks. In the case of significantly higher porosity of the altered zone (e.g., this is typical for carbonates) the effective diffusivity here can be much higher than the effective diffusivity of non-altered rocks. By introducing a small parameter that is the ratio of effective diffusivities in the non-altered and altered regions and applying the technique of perturbations, approximate analytical solutions for concentrations in the altered zone bordering the fracture and in the intact surrounding rocks are obtained. Based on these solutions, different regimes of diffusion into the rocks with different physical properties are modeled and analyzed. It is shown that, using experimentally obtained data, the orders of the fractional derivatives in the differential equations can be readily calibrated for the every specific rock. | |||||
BibTeX:
@article{Fomin2010,
author = {Fomin, Sergei and Chugunov, Vladimir and Hashida, Toshiyuki},
title = {Application of Fractional Differential Equations for Modeling the Anomalous Diffusion of Contaminant from Fracture into Porous Rock Matrix with Bordering Alteration Zone},
journal = {Transport in Porous Media},
publisher = {Springer Netherlands},
year = {2010},
volume = {81},
number = {2},
pages = {187--205},
url = {http://dx.doi.org/10.1007/s11242-009-9393-2}
}
|
|||||
| Fomin, S., Chugunov, V. and Hashida, T. | The Effect of Non-Fickian Diffusion into Surrounding Rocks on Contaminant Transport in a Fractured Porous Aquifer | 2005 | Proceedings: Mathematical, Physical and Engineering Sciences Vol. 461(2061), pp. 2923-2939 |
article | URL |
| Abstract: Solute transport in a fractured porous confined aquifer is modelled by using an equation with a fractional-in-time derivative of order γ, which may vary from 0 to 1. Accounting for non-Fickian diffusion into the surrounding rock mass, which is modelled by a fractional spatial derivative of order α, leads to the introduction of an additional fractional-in-time derivative of order α/(1 + α) in the equation for solute transport. Closed-form solutions for solute concentrations in the aquifer and surrounding rocks are obtained for an arbitrary time-dependent source of contamination located at the inlet of the aquifer. Based on these solutions, different regimes of contaminant transport in aquifers with various physical properties are modelled and analysed. | |||||
BibTeX:
@article{Fomin2005,
author = {Fomin, Sergei and Chugunov, Vladimir and Hashida, Toshiyuki},
title = {The Effect of Non-Fickian Diffusion into Surrounding Rocks on Contaminant Transport in a Fractured Porous Aquifer},
journal = {Proceedings: Mathematical, Physical and Engineering Sciences},
publisher = {The Royal Society},
year = {2005},
volume = {461},
number = {2061},
pages = {2923--2939},
url = {http://www.jstor.org/stable/30046395}
}
|
|||||
| Foppen, J.W., Orup, C., Adell, R., Poulalion, V. and Uhlenbrook, S. | Using multiple artificial DNA tracers in hydrology | 2011 | Hydrological Processes Vol. 25(19), pp. 3101-3106 |
article | URL |
| Abstract: Tracer testing is an efficient and versatile method to characterize hydrological processes both in surface waters and in the subsurface, and with synthetic DNA (deoxyribonucleic acid) experiments can be performed with a theoretically unlimited number of tracers. We explored the use of six synthetic DNA tracers in injection experiments in the Strijbeekse Beek and the Merkske, two small brooks in the Netherlands. We wanted to test the applicability of synthetic DNA markers in combination with the quantitative polymerase chain reaction (qPCR), an analytical technique used to determine DNA concentrations. The most important results from the two experiments were that DNA concentrations during breakthrough ranged from 0·1 to 100 fM (femtomolar = 10−15 mol/l), and that DNA mass transport in the stream was not retarded compared to transport of an injected NaCl mass. However, DNA mass was substantially reduced, most likely as a result of adsorption, attachment, decay and/or biological uptake processes in the stream itself. Although more insight in the various mass balance components of DNA mass in the stream is required, we concluded that the use of synthetic DNA markers in combination with qPCR has potential for spatially distributed surface water-groundwater interaction tracer experiments. | |||||
BibTeX:
@article{Foppen2011,
author = {Foppen, Jan Willem and Orup, Caesar and Adell, Renaud and Poulalion, Vincent and Uhlenbrook, Stefan},
title = {Using multiple artificial DNA tracers in hydrology},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2011},
volume = {25},
number = {19},
pages = {3101--3106},
url = {http://dx.doi.org/10.1002/hyp.8159}
}
|
|||||
| Ford, D.C. and Williams, P.W. | Karst hydrogeology and geomorphology [BibTeX] |
2007 | , pp. - | book | |
BibTeX:
@book{Ford2007,
author = {Ford, Derek C. and Williams, Paul W.},
title = {Karst hydrogeology and geomorphology},
publisher = {John Wiley & Sons},
year = {2007},
pages = {--},
edition = {Revised Edition}
}
|
|||||
| Forrer, N., Butté, A. and Morbidelli, M. | Chromatographic behavior of a polyclonal antibody mixture on a strong cation exchanger column. Part II: Adsorption modelling | 2008 | Journal of Chromatography A Vol. 1214(1-2), pp. 71-80 |
article | URL |
| Abstract: The adsorption of a polyclonal IgG mixture on a strong cation exchanger column is characterized using a detailed multi-component pore model. This model is explicit in all transport parameters and includes salt dependent isotherms. As discussed in the first part of this work, the IgG mixture can be simplified by considering two pseudo-variants only. Linear gradient experiments are used to fit the salt dependent adsorption isotherms and the mass transport parameters for the two pseudo-variants. Using the model, breakthrough curves are predicted with good accuracy. The model is also implemented to visualize the axial and radial concentration profiles of the two pseudo-variants in the column during a loading experiment. | |||||
BibTeX:
@article{Forrer2008,
author = {Forrer, Nicola and Butté, Alessandro and Morbidelli, Massimo},
title = {Chromatographic behavior of a polyclonal antibody mixture on a strong cation exchanger column. Part II: Adsorption modelling},
journal = {Journal of Chromatography A},
year = {2008},
volume = {1214},
number = {1-2},
pages = {71--80},
url = {http://www.sciencedirect.com/science/article/pii/S0021967308018001}
}
|
|||||
| Forsman, K., Johansson, H. and Jonsson, K. | The effects of partly irreversible solute exchange: comparison between conservative and sorptive transport in streams | 2002 | Journal of Hydrology Vol. 256(1-2), pp. 1-15 |
article | URL |
| Abstract: Contaminant transport in streams and rivers is often affected by the solute exchange between the main stream and various adjacent storage zones as well as chemical and biological processes. This paper focuses on the difference between the effects of conservative and reactive solute exchange, respectively, in terms of an analytical transport model that takes into account main stream advection, solute exchange with storage zones, instantaneous equilibrium sorption and first order reactions. The effects of longitudinal variation of water flow and hydraulic radius as well as transversal variation of streambed porosity were included in the analysis, which was conducted on a reach by reach basis. To be able to use a temporally variable upstream concentration as boundary concentration, the measured breakthroughs were divided into 30–150 segments of constant concentration and the solutions were obtained as the sum of solutions for all segments. An experiment in Uppland County in Sweden, constitutes the basis for this study. Results from a simultaneous injection of the tracers tritium, 3H2O, and chromium, 51Cr(III), made it possible to distinguish between conservative and reactive transport along a 30 km reach of the Säva Stream. The peak concentration of the reactive chromium decreased faster with distance, than that of tritium. The main hypothesis is that the chromium exchange is affected by both rapid sorption processes and slower reactions in the subsurface storage zones. In this framework, the slow processes appear as irreversible, which is true at least on the time scale represented by the data. The irreversibility is probably caused by the net effect of various slow chemical processes, e.g. solute precipitation/co-precipitation and irreversible sorption, which decreases the washout rate after the main bulk of the solute has passed by in the stream. A fully reversible exchange description, with instantaneous equilibrium partitioning, gives a clearly overestimated tail for chromium, which is not the case with the present concept. Results obtained by independently evaluating seven subreaches of the stream give mean Reaction Damköhler numbers for the storage zone equalling 2.63 for the transport of 51Cr and 0 for 3H2O. | |||||
BibTeX:
@article{Forsman2002,
author = {Forsman, K.Jonas and Johansson, Håkan and Jonsson, Karin},
title = {The effects of partly irreversible solute exchange: comparison between conservative and sorptive transport in streams},
journal = {Journal of Hydrology},
year = {2002},
volume = {256},
number = {1-2},
pages = {1--15},
url = {http://www.sciencedirect.com/science/article/pii/S0022169401005273}
}
|
|||||
| Fortiana, J. and Grané, A. | A scale-free goodness-of-fit statistic for the exponential distribution based on maximum correlations | 2002 | Journal of Statistical Planning and Inference Vol. 108(1-2)C.R. Rao 80th Birthday Felicitation Volume, Part II, pp. 85-97 |
article | URL |
| Abstract: We propose a goodness-of-fit statistic for testing exponentiality based on Hoeffding's maximum correlation. We study its small and large sample properties, we obtain its exact distribution, tables of exact and asymptotic critical values, and some power curves. We compare this statistic with the Gini statistic, the Shapiro–Wilk statistic for exponentiality and the Stephens’ modification of the latter. | |||||
BibTeX:
@article{Fortiana2002,
author = {Fortiana, J. and Grané, A.},
title = {A scale-free goodness-of-fit statistic for the exponential distribution based on maximum correlations},
booktitle = {C.R. Rao 80th Birthday Felicitation Volume, Part II},
journal = {Journal of Statistical Planning and Inference},
year = {2002},
volume = {108},
number = {1-2},
pages = {85--97},
url = {http://www.sciencedirect.com/science/article/pii/S0378375802002720}
}
|
|||||
| Fountain, A.G. | Effect of Snow and Firn Hydrology on the Physical and Chemical Characteristics of Glacial Runoff | 1996 | Hydrological Processes Vol. 10(4), pp. 509-521 |
article | URL |
| Abstract: Near-surface processes on glaciers, including water flow over bare ice and through seasonal snow and firn, have a significant effect on the speed, volume and chemistry of water flow through the glacier. The transient nature of the seasonal snow profoundly affects the water discharge and chemistry. Water flow through snow is fairly slow compared with flow over bare ice and a thinning snowpack on a glacier decreases the delay between peak meltwater input and peak stream discharge. Furthermore, early spring melt flushes the snowpack of solutes and by mid-summer the melt water flowing into the glacier is fairly clean by comparison. The firn, a relatively constant feature of glaciers, attenuates variations in water drainage into the glacier by temporarily storing water in saturated layer. Bare ice exerts opposite influences by accentuating variations in runoff by water flowing over the ice surface. The melt of firn and ice contributes relatively clean (solute-free) water to the glacier water system. | |||||
BibTeX:
@article{Fountain1996,
author = {Fountain, Andrew G.},
title = {Effect of Snow and Firn Hydrology on the Physical and Chemical Characteristics of Glacial Runoff},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {1996},
volume = {10},
number = {4},
pages = {509--521},
url = {http://dx.doi.org/10.1002/(SICI)1099-1085(199604)10:4<509::AID-HYP389>3.0.CO;2-3}
}
|
|||||
| Fournier, M., Massei, N., Bakalowicz, M., Dussart-Baptista, L., Rodet, J. and Dupont, J. | Using turbidity dynamics and geochemical variability as a tool for understanding the behavior and vulnerability of a karst aquifer | 2007 | Hydrogeology Journal Vol. 15(4), pp. 689-704 |
article | URL |
| Abstract: In a karst system, the characterization of transport properties is based on the comparison of natural tracers observed at the inlet (a swallow hole on the karst plateau) and the outlets of the system (a spring and a well). At Norville, northwest France, electrical conductivity (EC) and turbidity ( T ) were used as natural tracers for characterizing dissolved elements (surface water geochemistry) and particulate matter transport, respectively. Two methods were used for this study: (1) a comparison of the relations between EC, T and spring discharge ( Q ) by means of normalized EC– T – Q curves, and (2) a principal component analysis (PCA) including water geochemistry data in addition to EC, T and Q . Three different characteristic flood events have been chosen for the analyses. EC– T – Q curves highlighted the direct transfer, resuspension and deposition of particles during their transport in the karst network. Transport from the swallow hole to both the spring and the well appeared to be dominated by karst-conduit flow. On the other hand, PCA results showed a diffuse source of contamination of groundwaters by nitrate and a point-source contamination of groundwaters by streaming/runoff surface waters with high turbidity and phosphate concentration infiltrated at the swallow hole. | |||||
BibTeX:
@article{Fournier2007,
author = {Fournier, M. and Massei, N. and Bakalowicz, M. and Dussart-Baptista, L. and Rodet, J. and Dupont, J.},
title = {Using turbidity dynamics and geochemical variability as a tool for understanding the behavior and vulnerability of a karst aquifer},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2007},
volume = {15},
number = {4},
pages = {689--704},
url = {http://dx.doi.org/10.1007/s10040-006-0116-2}
}
|
|||||
| Fournier, M.-C., Falk, L. and Villermaux, J. | A new parallel competing reaction system for assessing micromixing efficiency—Experimental approach | 1996 | Chemical Engineering Science Vol. 51(22), pp. 5053-5064 |
article | URL |
| Abstract: Several kinds of methods can be used in order to study the state of mixing at molecular scale in stirred reactors. Conductometric and optical methods have not enough resolution. The aim of this work is therefore to propose a chemical reaction which acts as a molecular probe for assessing micromixing efficiency. A literature review shows that the number of available test reactions is limited. We propose a new system of parallel competing reactions A + B → R and C + νB → S whereby the state of micromixing in industrial reactors can be studied. The first reaction is a neutralization, the second one is the Dushman reaction between the iodide and iodate. We show that the formation of iodine (S) under the influence of an acid (B) in an alkaline medium (A) is a measure of segregation. This system makes it possible to study the influence of feed time, feed location and reactant concentrations on segregation. The method is validated by a study of mixing in standard stirred tanks of one and twenty litres. Scale-up rules are proposed. | |||||
BibTeX:
@article{Fournier1996,
author = {Fournier, M.-C. and Falk, L. and Villermaux, J.},
title = {A new parallel competing reaction system for assessing micromixing efficiency—Experimental approach},
journal = {Chemical Engineering Science},
year = {1996},
volume = {51},
number = {22},
pages = {5053--5064},
url = {http://www.sciencedirect.com/science/article/pii/0009250996002709}
}
|
|||||
| Fox, F. | Steady-state iem model: singular perturbation analysis near perfect-micromixing limit | 1989 | Chemical Engineering Science Vol. 44(12), pp. 2831-2842 |
article | URL |
| Abstract: A perturbation expansion of the steady-state IEM model is developed, valid in the fast-micromixing limit (tmixing∠treaction and τ). The resultant expression is applied to a complex, bistable reacting system for both a premixed and a nonpremixed feed. The predicted deviations from perfect micromixing are shown to be in accordance with those found using more complex micromixing models. The perturbation expansion thus provides a relatively simple tool for the qualitative study to the effect of micromixing on steady-state behavior near the perfect-micromixing limit. | |||||
BibTeX:
@article{Fox1989,
author = {Fox, F.O.},
title = {Steady-state iem model: singular perturbation analysis near perfect-micromixing limit},
journal = {Chemical Engineering Science},
year = {1989},
volume = {44},
number = {12},
pages = {2831--2842},
url = {http://www.sciencedirect.com/science/article/pii/0009250989850936}
}
|
|||||
| Fox, R. | Micromixing effects in the nicolis—puhl reaction: numerical bifurcation and stability analysis of the IEM model | 1991 | Chemical Engineering Science Vol. 46(7), pp. 1829-1847 |
article | URL |
| Abstract: The Nicolis—Puhl reaction, an isothermal, two-component, autocatalytic reaction exhibiting bistability, oscillatory solutons, and Takens-Bogdanov points in a perfectly micromixed CSTR has been shown to be sensitive to the degree of micromixing under non-premixed feed conditions. These properties make it an interesting theoretical model for exploring the effect of micromixing on the dynamics of nonlinear chemical reactions; in particular, for examining whether micromixing effects suffice to produce complex dynamics in an otherwise two-dimensional dynamical system. Here, the reaction is studied in conjunction with the interaction-by-exchange-with-the mean (IEM) model of micromixing. Numerical bifurcation and stability analysis techniques applicable to the specific class of integro-differential equations to which this model belongs are employed to carry out the analysis. For various values of the reaction rates, the micromixing rate and the inverse residence time have been used as bifurcation parameters to construct two-dimensional bifurcation sets containing saddle-node and Hopf bifurcation curves whose locations are shown to be strongly dependent on the degree of micromixing. As is observed experimentally by lowering the stirring rate for some real chemical reactions in flow reactors, regions of bistability and oscillatory behavior are shown to be accessible, by decreasing the micromixing rate, from regions exhibiting a single steady state. Manifolds of Takens-Bogdanov points for finite micromixing rates have also been computed; however, it is shown that the dynamical dimension of the IEM model remains the same for all values of the micromixing parameter. | |||||
BibTeX:
@article{Fox1991,
author = {Fox, R.O.},
title = {Micromixing effects in the nicolis—puhl reaction: numerical bifurcation and stability analysis of the IEM model},
journal = {Chemical Engineering Science},
year = {1991},
volume = {46},
number = {7},
pages = {1829--1847},
url = {http://www.sciencedirect.com/science/article/pii/000925099187030G}
}
|
|||||
| Fox, R. and Villermaux, J. | Unsteady-state IEM model: numerical simulation and multiple-scale perturbation analysis near perfect-micromixing limit | 1990 | Chemical Engineering Science Vol. 45(2), pp. 373-386 |
article | URL |
| Abstract: An unsteady-state version of the IEM model is derived for study of the dynamical behaviour of an imperfectly-micromixed CSTR. A numerical simulation proceeds for studying the model is developed and tested under both premixed and nonpremixed feed conditions. In addition, a perturbation expansion is derived, valid in the fast-mixing limit, and shown to yield a qualitatively good agreement with the numerical simulation predictions. These methods are studied using a simple reaction system and shown to yield excellent numerical stability with fewer differential equations than are required for simulation of the coalescence—dispersion model. | |||||
BibTeX:
@article{Fox1990,
author = {Fox, R.O. and Villermaux, J.},
title = {Unsteady-state IEM model: numerical simulation and multiple-scale perturbation analysis near perfect-micromixing limit},
journal = {Chemical Engineering Science},
year = {1990},
volume = {45},
number = {2},
pages = {373--386},
url = {http://www.sciencedirect.com/science/article/pii/000925099087023L}
}
|
|||||
| Frank G., S.I. | A model of transient mixing in a stirred tank | 1997 | Chemical Engineering Science Vol. 52(9), pp. 1459-1478 |
article | URL |
| Abstract: A model describing two-dimensional transient mixing phenomena of a single-phase fluid within a stirred tank has been developed. The model employs a k−ε turbulence model and uses Lagrangian tracer particles as indicators of mixing behavior. Calculations over a relatively coarse (20 × 30) mesh containing 4800 tracer particles are capable of producing a realistic depiction of slurry mixing behavior in a large-scale industrial vessel. | |||||
BibTeX:
@article{FrankG.1997,
author = {Frank G., Smith III},
title = {A model of transient mixing in a stirred tank},
journal = {Chemical Engineering Science},
year = {1997},
volume = {52},
number = {9},
pages = {1459--1478},
url = {http://www.sciencedirect.com/science/article/pii/S0009250996004721}
}
|
|||||
| Frederick, P. | A mass-balance code for the quantitative interpretation of fluid column profiles in ground-water studies | Computers & Geosciences(0), pp. - | article | URL | |
| Abstract: A simple mass-balance code allows effective modeling of conventional fluid column resistivity logs in dilution tests involving column replacement with either distilled water or dilute brine. Modeling a series of column profiles where the inflowing formation water introduces water quality interfaces propagating along the borehole gives effective estimates of the rate of borehole flow. Application of the dilution model yields estimates of borehole flow rates that agree with measurements made with the heat-pulse flowmeter under ambient and pumping conditions. Model dilution experiments are used to demonstrate how dilution logging can extend the range of borehole flow measurement at least an order of magnitude beyond that achieved with flowmeters. However, dilution logging has the same dynamic range limitation encountered with flowmeters because it is difficult to detect and characterize flow zones that contribute a small fraction of total flow when that contribution is superimposed on a larger flow. When the smaller contribution is located below the primary zone, ambient downflow may disguise the zone if pumping is not strong enough to reverse the outflow. This situation can be addressed by increased pumping. But this is likely to make the moveout of water quality interfaces too fast to measure in the upper part of the borehole, so that a combination of flowmeter and dilution method may be more appropriate. Numerical experiments show that the expected weak horizontal flow across the borehole at conductive zones would be almost impossible to recognize if any ambient vertical flow is present. In situations where natural water quality differences occur such as flowing boreholes or injection experiments, the simple mass-balance code can be used to quantitatively model the evolution of fluid column logs. Otherwise, dilution experiments can be combined with high-resolution flowmeter profiles to obtain results not attainable using either method alone. | |||||
BibTeX:
@article{Frederick,
author = {Frederick, Paillet},
title = {A mass-balance code for the quantitative interpretation of fluid column profiles in ground-water studies},
journal = {Computers & Geosciences},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0098300411004067}
}
|
|||||
| Frierdich, A.J., Hasenmueller, E.A. and Catalano, J.G. | Composition and structure of nanocrystalline Fe and Mn oxide cave deposits: Implications for trace element mobility in karst systems | 2011 | Chemical Geology Vol. 284(1-2), pp. 82-96 |
article | URL |
| Abstract: Fe and Mn oxides are ubiquitous, highly reactive minerals in the environment which often control the distribution and speciation of trace elements in soils and aquatic systems. Pautler Cave in Southwest Illinois contains Fe and Mn oxide deposits with properties that differ spatially and temporally. Two depositional environments exist in the cave: Fe and Mn precipitation where anoxic groundwater enters the oxic cave passage (seep deposition) and direct deposition from the cave stream. Seep waters have higher concentrations of Ca2+, Fe2+, and Mn2+, lower pH, and lower O2(aq) concentrations relative to stream waters. In addition, seep waters have nearly constant δ18O values that are similar to the yearly average of local precipitation, whereas cave stream waters have more erratic δ18O values and appear to be influenced by seasonal variations of δ18O in rainfall. These differences suggest that the seep water source has a longer residence time in the subsurface than the cave stream water. Fe oxides are solely found as seep deposits whereas Mn oxides are deposited both by groundwater seepage and cave streams. Freshly precipitated Fe oxides are composed of ferrihydrite and filamentous material consistent with biomineralization structures of the microbial genera Gallionella and Leptothrix. Mn oxide minerals consist of 7 and 10 Å phyllomanganates having a range of three dimensional order. Mn oxide samples show a greater heavy metal and trace element content compared to Fe oxides, and Mn oxides deposited by cave streams have higher concentrations of metals than Mn oxide seep deposits. In addition, phyllomanganate particle morphologies and crystallinity display a compositional dependence, with platelet size and phyllomanganate sheet stacking-order decreasing with increasing Ba and trace element content and decreasing Ca content; these properties also appear to correlate with dissolved Mn(II) in the source water. These observations suggest that Fe and Mn oxide minerals in oxic cave systems affect trace element concentrations in carbonate-fed springs, and illustrate a previously unrecognized limitation on the transport of inorganic nutrients and contaminants in karst aquifers. | |||||
BibTeX:
@article{Frierdich2011,
author = {Frierdich, Andrew J. and Hasenmueller, Elizabeth A. and Catalano, Jeffrey G.},
title = {Composition and structure of nanocrystalline Fe and Mn oxide cave deposits: Implications for trace element mobility in karst systems},
journal = {Chemical Geology},
year = {2011},
volume = {284},
number = {1-2},
pages = {82--96},
url = {http://www.sciencedirect.com/science/article/pii/S0009254111000763}
}
|
|||||
| Fries, D.M. and von Rohr, P.R. | Liquid mixing in gas–liquid two-phase flow by meandering microchannels | 2009 | Chemical Engineering Science Vol. 64(6), pp. 1326-1335 |
article | URL |
| Abstract: The influence of the channel radius on the mass transfer in rectangular meandering microchannels (width 200 – 400 μ m and height of 150 μ m ) has been investigated for gas–liquid flow. Laser induced velocimetry measurements have been compared with theoretical results. The symmetrical velocity profile, known from the straight channel, was found to change to an asymmetrical one for the meandering channel configuration. The changes in the secondary velocity profile lead to an enhanced radial mass transfer inside the liquid slug, resulting in a reduced mixing length. In the investigated experimental range (superficial gas velocity 0.08 m / s and superficial liquid velocity 0.01 – 0.07 m / s ) the mixing time was reduced eightfold solely due to changes in channel geometry. An experimental study on the liquid slug lengths, the pressure drop and their relation to the mass transfer have also been performed. Experimental results were validated by a simulation done in Comsol Multiphysics ® . To obtain information for higher velocity rates, simulations were performed up to 0.64 m / s . These velocity variations in the simulation indicate the occurrence of a different flow pattern for high velocities, leading to further mass transfer intensification. | |||||
BibTeX:
@article{Fries2009,
author = {Fries, Donata M. and von Rohr, Philipp Rudolf},
title = {Liquid mixing in gas–liquid two-phase flow by meandering microchannels},
journal = {Chemical Engineering Science},
year = {2009},
volume = {64},
number = {6},
pages = {1326--1335},
url = {http://www.sciencedirect.com/science/article/pii/S0009250908006398}
}
|
|||||
| Frind, E.O. | Rainfall-runoff relationships expressed by distribution parameters | 1969 | Journal of Hydrology Vol. 9(4), pp. 405-426 |
article | URL |
| Abstract: This study is concerned with the statistical parameters of precipitation and of runoff and the interrelations between corresponding parameters. Three processes are considered: the input process (mean annual effective precipitation), the transformation process (basin storage), and the output process (mean annual runoff). The input is assumed to be a pure-random series, with known statistical parameters. The transformation is characterized by an exponential recession curve with one parameter. With these assumptions, equations are developed expressing the statistical parameters of the output for any length of carryover. The validity of these equations is confirmed by means of computer-simulated series, which are analyzed for their moments. The type of distribution of the output is also established. | |||||
BibTeX:
@article{Frind1969,
author = {Frind, Emil O.},
title = {Rainfall-runoff relationships expressed by distribution parameters},
journal = {Journal of Hydrology},
publisher = {Elsevier},
year = {1969},
volume = {9},
number = {4},
pages = {405--426},
url = {http://www.sciencedirect.com/science/article/pii/0022169469900870}
}
|
|||||
| Frippiat, C.C. and Holeyman, A.E. | A comparative review of upscaling methods for solute transport in heterogeneous porous media | 2008 | Journal of Hydrology Vol. 362(1-2), pp. 150-176 |
article | URL |
| Abstract: The classical Fickian model for solute transport in porous media cannot correctly predict the spreading (the dispersion) of contaminant plumes in a heterogeneous subsurface unless its structure is completely characterized. Although the required precision is outside the reach of current field characterization methods, the advection–dispersion model remains the most widely used model among practitioners. Two approaches can be adopted to solve the effect of physical heterogeneity on transport. First, based on a given characterization of the spatial structure of the subsurface, upscaling methods allow the computation of apparent scale-dependent parameters (especially longitudinal dispersivity) to be used in the classical Fickian model. In the second approach, upscaled (non-Fickian) transport equations with scale-independent parameters are used. In this paper, efforts are made to classify and review upscaling methods for Fickian transport parameters and non-Fickian upscaled transport equations for solute transport, with an emphasis on their mathematical properties and their (one-dimensional) analytical formulations. In particular, their capacity to model scale effects in apparent longitudinal dispersion is investigated. Upscaling methods and upscaled models are illustrated in the case of two three-dimensional synthetic aquifers, with lognormal hydraulic conductivity distributions characterized by variance values of 2 and 8. | |||||
BibTeX:
@article{Frippiat2008,
author = {Frippiat, Christophe C. and Holeyman, Alain E.},
title = {A comparative review of upscaling methods for solute transport in heterogeneous porous media},
journal = {Journal of Hydrology},
year = {2008},
volume = {362},
number = {1-2},
pages = {150--176},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408004228}
}
|
|||||
| Fryar, A.E. and Schwartz, F.W. | Hydraulic-conductivity reduction, reaction-front propagation, and preferential flow within a model reactive barrier | 1998 | Journal of Contaminant Hydrology Vol. 32(3-4), pp. 333-351 |
article | URL |
| Abstract: Recent work has demonstrated the utility of reactive barriers for transformation or immobilization of contaminants in ground water. However, reaction-induced changes in hydraulic conductivity may compromise the reactive barrier by diverting flow or focusing breakthrough of contaminants. For an acidic, ferric solution flowing through calcareous sand in column experiments, we investigated how hydraulic-conductivity reduction, reaction-front propagation, and fingering depend upon the reactive solid volume, reactive surface area, and pore-water velocity. Hydraulic-conductivity reductions are greater with larger initial pore-water velocity, calcite surface area, or calcite volume. Reductions in hydraulic conductivity (up to four orders of magnitude) result primarily from CO2 (g) exsolution rather than from ferric oxyhydroxide precipitation and may be at least partly reversed as bubbles migrate. Although fingering is both driven and repressed by pore-scale hydraulic changes, the velocity of the reaction front, width of the primary reaction zone, and maximum length of the largest finger appear to be insensitive to macroscopic changes in hydraulic conductivity at a constant flow rate. Reaction-front velocity increases as the ratio of initial calcite volume to pore-water velocity decreases, whereas zonal width and maximum finger length appear to increase as the Damköhler number decreases for a given calcite grain-size distribution. These results offer guidelines for improving the efficiency of reactive barriers when the reaction rate equals or exceeds the rate of mass transfer. | |||||
BibTeX:
@article{Fryar1998,
author = {Fryar, Alan E and Schwartz, Franklin W},
title = {Hydraulic-conductivity reduction, reaction-front propagation, and preferential flow within a model reactive barrier},
journal = {Journal of Contaminant Hydrology},
year = {1998},
volume = {32},
number = {3-4},
pages = {333--351},
url = {http://www.sciencedirect.com/science/article/pii/S0169772298000576}
}
|
|||||
| Fuerhacker, M., Haile, T.M., Monai, B. and Mentler, A. | Performance of a filtration system equipped with filter media for parking lot runoff treatment | 2011 | Desalination Vol. 275(1-3), pp. 118-125 |
article | URL |
| Abstract: Stormwater runoff from automobile trafficked areas introduces significant loads of pollutants to receiving water bodies leading to an adverse long term effect. To control runoff pollutants from parking lot, a filtration treatment system with a layered filter media activated carbon, composite, vermiculite and zeolite was installed. The removal of the pollutant constituents was evaluated in this study. During a monitoring period of eighteen months eleven runoff samples were collected from the influent and effluent sections and analyzed for the mentioned pollutant parameters. The mean influent annual load of TSS, Cu and Zn were 2600, 2.1 and 3.5 kg respectively. For the monitoring period mean removal efficiencies of 85% for TSS, 75% for Cu, 73% for Zn, 83% for 16 EPA PAHs, 70 to 98% for individual PAHs, 93% for mineral oil, 71% for NH4–N and 52% for TOC were achieved. Greater than 60% of the Cu load was removed within the filter chambers, but > 60% of Zn and TSS loads were removed in the sedimentation tank, oil separator and geotextile filter mainly due to filtration, precipitation and sorption to sediments. Furthermore, except for chrysene heavier molecular weight PAH compounds were effectively removed than lighter molecular weight PAH compounds. The treatment mechanisms include: filtration, precipitation, adsorption and cation exchange. | |||||
BibTeX:
@article{Fuerhacker2011,
author = {Fuerhacker, Maria and Haile, Tadele Measho and Monai, Bernhard and Mentler, Axel},
title = {Performance of a filtration system equipped with filter media for parking lot runoff treatment},
journal = {Desalination},
year = {2011},
volume = {275},
number = {1--3},
pages = {118--125},
url = {http://www.sciencedirect.com/science/article/pii/S0011916411001676}
}
|
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| Fujikawa, Y. and Fukui, M. | Application of a simple model for assessment of underground radionuclide migration. Part I. Validity of first-order kinetic model approximation | 1993 | Journal of Hydrology Vol. 145(1-2), pp. 125-145 |
article | URL |
| Abstract: As an alternative to the Fickian model of solute diffusion-sorption in matrices of geological media, a first-order kinetic model with diffusion-equivalent rate parameters was developed using temporal moment analysis of breakthrough curves for a parallel fracture system, hollow cylindrical macropores, and cylindrical solid phase. Criteria on the difference between the breakthrough curves of the Fickian model and the first-order kinetic model were also derived through temporal moment analysis. The criterion for the parallel fracture system was examined in detail to determine the validity of a first-order kinetic model approximation in in-situ rock fracture systems. The accuracy of the approximation was greater for smaller fracture spacings, longer groundwater residence time, and larger matrix diffusion coefficients, but was independent of nuclide distribution coefficients. Existence of natural rock-fracture systems to which the kinetic model approximation can be applied was shown to be possible. | |||||
BibTeX:
@article{Fujikawa1993,
author = {Fujikawa, Yoko and Fukui, Masami},
title = {Application of a simple model for assessment of underground radionuclide migration. Part I. Validity of first-order kinetic model approximation},
journal = {Journal of Hydrology},
year = {1993},
volume = {145},
number = {1-2},
pages = {125--145},
url = {http://www.sciencedirect.com/science/article/pii/002216949390223V}
}
|
|||||
| Furman, E. | On a multivariate gamma distribution | 2008 | Statistics & Probability Letters Vol. 78(15), pp. 2353-2360 |
article | URL |
| Abstract: A multivariate probability model possessing a dependence structure that is reflected in its variance–covariance structure and gamma distributed univariate margins is introduced and studied. In particular, the higher order moments and cumulants, Chebyshev-type inequalities and multivariate probability density functions are derived. The model suggested herein is believed to be capable of describing dependent insurance losses. | |||||
BibTeX:
@article{Furman2008,
author = {Furman, Edward},
title = {On a multivariate gamma distribution},
journal = {Statistics & Probability Letters},
year = {2008},
volume = {78},
number = {15},
pages = {2353--2360},
url = {http://www.sciencedirect.com/science/article/pii/S0167715208001338}
}
|
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| Gabrovšek, F. and Dreybrodt, W. | Spreading of tracer plumes through confined telogenetic karst aquifers: A model | 2011 | Journal of Hydrology Vol. 409(1-2), pp. 20-29 |
article | URL |
| Abstract: To calculate spreading of a tracer or contaminant through an aquifer all details of the aquifer, e.g. distribution of hydraulic parameters, must be known. This is not possible in nature. To study the spreading of plumes through karst, we have used a digital model of a confined karst aquifer at different stages of early karstification. In these models all details such as fracture aperture widths, their lengths and widths, and the hydraulic boundary conditions are known. Therefore the flow velocity of water can be calculated in each fracture. Using this information a particle tracking method is employed to calculate the propagation and spreading of a plume caused by an instantaneous input pulse into selected regions of the aquifer. From this information the time dependence of the outflow of particles from any selected region is obtained. This function represents the transfer response function for an instantaneous Dirac δ-function input. Two digital karst models are designed. In the first, homogeneous one, the aperture widths of the fractures are statistically distributed but of similar width. In the second a coarse percolating net of prominent fractures with larger constant aperture width is embedded into the dense net of narrow fissures. Propagation of the plumes and the transfer-response function are presented at the onset of karstification and at different times of karst evolution. If particles are injected at the entrance of evolving karst channels propagating towards the output boundary tracer breakthrough times increase with increasing time of karst evolution until shortly before breakthrough of the karst conduit they drop to half of their maximal value. With increasing evolution of the karst aquifer the hydraulic heads are redistributed and regions of low hydraulic gradients in the upstream side of the aquifer are created. Particles injected into fractures which have stopped dissolutional widening of their aperture widths and are located in regions of low gradient are kept in these regions for long times in the order of 100 years until they have propagated towards regions of high hydraulic heads, where a “fan like” plume develops along the pathway of steepest gradient. | |||||
BibTeX:
@article{Gabrovsek2011,
author = {Gabrovšek, Franci and Dreybrodt, Wolfgang},
title = {Spreading of tracer plumes through confined telogenetic karst aquifers: A model},
journal = {Journal of Hydrology},
year = {2011},
volume = {409},
number = {1-2},
pages = {20--29},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411004859}
}
|
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| Gabrovsek, F., Romanov, D. and Dreybrodt, W. | Early karstification in a dual-fracture aquifer: the role of exchange flow between prominent fractures and a dense net of fissures | 2004 | Journal of Hydrology Vol. 299(1-2), pp. 45-66 |
article | URL |
| Abstract: The early evolution of flow and hydraulic conductivity in a dual-fracture karst aquifer is investigated by numerical modelling. The initial aquifer consists of a dense net of narrow fissures with aperture widths a0 and a coarser network of prominent fractures with aperture width A0>a0 embedded into it. Dissolutional widening by carbon dioxide containing waters aggressive to calcite increases hydraulic conductivity in the net and in the prominent fractures. To elucidate the effects of hydraulic and chemical coupling between these two flow systems the evolution of the karst aquifer has been modelled under constant head boundary conditions for various coupling strengths given by the ratio a0/A0=M. For an isolated net of prominent fractures, a0=0, and M=0 a conduit evolves along one of the percolating pathways and exhibits the well known breakthrough behaviour of single 1D conduits. With increasing coupling, M<0.3, the breakthrough times rise from 30 ky (M=0) to 60 ky (M=0.3), but the pattern of the fracture widening remains almost unchanged. With further increasing M the breakthrough times drop significantly and remain constant at values of about 4 ky for M>0.5. In these cases, owing to increasing a0, short cuts through the narrow fissures become more favourable than breakthrough along the meandering pathway of the prominent fractures. It is shown that exchange flow between the prominent fractures and the dense net of narrow fissures plays an important role in the evolution of the aquifer. Flow from prominent fractures into the net can either leave the aquifer through this net, or it can return back into a pathway of prominent fractures downstream. In the first case enhanced inflow of aggressive solution into the prominent fractures at the input increases the dissolution rates and reduces breakthrough time consequently. In the other case the solution which reenters into a prominent fracture has gained a calcium concentration closer to equilibrium than that in the prominent fracture. This reduces dissolution rates in its downstream part an retards karstification. Our model scenarios presented show a complex interplay between these two mechanisms. | |||||
BibTeX:
@article{Gabrovsek2004,
author = {Gabrovsek, F. and Romanov, D. and Dreybrodt, W.},
title = {Early karstification in a dual-fracture aquifer: the role of exchange flow between prominent fractures and a dense net of fissures},
journal = {Journal of Hydrology},
year = {2004},
volume = {299},
number = {1-2},
pages = {45--66},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404000897}
}
|
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| Gale L, C. | Environmental equity: Does it play a role in WTE siting? [BibTeX] |
1996 | Journal of Hazardous Materials Vol. 47(1-3), pp. 303-312 |
article | DOI URL |
BibTeX:
@article{GaleL1996,
author = {Gale L, Carr},
title = {Environmental equity: Does it play a role in WTE siting?},
journal = {Journal of Hazardous Materials},
year = {1996},
volume = {47},
number = {1-3},
pages = {303--312},
url = {http://www.sciencedirect.com/science/article/pii/0304389495001182},
doi = {http://dx.doi.org/10.1016/0304-3894(95)00118-2}
}
|
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| Ganjyal, G. and Hanna, M. | A Review on Residence Time Distribution (RTD) in Food Extruders and Study on the Potential of Neural Networks in RTD Modeling | 2002 | Journal of Food Science Vol. 67(6), pp. 1996-2002 |
article | URL |
| Abstract: Residence time distribution and mean residence time depend on process variables, namely feed rate, screw speed, feed moisture content, barrel temperature, die temperature and die diameter. Flow in an extruder has been modeled by simulating residence time distribution, assuming the extruder to be a series of continuous-stirred-tank or plug-flow reactors. Others have developed relationships for mean residence time as functions of process variables. Better models can be developed using neural networks. As an example, data from the literature were used to model mean residence time as a function of process variables using statistical regression and neural networks. Neural network models performed better than regression models. | |||||
BibTeX:
@article{Ganjyal2002,
author = {Ganjyal, G. and Hanna, M.},
title = {A Review on Residence Time Distribution (RTD) in Food Extruders and Study on the Potential of Neural Networks in RTD Modeling},
journal = {Journal of Food Science},
publisher = {Blackwell Publishing Ltd},
year = {2002},
volume = {67},
number = {6},
pages = {1996--2002},
url = {http://dx.doi.org/10.1111/j.1365-2621.2002.tb09491.x}
}
|
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| Gao, G., Zhan, H., Feng, S., Huang, G. and Mao, X. | Comparison of alternative models for simulating anomalous solute transport in a large heterogeneous soil column | 2009 | Journal of Hydrology Vol. 377(3-4), pp. 391-404 |
article | URL |
| Abstract: This study compared five different models for evaluating solute transport in a 1250-cm long, saturated and highly heterogeneous soil column. The five models were: the convection–dispersion equation (CDE), the mobile–immobile model (MIM), the convective lognormal transfer function model (CLT), the spatial fractional advection–dispersion equation (FADE) and the continuous time random walk model (CTRW). Each of these models was used to fit the breakthrough curve (BTC) at each distance individually and was also used to fit the BTCs at different distances simultaneously. Dependence of estimated parameters on distance was investigated. The estimated parameters at 200 cm were used to make predictions at subsequent distances. Highly anomalous transport behavior was observed in the column as the BTCs demonstrated significantly irregular shape and long tailing. This study indicated that CDE, CLT and FADE were unable to describe the anomalous BTCs adequately and their parameters changed with transport distance significantly. Compared to CDE, CLT and FADE, MIM better captured the evolution of anomalous BTCs. However, MIM did not explain the distinct BTC tailing satisfactorily. In contrast to MIM, CTRW better simulated the long tails of BTCs. The spreading parameter (β) of CTRW was close to one and remained approximately constant at different travel distances. To make the comparison of these five models more general beyond the specific transport condition in the soil column, a generic evaluation of the advantages and disadvantages of these five models was presented in terms of their theory framework and a priori knowledge of the model behaviors. | |||||
BibTeX:
@article{Gao2009,
author = {Gao, Guangyao and Zhan, Hongbin and Feng, Shaoyuan and Huang, Guanhua and Mao, Xiaomin},
title = {Comparison of alternative models for simulating anomalous solute transport in a large heterogeneous soil column},
journal = {Journal of Hydrology},
year = {2009},
volume = {377},
number = {3-4},
pages = {391--404},
url = {http://www.sciencedirect.com/science/article/pii/S002216940900540X}
}
|
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| García-Serna, J., García-Verdugo, E., Hyde, J.R., Fraga-Dubreuil, J., Yan, C., Poliakoff, M. and Cocero, M.J. | Modelling residence time distribution in chemical reactors: A novel generalised n-laminar model: Application to supercritical CO2 and subcritical water tubular reactors | 2007 | The Journal of Supercritical Fluids Vol. 41(1), pp. 82-91 |
article | URL |
| Abstract: A new two-parameter RTD model based on the one-parameter laminar flow model has been proposed. The model, ‘n-laminar model’, is defined in time domain and considers a generalization of the parabolic velocity profile across radial direction; its mathematical deduction is presented in text. The model has been validated for both supercritical and near critical CO2 and near critical H2O. It is shown how the proposed two-parameter model works much better than the classical models with one, two or even three parameters for both CO2 and H2O under near critical and supercritical conditions. A range of experiments at 10–30 MPa and 100–250 °C at different flowrates are presented. Traditional models, such as n-tanks in series or a combination of n-tanks with a plug flow resulted in a poor explanation of the behaviour in most cases with average errors over 100%. Laminar flow has shown the best results within all these classical models, with a mean average error of 50%. The proposed model predicts with an average error of less than 10–20%. Thus the generalization of the laminar flow to n-laminar is a significant improvement over traditional models. This model is the first successful attempt for the modelling of RTD curves at high pressures. | |||||
BibTeX:
@article{Garcia-Serna2007,
author = {García-Serna, J. and García-Verdugo, E. and Hyde, J. R. and Fraga-Dubreuil, J. and Yan, C. and Poliakoff, M. and Cocero, M. J.},
title = {Modelling residence time distribution in chemical reactors: A novel generalised n-laminar model: Application to supercritical CO2 and subcritical water tubular reactors},
journal = {The Journal of Supercritical Fluids},
year = {2007},
volume = {41},
number = {1},
pages = {82--91},
url = {http://www.sciencedirect.com/science/article/pii/S0896844606002294}
}
|
|||||
| Gardes, L., Girard, S. and Guillou, A. | Weibull tail-distributions revisited: A new look at some tail estimators | 2011 | Journal of Statistical Planning and Inference Vol. 141(1), pp. 429-444 |
article | URL |
| Abstract: In this paper, we propose to include Weibull tail-distributions in a more general family of distributions. In particular, the considered model also encompasses the whole Fréchet maximum domain of attraction as well as log-Weibull tail-distributions. The asymptotic normality of some tail estimators based on the log-spacings between the largest order statistics is established in a unified way within the considered family. This result permits to understand the similarity between most estimators of the Weibull tail-coefficient and the Hill estimator. Some different asymptotic properties, in terms of bias, rate of convergence, are also highlighted. | |||||
BibTeX:
@article{Gardes2011,
author = {Gardes, Laurent and Girard, Stéphane and Guillou, Armelle},
title = {Weibull tail-distributions revisited: A new look at some tail estimators},
journal = {Journal of Statistical Planning and Inference},
year = {2011},
volume = {141},
number = {1},
pages = {429--444},
url = {http://www.sciencedirect.com/science/article/pii/S0378375810003113}
}
|
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| Gasca, D. and Ross, D. | The use of wetland water balances to link hydrogeological processes to ecological effects | 2009 | Hydrogeology Journal Vol. 17(1), pp. 115-133 |
article | URL |
| Abstract: A methodology for modelling wetland water levels using the water balance approach was developed for Pulborough Brooks Site of Special Scientific Interest in West Sussex, in the UK. The methodology was applied to assess potential groundwater abstraction impacts on communities and species of ecological importance in the wetland. The modelling methodology links regional hydrogeological processes to wetland hydrology and ecology that is typically influenced by processes that take place at a more reduced spatial scale. To assess impacts, it is necessary to understand the hydrological sources of water that are affected by abstraction as well as to consider how the magnitude of these processes relates to other processes that influence wetland water levels. Water levels are commonly the most important factor determining the presence or absence of species or communities in a wetland and the model predicts wetland water levels and assesses how suitable these water levels are for species of ecological significance. Model results show that typical historic rates of abstraction have not resulted in an adverse effect on the integrity of the Pulborough Brooks relative to a ‘natural’ (no abstraction) scenario. | |||||
BibTeX:
@article{Gasca2009,
author = {Gasca, David and Ross, Don},
title = {The use of wetland water balances to link hydrogeological processes to ecological effects},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {115--133},
url = {http://dx.doi.org/10.1007/s10040-008-0407-x}
}
|
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| Gautam, P., Raj Pant, S. and Ando, H. | Mapping of subsurface karst structure with gamma ray and electrical resistivity profiles: a case study from Pokhara valley, central Nepal | 2000 | Journal of Applied Geophysics Vol. 45(2), pp. 97-110 |
article | URL |
| Abstract: Electrical resistivity (sounding with Schlumberger array and dipole–dipole imaging) and natural gamma ray intensity measurements were made over the karst features (subsurface flow-channels, solution cavities, sinkholes) in the Pokhara valley, central Nepal. In the Powerhouse area, the upper 60–80 m section of the basin-filling Quaternary sediments is represented by layered clastic sediments (gravel, silt, clay) that are represented by KQ-type (ρ1<ρ2>ρ3>ρ4) electrical sounding (ES) curves. The true electrical resistivity of the layers has a wide range of variation (a few hundreds to several tens of thousands of Ω m) such that it is possible to determine both the vertical and lateral subsurface geological variations by integrating the electrical resistivity profiling and sounding techniques. Total gamma ray intensity profiles measured over various karstified locations reveal significant anomalies (up to 100 counts per second, cps) over the known or unknown subsurface openings. In the Powerhouse area, presence of a network of at least three linear NNE–SSW oriented subsurface channels, made by past and present underground flow-channels, is inferred. In interpreted electrical image profiles, contours of elevated resistivity reflect the cross-sectional geometry of cavities. The gamma-ray method is sensitive to near-surface cavities while the electrical image effectively locates the void spaces at intermediate (up to 5–20 m) depths. An exploration program involving rapid radiometric mapping followed by selective electrical imaging is recommended for future exploration of karst-prone areas in the valley. | |||||
BibTeX:
@article{Gautam2000,
author = {Gautam, Pitambar and Raj Pant, Surendra and Ando, Hisao},
title = {Mapping of subsurface karst structure with gamma ray and electrical resistivity profiles: a case study from Pokhara valley, central Nepal},
journal = {Journal of Applied Geophysics},
year = {2000},
volume = {45},
number = {2},
pages = {97--110},
url = {http://www.sciencedirect.com/science/article/pii/S0926985100000227}
}
|
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| van Geen, A., Robertson, A.P. and Leckie, J.O. | Complexation of carbonate species at the goethite surface: Implications for adsorption of metal ions in natural waters | 1994 | Geochimica et Cosmochimica Acta Vol. 58(9), pp. 2073-2086 |
article | URL |
| Abstract: Headspace PCo2 was measured with an infrared gas analyzer over an equilibrated goethite suspension to determine adsorption of carbonate species in the pH range 3 to 8. For a 2 g/L goethite suspension in 0.1 N NaClO4 (~3 10−4 M surface sites), the fraction of carbonate species adsorbed increased from 0.15 at pH 3 to a maximum of 0.56 at pH 6. In 0.01 N NaClO4, the fraction of carbonate species adsorbed at pH 6 increased to 0.67. The total concentration of CO2 in the suspension increased from about 0.4 to 0.6 10−4 M in the pH range of these experiments. The development of surface charge at the goethite surface was determined in the pH range 4 to 11 by potentiometric titration under controlled low CO2 conditions. No hysteresis was observed between the acid and base legs of titrations in 0.10, 0.03, and 0.01 N NaClO4 resulting in a pHpzc of 8.9. The carbonate species adsorption data were modelled using the least squares optimization program FITEQL for the diffuse double-layer model and the triplelayer model using stoichiometries of the type Fe-OCOOH and Fe-OCOO− for surface bound carbonate species. The model results are consistent with separate experiments showing a significant reduction in chromate adsorption on goethite as the partial pressure of CO2 was increased from <5 to 450 and 40,000 μatm. Our data suggest that mineral oxide surface sites which control solid/solute partitioning of metal ions in natural systems may be largely bound to adsorbed carbonate species. | |||||
BibTeX:
@article{Geen1994,
author = {van Geen, Alexander and Robertson, Alexander P and Leckie, James O},
title = {Complexation of carbonate species at the goethite surface: Implications for adsorption of metal ions in natural waters},
journal = {Geochimica et Cosmochimica Acta},
year = {1994},
volume = {58},
number = {9},
pages = {2073--2086},
url = {http://www.sciencedirect.com/science/article/pii/0016703794902860}
}
|
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| Gelhar, L.W., Gutjahr, A.L. and Naff, R.L. | Stochastic analysis of macrodispersion in a stratified aquifer | 1979 | Water Resources Research Vol. 15(6), pp. 1387-1397 |
article | URL |
| Abstract: The longitudinal dispersion produced as a result of vertical variations of hydraulic conductivity in a stratified aquifer is analyzed by treating the variability of conductivity and concentration as homogeneous stochastic processes. The mass transport process is described using a first-order approximation which is analogous to that of G. I. Taylor for flow in tubes. The resulting stochastic differential equation describing the concentration field is solved using spectral representations. The results of the analysis demonstrate that for large time the longitudinal dispersivity approaches a constant value which is dependent on statistical properties of the medium. The analysis also describes the transient development of the dispersive process and some non-Fickian effects which occur early in the displacement process. | |||||
BibTeX:
@article{Gelhar1979,
author = {Gelhar, Lynn W. and Gutjahr, Allan L. and Naff, Richard L.},
title = {Stochastic analysis of macrodispersion in a stratified aquifer},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1979},
volume = {15},
number = {6},
pages = {1387--1397},
url = {http://dx.doi.org/10.1029/WR015i006p01387}
}
|
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| Gelhar, L.W., Welty, C. and Rehfeldt, K.R. | A critical review of data on field-scale dispersion in aquifers | 1992 | Water Resources Research Vol. 28(7), pp. 1955-1974 |
article | URL |
| Abstract: A critical review of dispersivity observations from 59 different field sites was developed by compiling extensive tabulations of information on aquifer type, hydraulic properties, flow configuration, type of monitoring network, tracer, method of data interpretation, overall scale of observation and longitudinal, horizontal transverse and vertical transverse dispersivities from original sources. This information was then used to classify the dispersivity data into three reliability classes. Overall, the data indicate a trend of systematic increase of the longitudinal dispersivity with observation scale but the trend is much less clear when the reliability of the data is considered. The longitudinal dispersivities ranged from 10−2 to 104 m for scales ranging from 10−1 to 105 m, but the largest scale for high reliability data was only 250 m. When the data are classified according to porous versus fractured media there does not appear to be any significant difference between these aquifer types. At a given scale, the longitudinal dispersivity values are found to range over 2–3 orders of magnitude and the higher reliability data tend to fall in the lower portion of this range. It is not appropriate to represent the longitudinal dispersivity data by a single universal line. The variations in dispersivity reflect the influence of differing degrees of aquifer heterogeneity at different sites. The data on transverse dispersivities are more limited but clearly indicate that vertical transverse dispersivities are typically an order of magnitude smaller than horizontal transverse dispersivities. Reanalyses of data from several of the field sites show that improved interpretations most often lead to smaller dispersivities. Overall, it is concluded that longitudinal dispersivities in the lower part of the indicated range are more likely to be realistic for field applications. | |||||
BibTeX:
@article{Gelhar1992,
author = {Gelhar, Lynn W. and Welty, Claire and Rehfeldt, Kenneth R.},
title = {A critical review of data on field-scale dispersion in aquifers},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1992},
volume = {28},
number = {7},
pages = {1955--1974},
url = {http://dx.doi.org/10.1029/92WR00607}
}
|
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| Gemai, C. | Generalized log-normal distributions with reliability application | 1995 | Computational Statistics & Data Analysis Vol. 19(3), pp. 309-319 |
article | URL |
| Abstract: A specific scale must be used to collect data in an experiment, but this scale may or may not be the appropriate scale to analyze the data thus collected. In this paper, we study a family of three-parameter distributions which includes the log-normal distribution as a special case, and one of the parameters plays the role of choosing a suitable scale for subsequent analysis. Some basic properties and maximum likelihood estimation of the unknown parameters are discussed, and an easy-to-use goodness-of-fit test is developed. A real data set, to which the usual Weibull, log-normal and gamma distributions cannot be fitted, is used to demonstrate the potential applicability of this family of distributions. | |||||
BibTeX:
@article{Gemai1995,
author = {Gemai, Chen},
title = {Generalized log-normal distributions with reliability application},
journal = {Computational Statistics & Data Analysis},
year = {1995},
volume = {19},
number = {3},
pages = {309--319},
url = {http://www.sciencedirect.com/science/article/pii/0167947393E00478}
}
|
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| Genthon, P., Wirrmann, D., Hoibian, T. and Allenbach, M. | Steady water level and temperature in a karstic system: The case of the coral Lifou Island (SW Pacific) | 2008 | Comptes Rendus Geoscience Vol. 340(8), pp. 513-522 |
article | URL |
| Abstract: Lifou is an atoll uplifted to a near 100 m height near the Vanuatu Trench. Extensive karstification is recorded in the outer coral rim and to a lesser extend in the lagoon type limestones of the inner island. The orientations found in the longest karstic networks correspond rather well to the main fracture directions, but near coasts, the galleries are controlled by the paleo-shoreline, suggesting that mixing corrosion might be involved during cave formation. The freshwater level and temperature, recorded during one year inside two caves present smooth variations, if tidal components near 12 and 24 h periods are removed, and are poorly correlated with rain. Comparison with data recorded in a continental karst (Baget, Pyrénées) and in the chalk of the Paris Basin indicates that Lifou lacks an organized channel network able to collect and transfer quickly rainwater toward the phreatic zone. | |||||
BibTeX:
@article{Genthon2008,
author = {Genthon, Pierre and Wirrmann, Denis and Hoibian, Thierry and Allenbach, Michel},
title = {Steady water level and temperature in a karstic system: The case of the coral Lifou Island (SW Pacific)},
journal = {Comptes Rendus Geoscience},
year = {2008},
volume = {340},
number = {8},
pages = {513--522},
url = {http://www.sciencedirect.com/science/article/pii/S1631071308001193}
}
|
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| Georgakakos, A.P. and Kabouris, J.C. | A streamflow model using physically-based instantaneous unit hydrographs | 1989 | Journal of Hydrology Vol. 111(1-4), pp. 107-131 |
article | URL |
| Abstract: The Geomorphologic Instantaneous Unit Hydrograph watershed modeling approach is extended to account for subsurface runoff. Watershed response to rainfall is modelled as a Markov process whose parameters can be related to physical watershed characteristics. Time-varying instantaneous unit hydrographs are subsequently derived and convoluted with antecedent rainfall intensities to generate total streamflow discharges. This watershed model was applied to simulate the Little River Watershed in southeast Georgia. Predicted streamflows were found to be in good agreement with streamgage measurements. | |||||
BibTeX:
@article{Georgakakos1989,
author = {Georgakakos, Aris P. and Kabouris, John C.},
title = {A streamflow model using physically-based instantaneous unit hydrographs},
journal = {Journal of Hydrology},
year = {1989},
volume = {111},
number = {1-4},
pages = {107--131},
url = {http://www.sciencedirect.com/science/article/pii/0022169489902552}
}
|
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| George, L.D. and Ponta, G.M. | Dye study tracks historical pathway of VOC-bearing industrial wastewater from failed pond at metals coating facility | 2002 | Engineering Geology Vol. 65(2-3)Engineering and Environmental Impacts of Karst, pp. 159-167 |
article | URL |
| Abstract: Nearly 10 years after initiating a ground water assessment and documenting a stable mass of VOC-bearing ground water in the upper karst aquifer, the Post-Closure Care regulatory process required a dye study to trace ground water movement. The regulatory impetus was the location of a major spring, regionally downgradient from the facility, used as a municipal drinking water supply. | |||||
BibTeX:
@article{George2002,
author = {George, Lois D and Ponta, Gheorghe M},
title = {Dye study tracks historical pathway of VOC-bearing industrial wastewater from failed pond at metals coating facility},
booktitle = {Engineering and Environmental Impacts of Karst},
journal = {Engineering Geology},
year = {2002},
volume = {65},
number = {2-3},
pages = {159--167},
url = {http://www.sciencedirect.com/science/article/pii/S0013795201001235}
}
|
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| Gessner, K., Kühn, M., Rath, V., Kosack, C., Blumenthal, M. and Clauser, C. | Coupled Process Models as a Tool for Analysing Hydrothermal Systems | 2009 | Surveys in Geophysics Vol. 30(3), pp. 133-162 |
article | URL |
| Abstract: Hydrothermal systems are characterised by complex interactions between heat transfer, fluid flow, deformation, species transport and chemical reactions. Numerical models can provide quantitatively constrained information in regions where acquisition of new data is difficult or expensive thus providing a means for reducing risks, costs, and effort during targeting, production, and management of resources linked to hydrothermal systems. Here we show how numerical simulations of hydrothermal processes can be used to better understand coupled reactive transport in modern geothermal systems and in ancient hydrothermal ore deposits. We give examples based on the Enhanced Geothermal System at Soultz-sous-Forêts in France, hydrothermal mineralisation at Mount Isa in Australia, and the geothermal resource at Hamburg-Allermöhe in Germany. | |||||
BibTeX:
@article{Gessner2009,
author = {Gessner, K. and Kühn, M. and Rath, V. and Kosack, C. and Blumenthal, M. and Clauser, C.},
title = {Coupled Process Models as a Tool for Analysing Hydrothermal Systems},
journal = {Surveys in Geophysics},
publisher = {Springer Netherlands},
year = {2009},
volume = {30},
number = {3},
pages = {133--162},
url = {http://dx.doi.org/10.1007/s10712-009-9067-1}
}
|
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| Gessner, T.P., Kadlec, R.H. and Reaves, R.P. | Wetland remediation of cyanide and hydrocarbons | 2005 | Ecological Engineering Vol. 25(4), pp. 457-469 |
article | URL |
| Abstract: Cyanide is a common constituent present in groundwater from historical aluminum industry landfills. Aluminum manufacturing produces wastes which contain cyanide, together with fluoride, a variety of metals, and some petroleum hydrocarbons. These leachates pose a moderate threat to receiving ecosystems and human health. Source control is virtually impossible, and physico-chemical removal processes are expensive and energy intensive. This pilot project investigated the use of free water surface wetlands for the reduction of complex and free cyanide and associated pollutants in water from a groundwater spring. Shallow basins, initially planted with cattail (Typha latifolia) and bulrush (Schoenoplectus tabernaemontani), subsequently converted to coontail (Ceratophyllum demersum) and pondweed (Potamageton spp.). Both total and free cyanide were effectively reduced during 7 d detention, by 56% and 88%, respectively. Gasoline range organics and diesel range organics were reduced by approximately 67%. These removals are lower bound estimates, because effluent concentrations were often below detection. First order areal removal rate constants were in the range 13–100 m/year for the various constituents. Preliminary, synoptic studies indicated little volatilization of the cyanide, but significant microbial degradation, and essentially no harmful by-products. The full-scale treatment wetland is entering the final design stages and is scheduled for construction in 2004. | |||||
BibTeX:
@article{Gessner2005,
author = {Gessner, Timothy P. and Kadlec, Robert H. and Reaves, Richard P.},
title = {Wetland remediation of cyanide and hydrocarbons},
journal = {Ecological Engineering},
year = {2005},
volume = {25},
number = {4},
pages = {457--469},
url = {http://www.sciencedirect.com/science/article/pii/S0925857405001825}
}
|
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| Geyer, T., Birk, S., Licha, T., Liedl, R. and Sauter, M. | Multitracer Test Approach to Characterize Reactive Transport in Karst Aquifers | 2007 | Ground Water Vol. 45(1), pp. 36-45 |
article | URL |
| Abstract: A method to estimate reactive transport parameters as well as geometric conduit parameters from a multitracer test in a karst aquifer is provided. For this purpose, a calibration strategy was developed applying the two-region nonequilibrium model CXTFIT. The ambiguity of the model calibration was reduced by first calibrating the model with respect to conservative tracer breakthrough and later transferring conservative transport parameters to the reactive model calibration. The reactive transport parameters were only allowed to be within a defined sensible range to get reasonable calibration values. This calibration strategy was applied to breakthrough curves obtained from a large-scale multitracer test, which was performed in a karst aquifer of the Swabian Alb, Germany. The multitracer test was conducted by the simultaneous injection of uranine, sulforhodamine G, and tinopal CBS-X. The model succeeds to represent the tracer breakthrough curves (TBCs) of uranine and sulforhodamine G and verifies that tracer-rock interactions preferably occur in the immobile fluid region, although the fraction of this region amounts to only 3.5% of the total water. However, the model failed to account for the long tailing observed in the TBC of tinopal CBS-X. Sensitivity analyses reveal that model results for the conservative tracer transport are most sensitive to average velocity and volume fraction of the mobile fluid region, while dispersion and mass transfer coefficients are least influential. Consequently, reactive tracer calibration allows the determination of sorption sites in the mobile and immobile fluid region at small retardation coefficients. | |||||
BibTeX:
@article{Geyer2007,
author = {Geyer, Tobias and Birk, Steffen and Licha, Tobias and Liedl, Rudolf and Sauter, Martin},
title = {Multitracer Test Approach to Characterize Reactive Transport in Karst Aquifers},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2007},
volume = {45},
number = {1},
pages = {36--45},
url = {http://dx.doi.org/10.1111/j.1745-6584.2006.00261.x}
}
|
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| Ghazi, A.T.I.M., Gunam Resul, M.F.M., Yunus, R. and Shean Yaw, T.C. | Preliminary design of oscillatory flow biodiesel reactor for continuous biodiesel production from jatropha triglycerides | 2008 | Journal of Engineering Science and Technology (JESTEC) Vol. 3(2), pp. 138-145 |
article | |
| Abstract: The concept of a continuous process in producing biodiesel from jatropha oil by using an Oscillatory Flow Biodiesel Reactor (OFBR) is discussed in this paper. It has been recognized that the batch stirred reactor is a primary mode used in the synthesis of biodiesel. However, pulsatile flow has been extensively researcehed and the fundamental principles have been successfully developed upon which its hydrodynamics are based. Oscillatory flow biodiesel reactor offers precise control of mixing by means of the baffle geometry and pulsation which facilitates to continuous operation, giving plug flow residence time distribution with high turbulence and enhanced mass and heat transfer. In conjunction with the concept of reactor design, parameters such as reactor dimensions, the hydrodynamic studies and physical properties of reactants must be considered prior to the design work initiated recently. The OFBR reactor design involves the use of simulation software, ASPEN PLUS and the reactor design fundamentals. Following this, the design parameters shall be applied in fabricating the OFBR for laboratory scale biodiesel production. | |||||
BibTeX:
@article{Ghazi2008,
author = {Ghazi, Azhari T. I. Mohd. and Gunam Resul, M. F. M. and Yunus, R. and Shean Yaw, T. C.},
title = {Preliminary design of oscillatory flow biodiesel reactor for continuous biodiesel production from jatropha triglycerides},
journal = {Journal of Engineering Science and Technology (JESTEC)},
year = {2008},
volume = {3},
number = {2},
pages = {138--145}
}
|
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| Ghiassi, M. and Nangoy, S. | A dynamic artificial neural network model for forecasting nonlinear processes | 2009 | Computers & Industrial Engineering Vol. 57(1)Collaborative e-Work Networks in Industrial Engineering, pp. 287-297 |
article | URL |
| Abstract: This paper presents the development of a dynamic architecture for artificial neural network (DAN2) model for solving nonlinear forecasting and pattern recognition problems. DAN2 is a data driven, feed forward, multilayer, dynamic architecture that is based on the principle of learning and accumulating knowledge at each layer and propagating and adjusting this knowledge forward to the next layer. Model building is automatically and dynamically repeated until a model that accurately captures the behavior of the process is determined. The resulting model is then used to forecast future values. To assess DAN2’s effectiveness, we present forecasting results for a variety of nonlinear processes that have been extensively studied in the literature and report comparative results. The set of nonlinear processes considered covers most nonlinear formulations facing researchers. We show DAN2 to be more accurate and to perform consistently better than alternative approaches employed in forecasting nonlinear processes. | |||||
BibTeX:
@article{Ghiassi2009,
author = {Ghiassi, M. and Nangoy, Stanley},
title = {A dynamic artificial neural network model for forecasting nonlinear processes},
booktitle = {Collaborative e-Work Networks in Industrial Engineering},
journal = {Computers & Industrial Engineering},
year = {2009},
volume = {57},
number = {1},
pages = {287--297},
url = {http://www.sciencedirect.com/science/article/pii/S036083520800315X}
}
|
|||||
| Gibilaro, L. | Residence time distributions in regions of continuous flow systems | 1979 | Chemical Engineering Science Vol. 34(5), pp. 697-702 |
article | URL |
| Abstract: The mean residence time of material in any arbitrarily defined internal region of a continuous flow system is shown to equal the holdup in that region divided by the flow rate through the system as a whole: it is thus independent of the flow rate through the region itself and the manner in which the region connects with the remainder of the system. If the region is well mixed, the region residence time distribution consists of an exponential term together with an impulse at time zero. | |||||
BibTeX:
@article{Gibilaro1979,
author = {Gibilaro, L.G.},
title = {Residence time distributions in regions of continuous flow systems},
journal = {Chemical Engineering Science},
year = {1979},
volume = {34},
number = {5},
pages = {697--702},
url = {http://www.sciencedirect.com/science/article/pii/0009250979851167}
}
|
|||||
| Gilbert, S.G. and Frevert, K. | Public Education [BibTeX] |
2009 | Information Resources in Toxicology, pp. 681-689 | inbook | DOI URL |
BibTeX:
@inbook{Gilbert2009,
author = {Gilbert, Steven G. and Frevert, Katie},
title = {Public Education},
booktitle = {Information Resources in Toxicology},
publisher = {Academic Press},
year = {2009},
pages = {681--689},
edition = {Fourth},
url = {http://www.sciencedirect.com/science/article/pii/B9780123735935000732},
doi = {http://dx.doi.org/10.1016/b978-0-12-373593-5.00073-2}
}
|
|||||
| Ginn, T., Murphy, E., Chilakapati, A. and Seeboonruang, U. | Stochastic-convective transport with nonlinear reaction and mixing: application to intermediate-scale experiments in aerobic biodegradation in saturated porous media | 2001 | Journal of Contaminant Hydrology Vol. 48(1-2), pp. 121-149 |
article | URL |
| Abstract: Aerobic biodegradation of benzoate by Pseudomonas cepacia sp. in a saturated heterogeneous porous medium was simulated using the stochastic-convective reaction (SCR) approach. A laboratory flow cell was randomly packed with low permeability silt-size inclusions in a high permeability sand matrix. In the SCR upscaling approach, the characteristics of the flow field are determined by the breakthrough of a conservative tracer. Spatial information on the actual location of the heterogeneities is not used. The mass balance equations governing the nonlinear and multicomponent reactive transport are recast in terms of reactive transports in each of a finite number of discrete streamtubes. The streamtube ensemble members represent transport via a steady constant average velocity per streamtube and a conventional Fickian dispersion term, and their contributions to the observed breakthroughs are determined by flux-averaging the streamtube solute concentrations. The resulting simulations were compared to those from a high-resolution deterministic simulation of the reactive transport, and to alternative ensemble representations involving (i) effective Fickian travel time distribution function, (ii) purely convective streamtube transport, and (iii) streamtube ensemble subset simulations. The results of the SCR simulation compare favorably to that of a sophisticated high-resolution deterministic approach. | |||||
BibTeX:
@article{Ginn2001,
author = {Ginn, T.R. and Murphy, E.M. and Chilakapati, A. and Seeboonruang, U.},
title = {Stochastic-convective transport with nonlinear reaction and mixing: application to intermediate-scale experiments in aerobic biodegradation in saturated porous media},
journal = {Journal of Contaminant Hydrology},
year = {2001},
volume = {48},
number = {1-2},
pages = {121--149},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200001686}
}
|
|||||
| Ginn, T.R. | Comment on “Groundwater age, life expectancy, and transit time distributions in advective–dispersive systems: 1. Generalized reservoir theory,” by F. Cornaton and P. Perrochet [BibTeX] |
2007 | Advances in Water Resources Vol. 30(4), pp. 1056-1057 |
article | URL |
BibTeX:
@article{Ginn2007,
author = {Ginn, Timothy R.},
title = {Comment on “Groundwater age, life expectancy, and transit time distributions in advective–dispersive systems: 1. Generalized reservoir theory,” by F. Cornaton and P. Perrochet},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {4},
pages = {1056--1057},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001722}
}
|
|||||
| Ginn, T.R. | On the distribution of multicomponent mixtures over generalized exposure time in subsurface flow and reactive transport: Batch and column applications involving residence-time distributions and non-Markovian reaction kinetics | 2000 | Water Resources Research Vol. 36(10), pp. 2895-2903 |
article | URL |
| Abstract: Generalized differential equations that track the evolution of material densities over space, time, and exposure time during reactive transport are specified for simple cases involving linear reversible reactions between two states. Solutions are obtained for demonstration problems involving batch and column conditions. The exposure-time coordinate serves as a measure of residence time of materials that are “convected” (aged) along this dimension depending on the phase in which the material resides, and this exposure-time convection is used to determine the way in which material residence-time (to a particular phase) distributions evolve during reactive transport. The model is simplified to the form of a generalized batch reactor, and the solution is developed by recognizing that this model is identical to the one-dimensional purely convective reactive transport model involving the same boundary conditions and reactions. This places the derived differential equation as the governing equation for the classical Giddings and Eyring [1955] solution for residence time distributions in the two-state Markov chain representation of the batch. In the more general case where reaction rate varies with memory of phase association, the present formulation may be viewed as an extension of composite Markov process modeling to generally non-Markovian reactions. The model is specified for reactive transport in a porous medium in a one-dimensional column and applied to bacterial transport data from a published study where residence time to surfaces controlled the reaction. The formulation and numerical solution are described, and the simulations illustrate the evolution of material density over space, time, and exposure time representing residence time sorbed. | |||||
BibTeX:
@article{Ginn2000,
author = {Ginn, Timothy R.},
title = {On the distribution of multicomponent mixtures over generalized exposure time in subsurface flow and reactive transport: Batch and column applications involving residence-time distributions and non-Markovian reaction kinetics},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2000},
volume = {36},
number = {10},
pages = {2895--2903},
url = {http://dx.doi.org/10.1029/2000WR900171}
}
|
|||||
| Ginn, T.R., Wood, B.D., Nelson, K.E., Scheibe, T.D., Murphy, E.M. and Clement, T. | Processes in microbial transport in the natural subsurface | 2002 | Advances in Water Resources Vol. 25(8-12), pp. 1017-1042 |
article | URL |
| Abstract: This is a review of physical, chemical, and biological processes governing microbial transport in the saturated subsurface. We begin with the conceptual models of the biophase that underlie mathematical descriptions of these processes and the physical processes that provide the framework for recent focus on less understood processes. Novel conceptual models of the interactions between cell surface structures and other surfaces are introduced, that are more realistic than the oft-relied upon DLVO theory of colloid stability. Biological processes reviewed include active adhesion/detachment (cell partitioning between aqueous and solid phase initiated by cell metabolism) and chemotaxis (motility in response to chemical gradients). We also discuss mathematical issues involved in upscaling results from the cell scale to the Darcy and field scales. Finally, recent studies at the Oyster, Virginia field site are discussed in terms of relating laboratory results to field scale problems of bioremediation and pathogen transport in the natural subsurface. | |||||
BibTeX:
@article{Ginn2002,
author = {Ginn, Timothy R. and Wood, Brian D. and Nelson, Kirk E. and Scheibe, Timothy D. and Murphy, Ellyn M. and Clement, T.Prabhakar},
title = {Processes in microbial transport in the natural subsurface},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {8-12},
pages = {1017--1042},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802000465}
}
|
|||||
| Ginn, T.R., Wood, B.D., Nelson, K.E., Scheibe, T.D., Murphy, E.M. and Clement, T. | Processes in microbial transport in the natural subsurface | 2002 | Advances in Water Resources Vol. 25(8-12), pp. 1017-1042 |
article | URL |
| Abstract: This is a review of physical, chemical, and biological processes governing microbial transport in the saturated subsurface. We begin with the conceptual models of the biophase that underlie mathematical descriptions of these processes and the physical processes that provide the framework for recent focus on less understood processes. Novel conceptual models of the interactions between cell surface structures and other surfaces are introduced, that are more realistic than the oft-relied upon DLVO theory of colloid stability. Biological processes reviewed include active adhesion/detachment (cell partitioning between aqueous and solid phase initiated by cell metabolism) and chemotaxis (motility in response to chemical gradients). We also discuss mathematical issues involved in upscaling results from the cell scale to the Darcy and field scales. Finally, recent studies at the Oyster, Virginia field site are discussed in terms of relating laboratory results to field scale problems of bioremediation and pathogen transport in the natural subsurface. | |||||
BibTeX:
@article{Ginn2002a,
author = {Ginn, Timothy R. and Wood, Brian D. and Nelson, Kirk E. and Scheibe, Timothy D. and Murphy, Ellyn M. and Clement, T.Prabhakar},
title = {Processes in microbial transport in the natural subsurface},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {8--12},
pages = {1017--1042},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802000465}
}
|
|||||
| Giona, M., Adrover, A. and Cerbelli, S. | On the use of the pulsed-convection approach for modelling advection-diffusion in chaotic flows—A prototypical example and direct numerical simulations | 2005 | Physica A: Statistical Mechanics and its Applications Vol. 348(0), pp. 37-73 |
article | URL |
| Abstract: This article addresses the application of pulsed system models (in which the advection operator is decoupled from the diffusion operator) for investigating the physics of dispersion/homogenization in deterministic chaotic flows. The analysis is organized along to main directions: (i) the development of a simplified time-continuous model which can be viewed as a generalization in a time-continuous frame of the baker's transformation, and which is amenable to analytical investigation, and (ii) the comparison of the results deriving from several typical pulsed-system models with the direct numerical simulation of the advection-diffusion equation. Both these approaches reveal the intrinsic ambiguity of the pulsed system approach in describing advection-diffusion problems. | |||||
BibTeX:
@article{Giona2005,
author = {Giona, M. and Adrover, A. and Cerbelli, S.},
title = {On the use of the pulsed-convection approach for modelling advection-diffusion in chaotic flows—A prototypical example and direct numerical simulations},
journal = {Physica A: Statistical Mechanics and its Applications},
year = {2005},
volume = {348},
number = {0},
pages = {37--73},
url = {http://www.sciencedirect.com/science/article/pii/S0378437104012774}
}
|
|||||
| Giraldi, D., de’Michieli Vitturi, M., Zaramella, M., Marion, A. and Iannelli, R. | Hydrodynamics of vertical subsurface flow constructed wetlands: Tracer tests with rhodamine WT and numerical modelling | 2009 | Ecological Engineering Vol. 35(2)Pollution control by wetlands, pp. 265-273 |
article | URL |
| Abstract: Typical unsteady unsaturated conditions can profoundly affect the hydrodynamics of vertical subsurface flow constructed wetlands. In this study we analyzed the hydrodynamics of a 33 m2 vertical flow pilot plant, treating municipal secondary effluents. Three different saturation conditions were analyzed under several constant flux regimes: complete saturation, partial saturation with the free water table 20 cm over the bottom of the bed, and complete drainage. Tracer tests were performed in steady state conditions by dosing rhodamine WT as square input signals. Breakthrough curves were analyzed by means of both a classical residence time distribution analysis and an originally developed numerical plug-flow model with longitudinal dispersion adapted to the unsaturated conditions. We found that the degree of global mixing in the vertical flow constructed wetland increased as the water content increased; this effect was controlled by the hydraulic residence time of the system. Conversely, the degree of local mixing was inversely affected by water content; the dispersivity was 4.5, 10, and 14 cm for fully saturated, partially saturated and draining conditions, respectively. We explain the dependency of dispersivity on water content in physical terms; however, further studies are needed to mathematically include this relationship in numerical models that describe the behaviour of vertical flow constructed wetlands. | |||||
BibTeX:
@article{Giraldi2009,
author = {Giraldi, David and de’Michieli Vitturi, Mattia and Zaramella, Mattia and Marion, Andrea and Iannelli, Renato},
title = {Hydrodynamics of vertical subsurface flow constructed wetlands: Tracer tests with rhodamine WT and numerical modelling},
booktitle = {Pollution control by wetlands},
journal = {Ecological Engineering},
year = {2009},
volume = {35},
number = {2},
pages = {265--273},
url = {http://www.sciencedirect.com/science/article/pii/S0925857408001262}
}
|
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| Gironás, J., Roesner, L.A., Rossman, L.A. and Davis, J. | A new applications manual for the Storm Water Management Model (SWMM) | 2010 | Environmental Modelling & Software Vol. 25(6), pp. 813-814 |
article | URL |
| Abstract: The EPA Storm Water Management Model (SWMM) is a widely used program for simulating urban runoff quantity and quality. Its existing documentation includes a User's Manual that describes how to run the program and a Reference Manual that covers its theory and algorithms. A new manual, the “SWMM Applications Manual”, has been added to this collection. It contains nine worked-out examples addressing common stormwater management and design problems encountered in practice. The manual will be especially useful for new SWMM users who need additional guidance in applying this powerful tool to urban drainage design and analysis. | |||||
BibTeX:
@article{Gironas2010,
author = {Gironás, Jorge and Roesner, Larry A. and Rossman, Lewis A. and Davis, Jennifer},
title = {A new applications manual for the Storm Water Management Model (SWMM)},
journal = {Environmental Modelling & Software},
year = {2010},
volume = {25},
number = {6},
pages = {813--814},
url = {http://www.sciencedirect.com/science/article/pii/S1364815209002989}
}
|
|||||
| Gisela, T. | Numerical simulations of air pollutant dispersion in a stratified planetary boundary layer | 1978 | Atmospheric Environment (1967) Vol. 12(6-7), pp. 1365-1369 |
article | URL |
| Abstract: A numerical model is described for computing pollutant concentration distributions downwind from a source. It is based on the three-dimensional dispersion equation governing the time-dependent advective and diffusive transport of air pollutants and is solved numerically by a mixed Lagrangian-Eulerian finite-difference scheme. The model includes the vertical wind shear, the turning of the actual wind, and vertical variations of the vertical eddy diffusivity. In this paper the model is used to simulate the pollutant dispersion process in a stratified planetary boundary layer. The vertical profiles of horizontal mean wind and vertical eddy diffusivities are calculated numerically from a planetary boundary layer model. The influence of the ground roughness and the atmospheric stability on the pollutant distribution is investigated. The results indicate that both parameters essentially determine the air pollutant dispersion process. | |||||
BibTeX:
@article{Gisela1978,
author = {Gisela, Tangermann},
title = {Numerical simulations of air pollutant dispersion in a stratified planetary boundary layer},
journal = {Atmospheric Environment (1967)},
year = {1978},
volume = {12},
number = {6-7},
pages = {1365--1369},
url = {http://www.sciencedirect.com/science/article/pii/000469817890077X}
}
|
|||||
| Göbel, P., Dierkes, C. and Coldewey, W. | Storm water runoff concentration matrix for urban areas | 2007 | Journal of Contaminant Hydrology Vol. 91(1-2)Issues in urban hydrology: The emerging field of urban contaminant hydrology, pp. 26-42 |
article | URL |
| Abstract: The infrastructure (roads, sidewalk, commercial and residential structures) added during the land development and urbanisation process is designed to collect precipitation and convey it out of the watershed, typically in existing surface water channels, such as streams and rivers. The quality of surface water, seepage water and ground water is influenced by pollutants that collect on impervious surfaces and that are carried by urban storm water runoff. Heavy metals, e.g. lead (Pb), zinc (Zn), copper (Cu), cadmium (Cd), polycyclic aromatic hydrocarbons (PAH), mineral oil hydrocarbons (MOH) and readily soluble salts in runoff, contribute to the degradation of water. An intensive literature search on the distribution and concentration of the surface-dependent runoff water has been compiled. Concentration variations of several pollutants derived from different surfaces have been averaged. More than 300 references providing about 1300 data for different pollutants culminate in a representative concentration matrix consisting of medians and extreme values. This matrix can be applied to long-term valuations and numerical modelling of storm water treatment facilities. | |||||
BibTeX:
@article{Goebel2007,
author = {Göbel, P. and Dierkes, C. and Coldewey, W.G.},
title = {Storm water runoff concentration matrix for urban areas},
booktitle = {Issues in urban hydrology: The emerging field of urban contaminant hydrology},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {91},
number = {1--2},
pages = {26--42},
url = {http://www.sciencedirect.com/science/article/pii/S0169772206001938}
}
|
|||||
| Gödeke, S., Richnow, H.-H., Weiβ, H., Fischer, A., Vogt, C., Borsdorf, H. and Schirmer, M. | Multi tracer test for the implementation of enhanced in-situ bioremediation at a BTEX-contaminated megasite | 2006 | Journal of Contaminant Hydrology Vol. 87(3-4), pp. 211-236 |
article | URL |
| Abstract: At the Centre for Environmental Research Leipzig-Halle (UFZ) research site in Zeitz, Germany, benzene contaminates the lower of two aquifers with concentrations of up to 20 mg/l. Since the benzene plume has a minimum length of approximately 1 km, enhanced natural attenuation measures are being considered as a remediation strategy. This study describes the performance and evaluation of a multi-species reactive tracer test using the tracers fluorescein and bromide as conservative tracers and toluene as reactive tracer. Sampling was performed over a period of six months using a detailed network of multilevel sampling wells. Toluene was only slightly retarded in comparison to bromide, whereas fluorescein was retarded considerably stronger. Therefore, it was not possible to use fluorescein as an in situ tracer for the determination of groundwater velocities. The ionic nature of fluorescein is assumed to be the major reason for its retardation. The results show that the infiltration conditions were suitable to produce a wide spreading of the tracer front along the full thickness of the aquifer. Thus, a large aquifer volume can be treated in future enhanced bioremediation measures. The total quantity of infiltrated toluene (24 l) was degraded under sulfate-reducing conditions over a flow path of 50 m. Benzylsuccinate was identified as a metabolite of toluene degradation under sulfate-reducing conditions at this site. The modelling results show that toluene degradation was described more accurately using Monod kinetics than first-order kinetics. Since toluene was only slightly retarded in comparison to bromide, sorption and desorption processes were considered to be negligible. | |||||
BibTeX:
@article{Goedeke2006,
author = {Gödeke, Stefan and Richnow, Hans-Hermann and Weiβ, Holger and Fischer, Anko and Vogt, Carsten and Borsdorf, Helko and Schirmer, Mario},
title = {Multi tracer test for the implementation of enhanced in-situ bioremediation at a BTEX-contaminated megasite},
journal = {Journal of Contaminant Hydrology},
year = {2006},
volume = {87},
number = {3-4},
pages = {211--236},
url = {http://www.sciencedirect.com/science/article/pii/S0169772206000945}
}
|
|||||
| Goderniaux, P., Brouyère, S., Gutierrez, A. and Baran, N. | Multi-tracer tests to evaluate the hydraulic setting of a complex aquifer system (Brévilles spring catchment, France) | 2010 | Hydrogeology Journal Vol. 18(7), pp. 1729-1740 |
article | URL |
| Abstract: For good management of groundwater resources, and to comply with European and national regulations, a detailed understanding of an aquifer’s hydraulic setting is required. In order to better characterize a sandy aquifer that is affected by diffuse pollution (Brévilles spring catchment, Val d’Oise, France), and to quantify the transfer time in the saturated zone, a multi-tracer test involving a new technique, the ‘finite volume point dilution method’, has been performed in natural flow conditions. In November 2005, injections of four different tracers took place in four piezometers involving different locations and depths in the aquifer. Recovery of the tracers was observed at two different places near the aquifer outlet. A particularly long and unusual monitoring exercise (27 months) demonstrated the existence of several different velocities within the sandy layer, which seems to be linked to the decrease of hydraulic conductivity with depth. The new insight and parameter quantification brought by interpretation of these tests contribute to a better characterization of the saturated zone. The particularly long-term monitoring exercise also gives new information to understand and forecast the trend and persistence of groundwater contamination by pesticides in the catchment. | |||||
BibTeX:
@article{Goderniaux2010,
author = {Goderniaux, Pascal and Brouyère, Serge and Gutierrez, Alexis and Baran, Nicole},
title = {Multi-tracer tests to evaluate the hydraulic setting of a complex aquifer system (Brévilles spring catchment, France)},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2010},
volume = {18},
number = {7},
pages = {1729--1740},
url = {http://dx.doi.org/10.1007/s10040-010-0633-x}
}
|
|||||
| Godsey, S.E., Aas, W., Clair, T.A., de Wit, H.A., Fernandez, I.J., Kahl, J.S., Malcolm, I.A., Neal, C., Neal, M., Nelson, S.J., Norton, S.A., Palucis, M.C., Skjelkvåle, B.L., Soulsby, C., Tetzlaff, D. and Kirchner, J.W. | Generality of fractal 1/f scaling in catchment tracer time series, and its implications for catchment travel time distributions | 2010 | Hydrological Processes Vol. 24(12), pp. 1660-1671 |
article | URL |
| Abstract: Catchment travel time distributions reflect how precipitation from different storms is stored and mixed as it is transported to the stream. Catchment travel time distributions can be described by the mean travel time and the shape of the distribution around the mean. Whereas mean travel times have been quantified in a range of catchment studies, only rarely has the shape of the distribution been estimated. The shape of the distribution affects both the short-term and long-term catchment response to a pulse input of a soluble contaminant. Travel time distributions are usually estimated from conservative tracer concentrations in precipitation and streamflow, which are analyzed using time-domain convolution or spectral methods. Of these two approaches, spectral methods are better suited to determining the shape of the distribution. Previous spectral analyses of both rainfall and streamflow tracer time series from several catchments in Wales showed that rainfall chemistry spectra resemble white noise, whereas the stream tracer spectra in these same catchments exhibit fractal 1/f scaling over three orders of magnitude. Here we test the generality of the observed fractal scaling of streamflow chemistry, using spectral analysis of long-term tracer time series from 22 catchments in North America and Europe. We demonstrate that 1/f fractal scaling of stream chemistry is a common feature of these catchments. These observations imply that catchments typically exhibit an approximate power-law distribution of travel times, and thus retain a long memory of past inputs. The observed fractal scaling places strong constraints on possible models of catchment behavior, because it is inconsistent with the exponential travel time distributions that are predicted by simple mixing models. | |||||
BibTeX:
@article{Godsey2010,
author = {Godsey, Sarah E. and Aas, Wenche and Clair, Thomas A. and de Wit, Heleen A. and Fernandez, Ivan J. and Kahl, J. Steve and Malcolm, Iain A. and Neal, Colin and Neal, Margaret and Nelson, Sarah J. and Norton, Stephen A. and Palucis, Marisa C. and Skjelkvåle, Brit Lisa and Soulsby, Chris and Tetzlaff, Doerthe and Kirchner, James W.},
title = {Generality of fractal 1/f scaling in catchment tracer time series, and its implications for catchment travel time distributions},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {12},
pages = {1660--1671},
url = {http://dx.doi.org/10.1002/hyp.7677}
}
|
|||||
| Goegebeur, Y. and Guillou, A. | Goodness-of-fit testing for Weibull-type behavior | 2010 | Journal of Statistical Planning and Inference Vol. 140(6), pp. 1417-1436 |
article | URL |
| Abstract: In the process of analyzing data, testing the fit of a model under consideration is a prerequisite for performing inference about the model parameters. In this paper we examine the goodness-of-fit testing problem for assessing whether a sample is consistent with the Weibull-type model. Inspired by the Jackson and the Lewis test statistics, originally proposed as goodness-of-fit tests for the exponential distribution, we introduce two new statistics for testing Weibull-type behavior, and study their asymptotic properties. Moreover, given that the statistics are ratios of estimators for the Weibull-tail coefficient, we obtain new estimators for the latter, and establish their consistency and asymptotic normality. The small sample behavior of our statistics and estimators is evaluated on the basis of a simulation study. | |||||
BibTeX:
@article{Goegebeur2010,
author = {Goegebeur, Yuri and Guillou, Armelle},
title = {Goodness-of-fit testing for Weibull-type behavior},
journal = {Journal of Statistical Planning and Inference},
year = {2010},
volume = {140},
number = {6},
pages = {1417--1436},
url = {http://www.sciencedirect.com/science/article/pii/S0378375809003784}
}
|
|||||
| Goeppert, N., Goldscheider, N. and Scholz, H. | Karst geomorphology of carbonatic conglomerates in the Folded Molasse zone of the Northern Alps (Austria/Germany) | 2011 | Geomorphology Vol. 130(3-4), pp. 289-298 |
article | URL |
| Abstract: The Folded Molasse zone of the Northern Alps consists of clastic sedimentary rocks that are usually not considered to be karstifiable. However, large areas within this zone are composed of carbonatic conglomerates. Numerous karst landforms have recently been discovered but are not recorded on official maps and in the literature. Therefore, a research programme was initiated at the Hochgrat site (Austria/Germany) that included geomorphological mapping and characterisation of the karst phenomena. Both fracture-controlled and hydrodynamically-controlled karren were observed on conglomerate outcrops. The predominant karst landforms, dolines, are typically circular, funnel shaped, most often 2 to 9 m in diameter, 1 to 6 m deep, and frequently act as swallow holes. Poljes that are atypically small (~ 1 ha) occur in either glacial cirques or syncline depressions, are flat floored and lined with sediment and soil, and drain underground via swallow holes. Short caves, springs with marked discharge variations and estavelles are further evidence for karst development. Karstic landforms are widespread in carbonatic conglomerate terrains, but their dimensions are smaller than in typical limestone karst. The practical implications of these findings are also briefly mentioned in this paper. | |||||
BibTeX:
@article{Goeppert2011,
author = {Goeppert, Nadine and Goldscheider, Nico and Scholz, Herbert},
title = {Karst geomorphology of carbonatic conglomerates in the Folded Molasse zone of the Northern Alps (Austria/Germany)},
journal = {Geomorphology},
year = {2011},
volume = {130},
number = {3-4},
pages = {289--298},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X11001802}
}
|
|||||
| Goldscheider, N. | A new quantitative interpretation of the long-tail and plateau-like breakthrough curves from tracer tests in the artesian karst aquifer of Stuttgart, Germany | 2008 | Hydrogeology Journal Vol. 16(7), pp. 1311-1317 |
article | URL |
| Abstract: In 1998 and 1999, two multi-tracer experiments were conducted in the artesian karst aquifer of the mineral springs of Stuttgart, Germany. The breakthrough curves (BTCs) monitored at the springs showed very long tails or developed plateau-like concentration levels for more than 200 days. Initially, this observation was qualitatively explained by exchange between cavities with stagnant water and the active conduits. Since then, a new analytical solution for tracer transport in karst aquifers has become available, the “two-region non-equilibrium model” (2RNE), which assumes the presence of mobile and immobile fluid regions, and mass transfer between these two regions. The experiments were thus revisited, and it was possible to provide a more quantitative explanation of the observed behaviour. The new model simulated all BTCs very well, thus confirming the earlier qualitative explanation. The prolonged BTCs can be attributed to intermediate storage in cavities containing quasi-immobile groundwater, and slow release into active fractures and conduits. The results also demonstrate that karst aquifers are not always fast-flushing systems, but contaminants can sometimes remain in immobile fluid regions for long periods. | |||||
BibTeX:
@article{Goldscheider2008a,
author = {Goldscheider, Nico},
title = {A new quantitative interpretation of the long-tail and plateau-like breakthrough curves from tracer tests in the artesian karst aquifer of Stuttgart, Germany},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2008},
volume = {16},
number = {7},
pages = {1311--1317},
url = {http://dx.doi.org/10.1007/s10040-008-0307-0}
}
|
|||||
| Goldscheider, N., Hunkeler, D. and Rossi, P. | Review: Microbial biocenoses in pristine aquifers and an assessment of investigative methods | 2006 | Hydrogeology Journal Vol. 14(6), pp. 926-941 |
article | URL |
| Abstract: The current knowledge of microbial biocenoses (communities) in pristine aquifers is presented in a review, which also discusses their relevance for questions of groundwater protection. Aquifers are heterogeneous on all scales and structured in a variety of habitats. The void spaces in many aquifers are small. The biocenoses are thus predominantly composed of microorganisms and, often, microinvertebrates. Larger voids and macroorganisms occur in karst cavities. Due to the absence of light, the biocenoses depend on chemical energy resources, which are, however, scarce in non-contaminated groundwater. The microorganisms thus show small cell sizes, low population densities and reduced activity; they developed specific strategies to survive oligotrophic conditions. The review also discusses the impact of contamination on the biocenoses, and the potential use of the biocenoses or specific organisms as indicators for groundwater quality, and the limits of this approach. Bacteria are either planktonic or attached to aquifer material, which requires both fluid and solid phase sampling. Most groundwater bacteria are viable but non-culturable. Consequently, cultivation techniques give an incomplete picture of the biocenoses, while methods from molecular microbiology provide genetic fingerprints of the entire community. Different analytical methods are available to count microorganisms, identify species, characterise microbial diversity, and measure activity. | |||||
BibTeX:
@article{Goldscheider2006,
author = {Goldscheider, Nico and Hunkeler, Daniel and Rossi, Pierre},
title = {Review: Microbial biocenoses in pristine aquifers and an assessment of investigative methods},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {6},
pages = {926--941},
url = {http://dx.doi.org/10.1007/s10040-005-0009-9}
}
|
|||||
| Goldscheider, N., Meiman, J., Pronk, M. and Smart, C. | Tracer tests in karst hydrogeology and speleology | 2008 | International Journal of Speleology Vol. 37(1), pp. 27-40 |
article | URL |
| Abstract: This article presents an introduction to the fundamentals of tracing techniques and their application in cave and karst environments, illustrated by case studies from the Mammoth Cave, USA, and a small experimental site in Switzerland. The properties and limitations of the most important artificial tracers are discussed, and the available methods of tracer injection, sampling, online monitoring and laboratory analysis are presented. Fully quantitative tracer experiments result in continuous or discrete concentration-time data series, i.e. breakthrough curves, and concomitant discharge data, which make it possible to obtain detailed information about groundwater flow and contaminant transport. Within the frame of speleological investigations, tracer tests can help to resolve the active and often inaccessible part of cave and conduit networks and to obtain indications about the geometry and volume of the conduits. For hydrogeological studies, caves can in turn be used as natural experimental and monitoring sites inside the unsaturated or saturated zone of karst aquifer systems. | |||||
BibTeX:
@article{Goldscheider2008b,
author = {Goldscheider, Nico and Meiman, Joe and Pronk, Michiel and Smart, Christopher},
title = {Tracer tests in karst hydrogeology and speleology},
journal = {International Journal of Speleology},
year = {2008},
volume = {37},
number = {1},
pages = {27--40},
url = {http://www.ijs.speleo.it/article.php?id_art=556}
}
|
|||||
| Golfier, F., Quintard, M. and Wood, B.D. | Comparison of theory and experiment for solute transport in weakly heterogeneous bimodal porous media | 2011 | Advances in Water Resources Vol. 34(7), pp. 899-914 |
article | URL |
| Abstract: In this work, the influence of non-equilibrium effects on solute transport in a weakly heterogeneous medium is discussed. Three macro-scale models (upscaled via the volume averaging technique) are investigated: (i) the two-equation non-equilibrium model, (ii) the one-equation asymptotic model and (iii) the one-equation local equilibrium model. The relevance of each of these models to the experimental system conditions (duration of the pulse injection, dispersivity values…) is analyzed. The numerical results predicted by these macroscale models are compared directly with the experimental data (breakthrough curves). Our results suggest that the preasymptotic zone (for which a non-Fickian model is required) increases as the solute input pulse time decreases. Beyond this limit, the asymptotic regime is recovered. A comparison with the results issued from the stochastic theory for this regime is performed. Results predicted by both approaches (volume averaging method and stochastic analysis) are found to be consistent. | |||||
BibTeX:
@article{Golfier2011,
author = {Golfier, Fabrice and Quintard, Michel and Wood, Brian D.},
title = {Comparison of theory and experiment for solute transport in weakly heterogeneous bimodal porous media},
journal = {Advances in Water Resources},
year = {2011},
volume = {34},
number = {7},
pages = {899--914},
url = {http://www.sciencedirect.com/science/article/pii/S0309170811000832}
}
|
|||||
| Gomes, O., Combes, C. and Dussauchoy, A. | Parameter estimation of the generalized gamma distribution | 2008 | Mathematics and Computers in Simulation Vol. 79(4)5th Vienna International Conference on Mathematical Modelling/Workshop on Scientific Computing in Electronic Engineering of the 2006 International Conference on Computational Science/Structural Dynamical Systems: Computational Aspects, pp. 955-963 |
article | URL |
| Abstract: This article focuses on the parameter estimation of the generalized gamma distribution. Because of many difficulties described in the literature to estimate the parameters, we propose here a new estimation method. The algorithm associated to this heuristic method is implemented in Splus. We validate the resulting routine on the particular cases of the generalized gamma distribution. | |||||
BibTeX:
@article{Gomes2008,
author = {Gomes, O. and Combes, C. and Dussauchoy, A.},
title = {Parameter estimation of the generalized gamma distribution},
booktitle = {5th Vienna International Conference on Mathematical Modelling/Workshop on Scientific Computing in Electronic Engineering of the 2006 International Conference on Computational Science/Structural Dynamical Systems: Computational Aspects},
journal = {Mathematics and Computers in Simulation},
year = {2008},
volume = {79},
number = {4},
pages = {955--963},
url = {http://www.sciencedirect.com/science/article/pii/S0378475408001043}
}
|
|||||
| Gómez-Gardeñes, J., Moreno, Y. and Floría, L. | Michaelis–Menten dynamics in complex heterogeneous networks | 2005 | Physica A: Statistical Mechanics and its Applications Vol. 352(2-4), pp. 265-281 |
article | URL |
| Abstract: Biological networks have been recently found to exhibit many topological properties of the so-called complex networks. It has been reported that they are, in general, both highly skewed and directed. In this paper, we report on the dynamics of a Michaelis–Menten like model when the topological features of the underlying network resemble those of real biological networks. Specifically, instead of using a random graph topology, we deal with a complex heterogeneous network characterized by a power-law degree distribution coupled to a continuous dynamics for each network's component. The dynamics of the model is very rich and stationary, periodic and chaotic states are observed upon variation of the model's parameters. We characterize these states numerically and report on several quantities such as the system's phase diagram and size distributions of clusters of stationary, periodic and chaotic nodes. The results are discussed in view of recent debate about the ubiquity of complex networks in nature and on the basis of several biological processes that can be well described by the dynamics studied. | |||||
BibTeX:
@article{Gomez-Gardenes2005,
author = {Gómez-Gardeñes, J. and Moreno, Y. and Floría, L.M.},
title = {Michaelis–Menten dynamics in complex heterogeneous networks},
journal = {Physica A: Statistical Mechanics and its Applications},
year = {2005},
volume = {352},
number = {2-4},
pages = {265--281},
url = {http://www.sciencedirect.com/science/article/pii/S037843710500035X}
}
|
|||||
| Gómez-Hernández, J.J. and Wen, X.-H. | To be or not to be multi-Gaussian? A reflection on stochastic hydrogeology | 1998 | Advances in Water Resources Vol. 21(1), pp. 47-61 |
article | URL |
| Abstract: The multivariate Gaussian random function model is commonly used in stochastic hydrogeology to model spatial variability of log-conductivity. The multi-Gaussian model is attractive because it is fully characterized by an expected value and a covariance function or matrix, hence its mathematical simplicity and easy inference. Field data may support a Gaussian univariate distribution for log hydraulic conductivity, but, in general, there are not enough field data to support a multi-Gaussian distribution. A univariate Gaussian distribution does not imply a multi-Gaussian model. In fact, many multivariate models can share the same Gaussian histogram and covariance function, yet differ by their patterns of spatial continuity at different threshold values. Hence the decision to use a multi-Gaussian model to represent the uncertainty associated with the spatial heterogeneity of log-conductivity is not databased. Of greatest concern is the fact that a multi-Gaussian model implies the minimal spatial correlation of extreme values, a feature critical for mass transport and a feature that may be in contradiction with some geological settings, e.g. channeling. The possibility for high conductivity values to be spatially correlated should not be discarded by adopting a congenial model just because data shortage prevents refuting it. In this study, three alternatives to a multi-Gaussian model, all sharing the same Gaussian histogram and the same covariance function, but with different continuity patterns for extreme values, were considered to model the spatial variability of log-conductivity. The three alternative models, plus the traditional multi-Gaussian model, are used to perform Monte Carlo analyses of groundwater travel times from a hypothetical nuclear repository to the ground surface through a synthetic formation similar to the Finnsjön site in Sweden. The results show that the groundwater travel times predicted by the multi-Gaussian model could be ten times slower than those predicted by the other models. The probabilities of very short travel times could be severely underestimated using the multi-Gaussian model. Consequently, if field measured data are not sufficient to determine the higher-order moments necessary to validate the multi-Gaussian model — which is the usual situation in practice — other alternative models to the multi-Gaussian one ought to be considered. | |||||
BibTeX:
@article{Gomez-Hernandez1998,
author = {Gómez-Hernández, J. Jaime and Wen, Xian-Huan},
title = {To be or not to be multi-Gaussian? A reflection on stochastic hydrogeology},
journal = {Advances in Water Resources},
year = {1998},
volume = {21},
number = {1},
pages = {47--61},
url = {http://www.sciencedirect.com/science/article/pii/S0309170896000310}
}
|
|||||
| Gondwe, B.R., Merediz-Alonso, G. and Bauer-Gottwein, P. | The influence of conceptual model uncertainty on management decisions for a groundwater-dependent ecosystem in karst | 2011 | Journal of Hydrology Vol. 400(1-2), pp. 24-40 |
article | URL |
| Abstract: Groundwater management in karst is often based on limited hydrologic understanding of the aquifer. The geologic heterogeneities controlling the water flow are often insufficiently mapped. As karst aquifers are very vulnerable to pollution, groundwater protection and land use management are crucial to preserve water resources and maintain ecosystem services. Multiple Model Simulation highlights the impact of model structure uncertainty on management decisions using several plausible conceptual models. Multiple Model Simulation was used for this purpose on the Yucatan Peninsula, which is one of the world’s largest karstic aquifers. The aquifer is the only available fresh water source for human users and ecosystems on the Peninsula. One of Mexico’s largest protected areas, the groundwater-dependent Sian Ka’an Biosphere Reserve (5280 km2) is fed by the aquifer’s thin freshwater lens. Increasing groundwater abstractions and pollution threatens the fresh water resource, and consequently the ecosystem integrity of both Sian Ka’an and the adjacent coastal environment. Seven different catchment-scale conceptual models were implemented in a distributed hydrological modelling approach. Equivalent porous medium conceptualizations with uniform and heterogeneous distributions of hydraulic conductivities were used. The models demonstrated that Sian Ka’an’s wetlands are indeed groundwater-fed. The water quantities in the wetlands and the flooding dynamics are determined by the larger groundwater catchment. The overall water balance for the model domain showed that recharge constitutes 4400 ± 700 million m3/year. Of this, 4–12% exits as overland flow, and 88–96% exits as groundwater flow. Net groundwater outflow from the model domain to the north via the Holbox fracture zone appears as an important cross-basin transfer between regions of the Peninsula. Probability maps of Sian Ka’an’s catchment were obtained through automatic calibration and stochastic modelling. Groundwater travel time zones were calculated based on different calibrated effective porosities. The spatial modelling results highlight the impact of regional-scale structures on the flow field and transport times. | |||||
BibTeX:
@article{Gondwe2011,
author = {Gondwe, Bibi R.N. and Merediz-Alonso, Gonzalo and Bauer-Gottwein, Peter},
title = {The influence of conceptual model uncertainty on management decisions for a groundwater-dependent ecosystem in karst},
journal = {Journal of Hydrology},
year = {2011},
volume = {400},
number = {1-2},
pages = {24--40},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411000485}
}
|
|||||
| Gooseff, M.N., Bencala, K.E., Scott, D.T., Runkel, R.L. and McKnight, D.M. | Sensitivity analysis of conservative and reactive stream transient storage models applied to field data from multiple-reach experiments | 2005 | Advances in Water Resources Vol. 28(5), pp. 479-492 |
article | URL |
| Abstract: The transient storage model (TSM) has been widely used in studies of stream solute transport and fate, with an increasing emphasis on reactive solute transport. In this study we perform sensitivity analyses of a conservative TSM and two different reactive solute transport models (RSTM), one that includes first-order decay in the stream and the storage zone, and a second that considers sorption of a reactive solute on streambed sediments. Two previously analyzed data sets are examined with a focus on the reliability of these RSTMs in characterizing stream and storage zone solute reactions. Sensitivities of simulations to parameters within and among reaches, parameter coefficients of variation, and correlation coefficients are computed and analyzed. Our results indicate that (1) simulated values have the greatest sensitivity to parameters within the same reach, (2) simulated values are also sensitive to parameters in reaches immediately upstream and downstream (inter-reach sensitivity), (3) simulated values have decreasing sensitivity to parameters in reaches farther downstream, and (4) in-stream reactive solute data provide adequate data to resolve effective storage zone reaction parameters, given the model formulations. Simulations of reactive solutes are shown to be equally sensitive to transport parameters and effective reaction parameters of the model, evidence of the control of physical transport on reactive solute dynamics. Similar to conservative transport analysis, reactive solute simulations appear to be most sensitive to data collected during the rising and falling limb of the concentration breakthrough curve. | |||||
BibTeX:
@article{Gooseff2005,
author = {Gooseff, Michael N. and Bencala, Kenneth E. and Scott, Durelle T. and Runkel, Robert L. and McKnight, Diane M.},
title = {Sensitivity analysis of conservative and reactive stream transient storage models applied to field data from multiple-reach experiments},
journal = {Advances in Water Resources},
year = {2005},
volume = {28},
number = {5},
pages = {479--492},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805000072}
}
|
|||||
| Gooseff, M.N., Benson, D.A., Briggs, M.A., Weaver, M., Wollheim, W., Peterson, B. and Hopkinson, C.S. | Residence time distributions in surface transient storage zones in streams: Estimation via signal deconvolution | 2011 | Water Resources Research Vol. 47(5), pp. W05509- |
article | URL |
| Abstract: Little is known about the impact of surface transient storage (STS) zones on reach-scale transport and the fate of dissolved nutrients in streams. Exchange with these locations may influence the rates of nutrient cycling often observed in whole-stream tracer experiments, particularly because they are sites of organic matter collection and lower flow velocities than those observed in the thalweg. We performed a conservative stream tracer experiment (slug of dissolved NaCl) in the Ipswich River in northeastern Massachusetts and collected solute tracer data both in the thalweg and adjacent STS zones at three locations in a fifth-order reach. Tracer time series observed in STS zones are an aggregate of residence time distributions (RTDs) of the upstream transport to that point (RTDTHAL) and that of the temporary storage within these zones (RTDSTS). Here we demonstrate the separation of these two RTDs to determine the RTDSTS specifically. Total residence times for these individual STS zones range from 4.5 to 7.5 h, suggesting that these zones have the potential to host important biogeochemical transformations in stream systems. All of the RTDSTS show substantial deviations from the ideal prescribed by the two-state (mobile/immobile) mass transfer equations. The deviations indicate a model mismatch and that parameter estimation based on the mass transfer equations will yield misleading values. | |||||
BibTeX:
@article{Gooseff2011,
author = {Gooseff, Michael N. and Benson, David A. and Briggs, Martin A. and Weaver, Mitchell and Wollheim, Wilfred and Peterson, Bruce and Hopkinson, Charles S.},
title = {Residence time distributions in surface transient storage zones in streams: Estimation via signal deconvolution},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2011},
volume = {47},
number = {5},
pages = {W05509--},
url = {http://dx.doi.org/10.1029/2010WR009959}
}
|
|||||
| Gooseff, M.N., Payn, R.A., Zarnetske, J.P., Bowden, W.B., McNamara, J.P. and Bradford, J.H. | Comparison of in-channel mobile–immobile zone exchange during instantaneous and constant rate stream tracer additions: Implications for design and interpretation of non-conservative tracer experiments | 2008 | Journal of Hydrology Vol. 357(1-2), pp. 112-124 |
article | URL |
| Abstract: The stream tracer experiment, including field tracer application and subsequent analysis of solute transport and storage, is an important tool in stream hydrology and ecology. However, there have been few comparisons of tracer dynamics between the commonly applied methods of instantaneous (IA) and constant rate (CRA) tracer additions. To determine whether there are fundamental differences between the two addition techniques due to surface storage zone loading and flushing during experiments, we compare longitudinal distributions of tracer dynamics of stream in-channel dead zones during IA and CRA experiments. Back-to-back IA and CRA additions were carried out in two morphologically distinct tundra stream reaches in Alaska. Dead zone tracer time series are determined by an aggregate of upstream transport and individual dead zone residence time distributions (RTDs). The dead zone breakthrough curves for both tracer addition techniques were not consistent, neither were aggregate RTDs observed in each dead zone. Flushing patterns of tracer from dead zones reveal that stream flushing after IA additions was slower than after CRA additions. However, whole-stream RTDs were similar between IA and CRA techniques in each reach. The implications of these findings are important to design and interpretation of IA and CRA stream tracer experiments, particularly those with reactive solutes whose transformations may depend on solute concentration. Thus, IA and CRA experiments may yield differing conclusions about non-conservative transport in streams because of the inherent differences in loading of transient storage zones between these two addition techniques, and potential differences in biogeochemical processing that may occur as a consequence. | |||||
BibTeX:
@article{Gooseff2008,
author = {Gooseff, Michael N. and Payn, Robert A. and Zarnetske, Jay P. and Bowden, William B. and McNamara, James P. and Bradford, John H.},
title = {Comparison of in-channel mobile–immobile zone exchange during instantaneous and constant rate stream tracer additions: Implications for design and interpretation of non-conservative tracer experiments},
journal = {Journal of Hydrology},
year = {2008},
volume = {357},
number = {1-2},
pages = {112--124},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408002291}
}
|
|||||
| Gooseff, M.N., Wondzell, S.M., Haggerty, R. and Anderson, J. | Comparing transient storage modeling and residence time distribution (RTD) analysis in geomorphically varied reaches in the Lookout Creek basin, Oregon, USA | 2003 | Advances in Water Resources Vol. 26(9)Modeling Hyporheic Zone Processes, pp. 925-937 |
article | URL |
| Abstract: The stream tracer technique has been widely used as a method of characterizing hyporheic exchange in stream-catchment studies, commonly incorporating the use of the numerical, transient storage model OTIS, which assumes an exponential residence time distribution. In this study, we compare OTIS and, a model that admits a general residence time distribution (RTD), called solute transport and multirate mass transfer-linear coordinates (STAMMT-L). Models were compared using slug-tracer injections of rhodamine WT (RWT) in three geomorphically distinct stream reaches in the Lookout Creek basin, Oregon USA: a second-order reach of a stream in Watershed 3 which is characterized by pool-step morphology; and two fourth-order reaches of Lookout Creek, one characterized by a single-thread, pool-step morphology, the other a morphologically complex reach with braided channels. OTIS modeling results tended to match short time scale concentrations well, including the advective peak, but the simulated late-time RTD of stream RWT concentrations was in error. The STAMMT-L model allowed for more accurate characterization of late-time stream RWT concentrations, and so characterized a larger portion of the entire RTD. Although both models are sensitive to morphologic differences among the studied stream reaches, they are also clearly different in the relative importance placed on short vs. long residence time distributions. Consequently the two models will result in different views of the hyporheic zone and its role in stream ecosystem processes. | |||||
BibTeX:
@article{Gooseff2003,
author = {Gooseff, Michael N. and Wondzell, Steve M. and Haggerty, Roy and Anderson, Justin},
title = {Comparing transient storage modeling and residence time distribution (RTD) analysis in geomorphically varied reaches in the Lookout Creek basin, Oregon, USA},
booktitle = {Modeling Hyporheic Zone Processes},
journal = {Advances in Water Resources},
year = {2003},
volume = {26},
number = {9},
pages = {925--937},
url = {http://www.sciencedirect.com/science/article/pii/S0309170803001052}
}
|
|||||
| Göppert, N. and Goldscheider, N. | Solute and Colloid Transport in Karst Conduits under Low- and High-Flow Conditions | 2008 | Ground Water Vol. 46(1), pp. 61-68 |
article | URL |
| Abstract: Solute and colloid transport in karst aquifers under low and high flows was investigated by tracer tests using fluorescent dyes (uranine) and microspheres of the size of pathogenic bacteria (1 μm) and Cryptosporidium cysts (5 μm), which were injected into a cave stream and sampled at a spring 2.5 km away. The two types of microspheres were analyzed using an epifluorescence microscope or a novel fluorescence particle counter, respectively. Uranine breakthrough curves (BTCs) were regular shaped and recovery approached 100%. Microsphere recoveries ranged between 27% and 75%. During low flow, the 1-μm spheres displayed an irregular BTC preceding the uranine peak. Only a very few 5-μm spheres were recovered. During high flow, the 1-μm-sphere BTC was regular and more similar to the uranine curve. BTCs were modeled analytically with CXTFIT using a conventional advection dispersion model (ADM) and a two-region nonequilibrium model (2RNE). The results show that (1) colloids travel at higher velocities than solutes during low flow; (2) colloids and solutes travel at similar velocities during high flow; (3) higher maximum concentrations occur during high flow; and (4) the 2RNE achieves a better fit, while the ADM is more robust, as it requires less parameters. | |||||
BibTeX:
@article{Goeppert2008,
author = {Göppert, Nadine and Goldscheider, Nico},
title = {Solute and Colloid Transport in Karst Conduits under Low- and High-Flow Conditions},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2008},
volume = {46},
number = {1},
pages = {61--68},
url = {http://dx.doi.org/10.1111/j.1745-6584.2007.00373.x}
}
|
|||||
| Gordon, W. | Environmental justice, impact assessment and the politics of knowledge: The implications of assessing the social distribution of environmental outcomes [BibTeX] |
2010 | Environmental Impact Assessment Review Vol. 30(5), pp. 312-318 |
article | DOI URL |
BibTeX:
@article{Gordon2010,
author = {Gordon, Walker},
title = {Environmental justice, impact assessment and the politics of knowledge: The implications of assessing the social distribution of environmental outcomes},
journal = {Environmental Impact Assessment Review},
year = {2010},
volume = {30},
number = {5},
pages = {312--318},
url = {http://www.sciencedirect.com/science/article/pii/S0195925510000661},
doi = {http://dx.doi.org/10.1016/j.eiar.2010.04.005}
}
|
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| Gotovac, H., Cvetković, V. and Andričević, R. | Adaptive Fup multi-resolution approach to flow and advective transport in highly heterogeneous porous media: Methodology, accuracy and convergence | 2009 | Advances in Water Resources Vol. 32(6), pp. 885-905 |
article | URL |
| Abstract: In this paper, we present a new Monte-Carlo methodology referred to as Adaptive Fup Monte-Carlo Method (AFMCM) based on compactly supported Fup basis functions and a multi-resolution approach. We consider for illustration 2-D steady, linear and unidirectional flow and advective transport defined on a domain of size 64IY ∗ 32IY with isotropic exponential correlation heterogeneity structure and σ Y 2 up to 8. Accuracy and convergence issues are rigorously analyzed for each realization as well as for the ensemble. Log-conductivity is presented by continuous function at high resolution level (nY = 4–32 points per integral scale) reproducing very accurately prescribed statistics. The flow problem is the most demanding Monte-Carlo step due to satisfying detailed log-conductivity properties. Presented methodology inherently gives continuous and mesh-free velocity fields, which enables the construction of a new efficient and accurate particle tracking algorithm. Results indicate that resolutions nY = 8 and nh = 32 enable very accurate flow solutions in each realization with mass balance error less than 3% and accurate ensemble velocity statistics. Results show that the proposed AFMCM enables tracking of an unlimited number of injected particles and calculates required transport variables as continuous functions with desired relative accuracy (0.1%) in each realization. Furthermore, we show that the resolution nY = 8 yields a quite accurate pdf of the transverse displacement and travel time. All required flow and transport variables require 500 Monte-Carlo realizations in order to stabilize fluctuations of the higher-order moments and the probability density functions. | |||||
BibTeX:
@article{Gotovac2009,
author = {Gotovac, Hrvoje and Cvetković, Vladimir and Andričević, Roko},
title = {Adaptive Fup multi-resolution approach to flow and advective transport in highly heterogeneous porous media: Methodology, accuracy and convergence},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {6},
pages = {885--905},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809000414}
}
|
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| Goulet, R.R., Pick, F.R. and Droste, R.L. | Test of the first-order removal model for metal retention in a young constructed wetland | 2001 | Ecological Engineering Vol. 17(4), pp. 357-371 |
article | URL |
| Abstract: The first-order removal model is widely used in constructed wetland design. The suitability of this model was tested to predict metal retention in a young constructed wetland receiving agricultural and urban runoff. During two years, water samples for total and dissolved metal analyses were collected every third day at both the inlet and the outlet. The wetland retained metals best during summer and fall whereas during winter the retention of metals was significantly lower. The first-order removal model predicted Fe and Mn retention in the spring and dissolved Zn retention from spring to fall in both years. During those periods, hydraulic retention times (HRTs) greater than 7 days provided maximum retention for Fe, Mn, and dissolved Zn. However, first-order removal models failed to fit summer, fall and winter data for almost every metal under investigation (Fe, Mn, dissolved Cu, dissolved As) suggesting that HRTs (<1–25 days) did not affect metal retention during these seasons. The metal loading to the wetland was low and the input of metals through internal loading may be more significant consequently decreasing the metal retention. Therefore, the first-order removal model is inadequate to predict metal retention on a seasonal basis. Models used to design constructed wetlands under cold climates must consider seasonal changes that affect biological as well as hydrological variables. | |||||
BibTeX:
@article{Goulet2001,
author = {Goulet, Richard R. and Pick, Frances R. and Droste, Ronald L.},
title = {Test of the first-order removal model for metal retention in a young constructed wetland},
journal = {Ecological Engineering},
year = {2001},
volume = {17},
number = {4},
pages = {357--371},
url = {http://www.sciencedirect.com/science/article/pii/S0925857400001373}
}
|
|||||
| Gouze, P. and Luquot, L. | X-ray microtomography characterization of porosity, permeability and reactive surface changes during dissolution | 2011 | Journal of Contaminant Hydrology Vol. 120-121(0)Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media, pp. 45-55 |
article | URL |
| Abstract: Numerical programs for simulating flow and reactive transport in porous media are essential tools for predicting reservoir properties changes triggered by CO2 underground injection. At reservoir scale, meshed models in which equations are solved assuming that constant macroscopic properties can be defined in each cells, are widely used. However, the parameterization of the dissolution–precipitation problem and of the feedback effects of these processes on the flow field is still challenging. The problem arises from the mismatch between the scales at which averaged parameters are defined in the meshed model and the scale at which chemical reactions occur and modify the pore network geometry. In this paper we investigate the links between the dissolution mechanisms that control the porosity changes and the related changes of the reactive surface area and of the permeability. First, the reactive surface area is computed from X-ray microtomography data obtained before and after a set of dissolution experiments of pure calcite rock samples using distinctly different brine–CO2 mixtures characterizing homogeneous to heterogeneous dissolution regimes. The results are used to validate the power law empirical model relating the reactive surface area to porosity proposed by Luquot and Gouze (2009). Second, we investigate the spatial distribution of the effective hydraulic radius and of the tortuosity, two structural parameters that control permeability, in order to explain the different porosity–permeability relationships observed for heterogeneous and homogeneous dissolution regimes. It is shown that the increase of permeability is due to the decrease of the tortuosity for homogeneous dissolution, whereas it is due to the combination of tortuosity decrease and hydraulic radius increase for heterogeneous dissolution. For the intermediate dissolution regime, identified to be the optimal regime for increasing permeability with small changes in porosity, the increase of permeability results from a large increase in the mean effective hydraulic radius of the sample. | |||||
BibTeX:
@article{Gouze2011,
author = {Gouze, Philippe and Luquot, Linda},
title = {X-ray microtomography characterization of porosity, permeability and reactive surface changes during dissolution},
booktitle = {Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {120-121},
number = {0},
pages = {45--55},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210000835}
}
|
|||||
| Gradshteĭn, I.S. and Ryzhik, I.M. | Table of integrals, series, and products [BibTeX] |
1965 | , pp. - | book | |
BibTeX:
@book{Gradshteĭn1965,
author = {Izrailʹ Solomonovich Gradshteĭn and Iosif Moiseevich Ryzhik},
title = {Table of integrals, series, and products},
publisher = {Academic Press Inc.},
year = {1965},
pages = {--},
edition = {Fourth}
}
|
|||||
| Graf, T. and Therrien, R. | Coupled thermohaline groundwater flow and single-species reactive solute transport in fractured porous media | 2007 | Advances in Water Resources Vol. 30(4), pp. 742-771 |
article | URL |
| Abstract: Summary A 3D numerical model has been developed to solve coupled fluid flow, heat and single-species reactive mass transport with variable fluid density and viscosity. We focus on a single reaction between quartz and its aqueous form silica. The fluid density and viscosity and the dissolution rate constant, equilibrium constant and activity coefficient are calculated as a function of the concentrations of major ions and temperature. Reaction and flow parameters, such as mineral surface area and permeability, are updated at the end of each time step with explicitly calculated reaction rates. Adaptive time stepping is used to increase or decrease the time step size according to the rate of temporal variation of the solution to prevent physically unrealistic results. The time step size depends on maximum changes in matrix porosity and/or fracture aperture. The model is verified against existing analytical solutions of heat transfer and reactive transport in fractured porous media. The complexity of the model formulation allows studying chemical reactions and variable-density flow in a more realistic way than done previously. | |||||
BibTeX:
@article{Graf2007,
author = {Graf, Thomas and Therrien, René},
title = {Coupled thermohaline groundwater flow and single-species reactive solute transport in fractured porous media},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {4},
pages = {742--771},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001084}
}
|
|||||
| Grayston, S., Vaughan, D. and Jones, D. | Rhizosphere carbon flow in trees, in comparison with annual plants: the importance of root exudation and its impact on microbial activity and nutrient availability | 1997 | Applied Soil Ecology Vol. 5(1), pp. 29-56 |
article | URL |
| Abstract: The release of organic substances from roots is a key process influencing nutrient availability in the rhizosphere. Rhizodeposition, including root exudation can influence plant growth directly by making cations available for uptake through processes such as chelation or indirectly by influencing soil microbial activity. It is important to gain knowledge about the range of compounds released and the factors influencing their release, to understand their effects on the microbial community and enable development of techniques to enhance microbial activity. | |||||
BibTeX:
@article{Grayston1997,
author = {Grayston, S.J. and Vaughan, D. and Jones, D.},
title = {Rhizosphere carbon flow in trees, in comparison with annual plants: the importance of root exudation and its impact on microbial activity and nutrient availability},
journal = {Applied Soil Ecology},
year = {1997},
volume = {5},
number = {1},
pages = {29--56},
url = {http://www.sciencedirect.com/science/article/pii/S0929139396001266}
}
|
|||||
| Green, T.R., Taniguchi, M., Kooi, H., Gurdak, J.J., Allen, D.M., Hiscock, K.M., Treidel, H. and Aureli, A. | Beneath the surface of global change: Impacts of climate change on groundwater | 2011 | Journal of Hydrology Vol. 405(3-4), pp. 532-560 |
article | URL |
| Abstract: Global change encompasses changes in the characteristics of inter-related climate variables in space and time, and derived changes in terrestrial processes, including human activities that affect the environment. As such, projected global change includes groundwater systems. Here, groundwater is defined as all subsurface water including soil water, deeper vadose zone water, and unconfined and confined aquifer waters. Potential effects of climate change combined with land and water management on surface waters have been studied in some detail. Equivalent studies of groundwater systems have lagged behind these advances, but research and broader interest in projected climate effects on groundwater have been accelerating in recent years. In this paper, we provide an overview and synthesis of the key aspects of subsurface hydrology, including water quantity and quality, related to global change. | |||||
BibTeX:
@article{Green2011,
author = {Green, Timothy R. and Taniguchi, Makoto and Kooi, Henk and Gurdak, Jason J. and Allen, Diana M. and Hiscock, Kevin M. and Treidel, Holger and Aureli, Alice},
title = {Beneath the surface of global change: Impacts of climate change on groundwater},
journal = {Journal of Hydrology},
year = {2011},
volume = {405},
number = {3-4},
pages = {532--560},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411002988}
}
|
|||||
| Gresch, M., Braun, D. and Gujer, W. | Using reactive tracers to detect flow field anomalies in water treatment reactors | 2011 | Water Research Vol. 45(5), pp. 1984-1994 |
article | URL |
| Abstract: The hydraulics of water and wastewater treatment reactors has a major impact on their performance and control. The residence time distribution as a measure for the hydraulics represents macroscopic mixing in an integrated way with no spatial information. However, with regard to optimal sensor location for process control and for process optimisation measures, spatial information about macro-mixing is helpful. Spatially distributed measurements of reactive tracers can provide this information. In this paper we generally discuss how reactive tracers can be used to detect and characterize distinct large scale flow structures. It is shown that tracer substances are particularly suited if their reaction time scale is similar to the time scale of the large scale flow structure. For nitrifying activated sludge systems, ammonium is identified to be a suitable tracer. In a comprehensive experimental study at a real aeration tank, two distinct large scale flow features were identified by distributed ammonium measurements. Flow velocity measurements using acoustic Doppler velocimetry clearly supported the nature of these flow field anomalies. Ion-selective electrodes are a well suited device for ammonium measurements providing the temporal resolution that is needed for such an analysis. | |||||
BibTeX:
@article{Gresch2011,
author = {Gresch, Markus and Braun, Daniel and Gujer, Willi},
title = {Using reactive tracers to detect flow field anomalies in water treatment reactors},
journal = {Water Research},
year = {2011},
volume = {45},
number = {5},
pages = {1984--1994},
url = {http://www.sciencedirect.com/science/article/pii/S0043135410007815}
}
|
|||||
| Grillakis, M., Koutroulis, A. and Tsanis, I. | Climate change impact on the hydrology of Spencer Creek watershed in Southern Ontario, Canada | 2011 | Journal of Hydrology Vol. 409(1-2), pp. 1-19 |
article | URL |
| Abstract: This study is for the assessment of climate change impact on the future hydrology of Spencer Creek watershed located in Southern Ontario, Canada under the A2 scenario of the Special Report on Emissions Scenarios (SRES). The study is particularly concerned with changes in the climate variables and the seasonal and interannual flow regimes of the study area. The analysis also addresses the annual exceedance probability of extreme precipitation, temperature and flow events. Potential hydrologic effects of climate change were assessed for the Spencer Creek by imposing changes in precipitation and temperature derived from the North American Regional Climate Change Assessment Program (NARCCAP) climate simulations between 2040 and 2069. The climate models results were used as input to three hydrological models to produce projections of Spencer Creek watershed discharges. The results were compared to the observed discharges between 1989 and 2008. Notwithstanding the variability between the different regional climate model and hydrological model projections that envelop the future climate scenarios and the hydrological modeling uncertainties, all future simulations show an increase in the average interannual discharge, but also a noteworthy change in the seasonal distribution of the discharges. While the former is mainly attributed to the average annual precipitation, which tends to increase, the change in seasonal distribution of discharges is in line with the temperature increase of the winter and spring seasons that results in earlier snowmelt. Important changes were found in the annual exceedance probability (recurrence interval) of the extreme precipitation, temperature and runoff events. | |||||
BibTeX:
@article{Grillakis2011,
author = {Grillakis, M.G. and Koutroulis, A.G. and Tsanis, I.K.},
title = {Climate change impact on the hydrology of Spencer Creek watershed in Southern Ontario, Canada},
journal = {Journal of Hydrology},
year = {2011},
volume = {409},
number = {1-2},
pages = {1--19},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411004276}
}
|
|||||
| Groffman, P.M., Altabet, M.A., Böhlke, J.K., Butterbach-Bahl, K., David, M.B., Firestone, M.K., Giblin, A.E., Kana, T.M., Nielsen, L.P. and Voytek, M.A. | Methods for Measuring Denitrification: Diverse Approaches to a Difficult Problem | 2006 | Ecological Applications Vol. 16(6), pp. 2091-2122 |
article | URL |
| Abstract: Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO₃⁺) and nitrite (NO₂⁺), to the gases nitric oxide (NO), nitrous oxide (N₂O), and dinitrogen (N₂), is important to primary production, water quality, and the chemistry and physics of the atmosphere at ecosystem, landscape, regional, and global scales. Unfortunately, this process is very difficult to measure, and existing methods are problematic for different reasons in different places at different times. In this paper, we review the major approaches that have been taken to measure denitrification in terrestrial and aquatic environments and discuss the strengths, weaknesses, and future prospects for the different methods. Methodological approaches covered include (1) acetylene-based methods, (2) ₁₅N tracers, (3) direct N₂ quantification, (4) N₂:Ar ratio quantification, (5) mass balance approaches, (6) stoichiometric approaches, (7) methods based on stable isotopes, (8) in situ gradients with atmospheric environmental tracers, and (9) molecular approaches. Our review makes it clear that the prospects for improved quantification of denitrification vary greatly in different environments and at different scales. While current methodology allows for the production of accurate estimates of denitrification at scales relevant to water and air quality and ecosystem fertility questions in some systems (e.g., aquatic sediments, well-defined aquifers), methodology for other systems, especially upland terrestrial areas, still needs development. Comparison of mass balance and stoichiometric approaches that constrain estimates of denitrification at large scales with point measurements (made using multiple methods), in multiple systems, is likely to propel more improvement in denitrification methods over the next few years. | |||||
BibTeX:
@article{Groffman2006,
author = {Groffman, Peter M. and Altabet, Mark A. and Böhlke, J. K. and Butterbach-Bahl, Klaus and David, Mark B. and Firestone, Mary K. and Giblin, Anne E. and Kana, Todd M. and Nielsen, Lars Peter and Voytek, Mary A.},
title = {Methods for Measuring Denitrification: Diverse Approaches to a Difficult Problem},
journal = {Ecological Applications},
publisher = {Ecological Society of America},
year = {2006},
volume = {16},
number = {6},
pages = {2091--2122},
url = {http://www.jstor.org/stable/40061945}
}
|
|||||
| Grossmann, M. | Economic value of the nutrient retention function of restored floodplain wetlands in the Elbe River basin | 2012 | Ecological Economics Vol. 83(0)Sustainability in Global Product Chains, pp. 108-117 |
article | URL |
| Abstract: This paper presents an application of an indirect method, the alternative or replacement cost method to value a regulatory ecosystem service: the retention of river nutrient loads by floodplain wetlands. The paper presents a cost-minimisation model for nutrient abatement measures for the River Elbe. The model is applied to estimate the shadow price of phosphate and nitrogen nutrient retention services by restored floodplains. It is shown that the shadow price of restored floodplain area is a function of the nutrient load reduction target for the river basin. The scope of the floodplain restoration projects is shown to have a lesser impact on the estimated shadow price. | |||||
BibTeX:
@article{Grossmann2012,
author = {Grossmann, Malte},
title = {Economic value of the nutrient retention function of restored floodplain wetlands in the Elbe River basin},
booktitle = {Sustainability in Global Product Chains},
journal = {Ecological Economics},
year = {2012},
volume = {83},
number = {0},
pages = {108--117},
url = {http://www.sciencedirect.com/science/article/pii/S092180091200122X}
}
|
|||||
| Guadagnini, A., Sanchez-Vila, X., Saaltink, M.W., Bussini, M. and Berkowitz, B. | Application of a mixing-ratios based formulation to model mixing-driven dissolution experiments | 2009 | Advances in Water Resources Vol. 32(5)Dispersion in Porous Media, pp. 756-766 |
article | URL |
| Abstract: We address the question of how one can combine theoretical and numerical modeling approaches with limited measurements from laboratory flow cell experiments to realistically quantify salient features of complex mixing-driven multicomponent reactive transport problems in porous media. Flow cells are commonly used to examine processes affecting reactive transport through porous media, under controlled conditions. An advantage of flow cells is their suitability for relatively fast and reliable experiments, although measuring spatial distributions of a state variable within the cell is often difficult. In general, fluid is sampled only at the flow cell outlet, and concentration measurements are usually interpreted in terms of integrated reaction rates. In reactive transport problems, however, the spatial distribution of the reaction rates within the cell might be more important than the bulk integrated value. Recent advances in theoretical and numerical modeling of complex reactive transport problems [De Simoni M, Carrera J, Sanchez-Vila X, Guadagnini A. A procedure for the solution of multicomponent reactive transport problems. Water Resour Res 2005;41:W11410. doi: 10.1029/2005WR004056, De Simoni M, Sanchez-Vila X, Carrera J, Saaltink MW. A mixing ratios-based formulation for multicomponent reactive transport. Water Resour Res 2007;43:W07419. doi: 10.1029/2006WR005256] result in a methodology conducive to a simple exact expression for the space–time distribution of reaction rates in the presence of homogeneous or heterogeneous reactions in chemical equilibrium. The key points of the methodology are that a general reactive transport problem, involving a relatively high number of chemical species, can be formulated in terms of a set of decoupled partial differential equations, and the amount of reactants evolving into products depends on the rate at which solutions mix. The main objective of the current study is to show how this methodology can be used in conjunction with laboratory experiments to properly describe the key processes that occur in a complex, geochemically-active system under chemical equilibrium conditions. We model three CaCO3 dissolution experiments reported in Singurindy et al. [Singurindy O, Berkowitz B, Lowell RP. Carbonate dissolution and precipitation in coastal environments: Laboratory analysis and theoretical consideration. Water Resour Res 2004;40:W04401. doi: 10.1029/2003WR002651, Singurindy O, Berkowitz B, Lowell RP. Correction to Carbonate dissolution and precipitation in coastal environments: laboratory analysis and theoretical consideration. Water Resour Res 2005;41:W11701. doi: 10.1029/2005WR004433], in which saltwater and freshwater were mixed in different proportions. The integrated reaction rate within the cell estimated from the experiments are modeled independently by means of (a) a state-of-the-art reactive transport code, and (b) the uncoupled methodology of [12, 13], both of which use dispersivity as a single, adjustable parameter. The good agreement between the results from both methodologies demonstrates the feasibility of using simple solutions to design and analyze laboratory experiments involving complex geochemical problems. | |||||
BibTeX:
@article{Guadagnini2009,
author = {Guadagnini, Alberto and Sanchez-Vila, Xavier and Saaltink, Maarten W. and Bussini, Michele and Berkowitz, Brian},
title = {Application of a mixing-ratios based formulation to model mixing-driven dissolution experiments},
booktitle = {Dispersion in Porous Media},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {5},
pages = {756--766},
url = {http://www.sciencedirect.com/science/article/pii/S030917080800119X}
}
|
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| Guber, A., Gish, T., Pachepsky, Y., van Genuchten, M., Daughtry, C., Nicholson, T. and Cady, R. | Temporal stability in soil water content patterns across agricultural fields | 2008 | Catena Vol. 73(1), pp. 125-133 |
article | URL |
| Abstract: When a field or a small watershed is repeatedly surveyed for soil water content, locations can often be identified where soil water contents are either consistently larger or consistently less than the study area average. This phenomenon has been called temporal stability, time stability, temporal persistence, or rank stability in spatial patterns of soil water contents. Temporal stability is of considerable interest in terms of facilitating upscaling of observed soil water contents to obtain average values across the observation area, improving soil water monitoring strategies, and correcting the monitoring results for missing data. The objective of this work was to contribute to the existing knowledge base on temporal stability in soil water patterns using frequent multi-depth measurements with Multisensor Capacitance Probes (MCPs) installed in a coarse-texture soil under multi-year corn production. Water contents at 10, 30, 50, and 80 cm depths were measured every 10 min for 20 months of continuous observation from May 2001 to December 2002. The MCPs revealed temporal stability in soil water content patterns. Temporal stability was found to increase with depth. The statistical hypothesis could not be rejected (P < 0.0001) that data collected each 10 min, each 2 h, each day, and each week had the same temporal stability. The locations that were best for estimating the average water contents were different for different depths. The best three locations for the whole observation period were the same as the best locations for a month of observations in about 60% of the cases. Temporal stability for a specific location and depth could serve as a good predictor of the utility of this location for estimating the area-average soil water content for that depth. Temporal stability could be efficiently used to correct area-average water contents for missing data. Soil water contents can be upscaled and efficiently monitored using the temporal stability of soil water content patterns. | |||||
BibTeX:
@article{Guber2008,
author = {Guber, A.K. and Gish, T.J. and Pachepsky, Y.A. and van Genuchten, M.T. and Daughtry, C.S.T. and Nicholson, T.J. and Cady, R.E.},
title = {Temporal stability in soil water content patterns across agricultural fields},
journal = {Catena},
year = {2008},
volume = {73},
number = {1},
pages = {125--133},
url = {http://www.sciencedirect.com/science/article/pii/S0341816207001488}
}
|
|||||
| Guérin, R., Baltassat, J.-M., Boucher, M., Chalikakis, K., Galibert, P.-Y., Girard, J.-F., Plagnes, V. and Valois, R. | Geophysical characterisation of karstic networks – Application to the Ouysse system (Poumeyssen, France) | 2009 | Comptes Rendus Geoscience Vol. 341(10-11)Hydrogéophysique Hydrogeophysics, pp. 810-817 |
article | URL |
| Abstract: In the framework of the management of karstic aquifers, geophysical reconnaissance can be used to locate conduits and caves, and to characterise the surrounding limestone matrix. Suitable characterisation of heterogeneities in the karstic environment is, however, challenging for ground-based geophysical methods. The present article describes the results, and evaluates the response and accuracy of combined geophysical measurements carried out at the Poumeyssen test site in France, involving electrical resistivity imaging (ERI), magnetic resonance sounding (MRS), “mise-à-la-masse” electrical mapping, and seismic tomography. This site provides the opportunity to study a relatively wide, shallow, water-filled conduit whose location and shape are known from topographic work carried out by cave divers. Seismic and MRS provided the exact location and width of the conduit, to within a few meters. The seismic and electrical data suggest that the limestone medium surrounding the conduit is not homogeneous. | |||||
BibTeX:
@article{Guerin2009,
author = {Guérin, Roger and Baltassat, Jean-Michel and Boucher, Marie and Chalikakis, Konstantinos and Galibert, Pierre-Yves and Girard, Jean-François and Plagnes, Valérie and Valois, Rémi},
title = {Geophysical characterisation of karstic networks – Application to the Ouysse system (Poumeyssen, France)},
booktitle = {Hydrogéophysique Hydrogeophysics},
journal = {Comptes Rendus Geoscience},
year = {2009},
volume = {341},
number = {10--11},
pages = {810--817},
url = {http://www.sciencedirect.com/science/article/pii/S1631071309001734}
}
|
|||||
| Guimerà, J. and Carrera, J. | A comparison of hydraulic and transport parameters measured in low-permeability fractured media | 2000 | Journal of Contaminant Hydrology Vol. 41(3-4), pp. 261-281 |
article | URL |
| Abstract: Data from 90 tracer experiments performed in low-permeability fractured media have been studied to explore correlations among parameters controlling flow and transport. The original data had been interpreted by different authors using different models, which prevents direct comparison of their estimated parameters. In order to produce comparable parameters, the data have been reexamined using simple models (homogeneous domain, steady-state flow regime, single porosity). Specifically, hydraulic conductivity has been derived as the ratio of water flux to head gradient and apparent porosity as the ratio of water velocity to water flux; the former estimated from both first and peak arrival times. Hydraulic conductivity and porosity correlate along a straight line of slope 1:3 in log scale. While the regression is too noisy to be of predictive use, it lends some support to the use of a generalized cubic law. The fact that correlation for first arrival time porosity (0.77) is larger than for peak arrival porosity (0.62) suggests that first arrival is controlled by the same flow paths as hydraulic conductivity. Apparent porosity derived from peak arrival time is found to grow with travel time along a line of 0.55 slope (again log scale). The correlation coefficient ranges between 0.73 and 0.80 (depending on the data set) for hard rocks. The fact that this correlation is maintained when varying the flow rate at a given site leads us to suggest that it is caused by diffusion mechanisms. This conclusion is further supported by the increase of apparent porosity with the matrix porosity of the rock on which the experiments were performed. | |||||
BibTeX:
@article{Guimera2000,
author = {Guimerà, Jordi and Carrera, Jesús},
title = {A comparison of hydraulic and transport parameters measured in low-permeability fractured media},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {41},
number = {3-4},
pages = {261--281},
url = {http://www.sciencedirect.com/science/article/pii/S0169772299000807}
}
|
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| Gulley, J., Martin, J.B., Screaton, E.J. and Moore, P.J. | River reversals into karst springs: A model for cave enlargement in eogenetic karst aquifers | 2011 | Geological Society of America Bulletin Vol. 123(3-4), pp. 457-467 |
article | URL |
| Abstract: Most conceptual models of epigenic conduit development assume that conduits sourcing karst springs form as water that is undersaturated with respect to carbonate minerals flows from recharge to discharge points. This process is not possible in springs fed by distributed recharge that is transmitted through aquifer matrix porosity, such as unconfined aquifers in eogenetic carbonate rocks. Diffusely recharged water has a long residence time within the aquifer, and thus would have equilibrated with the aquifer rocks prior to discharge to the conduits. The upper Floridan aquifer has high matrix permeability (∼10−13 m2), and many springs lack discrete inputs of undersaturated allogenic water in their recharge areas. Consequently, another explanation for their development is necessary. During flooding of the Suwannee River in north-central Florida, water highly undersaturated with respect to carbonate minerals commonly recharges the upper Floridan aquifer through spring vents, and solution scallops oriented away from the vents suggest most dissolution along conduit walls occurs during these flow reversals. During a single flow reversal at the Peacock Spring cave system, flood water was capable of dissolving up to 3.4 mm of the conduit wall rock. Dissolution occurs as flow reversals follow preexisting features that include joints and paleo–water-table caves. Lack of speleothems in conduits in the upper Floridan aquifer has been used as evidence that the caves formed in the phreatic zone; however, flooding would dissolve any speleothems that may have formed during previous subaerial exposure. Conduit enlargement during flow reversals suggests that dissolution can progress in the normal upstream directions, and this process may be an important driver of dissolution in any karst aquifer with outflows to surface water that are subject to flooding. Flow reversals would also introduce dissolved organic carbon and oxygen into the groundwater and provide important energy sources for cave ecosystems as well as altering redox chemistry of the aquifer water. | |||||
BibTeX:
@article{Gulley2011,
author = {Gulley, Jason and Martin, Jonathan B. and Screaton, Elizabeth J. and Moore, Paul J.},
title = {River reversals into karst springs: A model for cave enlargement in eogenetic karst aquifers},
journal = {Geological Society of America Bulletin},
year = {2011},
volume = {123},
number = {3-4},
pages = {457--467},
url = {http://gsabulletin.gsapubs.org/content/123/3-4/457.abstract}
}
|
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| Gunes, H., Dietz, D.C., Auclair, P.F. and Moore, A.H. | Modified goodness-of-fit tests for the inverse Gaussian distribution | 1997 | Computational Statistics & Data Analysis Vol. 24(1), pp. 63-77 |
article | URL |
| Abstract: Modified Kolmogorov-Smirnov (KS), Kuiper (V), Cramer-von Mises (CV), Watson (W), Anderson-Darling (AD) and sequential goodness-of-fit tests are developed for the inverse Gaussian distribution with unknown parameters. A Monte Carlo procedure is employed to generate critical values for a wide range of sample sizes and shape parameters. Power studies indicate that the W test is most effective against alternate distributions that are very similar in shape to the null inverse Gaussian distribution. Otherwise, the modified AD test generally demonstrates the highest power among single tests. To eliminate the need for extensive critical value tables, functional relationships between critical values, sample sizes, and shape parameters are reported. | |||||
BibTeX:
@article{Gunes1997,
author = {Gunes, Huseyin and Dietz, Dennis C. and Auclair, Paul F. and Moore, Albert H.},
title = {Modified goodness-of-fit tests for the inverse Gaussian distribution},
journal = {Computational Statistics & Data Analysis},
year = {1997},
volume = {24},
number = {1},
pages = {63--77},
url = {http://www.sciencedirect.com/science/article/pii/S0167947396000564}
}
|
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| Gunn, J., Bottrell, S., Lowe, D. and Worthington, S. | Deep groundwater flow and geochemical processes in limestone aquifers: evidence from thermal waters in Derbyshire, England, UK | 2006 | Hydrogeology Journal Vol. 14(6), pp. 868-881 |
article | URL |
| Abstract: Thermal waters potentially provide information on geochemical processes acting deep within aquifers. New isotopic data on groundwater sulphate, inorganic carbon and strontium in thermal and non-thermal waters of a major limestone aquifer system in Derbyshire, England, UK, are used to constrain sulphate sources and groundwater evolution. Shallow groundwaters gain sulphate from oxidation of sulphide minerals and have relatively 13C-depleted dissolved inorganic carbon (DIC). Thermal waters have relatively high Sr/Ca and more 13C-enriched DIC as a result of increased water–rock interaction. In other respects, the thermal waters define two distinct groups. Thermal waters rising at Buxton have higher Mg, Mn and 87Sr/86Sr and lower Ca and SO4, indicating flow from deep sandstone aquifers via a high permeability pathway in the limestone. By contrast, Matlock-type waters (97% of the thermal flux) have elevated sulphate concentrations derived from interaction with buried evaporites, with no chemical evidence for flow below the limestone. About 5% of the limestone area's groundwater flows to the Matlock group springs via deep regional flow and the remainder flows via local shallow paths to many non-thermal springs. Gypsum dissolution has produced significant tertiary porosity and tertiary permeability in the carbonate aquifer and this is an essential precursor to the development of karstic drainage. | |||||
BibTeX:
@article{Gunn2006,
author = {Gunn, John and Bottrell, Simon and Lowe, David and Worthington, Stephen},
title = {Deep groundwater flow and geochemical processes in limestone aquifers: evidence from thermal waters in Derbyshire, England, UK},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {6},
pages = {868--881},
url = {http://dx.doi.org/10.1007/s10040-006-0022-7}
}
|
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| Guo, Q., Liang, Q., Ni, J., Xu, S., Yu, G. and Yu, Z. | Markov chain model of residence time distribution in a new type entrained-flow gasifier | 2008 | Chemical Engineering and Processing: Process Intensification Vol. 47(12), pp. 2061-2065 |
article | URL |
| Abstract: A continuous-time Markov chain has been used to establish the residence time distribution (RTD) model in a new type entrained-flow gasifier, which is called entrained-flow gasifier with opposed multi-burner. According to the measurement results of the flow fields in the gasifier, the state transfer diagram of Markov chain formed in the case of the flow fields are simplified. The results show that this method is feasible in modeling the flow system which consists of ideal mixing cells and plug flow regions. The flow pattern of the gasifier is closed to continuous stirred tank reactor (CSTR). The simulation results are in good agreement with the experimental data. The established model has been applied to forecast the RTD in the industrial gasifier. | |||||
BibTeX:
@article{Guo2008,
author = {Guo, Qinghua and Liang, Qinfeng and Ni, Jianjun and Xu, Shouze and Yu, Guangsuo and Yu, Zunhong},
title = {Markov chain model of residence time distribution in a new type entrained-flow gasifier},
journal = {Chemical Engineering and Processing: Process Intensification},
year = {2008},
volume = {47},
number = {12},
pages = {2061--2065},
url = {http://www.sciencedirect.com/science/article/pii/S0255270107003522}
}
|
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| Gupta, A., Destouni, G. and Jensen, M.B. | Modelling tritium and phosphorus transport by preferential flow in structured soil | 1999 | Journal of Contaminant Hydrology Vol. 35(4), pp. 389-407 |
article | URL |
| Abstract: Subsurface solute transport through structured soil is studied by model interpretation of experimental breakthrough curves from tritium and phosphorus tracer tests in three intact soil monoliths. Similar geochemical conditions, with nearly neutral pH, were maintained in all the experiments. Observed transport differences for the same tracer are thus mainly due to differences in the physical transport process between the different monoliths. The modelling is based on a probabilistic Lagrangian approach that decouples physical and chemical mass transfer and transformation processes from pure and stochastic advection. Thereby, it enables explicit quantification of the physical transport process through preferential flow paths, honouring all independently available experimental information. Modelling of the tritium breakthrough curves yields a probability density function of non-reactive solute travel time that is coupled with a reaction model for linear, non-equilibrium sorption–desorption to describe the phosphorus transport. The tritium model results indicate that significant preferential flow occurs in all the experimental soil monoliths, ranging from 60–100% of the total water flow moving through only 25–40% of the total water content. In agreement with the fact that geochemical conditions were similar in all experiments, phosphorus model results yield consistent first-order kinetic parameter values for the sorption–desorption process in two of the three soil monoliths; phosphorus transport through the third monolith cannot be modelled because the apparent mean transport rate of phosphorus is anomalously rapid relative to the non-adsorptive tritium transport. The occurrence of preferential flow alters the whole shape of the phosphorus breakthrough curve, not least the peak mass flux and concentration values, and increases the transported phosphorus mass by 2–3 times relative to the estimated mass transport without preferential flow in the two modelled monoliths. | |||||
BibTeX:
@article{Gupta1999,
author = {Gupta, Archana and Destouni, Georgia and Jensen, Marina Bergen},
title = {Modelling tritium and phosphorus transport by preferential flow in structured soil},
journal = {Journal of Contaminant Hydrology},
year = {1999},
volume = {35},
number = {4},
pages = {389--407},
url = {http://www.sciencedirect.com/science/article/pii/S0169772298001077}
}
|
|||||
| Gupta, A.K. and Nadarajah, S. | Sums, products and ratios for Mckay’s bivariate gamma distribution | 2006 | Mathematical and Computer Modelling Vol. 43(1-2), pp. 185-193 |
article | URL |
| Abstract: Motivated by hydrological applications, we derive the exact distributions of R = X + Y , U = XY and W = X / ( X + Y ) and the corresponding moment properties when X and Y follow McKay’s bivariate gamma distribution. The expressions turn out to involve several special functions. We also provide computer programs for generating tabulations of the percentage points associated with the distributions. | |||||
BibTeX:
@article{Gupta2006,
author = {Gupta, Arjun K. and Nadarajah, Saralees},
title = {Sums, products and ratios for Mckay’s bivariate gamma distribution},
journal = {Mathematical and Computer Modelling},
year = {2006},
volume = {43},
number = {1-2},
pages = {185--193},
url = {http://www.sciencedirect.com/science/article/pii/S0895717705004681}
}
|
|||||
| Guswa, A.J. and Freyberg, D.L. | Slow advection and diffusion through low permeability inclusions | 2000 | Journal of Contaminant Hydrology Vol. 46(3-4), pp. 205-232 |
article | URL |
| Abstract: Heterogeneous porous media with low permeability lenses can produce contaminant plumes with extended tails. Highly asymmetric breakthrough curves cannot be described well by an advection–dispersion equation (ADE) with a uniform velocity and dispersion coefficient. The character of such a solute plume depends on many factors, including plume size, the geometry and arrangement of the low permeability inclusions, and the transport through such regions. We develop an inclusion Peclet number that effectively characterizes the relative importance of advection and diffusion for transport within a low permeability lens. This inclusion Peclet number is a function of the far-field velocity, the effective diffusion coefficient, the length scale of the inclusion, and the ratio of the permeability of the lens to that of the surrounding matrix. We investigate the effects of a single, elliptical inclusion on the arrival of a solute at a downgradient control plane with numerical particle tracking. Effects specific to advection or diffusion dominance within the inclusion are subtle: diffusion gives rise to more distributed tailing whereas advection produces behavior that is more abrupt. These slight differences are not enough to allow one to determine the dominant process within the inclusion by observing the first three temporal moments alone. The time scale for the dominant transport process within the inclusion is the primary factor affecting the contaminant tailing. For high inclusion Peclet numbers (when advection dominates), the characteristic time varies with the permeability contrast, the far-field velocity, and the size and geometry of the inclusion. For low inclusion Peclet numbers (when diffusion dominates), the characteristic time varies with the size of the inclusion and the effective diffusion coefficient. | |||||
BibTeX:
@article{Guswa2000,
author = {Guswa, Andrew J and Freyberg, David L},
title = {Slow advection and diffusion through low permeability inclusions},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {46},
number = {3-4},
pages = {205--232},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200001364}
}
|
|||||
| Gutierrez, C.G.C.C., Dias, E.F.T.S. and Gut, J.A.W. | Investigation of the residence time distribution in a plate heat exchanger with series and parallel arrangements using a non-ideal tracer detection technique | 2011 | Applied Thermal Engineering Vol. 31(10), pp. 1725-1733 |
article | URL |
| Abstract: The objective was to study the flow pattern in a plate heat exchanger (PHE) through residence time distribution (RTD) experiments. The tested PHE had flat plates and it was part of a laboratory scale pasteurization unit. Series flow and parallel flow configurations were tested with a variable number of passes and channels per pass. Owing to the small scale of the equipment and the short residence times, it was necessary to take into account the influence of the tracer detection unit on the RTD data. Four theoretical RTD models were adjusted: combined, series combined, generalized convection and axial dispersion. The combined model provided the best fit and it was useful to quantify the active and dead space volumes of the PHE and their dependence on its configuration. Results suggest that the axial dispersion model would present good results for a larger number of passes because of the turbulence associated with the changes of pass. This type of study can be useful to compare the hydraulic performance of different plates or to provide data for the evaluation of heat-induced changes that occur in the processing of heat-sensitive products. | |||||
BibTeX:
@article{Gutierrez2011,
author = {Gutierrez, Carola G. C. C. and Dias, Eduardo F. T. S. and Gut, Jorge A. W.},
title = {Investigation of the residence time distribution in a plate heat exchanger with series and parallel arrangements using a non-ideal tracer detection technique},
journal = {Applied Thermal Engineering},
year = {2011},
volume = {31},
number = {10},
pages = {1725--1733},
url = {http://www.sciencedirect.com/science/article/pii/S1359431111000950}
}
|
|||||
| Gutierrez, C.G.C.C., Dias, E.F.T.S. and Gut, J.A.W. | Residence time distribution in holding tubes using generalized convection model and numerical convolution for non-ideal tracer detection | 2010 | Journal of Food Engineering Vol. 98(2), pp. 248-256 |
article | URL |
| Abstract: A procedure is proposed for the determination of the residence time distribution (RTD) of curved tubes taking into account the non-ideal detection of the tracer. The procedure was applied to two holding tubes used for milk pasteurization in laboratory scale. Experimental data was obtained using an ionic tracer. The signal distortion caused by the detection system was considerable because of the short residence time. Four RTD models, namely axial dispersion, extended tanks in series, generalized convection and PFR + CSTR association, were adjusted after convolution with the E-curve of the detection system. The generalized convection model provided the best fit because it could better represent the tail on the tracer concentration curve that is caused by the laminar velocity profile and the recirculation regions. Adjusted model parameters were well correlated with the flow rate. | |||||
BibTeX:
@article{Gutierrez2010,
author = {Gutierrez, Carola G. C. C. and Dias, Eduardo F. T. S. and Gut, Jorge A. W.},
title = {Residence time distribution in holding tubes using generalized convection model and numerical convolution for non-ideal tracer detection},
journal = {Journal of Food Engineering},
year = {2010},
volume = {98},
number = {2},
pages = {248--256},
url = {http://www.sciencedirect.com/science/article/pii/S0260877410000063}
}
|
|||||
| Gutiérrez-Martín, F. and Dahab, M.F. | Issues of sustainability and pollution prevention in environmental engineering education | 1998 | PROCEEDINGSWater Science and Technology Vol. 38(11), pp. 271-278 |
article | DOI URL |
| Abstract: This paper discusses the concepts of sustainability and pollution prevention and their roles in environmental science and engineering education. It is argued that environmental engineering science and education must be re-oriented to focus primarily on pollution prevention technologies as a mechanism for attaining the goal of sustainability. While it is acknowledged that traditional pollution control will remain as an integral part of environmental science and engineering education, the paradigm shift (in favor of pollution prevention) must be completed in order for humanity to realize, albeit remotely, the goal of sustainability. The paper presents two case studies; at the University of Nebraska-Lincoln (USA) and at the Universidad Politeénica de Madrid (Spain) where efforts are being made to re-orient environmental engineering education to promote the concept of sustainability as the primary goal of environmental management. | |||||
BibTeX:
@article{PROCEEDINGGutierrez-Martin1998,
author = {Gutiérrez-Martín, F. and Dahab, M. F.},
title = {Issues of sustainability and pollution prevention in environmental engineering education},
journal = {PROCEEDINGSWater Science and Technology},
year = {1998},
volume = {38},
number = {11},
pages = {271--278},
note = {Selected Proceedings of the 19th Biennial Conference of the International Association on Water Quality},
url = {http://www.sciencedirect.com/science/article/pii/S0273122398006647},
doi = {http://dx.doi.org/10.1016/s0273-1223(98)00664-7}
}
|
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| Habchi, C., Lemenand, T., Della Valle, D. and Peerhossaini, H. | Liquid/liquid dispersion in a chaotic advection flow | 2009 | International Journal of Multiphase Flow Vol. 35(6), pp. 485-497 |
article | URL |
| Abstract: Mixing by chaotic advection in a twisted-pipe flow is used here to investigate the efficiency of this flow in the liquid/liquid dispersion process. This study focuses on water/oil dispersions produced by continuous water injection into a main oil flow, for small Dean numbers. The drop sizes obtained with the chaotic-advection twisted-pipe flow are compared with those in a straight pipe and a helically coiled flow for the same conditions. It is found that the resulting dispersions are finer and more mono-dispersed in the chaotic advection flow. These results are compared with the theoretical maximum diameter d max determined by the Grace theory in which the viscous stress controls the breakup phenomena. For this purpose, the kinematic field is computed from the theoretical formulae for Dean flow. The strain rate fields in the pipe cross-section are then analytically computed and used to predict the maximum drop diameter. The theoretical values are identical for the three configurations (straight, helically coiled, and twisted pipe) up to a critical Dean number, where the secondary flow becomes significant. Beyond this value, the shear stress is enhanced in the twisted-pipe flow compared with the straight-pipe flow, and the predicted drop diameters are smaller. An interpretation of the higher dispersive performance of the chaotic flow is provided by the Lagrangian trajectories of the particles. | |||||
BibTeX:
@article{Habchi2009,
author = {Habchi, Charbel and Lemenand, Thierry and Della Valle, Dominique and Peerhossaini, Hassan},
title = {Liquid/liquid dispersion in a chaotic advection flow},
journal = {International Journal of Multiphase Flow},
year = {2009},
volume = {35},
number = {6},
pages = {485--497},
url = {http://www.sciencedirect.com/science/article/pii/S030193220900038X}
}
|
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| Haddad, K. and Rahman, A. | Regional flood frequency analysis in eastern Australia: Bayesian GLS regression-based methods within fixed region and ROI framework – Quantile Regression vs. Parameter Regression Technique | 2012 | Journal of Hydrology Vol. 430–431(0), pp. 142-161 |
article | URL |
| Abstract: In this article, an approach using Bayesian Generalised Least Squares (BGLS) regression in a region-of-influence (ROI) framework is proposed for regional flood frequency analysis (RFFA) for ungauged catchments. Using the data from 399 catchments in eastern Australia, the BGLS-ROI is constructed to regionalise the flood quantiles (Quantile Regression Technique (QRT)) and the first three moments of the log-Pearson type 3 (LP3) distribution (Parameter Regression Technique (PRT)). This scheme firstly develops a fixed region model to select the best set of predictor variables for use in the subsequent regression analyses using an approach that minimises the model error variance while also satisfying a number of statistical selection criteria. | |||||
BibTeX:
@article{Haddad2012,
author = {Haddad, Khaled and Rahman, Ataur},
title = {Regional flood frequency analysis in eastern Australia: Bayesian GLS regression-based methods within fixed region and ROI framework – Quantile Regression vs. Parameter Regression Technique},
journal = {Journal of Hydrology},
year = {2012},
volume = {430–431},
number = {0},
pages = {142--161},
url = {http://www.sciencedirect.com/science/article/pii/S0022169412001102}
}
|
|||||
| Hagedorn, F. and Bundt, M. | The age of preferential flow paths | 2002 | Geoderma Vol. 108(1-2), pp. 119-132 |
article | URL |
| Abstract: Preferential flow is a common phenomenon in soils, but the temporal stability of the heterogeneous flow pattern is largely unknown. We give evidence that preferential flow paths in a structured forest soil are persistent for decades. After staining preferential flow paths in a fine-loamy Dystric Cambisol with a dye tracer, we sampled the soil from the preferential flow paths and from the unstained matrix at five sampling times during 1 year. In preferential flow paths, the activities of 137Cs, 210Pb and 239,240Pu, as well as concentrations of soil organic carbon (SOC), were enriched by a factor of up to 3.5 relative to those of the matrix. The 137Cs originates mainly from the Chernobyl accident in 1986, the 210Pb from a continuous ‘natural’ atmospheric deposition and the 239,240Pu from nuclear weapon tests in the 1950s and 1960s. Since all of these radionuclides are only mobile in the soil immediately after deposition, the increased activities of radionuclides in the recent flow paths sampled during our experiments indicate that these flow paths were stable for decades. This is supported by the total enrichment of SOC in preferential flow paths ranging between 740 and 960 g C m−2, which is high in comparison to published accumulation rates of SOC in forest bulk soils from 20 to 60 g C m−2 year−1. The gradient of radionuclide activity and of SOC concentrations between the two flow regions was relatively constant during the 1-year experiment. In all of the five sampling times, concentrations of SOC were larger by 37–46% and the activities of 137Cs were larger by 83–150% in the preferential flow paths than in the matrix down to a depth of 50 cm. This means that despite the differing boundary conditions at the different sampling times, the pathways of infiltrating water were persistent with time. | |||||
BibTeX:
@article{Hagedorn2002,
author = {Hagedorn, Frank and Bundt, Maya},
title = {The age of preferential flow paths},
journal = {Geoderma},
year = {2002},
volume = {108},
number = {1-2},
pages = {119--132},
url = {http://www.sciencedirect.com/science/article/pii/S0016706102001295}
}
|
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| Haggerty, R., McKenna, S.A. and Meigs, L.C. | On the late-time behavior of tracer test breakthrough curves | 2000 | Water Resources Research Vol. 36(12), pp. 3467-3479 |
article | URL |
| Abstract: We investigated the late-time (asymptotic) behavior of tracer test breakthrough curves (BTCs) with rate-limited mass transfer (e.g., in dual-porosity or multiporosity systems) and found that the late-time concentration c is given by the simple expression c = tadc0g − [m0(∂g/∂t)], for t ≫ tad and tα ≫ tad, where tad is the advection time, c0 is the initial concentration in the medium, m0 is the zeroth moment of the injection pulse, and tα is the mean residence time in the immobile domain (i.e., the characteristic mass transfer time). The function g is proportional to the residence time distribution in the immobile domain; we tabulate g for many geometries, including several distributed (multirate) models of mass transfer. Using this expression, we examine the behavior of late-time concentration for a number of mass transfer models. One key result is that if rate-limited mass transfer causes the BTC to behave as a power law at late time (i.e., C ∼ t−k), then the underlying density function of rate coefficients must also be a power law with the form αk−3 as a α → 0. This is true for both density functions of first-order and diffusion rate coefficients. BTCs with k < 3 persisting to the end of the experiment indicate a mean residence time longer than the experiment, and possibly an infinite residence time, and also suggest an effective rate coefficient that is either undefined or changes as a function of observation time. We apply our analysis to breakthrough curves from single-well injection-withdrawal tests at the Waste Isolation Pilot Plant, New Mexico. | |||||
BibTeX:
@article{Haggerty2000,
author = {Haggerty, Roy and McKenna, Sean A. and Meigs, Lucy C.},
title = {On the late-time behavior of tracer test breakthrough curves},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2000},
volume = {36},
number = {12},
pages = {3467--3479},
url = {http://dx.doi.org/10.1029/2000WR900214}
}
|
|||||
| Halihan, T. and Wicks, C.M. | Modeling of storm responses in conduit flow aquifers with reservoirs | 1998 | Journal of Hydrology Vol. 208(1-2), pp. 82-91 |
article | URL |
| Abstract: In aquifers containing large voids, such as karst aquifers with caves or basaltic aquifers with lava tubes, hydrographs at wells or springs are used to analyze the structure and response of the hydrogeological system. Numerical modeling of hydrograph response is commonly based on either inverse techniques or postulated flow geometries. However, the range of mechanisms for generating hydrograph responses have not been fully investigated. | |||||
BibTeX:
@article{Halihan1998a,
author = {Halihan, Todd and Wicks, Carol M.},
title = {Modeling of storm responses in conduit flow aquifers with reservoirs},
journal = {Journal of Hydrology},
year = {1998},
volume = {208},
number = {1-2},
pages = {82--91},
url = {http://www.sciencedirect.com/science/article/pii/S0022169498001498}
}
|
|||||
| Halihan, T., Wicks, C.M. and Engeln, J.F. | Physical response of a karst drainage basin to flood pulses: example of the Devil's Icebox cave system (Missouri, USA) | 1998 | Journal of Hydrology Vol. 204(1-4), pp. 24-36 |
article | URL |
| Abstract: In karst aquifers, water moves from the recharge area (sinkhole plains and swallets) to the discharge area (springs), traveling kilometers through the groundwater system in a period of hours to days. Transit times through karst aquifers are a function of the conduit geometry and connectedness, intensity and duration of the recharge event, and antecedent soil moisture. Often many of these factors are unknown or difficult to quantify. Therefore, predicting the response of a karst basin to recharge is difficult. Numerous researchers have attempted to understand the response of a karst basin, but a good understanding of whether the response is dependent on local features or regional effects is currently lacking. | |||||
BibTeX:
@article{Halihan1998,
author = {Halihan, Todd and Wicks, Carol M. and Engeln, Joseph F.},
title = {Physical response of a karst drainage basin to flood pulses: example of the Devil's Icebox cave system (Missouri, USA)},
journal = {Journal of Hydrology},
year = {1998},
volume = {204},
number = {1-4},
pages = {24--36},
url = {http://www.sciencedirect.com/science/article/pii/S0022169497001042}
}
|
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| Halil, K. | A third-order upwind scheme for the advection–diffusion equation using spreadsheets | 2007 | Advances in Engineering Software Vol. 38(10), pp. 688-697 |
article | URL |
| Abstract: In this study, numerical solution of advection–diffusion equation with third-order upwind scheme by using spreadsheet simulation (ADE-TUSS) is carried out. This is a user-friendly and a flexible solution algorithm for the numerical solution of the one dimensional advection–diffusion equation (ADE). The ADE-TUSS algorithm is based on the description of ADE by using the third-order upwind scheme (TU) for advection term and second-order central finite representation. For the solution of the governing equations, spreadsheet simulation (SS) technique is used instead of conventional solution techniques. The solution of ADE can be obtained for explicit, implicit and Crank–Nicolson schemes by only changing the values of temporal weighted parameter in the ADE-TUSS algorithm. It is clear in the literature that numerical diffusion causes great deviations in the model results when the first- or second-order upwind schemes are used. In order to decrease the numerical diffusion and to obtain oscillation free results, an artificial diffusion term is usually defined or sizes of the time step and/or grid sizes are set small values. Reduce of the grid sizes and/or time step increases the computational time and generally requires writing a fairly complex code when high order schemes are used. However, numerical solution of ADE by taking into account TU scheme has been carried out by using the iterative spreadsheet solution technique in the proposed solution algorithm. In order to simulate transient solution, a simple macro that carries out time cycle is defined with the help of VBA feature of spreadsheets. One of the most important advantages of ADE-TUSS algorithm is that it does not require the matrix algebra at each time step of the transient solutions. In order to test the ADE-TUSS model, two examples having numerical and analytical solutions are solved. Results showed that use of the high-order schemes in the spreadsheet simulation is very applicable for the numerical solution of ADE. Moreover, numerical diffusion problem is drastically prevented by using the ADE-TUSS model. | |||||
BibTeX:
@article{Halil2007,
author = {Halil, Karahan},
title = {A third-order upwind scheme for the advection–diffusion equation using spreadsheets},
journal = {Advances in Engineering Software},
year = {2007},
volume = {38},
number = {10},
pages = {688--697},
url = {http://www.sciencedirect.com/science/article/pii/S0965997806001748}
}
|
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| Halil, K. | Implicit finite difference techniques for the advection–diffusion equation using spreadsheets | 2006 | Advances in Engineering Software Vol. 37(9), pp. 601-608 |
article | URL |
| Abstract: This study proposes one-dimensional advection–diffusion equation (ADE) with finite differences method (FDM) using implicit spreadsheet simulation (ADEISS). By changing only the values of temporal and spatial weighted parameters with ADEISS implementation, solutions are implicitly obtained for the BTCS, Upwind and Crank–Nicolson schemes. The ADEISS uses iterative spreadsheet solution technique. Thus, it is not required a solution of simultaneous equations for each time step using matrix algebra. Two examples which, have the numerical and analytical solutions in literature, are solved in order to test the ADEISS performance. Both examples are solved for three schemes. It has been determined that the Crank–Nicolson scheme is in good agreement with the analytical solution; however the results of the BTCS and the Upwind schemes are lower than the analytical solution. The Upwind scheme suffers from considerably numerical diffusion whereas the BTCS scheme does not produce numerical diffusion. Thus, it provided better results than Upwind scheme which are closer to analytical results depending on the selected parameters. The ADEISS implementation is a computationally convenient procedure for the three well-known methods in the literature: The BTCS, Upwind and Crank–Nicolson. | |||||
BibTeX:
@article{Halil2006,
author = {Halil, Karahan},
title = {Implicit finite difference techniques for the advection–diffusion equation using spreadsheets},
journal = {Advances in Engineering Software},
year = {2006},
volume = {37},
number = {9},
pages = {601--608},
url = {http://www.sciencedirect.com/science/article/pii/S0965997806000111}
}
|
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| Ham, P., Prommer, H., Olsson, Å., Schotting, R. and Grathwohl, P. | Predictive modelling of dispersion controlled reactive plumes at the laboratory-scale | 2007 | Journal of Contaminant Hydrology Vol. 93(1-4), pp. 304-315 |
article | URL |
| Abstract: A model-based interpretation of laboratory-scale experimental data is presented. Hydrolysis experiments carried out using thin glass tanks filled with glass beads to construct a hypothetical and inert, homogeneous porous medium were analysed using a 2D numerical model. A new empirical formula, based upon results for non-reactive (tracer) experiments is used to calculate transversal dispersivity values for a range of grain sizes and any flow velocities. Combined with effective diffusion coefficients calculated from Stokes–Einstein type equations, plume lengths arising from mixing between two solutes can be predicted accurately using numerical modelling techniques. Moreover, pH and ion concentration profiles lateral to the direction of flow of the mixing species can be determined at any given point downstream, without the need for result fitting. In our case, this approach does not lead to overpredictions of lateral mixing, as previously reported when using parameters derived from non-reactive tracer experiments to describe reactive solute transport. The theory is based on the assumption of medium homogeneity. | |||||
BibTeX:
@article{Ham2007,
author = {Ham, P.A.S. and Prommer, H. and Olsson, Å.H. and Schotting, R.J. and Grathwohl, P.},
title = {Predictive modelling of dispersion controlled reactive plumes at the laboratory-scale},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {93},
number = {1-4},
pages = {304--315},
url = {http://www.sciencedirect.com/science/article/pii/S0169772207000502}
}
|
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| Ham, P. and Schotting, R. | Two-dimensional aquifer bioremediation: a (semi-) analytical approach | 2002 | Vol. 47Computational Methods in Water Resources Proceedings of the XIVth International Conference on Computational Methods in Water Resources (CMWR XIV), pp. 835-842 |
incollection | URL |
| Abstract: In this paper, a two-dimensional biodegradation model is considered including simultaneous transport and biodegradation of organic contaminant, electron acceptor and, moreover, growth and decay of micro-organisms. The problem studied relates to the injection of electron acceptor at a certain location in an aquifer. Initially, contaminant and biomass are present in the entire flow domain, while electron acceptor is absent. Injection of electron acceptor leads to the development of a dispersive mixing zone between the zone where the biomass is activated and the inactive, contaminated zone. The model consists of three coupled nonlinear partial differential equations. For the time-dependent case, these three equations are reduced to an auxillary linear equation. The solution of this auxillary problem is used to recast the three equations into two coupled equations. For the stationary case, the problem can be reduced further to a single PDE in terms of one of the dependent variables only, requiring a numerical solution. | |||||
BibTeX:
@incollection{Ham2002,
author = {Ham, Phil and Schotting, Ruud},
title = {Two-dimensional aquifer bioremediation: a (semi-) analytical approach},
booktitle = {Computational Methods in Water Resources Proceedings of the XIVth International Conference on Computational Methods in Water Resources (CMWR XIV)},
publisher = {Elsevier},
year = {2002},
volume = {47},
pages = {835--842},
url = {http://www.sciencedirect.com/science/article/pii/S0167564802801484}
}
|
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| Hamdan, E., Milthorpe, J.F. and Lai, J.C.S. | An extended macroscopic model for solute dispersion in confined porous media | 2008 | Chemical Engineering Journal Vol. 137(3), pp. 614-635 |
article | URL |
| Abstract: In the analysis of longitudinal dispersion data in a classical laboratory experiment, it is usually assumed that the dispersion of species undergoes Fickian behaviour with constant dispersivities. If the length and time scales of an experiment are not sufficient for a tracer to traverse the cylinder radius and sample the velocity variations, this could give rise to persisting non-Fickian transients that cannot be predicted by the conventional plug flow dispersion models. Such transients cause the deviation from the Gaussian concentration distribution predicted by the plug models. In this paper, some shortcomings of the Fickian model are examined and a more general non-Fickian macroscopic dispersion model is provided to give insight into some of the factors that contribute to the dispersion process. The analysis describes the transient development of the solute spread and some non-Fickian effects associated with it. The extended model provides a set of conditions under which the classical axial plug dispersion model can be applicable. The model results for tracer dispersion in cylindrical packed beds show that the longitudinal dispersion coefficient converges to its asymptotic value on a time-scale proportional to R2/〈DT〉 where R is the cylinder radius and 〈DT〉 represents the mean value of the radial dispersion coefficient DT(r) over the cross-section of the bed. | |||||
BibTeX:
@article{Hamdan2008,
author = {Hamdan, E. and Milthorpe, J. F. and Lai, J. C. S.},
title = {An extended macroscopic model for solute dispersion in confined porous media},
journal = {Chemical Engineering Journal},
year = {2008},
volume = {137},
number = {3},
pages = {614--635},
url = {http://www.sciencedirect.com/science/article/pii/S1385894707003671}
}
|
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| Hamed, M.M., Bedient, P.B. and Dawson, C.N. | Probabilistic modeling of aquifer heterogeneity using reliability methods | 1996 | Advances in Water Resources Vol. 19(5), pp. 277-295 |
article | URL |
| Abstract: A probabilistic model of groundwater contaminant transport is presented. The model is based on coupling first- and second-order reliability methods (FORM and SORM) with a two-dimensional finite element solution of groundwater transport equations. Uncertainty in aquifer media is considered by modeling hydraulic conductivity as a spatial random field with a prescribed correlation structure. FORM and SORM provide the probability that a contaminant exceeds a target level at a well, termed the probability of failure. Sensitivity of the probability of failure to basic variabilities in grid block conductivity is also obtained, at no additional computational effort. The effect of the choice of the predetermined target level at the observation well is provided, along with its effect on the relevant sensitivity information. Considerable saving in computational time was achieved by superimposing a coarse random variables mesh on a finer numerical mesh. The presence of regions of lower conductivity on the probabilistic event is analyzed, and the regions in which conductivity most affects the results are identified. | |||||
BibTeX:
@article{Hamed1996,
author = {Hamed, Maged M. and Bedient, Philip B. and Dawson, Clint N.},
title = {Probabilistic modeling of aquifer heterogeneity using reliability methods},
journal = {Advances in Water Resources},
year = {1996},
volume = {19},
number = {5},
pages = {277--295},
url = {http://www.sciencedirect.com/science/article/pii/0309170896000048}
}
|
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| Hampton, L., Graham, R. and Byl, T. | Lactate Induction of Ammonia-Oxidizing Bacteria and PCE Cometabolism | 2005 | U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160, pp. 190 | inproceedings | URL |
| Abstract: Water containing bacteria was collected from a PCE-contaminated karst aquifer in north-central Ten- nessee to establish liquid, 1-liter microcosms. The microcosms were spiked with known concentrations of perchloroethylene (PCE) and 11 different formulations of lactic acid. The ammonia-lactate formulation caused a rapid removal of PCE and oxygen (O2). Similar results that were achieved by using a second set of microcosms spiked with ammonia-lactate to re-test the removal rate of PCE and O2 indicated a possible cometabolic PCE-removal process. Although only one report of PCE-cometabolism was found in the liter- ature, ammonia-oxidizing bacteria indigenous to the karst aquifer were hypothesized to be capable of come- tabolizing PCE with the ammonia mono-oxygenase (AMO) pathway. To test this hypothesis, microcosms were established using different forms of ammonia (ammonia-lactate, ammonia-chloride, ammonium plus sodium lactate), reference controls (sterile, live without food, sodium lactate, sterile + ammonia lactate), and ammonia mono-oxygenase inhibitors [2-chloro-6-(trichloromethyl) pyridine, azide, and allylthiourea]. Microcosms treated with ammonia-lactate had the most rapid reduction of PCE and O2, followed by the ammonium + sodium-lactate treatment. The other live microcosms treated with ammonia also experienced significant drops in PCE and O2 after 24 hours. The control (sterile and live without food) microcosms did not experience a significant drop in PCE in the same time period. After 24 hours, the rapid PCE removal in all the ammonia-treated microcosms decreased due to the consumption of the oxygen. Tests with the AMO inhibitor in the presence of ammonia-lactate did not prevent the PCE removal or O2 consumption. Lactate may stimulate AMO or protect the enzyme from inhibition. Additional tests need to be conducted to prove that AMO is responsible for the removal of PCE. These preliminary results provide strong evidence that karst bacteria indigenous to this aquifer can cometabolize PCE. | |||||
BibTeX:
@inproceedings{Hampton2005,
author = {Hampton, LyTreese and Graham, Roneisha and Byl, T.D.},
title = {Lactate Induction of Ammonia-Oxidizing Bacteria and PCE Cometabolism},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2005},
pages = {190},
url = {pubs.usgs.gov/sir/2005/5160/index.html}
}
|
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| Hans Jürgen, H. | The GW-Fauna-Index: A first approach to a quantitative ecological assessment of groundwater habitats | 2006 | Limnologica - Ecology and Management of Inland Waters Vol. 36(2), pp. 119-137 |
article | URL |
| Abstract: Between June 2001 and December 2002, 18 hyporheic and groundwater bores were sampled for fauna and environmental data using phreatic traps. The bores were situated in three different natural geographic regions in Palatinate, Southwestern Germany. | |||||
BibTeX:
@article{HansJuergen2006,
author = {Hans Jürgen, Hahn},
title = {The GW-Fauna-Index: A first approach to a quantitative ecological assessment of groundwater habitats},
journal = {Limnologica - Ecology and Management of Inland Waters},
year = {2006},
volume = {36},
number = {2},
pages = {119--137},
url = {http://www.sciencedirect.com/science/article/pii/S0075951106000181}
}
|
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| Happel, J., Walter, E. and Lecourtier, Y. | Modeling transient tracer studies in plug-flow reactors | 1990 | Journal of Catalysis Vol. 123(1), pp. 12-20 |
article | URL |
| Abstract: The use of plug-flow reactors is common for kinetic studies in heterogeneous catalysis. Recently, transient tracing has been found to be advantageous in providing additional mechanistic information above that obtained by customary steady-state kinetics. Despite the advantages of transient tracing, it often suffers from incorrect data analysis in the case of plug flow because of failure to take into account the formalism needed to model plug-flow transient tracing as contrasted with that required to describe transient tracing in a gradientless recirculating reactor (CSTR). This paper presents a development of the appropriate differential equation system applying to plug-flow studies involving transient isotopic tracing superimposed on an overall steady-state kinetics. Closed mathematical expressions are presented for simple practical cases and used to illustrate important special characteristics of these systems. | |||||
BibTeX:
@article{Happel1990,
author = {Happel, John and Walter, Eric and Lecourtier, Yves},
title = {Modeling transient tracer studies in plug-flow reactors},
journal = {Journal of Catalysis},
year = {1990},
volume = {123},
number = {1},
pages = {12--20},
url = {http://www.sciencedirect.com/science/article/pii/002195179090153B}
}
|
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| Harden, H.S., Roeder, E., Hooks, M. and Chanton, J.P. | Evaluation of onsite sewage treatment and disposal systems in shallow karst terrain | 2008 | Water Research Vol. 42(10-11), pp. 2585-2597 |
article | URL |
| Abstract: Two conventional onsite sewage treatment and disposal systems (OSTDSs) at Manatee Springs State Park, Florida, USA, were studied to assess their impact on groundwater quality in a shallow karst environment. Sulfur hexafluoride (SF6) and fluorescein were used as tracers to establish connections between the drainfields and monitoring wells. Elevated nutrients were found in all wells where significant concentrations of both tracers were observed, with the mean of the highest nitrate (NO3) concentration observed at each well being 47.8±14.9 (n=11) mg/L NO3-N. The most elevated nutrient concentrations were found directly in the flow path of the effluent. Fecal coliform densities above 10 colony-forming units (cfu)/100 mL were observed in wells with the most rapid connection to the drainfield. The proximity and connectivity of the 0.4–4 m thick sandy surficial soils and the underlying karst aquifer allow rapid contaminant transport and limit the ability of conventional OSTDSs to attenuate NO3. | |||||
BibTeX:
@article{Harden2008,
author = {Harden, Harmon S. and Roeder, Eberhard and Hooks, Mark and Chanton, Jeffrey P.},
title = {Evaluation of onsite sewage treatment and disposal systems in shallow karst terrain},
journal = {Water Research},
year = {2008},
volume = {42},
number = {10-11},
pages = {2585--2597},
url = {http://www.sciencedirect.com/science/article/pii/S0043135408000158}
}
|
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| Harezlak, J., Coull, B.A., Laird, N.M., Magari, S.R. and Christiani, D.C. | Penalized solutions to functional regression problems | 2007 | Computational Statistics & Data Analysis Vol. 51(10), pp. 4911-4925 |
article | URL |
| Abstract: Recent technological advances in continuous biological monitoring and personal exposure assessment have led to the collection of subject-specific functional data. A primary goal in such studies is to assess the relationship between the functional predictors and the functional responses. The historical functional linear model (HFLM) can be used to model such dependencies of the response on the history of the predictor values. An estimation procedure for the regression coefficients that uses a variety of regularization techniques is proposed. An approximation of the regression surface relating the predictor to the outcome by a finite-dimensional basis expansion is used, followed by penalization of the coefficients of the neighboring basis functions by restricting the size of the coefficient differences to be small. Penalties based on the absolute values of the basis function coefficient differences (corresponding to the LASSO) and the squares of these differences (corresponding to the penalized spline methodology) are studied. The fits are compared using an extension of the Akaike Information Criterion that combines the error variance estimate, degrees of freedom of the fit and the norm of the basis function coefficients. The performance of the proposed methods is evaluated via simulations. The LASSO penalty applied to the linearly transformed coefficients yields sparser representations of the estimated regression surface, while the quadratic penalty provides solutions with the smallest L 2 -norm of the basis function coefficients. Finally, the new estimation procedure is applied to the analysis of the effects of occupational particulate matter (PM) exposure on heart rate variability (HRV) in a cohort of boilermaker workers. Results suggest that the strongest association between PM exposure and HRV in these workers occurs as a result of point exposures to the increased levels of PM corresponding to smoking breaks. | |||||
BibTeX:
@article{Harezlak2007,
author = {Harezlak, Jaroslaw and Coull, Brent A. and Laird, Nan M. and Magari, Shannon R. and Christiani, David C.},
title = {Penalized solutions to functional regression problems},
journal = {Computational Statistics & Data Analysis},
year = {2007},
volume = {51},
number = {10},
pages = {4911--4925},
url = {http://www.sciencedirect.com/science/article/pii/S016794730600346X}
}
|
|||||
| Harihar, R. | Time and scale dependent effective retardation factors in heterogeneous aquifers | 1997 | Advances in Water Resources Vol. 20(4), pp. 217-230 |
article | URL |
| Abstract: The time and scale dependence of the retardation factor is examined for transport of a linearly adsorbing solute in an aquifer with spatially variable distribution coefficient (Kd). The variability of 1n Kd and the logarithm of the hydraulic conductivity (ln K) are modeled as stationary random fields. Two definitions of the effective retardation factor are introduced: (i) the ratio of the ensemble average centroid velocities of a passive and retarded solute and (ii) the ratio of the ensemble average arrival time of a passive solute to that of a retarded solute. The effective retardation factor based on the first definition is shown to be time-dependent and that based on the second definition is shown to be distance (scale) dependent. Theoretical expressions are developed for computing the effective retardation factors based on a knowledge of statistical parameters of the ln K and ln Kd fields. Illustrative computations are presented for one-dimensional and three-dimensional heterogeneous media. | |||||
BibTeX:
@article{Harihar1997,
author = {Harihar, Rajaram},
title = {Time and scale dependent effective retardation factors in heterogeneous aquifers},
journal = {Advances in Water Resources},
year = {1997},
volume = {20},
number = {4},
pages = {217--230},
url = {http://www.sciencedirect.com/science/article/pii/S0309170896000218}
}
|
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| Harris, A.T., Davidson, J.F. and Thorpe, R.B. | Particle residence time distributions in circulating fluidised beds | 2003 | Chemical Engineering Science Vol. 58(11), pp. 2181-2202 |
article | URL |
| Abstract: This paper gives experimental measurements of the particle residence time distribution (RTD) made in the riser of a square cross section, cold model, circulating fluidised bed, using the fast response particle RTD technique developed by Harris et al. (Chem. Eng. J. 89 (2002a) 127). This technique depends upon all particles having phosphorescent properties. A small proportion of the particles become tracers when activated by a flash of light at the riser entry; the concentration of these phosphorescent particles can subsequently be detected by a photomultiplier. The influence of the solids circulation rate and superficial gas velocity on the RTD were investigated. The results presented are novel because (i) the experiments were performed in a system with closed boundaries and hence give the true residence time distribution in the riser and (ii) the measurement of the tracer concentration is exceedingly fast. The majority of previous studies have measured the RTD in risers with open boundaries, giving an erroneous measure of the RTD. | |||||
BibTeX:
@article{Harris2003,
author = {Harris, A. T. and Davidson, J. F. and Thorpe, R. B.},
title = {Particle residence time distributions in circulating fluidised beds},
journal = {Chemical Engineering Science},
year = {2003},
volume = {58},
number = {11},
pages = {2181--2202},
url = {http://www.sciencedirect.com/science/article/pii/S0009250903000824}
}
|
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| Hart, J. and Fellabaum, J. | Analyzing Campus Climate Studies: Seeking to Define and Understand [BibTeX] |
2008 | Journal of Diversity in Higher Education Vol. 1(4), pp. 222-234 |
article | DOI URL |
BibTeX:
@article{Hart2008,
author = {Hart, Jeni and Fellabaum, Jennifer},
title = {Analyzing Campus Climate Studies: Seeking to Define and Understand},
journal = {Journal of Diversity in Higher Education},
year = {2008},
volume = {1},
number = {4},
pages = {222--234},
url = {http://www.sciencedirect.com/science/article/pii/S1938892609600035},
doi = {http://dx.doi.org/10.1037/a0013627}
}
|
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| Hartmann, S., Odling, N. and West, L. | A multi-directional tracer test in the fractured Chalk aquifer of E. Yorkshire, UK | 2007 | Journal of Contaminant Hydrology Vol. 94(3-4), pp. 315-331 |
article | URL |
| Abstract: A multi-borehole radial tracer test has been conducted in the confined Chalk aquifer of E. Yorkshire, UK. Three different tracer dyes were injected into three injection boreholes and a central borehole, 25 m from the injection boreholes, was pumped at 330 m3/d for 8 days. The breakthrough curves show that initial breakthrough and peak times were fairly similar for all dyes but that recoveries varied markedly from 9 to 57%. The breakthrough curves show a steep rise to a peak and long tail, typical of dual porosity aquifers. The breakthrough curves were simulated using a 1D dual porosity model. Model input parameters were constrained to acceptable ranges determined from estimations of matrix porosity and diffusion coefficient, fracture spacing, initial breakthrough times and bulk transmissivity of the aquifer. The model gave equivalent hydraulic apertures for fractures in the range 363–384 μm, dispersivities of 1 to 5 m and matrix block sizes of 6 to 9 cm. Modelling suggests that matrix block size is the primary controlling parameter for solute transport in the aquifer, particularly for recovery. The observed breakthrough curves suggest results from single injection-borehole tracer tests in the Chalk may give initial breakthrough and peak times reasonably representative of the aquifer but that recovery is highly variable and sensitive to injection and abstraction borehole location. Consideration of aquifer heterogeneity suggests that high recoveries may be indicative of a high flow pathway adjacent, but not necessarily connected, to the injection and abstraction boreholes whereas low recoveries may indicate more distributed flow through many fractures of similar aperture. | |||||
BibTeX:
@article{Hartmann2007,
author = {Hartmann, S. and Odling, N.E. and West, L.J.},
title = {A multi-directional tracer test in the fractured Chalk aquifer of E. Yorkshire, UK},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {94},
number = {3-4},
pages = {315--331},
url = {http://www.sciencedirect.com/science/article/pii/S0169772207000927}
}
|
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| Harvey, C.F., Ashfaque, K.N., Yu, W., Badruzzaman, A., Ali, M.A., Oates, P.M., Michael, H.A., Neumann, R.B., Beckie, R., Islam, S. and Ahmed, M.F. | Groundwater dynamics and arsenic contamination in Bangladesh | 2006 | Chemical Geology Vol. 228(1-3)Controls on Arsenic Transport in Near-Surface Aquatic Systems, pp. 112-136 |
article | URL |
| Abstract: Although arsenic contaminated groundwater in Bangladesh is a serious health issue, little is known about the complex transient patterns of groundwater flow that flush solutes from aquifers and carry solutes into the subsurface. Hydrologic modeling results for our field site in the Munshiganj district indicate that groundwater flow is vigorous, flushing the aquifer over time-scales of decades to a century, and also transporting solute loads into the aquifer with recharge from ponds, rivers and rice fields. The combined hydrologic and biogeochemical results from our field site imply that the biogeochemistry of the aquifer system may not be in steady-state, and that the net effect of competing processes could either increase or decrease arsenic concentrations over the next decades. Modeling results suggest that irrigation has greatly changed the location, timing and chemical content of recharge to the aquifer, flushing water through the system more quickly, and also cycling large fluxes of water through rice fields during the dry season that could mobilize arsenic from oxides in near-surface sediments. Furthermore, the hydrologic model reveals that ponds, many of which have been excavated over the last 50 years, now provide much of the groundwater recharge. These ponds receive most of the waste from the villages and thus provide another potential source of organic carbon to the groundwater system. | |||||
BibTeX:
@article{Harvey2006,
author = {Harvey, Charles F. and Ashfaque, Khandaker N. and Yu, Winston and Badruzzaman, A.B.M. and Ali, M. Ashraf and Oates, Peter M. and Michael, Holly A. and Neumann, Rebecca B. and Beckie, Roger and Islam, Shafiqul and Ahmed, M. Feroze},
title = {Groundwater dynamics and arsenic contamination in Bangladesh},
booktitle = {Controls on Arsenic Transport in Near-Surface Aquatic Systems},
journal = {Chemical Geology},
year = {2006},
volume = {228},
number = {1-3},
pages = {112--136},
url = {http://www.sciencedirect.com/science/article/pii/S0009254106000350}
}
|
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| Harvey, J. and McCormick, P. | Groundwater’s significance to changing hydrology, water chemistry, and biological communities of a floodplain ecosystem, Everglades, South Florida, USA | 2009 | Hydrogeology Journal Vol. 17(1), pp. 185-201 |
article | URL |
| Abstract: The Everglades (Florida, USA) is one of the world’s larger subtropical peatlands with biological communities adapted to waters low in total dissolved solids and nutrients. Detecting how the pre-drainage hydrological system has been altered is crucial to preserving its functional attributes. However, reliable tools for hindcasting historic conditions in the Everglades are limited. A recent synthesis demonstrates that the proportion of surface-water inflows has increased relative to precipitation, accounting for 33% of total inputs compared with 18% historically. The largest new source of water is canal drainage from areas of former wetlands converted to agriculture. Interactions between groundwater and surface water have also increased, due to increasing vertical hydraulic gradients resulting from topographic and water-level alterations on the otherwise extremely flat landscape. Environmental solute tracer data were used to determine groundwater’s changing role, from a freshwater storage reservoir that sustained the Everglades ecosystem during dry periods to a reservoir of increasingly degraded water quality. Although some of this degradation is attributable to increased discharge of deep saline groundwater, other mineral sources such as fertilizer additives and peat oxidation have made a greater contribution to water-quality changes that are altering mineral-sensitive biological communities. | |||||
BibTeX:
@article{Harvey2009,
author = {Harvey, Judson and McCormick, Paul},
title = {Groundwater’s significance to changing hydrology, water chemistry, and biological communities of a floodplain ecosystem, Everglades, South Florida, USA},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {185--201},
url = {http://dx.doi.org/10.1007/s10040-008-0379-x}
}
|
|||||
| Harvey, R.W. | Microorganisms as tracers in groundwater injection and recovery experiments: a review | 1997 | FEMS Microbiology Reviews Vol. 20(3-4), pp. 461-472 |
article | URL |
| Abstract: Modern day injection and recovery techniques designed to examine the transport behavior of microorganisms in groundwater have evolved from experiments conducted in the late 1800s, in which bacteria that form red or yellow pigments were used to trace flow paths through karst and fractured-rock aquifers. A number of subsequent groundwater hydrology studies employed bacteriophage that can be injected into aquifers at very high concentrations (e.g., 1013 phage ml−1) and monitored through many log units of dilution to follow groundwater flow paths for great distances, particularly in karst terrain. Starting in the 1930s, microbial indicators of fecal contamination (particularly coliform bacteria and their coliphages) were employed as tracers to determine potential migration of pathogens in groundwater. Several injection and recovery experiments performed in the 1990s employed indigenous groundwater microorganisms (both cultured and uncultured) that are better able to survive under in situ conditions. Better methods for labeling native bacteria (e.g. by stable isotope labeling or inserting genetic markers, such as the ability to cause ice nucleation) are being developed that will not compromise the organisms' viability during the experimental time course. | |||||
BibTeX:
@article{Harvey1997,
author = {Harvey, Ronald W.},
title = {Microorganisms as tracers in groundwater injection and recovery experiments: a review},
journal = {FEMS Microbiology Reviews},
year = {1997},
volume = {20},
number = {3-4},
pages = {461--472},
url = {http://www.sciencedirect.com/science/article/pii/S0168644597000260}
}
|
|||||
| Harvey, R.W. and Ryan, J.N. | Use of PRD1 bacteriophage in groundwater viral transport, inactivation, and attachment studies | 2004 | FEMS Microbiology Ecology Vol. 49(1)Subsurface Microbiology, pp. 3-16 |
article | URL |
| Abstract: PRD1, an icosahedra-shaped, 62 nm (diameter), double-stranded DNA bacteriophage with an internal membrane, has emerged as an important model virus for studying the manner in which microorganisms are transported through a variety of groundwater environments. The popularity of this phage for use in transport studies involving geologic media is due, in part, to its relative stability over a range of temperatures and low degree of attachment in aquifer sediments. Laboratory and field investigations employing PRD1 are leading to a better understanding of viral attachment and transport behaviors in saturated geologic media and to improved methods for describing mathematically subsurface microbial transport at environmentally significant field scales. Radioisotopic labeling of PRD1 is facilitating additional information about the nature of viral interactions with solid surfaces in geologic media, the importance of iron oxide surfaces, and allowing differentiation between inactivation and attachment in field-scale tracer tests. | |||||
BibTeX:
@article{Harvey2004,
author = {Harvey, Ronald W and Ryan, Joseph N},
title = {Use of PRD1 bacteriophage in groundwater viral transport, inactivation, and attachment studies},
booktitle = {Subsurface Microbiology},
journal = {FEMS Microbiology Ecology},
year = {2004},
volume = {49},
number = {1},
pages = {3--16},
url = {http://www.sciencedirect.com/science/article/pii/S0168649604000960}
}
|
|||||
| Hashimoto, E.M., Ortega, E.M., Cancho, V.G. and Cordeiro, G.M. | The log-exponentiated Weibull regression model for interval-censored data | 2010 | Computational Statistics & Data Analysis Vol. 54(4), pp. 1017-1035 |
article | URL |
| Abstract: In interval-censored survival data, the event of interest is not observed exactly but is only known to occur within some time interval. Such data appear very frequently. In this paper, we are concerned only with parametric forms, and so a location-scale regression model based on the exponentiated Weibull distribution is proposed for modeling interval-censored data. We show that the proposed log-exponentiated Weibull regression model for interval-censored data represents a parametric family of models that include other regression models that are broadly used in lifetime data analysis. Assuming the use of interval-censored data, we employ a frequentist analysis, a jackknife estimator, a parametric bootstrap and a Bayesian analysis for the parameters of the proposed model. We derive the appropriate matrices for assessing local influences on the parameter estimates under different perturbation schemes and present some ways to assess global influences. Furthermore, for different parameter settings, sample sizes and censoring percentages, various simulations are performed; in addition, the empirical distribution of some modified residuals are displayed and compared with the standard normal distribution. These studies suggest that the residual analysis usually performed in normal linear regression models can be straightforwardly extended to a modified deviance residual in log-exponentiated Weibull regression models for interval-censored data. | |||||
BibTeX:
@article{Hashimoto2010,
author = {Hashimoto, Elizabeth M. and Ortega, Edwin M.M. and Cancho, Vicente G. and Cordeiro, Gauss M.},
title = {The log-exponentiated Weibull regression model for interval-censored data},
journal = {Computational Statistics & Data Analysis},
year = {2010},
volume = {54},
number = {4},
pages = {1017--1035},
url = {http://www.sciencedirect.com/science/article/pii/S0167947309003958}
}
|
|||||
| Hassan, A.E., Bekhit, H.M. and Chapman, J.B. | Uncertainty assessment of a stochastic groundwater flow model using GLUE analysis | 2008 | Journal of Hydrology Vol. 362(1-2), pp. 89-109 |
article | URL |
| Abstract: The use of the generalized likelihood uncertainty estimation (GLUE) methodology in analyzing the results of stochastic groundwater models is evaluated. The ability of the GLUE methodology to mitigate the effect of the selection of the input parameter prior distributions on the modeling results is investigated. This is important when no prior information is available or when significantly different priors come from different sources or experts. The different approaches that can be used to implement the GLUE methodology in analyzing the stochastic results of such models and quantifying the uncertainty in model prediction are evaluated. Recent debates about the GLUE methodology and the problem of using “less formal likelihood” functions are discussed in terms of the applicability of such issues to groundwater studies in general and a given field site specifically. These issues are investigated using a density-driven groundwater flow model of a nuclear testing site (Milrow) on Amchitka Island, Alaska. Results of the analysis highlight the subjectivity of the choice of the shape factor associated with the GLUE likelihood measures. However, the arbitrary choice of this factor can be tied to the level of confidence one can place on the available observations. While traditional GLUE applications focus on displaying prediction quantiles, GLUE can be used to develop uncertainty bounds that are qualitatively similar to predictive uncertainty. Interestingly, for the case study shown here the traditional GLUE quantiles and the uncertainty bounds are almost identical. Results also show that the GLUE-based ensemble averaging yields results that are controlled by the data more than by the prior distributions. The GLUE quantiles or GLUE-developed uncertainty bounds provide conditional predictions that are free from the artificial smoothing associated with ensemble averaging. | |||||
BibTeX:
@article{Hassan2008,
author = {Hassan, Ahmed E. and Bekhit, Hesham M. and Chapman, Jenny B.},
title = {Uncertainty assessment of a stochastic groundwater flow model using GLUE analysis},
journal = {Journal of Hydrology},
year = {2008},
volume = {362},
number = {1-2},
pages = {89--109},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408004265}
}
|
|||||
| Hatheway, A.W., Kanaori, Y. and Cheema, T. | Encompassing hydrogeology, environmental geology and the applied geosciences | 2003 | Engineering Geology Vol. 70(1-2), pp. 169-200 |
article | URL |
| Abstract: The year began with a good deal of international tension as well as various indications of recessional economics. Two weeks into the new year, a rash of bankruptcies visited the geoenvironmental consulting industry, in which some of the very companies that had grown by expansion in takeover of smaller firms were the unstable targets. The year ended with the demise of many established geotechnical and geoenvironmental consulting firms and the establishment of new entities, generally by the more substantial of the personnel becoming castaways in the reorganizations. | |||||
BibTeX:
@article{Hatheway2003,
author = {Hatheway, Allen W. and Kanaori, Yuji and Cheema, Tariq},
title = {Encompassing hydrogeology, environmental geology and the applied geosciences},
journal = {Engineering Geology},
year = {2003},
volume = {70},
number = {1-2},
pages = {169--200},
url = {http://www.sciencedirect.com/science/article/pii/S001379520300084X}
}
|
|||||
| Haugh, C.J. | Hydrogeology and Ground-Water Flow Simulation of a Karst Ground-Water Basin in the Valley and Ridge Physiographic Province near Hixson, Tennessee [BibTeX] |
2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 68 | inproceedings | URL |
BibTeX:
@inproceedings{Haugh2001,
author = {Haugh, Connor J.},
title = {Hydrogeology and Ground-Water Flow Simulation of a Karst Ground-Water Basin in the Valley and Ridge Physiographic Province near Hixson, Tennessee},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {68},
url = {http://water.usgs.gov/ogw/karst/kigconference/cjh_hydrogeology.htm}
}
|
|||||
| Hauns, M., Jeannin, P. and Atteia, O. | Dispersion, retardation and scale effect in tracer breakthrough curves in karst conduits | 2001 | Journal of Hydrology Vol. 241(3-4), pp. 177-193 |
article | URL |
| Abstract: Characteristics of tracer breakthrough curves in karst conduits are examined and compared to results generated using well known equations applied to porous media. The equations of the turbulent dispersion lead to a transport equation similar to the classical advection–dispersion equation for porous media with a slightly different meaning for the dispersion and advection terms. | |||||
BibTeX:
@article{Hauns2001,
author = {Hauns, M. and Jeannin, P.Y. and Atteia, O.},
title = {Dispersion, retardation and scale effect in tracer breakthrough curves in karst conduits},
journal = {Journal of Hydrology},
year = {2001},
volume = {241},
number = {3-4},
pages = {177--193},
url = {http://www.sciencedirect.com/science/article/pii/S0022169400003668}
}
|
|||||
| Haywood, J. and Khmaladze, E. | On distribution-free goodness-of-fit testing of exponentiality | 2008 | Journal of Econometrics Vol. 143(1)Specification testing, pp. 5-18 |
article | URL |
| Abstract: There is a need to test the hypothesis of exponentiality against a wide variety of alternative hypotheses, across many areas of economics and finance. Local or contiguous alternatives are the closest alternatives against which it is still possible to have some power. Hence goodness-of-fit tests should have some power against all, or a huge majority, of local alternatives. Such tests are often based on nonlinear statistics, with a complicated asymptotic null distribution. Thus a second desirable property of a goodness-of-fit test is that its statistic will be asymptotically distribution free. We suggest a whole class of goodness-of-fit tests with both of these properties, by constructing a new version of empirical process that weakly converges to a standard Brownian motion under the hypothesis of exponentiality. All statistics based on this process will asymptotically behave as statistics from a standard Brownian motion and so will be asymptotically distribution free. We show the form of transformation is especially simple in the case of exponentiality. Surprisingly there are only two asymptotically distribution free versions of empirical process for this problem, and only this one has a convenient limit distribution. Many tests of exponentiality have been suggested based on asymptotically linear functionals from the empirical process. We illustrate none of these can be used as goodness-of-fit tests, contrary to some previous recommendations. Of considerable interest is that a selection of well-known statistics all lead to the same test asymptotically, with negligible asymptotic power against a great majority of local alternatives. Finally, we present an extension of our approach that solves the problem of multiple testing, both for exponentiality and for other, more general hypotheses. | |||||
BibTeX:
@article{Haywood2008,
author = {Haywood, John and Khmaladze, Estate},
title = {On distribution-free goodness-of-fit testing of exponentiality},
booktitle = {Specification testing},
journal = {Journal of Econometrics},
year = {2008},
volume = {143},
number = {1},
pages = {5--18},
url = {http://www.sciencedirect.com/science/article/pii/S0304407607001613}
}
|
|||||
| Headley, T.R., Herity, E. and Davison, L. | Treatment at different depths and vertical mixing within a 1-m deep horizontal subsurface-flow wetland | 2005 | Ecological Engineering Vol. 25(5)Constructed wetlands for wastewater treatment, pp. 567-582 |
article | URL |
| Abstract: The aim of this study was to examine the variation in treatment performance at three depths, and the degree of vertical mixing, within a 1.0 m deep horizontal subsurface-flow constructed wetland (HSSF-CW) planted with Schoenoplectus tabernaemontani (Gmel.) Palla, and treating primary settled municipal wastewater in sub-tropical New South Wales, Australia. Water samples were collected from the upper (0.17 m), middle (0.5 m), and lower (0.83 m) depths at five equi-spaced sample points along the longitudinal axis of the 8.8 m2 bed during two trials. Analysis of covariance (ANCOVA) indicated that the rate of pollutant concentration reduction between the three depths was not significantly different (p > 0.05) for all of the measured parameters (dissolved oxygen (DO), hydrogen electrode potentials (Eh), 5-day biochemical oxygen demand (BOD5)) total nitrogen (TN), TKN, and NH4-N. Thus, it can be concluded that the break-down of contaminants as wastewater moved through the HSSF-CW was approximately uniform across the 1.0 m depth profile. The lack of a significant depth effect can be largely explained by the substantial amount of vertical mixing that was observed when a pulse of lithium tracer was injected into the middle depth of the first intermediate sampling point. The tracer rapidly migrated vertically into the upper and lower depths as water moved through the bed and was almost completely mixed between the three depths by the time it reached the last intermediate sampling point. | |||||
BibTeX:
@article{Headley2005,
author = {Headley, Thomas R. and Herity, Eamon and Davison, Leigh},
title = {Treatment at different depths and vertical mixing within a 1-m deep horizontal subsurface-flow wetland},
booktitle = {Constructed wetlands for wastewater treatment},
journal = {Ecological Engineering},
year = {2005},
volume = {25},
number = {5},
pages = {567--582},
url = {http://www.sciencedirect.com/science/article/pii/S0925857405001515}
}
|
|||||
| Healy, R.W. and Russell, T.F. | Solution of the advection-dispersion equation in two dimensions by a finite-volume Eulerian-Lagrangian localized adjoint method | 1998 | Advances in Water Resources Vol. 21(1), pp. 11-26 |
article | URL |
| Abstract: We extend the finite-volume Eulerian-Lagrangian localized adjoint method (FVELLAM) for solution of the advection-dispersion equation to two dimensions. The method can conserve mass globally and is not limited by restrictions on the size of the grid Peclet or Courant number. Therefore, it is well suited for solution of advection-dominated ground-water solute transport problems. In test problem comparisons with standard finite differences, FVELLAM is able to attain accurate solutions on much coarser space and time grids. On fine grids, the accuracy of the two methods is comparable. A critical aspect of FVELLAM (and all other ELLAMs) is evaluation of the mass storage integral from the preceding time level. In FVELLAM this may be accomplished with either a forward or backtracking approach. The forward tracking approach conserves mass globally and is the preferred approach. The backtracking approach is less computationally intensive, but not globally mass conservative. Boundary terms are systematically represented as integrals in space and time which are evaluated by a common integration scheme in conjunction with forward tracking through time. Unlike the one-dimensional case, local mass conservation cannot be guaranteed, so slight oscillations in concentration can develop, particularly in the vicinity of inflow or outflow boundaries. | |||||
BibTeX:
@article{Healy1998,
author = {Healy, Richard W. and Russell, Thomas F.},
title = {Solution of the advection-dispersion equation in two dimensions by a finite-volume Eulerian-Lagrangian localized adjoint method},
journal = {Advances in Water Resources},
year = {1998},
volume = {21},
number = {1},
pages = {11--26},
url = {http://www.sciencedirect.com/science/article/pii/S0309170896000334}
}
|
|||||
| Hebel, P., Faivre, R., Goffinet, B. and Wallach, D. | Shrinkage Estimators Applied to Prediction of French Winter Wheat Yield | 1993 | Biometrics Vol. 49(1), pp. 281-293 |
article | URL |
| Abstract: The paper shows that it is possible to pool departmental information to predict regional wheat yield. In an MSEP (mean squared error of prediction) context, shrinkage estimation in linear agrometeorological models improves regional prediction. Cross-validation is not precise enough to enable comparison between models. The authors calculate the MSEP using the hypothesis of a multinormal distribution in simple cases (the distribution parameters are estimated with data input) and simulations are used for complex cases. Stein-like estimators are shown to be a superior alternative to the conventional estimators usually applied for prediction. | |||||
BibTeX:
@article{Hebel1993a,
author = {Hebel, Pascale and Faivre, Robert and Goffinet, Bruno and Wallach, Daniel},
title = {Shrinkage Estimators Applied to Prediction of French Winter Wheat Yield},
journal = {Biometrics},
publisher = {International Biometric Society},
year = {1993},
volume = {49},
number = {1},
pages = {281--293},
url = {http://www.jstor.org/stable/2532623}
}
|
|||||
| Hedmark, Å. and Scholz, M. | Review of environmental effects and treatment of runoff from storage and handling of wood | 2008 | Bioresource Technology Vol. 99(14), pp. 5997-6009 |
article | URL |
| Abstract: This review paper summarises the environmental effects of runoff from wood handling sites including log yards. The characteristics of site runoff and the corresponding effects on the receiving watercourses are presented for worldwide case studies, highlighting the urgent need to address the water pollution problem associated with the wood industry. The methods used to reduce the negative environmental impact of the runoff, such as constructed wetlands, soil infiltration and chemical oxidation, are evaluated. The principal environmental problem of runoff is usually the high concentration of organic substances originating from the wood and bark, some of which are toxic to aquatic life. Phosphorus is also a problem according to some studies. The toxicity of the runoff varies greatly, and depends on the species of tree stored, the amount of water the wood has been in contact with and the degree of runoff treatment. | |||||
BibTeX:
@article{Hedmark2008,
author = {Hedmark, Åsa and Scholz, Miklas},
title = {Review of environmental effects and treatment of runoff from storage and handling of wood},
journal = {Bioresource Technology},
year = {2008},
volume = {99},
number = {14},
pages = {5997--6009},
url = {http://www.sciencedirect.com/science/article/pii/S0960852407010668}
}
|
|||||
| Helmreich, B., Hilliges, R., Schriewer, A. and Horn, H. | Runoff pollutants of a highly trafficked urban road – Correlation analysis and seasonal influences | 2010 | Chemosphere Vol. 80(9), pp. 991-997 |
article | URL |
| Abstract: The quality of road runoff at a highly trafficked road has been studied for 2 years. 63 storm events have been sampled and analyzed. Besides pH value and electric conductivity the concentrations of zinc (Zn), copper (Cu), lead (Pb), nickel (Ni) and cadmium (Cd), both in dissolved and particulate form, de-icing salt, total and dissolved organic carbon (TOC and DOC), suspended solids (SS) have been monitored. Correlation analysis showed a significant relationship between the total metal concentrations with TOC and SS. A considerable seasonal increase in pollutant concentrations has been observed for Cu, TOC, SS, pH value and especially for Zn during the cold season. The mean values during winter time were multiple times higher than measured during the warm season. In contrast, the fractionation of heavy metals was not affected by seasonal variations, but remarkable fluctuations were observed between different rain events with dissolved fractions above 90%. As a result of this and due to the high pollutant load on fine particles, best management practices (BMPs) only implementing sedimentation are not recommended for treatment of heavily polluted urban road runoff. From the data obtained it can be concluded, that the de-icing salt has only a weak influence for higher pollutant concentrations. The increase of heavy metal concentrations occurs because of increased tear and wear due to application of gravel at cold weather conditions. No significant influence of the length of antecedent dry weather periods could be observed most likely due to street sweeping, winds and air turbulences caused by traffic. | |||||
BibTeX:
@article{Helmreich2010,
author = {Helmreich, Brigitte and Hilliges, Rita and Schriewer, Alexander and Horn, Harald},
title = {Runoff pollutants of a highly trafficked urban road – Correlation analysis and seasonal influences},
journal = {Chemosphere},
year = {2010},
volume = {80},
number = {9},
pages = {991--997},
url = {http://www.sciencedirect.com/science/article/pii/S0045653510006132}
}
|
|||||
| Henderson, A.R. | Testing experimental data for univariate normality | 2006 | Clinica Chimica Acta Vol. 366(1-2), pp. 112-129 |
article | URL |
| Abstract: Many experimentally-derived data sets are generated in the practice of clinical chemistry. Graphical presentation is essential to assess the data distribution. The distribution must also be assessed quantitatively. These approaches will determine if the data is Normal or not. Finally the results of these tests of Normality must be shown to be free of sample size effects. Methods Four experimentally-derived data sets were used. They represented normal, positive kurtotic, positive- and negatively-skewed distributions. These data sets were examined by graphical techniques, by moment tests, by tests of Normality, and monitored for sample size effects. Results The preferred graphical techniques are the histogram and the box-and-whisker plots that may be supplemented, with advantage, by quantile–quantile or probability–probability plots. Classical tests of skewness and kurtosis can produce conflicting and often confusing results and, as a consequence, the alternative use of the newer L-moments is advocated. Normality tests included the Kolmogorov–Smirnov (Lilliefors modification), Cramér-von Mises and Anderson–Darling tests (empirical distribution function statistics) and the Gan–Koehler, Shapiro–Wilk, Shapiro–Francia, and Filliben tests (regression/correlation techniques). Of these only the Anderson–Darling, Shapiro–Wilk, and Shapiro–Francia tests correctly classified all four test samples. The effect of sample size on the resulting p-value was investigated using Royston's V′ / v′ graphical test. Conclusions A systematic approach to Normality testing should follow the route of graphical presentation, the use of L-moments, the use of Anderson–Darling, Shapiro–Wilk, or Shapiro–Francia testing, and Royston's sample size monitoring. | |||||
BibTeX:
@article{Henderson2006,
author = {Henderson, A. Ralph},
title = {Testing experimental data for univariate normality},
journal = {Clinica Chimica Acta},
year = {2006},
volume = {366},
number = {1-2},
pages = {112--129},
url = {http://www.sciencedirect.com/science/article/pii/S0009898105006790}
}
|
|||||
| Herman, E.K., Toran, L. and White, W.B. | Quantifying the place of karst aquifers in the groundwater to surface water continuum: A time series analysis study of storm behavior in Pennsylvania water resources | 2009 | Journal of Hydrology Vol. 376(1-2), pp. 307-317 |
article | URL |
| Abstract: Though karst aquifers have commonly been identified, with respect to their behavior, as intermediate between ground and surface water, their putative location between these end members is generally descriptive rather than quantitative. Autocorrelation and spectral analysis of data from four karst springs, three wells, and eight stream gauges in Pennsylvania illustrate that specific karst water resources exhibit widely varying inertia with lag times that overlap those of groundwater and surface water. When analyzed in the frequency domain, the same data reveal distinctive patterns for each type of water resource. | |||||
BibTeX:
@article{Herman2009,
author = {Herman, Ellen K. and Toran, Laura and White, William B.},
title = {Quantifying the place of karst aquifers in the groundwater to surface water continuum: A time series analysis study of storm behavior in Pennsylvania water resources},
journal = {Journal of Hydrology},
year = {2009},
volume = {376},
number = {1-2},
pages = {307--317},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409004430}
}
|
|||||
| Herman, E.K., Toran, L. and White, W.B. | Threshold events in spring discharge: Evidence from sediment and continuous water level measurement | 2008 | Journal of Hydrology Vol. 351(1-2), pp. 98-106 |
article | URL |
| Abstract: Summary In September 2004, three major hurricanes, Frances, Ivan, and Jeanne, traveled up the eastern United States from the Gulf Coast bringing large amounts of rain to Central Pennsylvania. Monitoring equipment in place at Arch Spring, Blair County, PA captured the effects of these storms on the karstic spring flow. Together these storms revealed a quantitative limit for the carrying capacity of the conduit system. Ivan was a much more devastating storm to the area because rain fell on ground already saturated by Frances, but the net stage increase at the spring was greater during the earlier Frances storm, a 74 cm stage increase versus a 54 cm increase. Storm water not transported through the Arch Spring system was diverted into surface channels during these storms. | |||||
BibTeX:
@article{Herman2008,
author = {Herman, Ellen K. and Toran, Laura and White, William B.},
title = {Threshold events in spring discharge: Evidence from sediment and continuous water level measurement},
journal = {Journal of Hydrology},
year = {2008},
volume = {351},
number = {1-2},
pages = {98--106},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407007263}
}
|
|||||
| Herrera, P.A., Valocchi, A.J. and Beckie, R.D. | A multidimensional streamline-based method to simulate reactive solute transport in heterogeneous porous media | 2010 | Advances in Water Resources Vol. 33(7), pp. 711-727 |
article | URL |
| Abstract: We present a new streamline-based numerical method for simulating reactive solute transport in porous media. The key innovation of the method is that both longitudinal and transverse dispersion are incorporated accurately without numerical dispersion. Dispersion is approximated in a flow-oriented grid using a combination of a one-dimensional finite difference scheme and a meshless approximation. In contrast to previous hybrid alternatives to incorporate dispersion in streamline-based simulations, the proposed scheme does not require a grid and, hence, it does not introduce numerical dispersion. In addition, the proposed scheme eliminates numerical oscillations and negative concentration values even when the dispersion tensor includes the off-diagonal coefficients and the flow field is non-uniform. We demonstrate that for a set of two- and three-dimensional benchmark problems, the new proposed streamline-based formulation compares favorably to two state of the art finite volume and hybrid Eulerian–Lagrangian solvers. | |||||
BibTeX:
@article{Herrera2010,
author = {Herrera, Paulo A. and Valocchi, Albert J. and Beckie, Roger D.},
title = {A multidimensional streamline-based method to simulate reactive solute transport in heterogeneous porous media},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {7},
pages = {711--727},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810000424}
}
|
|||||
| Hers, I., Atwater, J., Li, L. and Zapf-Gilje, R. | Evaluation of vadose zone biodegradation of BTX vapours | 2000 | Journal of Contaminant Hydrology Vol. 46(3-4), pp. 233-264 |
article | URL |
| Abstract: Soil vapour transport to indoor air is an important potential exposure pathway at many sites impacted by subsurface volatile organic compounds (VOCs). The inclusion of biodegradation in vadose zone transport models for benzene, toluene and xylene (BTX) and fuel hydrocarbons has been proposed; however, there is still significant uncertainty regarding biodegradation rates and the local effects of buildings or ground surface cover on fate and transport processes. The objective of this study was to evaluate biodegradation processes through comprehensive monitoring at a site contaminated with BTX and model simulation. Study methods included extensive vertical profiling of BTX vapour and light gas (oxygen and carbon dioxide) concentrations and moisture content, and semi-continuous monitoring of oxygen and pressure below a building floor slab. Significant vadose zone biodegradation over a relatively small depth interval was observed. Based on the observed soil vapour profile, first-order biodegradation rates were estimated by fitting an analytical solution for diffusion and biodecay to the data. Degradation rates were found to compare well to other reported laboratory and field data. A two-dimensional (2-D) numerical model incorporating vapour-phase diffusion, advection, sorption and biodegradation was used to simulate the effect of a building floor slab on transport processes. Model results demonstrate the sensitivity of vapour-phase BTX and oxygen transport to partial barriers to diffusion (e.g. building foundation) and highlight the importance of using a model that ties biodecay to oxygen availability. In addition, depressurization within a building and advective transport is shown to have a potentially significant effect on BTX fate, in soil below. | |||||
BibTeX:
@article{Hers2000,
author = {Hers, Ian and Atwater, Jim and Li, Loretta and Zapf-Gilje, Reidar},
title = {Evaluation of vadose zone biodegradation of BTX vapours},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {46},
number = {3-4},
pages = {233--264},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200001352}
}
|
|||||
| Hess, J.W. and White, W.B. | Groundwater geochemistry of the carbonate karst aquifer, southcentral Kentucky, U.S.A. | 1993 | Applied Geochemistry Vol. 8(2), pp. 189-204 |
article | URL |
| Abstract: Analyses of 441 water samples from 15 sample sites, mainly springs and sinking creeks in the southcentral Kentucky karst, were used to determine hardness, PCO2, and state of saturation with respect to calcite and dolomite. Most of the waters are undersaturated with respect to calcite and more undersaturated with respect to dolomite, in agreement with recent kinetic models. Time series data revealed chemical fluctuations on both weekly and seasonal time scales. Much of the short-term variation and some of the seasonal variation in the hardness and saturation index parameters can be accounted for by dilution effects from storm and seasonal runoff. Seasonal cycles in CO2 partial pressure arise from a dependence of soil CO2 on temperature and the growing season. Waters from different locations in the aquifer system are chemically distinct and fit into the concept of a hydrochemical facies. | |||||
BibTeX:
@article{Hess1993,
author = {Hess, John W. and White, William B.},
title = {Groundwater geochemistry of the carbonate karst aquifer, southcentral Kentucky, U.S.A.},
journal = {Applied Geochemistry},
year = {1993},
volume = {8},
number = {2},
pages = {189--204},
url = {http://www.sciencedirect.com/science/article/pii/088329279390034E}
}
|
|||||
| Hess, J.W. and White, W.B. | Storm response of the karstic carbonate aquifer of southcentral Kentucky | 1988 | Journal of Hydrology Vol. 99(3-4), pp. 235-252 |
article | URL |
| Abstract: Temperature and specific conductance were continuously measured in the downstream drainage of the Turnhole Spring subbasin in the southcentral Kentucky karst. Precipitation was monitored with a rain gage network in the catchment area so that the storm response of specific conductance and temperature could be examined. The aquifer feeding the Turnhole Spring is highly karstic with much of the discharge through integrated open conduits some of which carry water from surface sinking stream catchments. Both temperature and specific conductance fluctuate rapidly in response to storm events. The conductivity curves and to a lesser extent the temperature curves show a sharp dip that lags some hours behind the storm pulse. At the onset of the dip is a complicated sequence of fine structures that is interpreted to be the inputs from conduit tributaries to the master trunk drainage system. The recovery curves have an exponential form that can be fitted to produce a characteristic response time for the conduit system. | |||||
BibTeX:
@article{Hess1988,
author = {Hess, Jonn W. and White, William B.},
title = {Storm response of the karstic carbonate aquifer of southcentral Kentucky},
journal = {Journal of Hydrology},
year = {1988},
volume = {99},
number = {3-4},
pages = {235--252},
url = {http://www.sciencedirect.com/science/article/pii/0022169488900510}
}
|
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| Heße, F., Radu, F., Thullner, M. and Attinger, S. | Upscaling of the advection–diffusion–reaction equation with Monod reaction | 2009 | Advances in Water Resources Vol. 32(8), pp. 1336-1351 |
article | URL |
| Abstract: The need for reliable models for the reactive transport of contaminants in the subsurface is well recognized. The predictive power of these models is determined by the accurate description of bioavailability of contaminants to microorganisms in porous media. Among many other factors influencing bioavailability, diffusive mass transfer processes may limit the substrate availability at the pore scale and hence reduce the effective degradation rate considerably. In this study we used a combination of analytical and numerical methods to upscale surface catalyzed Monod-type reaction rates within a single pore, to obtain effective rate expression at a larger scale. Results show that in the upscaled description Monod kinetics lead to a concentration dependent transition between a reaction and diffusion-limited regime. Strictly, the effective rate repression does not follow Monod-type kinetics. However, we can present appropriate effective parameters relations, which provide an acceptable approximation of degradation dynamics using an effective Monod-type reaction rate. | |||||
BibTeX:
@article{Hesse2009,
author = {Heße, F. and Radu, F.A. and Thullner, M. and Attinger, S.},
title = {Upscaling of the advection–diffusion–reaction equation with Monod reaction},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {8},
pages = {1336--1351},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809000918}
}
|
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| Hessel, V., Löwe, H. and Schönfeld, F. | Micromixers—a review on passive and active mixing principles | 2005 | Chemical Engineering Science Vol. 60(8-9)5th International Symposium on Mixing in Industrial Processes (ISMIP5), pp. 2479-2501 |
article | URL |
| Abstract: A review on microstructured mixer devices and their mixing principles concerning miscible liquids (and gases) is given. This is supplemented by the description of typical mixing element designs, methods for mixing characterisation, and application fields. The mixing principles applied can be divided in two classes relying either on the pumping energy or provision of other external energy to achieve mixing, termed passive and active mixing, respectively. As far as passive mixing is concerned, devices and techniques such as Y- and T-type flow-, multi-laminating-, split-and-recombine-, chaotic-, jet colliding-, recirculation flow-mixers and others are discussed. Active mixing can be accomplished by time-pulsing flow owing to a periodical change of pumping energy or electrical fields, acoustic fluid shaking, ultrasound, electrowetting-based droplet shaking, microstirrers, and others. | |||||
BibTeX:
@article{Hessel2005,
author = {Hessel, Volker and Löwe, Holger and Schönfeld, Friedhelm},
title = {Micromixers—a review on passive and active mixing principles},
booktitle = {5th International Symposium on Mixing in Industrial Processes (ISMIP5)},
journal = {Chemical Engineering Science},
year = {2005},
volume = {60},
number = {8--9},
pages = {2479--2501},
url = {http://www.sciencedirect.com/science/article/pii/S0009250904009364}
}
|
|||||
| Hilger, H. and Embry, I. | Towards a New Vision of Social Sustainability [BibTeX] |
2010 | EWRI Currents Vol. 12(4), pp. 10-11 |
article | |
BibTeX:
@article{Hilger2010,
author = {Hilger, Helene and and Embry, Irucka},
title = {Towards a New Vision of Social Sustainability},
journal = {EWRI Currents},
year = {2010},
volume = {12},
number = {4},
pages = {10--11}
}
|
|||||
| Hill Jr., C.G. | An Introduction to Chemical Engineering Kinetics & Reactor Design [BibTeX] |
1977 | , pp. - | book | |
BibTeX:
@book{Hill1977,
author = {Hill, Jr., Charles G.},
title = {An Introduction to Chemical Engineering Kinetics & Reactor Design},
publisher = {John Wiley & Sons, Inc.},
year = {1977},
pages = {--}
}
|
|||||
| Hill, M.E., Martin, A. and Stewart, M.T. | Performance Evaluation of the MODFLOW-2005 Conduit Flow Process Applied to a Karst Aquifer Underlying West-Central Florida | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 93-98 | inproceedings | URL |
| Abstract: The MODFLOW-2005 Conduit Flow Process (CFP) was used to simulate discharge and matrix-conduit water levels in a dual-permeability karst aquifer in the vicinity of Weeki Wachee, west-central Florida. The performance of MODFLOW-2005 with an equivalent continuum model, which simulates only laminar flow, relative to MODFLOW-2005 CFP Mode 1, which simulates both laminar and turbulent flow, as well as fluid exchange between the matrix and conduit networks in a dual-conductivity model, was evaluated. Simulated water levels in the matrix and conduit networks were evaluated by comparing these levels to observed values from monitoring wells penetrating the matrix and conduit networks. Additionally, observed discharge hydrographs following convective and tropical storms, as well as drought conditions, were compared to simulated discharges from transient simulations using MODFLOW-2005 and MODFLOW-2005 CFP Mode 1. Results indicate that the application of MODFLOW-2005 CFP Mode 1, with the dual-conductivity model, improves the overall match between simulated and observed discharges by 12 to 40%. We conclude that the dual-conductivity model, using MODFLOW-2005 CFP Mode 1 is a better tool for simulating discharge from the dual-permeability Upper Floridan aquifer, particularly during periods of low net recharge, than the equivalent continuum model using MODFLOW-2005. | |||||
BibTeX:
@inproceedings{Hill2008,
author = {Hill, Melissa E. and Martin, Angel and Stewart, Marc T.},
title = {Performance Evaluation of the MODFLOW-2005 Conduit Flow Process Applied to a Karst Aquifer Underlying West-Central Florida},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {93--98},
url = {http://pubs.usgs.gov/sir/2008/5023/37hill.htm}
}
|
|||||
| Hiller, T., Kaufmann, G. and Romanov, D. | Karstification beneath dam-sites: From conceptual models to realistic scenarios | 2011 | Journal of Hydrology Vol. 398(3-4), pp. 202-211 |
article | URL |
| Abstract: Dam-sites and reservoirs located above soluble rock are often damaged by increased leakage through the sub-surface within the life-time of the structure. The high hydraulic gradients driving the water through the fracture and fissure system of the bedrock have a strong impact on the aquifer evolution. The increased permeability, if not prevented, leads to an imminent danger of high leakage rates (breakthrough) as well. As a result, the structural safety of the dam-site itself is at risk. Past experience has shown that this may have large environmental and economical consequences. | |||||
BibTeX:
@article{Hiller2011,
author = {Hiller, Thomas and Kaufmann, Georg and Romanov, Douchko},
title = {Karstification beneath dam-sites: From conceptual models to realistic scenarios},
journal = {Journal of Hydrology},
year = {2011},
volume = {398},
number = {3-4},
pages = {202--211},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410007791}
}
|
|||||
| von Hippel, P.T. | Mean, Median, and Skew: Correcting a Textbook Rule | 2005 | Journal of Statistics Education Vol. 13(2) |
article | URL |
| Abstract: Many textbooks teach a rule of thumb stating that the mean is right of the median under right skew, and left of the median under left skew. This rule fails with surprising frequency. It can fail in multimodal distributions, or in distributions where one tail is long but the other is heavy. Most commonly, though, the rule fails in discrete distributions where the areas to the left and right of the median are not equal. Such distributions not only contradict the textbook relationship between mean, median, and skew, they also contradict the textbook interpretation of the median. We discuss ways to correct ideas about mean, median, and skew, while enhancing the desired intuition. | |||||
BibTeX:
@article{Hippel2005,
author = {von Hippel, Paul T.},
title = {Mean, Median, and Skew: Correcting a Textbook Rule},
journal = {Journal of Statistics Education},
year = {2005},
volume = {13},
number = {2},
url = {http://www.amstat.org/publications/jse/v13n2/vonhippel.html}
}
|
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| Holland, J.F., Martin, J.F., Granata, T., Bouchard, V., Quigley, M. and Brown, L. | Analysis and modeling of suspended solids from high-frequency monitoring in a stormwater treatment wetland | 2005 | Ecological Engineering Vol. 24(3), pp. 157-174 |
article | URL |
| Abstract: Tools for modeling pulsed flows and constituent fluxes in wetlands, although well developed in theory, have not been well tested in practice. High-frequency monitoring of suspended solids and flows in a stormwater treatment wetland enabled application and analysis of these tools. A dynamic flow- and volume-weighted time variable, analogous to the retention time in steady-flow systems, is one important tool tested in this study. Cross-correlations with time lags demonstrated that the dynamic time variable was a better predictive variable of pulsed events than was the standard, static time variable. Although plug-flow models are typically used for steady-flow wetlands, residence time distribution (RTD) models are indispensable for describing pulsed flows and constituent fluxes in wetlands. This study demonstrated that RTD modeling with reaction kinetics of suspended solids during storm events produces a better explanation of outflow data than possible with steady, plug-flow models. Using only input and output data, an RTD model explained sedimentation rates with less unexplained variance than the standard, plug-flow model. The results of this study underscore the importance and utility of RTD modeling for complex flows. | |||||
BibTeX:
@article{Holland2005,
author = {Holland, Jeff F. and Martin, Jay F. and Granata, Timothy and Bouchard, Virginie and Quigley, Martin and Brown, Larry},
title = {Analysis and modeling of suspended solids from high-frequency monitoring in a stormwater treatment wetland},
journal = {Ecological Engineering},
year = {2005},
volume = {24},
number = {3},
pages = {157--174},
url = {http://www.sciencedirect.com/science/article/pii/S0925857404001326}
}
|
|||||
| Holland, J.F., Martin, J.F., Granata, T., Bouchard, V., Quigley, M. and Brown, L. | Effects of wetland depth and flow rate on residence time distribution characteristics | 2004 | Ecological Engineering Vol. 23(3), pp. 189-203 |
article | URL |
| Abstract: The residence time distribution (RTD) representing the hydraulics of a wetland is an important tool for modeling and designing treatment wetlands for optimal constituent removal. To correctly use RTD results, it is necessary to understand the conditions under which this distribution remains stable. Dye tracer experiments were conducted on a stormwater treatment wetland to investigate hydrologic factors affecting RTD characteristics. Dye was introduced into the inflow under normal flow conditions and during simulated storm flows, providing a range of flow rates and water levels. Dye distribution in the outlet was measured using an in situ fluorometer. Results indicate that flow rates did not have a significant effect on RTD characteristics. The RTDs normalized for volume and flow demonstrated a greater amount of short-circuiting and a larger mixing scale when water depth increased, demonstrating that water level can have a direct impact on the RTD of a wetland. This effect suggests that more than one RTD may be necessary for analyzing a wetland subject to changing water levels. For the wetland in this study, increasing the water depth elicited a decrease in hydraulic efficiency. Understanding such factors that affect hydraulic efficiency will aid in the design and management of wetlands. | |||||
BibTeX:
@article{Holland2004,
author = {Holland, Jeff F. and Martin, Jay F. and Granata, Timothy and Bouchard, Virginie and Quigley, Martin and Brown, Larry},
title = {Effects of wetland depth and flow rate on residence time distribution characteristics},
journal = {Ecological Engineering},
year = {2004},
volume = {23},
number = {3},
pages = {189--203},
url = {http://www.sciencedirect.com/science/article/pii/S0925857404001284}
}
|
|||||
| Holliday, B.G. | The History and Visions of African American Psychology: Multiple Pathways to Place, Space, and Authority | 2009 | Cultural Diversity and Ethnic Minority Psychology Vol. 15(4), pp. 317-337 |
article | URL |
| Abstract: The author describes the multiple pathways of events and strategies that served to nurture African American psychology in the United States. Special attention is given to strategies for inclusion and empowerment used in 4 psychological professional and scholarly associations: the American Counseling Association, the American Psychological Association, the Association of Black Psychologists, and the Society for Research in Child Development. In addition, the author describes 4 major intellectual traditions that informed not only the strategies of inclusion but also the theoretical, research, and intervention perspectives and other professional and academic efforts of African American psychologists. Those perspectives are the Afrocentric/African-centered tradition derived from longstanding nationalist/Pan-African and culturally centered traditions within African American communities; the social contextual/multidisciplinary research tradition of the University of Chicago School of Social Science; the empirical social science research tradition of the University of Michigan; and the Black scholar/activist tradition of Howard University. This article also presents a chronological timeline of major events in the history of African American psychology. | |||||
BibTeX:
@article{Holliday2009,
author = {Holliday, Bertha Garrett},
title = {The History and Visions of African American Psychology: Multiple Pathways to Place, Space, and Authority},
journal = {Cultural Diversity and Ethnic Minority Psychology},
year = {2009},
volume = {15},
number = {4},
pages = {317--337},
url = {http://www.sciencedirect.com/science/article/pii/S1099980909600348}
}
|
|||||
| Hoque, S., Farouk, B. and Haas, C.N. | Development of metamodels for predicting aerosol dispersion in ventilated spaces | 2011 | Atmospheric Environment Vol. 45(10), pp. 1876-1887 |
article | URL |
| Abstract: Artificial neural network (ANN) based metamodels were developed to describe the relationship between the design variables and their effects on the dispersion of aerosols in a ventilated space. A Hammersley sequence sampling (HSS) technique was employed to efficiently explore the multi-parameter design space and to build numerical simulation scenarios. A detailed computational fluid dynamics (CFD) model was applied to simulate these scenarios. The results derived from the CFD simulations were used to train and test the metamodels. Feed forward ANN’s were developed to map the relationship between the inputs and the outputs. The predictive ability of the neural network based metamodels was compared to linear and quadratic metamodels also derived from the same CFD simulation results. The ANN based metamodel performed well in predicting the independent data sets including data generated at the boundaries. Sensitivity analysis showed that particle tracking time to residence time and the location of input and output with relation to the height of the room had more impact than the other dimensionless groups on particle behavior. | |||||
BibTeX:
@article{Hoque2011,
author = {Hoque, Shamia and Farouk, Bakhtier and Haas, Charles N.},
title = {Development of metamodels for predicting aerosol dispersion in ventilated spaces},
journal = {Atmospheric Environment},
year = {2011},
volume = {45},
number = {10},
pages = {1876--1887},
url = {http://www.sciencedirect.com/science/article/pii/S1352231010010824}
}
|
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| Hormann, V. and Kirchner, G. | Prediction of the effects of soil-based countermeasures on soil solution chemistry of soils contaminated with radiocesium using the hydrogeochemical code PHREEQC | 2002 | Science of The Total Environment Vol. 289(1–3), pp. 83-95 |
article | URL |
| Abstract: For agriculturally used areas, which are contaminated by the debris from a nuclear accident, the use of chemical amendmends (e.g. potassium chloride and lime) is among the most common soil-based countermeasures. These countermeasures are intended to reduce the plant uptake of radionuclides (mainly137Cs and 90Sr) by competitive inhibition by chemically similar ions. So far, the impacts of countermeasures on soil solution composition — and thus, their effectiveness — have almost exclusively been established experimentally, since they depend on mineral composition and chemical characteristics of the soil affected. In this study, which focuses on caesium contamination, the well-established code PHREEQC was used as a geochemical model to calculate the changes in the ionic compositions of soil solutions, which result from the application of potassium or ammonium in batch equilibrium experiments. The simple ion exchange model used by PHREEQC was improved by taking into account selective sorption of Cs+, NH4+ and K+ by clay minerals. Calculations were performed with three different initial soil solution compositions, corresponding to particular soil types (loam, sand, peat). For loamy and sandy soils, our calculational results agree well with experimental data reported by Nisbet (Effectiveness of soil-based countermeasures six months and one year after contamination of five diverse soil types with caesium-134 and strontium-90. Contract Report NRPB-M546, National Radiation Protection Board, Chilton, 1995.). For peat, discrepancies were found indicating that for organic soils a reliable set of exchange constants of the relevant cations still has to be determined experimentally. For cesium, however, these discrepancies almost disappeared if selective sites were assumed to be inaccessible. Additionally, results of sensitivity analyses are presented by which the influence of the main soil parameters on Cs+ concentrations in solution after soil treatment has been systematically studied. It is shown that calculating the impacts of soil-based chemical countermeasures on soil solution chemistry using geochemical codes such as PHREEQC offers an attractive alternative to establishing these impacts by often time-consuming and site-specific experiments. | |||||
BibTeX:
@article{Hormann2002,
author = {Hormann, Volker and Kirchner, Gerald},
title = {Prediction of the effects of soil-based countermeasures on soil solution chemistry of soils contaminated with radiocesium using the hydrogeochemical code PHREEQC},
journal = {Science of The Total Environment},
year = {2002},
volume = {289},
number = {1–3},
pages = {83--95},
url = {http://www.sciencedirect.com/science/article/pii/S0048969701010269}
}
|
|||||
| Horst, A. | A convexity property of the median of the gamma distribution | 2006 | Statistics & Probability Letters Vol. 76(14), pp. 1510-1513 |
article | URL |
| Abstract: Let λ n be the median of the gamma distribution of order n + 1 with parameter 1. We prove that the sequence λ n is strictly convex for n = 0 , 1 , 2 , … . | |||||
BibTeX:
@article{Horst2006,
author = {Horst, Alzer},
title = {A convexity property of the median of the gamma distribution},
journal = {Statistics & Probability Letters},
year = {2006},
volume = {76},
number = {14},
pages = {1510--1513},
url = {http://www.sciencedirect.com/science/article/pii/S0167715206000927}
}
|
|||||
| Hosseini, A.H., Deutsch, C.V., Mendoza, C.A. and Biggar, K.W. | Inverse modeling for characterization of uncertainty in transport parameters under uncertainty of source geometry in heterogeneous aquifers | 2011 | Journal of Hydrology Vol. 405(3-4), pp. 402-416 |
article | URL |
| Abstract: In petroleum hydrocarbon contamination scenarios, assessment of the dimensions of contaminant plumes and prediction of their fate requires predictions of the rate of dissolution of contaminants from residual non-aqueous-phase-liquid (NAPLs) into the aquifer and the rate of contaminant removal through biodegradation. The central idea in this paper is to present an inverse modeling methodology for characterization of structural uncertainty in these parameters by tailoring their estimation to the distributions of source geometry and hydraulic conductivity field. For this purpose, a synthetic study site with two reference cases is established and a Monte Carlo type inverse modeling methodology is presented where dissolution and first-order biodegradation rates of the contaminants are estimated for joint realizations of source and hydraulic conductivity. The joint realizations are constructed by the distance-function (DF) and sequential self-calibration (SSC) approaches and a gradient-based optimization is adapted to solve the inversion problem. The results show larger uncertainty in the estimated dissolution rate and a moderate positive correlation between the two parameters. It is also observed that tailoring the estimation of the parameters to the constructed joint realizations can effectively reduce the uncertainty in the shape and size of the plume, and this uncertainty, as well as the uncertainty in the source size, can be further reduced by ranking and screening the conditional realizations based on the value of the objective function. The effects of measurement errors in head and concentration observations on uncertainty in the predicted parameters are shown to be as expected; measurement error translates to substantially greater uncertainty. | |||||
BibTeX:
@article{Hosseini2011,
author = {Hosseini, Amir H. and Deutsch, Clayton V. and Mendoza, Carl A. and Biggar, Kevin W.},
title = {Inverse modeling for characterization of uncertainty in transport parameters under uncertainty of source geometry in heterogeneous aquifers},
journal = {Journal of Hydrology},
year = {2011},
volume = {405},
number = {3-4},
pages = {402--416},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411003672}
}
|
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| Hrachowitz, M., Soulsby, C., Tetzlaff, D. and Malcolm, I.A. | Sensitivity of mean transit time estimates to model conditioning and data availability | 2011 | Hydrological Processes Vol. 25(6), pp. 980-990 |
article | URL |
| Abstract: Mean transit times (MTTs) can give useful insights into the internal processes of hydrological systems. However, varying model conditioning assumptions and data availability can limit the use of MTT, particularly in terms of comparing the results of studies using different assumptions and data records of varying lengths. We present a systematic analysis of sensitivity of MTT estimates to different methods of artificially extending the data record, varying model warm-up period lengths and varying sampling intervals for a small upland catchment in the Scottish Highlands. The analysis was based on Cl− data in conjunction with the convolution integral model using the gamma distribution as transit time distribution. It could be shown that three out of four different methods to artificially extend the data record and to generate a warm-up period give mostly equivalent results. The required minimum warm-up period length to reliably estimate MTT for a 3-year period of data was observed to be about 2 years or 3 times the MTT, implying that ∼95% of the tracer signal entering the stream at day 1 of the warm-up period has to be recovered by the end of the warm-up period in order to avoid significant deviations from the best available MTT estimates. It was furthermore found that sampling intervals of up to 4 weeks can produce MTT estimates within about 0·25 times the best available MTT estimate, albeit with potentially increased process misrepresentation in terms of the gamma distribution parameter α. | |||||
BibTeX:
@article{Hrachowitz2011,
author = {Hrachowitz, M. and Soulsby, C. and Tetzlaff, D. and Malcolm, I. A.},
title = {Sensitivity of mean transit time estimates to model conditioning and data availability},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2011},
volume = {25},
number = {6},
pages = {980--990},
url = {http://dx.doi.org/10.1002/hyp.7922}
}
|
|||||
| Hrachowitz, M., Soulsby, C., Tetzlaff, D., Malcolm, I.A. and Schoups, G. | Gamma distribution models for transit time estimation in catchments: Physical interpretation of parameters and implications for time-variant transit time assessment | 2010 | Water Resources Research Vol. 46(10), pp. W10536- |
article | URL |
| Abstract: In hydrological tracer studies, the gamma distribution can serve as an appropriate transit time distribution (TTD) as it allows more flexibility to account for nonlinearities in the behavior of catchment systems than the more commonly used exponential distribution. However, it is unclear which physical interpretation can be ascribed to its two parameters (α, β). In this study, long-term tracer data from three contrasting catchments in the Scottish Highlands were used for a comparative assessment of interannual variability in TTDs and resulting mean transit times (MTT = αβ) inferred by the gamma distribution model. In addition, spatial variation in the long-term average TTDs from these and six additional catchments was also assessed. The temporal analysis showed that the β parameter was controlled by precipitation intensities above catchment-specific thresholds. In contrast, the α parameter, which showed little temporal variability and no relationship with precipitation intensity, was found to be closely related to catchment landscape organization, notably the hydrological characteristics of the dominant soils and the drainage density. The relationship between β and precipitation intensity was used to express β as a time-varying function within the framework of lumped convolution integrals to examine the nonstationarity of TTDs. The resulting time-variant TTDs provided more detailed and potentially useful information about the temporal dynamics and the timing of solute fluxes. It was shown that in the wet, cool climatic conditions of the Scottish Highlands, the transit times from the time-variant TTD were roughly consistent with the variations of MTTs revealed by interannual analysis. | |||||
BibTeX:
@article{Hrachowitz2010,
author = {Hrachowitz, M. and Soulsby, C. and Tetzlaff, D. and Malcolm, I. A. and Schoups, G.},
title = {Gamma distribution models for transit time estimation in catchments: Physical interpretation of parameters and implications for time-variant transit time assessment},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2010},
volume = {46},
number = {10},
pages = {W10536--},
url = {http://dx.doi.org/10.1029/2010WR009148}
}
|
|||||
| Hsu, S.-H., Stamatis, S.D., Caruthers, J.M., Delgass, W.N., Venkatasubramanian, V., Blau, G.E., Lasinski, M. and Orcun, S. | Bayesian Framework for Building Kinetic Models of Catalytic Systems | 2009 | Industrial & Engineering Chemistry Research Vol. 48(10), pp. 4768-4790 |
article | DOI URL |
| Abstract: Recent advances in statistical procedures, coupled with the availability of high performance computational resources and the large mass of data generated from high throughput screening, have enabled a new paradigm for building mathematical models of the kinetic behavior of catalytic reactions. A Bayesian approach is used to formulate the model building problem, estimate model parameters by Monte Carlo based methods, discriminate rival models, and design new experiments to improve the discrimination and fidelity of the parameter estimates. The methodology is illustrated with a typical, model building problem involving three proposed Langmuir?Hinshelwood rate expressions. The Bayesian approach gives improved discrimination of the three models and higher quality model parameters for the best model selected as compared to the traditional methods that employ linearized statistical tools. This paper describes the methodology and its capabilities in sufficient detail to allow kinetic model builders to evaluate and implement its improved model discrimination and parameter estimation features. Recent advances in statistical procedures, coupled with the availability of high performance computational resources and the large mass of data generated from high throughput screening, have enabled a new paradigm for building mathematical models of the kinetic behavior of catalytic reactions. A Bayesian approach is used to formulate the model building problem, estimate model parameters by Monte Carlo based methods, discriminate rival models, and design new experiments to improve the discrimination and fidelity of the parameter estimates. The methodology is illustrated with a typical, model building problem involving three proposed Langmuir?Hinshelwood rate expressions. The Bayesian approach gives improved discrimination of the three models and higher quality model parameters for the best model selected as compared to the traditional methods that employ linearized statistical tools. This paper describes the methodology and its capabilities in sufficient detail to allow kinetic model builders to evaluate and implement its improved model discrimination and parameter estimation features. |
|||||
BibTeX:
@article{Hsu2009,
author = {Hsu, Shuo-Huan and Stamatis, Stephen D. and Caruthers, James M. and Delgass, W. Nicholas and Venkatasubramanian, Venkat and Blau, Gary E. and Lasinski, Mike and Orcun, Seza},
title = {Bayesian Framework for Building Kinetic Models of Catalytic Systems},
journal = {Industrial & Engineering Chemistry Research},
publisher = {American Chemical Society},
year = {2009},
volume = {48},
number = {10},
pages = {4768--4790},
url = {http://dx.doi.org/10.1021/ie801651y},
doi = {http://dx.doi.org/10.1021/ie801651y}
}
|
|||||
| Hsu, T., Mou, C. and Lee, D. | Effects of Macromixing on the oregonator model of the belousov — zhabotinsky reaction in a stirred reactor | 1994 | Chemical Engineering Science Vol. 49(24, Part 2), pp. 5291-5305 |
article | URL |
| Abstract: Macromixing effects on the oscillating Belousov—Zhabotinsky reaction based on the global fluid field have been investigated. The three-variable irreversible Oregonator and the networks-of-zones model with 2 × N × N zones were chosen for describing the chemical kinetics and the flow field, respectively. With high stirring rate, all zones in the tank will oscillate synchronously and the tank can be taken as an ideally well-mixing continuous-flow stirred-tank reactor. When stirring rate is decreased, locally simple oscillation patterns were found to be sustained, and the oscillation period was decreased accordingly. It is proposed that the output zone acts as an excitable nucleus which determines the overall oscillations. When stirring rate is reduced further, many local zones can be excited as nuclei, and apparent complex oscillations can result. | |||||
BibTeX:
@article{Hsu1994,
author = {Hsu, T.J. and Mou, C.Y. and Lee, D.J.},
title = {Effects of Macromixing on the oregonator model of the belousov — zhabotinsky reaction in a stirred reactor},
journal = {Chemical Engineering Science},
year = {1994},
volume = {49},
number = {24, Part 2},
pages = {5291--5305},
url = {http://www.sciencedirect.com/science/article/pii/0009250994002789}
}
|
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| Huang, Q., Huang, G. and Zhan, H. | A finite element solution for the fractional advection–dispersion equation | 2008 | Advances in Water Resources Vol. 31(12), pp. 1578-1589 |
article | URL |
| Abstract: The fractional advection–dispersion equation (FADE) known as its non-local dispersion, has been proven to be a promising tool to simulate anomalous solute transport in groundwater. We present an unconditionally stable finite element (FEM) approach to solve the one-dimensional FADE based on the Caputo definition of the fractional derivative with considering its singularity at the boundaries. The stability and accuracy of the FEM solution is verified against the analytical solution, and the sensitivity of the FEM solution to the fractional order α and the skewness parameter β is analyzed. We find that the proposed numerical approach converge to the numerical solution of the advection–dispersion equation (ADE) as the fractional order α equals 2. The problem caused by using the first- or third-kind boundary with an integral-order derivative at the inlet is remedied by using the third-kind boundary with a fractional-order derivative there. The problems for concentration estimation at boundaries caused by the singularity of the fractional derivative can be solved by using the concept of transition probability conservation. The FEM solution of this study has smaller numerical dispersion than that of the FD solution by Meerschaert and Tadjeran (J Comput Appl Math 2004). For a given α, the spatial distribution of concentration exhibits a symmetric non-Fickian behavior when β = 0. The spatial distribution of concentration shows a Fickian behavior on the left-hand side of the spatial domain and a notable non-Fickian behavior on the right-hand side of the spatial domain when β = 1, whereas when β = −1 the spatial distribution of concentration is the opposite of that of β = 1. Finally, the numerical approach is applied to simulate the atrazine transport in a saturated soil column and the results indicat that the FEM solution of the FADE could better simulate the atrazine transport process than that of the ADE, especially at the tail of the breakthrough curves. | |||||
BibTeX:
@article{Huang2008,
author = {Huang, Quanzhong and Huang, Guanhua and Zhan, Hongbin},
title = {A finite element solution for the fractional advection–dispersion equation},
journal = {Advances in Water Resources},
year = {2008},
volume = {31},
number = {12},
pages = {1578--1589},
url = {http://www.sciencedirect.com/science/article/pii/S0309170808001115}
}
|
|||||
| Huang, W.-J. and Chang, S.-H. | On some characterizations of the mixture of gamma distributions | 2007 | Journal of Statistical Planning and Inference Vol. 137(9), pp. 2964-2974 |
article | URL |
| Abstract: Following Gupta and Wesolowski [1997. Uniform mixtures via posterior means. Ann. Inst. Statist. Math. 49, 171–180], in this work, under the condition X / U and U are independent, X / U has a B e ( p , q ) distribution, and given X the conditional expectation of a certain function of ( U , X ) is constant, we characterize the distribution of ( U , X ) . This problem is related to Lukacs type characterization, where both X and Y have to be gamma distributed with the same scale parameter, if both X and Y, and X / ( X + Y ) and X + Y are independent. Among others, we prove if q = 1 , and for some integer n ⩾ 1 , E ( ∑ i = 1 n a i ( U - X ) i | X ) = b , where a 1 , … , a n , b , are real constants such that a 1 2 + ⋯ + a n 2 ≠ 0 and b ≠ 0 , or for some real number n > 0 , E ( ( U - X ) n | X ) = b , where b > 0 is a constant, then the distribution of ( U , X ) can be determined. | |||||
BibTeX:
@article{Huang2007,
author = {Huang, Wen-Jang and Chang, Shu-Huey},
title = {On some characterizations of the mixture of gamma distributions},
journal = {Journal of Statistical Planning and Inference},
year = {2007},
volume = {137},
number = {9},
pages = {2964--2974},
url = {http://www.sciencedirect.com/science/article/pii/S0378375807000419}
}
|
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| Huber, M.T. | Caring for students: Pedagogy and professionalism in an age of anxiety | 2010 | Emotion, Space and Society Vol. 3(2), pp. 71-79 |
article | URL |
| Abstract: University teachers are strongly motivated by the care they feel for their students. Yet today, many are frustrated. On the one hand, it is becoming harder to teach well, as more diverse student populations, new media, and new educational priorities challenge conventional pedagogical postures and styles. On the other hand, teachers are wary of calls for greater pedagogical professionalism in an increasingly managed and de-motivating professional environment. This essay examines two movements in the United States that attempt to sustain teachers' motivation by rethinking what caring for students requires them to do. The first, a call for a “scholarship of teaching and learning,” directs the professor's attention outward, towards inquiry into their students' learning; the second directs attention inwards, encouraging exploration of “the inner landscape of a teacher's life.” While both movements oppose a narrow view of pedagogy as simply technique, they address the challenge of caring for students in different ways and point to resolutions that appear to have different potential to alter the teaching environment itself. These tensions around teaching inscribe in higher education wider debates about the value of the professions, the nature of expert practice, and how to recover and ensure professionals' capacity for care. | |||||
BibTeX:
@article{Huber2010,
author = {Huber, Mary Taylor},
title = {Caring for students: Pedagogy and professionalism in an age of anxiety},
journal = {Emotion, Space and Society},
year = {2010},
volume = {3},
number = {2},
pages = {71--79},
url = {http://www.sciencedirect.com/science/article/pii/S1755458609000383}
}
|
|||||
| Humphreys, W. | Hydrogeology and groundwater ecology: Does each inform the other? | 2009 | Hydrogeology Journal Vol. 17(1), pp. 5-21 |
article | URL |
| Abstract: The known, perceived and potential relationships between hydrogeology and groundwater ecology are explored, along with the spatial and temporal scale of these relations, the limit of knowledge and areas in need of research. Issues concerned with the subterranean part of the water cycle are considered from the perspective of the biology of those invertebrate animals that live, of necessity, in groundwater and the microbiological milieu essential for their survival. Groundwater ecosystems are placed in a hydrogeological context including the groundwater evolution along a flowpath, the significance of the biodiversity and of the ecosystem services potentially provided. This is considered against a background of three major components essential to the functioning of groundwater ecosystems, each of which can be affected by activities over which hydrogeologists often have control, and each, in turn, may have implications for groundwater management; these are, a place to live, oxygen and food (energy). New techniques and increasing awareness amongst hydrogeologists of the diversity and broad distribution of groundwater ecosystems offer new opportunities to develop cross disciplinary work between hydrogeologists and groundwater ecologists, already demonstrated to be a field for collaboration with broad benefits. | |||||
BibTeX:
@article{Humphreys2009,
author = {Humphreys, W.},
title = {Hydrogeology and groundwater ecology: Does each inform the other?},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {5--21},
url = {http://dx.doi.org/10.1007/s10040-008-0349-3}
}
|
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| Hunt, A.G., Skinner, T.E., Ewing, R.P. and Ghanbarian-Alavijeh, B. | Dispersion of solutes in porous media | 2011 | The European Physical Journal B - Condensed Matter and Complex Systems Vol. 80(4), pp. 411-432 |
article | URL |
| Abstract: A recently introduced theory of solute transport in porous media is tested by comparison with experiment. The solute transport is predicted using an adaptation of the cluster statistics of percolation theory to critical path analysis together with knowledge of how the structure of such percolation clusters affects the time of transport across them. Only the effects of a single scale of medium heterogeneity are incorporated, and a minimal amount of information regarding the structure of the medium is required. This framework is used to find effectively the distributions of solute velocities and travel distances and thus generate arrival time distributions. The comparison with experiment focuses on the dispersivity (the ratio of the second to the first moment of the spatial solute distribution). The predictions of the theory in the absence of diffusion are verified by comparing with over 2200 experiments over length scales from a few microns to 100 km. At larger length scales (centimeters on up) about 95% of the data lie within our predicted bounds. At smaller length scales approximately 99.8% of the data lie where we predict. These comparisons are not trivial as the typical values of the dispersivity increase by ten orders of magnitude over ten orders of magnitude of length scale. Noteworthy is that the classical advection-dispersion (ADE) equation predicts that the dispersivity should be independent of length scale! This agreement with experiment requires rethinking of the relevance of diffusion and multi-scale heterogeneity and would also appear to signal the complete inappropriateness of using the classical ADE or any of its derivatives to model solute transport. | |||||
BibTeX:
@article{Hunt2011,
author = {Hunt, A. G. and Skinner, T. E. and Ewing, R. P. and Ghanbarian-Alavijeh, B.},
title = {Dispersion of solutes in porous media},
journal = {The European Physical Journal B - Condensed Matter and Complex Systems},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {80},
number = {4},
pages = {411--432},
url = {http://dx.doi.org/10.1140/epjb/e2011-10805-y}
}
|
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| Husak, G.J., Michaelsen, J. and Funk, C. | Use of the gamma distribution to represent monthly rainfall in Africa for drought monitoring applications | 2007 | International Journal of Climatology Vol. 27(7), pp. 935-944 |
article | URL |
| Abstract: Evaluating a range of scenarios that accurately reflect precipitation variability is critical for water resource applications. Inputs to these applications can be provided using location- and interval-specific probability distributions. These distributions make it possible to estimate the likelihood of rainfall being within a specified range. In this paper, we demonstrate the feasibility of fitting cell-by-cell probability distributions to grids of monthly interpolated, continent-wide data. Future work will then detail applications of these grids to improved satellite-remote sensing of drought and interpretations of probabilistic climate outlook forum forecasts. The gamma distribution is well suited to these applications because it is fairly familiar to African scientists, and capable of representing a variety of distribution shapes. This study tests the goodness-of-fit using the Kolmogorov–Smirnov (KS) test, and compares these results against another distribution commonly used in rainfall events, the Weibull. The gamma distribution is suitable for roughly 98% of the locations over all months. The techniques and results presented in this study provide a foundation for use of the gamma distribution to generate drivers for various rain-related models. These models are used as decision support tools for the management of water and agricultural resources as well as food reserves by providing decision makers with ways to evaluate the likelihood of various rainfall accumulations and assess different scenarios in Africa. Copyright © 2006 Royal Meteorological Society | |||||
BibTeX:
@article{Husak2007,
author = {Husak, Gregory J. and Michaelsen, Joel and Funk, Chris},
title = {Use of the gamma distribution to represent monthly rainfall in Africa for drought monitoring applications},
journal = {International Journal of Climatology},
publisher = {John Wiley & Sons, Ltd.},
year = {2007},
volume = {27},
number = {7},
pages = {935--944},
url = {http://dx.doi.org/10.1002/joc.1441}
}
|
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| Hutter, C., Zenklusen, A., Lang, R. and Rudolf von Rohr, P. | Axial dispersion in metal foams and streamwise-periodic porous media | 2011 | Chemical Engineering Science Vol. 66(6), pp. 1132-1141 |
article | URL |
| Abstract: We present a study on the axial dispersion in metal foams and laser sintered reactors. Commercially available metal foams of 20 and 30 ppi are compared to a designed streamwise-periodic structure in terms of axial dispersion coefficients and pressure drops. Therefore tracer pulse experiments were performed and post processed by means of a deconvolution method. The Peclet number Pep based on the pore size is ranging from 5 × 10 4 to 8 × 10 5 which is attributed to the increased velocities due to the high porosity of the material compared to fixed bed reactors. The attained dispersion coefficients ranging from 1.3 × 10 − 4 to 6.7 × 10 − 3 m 2 / s demonstrate the trend of packed beds and common packing materials and increase monotone with the Peclet number Pep. The pressure drop versus the interstitial bulk velocity follows the Forchheimer equation and can be described by the conventional Ergun model for all investigated porous media. The parameters obtained correspond to values found in literature. The results of this study show the high potential of foam reactors for catalyst driven reactions. They provide the same or even a higher surface area per volume of catalyst bed while inducing a much smaller pressure drop than corresponding fixed beds. | |||||
BibTeX:
@article{Hutter2011,
author = {Hutter, C. and Zenklusen, A. and Lang, R. and Rudolf von Rohr, Ph.},
title = {Axial dispersion in metal foams and streamwise-periodic porous media},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {6},
pages = {1132--1141},
url = {http://www.sciencedirect.com/science/article/pii/S0009250910007293}
}
|
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| Ibarra, A.A., Zambrano, L., Valiente, E.L. and Ramos-Bueno, A. | Enhancing the potential value of environmental services in urban wetlands: An agro-ecosystem approach | 2013 | Cities Vol. 31(0), pp. 438-443 |
article | URL |
| Abstract: This paper proposes a three-tier process for supporting policy planning of urban agroecosystems. It comprises the following steps: (i) definition of the agro-environmental unit; (ii) measurement of the non-market values; (iii) estimation of opportunity cost. An application to an urban wetland agro-ecosystem within Mexico City is used for illustrating our methodology. We estimated that the wetland agro-ecosystem has a lower-bound monetary value between $15.6 million and $31.5 million USD/ha/y. As the land conversion rate is about 3.73 ha/y, the opportunity cost would be between $22,300 and $44,900 USD/ha/y. Such figures are an objective way to appreciate both the potential enhancement value and the opportunity cost of ecosystem services adjacent to urban areas, providing both urban and environmental policy guidance. We argue that this framework allows for multi-scale analysis and may be applied for other urban ecosystems as well. | |||||
BibTeX:
@article{Ibarra2013,
author = {Ibarra, Alonso Aguilar and Zambrano, Luis and Valiente, Elsa L. and Ramos-Bueno, Arturo},
title = {Enhancing the potential value of environmental services in urban wetlands: An agro-ecosystem approach},
journal = {Cities},
year = {2013},
volume = {31},
number = {0},
pages = {438--443},
url = {http://www.sciencedirect.com/science/article/pii/S0264275112001412}
}
|
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| Ibrahim, K. | Application of iterated Laplace transformation to tracer transients in heterogeneous porous media | 2011 | Journal of the Franklin Institute Vol. 348(7)Special issue on Modeling, Simulation and Applied Optimization ICMSAO-09 The Third International Conference on Modeling, Simulation, and Applied Optimization, pp. 1339-1362 |
article | URL |
| Abstract: The Laplace transformation technique has been widely applied to modeling of tracer transport in oil and geothermal reservoirs, and in groundwater aquifers. However, mathematical models of many flow and transport problems could only be obtained as Laplace space solutions, and hence, their computations had to involve a numerical inversion technique. | |||||
BibTeX:
@article{Ibrahim2011,
author = {Ibrahim, Kocabas},
title = {Application of iterated Laplace transformation to tracer transients in heterogeneous porous media},
booktitle = {Special issue on Modeling, Simulation and Applied Optimization ICMSAO-09 The Third International Conference on Modeling, Simulation, and Applied Optimization},
journal = {Journal of the Franklin Institute},
year = {2011},
volume = {348},
number = {7},
pages = {1339--1362},
url = {http://www.sciencedirect.com/science/article/pii/S0016003210000980}
}
|
|||||
| Iliuta, I. and Larachi, F. | Modeling simultaneous biological clogging and physical plugging in trickle-bed bioreactors for wastewater treatment | 2005 | Chemical Engineering Science Vol. 60(5), pp. 1477-1489 |
article | URL |
| Abstract: A major drawback limiting the use of trickle-bed bioreactors for biological wastewater treatment is ascribed to the concomitant biological clogging and physical plugging phenomena induced, respectively, by the formation of an excessive amount of biomass and the retention of inert suspended fine particles advected in the liquid influent stream. Biomass growth and fine particles deposition permanently reshape the bed pore structure and narrow the free interstitial space left to the fluids flow thus occasioning progressive bed obstruction often accompanied with pressure drop build-up for the cocurrent gas–liquid flows taking place in trickle-bed biofilters. In these circumstances, for maintaining acceptable operating cycles, the unit must be backwashed and/or shutdown regularly for removing the excess biomass and for cleaning from the specific solid deposit. A predictive two-dimensional dynamic model linking the two-phase flow hydrodynamics to the space-time distribution of bioclogging/biokinetics and of inert fine particles deposition via deep-bed filtration in trickle-bed bioreactors for wastewater treatment was developed. The model was based on the volume-average mass and momentum balance equations for the gas and liquid phases and continuity equation for the solid phase, the volume-average species balance for the fine particles, simultaneous transport and consumption of substrate (pollutant) and oxygen within the biofilm and collecting solid particle, and the volume-average species balance equations in the liquid and gas phases. Phenol biodegradation by Pseudomonas putida as the predominant species immobilized on activated carbon was chosen as a case study to illustrate the incidence of biomass accumulation on trickle-bed bioreactor hydrodynamics. | |||||
BibTeX:
@article{Iliuta2005,
author = {Iliuta, Ion and Larachi, Faı¨çal},
title = {Modeling simultaneous biological clogging and physical plugging in trickle-bed bioreactors for wastewater treatment},
journal = {Chemical Engineering Science},
year = {2005},
volume = {60},
number = {5},
pages = {1477--1489},
url = {http://www.sciencedirect.com/science/article/pii/S0009250904008243}
}
|
|||||
| Iliuta, I. and Larachi, F. | Wet air oxidation solid catalysis analysis of fixed and sparged three-phase reactors | 2001 | Chemical Engineering and Processing: Process Intensification Vol. 40(2), pp. 175-185 |
article | URL |
| Abstract: Compared with other mature industrial fields where multiphase reactors are prevalent, the design of three-phase catalytic reactors for wet air oxidation processes is still in emergence. A series of detailed isothermal unsteady-state two-dimensional models is therefore developed and solved in the context of sub-critical catalytic wet oxidation with a non-deactivating catalyst of organic-containing contaminated wastewaters. A comparative analysis is made for trickle-bed reactors, packed-bubble columns, three-phase fluidized beds and slurry bubble columns. This paper discusses from a multiphase reactor engineering perspective, the design of such contactors by setting an exhaustive modeling framework of catalytic wet oxidation in which the molecular, particle and reactor scales are integrated. The simulation results indicate that when wet oxidation is liquid-reactant limited, packed bubble columns outperform trickle beds regardless of the pressure level, whereas three-phase fluidized beds exhibit a critical particle size maximizing the pollutant conversion. At equal effluent residence times, slurry bubble columns are found less efficient than three-phase fluidized bed reactors. | |||||
BibTeX:
@article{Iliuta2001,
author = {Iliuta, Ion and Larachi, Faı̈çal},
title = {Wet air oxidation solid catalysis analysis of fixed and sparged three-phase reactors},
journal = {Chemical Engineering and Processing: Process Intensification},
year = {2001},
volume = {40},
number = {2},
pages = {175--185},
url = {http://www.sciencedirect.com/science/article/pii/S0255270100001379}
}
|
|||||
| Iliuta, I., Thyrion, F., Muntean, O. and Giot, M. | Residence time distribution of the liquid in gas-liquid cocurrent upflow fixed-bed reactors | 1996 | Chemical Engineering Science Vol. 51(20), pp. 4579-4593 |
article | URL |
| Abstract: The authors present an experimental investigation of the residence time distribution (RTD) of the liquid in a gas-liquid upflow fixed-bed reactor with porous and nonporous particles and air/Newtonian or non-Newtonian systems. The piston-dispersion-exchange model with Danckwerts boundary conditions was used to describe the liquid flow. In the case of porous particles, the dynamic evolution of the tracer concentration in the particles was described in terms of diffusion phenomena. An imperfect pulse method was used to estimate the model parameters directly from the experimentally nonideal input and output response. | |||||
BibTeX:
@article{Iliuta1996,
author = {Iliuta, I. and Thyrion, F.C. and Muntean, O. and Giot, M.},
title = {Residence time distribution of the liquid in gas-liquid cocurrent upflow fixed-bed reactors},
journal = {Chemical Engineering Science},
year = {1996},
volume = {51},
number = {20},
pages = {4579--4593},
url = {http://www.sciencedirect.com/science/article/pii/000925099600303X}
}
|
|||||
| Illman, W.A., Berg, S.J. and Yeh, T.-C.J. | Comparison of Approaches for Predicting Solute Transport: Sandbox Experiments | 2011 | Ground Water, pp. no-no | article | URL |
| Abstract: The main purpose of this paper was to compare three approaches for predicting solute transport. The approaches include: (1) an effective parameter/macrodispersion approach (Gelhar and Axness 1983); (2) a heterogeneous approach using ordinary kriging based on core samples; and (3) a heterogeneous approach based on hydraulic tomography. We conducted our comparison in a heterogeneous sandbox aquifer. The aquifer was first characterized by taking 48 core samples to obtain local-scale hydraulic conductivity (K). The spatial statistics of these K values were then used to calculate the effective parameters. These K values and their statistics were also used for kriging to obtain a heterogeneous K field. In parallel, we performed a hydraulic tomography survey using hydraulic tests conducted in a dipole fashion with the drawdown data analyzed using the sequential successive linear estimator code (Yeh and Liu 2000) to obtain a K distribution (or K tomogram). The effective parameters and the heterogeneous K fields from kriging and hydraulic tomography were used in forward simulations of a dipole conservative tracer test. The simulated and observed breakthrough curves and their temporal moments were compared. Results show an improvement in predictions of drawdown behavior and tracer transport when the K tomogram from hydraulic tomography was used. This suggests that the high-resolution prediction of solute transport is possible without collecting a large number of small-scale samples to estimate flow and transport properties that are costly to obtain at the field scale. | |||||
BibTeX:
@article{Illman2011,
author = {Illman, Walter A. and Berg, Steven J. and Yeh, Tian-Chyi Jim},
title = {Comparison of Approaches for Predicting Solute Transport: Sandbox Experiments},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {2011},
pages = {no--no},
url = {http://dx.doi.org/10.1111/j.1745-6584.2011.00859.x}
}
|
|||||
| Illman, W.A., Zhu, J., Craig, A.J. and Yin, D. | Comparison of aquifer characterization approaches through steady state groundwater model validation: A controlled laboratory sandbox study | 2010 | Water Resources Research Vol. 46(4), pp. W04502- |
article | URL |
| Abstract: Groundwater modeling has become a vital component to water supply and contaminant transport investigations. An important component of groundwater modeling under steady state conditions is selecting a representative hydraulic conductivity (K) estimate or set of estimates which defines the K field of the studied region. Currently, there are a number of characterization approaches to obtain K at various scales and in varying degrees of detail, but there is a paucity of information in terms of which characterization approach best predicts flow through aquifers or drawdowns caused by some drawdown inducing events. The main objective of this paper is to assess K estimates obtained by various approaches by predicting drawdowns from independent cross-hole pumping tests and total flow rates through a synthetic heterogeneous aquifer from flow-through tests. Specifically, we (1) characterize a synthetic heterogeneous aquifer built in the sandbox through various techniques (permeameter analyses of core samples, single-hole, cross-hole, and flow-through testing), (2) obtain mean K fields through traditional analysis of test data by treating the medium to be homogeneous, (3) obtain heterogeneous K fields through kriging and steady state hydraulic tomography, and (4) conduct forward simulations of 16 independent pumping tests and six flow-through tests using these homogeneous and heterogeneous K fields and comparing them to actual data. Results show that the mean K and heterogeneous K fields estimated through kriging of small-scale K data (core and single-hole tests) yield biased predictions of drawdowns and flow rates in this synthetic heterogeneous aquifer. In contrast, the heterogeneous K distribution or “K tomogram” estimated via steady state hydraulic tomography yields excellent predictions of drawdowns of pumping tests not used in the construction of the tomogram and very good estimates of total flow rates from the flow-through tests. These results suggest that steady state groundwater model validation is possible in this laboratory sandbox aquifer if the heterogeneous K distribution and forcing functions (boundary conditions and source/sink terms) are characterized sufficiently. | |||||
BibTeX:
@article{Illman2010,
author = {Illman, Walter A. and Zhu, Junfeng and Craig, Andrew J. and Yin, Danting},
title = {Comparison of aquifer characterization approaches through steady state groundwater model validation: A controlled laboratory sandbox study},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2010},
volume = {46},
number = {4},
pages = {W04502--},
url = {http://dx.doi.org/10.1029/2009WR007745}
}
|
|||||
| Imhoff, P.T. and Pirestani, K. | Influence of mass transfer resistance on detection of nonaqueous phase liquids with partitioning tracer tests | 2004 | Advances in Water Resources Vol. 27(4)A Tribute to George F. Pinder, pp. 429-444 |
article | URL |
| Abstract: Partitioning interwell tracer tests (PITTs) are a relatively new technique for measuring the amount of nonaqueous phase liquid (NAPL) within saturated porous media. In this work we examined the influence of mass transfer limitations on the accuracy of measured NAPL from PITTs. Two mathematical models were used along with laboratory column experiments to explore the influence of tracer partition coefficient, tracer detection limit, and injected tracer mass on NAPL measurements. When dimensionless mass transfer coefficients were small, NAPL measurement errors decreased with decreasing tracer partition coefficient, decreasing tracer detection limit, and increasing injected tracer mass. Extrapolating breakthrough curves exponentially reduced but did not eliminate systematic errors in NAPL measurement. Although transport in a single stream tube was used in the mathematical models and laboratory experiments, the results from this simplified domain were supported by data taken from a three-dimensional computational experiment, where the NAPL resided as large pool. Based on these results, we suggest guidelines for interpreting tracer breakthrough data to ascertain the importance of mass transfer limitations on NAPL measurements. | |||||
BibTeX:
@article{Imhoff2004,
author = {Imhoff, Paul T and Pirestani, Katayoun},
title = {Influence of mass transfer resistance on detection of nonaqueous phase liquids with partitioning tracer tests},
booktitle = {A Tribute to George F. Pinder},
journal = {Advances in Water Resources},
year = {2004},
volume = {27},
number = {4},
pages = {429--444},
url = {http://www.sciencedirect.com/science/article/pii/S0309170804000223}
}
|
|||||
| Inamdar, S.P. and Mitchell, M.J. | Contributions of riparian and hillslope waters to storm runoff across multiple catchments and storm events in a glaciated forested watershed | 2007 | Journal of Hydrology Vol. 341(1-2), pp. 116-130 |
article | URL |
| Abstract: The contributions of hillslope and riparian sources of runoff to streamflow were determined for four catchments (1.6–696 ha) in the Point Peter Brook watershed, a glaciated, forested, watershed in Western New York, USA. Investigations were performed for 10 storm events of varying size, intensity, and antecedent moisture conditions. Hydrometric, geochemical, and landscape analysis procedures were used to characterize the sources of runoff and the influence of topography on hydrologic response. Using end member mixing analysis (EMMA), throughfall, groundwater discharged at hillslope seeps, and valley-bottom riparian water were identified as the controlling end-members for storm-event runoff. Contribution from seep groundwater was highest during baseflow, contributions from throughfall increased through the rising limb of the hydrograph, while riparian water amounts were highest at or after the peak in discharge. The delayed response of riparian water was attributed to displacement by hillslope interflow. The relative contributions of the end-members varied with catchment size and storm event conditions. Riparian water contributions were greater at the large catchment size (696 ha) while seep groundwater was important for the small headwater catchments. Steep hillslope gradients and moist valley-bottoms allowed for a greater expression of hillslope seep water in runoff during baseflow conditions. Percent contributions of riparian water to streamflow were higher for larger storm events while small events and wet antecedent conditions increased the expression of seep groundwater. This study underscored the need for three-dimensional or volume-based assessments to characterize the contributions of valley-bottom riparian and wetland areas to streamflow. | |||||
BibTeX:
@article{Inamdar2007,
author = {Inamdar, Shreeram P. and Mitchell, Myron J.},
title = {Contributions of riparian and hillslope waters to storm runoff across multiple catchments and storm events in a glaciated forested watershed},
journal = {Journal of Hydrology},
year = {2007},
volume = {341},
number = {1--2},
pages = {116--130},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407002764}
}
|
|||||
| Indelman, P. and Rubin, Y. | Average flow in heterogeneous media of trending hydraulic conductivity | 1996 | Journal of Hydrology Vol. 183(1-2), pp. 57-68 |
article | URL |
| Abstract: In this paper, we present a solution of the flow problem in heterogeneous, non-stationary media, where the non-stationarity is manifested as a linear trend in the mean log-conductivity. The flow problem is posed in a stochastic framework, and our goal is to define an average flow equation and to derive the relationship between the mean gradient and the mean flux. For a stationary medium, such an approach would amount to the definition of the effective conductivity tensor, but in the present case, since due to the specific boundary condition the coefficient proportionality between the mean gradient and the mean flux depends on the angle between the trend and the mean gradient, we refer to it as the tensor of equivalent conductivity. We derive this tensor for one-, two- and three-dimensional flow equations. | |||||
BibTeX:
@article{Indelman1996,
author = {Indelman, Peter and Rubin, Yoram},
title = {Average flow in heterogeneous media of trending hydraulic conductivity},
journal = {Journal of Hydrology},
year = {1996},
volume = {183},
number = {1-2},
pages = {57--68},
url = {http://www.sciencedirect.com/science/article/pii/S0022169496800345}
}
|
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| Ireson, A., Mathias, S., Wheater, H., Butler, A. and Finch, J. | A model for flow in the chalk unsaturated zone incorporating progressive weathering | 2009 | Journal of Hydrology Vol. 365(3-4), pp. 244-260 |
article | URL |
| Abstract: Groundwater from unconfined chalk aquifers constitutes a major water resource in the UK. The unsaturated zone in such systems plays a crucial role in the hydrological cycle, determining the timing and magnitude of recharge, and the transport and fate of nutrients. However, despite more than three decades of study, our physical understanding of this system is incomplete. In this research, state of the art instrumentation provided high temporal resolution readings of soil moisture status, rainfall and actual evaporation from two sites in the Pang and Lambourn catchments (Berkshire, UK), for a continuous two year period (2004/5). A parsimonious, physically based model for the flow of water through the chalk unsaturated zone, including a novel representation of the soil and weathered chalk layers, was developed. The parameters were identified by inverse modelling using field measurements of water content and matric potential. The model was driven by rainfall and evaporation data, and simulated fluxes throughout the profile (including the discrete matrix and fracture components), down to the water table (but not the water table response). Results showed that the model was able to reproduce closely the observed changes in soil moisture status. Recharge was predominantly through the matrix, and the recharge response was strongly attenuated with depth. However, the activation of fast recharge pathways through fractures in the chalk unsaturated zone was highly sensitive to rainfall intensity. Relatively modest increases in rainfall led to dramatically different recharge patterns, with potentially important implications for groundwater flooding. The development and migration of zero flux planes with time and depth were simulated. The simulations also provided strong evidence that, for water table depths greater than 5 m, recharge fluxes persist throughout the entire year, even during drought conditions, with important implications for the calculation of specific yield from baseflow estimates and the representation of recharge in groundwater models. | |||||
BibTeX:
@article{Ireson2009,
author = {Ireson, A.M. and Mathias, S.A. and Wheater, H.S. and Butler, A.P. and Finch, J.},
title = {A model for flow in the chalk unsaturated zone incorporating progressive weathering},
journal = {Journal of Hydrology},
year = {2009},
volume = {365},
number = {3-4},
pages = {244--260},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408005891}
}
|
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| Irina, G. | Equilibrium-type and link-type lattice Boltzmann models for generic advection and anisotropic-dispersion equation | 2005 | Advances in Water Resources Vol. 28(11), pp. 1171-1195 |
article | URL |
| Abstract: We extend lattice Boltzmann (LB) methods to advection and anisotropic-dispersion equations (AADE). LB methods are advocated for the exactness of their conservation laws, the handling of different length and time scales for flow/transport problems, their locality and extreme simplicity. Their extension to anisotropic collision operators (L-model) and anisotropic equilibrium distributions (E-model) allows to apply them to generic diffusion forms. The AADE in a conventional form can be solved by the L-model. Based on a link-type collision operator, the L-model specifies the coefficients of the symmetric diffusion tensor as linear combination of its eigenvalue functions. For any type of collision operator, the E-model constructs the coefficients of the transformed diffusion tensors from linear combinations of the relevant equilibrium projections. The model is able to eliminate the second order tensor of its numerical diffusion. Both models rely on mass conserving equilibrium functions and may enhance the accuracy and stability of the isotropic convection–diffusion LB models. | |||||
BibTeX:
@article{Irina2005,
author = {Irina, Ginzburg},
title = {Equilibrium-type and link-type lattice Boltzmann models for generic advection and anisotropic-dispersion equation},
journal = {Advances in Water Resources},
year = {2005},
volume = {28},
number = {11},
pages = {1171--1195},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805000874}
}
|
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| Irina, G. | Generic boundary conditions for lattice Boltzmann models and their application to advection and anisotropic dispersion equations | 2005 | Advances in Water Resources Vol. 28(11), pp. 1196-1216 |
article | URL |
| Abstract: We address a “multi-reflection” approach to model Dirichlet and Neumann time-dependent boundary conditions in lattice Boltzmann methods for arbitrarily shaped surfaces. The multi-reflection condition for an incoming population represents a linear combination of the known population solutions. The closure relations are first established for symmetric and anti-symmetric parts of the equilibrium functions, independently of the nature of the problem. The symmetric part is tuned to build second- and third-order accurate Dirichlet boundary conditions for the scalar function specified by the equilibrium distribution. The focus is on two approaches to advection and anisotropic-dispersion equations (AADE): the equilibrium technique when the coefficients of the expanded equilibrium functions match the coefficients of the transformed dispersion tensor, and the eigenvalue technique when the coefficients of the dispersion tensor are built as linear combinations of the eigenvalue functions associated with the link-type collision operator. As a particular local boundary technique, the “anti-bounce-back” condition is analyzed. The anti-symmetric part of the generic closure relation allows to specify normal flux conditions without inversion of the diffusion tensor. Normal and tangential constraints are derived for bounce-back and specular reflections. The bounce-back closure relation is released from the non-physical tangential flux restriction at leading orders. Solutions for the Poisson equation and for convection–diffusion equations are presented for isotropic/anisotropic configurations with specified Dirichlet and Neumann boundary conditions. | |||||
BibTeX:
@article{Irina2005a,
author = {Irina, Ginzburg},
title = {Generic boundary conditions for lattice Boltzmann models and their application to advection and anisotropic dispersion equations},
journal = {Advances in Water Resources},
year = {2005},
volume = {28},
number = {11},
pages = {1196--1216},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805000886}
}
|
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| Ivars, N. | A stochastic multi-channel model for solute transport—analysis of tracer tests in fractured rock | 2002 | Journal of Contaminant Hydrology Vol. 55(3-4), pp. 175-211 |
article | URL |
| Abstract: Some of the basic assumptions of the advection–dispersion model (AD-model) are revisited. This model assumes a continuous mixing along the flowpath similar to Fickian diffusion. This implies that there is a constant dispersion length irrespective of observation distance. This is contrary to most field observations. The properties of an alternative model based on the assumption that individual water packages can retain their identity over long distances are investigated. The latter model is called the multi-channel model (MCh-model). Inherent in the latter model is that if the waters in the different pathways are collected and mixed, the “dispersion length” is proportional to distance. The conditions for when non-mixing between adjacent streams can be assumed are explored. | |||||
BibTeX:
@article{Ivars2002,
author = {Ivars, Neretnieks},
title = {A stochastic multi-channel model for solute transport—analysis of tracer tests in fractured rock},
journal = {Journal of Contaminant Hydrology},
year = {2002},
volume = {55},
number = {3-4},
pages = {175--211},
url = {http://www.sciencedirect.com/science/article/pii/S0169772201001954}
}
|
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| Izquierdo, J. and Iglesias, P. | Mathematical modelling of hydraulic transients in simple systems | 2002 | Mathematical and Computer Modelling Vol. 35(7–8), pp. 801-812 |
article | URL |
| Abstract: Efficiency and economy in the design and operation of a hydraulic system, as well as its safety, are objectives needing precise calculations of pressures and flowrates within the system. The calculations are typically very time-consuming and, depending on the characteristics of the system, very complicated and difficult to organize. A suitable mathematical modelling of the different ingredients in a hydraulic system is necessary to get useful results, which help fulfill those objectives. In this paper, the mathematical modelling used to develop a computer program to simulate hydraulic transients in a simple system is described. The program (DYAGATS), developed by the authors, is currently being used by organizations and consultancies to simulate and, consequently, analyze hydraulic transients in water systems. It makes use of the so-called elastic model, also known as waterhammer, to model the behavior of the fluid within the pipes. Also, lump models for the different elements that introduce, damp, modify, absorb, etc., perturbations in the systems are presented in a unified treatment. The main objective is to provide users with a powerful tool to devise the potential risks to which an installation may be exposed and to develop suitable protection strategies. | |||||
BibTeX:
@article{Izquierdo2002,
author = {Izquierdo, J. and Iglesias, P.L.},
title = {Mathematical modelling of hydraulic transients in simple systems},
journal = {Mathematical and Computer Modelling},
year = {2002},
volume = {35},
number = {7–8},
pages = {801--812},
url = {http://www.sciencedirect.com/science/article/pii/S0895717702000511}
}
|
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| Jackson, B.M., Wheater, H.S., Mathias, S.A., McIntyre, N. and Butler, A.P. | A simple model of variable residence time flow and nutrient transport in the chalk | 2006 | Journal of Hydrology Vol. 330(1-2)Hydro-ecological functioning of the Pang and Lambourn catchments, UK Results from the Lowland Catchment Research (LOCAR) initiative, pp. 221-234 |
article | URL |
| Abstract: A basic problem of modelling flow and transport in Chalk catchments arises from the existence of a deep unsaturated zone, with complex interactions between flow in fractures and water held in the fine pores of the rock matrix. The response of the water table to major infiltration episodes is rapid (of the order of days). However, chemical signals are strongly damped, suggesting that this water is of varying age, with a corresponding mixed history of nutrient loading. Clearly this effect should be represented in any model of nutrients in Chalk systems. | |||||
BibTeX:
@article{Jackson2006,
author = {Jackson, Bethanna M. and Wheater, Howard S. and Mathias, Simon A. and McIntyre, Neil and Butler, Adrian P.},
title = {A simple model of variable residence time flow and nutrient transport in the chalk},
booktitle = {Hydro-ecological functioning of the Pang and Lambourn catchments, UK Results from the Lowland Catchment Research (LOCAR) initiative},
journal = {Journal of Hydrology},
year = {2006},
volume = {330},
number = {1-2},
pages = {221--234},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406002022}
}
|
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| Jackson, D.A. | An evaluation of physical and chemical discharge parameters at a spring that drains the epikarst: Kentucky, USA | 2012 | Carbonates and Evaporites Vol. 27(2), pp. 173-184 |
article | URL |
| Abstract: Physical and chemical parameters measured at a spring discharge can be used to infer recharge type to the epikarstic catchment that recharges a spring. This study showed that conductivity, temperature, and stage, measured by a digital datalogger, can be used to determine the type and percentage of recharge, seepage versus concentrated, that contribute to a spring’s discharge point. Ewers Alley Spring is a small perennial spring which drains a groundwater basin developed solely within the epikarst. This spring was fitted with a digital datalogger to determine if changes in temperature, conductivity, and stage, which have been used to characterize springs that drain mature karst basins, can also be used to characterize recharge to a basin that is charged solely from groundwater stored in the epikarst. The study determined that changes in temperature, conductivity, and stage, in response to precipitation events, are reliable measures in determining recharge type to a drainage basin located solely in the epikarst. Changes in temperature, conductivity, and stage revealed that Ewers Ally Spring is dominated by seepage recharge conditions, and at baseflow, the groundwater in all probability is saturated in respect to calcium carbonate. During wetter periods of the year, when flow from the epikarst is greater, groundwater discharge from the spring is prone to be undersaturated in respect to calcium carbonate; this is due to the influx of stormwater into the epikarstic system. In spite of the fact that seepage recharge conditions are dominant, numerous vertical conduits and open channels present at this location can transmit water rapidly into the system. This results in quick-flow conditions that can travel quickly to groundwater springs in the basin. However, the effects of quick-flow conditions on Ewers Alley Spring, as a result of concentrated recharge, are limited due to the predominance of the overlying soil cover and the restricted radius of influence of open pits and shafts. Normalized Base Flow per unit discharge applied to Ewers Ally Spring calculates a spring recharge area, or basin size of 29,541 m 2 . | |||||
BibTeX:
@article{Jackson2012,
author = {Jackson, David A.},
title = {An evaluation of physical and chemical discharge parameters at a spring that drains the epikarst: Kentucky, USA},
journal = {Carbonates and Evaporites},
publisher = {Springer Berlin / Heidelberg},
year = {2012},
volume = {27},
number = {2},
pages = {173--184},
note = {From the issue entitled "Special Issue on Integrating Science and Engineering to Solve Karst Problems, Part I"},
url = {http://dx.doi.org/10.1007/s13146-012-0103-8}
}
|
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| Jacques, D., Šimůnek, J., Mallants, D. and van Genuchten, M. | Operator-splitting errors in coupled reactive transport codes for transient variably saturated flow and contaminant transport in layered soil profiles | 2006 | Journal of Contaminant Hydrology Vol. 88(3-4), pp. 197-218 |
article | URL |
| Abstract: One possible way of integrating subsurface flow and transport processes with (bio)geochemical reactions is to couple by means of an operator-splitting approach two completely separate codes, one for variably-saturated flow and solute transport and one for equilibrium and kinetic biogeochemical reactions. This paper evaluates the accuracy of the operator-splitting approach for multicomponent systems for typical soil environmental problems involving transient atmospheric boundary conditions (precipitation, evapotranspiration) and layered soil profiles. The recently developed HP1 code was used to solve the coupled transport and chemical equations. For steady-state flow conditions, the accuracy was found to be mainly a function of the adopted spatial discretization and to a lesser extent of the temporal discretization. For transient flow situations, the accuracy depended in a complex manner on grid discretization, time stepping and the main flow conditions (infiltration versus evaporation). Whereas a finer grid size reduced the numerical errors during steady-state flow or the main infiltration periods, the errors sometimes slightly increased (generally less than 50%) when a finer grid size was used during periods with a high evapotranspiration demand (leading to high pressure head gradients near the soil surface). This indicates that operator-splitting errors are most significant during periods with high evaporative boundary conditions. The operator-splitting errors could be decreased by constraining the time step using the performance index (the product of the grid Peclet and Courant numbers) during infiltration, or the maximum time step during evapotranspiration. Several test problems were used to provide guidance for optimal spatial and temporal discretization. | |||||
BibTeX:
@article{Jacques2006,
author = {Jacques, D. and Šimůnek, J. and Mallants, D. and van Genuchten, M.Th.},
title = {Operator-splitting errors in coupled reactive transport codes for transient variably saturated flow and contaminant transport in layered soil profiles},
journal = {Journal of Contaminant Hydrology},
year = {2006},
volume = {88},
number = {3-4},
pages = {197--218},
url = {http://www.sciencedirect.com/science/article/pii/S0169772206001185}
}
|
|||||
| Jain, R., Mathur, M., Sikarwar, S. and Mittal, A. | Removal of the hazardous dye rhodamine B through photocatalytic and adsorption treatments | 2007 | Journal of Environmental Management Vol. 85(4), pp. 956-964 |
article | URL |
| Abstract: This paper reports on photocatalytic and adsorptive treatment of a hazardous xanthene dye, Rohdamine B, in wastewater. The photocatalytic degradation was carried out in the presence of the catalyst TiO2 and the effects of pH, concentration of the dye, amount of TiO2, temperature and electron acceptor H2O2 on the degradation process were observed. It was found that photocatalytic degradation by TiO2 is an effective, economical and faster mode of removing Rohdamine B from aqueous solutions. Attempts were also made to utilize activated carbon and rice husk as potential adsorbents to remove Rhodamine B from wastewater. The adsorption studies were carried out at 40, 50 and 60 °C, and the effects of pH, temperature, amount of adsorbents, concentration of adsorbate, etc., on the adsorption were measured. On the basis of adsorption data the Langmuir and Freundlich adsorption isotherm models were also confirmed. The adsorption isotherm constants thus obtained were employed to calculate thermodynamic parameters like Gibb's free energy, change in enthalpy and entropy. In order to observe the quality of wastewater COD measurements were also carried out before and after the treatments. A significant decrease in the COD values was observed, which clearly indicates that both photocatalytic and adsorption methods offer good potential to remove Rhodamine B from industrial effluents. | |||||
BibTeX:
@article{Jain2007,
author = {Jain, Rajeev and Mathur, Megha and Sikarwar, Shalini and Mittal, Alok},
title = {Removal of the hazardous dye rhodamine B through photocatalytic and adsorption treatments},
journal = {Journal of Environmental Management},
year = {2007},
volume = {85},
number = {4},
pages = {956--964},
url = {http://www.sciencedirect.com/science/article/pii/S0301479706003483}
}
|
|||||
| Jakobsen, H.A., Lindborg, H. and Handeland, V. | A numerical study of the interactions between viscous flow, transport and kinetics in fixed bed reactors | 2002 | Computers & Chemical Engineering Vol. 26(3), pp. 333-357 |
article | URL |
| Abstract: A numerical method is tailored for the solution of a reduced set of model equations developed for the description of reactive flows in chemical reactors. The numerical method synthesis intends to utilize experience both in chemical engineering solving dispersion models containing complex reaction kinetics, phase equilibria and non-ideal thermodynamics, and in fluid dynamics applying classical numerical algorithms constructed for pure flow calculations. The two types of model equations involved in reactive flow simulations reflect very different physics. A modular method is therefore suggested enabling a split between the flow- and chemistry model parts. In this way more optimal solution methods can be adopted for each operator, in contrast to more traditional computational fluid dynamics (CFD) methods where all equations (and operators) are normally solved by the numerical solvers originally intended for pure flow calculations. In addition, emphasis has been put on modularity enabling the same model framework to be used both for the more traditional 1D and 2D dispersion models with simple 1D flow calculations, as well as for the more elaborate 2D and 3D reactive flow calculations. In the flow part of the algorithm a fractional-step algorithm is constructed for the simulation of dynamic reactive flows in chemical reactors. The numerical scheme is based on the compressible transport equations in the low-Mach-number limit. The method can handle real gas (and liquid) mixtures with variable density as well as constant density fluids. The velocity field is advanced using a projection scheme, which consists of a partial convection–diffusion update followed by a pressure correction step with an intermediate an-elastic filter. A variable density corrector step is implemented for variable density systems in order to couple the evolution of the density and the velocity fields. In the chemistry part of the model all scalar fields are updated using Strang-type operator-split integration steps that combine several explicit convection and semi-implicit diffusion transport operators with a suitable solver tailored for non-linear sink/source terms. Diffusion terms are discretized with a second order central difference scheme in space. Convection terms are discretized with a second order TVD scheme in space. The temperature advection is discretized using a second order upwind scheme. The chemical reaction part of the model is discretized by an implicit Euler approximation, and the resulting set of algebraic equations is solved using a Broyden subroutine. The other source terms are solved using an explicit Euler approximation. The performance and behavior of the operator-split scheme are assessed based on simulations of two industrial chemical processes (i.e. the synthesis gas and methanol production processes) performed in multi-tube fixed bed reactors. These processes are important parts of the Statoil methanol plant at Tjeldbergodden in mid Norway. Both 1D and 2D pseudo-homogeneous dispersion models (i.e. heat and mass balances) with prescribed velocity, mixture density and total pressure profiles are used describing the reactor performance. The predicted profiles for both the methanol and synthesis gas processes were in accordance with results reported in the literature. An oscillatory radial void fraction distribution was then implemented in the 2D model. It was found that the non-uniform void fraction distribution had no significant effect on the temperature and mole fraction profiles. A 1D CFD simulation was performed to evaluate the effect of the variations in velocity, pressure and mixture density on the reactor performance. The changes in these variables significantly effect the composition and conversion in the reactor. A 2D CFD model was then developed for further studies of the multi-tube fixed bed reactor for the synthesis gas process, analyzing the influence of non-uniform void fraction distributions on the flow and chemical conversion. The non-uniform void fraction distribution induces a significant reduction in axial pressure drop and a much higher fluid velocity close to the wall. However, the influence on the temperature and mole fraction profiles was hardly noticeable. Mass- and enthalpy budgets were implemented for the heat and mass quantities in the program. These budgets show that the enthalpy and both the mixture and component mass balances are fulfilled in the simulations. The numerical CFD algorithm developed in this paper has been found to be both computationally stable and accurate. Computational efficiency analysis shows that the Poisson solver requires about 75% of the total computational time. The computational time spend on the chemistry part of the model is about 15% of the total time. About 10% of the cost used on the chemistry part is spend on the chemistry solver. | |||||
BibTeX:
@article{Jakobsen2002,
author = {Jakobsen, Hugo A. and Lindborg, Håvard and Handeland, Vemund},
title = {A numerical study of the interactions between viscous flow, transport and kinetics in fixed bed reactors},
journal = {Computers & Chemical Engineering},
year = {2002},
volume = {26},
number = {3},
pages = {333--357},
url = {http://www.sciencedirect.com/science/article/pii/S009813540100758X}
}
|
|||||
| Jalbert, M., Dane, J.H. and Bahaminyakamwe, L. | Influence of porous medium and NAPL distribution heterogeneities on partitioning inter-well tracer tests: a laboratory investigation | 2003 | Journal of Hydrology Vol. 272(1-4)Soil Hydrological Properties and Processes and their Variability in Space and Time, pp. 79-94 |
article | URL |
| Abstract: The inter-well partitioning tracer test seemingly provides an attractive way of investigating the presence of non-aqueous phase liquids (NAPLs) in aquifers. Although the feasibility of this rather new technique has been tested in the field, only few laboratory experiments have been performed to test its validity at scales greater than the column scale. In this study, a partitioning tracer test was conducted in a nominally two-dimensional, intermediate-scale flow cell containing a tetrachloroethene (PCE) spill. Tracer breakthrough curves were obtained at 14 sampling ports and an extraction well containing three outlets. Estimated PCE contents resulting from the tracer technique were compared to PCE saturations obtained at 800 locations by gamma radiation. An inverse procedure, based on the two-site, non-equilibrium convection–dispersion equation, was used in addition to the moment method for sampling port data analysis. Although the inverse procedure produced slightly better results than the moment method, the tracer technique generally underestimated the amount of DNAPL contained in our aquifer model. Notably, our results showed that the pooled part of the DNAPL spill was not detected. This was attributed to the low aqueous phase permeability within the DNAPL pool in combination with rate-limited partitioning of the tracers into the DNAPL. Our analysis indicate a general difficulty for the tracer technique to detect NAPL located in pools or large lenses. | |||||
BibTeX:
@article{Jalbert2003,
author = {Jalbert, Marc and Dane, Jacob H and Bahaminyakamwe, Laurent},
title = {Influence of porous medium and NAPL distribution heterogeneities on partitioning inter-well tracer tests: a laboratory investigation},
booktitle = {Soil Hydrological Properties and Processes and their Variability in Space and Time},
journal = {Journal of Hydrology},
year = {2003},
volume = {272},
number = {1-4},
pages = {79--94},
url = {http://www.sciencedirect.com/science/article/pii/S0022169402002561}
}
|
|||||
| James, S.C. and Chrysikopoulos, C.V. | Analytical solutions for monodisperse and polydisperse colloid transport in uniform fractures | 2003 | Colloids and Surfaces A: Physicochemical and Engineering Aspects Vol. 226(1-3), pp. 101-118 |
article | URL |
| Abstract: Analytical solutions are derived describing the transport of suspensions of monodisperse as well as polydisperse colloid plumes of neutral buoyancy within a fracture with uniform aperture. Various initial and boundary conditions are considered. It is shown that both the finite colloid size and the characteristics of the colloid diameter distribution significantly affect the shape of colloid concentration breakthrough curves. Furthermore, increasing the standard deviation of the colloid diameter enhances colloid spreading and increases the number of attached colloids when colloid–wall interactions are taken into account. Excellent agreement between available experimental data and the analytical solution for the case of an instantaneous release of monodisperse colloids in a natural fracture is observed. | |||||
BibTeX:
@article{James2003,
author = {James, Scott C and Chrysikopoulos, Constantinos V},
title = {Analytical solutions for monodisperse and polydisperse colloid transport in uniform fractures},
journal = {Colloids and Surfaces A: Physicochemical and Engineering Aspects},
year = {2003},
volume = {226},
number = {1-3},
pages = {101--118},
url = {http://www.sciencedirect.com/science/article/pii/S0927775703003169}
}
|
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| Jang, J., Narsilio, G.A. and Santamarina, J.C. | Hydraulic conductivity in spatially varying media—a pore-scale investigation | 2011 | Geophysical Journal International Vol. 184(3), pp. 1167-1179 |
article | URL |
| Abstract: The hydraulic conductivity can control geotechnical design, resource recovery and waste disposal. We investigate the effect of pore-scale spatial variability on flow patterns and hydraulic conductivity using network models realized with various tube size distributions, coordination number, coefficient of variation, correlation and anisotropy. In addition, we analyse flow patterns to understand observed trends in hydraulic conductivity. In most cases, the hydraulic conductivity decreases as the variance in pore size increases because flow becomes gradually localized along fewer flow paths; as few as 10 per cent of pores may be responsible for 50 per cent of the total flow in media with high pore-size variability. Spatial correlation reduces the probability of small tubes being next to large ones and leads to higher hydraulic conductivity while focused fluid flow takes place along interconnected regions of high conductivity. A pronounced decrease in tortuosity is observed when pore size and spatial correlation in the flow direction are higher than in the transverse direction. These results highlight the relevance of grain size and formation history dependent pore size distribution and spatial variability on hydraulic conductivity, related geo-process and engineering applications. | |||||
BibTeX:
@article{Jang2011,
author = {Jang, J. and Narsilio, G. A. and Santamarina, J. C.},
title = {Hydraulic conductivity in spatially varying media—a pore-scale investigation},
journal = {Geophysical Journal International},
publisher = {Blackwell Publishing Ltd},
year = {2011},
volume = {184},
number = {3},
pages = {1167--1179},
url = {http://dx.doi.org/10.1111/j.1365-246X.2010.04893.x}
}
|
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| Jang, S., Cho, M., Yoon, J., Yoon, Y., Kim, S., Kim, G., Kim, L. and Aksoy, H. | Using SWMM as a tool for hydrologic impact assessment | 2007 | Desalination Vol. 212(1-3), pp. 344-356 |
article | URL |
| Abstract: Hydrologic impact assessment is necessary for a planned development area in designing detention storage for urban drainage systems to minimize the effect of urbanization. It also has strong implication on pollutant loads from urban areas. For such assessment, single or two hydrologic models can be paired for pre- and post- development conditions. Typical pairings are the use of synthetic hydrograph methods for both conditions or synthetic hydrograph for pre-development and urban hydrology model for post-development condition. The former has the difficulty of accounting for drainage structure for post-development condition and the latter can run into erratic evaluation as the error can be introduced due to different model conceptualizations and parameterizations. In order to overcome the aforementioned shortcomings, the use of Storm Water Management Model (SWMM) for both pre- and postdevelopment conditions is proposed in this study. The SWMM was applied to four planned development areas in Korea. The comparison of the results with previous assessments done for the same sites showed that the new approach can resolve the irrationalities that can occur with the combination of two different models such as smaller peak flow and longer time to peak for post-development condition. It is thought that the proposed method improves the accountability of the hydrologic impact assessment on planned development areas. | |||||
BibTeX:
@article{Jang2007,
author = {Jang, Suhyung and Cho, Minock and Yoon, Jaeyoung and Yoon, Yongnam and Kim, Sangdan and Kim, Geonha and Kim, Leehyung and Aksoy, Hafzullah},
title = {Using SWMM as a tool for hydrologic impact assessment},
journal = {Desalination},
year = {2007},
volume = {212},
number = {1-3},
pages = {344--356},
url = {http://www.sciencedirect.com/science/article/pii/S0011916407002834}
}
|
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| Jaquet, O., Siegel, P., Klubertanz, G. and Benabderrhamane, H. | Stochastic discrete model of karstic networks | 2004 | Advances in Water Resources Vol. 27(7), pp. 751-760 |
article | URL |
| Abstract: Karst aquifers are characterised by an extreme spatial heterogeneity that strongly influences their hydraulic behaviour and the transport of pollutants. These aquifers are particularly vulnerable to contamination because of their highly permeable networks of conduits. A stochastic model is proposed for the simulation of the geometry of karstic networks at a regional scale. The model integrates the relevant physical processes governing the formation of karstic networks. The discrete simulation of karstic networks is performed with a modified lattice-gas cellular automaton for a representative description of the karstic aquifer geometry. Consequently, more reliable modelling results can be obtained for the management and the protection of karst aquifers. The stochastic model was applied jointly with groundwater modelling techniques to a regional karst aquifer in France for the purpose of resolving surface pollution issues. | |||||
BibTeX:
@article{Jaquet2004,
author = {Jaquet, O. and Siegel, P. and Klubertanz, G. and Benabderrhamane, H.},
title = {Stochastic discrete model of karstic networks},
journal = {Advances in Water Resources},
year = {2004},
volume = {27},
number = {7},
pages = {751--760},
url = {http://www.sciencedirect.com/science/article/pii/S0309170804000703}
}
|
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| Jarman, K.D. and Tartakovsky, A.M. | Divergence of solutions to perturbation-based advection–dispersion moment equations | 2011 | Advances in Water Resources Vol. 34(5), pp. 659-670 |
article | URL |
| Abstract: Moment equation methods are popular and powerful tools for modeling transport processes in randomly heterogeneous porous media, but the application of these methods to advection–dispersion equations often leads to erroneous oscillations. Perturbative methods, required to close systems of moment equations, become inaccurate for large perturbations; however, little quantitative theory exists for determining when this occurs for advection–dispersion equations. We consider three different methods (asymptotic approximation, Eulerian truncation, and iterative solution) for closing and solving advection–dispersion moment equations describing transport in stratified porous media with random permeability. We obtain approximate analytical expressions for time above which the asymptotic approximation to the mean diverges, in particular quantifying the impact that dispersion has on delaying—but not eliminating—divergence. We demonstrate that Eulerian truncation and iterative solution methods do not eliminate divergent behavior either. Our divergence criteria provide a priori estimates that signal a warning to the practitioner of stochastic advection–dispersion equations to carefully consider whether to apply perturbative approaches. | |||||
BibTeX:
@article{Jarman2011,
author = {Jarman, Kenneth D. and Tartakovsky, Alexandre M.},
title = {Divergence of solutions to perturbation-based advection–dispersion moment equations},
journal = {Advances in Water Resources},
year = {2011},
volume = {34},
number = {5},
pages = {659--670},
url = {http://www.sciencedirect.com/science/article/pii/S0309170811000510}
}
|
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| Jarošík, V., Konvička, M., Pyšek, P., Kadlec, T. and Beneš, J. | Conservation in a city: Do the same principles apply to different taxa? | 2011 | Biological Conservation Vol. 144(1), pp. 490-499 |
article | URL |
| Abstract: Factors shaping overall species richness and representation of endangered species of vascular flora and butterflies were determined in 48 nature reserves in Prague, Czech Republic. Total species richness of both groups, and the presence of endangered butterflies, reflect the present status of habitats, while that of endangered plants reflects habitat composition at the time of reserve establishment. Reserve area has a much stronger effect on the species richness of sessile plants than mobile butterflies which, especially endangered species, respond more positively to heterogeneity than to area. Both species richness and endangered species peak in reserves half covered with forest, likely because they harbor species of both woodland and non-woodland habitats, and edge specialists. Solely relying on area and disregarding habitat quality, or a failure to conserve small but high quality sites, may be counterproductive for conserving endangered plant and butterfly species. To conserve diversity of plants and butterflies current management practices, often aimed at maintaining large blocks of pre-selected plant communities, should change to include maintenance of fallows, edges and transient zones. | |||||
BibTeX:
@article{Jarosik2011,
author = {Jarošík, Vojtěch and Konvička, Martin and Pyšek, Petr and Kadlec, Tomáš and Beneš, Jiří},
title = {Conservation in a city: Do the same principles apply to different taxa?},
journal = {Biological Conservation},
year = {2011},
volume = {144},
number = {1},
pages = {490--499},
url = {http://www.sciencedirect.com/science/article/pii/S0006320710004350}
}
|
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| Jazi, M.A., Lai, C.-D. and Alamatsaz, M.H. | A discrete inverse Weibull distribution and estimation of its parameters | 2010 | Statistical Methodology Vol. 7(2), pp. 121-132 |
article | URL |
| Abstract: A discrete analogue of the standard continuous Weibull distribution was proposed in the literature to meet the need of fitting discrete-time reliability and survival data sets. Its properties were studied and the methods of estimation of its parameters were also investigated by various authors. Analogous to its continuous counterpart, the discrete Weibull does not provide a good fit to data sets that exhibit non-monotonic hazard rate shapes. | |||||
BibTeX:
@article{Jazi2010,
author = {Jazi, Mansour Aghababaei and Lai, Chin-Diew and Alamatsaz, Mohammad Hossein},
title = {A discrete inverse Weibull distribution and estimation of its parameters},
journal = {Statistical Methodology},
year = {2010},
volume = {7},
number = {2},
pages = {121--132},
url = {http://www.sciencedirect.com/science/article/pii/S1572312709000707}
}
|
|||||
| Jeffrey, A. | Handbook of mathematical formulas and integrals [BibTeX] |
2004 | , pp. - | book | |
BibTeX:
@book{Jeffrey2004,
author = {Jeffrey, Alan},
title = {Handbook of mathematical formulas and integrals},
publisher = {Elsevier Academic Press},
year = {2004},
pages = {--},
edition = {Third}
}
|
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| Jenkins, A., Ferrier, R.C., Harriman, R. and Ogunkoya, Y.O. | A case study in catchment hydrochemistry: Conflicting interpretations from hydrological and chemical observations | 1994 | Hydrological Processes Vol. 8(4), pp. 335-349 |
article | URL |
| Abstract: Soil water, stream water, groundwater and rain water were sampled through a storm event in a moorland catchment. Samples were analysed for major ions and deuterium. Chloride and deuterium are used as tracers to enable separation of the stream runoff hydrograph into three components: rain, soil and groundwater. The results indicate that rain water arrives in the stream quickly during the event and contributes a significant volume to the runoff peak. The chemical signal in the rain water is, however, significantly damped, apparently due to mixing with soil water held in the catchment before the event. This is further modified before reaching the stream, apparently through mixing with a deeper groundwater component. Interpretation of tracer, chemistry and hydrological data to present an integrated picture of catchment hydrochemical response is difficult due to problems in the chemical and conceptual definition of the flow components. | |||||
BibTeX:
@article{Jenkins1994,
author = {Jenkins, Alan and Ferrier, Robert C. and Harriman, Ron and Ogunkoya, Yinka O.},
title = {A case study in catchment hydrochemistry: Conflicting interpretations from hydrological and chemical observations},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {1994},
volume = {8},
number = {4},
pages = {335--349},
url = {http://dx.doi.org/10.1002/hyp.3360080406}
}
|
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| Jernigan, J.W. and Swift, R.J. | A mathematical model of air temperature in Mammoth Cave, Kentucky | 2001 | Journal of Cave and Karst Studies Vol. 63(1), pp. 3-8 |
article | URL |
| Abstract: Alterations made to the Natural (Historic) Entrance into Mammoth Cave over the past two centuries have resulted in disrupted atmospheric conditions in the Historic Section of Mammoth Cave. In an effort to understand atmospheric phenomena in this section of the cave, Division of Science and Resources Management personnel at Mammoth Cave National Park collected atmospheric data from various sites throughout the Historic Section of Mammoth Cave. These data are used to construct a mathematical model that predicts air temperature at various sites within the cave system. First, an approximate mathematical model is constructed that could apply to any cave system with characteristics (such as cave geometry and the natural force driving airflow) similar to those in Mammoth Cave. Then, the regression analysis of atmospheric data and the use of the derived model allow the construction of a mathematical model that is specific to the Historic Section of Mammoth Cave. |
|||||
BibTeX:
@article{Jernigan2001,
author = {Jernigan, Jonathan W. and Swift, Randall J.},
title = {A mathematical model of air temperature in Mammoth Cave, Kentucky},
journal = {Journal of Cave and Karst Studies},
year = {2001},
volume = {63},
number = {1},
pages = {3--8},
url = {http://www.caves.org/pub/journal/PDF/V63/v63n1-Jernigan.htm}
}
|
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| Ji, L., Wu, B., Chen, K. and Zhu, J. | Experimental study and modeling of residence time distribution in impinging stream reactor with GDB model | 2010 | Journal of Industrial and Engineering Chemistry Vol. 16(4), pp. 646-650 |
article | URL |
| Abstract: Residence time distribution (RTD) in an impinging streams reactor with two or four nozzles was investigated with KCl solution as a tracer. The results showed that the flow pattern in the reactor was close to that in a continuous stirred tank reactor (CSTR). Macromixing process in the reactor was improved obviously when the opposite nozzles were added. Based on the analysis of flow region in the reactor, gamma distribution model with bypass (GDB) was applied for study on the RTD of the reactor. It was found that RTD in the impinging streams reactor could be finely described by the model. Also the effects of experimental conditions on parameters of model were analyzed according to the correlated values of the model parameters. | |||||
BibTeX:
@article{Ji2010,
author = {Ji, Lijun and Wu, Bin and Chen, Kui and Zhu, Jiawen},
title = {Experimental study and modeling of residence time distribution in impinging stream reactor with GDB model},
journal = {Journal of Industrial and Engineering Chemistry},
year = {2010},
volume = {16},
number = {4},
pages = {646--650},
url = {http://www.sciencedirect.com/science/article/pii/S1226086X10000560}
}
|
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| Jiang, J. and Wu, J. | A transition rate transformation method for solving advection–dispersion equation | 2011 | Journal of Computational Physics Vol. 230(14), pp. 5556-5563 |
article | URL |
| Abstract: Advection–dispersion equation is widely used to describe solute transport in hydrology. However, using conventional methods, e.g., finite difference method, to solve this equation may result in numerical dispersion and oscillation, especially when the advection velocity is large. This paper presents a novel transition rate transformation (TRT) method to simulate the advection–dispersion process. Advection–dispersion equation is invariant as the transition rate function is transformed under the condition that the first and second spatial moments of the transition rate are kept unchanged. According to this invariance, the TRT method constructs simple transition rate functions to solve the advection–dispersion equation. Our simulation shows that the results obtained by the TRT method agree well with analytical solutions. The freedom of the selection of transition rate functions may be very useful for the simulations of the advection–dispersion problems. | |||||
BibTeX:
@article{Jiang2011,
author = {Jiang, Jianguo and Wu, Jichun},
title = {A transition rate transformation method for solving advection–dispersion equation},
journal = {Journal of Computational Physics},
year = {2011},
volume = {230},
number = {14},
pages = {5556--5563},
url = {http://www.sciencedirect.com/science/article/pii/S0021999111001859}
}
|
|||||
| Jiang, W. and Lin, Y. | Approximate solution of the fractional advection–dispersion equation | 2010 | Computer Physics Communications Vol. 181(3), pp. 557-561 |
article | URL |
| Abstract: In this paper, we consider practical numerical method to solve a space–time fractional advection–dispersion equation with variable coefficients on a finite domain. The equation is obtained from the standard advection–dispersion equation by replacing the first-order time derivative by the Caputo fractional derivative, and the first-order and second-order space derivatives by the Riemann–Liouville fractional derivative, respectively. Here, a new method for solving this equation is proposed in the reproducing kernel space. The representation of solution is given by the form of series and the n-term approximation solution is obtained by truncating the series. The method is easy to implement and the numerical results show the accuracy of the method. | |||||
BibTeX:
@article{Jiang2010,
author = {Jiang, Wei and Lin, Yingzhen},
title = {Approximate solution of the fractional advection–dispersion equation},
journal = {Computer Physics Communications},
year = {2010},
volume = {181},
number = {3},
pages = {557--561},
url = {http://www.sciencedirect.com/science/article/pii/S001046550900352X}
}
|
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| Jiang, X. and Tay, J.H. | Removal mechanisms of H2S using exhausted carbon in biofiltration | 2011 | Journal of Hazardous Materials Vol. 185(2-3), pp. 1543-1549 |
article | URL |
| Abstract: Exhausted carbon which comes from the H2S adsorption process may be a hazardous waste. In this study, exhausted carbon was re-used in biofiltration for H2S removal. Two identical columns were used for exhausted carbon (Column A) and fresh carbon (Column B). They were operated in the same mode with 35 ppmv of H2S gas at an empty bed residence time (EBRT) of 10 s. The results show that the removal efficiency of H2S in the two columns was almost identical at 95–100%. The removal mechanisms of H2S was explored and explained by developing a mathematical model. The model incorporated mass transfer, biodegradation, adsorption, as well as biofilm growth. The developed model can predict the experimental results very well. The modeled results suggest that the removal of H2S in Column A was attributed to the adsorption mechanism much less than in Column B during the start-up stage, while the removal of H2S by the biodegradation in Column A was much higher. The removal of H2S by the adsorption was significantly affected by the biodegradation. The simulation results also suggest that column A achieved the steady-state biodegradation in a shorter time than in Column B. This could result from higher biomass concentration of biofilm in Column A, due to the extra sulfur source from pre-adsorbed sulfur on exhausted carbon besides H2S gas feeding. | |||||
BibTeX:
@article{Jiang2011a,
author = {Jiang, Xia and Tay, Joo Hwa},
title = {Removal mechanisms of H2S using exhausted carbon in biofiltration},
journal = {Journal of Hazardous Materials},
year = {2011},
volume = {185},
number = {2-3},
pages = {1543--1549},
url = {http://www.sciencedirect.com/science/article/pii/S0304389410013737}
}
|
|||||
| Jiang, Y., Wu, Y., Groves, C., Yuan, D. and Kambesis, P. | Natural and anthropogenic factors affecting the groundwater quality in the Nandong karst underground river system in Yunan, China | 2009 | Journal of Contaminant Hydrology Vol. 109(1-4), pp. 49-61 |
article | URL |
| Abstract: The Nandong Underground River System (NURS) is located in a typical karst agriculture dominated area in the southeast Yunnan Province, China. Groundwater plays an important role for social and economical development in the area. However, with the rapid increase in population and expansion of farm land, groundwater quality has degraded. 42 groundwater samples collected from springs in the NURS showed great variation of chemical compositions across the study basin. With increased anthropogenic contamination in the area, the groundwater chemistry has changed from the typical Ca–HCO3 or Ca (Mg)–HCO3 type in karst groundwater to the Ca–Cl (+ NO3) or Ca (Mg)–Cl (+ NO3), and Ca–Cl (+ NO3 + SO4) or Ca (Mg)–Cl (+ NO3 + SO4) type, indicating increases in NO3−, Cl− and SO42− concentrations that were caused most likely by human activities in the region. This study implemented the R-mode factor analysis to investigate the chemical characteristics of groundwater and to distinguish the natural and anthropogenic processes affecting groundwater quality in the system. The R-mode factor analysis together with geology and land uses revealed that: (a) contamination from human activities such as sewage effluents and agricultural fertilizers; (b) water–rock interaction in the limestone-dominated system; and (c) water–rock interaction in the dolomite-dominated system were the three major factors contributing to groundwater quality. Natural dissolution of carbonate rock (water–rock interaction) was the primary source of Ca2+ and HCO3− in groundwater, water–rock interaction in dolomite-dominated system resulted in higher Mg2+ in the groundwater, and human activities were likely others sources. Sewage effluents and fertilizers could be the main contributor of Cl−, NO3−, SO42−, Na+ and K+ to the groundwater system in the area. This study suggested that both natural and anthropogenic processes contributed to chemical composition of groundwater in the NURS, human activities played the most important role, however. | |||||
BibTeX:
@article{Jiang2009,
author = {Jiang, Yongjun and Wu, Yuexia and Groves, Chris and Yuan, Daoxian and Kambesis, Pat},
title = {Natural and anthropogenic factors affecting the groundwater quality in the Nandong karst underground river system in Yunan, China},
journal = {Journal of Contaminant Hydrology},
year = {2009},
volume = {109},
number = {1-4},
pages = {49--61},
url = {http://www.sciencedirect.com/science/article/pii/S0169772209001077}
}
|
|||||
| Jianqiang C., W. | Sample distribution function based goodness-of-fit test for complex surveys | 2012 | Computational Statistics & Data Analysis Vol. 56(3), pp. 664-679 |
article | URL |
| Abstract: Testing the parametric distribution of a random variable is a fundamental problem in exploratory and inferential statistics. Classical empirical distribution function based goodness-of-fit tests typically require the data to be an independent and identically distributed realization of a certain probability model, and thus would fail when complex sampling designs introduce dependency and selection bias to the realized sample. In this paper, we propose goodness-of-fit procedures for a survey variable. To this end, we introduce several divergence measures between the design weighted estimator of distribution function and the hypothesized distribution, and propose goodness-of-fit tests based on these divergence measures. The test procedures are substantiated by theoretical results on the convergence of the estimated distribution function to the superpopulation distribution function on a metric space. We also provide computational details on how to calculate test p-values, and demonstrate the performance of the proposed test through simulation experiments. Finally, we illustrate the utility of the proposed test through the analysis of US 2004 presidential election data. | |||||
BibTeX:
@article{JianqiangC.2012,
author = {Jianqiang C., Wang},
title = {Sample distribution function based goodness-of-fit test for complex surveys},
journal = {Computational Statistics & Data Analysis},
year = {2012},
volume = {56},
number = {3},
pages = {664--679},
url = {http://www.sciencedirect.com/science/article/pii/S0167947311003343}
}
|
|||||
| Jobson, H.E. | Estimation of dispersion and first-order rate coeft by Numerical Routing | 1987 | Water Resources Research Vol. 23(1), pp. 169-180 |
article | URL |
| Abstract: The engineer is often required to estimate dispersion and first-order reaction coefficients from data obtained in natural streams. One way to accomplish this is by use of routing methods, in which the coefficients are determined such that the convective-dispersion (transport) equation most nearly describes the observed concentrations. In the past, analytic solutions to the transport equation have generally been used with the routing method (especially when determining dispersion coefficients) because numerical solutions often contained too much numerical dispersion for the results to be realistic. It is shown that a Lagrangian model can be used to determine realistic estimates of dispersion and reaction coefficients by use of the routing method. The numerical routing procedure is tested using data obtained analytically, under steady flow in a large and small river, in a river with unsteady flow and in a river with steady but highly nonuniform flow conditions. The numerical routing procedure based on a Lagrangian solution scheme performed well in all cases while offering the flexibility that only a numerical solution scheme can offer. | |||||
BibTeX:
@article{Jobson1987,
author = {Jobson, Harvey E.},
title = {Estimation of dispersion and first-order rate coeft by Numerical Routing},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1987},
volume = {23},
number = {1},
pages = {169--180},
url = {http://dx.doi.org/10.1029/WR023i001p00169}
}
|
|||||
| John C., R. | Effect of fracture spacing distribution on pressure transient response in naturally fractured reservoirs | 1998 | Journal of Petroleum Science and Engineering Vol. 20(1-2), pp. 31-47 |
article | URL |
| Abstract: This paper presents a new model for pressure transient and derivative analysis for multi-porosity reservoirs that have a distribution of matrix block sizes. To highlight the effect of varying fracture spacing, this model uses matrix domain storativity parameters instead of the fracture storativity parameter introduced by Warren and Root. Unlike existing multi-porosity models, it provides a simple expression for the pressure transient response in the time domain. The paper also presents a method for determining shape factors for the different matrix domains of multi-porosity reservoirs that is based on measured fracture spacing distributions. For an example reservoir studied, the pressure transient response for double-porosity reservoirs was found to be very similar to that of triple- or quadruple-porosity reservoirs, as long as the volume fractions of the matrix domains for each respective model were equal. Because of this, multi-porosity models may not provide significantly more information about the reservoir than the simpler double-porosity models. The transition period began somewhat earlier and ended later when more matrix domains were included in the model. When the volume fractions for the different matrix domains were significantly different, the calculated pressure transient response was impacted. | |||||
BibTeX:
@article{JohnC.1998,
author = {John C., Reis},
title = {Effect of fracture spacing distribution on pressure transient response in naturally fractured reservoirs},
journal = {Journal of Petroleum Science and Engineering},
year = {1998},
volume = {20},
number = {1-2},
pages = {31--47},
url = {http://www.sciencedirect.com/science/article/pii/S0920410597000521}
}
|
|||||
| John E., A. | Goodness-of-fit tests for exponentiality based on a loss-of-memory type functional equation | 1982 | Journal of Statistical Planning and Inference Vol. 6(3), pp. 241-251 |
article | URL |
| Abstract: Three goodness-of-fit tests for exponentiality based on the functional equation characterization 1−F(2x)=[1−F(x)]2 for every x⩾0 are proposed and shown to compare well to several popular tests against common alternative cdf's. Small-sample critical values for α=0.10,0.05 are developed for the two superior test statistics and the asymptotic null-distributions are characterized. | |||||
BibTeX:
@article{JohnE.1982,
author = {John E., Angus},
title = {Goodness-of-fit tests for exponentiality based on a loss-of-memory type functional equation},
journal = {Journal of Statistical Planning and Inference},
year = {1982},
volume = {6},
number = {3},
pages = {241--251},
url = {http://www.sciencedirect.com/science/article/pii/0378375882900295}
}
|
|||||
| John, B. | Characterisation of hydrogeologically significant fracture distributions in the Chalk: an example from the Upper Chalk of southern England | 1996 | Journal of Hydrology Vol. 184(3-4), pp. 355-379 |
article | URL |
| Abstract: Fractures pervade the Chalk, and are the primary pathways for rapid flow and contaminant migration. Improved quantitative descriptions of their geometry and scaling characteristics are essential for the development of predictive transport models. Fracture aperture and fracture connectivity are the most critical properties in controlling transport. To provide examples of fracture characteristics in the Upper Chalk, four fracture parameters—fracture orientation, trace length, spacing and aperture—have been measured using section and scan-line surveys at Play Hatch Quarry, near Reading, Berkshire. Three fracture types have been investigated: joints, bedding plane fractures and faults. Unrefined, or global, joint trace length and spacing measurements approximate to negative exponential distributions, with means of 0.09 m and 0.02 m. The trace length and spacing distributions of the two dominant joint sets, i.e. the bedding parallel joint set and the joints at a high angle to bedding, approximate to log-normal distributions, with geometric mean trace lengths of 0.15 m and 0.3 m, and spacings of 0.10 m and 0.12 m, respectively. Calculated fracture interconnectivity indices suggest that the bedding parallel joint set is likely to be of greater hydraulic importance than the high-angle joint set. Aperture measurements obtained for a single bedding plane fracture range from less than 0.5 mm to 23.5 mm. Apertures approximate to a negative exponential distribution below 7 mm, and to a log-normal distribution above 7 mm. It is inferred that the larger apertures have been affected by solution processes and that flow through bedding plane fractures is channelled across 10–20% of the fracture surface area. There are insufficient data for a rigorous analysis of the faulting at Play Hatch Quarry, but it is expected that faulting in the Chalk will show scale-invariant length and spacing characteristics. The results of the study are consistent with a visualisation of the Chalk consisting of scale-invariant fault-bounded segments, where the internal fracture architecture of each segment is dominated by continuous bedding plane fractures, and subordinate, scale-dependent, arrays of joints. The scale of jointing within a given fault-bounded segment is a function of bedding thickness. | |||||
BibTeX:
@article{John1996,
author = {John, Bloomfield},
title = {Characterisation of hydrogeologically significant fracture distributions in the Chalk: an example from the Upper Chalk of southern England},
journal = {Journal of Hydrology},
year = {1996},
volume = {184},
number = {3-4},
pages = {355--379},
url = {http://www.sciencedirect.com/science/article/pii/0022169495029540}
}
|
|||||
| Johnson, J.L., Fan, L.T. and Wu, Y.S. | Comparison of Moments, S-Plane, and Frequency Response Methods for Analyzing Pulse Testing Data from Flow Systems [BibTeX] |
1971 | Industrial & Engineering Chemistry Process Design and Development Vol. 10(4), pp. 425-431 |
article | DOI URL |
BibTeX:
@article{Johnson1971,
author = {Johnson, J. L. and Fan, L. T. and Wu, Y. S.},
title = {Comparison of Moments, S-Plane, and Frequency Response Methods for Analyzing Pulse Testing Data from Flow Systems},
journal = {Industrial & Engineering Chemistry Process Design and Development},
publisher = {American Chemical Society},
year = {1971},
volume = {10},
number = {4},
pages = {425--431},
url = {http://dx.doi.org/10.1021/i260040a001},
doi = {http://dx.doi.org/10.1021/i260040a001}
}
|
|||||
| Jones, A. and Smart, P. | Spatial and temporal changes in the structure of groundwater nitrate concentration time series (1935–1999) as demonstrated by autoregressive modelling | 2005 | Journal of Hydrology Vol. 310(1-4), pp. 201-215 |
article | URL |
| Abstract: Autoregressive modelling is used to investigate the internal structure of long-term (1935–1999) records of nitrate concentration for five karst springs in the Mendip Hills. There is a significant short term (1–2 months) positive autocorrelation at three of the five springs due to the availability of sufficient nitrate within the soil store to maintain concentrations in winter recharge for several months. The absence of short term (1–2 months) positive autocorrelation in the other two springs is due to the marked contrast in land use between the limestone and swallet parts of the catchment, rapid concentrated recharge from the latter causing short term switching in the dominant water source at the spring and thus fluctuating nitrate concentrations. Significant negative autocorrelation is evident at lags varying from 4 to 7 months through to 14–22 months for individual springs, with positive autocorrelation at 19–20 months at one site. This variable timing is explained by moderation of the exhaustion effect in the soil by groundwater storage, which gives longer residence times in large catchments and those with a dominance of diffuse flow. The lags derived from autoregressive modelling may therefore provide an indication of average groundwater residence times. Significant differences in the structure of the autocorrelation function for successive 10-year periods are evident at Cheddar Spring, and are explained by the effect the ploughing up of grasslands during the Second World War and increased fertiliser usage on available nitrogen in the soil store. This effect is moderated by the influence of summer temperatures on rates of mineralization, and of both summer and winter rainfall on the timing and magnitude of nitrate leaching. The pattern of nitrate leaching also appears to have been perturbed by the 1976 drought. | |||||
BibTeX:
@article{Jones2005,
author = {Jones, A.L. and Smart, P.L.},
title = {Spatial and temporal changes in the structure of groundwater nitrate concentration time series (1935–1999) as demonstrated by autoregressive modelling},
journal = {Journal of Hydrology},
year = {2005},
volume = {310},
number = {1-4},
pages = {201--215},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405000041}
}
|
|||||
| Joodi, A., Sizaret, S., Binet, S., Bruand, A., Alberic, P. and Lepiller, M. | Development of a Darcy-Brinkman model to simulate water flow and tracer transport in a heterogeneous karstic aquifer (Val d’Orléans, France) | 2010 | Hydrogeology Journal Vol. 18(2), pp. 295-309 |
article | URL |
| Abstract: Darcy’s law is the equation of reference widely used to model aquifer flows. However, its use to model karstic aquifers functioning with large pores is problematic. The physics occurring within the karstic conduits requires the use of a more representative macroscopic equation. A hydrodynamic model is presented which is adapted to the karstic aquifer of the Val d’Orléans (France) using two flow equations: (1) Darcy’s law, used to describe water flow within the massive limestone, and (2) the Brinkman equation, used to model water flow within the conduits. The flow equations coupled with the transport equation allow the prediction of the karst transfer properties. The model was tested by using six dye tracer tests and compared to a model that uses Darcy’s law to describe the flow in karstic conduits. The simulations show that the conduit permeability ranges from 5 × 10 −6 to 5.5 × 10 −5 m 2 and the limestone permeability ranges from 8 × 10 −11 to 6 × 10 −10 m 2 . The dispersivity coefficient ranges from 23 to 53 m in the conduits and from 1 to 5 m in the limestone. The results of the simulations carried out using Darcy’s law in the conduits show that the dispersion towards the fractures is underestimated. | |||||
BibTeX:
@article{Joodi2010,
author = {Joodi, Ali and Sizaret, Stanislas and Binet, Stéphane and Bruand, Ary and Alberic, Patrick and Lepiller, Michel},
title = {Development of a Darcy-Brinkman model to simulate water flow and tracer transport in a heterogeneous karstic aquifer (Val d’Orléans, France)},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2010},
volume = {18},
number = {2},
pages = {295--309},
url = {http://dx.doi.org/10.1007/s10040-009-0536-x}
}
|
|||||
| Jukić, D. and Denić-Jukić, V. | Groundwater balance estimation in karst by using a conceptual rainfall–runoff model | 2009 | Journal of Hydrology Vol. 373(3-4), pp. 302-315 |
article | URL |
| Abstract: A conceptual rainfall–runoff model is proposed for the estimation of groundwater balance components including the influences of time-variant catchment boundaries and intercatchment groundwater flows. Karst underground is considered as a lumped system that contains: (1) soil cover, (2) epikarst zone and (3) vadose and phreatic zones. The soil cover receives an average rainfall in catchment as the input into the system. The epikarst zone is composed of a production store and a routing store. The production store contributes to the loss of water in process of evapotranspiration. The routing store contributes to the retention of percolated water and the lateral distribution of groundwater recharge between internal runoff and diffuse infiltration. The vadose and phreatic zones accumulate groundwater in fissures, fractures and vertical shafts, and produce the vadose seepage, vadose flow and shaft flow components of the karst spring discharge. The parameter estimation and calculation procedure assemble the moisture balance and the groundwater-balance approaches. The rainfall–runoff model is divided in two sub-models. The sub-model based on the moisture balance of soil cover and epikarst production store calculates effective rainfalls. The sub-model based on the groundwater balance of vadose and phreatic zone calculates groundwater recharges. The difference between the effective rainfalls and the groundwater recharges represents the contribution of epikarst zone and non-conservative and time-variant components to the groundwater balance. The proposed methodology is applied to the Jadro Spring located near the city of Split in Croatia. The calculated groundwater balance shows that the Jadro Spring aquifer contains a significant storage capacity in the vadose and phreatic zones. During the year, the aquifer may accumulate up to 140 millions m3. The variability of calculated catchment area is explained with the time-variant catchment boundary dependent on groundwater levels and the intercatchment groundwater flows from neighboring catchments. The average catchment area of 396 km2 is estimated by using the average monthly effective rainfalls and the average monthly groundwater recharges. | |||||
BibTeX:
@article{Jukic2009,
author = {Jukić, Damir and Denić-Jukić, Vesna},
title = {Groundwater balance estimation in karst by using a conceptual rainfall–runoff model},
journal = {Journal of Hydrology},
year = {2009},
volume = {373},
number = {3-4},
pages = {302--315},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409002868}
}
|
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| Jukić, D. and Denić-Jukić, V. | Nonlinear kernel functions for karst aquifers | 2006 | Journal of Hydrology Vol. 328(1-2)Measurement and Parameterization of Rainfall Microstructure, pp. 360-374 |
article | URL |
| Abstract: This paper presents a form of kernel function for karst aquifers derived from the time-invariant and non-anticipatory Volterra series. The shape of the kernel function depends on the current value of an index of antecedent recharge that is considered as an indicator of groundwater levels and vadose zone saturation. The proposed nonlinear form preserves specific characteristics of instantaneous unit hydrographs. By using analogies with the conceptual model of nonlinear reservoir, it is shown that the second component of the kernel function characterizes the prevailing type of groundwater flow. If the second component is positive, the free-surface flow is dominant, whereas the negative value indicates that the flow under pressure prevails. Groundwater recharge rates are calculated by using a groundwater recharge model based on the Palmer’s soil-moisture balance method. The values of parameters of the groundwater recharge model are estimated by the spectral method which is modified to avoid the assumption about exponential forms of autocorrelation functions of input and output time series. This paper analyzes also the practical applicability of nonlinear kernels for the preliminary characterization of karst aquifers and the karst springs discharge modeling. The results of applications on the springs zones of the rivers Krka and Krčić are in accordance with previous assumptions that the Main Krka Spring is an ascending karst spring which aquifer is situated deeply inside the karst underground, whereas the Main Krčić Spring function as a descending karst spring. | |||||
BibTeX:
@article{Jukic2006,
author = {Jukić, Damir and Denić-Jukić, Vesna},
title = {Nonlinear kernel functions for karst aquifers},
booktitle = {Measurement and Parameterization of Rainfall Microstructure},
journal = {Journal of Hydrology},
year = {2006},
volume = {328},
number = {1-2},
pages = {360--374},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406000114}
}
|
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| Jukić, D. and Denić-Jukić, V. | A frequency domain approach to groundwater recharge estimation in karst | 2004 | Journal of Hydrology Vol. 289(1-4), pp. 95-110 |
article | URL |
| Abstract: This paper presents an alternative method for determining the values of parameters of a groundwater recharge model. The phreatic zone of a karst aquifer is considered as the linear and time-invariant filter that transforms the input signal of groundwater recharge rates into the output signal of spring discharges. Similarities between transfer functions of total rainfall rates and transfer functions of groundwater recharge rates are the basis for developing the parametric periodogram depending on parameters of a groundwater recharge model. The values of parameters are estimated by minimizing the differences between the parametric periodogram and a periodogram of spring discharges. The approximate Whittle log likelihood function is the criterion for determining the optimal values of the parameters. By using this frequency domain approach, groundwater-balance calculations are avoided so the method can be applied on unexplored karst aquifers when groundwater-balance cannot be achieved without extensive geologic and hydrogeologic investigations. The results of the applications on two springs located in the Dinaric karst area in Croatia are discussed. | |||||
BibTeX:
@article{Jukic2004,
author = {Jukić, Damir and Denić-Jukić, Vesna},
title = {A frequency domain approach to groundwater recharge estimation in karst},
journal = {Journal of Hydrology},
year = {2004},
volume = {289},
number = {1-4},
pages = {95--110},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403004517}
}
|
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| K., M. | The role of fluid residence time and topographic scales in determining chemical fluxes from landscapes | 2011 | Earth and Planetary Science Letters Vol. 312(1-2), pp. 48-58 |
article | URL |
| Abstract: The role of fluid residence time and catchment length scales in controlling the chemical composition of rivers is evaluated by comparing numerical simulations and scaling arguments to concentration–discharge data from small catchments. The analysis suggests that poorly-crystalline aluminosilicates are an important control on the composition of stream waters and therefore chemical equilibrium between the dissolving and precipitating phases determines the maximum concentration and the maximum silicate weathering flux. The modeling results suggest that the residence time of fluid relative to the residence time required to approach chemical equilibrium can be used to assess the controls on solute fluxes in small catchments, and possibly larger rivers. Catchments that show little variability in concentration with discharge (or “chemostatic behavior”) likely have average fluid residence times that exceed the time required to reach chemical equilibrium. Conversely, decreases in concentration with increasing discharge are explained by average residence times shorter than required to approach chemical equilibrium, resulting in dilution. Solute fluxes are also strongly impacted by the distribution of fluid residence times in a basin. The fluid residence time model provides an alternative framework for assessing both the relationship between discharge and concentration observed for individual catchments, and controls on the solute fluxes of rivers. If fluid residence times are a dominant control on weathering fluxes, the chemistry of different rivers could vary entirely as a function of the nature subsurface flow paths and the composition of the system at equilibrium, which is complex to predict and strongly coupled to biological processes, temperature and the composition of the system. As a result of thermodynamic and hydrologic restrictions on the amount of weathering, global solute fluxes may depend more strongly on the geometry, relief, runoff and permeability of basins then on temperature and rates of erosion. | |||||
BibTeX:
@article{K.2011,
author = {K., Maher},
title = {The role of fluid residence time and topographic scales in determining chemical fluxes from landscapes},
journal = {Earth and Planetary Science Letters},
year = {2011},
volume = {312},
number = {1-2},
pages = {48--58},
url = {http://www.sciencedirect.com/science/article/pii/S0012821X11005607}
}
|
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| Kaboudan, M. | Genetically evolved models and normality of their fitted residuals | 2001 | Journal of Economic Dynamics and Control Vol. 25(11), pp. 1719-1749 |
article | URL |
| Abstract: This paper evaluates performance of genetically evolved models. GPQuick, a genetic programming software written in C++, is used to evolve best-fit regression models for simulated and real world data. Simulated data are twelve time series with different but known dynamical structures. Predicted values from best models are compared with originally simulated data and the residuals are statistically evaluated. The results suggest that genetic programming approximates less complex and less noisy data better than it does more complex and noisy data. GPQuick is then used to evolve models of real world data extracted from Canadian lynx and sunspot numbers. | |||||
BibTeX:
@article{Kaboudan2001,
author = {Kaboudan, M.A.},
title = {Genetically evolved models and normality of their fitted residuals},
journal = {Journal of Economic Dynamics and Control},
year = {2001},
volume = {25},
number = {11},
pages = {1719--1749},
url = {http://www.sciencedirect.com/science/article/pii/S016518890000004X}
}
|
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| Kadalbajoo, M.K. and Gupta, V. | A brief survey on numerical methods for solving singularly perturbed problems | 2010 | Applied Mathematics and Computation Vol. 217(8), pp. 3641-3716 |
article | URL |
| Abstract: In the present paper, a brief survey on computational techniques for the different classes of singularly perturbed problems is given. This survey is a continuation of work performed earlier by the first author and contains the literature of the work done by the researchers during the years 2000–2009. However some older important relevant papers are also included in this survey. We also mentioned those papers which are not surveyed in the previous survey papers by the first author of this paper, see [Appl. Math. Comput. 30 (1989) 223–259, 130 (2002) 457–510, 134 (2003) 371–429] for details. Thus this survey paper contains a surprisingly large amount of literature on singularly perturbed problems and indeed can serve as an introduction to some of the ideas and methods for the singular perturbation problems. | |||||
BibTeX:
@article{Kadalbajoo2010,
author = {Kadalbajoo, Mohan K. and Gupta, Vikas},
title = {A brief survey on numerical methods for solving singularly perturbed problems},
journal = {Applied Mathematics and Computation},
year = {2010},
volume = {217},
number = {8},
pages = {3641--3716},
url = {http://www.sciencedirect.com/science/article/pii/S0096300310010532}
}
|
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| Kadlec, R. | Comparison of free water and horizontal subsurface treatment wetlands | 2009 | Ecological Engineering Vol. 35(2)Pollution control by wetlands, pp. 159-174 |
article | URL |
| Abstract: The two most prevalent types of treatment wetland, especially during the early history of the technology, are free water surface (FWS) and horizontal subsurface flow (HSSF) wetlands. The several factors involved in the choice of which alternative to choose include size, cost, operability, together with health and nuisance issues and ancillary benefits. Contaminant removal performance differs by constituent, with the advantage to FWS for moderate to high biochemical oxygen demand (BOD), TSS, ammonia, total nitrogen and phosphorus. HSSF are more effective for tertiary BOD levels, nitrate and pathogens. Superpositions of the loading data show that the respective data clouds overlap virtually entirely for HSSF and FWS wetlands. There is little or no performance difference when they are compared on this areal basis. In general, there is little or no advantage of HSSF for space saving. In cold climates, HSSF systems are less cold sensitive, and easier to insulate for winter operation. The use of winter storage enables FWS to be used in freezing conditions, but the cost makes that option comparable to the more expensive HSSF. In general, economics do not favor the choice of HSSF wetlands. Factors other than reduction performance are also important in the selection process. Other principal reasons for selecting the HSSF option over the FWS option are prevention of human health contact problems, mosquito control and minimization of wildlife interactions. | |||||
BibTeX:
@article{Kadlec2009,
author = {Kadlec, R.H.},
title = {Comparison of free water and horizontal subsurface treatment wetlands},
booktitle = {Pollution control by wetlands},
journal = {Ecological Engineering},
year = {2009},
volume = {35},
number = {2},
pages = {159--174},
url = {http://www.sciencedirect.com/science/article/pii/S0925857408000840}
}
|
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| Kadlec, R. | The effects of wetland vegetation and morphology on nitrogen processing | 2008 | Ecological Engineering Vol. 33(2), pp. 126-141 |
article | URL |
| Abstract: This paper reports data and models for nitrogen processing for the demonstration-scale Tres Rios, Arizona, wetlands. Four field-scale wetlands of approximately 1 ha each were operated under varying conditions at a site west of the City of Phoenix. The water supply was partially nitrified effluent from a City wastewater treatment plant. Total nitrogen was reduced by about 60%, from an inflow concentration between 6 mg/L and 8 mg/L. Speciation of the inflow was approximately 25% organic nitrogen, 25% ammonium nitrogen and 50% nitrate nitrogen. Typical outflow concentrations were about 1.2 mg/L organic, 0.5 mg/L ammonium, and 0.0–2.5 mg/L nitrate. Two wetlands were reconfigured with channelization parallel to flow, and the other two lost vegetation. This paper compares the before and after performance for both changes. Rate constants for nitrate and total nitrogen were decreased by the changes. For loss of vegetation, nitrate k20-values decreased from 76 m/yr to 23 m/yr, and total nitrogen k20-values decreased from 54 m/yr to 11 m/yr. For reconfiguration, nitrate k20-values decreased from 83 m/yr to 47 m/yr, and total nitrogen k20-values decreased from 49 m/yr to 32 m/yr. Rate constants were found to be temperature sensitive. It is concluded that the reconfiguration and loss of vegetation both markedly lessened the ability of the wetlands to process nitrogen. Further, reconfiguration was ineffective for mosquito control. | |||||
BibTeX:
@article{Kadlec2008,
author = {Kadlec, R.H.},
title = {The effects of wetland vegetation and morphology on nitrogen processing},
journal = {Ecological Engineering},
year = {2008},
volume = {33},
number = {2},
pages = {126--141},
url = {http://www.sciencedirect.com/science/article/pii/S0925857408000463}
}
|
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| Kadlec, R.H. | Nitrate dynamics in event-driven wetlands | 2010 | Ecological Engineering Vol. 36(4), pp. 503-516 |
article | URL |
| Abstract: The dynamics nitrate retention and export were studied at the Des Plaines River wetland demonstration site. Seven wetlands received pulses of river water in discrete pumping events. Twenty-eight wetland events were monitored over 4 years for all hydrologic variables, pumping, rain, storage change, and outflow. Nitrate was measured at high frequency for the ouflows, and at lower frequency for inflows and interior stations. Most events were isolated in time, with sufficient inter-event spacing to allow complete equilibration before the subsequent event. Pumping was selected to provide up to 45 displacements of the wetland water volume. River water averaged 2.3 mg/L of nitrate nitrogen, and wetland effluent averaged 0.9 mg/L. The average mass removal of nitrate was 67% over all events, with a range from 17% to 100%. A calibrated dynamic water mass balance was developed as the framework for interpreting results. Internal hydraulics were characterized by tanks-in-series (TIS) models calibrated to tracer studies. Residence time distributions were describable by three TIS (three wetlands) and five TIS (four wetlands). Dynamic nitrate mass balances were used, in conjunction with a first order areal uptake model, to model the time sequence of NO3N concentrations and flows. Parameter estimation, based on NO3N mass flow fitting, produced rate constants that best described the series of events the wetlands. Rate constants were much higher for the events than for previous steady state performance for the wetlands (k20 = 107 vs. 37 m/yr). Rate coefficients increased at higher water temperatures, with a modified Arrhenius temperature factor of 1.090. Performance for N removal was found to be partially due to displacement of antecedent treated water, and partially due to treatment occurring during the event, and partially due to treatment after the event. Carbon availability was estimated not to limit denitrification, except possibly at the highest nitrate loadings. | |||||
BibTeX:
@article{Kadlec2010c,
author = {Kadlec, Robert H.},
title = {Nitrate dynamics in event-driven wetlands},
journal = {Ecological Engineering},
year = {2010},
volume = {36},
number = {4},
pages = {503--516},
url = {http://www.sciencedirect.com/science/article/pii/S0925857409003218}
}
|
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| Kadlec, R.H. | Wastewater treatment at the Houghton lake wetland: Soils and sediments | 2009 | Ecological Engineering Vol. 35(9)The Houghton Lake wetland treatment project, pp. 1333-1348 |
article | URL |
| Abstract: This paper describes the sediment and soils responses in a very long-running study of the capacity of a natural peatland to remove nutrients from treated wastewater. Data are here presented and analyzed from three decades of full-scale operation (1978–2007), during which large changes in the wetland soils occurred. An average of 600,000 m3 y−1 of treated water was discharged each warm season to the Porter Ranch peatland near the community of Houghton Lake, Michigan. This discharge was seasonal, commencing no sooner than May 1 and ending no later than October 31. During the winter half-year, treated wastewater was stored at the lagoon site. This water contained 3.5 mg/L of total phosphorus, and 7 mg/L of dissolved inorganic nitrogen. Nutrients were stored in the 100 ha irrigation area, which removed 94% of the phosphorus (53 t) and 95% of the dissolved inorganic nitrogen. Phosphorus was stored in new biomass, increased soil sorption, and accretion of new soils and sediments, with accretion being dominant. Peat probings, water level increases and topographical surveys established quantitative measures of soil accretion. Over 30 cm of new soil developed, in which nutrient storage occurred. Phosphorus concentrations in the new soil were approximately 2000 mg P/kg, and the nitrogen concentration was 2–3%DW. The removal of TSS was effective, but minor in comparison to the internal generation and cycling of produced particulates. Later in the project history, the interior portion of impacted area became a floating mat. Sedimentation processes then occurred with no exposure to above-mat detrital processes. Trace element analyses showed no appreciable accumulation of heavy metals, other than the calcium and iron that characterized the antecedent wetland and the incoming water. Biomass cycling models were found to produce reasonable estimates of the measured nutrient accumulations. The light loadings of nutrients to this system produced dramatic effects in the ecosystem, but were lower than the range seen in some other treatment wetlands. Insufficient nitrogen was added to support the new biomass, and nitrogen fixation was identified as a possible compensatory mechanism. | |||||
BibTeX:
@article{Kadlec2009a,
author = {Kadlec, Robert H.},
title = {Wastewater treatment at the Houghton lake wetland: Soils and sediments},
booktitle = {The Houghton Lake wetland treatment project},
journal = {Ecological Engineering},
year = {2009},
volume = {35},
number = {9},
pages = {1333--1348},
url = {http://www.sciencedirect.com/science/article/pii/S0925857409000640}
}
|
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| Kadlec, R.H. | Free surface wetlands for phosphorus removal: The position of the Everglades Nutrient Removal Project | 2006 | Ecological Engineering Vol. 27(4)The Everglades Nutrient Removal Project, pp. 361-379 |
article | URL |
| Abstract: The Everglades Nutrient Removal Project (ENRP) was one of the largest treatment wetlands ever built. In North America, it has been exceeded only by the Stormwater Treatment Areas, the designs for which it was developed to support. The five cells of the ENRP contained varying mixtures of submerged, emergent and floating vegetation, and produced concomitantly variable phosphorus (P) removal. The range of first–order settling rates for total P (TP) removal was from 12 to 73 m/year for the individual cells, compared to a range of 13–23 m/year for Boney Marsh, Water Conservation Area 2A, and Orlando Easterly Wetlands. The mean TP settling rate in the ENRP of 23 m/year compares well to a mean of 16 m/year for 77 other wetland systems. No seasonal trends were detected in the ENRP, but there was ±50% variability for outlet TP concentrations. The ENRP operated at the low end of the spectrum of P concentrations and loadings for treatment marshes in general, with a mean inlet TP of about 100 μg P/L, while producing 21 μg P/L in the effluent over a 6-year period of record. Consequently, vegetation density and P content were low compared to other wetland systems. The biogeochemical cycle in the ENRP resulted in accreting residuals that had about 1000 mg P/kg dry weight. The project was built economically, but large sums were spent on research. The regulatory concept of a TP 12-month rolling average was initiated for the first time. The project fulfilled its goal of confirming and refining the information from earlier prototype systems. In turn, much of the ENRP design has been replicated in the full-scale STAs, with moderate success. | |||||
BibTeX:
@article{Kadlec2006,
author = {Kadlec, Robert H.},
title = {Free surface wetlands for phosphorus removal: The position of the Everglades Nutrient Removal Project},
booktitle = {The Everglades Nutrient Removal Project},
journal = {Ecological Engineering},
year = {2006},
volume = {27},
number = {4},
pages = {361--379},
url = {http://www.sciencedirect.com/science/article/pii/S0925857406001030}
}
|
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| Kadlec, R.H. | Water temperature and evapotranspiration in surface flow wetlands in hot arid climate | 2006 | Ecological Engineering Vol. 26(4), pp. 328-340 |
article | URL |
| Abstract: This paper reports data and models for temperatures and energy flows for the Tres Rios surface flow wetlands. Treatment wetlands are solar powered ecosystems, resulting in annually cyclic temperatures. There is also a daily cycle in wetland water temperature of several degrees amplitude. The timing of individual daily measurements may therefore bias the result to values different from the daily mean. The energy balance is dominated by radiation to and from the wetland, heat transfer from air, and evaporative losses. Transpiration causes energy dissipation from the canopy, while evaporation causes energy loss from and cooling of the surface water. Transpiration was found to dominate the water loss. Downstream daily average water temperatures are cooler than daily average air temperatures at all times of the year, due to evaporative cooling. Water cools as it passes from inlet to outlet. The excess sensible heat is dissipated during travel through the inlet region of the wetland. For long detention times, longer than about five days, water temperature reaches a balance condition. Up to that time, sensible heat from the source water also influences evaporation and water temperature. Balance water temperatures ranged from 3.9 °C in winter to 27.2 °C in summer, while mean daily air temperatures ranged from 5.3 to 37.2 °C. Diel variations were found to range up to 6 °C. Stochastic variability produced a band width of ±5 °C. Energy balance models provide a good representation of these phenomena, but are subject to large sensitivity to input variables, especially air temperature, humidity and wind. Evapotranspiration was higher than that predicted for a balance condition, because of the warmth of the incoming water. It was less than that predicted for a grass crop. | |||||
BibTeX:
@article{Kadlec2006a,
author = {Kadlec, Robert H.},
title = {Water temperature and evapotranspiration in surface flow wetlands in hot arid climate},
journal = {Ecological Engineering},
year = {2006},
volume = {26},
number = {4},
pages = {328--340},
url = {http://www.sciencedirect.com/science/article/pii/S092585740600022X}
}
|
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| Kadlec, R.H. | Effects of pollutant speciation in treatment wetlands design | 2003 | Ecological Engineering Vol. 20(1), pp. 1-16 |
article | URL |
| Abstract: This paper reports on observed and potential effects of distributions of detention times and first order removal rate constants. Rate constants are distributed across the species that make up a grouped class of contaminants, such as total suspended solids (TSS) and biochemical oxygen demand (BOD). The existence of these distributions is shown to invalidate the plug flow (PF) model assumption in almost all cases. The tanks-in-series (TIS) model is shown to offer a better platform to accommodate distributed parameters. Detention time distributions (DTDs) and k-value distributions (kVDs) are shown to both lead to TIS models. Discrete, uniform and gamma distributions for detention and k-values are explored. The greater the variance, the more important the impacts on performance modeling. Data for the reduction of TSS are analyzed from the perspective of particle size distributions, and shown to result in the appearance of TIS behavior for the lumped TSS measure. The retarded rate constant concept is shown to be subsumed by the idea of a weathering mixture with a distribution of rate constants. | |||||
BibTeX:
@article{Kadlec2003,
author = {Kadlec, Robert H},
title = {Effects of pollutant speciation in treatment wetlands design},
journal = {Ecological Engineering},
year = {2003},
volume = {20},
number = {1},
pages = {1--16},
url = {http://www.sciencedirect.com/science/article/pii/S0925857402001180}
}
|
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| Kadlec, R.H. | The inadequacy of first-order treatment wetland models | 2000 | Ecological Engineering Vol. 15(1–2), pp. 105-119 |
article | URL |
| Abstract: First-order models are in common use for design of treatment wetlands. These are frequently based on input/output (I/O) data; less frequently, on internal longitudinal transect data. The presumption is often made that the parameters of these models, i.e. the rate constants, are true constants and do not depend on factors such as hydraulic loading rate and inlet concentration. Another common presumption is that plug flow is a reasonable approximation to the hydraulic conditions in the wetland. This paper assembles a test wetland simulation, based on known information about vegetation resistance, treatment effects of vegetation, and residence time distributions. The test wetland is then used to provide simulations of different experimental and design protocols, such as transect measurements and I/O data from parallel and sequential detention time studies. Those simulations are shown to be consistent with real system data, thus confirming the data foundation of the test wetland behavior. The test wetland results, in common with the observations for nearly all treatment wetlands, show declining concentrations that approach a plateau at long detention times. The synthetic ‘data’ so produced is free from the stochastic vagaries of real wetlands, and thus provides a platform for understanding the deterministic component of behavior. The several variations of the plug flow model were then fit to the ‘data’, with generally excellent correlation coefficients (R2>0.95). However, the parameters (rate constants and apparent background concentrations) were found to be very strong functions of hydraulic loading and inlet concentration. This variability renders the models incapable of acceptable performance in design. Addition of a third parameter, such as a dispersion number, does not solve the inherent problems; nor does the retreat to loading regressions. It is suggested that new paradigms are needed that incorporate the ability to describe short-circuiting and spatial distributions of vegetation. | |||||
BibTeX:
@article{Kadlec2000,
author = {Kadlec, Robert H.},
title = {The inadequacy of first-order treatment wetland models},
journal = {Ecological Engineering},
year = {2000},
volume = {15},
number = {1–2},
pages = {105--119},
url = {http://www.sciencedirect.com/science/article/pii/S0925857499000397}
}
|
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| Kadlec, R.H. | An autobiotic wetland phosphorus model | 1997 | Ecological Engineering Vol. 8(2), pp. 145-172 |
article | URL |
| Abstract: Constructed and natural wetlands are capable of absorbing new phosphorus loadings, and in appropriate circumstances can provide a low cost alternative to chemical and biological treatment. Phosphorus (P) interacts strongly with wetland soils and biota, which provide both short term and sustainable long term storage of this nutrient. Soil sorption may provide initial removal, but this partly reversible storage eventually becomes saturated. Uptake by biota, including bacteria, algae, and duckweed, as well as macrophytes, forms an initial removal mechanism. Cycling through growth, death and decomposition returns most of the biotic uptake, but an important residual contributes to long term accretion in newly formed sediments and soils. Despite the apparent complexity of these several removal mechanisms, data analysis shows that relatively simple equations can describe the sustainable processes. Previous global first order removal rates characterize the sustainable removal, but do not incorporate any biotic features. This paper presents an autobiotic model, based upon cycling through the biomass compartments, and calibrates it to data from 17 years of operation of the Houghton Lake, MI treatment wetland. This model replaces a first order concentration-based rate with a first order biomass-based rate. When coupled with mass balances, it describes the spatial distribution of both biomass and P concentrations, as well as the evolution of the new standing crop. | |||||
BibTeX:
@article{Kadlec1997,
author = {Kadlec, Robert H.},
title = {An autobiotic wetland phosphorus model},
journal = {Ecological Engineering},
year = {1997},
volume = {8},
number = {2},
pages = {145--172},
url = {http://www.sciencedirect.com/science/article/pii/S0925857497002577}
}
|
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| Kadlec, R.H. | Overview: Surface Flow Constructed Wetlands | 1995 | Water Science and Technology Vol. 32(3), pp. 1-12 |
article | URL |
| Abstract: Several hundreds of marshes have now been built primarily for the purposes of water quality improvement. This paper reviews statistics on the types and numbers and character of these low-tech water treatment wetlands. The operational processes are discussed, including sedimentation, plant uptake, sorption, nutrient cycling, and chemical and microbial conversion. Performance has been good for reduction of suspended solids, biological oxygen demand, phosphorus, nitrogen, metals and some anthropogenic chemicals. Design procedures are evaluated, showing that the overly simplistic techniques used in the infancy of the technology may now be replaced by rational procedures based on the large and rapidly growing information base for constructed surface flow treatment wetlands. Ancillary wildlife and human use is an important part of this type of wetland, and should be acknowledged in design. Capital costs are low, but the principal financial advantage is the extremely low base cost of operation. | |||||
BibTeX:
@article{Kadlec1995,
author = {Kadlec, Robert H.},
title = {Overview: Surface Flow Constructed Wetlands},
journal = {Water Science and Technology},
year = {1995},
volume = {32},
number = {3},
pages = {1--12},
url = {http://www.iwaponline.com/wst/03203/wst032030001.htm}
}
|
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| Kadlec, R.H., Bays, J.S., Mokry, L.E., Andrews, D. and Ernst, M.R. | Performance analysis of the Richland-Chambers treatment wetlands | 2011 | Ecological Engineering Vol. 37(2), pp. 176-190 |
article | URL |
| Abstract: The Tarrant Regional Water District (TRWD) is supplementing the flows to Richland-Chambers Reservoir, to meet future water supply needs of Dallas-Ft. Worth, TX. The Trinity River is the new source, but quality is not adequate. TRWD has constructed and investigated treatment wetland facilities located near the reservoir to upgrade river water quality, from an eight-year study at a 0.72 ha pilot site, and a five-year study at a 102 ha field-scale site. Both systems had a sedimentation basin followed by wetland cells in series. The pilot had two basins feeding three trains of three wetland cells each, while the field-scale system had one basin followed by four wetland cells in series. Water depths were about 30 cm for the pilot, and 40 cm for the field-scale. Design nominal detention times were roughly 5 and 9 days for pilot basins and wetland trains; and 1.5 and 8 days for the field-scale. The systems ran year-round, supplied with water pumped from the river, which at times was predominantly treated wastewater from the Dallas-Fort Worth metroplex. The primary target contaminants were suspended solids, nitrogen, and phosphorus. Nitrogen forms in pumped flows from the river were dominated by oxidized nitrogen, which was mostly nitrate nitrogen. Pilot nitrate removal from the river water was 92%, and 61% for phosphorus, while sediment removal was 97%. Field-scale nitrate removal from the river water was 77%, and 45% for phosphorus, while sediment removal was 96%. The field-scale project is located on land owned by the Texas Parks and Wildlife Department, and they participate in management of the wetlands for the secondary purpose of wildlife habitat. | |||||
BibTeX:
@article{Kadlec2011,
author = {Kadlec, Robert H. and Bays, James S. and Mokry, Loretta E. and Andrews, Darrel and Ernst, Mark R.},
title = {Performance analysis of the Richland-Chambers treatment wetlands},
journal = {Ecological Engineering},
year = {2011},
volume = {37},
number = {2},
pages = {176--190},
url = {http://www.sciencedirect.com/science/article/pii/S0925857410002697}
}
|
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| Kadlec, R.H. and Bevis, F.B. | Wastewater treatment at the Houghton Lake wetland: Vegetation response | 2009 | Ecological Engineering Vol. 35(9)The Houghton Lake wetland treatment project, pp. 1312-1332 |
article | URL |
| Abstract: This paper describes the vegetation responses in a very long-running study of the capacity of a natural peatland to remove nutrients from treated wastewater. Data are here presented and analyzed from three decades of full-scale operation, during which large changes in the plant communities occurred. An average of 600,000 m3 year−1 of treated wastewater was discharged seasonally (May 1–October 31) to the Porter Ranch peatland near the community of Houghton Lake, Michigan. This discharge was seasonal, commencing no sooner than May 1 and ending no later than October 31. During the winter half-year, treated wastewater was stored at the lagoon site. This water contained 3.5 mg/L of total phosphorus, and 7 mg/L of dissolved inorganic nitrogen (DIN). Nutrients were stored in the 100 ha irrigation area, which removed 94% of the phosphorus (53 metric tons) and 95% of the dissolved inorganic nitrogen. Phosphorus was stored in new biomass, increased soil sorption, and accretion of new soils and sediments, with accretion being dominant. The irrigation area underwent large changes in ecosystem structure, in which the original plant communities were displaced by Typha spp. There was an initial fertilizer response, characterized by much larger standing crops of vegetation, at about triple the crop in control areas. Increased biomass was accompanied by increases in tissue nitrogen and phosphorus content, by factors of two and three, respectively. The plant community shift, from the initial sedge-willow and leatherleaf-bog birch cover types to a cattail-dominant cover type, progressed to a 83-ha area over the 30-year period of record (POR). The interior portion of this new cattail patch became a floating mat. There were large gradients in stem densities and stem heights within the impacted area. The response times of the vegetative community shifts were on the order of 10 years for 63% of the final impact zone development. The grow-in time for development of a new larger standing crop in the discharge zone was also 10 years. The impacted area was stable at the 30-year time, without any further moving fronts. Around the cattail zone, there were fringe areas that contained a mixture of the original cover types intruded by relatively small amounts of cattail. | |||||
BibTeX:
@article{Kadlec2009d,
author = {Kadlec, Robert H. and Bevis, Frederick B.},
title = {Wastewater treatment at the Houghton Lake wetland: Vegetation response},
booktitle = {The Houghton Lake wetland treatment project},
journal = {Ecological Engineering},
year = {2009},
volume = {35},
number = {9},
pages = {1312--1332},
url = {http://www.sciencedirect.com/science/article/pii/S0925857408002656}
}
|
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| Kadlec, R.H., Cuvellier, C. and Stober, T. | Performance of the Columbia, Missouri, treatment wetland | 2010 | Ecological Engineering Vol. 36(5)Carbon, nutrient and metal retention in wetlands in a restoration context, pp. 672-684 |
article | URL |
| Abstract: Constructed treatment wetlands have served the City of Columbia, MO, for fourteen years. Four free water surface wetland units in series, comprised of 23 cells, are an addition to the activated sludge wastewater treatment plant, for the purpose of added biochemical oxygen demand (BOD) and total suspended solids (TSS) control. The system operates year-round, and supplies water to the Eagle Bluffs Conservation Area for wetland maintenance. The cattail wetlands processed an average of 57,000 m3/d, at a water depth of 20 cm. The resulting detention time was approximately 2 days, and the hydraulic loading was 13 cm/d. Water temperatures were warm leaving the treatment plant and in the wetlands in winter, because of the short detention. The period of record average carbonaceous biochemical oxygen demand (CBOD) leaving the wetlands was 5.0 mg/L, and the TSS was 14.7 mg/L. Dissolved oxygen was depressed in summer, likely because of the high sediment demand. Nutrient concentrations were only minimally reduced, total nitrogen (TN) by 22% and total phosphorus (TP) by 6%. However, load reductions were maximal, 98 t/yr for nitrogen, and 3.6 t/yr for phosphorus. Fecal coliforms were reduced by 98%, and E. coli by 95%. First order rate coefficients were high for CBOD (64 m/yr), nitrate (61 m/yr) and organic nitrogen (42 m/yr), but relatively low for ammonia (8 m/yr) and phosphorus (5.7 m/yr). Nitrogen removal was strongly affected by vegetative uptake. Sediment accretion in the wetland inlets was substantial, at 1.6 cm/yr in the inlets to the upstream wetland units. Muskrats caused vegetation damage, and waterfowl use was high in winter, causing TSS excursions. | |||||
BibTeX:
@article{Kadlec2010b,
author = {Kadlec, Robert H. and Cuvellier, Craig and Stober, Trent},
title = {Performance of the Columbia, Missouri, treatment wetland},
booktitle = {Carbon, nutrient and metal retention in wetlands in a restoration context},
journal = {Ecological Engineering},
year = {2010},
volume = {36},
number = {5},
pages = {672--684},
url = {http://www.sciencedirect.com/science/article/pii/S0925857409003553}
}
|
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| Kadlec, R.H., Martin, D.C. and Tsao, D. | Constructed marshes for control of chlorinated ethenes: An 11-year study | Ecological Engineering(0), pp. - | article | URL | |
| Abstract: A 1.28 ha free water surface wetland was constructed and operated for 11 years for the purpose of reducing chlorinated ethenes in a contaminated groundwater plume in midwestern USA. The gravity fed wetland received an average of 148 m3/d of intercepted groundwater at a mean annual temperature of 12.4 °C. After startup, plume concentrations were approximately 2000 μg/L of trichloroethylene (TCE) and 1000 μg/L of cis-1,2-dichloroethylene (DCE), and were reduced to below 25 μg/L each on an annual basis. Vinyl chloride (VC) was reduced from 21 μg/L in the plume to 2.9 μg/L at the wetland outlet annually, below regulatory limits. Rates of removal were the highest in spring, and the lowest in winter. Flows were mildly variable across seasons, but dissolved oxygen (DO) was very high in spring, and very low in late summer. Tracer tests helped to delineate flow patterns. During the project lifetime, modifications were made, including filling deep zones to discourage muskrats, adding interior finger berms to improve hydraulics, and adding an effluent recirculation (recycle) system to degrade VC during times of low DO. The wetland system developed rapidly to a vegetatively diverse and healthy ecosystem, supporting over 60 bird species and numerous other animal species. | |||||
BibTeX:
@article{Kadlec,
author = {Kadlec, Robert H. and Martin, Dianne C. and Tsao, David},
title = {Constructed marshes for control of chlorinated ethenes: An 11-year study},
journal = {Ecological Engineering},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0925857412001590}
}
|
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| Kadlec, R.H., Roy, S.B., Munson, R.K., Charlton, S. and Brownlie, W. | Water quality performance of treatment wetlands in the Imperial Valley, California | 2010 | Ecological Engineering Vol. 36(8), pp. 1093-1107 |
article | URL |
| Abstract: Two demonstration treatment wetland systems were studied for over four years. Both consisted of sedimentation basins, followed by wetland cells. The Imperial, CA system had four wetland cells totaling 4.7 ha, 25% vegetated with bulrushes (Schoenoplectus californicus), and the Brawley, CA system had two wetland cells totaling 1.8 ha, also 25% vegetated with bulrushes. Imperial received irrigation runoff water at 30 cm/day, and Brawley received New River water at 11 cm/day, both with moderately high levels of nutrients, sediments and pathogens. The systems seeped 40–60% of the incoming water. The hydraulic efficiencies of the systems were high because of compartmentalization and high aspect ratios. Concentration reductions of TN, TP and TSS were 50%, 39%, and 97% at Imperial, and 73%, 50% and 96% at Brawley. Imperial achieved about 1.5 log10 reductions in total coliforms, fecal coliforms and Escherichia coli, while Brawley achieved about 2.7 log10 reductions. The sedimentation basins settled most of the incoming TSS, as well as the algal solids that were generated in the basins. Algal uptake removed nutrients in the basins, which were supersaturated with oxygen. The wetlands were effective in denitrification, and trapped the remaining and generated TSS. Removal rate constants, corrected for infiltration, were at the high end of those reported for other wetlands. | |||||
BibTeX:
@article{Kadlec2010,
author = {Kadlec, Robert H. and Roy, Sujoy B. and Munson, Ronald K. and Charlton, Stephen and Brownlie, William},
title = {Water quality performance of treatment wetlands in the Imperial Valley, California},
journal = {Ecological Engineering},
year = {2010},
volume = {36},
number = {8},
pages = {1093--1107},
url = {http://www.sciencedirect.com/science/article/pii/S092585741000114X}
}
|
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| Kadlec, R.H., Tanner, C.C., Hally, V.M. and Gibbs, M.M. | Nitrogen spiraling in subsurface-flow constructed wetlands: Implications for treatment response | 2005 | Ecological Engineering Vol. 25(4), pp. 365-381 |
article | URL |
| Abstract: Nitrogen processing in treatment wetlands was investigated by use of the stable isotope 15N introduced as ammonium. Two small field-scale, gravel-bed wetlands with horizontal subsurface-flow (SSF) received primary meat processing water. Four SSF cascade mesocosms, each comprising five tanks in series, received primary meat processing water, primary dairy water, secondary dairy water or aerated secondary dairy water. The mesocosms and one of the field-scale wetland contained well-established bulrushes (Schoenoplectus tabernaemontani), and the other field-scale wetland remained unvegetated. The systems were operated at steady inflows, with a nominal detention times of 4–5 days. The incoming ammonium nitrogen ranged from 18.5 to 177 g m−3, and removals ranged from 15 to 90% for the various feed waters. Each system was dosed with a single pulse of 15N ammonium mixed into the feed wastewater, and the fate and transport of the isotopic nitrogen were determined. The 15N pulses took 120 days to clear the heavily loaded field-scale wetlands. During this period small reductions in 15N were attributable to nitrification/denitrification, and a larger reduction due to plant uptake. Mesocosm tests ran for 24 days, during which only 1–16% of the tracer exited with water, increasing with N loading. Very little tracer gas emission was found (∼1%). The majority of the tracer was found in plants (6–48%) and sediments (28–37%). These results indicated a rapid absorption of ammonium into a large sediment storage pool, of which only a small proportion was denitrified during the period of the experiment. Plant uptake claimed a fraction of the ammonium, determined mainly by the plants requirement for growth rather than the magnitude of the nitrogen supply. A rapid return of ammonium to the water was also found, so that movement of 15N through the wetland mesocosms was comprised of a spiral of uptake and release along the flow path. A two compartment model was found to reasonably represent the isotope progress through the wetlands. First order exchanges and removals were employed in dynamic mass balances on water and solids. It is concluded that interpretation of nitrogen dynamics in wetlands must include the nitrogen spiral through the wetland, as well as plant uptake. This greatly increases the N residence time in treatment wetlands relative to the hydraulic detention time, resulting in long delays of treatment system response to changes in N loading and attenuation of short-term fluctuations in loading. | |||||
BibTeX:
@article{Kadlec2005,
author = {Kadlec, Robert H. and Tanner, Chris C. and Hally, Vera M. and Gibbs, Max M.},
title = {Nitrogen spiraling in subsurface-flow constructed wetlands: Implications for treatment response},
journal = {Ecological Engineering},
year = {2005},
volume = {25},
number = {4},
pages = {365--381},
url = {http://www.sciencedirect.com/science/article/pii/S0925857405001448}
}
|
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| Kadlec, R.H. and Zmarthie, L.A. | Wetland treatment of leachate from a closed landfill | 2010 | Ecological Engineering Vol. 36(7), pp. 946-957 |
article | URL |
| Abstract: A wetland system has operated seasonally at Saginaw Township, MI, USA, for ten years. The system consists of extraction, aeration, settling, intermittent vertical sand filtration, a surface flow wetland treatment with recycle, and discharge to the Tittibawassee River. The 0.85 ha cattail wetland treats the full leachate flow, with a total system detention time of 180 days. The high recycle rate creates a lesser wetland detention time of 60 days. Ammonia is the principal contaminant of concern, because it occurs at high concentrations, typically 300–500 mg/L. Ammonia mass reduction averaged 99.5% for the last nine years, with a 95% mass removal in the startup year. Metals were not present in all samples, with modest reductions in those always present (zinc 16%, arsenic 29%, barium 78%, chromium 67%). Volatile organic compounds were removed to below detection, excepting BTEX, which occurred in only 2% of the outflow samples. Base neutral organics, PCBs and pesticides were also removed to below detection, excepting phthalates with an outlet detection frequency of 29%. No pesticides or PCBs were detected in the system outflow. The ammonia removal rate coefficients for the wetland (12 m/yr) was at the 55th percentile of the distribution for other surface flow wetlands. The vertical filter was likely oxygen limited, and functioned with an apparent oxygen utilization of 30 gO/(m2 d). | |||||
BibTeX:
@article{Kadlec2010a,
author = {Kadlec, Robert H. and Zmarthie, Linda A.},
title = {Wetland treatment of leachate from a closed landfill},
journal = {Ecological Engineering},
year = {2010},
volume = {36},
number = {7},
pages = {946--957},
url = {http://www.sciencedirect.com/science/article/pii/S0925857410000868}
}
|
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| Kadlec, T., Benes, J., Jarosik, V. and Konvicka, M. | Revisiting urban refuges: Changes of butterfly and burnet fauna in Prague reserves over three decades | 2008 | Landscape and Urban Planning Vol. 85(1), pp. 1-11 |
article | URL |
| Abstract: We studied changes in the composition of butterfly and burnet fauna in 25 reserves of xeric grasslands within the city Prague, Czech Republic, based on a recent repetition of a survey conducted three decades ago. The past and recent survey detected 91 and 84 species, 12 species were lost and four were gained between the surveys. There was no significant change in mean numbers of species per reserve or in mean species incidences, even if the categories of the habitat association, mobility and body size were analysed separately. Contrary to these comparisons, ordination analyses indicated a significant shift in species composition in individual reserves. Species of short-sward xeric grasslands tended to be associated with the past survey, whereas species of taller grasslands and xeric scrub were associated with recent survey. These shifts were more prominent in large reserves with high proportion of natural (as opposed to urban) perimeter, connected with other reserves, having diverse topography and high plant and biotope richness. We interpret this by gradual successional changes which affect the reserves despite conservation management. Despite these changes, butterfly losses were lower than in comparable surveys recently conducted elsewhere in Central Europe, partly because major losses occurred long before the 1980s survey and partly owing to a high heterogeneity of the urban landscape surrounding the reserves. | |||||
BibTeX:
@article{Kadlec2008a,
author = {Kadlec, Tomas and Benes, Jiri and Jarosik, Vojtech and Konvicka, Martin},
title = {Revisiting urban refuges: Changes of butterfly and burnet fauna in Prague reserves over three decades},
journal = {Landscape and Urban Planning},
year = {2008},
volume = {85},
number = {1},
pages = {1--11},
url = {http://www.sciencedirect.com/science/article/pii/S0169204607001703}
}
|
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| Kaffashi, S., Shamsudin, M.N., Radam, A., Yacob, M.R., Rahim, K.A. and Yazid, M. | Economic valuation and conservation: Do people vote for better preservation of Shadegan International Wetland? | 2012 | Biological Conservation Vol. 150(1), pp. 150-158 |
article | URL |
| Abstract: Shadegan International Wetland (SIW) is a unique natural ecosystem with great national and international significance, designated under Ramsar Convention. Located in southern part of Iran, this wetland serves many functions. Among them the rich biodiversity, ecological, hydrological, and economic functions are the most important. Despite the great opportunities for sustainable development of this wetland, it is currently under serious threats from a diverse range of non-sustainable activities. Underestimating SIWâs non-market values in development decisions is a major reason for the conversion and excessive depletion of its resources. The aim of this study was therefore to estimate the economic benefit of SIW as a very useful instrument to reflect the values of this unique ecosystem to society members. A choice experiment (CE) survey was undertaken to estimate the value of different nonmarket attributes of SIW. In addition to the overall model, users and nonusers preferences were also estimated. Random parameter logit (RPL) model was employed to derive the marginal value of the respondents for different attributes of the nonmarket values of SIW. Results indicated the respondentsâ positive preferences towards better conservation of SIW. | |||||
BibTeX:
@article{Kaffashi2012,
author = {Kaffashi, Sara and Shamsudin, Mad Nasir and Radam, Alias and Yacob, Mohd Rusli and Rahim, Khalid Abdul and Yazid, Muhammad},
title = {Economic valuation and conservation: Do people vote for better preservation of Shadegan International Wetland?},
journal = {Biological Conservation},
year = {2012},
volume = {150},
number = {1},
pages = {150--158},
url = {http://www.sciencedirect.com/science/article/pii/S000632071200136X}
}
|
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| Kamara, B., Spear, L., Cobb, C., Bachus, K., Painter, R., Sharpe, L. and Byl, T. | Are Karst Bedrock Aquifers at Greater Risk from Alternative Alcohol-Fuel Mixes Compared to Regular Gasoline? | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 74 | inproceedings | URL |
| Abstract: The United States government is promoting alternative fuels that reduce our dependency on foreign oil. Tennessee is promoting E-85, a fuel that consists of 85 percent ethanol and 15 percent gasoline. The environmental fate of gas-alcohol mixtures, however, has not been investigated. The consequences of an uncontrolled spill of E-85 or a related mixture would, therefore, be very difficult to predict. The objective of this research was to determine if a commercial grade E-85 mixture would dissolve more readily in water and move faster through water-saturated soil than regular gasoline. A better understanding of E-85 mobility in the subsurface is of practical importance if E-85 is to become widely used and stored in underground storage tanks like conventional fuels. Solubility-in-water studies comparing gasoline with E-85 found that the ethanol component in E-85 acted as a co-solvent and enabled aromatic compounds to dissolve five times more rapidly in water than regular gasoline. These enhanced solubility characteristics may allow the aromatic rings to move faster and further through water-saturated soils and karst conduits than regular gasoline. Additional experiments were conducted to determine if regolith soils would affect the dispersal rate of E-85 fuel compounds. Sterile soil-column studies using soils collected from karst regions of Middle Tennessee demonstrated that aromatic compounds, such as benzene, toluene or xylene (BTX), from the E-85 moved 3 to 4 times faster than BTX compounds in regular gasoline when transported by water through the soil. These results suggest that leakage of E-85 from underground storage tanks could result in wider contamination of aquifer materials in a shorter time than regular gasoline. Additional work compared the biodegradation of E-85 with regular gasoline. Using static reactors with karst bacteria, E-85 biodegradation rates were almost 5 times greater than regular gasoline. This is in agreement with previous reports finding that dissolved-phase fuels were more bioavailable and degraded faster. Additional studies are needed to more thoroughly address issues concerning E-85 solubility and biodegradation. | |||||
BibTeX:
@inproceedings{Kamara2008,
author = {Kamara, Baibai and Spear, Loreal and Cobb, Carlton and Bachus, Keyshon and Painter, Roger and Sharpe, Lonnie and Byl, Tom},
title = {Are Karst Bedrock Aquifers at Greater Risk from Alternative Alcohol-Fuel Mixes Compared to Regular Gasoline?},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {74},
url = {http://pubs.usgs.gov/sir/2008/5023/29kamara.htm}
}
|
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| van der Kamp, G. and Hayashi, M. | Groundwater-wetland ecosystem interaction in the semiarid glaciated plains of North America | 2009 | Hydrogeology Journal Vol. 17(1), pp. 203-214 |
article | URL |
| Abstract: The prairie wetlands of northern USA and Canada exist in numerous topographical depressions within the glaciated landscape. The wetlands are disconnected from each other most of the time with respect to surface-water drainage. The wetland water balance is controlled by snowmelt runoff and snowdrift from the surrounding uplands, precipitation, evapotranspiration, groundwater exchange, and occasional “fill-spill” connections to other wetlands. Salinity of water and the seasonal variability of water level in these wetlands have a strong influence on the ecosystem. Clay-rich glacial tills, covering much of the region, have very low (0.001–0.01 m/yr) hydraulic conductivity, except for the top several meters where the factures and macropores increase conductivity up to 1,000 m/yr. Transpiration in the wetland margin induces infiltration and lateral flow of shallow groundwater from wetland ponds through the high-conductivity zone, which strongly affects the water balance of wetlands. In contrast, groundwater flow in the deeper low-conductivity till has minor effects on water balance, but has a strong influence on salinity because the flow direction determines if the salts accumulate in wetlands (upward flow) or are leached out (downward flow) under wetlands. Understanding of the roles of shallow and deep groundwater systems will improve the hydrological conceptual framework for the management of wetland ecosystems. | |||||
BibTeX:
@article{Kamp2009,
author = {van der Kamp, Garth and Hayashi, Masaki},
title = {Groundwater-wetland ecosystem interaction in the semiarid glaciated plains of North America},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {203--214},
url = {http://dx.doi.org/10.1007/s10040-008-0367-1}
}
|
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| Kampas, A. and Adamidis, K. | Discussion of the paper “Cost effective policies for alternative distributions of stochastic water pollution” by Gren, Destouni and Tempone☆ | 2005 | Journal of Environmental Management Vol. 74(4), pp. 383-388 |
article | URL |
| Abstract: This discussion addresses some aspects of a recent paper appearing in this journal which investigates cost effective coastal water management based on different assumptions of the probability distributions (normal and log-normal) of pollutant transport. We also suggest an alternative approach to overcome the technical problems of using the theoretical correct distribution for characterising environmental data (log-normal) within a probabilistic programming framework. | |||||
BibTeX:
@article{Kampas2005,
author = {Kampas, Athanasios and Adamidis, Konstantinos},
title = {Discussion of the paper “Cost effective policies for alternative distributions of stochastic water pollution” by Gren, Destouni and Tempone☆},
journal = {Journal of Environmental Management},
year = {2005},
volume = {74},
number = {4},
pages = {383--388},
url = {http://www.sciencedirect.com/science/article/pii/S0301479704002130}
}
|
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| Kanney, J.F., Miller, C.T. and Barry, D. | Comparison of fully coupled approaches for approximating nonlinear transport and reaction problems | 2003 | Advances in Water Resources Vol. 26(4), pp. 353-372 |
article | URL |
| Abstract: The purpose of this work is to evaluate the computational efficiency of fully coupled approaches for approximating a common class of nonlinear, two-phase advective–dispersive–reactive equations. The general problem considered includes homogeneous phase chemical kinetics, equilibrium interphase mass transfer, and rate-controlled interphase mass transfer––all of which may be nonlinear. Aspects of the problem investigated include discrete mass conservative formulations, temporal discretization approaches, and nonlinear equation solution methods. Their effect on computational efficiency is investigated through a series of numerical experiments using a nondimensional model problem. The effect of problem characteristics such as large sorption capacity, strong sorption nonlinearity, fast mass transfer, fast reactions, and strong diffusion is investigated. Comparisons of solution efficiency show that the optimal approach depends upon: (1) the characteristics of the problem considered, which may be described in a nondimensional form; and (2) the accuracy achieved in the solution. Results offer general guidance for selecting solution approaches for the class of problems investigated and introduce some new solution approaches to the water resources field that may be applicable to other problems. | |||||
BibTeX:
@article{Kanney2003,
author = {Kanney, Joseph F and Miller, Cass T and Barry, D.Andrew},
title = {Comparison of fully coupled approaches for approximating nonlinear transport and reaction problems},
journal = {Advances in Water Resources},
year = {2003},
volume = {26},
number = {4},
pages = {353--372},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802001884}
}
|
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| Kanse, N.G. and Dawande, S.D. | RTD Studies in Plug Flow Reactor and its Simulation with Comparing Non Ideal Reactors | 2012 | Research Journal of Recent Sciences Vol. 1(2), pp. 42-48 |
article | |
| Abstract: This paper proposes RTD studies in plug flow reactor and comparison of non-ideal reactors using residence time distribution function. The model also gives a prediction of the number of ideal continuous stirred tank reactors (CSTR) that could represent the non-ideal plug flow reactor (PFR) in question. Simulated results reveal that 10 numbers of ideal stirred tanks in series would represent the non-ideal plug flow reactor under study. The graphical result of all four reactors is generated directly by polymath. Most of the chemical reactors in the industries have non-ideal regime. The non-ideal plug flow reactor (PFR) is one whose attributes deviate from that of the ideal plug flow reactors. Therefore, an in-depth knowledge of the residence time distribution (RTD) of components in the reactor is necessary for its analysis. The residence time distribution indicates how much time each fraction of a charged material spends in the vessel. The residence time distribution of reactants or tracers in a flow vessel is a key datum for determining reactor performance. |
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BibTeX:
@article{Kanse2012,
author = {Kanse, Nitin G. and Dawande, S. D.},
title = {RTD Studies in Plug Flow Reactor and its Simulation with Comparing Non Ideal Reactors},
journal = {Research Journal of Recent Sciences},
year = {2012},
volume = {1},
number = {2},
pages = {42--48}
}
|
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| Kaplowitz, M.D. and Lupi, F. | Stakeholder preferences for best management practices for non-point source pollution and stormwater control | 2012 | Landscape and Urban Planning Vol. 104(3-4), pp. 364-372 |
article | URL |
| Abstract: Typically, communities implement some subset of best management practices (BMP) to control their stormwater flows and NPS. Phase II of the U.S. Clean Water Act (CWA) requires public input, education, and participation, among other things, as part of watershed management planning processes for addressing nonpoint source pollution. It has been recognized that integrating stakeholders’ input and values into decision-making processes often results in good public policies adequately supported by the public. Choice experiment survey approaches are well suited as a means for increasing public participation in watershed decisions and for evaluating the relative attractiveness of alternative BMP for stormwater management and non-point source pollution control. Therefore we designed and implemented a choice experiment survey to learn about public preferences for alternative best management practices (BMP) for stormwater water management, identify BMP combinations likely to be supported by local stakeholders, and to increase public participation in watershed management decision making. The results demonstrate the effectiveness of choice experiments for evaluating preferences for alternative BMP for watershed management. Furthermore, the results reveal that stakeholders clearly prefer some BMP to others and that the extent of each BMP's application in a watershed plan matters to stakeholders. | |||||
BibTeX:
@article{Kaplowitz2012,
author = {Kaplowitz, Michael D. and Lupi, Frank},
title = {Stakeholder preferences for best management practices for non-point source pollution and stormwater control},
journal = {Landscape and Urban Planning},
year = {2012},
volume = {104},
number = {3--4},
pages = {364--372},
url = {http://www.sciencedirect.com/science/article/pii/S0169204611003355}
}
|
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| Karlin, I., Asinari, P. and Succi, S. | Matrix lattice Boltzmann reloaded | 2011 | Philosophical Transactions of the Royal Society A: Mathematical,Physical and Engineering Sciences Vol. 369(1944), pp. 2202-2210 |
article | URL |
| Abstract: The lattice Boltzmann equation was introduced about 20 years ago as a new paradigm for computational fluid dynamics. In this paper, we revisit the main formulation of the lattice Boltzmann collision integral (matrix model) and introduce a new two-parametric family of collision operators, which permits us to combine enhanced stability and accuracy of matrix models with the outstanding simplicity of the most popular single-relaxation time schemes. The option of the revised lattice Boltzmann equation is demonstrated through numerical simulations of a three-dimensional lid-driven cavity. | |||||
BibTeX:
@article{Karlin2011,
author = {Karlin, Ilya and Asinari, Pietro and Succi, Sauro},
title = {Matrix lattice Boltzmann reloaded},
journal = {Philosophical Transactions of the Royal Society A: Mathematical,Physical and Engineering Sciences},
year = {2011},
volume = {369},
number = {1944},
pages = {2202--2210},
url = {http://rsta.royalsocietypublishing.org/content/369/1944/2202.abstract}
}
|
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| Karlis, D. and Meligkotsidou, L. | Finite mixtures of multivariate Poisson distributions with application | 2007 | Journal of Statistical Planning and Inference Vol. 137(6), pp. 1942-1960 |
article | URL |
| Abstract: In the present paper we examine finite mixtures of multivariate Poisson distributions as an alternative class of models for multivariate count data. The proposed models allow for both overdispersion in the marginal distributions and negative correlation, while they are computationally tractable using standard ideas from finite mixture modelling. An EM type algorithm for maximum likelihood (ML) estimation of the parameters is developed. The identifiability of this class of mixtures is proved. Properties of ML estimators are derived. A real data application concerning model based clustering for multivariate count data related to different types of crime is presented to illustrate the practical potential of the proposed class of models. | |||||
BibTeX:
@article{Karlis2007,
author = {Karlis, Dimitris and Meligkotsidou, Loukia},
title = {Finite mixtures of multivariate Poisson distributions with application},
journal = {Journal of Statistical Planning and Inference},
year = {2007},
volume = {137},
number = {6},
pages = {1942--1960},
url = {http://www.sciencedirect.com/science/article/pii/S0378375806001753}
}
|
|||||
| Katz, B.G. | A Multracer Approach for Assessing the Susceptibility of Ground-Water Contamination in the Woodville Karst Plain, Northern Florida [BibTeX] |
2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 167-176 | inproceedings | URL |
BibTeX:
@inproceedings{Katz2001,
author = {Katz, Brian G.},
title = {A Multracer Approach for Assessing the Susceptibility of Ground-Water Contamination in the Woodville Karst Plain, Northern Florida},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {167--176},
url = {http://water.usgs.gov/ogw/karst/kigconference/bgk_multracer.htm}
}
|
|||||
| Katz, B.G., Chelette, A.R. and Pratt, T.R. | Use of chemical and isotopic tracers to assess nitrate contamination and ground-water age, Woodville Karst Plain, USA | 2004 | Journal of Hydrology Vol. 289(1-4), pp. 36-61 |
article | URL |
| Abstract: Concerns regarding ground-water contamination in the Woodville Karst Plain have arisen due to a steady increase in nitrate-N concentrations (0.25–0.90 mg/l) during the past 30 years in Wakulla Springs, a large regional discharge point for water (9.6 m3/s) from the Upper Floridan aquifer (UFA). Multiple isotopic and chemical tracers were used with geochemical and lumped-parameter models (exponential mixing (EM), dispersion, and combined exponential piston flow) to assess: (1) the sources and extent of nitrate contamination of ground water and springs, and (2) mean transit times (ages) of ground water. Delta 15N-NO3 values (1.7–13.8‰) indicated that nitrate in ground water originated from localized sources of inorganic fertilizer and human/animal wastes. Nitrate in spring waters (δ15N-NO3=5.3–8.9‰) originated from both inorganic and organic N sources. Nitrate-N concentrations (<0.02–16 mg/l) were highly variable both spatially and vertically in the oxic UFA, based on water samples from 46 wells and four springs collected from 1997 to 2000. During high-flow conditions, spring waters had decreased nitrate and increased DOC concentrations that resulted from mixtures of 20–95% surface water. Although higher nitrate-N concentrations (>1.0 mg/l) were associated with shallow wells (open intervals less than 15 m below land surface), elevated nitrate concentrations in deeper wells are consistent with mixtures of water from shallow and deep zones in the UFA as indicated from geochemical mixing models and the distribution of mean transit times (5–90 years) estimated using lumped-parameter flow models. Ground water with mean transit times of 10 years or less tended to have higher dissolved organic carbon concentrations, lower dissolved solids, and lower calcite saturation indices than older waters, indicating mixing with nearby surface water that directly recharges the aquifer through sinkholes. Significantly higher values of pH, magnesium, dolomite saturation index, and phosphate in springs and deep water (>45 m) relative to a shallow zone (<45 m) were associated with longer ground-water transit times (50–90 years). Chemical differences with depth in the aquifer result from deep regional flow of water recharged through low permeability sediments (clays and clayey sands of the Hawthorn Formation) that overlie the UFA upgradient from the karst plain. | |||||
BibTeX:
@article{Katz2004,
author = {Katz, Brian G. and Chelette, Angela R. and Pratt, Thomas R.},
title = {Use of chemical and isotopic tracers to assess nitrate contamination and ground-water age, Woodville Karst Plain, USA},
journal = {Journal of Hydrology},
year = {2004},
volume = {289},
number = {1-4},
pages = {36--61},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403004463}
}
|
|||||
| Katz, B.G., Griffin, D.W. and Davis, J.H. | Groundwater quality impacts from the land application of treated municipal wastewater in a large karstic spring basin: Chemical and microbiological indicators | 2009 | Science of The Total Environment Vol. 407(8), pp. 2872-2886 |
article | URL |
| Abstract: Geochemical and microbiological techniques were used to assess water-quality impacts from the land application of treated municipal wastewater in the karstic Wakulla Springs basin in northern Florida. Nitrate-N concentrations have increased from about 0.2 to as high as 1.1 mg/L (milligrams per liter) during the past 30 years in Wakulla Springs, a regional discharge point for groundwater (mean flow about 11.3 m3/s) from the Upper Floridan aquifer (UFA). A major source of nitrate to the UFA is the approximately 64 million L/d (liters per day) of treated municipal wastewater applied at a 774 ha (hectare) sprayfield farming operation. About 260 chemical and microbiological indicators were analyzed in water samples from the sprayfield effluent reservoir, wells upgradient from the sprayfield, and from 21 downgradient wells and springs to assess the movement of contaminants into the UFA. Concentrations of nitrate-N, boron, chloride, were elevated in water samples from the sprayfield effluent reservoir and in monitoring wells at the sprayfield boundary. Mixing of sprayfield effluent water was indicated by a systematic decrease in concentrations of these constituents with distance downgradient from the sprayfield, with about a 10-fold dilution at Wakulla Springs, about 15 km (kilometers) downgradient from the sprayfield. Groundwater with elevated chloride and boron concentrations in wells downgradient from the sprayfield and in Wakulla Springs had similar nitrate isotopic signatures, whereas the nitrate isotopic composition of water from other sites was consistent with inorganic fertilizers or denitrification. The sprayfield operation was highly effective in removing most studied organic wastewater and pharmaceutical compounds and microbial indicators. Carbamazepine (an anti-convulsant drug) was the only pharmaceutical compound detected in groundwater from two sprayfield monitoring wells (1–2 ppt). One other detection of carbamazepine was found in a distant well water sample where enteroviruses also were detected, indicating a likely influence from a nearby septic tank. | |||||
BibTeX:
@article{Katz2009,
author = {Katz, Brian G. and Griffin, Dale W. and Davis, J. Hal},
title = {Groundwater quality impacts from the land application of treated municipal wastewater in a large karstic spring basin: Chemical and microbiological indicators},
journal = {Science of The Total Environment},
year = {2009},
volume = {407},
number = {8},
pages = {2872--2886},
url = {http://www.sciencedirect.com/science/article/pii/S0048969709000266}
}
|
|||||
| Kaufmann, G. | Modelling karst geomorphology on different time scales | 2009 | Geomorphology Vol. 106(1-2)Recent developments in surface and subsurface karst geomorphology, pp. 62-77 |
article | URL |
| Abstract: The evolution and flow in a karst aquifer is studied with numerical simulations, based on the KARST model (Karst AquifeR Simulation Tool). The aquifer consists of a three-dimensional interconnected network of conduits representing fractures in the rock, and a porous rock matrix representing the finer fissured system in the rock. Flow through the aquifer can be driven by both diffuse recharge from precipitation and localised sinking streams, and the aquifer drains towards a large karst resurgence representing the base level. Superimposed onto the karst aquifer is a landscape, which can evolve with time by small-scale diffusive processes, large-scale river erosion, and karst denudation. | |||||
BibTeX:
@article{Kaufmann2009,
author = {Kaufmann, Georg},
title = {Modelling karst geomorphology on different time scales},
booktitle = {Recent developments in surface and subsurface karst geomorphology},
journal = {Geomorphology},
year = {2009},
volume = {106},
number = {1-2},
pages = {62--77},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X08004091}
}
|
|||||
| Kaufmann, G. | A model comparison of karst aquifer evolution for different matrix-flow formulations | 2003 | Journal of Hydrology Vol. 283(1-4), pp. 281-289 |
article | URL |
| Abstract: The evolution of permeability and flow in a karst aquifer is studied by numerical simulations. The aquifer considered consists of a large central fracture, a network of finer fissures, and a porous rock matrix. Enlargement of both the central fracture and the fissures by chemical dissolution is possible, hence the conductivities in the fracture and the fissure system can increase with time. No dissolution is allowed in the porous rock matrix, which has a constant conductivity. Flow is driven by a simple fixed head boundary condition representative for the initial phase of karstification. A systematic parameter study is carried out by varying the initial width of the fissure network and the conductivity of the rock matrix, while keeping the initial width of the central fracture fixed. Key parameters such as flowrates, breakthrough times, and conductivities for the different models are compared. If either the conductivity of the rock matrix is high enough or the initial width of the fissures is large enough to carry flow, breakthrough times of the aquifer are significantly reduced, when compared to a model with low matrix conductivity and small fissures. However, due to the dissolutional widening of fissures the evolution of the aquifer is distinctively different for models with rock matrix simulated by a porous medium or a fissure network. | |||||
BibTeX:
@article{Kaufmann2003,
author = {Kaufmann, Georg},
title = {A model comparison of karst aquifer evolution for different matrix-flow formulations},
journal = {Journal of Hydrology},
year = {2003},
volume = {283},
number = {1-4},
pages = {281--289},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403002701}
}
|
|||||
| Kaufmann, G., Romanov, D. and Hiller, T. | Modeling three-dimensional karst aquifer evolution using different matrix-flow contributions | 2010 | Journal of Hydrology Vol. 388(3-4), pp. 241-250 |
article | URL |
| Abstract: We have developed the program package KARSTAQUIFER, which simulates flow and transport in a three-dimensional transient karst aquifer consisting of fractures and matrix elements. The fractures can be enlarged by chemical dissolution of calcite, increasing the secondary permeability of the karst aquifer. Boundary conditions for our model setup are guided by published benchmark models for karst aquifer evolution in two dimensions (length and width), with a 100 m high hydraulic head difference across the model domain responsible for relatively fast evolution of the aquifer. | |||||
BibTeX:
@article{Kaufmann2010,
author = {Kaufmann, Georg and Romanov, Douchko and Hiller, Thomas},
title = {Modeling three-dimensional karst aquifer evolution using different matrix-flow contributions},
journal = {Journal of Hydrology},
year = {2010},
volume = {388},
number = {3-4},
pages = {241--250},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410002441}
}
|
|||||
| Kavcar, P., Sofuoglu, A. and Sofuoglu, S.C. | A health risk assessment for exposure to trace metals via drinking water ingestion pathway | 2009 | International Journal of Hygiene and Environmental Health Vol. 212(2), pp. 216-227 |
article | URL |
| Abstract: A health risk assessment was conducted for exposure to trace metals via drinking water ingestion pathway for Province of İzmir, Turkey. Concentrations of 11 trace metals were measured in drinking waters collected from 100 population weighted random sampling units (houses). The samples were analyzed in atomic absorption spectrometry for arsenic, and inductively coupled plasma-optical emission spectrometry for Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn. Questionnaires were administered to a participant from each sampling unit to determine drinking water consumption related information and demographics. Exposure and risks were estimated for each individual by direct calculation, and for İzmir population by Monte Carlo simulation. Six trace metals (As, Cr, Cu, Mn, Ni, and Zn) were detected in >50% of the samples. Concentrations of As and Ni exceeded the corresponding standards in 20% and 58% of the samples, respectively. As a result, arsenic noncarcinogenic risks were higher than the level of concern for 19% of the population, whereas carcinogenic risks were >10−4 for 46%, and >10−6 for 90% of the population. | |||||
BibTeX:
@article{Kavcar2009,
author = {Kavcar, Pınar and Sofuoglu, Aysun and Sofuoglu, Sait C.},
title = {A health risk assessment for exposure to trace metals via drinking water ingestion pathway},
journal = {International Journal of Hygiene and Environmental Health},
year = {2009},
volume = {212},
number = {2},
pages = {216--227},
url = {http://www.sciencedirect.com/science/article/pii/S1438463908000333}
}
|
|||||
| Kavouri, K., Plagnes, V., Tremoulet, J., Dörfliger, N., Rejiba, F. and Marchet, P. | PaPRIKa: a method for estimating karst resource and source vulnerability—application to the Ouysse karst system (southwest France) | 2011 | Hydrogeology Journal Vol. 19(2), pp. 339-353 |
article | URL |
| Abstract: The intrinsic vulnerability mapping method, PaPRIKa, is proposed as a common basis for karst groundwater protection in France. PaPRIKa is a specialized method for studying karst aquifers, derived from updating the RISKE and EPIK methods. Both the structure and functioning of karst aquifers are considered in order to develop a resource and source-vulnerability mapping method. PaPRIKa means P rotection of a quifers from the assessment of four criteria: P for protection (considering the most protective aspects among parameters related to soil cover, unsaturated zone and epikarst behavior), R for rock type, I for infiltration and Ka for karstification degree. The Ouysse karst system, located in the Causses area in southwest France, is one of the nine pilot sites where this method was tested and standardized. The specificities of the Ouysse system such as the size of the catchment area, the spatial variability of the karst network development, the thick infiltration zone and the system’s dual character (both karst and non-karst areas), have provided a valuable field of application. The vulnerability of the resource was assessed for the entire catchment area, while source-orientated cartography was attempted for the catchment areas of the three different capture works used for drinking water. | |||||
BibTeX:
@article{Kavouri2011,
author = {Kavouri, Konstantina and Plagnes, Valérie and Tremoulet, Joël and Dörfliger, Nathalie and Rejiba, Fayçal and Marchet, Pierre},
title = {PaPRIKa: a method for estimating karst resource and source vulnerability—application to the Ouysse karst system (southwest France)},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {19},
number = {2},
pages = {339--353},
url = {http://dx.doi.org/10.1007/s10040-010-0688-8}
}
|
|||||
| Kawas, M. and Karakas, A. | On the stochastic theory of solute transport by unsteady and steady groundwater flow in heterogeneous aquifers | 1996 | Journal of Hydrology Vol. 179(1-4), pp. 321-351 |
article | URL |
| Abstract: In this study the exact and approximate deterministic partial differential equations of the time-space evolution of mean solute concentration, of solute concentration two-point moment and of solute concentration n-point moment for conservative solute transport by unsteady and steady groundwater flow in a heterogeneous aquifer were developed in the real time-space domain under second-order cumulant expansion. These derivations were performed by means of the cumulant expansion method, combined with the calculus for the time-ordered exponential and with the calculus for Lie operator. The mean solute transport equations which describe the time-space evolution of mean conservative solute concentration under transport by unsteady and steady groundwater flows in a heterogeneous aquifer have convective-dispersive forms whose convective and dispersive coefficients are defined precisely in terms of the mean and covariance functions of the pore flow velocity random field. However, owing to the spatial nonuniformity of groundwater flow in heterogeneous porous media a new convective coefficient, besides the standard mean velocity vector, appeared in the derived mean solute transport equations in the case of steady flows. In the case of transport by unsteady groundwater flow in a heterogeneous aquifer, the new convective coefficient (besides the standard mean velocity vector) is due to the non-zero divergence of the pore flow velocity. The fundamental reason for the convective-dispersive form of the mean transport equations is the second-order truncation of the formal cumulant expansion. In the derived mean solute transport equations the macroscopic dispersion coefficient emerges as the time integral of the covariance function of the pore flow velocity. However, both in the case of transport by unsteady groundwater flow and in the case of transport by steady spatially nonstationary-nonuniform groundwater flow the macroscopic dispersion coefficients and convective coefficients vary with spatial locations within the porous medium. Only in the case of transport by steady spatially stationary-nonuniform flow are both the macroscopic dispersion coefficient and the convective coefficient constant with respect to spatial location within the heterogenous aquifer. Therefore, only in the case of conservative solute transport by steady spatially stationary-nonuniform groundwater flow in a heterogeneous aquifer does the mean transport equation apply to all spatial locations within the aquifer with the same parameter values at each time instant. | |||||
BibTeX:
@article{Kawas1996,
author = {Kawas, M.L. and Karakas, A.},
title = {On the stochastic theory of solute transport by unsteady and steady groundwater flow in heterogeneous aquifers},
journal = {Journal of Hydrology},
year = {1996},
volume = {179},
number = {1-4},
pages = {321--351},
url = {http://www.sciencedirect.com/science/article/pii/0022169495028358}
}
|
|||||
| Kaygusuz, K. | Energy services and energy poverty for sustainable rural development | 2011 | Renewable and Sustainable Energy Reviews Vol. 15(2), pp. 936-947 |
article | URL |
| Abstract: In many rural areas, poor people still depend on wood and other biomass fuels for most of their household and income-generating activities. The difficult, time-consuming work of collecting and managing traditional fuels is widely viewed as women's responsibility, which is a factor in women's disproportionate lack of access to education and income, and inability to escape from poverty. Therefore, it is important for energy access programs to have a special focus on women. New options for energy access and sustainable livelihoods, like small-scale biofuels production, can have dramatic benefits for rural women, and their families and communities. Energy development, as both a driving force and a consequence of such tremendous changes, has had profound impact on economic, social, and environmental development. Rural energy has always been a critical issue due to years of energy shortage for both households and industries. Biomass, for long time, has been the only available fuel in many rural areas. The situation in rural areas is even more critical as local demand for energy outstrips availability and the vast majority of people depend on non-commercial energy supplies. Energy is needed for household uses, such as cooking, lighting, heating; for agricultural uses, such as tilling, irrigation and post-harvest processing; and for rural industry uses, such as milling and mechanical energy and process heat. Energy is also an input to water supply, communication, commerce, health, education and transportation in rural areas. | |||||
BibTeX:
@article{Kaygusuz2011,
author = {Kaygusuz, K.},
title = {Energy services and energy poverty for sustainable rural development},
journal = {Renewable and Sustainable Energy Reviews},
year = {2011},
volume = {15},
number = {2},
pages = {936--947},
url = {http://www.sciencedirect.com/science/article/pii/S1364032110003722}
}
|
|||||
| Kayid, M., Diab, L. and Alzughaibi, A. | Testing NBU(2) class of life distribution based on goodness of fit approach | 2010 | Journal of King Saud University - Science Vol. 22(4), pp. 241-245 |
article | URL |
| Abstract: In this paper, new testing procedures for exponentiality against the NBU(2) class is addressed based on the goodness of fit approach. It is shown that the proposed test has high relative efficiency for some commonly used alternative and enjoys a good power. The critical values of the proposed statistic are calculated and some applications are given to elucidate the use of the proposed test in reliability analysis. | |||||
BibTeX:
@article{Kayid2010,
author = {Kayid, M. and Diab, L.S. and Alzughaibi, A.},
title = {Testing NBU(2) class of life distribution based on goodness of fit approach},
journal = {Journal of King Saud University - Science},
year = {2010},
volume = {22},
number = {4},
pages = {241--245},
url = {http://www.sciencedirect.com/science/article/pii/S1018364710000480}
}
|
|||||
| Kaza, N. and BenDor, T.K. | The land value impacts of wetland restoration | 2013 | Journal of Environmental Management Vol. 127(0), pp. 289-299 |
article | URL |
| Abstract: Abstract U.S. regulations require offsets for aquatic ecosystems damaged during land development, often through restoration of alternative resources. What effect does large-scale wetland and stream restoration have on surrounding land values? Restoration effects on real estate values have substantial implications for protecting resources, increasing tax base, and improving environmental policies. Our analysis focuses on the three-county RaleighâDurhamâChapel Hill, North Carolina region, which has experienced rapid development and extensive aquatic ecological restoration (through the state's Ecosystem Enhancement Program [EEP]). Since restoration sites are not randomly distributed across space, we used a genetic algorithm to match parcels near restoration sites with comparable control parcels. Similar to propensity score analysis, this technique facilitates statistical comparison and isolates the effects of restoration sites on surrounding real estate values. Compared to parcels not proximate to any aquatic resources, we find that, 1) natural aquatic systems steadily and significantly increase parcel values up to 0.75 mi away, and 2) parcels <0.5 mi from EEP restoration sites have significantly lower sale prices, while 3) parcels >0.5 mi from EEP sites gain substantial amenity value. When we control for intervening water bodies (e.g. un-restored streams and wetlands), we find a similar inflection point whereby parcels <0.5 mi from EEP sites exhibit lower values, and sites 0.5â0.75 mi away exhibit increased values. Our work points to the need for higher public visibility of aquatic ecosystem restoration programs and increased public information about their value. | |||||
BibTeX:
@article{Kaza2013,
author = {Kaza, Nikhil and BenDor, Todd K.},
title = {The land value impacts of wetland restoration},
journal = {Journal of Environmental Management},
year = {2013},
volume = {127},
number = {0},
pages = {289--299},
url = {http://www.sciencedirect.com/science/article/pii/S0301479713002971}
}
|
|||||
| Kazezyılmaz-Alhan, C.M. and Medina Jr., M.A. | Stream solute transport incorporating hyporheic zone processes | 2006 | Journal of Hydrology Vol. 329(1-2), pp. 26-38 |
article | URL |
| Abstract: The behavior of solute transport in pool and riffle, or meandering types of streams, is greatly influenced by surface/subsurface flow and solute transport interactions. It is important to model these processes accurately in rivers and streams to improve downstream water quality. Two decades ago, Bencala and Walters (1983) [Bencala, K.E., Walters, R.A., 1983, Simulation of solute transport in a mountain pool-and-riffle stream – a transient storage model. Water Resources Research 19(3), 718–724] introduced the transient storage model to represent the movement of solute from main streams into stagnant zones and back to the main stream. This model includes the effect of both surface storage, in which water is stationary relative to the main channel and the hyporheic zone, to which water moves from the main channel, flows through and returns to the main channel. However, their simplified approach lumped the surface storage and hyporheic zones together in a single storage zone. In this study, we take a step towards a mechanistic model to explain the physics of water exchange between the surface water and the porous media by developing an improved mathematical model. For this purpose, we include the advection and dispersion processes into the transient storage zone, and we consider the hyporheic zone as a transient porous media from surface water to ground water. We use this improved model to solve a test problem in order to demonstrate its capabilities. Finally, we simulate the Uvas Creek experiment and compare our results to the observations described in Bencala and Walters (1983) [Bencala, K.E., Walters, R.A., 1983, Simulation of solute transport in a mountain pool-and-riffle stream – a transient storage model. Water Resources Research 19(3), 718–724] and to results of the existing transient storage model obtained by using OTIS. | |||||
BibTeX:
@article{Kazezyilmaz-Alhan2006,
author = {Kazezyılmaz-Alhan, Cevza Melek and Medina, Jr., Miguel A.},
title = {Stream solute transport incorporating hyporheic zone processes},
journal = {Journal of Hydrology},
year = {2006},
volume = {329},
number = {1-2},
pages = {26--38},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406000710}
}
|
|||||
| Keller, A.A. and Auset, M. | A review of visualization techniques of biocolloid transport processes at the pore scale under saturated and unsaturated conditions | 2007 | Advances in Water Resources Vol. 30(6-7)Biological processes in porous media: From the pore scale to the field, pp. 1392-1407 |
article | URL |
| Abstract: Field and column studies of biocolloid transport in porous media have yielded a large body of information, used to design treatment systems, protect water supplies and assess the risk of pathogen contamination. However, the inherent “black-box” approach of these larger scales has resulted in generalizations that sometimes prove inaccurate. Over the past 10–15 years, pore scale visualization techniques have improved substantially, allowing the study of biocolloid transport in saturated and unsaturated porous media at a level that provides a very clear understanding of the processes that govern biocolloid movement. For example, it is now understood that the reduction in pathways for biocolloids as a function of their size leads to earlier breakthrough. Interception of biocolloids by the porous media used to be considered independent of fluid flow velocity, but recent work indicates that there is a relationship between them. The existence of almost stagnant pore water regions within a porous medium can lead to storage of biocolloids, but this process is strongly colloid-size dependent, since larger biocolloids are focused along the central streamlines in the flowing fluid. Interfaces, such as the air–water interface, the soil–water interface and the soil–water–air interface, play a major role in attachment and detachment, with significant implications for risk assessment and system design. Important research questions related to the pore-scale factors that control attachment and detachment are key to furthering our understanding of the transport of biocolloids in porous media. | |||||
BibTeX:
@article{Keller2007,
author = {Keller, Arturo A. and Auset, Maria},
title = {A review of visualization techniques of biocolloid transport processes at the pore scale under saturated and unsaturated conditions},
booktitle = {Biological processes in porous media: From the pore scale to the field},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {6-7},
pages = {1392--1407},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001242}
}
|
|||||
| Kelley, H. and Busemeyer, J. | A comparison of models for learning how to dynamically integrate multiple cues in order to forecast continuous criteria | 2008 | Journal of Mathematical Psychology Vol. 52(4), pp. 218-240 |
article | URL |
| Abstract: Is human learning strongly adapted to the specific function learning task to which it is applied or is it a more general characteristic? This study addresses this question by empirically comparing the performance of five dynamic learning models across eleven different continuous criterion function learning tasks. We contrast three variants of rule-based and associative ‘neural network’ models with two variants of a Bayesian regression forecasting model. The tasks involve: deterministic and stochastic functions, functions with equal and unequal stimuli weights, functions with large and small numbers of stimuli, and linear and nonlinear functions. Evidence of task specificity would be implied if the most descriptive model of learning does systematically vary by task and subject; the alternative independence hypothesis is implied if there are no performance differences. We find two primary results: first, there is evidence of the task independence of learning; and the most valid model is a neural network variant. However, if the criterion variance is large or there are a large number of cues relevant for making predictions, the results favor Bayesian forecasting methods for providing reliable and valid predictions of human responses. | |||||
BibTeX:
@article{Kelley2008,
author = {Kelley, Hugh and Busemeyer, Jerome},
title = {A comparison of models for learning how to dynamically integrate multiple cues in order to forecast continuous criteria},
journal = {Journal of Mathematical Psychology},
year = {2008},
volume = {52},
number = {4},
pages = {218--240},
url = {http://www.sciencedirect.com/science/article/pii/S0022249608000217}
}
|
|||||
| Kelly, K.S. and Krzysztofowicz, R. | A bivariate meta-Gaussian density for use in hydrology | 1997 | Stochastic Hydrology and Hydraulics Vol. 11(1), pp. 17-31 |
article | URL |
| Abstract: Convenient bivariate densities found in the literature are often unsuitable for modeling hydrologic variates. They either constrain the range of association between variates, or fix the form of the marginal distributions. The bivariate meta-Gaussian density is constructed by embedding the normal quantile transform of each variate into the Gaussian law. The density can represent a full range of association between variates and admits arbitrarily specified marginal distributions. Modeling and estimation can be decomposed into i) independent analyses of the marginal distributions, and ii) investigation of the dependence structure. Both statistical and judgmental estimation procedures are possible. Some comparisons to recent applications of bivariate densities in the hydrologic literature motivate and illustrate the model. | |||||
BibTeX:
@article{Kelly1997,
author = {Kelly, K. S. and Krzysztofowicz, R.},
title = {A bivariate meta-Gaussian density for use in hydrology},
journal = {Stochastic Hydrology and Hydraulics},
publisher = {Springer Berlin / Heidelberg},
year = {1997},
volume = {11},
number = {1},
pages = {17--31},
url = {http://dx.doi.org/10.1007/BF02428423}
}
|
|||||
| Kelly, P. | Engineering, a civilising influence? | 2010 | Futures Vol. 42(10)Global Mindset Change, pp. 1110-1118 |
article | URL |
| Abstract: The global environment is increasingly under threat and we face a challenge with little time to respond. Are we prepared to change the actions and attitudes that have led to this parlous situation, and if we are, how do we do it? Is the world ready for a more ecologically benign, less economically driven, peaceful and spiritually oriented way of living? My challenge lies in higher education. How do you encourage such values in a tertiary education system which has spent many years applying and rewarding a ‘respond to the market’ discourse? My responses are grounded in transformative education research with large diverse cohorts of first year engineering students. This paper also uses a critical futures methodology, Causal Layered Analysis, to update my concerns about Australian engineering education and the profession, using two recent reports. The aim is to offer constructive insights that may be transferable to educators in other contexts. | |||||
BibTeX:
@article{Kelly2010,
author = {Kelly, Patricia},
title = {Engineering, a civilising influence?},
booktitle = {Global Mindset Change},
journal = {Futures},
year = {2010},
volume = {42},
number = {10},
pages = {1110--1118},
url = {http://www.sciencedirect.com/science/article/pii/S0016328710001813}
}
|
|||||
| Kelly, P. | Letter from the oasis: Helping engineering students to become sustainability professionals | 2006 | Futures Vol. 38(6)Futures studies and action research, pp. 696-707 |
article | URL |
| Abstract: Sustainability scientists call for education that produces ‘sustainability professionals’, who understand the need for sustainability and can work towards it. However, students often have very different ideas, usually based on an expectation of continued unlimited economic growth. This paper, based on research with large, diverse, first year engineering cohorts, argues that a reflective process and on-line support can contribute to a learning oasis—a supportive environment that encourages students to leave their cultural and intellectual comfort zones. In these circumstances, most students will engage with the personal and professional challenges of what it means to be Globo sapiens, a wise global citizen and global sustainability professional for an increasingly complex century. [An earlier version of this paper was presented at the International Conference in Sustainability Engineering and Science, Auckland, New Zealand/Aotearoa, 6–9 July, 2004 and is included in the CDROM of proceedings from that conference.] | |||||
BibTeX:
@article{Kelly2006,
author = {Kelly, Patricia},
title = {Letter from the oasis: Helping engineering students to become sustainability professionals},
booktitle = {Futures studies and action research},
journal = {Futures},
year = {2006},
volume = {38},
number = {6},
pages = {696--707},
url = {http://www.sciencedirect.com/science/article/pii/S0016328705001758}
}
|
|||||
| Kendall, S.M.G., Stuart, A. and Ord, J.K. | Kendall's advanced theory of statistics: Volume 1: Distribution Theory [BibTeX] |
1994 | Vol. 1, pp. - |
book | |
BibTeX:
@book{Kendall1994,
author = {Kendall, Sir Maurice G. and Stuart, Alan and Ord, J. K.},
title = {Kendall's advanced theory of statistics: Volume 1: Distribution Theory},
publisher = {Arnold, a member of the Hodder-Headline Group},
year = {1994},
volume = {1},
pages = {--},
edition = {Sixth}
}
|
|||||
| Kenyon, C.M., Savage, S. and Ball, B. | Equivalence of linear deviation about the mean and mean absolute deviation about the mean objective functions | 1999 | Operations Research Letters Vol. 24(4), pp. 181-185 |
article | URL |
| Abstract: Konno (Oper. Res. Soc. Japan 33 (1990) 139–156). introduced a piecewise linear objective function for portfolio optimization to measure the deviation from a mean return. An apparently asymmetric objective function can be obtained by changing the gradients either side of the mean. However, we show that when the linear deviations are taken relative to the mean, any two piece linear objective function is equivalent to the mean absolute deviation, which is symmetric. Equivalent is used here to mean that one function is proportional to the other. Also we show that emphasizing upside risk is exactly equal to emphasizing downside risk when these are taken relative to the mean. No distributional assumptions are required beyond the existence of the first moment. In this case an investor changing from upside to downside risk would not change his solution at all, despite what the investor intended to achieve. | |||||
BibTeX:
@article{Kenyon1999,
author = {Kenyon, C. M and Savage, S. and Ball, B.},
title = {Equivalence of linear deviation about the mean and mean absolute deviation about the mean objective functions},
journal = {Operations Research Letters},
year = {1999},
volume = {24},
number = {4},
pages = {181--185},
url = {http://www.sciencedirect.com/science/article/pii/S0167637799000115}
}
|
|||||
| Keshtkar, A., Meyssami, B., Abolhamd, G., Ghaforian, H. and Khalagi Asadi, M. | Mathematical modeling of non-ideal mixing continuous flow reactors for anaerobic digestion of cattle manure | 2003 | Bioresource Technology Vol. 87(1), pp. 113-124 |
article | URL |
| Abstract: Most conventional digesters used for animal wastewater treatment include continuously stirred-tank reactors. While imperfect mixing patterns are more common than ideal ones in real reactors, anaerobic digestion models often assume complete mixing conditions. Therefore, their applicability appears to be limited. In this study, a mathematical model for anaerobic digestion of cattle manure was developed to describe the dynamic behavior of non-ideal mixing continuous flow reactors. The microbial kinetic model includes an enzymatic hydrolysis step and four microbial growth steps, together with the effects of substrate inhibition, pH and thermodynamic considerations. The biokinetic expressions were linked to a simple two-region liquid mixing model, which considered the reactor volume in two separate sections, the flow-through and the retention regions. Deviations from an ideal completely mixed regime were represented by changing the relative volume of the flow-through region (a) and the ratio of the internal exchange flow rate to the feed flow rate (b). The effects of the hydraulic retention time, the composition of feed, the initial conditions of the reactor and the degree of mixing on process performance can be evaluated by the dynamic model. The simulation results under different conditions showed that deviations from the ideal mixing regime decreased the methane yield and resulted in a reduced performance of the anaerobic reactors. The evaluation of the impact of the characteristic mixing parameters (a) and (b) on the anaerobic digestion of cattle manure showed that both liquid mixing parameters had significant effects on reactor performance. | |||||
BibTeX:
@article{Keshtkar2003,
author = {Keshtkar, A. and Meyssami, B. and Abolhamd, G. and Ghaforian, H. and Khalagi Asadi, M.},
title = {Mathematical modeling of non-ideal mixing continuous flow reactors for anaerobic digestion of cattle manure},
journal = {Bioresource Technology},
year = {2003},
volume = {87},
number = {1},
pages = {113--124},
url = {http://www.sciencedirect.com/science/article/pii/S0960852402001049}
}
|
|||||
| Kim, J.S. and Yum, B.-J. | Selection between Weibull and lognormal distributions: A comparative simulation study | 2008 | Computational Statistics & Data Analysis Vol. 53(2), pp. 477-485 |
article | URL |
| Abstract: How to select the correct distribution for a given set of data is an important issue, especially when the tail probabilities are of interest as in lifetime data analysis. The Weibull and lognormal distributions are assumed most often in analyzing lifetime data, and in many cases, they are competing with each other. In addition, lifetime data are usually censored due to the constraint on the amount of testing time. A literature review reveals that little attention has been paid to the selection problems for the case of censored samples. In this article, relative performances of the two selection procedures, namely, the maximized likelihood and scale invariant procedures are compared for selecting between the Weibull and lognormal distributions for the cases of not only complete but also censored samples. Monte Carlo simulation experiments are conducted for various combinations of the censoring rate and sample size, and the performance of each procedure is evaluated in terms of the probability of correct selection (PCS) and average error rate. Then, previously unknown behaviors and relative performances of the two procedures are summarized. Computational results suggest that the maximized likelihood procedure can be generally recommended for censored as well as complete sample cases. | |||||
BibTeX:
@article{Kim2008,
author = {Kim, Jin Seon and Yum, Bong-Jin},
title = {Selection between Weibull and lognormal distributions: A comparative simulation study},
journal = {Computational Statistics & Data Analysis},
year = {2008},
volume = {53},
number = {2},
pages = {477--485},
url = {http://www.sciencedirect.com/science/article/pii/S0167947308004258}
}
|
|||||
| Kim, K.-C., Park, G.-H., Jung, S.-H., Lee, J.-L. and Suh, K.-S. | Analysis on the characteristics of a pollutant dispersion in river environment | 2011 | Annals of Nuclear Energy Vol. 38(2-3), pp. 232-237 |
article | URL |
| Abstract: A tracer experiment using a radioisotope was carried out to investigate the characteristics of pollutant transport and to estimate the dispersion coefficients in a river system. A well-known radioisotope tracer technique was applied to measure the dispersion coefficients in Daejong river which is located in the southeast area in Korea. The dispersion coefficients were determined by moment, routing and analytical methods based on the measured radioisotope data. Two-dimensional numerical models were used to simulate the flow fields and the concentration distributions of the radioisotope injected into the river. The calculated results were compared with the measurements. As a comparative study, the computed concentration distributions agreed well in the case of the usage of the dispersion coefficients determined by the moment method. | |||||
BibTeX:
@article{Kim2011,
author = {Kim, Ki-Chul and Park, Geon-Hyeong and Jung, Sung-Hee and Lee, Jung-Lyul and Suh, Kyung-Suk},
title = {Analysis on the characteristics of a pollutant dispersion in river environment},
journal = {Annals of Nuclear Energy},
year = {2011},
volume = {38},
number = {2-3},
pages = {232--237},
url = {http://www.sciencedirect.com/science/article/pii/S0306454910003920}
}
|
|||||
| Kincaid, T.R. | Groundwater Tracing in the Woodville Karst Plain - Part I: An Overview of Groundwater Tracing | 2003 | DIR Quest (Journal of the Global Underwater Explorers) Vol. 4(4), pp. 31-37 |
article | URL |
| Abstract: The purpose of this presentation is to provide an overview of recent groundwater tracing efforts in North Central Florida that have been undertaken as part of a broader effort to protect the water quality in Wakulla Spring and a discussion of some implications to development strategies and land use practices and that have arisen from these efforts. The specific tracer tests that will be discussed have been made possible by GUE support and its WKPP project divers. Funding support was provided by the Florida Geological Survey (FGS) and carried out by GUE VP/Science director Dr. Todd Kincaid in cooperation with H2H Associates and the Florida State University Oceanography Department in a cooperative effort led by the Florida State University Geophysical Fluid Dynamics Institute and the Hydrogeology Consortium. | |||||
BibTeX:
@article{Kincaid2003,
author = {Kincaid, Todd R.},
title = {Groundwater Tracing in the Woodville Karst Plain - Part I: An Overview of Groundwater Tracing},
journal = {DIR Quest (Journal of the Global Underwater Explorers)},
year = {2003},
volume = {4},
number = {4},
pages = {31--37},
url = {http://www.gue.com/?q=en/node/798}
}
|
|||||
| Kincaid, T.R. and Werner, C.L. | Conduit Flow Paths and Conduit/Matrix Interactions Defined by Quantitative Groundwater Tracing in the Floridan Aquifer | 2008 | Vol. 327(41003)Sinkholes and the Engineering and Environmental Impacts of Karst (GSP 183) -- Proceedings of the ASCE Eleventh Multidisciplinary Conference, pp. 28-28 |
inproceedings | URL |
| Abstract: Groundwater tracing and cave mapping conducted in the Woodville Karst Plain of north Florida have revealed an extensive dendritic network of saturated conduits, more than 70 km in total length, that convey water to Wakulla Spring from the northeast, north, northwest, and south. In some places, the conduits are known to connect to swallets and in others are known to extend up‐gradient into the aquifer matrix. Two sets of tracer tests were performed in 2005 and 2006 to map groundwater flow pathways between the Ames Sink group of swallets, which receive approximately 60% of the City of Tallahassee's storm water runoff, and the City's wastewater spray field, and characterize groundwater velocities along those pathways. The results of these tests revealed that water flows rapidly from both locations to Wakulla Spring. Groundwater velocities through the swimmable portion of the conduit network range from ∼1500 to >2000 m/day and velocities through the smaller conduit pathways range from 250 to > 800 m/day. We have also compared the shape and timing of the tracer concentration recovery curves to groundwater levels and swallet stage during the tested periods. The results indicate that the aquifer is composed of conduits with varying capacities to convey water and that those capacities establish controls on local hydraulic gradients in the aquifer. More broadly, the results of these tracer studies indicate that tracer recovery curves can reveal significant and potentially quantifiable insights about the hydraulic dynamics of the aquifer when interpreted relative to continuously measured hydraulic data such as heads and flows within the region being tested. | |||||
BibTeX:
@inproceedings{Kincaid2008,
author = {Kincaid, Todd R. and Werner, Christopher L.},
title = {Conduit Flow Paths and Conduit/Matrix Interactions Defined by Quantitative Groundwater Tracing in the Floridan Aquifer},
booktitle = {Sinkholes and the Engineering and Environmental Impacts of Karst (GSP 183) -- Proceedings of the ASCE Eleventh Multidisciplinary Conference},
publisher = {American Society of Civil Engineers (ASCE)},
year = {2008},
volume = {327},
number = {41003},
pages = {28--28},
url = {http://dx.doi.org/10.1061/41003(327)28}
}
|
|||||
| King, E., Tuncay, K., Ortoleva, P. and Meile, C. | Modeling biogeochemical dynamics in porous media: Practical considerations of pore scale variability, reaction networks, and microbial population dynamics in a sandy aquifer | 2010 | Journal of Contaminant Hydrology Vol. 112(1-4)Frontiers in Reactive Transport: Microbial Dynamics nad Redox Zonation in the Subsurface, pp. 130-140 |
article | URL |
| Abstract: Prediction of the fate and environmental impacts of groundwater contaminants requires the identification of relevant biogeochemical processes and necessitates the macroscopic representation of microbial activity occurring at the microscale. Using a well-studied sandy aquifer environment, we evaluate the importance of pore distribution on organic matter respiration in a porous medium environment by performing spatially explicit simulations of microbial metabolism at the sub-millimeter scale. Model results using an idealized porous medium under non-biofilm forming conditions indicate that while some heterogeneity is observed for flow rates, distributions of microbes and dissolved organic substrates remain relatively homogenous at the grain scale. At the macroscale in the same environment, we assess the impact of a comprehensive reaction network description for a phenolic contaminant plume, and compare the findings to a setting describing organic matter breakdown in a coastal marine sediment. This comparison reveals the importance of reactions recycling reduced metabolites at redox interfaces, leading to a competition for oxidants. When the spatio-temporal dynamics of microbial groups are accounted for, our simulations show the importance of reaction energetics and nutrient limitations such as microbial nitrogen demands. | |||||
BibTeX:
@article{King2010,
author = {King, E.L. and Tuncay, K. and Ortoleva, P. and Meile, C.},
title = {Modeling biogeochemical dynamics in porous media: Practical considerations of pore scale variability, reaction networks, and microbial population dynamics in a sandy aquifer},
booktitle = {Frontiers in Reactive Transport: Microbial Dynamics nad Redox Zonation in the Subsurface},
journal = {Journal of Contaminant Hydrology},
year = {2010},
volume = {112},
number = {1-4},
pages = {130--140},
url = {http://www.sciencedirect.com/science/article/pii/S0169772209001636}
}
|
|||||
| King, K., Balogh, J. and Harmel, R. | Nutrient flux in storm water runoff and baseflow from managed turf | 2007 | Environmental Pollution Vol. 150(3), pp. 321-328 |
article | URL |
| Abstract: The urban landscape is comprised of many land uses, none more intensively managed than turfgrass; however, quantification of nutrient losses from specific land uses within urban watersheds, specifically golf courses is limited. Nitrate (NO3-N) and dissolved reactive phosphorus (DRP) were measured on a golf course in Austin, TX, USA from April 1, 1998 to March 31, 2003. NO3-N and DRP concentrations measured in storm flow were significantly greater exiting the course compared to those entering the course. Significant differences were also measured in baseflow NO3-N concentrations. The measured loading from the course was 4.0 kg NO3-N ha−1 yr−1 (11% of applied) and 0.66 kg DRP ha−1 yr−1 (8% of applied). The resulting concentrations contributed by the course were 1.2 mg L−1 NO3-N and 0.2 mg L−1 DRP. At these levels, NO3-N poses minimal environmental risk. However, the DRP concentration is twice the recommended level to guard against eutrophication. | |||||
BibTeX:
@article{King2007,
author = {King, K.W. and Balogh, J.C. and Harmel, R.D.},
title = {Nutrient flux in storm water runoff and baseflow from managed turf},
journal = {Environmental Pollution},
year = {2007},
volume = {150},
number = {3},
pages = {321--328},
url = {http://www.sciencedirect.com/science/article/pii/S0269749107000802}
}
|
|||||
| King, L., Byl Thomas and Painter, R. | Research approach to teaching groundwater biodegradation in karst aquifers | 2006 | American Society for Engineering Education (ASEE) Annual Conference and Exposition, Conference Proceedings 2006-1662 | inproceedings | |
| Abstract: TSU in partnership with the USGS has conducted extensive research regarding biodegradation of contaminants in karst aquifers. This research resulted in the development of a numerical approach to modeling biodegradation of contaminants in karst aquifers that is taught to environmental engineering students in several steps. First, environmental engineering students are taught chemical-reaction engineering principles relating to a wide variety of environmental fate and transport issues. Second, as part of TSU’s engineering course curriculum, students use a non-ideal flow laboratory reactor system and run a tracer study to establish residence time distribution (RTD). Next, the students couple that formula to a first-order biodegradation rate and predict the removal of a biodegradable contaminant as a function of residence time. Following this, students are shown data collected from karst bedrock wells that suggest that karst aquifers are analogous to non-ideal flow reactors. The students are challenged to develop rates of biodegradation through lab studies and use their results to predict biodegradaton at an actual contaminated karst site. Field studies are also conducted to determine the accuracy of the students’ predictions. This academic approach teaches biodegradation processes, rate-kinetic processes, hydraulic processes and numerical principles. The students are able to experience how chemical engineering principles can be applied to other situations, such as, modeling biodegradation of contaminants in karst aquifers. This paper provides background on the chemical engineering principles and karst issues used in the research-enhanced curriculum. | |||||
BibTeX:
@inproceedings{King2006,
author = {King, Lashun and Byl, Thomas, and Painter, Roger},
title = {Research approach to teaching groundwater biodegradation in karst aquifers},
booktitle = {American Society for Engineering Education (ASEE) Annual Conference and Exposition, Conference Proceedings 2006-1662},
publisher = {American Society for Engineering Education (ASEE)},
year = {2006}
}
|
|||||
| King, L.K., Painter, R.D. and Byl, T. | Adaptation of the Residence Time Distribution (RTD)-Biodegradation Model to Quantify Peroxide-Enhanced Fuel Biodegradation in a Single Karst Well | 2005 | U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160, pp. 174-179 | inproceedings | URL |
| Abstract: This field study was conducted to determine if a numerical model incorporating residence time distri- bution (RTD) coupled to a first-order rate of biodegradation (k') could be used to quantify toluene and ben- zene removal in a single karst-well injection system. This study involved injecting sodium chloride (NaCl) as a conservative tracer, as well as hydrogen peroxide (H2O2), to enhance aerobic biodegradation of toluene and benzene. A 100-gallon volume of fuel-contaminated karst aquifer water was pumped into a container. NaCl (1.25 kilograms) and 33 percent H2O2 (4 liters) were mixed into the water and injected back into the bedrock aquifer. The NaCl, dissolved oxygen, benzene and toluene concentrations were monitored for sev- eral weeks. Results show that benzene and toluene concentrations declined approximately 10 times faster than the NaCl concentrations, indicating enhanced biodegradation. The RTD was calculated by using the declining NaCl-concentration curve through time. The biodegradation rate was derived from the benzene and toluene data. The RTD-biodegradation formula (described in this paper) was used to predict and quan- tify the enhanced biodegradation of benzene and toluene in the karst aquifer. The RTD-biodegradation for- mula predicted benzene and toluene concentrations in the well through time to within 1 microgram per liter (µg/L) of the actual concentration. This close agreement between the RTD-biodegradation model predic- tion and the measured concentration confirms that this method can be used to quantify enhanced biodegra- dation in a single karst injection well. | |||||
BibTeX:
@inproceedings{King2005,
author = {King, Lashun K. and Painter, Roger D. and Byl, T.D.},
title = {Adaptation of the Residence Time Distribution (RTD)-Biodegradation Model to Quantify Peroxide-Enhanced Fuel Biodegradation in a Single Karst Well},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2005},
pages = {174--179},
url = {pubs.usgs.gov/sir/2005/5160/index.html}
}
|
|||||
| Kingsbury, J.A. | Relation Between Flow and Temporal Variations of Nitrate and Pesticides in Two Karst Springs in Northern Alabama1 | 2008 | JAWRA Journal of the American Water Resources Association Vol. 44(2), pp. 478-488 |
article | URL |
| Abstract: Abstract: Two karst springs in the Mississippian Carbonate Aquifer of northern Alabama were sampled between March 1999 and March 2001 to characterize the variability in concentration of nitrate, pesticides, selected pesticide degradates, water temperature, and inorganic constituents. Water temperature and inorganic ion data for McGeehee Spring indicate that this spring represents a shallow flow system with a relatively short average ground-water residence time. Water issuing from the larger of the two springs, Meridianville Spring, maintained a constant temperature, and inorganic ion data indicate that this water represents a deeper flow system having a longer average ground-water residence time than McGeehee Spring. Although water-quality data indicate differing short-term responses to rainfall at the two springs, the seasonal variation of nitrate and pesticide concentrations generally is similar for the two springs. With the exception of pesticides detected at low concentrations, the coefficient of variation for most constituent concentrations was less than that of flow at both springs, with greater variability in concentration at McGeehee Spring. Degradates of the herbicides atrazine and fluometuron were detected at concentrations comparable to or greater than the parent pesticides. Decreases in concentration of the principal degradate of fluometuron from about July to November indicate that the degradation rate may decrease as fluometuron (demethylfluometuron) moves deeper into the soil after application. Data collected during the study show that from about November to March when recharge rates increase, nitrate and residual pesticides in the soil, unsaturated zone, and storage within the aquifer are transported to the spring discharges. Because of the increase in recharge, fluometuron loads discharged from the springs during the winter were comparable to loads discharged at the springs during the growing season. | |||||
BibTeX:
@article{Kingsbury2008,
author = {Kingsbury, James A.},
title = {Relation Between Flow and Temporal Variations of Nitrate and Pesticides in Two Karst Springs in Northern Alabama1},
journal = {JAWRA Journal of the American Water Resources Association},
publisher = {Blackwell Publishing Ltd},
year = {2008},
volume = {44},
number = {2},
pages = {478--488},
url = {http://dx.doi.org/10.1111/j.1752-1688.2008.00176.x}
}
|
|||||
| Kirchner, G. and Daillant, O. | Accumulation of 210Pb, 226Ra and radioactive cesium by fungi | 1998 | Science of The Total Environment Vol. 222(1–2), pp. 63-70 |
article | URL |
| Abstract: Fungi sampled in three areas in France were analyzed by γ-spectrometry for their concentrations of 134Cs, 137Cs, 210Pb and 226Ra. In most of the samples radioactive cesium was detected with a maximum of 2860 Bq kg−1 (dry wt.). Activity concentrations of 210Pb were in the range <1.76–36.5 Bq kg−1 (dry wt.). Activity concentrations of 226Ra were consistently lower, often by one order of magnitude. Models are developed to estimate the contributions of atmospheric 210Pb deposited onto the fruit bodies to the measured 210Pb concentrations and of the uptake of 222Rn soluted in soil pore water which subsequently decays into 210Pb. It is shown that both pathways are of only minor importance. Comparison with the soil–mushroom concentration ratios of stable lead, which were determined for some of the samples, confirmed that 210Pb in mushrooms mainly originates from direct uptake of 210Pb present in the soil. Despite of the high concentrations of 137Cs detected in most of the mushrooms, radiation doses to individuals due to mushroom consumption are dominated by 210Pb for the majority of the edible mushrooms sampled. | |||||
BibTeX:
@article{Kirchner1998,
author = {Kirchner, Gerald and Daillant, Olivier},
title = {Accumulation of 210Pb, 226Ra and radioactive cesium by fungi},
journal = {Science of The Total Environment},
year = {1998},
volume = {222},
number = {1–2},
pages = {63--70},
url = {http://www.sciencedirect.com/science/article/pii/S0048969798002885}
}
|
|||||
| Kirchner, J.W., Feng, X. and Neal, C. | Catchment-scale advection and dispersion as a mechanism for fractal scaling in stream tracer concentrations | 2001 | Journal of Hydrology Vol. 254(1–4), pp. 82-101 |
article | URL |
| Abstract: Time series of chemical tracers in rainfall and streamflow can be used to probe the internal workings of catchments. We have recently proposed that catchments act as fractal filters for inert chemical tracers like chloride, converting ‘white noise’ rainfall chemistry inputs into fractal ‘1/f noise’ chemical time series in runoff [Nature 403 (2000) 524]. This implies that catchments have long-tailed travel-time distributions, and thus retain soluble contaminants for unexpectedly long timespans. Here we show that these long-tailed travel-time distributions, and the fractal tracer time series that they imply, can be generated by advection and dispersion of spatially distributed rainfall inputs as they travel toward a channel. Tracer pulses that land close to the stream reach it promptly, with relatively little dispersion. Tracer pulses that land farther upslope must travel farther to reach the stream, and undergo more dispersion. The tracer signal in the stream will be the integral of the contributions from each point along the length of the hillslope, with a peak at short lag times (reflecting tracers landing near the stream) and a long tail (reflecting tracers landing farther from the stream). Here we integrate the advection–dispersion equation for rainfall tracers landing at all points on a simple model hillslope, and show that it yields fractal tracer behavior, as well as a travel-time distribution nearly equivalent to that found empirically [Nature 403 (2000) 524]. However, it does so only when the dispersion length scale approaches the length of the hillslope, implying that subsurface transport is dominated by large conductivity contrasts related to macropores, fracture networks, and similar large-scale heterogeneities in subsurface conductivity. Thus, the 1/f scaling observed at our study sites indicates that these catchments are dominated by flowpaths that exhibit macro-dispersion over the longest possible length scales. | |||||
BibTeX:
@article{Kirchner2001,
author = {Kirchner, James W. and Feng, Xiahong and Neal, Colin},
title = {Catchment-scale advection and dispersion as a mechanism for fractal scaling in stream tracer concentrations},
journal = {Journal of Hydrology},
year = {2001},
volume = {254},
number = {1–4},
pages = {82--101},
url = {http://www.sciencedirect.com/science/article/pii/S0022169401004875}
}
|
|||||
| Kirchner, J.W., Feng, X. and Neal, C. | Fractal stream chemistry and its implications for contaminant transport in catchments | 2000 | Nature Vol. 403(6769), pp. 524-527 |
article | URL |
| Abstract: The time it takes for rainfall to travel through a catchment and reach the stream is a fundamental hydraulic parameter that controls the retention of soluble contaminants and thus the downstream consequences of pollution episodes1, 2. Catchments with short flushing times will deliver brief, intense contaminant pulses to downstream waters, whereas catchments with longer flushing times will deliver less intense but more sustained contaminant fluxes. Here we analyse detailed time series of chloride, a natural tracer, in both rainfall and runoff from headwater catchments at Plynlimon, Wales. We show that, although the chloride concentrations in rainfall have a white noise spectrum, the chloride concentrations in streamflow exhibit fractal 1/f scaling over three orders of magnitude. The fractal fluctuations in tracer concentrations indicate that these catchments do not have characteristic flushing times. Instead, their travel times follow an approximate power-law distribution implying that they will retain a long chemical memory of past inputs. Contaminants will initially be flushed rapidly, but then low-level contamination will be delivered to streams for a surprisingly long time. | |||||
BibTeX:
@article{Kirchner2000,
author = {Kirchner, James W. and Feng, Xiahong and Neal, Colin},
title = {Fractal stream chemistry and its implications for contaminant transport in catchments},
journal = {Nature},
year = {2000},
volume = {403},
number = {6769},
pages = {524--527},
url = {http://dx.doi.org/10.1038/35000537}
}
|
|||||
| Kirchner, J.W., Hooper, R.P., Kendall, C., Neal, C. and Leavesley, G. | Testing and validating environmental models | 1996 | Science of The Total Environment Vol. 183(1–2)Modelling in Environmental Studies, pp. 33-47 |
article | URL |
| Abstract: Generally accepted standards for testing and validating ecosystem models would benefit both modellers and model users. Universally applicable test procedures are difficult to prescribe, given the diversity of modelling approaches and the many uses for models. However, the generally accepted scientific principles of documentation and disclosure provide a useful framework for devising general standards for model evaluation. Adequately documenting model tests requires explicit performance criteria, and explicit benchmarks against which model performance is compared. A model's validity, reliability, and accuracy can be most meaningfully judged by explicit comparison against the available alternatives. In contrast, current practice is often characterized by vague, subjective claims that model predictions show ‘acceptable’ agreement with data; such claims provide little basis for choosing among alternative models. Strict model tests (those that invalid models are unlikely to pass) are the only ones capable of convincing rational skeptics that a model is probably valid. However, ‘false positive’ rates as low as 10% can substantially erode the power of validation tests, making them insufficiently strict to convince rational skeptics. Validation tests are often undermined by excessive parameter calibration and overuse of ad hoc model features. Tests are often also divorced from the conditions under which a model will be used, particularly when it is designed to forecast beyond the range of historical experience. In such situations, data from laboratory and field manipulation experiments can provide particularly effective tests, because one can create experimental conditions quite different from historical data, and because experimental data can provide a more precisely defined ‘target’ for the model to hit. We present a simple demonstration showing that the two most common methods for comparing model predictions to environmental time series (plotting model time series against data time series, and plotting predicted versus observed values) have little diagnostic power. We propose that it may be more useful to statistically extract the relationships of primary interest from the time series, and test the model directly against them. | |||||
BibTeX:
@article{Kirchner1996,
author = {Kirchner, James W. and Hooper, Richard P. and Kendall, Carol and Neal, Colin and Leavesley, George},
title = {Testing and validating environmental models},
booktitle = {Modelling in Environmental Studies},
journal = {Science of The Total Environment},
year = {1996},
volume = {183},
number = {1–2},
pages = {33--47},
url = {http://www.sciencedirect.com/science/article/pii/0048969795049711}
}
|
|||||
| Kirchner, J.W., Tetzlaff, D. and Soulsby, C. | Comparing chloride and water isotopes as hydrological tracers in two Scottish catchments | 2010 | Hydrological Processes Vol. 24(12), pp. 1631-1645 |
article | URL |
| Abstract: Time series of chloride concentrations and oxygen-18 isotopic ratios are widely used for tracing catchment storage and mixing processes and for inferring catchment travel-time distributions. However, neither chloride nor oxygen-18 is an ideal hydrologic tracer: chloride concentrations in streamwater can be affected by dry deposition, evapoconcentration and biogeochemical cycling, and water isotopes can be fractionated by evaporation. One way to test the reliability of these tracers is to determine whether, despite artifacts such as these, both tracers lead to similar inferences when measured in the same catchment. Here, we compare chloride and oxygen-18 time series in the Girnock and Allt' a Mharcaidh catchments in Scotland. Semivariograms and power spectra for both tracers exhibit similar patterns of fluctuation damping, implying that the travel-time distributions of the two tracers have similar shapes. Fluctuations of both tracers are strongly damped in streamflow compared to precipitation, implying that these catchments integrate tracer signatures over many different storm events. Streamflow fluctuations of both tracers are more strongly damped at the Allt' a Mharcaidh catchment, implying longer storage and greater mixing of waters of different ages, compared to the Girnock catchment. At both sites, streamflow fluctuations of oxygen-18 are more strongly damped, relative to precipitation, than those of chloride, leading to estimates of mean travel times that are longer, by a factor of 2–3, for oxygen-18 than for chloride. The greater variability of chloride compared to oxygen-18 may arise from spatially and temporally varying occult deposition and evapoconcentration. Nonetheless, the similarities in the behaviour of the two tracers imply that the strong tracer damping and long travel times that have been observed in many catchment studies are not artifacts, but instead reflect storage and mixing of waters over long time scales. | |||||
BibTeX:
@article{Kirchner2010,
author = {Kirchner, James W. and Tetzlaff, Doerthe and Soulsby, Chris},
title = {Comparing chloride and water isotopes as hydrological tracers in two Scottish catchments},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {12},
pages = {1631--1645},
url = {http://dx.doi.org/10.1002/hyp.7676}
}
|
|||||
| Kitron, A., Elperin, T. and Tamir, A. | Monte Carlo simulation of gas-solids suspension flows in impinging streams reactors | 1990 | International Journal of Multiphase Flow Vol. 16(1), pp. 1-17 |
article | URL |
| Abstract: Impinging streams reactors have been employed in various fields of chemical engineering, as a means of enhancing the rates of convective transfer processes. The analysis of the hydrodynamics of gas-solids suspension flows in these reactors requires that collisions between particles be taken into account. The stochastic model for gas-solids suspension flows, based on the Boltzmann transport equation, is presented. The system of nonlinear integro-differential transport equations is solved using the Monte Carlo method. A qualitative agreement is obtained between the predicted and experimental results for the particle concentration distribution in an impinging streams reactor. The particle concentrations in the impingement zone of two particle-laden jets are strongly reduced by the effects of inter-particle collisions. The analysis of laminar pipe flows in the absence of gravity and lift forces (Saffman force etc.) reveals a collision-induced migration of particles towards the pipe wall and, to a lesser extent, towards the core. In turbulent vertical pipe flow, particles migrate towards the pipe core and the laminar sublayer. Collison-induced effects become more pronounced in mixture flows with particles of different sizes and densities. | |||||
BibTeX:
@article{Kitron1990,
author = {Kitron, A and Elperin, T. and Tamir, A.},
title = {Monte Carlo simulation of gas-solids suspension flows in impinging streams reactors},
journal = {International Journal of Multiphase Flow},
year = {1990},
volume = {16},
number = {1},
pages = {1--17},
url = {http://www.sciencedirect.com/science/article/pii/030193229090033F}
}
|
|||||
| Klaus, E. | A new equation for correlating a pipe flow reactor with a cascade of mixed reactors | 1996 | Chemical Engineering Science Vol. 51(23), pp. 5077-5080 |
article | URL |
| Abstract: For many reactions, a pipe flow reactor and a cascade of ideally mixed reactors yield similar results, if we use a proper correlation between the Bodenstein number of the pipe flow reactor and the number of stages for the cascade. However, existing equations for this correlation, which are derived from residence time considerations, apply only for Bodenstein numbers greater than 7 or stage numbers greater than 6. In this paper a new equation is developed by comparing the governing equations for the reaction in both systems. It is shown that this correlation yields good agreement of the output concentrations for all stage numbers down to a single stage, respectively, zero Bodenstein number, even for a successive reaction. | |||||
BibTeX:
@article{Klaus1996,
author = {Klaus, Elgeti},
title = {A new equation for correlating a pipe flow reactor with a cascade of mixed reactors},
journal = {Chemical Engineering Science},
year = {1996},
volume = {51},
number = {23},
pages = {5077--5080},
url = {http://www.sciencedirect.com/science/article/pii/S0009250996003429}
}
|
|||||
| Kliche, D.V., Smith, P.L. and Johnson, R.W. | L-Moment Estimators as Applied to Gamma Drop Size Distributions | 2008 | Journal of Applied Meteorology and Climatology Vol. 47(12), pp. 3117-3130 |
article | URL |
| Abstract: The traditional approach with experimental raindrop size data has been to use the method of moments in the fitting procedure to estimate the parameters for the raindrop size distribution function. However, the moment method is known to be biased and can have substantial errors. Therefore, the L-moment method, which is widely used by hydrologists, was investigated as an alternative. The L-moment method was applied, along with the moment and maximum likelihood methods, to samples taken from simulated gamma raindrop populations. A comparison of the bias and the errors involved in the L-moments, moments, and maximum likelihood procedures shows that, with samples covering the full range of drop sizes, L-moments and maximum likelihood outperform the method of moments. For small sample sizes the moment method gives a large bias and large error while the L-moment method gives results close to the true population values, outperforming even maximum likelihood results. Because the goal of this work is to understand the properties of the various fitting procedures, the investigation was expanded to include the effects of the absence of small drops in the samples (typical disdrometer minimum size thresholds are 0.3–0.5 mm). The results show that missing small drops (due to the instrumental constraint) can result in a large bias in the case of the L-moment and maximum likelihood fitting methods; this bias does not decrease much with increasing sample size. Because the very small drops have a negligible contribution to moments of order 2 or higher, the bias in the moment methods seems to be about the same as in the case of full samples. However, when moments of order less than 2 are needed (as in the case of modelers using moments 0 and 3), the moment method gives much larger bias. Therefore a modification of these methods is needed to handle the truncated-data situation. | |||||
BibTeX:
@article{Kliche2008,
author = {Kliche, Donna V. and Smith, Paul L. and Johnson, Roger W.},
title = {L-Moment Estimators as Applied to Gamma Drop Size Distributions},
journal = {Journal of Applied Meteorology and Climatology},
publisher = {American Meteorological Society},
year = {2008},
volume = {47},
number = {12},
pages = {3117--3130},
url = {http://dx.doi.org/10.1175/2008JAMC1936.1}
}
|
|||||
| Kluge, T., Riechelmann, D., Wieser, M., Spötl, C., Sültenfuß, J., Schröder-Ritzrau, A., Niggemann, S. and Aeschbach-Hertig, W. | Dating cave drip water by tritium | 2010 | Journal of Hydrology Vol. 394(3-4), pp. 396-406 |
article | URL |
| Abstract: Speleothems are increasingly used as an archive of past climate, but some of the proxy signals encoded in these deposits reflect hydrological characteristics of the karst aquifer (and not necessarily climate variability). A central aspect in karst hydrology is the time required for the rainwater to reach the point of discharge in a cave, e.g. the tip of the stalactite. One promising approach in determining this residence time is drip-water dating by tritium (3H). In contrast to traditional tritium dating, we do not refer directly to tritium concentrations in precipitation as input function, but to an infiltration-weighted annual mean of the rainwater values. Using concentration differences between this infiltration-weighted mean and the drip water, an age is calculated from the radioactive decay law, assuming piston flow. | |||||
BibTeX:
@article{Kluge2010,
author = {Kluge, T. and Riechelmann, D.F.C. and Wieser, M. and Spötl, C. and Sültenfuß, J. and Schröder-Ritzrau, A. and Niggemann, S. and Aeschbach-Hertig, W.},
title = {Dating cave drip water by tritium},
journal = {Journal of Hydrology},
year = {2010},
volume = {394},
number = {3-4},
pages = {396--406},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410005950}
}
|
|||||
| Knutson, C., Valocchi, A. and Werth, C. | Comparison of continuum and pore-scale models of nutrient biodegradation under transverse mixing conditions | 2007 | Advances in Water Resources Vol. 30(6-7)Biological processes in porous media: From the pore scale to the field, pp. 1421-1431 |
article | URL |
| Abstract: Recent studies indicate that during in situ bioremediation of contaminated groundwater, degradation occurs primarily along transverse mixing zones. Classical reactive-transport models overpredict the amount of degradation because solute spreading and mixing are not distinguished. Efforts to correct this have focused on modifying both dispersion and reaction terms, but no consensus on the best approach has emerged. In this work, a pore-scale model was used to simulate degradation along a transverse mixing zone between two required nutrients, and a continuum model with fitted parameters was used to match degradation rates from the pore-scale model. The pore-scale model solves for the flow field, concentration field, and biomass development within pore spaces of porous medium. For the continuum model, the flow field and biomass distributions are assumed to be homogeneous, and the fitting parameters are the transverse dispersion coefficient (DT) and maximum substrate utilization rate (kS,c). Results from the pore-scale model show that degradation rates near the system inlet are limited by the reaction rate, while degradation rates downgradient are limited by transverse mixing. For the continuum model, the value of DT may be adjusted so that the degradation rate with distance matches that from the pore-scale model in the mixing-limited region. However, adjusting the value of kS only improves the fit to pore-scale results within the reaction-limited region. Comparison with field and laboratory experiments suggests that the length of the reaction rate-limited region is small compared to the length scale over which degradation occurs. This indicates that along transverse mixing zones in the field, values of kS are unimportant and only the value of DT must be accurately fit. | |||||
BibTeX:
@article{Knutson2007,
author = {Knutson, Chad and Valocchi, Albert and Werth, Charles},
title = {Comparison of continuum and pore-scale models of nutrient biodegradation under transverse mixing conditions},
booktitle = {Biological processes in porous media: From the pore scale to the field},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {6-7},
pages = {1421--1431},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001266}
}
|
|||||
| Koch, D.L. and Brady, J.F. | Nonlocal dispersion in porous media: Nonmechanical effects | 1987 | Chemical Engineering Science Vol. 42(6), pp. 1377-1392 |
article | URL |
| Abstract: Nonmechanical dispersion mechanisms at high Peclet number in porous media give rise to persistent transients that cannot be predicted by a local Fickian macrotransport equation. Instead, a nonlocal macrotransport equation is derived, which relates the average mass flux to a convolution integral in space and time between the average concentration gradient and a spatial- and temporal-wavelength-dependent effective diffusivity. The nonlocal diffusivity is derived from the fundamental microstructural transport processes. The transient effects arising due to stagnant and recirculating regions in the medium and due to a diffusive boundary layer near solid surfaces are shown to affect the residence-time distribution (RTD) of media whose overall length to microscale size ratio L/a is not large compared to Pe and Pe1/3, respectively. Here, the Peclet number, Pe = Ua/D, is based on the average velocity through the medium U, the microstructural length scale a and the molecular diffusivity D in the medium. The nonlocal dispersion theory allows a calculation of the full form of the RTDs, which may be bimodal and generally exhibit long-time tails in media of short to moderate length. Experimental measurements of transient dispersion in consolidated media are shown to be in agreement with the theoretical prediction of dispersion due to the diffusive boundary layers near solid surfaces. | |||||
BibTeX:
@article{Koch1987,
author = {Koch, Donald L. and Brady, John F.},
title = {Nonlocal dispersion in porous media: Nonmechanical effects},
journal = {Chemical Engineering Science},
year = {1987},
volume = {42},
number = {6},
pages = {1377--1392},
url = {http://www.sciencedirect.com/science/article/pii/0009250987850108}
}
|
|||||
| Koch, S. and Flühler, H. | Non-reactive solute transport with micropore diffusion in aggregated porous media determined by a flow-interruption method | 1993 | Journal of Contaminant Hydrology Vol. 14(1), pp. 39-54 |
article | URL |
| Abstract: Water-saturated column experiments were conducted under conditions of steady flow. The columns were packed with artificial porous material having a distinctly unimodal or bimodal pore size distribution. Experimental breakthrough curves were modelled with the convection-dispersion equation and a bicontinuum spherical diffusion model. Using the convection-dispersion equation for modelling the transport of solute in aggregated porous media, a quadratic relation was found between the dispersion coefficient and the pore velocity. Column experiments in which the flow was interrupted showed the large impact of micropore diffusion. By using this method the contributions of macro- and micropore transport mechanisms can be separated. A sensitivity analysis for such experiments is given. | |||||
BibTeX:
@article{Koch1993,
author = {Koch, Sabine and Flühler, Hannes},
title = {Non-reactive solute transport with micropore diffusion in aggregated porous media determined by a flow-interruption method},
journal = {Journal of Contaminant Hydrology},
year = {1993},
volume = {14},
number = {1},
pages = {39--54},
url = {http://www.sciencedirect.com/science/article/pii/016977229390040Y}
}
|
|||||
| Kockmann, N., Kiefer, T., Engler, M. and Woias, P. | Convective mixing and chemical reactions in microchannels with high flow rates | 2006 | Sensors and Actuators B: Chemical Vol. 117(2)Transducers '05 Selected Papers from TRANSDUCERS '05. The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, pp. 495-508 |
article | URL |
| Abstract: This work presents a theoretical and experimental investigation of convective micromixing in various mixer structures and combinations with the aim of high mixing intensity and a high throughput. Different mixing elements are integrated on a silicon chip to achieve a device for high flow rates above 20 kg/h. Test structures are fabricated and characterized according to their flow behavior and mixing performance. Flow measurements with pH neutralization and indication by bromothymol blue confirm the numerical simulations of the flow characteristics and concentration fields. The integral mixing quality in the micromixer is measured with the iodide–iodate reaction (Villermaux–Dushman) and shows excellent values for high Re numbers. This offers the potential to use microstructures for new applications in the production of chemicals. With the help of the obtained experimental and theoretical results, a new class of dimensionless numbers is proposed which characterizes the effectiveness of a mixing device and of the mixing process and compares different mixing times. | |||||
BibTeX:
@article{Kockmann2006,
author = {Kockmann, Norbert and Kiefer, Thomas and Engler, Michael and Woias, Peter},
title = {Convective mixing and chemical reactions in microchannels with high flow rates},
booktitle = {Transducers '05 Selected Papers from TRANSDUCERS '05. The 13th International Conference on Solid-State Sensors, Actuators and Microsystems},
journal = {Sensors and Actuators B: Chemical},
year = {2006},
volume = {117},
number = {2},
pages = {495--508},
url = {http://www.sciencedirect.com/science/article/pii/S0925400506000220}
}
|
|||||
| Kogovšek, J. and Petric, M. | Advantages of longer–term tracing -- three case studies from Slovenia | 2004 | Environmental Geology Vol. 47(1), pp. 76-83 |
article | URL |
| Abstract: A variety of human activities can negatively impact on sensitive karst environments, especially on karst water. To protect such water adequately it is necessary to obtain as much information as possible on the extent of the recharge zones and characteristics of the groundwater flow. The authors’ experience has shown tracer tests to be a very useful tool in acquiring such information. Three examples from Slovenia are presented in this paper. In the first, an estimate was made of the danger of water contamination resulting from a petrochemical storage depot. In the second, the possible impacts of an area used for military training were studied. In the third, the effects of the construction of a railway line on regionally important water resources were assessed. Besides basic information about the direction and velocity of groundwater flow, some methodological principles were also identified by the studies. In all three test areas sampling was carried out for a lengthy period and continued after the detection of the peak concentrations. The results show that only the use of such lengthy tracer tests enable the definition of those flow paths, which are activated in extreme hydrological conditions. | |||||
BibTeX:
@article{Kogovsek2004,
author = {Kogovšek, Janja and Petric, Metka},
title = {Advantages of longer–term tracing -- three case studies from Slovenia},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2004},
volume = {47},
number = {1},
pages = {76--83},
url = {http://dx.doi.org/10.1007/s00254-004-1135-8}
}
|
|||||
| Koh, D.-C., Mayer, B., Lee, K.-S. and null Ko, K.-S. | Land-use controls on sources and fate of nitrate in shallow groundwater of an agricultural area revealed by multiple environmental tracers | 2010 | Journal of Contaminant Hydrology Vol. 118(1-2), pp. 62-78 |
article | URL |
| Abstract: Sources and transformation processes of nitrate in groundwater from shallow aquifers were investigated in an agricultural area in the mid-western part of South Korea using a multi-tracer approach including δ2H and δ18O values of water, δ15N and δ18O values of nitrate, Cl/Br ratios and chlorofluorocarbons (CFCs). The study area was comprised of four land-use types with natural areas at higher altitudes, upland areas with fruit orchards, paddy fields and residential areas at lower elevations. The isotopic composition of water was suitable for distinguishing groundwater that had infiltrated in the higher elevation natural areas with lower δ2H and δ18O values from groundwater underneath paddy fields that was characterized by elevated δ2H and δ18O values due to evaporation. δ18O–H2O values and Cl− concentrations indicated that groundwater and contaminant sources were derived from three land-use types: natural areas, residential areas and paddy fields. Groundwater age determination based on CFCs showed that nitrate contamination of groundwater is primarily controlled by historic nitrogen loadings at least in areas with higher nitrate contamination. Nitrate sources were identified using the stable isotope composition of nitrate and Cl/Br ratios. Higher δ15N–NO3− values and Cl/Br ratios of 300 to 800 in residential areas indicated that waste water and septic effluents were major nitrate sources whereas lower δ15N–NO3− values and Cl/Br ratios of 100 to 700 in upland areas suggested that synthetic fertilizers constituted a major source of nitrate contamination of aquifers. With only few exceptions in the natural area, contributions of atmospheric nitrate were insignificant due to the resetting of δ18O–NO3− values via immobilization and re-mineralization of nitrate in the soil zone. In groundwater underneath paddy fields, 30% of samples had δ18O–NO3− values at least 2‰ higher than expected for nitrate formed by chemolithoautotrophic nitrification; these samples were also characterized by low DO and NO3–N concentrations and elevated Cl and Mn concentrations indicating anthropogenic contamination and denitrification in the aquifer. These conditions were observed primarily in aquifers on floodplains. Statistical comparison between land-use groups revealed that Cl/Br ratios were more diagnostic for the impact of different land-use types on groundwater quality than stable isotope compositions of nitrate. This indicates that the former is an additional efficient tracer for the effect of land use on groundwater quality in agricultural areas. We conclude that the combination of groundwater age dating together with the use of chemical and isotopic parameters is a highly effective but yet underutilized approach for elucidating the sources and the fate of nitrate in aquifers in Asia. | |||||
BibTeX:
@article{Koh2010,
author = {Koh, Dong-Chan and Mayer, Bernhard and Lee, Kwang-Sik and , Ko, Kyung-Seok},
title = {Land-use controls on sources and fate of nitrate in shallow groundwater of an agricultural area revealed by multiple environmental tracers},
journal = {Journal of Contaminant Hydrology},
year = {2010},
volume = {118},
number = {1-2},
pages = {62--78},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210000938}
}
|
|||||
| Kohler, E., Poole, V., Reicher, Z. and Turco, R. | Nutrient, metal, and pesticide removal during storm and nonstorm events by a constructed wetland on an urban golf course | 2004 | Ecological Engineering Vol. 23(4-5), pp. 285-298 |
article | URL |
| Abstract: Created wetlands used on a golf course have the potential for accepting, storing and filtering runoff from within the course and from neighboring areas. Our 4-year study was initiated on a renovated 18-hole golf course to evaluate the effect of created wetlands on pollutants originating from both urban runoff and golf course tile drainage systems. During sampled storm events between the period October 1998 and November 2000, golf course wetlands were effective in reducing 11 of the 17 non-zero parameters. These included NO3, NO2, NH3, P, chemical oxygen demand, total organic carbon, Ca, Cl, Mg, Mn, and Na. (A total of 83 chemicals were measured but only 17 were above zero.) Therefore, stormwater exiting the golf course wetlands was an insignificant source of contamination for the watershed. During nonstorm events between the period April 2001 and November 2002, Al, Fe, Na, and SO4 were elevated in concentration in water at the discharge point compared to water at the entrance point of the wetland. However, during nonstorm operations all of the water was held within the golf course's wetland system resulting in no flow or discharge. Our study showed that a golf course wetland can exert a positive effect on water quality compared to water entering the golf course or water in the larger watershed. The created wetland system in our study was efficient in improving quality of water originating during storm runoff and from golf course tile drainage. However, to insure maximum water quality improvement, wetlands should be sized to maximize water holding during storm events and to minimize outputs during nonstorm periods. | |||||
BibTeX:
@article{Kohler2004,
author = {Kohler, E.A. and Poole, V.L. and Reicher, Z.J. and Turco, R.F.},
title = {Nutrient, metal, and pesticide removal during storm and nonstorm events by a constructed wetland on an urban golf course},
journal = {Ecological Engineering},
year = {2004},
volume = {23},
number = {4--5},
pages = {285--298},
url = {http://www.sciencedirect.com/science/article/pii/S0925857404001442}
}
|
|||||
| Köhne, J.M., Köhne, S. and Šimůnek, J. | A review of model applications for structured soils: a) Water flow and tracer transport | 2009 | Journal of Contaminant Hydrology Vol. 104(1-4)Preferential Flow, pp. 4-35 |
article | URL |
| Abstract: Although it has many positive effects, soil structure may adversely affect the filtering function of the vadose zone that protects natural water resources from various sources of pollution. Physically based models have been developed to analyze the impacts of preferential water flow (PF) and physical non-equilibrium (PNE) solute transport on soil and water resources. This review compiles results published over the past decade on the application of such models for simulating PF and PNE non-reactive tracer transport for scales ranging from the soil column to the catchment area. Recent progress has been made in characterizing the hydraulically relevant soil structures, dynamic flow conditions, inverse parameter and uncertainty estimations, independent model parameterizations, stochastic descriptions of soil heterogeneity, and 2D or 3D extensions of PNE models. Two-region models are most widely used across all scales; as a stand-alone approach to be used up to the field scale, or as a component of distributed, larger scale models. Studies at all scales suggest that inverse identification of parameters related to PF is generally not possible based on a hydrograph alone. Information on flux-averaged and spatially distributed local resident concentrations is jointly required for quantifying PNE transport. At the column and soil profile scale, model predictions of PF are becoming increasingly realistic through the implementation of the 3D soil structure as derived from hydrogeophysical and tracer techniques. At the field scale, integrating effects of the soil structure and its spatial variability has been attempted by combining 1D PNE approaches with stochastic parameter sampling. At the catchment area scale, the scarcity of data makes validation of PF related model components a task yet to be accomplished. The quest for easily measurable proxy variables, as ‘the missing link’ between soil structure and model parameters, continues in order to improve the practical predictive capability of PF–PNE models. A follow-up paper complementing this manuscript reviews model applications involving non-equilibrium transport of pesticides, as representatives of reactive solutes. | |||||
BibTeX:
@article{Koehne2009,
author = {Köhne, John Maximilian and Köhne, Sigrid and Šimůnek, Jirka},
title = {A review of model applications for structured soils: a) Water flow and tracer transport},
booktitle = {Preferential Flow},
journal = {Journal of Contaminant Hydrology},
year = {2009},
volume = {104},
number = {1-4},
pages = {4--35},
url = {http://www.sciencedirect.com/science/article/pii/S016977220800171X}
}
|
|||||
| Kolev, S.D. | Mathematical modelling of flow-injection systems | 1995 | Analytica Chimica Acta Vol. 308(1-3)Papers Presented at the Sixth International Conference on Flow Analysis, pp. 36-66 |
article | URL |
| Abstract: Analysis of the great variety of flow-injection (FI) manifolds used in analytical practice nowadays has shown that most of them can be decomposed into two basic flow configurations, i.e., the single-line and the conjugated two-line system. The former system has one influent and one effluent stream through which it can contact with the environment. The conduit walls are totally impermeable. The most distinctive characteristic of a conjugated two-line system is the existence of a flow-through section with two separate streams (e.g., donor and acceptor) which exchange matter continuously along a common semipermeable interface (e.g., membrane). It can be concluded that two of the cornerstones in the modelling of FI manifolds are the successful mathematical description of the two basic flow systems mentioned above. Numerous mathematical models of FI systems employing ideas from different scientific areas (e.g., statistics, chemical engineering, artificial intelligence, chromatography) have been developed so far. It should be pointed out that the majority of them describe only single-line FI systems. A classification of all these models based on the main principles on which they are built, is proposed. The models have been compared with respect to their predictive power, the complexity of their mathematical treatment, and the requirements for computation time when applied to single-line and conjugated two-line FI systems. It is concluded that the axially dispersed plug flow model deserves special attention because it offers an acceptable compromise between the conflicting requirements for maximal possible mathematical simplicity and maximal possible precision. It can be used as the basis for an unified approach to the modelling of FI systems. | |||||
BibTeX:
@article{Kolev1995,
author = {Kolev, Spas D.},
title = {Mathematical modelling of flow-injection systems},
booktitle = {Papers Presented at the Sixth International Conference on Flow Analysis},
journal = {Analytica Chimica Acta},
year = {1995},
volume = {308},
number = {1-3},
pages = {36--66},
url = {http://www.sciencedirect.com/science/article/pii/0003267094005746}
}
|
|||||
| Kompas, T. and Chu, L. | Comparing approximation techniques to continuous-time stochastic dynamic programming problems: Applications to natural resource modelling | 2012 | Environmental Modelling & Software Vol. 38(0), pp. 1-12 |
article | URL |
| Abstract: Dynamic programming problems are common in economics, finance and natural resource management. However, exact solutions to these problems are exceptional. Instead, solutions typically rely on numerical approximation techniques which vary in use, complexity and computational requirements. Perturbation, projection and linear programming approaches are among the most useful of these numerical techniques. In this paper, we extend the parametric linear programming technique to include continuous-time problems with jump-diffusion processes, and compare it to projection and perturbation techniques for solving dynamic programming problems in terms of computational speed, accuracy, ease of use and scope. The comparisons are drawn from solutions to two fisheries management problems – a unidimensional model of optimal harvest and a multidimensional model for optimal marine reserve size. Available computer code illustrates how each technique solves these problems and how they can be applied to other comparable problems in natural resource modelling. | |||||
BibTeX:
@article{Kompas2012,
author = {Kompas, Tom and Chu, Long},
title = {Comparing approximation techniques to continuous-time stochastic dynamic programming problems: Applications to natural resource modelling},
journal = {Environmental Modelling & Software},
year = {2012},
volume = {38},
number = {0},
pages = {1--12},
url = {http://www.sciencedirect.com/science/article/pii/S1364815212001284}
}
|
|||||
| Konikow, L.F. | The Secret to Successful Solute-Transport Modeling | 2011 | Ground Water Vol. 49(2), pp. 144-159 |
article | URL |
| Abstract: Modeling subsurface solute transport is difficult—more so than modeling heads and flows. The classical governing equation does not always adequately represent what we see at the field scale. In such cases, commonly used numerical models are solving the wrong equation. Also, the transport equation is hyperbolic where advection is dominant, and parabolic where hydrodynamic dispersion is dominant. No single numerical method works well for all conditions, and for any given complex field problem, where seepage velocity is highly variable, no one method will be optimal everywhere. Although we normally expect a numerically accurate solution to the governing groundwater-flow equation, errors in concentrations from numerical dispersion and/or oscillations may be large in some cases. The accuracy and efficiency of the numerical solution to the solute-transport equation are more sensitive to the numerical method chosen than for typical groundwater-flow problems. However, numerical errors can be kept within acceptable limits if sufficient computational effort is expended. But impractically long simulation times may promote a tendency to ignore or accept numerical errors. One approach to effective solute-transport modeling is to keep the model relatively simple and use it to test and improve conceptual understanding of the system and the problem at hand. It should not be expected that all concentrations observed in the field can be reproduced. Given a knowledgeable analyst, a reasonable description of a hydrogeologic framework, and the availability of solute-concentration data, the secret to successful solute-transport modeling may simply be to lower expectations. | |||||
BibTeX:
@article{Konikow2011,
author = {Konikow, Leonard F.},
title = {The Secret to Successful Solute-Transport Modeling},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {2011},
volume = {49},
number = {2},
pages = {144--159},
url = {http://dx.doi.org/10.1111/j.1745-6584.2010.00764.x}
}
|
|||||
| van Kooten, J. | A method to solve the advection-dispersion equation with a kinetic adsorption isotherm | 1996 | Advances in Water Resources Vol. 19(4), pp. 193-206 |
article | URL |
| Abstract: This study deals with a method to solve the transport equations for a kinetically adsorbing solute in a porous medium with spatially varying velocity field and dispersion coefficients. Making use of the stochastic nature of a first-order kinetic process, we show that the advection-dispersion equation and the adsorption isotherm can be decoupled. Once the solution for a non-adsorbing solute is known, the method provides an exact solution for the kinetically adsorbing solute. The method is worked out in four examples. In particular we demonstrate how the method can be applied simultaneously with a numerical transport code: the advective-dispersive transport is computed numerically, whereas kinetic effects are incorporated analytically. The proposed approach may be useful in field scale applications with complex flow patterns. | |||||
BibTeX:
@article{vanKooten1996,
author = {van Kooten, J.J.A.},
title = {A method to solve the advection-dispersion equation with a kinetic adsorption isotherm},
journal = {Advances in Water Resources},
year = {1996},
volume = {19},
number = {4},
pages = {193--206},
url = {http://www.sciencedirect.com/science/article/pii/0309170895000453}
}
|
|||||
| Korn, G.A. and Korn, T.M. | Mathematical handbook for scientists and engineers: definitions, theorems, and formulas for reference and review [BibTeX] |
1968 | , pp. - | book | |
BibTeX:
@book{Korn1968,
author = {Korn, Granino Arthur and Korn, Theresa M.},
title = {Mathematical handbook for scientists and engineers: definitions, theorems, and formulas for reference and review},
publisher = {McGraw-Hill Book Company},
year = {1968},
pages = {--},
edition = {Second enlarged and revised edition}
}
|
|||||
| Kostoulas, P., Nielsen, S.S., Browne, W.J. and Leontides, L. | A Bayesian Weibull survival model for time to infection data measured with delay | 2010 | Preventive Veterinary Medicine Vol. 94(3-4), pp. 191-201 |
article | URL |
| Abstract: Survival analysis methods can be used to identify factors associated with the time to induction of infection. In the absence of a perfect test, detection of infection is generally delayed and depends on the duration of the latent infection period. We assess, via simulations, the impact of ignoring the delayed detection of infection on estimated survival times and propose a Bayesian Weibull regression model, which adjusts for the delayed detection of infection. The presence of non-differential detection delay seriously biased the baseline hazard and the shape of the hazard function. For differential detection delay, the associated regression coefficients were also biased. The extent of bias largely depended on the longevity of the delay. In all considered simulation scenarios our model led to corrected estimates. We utilized the proposed model in order to assess the age at natural infection with Mycobacterium avium subsp. paratuberculosis (MAP) in Danish dairy cattle from the analysis of available time to milk-seropositivity data that detected infection with delay. The proposed model captured the inverse relationship between the incidence rate of infection and that of seroconversion with time: susceptibility to infection decreases with time (shape parameter under the proposed model was ρ = 0.56 < 1), while older animals had a higher probability of sero-converting (ρ = 2.67 > 1, under standard Weibull regression). Cows infected earlier in their lives were more likely to subsequently shed detectable levels of MAP and, hence, be a liability to herd-mates. Our approach can be particularly useful in the case of chronic infections with a long latent infection period, which, if ignored, severely affects survival estimates. | |||||
BibTeX:
@article{Kostoulas2010,
author = {Kostoulas, Polychronis and Nielsen, Søren S. and Browne, William J. and Leontides, Leonidas},
title = {A Bayesian Weibull survival model for time to infection data measured with delay},
journal = {Preventive Veterinary Medicine},
year = {2010},
volume = {94},
number = {3-4},
pages = {191--201},
url = {http://www.sciencedirect.com/science/article/pii/S0167587710000097}
}
|
|||||
| Koszalka, I., Bracco, A., Pasquero, C. and Provenzale, A. | Plankton cycles disguised by turbulent advection | 2007 | Theoretical Population Biology Vol. 72(1), pp. 1-6 |
article | URL |
| Abstract: Mathematical models used to represent plankton dynamics often display limit-cycle behavior in a range of realistic parameter values. However, experimental data do not show evidence of plankton oscillations besides externally driven seasonal blooms, casting doubts on the validity of the models themselves. In this work we show that spatial–temporal variability, coupled with advection by mesoscale turbulence, can disguise limit-cycle behavior to the point that it cannot be detected in fixed-point measurements of plankton abundance. The results presented here have more general implications as they indicate that the behavior of ecosystem models in the presence of advection can be very different from that occurring for homogeneous conditions. Care should thus be exercised in drawing general conclusions from the analysis of homogeneous ecosystem models. | |||||
BibTeX:
@article{Koszalka2007,
author = {Koszalka, I. and Bracco, A. and Pasquero, C. and Provenzale, A.},
title = {Plankton cycles disguised by turbulent advection},
journal = {Theoretical Population Biology},
year = {2007},
volume = {72},
number = {1},
pages = {1--6},
url = {http://www.sciencedirect.com/science/article/pii/S0040580907000263}
}
|
|||||
| Kotlarski, I. | On characterizing the gamma and the normal distribution | 1967 | Pacific Journal of Mathematics Vol. 20(1), pp. 69-76 |
article | URL |
| Abstract: We will characterize the gamma distribution by the nature of the joint distribution of the two quotients X1/X3, X2/X3 for three identically gamma distributed random variables. | |||||
BibTeX:
@article{Kotlarski1967,
author = {Kotlarski, Ignacy},
title = {On characterizing the gamma and the normal distribution},
journal = {Pacific Journal of Mathematics},
year = {1967},
volume = {20},
number = {1},
pages = {69--76},
url = {http://projecteuclid.org/euclid.pjm/1102992970}
}
|
|||||
| Kottegoda, N.T. and Rosso, R. | Statistics, Probability, and Reliability for Civil and Environmental Engineers [BibTeX] |
1997 | , pp. - | book | |
BibTeX:
@book{Kottegoda1997,
author = {Kottegoda, Nathabandu T. and Rosso, Renzo},
title = {Statistics, Probability, and Reliability for Civil and Environmental Engineers},
publisher = {The McGraw-Hill Companies, Inc.},
year = {1997},
pages = {--}
}
|
|||||
| Kotz, S. and Neumann, J. | On the Distribution of Precipitation Amounts for Periods of Increasing Length | 1963 | Journal of Geophysical Research Vol. 68(12), pp. 3635-3640 |
article | URL |
| Abstract: If the distribution of precipitation amounts for an initial time interval (daily, or weekly, etc., periods) at a station may be represented by a gamma distribution, it is shown that the distribution of precipitation amounts for longer intervals can be predicted, provided that (a) the correlation between the precipitation amounts of the initial interval is low and (b) the statistical process can be looked upon as a stationary process. Prediction for periods shorter than the initial interval is also possible if the correlation between the amounts of the shortest period desired is not too high. The equations are applied to data of a precipitation station, the initial interval being taken as the daily period (correlation between the daily amounts is about 1/3). Predictions are made for periods 15, 30, 45, and 90 days long with good results. | |||||
BibTeX:
@article{Kotz1963,
author = {Kotz, S. and Neumann, J.},
title = {On the Distribution of Precipitation Amounts for Periods of Increasing Length},
journal = {Journal of Geophysical Research},
publisher = {American Geophysical Union (AGU)},
year = {1963},
volume = {68},
number = {12},
pages = {3635--3640},
url = {http://dx.doi.org/10.1029/JZ068i012p03635}
}
|
|||||
| Koukou, M.K., Papayannakos, N. and Markatos, N.C. | On the importance of non-ideal flow effects in the operation of industrial-scale adiabatic membrane reactors | 2001 | Chemical Engineering Journal Vol. 83(2), pp. 95-105 |
article | URL |
| Abstract: A mathematical model taking into account mass dispersion is presented for the simulation of the performance of an adiabatic full-scale membrane reactor. Results are presented from the application of this model to a membrane reactor, that is introduced in an integrated gasification combined cycle plant, to control carbon dioxide emissions. The performance of this reactor equipped with highly selective membranes is studied in detail. The extent of the impact of the non-ideal flow effects on the membrane reactor operation is discussed. It is shown that dispersion effects have a negative influence on the performance of industrial-scale membrane reactors and they must be considered as a basic parameter to their design. | |||||
BibTeX:
@article{Koukou2001,
author = {Koukou, M. K. and Papayannakos, N. and Markatos, N. C.},
title = {On the importance of non-ideal flow effects in the operation of industrial-scale adiabatic membrane reactors},
journal = {Chemical Engineering Journal},
year = {2001},
volume = {83},
number = {2},
pages = {95--105},
url = {http://www.sciencedirect.com/science/article/pii/S1385894700002436}
}
|
|||||
| Koukou, M.K., Papayannakos, N., Markatos, N.C., Bracht, M., Van Veen, H.M. and Roskam, A. | Performance of ceramic membranes at elevated pressure and temperature: effect of non-ideal flow conditions in a pilot scale membrane separator | 1999 | Journal of Membrane Science Vol. 155(2), pp. 241-259 |
article | URL |
| Abstract: Microporous silica membrane manufacturing technology has been scaled-up and tubes with several hundred cm2 of membrane surface area have been prepared. Practical problems in applying high-temperature ceramic membrane technology, such as sealing and ceramic metal joining, have been solved successfully on pilot scale. Experiments show that membranes developed are capable of selectively separating hydrogen from a gas mixture containing hydrogen at elevated pressures and temperatures. Permselectivity values for H2/CH4 separation are as high as 28. | |||||
BibTeX:
@article{Koukou1999,
author = {Koukou, M. K. and Papayannakos, N. and Markatos, N. C. and Bracht, M. and Van Veen, H. M. and Roskam, A.},
title = {Performance of ceramic membranes at elevated pressure and temperature: effect of non-ideal flow conditions in a pilot scale membrane separator},
journal = {Journal of Membrane Science},
year = {1999},
volume = {155},
number = {2},
pages = {241--259},
url = {http://www.sciencedirect.com/science/article/pii/S0376738898003159}
}
|
|||||
| Kovacic, D.A., Twait, R.M., Wallace, M.P. and Bowling, J.M. | Use of created wetlands to improve water quality in the Midwest—Lake Bloomington case study | 2006 | Ecological Engineering Vol. 28(3)The Growth of Ecological Engineering: The Fifth Annual Conference of the American Ecological Engineering Society, pp. 258-270 |
article | URL |
| Abstract: Agricultural watersheds of the Midwest typically export nitrogen (N) and phosphorus (P) to surface waters causing contamination of drinking water reservoirs and, ultimately, hypoxia in the Gulf of Mexico. Two agricultural runoff wetlands, W1 (area 0.16 ha, volume 660 m3) and W2 (area 0.4 ha, volume 1780 m3), intercepting surface and tile drainage in the Lake Bloomington, Illinois, watershed were constructed in 1996 on forest soils (alfisols) between upland cropland and Lake Bloomington. They were created to determine whether wetlands could reduce agricultural nonpoint source pollution before it entered the Lake Bloomington drinking water reservoir. Water (precipitation, tile inflow, surface inflow, outflow, seepage and evaporation) and nutrient (N, P and carbon [C]) budgets were determined from 1 April 1998 to 30 December 1999 for each wetland. Combined, the wetlands received 746 kg NO3-N as tile loading, 104 kg as surface loading and exported 545 kg of NO3-N as outflow and seepage. Mass NO3-N retention was 36%. Following wetland treatment, overall volume-weighted NO3−-N concentrations were reduced by 42% (W1) and 31% (W2). Combined P mass retention was 53%, and combined total organic carbon (TOC) mass retention was 9%. Wetlands were constructed in a sloping drainage (5%) where surface runoff was a major component of flow. Nutrient dynamics of P and C were affected by site slopes. Calculations made by extrapolating these results indicate that a wetland area of 450 ha would be required in the Lake Bloomington watershed to reduce N loading by 46%, at a construction cost ranging from 3 to 3.5 million dollars. Results support the growing evidence that agricultural runoff wetlands can effectively reduce NPS pollution loading in the Mississippi River Basin. | |||||
BibTeX:
@article{Kovacic2006,
author = {Kovacic, David A. and Twait, Richard M. and Wallace, Michael P. and Bowling, Juliane M.},
title = {Use of created wetlands to improve water quality in the Midwest—Lake Bloomington case study},
booktitle = {The Growth of Ecological Engineering: The Fifth Annual Conference of the American Ecological Engineering Society},
journal = {Ecological Engineering},
year = {2006},
volume = {28},
number = {3},
pages = {258--270},
url = {http://www.sciencedirect.com/science/article/pii/S0925857406001601}
}
|
|||||
| Kovács, A., Perrochet, P., Király, L. and Jeannin, P.-Y. | A quantitative method for the characterisation of karst aquifers based on spring hydrograph analysis | 2005 | Journal of Hydrology Vol. 303(1-4), pp. 152-164 |
article | URL |
| Abstract: This paper presents a method for characterizing flow systems in karst aquifers by acquiring quantitative information about the geometric and hydraulic aquifer parameters from spring hydrograph analysis. Numerical sensitivity analyses identified two fundamentally different flow domains, depending on the overall configuration of aquifer parameters. These two domains have been quantitatively characterized by deducing analytical solutions for the global hydraulic response of simple two-dimensional model geometries. | |||||
BibTeX:
@article{Kovacs2005,
author = {Kovács, Attila and Perrochet, Pierre and Király, László and Jeannin, Pierre-Yves},
title = {A quantitative method for the characterisation of karst aquifers based on spring hydrograph analysis},
journal = {Journal of Hydrology},
year = {2005},
volume = {303},
number = {1-4},
pages = {152--164},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404003956}
}
|
|||||
| Kozar1and, M.D. and McCoy, K.J. | Simulation of Ground-Water Flow in a Fractured-Rock Karst Aquifer, Shenandoah Valley, Leetown, West Virginia | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 91 | inproceedings | URL |
| Abstract: Karst scientists are sometimes reluctant to pursue ground-water modeling of karst terranes. This is largely because many of the assumptions of Darcian flow on which models are predicated are violated in the turbulent flow systems of karst aquifers, especially within large conduit drains and caverns. However, ground-water models have been effectively developed for numerous karst systems. This abstract presents the results of a ground-water flow model developed for a fractured rock dominated karst aquifer beneath the Leetown Science Center (LSC) in the Shenandoah Valley of West Virginia, Leetown, West Virginia. The aquifer is a karst system but with a significant diffuse-flow component. As a result, both classic dye tracing and fractured rock techniques were used to collect the data necessary to develop the ground-water flow model. The LSC is a research facility operated by the U.S. Geological Survey that occupies approximately 455-acres near Kearneysville, Jefferson County, West Virginia. The recent construction of a second research facility (National Center for Cool and Cold Water Aquaculture) operated by the U.S. Department of Agriculture and co-located on Center property has placed additional demands on available water resources in the area. To address the concerns of future water availability, a three-dimensional steady-state finite-difference ground-water flow model was developed to simulate ground-water flow in the Leetown area under normal and drought conditions. Results of geologic mapping, LiDAR derived DEMs, and surface-geophysical surveys verified the presence of several prominent thrust faults and identified additional faults and other complex geologic structures (including overturned anticlines and synclines) in the area. These geologic structures are known to control ground-water flow in the region. Results of this study indicate that cross-strike faults and fracture zones are major avenues of ground-water flow. Prior to this investigation, the conceptual model of ground-water flow for the region focused primarily on bedding planes and strike-parallel faults and joints as controls on ground-water flow but did not recognize the importance of cross-strike faults and fracture zones that allow ground water to flow down gradient across or through less permeable geologic formations. Results of the ground-water flow simulation indicate that current operations at the Center do not substantially affect either streamflow (less than a 5-percent reduction in annual streamflow) or ground-water levels under normal climatic conditions but potentially could have greater effects on streamflow during long-term drought (reduction in streamflow of approximately 14 percent). On the basis of simulation results, ground-water withdrawals based on the anticipated need for an additional 150 to 200 gal/min (gallons per minute) of water at the Center also would not seriously affect streamflow (less than 8 to 9 percent reduction in streamflow) or ground-water levels during normal climatic conditions. During drought conditions, however, the effects of current ground-water withdrawals and anticipated additional withdrawals of 150 to 200 gal/min to augment existing supplies result in moderate to substantial declines in water levels of 0.5-1.2 feet (ft) in the vicinity of the Center's springs and production wells. Streamflow was predicted to be reduced locally by approximately 21 percent. Such withdrawals during a drought or prolonged period of below normal ground-water levels would result in substantial declines in the flow of the Center's springs and likely would not be sustainable for more than a few months. The potential reduction in streamflow is a result of capture of ground water that would otherwise have been discharged to Hopewell Run or its tributaries as base-flow discharge. The net effect on streamflow downstream of the facility is minimal, as the majority of water withdrawn is returned to the stream after treatment. |
|||||
BibTeX:
@inproceedings{Kozar1and2008,
author = {Kozar1and, Mark D. and McCoy, Kurt J.},
title = {Simulation of Ground-Water Flow in a Fractured-Rock Karst Aquifer, Shenandoah Valley, Leetown, West Virginia},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {91},
url = {http://pubs.usgs.gov/sir/2008/5023/35kozar.htm}
}
|
|||||
| Kramers, H. and Alberda, G. | Frequency response analysis of continuous flow systems | 1953 | Chemical Engineering Science Vol. 2(4), pp. 173-181 |
article | URL |
| Abstract: The distribution of residence times in a continuous flow system can be deduced from experiments concerning the behaviour of longitudinal concentration gradients on their course through the system. In this paper the application of sinusoidally varying concentrations is treated from a theoretical and experimental viewpoint. As an illustration of this frequency response analysis, experimental results are given for longitudinal diffusion in liquid flow through packed Raschig rings and for back-mixing of a liquid flowing over the packing of an absorption column. | |||||
BibTeX:
@article{Kramers1953,
author = {Kramers, H. and Alberda, G.},
title = {Frequency response analysis of continuous flow systems},
journal = {Chemical Engineering Science},
year = {1953},
volume = {2},
number = {4},
pages = {173--181},
url = {http://www.sciencedirect.com/science/article/pii/0009250953800394}
}
|
|||||
| Kreft, A. and Zuber, A. | On the use of the dispersion model of fluid flow | 1979 | The International Journal of Applied Radiation and Isotopes Vol. 30(11), pp. 705-708 |
article | URL |
| Abstract: There are two definitions of the concentration of dissolved or suspended material in a flowing fluid, namely the resident concentration and the flux concentration. The validity of the dispersion equation with a chemical reaction term is considered for the case of the flux concentration. This concentration has to be considered when the mass transfer is of interest. Depending on the injection-detection mode the solute is either injected and measured in terms of the flux concentration or in terms of the resident concentration. It is shown which solutions to the dispersion equation are most adequate to the common experimental situations. Problems related to the determination of the mean flow velocity and the dispersion coefficient from tracer experiments are considered. A new simple method of interpretation suitable for highly dispersive systems is proposed. | |||||
BibTeX:
@article{Kreft1979a,
author = {Kreft, Andrzej and Zuber, Andrzej},
title = {On the use of the dispersion model of fluid flow},
journal = {The International Journal of Applied Radiation and Isotopes},
year = {1979},
volume = {30},
number = {11},
pages = {705--708},
url = {http://www.sciencedirect.com/science/article/pii/0020708X79901133}
}
|
|||||
| Kreft, A. and Zuber, A. | On the physical meaning of the dispersion equation and its solutions for different initial and boundary conditions [BibTeX] |
1978 | Chemical Engineering Science Vol. 33(11), pp. 1471-1480 |
article | URL |
BibTeX:
@article{Kreft1978,
author = {Kreft, A. and Zuber, A.},
title = {On the physical meaning of the dispersion equation and its solutions for different initial and boundary conditions},
journal = {Chemical Engineering Science},
year = {1978},
volume = {33},
number = {11},
pages = {1471--1480},
url = {http://www.sciencedirect.com/science/article/pii/0009250978851963}
}
|
|||||
| Kreutzer, M.T., Kapteijn, F., Moulijn, J.A. and Heiszwolf, J.J. | Multiphase monolith reactors: Chemical reaction engineering of segmented flow in microchannels | 2005 | Chemical Engineering Science Vol. 60(22)7th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering 7th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering, pp. 5895-5916 |
article | URL |
| Abstract: The use of segmented flow in capillaries, also known as Taylor flow, for reaction engineering purposes has soared in recent years. On the one hand, Taylor flow has been used in honeycomb monolith catalyst supports. On the other hand, Taylor flow is the common flow pattern in multiphase microchannel reactors. This contribution reviews the fluid mechanical aspects of this flow pattern in quite general terms, with an emphasis on the underlying principles. From very simple analysis, design estimates for mass transfer, pressure drop and residence time distribution may be obtained with relative ease and—for multiphase reactors—surprising accuracy. | |||||
BibTeX:
@article{Kreutzer2005,
author = {Kreutzer, Michiel T. and Kapteijn, Freek and Moulijn, Jacob A. and Heiszwolf, Johan J.},
title = {Multiphase monolith reactors: Chemical reaction engineering of segmented flow in microchannels},
booktitle = {7th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering 7th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering},
journal = {Chemical Engineering Science},
year = {2005},
volume = {60},
number = {22},
pages = {5895--5916},
url = {http://www.sciencedirect.com/science/article/pii/S0009250905002526}
}
|
|||||
| Krieg, E.J. and Faber, D.R. | Not so Black and White: environmental justice and cumulative impact assessments | 2004 | Environmental Impact Assessment Review Vol. 24(7-8)Environment and Health: new answers, new questions., pp. 667-694 |
article | URL |
| Abstract: A growing number of scientific studies in recent years have investigated disparate exposure to ecological hazards in American society. Working from an environmental justice perspective, this body of research consistently reveals that poor communities of color are most likely to bear a disproportionate burden of negative externalities. These studies utilize a wide range of research methodologies, including various indicators of ecological hazards (e.g., proximity to waste sites, industrial emissions, ambient air quality), but few, if any, utilize composite measures to approximate cumulative environmental impact. Consequently, the environmental justice (EJ) literature is characterized by a failure to effectively measure overall impact from an extensive range of ecological hazards. Limitations on available data make this a serious problem for present and future studies. We argue that cumulative measures of environmental impact can play an important role in furthering our understanding of environmental injustices in the United States. In this study of Massachusetts, we develop and implement such a cumulative measure of negative environmental impacts. By controlling for the density and severity of ecological hazardous sites and facilities within every community in the state, we demonstrate that exposure patterns take a generally linear distribution when analyzed by race and class. So, while our results reaffirm previous findings that low-income communities and communities of color bear significantly greater ecological burdens than predominantly White and more affluent communities, our findings also suggest that environmental injustices exist on a remarkably consistent continuum for nearly all communities. In other words, as the minority population and lower-income composition of a community increases, correspondingly, so does cumulative exposure to environmental hazards. In this respect, communities which are more racially mixed and of moderate income status that are not typically identified as meeting EJ criteria (in demographic terms) also face more significant ecological hazards. Thus, the strict bifurcation of communities into categories of Environmental Justice and Non-Environmental Justice is problematic, and poses a serious dilemma for policy makers, public health officials, and community activists. To overcome this challenge requires the adoption of a cumulative environmental justice impact assessment (CEJIA), which in addition to the demographic characteristics of a community, also takes into account the total environmental burden and related health impacts upon residents. Furthermore, through the adoption of the precautionary principle, source reduction, and alternative forms of “cleaner” production, environmental justice advocates must work for policies which reduce the environmental threat for the full range of communities, as well as their own. | |||||
BibTeX:
@article{Krieg2004,
author = {Krieg, Eric J. and Faber, Daniel R.},
title = {Not so Black and White: environmental justice and cumulative impact assessments},
booktitle = {Environment and Health: new answers, new questions.},
journal = {Environmental Impact Assessment Review},
year = {2004},
volume = {24},
number = {7-8},
pages = {667--694},
url = {http://www.sciencedirect.com/science/article/pii/S0195925504000708}
}
|
|||||
| Krieg, E.J. and Faber, D.R. | Not so Black and White: environmental justice and cumulative impact assessments | 2004 | Environmental Impact Assessment Review Vol. 24(7-8)Environment and Health: new answers, new questions., pp. 667-694 |
article | URL |
| Abstract: A growing number of scientific studies in recent years have investigated disparate exposure to ecological hazards in American society. Working from an environmental justice perspective, this body of research consistently reveals that poor communities of color are most likely to bear a disproportionate burden of negative externalities. These studies utilize a wide range of research methodologies, including various indicators of ecological hazards (e.g., proximity to waste sites, industrial emissions, ambient air quality), but few, if any, utilize composite measures to approximate cumulative environmental impact. Consequently, the environmental justice (EJ) literature is characterized by a failure to effectively measure overall impact from an extensive range of ecological hazards. Limitations on available data make this a serious problem for present and future studies. We argue that cumulative measures of environmental impact can play an important role in furthering our understanding of environmental injustices in the United States. In this study of Massachusetts, we develop and implement such a cumulative measure of negative environmental impacts. By controlling for the density and severity of ecological hazardous sites and facilities within every community in the state, we demonstrate that exposure patterns take a generally linear distribution when analyzed by race and class. So, while our results reaffirm previous findings that low-income communities and communities of color bear significantly greater ecological burdens than predominantly White and more affluent communities, our findings also suggest that environmental injustices exist on a remarkably consistent continuum for nearly all communities. In other words, as the minority population and lower-income composition of a community increases, correspondingly, so does cumulative exposure to environmental hazards. In this respect, communities which are more racially mixed and of moderate income status that are not typically identified as meeting EJ criteria (in demographic terms) also face more significant ecological hazards. Thus, the strict bifurcation of communities into categories of Environmental Justice and Non-Environmental Justice is problematic, and poses a serious dilemma for policy makers, public health officials, and community activists. To overcome this challenge requires the adoption of a cumulative environmental justice impact assessment (CEJIA), which in addition to the demographic characteristics of a community, also takes into account the total environmental burden and related health impacts upon residents. Furthermore, through the adoption of the precautionary principle, source reduction, and alternative forms of “cleaner” production, environmental justice advocates must work for policies which reduce the environmental threat for the full range of communities, as well as their own. | |||||
BibTeX:
@article{Krieg2004a,
author = {Krieg, Eric J. and Faber, Daniel R.},
title = {Not so Black and White: environmental justice and cumulative impact assessments},
booktitle = {Environment and Health: new answers, new questions.},
journal = {Environmental Impact Assessment Review},
year = {2004},
volume = {24},
number = {7--8},
pages = {667--694},
url = {http://www.sciencedirect.com/science/article/pii/S0195925504000708}
}
|
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| Krudysz, M.A., Froines, J.R., Fine, P.M. and Sioutas, C. | Intra-community spatial variation of size-fractionated PM mass, OC, EC, and trace elements in the Long Beach, CA area | 2008 | Atmospheric Environment Vol. 42(21), pp. 5374-5389 |
article | URL |
| Abstract: Local traffic patterns and proximity to pollution sources are important in assessing particulate matter (PM) exposure in urban communities. This study investigated the intra-community spatial variation of PM in an urban area impacted by numerous local and regional sources. Weekly size-segregated (<0.25, 0.25–2.5, and >2.5 μm) PM samples were collected in the winter of 2005. During each 1-week sampling cycle, data were collected concurrently at four sites within four miles of one another in the Long Beach, CA area. Coefficients of divergence analyses for size-fractionated PM mass, organic and elemental carbon, sulfur, and 18 other metals and trace elements suggest a wide range of spatial divergence. High spatial variability was observed in the <0.25 μm and 0.25–2.5 μm PM fractions for many elements associated with motor vehicle emissions. Relatively lower spatial divergence was observed in the coarse fraction, although road dust components were spatially diverse but highly correlated with each other. Mass and OC concentrations were homogeneously distributed over the sampling sites. Possible oil combustion sources were identified using previously documented markers such as vanadium and nickel and by distinguishing between primary sulfur and secondary sulfate contributions. This study shows that, although PM mass in different size fractions is spatially homogeneous within a community, the spatial distribution of some elemental components can be heterogeneous. This is evidence for the argument that epidemiological studies using only PM mass concentrations from central sites may not accurately assess exposure to toxicologically relevant PM components. | |||||
BibTeX:
@article{Krudysz2008,
author = {Krudysz, Margaret A. and Froines, John R. and Fine, Philip M. and Sioutas, Constantinos},
title = {Intra-community spatial variation of size-fractionated PM mass, OC, EC, and trace elements in the Long Beach, CA area},
journal = {Atmospheric Environment},
year = {2008},
volume = {42},
number = {21},
pages = {5374--5389},
url = {http://www.sciencedirect.com/science/article/pii/S1352231008002148}
}
|
|||||
| Krueger, R. and Agyeman, J. | Sustainability schizophrenia or “actually existing sustainabilities?” toward a broader understanding of the politics and promise of local sustainability in the US | 2005 | Geoforum Vol. 36(4), pp. 410-417 |
article | URL |
| Abstract: As an approach to development, many see capitalism as reaching across an enormous range of scholarly domains and political interests. For some time geographers and others have begun to conceptualize capitalism as less of a system of intrinsic economic logic and more a collection of social and discursive relationships. By bringing capitalism into the “discursive world” these commentators and others have provided the theoretical ground for an exploration of alternative economic forms, especially those that are more socially and ecologically just. This paper makes an argument for putting sustainable development through the same theoretical scrutiny. Drawing on examples from the US we recruit the concept of “actually existing sustainabilities” from Altvater’s concept “actually existing socialisms” as an entry point to this conversation. Our purpose is to show that the potential for sustainability in the US exists in current local policies and practices if we rethink how we frame it. | |||||
BibTeX:
@article{Krueger2005a,
author = {Krueger, Rob and Agyeman, Julian},
title = {Sustainability schizophrenia or “actually existing sustainabilities?” toward a broader understanding of the politics and promise of local sustainability in the US},
journal = {Geoforum},
year = {2005},
volume = {36},
number = {4},
pages = {410--417},
url = {http://www.sciencedirect.com/science/article/pii/S0016718504001034}
}
|
|||||
| Kumar, A., Ganjyal, G.M., Jones, D.D. and Hanna, M.A. | Modeling residence time distribution in a twin-screw extruder as a series of ideal steady-state flow reactors | 2008 | Journal of Food Engineering Vol. 84(3), pp. 441-448 |
article | DOI URL |
| Abstract: Knowledge about and control of residence time distribution (RTD) is critical for determining optimal conditions in an extrusion process. In this paper, previously proposed models for RTD have been summarized and compared with the experimental data. The best-fit model was found to be a plug flow in series with a finite number of constantly stirred tank reactors having dead volume fractions. Parameters of the best-fit model were predicted from input variables (moisture content, screw speed, nozzle diameter and barrel temperature). Predicted RTD from the input variables had a r2 > 0.96. Experiments were conducted using a full factorial design with moisture contents of 16, 20, 24 and 28% (wb); screw speeds of 80, 120 and 160 rpm; nozzle diameters of 3, 4 and 5 mm; and barrel temperatures of 120 and 140 °C. Each experiment was replicated twice. It was found that, within the range of conditions studied, moisture content, screw speed, barrel temperature and nozzle diameter had significant effects on RTD. | |||||
BibTeX:
@article{Kumar2008,
author = {Kumar, Ajay and Ganjyal, Girish M. and Jones, David D. and Hanna, Milford A.},
title = {Modeling residence time distribution in a twin-screw extruder as a series of ideal steady-state flow reactors},
journal = {Journal of Food Engineering},
publisher = {Elsevier Ltd},
year = {2008},
volume = {84},
number = {3},
pages = {441--448},
url = {http://www.sciencedirect.com/science/article/pii/S0260877407003445},
doi = {http://dx.doi.org/10.1016/j.jfoodeng.2007.06.017}
}
|
|||||
| Kumar, G.S. and Ghassemi, A. | Numerical modeling of non-isothermal quartz dissolution/precipitation in a coupled fracture–matrix system | 2005 | Geothermics Vol. 34(4), pp. 411-439 |
article | URL |
| Abstract: A numerical model is developed to simulate the combined effect of thermal and reactive solute transport in a coupled fracture–matrix system using dual porosity concepts. The model includes solute dispersion in the fracture, lateral diffusion-limited transport of solutes from the fracture into the reservoir matrix, lateral conduction-limited thermal flux from the reservoir into the fracture, as well as thermal conduction and dispersion in the fracture. The model is applied to examine the mass of silica dissolved/precipitated along a fracture and to compute the change in fracture aperture. Results show that the maximum increase in the fracture aperture occurs near its inlet. A parametric study indicates that the reservoir thermal conductivity, reservoir porosity, reservoir effective diffusion coefficient, water velocity in the fracture, and the initial fracture aperture have dominant roles in quartz dissolution/precipitation mechanisms. | |||||
BibTeX:
@article{Kumar2005,
author = {Kumar, G. Suresh and Ghassemi, Ahmad},
title = {Numerical modeling of non-isothermal quartz dissolution/precipitation in a coupled fracture–matrix system},
journal = {Geothermics},
year = {2005},
volume = {34},
number = {4},
pages = {411--439},
url = {http://www.sciencedirect.com/science/article/pii/S0375650505000507}
}
|
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| Kumar, V., Guerrero, F.M., Tansel, B. and Savabi, M.R. | Hydro-physical characteristics of selected media used for containerized agriculture systems | 2010 | Agricultural Water Management Vol. 98(2), pp. 314-320 |
article | URL |
| Abstract: Containerized plant production represents an extremely intensive agricultural practice with large amounts of moisture and fertilizer application. Hydro-physical characteristics such as water infiltration, texture and structure, particle size distribution affect the quality of the media used in containerized agricultural systems and the water availability to plants. Water retention characteristics depend on particle size distribution as well as the composition of the media used. Materials with coarser particles allow faster percolation of water and also retain relatively higher amounts moisture per unit weight due to higher porosity, while draining faster due to smaller surface area per unit weight. Faster drainage can result into airflow through coarser materials causing the media to dry. The objectives of this study were to characterize the selected hydro-physical properties of plant growth media that are commonly used by nurseries in South Florida. Characterization of the plant growing media can allow modeling of soil–water interactions and development of best management practices for more efficient use of water and agrochemicals by nurseries. Experimental analyses were performed to characterize the plant growth mixtures in terms of particle size distribution and hydraulic conductivity using three different methods (i.e., constant head permeability, falling head permeability test, and tension infiltrometer test). The saturated hydraulic conductivity of the mixtures measured by constant head method ranged from 0.029 to 0.042 cm/s (104–151 cm/h) and by falling head method ranged from 0.078 to 0.112 cm/s (281–403 cm/h). The saturated hydraulic conductivity of the mixtures measured by tension infiltrometer ranged from 0.02 to 0.34 cm/h. Understanding water retention and permeation characteristics of the plant growing media could assist development of best management practices (BMP) for containerized agricultural systems for efficient management of irrigation water and agrochemical use. | |||||
BibTeX:
@article{Kumar2010,
author = {Kumar, Vivek and Guerrero, Felipe M. and Tansel, Berrin and Savabi, M. Reza},
title = {Hydro-physical characteristics of selected media used for containerized agriculture systems},
journal = {Agricultural Water Management},
year = {2010},
volume = {98},
number = {2},
pages = {314--320},
url = {http://www.sciencedirect.com/science/article/pii/S0378377410002908}
}
|
|||||
| Kumar, V., Paraschivoiu, M. and Nigam, K. | Single-phase fluid flow and mixing in microchannels | 2011 | Chemical Engineering Science Vol. 66(7)Microfluidic Engineering, pp. 1329-1373 |
article | URL |
| Abstract: In the last decade there has been an exponential increase in microfluidic applications due to high surface-to-volume ratios and compactness of microscale devices, which makes them attractive alternatives to conventional systems. The continuing growing trends of microfluidic highlights the importance to understand the mechanism and fundamental differences involved in fluid flow and mixing at microscale. In the present article, the experimental research efforts in the area of microscale single-phase fluid flow and issues associated with investigations at microscale flow have been summarized. The experimental data are being analyzed in terms of friction factor, laminar-to-turbulent transition, and the effect of roughness on fluid hydrodynamics for different cross-sectional geometries. The differences in the uncharacteristic behavior of the transport mechanisms through microchannels due to compressibility and rarefaction, relative roughness, property variations and viscous dissipation effects are discussed. Finally, progress on recent development of micromixers has been reported for different micromixer types and designs. The micromixers have been quantified based on their operating ranges (in terms of characteristic dimensionless numbers such as Reynolds number Re, Peclet number Pe, and Strouhal number St) and mixing characteristics. | |||||
BibTeX:
@article{Kumar2011,
author = {Kumar, Vimal and Paraschivoiu, Marius and Nigam, K.D.P.},
title = {Single-phase fluid flow and mixing in microchannels},
booktitle = {Microfluidic Engineering},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {7},
pages = {1329--1373},
url = {http://www.sciencedirect.com/science/article/pii/S0009250910004835}
}
|
|||||
| Kun, Z., Hui, C., Guanghe, L. and Zhaochang, L. | In situ remediation of petroleum compounds in groundwater aquifer with chlorine dioxide [BibTeX] |
1998 | Water Research Vol. 32(5), pp. 1471-1480 |
article | DOI URL |
BibTeX:
@article{Kun1998,
author = {Kun, Zhu and Hui, Chen and Guanghe, Li and Zhaochang, Liu},
title = {In situ remediation of petroleum compounds in groundwater aquifer with chlorine dioxide},
journal = {Water Research},
year = {1998},
volume = {32},
number = {5},
pages = {1471--1480},
url = {http://www.sciencedirect.com/science/article/pii/S0043135497003746},
doi = {http://dx.doi.org/10.1016/s0043-1354(97)00374-6}
}
|
|||||
| Kuniansky, E.L., Fahlquist, L. and Ardis, A.F. | Travel Times Along Selected Flow Paths of the Edwards Aquifer, Central Texas | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 69-77 | inproceedings | URL |
| Abstract: Flow path travel times in the structurally controlled, karstic Edwards aquifer were estimated using simulated ground-water levels obtained from a finite-element model. For this analysis, simulated monthly ground-water levels were averaged over an 11-year calibration period to minimize the transient effect of short-term recharge and discharge events. The 1978-89 calibration period was characterized by average to wetter-than-average climatic conditions; simulated water-level and spring-flow compared favorably with measured data. Flow paths for which travel times were estimated range from 1,250 to 10,000 feet wide and from about 8 to 180 miles long. Effective aquifer thickness and effective porosity can be highly variable and is poorly defined throughout most of the aquifer. Accordingly, travel-time estimates were computed within known or inferred thicknesses and porosities within known or inferred ranges of 350 to 850 feet and 15 to 35 percent, respectively. The minimum rock matrix porosity for each element was divided by 10 to estimate a minimum time of travel (a worst case time of travel). Travel times range from 14 to 160 years for a flow path from the Blanco River Basin to San Marcos Springs and from 350 to 4,300 years for a flow path from the West Nueces River Basin to Comal Springs. Travel times near the minimum of the ranges are similar in magnitude to those determined from tritium isotopes in spring water, thus supporting the hypothesis that effective porosity and effective thickness of the aquifer is less than the respective ranges. | |||||
BibTeX:
@inproceedings{Kuniansky2001,
author = {Kuniansky, Eve L. and Fahlquist, Lynne and Ardis, Ann F.},
title = {Travel Times Along Selected Flow Paths of the Edwards Aquifer, Central Texas},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {69--77},
url = {http://water.usgs.gov/ogw/karst/kigconference/elk_traveltimes.htm}
}
|
|||||
| Kuniansky, E.L., Halford, K.J. and Shoemaker, W.B. | Simulation of Turbulent Ground-Water Flow with MODFLOW-2005-Overview | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 87-88 | inproceedings | URL |
| Abstract: The Conduit Flow Process (CFP) is a recently released module for MODFLOW-2005 that can simulate turbulent flow in aquifers with pipe-like (such as karst) features or preferential flow layers. The CFP simulates turbulent flow as a discrete pipe network connected to the MODFLOW cells via head-dependent flux terms using Mode 1 (CFPM1), or as continuous preferential flow layers where flow can transition between laminar and turbulent in the row and column direction using Mode 2 (CFPM2). Additionally, both a pipe network and preferential flow layers can be simulated in the same model, Mode 3 (CFPM3). Preferential flow layers in CFPM2 simulate flow through interconnected pores and vugs more than 0.01 m in diameter, such as those that are present in the carbonate rock making up the Biscayne aquifer in southern Florida. CFPM2 requires less data than CFPM1 or CFPM3 because discrete pipe networks are not simulated. However, CFPM1 is designed to simulate laminar and turbulent flow in large networks of submerged conduits (partially filled conduits can be simulated, but should have almost no slope). CFPM1 is an update of subroutines to MODFLOW-2005 (Harbaugh, 2005) from the Carbonate Aquifer Void Evolution (CAVE) code previously published (Teutsch, 1993; Sauter, 1993; Clemens and others, 1996; Clemens, 1998; Hückinghaus, 1998; Bauer and others, 2000; 2003; Liedl and others, 2003; and Birk, 2002). CFPM2 is a new simple empirical algorithm for simulation of turbulent flow in preferential flow layers modified from Halford (2000). This oral presentation focuses on the theory of the code and the validation of the new algorithm for CFPM2. The code and documentation is public domain and will be available through the U.S. Geological Survey website (Shoemaker and others, 2008): http://water.usgs.gov/software/ground_water.html | |||||
BibTeX:
@inproceedings{Kuniansky2008,
author = {Kuniansky, Eve L. and Halford, Keith J. and Shoemaker, W. Barclay},
title = {Simulation of Turbulent Ground-Water Flow with MODFLOW-2005-Overview},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {87--88},
url = {http://pubs.usgs.gov/sir/2008/5023/33kuniansky.htm}
}
|
|||||
| Kuntz, D. and Grathwohl, P. | Comparison of steady-state and transient flow conditions on reactive transport of contaminants in the vadose soil zone | 2009 | Journal of Hydrology Vol. 369(3-4)Transfer of pollutants in soils, sediments and water systems: From small to large scale (AquaTerra), pp. 225-233 |
article | URL |
| Abstract: This paper investigates transport and fate of reactive compounds in the unsaturated subsoil (vadose zone) using numerical simulations of steady-state and transient flow scenarios. The objective is to investigate whether steady-state flow simulations accurately describe reactive contaminant transport under transient conditions in the field. The focus lies on organic compounds; advection, kinetic sorption and biodegradation are considered as relevant processes. In model scenarios the impact of steady-state and transient seepage water flow on solute concentrations at the groundwater table was evaluated. Sorption and degradation kinetics relative to the advective transport velocity were characterized by dimensionless Damköhler numbers for degradation (Dad) and sorption (Das). Compound properties representing two frequent pollutants (Lindane and Phenanthrene) and two types of sources were investigated: a constant inflow concentration (infinite source, with Phenanthrene) and a decreasing concentration due to desorption of the compound (finite source, with Lindane). Total mass degraded vs. cumulative flux to the groundwater (the lower model boundary), as well as the maximum breakthrough concentration at the outflow were evaluated. For each source type, combinations of sorption and degradation kinetics were identified, at which the transient simulation showed deviations from the predictions based on the steady-state simulation. Results are plotted as the difference in the observed maximum breakthrough concentration and the difference in cumulative mass fluxes as functions of degradation and sorption kinetics (“Damköhler plots”). Overall results indicate that steady-state flow conditions are appropriate for most field scenarios; only extreme infiltration events lead to higher pollutant concentrations in transient simulations because of the short residence time of seepage water in the unsaturated zone and thus reduced biodegradation and sorption. | |||||
BibTeX:
@article{Kuntz2009,
author = {Kuntz, David and Grathwohl, Peter},
title = {Comparison of steady-state and transient flow conditions on reactive transport of contaminants in the vadose soil zone},
booktitle = {Transfer of pollutants in soils, sediments and water systems: From small to large scale (AquaTerra)},
journal = {Journal of Hydrology},
year = {2009},
volume = {369},
number = {3-4},
pages = {225--233},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409001085}
}
|
|||||
| Kurt O, K. | Diversity of bacterial iron mineralization | 1998 | Earth-Science Reviews Vol. 43(3-4), pp. 91-121 |
article | URL |
| Abstract: Bacterial cells, growing naturally in freshwater and marine environments or experimentally in culture, can precipitate a variety of authigenic iron minerals. With the vast majority of bacteria biomineralization is a two-step process: initially metals are electrostatically bound to the anionic surfaces of the cell wall and surrounding organic polymers, where they subsequently serve as nucleation sites for crystal growth. The biogenic minerals have crystal habits and chemical compositions similar to those produced by precipitation from inorganic solutions because they are governed by the same equilibrium principles that control mineralization of their inorganic counterparts. As the latter stages of mineralization are inorganically driven, the type of biomineral formed is inevitably dependent on the available counter-ions, and hence, the chemical composition of the waters in which the microorganisms are growing. In oxygenated waters, iron hydroxides are a common precipitate and can form passively through the binding of dissolved ferric species to negatively charged polymers or when soluble ferrous iron spontaneously reacts with dissolved oxygen to precipitate as ferric hydroxide on available nucleation sites (e.g. bacteria). Alternatively, the metabolic activity of Fe(II)-oxidizing bacteria can induce ferric hydroxide precipitation as a secondary by-product. Ferric hydroxide may then serve as a precursor for more stable iron oxides, such as goethite and hematite via dissolution–reprecipitation or dehydration, respectively, or it may react with dissolved silica, phosphate or sulphate to form other authigenic mineral phases. Under suboxic to anoxic conditions, ferric hydroxide may be converted to magnetite, siderite, and iron sulphides through various reductive processes associated with organic matter mineralization. Under biologically controlled conditions, where mineralization is completely regulated, magnetotactic bacteria form magnetite and greigite as navigational tools to guide themselves into their preferred habitat. In general, the formation of iron biominerals is not difficult to achieve, bacteria simply provide charged surfaces that bind metals and they excrete metabolic waste products into the surrounding environment that induce mineralization. The ubiquitous presence of bacteria in aquatic systems and their inherent ability to biomineralize, therefore, makes them extremely important agents in driving both modern and ancient geochemical cycles. | |||||
BibTeX:
@article{KurtO1998,
author = {Kurt O, Konhauser},
title = {Diversity of bacterial iron mineralization},
journal = {Earth-Science Reviews},
year = {1998},
volume = {43},
number = {3-4},
pages = {91--121},
url = {http://www.sciencedirect.com/science/article/pii/S0012825297000366}
}
|
|||||
| Kurtenbach, A., Möller, S., Krein, A. and Symader, W. | On the relationship between hydrographs and chemographs | 2006 | Hydrological Processes Vol. 20(14), pp. 2921-2934 |
article | URL |
| Abstract: The spatial representativeness of gauging stations was investigated in two low-mountainous river basins near the city of Trier, southwest Germany. Longitudinal profiles during low and high flow conditions were sampled in order to identify sources of solutes and to characterize the alteration of flood wave properties during its travel downstream. Numerous hydrographs and chemographs of natural flood events were analysed in detail. Additionally, artificial flood events were investigated to study in-channel transport processes. During dry weather conditions the gauging station was only representative for a short river segment upstream, owing to discharge and solute concentrations of sources contiguous to the measurement site. During artificial flood events the kinematic wave velocity was considerably faster than the movement of water body and solutes, refuting the idea of a simple mixing process of individual runoff components. Depending on hydrological boundary conditions, the wave at a specific gauge could be entirely composed of old in-channel water, which notably reduces the spatial representativeness of a sampling site. Natural flood events were characterized by a superimposition of local overland flow, riparian water and the kinematic wave process comprising the downstream conveyance of solutes. Summer floods in particular were marked by a chronological occurrence of distinct individual runoff components originating only from a few contributing areas adjacent to the stream and gauge. Thus, the representativeness of a gauge for processes in the whole basin depends on the distance of the nearest significant source to the station. The consequence of our study is that the assumptions of mixing models are not satisfied in river basins larger than 3 km2. | |||||
BibTeX:
@article{Kurtenbach2006,
author = {Kurtenbach, Andreas and Möller, Steffen and Krein, Andreas and Symader, Wolfhard},
title = {On the relationship between hydrographs and chemographs},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2006},
volume = {20},
number = {14},
pages = {2921--2934},
url = {http://dx.doi.org/10.1002/hyp.6169}
}
|
|||||
| Kurtulus, B. and Razack, M. | Modeling daily discharge responses of a large karstic aquifer using soft computing methods: Artificial neural network and neuro-fuzzy | 2010 | Journal of Hydrology Vol. 381(1-2), pp. 101-111 |
article | URL |
| Abstract: This paper compares two methods for modeling karst aquifers, which are heterogeneous, highly non-linear, and hierarchical systems. There is a clear need to model these systems given the crucial role they play in water supply in many countries. In recent years, the main components of soft computing (fuzzy logic (FL), and Artificial Neural Networks, (ANNs)) have come to prevail in the modeling of complex non-linear systems in different scientific and technologic disciplines. In this study, Artificial Neural Networks and Adaptive Neuro-Fuzzy Interface System (ANFIS) methods were used for the prediction of daily discharge of karstic aquifers and their capability was compared. The approach was applied to 7 years of daily data of La Rochefoucauld karst system in south-western France. In order to predict the karst daily discharges, single-input (rainfall, piezometric level) vs. multiple-input (rainfall and piezometric level) series were used. In addition to these inputs, all models used measured or simulated discharges from the previous days with a specified delay. The models were designed in a Matlab™ environment. An automatic procedure was used to select the best calibrated models. Daily discharge predictions were then performed using the calibrated models. Comparing predicted and observed hydrographs indicates that both models (ANN and ANFIS) provide close predictions of the karst daily discharges. The summary statistics of both series (observed and predicted daily discharges) are comparable. The performance of both models is improved when the number of inputs is increased from one to two. The root mean square error between the observed and predicted series reaches a minimum for two-input models. However, the ANFIS model demonstrates a better performance than the ANN model to predict peak flow. The ANFIS approach demonstrates a better generalization capability and slightly higher performance than the ANN, especially for peak discharges. | |||||
BibTeX:
@article{Kurtulus2010,
author = {Kurtulus, Bedri and Razack, Moumtaz},
title = {Modeling daily discharge responses of a large karstic aquifer using soft computing methods: Artificial neural network and neuro-fuzzy},
journal = {Journal of Hydrology},
year = {2010},
volume = {381},
number = {1-2},
pages = {101--111},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409007495}
}
|
|||||
| Kurtzman, D., Nativ, R. and Adar, E.M. | The conceptualization of a channel network through macroscopic analysis of pumping and tracer tests in fractured chalk | 2005 | Journal of Hydrology Vol. 309(1-4), pp. 241-257 |
article | URL |
| Abstract: A better conceptual understanding of flow and transport in fractured rocks can be gained through macroscopic interpretation of multi-borehole interference and tracer tests. A homogeneous dilution factor, expected in the pumping borehole in a forced-gradient tracer test, was developed based on flow-dimension analysis of an interference test. This expected dilution factor (HEDF) can be compared to the actual dilution factor (DF) inferred from an advection-based interpretation of the tracer test. These analyses were applied to tests performed in inclined boreholes intersecting fractured chalk in the Negev desert, Israel. The flow dimension observed in the interference test, the large differences between the HEDF and the DF calculated from the interference and tracer tests, respectively, combined with independent results of fracture surveys in nearby outcrops, imply that the dominant feature controlling flow at the site is a network of channels. This finding implies that parallel-plate-fracture transport models probably overestimate the role of matrix diffusion where channel flow predominates. A horizontal, homogeneous, isotropic channel dilution factor (HHICDF) was developed as a DF estimator, using interference-test analysis, and provided reasonable estimates of the dilution in the pumping borehole, for two independent tracer tests. This estimator can be used to predict the dilution of a solute injected near a pumping borehole. Finally, a simple method to estimate the contributions of fluxes from different injection boreholes to the pumping borehole in a multi-borehole tracer test is described. Such estimates can improve our understanding of aquifer anisotropy and heterogeneity at investigated sites. | |||||
BibTeX:
@article{Kurtzman2005,
author = {Kurtzman, Daniel and Nativ, Ronit and Adar, Eilon M.},
title = {The conceptualization of a channel network through macroscopic analysis of pumping and tracer tests in fractured chalk},
journal = {Journal of Hydrology},
year = {2005},
volume = {309},
number = {1-4},
pages = {241--257},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404005852}
}
|
|||||
| Laatar, A., Benahmed, M., Belghith, A. and Le Quéré, P. | 2D large eddy simulation of pollutant dispersion around a covered roadway | 2002 | Journal of Wind Engineering and Industrial Aerodynamics Vol. 90(6), pp. 617-637 |
article | URL |
| Abstract: In big cities, vehicle exhaust gases can be trapped inside deep and poorly ventilated urban complex geometries (street-canyons, tunnels and covered roadways). The covered roadway is a typical configuration characterized by high emissions, poor ventilation and exposure to large numbers of people. High concentration of pollutant gases may be expected with low winds, or when the wind is oriented perpendicular to the covered roadway axis. To understand the wind effects on the transport and dispersion processes close to a covered roadway, we have conducted a numerical modeling study using the 2D Large Eddy Simulation approach. The Navier–Stokes equations are integrated by a finite volume method and then solved in time using the projection method, allowing for decoupling pressure from velocity. For the turbulence, a dynamic mixed subgrid scale model is introduced to take into account the unresolved small-scale effects. The covered section is open to one side; two aspect ratios (width to height) for the covered section are tested: 3.6 and 7.2. Two wind direction cases are studied. Our results, compared with the wind-tunnel experiment of Dabberdt et al. Int. J. Vehicule Design, 20(1–4) (1998) 96, show good agreement. The numerical simulations give detailed information on pollutant transport mechanism within the covered section. The dispersion process is highly dependent on the flow turbulence and is influenced by both the geometry of covered section and the wind direction. When the open end of the covered section is to windward, a dominant anticyclonic vortex occupies the entrance of the covered section. The dispersion process is advection dominated due to the fact that the pollutant is carried outside the covered region by large unsteady structures produced in the shear region. When the open section is to leeward, the transient solutions confirm that the gas dispersion from the covered section takes place through an intermittent “vortex and purging” release, governed by the interactions between the large structures in the vicinity of the open side. | |||||
BibTeX:
@article{Laatar2002,
author = {Laatar, A.H. and Benahmed, M. and Belghith, A. and Le Quéré, P.},
title = {2D large eddy simulation of pollutant dispersion around a covered roadway},
journal = {Journal of Wind Engineering and Industrial Aerodynamics},
year = {2002},
volume = {90},
number = {6},
pages = {617--637},
url = {http://www.sciencedirect.com/science/article/pii/S0167610502001538}
}
|
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| Labadie, J.W. and Wan, Y. | Fuzzy optimal control of reservoir-assisted stormwater treatment areas for aquatic ecosystem restoration | 2010 | Environmental Modelling & Software Vol. 25(12), pp. 1692-1701 |
article | URL |
| Abstract: Attachment of stormwater treatment areas (STAs) or constructed wetlands to stormwater retention reservoirs can achieve substantial reductions in pollutant loadings if properly operated and maintained. Besides water quality improvement, optimally operated reservoir-assisted STAs provide support for ecosystem remediation, flood control, and supplemental water supply. An adaptive, multiobjective real-time control model is developed for reservoir-assisted STA systems that incorporates fuzzy rule-based operating rules optimized using a genetic algorithm interacting with a simulation model of the system. The model is applied to the North Fork reservoir-assisted STA located in the watershed of the St. Lucie Estuary, Florida. Optimal daily feedback operational policies are developed for managing freshwater discharges to the Estuary for coastal ecosystem restoration, maximizing the natural treatment efficiency and of the STA, and providing supplemental water supply for irrigation. Testing and validation results from application of the fuzzy optimal control model confirm achievement of multiple targets and criteria for the North Fork project, while demonstrating potential for adaptive management of reservoir-assisted STA systems throughout the coastal regions of south Florida. | |||||
BibTeX:
@article{Labadie2010,
author = {Labadie, John W. and Wan, Yongshan},
title = {Fuzzy optimal control of reservoir-assisted stormwater treatment areas for aquatic ecosystem restoration},
journal = {Environmental Modelling & Software},
year = {2010},
volume = {25},
number = {12},
pages = {1692--1701},
url = {http://www.sciencedirect.com/science/article/pii/S1364815210001404}
}
|
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| Lacelle, D., Pellerin, A., Clark, I.D., Lauriol, B. and Fortin, D. | (Micro)morphological, inorganic–organic isotope geochemisty and microbial populations in endostromatolites (cf. fissure calcretes), Haughton impact structure, Devon Island, Canada: The influence of geochemical pathways on the preservation of isotope biomarkers | 2009 | Earth and Planetary Science Letters Vol. 281(3-4), pp. 202-214 |
article | URL |
| Abstract: Endostromatolites (cf. fissure calcretes), which possess microbial evidence for a biogenic origin, are also thought to preserve isotopic biosignatures. In this study, a multi-proxy approach combining (micro)morphological, geochemical and isotopic analyses of middle Holocene age endostromatolites within sub-horizontal fissures in dolomitic limestone outcrops in the Haughton impact crater region (Devon Island, NU) was used to determine their origin (abiotic versus biogenic) and to identify potential isotope biosignatures. The micro-morphologies of the endostromatolites revealed some structures typical of a physico-chemical origin, whereas the presence of rod-shape particles and filamentous structures was more reminiscent of biologically-induced forms. The endostromatolites have δ13C and δ18O compositions reaching maximum values of 7.2‰ and − 11.2‰, respectively. Positive relations between the elemental (Mg, Sr) and isotopic (δ18O and δ13C) composition of the endostromatolites are indicative of an evaporative enrichment process of the meteoric water infiltrating the fissures prior to calcite precipitation. However, the positive δ13CTOC–δ13CCaCO3 relation in the endostromatolites is strongly indicative that they were microbially-mediated. In support of a microbial origin, mostly aerobic heterotrophic bacteria that have been linked to both carbonate dissolution and mineralization were observed in the microbial diversity of the endostromatolites. However, the results are inconclusive to attribute the formation of the endostromatolites solely to a biologically-induced mineralization, but instead, favor a more complex origin that involved abiotic (evaporation), and to some extent, biological processes prior to and during calcite precipitation. Considering that the endostromatolites result from microbially-influenced mineralization, the effects of physico-chemical processes on the geochemical and isotopic composition of the endostromatolites were much greater than the effect of the biological processes. Thus, it seems that preservation of isotopic biosignatures in secondary carbonate precipitates is dependent on the sequence of processes generating chemical and isotopic modifications of the solution prior to calcite precipitation, the mechanism and condition (equilibrium or kinetic) of formation and post-fossilization alteration processes. | |||||
BibTeX:
@article{Lacelle2009,
author = {Lacelle, Denis and Pellerin, André and Clark, Ian D. and Lauriol, Bernard and Fortin, Danielle},
title = {(Micro)morphological, inorganic–organic isotope geochemisty and microbial populations in endostromatolites (cf. fissure calcretes), Haughton impact structure, Devon Island, Canada: The influence of geochemical pathways on the preservation of isotope biomarkers},
journal = {Earth and Planetary Science Letters},
year = {2009},
volume = {281},
number = {3-4},
pages = {202--214},
url = {http://www.sciencedirect.com/science/article/pii/S0012821X09001101}
}
|
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| Ladouche, B., Luc, A. and Nathalie, D. | Chemical and isotopic investigation of rainwater in Southern France (1996–2002): Potential use as input signal for karst functioning investigation | 2009 | Journal of Hydrology Vol. 367(1-2), pp. 150-164 |
article | URL |
| Abstract: Several recharge processes may be defined for karst systems. However, their respective influence is difficult to determine from spring-water chemistry without a good knowledge of the input signal, i.e. rainfall chemistry. Given the little data published concerning rainfall chemistry in the French Mediterranean area, two rainfall gauges networks were installed – one along a transect from the Mediterranean coast to the most elevated part of the Hérault region, which was monitored over two hydrological cycles (1996–1998), and a second on the catchment area of the main karst aquifer of the Gard region (Fontaine de Nîmes karst system), which was monitored over four hydrological cycles (1998–2002). | |||||
BibTeX:
@article{Ladouche2009,
author = {Ladouche, Bernard and Luc, Aquilina and Nathalie, Dörfliger},
title = {Chemical and isotopic investigation of rainwater in Southern France (1996–2002): Potential use as input signal for karst functioning investigation},
journal = {Journal of Hydrology},
year = {2009},
volume = {367},
number = {1-2},
pages = {150--164},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409000201}
}
|
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| Lafolie, F. and Hayot, C. | One-dimensional solute transport modelling in aggregated porous media Part 1. Model description and numerical solution | 1993 | Journal of Hydrology Vol. 143(1-2)XVI General Assembly of the European Geophysical Society, pp. 63-83 |
article | URL |
| Abstract: A model for the simulation of solute transport in aggregated porous media is presented. Transport by convection and dispersion in the mobile phase, diffusion of solute inside aggregates of arbitrary shapes and sizes, external mass transfer resistance and linear adsorption are considered. Depth-dependent properties of porous media and size distribution of aggregates are accounted for. The problem of solute diffusion inside arbitrarily shaped aggregates is rigorously and easily treated by application of the Laplace transformation and by introduction of an ‘aggregate shape function’. The whole system of equations is solved by: (1) application of the Laplace transformation; (2) introduction of the ‘aggregate shape function’ to reduce the transport problem to a single ordinary differential equation whatever the geometry of aggregates and the phenomena accounted for (kinetic or instantaneous adsorption, external mass transfer resistance); (3) finite-difference numerical solution of this differential equation; (4) numerical inversion of the solution obtained in the Laplace space. | |||||
BibTeX:
@article{Lafolie1993,
author = {Lafolie, F. and Hayot, Ch.},
title = {One-dimensional solute transport modelling in aggregated porous media Part 1. Model description and numerical solution},
booktitle = {XVI General Assembly of the European Geophysical Society},
journal = {Journal of Hydrology},
year = {1993},
volume = {143},
number = {1-2},
pages = {63--83},
url = {http://www.sciencedirect.com/science/article/pii/002216949390089R}
}
|
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| Lai, D.Y. and Lam, K.C. | Phosphorus sorption by sediments in a subtropical constructed wetland receiving stormwater runoff | 2009 | Ecological Engineering Vol. 35(5), pp. 735-743 |
article | URL |
| Abstract: This study investigated the potential of using a mixture of fishpond bund material, completely decomposed granite and river sand as substrate in a constructed wetland for phosphorus removal. Core samples were collected from the newly constructed Hong Kong Wetland Park (HKWP) receiving influent stormwater from a nearby new town, and batch incubation experiments were conducted to determine the P sorption characteristics of sediments. The HKWP sediments adsorbed the majority of available P in the initial 20 min of incubation, with a first-order rate constant of 1.01–2.11 h−1. Sediments in the reedbeds and freshwater marshes possessed a great capacity for P adsorption with the high Langmuir sorption maxima (478–858 mg kg−1) and Freundlich adsorption constants (417–672 L kg−1) obtained, attributable to the high amorphous iron and aluminium concentrations compared to other constructed wetlands. Moreover, sediment equilibrium P concentrations were generally low (4.6–23.6 μg L−1), facilitating a net P adsorption by sediments under moderate P loadings. Yet, the amount of P adsorbed by the HKWP sediments was limited by the low ambient porewater P concentrations and there was even a risk of P desorption when sediments in the freshwater marshes were resuspended into the water column. While substrates in the HKWP demonstrated a great potential for P adsorption, consideration should also be given to P loadings in influent water to fully utilize the P sorption capacity of sediments and enhance the P removal efficiency of constructed wetlands. | |||||
BibTeX:
@article{Lai2009,
author = {Lai, Derrick Y.F. and Lam, Kin Che},
title = {Phosphorus sorption by sediments in a subtropical constructed wetland receiving stormwater runoff},
journal = {Ecological Engineering},
year = {2009},
volume = {35},
number = {5},
pages = {735--743},
url = {http://www.sciencedirect.com/science/article/pii/S092585740800270X}
}
|
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| Laio, F., Porporato, A., Ridolfi, L. and Rodriguez-Iturbe, I. | Plants in water-controlled ecosystems: active role in hydrologic processes and response to water stress: II. Probabilistic soil moisture dynamics | 2001 | Advances in Water Resources Vol. 24(7), pp. 707-723 |
article | URL |
| Abstract: A stochastic model for soil moisture dynamics at a point is studied in detail. Rainfall is described as a marked Poisson process, producing a state-dependent infiltration into the soil. Losses due to leakage and evapotranspiration also depend on the existing level of soil moisture through a simplifying but realistic representation of plant physiological characteristics and soil properties. The analytic solution of the steady-state probability distributions is investigated to assess the role of climate, soil, and vegetation in soil moisture dynamics and water balance. | |||||
BibTeX:
@article{Laio2001,
author = {Laio, F. and Porporato, A. and Ridolfi, L. and Rodriguez-Iturbe, I.},
title = {Plants in water-controlled ecosystems: active role in hydrologic processes and response to water stress: II. Probabilistic soil moisture dynamics},
journal = {Advances in Water Resources},
year = {2001},
volume = {24},
number = {7},
pages = {707--723},
url = {http://www.sciencedirect.com/science/article/pii/S0309170801000057}
}
|
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| Lakatos, B.G., Bárkányi, Á. and Németh, S. | Continuous stirred tank coalescence/redispersion reactor: A simulation study | 2011 | Chemical Engineering Journal Vol. 169(1-3), pp. 247-257 |
article | URL |
| Abstract: This paper presents an analysis and detailed numerical study of the continuous stirred tank coalescence/redispersion reactor (CSTCRR), developed as a multidimensional population balance model combining a well-stirred reactor with the generalized coalescence/redispersion (gCR) model of micromixing. The gCR micromixing model is based on the concept of interactive population of fluid elements, identified as Kolmogorov microscale eddies under the given turbulence conditions, and represents mixing of chemical species on microscale by collision induced mass exchange processes. This model allows modelling diverse micromixing rates for different chemical species depending on their molecular diffusion properties. An infinite order multivariate moment equation model was elaborated by applying the joint moments of concentrations of chemical species from which a second order moment equation reduction was obtained by means of the cumulant-neglect closure method. The simulation results obtained by the second order moment equation model for the irreversible quasi-linear bimolecular and quadratic autocatalytic with linear decay reactions, and for the Van de Vusse reaction network revealed that the CSTCRR spans the whole range of variation of the micromixing intensity between the two micromixing extremes, i.e. perfect mixing and complete segregation, and it produces a smooth monotone sequence of product yields in the mixing space as the micromixing intensity is varied between these two extremes by modulating the rate determining parameters. | |||||
BibTeX:
@article{Lakatos2011,
author = {Lakatos, Béla G. and Bárkányi, Ágnes and Németh, Sándor},
title = {Continuous stirred tank coalescence/redispersion reactor: A simulation study},
journal = {Chemical Engineering Journal},
year = {2011},
volume = {169},
number = {1-3},
pages = {247--257},
url = {http://www.sciencedirect.com/science/article/pii/S1385894711000696}
}
|
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| Landwehr, J.M., Matalas, N.C. and Wallis, J.R. | Some comparisons of flood statistics in real and log space | 1978 | Water Resources Research Vol. 14(5), pp. 902-920 |
article | URL |
| Abstract: Some statistics of historical and simulated flood sequences were examined in real and log space. It was found that several statistical properties of floods in real space could not be inferred from those in log space without extensive knowledge of the distribution of floods in real space as well as information about their sampling characteristics. It is shown that the construction and use of regional skew maps in log space are most likely counterproductive. | |||||
BibTeX:
@article{Landwehr1978,
author = {Landwehr, J. Maciunas and Matalas, N. C. and Wallis, J. R.},
title = {Some comparisons of flood statistics in real and log space},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1978},
volume = {14},
number = {5},
pages = {902--920},
url = {http://dx.doi.org/10.1029/WR014i005p00902}
}
|
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| Lane, C.R., Reiss, K.C., DeCelles, S. and Brown, M.T. | Benthic diatom composition in isolated forested wetlands subject to drying: Implications for monitoring and assessment | 2009 | Ecological Indicators Vol. 9(6), pp. 1121-1128 |
article | URL |
| Abstract: The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal changes in hydrology and target indicator organism biology. To determine if benthic diatoms could be used as a multi-season biological indicator of wetland condition in isolated forested wetlands of Florida, USA, 11 wetlands were sampled twice during a 5-month period, once when dry, then again when hydrated. Sites sampled when dry had significantly higher diatom taxa richness at genus and species levels. Non-metric multidimensional scaling and multiple response permutation process analyses resulted in no obvious or significant wet/dry grouping of species or genus level abundance data. Five of seven diatom metrics of the Florida Wetland Condition Index (FWCI) for depressional forested wetlands were significantly linearly correlated (p < 0.05), while only one of seven metrics (a dissolved oxygen indicator) had a significantly different mean in paired t-test analyses. The final FWCI was significantly correlated (Pearson's r = 0.85, p < 0.001) between wet and dry sites, and no difference was found in mean FWCI score between wet and dry sites (t = −1.98, p = 0.076), suggesting that with additional research, benthic diatoms may be used to monitor and assess wetland condition regardless of season or site hydrologic conditions. | |||||
BibTeX:
@article{Lane2009,
author = {Lane, Charles R. and Reiss, Kelly C. and DeCelles, Susanna and Brown, Mark T.},
title = {Benthic diatom composition in isolated forested wetlands subject to drying: Implications for monitoring and assessment},
journal = {Ecological Indicators},
year = {2009},
volume = {9},
number = {6},
pages = {1121--1128},
url = {http://www.sciencedirect.com/science/article/pii/S1470160X08001908}
}
|
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| Langston, A.L. | The Relationship Between Specific Conductivity and Flow Paths in a Karst Aquifer, North-Central Florida | 2009 | School: University of Florida | mastersthesis | |
| Abstract: The Floridan aquifer system is the primary source of drinking water in north-central Florida and provides a source of recreation where it discharges at Florida’s springs. At O’Leno State Park, the Santa Fe River flows into the Floridan Aquifer system via a 36-meter-deep sinkhole, flows through a conduit system, and re-emerges 5 km from its sink at a first magnitude spring. Research conducted at O’Leno State Park investigated the response of the unconfined upper Floridan aquifer to two flood events on the Santa Fe River, one in March 2008 and one from Tropical Storm Fay in August 2008. The March 2008 event was largely a result of local diffuse recharge, in contrast to a large flood pulse from upstream during Tropical Storm Fay. The aquifer matrix surrounding the conduit system was monitored by 4 nested well pairs equipped with data loggers that recorded water level, temperature, and specific conductivity. Both diffuse recharge and conduit-influenced responses were detected at water table wells, but no recharge response was detected in wells screened at the level of the conduit. This result contrasted with expectations that conduit water would invade the matrix uniformly around the conduit passages. Slug tests conducted as part of this study indicate that the matrix at the water table has hydraulic conductivity up to one order of magnitude higher than deeper in the aquifer. A two-dimensional groundwater model was constructed to determine the conditions necessary to observe conduit water flowing in significant quantities to the water table, as indicated by the monitoring results. The model was constructed using input parameters based on published total porosities, hydraulic conductivities calculated for this study, and gradients from collected water level data. The major parameter adjusted in the modeling was effective porosity. Reducing the effective porosity mimics a small conduit or preferential flow path, and allows water to move faster along the water table. The results of this study alter conceptual models about how allogenic recharge flows through a karst aquifer and the role of the water table as a dynamic area of water flow. This study also emphasizes the contamination risk to karst aquifers. Contaminants have ample access to the unconfined Floridan Aquifer through diffuse recharge as well as point source contamination. If the higher hydraulic conductivity and lower effective porosity along the water table is a common feature, it would provide transport paths for the rapid flow of contaminants. | |||||
BibTeX:
@mastersthesis{Langston2009,
author = {Langston, Abigail L.},
title = {The Relationship Between Specific Conductivity and Flow Paths in a Karst Aquifer, North-Central Florida},
school = {University of Florida},
year = {2009}
}
|
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| van der Lans, R., Glarborg, P., Dam-Johansen, K. and Larsen, P. | Residence time distributions in a cold, confined swirl flow: Implications for chemical engineering combustion modelling | 1997 | Chemical Engineering Science Vol. 52(16), pp. 2743-2756 |
article | URL |
| Abstract: Residence time distributions (RTD) in a confined, cold swirling flow have been measured with a fast-response probe and helium as a tracer. The test-rig represented a scaled down version of a burner. The effect of variation of flow velocities and swirl angle on the flow pattern in the near-burner zone of the laboratory furnace-model were studied. RTD results have been used to derive a chemical reaction engineering model for the mixing process. The model is based on a combination of plug flow reactors and continuous stirred tank reactors, which represent the main flow characteristics in regard of mixing in the near-burner zone. The model is well suited to handle mixing in complex flows with several zones of recirculation. Simulated RTD curves compared well with those of the experiment at the two swirl numbers studied. Modelling of the mixing is a prerequisite to handle the chemistry. A simplified, well characterised flow pattern makes it possible to investigate the importance of mixing intensity on the (pollution) chemistry in furnaces. The reactor model developed here will be the basis for the development of a chemical reaction engineering combustion model. | |||||
BibTeX:
@article{Lans1997,
author = {van der Lans, R.P. and Glarborg, P. and Dam-Johansen, K. and Larsen, P.S.},
title = {Residence time distributions in a cold, confined swirl flow: Implications for chemical engineering combustion modelling},
journal = {Chemical Engineering Science},
year = {1997},
volume = {52},
number = {16},
pages = {2743--2756},
url = {http://www.sciencedirect.com/science/article/pii/S0009250997000869}
}
|
|||||
| Laquerbe, C., Laborde, J., Soares, S., Ricciardi, L., Floquet, P., Pibouleau, L. and Domenech, S. | Computer aided synthesis of RTD models to simulate the air flow distribution in ventilated rooms | 2001 | Chemical Engineering Science Vol. 56(20), pp. 5727-5738 |
article | URL |
| Abstract: In order to achieve a satisfactory level of hygiene and comfort in ventilated premises and to assess the pollutant transfers, it is necessary to control the air flow distribution. An intermediate approach between predictive numerical simulations and experimental determinations of aerodynamic parameters characterizing air distribution in rooms, is constituted by the systemic approach. This article presents the main principles of this approach, which is based on the residence time distribution (RTD) theory, commonly used in chemical engineering, and gives an illustration of its potential extension to ventilation problems. The aim of the IDTS code developed is to build a model from a combination of elementary systems representing basic ideal flow patterns (perfect mixed flow, plug flow,…). The adjustment of the model lies in the comparison of the response to a stimulus injected into the model with an experimental tracer emission performed in a ventilated room inlet. | |||||
BibTeX:
@article{Laquerbe2001,
author = {Laquerbe, C and Laborde, J.C and Soares, S and Ricciardi, L and Floquet, P and Pibouleau, L and Domenech, S},
title = {Computer aided synthesis of RTD models to simulate the air flow distribution in ventilated rooms},
journal = {Chemical Engineering Science},
year = {2001},
volume = {56},
number = {20},
pages = {5727--5738},
url = {http://www.sciencedirect.com/science/article/pii/S0009250901002925}
}
|
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| Larm, T. | Stormwater quantity and quality in a multiple pond–wetland system: Flemingsbergsviken case study | 2000 | Ecological Engineering Vol. 15(1–2), pp. 57-75 |
article | URL |
| Abstract: This study aims at presenting a methodology for quantifying yearly and monthly material transport into and out of stormwater treatment facilities (STFs) and at presenting problems related to monitoring and estimation of reduction efficiency. The model developed uses a sub-watershed approach. It employs standard values of runoff coefficients and pollutant concentrations together with precipitation data and estimated areas of different land uses within sub-watersheds. Both standard concentrations and field sampling data show that the inflow water to the facilities at Flemingsbergsviken is nutrient rich. The metal concentrations of lead, copper and zinc are relatively low, but may nevertheless increase the risk for negative impacts on aquatic life. The monthly values of runoff coefficients, used to estimate the monthly runoff water flow, vary largely between years and months. This makes the estimation of flow uncertain. A comparison of standard concentrations with measurements shows good correlation for nitrogen. The standard concentrations of total phosphorus and metals were higher than most of the sampled concentrations. However, the sampled concentrations are uncertain since they have been sampled instantaneously. An improved strategy concerning monitoring is discussed. | |||||
BibTeX:
@article{Larm2000,
author = {Larm, Thomas},
title = {Stormwater quantity and quality in a multiple pond–wetland system: Flemingsbergsviken case study},
journal = {Ecological Engineering},
year = {2000},
volume = {15},
number = {1–2},
pages = {57--75},
url = {http://www.sciencedirect.com/science/article/pii/S092585749900035X}
}
|
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| LaSage, D.M., Fryar, A.E., Mukherjee, A., Sturchio, N.C. and Heraty, L.J. | Groundwater-derived contaminant fluxes along a channelized Coastal Plain stream | 2008 | Journal of Hydrology Vol. 360(1-4), pp. 265-280 |
article | URL |
| Abstract: Recent studies in various settings across eastern North America have examined the movement of volatile organic compound (VOC) plumes from groundwater to streams, but few studies have addressed focused discharge of such plumes in unlithified sediments. From 1999 through 2002, we monitored concentrations of trichloroethene (TCE) and the non-volatile co-contaminant technetium-99 (99Tc) along Little Bayou Creek, a first-order perennial stream in the Coastal Plain of western Kentucky. Spring flow contributed TCE and 99Tc to the creek, and TCE concentrations tended to vary with 99Tc in springs. Contaminant concentrations in stream water fluctuated seasonally, but not always synchronously with stream flow. However, contaminant influxes varied seasonally with stream flow and were dominated by a few springs. Concentrations of O2, NO 3 - , and SO 4 2 - , values of δ37ClDOCl in groundwater, and the lack of less-chlorinated ethenes in groundwater and stream water indicated that anaerobic biodegradation of TCE was unlikely. Losses of TCE along Little Bayou Creek resulted mainly from volatilization, in contrast to streams receiving diffuse contaminated discharge, where intrinsic bioremediation of VOCs appears to be prevalent. | |||||
BibTeX:
@article{LaSage2008,
author = {LaSage, Danita M. and Fryar, Alan E. and Mukherjee, Abhijit and Sturchio, Neil C. and Heraty, Linnea J.},
title = {Groundwater-derived contaminant fluxes along a channelized Coastal Plain stream},
journal = {Journal of Hydrology},
year = {2008},
volume = {360},
number = {1-4},
pages = {265--280},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408003636}
}
|
|||||
| Latour, L., Kleinberg, R., Mitra, P. and Sotak, C. | Pore-Size Distributions and Tortuosity in Heterogeneous Porous Media | 1995 | Journal of Magnetic Resonance, Series A Vol. 112(1), pp. 83-91 |
article | URL |
| Abstract: The diffusion coefficient, measured at long observation times by pulsed-held-gradient NMR, can in principle be used to estimate the tortuosity of a porous medium. This method is useful for glass-sphere packs, but we find that it does not generally work for porous sedimentary rock. Natural sedimentary rocks are characterized by complex microgeometries and broad distributions of pore sizes, which cannot be adequately sampled by diffusing molecules in experimentally accessible observation times. The time-dependent diffusion coefficient D(t) can be distinctly irregular for rocks with very large pores. In heterogeneous porous media, determination of pore-size distribution by relaxation-time measurements and tortuosity by PFG diffusion measurements are mutually exclusive. | |||||
BibTeX:
@article{Latour1995,
author = {Latour, L.L. and Kleinberg, R.L. and Mitra, P.P. and Sotak, C.H.},
title = {Pore-Size Distributions and Tortuosity in Heterogeneous Porous Media},
journal = {Journal of Magnetic Resonance, Series A},
year = {1995},
volume = {112},
number = {1},
pages = {83--91},
url = {http://www.sciencedirect.com/science/article/pii/S1064185885710121}
}
|
|||||
| Le Goc, R., de Dreuzy, J.-R. and Davy, P. | Statistical characteristics of flow as indicators of channeling in heterogeneous porous and fractured media | 2010 | Advances in Water Resources Vol. 33(3), pp. 257-269 |
article | URL |
| Abstract: We introduce two new channeling indicators Dic and Dcc based on the Lagrangian distribution of flow rates. On the basis of the participation ratio, these indicators characterize the extremes of both the flow-tube width distribution and the flow rate variation along flow lines. The participation ratio is an indicator biased toward the larger values of a distribution and is equal to the normalized ratio of the square of the first-order moment to the second-order moment. Compared with other existing indicators, they advantageously provide additional information on the flow channel geometry, are consistently applicable to both porous and fractured media, and are generally less variable for media generated using the same parameters than other indicators. Based on their computation for a broad range of porous and fracture permeability fields, we show that they consistently characterize two different geometric properties of channels. Dic gives a characteristic scale of low-flow zones in porous media and a characteristic distance between effectively flowing structures in fractured cases. Dcc gives a characteristic scale of the extension of high-flow zones in porous media and a characteristic channel length in fractured media. Dic is mostly determined by channel density and permeability variability. Dcc is, however, more affected by the nature of the correlation structure like the presence of permeability channels or fractures in porous media and the length distribution in fracture networks. | |||||
BibTeX:
@article{LeGoc2010,
author = {Le Goc, R. and de Dreuzy, J.-R. and Davy, P.},
title = {Statistical characteristics of flow as indicators of channeling in heterogeneous porous and fractured media},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {3},
pages = {257--269},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809001936}
}
|
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| Le Moullec, Y., Potier, O., Gentric, C. and Pierre Leclerc, J. | Flow field and residence time distribution simulation of a cross-flow gas–liquid wastewater treatment reactor using CFD | 2008 | Chemical Engineering Science Vol. 63(9), pp. 2436-2449 |
article | URL |
| Abstract: A three-dimensional Eulerian–Eulerian two-phase approach has been used for the simulation of a cross-flow gas–liquid wastewater treatment reactor. Two different turbulence models have been tested: the k – ε and Reynolds Stress Model (RSM) models. Bubble induced turbulence source terms have been added to these models. Numerical results have been validated using Laser Doppler Velocimetry (LDV) measurements. Simulations with both turbulence models successfully predicted the hydrodynamics of the reactor. Then particle tracking with a stochastic approach has been used to calculate residence time distributions (RTD) with the flow previously simulated. It has been shown that dispersion in the reactor is primarily due to turbulence. Results have been compared with experimental RTD for various liquid and gas flowrates both on a bench scale and full scale plant. The RSM model accurately predicted the dispersion whereas the standard k – ε model slightly underestimated the dispersion. | |||||
BibTeX:
@article{LeMoullec2008,
author = {Le Moullec, Yann and Potier, Olivier and Gentric, Caroline and Pierre Leclerc, Jean},
title = {Flow field and residence time distribution simulation of a cross-flow gas–liquid wastewater treatment reactor using CFD},
journal = {Chemical Engineering Science},
year = {2008},
volume = {63},
number = {9},
pages = {2436--2449},
url = {http://www.sciencedirect.com/science/article/pii/S0009250908000614}
}
|
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| Lee, B.-H. and Scholz, M. | Application of the self-organizing map (SOM) to assess the heavy metal removal performance in experimental constructed wetlands | 2006 | Water Research Vol. 40(18), pp. 3367-3374 |
article | URL |
| Abstract: The self-organizing map (SOM) model was applied to elucidate heavy metal removal mechanisms and to predict heavy metal concentrations in experimental constructed wetlands treating urban runoff. A newly developed SOM map showed that nickel in constructed wetland filters is likely to leach under high conductivity in combination with low pH in winter. In contrast, influent pH and conductivity were not shown to have clear relationships with copper (Cu) concentrations in the effluent, suggesting that the mobility of Cu was not considerably affected by salt increase during winter. The accuracy of prediction with SOM was highly satisfactory, suggesting heavy metals can be efficiently estimated by applying the SOM model with input variables such as conductivity, pH, temperature and redox potential, which can be monitored in real time. Moreover, domain understanding was not required to implement the SOM model for prediction of heavy metal removal efficiencies. | |||||
BibTeX:
@article{Lee2006,
author = {Lee, Byoung-Hwa and Scholz, Miklas},
title = {Application of the self-organizing map (SOM) to assess the heavy metal removal performance in experimental constructed wetlands},
journal = {Water Research},
year = {2006},
volume = {40},
number = {18},
pages = {3367--3374},
url = {http://www.sciencedirect.com/science/article/pii/S0043135406004374}
}
|
|||||
| Lee, E.S. and Krothe, N.C. | A four-component mixing model for water in a karst terrain in south-central Indiana, USA. Using solute concentration and stable isotopes as tracers | 2001 | Chemical Geology Vol. 179(1-4)Hydrochemistry of Springs, pp. 129-143 |
article | URL |
| Abstract: The study area lies in a highly karstified carbonate terrain in south central Indiana. Sinkholes, conduits, and caves form large secondary pathways for the subsurface flow. As a result, the discharge from a main emergence point for the subsurface flow system, the Orangeville Rise, quickly responds to the storm events and shows wide variations in flow rate, water chemistry, and stable isotopic compositions. These responses are attributed to the mixing of water in secondary pathways. In the study area, recharge occurs through the thick, mantled karst plain and the sinkhole plains, and the role of soil layer and epikarst in the recharge process is of great importance. Rain (DIC: 2 HCO3− mg/l, δ13CDIC: −7‰), soil water (DIC: 544 HCO3− mg/l, δ13CDIC: −14.7‰), epikarstic water (DIC: 224 HCO3− mg/l, δ13CDIC: −13.6‰), and phreatic diffuse flow water (DIC: 299 HCO3− mg/l, δ13CDIC: −11.8‰) generally showed unique and constant dissolved inorganic carbon (DIC) and δ13CDIC values over time. Using DIC and δ13CDIC as tracers, a four-component mixing model was established for the karstic flow system. By constructing the discharge hydrograph separation curves, the mixing ratio of each component, rain (10.6%), soil (3.1%), epikarstic (52.3%), and phreatic (34.0%) water, was determined for the Orangeville Rise discharge over the testing period of 104 h after the storm event of 10/4/90. Vadose water occupied 55.4% of spring discharge and this demonstrates the importance of the unsaturated zone, especially the epikarst, in the karstic flow systems. | |||||
BibTeX:
@article{Lee2001,
author = {Lee, Eung Seok and Krothe, Noel C.},
title = {A four-component mixing model for water in a karst terrain in south-central Indiana, USA. Using solute concentration and stable isotopes as tracers},
booktitle = {Hydrochemistry of Springs},
journal = {Chemical Geology},
year = {2001},
volume = {179},
number = {1-4},
pages = {129--143},
url = {http://www.sciencedirect.com/science/article/pii/S0009254101003199}
}
|
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| Lee, H.-M., Lee, W.-C., Lei, C.-L. and Wu, J.-W. | Computational procedure of assessing lifetime performance index of Weibull lifetime products with the upper record values | 2011 | Mathematics and Computers in Simulation Vol. 81(6), pp. 1177-1189 |
article | URL |
| Abstract: Process capability indices (PCIs) are used to measure process potential and performance. This study constructs an uniformly minimum variance unbiased estimator (UMVUE) of the lifetime performance index based on the upper record values for Weibull lifetime model. Then the UMVUE of the lifetime performance index is utilized to develop the new hypothesis testing procedure in the condition of known lower specification limit. Finally, two examples are presented to assess the behavior of this test statistic for testing null hypothesis under given significance level. Moreover, the product managers can then employ the new testing procedure to determine whether the process adheres to the required level. | |||||
BibTeX:
@article{Lee2011,
author = {Lee, Hsiu-Mei and Lee, Wen-Chuan and Lei, Chia-Ling and Wu, Jong-Wuu},
title = {Computational procedure of assessing lifetime performance index of Weibull lifetime products with the upper record values},
journal = {Mathematics and Computers in Simulation},
year = {2011},
volume = {81},
number = {6},
pages = {1177--1189},
url = {http://www.sciencedirect.com/science/article/pii/S0378475410003861}
}
|
|||||
| van der Lee, J., De Windt, L., Lagneau, V. and Goblet, P. | Module-oriented modeling of reactive transport with HYTEC | 2003 | Computers & Geosciences Vol. 29(3)Reactive Transport Modeling in the Geosciences, pp. 265-275 |
article | URL |
| Abstract: The paper introduces HYTEC, a coupled reactive transport code currently used for groundwater pollution studies, safety assessment of nuclear waste disposals, geochemical studies and interpretation of laboratory column experiments. Based on a known permeability field, HYTEC evaluates the groundwater flow paths, and simulates the migration of mobile matter (ions, organics, colloids) subject to geochemical reactions. The code forms part of a module-oriented structure which facilitates maintenance and improves coding flexibility. In particular, using the geochemical module CHESS as a common denominator for several reactive transport models significantly facilitates the development of new geochemical features which become automatically available to all models. A first example shows how the model can be used to assess migration of uranium from a sub-surface source under the effect of an oxidation front. The model also accounts for alteration of hydrodynamic parameters (local porosity, permeability) due to precipitation and dissolution of mineral phases, which potentially modifies the migration properties in general. The second example illustrates this feature. | |||||
BibTeX:
@article{Lee2003,
author = {van der Lee, Jan and De Windt, Laurent and Lagneau, Vincent and Goblet, Patrick},
title = {Module-oriented modeling of reactive transport with HYTEC},
booktitle = {Reactive Transport Modeling in the Geosciences},
journal = {Computers & Geosciences},
year = {2003},
volume = {29},
number = {3},
pages = {265--275},
url = {http://www.sciencedirect.com/science/article/pii/S0098300403000049}
}
|
|||||
| Lee, J., Nez, V.E., Feng, X., Kirchner, J.W., Osterhuber, R. and Renshaw, C.E. | A study of solute redistribution and transport in seasonal snowpack using natural and artificial tracers | 2008 | Journal of Hydrology Vol. 357(3–4), pp. 243-254 |
article | URL |
| Abstract: Solute releases from a seasonal snowpack are important features of spring runoff in temperate climate zones because meltwater accounts for a significant proportion of contaminant loading to catchments. Here we report a study that traces the movement of natural and artificial solutes in snow through the processes of snow deposition, snowpack metamorphism, and snowmelt at the Central Sierra Snow Laboratory (CSSL), Soda Springs, California, USA. Rare earth elements (REEs) were added to the snowpack to mark individual snow layers. New snow, snowpack profiles and snowmelt were sampled and analyzed for REE and anion ( SO 4 2 - , Cl− and NO 3 - ) concentrations. | |||||
BibTeX:
@article{Lee2008,
author = {Lee, Jeonghoon and Nez, Valisa E. and Feng, Xiahong and Kirchner, James W. and Osterhuber, Randall and Renshaw, Carl E.},
title = {A study of solute redistribution and transport in seasonal snowpack using natural and artificial tracers},
journal = {Journal of Hydrology},
year = {2008},
volume = {357},
number = {3–4},
pages = {243--254},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408002266}
}
|
|||||
| Lee, J.-Y. and Lee, K.-K. | Use of hydrologic time series data for identification of recharge mechanism in a fractured bedrock aquifer system | 2000 | Journal of Hydrology Vol. 229(3-4), pp. 190-201 |
article | URL |
| Abstract: Correlations between hydrologic time series data were analyzed to characterize the hydrogeologic processes of a fractured bedrock aquifer system in Wonju, Korea. The natural groundwater-level fluctuations and site rainfall data were used for the analyses. Wells of different depths at the same site show distinct transformation behaviors for the same input stress (rainfall). A shallow well in the soil zone responds quickly to rainfall at the site while a deep well in the fractured zone shows slower response but longer duration. These differences are mainly related to the different recharge mechanisms of direct infiltration through the upper soil zone and the somewhat regional recharge from a distance through a network of fractures. The seasonal difference in the system responses can be explained by the fall or rise of the water level that changes the transmission properties of the pressure pulse generated by rainfall. Time delay, specific storage and porosity computed from the time series data are highly consistent with the analysis results of aquifer and tracer tests at this site. | |||||
BibTeX:
@article{Lee2000,
author = {Lee, Jin-Yong and Lee, Kang-Kun},
title = {Use of hydrologic time series data for identification of recharge mechanism in a fractured bedrock aquifer system},
journal = {Journal of Hydrology},
year = {2000},
volume = {229},
number = {3-4},
pages = {190--201},
url = {http://www.sciencedirect.com/science/article/pii/S002216940000158X}
}
|
|||||
| Lee, M.E. and Seo, I.W. | Analysis of pollutant transport in the Han River with tidal current using a 2D finite element model | 2007 | Journal of Hydro-environment Research Vol. 1(1), pp. 30-42 |
article | URL |
| Abstract: Pollutant transport in the Han River, which is one of the most important rivers in Korea, was studied using the 2D advection-dispersion model developed in this research. The numerical model was developed based on the streamline-upwind Petrov-Galerkin (SUPG) where a finite element grid was used in order to treat the complex geometry of the natural water bodies. Velocity fields for the input data of pollutant transport simulation were obtained using a 2D hydrodynamic model, RMA2. The pollutant transport simulations in both the steady state flow and in the tidal currents were carried out to analyze the effects of tidal currents on the 2D concentration distribution in the region of application. The simulation results show that, with increasing water level period under tidal conditions, very large recirculation zones occurs and water flows in the upstream direction. Therefore, within the tidal currents, the polluted water goes back and forth with variations in the flow direction. As a result of this movement of pollutant, an oscillation in the concentration appears over time, which reflects both the significantly complex periodic variation in the flow pattern and large circulations. | |||||
BibTeX:
@article{Lee2007,
author = {Lee, Myung Eun and Seo, Il Won},
title = {Analysis of pollutant transport in the Han River with tidal current using a 2D finite element model},
journal = {Journal of Hydro-environment Research},
year = {2007},
volume = {1},
number = {1},
pages = {30--42},
url = {http://www.sciencedirect.com/science/article/pii/S1570644307000056}
}
|
|||||
| Lee, T., Wang, F. and Newell, R. | Dynamic modelling and simulation of activated sludge process using orthogonal collocation approach | 1999 | Water Research Vol. 33(1), pp. 73-86 |
article | URL |
| Abstract: This paper deals with the improvement in modelling of the dynamics of activated sludge wastewater treatment process using a distributed parameter approach. A computational algorithm, based on the global orthogonal collocation technique, for the activated sludge process is developed in this work. Steady-state and dynamic simulations are performed based on this algorithm. The system configuration considers backmixing or intermixing, which can represent the actual process more accurately than the idealised flow schemes commonly employed for the design and modelling of the activated sludge reactors. Based on a dispersed plug flow model for activated sludge bioreactor formulated in this work, a Peclet number in the order of 0.5 to 5 and 5 to 7 internal collocation points are recommended for modelling channel-type activated sludge bioreactor. The dynamics of substrate is predicted well whereas the prediction for biomass is fair, when compared to the experimental data. It is also demonstrated in this paper that the proposed algorithm can give superior prediction of process dynamics than the commonly-used tanks-in-series technique. Dynamic responses caused by disturbances in the influent wastewater which propagates at various spatial positions along the bioreactor can be correctly predicted through simulations. | |||||
BibTeX:
@article{Lee1999,
author = {Lee, T.T. and Wang, F.Y. and Newell, R.B.},
title = {Dynamic modelling and simulation of activated sludge process using orthogonal collocation approach},
journal = {Water Research},
year = {1999},
volume = {33},
number = {1},
pages = {73--86},
url = {http://www.sciencedirect.com/science/article/pii/S0043135498001973}
}
|
|||||
| Lee, W.-C., Wu, J.-W. and Lei, C.-L. | Evaluating the lifetime performance index for the exponential lifetime products | 2010 | Applied Mathematical Modelling Vol. 34(5), pp. 1217-1224 |
article | URL |
| Abstract: Process capability indices (PCIs) are used to measure process potential and performance. Since the lifetime of products generally may possess an exponential, gamma or Weibull distribution, etc., so under a two-parameter exponential distribution, this study constructs a uniformly minimum variance unbiased estimator (UMVUE) of the lifetime performance index based on the right type II censored sample. Then the UMVUE of the lifetime performance index is utilized to develop the new hypothesis testing procedure in the condition of known L. Finally, a practical example is illustrated to employ the testing procedure to determine whether the process is capable. | |||||
BibTeX:
@article{Lee2010,
author = {Lee, Wen-Chuan and Wu, Jong-Wuu and Lei, Chia-Ling},
title = {Evaluating the lifetime performance index for the exponential lifetime products},
journal = {Applied Mathematical Modelling},
year = {2010},
volume = {34},
number = {5},
pages = {1217--1224},
url = {http://www.sciencedirect.com/science/article/pii/S0307904X0900239X}
}
|
|||||
| Leij, F.J. and Bradford, S.A. | Combined physical and chemical nonequilibrium transport model: Analytical solution, moments, and application to colloids | 2009 | Journal of Contaminant Hydrology Vol. 110(3–4), pp. 87-99 |
article | URL |
| Abstract: The transport of solutes and colloids in porous media is influenced by a variety of physical and chemical nonequilibrium processes. A combined physical–chemical nonequilibrium (PCNE) model was therefore used to describe general mass transport. The model partitions the pore space into “mobile” and “immobile” flow regions with first-order mass transfer between these two regions (i.e, “physical” nonequilibrium or PNE). Partitioning between the aqueous and solid phases can either proceed as an equilibrium or a first-order process (i.e, “chemical” nonequilibrium or CNE) for both the mobile and immobile regions. An analytical solution for the PCNE model is obtained using iterated Laplace transforms. This solution complements earlier semi-analytical and numerical approaches to model solute transport with the PCNE model. The impact of selected model parameters on solute breakthrough curves is illustrated. As is well known, nonequilibrium results in earlier solute breakthrough with increased tailing. The PCNE model allows greater flexibility to describe this trend; for example, a closer resemblance between solute input and effluent pulse. Expressions for moments and transfer functions are presented to facilitate the analytical use of the PCNE model. Contours of mean breakthrough time, variance, and spread of the colloid breakthrough curves as a function of PNE and CNE parameters demonstrate the utility of a model that accounts for both physical and chemical nonequilibrium processes. The model is applied to describe representative colloid breakthrough curves in Ottawa sands reported by Bradford et al. (2002). An equilibrium model provided a good description of breakthrough curves for the bromide tracer but could not adequately describe the colloid data. A considerably better description was provide by the simple CNE model but the best description, especially for the larger 3.2-µm colloids, was provided by the PCNE model. | |||||
BibTeX:
@article{Leij2009,
author = {Leij, Feike J. and Bradford, Scott A.},
title = {Combined physical and chemical nonequilibrium transport model: Analytical solution, moments, and application to colloids},
journal = {Journal of Contaminant Hydrology},
year = {2009},
volume = {110},
number = {3–4},
pages = {87--99},
url = {http://www.sciencedirect.com/science/article/pii/S0169772209001302}
}
|
|||||
| Leij, F.J., Toride, N. and van Genuchten, M.T. | Analytical solutions for non-equilibrium solute transport in three-dimensional porous media | 1993 | Journal of Hydrology Vol. 151(2-4), pp. 193-228 |
article | URL |
| Abstract: The movement of water and chemicals in soils is generally better described with multidimensional non-equilibrium models than with more commonly used one-dimensional and/or equilibrium models. This paper presents analytical solutions for non-equilibrium solute transport in semi-infinite porous media during steady unidirectional flow. The solutions can be used to model transport in porous media where the liquid phase consists of a mobile and an immobile region (physical non-equilibrium) or where solute sorption is governed by either an equilibrium or a first-order rate process (chemical non-equilibrium). The transport equation incorporates terms accounting for advection, dispersion, zero-order production, and first-order decay. General solutions were derived for the boundary, initial, and production value problems with the help of Laplace and Fourier transforms. A comprehensive set of specific solutions is presented using Dirac functions for the input and initial distribution, and/or Heaviside or exponential functions for the input, initial, and production profiles. A rectangular or circular inflow area was specified for the boundary value problem while for the initial and production value problems the respective initial and production profiles were located in parallelepipedal, cylindrical, or spherical regions of the soil. Solutions are given for both the volume-averaged or resident concentration as well as the flux-averaged or flowing concentration. Examples of concentration profiles versus time and position are presented for selected problems. Results show that the effects of non-equilibrium on three-dimensional transport are very similar to those for one-dimensional transport. | |||||
BibTeX:
@article{Leij1993,
author = {Leij, Feike J. and Toride, Nobuo and van Genuchten, Martinus Th.},
title = {Analytical solutions for non-equilibrium solute transport in three-dimensional porous media},
journal = {Journal of Hydrology},
year = {1993},
volume = {151},
number = {2-4},
pages = {193--228},
url = {http://www.sciencedirect.com/science/article/pii/0022169493902363}
}
|
|||||
| Leitman, R.H. and Ziegler, E.N. | Stirred tank reactor studies part II. Conversion models | 1972 | The Chemical Engineering Journal Vol. 3(0), pp. 245-255 |
article | DOI URL |
| Abstract: Conversion data for the continuous hydrolysis of ethyl acetate has been studied in the same stirred tank vessel previously used for mixing parameter determinations. Two solutions, pure water and aqueous ethylene oxide, were used as reaction media at various stirring speeds. The reaction conversion was found to approach that of ideal microscopic mixing at stirrer speeds above 800 rpm in pure water. The segregated model worked well for Polyox solutions above 400 rpm. A large number of runs were inaccurately described by the zero parameter models (p.f.r., m.f.r., segregated and maximum-mixedness) or by single parameter models (tanks-in-series, dispersion and recycle). | |||||
BibTeX:
@article{Leitman1972,
author = {Leitman, Richard H. and Ziegler, Edward N.},
title = {Stirred tank reactor studies part II. Conversion models},
journal = {The Chemical Engineering Journal},
year = {1972},
volume = {3},
number = {0},
pages = {245--255},
url = {http://www.sciencedirect.com/science/article/pii/0300946772850287},
doi = {http://dx.doi.org/10.1016/0300-9467(72)85028-7}
}
|
|||||
| Lenczewski, M., Jardine, P., McKay, L. and Layton, A. | Natural attenuation of trichloroethylene in fractured shale bedrock [BibTeX] |
2003 | Journal of Contaminant Hydrology Vol. 64(3-4), pp. 151-168 |
article | DOI URL |
BibTeX:
@article{Lenczewski2003,
author = {Lenczewski, M. and Jardine, P. and McKay, L. and Layton, A.},
title = {Natural attenuation of trichloroethylene in fractured shale bedrock},
journal = {Journal of Contaminant Hydrology},
year = {2003},
volume = {64},
number = {3-4},
pages = {151--168},
url = {http://www.sciencedirect.com/science/article/pii/S0169772202000906},
doi = {http://dx.doi.org/10.1016/s0169-7722(02)00090-6}
}
|
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| Leonard, E.F., Aucoin, C.P. and Nanne, E.E. | Measurement of diffusion in flowing complex fluids | 2006 | Colloids and Surfaces A: Physicochemical and Engineering Aspects Vol. 282–283(0)A Collection of Papers in Honor of Professor Ivan B. Ivanov (Laboratory of Chemical Physics and Engineering, University of Sofia) Celebrating his Contributions to Colloid and Surface Science on the Occasion of his 70th Birthday, pp. 75-78 |
article | URL |
| Abstract: A microfluidic device for the measurement of solute diffusion as well as particle diffusion and migration in flowing complex fluids is described. The device is particularly suited to obtaining diffusivities in such fluids, which require a desired flow state to be maintained during measurement. A method based on the Loschmidt diffusion theory and short times of exposure is presented to allow calculation of diffusivities from concentration differences in the flow streams leaving the cell. | |||||
BibTeX:
@article{Leonard2006,
author = {Leonard, Edward F. and Aucoin, Christian P. and Nanne, Edgar E.},
title = {Measurement of diffusion in flowing complex fluids},
booktitle = {A Collection of Papers in Honor of Professor Ivan B. Ivanov (Laboratory of Chemical Physics and Engineering, University of Sofia) Celebrating his Contributions to Colloid and Surface Science on the Occasion of his 70th Birthday},
journal = {Colloids and Surfaces A: Physicochemical and Engineering Aspects},
year = {2006},
volume = {282–283},
number = {0},
pages = {75--78},
url = {http://www.sciencedirect.com/science/article/pii/S0927775706001968}
}
|
|||||
| Levenspiel, O. | Modeling in chemical engineering | 2002 | Chemical Engineering Science Vol. 57(22–23)Festschrift in Honour of Dr Winn van Swaaij, pp. 4691-4696 |
article | URL |
| Abstract: In its 90 year life what has chemical engineering (ChE) contributed to society? Firstly, we have invented and developed processes to create new materials, more gently and more efficiently, so as to make life easier for all. | |||||
BibTeX:
@article{Levenspiel2002,
author = {Levenspiel, Octave},
title = {Modeling in chemical engineering},
booktitle = {Festschrift in Honour of Dr Winn van Swaaij},
journal = {Chemical Engineering Science},
year = {2002},
volume = {57},
number = {22–23},
pages = {4691--4696},
url = {http://www.sciencedirect.com/science/article/pii/S0009250902002804}
}
|
|||||
| Levenspiel, O. | Chemical reaction engineering [BibTeX] |
1999 | , pp. - | book | |
BibTeX:
@book{Levenspiel1999,
author = {Levenspiel, Octave},
title = {Chemical reaction engineering},
publisher = {John Wiley & Sons, Inc.},
year = {1999},
pages = {--},
edition = {Third}
}
|
|||||
| Levenspiel, O. | Notes on the diffusion-type model for the longitudinal mixing of fluids in flow: O. Levenspiel and W. K. Smith, Chem. Engng Sci. 6: 227–233, 1957 | 1995 | Chemical Engineering Science Vol. 50(24)Frontiers of Chemical Engineering Science, pp. 3889- |
article | URL |
| Abstract: Turbulence, velocity gradients, and molecular diffusion-all these cause material to move at different speeds in a flowing stream. The overall effect of these factors can be accounted for by a single quantity, a sort of diffusion coefficient. This paper shows how to find this coefficient by a pulse tracer experiment. | |||||
BibTeX:
@article{Levenspiel1995a,
author = {Levenspiel, Octave},
title = {Notes on the diffusion-type model for the longitudinal mixing of fluids in flow: O. Levenspiel and W. K. Smith, Chem. Engng Sci. 6: 227–233, 1957},
booktitle = {Frontiers of Chemical Engineering Science},
journal = {Chemical Engineering Science},
year = {1995},
volume = {50},
number = {24},
pages = {3889--},
url = {http://www.sciencedirect.com/science/article/pii/0009250996818161}
}
|
|||||
| Levenspiel, O. | Comment on mean residence time in flow systems [BibTeX] |
1985 | Chemical Engineering Science Vol. 40(8), pp. 1614- |
article | URL |
BibTeX:
@article{Levenspiel1985,
author = {Levenspiel, Octave},
title = {Comment on mean residence time in flow systems},
journal = {Chemical Engineering Science},
year = {1985},
volume = {40},
number = {8},
pages = {1614--},
url = {http://www.sciencedirect.com/science/article/pii/000925098580110X}
}
|
|||||
| Levenspiel, O. | Comparison of the tanks-in-series and the dispersion models for non ideal flow of fluid [BibTeX] |
1962 | Chemical Engineering Science Vol. 17(7), pp. 576-577 |
article | URL |
BibTeX:
@article{Levenspiel1962,
author = {Levenspiel, Octave},
title = {Comparison of the tanks-in-series and the dispersion models for non ideal flow of fluid},
journal = {Chemical Engineering Science},
year = {1962},
volume = {17},
number = {7},
pages = {576--577},
url = {http://www.sciencedirect.com/science/article/pii/0009250962870109}
}
|
|||||
| Levenspiel, O., Fitzgerald, T. and Khang, S.J. | Comments on the general environment model for micromixing [BibTeX] |
1974 | Chemical Engineering Science Vol. 29(1), pp. 300-303 |
article | URL |
BibTeX:
@article{Levenspiel1974,
author = {Levenspiel, Octave and Fitzgerald, Thomas and Khang, S. J.},
title = {Comments on the general environment model for micromixing},
journal = {Chemical Engineering Science},
year = {1974},
volume = {29},
number = {1},
pages = {300--303},
url = {http://www.sciencedirect.com/science/article/pii/000925097485061X}
}
|
|||||
| Levenspiel, O. and Fitzgerald, T.J. | A Warning on the misuse of the dispersion model [BibTeX] |
1983 | Chemical Engineering Science Vol. 38(3), pp. 489-491 |
article | URL |
BibTeX:
@article{Levenspiel1983,
author = {Levenspiel, Octave and Fitzgerald, T. J.},
title = {A Warning on the misuse of the dispersion model},
journal = {Chemical Engineering Science},
year = {1983},
volume = {38},
number = {3},
pages = {489--491},
url = {http://www.sciencedirect.com/science/article/pii/0009250983801717}
}
|
|||||
| Levenspiel, O., Lai, B.W. and Chatlynne, C.Y. | Tracer curves and the residence time distribution | 1970 | Chemical Engineering Science Vol. 25(10), pp. 1611-1613 |
article | URL |
| Abstract: For a pulse input the shape of the output tracer curve depends on the way tracer is distributed across the flowing fluid, and the way it is measured. This paper properly relates the different curves which may be obtained for flows with negligible cross diffusion, and shows which one of these represents directly the residence time distribution of the flowing fluid. | |||||
BibTeX:
@article{Levenspiel1970a,
author = {Levenspiel, Octave and Lai, B. W. and Chatlynne, C. Y.},
title = {Tracer curves and the residence time distribution},
journal = {Chemical Engineering Science},
year = {1970},
volume = {25},
number = {10},
pages = {1611--1613},
url = {http://www.sciencedirect.com/science/article/pii/0009250970850849}
}
|
|||||
| Levenspiel, O. and Smith, W.K. | Notes on the diffusion-type model for the longitudinal mixing of fluids in flow | 1995 | Chemical Engineering Science Vol. 50(24)Frontiers of Chemical Engineering Science, pp. 3891-3896 |
article | URL |
| Abstract: The longitudinal mixing of fluids in flow can sometimes be characterized by a single parameter D, the “longitudinal dispersion coefficient,” which is analogous to and has the same units as the coefficient of molecular diffusion. The results of a study of this model show that a dimensionless parameter, the Peclet number can be used as the similarity criterion for longitudinal mixing. Also, it is pointed out that the obvious and direct method of calculating the mean velocity of flow, by injecting a tracer into the fluid stream at one point and measuring its maximum concentration at a given point downstream, may in some cases lead to an appreciable error, even in situations where the diffusion-type model is applicable. Methods are shown for evaluating D from experimental measurements, examples are worked out and conditions for applicability of the model are discussed. | |||||
BibTeX:
@article{Levenspiel1995,
author = {Levenspiel, Octave and Smith, W. K.},
title = {Notes on the diffusion-type model for the longitudinal mixing of fluids in flow},
booktitle = {Frontiers of Chemical Engineering Science},
journal = {Chemical Engineering Science},
year = {1995},
volume = {50},
number = {24},
pages = {3891--3896},
url = {http://www.sciencedirect.com/science/article/pii/0009250996818173}
}
|
|||||
| Levenspiel, O. and Turner, J.C.R. | The interpretation of residence-time experiments | 1970 | Chemical Engineering Science Vol. 25(10), pp. 1605-1609 |
article | URL |
| Abstract: The results of tracer experiments can depend on the methods of injection and measurement of the tracer when the fluid velocity is not uniform through the injection and measurement planes. Some simple examples show that incorrect residence-time distributions will be derived if this fact is not considered. For laminar flow in a tube the results obtained will differ widely, depending on the techniques used. | |||||
BibTeX:
@article{Levenspiel1970,
author = {Levenspiel, Octave and Turner, J. C. R.},
title = {The interpretation of residence-time experiments},
journal = {Chemical Engineering Science},
year = {1970},
volume = {25},
number = {10},
pages = {1605--1609},
url = {http://www.sciencedirect.com/science/article/pii/0009250970850837}
}
|
|||||
| Lewis, F.M., Voss, C.I. and Rubin, J. | Solute transport with equilibrium aqueous complexation and either sorption or ion exchange: Simulation methodology and applications | 1987 | Journal of Hydrology Vol. 90(1-2), pp. 81-115 |
article | URL |
| Abstract: Methodologies that account for specific types of chemical reactions in the simulation of solute transport can be developed so they are compatible with solution algorithms employed in existing transport codes. This enables the simulation of reactive transport in complex multidimensional flow regimes, and provides a means for existing codes to account for some of the fundamental chemical processes that occur among transported solutes. Two equilibrium-controlled reaction systems demonstrate a methodology for accommodating chemical interaction into models of solute transport. One system involves the sorption of a given chemical species, as well as two aqueous complexations in which the sorbing species is a participant. The other reaction set involves binary ion exchange coupled with aqueous complexation involving one of the exchanging species. The methodology accommodates these reaction systems through the addition of nonlinear terms to the transport equations for the sorbing species. Example simulation results show (1) the effect equilibrium chemical parameters have on the spatial distributions of concentration for complexing solutes; (2) that an interrelationship exists between mechanical dispersion and the various reaction processes; (3) that dispersive parameters of the porous media cannot be determined from reactive concentration distributions unless the reaction is accounted for or the influence of the reaction is negligible; (4) how the concentration of a chemical species may be significantly affected by its participation in an aqueous complex with a second species which also sorbs; and (5) that these coupled chemical processes influencing reactive transport can be demonstrated in two-dimensional flow regimes. | |||||
BibTeX:
@article{Lewis1987,
author = {Lewis, Frank M. and Voss, Clifford I. and Rubin, Jacob},
title = {Solute transport with equilibrium aqueous complexation and either sorption or ion exchange: Simulation methodology and applications},
journal = {Journal of Hydrology},
year = {1987},
volume = {90},
number = {1-2},
pages = {81--115},
url = {http://www.sciencedirect.com/science/article/pii/0022169487901740}
}
|
|||||
| Li, G. | Spatially Varying Dispersion to Model Breakthrough Curves | 2011 | Ground Water Vol. 49(4), pp. 584-592 |
article | URL |
| Abstract: Often the water flowing in a karst conduit is a combination of contaminated water entering at a sinkhole and cleaner water released from the limestone matrix. Transport processes in the conduit are controlled by advection, mixing (dilution and dispersion), and retention-release. In this article, a karst transport model considering advection, spatially varying dispersion, and dilution (from matrix seepage) is developed. Two approximate Green's functions are obtained using transformation of variables, respectively, for the initial-value problem and for the boundary-value problem. A numerical example illustrates that mixing associated with strong spatially varying conduit dispersion can cause strong skewness and long tailing in spring breakthrough curves. Comparison of the predicted breakthrough curve against that measured from a dye-tracing experiment between Ames Sink and Indian Spring, Northwest Florida, shows that the conduit dispersivity can be as large as 400 m. Such a large number is believed to imply strong solute interaction between the conduit and the matrix and/or multiple flow paths in a conduit network. It is concluded that Taylor dispersion is not dominant in transport in a karst conduit, and the complicated retention-release process between mobile- and immobile waters may be described by strong spatially varying conduit dispersion. | |||||
BibTeX:
@article{Li2011d,
author = {Li, Guangquan},
title = {Spatially Varying Dispersion to Model Breakthrough Curves},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {2011},
volume = {49},
number = {4},
pages = {584--592},
url = {http://dx.doi.org/10.1111/j.1745-6584.2010.00777.x}
}
|
|||||
| Li, G. | Analytical Solution of Advective Mixing in a Conduit | 2009 | Ground Water Vol. 47(5), pp. 714-722 |
article | URL |
| Abstract: The permeable conduit wall in a karst aquifer allows for water and solute to be exchanged between conduits and the limestone matrix. Contaminant sequestered in the limestone matrix is flushed into conduits following flood events. The contaminant released from the permeable wall will then mix with conduit water and will be transported downgradient in the conduit. A one-dimensional advection-dispersion equation is presented to describe this mixing-transport incorporating water flow and solute flux through the conduit wall. An analytical solution ignoring conduit dispersion is derived using the method of characteristics. Scale analysis is performed to provide a general guideline to estimate when conduit dispersion can be neglected. The solution also can be used to compute the distribution of solute in the matrix before flushing. | |||||
BibTeX:
@article{Li2009a,
author = {Li, Guangquan},
title = {Analytical Solution of Advective Mixing in a Conduit},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2009},
volume = {47},
number = {5},
pages = {714--722},
url = {http://dx.doi.org/10.1111/j.1745-6584.2009.00575.x}
}
|
|||||
| Li, L., Zhou, H. and Gómez-Hernández, J.J. | Transport upscaling using multi-rate mass transfer in three-dimensional highly heterogeneous porous media | 2011 | Advances in Water Resources Vol. 34(4), pp. 478-489 |
article | URL |
| Abstract: A methodology for transport upscaling of three-dimensional highly heterogeneous formations is developed and demonstrated. The overall approach requires a prior hydraulic conductivity upscaling using an interblock-centered full-tensor Laplacian-with-skin method followed by transport upscaling. The coarse scale transport equation includes a multi-rate mass transfer term to compensate for the loss of heterogeneity inherent to all upscaling processes. The upscaling procedures for flow and transport are described in detail and then applied to a three-dimensional highly heterogeneous synthetic example. The proposed approach not only reproduces flow and transport at the coarse scale, but it also reproduces the uncertainty associated with the predictions as measured by the ensemble variability of the breakthrough curves. | |||||
BibTeX:
@article{Li2011,
author = {Li, Liangping and Zhou, Haiyan and Gómez-Hernández, J. Jaime},
title = {Transport upscaling using multi-rate mass transfer in three-dimensional highly heterogeneous porous media},
journal = {Advances in Water Resources},
year = {2011},
volume = {34},
number = {4},
pages = {478--489},
url = {http://www.sciencedirect.com/science/article/pii/S0309170811000029}
}
|
|||||
| Li, L., Zhou, H. and Gómez-Hernández, J.J. | A comparative study of three-dimensional hydraulic conductivity upscaling at the macro-dispersion experiment (MADE) site, Columbus Air Force Base, Mississippi (USA) | 2011 | Journal of Hydrology Vol. 404(3-4), pp. 278-293 |
article | URL |
| Abstract: Simple averaging, simple-Laplacian, Laplacian-with-skin, and non-uniform coarsening are the techniques investigated in this comparative study of three-dimensional hydraulic conductivity upscaling. The reference is a fine scale conditional realization of the hydraulic conductivities at the MAcro-Dispersion Experiment site on Columbus Air Force Base in Mississippi (USA). This realization was generated using a hole-effect variogram model and it was shown that flow and transport modeling in this realization (at this scale) can reproduce the observed non-Fickian spreading of the tritium plume. The purpose of this work is twofold, first to compare the effectiveness of different upscaling techniques in yielding upscaled models able to reproduce the observed transport behavior, and second to demonstrate and analyze the conditions under which flow upscaling can provide a coarse model in which the standard advection–dispersion equation can be used to model transport in seemingly non-Fickian scenarios. Specifically, the use of Laplacian-based upscaling technique coupled with a non-uniform coarsening scheme yields the best results both in terms of flow and transport reproduction, for this case study in which the coarse blocks are smaller than the correlation ranges of the fine scale conductivities. | |||||
BibTeX:
@article{Li2011a,
author = {Li, Liangping and Zhou, Haiyan and Gómez-Hernández, J. Jaime},
title = {A comparative study of three-dimensional hydraulic conductivity upscaling at the macro-dispersion experiment (MADE) site, Columbus Air Force Base, Mississippi (USA)},
journal = {Journal of Hydrology},
year = {2011},
volume = {404},
number = {3-4},
pages = {278--293},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411002976}
}
|
|||||
| Li, L., Zhou, H., Hendricks Franssen, H.J. and Gómez-Hernández, J.J. | Groundwater flow inverse modeling in non-MultiGaussian media: performance assessment of the normal-score Ensemble Kalman Filter | 2011 | Hydrology and Earth System Sciences Vol. 8(4), pp. 6749-6788 |
article | DOI URL |
| Abstract: The normal-score ensemble Kalman filter (NS-EnKF) is tested on a synthetic aquifer characterized by the presence of channels with a bimodal distribution of its hydraulic conductivities. Fourteen scenarios are analyzed which differ among them in one or various of the following aspects: the prior random function model, the boundary conditions of the flow problem, the number of piezometers used in the assimilation process, or the use of covariance localization in the implementation of the Kalman filter. The performance of the NS-EnKF is evaluated through the ensemble mean and variance maps, the connectivity patterns of the individual conductivity realizations and the degree of reproduction of the piezometric heads. The results show that (i) the localized NS-EnKF can identify correctly the channels when a large number of conditioning piezometers are used even when an erroneous prior random function model is used, (ii) localization plays an important role to prevent filter inbreeding and results in a better logconductivity characterization, and (iii) the NS-EnKF works equally well under very different flow configurations. | |||||
BibTeX:
@article{Li2011b,
author = {Li, L. and Zhou, H. and Hendricks Franssen, H. J. and Gómez-Hernández, J. J.},
title = {Groundwater flow inverse modeling in non-MultiGaussian media: performance assessment of the normal-score Ensemble Kalman Filter},
journal = {Hydrology and Earth System Sciences},
publisher = {Copernicus Publications},
year = {2011},
volume = {8},
number = {4},
pages = {6749--6788},
url = {http://www.hydrol-earth-syst-sci-discuss.net/8/6749/2011/},
doi = {http://dx.doi.org/10.5194/hessd-8-6749-2011}
}
|
|||||
| Li, N. and Ren, L. | Application of continuous time random walk theory to nonequilibrium transport in soil | 2009 | Journal of Contaminant Hydrology Vol. 108(3-4), pp. 134-151 |
article | URL |
| Abstract: Continuous time random walk (CTRW) formulations have been demonstrated to provide a general and effective approach that quantifies the behavior of solute transport in heterogeneous media in field, laboratory, and numerical experiments. In this paper we first apply the CTRW approach to describe the sorbing solute transport in soils under chemical (or) and physical nonequilibrium conditions by curve-fitting. Results show that the theoretical solutions are in a good agreement with the experimental measurements. In case that CTRW parameters cannot be determined directly or easily, an alternative method is then proposed for estimating such parameters independently of the breakthrough curve data to be simulated. We conduct numerical experiments with artificial data sets generated by the HYDRUS-1D model for a wide range of pore water velocities (υ) and retardation factors (R) to investigate the relationship between CTRW parameters for a sorbing solute and these two quantities (υ, R) that can be directly measured in independent experiments. A series of best-fitting regression equations are then developed from the artificial data sets, which can be easily used as an estimation or prediction model to assess the transport of sorbing solutes under steady flow conditions through soil. Several literature data sets of pesticides are used to validate these relationships. The results show reasonable performance in most cases, thus indicating that our method could provide an alternative way to effectively predict sorbing solute transport in soils. While the regression relationships presented are obtained under certain flow and sorption conditions, the methodology of our study is general and may be extended to predict solute transport in soils under different flow and sorption conditions. | |||||
BibTeX:
@article{Li2009,
author = {Li, Na and Ren, Li},
title = {Application of continuous time random walk theory to nonequilibrium transport in soil},
journal = {Journal of Contaminant Hydrology},
year = {2009},
volume = {108},
number = {3-4},
pages = {134--151},
url = {http://www.sciencedirect.com/science/article/pii/S0169772209000904}
}
|
|||||
| Li, Q., Sun, H., Han, J., Liu, Z. and Yu, L. | High-resolution study on the hydrochemical variations caused by the dilution of precipitation in the epikarst spring: an example spring of Landiantang at Nongla, Mashan, China | 2008 | Environmental Geology Vol. 54(2), pp. 347-354 |
article | URL |
| Abstract: In addition to rainfall, high-resolution measurements of water level, pH, specific conductivity and temperature of Landiantang epikarst spring at Nongla, Mashan county in Guangxi Province, China were recorded in summer rainy season by using a data logger with time interval of fifteen minutes. Water from the spring issues along a karst conduit. During the rainstorms in summer, it was found that the pH and temperature of Landiantang spring increased while its specific conductivity decreased. As HCO 3 − , Ca 2+ and Mg 2+ are the dominant ions, linear relationships between concentrations of those ions and specific conductivity were developed. According to the ion concentrations from the linear relationships, the saturation indexes of calcite (SI C ), the saturation indexes of dolomite (SI D ) and CO 2 partial pressure (Log $$ P_CO_2 $$) of the spring were calculated. Results indicated that the Log $$ P_CO_2 $$ of the spring during the rainstorms was lower than that without rain, and its SI C and SI D was also lower. Combined with the characteristics of the epikarst zone, it was inferred that the above results were caused by the dilution of rainwater, because overland flow with high pH (due to neutralization of carbonate rock dusts in the air to rainwater) and low specific conductivity traveling through the conduit rapidly during rainstorms, showed greater influences on the hydrochemical variations of the epikarst spring. | |||||
BibTeX:
@article{Li2008b,
author = {Li, Qiang and Sun, Hailong and Han, Jun and Liu, Zaihua and Yu, Longjiang},
title = {High-resolution study on the hydrochemical variations caused by the dilution of precipitation in the epikarst spring: an example spring of Landiantang at Nongla, Mashan, China},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {2008},
volume = {54},
number = {2},
pages = {347--354},
url = {http://dx.doi.org/10.1007/s00254-007-0821-8}
}
|
|||||
| Li, S.-H., Huang, W.-J. and Huang, M.-N.L. | Characterizations of the Poisson process as a renewal process via two conditional moments | 1994 | Annals of the Institute of Statistical Mathematics Vol. 46(2), pp. 351-360 |
article | URL |
| Abstract: Given two independent positive random variables, under some minor conditions, it is known that from E (X r ?X+Y)=a(X+Y) r and E (X s ?X+Y)=b(X+Y) s , for certain pairs of r and s , where a and b are two constants, we can characterize X and Y to have gamma distributions. Inspired by this, in this article we will characterize the Poisson process among the class of renewal processes via two conditional moments. More precisely, let A(t), t= 0 be a renewal process, with S k , k=1 the sequence of arrival times, and F the common distribution function of the inter-arrival times. We prove that for some fixed n and k, k=n , if E (S k r ?A(t)=n)=at r and E (S k s ?A(t)=n)=bt s , for certain pairs of r and s , where a and b are independent of t , then A(t), t =0 has to be a Poisson process. We also give some corresponding results about characterizing F to be geometric when F is discrete. | |||||
BibTeX:
@article{Li1994,
author = {Li, Shun-Hwa and Huang, Wen-Jang and Huang, Mong-Na Lo},
title = {Characterizations of the Poisson process as a renewal process via two conditional moments},
journal = {Annals of the Institute of Statistical Mathematics},
publisher = {Springer Netherlands},
year = {1994},
volume = {46},
number = {2},
pages = {351--360},
url = {http://dx.doi.org/10.1007/BF01720591}
}
|
|||||
| Li, W., Yu, L.-j., He, Q.-f., Wu, Y., Yuan, D.-x. and Cao, J.-h. | Effects of microbes and their carbonic anhydrase on Ca2+ and Mg2+ migration in column-built leached soil-limestone karst systems | 2005 | Applied Soil Ecology Vol. 29(3), pp. 274-281 |
article | URL |
| Abstract: In natural karst systems, limestone diagenesis can be significantly influenced by bacterial activity in the soil horizon. Here, we investigate the effects of microorganisms on the elements migration of calcium and magnesium in karst soil systems by using different microbial treatments in simulated soil-limestone systems. Two bacterial strains, GLRT102Ca and JFSRT303 were specially studied. The leaching and release of Ca2+ in the experiments was characterized by a rapid initial increase followed by a sharp decrease before a gradual approach to equilibrium. In contrast, the Mg2+ concentrations in the leachates showed an initial decrease before a gradual approach to equilibrium. Microorganisms significantly promoted Ca2+ and Mg2+ migration in the simulated systems. The total amounts of Ca2+ and Mg2+ in leachates varied with microbial treatments. The soil + GLRT102Ca columns showed the highest total amount of Ca2+ in leachates. This increased by a factor of 2.2 relative to the control columns. The highest total amount of Mg2+ in leachates was presented in the soil + JFSRT303 columns, which leached 58.0% more total amounts of Mg2+ than the control columns. The activities of a microbial specific enzyme, carbonic anhydrase (CA), present in the investigated columns were also examined. Varying levels of CA activities were detected in the leachates collected from soil columns with microbial activity. This suggests that the microbes in soil columns produced and released CA. The mean activity of CA in leachates was significantly correlated with total amount of Ca2+ in leachates (r = 0.86, P < 0.01). This implied that microbially produced CA might be a major factor influencing Ca2+ release and leaching in natural karst systems. | |||||
BibTeX:
@article{Li2005,
author = {Li, Wei and Yu, Long-jiang and He, Qiu-fang and Wu, Yun and Yuan, Dao-xian and Cao, Jian-hua},
title = {Effects of microbes and their carbonic anhydrase on Ca2+ and Mg2+ migration in column-built leached soil-limestone karst systems},
journal = {Applied Soil Ecology},
year = {2005},
volume = {29},
number = {3},
pages = {274--281},
url = {http://www.sciencedirect.com/science/article/pii/S0929139305000028}
}
|
|||||
| Li, X.-D., Liu, C.-Q., Harue, M., Li, S.-L. and Liu, X.-L. | The use of environmental isotopic (C, Sr, S) and hydrochemical tracers to characterize anthropogenic effects on karst groundwater quality: A case study of the Shuicheng Basin, SW China | 2010 | Applied Geochemistry Vol. 25(12), pp. 1924-1936 |
article | URL |
| Abstract: Rapidly increasing populations, and associated intensification of agriculture, urbanization and industrialization, place increased demands on water resources and increased likelihood of pollution in many areas of the world. The Shuicheng Basin, southwestern China, is one such area and in order to understand water–rock interactions (carbonate dissolution) and anthropogenic impacts on groundwater quality in this karstic landform-dominated area, chemical as well as C, Sr and S isotopic compositions of groundwater (spring and well) and surface water (river) were measured during and following rainy seasons. The concentrations of various ions in groundwater were characterized by the dominant cations (Ca2+, Mg2+) and anions ( HCO 3 - , SO 4 2 - ), which account for more than 80% of the total ion concentration. Strontium isotope ratios (87Sr/86Sr, 0.70760–0.70918, mean 0.70831) and δ13CDIC (−14.2‰ to −8.4‰, mean −10.7‰) indicate that the weathering dissolution of limestone controls Ca2+ and HCO 3 - . The decrease in δ13CDIC values with increasing concentrations of anthropogenic species (Cl−, NO 3 - and Na+) shows that the C isotopic composition of DIC can be a useful tracer of contaminants. Chemical compositions, hydrogeological conditions and δ34S analyses showed increasing SO 4 2 - concentration, resulting from domestic wastewater, fertilizer applications, atmospheric inputs through coal combustion, and oxidation of sulfide minerals, which typically are abundant in coal formations in the basin. Groundwater from the old downtown, industrial and agricultural areas exhibited high concentrations of Cl−, NO 3 - , SO 4 2 - and Na+, suggesting the groundwater is impacted by significant levels of contamination from human activities. | |||||
BibTeX:
@article{Li2010,
author = {Li, Xiao-Dong and Liu, Cong-Qiang and Harue, Masuda and Li, Si-Liang and Liu, Xiao-Long},
title = {The use of environmental isotopic (C, Sr, S) and hydrochemical tracers to characterize anthropogenic effects on karst groundwater quality: A case study of the Shuicheng Basin, SW China},
journal = {Applied Geochemistry},
year = {2010},
volume = {25},
number = {12},
pages = {1924--1936},
url = {http://www.sciencedirect.com/science/article/pii/S0883292710002295}
}
|
|||||
| Li, Y., Deletic, A. and Fletcher, T. | Modelling wet weather sediment removal by stormwater constructed wetlands: Insights from a laboratory study | 2007 | Journal of Hydrology Vol. 338(3–4), pp. 285-296 |
article | URL |
| Abstract: Summary Constructed wetlands are now commonly used to control polluted urban stormwater discharges. A laboratory study was conducted to investigate the treatment of solids in these systems. Three mesocosm stormwater wetlands (vegetated with a well-established canopy of different densities) and one mesocosm non-vegetated pond were used, all sized to achieve particle fall number (Nf, a ratio between the times of the particle travel in horizontal and vertical directions) and Particle Shear Velocity Reynolds Number, Re∗, which are reflective of full-scale systems. The mesocosm vegetated systems had also similar turbulent Reynolds Numbers (ReT) to those funds in full-scale systems. Ten groups of steady-state experiments were carried out, all with different hydraulic loadings and sediment inflow concentrations (also maintained within the ranges found in real systems during wet weather). Samples were taken along the mesocosms and analysed for Total Suspended Solids concentrations (TSS) and Particle Size Distribution (PSD). It was found that both Re∗ and ReT do not significantly influence the trapping of sediments, and therefore the particle re-suspension induced by water flow is not important for sedimentation in constructed stormwater wetlands. Vegetation density was found not to be an important factor, while particle diameter, and flow characteristics (e.g., flow rate and velocity) do influence trapping efficiency of particles. It was concluded that sediment trapping correlates strongly with particle fall number, Nf, and therefore can be explained by this single non-dimensional number. A simple non-linear two-parameter regression model is proposed for prediction of particle trapping efficiency in constructed stormwater wetlands. However, further work is needed before the method can be used in practice. The aim of the ongoing work is to test whether the proposed model could be used across a number of real stormwater constructed wetlands without any further calibration. The data collected from a number of stormwater treatment systems in Melbourne, Australia, will be used in this study. | |||||
BibTeX:
@article{Li2007,
author = {Li, Y. and Deletic, A. and Fletcher, T.D.},
title = {Modelling wet weather sediment removal by stormwater constructed wetlands: Insights from a laboratory study},
journal = {Journal of Hydrology},
year = {2007},
volume = {338},
number = {3–4},
pages = {285--296},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407001540}
}
|
|||||
| Li, Y. and Huang, P. | A coupled lattice Boltzmann model for advection and anisotropic dispersion problem in shallow water | 2008 | Advances in Water Resources Vol. 31(12), pp. 1719-1730 |
article | URL |
| Abstract: A coupled lattice Boltzmann model (CLBM) for 2D advection and anisotropic dispersion equation (AADE) and shallow water equations is formulated and implemented. Multi-relaxation-time (MRT) method is used for the flow field and the L-basis two-relaxation-time (TRT) method is used for the pollutant field. The relaxation time for the antisymmetric part of the pollutant deviates from a constant for flows with variable free surface water depth. Numerical tests show that this scheme strictly obeys conservation of mass and momentum. And the model has a better accuracy when τ D is closer to 1 2 and τ e is closer to ∑ τ D ∗ 9 . Excellent agreement is obtained between numerical predictions and analytical solutions in pure dispersion problem and advection–dispersion problem. Comparison with finite different method indicates that the variation of the free surface water depth does not affect the mass and momentum conservation of the model and that the model has the ability to simulate complex bed topography problem. Comparison with finite volume method in the 2D steady flow around a rectangular column with non-slip boundary shows that the LB scheme has the capacity to solve the complex advection–dispersion problems in shallow water. | |||||
BibTeX:
@article{Li2008a,
author = {Li, Yineng and Huang, Ping},
title = {A coupled lattice Boltzmann model for advection and anisotropic dispersion problem in shallow water},
journal = {Advances in Water Resources},
year = {2008},
volume = {31},
number = {12},
pages = {1719--1730},
url = {http://www.sciencedirect.com/science/article/pii/S0309170808001528}
}
|
|||||
| Liang, C.-H., Chiang, P.-C. and Chang, E.-E. | Modeling the behaviors of adsorption and biodegradation in biological activated carbon filters | 2007 | Water Research Vol. 41(15), pp. 3241-3250 |
article | URL |
| Abstract: This investigation developed a non-steady-state numerical model to differentiate the adsorption and biodegradation quantities of a biological activated carbon (BAC) column. The mechanisms considered in this model are adsorption, biodegradation, convection and diffusion. Simulations were performed to evaluate the effects of the major parameters, the packing media size and the superficial velocity, on the adsorption and biodegradation performances for the removal of dissolved organic carbon based on dimensionless analysis. | |||||
BibTeX:
@article{Liang2007,
author = {Liang, Chung-Huei and Chiang, Pen-Chi and Chang, E-E},
title = {Modeling the behaviors of adsorption and biodegradation in biological activated carbon filters},
journal = {Water Research},
year = {2007},
volume = {41},
number = {15},
pages = {3241--3250},
url = {http://www.sciencedirect.com/science/article/pii/S0043135407003272}
}
|
|||||
| Liao, C.-M. and Liang, H.-M. | A linear model of the effects of residence time distribution on mixing pattern in a ventilated airspace | 2003 | Building and Environment Vol. 38(1), pp. 11-21 |
article | URL |
| Abstract: The ability of a simple linear response model is evaluated to explain the mixing efficiencies in an incomplete mixing ventilated airspace. Data interpretation and mean residence time calculation for a specified output concentration profile can also be evaluated. The residence time distribution (RTD) functions take the form of the two-parameter gamma distribution and account for different mixing types such as complete mixing, piston flow (no mixing), incomplete mixing, and various combinations of the above types. In these combinations, the different mixing types simulated by different RTDs conceptually represent airflow regions in series. The mixing efficiency was introduced to characterize the extent or degree of mixing in a ventilation system in that mixing efficiency equals zero for piston flow (no mixing), unity for complete mixing, and a value in between these two extremes for incomplete mixing. An environmental chamber experiment was conducted to generate several output profiles to evaluate the applicability of the model. Carbon dioxide was employed as the tracer gas. Our results show that an overall root-mean-squared error value of 8.64±5.25 ppm is low, indicating that the combination mixing patterns are generally found to be minimally biased and give better fitting than other simpler mixing patterns. Despite their neglect of molecular diffusion and possible temporal/spatial nonlinearities, these linear response models appear reasonably robust, making them at least as useful to building microenvironment designers in reconsidering the possibilities and consequences of various forms of incomplete mixing related to indoor air quality problems. | |||||
BibTeX:
@article{Liao2003,
author = {Liao, Chung-Min and Liang, Huang-Min},
title = {A linear model of the effects of residence time distribution on mixing pattern in a ventilated airspace},
journal = {Building and Environment},
year = {2003},
volume = {38},
number = {1},
pages = {11--21},
url = {http://www.sciencedirect.com/science/article/pii/S0360132302000264}
}
|
|||||
| Lightbody, A.F., Nepf, H.M. and Bays, J.S. | Mixing in deep zones within constructed treatment wetlands | 2007 | Ecological Engineering Vol. 29(2), pp. 209-220 |
article | URL |
| Abstract: Transverse deep zones are often included in treatment wetlands due to an expectation that they can improve contaminant removal by these natural systems. This paper explores the hydraulic behavior of deep zones to provide a better understanding of their potential benefit. First, we use a bench-scale model to show that recirculation within a deep zone is likely under field conditions. Recirculation is believed to provide a mechanism for mixing. We then use a mathematical model to explore the effect on the outlet concentration of replacing a section of a wetland marsh with a deep zone that provides mixing. We observe that even when deep zones have a lower volumetric removal rate than the marsh areas they replace, the presence of a deep zone may decrease the outlet concentration and hence improve the performance of the wetland segment. | |||||
BibTeX:
@article{Lightbody2007,
author = {Lightbody, Anne F. and Nepf, Heidi M. and Bays, James S.},
title = {Mixing in deep zones within constructed treatment wetlands},
journal = {Ecological Engineering},
year = {2007},
volume = {29},
number = {2},
pages = {209--220},
url = {http://www.sciencedirect.com/science/article/pii/S0925857406002783}
}
|
|||||
| Lijoi, A. | Approximating priors by finite mixtures of conjugate distributions for an exponential family | 2003 | Journal of Statistical Planning and Inference Vol. 113(2), pp. 419-435 |
article | URL |
| Abstract: The problem of approximating a prior by a suitable finite mixture of distributions, with respect to Prokhorov's metric, is considered. We give explicit estimates of the error of approximation when the statistical model is a suitable exponential family. An illustrative example shows an application of the approximation technique. In an attempt to generalize these results to an arbitrary natural exponential family model, rates of convergence of the mixture to the approximated prior are given. | |||||
BibTeX:
@article{Lijoi2003,
author = {Lijoi, Antonio},
title = {Approximating priors by finite mixtures of conjugate distributions for an exponential family},
journal = {Journal of Statistical Planning and Inference},
year = {2003},
volume = {113},
number = {2},
pages = {419--435},
url = {http://www.sciencedirect.com/science/article/pii/S016771520100205X}
}
|
|||||
| Lilyann Novak, F. | One stop mycology [BibTeX] |
1997 | Mycological Research Vol. 101(1), pp. 102-128 |
article | URL |
BibTeX:
@article{LilyannNovak1997,
author = {Lilyann Novak, Frazer},
title = {One stop mycology},
journal = {Mycological Research},
year = {1997},
volume = {101},
number = {1},
pages = {102--128},
url = {http://www.sciencedirect.com/science/article/pii/S0953756208605900}
}
|
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| Limousin, G., Gaudet, J.-P., Charlet, L., Szenknect, S., Barthès, V. and Krimissa, M. | Sorption isotherms: A review on physical bases, modeling and measurement | 2007 | Applied Geochemistry Vol. 22(2), pp. 249-275 |
article | URL |
| Abstract: The retention (or release) of a liquid compound on a solid controls the mobility of many substances in the environment and has been quantified in terms of the “sorption isotherm”. This paper does not review the different sorption mechanisms. It presents the physical bases underlying the definition of a sorption isotherm, different empirical or mechanistic models, and details several experimental methods to acquire a sorption isotherm. For appropriate measurements and interpretations of isotherm data, this review emphasizes 4 main points: (i) the adsorption (or desorption) isotherm does not provide automatically any information about the reactions involved in the sorption phenomenon. So, mechanistic interpretations must be carefully verified. (ii) Among studies, the range of reaction times is extremely wide and this can lead to misinterpretations regarding the irreversibility of the reaction: a pseudo-hysteresis of the release compared with the retention is often observed. The comparison between the mean characteristic time of the reaction and the mean residence time of the mobile phase in the natural system allows knowing if the studied retention/release phenomenon should be considered as an instantaneous reversible, almost irreversible phenomenon, or if reaction kinetics must be taken into account. (iii) When the concentration of the retained substance is low enough, the composition of the bulk solution remains constant and a single-species isotherm is often sufficient, although it remains strongly dependent on the background medium. At higher concentrations, sorption may be driven by the competition between several species that affect the composition of the bulk solution. (iv) The measurement method has a great influence. Particularly, the background ionic medium, the solid/solution ratio and the use of flow-through or closed reactor are of major importance. The chosen method should balance easy-to-use features and representativity of the studied natural conditions. | |||||
BibTeX:
@article{Limousin2007,
author = {Limousin, G. and Gaudet, J.-P. and Charlet, L. and Szenknect, S. and Barthès, V. and Krimissa, M.},
title = {Sorption isotherms: A review on physical bases, modeling and measurement},
journal = {Applied Geochemistry},
year = {2007},
volume = {22},
number = {2},
pages = {249--275},
url = {http://www.sciencedirect.com/science/article/pii/S0883292706002629}
}
|
|||||
| Lin, A.Y.-C., Debroux, J.-F., Cunningham, J.A. and Reinhard, M. | Comparison of rhodamine WT and bromide in the determination of hydraulic characteristics of constructed wetlands | 2003 | Ecological Engineering Vol. 20(1), pp. 75-88 |
article | URL |
| Abstract: Hydraulic tracer tests were performed in the Prado Wetlands, Riverside County, California, USA. The goals of the tests were (1) to evaluate the suitability of rhodamine WT (RWT) as a tracer for wetlands studies, and (2) to determine the residence time distribution of the wetlands. The performance of RWT was evaluated by comparing the breakthrough curve (BTC) of RWT to that of bromide in a pilot-scale test. The BTCs of RWT and bromide indicated equal results. After the pilot test, a full-scale test was conducted by releasing a RWT pulse at the wetlands inlet and monitoring for RWT arrival near the wetlands outlet. The BTC indicated 10 and 90% (of the total mass recovered) breakthrough times of 25 and 112 h, respectively, but these must be considered approximations because only 29% of the injected RWT mass was recovered. Laboratory experiments suggest irreversible sorption to be the principal loss mechanism of RWT during transport through the wetlands. RWT is a suitable tracer in wetlands that are relatively small (less than 1 week residence time) and deep (at least 0.6 m) with limited sediment contact, but RWT yields only approximate results for the extended wetlands system. | |||||
BibTeX:
@article{Lin2003a,
author = {Lin, Angela Yu-Chen and Debroux, Jean-François and Cunningham, Jeffrey A. and Reinhard, Martin},
title = {Comparison of rhodamine WT and bromide in the determination of hydraulic characteristics of constructed wetlands},
journal = {Ecological Engineering},
year = {2003},
volume = {20},
number = {1},
pages = {75--88},
url = {http://www.sciencedirect.com/science/article/pii/S0925857403000053}
}
|
|||||
| Lin, W. and Lee, D. | Micromixing effects in aerated stirred tank | 1997 | Chemical Engineering Science Vol. 52(21-22)Gas-Liquid-Solid Reactor Engineering, pp. 3837-3842 |
article | URL |
| Abstract: Micromixing efficiency in an aerated stirred tank is measured quantitatively on the basis of a new parallel competing reaction scheme proposed by Villermaux and co-workers. The segregation index is strongly influenced by both mechanical stirring and gas-flow agitation. In the region near the impeller tip, the agitation by bulk gas column or dispersed tiny bubbles can provide an efficient micromixed environment. Stirring effect becomes secondary. In the near-wall regions far from tip, however, the occurrence of flooding markedly reduces the micromixing efficiency. Possible role of bubbles on agitation is discussed. | |||||
BibTeX:
@article{Lin1997,
author = {Lin, W.W. and Lee, D.J.},
title = {Micromixing effects in aerated stirred tank},
booktitle = {Gas-Liquid-Solid Reactor Engineering},
journal = {Chemical Engineering Science},
year = {1997},
volume = {52},
number = {21-22},
pages = {3837--3842},
url = {http://www.sciencedirect.com/science/article/pii/S0009250997002273}
}
|
|||||
| Lin, Y.-C., Chang, M.-S. and Medina Jr., M.A. | A methodology for solute transport in unsteady, nonuniform streamflow with subsurface interaction | 2005 | Advances in Water Resources Vol. 28(8), pp. 871-883 |
article | URL |
| Abstract: An advection-dispersion-reaction model can generally be used to describe one-dimensional stream solute transport if the flow is steady and if the channel is smooth and uniform. When applied to unsteady, nonuniform streamflows, a model based on the Fickian analogy needs to be modified to account for the temporal and spatial variation of the cross-sectional area of the stream channel. In this paper, we explore this topic with a simple approximation method as well as an elaborate one, both of which are incorporated into a conjunctive stream–aquifer transport model and are applied to a hypothetical stream–aquifer setting. The simple method, while easier to implement, displays a persistent pattern of error in simulation results. The elaborate method, while accurate in computation, results in a more complicated model and requires extensive procedures to overcome the efficiency problem when simulating complex stream–aquifer interactions. However, by coupling the latter with the adaptive stepsize control for the Runge–Kutta method in a conjunctive stream–aquifer model, it not only greatly improves model efficiency but also results in more realistic modeling than previously reported. | |||||
BibTeX:
@article{Lin2005,
author = {Lin, Yi-Chang and Chang, Ming-Shien and Medina Jr., Miguel A.},
title = {A methodology for solute transport in unsteady, nonuniform streamflow with subsurface interaction},
journal = {Advances in Water Resources},
year = {2005},
volume = {28},
number = {8},
pages = {871--883},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805000394}
}
|
|||||
| Lin, Y.-C. and Medina Jr., M.A. | Incorporating transient storage in conjunctive stream–aquifer modeling | 2003 | Advances in Water Resources Vol. 26(9)Modeling Hyporheic Zone Processes, pp. 1001-1019 |
article | URL |
| Abstract: There has been growing interest in incorporating the transient storage effect into modeling solute transport in streams. In particular, for a smaller mountain stream where flow is fast and the flow field is irregular (a favorable environment to induce dead zones along the stream), long tails are normally observed in the stream tracer data, and adding transient storage terms in the advection–dispersion transport equation can result in more accurate simulation. While previous studies on transient storage modeling account for temporary, localized exchange between the stream and the shallow groundwater in the hyporheic zone, larger-scale exchange with the groundwater in the underlying aquifer has rarely been included or properly coupled to surface water modeling. In this paper, we complement previous modeling efforts by incorporating the transient storage concept in a conjunctive stream–aquifer model. Three well-documented and widely used USGS models have been coupled to form the core of this conjunctive model: MODFLOW handles the groundwater flow in the aquifer; DAFLOW accurately computes unsteady streamflow by means of the diffusive wave routing technique, as well as stream–aquifer exchange simulated as streambed leakage; and MOC3D computes solute transport in the groundwater zone. In addition, an explicit finite difference package was developed to incorporate the one-dimensional transient storage equations for solute transport in streams. The quadratic upstream interpolation (QUICK) algorithm is employed to improve the accuracy of spatial differencing. An adaptive stepsize control algorithm for the Runge–Kutta method is incorporated to increase overall model efficiency. Results show that the conjunctive stream–aquifer model with transient storage can handle well the bank storage effect under a flooding event. When it is applied over a stream network, the results also show that the stream–aquifer interaction acts as a strong source or sink along the stream and is too significant to be ignored. The adaptive stepsize control for stream solute transport improves overall model performance. | |||||
BibTeX:
@article{Lin2003,
author = {Lin, Yi-Chang and Medina Jr., Miguel A.},
title = {Incorporating transient storage in conjunctive stream–aquifer modeling},
booktitle = {Modeling Hyporheic Zone Processes},
journal = {Advances in Water Resources},
year = {2003},
volume = {26},
number = {9},
pages = {1001--1019},
url = {http://www.sciencedirect.com/science/article/pii/S0309170803000812}
}
|
|||||
| Lindsay, S., Wood, G. and Woollons, R. | Stand table modelling through the Weibull distribution and usage of skewness information | 1996 | Forest Ecology and Management Vol. 81(1-3), pp. 19-23 |
article | URL |
| Abstract: A very common practice in forest modelling is to summarise diameter distribution data through use of probability density functions. By far the most popular model is the Weibull which, as well as being versatile, has the distinct advantage that its parameters are readily estimable. In practice, the location parameter a is usually equated to a minimum (sample) value. The scale and shape parameters are estimated iteratively or (approximately) explicitly, through use of moments or percentiles. Here, we expand and develop the use of moments to estimate all three parameters; the essential enhancement is that information concerning the distribution asymmetry is utilised, via the sample skewness statistic. Normally, this information is ignored. Applying the methodology to a Pinus radiata dataset showed that the goodness of fit was improved on average by 15%. On modem computers the method is easily and quickly assayed, so its usage is recommended. There are grounds for suggesting that the method could be embedded in diameter distribution growth-and-yield systems to good effect. | |||||
BibTeX:
@article{Lindsay1996,
author = {Lindsay, S.R. and Wood, G.R. and Woollons, R.C.},
title = {Stand table modelling through the Weibull distribution and usage of skewness information},
journal = {Forest Ecology and Management},
year = {1996},
volume = {81},
number = {1-3},
pages = {19--23},
url = {http://www.sciencedirect.com/science/article/pii/0378112795036695}
}
|
|||||
| Liong, S., Chan, W. and Law, C. | An expert system for storm water management modelling, and its application | 1991 | Engineering Applications of Artificial Intelligence Vol. 4(5), pp. 367 - 375 |
article | DOI URL |
| Abstract: The essential features of the KBSWMM model, a knowledge-based system for model calibration of the Runoff Block of the Storm Water Management Model (SWMM), are discussed in detail. The model is then applied to predict runoff of a 6.2 km2 catchment in Singapore. Model calibration and verification runs are performed. Results show that KBSWMM not only requires less time and experience of the user, but also achieves reasonably good runoff predictions. | |||||
BibTeX:
@article{Liong1991,
author = {Liong, S.Y. and Chan, W.T. and Law, C.L.},
title = {An expert system for storm water management modelling, and its application},
journal = {Engineering Applications of Artificial Intelligence},
year = {1991},
volume = {4},
number = {5},
pages = {367 - 375},
url = {http://www.sciencedirect.com/science/article/pii/095219769190005Q},
doi = {http://dx.doi.org/10.1016/0952-1976(91)90005-Q}
}
|
|||||
| Liong, S.-Y., Ibrahim, Y., Chan, W.T. and Law, C.L. | Computer-aided catchment-calibration model | 1993 | Advances in Engineering Software Vol. 17(3), pp. 147-154 |
article | URL |
| Abstract: A new version of a computer-aided catchment model, KBSWMM (Version 2), is presented and discussed. The model essentially contains the following features: (i) preprocessors for the Runoff and Extran blocks of the widely used Storm Water Management Model, SWMM. These preprocessors are developed on X Window system, X11; (ii) flow-routing components of the Runoff and Extran blocks; (iii) a probablistic-based catchment calibration model; and (iv) a postprocessor to display the computational results in both text and graphical forms. The application of KBSWMM is demonstrated on a catchment in Singapore. The data entry of KBSWMM is very user-friendly, the built-in automatic catchment-calibration process requires minimal effort to achieve the optimum set of values for the calibration parameters, and the computational results are presented in self-explanatory graphical forms. | |||||
BibTeX:
@article{Liong1993,
author = {Liong, Shie-Yui and Ibrahim, Yaacob and Chan, Weng Tat and Law, Chee Liang},
title = {Computer-aided catchment-calibration model},
journal = {Advances in Engineering Software},
year = {1993},
volume = {17},
number = {3},
pages = {147--154},
url = {http://www.sciencedirect.com/science/article/pii/0965997893900744}
}
|
|||||
| Liou, C.-T. and Chien, Y.-S. | The effect of micromixing on steady-state multiplicity for autocatalytic reactions in a nonideal mixing of CSTR | 1995 | Chemical Engineering Science Vol. 50(22), pp. 3637-3644 |
article | URL |
| Abstract: The effect of micromixing on steady-state multiplicity is not displayed by the universal reaction model (URM) since this URM has considered any chemical species having the same mixing time constant. The modified universal reaction model (MURM) is derived for overcoming the above limitation. The design equations are first derived. Furthermore, the MURM is employed for studying the effect of micromixing on the multiplicity for autocatalytic, isothermal reactions of the type A + B → (η + 1)B + product with the overall rate expression being −γa = kCapCbr in a CSTR. The effects of micromixing on necessary and sufficient, conditions for multiplicity are presented. | |||||
BibTeX:
@article{Liou1995,
author = {Liou, Ching-Tien and Chien, Yu-Shu},
title = {The effect of micromixing on steady-state multiplicity for autocatalytic reactions in a nonideal mixing of CSTR},
journal = {Chemical Engineering Science},
year = {1995},
volume = {50},
number = {22},
pages = {3637--3644},
url = {http://www.sciencedirect.com/science/article/pii/0009250995001939}
}
|
|||||
| Liou, T.-S. and Yeh, H.-D. | Conditional expectation for evaluation of risk groundwater flow and solute transport: one-dimensional analysis | 1997 | Journal of Hydrology Vol. 199(3-4), pp. 378-402 |
article | URL |
| Abstract: A one-dimensional groundwater transport equation with two uncertain parameters, groundwater velocity and longitudinal dispersivity, is investigated in this paper. The analytical uncertainty of the predicted contaminant concentration is derived by the first-order mean-centered uncertainty analysis. The risk of the contaminant transport is defined as the probability that the concentration exceeds a maximum acceptable upper limit. Five probability density functions including the normal, lognormal, gamma, Gumbel, and Weibull distributions are chosen as the models for predicting the concentration distribution. The risk for each distribution is derived analytically based on the conditional probability. The mean risk and confidence interval are then computed by Monte Carlo simulation where the groundwater velocity and longitudinal dispersivity are assumed to be lognormally and normally distributed, respectively. Results from the conditional expectation of an assumed damage function show that the unconditional expectation generally underestimates the damage for low risk events. It is found from the sensitivity analysis that the mean longitudinal dispersivity is the most sensitive parameter and the variance of longitudinal dispersivity is the least sensitive one among those distribution models except the gamma and Weibull distributions. | |||||
BibTeX:
@article{Liou1997,
author = {Liou, Tai-Sheng and Yeh, Hund-Der},
title = {Conditional expectation for evaluation of risk groundwater flow and solute transport: one-dimensional analysis},
journal = {Journal of Hydrology},
year = {1997},
volume = {199},
number = {3-4},
pages = {378--402},
url = {http://www.sciencedirect.com/science/article/pii/S0022169497000255}
}
|
|||||
| Lischeid, G. and Bittersohl, J. | Tracing biogeochemical processes in stream water and groundwater using non-linear statistics | 2008 | Journal of Hydrology Vol. 357(1-2), pp. 11-28 |
article | URL |
| Abstract: Stream water and groundwater solute concentration are subject to a multitude of biogeochemical processes that act at different scales and are often characterized by non-linear relationships and feedback loops. Different multivariate statistical methods were applied to investigate the interplay of different processes. The data set from the Lehstenbach catchment in South Germany comprised 2641 stream water and groundwater samples from 38 different sites in the catchment, where 13 different solutes had been determined. According to the correlation dimension analysis, the number of dominant processes was four. The first four components determined via principal component analysis comprised 88% of the total variance, whereas the non-linear isometric feature mapping explained 92% with the first four components. These components were ascribed to prevailing biogeochemical processes and were used to investigate spatial and temporal patterns. Redox processes and contamination by road salt explained 35% of the variance each. Another 13% were ascribed to near-surface runoff in the acidified topsoil, and 9% to the impact of contaminated filter gravel in some of the groundwater wells. | |||||
BibTeX:
@article{Lischeid2008,
author = {Lischeid, Gunnar and Bittersohl, Jochen},
title = {Tracing biogeochemical processes in stream water and groundwater using non-linear statistics},
journal = {Journal of Hydrology},
year = {2008},
volume = {357},
number = {1-2},
pages = {11--28},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408001467}
}
|
|||||
| Liu, G., Chen, Y. and Zhang, D. | Investigation of flow and transport processes at the MADE site using ensemble Kalman filter | 2008 | Advances in Water Resources Vol. 31(7), pp. 975-986 |
article | URL |
| Abstract: In this work the ensemble Kalman filter (EnKF) is applied to investigate the flow and transport processes at the macro-dispersion experiment (MADE) site in Columbus, MS. The EnKF is a sequential data assimilation approach that adjusts the unknown model parameter values based on the observed data with time. The classic advection–dispersion (AD) and the dual-domain mass transfer (DDMT) models are employed to analyze the tritium plume during the second MADE tracer experiment. The hydraulic conductivity (K), longitudinal dispersivity in the AD model, and mass transfer rate coefficient and mobile porosity ratio in the DDMT model, are estimated in this investigation. Because of its sequential feature, the EnKF allows for the temporal scaling of transport parameters during the tritium concentration analysis. Inverse simulation results indicate that for the AD model to reproduce the extensive spatial spreading of the tritium observed in the field, the K in the downgradient area needs to be increased significantly. The estimated K in the AD model becomes an order of magnitude higher than the in situ flowmeter measurements over a large portion of media. On the other hand, the DDMT model gives an estimation of K that is much more comparable with the flowmeter values. In addition, the simulated concentrations by the DDMT model show a better agreement with the observed values. The root mean square (RMS) between the observed and simulated tritium plumes is 0.77 for the AD model and 0.45 for the DDMT model at 328 days. Unlike the AD model, which gives inconsistent K estimates at different times, the DDMT model is able to invert the K values that consistently reproduce the observed tritium concentrations through all times. | |||||
BibTeX:
@article{Liu2008,
author = {Liu, Gaisheng and Chen, Yan and Zhang, Dongxiao},
title = {Investigation of flow and transport processes at the MADE site using ensemble Kalman filter},
journal = {Advances in Water Resources},
year = {2008},
volume = {31},
number = {7},
pages = {975--986},
url = {http://www.sciencedirect.com/science/article/pii/S0309170808000481}
}
|
|||||
| Liu, G., Zheng, C. and Gorelick, S.M. | Limits of applicability of the advection-dispersion model in aquifers containing connected high-conductivity channels | 2004 | Water Resources Research Vol. 40(8), pp. W08308- |
article | URL |
| Abstract: The macrodispersion model from stochastic transport theory is demonstrated to be of limited utility when applied to heterogeneous aquifer systems containing narrow connected pathways. This is so even when contrasts in hydraulic conductivity (K) are small and variance in ln K is less than 0.10. We evaluated how well an advection-dispersion model (ADM) could be used to represent solute plumes transported through mildly heterogeneous three-dimensional (3-D) systems characterized by a well-connected dendritic network of 10 cm wide high-K channels. Each high-K channel network was generated using an invasion percolation algorithm and consisted of ∼10% by volume high-K regions. Contrasts in K between the channels and matrix were varied systematically from 2:1 to 30:1, corresponding to ln K values ranging from 0.04 to 1.05. Simulations involved numerical models with 3-D decimeter discretization, and each model contained 2–4 million active cells. Transport through each channel network considered only the processes of advection and molecular diffusion. In every case, the temporal change in the second spatial moment of concentrations was linear, with R2 values ranging from 0.97 to 0.99. The third spatial moment, or alternatively, the skewness coefficient values, indicated significant tailing downstream of the plume center. For each case, a corresponding ADM was used to simulate transport through the system. The corresponding ADM employed the effective mean hydraulic conductivity that reproduced the total discharge through the channel network system under an identical ambient gradient. Dispersivity values used in the ADM were obtained from the temporal change in the second spatial moments of concentrations for the plumes in the channel network systems and ranged from 0.014 m to 0.85 m. The results indicate that as the conductivity contrast between the channels and matrix increased, the simulated plumes in the channel network system became more and more asymmetric, with little solute dispersed upstream of the plume center and extensive downstream spreading of low concentrations. Distinctly different spreading was found upstream versus downstream of the plume center. The ADM failed to capture this asymmetry. Comparison of each plume in the channel network system with the corresponding plume produced using the corresponding ADM showed a maximum correlation of only 0.64 and a minimum fractional error of 0.29 for cases in which the log K variance was ∼0.20 (ln K variance was ∼1.0). At early times the correlations were as low as 0.40. The greatest correlation occurred at late times and for cases in which a wide source was considered. | |||||
BibTeX:
@article{Liu2004,
author = {Liu, Gaisheng and Zheng, Chunmiao and Gorelick, Steven M.},
title = {Limits of applicability of the advection-dispersion model in aquifers containing connected high-conductivity channels},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2004},
volume = {40},
number = {8},
pages = {W08308--},
url = {http://dx.doi.org/10.1029/2003WR002735}
}
|
|||||
| Liu, H. and Dane, J. | An interpolation-corrected modified method of characteristics to solve advection-dispersion equations | 1996 | Advances in Water Resources Vol. 19(6), pp. 359-368 |
article | URL |
| Abstract: Numerical dispersion, numerical oscillation, and peak clipping are common numerical difficulties in solving advection-dispersion equations. The development of numerical approaches that can handle these numerical difficulties with reasonable computational efforts is an ongoing challenge. In this paper, an interpolation-corrected modified method of characteristics (ICMMOC) is proposed for solving advection-dispersion equations. The ICMMOC is an improved version of the modified method of characteristics (MMOC). It uses a high-order (second-order or higher) interpolation scheme to reduce numerical dispersion and an interpolation-correction procedure to eliminate numerical oscillation. A simple peak capturing scheme to overcome the peak clipping problem is also developed in this study. Simulation results show that the ICMMOC is able to overcome the aforementioned numerical difficulties for a large range of grid Peclet numbers. | |||||
BibTeX:
@article{Liu1996,
author = {Liu, H.H. and Dane, J.H.},
title = {An interpolation-corrected modified method of characteristics to solve advection-dispersion equations},
journal = {Advances in Water Resources},
year = {1996},
volume = {19},
number = {6},
pages = {359--368},
url = {http://www.sciencedirect.com/science/article/pii/0309170896000140}
}
|
|||||
| Liu, J., Bodvarsson, G. and Wu, Y.-S. | Analysis of flow behavior in fractured lithophysal reservoirs | 2003 | Journal of Contaminant Hydrology Vol. 62–63(0)JCH SI. Yucca Mountain, pp. 189-211 |
article | URL |
| Abstract: This study develops a mathematical model for the analysis of pressure behavior in fractured lithophysal reservoirs. The lithophysal rock is described as a tri-continuum medium, consisting of fractures, rock matrices, and cavities. In the conceptual model, fractures have homogeneous properties throughout and interact with rock matrices and cavities that have different permeabilities and porosities. Global flow occurs through the fracture network only, while rock matrices and cavities contain the majority of fluid storage and provide fluid drainage to the fractures. Interporosity flows between the triple media are described using a pseudosteady-state concept and the system is characterized by interporosity transmissivity ratios and storativity ratio of each continuum. Pressure behavior is analyzed by examining the pressure drawdown curves, the derivative plots, and the effects of the characteristic parameters. Typical pressure responses from fractures, matrices, and cavities are represented by three semilog straight lines; the transitions by two troughs below the stabilization lines in the derivative plots. The analytical solution to the proposed model is further verified using a numerical simulation. The analytical model has also been applied to a published field-buildup well test and is able to match the pressure buildup data. | |||||
BibTeX:
@article{Liu2003,
author = {Liu, Jianchun and Bodvarsson, G.S. and Wu, Yu-Shu},
title = {Analysis of flow behavior in fractured lithophysal reservoirs},
booktitle = {JCH SI. Yucca Mountain},
journal = {Journal of Contaminant Hydrology},
year = {2003},
volume = {62–63},
number = {0},
pages = {189--211},
url = {http://www.sciencedirect.com/science/article/pii/S0169772202001699}
}
|
|||||
| Liu, L. and Chen, X. | Hydrodynamic and hydrochemical study of water in a karst aquifer-A case study in Houzhai karstic water system, Guizhou Province, China | 2011 | Vol. 1Water Resource and Environmental Protection (ISWREP), 2011 International Symposium on DOI - 10.1109/ISWREP.2011.5892936, pp. 24-27 |
inproceedings | |
| Abstract: In order to compare the characteristics and the functioning of the springs and water circulation in Houzhai karstic water system, twenty physical and chemical parameters in ten representative stations are considered all together to identify the main factors responsible for the diversity of hydrological and hydrochemical responses of the considered karst systems. Based on principal component analysis, the twenty variables were analyzed in ten representative stations from 1995 to 1996. The results show that the first two principal components carry the 89.3% information of the whole. The main controlling factor on the variation of hydrochemistry type in this karstic water system is the lithology the water flowing through. The secondary factor is hydrodynamic condition, especially the runoff depth of groundwater. The information of hydrogeochemistry has an important indicative significance on the analysis of the hydrodynamic characteristics. However, the principal component analysis coupling the hydrodynamic and hydrochemistry information provides a way to understand the hydrodynamic and hydrochemistry characteristics of karstic water system. | |||||
BibTeX:
@inproceedings{Liu2011,
author = {Liu, Lihong and Chen, Xunhong},
title = {Hydrodynamic and hydrochemical study of water in a karst aquifer-A case study in Houzhai karstic water system, Guizhou Province, China},
booktitle = {Water Resource and Environmental Protection (ISWREP), 2011 International Symposium on DOI - 10.1109/ISWREP.2011.5892936},
year = {2011},
volume = {1},
pages = {24--27}
}
|
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| Liu, R.-L., Li, N., Feng, Q.-f., Hai, C. and Wang, K.-w. | Application of the triple porosity model in well–log effectiveness estimation of the carbonate reservoir in Tarim oilfield | 2009 | Journal of Petroleum Science and Engineering Vol. 68(1-2), pp. 40-46 |
article | URL |
| Abstract: In carbonate reservoirs, effectiveness estimation using logging data has great challenges. According to the pore structure characteristics of the fractured and vuggy carbonate reservoir, Aguilera and Aguilera [Roberto F. Aguilera and Roberto Aguilera, 2004. A Triple Porosity Model for Petrophysical Analysis of Naturally Fractured Reservoir, Petrophysics, 45(2):157–166.] presented a triple porosity model, in which the secondary porosity was divided into connected fractured (and/or) vuggy porosity and non-connected vuggy porosity. In this paper, a new technology is presented to determine the values of the different porosity in the triple porosity model. Based on lateral logs responses, we derive analytical equations that contain connected fractured (and/or vuggy) porosity, non-connected vuggy porosity, matrix porosity and so on. Using these equations and the conventional log data, we can obtain the petrophysical parameters, such as connected fractured porosity, non-connected vuggy porosity and so on. Then the connected fractured (and/or vuggy) porosity and its percentage in the total porosity are used to indicate the effectiveness of the carbonate reservoir. This method has been applied for the well log interpretation of the 123 testing intervals from the 52 wells in Tarim oil field. Agreement ratio of the interpretation results is 91%, which verifies the validity of the presented method. | |||||
BibTeX:
@article{Liu2009,
author = {Liu, Rui-Lin and Li, Ning and Feng, Qing-fu and Hai, Chuan and Wang, Ke-wen},
title = {Application of the triple porosity model in well–log effectiveness estimation of the carbonate reservoir in Tarim oilfield},
journal = {Journal of Petroleum Science and Engineering},
year = {2009},
volume = {68},
number = {1-2},
pages = {40--46},
url = {http://www.sciencedirect.com/science/article/pii/S0920410509001259}
}
|
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| Liu, S.-h., Zhao, S.-l. and Luo, Q.-s. | Simulation of low-concentration sediment-laden flow based on two-phase flow theory | 2007 | Journal of Hydrodynamics, Ser. B Vol. 19(5), pp. 653-660 |
article | URL |
| Abstract: Low concentration sediment-laden flow is usually involved in water conservancy, environmental protection, navigation and so on. In this article, a mathematical model for low-concentration sediment-laden flow was suggested based on the two-phase flow theory, and a solving scheme for the mathematical model in curvilinear grids was worked out. The observed data in the Zhang River in China was used for the verification of the model, and the calculated results of the water level, velocity and river bed deformation are in agreement with the observed ones. | |||||
BibTeX:
@article{Liu2007a,
author = {Liu, Shi-he and Zhao, Shi-lai and Luo, Qiu-shi},
title = {Simulation of low-concentration sediment-laden flow based on two-phase flow theory},
journal = {Journal of Hydrodynamics, Ser. B},
year = {2007},
volume = {19},
number = {5},
pages = {653--660},
url = {http://www.sciencedirect.com/science/article/pii/S1001605807601668}
}
|
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| Liu, Z., Groves, C., Yuan, D., Meiman, J., Jiang, G., He, S. and Li, Q. | Hydrochemical variations during flood pulses in the south-west China peak cluster karst: impacts of CaCO3–H2O–CO2 interactions | 2004 | Hydrological Processes Vol. 18(13), pp. 2423-2437 |
article | URL |
| Abstract: High-resolution measurements of rainfall, water level, pH, conductivity, temperature and carbonate chemistry parameters of groundwater at two adjacent locations within the peak cluster karst of the Guilin Karst Experimental Site in Guangxi Province, China, were made with different types of multiparameter sonde. The data were stored using data loggers recording with 2 min or 15 min resolution. Waters from a large, perennial spring represent the exit for the aquifer's conduit flow, and a nearby well measures water in the conduit-adjacent, fractured media. During flood pulses, the pH of the conduit flow water rises as the conductivity falls. In contrast, and at the same time, the pH of groundwater in the fractures drops, as conductivity rises. As Ca2+ and HCO3− were the dominant (>90%) ions, we developed linear relationships (both r2 > 0·91) between conductivity and those ions, respectively, and in turn calculated variations in the calcite saturation index (SIC) and CO2 partial pressure (P CO 2) of water during flood pulses. Results indicate that the P CO 2 of fracture water during flood periods is higher than that at lower flows, and its SIC is lower. Simultaneously, P CO 2 of conduit water during the flood period is lower than that at lower flows, and its SIC also is lower. From these results we conclude that at least two key processes are controlling hydrochemical variations during flood periods: (i) dilution by precipitation and (ii) water–rock–gas interactions. To explain hydrochemical variations in the fracture water, the water–rock–gas interactions may be more important. For example, during flood periods, soil gas with high CO2 concentrations dissolves in water and enters the fracture system, the water, which in turn has become more highly undersaturated, dissolves more limestone, and the conductivity increases. Dilution of rainfall is more important in controlling hydrochemical variations of conduit water, because rainfall with higher pH (in this area apparently owing to interaction with limestone dust in the lower atmosphere) and low conductivity travels through the conduit system rapidly. These results illustrate that to understand the hydrochemical variations in karst systems, considering only water–rock interactions is not sufficient, and the variable effects of CO2 on the system should be evaluated. Consideration of water–rock–gas interactions is thus a must in understanding variations in karst hydrochemistry. Copyright © 2004 John Wiley & Sons, Ltd. | |||||
BibTeX:
@article{Liu2004a,
author = {Liu, Zaihua and Groves, Chris and Yuan, Daoxian and Meiman, Joe and Jiang, Guanghui and He, Shiyi and Li, Qiang},
title = {Hydrochemical variations during flood pulses in the south-west China peak cluster karst: impacts of CaCO3–H2O–CO2 interactions},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2004},
volume = {18},
number = {13},
pages = {2423--2437},
url = {http://dx.doi.org/10.1002/hyp.1472}
}
|
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| Liu, Z., Li, Q., Sun, H. and Wang, J. | Seasonal, diurnal and storm-scale hydrochemical variations of typical epikarst springs in subtropical karst areas of SW China: Soil CO2 and dilution effects | 2007 | Journal of Hydrology Vol. 337(1-2), pp. 207-223 |
article | URL |
| Abstract: Summary Two-year continuous pH, conductivity, temperature and water stage of the two typical epikarst springs, Nongla spring and Maolan spring (about 200 km apart) in subtropical karst areas of SW China were presented. Our primary study objective was to understand how karst systems respond hydrochemically to recharge at different time scales, and what the biogeochemical processes and controlling factors in the SW China epikarst environment are. A thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of CO2 partial pressures and calcite/dolomite saturation levels on a continuous basis. Marked seasonal, diurnal and storm-scale variations were observed for pH, conductivity, CO2 partial pressures and calcite/dolomite saturation indexes of the springs, indicating that both springs are dynamic and variable systems. However, the coefficients of variation of these hydrogeochemical features tends to be in the order of seasonal ⩾ storm-scale > diurnal. The seasonal and diurnal variations of these features (higher conductivity and lower pH in summer and at daytime; lower conductivity and higher pH in winter and at nighttime) tend to co-vary with temperature which influences the production of CO2 in soils, thus being the driving force for the variations (soil CO2 effect). The storm-scale fluctuations occur during the spring-summer rainy days due to the storm-events. Depending on the rainfall intensities, however, there are differences in magnitudes and direction of the variations of these features. At very high rainfall intensity, the dilution effect dominates the variations, characterized by the decrease in both conductivity and calcite/dolomite saturation of the springs, while soil CO2 effect determines the variations at lower rainfall intensity, characterized by increase in CO2 partial pressure and conductivity but decrease in pH and calcite/dolomite saturation. In a word, the hydrodynamic aspects together with hydrobiogeochemical characteristics need to be taken into account to correctly explain the hydrochemical variations of the epikarst springs. Results from the study demonstrate the need to redesign hydrogeochemical sampling strategies for epikarst springs in karst areas with monsoon climate like SW China (i.e., with remarkable seasonal matching fluctuations in temperature, rainfall and vegetation). | |||||
BibTeX:
@article{Liu2007,
author = {Liu, Zaihua and Li, Qiang and Sun, Hailong and Wang, Jinliang},
title = {Seasonal, diurnal and storm-scale hydrochemical variations of typical epikarst springs in subtropical karst areas of SW China: Soil CO2 and dilution effects},
journal = {Journal of Hydrology},
year = {2007},
volume = {337},
number = {1-2},
pages = {207--223},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407000649}
}
|
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| Loáiciga, H.A. | Special Section: Applications of Hydrologic Tracers [BibTeX] |
2008 | Journal of Hydrologic Engineering Vol. 13(11), pp. 999-1001 |
article | URL |
BibTeX:
@article{Loáiciga2008,
author = {Loáiciga, Hugo A.},
title = {Special Section: Applications of Hydrologic Tracers},
journal = {Journal of Hydrologic Engineering},
publisher = {ASCE},
year = {2008},
volume = {13},
number = {11},
pages = {999--1001},
url = {http://dx.doi.org/10.1061/(ASCE)1084-0699(2008)13:11(999)}
}
|
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| Loáiciga, H.A. | Residence time, groundwater age, and solute output in steady-state groundwater systems | 2004 | Advances in Water Resources Vol. 27(7), pp. 681-688 |
article | URL |
| Abstract: The total travel distance and the hydraulic conductivity in steady-state groundwater flow systems are modeled with asymmetric gamma distribution functions. The ratio of the total travel distance over the hydraulic conductivity, scaled by a factor involving the hydraulic gradient and the aquifer porosity, equals the residence time of groundwater. The residence time measures the period elapsed between recharge and discharge of groundwater from an aquifer flow system. The residence time is a random variable whose probability density function (p.d.f.) is determined by those of the total travel distance and the hydraulic conductivity. The p.d.f. of the residence time was derived and from that, applying basic mass-balance considerations, followed that of the groundwater age. The age is the time elapsed since the recharge of groundwater in transit through an aquifer flow system. It is shown that the p.d.f.s of the residence time and the groundwater age are related by a first-order, linear, differential equation. The cumulative distribution functions of the residence time and the groundwater age and their first and second moments are also derived, and so is the output concentration of a solute that enters a steady-state groundwater flow system dissolved in recharge. A computational example illustrates the advantage of treating the residence time and the groundwater age statistically and constraining them with Darcy's law and mass-balance principles. Solute output shows a complex structure with stable and radioactive solutes in deceptively simple steady-state groundwater flow regimes. | |||||
BibTeX:
@article{Loáiciga2004,
author = {Loáiciga, Hugo A},
title = {Residence time, groundwater age, and solute output in steady-state groundwater systems},
journal = {Advances in Water Resources},
year = {2004},
volume = {27},
number = {7},
pages = {681--688},
url = {http://www.sciencedirect.com/science/article/pii/S030917080400082X}
}
|
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| Loáiciga, H.A. and Leipnik, R.B. | Correlated gamma variables in the analysis of microbial densities in water | 2005 | Advances in Water Resources Vol. 28(4), pp. 329-335 |
article | URL |
| Abstract: The probability density function (p.d.f.) of the ratio of two correlated gamma variables is derived and used to fit aquatic microbial-density data. The ratio p.d.f. is tackled by first taking the Fourier transform of a generalized Kibble–Gaver, unsymmetrical, characteristic function (c.f.) to obtain the corresponding bivariate p.d.f. of two correlated gamma variables with different shape and scale parameters. The ratio p.d.f. follows by weighted integration of the bivariate p.d.f. The derivation of the gamma bivariate and ratio p.d.f.s relies on the use of weighted Laguerre–Charlier polynomials that lead to p.d.f.s amenable to computation. The bivariate gamma p.d.f. and the ratio p.d.f. of correlated gamma variables are useful statistical tools in the analysis of skewed water-resources data. Computational examples illustrate the calculation of bivariate p.d.f.s for positive and negative correlation and the fitting of the ratio p.d.f. to correlated bacterial densities in stream water. | |||||
BibTeX:
@article{Loáiciga2005,
author = {Loáiciga, Hugo A. and Leipnik, Roy B.},
title = {Correlated gamma variables in the analysis of microbial densities in water},
journal = {Advances in Water Resources},
year = {2005},
volume = {28},
number = {4},
pages = {329--335},
url = {http://www.sciencedirect.com/science/article/pii/S0309170804002131}
}
|
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| Loáiciga, H.A. and Leipnik, R.B. | Analysis of extreme hydrologic events with Gumbel distributions: marginal and additive cases | 1999 | Stochastic Environmental Research and Risk Assessment Vol. 13(4), pp. 251-259 |
article | URL |
| Abstract: The importance of the Gumbel probability distribution for the description of extreme hydrologic events is examined in this article. The key findings of this work are: (1) an iterative method of least squares was developed and found to be well-suited for the efficient fitting of the two-parameter Gumbel distribution to hydrologic extremes; (2) negative truncation is necessary to adequately describe hydrologic minima (non-negative) data, while the standard Gumbel distribution for maxima is well-suited for modeling extreme (large) hydrologic events; (3) the distribution function of the sum of two independent Gumbel variables, of importance in hydrology, has been derived and successfully applied to spring flow data. Several examples that involve the modeling of hydrologic extremes are presented and analyzed. | |||||
BibTeX:
@article{Loáiciga1999,
author = {Loáiciga, H. A. and Leipnik, R. B.},
title = {Analysis of extreme hydrologic events with Gumbel distributions: marginal and additive cases},
journal = {Stochastic Environmental Research and Risk Assessment},
publisher = {Springer Berlin / Heidelberg},
year = {1999},
volume = {13},
number = {4},
pages = {251--259},
url = {http://dx.doi.org/10.1007/s004770050042}
}
|
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| Loffill, E., Alkhaddar, R., Phipps, D.A., Faram, M.G. and Papaefthimiou, G. | Residence Time Distribution and the Investigation of Bed Movement in a Continuously Operated Upflow Filter (COUF) for Tertiary Wastewater Treatment | 2010 | Vol. 371(41114)ASCE Conference Proceedings of the World Environmental and Water Resources Congress 2010: Challenges of Change, pp. 382-382 |
inproceedings | URL |
| Abstract: This paper describes an investigation to define the liquid phase flow regime in a continuously operated upflow filter (COUF) together with an assessment of the relative motion of the solid (filter media) phase. The importance of such measurements in the development of a model for these systems, including aerated biological filtration versions is discussed. Initial work was carried out on a model‐scale demonstrator unit using Rhodamine WT fluorescent dye tracing for liquid phase studies. Initial outputs show that the liquid phase residence time distribution (RTD) is well approximated by a plug flow assumption. The pattern in which individual particles of the bed move during the operation of the COUF was also investigated on the demonstrator using colored beads as a tracer. The gross movement of the bed and the internal mixing regime described can be regarded as analogous to RTD. Techniques were developed whereby bed movement in the cleaning process could be measured and assessed over time, leading to the generation of 3D bed movement visualisation plots. This work could potentially lead to developments of technologies that could better clean the media and lead to a more even bed movement allowing the filter to operate more efficiently. | |||||
BibTeX:
@inproceedings{Loffill2010,
author = {Loffill, E. and Alkhaddar, R.M. and Phipps, D. A. and Faram, M. G. and Papaefthimiou, G.},
title = {Residence Time Distribution and the Investigation of Bed Movement in a Continuously Operated Upflow Filter (COUF) for Tertiary Wastewater Treatment},
booktitle = {ASCE Conference Proceedings of the World Environmental and Water Resources Congress 2010: Challenges of Change},
publisher = {ASCE},
year = {2010},
volume = {371},
number = {41114},
pages = {382--382},
url = {http://dx.doi.org/10.1061/41114(371)382}
}
|
|||||
| Lolcama, J.L., Cohen, H.A. and Tonkin, M.J. | Deep karst conduits, flooding, and sinkholes: lessons for the aggregates industry | 2002 | Engineering Geology Vol. 65(2-3)Engineering and Environmental Impacts of Karst, pp. 151-157 |
article | URL |
| Abstract: Limestone aggregate quarries in deeply penetrating karst terrain are often at considerable risk of artesian inflow from groundwater or surface water channeled through the karstic aquifer. The inflow occurs through what are likely to be complex conduits that penetrate hundreds of feet into bedrock. Rates of inflow can exceed the operation's pumping capabilities proving to be uneconomic to manage over the long term. Over time, inflow rates can increase dramatically as turbulent flow through the conduit erodes its soft residual clay-rich fill. One recent investigation observed an inflow rate of more than 40,000 gpm from a surface water source. Floodwater persistently laden with sediment is an indicator of conduit washout and implies increasing inflow rates over time. | |||||
BibTeX:
@article{Lolcama2002,
author = {Lolcama, James L and Cohen, Harvey A and Tonkin, Matthew J},
title = {Deep karst conduits, flooding, and sinkholes: lessons for the aggregates industry},
booktitle = {Engineering and Environmental Impacts of Karst},
journal = {Engineering Geology},
year = {2002},
volume = {65},
number = {2-3},
pages = {151--157},
url = {http://www.sciencedirect.com/science/article/pii/S0013795201001223}
}
|
|||||
| Long, A., Sawyer, J. and Putnam, L. | Environmental tracers as indicators of karst conduits in groundwater in South Dakota, USA | 2008 | Hydrogeology Journal Vol. 16(2), pp. 263-280 |
article | URL |
| Abstract: Environmental tracers sampled from the carbonate Madison aquifer on the eastern flank of the Black Hills, South Dakota, USA indicated the approximate locations of four major karst conduits. Contamination issues are a major concern because these conduits are characterized by direct connections to sinking streams, high groundwater velocities, and proximity to public water supplies. Objectives of the study were to estimate approximate conduit locations and assess possible anthropogenic influences associated with conduits. Anomalies of young groundwater based on chlorofluorocarbons (CFCs), tritium, and electrical conductivity (EC) indicated fast moving, focused flow and thus the likely presence of conduits. δ 18 O was useful for determining sources of recharge for each conduit, and nitrate was a useful tracer for assessing flow paths for anthropogenic influences. Two of the four conduits terminate at or near a large spring complex. CFC apparent ages ranged from 15 years near conduits to >50 years in other areas. Nitrate-N concentrations >0.4 mg/L in groundwater were associated with each of the four conduits compared with concentrations ranging from <0.1 to 0.4 mg/L in other areas. These higher nitrate-N concentrations probably do not result from sinking streams but rather from other areas of infiltration. | |||||
BibTeX:
@article{Long2008,
author = {Long, Andrew and Sawyer, J. and Putnam, Larry},
title = {Environmental tracers as indicators of karst conduits in groundwater in South Dakota, USA},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2008},
volume = {16},
number = {2},
pages = {263--280},
url = {http://dx.doi.org/10.1007/s10040-007-0232-7}
}
|
|||||
| Long, A.J. | Hydrograph separation for karst watersheds using a two-domain rainfall–discharge model | 2009 | Journal of Hydrology Vol. 364(3-4), pp. 249-256 |
article | URL |
| Abstract: Highly parameterized, physically based models may be no more effective at simulating the relations between rainfall and outflow from karst watersheds than are simpler models. Here an antecedent rainfall and convolution model was used to separate a karst watershed hydrograph into two outflow components: one originating from focused recharge in conduits and one originating from slow flow in a porous annex system. In convolution, parameters of a complex system are lumped together in the impulse-response function (IRF), which describes the response of the system to an impulse of effective precipitation. Two parametric functions in superposition approximate the two-domain IRF. The outflow hydrograph can be separated into flow components by forward modeling with isolated IRF components, which provides an objective criterion for separation. As an example, the model was applied to a karst watershed in the Madison aquifer, South Dakota, USA. Simulation results indicate that this watershed is characterized by a flashy response to storms, with a peak response time of 1 day, but that 89% of the flow results from the slow-flow domain, with a peak response time of more than 1 year. This long response time may be the result of perched areas that store water above the main water table. Simulation results indicated that some aspects of the system are stationary but that nonlinearities also exist. | |||||
BibTeX:
@article{Long2009a,
author = {Long, Andrew J.},
title = {Hydrograph separation for karst watersheds using a two-domain rainfall–discharge model},
journal = {Journal of Hydrology},
year = {2009},
volume = {364},
number = {3-4},
pages = {249--256},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408005398}
}
|
|||||
| Long, A.J. and Derickson, R.G. | Linear systems analysis in a karst aquifer | 1999 | Journal of Hydrology Vol. 219(3–4), pp. 206-217 |
article | URL |
| Abstract: A linear systems analysis applied to groundwater flow is presented as an alternative modeling technique to traditional discretized groundwater models (i.e. finite-difference and finite-element), which require elaborate parameters and boundary conditions. Linear systems analysis has been used extensively for surface-water modeling and to a lesser extent for groundwater applications. We present a method for the analysis of an aquifer's response in hydraulic head to recharge that comprises two major components. The first component is to predict the drop in hydraulic head over time if recharge is eliminated. By fitting logarithmic curves to selected short-term hydraulic head recession periods, a long-term recession or “base head” can be established. The estimation of base head is necessary for the second component of the method, which is the derivation of an impulse response function or transfer function. The transfer function was derived by deconvolution of two time series data sets—estimated recharge and the measured response in hydraulic head. An aquifer's response to recharge can be characterized and modeled by using the transfer function, which also establishes the time to peak response, the response time distribution, and the total memory length of the system. The method requires fitting smooth curves to the oscillatory transfer function derived by deconvolution in the Fourier transform domain. The smooth curve is considered to be the physically valid transfer function. In this analysis, curve fitting was more effective than other smoothing techniques commonly used. We applied the method to the karstic Madison aquifer and found that the time to peak response is less than one month, the system's total memory is about six years, and a logarithmic curve best fits the system response. This method has potential to be useful as a predictive tool in aquifer management. | |||||
BibTeX:
@article{Long1999,
author = {Long, A. J. and Derickson, R. G.},
title = {Linear systems analysis in a karst aquifer},
journal = {Journal of Hydrology},
year = {1999},
volume = {219},
number = {3–4},
pages = {206--217},
url = {http://www.sciencedirect.com/science/article/pii/S002216949900058X}
}
|
|||||
| Long, A.J. and Gilcrease, P.C. | A one-dimensional heat-transport model for conduit flow in karst aquifers | 2009 | Journal of Hydrology Vol. 378(3-4), pp. 230-239 |
article | URL |
| Abstract: A one-dimensional heat-transport model for conduit flow in karst aquifers is presented as an alternative to two or three-dimensional distributed-parameter models, which are data intensive and require knowledge of conduit locations. This model can be applied for cases where water temperature in a well or spring receives all or part of its water from a phreatic conduit. Heat transport in the conduit is simulated by using a physically-based heat-transport equation that accounts for inflow of diffuse flow from smaller openings and fissures in the surrounding aquifer during periods of low recharge. Additional diffuse flow that is within the zone of influence of the well or spring but has not interacted with the conduit is accounted for with a binary mixing equation to proportion these different water sources. The estimation of this proportion through inverse modeling is useful for the assessment of contaminant vulnerability and well-head or spring protection. The model was applied to 7 months of continuous temperature data for a sinking stream that recharges a conduit and a pumped well open to the Madison aquifer in western South Dakota. The simulated conduit-flow fraction to the well ranged from 2% to 31% of total flow, and simulated conduit velocity ranged from 44 to 353 m/d. | |||||
BibTeX:
@article{Long2009b,
author = {Long, Andrew J. and Gilcrease, Patrick C.},
title = {A one-dimensional heat-transport model for conduit flow in karst aquifers},
journal = {Journal of Hydrology},
year = {2009},
volume = {378},
number = {3-4},
pages = {230--239},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409005873}
}
|
|||||
| Long, A.J. and Putnam, L.D. | Age-distribution estimation for karst groundwater: Issues of parameterization and complexity in inverse modeling by convolution | 2009 | Journal of Hydrology Vol. 376(3-4), pp. 579-588 |
article | URL |
| Abstract: Convolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers. The framework of a quasi-transient convolution model that is applicable to two-domain flow in karst aquifers is presented. The model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon (CFC) and tritium (3H) data are available. We show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined. As an example, the model was applied to water from a pumped well open to the Madison aquifer in central USA with input functions of CFC-11, CFC-12, CFC-113, and 3H, and was calibrated to several samples collected during a 16-year period. A bimodal age distribution was modeled to represent quick and slow flow less than 50 years old. The effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow. Quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0–2 and 26–41 years, respectively. The fraction of long-term flow (>50 years) was estimated but was not dateable. The different tracers had different degrees of influence on parameter estimation and uncertainty assessments, where 3H was the most critical, and CFC-113 was least influential. | |||||
BibTeX:
@article{Long2009c,
author = {Long, Andrew J. and Putnam, Larry D.},
title = {Age-distribution estimation for karst groundwater: Issues of parameterization and complexity in inverse modeling by convolution},
journal = {Journal of Hydrology},
year = {2009},
volume = {376},
number = {3-4},
pages = {579--588},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409004740}
}
|
|||||
| Long, A.J. and Putnam, L.D. | Translating CFC-based piston ages into probability density functions of ground-water age in karst | 2006 | Journal of Hydrology Vol. 330(3-4), pp. 735-747 |
article | URL |
| Abstract: Temporal age distributions are equivalent to probability density functions (PDFs) of transit time. The type and shape of a PDF provides important information related to ground-water mixing at the well or spring and the complex nature of flow networks in karst aquifers. Chlorofluorocarbon (CFC) concentrations measured for samples from 12 locations in the karstic Madison aquifer were used to evaluate the suitability of various PDF types for this aquifer. Parameters of PDFs could not be estimated within acceptable confidence intervals for any of the individual sites. Therefore, metrics derived from CFC-based apparent ages were used to evaluate results of PDF modeling in a more general approach. The ranges of these metrics were established as criteria against which families of PDFs could be evaluated for their applicability to different parts of the aquifer. Seven PDF types, including five unimodal and two bimodal models, were evaluated. Model results indicate that unimodal models may be applicable to areas close to conduits that have younger piston (i.e., apparent) ages and that bimodal models probably are applicable to areas farther from conduits that have older piston ages. The two components of a bimodal PDF are interpreted as representing conduit and diffuse flow, and transit times of as much as two decades may separate these PDF components. Areas near conduits may be dominated by conduit flow, whereas areas farther from conduits having bimodal distributions probably have good hydraulic connection to both diffuse and conduit flow. | |||||
BibTeX:
@article{Long2006,
author = {Long, Andrew J. and Putnam, Larry D.},
title = {Translating CFC-based piston ages into probability density functions of ground-water age in karst},
journal = {Journal of Hydrology},
year = {2006},
volume = {330},
number = {3-4},
pages = {735--747},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406002691}
}
|
|||||
| Long, A.J. and Valder, J.F. | Multivariate analyses with end-member mixing to characterize groundwater flow: Wind Cave and associated aquifers | 2011 | Journal of Hydrology Vol. 409(1-2), pp. 315-327 |
article | URL |
| Abstract: Principal component analysis (PCA) applied to hydrochemical data has been used with end-member mixing to characterize groundwater flow to a limited extent, but aspects of this approach are unresolved. Previous similar approaches typically have assumed that the extreme-value samples identified by PCA represent end members. The method presented herein is different from previous work in that (1) end members were not assumed to have been sampled but rather were estimated and constrained by prior knowledge; (2) end-member mixing was quantified in relation to hydrogeologic domains, which focuses model results on major hydrologic processes; (3) a method to select an appropriate number of end members using a series of cluster analyses is presented; and (4) conservative tracers were weighted preferentially in model calibration, which distributed model errors of optimized values, or residuals, more appropriately than would otherwise be the case. The latter item also provides an estimate of the relative influence of geochemical evolution along flow paths in comparison to mixing. This method was applied to groundwater in Wind Cave and the associated karst aquifer in the Black Hills of South Dakota, USA. The end-member mixing model was used to test a hypothesis that five different end-member waters are mixed in the groundwater system comprising five hydrogeologic domains. The model estimated that Wind Cave received most of its groundwater inflow from local surface recharge with an additional 33% from an upgradient aquifer. Artesian springs in the vicinity of Wind Cave primarily received water from regional groundwater flow. | |||||
BibTeX:
@article{Long2011,
author = {Long, Andrew J. and Valder, Joshua F.},
title = {Multivariate analyses with end-member mixing to characterize groundwater flow: Wind Cave and associated aquifers},
journal = {Journal of Hydrology},
year = {2011},
volume = {409},
number = {1-2},
pages = {315--327},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411005749}
}
|
|||||
| Loper, D. | Steps Toward Better Models of Transport in Karstic Aquifers | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 56-57 | inproceedings | URL |
| Abstract: One of the most difficult challenges of geophysical sciences is the accurate modeling of contaminant transport in karstic aquifers. This task requires expertise, knowledge and resources which transcend any single agency, company or university; a cooperative approach to this problem is needed. The Hydrogeology Consortium is a new scientific organization seeking to catalyze the development and use of better models of flow and transport in karstic aquifers; see hydrogeologyconsortium.org. A new conceptual model of karstic aquifers has been developed and will provide the basis for the development of a new mathematical and computational model. | |||||
BibTeX:
@inproceedings{Loper2001,
author = {Loper, David},
title = {Steps Toward Better Models of Transport in Karstic Aquifers},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {56--57},
url = {http://water.usgs.gov/ogw/karst/kigconference/dl_stepstoward.htm}
}
|
|||||
| Lopes, R.J., Perdigoto, M. and Quinta-Ferreira, R.M. | Mathematical modelling of catalytic wet oxidation in trickle-bed reactors by a diffusion-convection-reaction approach embedded with an interstitial CFD framework | Applied Mathematical Modelling(0), pp. - | article | URL | |
| Abstract: In this work, we propose a diffusion-convection-reaction methodology to gain further insights into the heterogeneous multiphase flow of trickle beds. Our case-study encompasses a multi-fluid model embedded within an interstitial framework on the numerical simulation of continuous catalytic wet oxidation of hazardous compounds. First, with the proviso that phase holdup, pressure drop, and liquid distribution are fundamental criteria for the efficient design of trickle beds, the multiphase flow constitutive equations have been developed and solved by the conservative unstructured finite volume method. Second, several numerical variables were parametrically optimized based on the application of different under-relaxation parameters, mesh densities, and time stepping strategies. The segregated solver has been found to reveal good properties in terms of convergence and stability criteria, which endorsed the further corroboration. Finally, this theoretical probing-sensing scheme enabled the characterization of liquid flow texture accomplished by three-dimensional flow patterns exposing their deviation from ideal plug flow. The diffusion-convection-reaction framework coupled within a CFD model can then be further exploited on the simulation of complex multiphase reactive flows with adjustable parameters. | |||||
BibTeX:
@article{Lopes,
author = {Lopes, Rodrigo J.G. and Perdigoto, M.L.N. and Quinta-Ferreira, Rosa M.},
title = {Mathematical modelling of catalytic wet oxidation in trickle-bed reactors by a diffusion-convection-reaction approach embedded with an interstitial CFD framework},
journal = {Applied Mathematical Modelling},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0307904X11007682}
}
|
|||||
| Lopes, R.J. and Quinta-Ferreira, R.M. | Numerical assessment of diffusion–convection–reaction model for the catalytic abatement of phenolic wastewaters in packed-bed reactors under trickling flow conditions | 2011 | Computers & Chemical Engineering Vol. 35(12), pp. 2706-2715 |
article | URL |
| Abstract: Computational fluid dynamics (CFD) modeling of trickle-bed reactors with detailed interstitial flow solvers has remained elusive mostly due to the extreme CPU and memory intensive constraints. Here, we developed a comprehensible and scalable CFD model based on the conservative unstructured finite volume methodology to bring new insights from the perspective of catalytic reactor engineering to gas–liquid–solid catalytic wet oxidation. First, the heterogeneous flow constitutive equations of the trickle bed system have been derived by means of diffusion–convection–reaction model coupled within a Volume-of-Fluid framework. The multiphase model was investigated to gain further evidence on how the effect of process variables such as liquid velocity, surface tension and wetting phenomena affect the overall performance of high-pressure trickle-bed reactor. Second, as long as the application of under-relaxation parameters, mesh density, and time stepping strategy play a major role on the final corroboration, several computational runs on the detoxification of liquid pollutants were validated accordingly and evaluated in terms of convergence and stability criteria. Finally, the analysis of spatial mappings for the reaction properties enables us to identify the existence of relevant dry zones and unveil the channeling phenomena within in the trickle-bed reactor. | |||||
BibTeX:
@article{Lopes2011,
author = {Lopes, Rodrigo J.G. and Quinta-Ferreira, Rosa M.},
title = {Numerical assessment of diffusion–convection–reaction model for the catalytic abatement of phenolic wastewaters in packed-bed reactors under trickling flow conditions},
journal = {Computers & Chemical Engineering},
year = {2011},
volume = {35},
number = {12},
pages = {2706--2715},
url = {http://www.sciencedirect.com/science/article/pii/S0098135411000238}
}
|
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| Lord, D. and Miranda-Moreno, L.F. | Effects of low sample mean values and small sample size on the estimation of the fixed dispersion parameter of Poisson-gamma models for modeling motor vehicle crashes: A Bayesian perspective | 2008 | Safety Science Vol. 46(5), pp. 751-770 |
article | URL |
| Abstract: There has been considerable research conducted on the development of statistical models for predicting motor vehicle crashes on highway facilities. Over the last few years, there has been a significant increase in the application hierarchical Bayes methods for modeling motor vehicle crash data. Whether the inferences are estimated using classical or Bayesian methods, the most common probabilistic structure used for modeling this type of data remains the traditional Poisson-gamma (or Negative Binomial) model. Crash data collected for highway safety studies often have the unusual attributes of being characterized by low sample mean values and, due to the prohibitive costs of collecting data, small sample sizes. Previous studies have shown that the dispersion parameter of Poisson-gamma models can be seriously mis-estimated when the models are estimated using the maximum likelihood estimation (MLE) method for these extreme conditions. Despite important work done on this topic for the MLE, nobody has so far examined how low sample mean values and small sample sizes affect the posterior mean of the dispersion parameter of Poisson-gamma models estimated using the hierarchical Bayes method. The inverse dispersion parameter plays an important role in various types of highway safety studies. It is therefore vital to determine the conditions in which the inverse dispersion parameter may be mis-estimated for this category of models. | |||||
BibTeX:
@article{Lord2008,
author = {Lord, Dominique and Miranda-Moreno, Luis F.},
title = {Effects of low sample mean values and small sample size on the estimation of the fixed dispersion parameter of Poisson-gamma models for modeling motor vehicle crashes: A Bayesian perspective},
journal = {Safety Science},
year = {2008},
volume = {46},
number = {5},
pages = {751--770},
url = {http://www.sciencedirect.com/science/article/pii/S0925753507000355}
}
|
|||||
| Loregian, A., Mercuri, L. and Rroji, E. | Approximation of the variance gamma model with a finite mixture of normals | 2012 | Statistics & Probability Letters Vol. 82(2), pp. 217-224 |
article | URL |
| Abstract: We investigate the possibility of approximating the variance gamma distribution with a finite mixture of normals. Therefore, we apply this result to derive a simple historical estimation procedure by means of the Expectation Maximization algorithm. | |||||
BibTeX:
@article{Loregian2012,
author = {Loregian, Angela and Mercuri, Lorenzo and Rroji, Edit},
title = {Approximation of the variance gamma model with a finite mixture of normals},
journal = {Statistics & Probability Letters},
year = {2012},
volume = {82},
number = {2},
pages = {217--224},
url = {http://www.sciencedirect.com/science/article/pii/S0167715211003257}
}
|
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| Lorenzo Bermejo, J., Roehe, R., Rave, G. and Kalm, E. | Comparison of linear and nonlinear functions and covariance structures to estimate feed intake pattern in growing pigs | 2003 | Livestock Production Science Vol. 82(1), pp. 15-26 |
article | URL |
| Abstract: The objective of this study was to find the best function and covariance structure to estimate feed intake pattern in growing pigs for breeding purposes in order to optimise the feed intake curve corresponding to lean growth rate. Daily feed intake from 81 group-housed pigs was recorded using electronic feeders. The animals were tested during 120 days on average, from 30 to 119 kg. Polynomials, Kanis, yield–density, segmented and sigmoidal functions showed high similarity in goodness-of-fit. For selection on early feed intake, linear-segmented, logistic and Richards functions resulted in the most usable estimates within the test period. As shown by simulation, parameters of logistic function resulted in the lowest bias. Covariance among residuals of subsequent daily feed intakes was accounted for using the structures variance components, compound symmetry (CS), first-order autoregressive AR[1], first-order autoregressive moving-average ARMA[1,1], heterogeneous CS, heterogeneous AR[1] and the power-of-the-mean variance model. Correlation structure ARMA[1,1] resulted in the best fit of the data, with estimates for autoregressive parameter ρ from 0.90 to 0.97 and for moving average parameter λ from 0.35 to 0.51. The power-of-the-mean variance model was a good characterisation of variance heterogeneity and the final estimated power was 2.008 with standard error 0.3245. Based on these results, linear-segmented and logistic functions were the most parsimonious functions to characterise feed intake from which selection criteria can be derived, such as the age at which the feed intake plateau or the age at which the maximum increment in feed intake per day is reached in order to change feed intake curve corresponding to lean growth curve. | |||||
BibTeX:
@article{LorenzoBermejo2003,
author = {Lorenzo Bermejo, J. and Roehe, R. and Rave, G. and Kalm, E.},
title = {Comparison of linear and nonlinear functions and covariance structures to estimate feed intake pattern in growing pigs},
journal = {Livestock Production Science},
year = {2003},
volume = {82},
number = {1},
pages = {15--26},
url = {http://www.sciencedirect.com/science/article/pii/S0301622603000058}
}
|
|||||
| Louati, M. | Mixture of the Riesz distribution with respect to the generalized multivariate gamma distribution | Journal of the Korean Statistical Society(0), pp. - | article | URL | |
| Abstract: Wishart natural exponential families (NEFs) characterized by Letac (1989) are extended to the Riesz NEFs on symmetric matrices. These families are characterized by their variance functions defined in Hassairi and Lajmi (2001). This work uses a particular basis of these NEFs to describe the class of the generalized multivariate gamma distributions and then to study the statistical model obtained by the mixture of this distribution with the Riesz one on the space of symmetric matrices. | |||||
BibTeX:
@article{Louati,
author = {Louati, Mahdi},
title = {Mixture of the Riesz distribution with respect to the generalized multivariate gamma distribution},
journal = {Journal of the Korean Statistical Society},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S1226319212000609}
}
|
|||||
| Lu, J., Chai, Z., Shi, B., Guo, Z. and Hou, G. | Rectangular lattice Boltzmann model for nonlinear convection–diffusion equations | 2011 | Philosophical Transactions of the Royal Society A: Mathematical,Physical and Engineering Sciences Vol. 369(1944), pp. 2311-2319 |
article | URL |
| Abstract: In this paper, a rectangular lattice Boltzmann model is proposed for nonlinear convection–diffusion equations (NCDEs). The model can be used to solve NCDEs with very general form by using a real/complex-valued quadric equilibrium distribution function and relaxation time. Detailed simulations on several examples are performed to validate the model. The numerical results show good agreement with the analytical solutions, and the numerical accuracy is much better than that of the models with a linear equilibrium distribution function. | |||||
BibTeX:
@article{Lu2011,
author = {Lu, Jianhua and Chai, Zhenhua and Shi, Baochang and Guo, Zhaoli and Hou, Guoxiang},
title = {Rectangular lattice Boltzmann model for nonlinear convection–diffusion equations},
journal = {Philosophical Transactions of the Royal Society A: Mathematical,Physical and Engineering Sciences},
year = {2011},
volume = {369},
number = {1944},
pages = {2311--2319},
url = {http://rsta.royalsocietypublishing.org/content/369/1944/2311.abstract}
}
|
|||||
| Lu, M. and Connell, L.D. | A model for the flow of gas mixtures in adsorption dominated dual porosity reservoirs incorporating multi-component matrix diffusion: Part I. Theoretical development | 2007 | Journal of Petroleum Science and Engineering Vol. 59(1-2), pp. 17-26 |
article | URL |
| Abstract: A matrix-fracture transfer function for multi-species gas flow with adsorption behavior is presented. This transfer function is developed from the extended Fick's law and therefore the coupling effect of mutual-diffusivity is included in the representation. The transfer function is formulated based on an exact formal solution of a set of linear partial differential equations for matrix blocks with regular geometry, and is expressed in the form of a series expansion with history-dependent integrals. This series, at first order, reduces to a simple algebraic expression that is of an equivalent computational efficiency in comparison with the extended Warren–Root model in which the mutual-diffusion effect is not present. | |||||
BibTeX:
@article{Lu2007,
author = {Lu, Meng and Connell, Luke D.},
title = {A model for the flow of gas mixtures in adsorption dominated dual porosity reservoirs incorporating multi-component matrix diffusion: Part I. Theoretical development},
journal = {Journal of Petroleum Science and Engineering},
year = {2007},
volume = {59},
number = {1-2},
pages = {17--26},
url = {http://www.sciencedirect.com/science/article/pii/S0920410507000393}
}
|
|||||
| Lubczynski, M. | The hydrogeological role of trees in water-limited environments | 2009 | Hydrogeology Journal Vol. 17(1), pp. 247-259 |
article | URL |
| Abstract: Field experiments have already proven that many tree species in water-limited environments (WLE) depend on groundwater. Typically, such trees survive dry seasons and droughts by uptake of water, directly from the groundwater body or from the capillary fringe, by rooting systems that may extend to several tens of meters depth. Such trees are also very efficient in finding soil moisture in the unsaturated zone, reducing groundwater recharge. Considering that WLE are typically characterized by low recharge, and that trees may use a significant amount of groundwater, this groundwater “consumption” should not be neglected in groundwater balancing, modeling and resources management. In practice, groundwater uptake by trees in WLE is either underestimated or disregarded because of limited knowledge about that phenomenon. This review discusses the current understanding of the hydrogeological role of trees in water-limited environments, the partitioning of tree transpiration into groundwater and unsaturated zone contributions and the integration of that partitioning in numerical groundwater models. Problems involved in this research are highlighted and possible future research directions are discussed. | |||||
BibTeX:
@article{Lubczynski2009,
author = {Lubczynski, M.},
title = {The hydrogeological role of trees in water-limited environments},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {247--259},
url = {http://dx.doi.org/10.1007/s10040-008-0357-3}
}
|
|||||
| Lucy, J. | Political ecology as ethical practice | 2004 | Political Geography Vol. 23(7)Ethics in Political Ecology, pp. 917-927 |
article | URL |
| Abstract: Pedagogy is not an issue generally addressed in discussions of ethics in political ecology. These discussions commonly focus upon research agendas and methodology and do not consider teaching and learning political ecology as ethical and political practice. This paper argues that public scholarship can make political ecology's approach more concrete for students, because it focuses upon problems of inequality and resource access in their own communities and can foster ethically informed research projects useful to state and nongovernmental organizations while opening new research venues for students, teachers and community members. The paper's argument consists of three parts. In the first, I provide an overview of ethics in geography. Next I discuss the relevance of radical pedagogy to critical human geography and to political ecology and rework radical pedagogy's definition to include a consideration of public scholarship. Finally, I demonstrate how political ecology as an approach to public scholarship may spark and sustain student activism and value-driven forms of learning and teaching in an undergraduate classroom. | |||||
BibTeX:
@article{Lucy2004,
author = {Lucy, Jarosz},
title = {Political ecology as ethical practice},
booktitle = {Ethics in Political Ecology},
journal = {Political Geography},
year = {2004},
volume = {23},
number = {7},
pages = {917--927},
url = {http://www.sciencedirect.com/science/article/pii/S0962629804000708}
}
|
|||||
| Lugg, A. and Probert, D. | Indoor radon gas: A potential health hazard resulting from implementing energy-efficiency measures | 1997 | Applied Energy Vol. 56(2)Indoor Radon Gas, pp. 93-196 |
article | URL |
| Abstract: Most members of the general public tend to regard their homes and the buildings in which they work as relatively safe havens from the physical and chemical stresses of the ambient environment. However, during recent decades a hazardous phenomenon concerning the built environment has become apparent: it can have a detrimental effect on occupants' health and has implications for energy usage. Radon gas is the culprit! It has no taste, smell or colour and its presence is therefore neither immediately apparent or readily detectable. | |||||
BibTeX:
@article{Lugg1997,
author = {Lugg, Andrew and Probert, Douglas},
title = {Indoor radon gas: A potential health hazard resulting from implementing energy-efficiency measures},
booktitle = {Indoor Radon Gas},
journal = {Applied Energy},
year = {1997},
volume = {56},
number = {2},
pages = {93--196},
url = {http://www.sciencedirect.com/science/article/pii/S0306261997000020}
}
|
|||||
| Luhmann, A.J., Covington, M.D., Alexander, S.C., Chai, S.Y., Schwartz, B.F., Groten, J.T. and Alexander Jr., E.C. | Comparing conservative and nonconservative tracers in karst and using them to estimate flow path geometry | 2012 | Journal of Hydrology Vol. 448–449(0), pp. 201-211 |
article | URL |
| Abstract: A controlled recharge event was conducted with multiple tracers in a karst aquifer in southeastern Minnesota. A pool adjacent to a sinkhole was filled with approximately 13,000 L of water. After tracers were added and thoroughly mixed, the pool was emptied into the sinkhole. Data were collected at Freiheit Spring approximately 95 m north of the sinkhole to monitor spring responses. | |||||
BibTeX:
@article{Luhmann2012,
author = {Luhmann, Andrew J. and Covington, Matthew D. and Alexander, Scott C. and Chai, Su Yi and Schwartz, Benjamin F. and Groten, Joel T. and Alexander Jr., E. Calvin},
title = {Comparing conservative and nonconservative tracers in karst and using them to estimate flow path geometry},
journal = {Journal of Hydrology},
year = {2012},
volume = {448–449},
number = {0},
pages = {201--211},
url = {http://www.sciencedirect.com/science/article/pii/S0022169412003447}
}
|
|||||
| Luhmann, A.J., Covington, M.D., Peters, A.J., Alexander, S.C., Anger, C.T., Green, J.A., Runkel, A.C. and Alexander, E.C. | Classification of Thermal Patterns at Karst Springs and Cave Streams | 2011 | Ground Water Vol. 49(3), pp. 324-335 |
article | URL |
| Abstract: Thermal patterns of karst springs and cave streams provide potentially useful information concerning aquifer geometry and recharge. Temperature monitoring at 25 springs and cave streams in southeastern Minnesota has shown four distinct thermal patterns. These patterns can be divided into two types: those produced by flow paths with ineffective heat exchange, such as conduits, and those produced by flow paths with effective heat exchange, such as small fractures and pore space. Thermally ineffective patterns result when water flows through the aquifer before it can equilibrate to the rock temperature. Thermally ineffective patterns can be either event-scale, as produced by rainfall or snowmelt events, or seasonal scale, as produced by input from a perennial surface stream. Thermally effective patterns result when water equilibrates to rock temperature, and the patterns displayed depend on whether the aquifer temperature is changing over time. Shallow aquifers with seasonally varying temperatures display a phase-shifted seasonal signal, whereas deeper aquifers with constant temperatures display a stable temperature pattern. An individual aquifer may display more than one of these patterns. Since karst aquifers typically contain both thermally effective and ineffective routes, we argue that the thermal response is strongly influenced by recharge mode. | |||||
BibTeX:
@article{Luhmann2011,
author = {Luhmann, Andrew J. and Covington, Matthew D. and Peters, Andrew J. and Alexander, Scott C. and Anger, Cale T. and Green, Jeffrey A. and Runkel, Anthony C. and Alexander, E. Calvin},
title = {Classification of Thermal Patterns at Karst Springs and Cave Streams},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {2011},
volume = {49},
number = {3},
pages = {324--335},
url = {http://dx.doi.org/10.1111/j.1745-6584.2010.00737.x}
}
|
|||||
| Lundh, M. and Jonsson, L. | Residence Time Distribution Characterization of the Flow Structure in Dissolved Air Flotation | 2005 | Journal of Environmental Engineering Vol. 131(1), pp. 93-101 |
article | URL |
| Abstract: A numerical and analytical investigation is performed on a dissolved air flotation (DAF) pilot tank by using the residence time distribution (RTD) of the conservative dye rhodamine measured with a fluorometer. The experiments are numerically analyzed with regard to the total volume of the DAF tank separation zone in order to detect differences between observed separation zone flow structures in previous studies. The mean hydraulic detention time, the variance, and the estimated number of completely mixed tanks (Ncstr) in a series model are calculated. The variance is found to relate to the flow structure and the Ncstr is used for characterizing the occurrence of a stratified flow structure, which is beneficial for particle separation by DAF. The result shows a significant difference in RTD depending on expected flow structure. Analytically, a conceptual model is defined by dividing the DAF tank into an upper and a lower layer. In the upper layer, the water flow is horizontal and in the lower the water flow is vertical. The hypothesis is that mixing of the tracer takes place in the upper layer and that there is no significant mixing in the lower layer. Two simple mixing models are evaluated for the upper layer; the completely mixed tanks in series model, characterized by the number of tanks, and the dispersed plug flow model, characterized by the Peclet number. The models show good agreement with the experiments when the stratified flow structure is expected, but less agreement when the flow deviates from the stratified flow structure. The dispersed plug flow model shows the best fit with the experiments. The completely mixed tanks in series model is less sensitive, generating greater changes to the modeled RTD curve, which makes it more difficult to fit the model to the experiments. | |||||
BibTeX:
@article{Lundh2005,
author = {Lundh, Mans and Jonsson, Lennart},
title = {Residence Time Distribution Characterization of the Flow Structure in Dissolved Air Flotation},
journal = {Journal of Environmental Engineering},
publisher = {ASCE},
year = {2005},
volume = {131},
number = {1},
pages = {93--101},
url = {http://dx.doi.org/10.1061/(ASCE)0733-9372(2005)131:1(93)}
}
|
|||||
| Luo, H.-P. and Al-Dahhan, M.H. | Verification and validation of CFD simulations for local flow dynamics in a draft tube airlift bioreactor | 2011 | Chemical Engineering Science Vol. 66(5), pp. 907-923 |
article | URL |
| Abstract: Airlift reactors have been recognized as one of the promising photobioreactors for biomass/bio-energy production, where mixing has significant impact on the reactor performance. In recent years, using CFD simulations to track microorganism cells and to generate their trajectories in the reactor for reactor performance evaluations becomes more common. However, there is a lack of systematic and rigorous verifications and validations of the reliability of CFD models in particle tracking against experimental measurements in the open literature, which is vital for the faithful application of CFD in reactor design and scale-ups. In this work, we attempt to evaluate the reliability of using CFD simulations to generate trajectories of microorganisms in a draft tube column photobioreactor. A computationally promising CFD simulation model based on CFX5.7 was validated against a benchmark experimental database reported in Luo and Al-Dahhan (2008a, b, 2010). This model was then used to generate typical trajectories of microorganisms in the studied airlift column, which was further validated against experimentally measured tracer trajectories. The results indicated that the CFD model reasonably predicted the recirculation of the microorganism around the draft tube, however over-estimated the cells' residence time in the wall regions. Proper treatment for the wall region such as griding and wall function is needed to better capture the movement of microorganism cells in such bioreactors. | |||||
BibTeX:
@article{Luo2011,
author = {Luo, Hu-Ping and Al-Dahhan, Muthanna H.},
title = {Verification and validation of CFD simulations for local flow dynamics in a draft tube airlift bioreactor},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {5},
pages = {907--923},
url = {http://www.sciencedirect.com/science/article/pii/S0009250910007001}
}
|
|||||
| Luo, X.-s., Yu, S., Zhu, Y.-g. and Li, X.-d. | Trace metal contamination in urban soils of China | 2012 | Science of The Total Environment Vol. 421–422(0)Special Section: Reviews of Trace Metal Pollution in China, pp. 17-30 |
article | URL |
| Abstract: The contamination of urban soils can affect the health of people living in urban areas, and the surrounding ecosystems. Urbanization in China has taken place at an unprecedented pace in the last three decades. This paper provides an overview of studies on the quality of urban soils in China with special reference to trace metal contamination. It summarizes the characteristics of accumulation, spatial and temporal distribution, and major sources of various toxic or potentially toxic trace metals in urban soils as reported in recent literature. Levels of pollution in urban soil and road dust were discussed using the concentrations, enrichment factors, pollution indexes, and chemical fractionation of trace metals in major cities of China, and compared with other countries. In future studies, more pollutants in urban environments need to be included in multi-compartmental environmental surveillance for potential risk assessments. In addition to routine urban soil surveys by a harmonized methodology, a comprehensive assessment of soil quality is needed for the control and management of many urban brownfield sites. Taking into consideration pathways of exposure and site characteristics, risk assessment frameworks for major pollutants in urban soils, which integrate land use type and environmental availability, may be developed in the future. | |||||
BibTeX:
@article{Luo2012,
author = {Luo, Xiao-san and Yu, Shen and Zhu, Yong-guan and Li, Xiang-dong},
title = {Trace metal contamination in urban soils of China},
booktitle = {Special Section: Reviews of Trace Metal Pollution in China},
journal = {Science of The Total Environment},
year = {2012},
volume = {421–422},
number = {0},
pages = {17--30},
url = {http://www.sciencedirect.com/science/article/pii/S0048969711003779}
}
|
|||||
| Macian-Juan, R. and Mahaffy, J.H. | Numerical diffusion and the tracking of solute fields in system codes: Part I. One-dimensional flows | 1998 | Nuclear Engineering and Design Vol. 179(3), pp. 297-319 |
article | URL |
| Abstract: Advances in neutronics and thermohydraulic modeling have resulted in system codes capable of describing local interactions between the core neutronic behavior and the thermohydraulic conditions inside the vessel with full 3-dimensional real time coupling. Making use of these advances in the analysis of boron dilution transients requires a good description of the boron field inside the core, and of its transport along the primary system. However, the relatively low accuracy displayed by advanced system codes in the simulation of solute transport as a result of numerical diffusion is a major obstacle to performing accurate boron dilution studies. Implementation of high order numerical methods in system codes can considerably improve their accuracy when modeling solute transport by reducing the numerical diffusion to a level that is less than the physical diffusion expected from the turbulence of the flow; even when using relatively coarse noding schemes. In order to show this is feasible, the explicit QUICKEST-ULTIMATE scheme for 1-dimensional flow was adapted to the integration procedures used in system codes and implemented in TRAC-PF1/MOD2. Numerical tests were used to assess the performance of the method's implementation. A statistical methodology adapted from its original experimental formulation to the quantitative characterization of numerical diffusion in system codes was used for the analysis of the results. They showed that, for flow conditions commonly found in nuclear system simulations, high order tracking of a solute field can provide results whose diffusion is considerably less than that expected from the turbulence and characteristics of the flow field. | |||||
BibTeX:
@article{Macian-Juan1998,
author = {Macian-Juan, Rafael and Mahaffy, John H.},
title = {Numerical diffusion and the tracking of solute fields in system codes: Part I. One-dimensional flows},
journal = {Nuclear Engineering and Design},
year = {1998},
volume = {179},
number = {3},
pages = {297--319},
url = {http://www.sciencedirect.com/science/article/pii/S0029549397002902}
}
|
|||||
| Mackay, D., Ball, W. and Durant, M. | Variability of aquifer sorption properties in a field experiment on groundwater transport of organic solutes: Methods and preliminary results | 1986 | Journal of Contaminant Hydrology Vol. 1(1-2)Transport and Transformations of Organic Contaminants, pp. 119-132 |
article | URL |
| Abstract: Methods to characterize the organic solute sorption distribution coefficient, organic carbon content, and specific surface area of aquifer solids from the site of a field experiment on solute transport in groundwater were refined for application to small subsamples of 10-cm depth increments taken from 5-cm diameter cores. Initial results indicate that the average sorption characteristics of the Borden aquifer do not vary appreciably along the trajectory of the solute plumes. However, the sorption distribution coefficient of tetrachloroethylene varied over nearly an order of magnitude among 10-cm depth increments in one core sample. Preliminary evidence suggests that the sorption distribution coefficients for four halogenated organic solutes vary proportionally among core strata. However, the distribution coefficients for sorption of tetrachloroethylene on various depth increments are not well correlated with either organic carbon content or specific surface area, suggesting that as yet unidentified mineral phases may play a significant role in sorption of such solutes by the sandy aquifer solids. | |||||
BibTeX:
@article{Mackay1986,
author = {Mackay, D.M. and Ball, W.P. and Durant, M.G.},
title = {Variability of aquifer sorption properties in a field experiment on groundwater transport of organic solutes: Methods and preliminary results},
booktitle = {Transport and Transformations of Organic Contaminants},
journal = {Journal of Contaminant Hydrology},
year = {1986},
volume = {1},
number = {1-2},
pages = {119--132},
url = {http://www.sciencedirect.com/science/article/pii/0169772286900112}
}
|
|||||
| MacMullin, R.B. and Weber, M. | The theory of short-circuiting in continuous-flow mixing vessels in series and kinetics of chemical reactions in such systems [BibTeX] |
1935 | Transactions of American Institute of Chemical Engineers Vol. 31(2), pp. 409-458 |
article | |
BibTeX:
@article{MacMullin1935,
author = {MacMullin, R. B. and Weber, M.},
title = {The theory of short-circuiting in continuous-flow mixing vessels in series and kinetics of chemical reactions in such systems},
journal = {Transactions of American Institute of Chemical Engineers},
year = {1935},
volume = {31},
number = {2},
pages = {409--458}
}
|
|||||
| MacQuarrie, K.T. and Mayer, K.U. | Reactive transport modeling in fractured rock: A state-of-the-science review | 2005 | Earth-Science Reviews Vol. 72(3-4), pp. 189-227 |
article | URL |
| Abstract: The field of reactive transport modeling has expanded significantly in the past two decades and has assisted in resolving many issues in Earth Sciences. Numerical models allow for detailed examination of coupled transport and reactions, or more general investigation of controlling processes over geologic time scales. Reactive transport models serve to provide guidance in field data collection and, in particular, enable researchers to link modeling and hydrogeochemical studies. In this state-of-science review, the key objectives were to examine the applicability of reactive transport codes for exploring issues of redox stability to depths of several hundreds of meters in sparsely fractured crystalline rock, with a focus on the Canadian Shield setting. | |||||
BibTeX:
@article{MacQuarrie2005,
author = {MacQuarrie, Kerry T.B. and Mayer, K. Ulrich},
title = {Reactive transport modeling in fractured rock: A state-of-the-science review},
journal = {Earth-Science Reviews},
year = {2005},
volume = {72},
number = {3-4},
pages = {189--227},
url = {http://www.sciencedirect.com/science/article/pii/S0012825205001054}
}
|
|||||
| MacQuarrie, K.T. and Sudicky, E.A. | Multicomponent simulation of wastewater-derived nitrogen and carbon in shallow unconfined aquifers: I. Model formulation and performance | 2001 | Journal of Contaminant Hydrology Vol. 47(1), pp. 53-84 |
article | URL |
| Abstract: One of the most common methods to dispose of domestic wastewater involves the release of septic effluent from drains located in the unsaturated zone. Nitrogen from such systems is currently of concern because of nitrate contamination of drinking water supplies and eutrophication of coastal waters. The objectives of this study are to develop and assess the performance of a mechanistic flow and reactive transport model which couples the most relevant physical, geochemical and biochemical processes involved in wastewater plume evolution in sandy aquifers. The numerical model solves for variably saturated groundwater flow and reactive transport of multiple carbon- and nitrogen-containing species in a three-dimensional porous medium. The reactive transport equations are solved using the Strang splitting method which is shown to be accurate for Monod and first- and second-order kinetic reactions, and two to four times more efficient than sequential iterative splitting. The reaction system is formulated as a fully kinetic chemistry problem, which allows for the use of several special-purpose ordinary differential equation (ODE) solvers. For reaction systems containing both fast and slow kinetic reactions, such as the combined nitrogen–carbon system, it is found that amull specialized stiff explicit solver fails to obtain a solution. An implicit solver is more robust and its computational performance is improved by scaling of the fastest reaction rates. The model is used to simulate wastewater migration in a 1-m-long unsaturated column and the results show significant oxidation of dissolved organic carbon (DOC), the generation of nitrate by nitrification, and a slight decrease in pH. | |||||
BibTeX:
@article{MacQuarrie2001,
author = {MacQuarrie, Kerry T.B. and Sudicky, Edward A.},
title = {Multicomponent simulation of wastewater-derived nitrogen and carbon in shallow unconfined aquifers: I. Model formulation and performance},
journal = {Journal of Contaminant Hydrology},
year = {2001},
volume = {47},
number = {1},
pages = {53--84},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200001376}
}
|
|||||
| Madhuranthakam, C.M.R., Pan, Q. and Rempel, G.L. | Numerical investigation and experimental validation of the performance of a tubular packed bed reactor for hydrogenation of diene-based polymers | 2009 | Polym Eng Sci Vol. 49(10), pp. 1979-1989 |
article | URL |
| Abstract: A process which comprised a tubular reactor (that can be packed with different internal structures) has been modeled and theoretically analyzed for conducting the hydrogenation of nitrile butadiene rubber (NBR). The dynamics of the tubular reactor and the intrinsic hydrogenation kinetics are coupled, and detailed numerical simulations are performed under isothermal and isobaric conditions. The proposed model thus obtained involves coupled, nonlinear, partial differential equations (distributed parameter system). The effect of different reactor design parameters such as Peclet number, carbon–carbon double bond loading, mass transfer to reaction resistance, and solubility of hydrogen with respect to hydrogenation of the NBR has been investigated numerically. The conversions predicted using the proposed model for tubular packed bed reactor are compared with those possible in conventional plug flow reactor and continuous stirred tank reactor models. The optimal parameters and operating conditions for efficient production of hydrogenated NBR are suggested. Finally, the validity of the proposed model is confirmed by comparing the predicted and the experimental degree of hydrogenation obtained in a tubular reactor packed with Intalox saddles. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers | |||||
BibTeX:
@article{Madhuranthakam2009,
author = {Madhuranthakam, Chandra Mouli R. and Pan, Qinmin and Rempel, Garry L.},
title = {Numerical investigation and experimental validation of the performance of a tubular packed bed reactor for hydrogenation of diene-based polymers},
journal = {Polym Eng Sci},
publisher = {Wiley Subscription Services, Inc., A Wiley Company},
year = {2009},
volume = {49},
number = {10},
pages = {1979--1989},
url = {http://dx.doi.org/10.1002/pen.21433}
}
|
|||||
| Maejima, M. and Ueda, Y. | A note on a bivariate gamma distribution | 2010 | Statistics & Probability Letters Vol. 80(23-24), pp. 1991-1994 |
article | URL |
| Abstract: Vere-Jones (1967) introduced a bivariate generalization of gamma distributions and proved its infinite divisibility. Maejima and Ueda (2010) and others studied α-selfdecomposability, which is a generalization of selfdecomposability. In this paper, the (−2)-selfdecomposability of bivariate gamma distributions is shown. | |||||
BibTeX:
@article{Maejima2010,
author = {Maejima, Makoto and Ueda, Yohei},
title = {A note on a bivariate gamma distribution},
journal = {Statistics & Probability Letters},
year = {2010},
volume = {80},
number = {23-24},
pages = {1991--1994},
url = {http://www.sciencedirect.com/science/article/pii/S0167715210002543}
}
|
|||||
| Magal, E., Weisbrod, N., Yakirevich, A. and Yechieli, Y. | The use of fluorescent dyes as tracers in highly saline groundwater | 2008 | Journal of Hydrology Vol. 358(1-2), pp. 124-133 |
article | URL |
| Abstract: The capability of five fluorescent dyes to serve as conservative tracers in highly saline groundwater was evaluated by a series of batch experiments on pure minerals and natural sediments. Dye sorption was tested in four different salinities (from fresh rainwater to Dead Sea water) on five pure minerals and four natural sediments taken from boreholes drilled along the Dead Sea shore. It was found that the dyes Sulfo-Rhodamine B and Eosin are strongly adsorbed on pure minerals and sediments and therefore cannot be used as conservative tracers in saline groundwater. Uranine and Pyranine sorption is increased at higher salinities, therefore they can be used as tracers in moderately saline groundwater only. Na Naphthionate was found to be the best tracer for fresh and saline water, with minimal sorption in all cases. Sorption of the dyes on four natural sediments was measured and values were found to be in accord with those of previous sorption on pure minerals. Sorption on natural sediments was also estimated based on the mineral composition of the sediment and the known sorption on the pure minerals. The estimated sorption values were usually 25% lower than those of the sorption directly measured. Nevertheless, sorption on pure minerals can be used as a first approximation for sorption on natural sediments. | |||||
BibTeX:
@article{Magal2008,
author = {Magal, Einat and Weisbrod, Noam and Yakirevich, Alex and Yechieli, Yoseph},
title = {The use of fluorescent dyes as tracers in highly saline groundwater},
journal = {Journal of Hydrology},
year = {2008},
volume = {358},
number = {1-2},
pages = {124--133},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408002679}
}
|
|||||
| Magruder, I.A., Woessner, W.W. and Running, S.W. | Ecohydrologic Process Modeling of Mountain Block Groundwater Recharge | 2009 | Ground Water Vol. 47(6), pp. 774-785 |
article | URL |
| Abstract: Regional mountain block recharge (MBR) is a key component of alluvial basin aquifer systems typical of the western United States. Yet neither water scientists nor resource managers have a commonly available and reasonably invoked quantitative method to constrain MBR rates. Recent advances in landscape-scale ecohydrologic process modeling offer the possibility that meteorological data and land surface physical and vegetative conditions can be used to generate estimates of MBR. A water balance was generated for a temperate 24,600-ha mountain watershed, elevation 1565 to 3207 m, using the ecosystem process model Biome-BGC (BioGeochemical Cycles) (Running and Hunt 1993). Input data included remotely sensed landscape information and climate data generated with the Mountain Climate Simulator (MT-CLIM) (Running et al. 1987). Estimated mean annual MBR flux into the crystalline bedrock terrain is 99,000 m3/d, or approximately 19% of annual precipitation for the 2003 water year. Controls on MBR predictions include evapotranspiration (radiation limited in wet years and moisture limited in dry years), soil properties, vegetative ecotones (significant at lower elevations), and snowmelt (dominant recharge process). The ecohydrologic model is also used to investigate how climatic and vegetative controls influence recharge dynamics within three elevation zones. The ecohydrologic model proves useful for investigating controls on recharge to mountain blocks as a function of climate and vegetation. Future efforts will need to investigate the uncertainty in the modeled water balance by incorporating an advanced understanding of mountain recharge processes, an ability to simulate those processes at varying scales, and independent approaches to calibrating MBR estimates. | |||||
BibTeX:
@article{Magruder2009,
author = {Magruder, Ian A. and Woessner, William W. and Running, Steve W.},
title = {Ecohydrologic Process Modeling of Mountain Block Groundwater Recharge},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2009},
volume = {47},
number = {6},
pages = {774--785},
url = {http://dx.doi.org/10.1111/j.1745-6584.2009.00615.x}
}
|
|||||
| Maher, K. | The dependence of chemical weathering rates on fluid residence time | 2010 | Earth and Planetary Science Letters Vol. 294(1-2), pp. 101-110 |
article | URL |
| Abstract: In order to evaluate the importance of hydrologic processes in controlling chemical weathering rates, a reactive transport analysis is used to interpret chemical weathering rate data for a range of systems. An analysis of weathering rates for granitic material shows that weathering rates depend most strongly on fluid residence times and fluid flow rates, and depend very weakly on material age. Over moderate fluid residence times from 5 days to 10 yr, characteristic of soils and some aquifers, transport-controlled weathering explains the orders of magnitude variation in weathering rates to a better extent than material age. For fluid residence times greater than 10 yr, characteristic of some aquifers, saprolites, and most marine sediments, a purely thermodynamic-control on chemical weathering rates sustains chemical weathering—this control may be due to clay precipitation, which can drive weathering of primary minerals, or microbial processes which alter the fluid chemistry via the oxidation of organic matter. In addition, this analysis suggests that the apparent time dependence of chemical weathering rates commonly used to model the evolution of Earth's landforms may be attributable to transport-controlled weathering and the evolution of hydrologic properties over time. If hydrologic processes are the primary control on chemical weathering rates, the nature of the temperature dependence of chemical weathering rates is also altered. | |||||
BibTeX:
@article{Maher2010,
author = {Maher, K.},
title = {The dependence of chemical weathering rates on fluid residence time},
journal = {Earth and Planetary Science Letters},
year = {2010},
volume = {294},
number = {1-2},
pages = {101--110},
url = {http://www.sciencedirect.com/science/article/pii/S0012821X10001810}
}
|
|||||
| Mahler, B. and Massei, N. | Anthropogenic contaminants as tracers in an urbanizing karst aquifer | 2007 | Journal of Contaminant Hydrology Vol. 91(1-2)Issues in urban hydrology: The emerging field of urban contaminant hydrology, pp. 81-106 |
article | URL |
| Abstract: Karst aquifers are uniquely vulnerable to contamination. In the Barton Springs segment of the karstic Edwards aquifer (Texas, U.S.A.), urban contaminants such as pesticides and volatile organic compounds frequently are detected in spring base flow. To determine whether contaminant concentrations change in response to storms, and if they therefore might act as tracers of focused recharge, samples were collected from Barton Springs at closely spaced intervals following three storms. Two herbicides (atrazine and simazine), two insecticides (carbaryl and diazinon), and a solvent (tetrachloroethene) described breakthrough curves over a 1-week period following one or more storms. The breakthrough curves were decomposed into two to five log-normal subcurves, which were interpreted as representing pulses of contaminants moving through the aquifer. Each subcurve could be used in the same way as an artificial tracer to determine travel time to and recovery at the spring. The contaminants have several advantages over artificial tracers: they represent the actual compounds of interest, they are injected essentially simultaneously at several points, and they are injected under those conditions when transport is of the most interest, i.e., following storms. The response of storm discharge, specific conductance, and contaminant loading at the spring depended on initial aquifer flow conditions, which varied from very low (spring discharge of 0.48 m3/s) to high (spring discharge of 2.7 m3/s): concentrations and recovery were the highest when initial aquifer flow conditions were low. This behavior provides information about aquifer structure and the influence of aquifer flow condition on transport properties. | |||||
BibTeX:
@article{Mahler2007,
author = {Mahler, Barbara and Massei, Nicolas},
title = {Anthropogenic contaminants as tracers in an urbanizing karst aquifer},
booktitle = {Issues in urban hydrology: The emerging field of urban contaminant hydrology},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {91},
number = {1-2},
pages = {81--106},
url = {http://www.sciencedirect.com/science/article/pii/S0169772206001963}
}
|
|||||
| Mahler, B., Personné, J.-C., Lods, G. and Drogue, C. | Transport of free and particulate-associated bacteria in karst | 2000 | Journal of Hydrology Vol. 238(3-4), pp. 179-193 |
article | URL |
| Abstract: Karst aquifers, because of their unique hydrogeologic characteristics, are extremely susceptible to contamination by pathogens. Here we present the results of an investigation of contamination of a karst aquifer by fecal indicator bacteria. Two wells intercepting zones with contrasting effective hydraulic conductivities, as determined by pump test, were monitored both during the dry season and in response to a rain event. Samples were also collected from the adjacent ephemeral surface stream, which is known to be impacted by an upstream wastewater treatment plant after rainfall. Whole water and suspended sediment samples were analyzed for fecal coliforms and enterococci. During the dry season, pumping over a 2-day period resulted in increases in concentrations of fecal coliforms to greater than 10,000 CFU/100 ml in the high-conductivity well; enterococci and total suspended solids also increased, to a lesser degree. Toward the end of the pumping period, as much as 50% of the fecal coliforms were associated with suspended sediment. Irrigation of an up-gradient pine plantation with primary-treated wastewater is the probable source of the bacterial contamination. Sampling after a rain event revealed the strong influence of water quality of the adjacent Terrieu Creek on the ground water. Bacterial concentrations in the wells showed a rapid response to increased concentrations in the surface water, with fecal coliform concentrations in ground water ultimately reaching 60,000 CFU/100 ml. Up to 100% of the bacteria in the ground water was associated with suspended sediment at various times. The results of this investigation are evidence of the strong influence of surface water on ground water in karst terrain, including that of irrigation water. The large proportion of bacteria associated with particulates in the ground water has important implications for public health, as bacteria associated with particulates may be more persistent and more difficult to inactivate. The high bacterial concentrations found in both wells, despite the difference in hydraulic conductivity, demonstrates the difficulty of predicting vulnerability of individual wells to bacterial contamination in karst. The extreme temporal variability in bacterial concentrations underscores the importance of event-based monitoring of the bacterial quality of public water supplies in karst. | |||||
BibTeX:
@article{Mahler2000,
author = {Mahler, B.J and Personné, J.-C and Lods, G.F and Drogue, C},
title = {Transport of free and particulate-associated bacteria in karst},
journal = {Journal of Hydrology},
year = {2000},
volume = {238},
number = {3-4},
pages = {179--193},
url = {http://www.sciencedirect.com/science/article/pii/S0022169400003243}
}
|
|||||
| Mahler, B., Valdes, D., Musgrove, M. and Massei, N. | Nutrient dynamics as indicators of karst processes: Comparison of the Chalk aquifer (Normandy, France) and the Edwards aquifer (Texas, U.S.A.) | 2008 | Journal of Contaminant Hydrology Vol. 98(1-2), pp. 36-49 |
article | URL |
| Abstract: Karst aquifers display a range of geologic and geomorphic characteristics in a wide range of climatic and land-use settings; identification of transport dynamics representative of karst aquifers in general could help advance our understanding of these complex systems. To this end, nutrient, turbidity, and major ion dynamics in response to storms were compared at multiple sites in two karst aquifers with contrasting characteristics and settings: the Chalk aquifer (Eure Department, Normandy, France) and the Barton Springs segment of the Edwards Aquifer (Texas, U.S.A.). The Chalk aquifer is typified by high matrix porosity, thick surficial deposits (up to 30 m thick), and agricultural land use; the Barton Springs segment is typified by low matrix porosity, outcropping limestone, and urban land use. Following one to three storms, from 5 to 16 samples from springs and wells were analyzed for major ions, and specific conductance and turbidity were monitored continuously. Comparison of the chemographs indicated some generalized responses, including an increase in turbidity and potassium concentrations and a decrease in major ion and nitrate concentrations with infiltrating storm runoff. Factor analysis of major ions and turbidity revealed strikingly similar behavior of the chemical variables for the two aquifers: The first two factors, explaining more than 75% of the variability, illustrate that dynamics of most major ions (including nitrate) are opposed to those of turbidity and of potassium. The results demonstrate that potassium and nitrate are effective tracers of infiltrating storm runoff and resident ground water, respectively, and the similar results for these two highly contrasting aquifers suggest that the dynamics identified might be applicable to karst systems in general. | |||||
BibTeX:
@article{Mahler2008,
author = {Mahler, B.J. and Valdes, D. and Musgrove, M. and Massei, N.},
title = {Nutrient dynamics as indicators of karst processes: Comparison of the Chalk aquifer (Normandy, France) and the Edwards aquifer (Texas, U.S.A.)},
journal = {Journal of Contaminant Hydrology},
year = {2008},
volume = {98},
number = {1-2},
pages = {36--49},
url = {http://www.sciencedirect.com/science/article/pii/S0169772208000260}
}
|
|||||
| Mahler, B.J., Bennett, P.C. and Zimmerman, M. | Lanthanide-Labeled Clay: A New Method for Tracing Sediment Transport in Karst | 1998 | Ground Water Vol. 36(5), pp. 835-843 |
article | URL |
| Abstract: Mobile sediment is a fundamental yet poorly characterized aspect of mass transport through karst aquifers. Here the development and field testing of an extremely sensitive particle tracer that may be used to characterize sediment transport in karst aquifers is described. The tracer consists of micron-size montmorillonite particles homoionized to the lanthanide form; after injection and retrieval from a ground water system, the lanthanide ions are chemically stripped from the clay and quantified by high performance liquid chromatography. The tracer meets the following desired criteria: low detection limit; a number of differentiable signatures; inexpensive production and quantification using standard methods; no environmental risks; and hydrodynamic properties similar to the in situ sediment it is designed to trace. The tracer was tested in laboratory batch experiments and field tested in both surface water and ground water systems. In surface water, arrival times of the tracer were similar to those of a conservative water tracer, although a significant amount of material was lost due to settling. Two tracer tests were undertaken in a karst aquifer under different flow conditions. Under normal flow conditions, the time of arrival and peak concentration of the tracer were similar to or preceded that of a conservative water tracer. Under low flow conditions, the particle tracer was not detected, suggesting that in low flow the sediment settles out of suspension and goes into storage. | |||||
BibTeX:
@article{Mahler1998,
author = {Mahler, Barbara J. and Bennett, Philip C. and Zimmerman, Mitch},
title = {Lanthanide-Labeled Clay: A New Method for Tracing Sediment Transport in Karst},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {1998},
volume = {36},
number = {5},
pages = {835--843},
url = {http://dx.doi.org/10.1111/j.1745-6584.1998.tb02202.x}
}
|
|||||
| Mahler, B.J. and Lynch, F. | Muddy waters: temporal variation in sediment discharging from a karst spring | 1999 | Journal of Hydrology Vol. 214(1-4), pp. 165-178 |
article | URL |
| Abstract: Karst aquifers are capable of transporting and discharging large quantities of suspended sediment, which can have an important impact on water quality. Here we present the results of intensive monitoring of sediment discharging from a karst spring in response to two storm events, one following a wet season and the other following a dry season; we describe temporal changes in total suspended solids (TSS), mineralogy, and particle size distribution. Peak concentrations of suspended sediment coincided with changes in aqueous chemistry indicating arrival of surface water, suggesting that much of the discharging sediment had an allochthonous origin. Concentrations of suspended sediment peaked 14–16 h after rainfall, and the bulk of the sediment (approximately 1 metric ton in response to each storm) discharged within 24 h after rainfall. Filtered material included brightly colored fibers and organic matter. Suspended sediments consisted of dolomite, calcite, quartz, and clay. Proportions of each mineral constituent changed as the aquifer response to the storm progressed, indicating varying input from different sediment sources. The hydraulic response of the aquifer to precipitation was well described by changes in parameters obtained from the particle size distribution function, and corresponded to changes seen in TSS and mineralogy. Differences between storms in the quantity and mineralogy of sediment transported suggest that seasonal effects on surface sediment supply may be important. The quantity of sediment discharging and its potential to sorb and transport contaminants indicates that a mobile solid phase should be included in contaminant monitoring and contaminant transport models of karst. Temporal changes in sediment quantity and characteristics and differences between responses to the two storms, however, demonstrate that the process is not easily generalized. | |||||
BibTeX:
@article{Mahler1999,
author = {Mahler, Barbara J. and Lynch, F.Leo},
title = {Muddy waters: temporal variation in sediment discharging from a karst spring},
journal = {Journal of Hydrology},
year = {1999},
volume = {214},
number = {1-4},
pages = {165--178},
url = {http://www.sciencedirect.com/science/article/pii/S002216949800287X}
}
|
|||||
| Mahmood, R., Leeper, R. and Quintanar, A.I. | Sensitivity of planetary boundary layer atmosphere to historical and future changes of land use/land cover, vegetation fraction, and soil moisture in Western Kentucky, USA | 2011 | Global and Planetary Change Vol. 78(1-2), pp. 36-53 |
article | URL |
| Abstract: Changes in land use land cover (LULCC), vegetation fraction (FV), and soil moisture affects land surface atmosphere interactions, characteristics of planetary boundary layer (PBL), and near surface atmospheric moisture content. Previous studies have investigated impacts of LULC, FV, and soil moisture changes on atmosphere separately. The present study investigates the combined impacts of changes in LULC, FV, and soil moisture, on PBL atmosphere and near surface atmospheric moisture content. The study is set in western region of Kentucky, USA. We have used the Noah land surface scheme and MM5 model for this purpose. The study used two nested domains. The current land use land cover of the inner domain was changed to grass, forest, and bare soil to represent historical changes and potential near future modifications. Subsequently, FV and soil moisture were systematically changed for each of the land uses. The simulations have found that changes of current land use to grass within the inner domain increases latent heat flux, dew point temperature, relative humidity, and equivalent potential temperature. It was found that height of the PBL was reduced and development of circulation cells was visible along land use land cover discontinuity. Changes in horizontal and vertical wind field were also reported. FV changes for grass further magnified these impacts. For example, decrease or increase in FV has decreased or increased latent heat flux. Similar response of other PBL parameters could be found for changes in FV along with LULC. It was also found that if we replaced forest with lower FV by grass with higher FV, the impacts could cancel each other. Changes to forest and bare soil land use types and lower FV for forest also produced generally similar types of responses. Soil moisture changes, particularly drying, further impacted these responses. This study finds that increase in FV counteracts impacts of soil moisture reduction up to a level. Overall, grass produced moister PBL and lowered the height of PBL and LCL. It is interesting to note that during nighttime the impacts of LULC, FV and soil moisture changes were diminished. These changes not only modified meso-scale wind fields but also potential for convective development. It was concluded that similar experiments needed to be undertaken for convectively conducive environments to better understand the combined impacts of changes in LULC, FV and soil moisture. | |||||
BibTeX:
@article{Mahmood2011,
author = {Mahmood, Rezaul and Leeper, Ronnie and Quintanar, Arturo I.},
title = {Sensitivity of planetary boundary layer atmosphere to historical and future changes of land use/land cover, vegetation fraction, and soil moisture in Western Kentucky, USA},
journal = {Global and Planetary Change},
year = {2011},
volume = {78},
number = {1-2},
pages = {36--53},
url = {http://www.sciencedirect.com/science/article/pii/S0921818111000786}
}
|
|||||
| Maillard, E., Payraudeau, S., Faivre, E., Grégoire, C., Gangloff, S. and Imfeld, G. | Removal of pesticide mixtures in a stormwater wetland collecting runoff from a vineyard catchment | 2011 | Science of The Total Environment Vol. 409(11), pp. 2317-2324 |
article | URL |
| Abstract: Wetlands can collect contaminated runoff from agricultural catchments and retain dissolved and particle-laden pesticides. However, knowledge about the capacity and functioning of wetland systems with respect to the removal of pesticides is very limited. Here we show that stormwater wetlands can efficiently remove pesticides in runoff from vineyard catchments during the period of pesticide application, although flow and hydrochemical conditions of the wetland largely vary over time. During the entire agricultural season, the inflowing load of nine fungicides, six herbicides, one insecticide and four degradation products was 8.039 g whereas the outflowing load was 2.181 g. Removal rates of dissolved loads by the wetland ranged from 39% (simazine) to 100% (cymoxanil, gluphosinate, kresoxim methyl and terbuthylazine). Dimethomorph, diuron, glyphosate, metalaxyl and tetraconazole were more efficiently removed in spring than in summer. More than 88% of the input mass of suspended solids was retained, underscoring the capability of the wetland to trap pesticide-laden particles via sedimentation. Only the insecticide flufenoxuron was frequently detected in the wetland sediments. Our results demonstrate that stormwater wetlands can efficiently remove pesticide mixtures in agricultural runoff during critical periods of pesticide application, although fluctuations in the runoff regime and hydrochemical characteristics can affect the removal rates of individual pesticides. | |||||
BibTeX:
@article{Maillard2011,
author = {Maillard, Elodie and Payraudeau, Sylvain and Faivre, Etienne and Grégoire, Caroline and Gangloff, Sophie and Imfeld, Gwenaël},
title = {Removal of pesticide mixtures in a stormwater wetland collecting runoff from a vineyard catchment},
journal = {Science of The Total Environment},
year = {2011},
volume = {409},
number = {11},
pages = {2317--2324},
url = {http://www.sciencedirect.com/science/article/pii/S0048969711001161}
}
|
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| Majda, A.J. and Kramer, P.R. | Simplified models for turbulent diffusion: Theory, numerical modelling, and physical phenomena | 1999 | Physics Reports Vol. 314(4-5), pp. 237-574 |
article | URL |
| Abstract: Several simple mathematical models for the turbulent diffusion of a passive scalar field are developed here with an emphasis on the symbiotic interaction between rigorous mathematical theory (including exact solutions), physical intuition, and numerical simulations. The homogenization theory for periodic velocity fields and random velocity fields with short-range correlations is presented and utilized to examine subtle ways in which the flow geometry can influence the large-scale effective scalar diffusivity. Various forms of anomalous diffusion are then illustrated in some exactly solvable random velocity field models with long-range correlations similar to those present in fully developed turbulence. Here both random shear layer models with special geometry but general correlation structure as well as isotropic rapidly decorrelating models are emphasized. Some of the issues studied in detail in these models are superdiffusive and subdiffusive transport, pair dispersion, fractal dimensions of scalar interfaces, spectral scaling regimes, small-scale and large-scale scalar intermittency, and qualitative behavior over finite time intervals. Finally, it is demonstrated how exactly solvable models can be applied to test and design numerical simulation strategies and theoretical closure approximations for turbulent diffusion. | |||||
BibTeX:
@article{Majda1999,
author = {Majda, Andrew J. and Kramer, Peter R.},
title = {Simplified models for turbulent diffusion: Theory, numerical modelling, and physical phenomena},
journal = {Physics Reports},
year = {1999},
volume = {314},
number = {4-5},
pages = {237--574},
url = {http://www.sciencedirect.com/science/article/pii/S0370157398000830}
}
|
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| Majone, B., Bellin, A. and Borsato, A. | Runoff generation in karst catchments: multifractal analysis | 2004 | Journal of Hydrology Vol. 294(1-3)Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media, pp. 176-195 |
article | URL |
| Abstract: Time series of hydrological and geochemical signals at two karst springs, located in the Dolomiti del Brenta region, near Trento, Italy, are used to infer how karst catchments work internally to generate runoff. The data analyzed include precipitation, spring flow and electric conductivity of the spring water. All the signals show the signature of multifractality but with different intermittency and non-stationarity. In particular, precipitation and spring flow are shown to have nearly the same degree of non-stationarity and intermittency, while electric conductivity, which mimics the travel time distribution of water in the karst system, is less intermittent and smoother than both spring flow and precipitations. We found that spring flow can be obtained from precipitation through fractional convolution with a power law transfer function. An important result of our study is that the probability distribution of travel times is inconsistent with the advection dispersion equation, while it supports the anomalous transport model. This result is in line with what was observed by Painter et al. [Geophys. Res. Lett. 29 (2002) 21.1] for transport in fractured rocks. | |||||
BibTeX:
@article{Majone2004,
author = {Majone, Bruno and Bellin, Alberto and Borsato, Andrea},
title = {Runoff generation in karst catchments: multifractal analysis},
booktitle = {Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media},
journal = {Journal of Hydrology},
year = {2004},
volume = {294},
number = {1-3},
pages = {176--195},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404000964}
}
|
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| Majone, B., Bertagnoli, A. and Bellin, A. | A non-linear runoff generation model in small Alpine catchments | 2010 | Journal of Hydrology Vol. 385(1-4), pp. 300-312 |
article | URL |
| Abstract: We present a simple non-linear hydrological model that conceptualizes the processes controlling runoff generation at the hillslope scale by using a pragmatic “downward” approach where only the most relevant processes are considered. | |||||
BibTeX:
@article{Majone2010,
author = {Majone, Bruno and Bertagnoli, Andrea and Bellin, Alberto},
title = {A non-linear runoff generation model in small Alpine catchments},
journal = {Journal of Hydrology},
year = {2010},
volume = {385},
number = {1-4},
pages = {300--312},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410001228}
}
|
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| Makarewicz, J.C., Lewis, T.W., Boyer, G.L. and Edwards, W.J. | The influence of streams on nearshore water chemistry, Lake Ontario | Journal of Great Lakes Research(0), pp. - | article | URL | |
| Abstract: Large lakes have characteristics, such as a spring thermal bar; nearshore offshore gradients of nutrients, sediment, and biota; and the development of a nearshore zone often chemically, biologically, and physically different from the offshore region, that are not commonly observed in smaller lakes. The research presented here focuses on the role of rivers affecting the cross margin transport of terrigenous materials delivered during the summer on nearshore waters of Lake Ontario. On the south shore of Lake Ontario, levels of chlorophyll, total phosphorus (TP), and total coliform were higher in the Oak Orchard Creek river plume than out of it. Similarly at the Genesee River polygon, turbidity, specific conductance, temperature, TP, and chlorophyll were substantially higher in the plumes than outside of the plumes. Graphic depictions and the strong correlations (r > = 0.70) between specific conductance and TP, soluble reactive phosphorus , temperature, chlorophyll, total Kjeldahl nitrogen, and turbidity indicate the plumes of water are from the Genesee River and Oak Orchard Creek. The load from all creeks on the New York shore of Lake Ontario ranged from ~ 18 to 25% of the annual phosphorus load of the Niagara River. The cumulative impact of these small streams entering the nearshore and embayments of Lake Ontario is potentially great, as the mixing of plume and lake water appears to be limited to the nearshore areas. Terrigenous inputs likely provide the nutrient, phosphorus, which contributes to the periodic development of benthic algae blooms observed along the south shore of Lake Ontario. The conclusion that river plumes impact and sustain the nearshore of large lakes is suggested by the data. | |||||
BibTeX:
@article{Makarewicz,
author = {Makarewicz, Joseph C. and Lewis, Theodore W. and Boyer, Gregory L. and Edwards, William J.},
title = {The influence of streams on nearshore water chemistry, Lake Ontario},
journal = {Journal of Great Lakes Research},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0380133012000457}
}
|
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| Makinia, J. and Wells, S.A. | Evaluation of empirical formulae for estimation of the longitudinal dispersion in activated sludge reactors | 2005 | Water Research Vol. 39(8), pp. 1533-1542 |
article | URL |
| Abstract: Tracer studies are widely applied to characterize the hydraulic properties of reactors. In the case of activated sludge reactors, however, tracer test results are difficult to interpret due to internal and returned activated sludge recirculation. Empirical formulae can be considered as an alternative method of estimating the hydraulic conditions within the activated sludge reactor. The aim of this study is to evaluate accuracy of four empirical formulae for the full-scale conditions based on the results of tracer studies performed at the Rock Creek Wastewater Treatment Plant (WWTP) in Hillsboro, OR (USA). Values of the dispersion coefficient, EL, were first estimated using a 1-D advection–dispersion equation and setting a sum of squares of differences between the observed and calculated tracer concentrations to a minimum. The estimated values of EL coefficient remained within the range of 1043–1580 m2/h. The best approximation of dispersion was obtained from the formula of Fujie et al. (1983, J. Ferment. Technol. 63(3), 295). Also the formula of Murphy and Boyko (1970, J. San. Eng. ASCE 96(2), 211) generated EL values of the same order as the optimum EL. The accuracy of these formulae was further confirmed based on the results of studies reported in the literature. | |||||
BibTeX:
@article{Makinia2005,
author = {Makinia, Jacek and Wells, Scott A.},
title = {Evaluation of empirical formulae for estimation of the longitudinal dispersion in activated sludge reactors},
journal = {Water Research},
year = {2005},
volume = {39},
number = {8},
pages = {1533--1542},
url = {http://www.sciencedirect.com/science/article/pii/S004313540500059X}
}
|
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| Makkawi, M.H. | Effect of porous medium heterogeneity on water flow: a stochastic hydrofacies approach | 2004 | Hydrogeology Journal Vol. 12(5), pp. 481-487 |
article | URL |
| Abstract: A stochastic hydrofacies (descriptive-numerical) approach is evaluated by investigating the influence of hydrogeological heterogeneity on the unsaturated zone water dynamics. The approach develops a reliable means for simulating the volumetric water content (θ) and water front arrival time (t a ) in both space and time domains. The methodology designed for this purpose integrates Sequential Indicator Simulation (SIS) and Monte Carlo (MC) procedure to generate descriptive realizations of flow units and convert them into numerical hydrofacies. Flow simulation output indicates that the statistical distribution captures θ experimental measurements. In addition, mode values of the stochastic approach fairly represent the observed θ values. The absolute error between mode and field-measured θ values reaches up to 7%. This small error supports the practicality of the approach as opposed to different deterministic methods. The simulation result also reveals that t a probability distribution function depicts, properly, the effect of medium heterogeneity on flow dynamics and suggests the utilization of this approach in decision-making procedures. | |||||
BibTeX:
@article{Makkawi2004,
author = {Makkawi, Mohammad H.},
title = {Effect of porous medium heterogeneity on water flow: a stochastic hydrofacies approach},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2004},
volume = {12},
number = {5},
pages = {481--487},
url = {http://dx.doi.org/10.1007/s10040-004-0342-4}
}
|
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| Makokha, A.B., Moys, M.H. and Bwalya, M.M. | Modeling the RTD of an industrial overflow ball mill as a function of load volume and slurry concentration | 2011 | Minerals Engineering Vol. 24(3–4)Special issue: Comminution, pp. 335-340 |
article | URL |
| Abstract: The role of residence time distribution (RTD) in the accuracy of milling simulation is well appreciated in literature. Accordingly, the development of models that can accurately predict the RTD at various mill operating conditions would be of considerable benefit to the milling industry. In this paper, a 3-parameter RTD model has been derived using the concept of serial stirred mixers with a dead zone. The model parameters were optimized by minimizing the error between experimental tracer response data and model predictions using a MATLAB algorithm. Based on the optimum values of the model parameters, the mean residence time of slurry was evaluated and the effects of ball load volume and slurry concentration examined. The results revealed that the mean residence time of slurry inside the mill is affected to a larger extent by slurry concentration than the ball load volume. An empirical correlation was developed to predict the mean residence time as a function of slurry concentration, ball load volume and slurry feed rate. Over the range of conditions investigated, the mean residence time was observed to vary linearly with slurry concentration and ball load volume but inversely with feed flow rate. Lastly, a test case of the simulated mill product size distribution using the predicted RTD is presented displaying a close match with experimental data. | |||||
BibTeX:
@article{Makokha2011,
author = {Makokha, Augustine B. and Moys, Michael H. and Bwalya, Mulenga M.},
title = {Modeling the RTD of an industrial overflow ball mill as a function of load volume and slurry concentration},
booktitle = {Special issue: Comminution},
journal = {Minerals Engineering},
year = {2011},
volume = {24},
number = {3–4},
pages = {335--340},
url = {http://www.sciencedirect.com/science/article/pii/S0892687510003183}
}
|
|||||
| Malard, F. and Chapuis, R. | Temperature logging to describe the movement of sewage-polluted surface water infiltrating into a fractured rock aquifer | 1995 | Journal of Hydrology Vol. 173(1-4), pp. 191-217 |
article | URL |
| Abstract: In 1992–1993, temperature logs were used to study the movement of sewage-polluted surface water infiltrating into the fractured limestone of an experimental site located in the southeastern part of the Lez Basin (Southern France). The wells investigated were located on either side of a sewage-polluted stream and intersected water-bearing fractures characterised by large contrasts in hydraulic conductivity. From the results of temperature-depth profiles measured in four closely spaced wells of 60 m depth (W7, W8, W 10 and W 16) during the period February 1992–June 1993 and the findings of a previous and more extensive geothermal survey, we examined the spatial distribution and the temporal variability of ground-water temperature during periods influenced or not influenced by percolating sewage-polluted water. Results of this thermal survey, which were in good agreement with those of a physico-chemical and bacteriological survey simultaneously carried out at the site, provided a substantial amount of information on the distribution of contaminant flow pathways. Well W8, which showed high fluctuating ground-water temperature anomalies, intersected a solution-enlarged part of a bedding joint which seemed to carry much of the sewage-polluted infiltrating water. Ground water in this conductive opening also had a low physico-chemical and bacteriological ‘stability’ and the highest average contaminant concentrations. In contrast, Wells W10, W16 and, to a lesser extent, Well W7 displayed only low ground-water temperature anomalies during periods influenced by percolating sewage-polluted water. Ground water circulating through the thin and rather closed fissures intersected by these wells was less sensitive to pollution, as it had a greater thermal, physico-chemical and bacteriological ‘stability’ and the lowest average. contaminant concentrations. Thus, we suggest that in advance of more focused monitoring programmes, temperature-depth profiles in wells could effectively be used to described the effect of the structural features of fractures limestone aquifers on the movement of infiltrating contaminants. | |||||
BibTeX:
@article{Malard1995,
author = {Malard, Florian and Chapuis, Renaud},
title = {Temperature logging to describe the movement of sewage-polluted surface water infiltrating into a fractured rock aquifer},
journal = {Journal of Hydrology},
year = {1995},
volume = {173},
number = {1-4},
pages = {191--217},
url = {http://www.sciencedirect.com/science/article/pii/002216949502711W}
}
|
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| Maloszewski, P., Rauert, W., Trimborn, P., Herrmann, A. and Rau, R. | Isotope hydrological study of mean transit times in an alpine basin (Wimbachtal, Germany) | 1992 | Journal of Hydrology Vol. 140(1-4), pp. 343-360 |
article | URL |
| Abstract: Measurements of tritium and 18O concentrations in precipitation and runoff were used to provide further insight into the groundwater storage properties of the Wimbachtal Valley, a catchment area of 33.4 km2, extending between 636 and 2713 m a.s.l. in the Berchtesgaden Alps. The catchment includes three aquifer types: a dominant porous aquifer; a fractured dolomite; a karstic limestone aquifer. Employing a simple hydrological model, information about mean transit times of environmental tracers is derived for the groundwater runoff component and several karst springs from the application of the exponential and dispersion flow models to the isotopic input and output data. The mean transit times calculated from a dispersion model with transit times of 4.1 years for 18O and 4.2 years for tritium, which agree well, allow calculation of total (mobile + stagnant) groundwater storage volume, which is equivalent to 6.6 m of water depth. Direct runoff appears negligible as in many other cases. | |||||
BibTeX:
@article{Maloszewski1992,
author = {Maloszewski, Piotr and Rauert, Werner and Trimborn, Peter and Herrmann, Andreas and Rau, Rolf},
title = {Isotope hydrological study of mean transit times in an alpine basin (Wimbachtal, Germany)},
journal = {Journal of Hydrology},
year = {1992},
volume = {140},
number = {1-4},
pages = {343--360},
url = {http://www.sciencedirect.com/science/article/pii/002216949290247S}
}
|
|||||
| Maloszewski, P. and Zuber, A. | Principles and practice of calibration and validation of mathematical models for the interpretation of environmental tracer data in aquifers | 1993 | Advances in Water Resources Vol. 16(3), pp. 173-190 |
article | URL |
| Abstract: Calibration and validation processes of mathematical models applied to environmental tracer dating of groundwater are discussed and their importance exemplified by a number of case studies. The calibration procedures are shown to be often ambiguous due to the scarcity of data, approximate nature of models, and interplay of fitting parameters when their number is too large. A unique calibration is a necessary condition, though not sufficient, for validation. A satisfactory agreement of the values of parameters obtained by calibration with those known from independent methods may be regarded as an indirect validation. Direct or indirect validation is usually obtainable only with respect to some quantities or parameters and in such cases it should be regarded as a partial validation. Very often validation is unavailable, and, consequently, the model and the values of its parameters are questionable, but still can serve as starting points for further studies. Case studies discussed demonstrate that sometimes several properly calibrated and partly validated mathematical models, based on different conceptual models, can be used. In such cases the conceptual model of flow pattern and hydrochemistry remains unidentified. | |||||
BibTeX:
@article{Maloszewski1993,
author = {Maloszewski, P. and Zuber, A.},
title = {Principles and practice of calibration and validation of mathematical models for the interpretation of environmental tracer data in aquifers},
journal = {Advances in Water Resources},
year = {1993},
volume = {16},
number = {3},
pages = {173--190},
url = {http://www.sciencedirect.com/science/article/pii/030917089390036F}
}
|
|||||
| Manda, A.K. and Gross, M.R. | Identifying and characterizing solution conduits in karst aquifers through geospatial (GIS) analysis of porosity from borehole imagery: An example from the Biscayne aquifer, South Florida (USA) | 2006 | Advances in Water Resources Vol. 29(3), pp. 383-396 |
article | URL |
| Abstract: We apply geospatial analysis to borehole imagery in an effort to develop new techniques to evaluate the spatial distribution and internal structure of karst conduits. Remote sensing software is used to classify a high resolution, digital borehole image of limestone bedrock from the Biscayne aquifer (South Florida, USA) into a binary image divided into cells of rock matrix and pores. Within a GIS, 2D porosity is calculated for a series of rectangular sampling windows placed over the binary image and then plotted as a function of depth. Potential conduits that intersect the borehole are identified as peaks of high porosity. A second GIS technique identifies a conduit as a continuous object that spans the entire borehole width. According to these criteria, geospatial analysis reveals ∼10 discrete conduits along the ∼15 m borehole image. Continuous sampling of the geologic medium intersected by the borehole provides insight into the internal structure of karst aquifers and the evolution of karst features. Most importantly, this pilot study demonstrates that GIS-based techniques are capable of quantifying the depths, dimensions, shapes, apertures and connectivity of potential conduits, physical attributes that impact flow in karst aquifers. | |||||
BibTeX:
@article{Manda2006,
author = {Manda, Alex K. and Gross, Michael R.},
title = {Identifying and characterizing solution conduits in karst aquifers through geospatial (GIS) analysis of porosity from borehole imagery: An example from the Biscayne aquifer, South Florida (USA)},
journal = {Advances in Water Resources},
year = {2006},
volume = {29},
number = {3},
pages = {383--396},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805001570}
}
|
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| Mandal, A., Huang, W., Bhandari, S. and Basu, A. | Goodness-of-fit testing in growth curve models: A general approach based on finite differences | 2011 | Computational Statistics & Data Analysis Vol. 55(2), pp. 1086-1098 |
article | URL |
| Abstract: Growth curve models are routinely used in various fields such as biology, ecology, demography, population dynamics, finance, econometrics, etc. to study the growth pattern of different populations and the variables linked with them. Many different kinds of growth patterns have been used in the literature to model the different types of realistic growth mechanisms. It is generally a matter of substantial benefit to the data analyst to have a reasonable idea of the nature of the growth pattern under study. As a result, goodness-of-fit tests for standard growth models are often of considerable practical value. In this paper we develop some natural goodness-of-fit tests based on finite differences of the size variables under consideration. The method is general in that it is not limited to specific parametric forms underlying the hypothesized model so long as an appropriate finite difference of some function of the size variables can be made to vanish. In addition it allows the testing process to be carried out under a set up which manages to relax most of the assumptions made by Bhattacharya et al. (2009); these assumptions are generally reasonable but not guaranteed to hold universally. Thus our proposed method has a very wide scope of application. The performance of the theory developed is illustrated numerically through several sets of real data and through simulations. | |||||
BibTeX:
@article{Mandal2011,
author = {Mandal, A. and Huang, W.T. and Bhandari, S.K. and Basu, A.},
title = {Goodness-of-fit testing in growth curve models: A general approach based on finite differences},
journal = {Computational Statistics & Data Analysis},
year = {2011},
volume = {55},
number = {2},
pages = {1086--1098},
url = {http://www.sciencedirect.com/science/article/pii/S0167947310003464}
}
|
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| Manjhi, N., Verma, N., Salem, K. and Mewes, D. | Lattice Boltzmann modelling of unsteady-state 2D concentration profiles in adsorption bed | 2006 | Chemical Engineering Science Vol. 61(8), pp. 2510-2521 |
article | URL |
| Abstract: This study describes a lattice Boltzmann model (LBM) developed to simulate two-dimensional (2D) unsteady-state concentration profiles, including breakthrough curves, in a tubular column packed with adsorbents. The model using d 3 q 19 (three dimensions and 19 speeds) lattice solves the 3D time-dependent convection–diffusion–adsorption equation for an ideal binary gaseous mixture assuming different velocity profiles in the column, including radially flat (plug flow) and non-uniform across the column's cross-section. The simulation results show significant concentration gradient across the cross-section depending upon the d / d p ratio. The model results corroborate the experimental measurements made in the adsorption bed that the concentration due to breakthrough may be larger near the wall than at the core of the column due to the relatively larger local velocity in the vicinity of the wall. The LBM results have significance from the perspective of the physical understanding of the concentration profiles prevalent in the adsorption bed as well as effective design of a large-scale column. The model results are validated with the analytical solution to 1D axial dispersion problem, and to a few simple flow problems, such as Poiseuille and Couette flows. | |||||
BibTeX:
@article{Manjhi2006,
author = {Manjhi, Nilesh and Verma, Nishith and Salem, Karijm and Mewes, Dieter},
title = {Lattice Boltzmann modelling of unsteady-state 2D concentration profiles in adsorption bed},
journal = {Chemical Engineering Science},
year = {2006},
volume = {61},
number = {8},
pages = {2510--2521},
url = {http://www.sciencedirect.com/science/article/pii/S0009250905008596}
}
|
|||||
| Mansour-Rezaei, S., Naser, G. and Sadiq, R. | A comparison of various uncertainty models: An example of subsurface contaminant transport | Journal of Hydro-environment Research(0), pp. - | article | URL | |
| Abstract: Groundwater resources are under increasing threat of contamination and wasteful use in many parts of the world. Groundwater flow and integrated contaminant transport models are commonly used to predict the fate of contaminants in the subsurface environment. However, the lack of reliable data and complexity of the natural environmental systems, the predictions are subjected to large uncertainties. For reliable decision-making, these contaminant transport models are required to explicitly consider associated uncertainties in their parameters. This paper aims to compare the results of four common uncertainty models using an example of contaminant transport in groundwater. The research employed an advection–dispersion equation (ADE) to describe the transport of a contaminant in groundwater. For simplicity, two parameters – dispersion coefficient and velocity – were considered in the uncertainty analysis. Fuzzy set theory, one- and two-dimensional (1-D and 2-D) Monte Carlo simulations, and Probability Box (P-Box) methods were investigated. The cumulative distribution functions generated from these analyses were compared to evaluate the capabilities of these methods. The comparison showed that P-Box method provides a more comprehensive analysis with lesser assumptions as compared to other methods, and also found to be more pragmatic way to describe and propagate uncertainties in complex environmental systems. Furthermore, execution time required to perform uncertainty analysis using P-Box method is comparatively much less than 2-D Monte Carlo simulations. | |||||
BibTeX:
@article{Mansour-Rezaei,
author = {Mansour-Rezaei, Saheb and Naser, Gholamreza and Sadiq, Rehan},
title = {A comparison of various uncertainty models: An example of subsurface contaminant transport},
journal = {Journal of Hydro-environment Research},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S1570644311000797}
}
|
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| Mao, D., Edwards, J., Kuznetsov, A. and Srivastava, R. | Particle flow, mixing, and chemical reaction in circulating fluidized bed absorbers | 2002 | Chemical Engineering Science Vol. 57(15), pp. 3107-3117 |
article | URL |
| Abstract: A mixing model has been developed to simulate the particle residence time distribution (RTD) in a circulating fluidized bed absorber (CFBA). Also, a gas/solid reaction model for sulfur dioxide (SO2) removal by lime has been developed. For the reaction model that considers RTD distribution inside the core and annulus regions of a CFBA, a macrochemical reaction can be simulated based on microchemical reaction dynamics. The presented model can predict SO2 and lime concentration distributions inside the CFBA, and give the amount of lime needed to remove a given percentage of SO2. It is found that SO2 concentration decreases with the increase of CFBA distance from the bottom in the core region. However, lime concentration exhibits a very slight variation in the core region. This means that lime is efficiently utilized to remove SO2. The model also predicts that SO2 partial pressure at the exit of the CFBA decreases with the increase in the percentage of fresh lime injected in the CFBA. | |||||
BibTeX:
@article{Mao2002,
author = {Mao, D. and Edwards, J.R. and Kuznetsov, A.V. and Srivastava, R.},
title = {Particle flow, mixing, and chemical reaction in circulating fluidized bed absorbers},
journal = {Chemical Engineering Science},
year = {2002},
volume = {57},
number = {15},
pages = {3107--3117},
url = {http://www.sciencedirect.com/science/article/pii/S0009250902001689}
}
|
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| Maraqa, M.A., Zhao, X., Lee, J.-u., Allan, F. and Voice, T.C. | Comparison of nonideal sorption formulations in modeling the transport of phthalate esters through packed soil columns | 2011 | Journal of Contaminant Hydrology Vol. 125(1-4), pp. 57-69 |
article | URL |
| Abstract: Sorption of dimethyl phthalate (DMP), diethyl phthalate (DEP) and dipropyl phthalate (DPP) to two soil materials that vary in organic matter content was investigated using miscible displacement experiments under saturated flow conditions. Generated breakthrough curves (BTCs) were inversely simulated using linear, equilibrium sorption (LE), nonlinear, equilibrium sorption (NL), linear, first-order nonequilibrium sorption (LFO), linear, radial diffusion (LRD), and nonlinear, first-order nonequilibrium sorption (NFO) models. The Akaike information criterion was utilized to determine the preferred model. The LE model could not adequately describe phthalate ester (PE) BTCs in higher organic matter soil or for more hydrophobic PEs. The LFO and LRD models adequately described the BTCs but a slight improvement in curve-fitting was gained in some cases when the NFO model was used. However, none of the models could properly describe the desorptive tail of DPP for the high organic matter soil. Transport of DPP through this soil was adequately predicted when degradation or sorption hysteresis was considered. Using the optimized parameter values along with values reported by others it was shown that the organic carbon distribution coefficient (Koc) of PEs correlates well with the octanol/water partition coefficient (Kow). Also, a strong relationship was found between the first-order sorption rate coefficient normalized to injection pulse size and compound residence time. A similar trend of timescale dependence was found for the rate parameter in the radial diffusion model. Results also revealed that the fraction of instantaneous sorption sites is dependent on Kow and appears to decrease with the increase in the sorption rate parameter. | |||||
BibTeX:
@article{Maraqa2011,
author = {Maraqa, Munjed A. and Zhao, Xianda and Lee, Jae-ug and Allan, Fathi and Voice, Thomas C.},
title = {Comparison of nonideal sorption formulations in modeling the transport of phthalate esters through packed soil columns},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {125},
number = {1-4},
pages = {57--69},
url = {http://www.sciencedirect.com/science/article/pii/S0169772211000519}
}
|
|||||
| Maria Clasina, A. | Balancing responsibility for sanitation [BibTeX] |
2002 | Social Science & Medicine Vol. 55(9), pp. 1539-1551 |
article | DOI URL |
BibTeX:
@article{MariaClasina2002,
author = {Maria Clasina, Allison},
title = {Balancing responsibility for sanitation},
journal = {Social Science & Medicine},
year = {2002},
volume = {55},
number = {9},
pages = {1539--1551},
url = {http://www.sciencedirect.com/science/article/pii/S0277953601002866},
doi = {http://dx.doi.org/10.1016/s0277-9536(01)00286-6}
}
|
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| Mariethoz, G., Renard, P., Cornaton, F. and Jaquet, O. | Truncated Plurigaussian Simulations to Characterize Aquifer Heterogeneity | 2009 | Ground Water Vol. 47(1), pp. 13-24 |
article | URL |
| Abstract: Integrating geological concepts, such as relative positions and proportions of the different lithofacies, is of highest importance in order to render realistic geological patterns. The truncated plurigaussian simulation method provides a way of using both local and conceptual geological information to infer the distributions of the facies and then those of hydraulic parameters. The method (Le Loc’h and Galli 1994) is based on the idea of truncating at least two underlying multi-Gaussian simulations in order to create maps of categorical variable. In this article, we show how this technique can be used to assess contaminant migration in highly heterogeneous media. We illustrate its application on the biggest contaminated site of Switzerland. It consists of a contaminant plume located in the lower fresh water Molasse on the western Swiss Plateau. The highly heterogeneous character of this formation calls for efficient stochastic methods in order to characterize transport processes. | |||||
BibTeX:
@article{Mariethoz2009,
author = {Mariethoz, Grégoire and Renard, Philippe and Cornaton, Fabien and Jaquet, Olivier},
title = {Truncated Plurigaussian Simulations to Characterize Aquifer Heterogeneity},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2009},
volume = {47},
number = {1},
pages = {13--24},
url = {http://dx.doi.org/10.1111/j.1745-6584.2008.00489.x}
}
|
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| Markovic, R.D. | Probability Functions of Best Fit to Distributions of Annual Precipitation and Runoff | 1965 | (8)Hydrology Papers No. 8 (August 1965), pp. 1-33 | article | |
| Abstract: Distributions of annual precipitation and annual river flow are studied on 2506 selected precipitation and river gaging stations in the Western United States and Southwestern Canada. Five probability functions -- Normal, Log-normal with 2, Log-normal with 3, Gamma with 2 and Gamma with 3 parameters -- are fitted to each individual observed distribution. The maximum likelihood method is used for estimating the functions' parameters from observed data. The probability of chi-square is used as a measure of goodness of fit of each function to every observed sample distribution. These five functions are then tested on all station samples grouped into four large ensembles: homogeneous precipitation, non-homogeneous precipitation, river flow, and river flow corrected for the change in carryover. As results of this study, it has been found that all five probability functions investigated are applicable. No one function is more suitable than the other in fitting an observed individual station sample precipitation or river flow distribution. However, distributions of annual precipitation in homogeneous ensemble (1141 samples) and nonhomogeneous ensemble (473 samples) are best fitted by the Log-normal 2 parameter function. Distributions of annual runoff in river flow ensemble (446 samples) and river flow ensemble corrected for the change in carryover (446 samples) are best fitted by the Gamma 2 parameter function. The difference in goodness of fit in ensemble analysis between these two functions is negligible for all practical purposes, and both could be used interchangeably for all four ensembles. |
|||||
BibTeX:
@article{PaperMarkovic1965,
author = {Markovic, Radmilo D.},
title = {Probability Functions of Best Fit to Distributions of Annual Precipitation and Runoff},
booktitle = {Hydrology Papers No. 8 (August 1965)},
publisher = {Colorado State University},
year = {1965},
number = {8},
pages = {1--33},
note = {Colorado State University Hydrology Papers 1-9}
}
|
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| Markus, W. | An infiltration model based on flow variability in macropores: development, sensitivity analysis and applications | 2005 | Journal of Hydrology Vol. 310(1-4), pp. 294-315 |
article | URL |
| Abstract: Simulating infiltration in soils containing macropores still provides unsatisfactory results, as existing models seem not to capture all relevant processes. Recent studies of macropore flow initiation in natural soils containing earthworm channels revealed a distinct flow rate variability in the macropores depending on the initiation process. When macropore flow was initiated at the soil surface, most of the macropores received very little water while a few macropores received a large proportion of the total inflow. In contrast, when macropore flow was initiated from a saturated or nearly saturated soil layer, macropore flow rate variation was much lower. The objective of this study was to develop, evaluate, and test a model, which combines macropore flow variability with several established approaches to model dual permeability soils. We then evaluate the INfiltration–INitiation–INteraction Model (IN3M) to explore the influence of macropore flow variability on infiltration behavior by performing a sensitivity analysis and applying IN3M to sprinkling and dye tracer experiments at three field sites with different macropore and soil matrix properties. The sensitivity analysis showed that the flow variability in macropores reduces interaction between the macropores and the surrounding soil matrix and thus increases bypass flow, especially for surface initiation of macropore flow and at higher rainfall intensities. The model application shows reasonable agreement between IN3M simulations and field data in terms of water balance, water content change, and dye patterns. The influence of macropore flow variability on the hydrological response of the soil was considerable and especially pronounced for soils where initiation occurs at the soil surface. In future, the model could be applied to explore other types of preferential flow and hence to get a generally better understanding of macropore flow. | |||||
BibTeX:
@article{Markus2005,
author = {Markus, Weiler},
title = {An infiltration model based on flow variability in macropores: development, sensitivity analysis and applications},
journal = {Journal of Hydrology},
year = {2005},
volume = {310},
number = {1-4},
pages = {294--315},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405000132}
}
|
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| Marsili-Libelli, S. and Checchi, N. | Identification of dynamic models for horizontal subsurface constructed wetlands | 2005 | Ecological Modelling Vol. 187(2–3), pp. 201-218 |
article | URL |
| Abstract: The current trend in horizontal subsurface constructed wetlands (HSSCW) modelling advocates structures of increasing complexity, which however have produced a limited improvement in the understanding of their internal functioning or in the reliable estimation of their parameters. Following a different approach, this paper proposes the combination of a set of simple structures and a robust identification method to approximate the dispersed flow and pollution reduction dynamics. The models are based on combinations of series/parallel CSTRs of unequal volumes in series with a plug-flow reactor. After introducing the model structures, their identifiability is assessed with a method based on approximate parameter confidence regions based on either the Fisher information matrix (FIM) or the Hessian matrix. Their relative agreement or disagreement yields information about model structural robustness and parameter identifiability. To demonstrate the method, the proposed models are calibrated with data sets from several constructed wetlands, with widely differing hydraulics and pollution removal characteristics. The identification method can assist in the selection of the best combination of hydraulics and kinetics to obtain robust and yet simple models for HSSCW. In particular, it is shown that the estimated volumes can be used for the wetland design and the pollution reduction kinetics are reassessed in terms of identifiability, providing a guideline to decide between first order and Monod kinetics. | |||||
BibTeX:
@article{Marsili-Libelli2005,
author = {Marsili-Libelli, Stefano and Checchi, Nicola},
title = {Identification of dynamic models for horizontal subsurface constructed wetlands},
journal = {Ecological Modelling},
year = {2005},
volume = {187},
number = {2–3},
pages = {201--218},
url = {http://www.sciencedirect.com/science/article/pii/S0304380005000839}
}
|
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| Martin A., S.J. | A one-dimensional transient model of down-flow through a swelling packed porous bed | 2006 | Chemical Engineering Science Vol. 61(8), pp. 2688-2700 |
article | URL |
| Abstract: A transient model of down-flow through an ion-exchange column in which the resin swells has been developed. The model is herein described and results are presented. Wall friction can lead to high bed stresses when the resin in columns with high length to diameter ratios swells. These stresses can lead to high and potentially excursive hydraulic pressure drops along a column. A non-dimensional grouping that effectively correlates the final steady-state hydraulic behavior of a column, with the resin compressibility and column geometric and flow parameters, has been determined. | |||||
BibTeX:
@article{MartinA.2006,
author = {Martin A., Shadday Jr.},
title = {A one-dimensional transient model of down-flow through a swelling packed porous bed},
journal = {Chemical Engineering Science},
year = {2006},
volume = {61},
number = {8},
pages = {2688--2700},
url = {http://www.sciencedirect.com/science/article/pii/S0009250905008882}
}
|
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| Martin, A.D. | Interpretation of residence time distribution data | 2000 | Chemical Engineering Science Vol. 55(23), pp. 5907-5917 |
article | URL |
| Abstract: “Tracer” or Residence time distribution (RTD) studies are commonly exploited as a means of developing an understanding of the “mixing” status of vessels of various types. The effort involved in the setting up of such plant studies can be considerable and the execution of the experiment its self is often a test of endurance. In the past full interpretation of the results has not been easy and as a consequence superficial treatments have been employed. This paper presents an alternative method for interpreting RTD data, which is relatively easy to use and addresses some of the weaknesses of more conventional methods. An extention to the “tanks in series” concept is presented (ETIS) and united with the “reactor network” formulation. The suitability and appropriateness of the model is discussed and compared with the “closed” dispersion model | |||||
BibTeX:
@article{Martin2000,
author = {Martin, A. D.},
title = {Interpretation of residence time distribution data},
journal = {Chemical Engineering Science},
year = {2000},
volume = {55},
number = {23},
pages = {5907--5917},
url = {http://www.sciencedirect.com/science/article/pii/S0009250900001081}
}
|
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| Martin, J.B. and Dean, R.W. | Exchange of water between conduits and matrix in the Floridan aquifer | 2001 | Chemical Geology Vol. 179(1-4)Hydrochemistry of Springs, pp. 145-165 |
article | URL |
| Abstract: Flow through carbonate aquifers may be dominated by conduits where they are present, by intergranular or fracture porosity where conduits are missing, or may occur in conduits and matrix porosity where both are well developed. In the latter case, the exchange of water between conduits and matrix could have important implications for water management and hydrodynamic modeling. An extensive conduit system has been mapped by dye trace studies and cave diving exploration at the Santa Fe Sink/Rise system located in largely unaltered rocks of the Floridan aquifer of north-central Florida. In this area, the Santa Fe River flows underground at the River Sink and returns to the surface ∼5 km to the south at a first magnitude spring called the River Rise. Limited data show that discharge is greater by 27–96% at the River Rise than at the Sink and that the downstream increase in discharge is inversely related to discharge of the river. Natural SO42− concentrations indicate that ∼25% of the water discharging from the Rise originates from the Sink during low flow. Conversely, SO42− and other solute concentrations indicate that most of the water discharging from the Rise originates from the Sink during floods. Ar ∼40% decrease in Na+ and Cl− concentrations over a 5 1/2-month period at a down-gradient water supply well may reflect flow of dilute flood water from the conduits into and through the matrix at rates estimated to be between 9 and 65 m/day. Calcium concentrations remain constant through time at the well, although flood waters have ∼90% lower Ca2+ concentrations than ground water, perhaps reflecting dissolution of the matrix rocks. This apparent exchange of water between matrix and conduits is important for regional ground water quality and dissolution reactions. | |||||
BibTeX:
@article{Martin2001,
author = {Martin, Jonathan B and Dean, Randolph W},
title = {Exchange of water between conduits and matrix in the Floridan aquifer},
booktitle = {Hydrochemistry of Springs},
journal = {Chemical Geology},
year = {2001},
volume = {179},
number = {1-4},
pages = {145--165},
url = {http://www.sciencedirect.com/science/article/pii/S0009254101003205}
}
|
|||||
| Martin, J.B. and Screaton, E.J. | Exchange of Matrix and Conduit Water with Examples from the Floridan Aquifer | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 38-44 | inproceedings | URL |
| Abstract: Rapid infiltration of surface water and contaminants occurs in karst aquifers because of extensive conduit development, but contamination of ground water supplies requires loss of conduit water to the matrix. This process is also important for ground water management and for dissolution and diagenetic reactions. Many factors control exchange between conduits and matrix including the head gradient between matrix and conduits, the permeability of the matrix, the gradients of the regional water table and the conduits, and the relative elevation of the conduits and regional water table. The Floridan Aquifer, which is characterized by high matrix porosity and permeability, provides several examples. | |||||
BibTeX:
@inproceedings{Martin2001a,
author = {Martin, Jonathan B. and Screaton, Elizabeth J.},
title = {Exchange of Matrix and Conduit Water with Examples from the Floridan Aquifer},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {38--44},
url = {http://water.usgs.gov/ogw/karst/kigconference/jbm_exchangematrix.htm}
}
|
|||||
| Martin, M. and Painter, R. | Use of Independent Gamma Distribution to Describe Tracer Break-Through Curves | 2009 | Proceedings of the 19th Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 15 - 17, 2009, pp. P-10-P-10 | inproceedings | |
| Abstract: The advection-dispersion equation (ADE) is widely used as a predictor of residence time distributions (RTDs) for tracer breakthrough curves for karst systems. Solutions of the ADE for tracer breakthrough studies with near plug flow behavior are characteristically Gaussian in appearance. However, very few, if any, quantitative tracer studies result in tracer concentrations that have symmetrical distribution about the mean residence time. While the symmetry of Gaussian breakthrough curves often correctly predicts finite tracer concentrations at zero time, it generally does not accurately predict actual tracer breakthrough curves, which invariably are characterized by relatively long tails. This suggests that a different conceptual approach may be appropriate for describing tracer breakthrough curves and the hydrologic systems they represent. The objective of this project was to develop a more descriptive approach of tracer break-through data based on the gamma probability density function. The tracer travel distance and tracer linear velocity were assumed to be randomly distributed variables with gamma distributions. The RTD for tracer breakthrough curves was derived from the individual distributions of tracer travel distance and linear velocity. This approach was compared and contrasted with the traditional approach based on the ADE for modeling tracer breakthrough data from tracer studies conducted at Mammoth Cave National Park storm filters. | |||||
BibTeX:
@inproceedings{Martin2009,
author = {Martin, Marquan and Painter, Roger},
title = {Use of Independent Gamma Distribution to Describe Tracer Break-Through Curves},
booktitle = {Proceedings of the 19th Tennessee Water Resources Symposium, Burns, Tennessee, USA, April 15 - 17, 2009},
year = {2009},
pages = {P-10--P-10}
}
|
|||||
| Martin, T. | Comparison of bioclogging effects in saturated porous media within one- and two-dimensional flow systems | 2010 | Ecological Engineering Vol. 36(2)Special Issue: BioGeoCivil Engineering, pp. 176-196 |
article | URL |
| Abstract: The accumulation of microbial biomass in a porous medium can lead to a reduction of pore space and an associated decrease in the hydraulic conductivity of the medium – an effect called bioclogging. This phenomenon may occur in several natural and engineered subsurface systems and can be relevant in fields ranging from contaminant hydrology to civil and environmental engineering, as well as for enhanced oil recovery. During the last decades bioclogging has been studied in various laboratory and theoretical studies. Most of these studies considered only one-dimensional flow fields inside a porous medium. Although these studies provided valuable information on bioclogging and factors controlling it, recent studies showed that an extrapolation of these results to multi-dimensional flow fields is not straight forward. This paper reviews the experimental results obtained for one- and two-dimensional flow fields and compares the modeling results obtained using different conceptualizations of the pore space. | |||||
BibTeX:
@article{Martin2010,
author = {Martin, Thullner},
title = {Comparison of bioclogging effects in saturated porous media within one- and two-dimensional flow systems},
booktitle = {Special Issue: BioGeoCivil Engineering},
journal = {Ecological Engineering},
year = {2010},
volume = {36},
number = {2},
pages = {176--196},
url = {http://www.sciencedirect.com/science/article/pii/S0925857409000470}
}
|
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| Martínez, A., Bergamaschi, L., Caliari, M. and Vianello, M. | A massively parallel exponential integrator for advection-diffusion models | 2009 | Journal of Computational and Applied Mathematics Vol. 231(1), pp. 82-91 |
article | URL |
| Abstract: This work considers the Real Leja Points Method (ReLPM), [M. Caliari, M. Vianello, L. Bergamaschi, Interpolating discrete advection-diffusion propagators at spectral Leja sequences, J. Comput. Appl. Math. 172 (2004) 79–99], for the exponential integration of large-scale sparse systems of ODEs, generated by Finite Element or Finite Difference discretizations of 3-D advection-diffusion models. We present an efficient parallel implementation of ReLPM for polynomial interpolation of the matrix exponential propagators exp ( Δ t A ) v and φ ( Δ t A ) v , φ ( z ) = ( exp ( z ) − 1 ) / z . A scalability analysis of the most important computational kernel inside the code, the parallel sparse matrix–vector product, has been performed, as well as an experimental study of the communication overhead. As a result of this study an optimized parallel sparse matrix–vector product routine has been implemented. The resulting code shows good scaling behavior even when using more than one thousand processors. The numerical results presented on a number of very large test cases gives experimental evidence that ReLPM is a reliable and efficient tool for the simulation of complex hydrodynamic processes on parallel architectures. | |||||
BibTeX:
@article{Martinez2009,
author = {Martínez, A. and Bergamaschi, L. and Caliari, M. and Vianello, M.},
title = {A massively parallel exponential integrator for advection-diffusion models},
journal = {Journal of Computational and Applied Mathematics},
year = {2009},
volume = {231},
number = {1},
pages = {82--91},
url = {http://www.sciencedirect.com/science/article/pii/S0377042709000429}
}
|
|||||
| Martínez-Santos, P. and Andreu, J. | Lumped and distributed approaches to model natural recharge in semiarid karst aquifers | 2010 | Journal of Hydrology Vol. 388(3-4), pp. 389-398 |
article | URL |
| Abstract: Recharge is a key component of the hydrological balance in groundwater systems. Particularly in arid and semiarid settings recharge often takes place during isolated rainfall episodes. As a result pumping might cause groundwater levels to fall continuously for long periods of time, even if yearly abstractions remain below the average replenishment rate. Recharge is naturally difficult to quantify, as it depends on a complex variety of factors. Indirect techniques based on mathematical models have long since been advocated as valuable means to estimate recharge. This paper presents a methodology to estimate groundwater recharge in quick-response semiarid karst aquifers. Lumped and distributed models are used to evaluate the fraction of rainfall that ultimately results in aquifer recharge, as well as the correlation between the magnitude of rainfall events and infiltration rates. Modelling results are then compared with direct observations of the recharge processes and discussed to evaluate the implications of time scales. This study is demonstrated through a case-specific application to the Ventós aquifer, an intensively exploited carbonate system located in one of the driest areas of peninsular Spain. Overall, both approaches perform similarly, although the lumped model exhibits a better agreement with field records. Results reflect the nonlinear nature of the rainfall/recharge ratio. The fraction of rainfall that ultimately recharges the aquifer seems to increase exponentially with the magnitude of the event. | |||||
BibTeX:
@article{Martinez-Santos2010,
author = {Martínez-Santos, P. and Andreu, J.M.},
title = {Lumped and distributed approaches to model natural recharge in semiarid karst aquifers},
journal = {Journal of Hydrology},
year = {2010},
volume = {388},
number = {3-4},
pages = {389--398},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410002945}
}
|
|||||
| Mary Taylor, H. | Caring for students: Pedagogy and professionalism in an age of anxiety [BibTeX] |
2010 | Emotion, Space and Society Vol. 3(2), pp. 71-79 |
article | DOI URL |
BibTeX:
@article{MaryTaylor2010,
author = {Mary Taylor, Huber},
title = {Caring for students: Pedagogy and professionalism in an age of anxiety},
journal = {Emotion, Space and Society},
year = {2010},
volume = {3},
number = {2},
pages = {71--79},
url = {http://www.sciencedirect.com/science/article/pii/S1755458609000383},
doi = {http://dx.doi.org/10.1016/j.emospa.2009.06.002}
}
|
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| Marzal, P., Seco, A., Ferrer, J. and Gabaldón, C. | Modeling multiple reactive solute transport with adsorption under equilibrium and nonequilibrium conditions | 1994 | Advances in Water Resources Vol. 17(6), pp. 363-374 |
article | URL |
| Abstract: A coupled transport-chemistry hydrogeochemical model is presented. The model has been formulated for groundwater flow systems with multiple physicochemical interactions among the chemical components in the aqueous and solid phases (acid-base, complexation, precipitation-dissolution, oxidation-reduction and adsorption-desorption). A nonequilibrium surface complexation model has been introduced to account for adsorption nonequilibrium resulting from external mass transfer, intraparticle mass transfer or chemical kinetics. The model formulation and a series of example problems are included. The results show that nonequilibrium adsorption entails a different time distribution of kinetically controlled adsorbate concentrations from the local equilibrium assumption. The effect of the pH on the evolution of precipitation-redissolution fronts, and the development of contamination plumes with greater concentrations that in the incoming solution may be derived from competitive adsorbate transport are also shown. | |||||
BibTeX:
@article{Marzal1994,
author = {Marzal, Paula and Seco, Aurora and Ferrer, Jose and Gabaldón, Carmen},
title = {Modeling multiple reactive solute transport with adsorption under equilibrium and nonequilibrium conditions},
journal = {Advances in Water Resources},
year = {1994},
volume = {17},
number = {6},
pages = {363--374},
url = {http://www.sciencedirect.com/science/article/pii/0309170894900124}
}
|
|||||
| Masaru, Y. | Contributions of C3/C4 organic materials and carbonate rock to dissolved inorganic carbon in a karst groundwater system on Miyakojima Island, southwestern Japan | 2012 | Journal of Hydrology Vol. 412-413(0)Hydrology Conference 2010, pp. 151-169 |
article | URL |
| Abstract: Groundwater δ13C values and chemical compositions were employed to quantitatively evaluate the controlling processes and sources of dissolved inorganic carbon in a karst aquifer system on Miyakojima Island (MI), southwestern Japan. Most MI groundwater is Ca–HCO3 type water, but some Na–Cl, Ca–Cl, or Na–HCO3 type groundwaters occur, formed mainly by seawater intrusion and partly by cation exchange reactions. Calculations using the WATEQ4F and PHREEQC programs revealed that all MI groundwater, not just the Ca–HCO3 type, was strongly influenced by calcite dissolution in a karst aquifer system open with respect to soil CO2, initially derived from organic materials with mainly around 10–50 matm as pCO2, and that most groundwater was saturated with respect to calcite. Moreover, oxidation of ammonium sulfate (applied as fertilizer) added H+ to the MI groundwater, resulting in surplus calcite dissolution. These processes sufficiently explained contents of alkalinity, DIC, and Ca2+ in the groundwater, and were evaluated by model calculation using the PHREEQC program with measured groundwater δ13C and pH values. The results showed that the average mass fractions of dissolved inorganic carbon (DIC) initially from calcite dissolution and C3 and C4 organic materials in the groundwater were 46.4%, 18.5%, and 35.1%, respectively. The model results regarding the origins of DIC in the groundwater agreed fairly well with land use distributions on MI, in particular, with the spatial distribution of forest and sugarcane fields, and gave us some constrains of groundwater recharge areas and flowpaths. | |||||
BibTeX:
@article{Masaru2012,
author = {Masaru, Yamanaka},
title = {Contributions of C3/C4 organic materials and carbonate rock to dissolved inorganic carbon in a karst groundwater system on Miyakojima Island, southwestern Japan},
booktitle = {Hydrology Conference 2010},
journal = {Journal of Hydrology},
year = {2012},
volume = {412-413},
number = {0},
pages = {151--169},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411005257}
}
|
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| Masciopinto, C., Volpe, A., Palmiotta, D. and Cherubini, C. | A combined PHREEQC-2/parallel fracture model for the simulation of laminar/non-laminar flow and contaminant transport with reactions | 2010 | Journal of Contaminant Hydrology Vol. 117(1-4), pp. 94-108 |
article | URL |
| Abstract: A combination of a parallel fracture model with the PHREEQC-2 geochemical model was developed to simulate sequential flow and chemical transport with reactions in fractured media where both laminar and turbulent flows occur. The integration of non-laminar flow resistances in one model produced relevant effects on water flow velocities, thus improving model prediction capabilities on contaminant transport. The proposed conceptual model consists of 3D rock-blocks, separated by horizontal bedding plane fractures with variable apertures. Particle tracking solved the transport equations for conservative compounds and provided input for PHREEQC-2. For each cluster of contaminant pathways, PHREEQC-2 determined the concentration for mass-transfer, sorption/desorption, ion exchange, mineral dissolution/precipitation and biodegradation, under kinetically controlled reactive processes of equilibrated chemical species. Field tests have been performed for the code verification. As an example, the combined model has been applied to a contaminated fractured aquifer of southern Italy in order to simulate the phenol transport. The code correctly fitted the field available data and also predicted a possible rapid depletion of phenols as a result of an increased biodegradation rate induced by a simulated artificial injection of nitrates, upgradient to the sources. | |||||
BibTeX:
@article{Masciopinto2010,
author = {Masciopinto, Costantino and Volpe, Angela and Palmiotta, Domenico and Cherubini, Claudia},
title = {A combined PHREEQC-2/parallel fracture model for the simulation of laminar/non-laminar flow and contaminant transport with reactions},
journal = {Journal of Contaminant Hydrology},
year = {2010},
volume = {117},
number = {1-4},
pages = {94--108},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210000823}
}
|
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| Massei, N., Mahler, B., Bakalowicz, M., Fournier, M. and Dupont, J. | Quantitative Interpretation of Specific Conductance Frequency Distributions in Karst | 2007 | Ground Water Vol. 45(3), pp. 288-293 |
article | URL |
| Abstract: Use of the coefficient of variation (CV) of specific conductance has been a simple and popular approach to classifying karst aquifers; however, problems with this approach arise because specific conductance frequency distributions (CFDs) are usually multimodal and the use of the CV sometimes erroneously classifies aquifers in terms of their dominant flow type or recharge type. Here, we demonstrate a more rigorous analysis of the CFD, which gives insight into the water types contributing to spring flow. The CFD for a water year is separated into an additive series of normal distributions, each related to a hydrogeochemical population. For each water type, its mean, variance, and contribution to the overall CFD can be quantified and compared between water types and water years. We applied this method to 4 years of data collected at Barton Springs, Austin, Texas. Although the overall shape of the CFD changed from year to year, it could consistently be separated into the same set of normally distributed populations. We suggest that each population represents a water type resulting from a particular mode of aquifer functioning. Changes in the parameters describing the curves reflect aquifer response to climatic variations. The results suggest that no single parameter of specific conductance can be used to describe the degree of karst behavior of an aquifer but that the degree of karst behavior itself varies from year to year depending on hydrologic conditions. | |||||
BibTeX:
@article{Massei2007,
author = {Massei, N and Mahler, B.J. and Bakalowicz, M. and Fournier, M. and Dupont, J.P.},
title = {Quantitative Interpretation of Specific Conductance Frequency Distributions in Karst},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2007},
volume = {45},
number = {3},
pages = {288--293},
url = {http://dx.doi.org/10.1111/j.1745-6584.2006.00291.x}
}
|
|||||
| Massei, N., Wang, H., Field, M., Dupont, J., Bakalowicz, M. and Rodet, J. | Interpreting tracer breakthrough tailing in a conduit-dominated karstic aquifer | 2006 | Hydrogeology Journal Vol. 14(6), pp. 849-858 |
article | URL |
| Abstract: Breakthrough tailing has been observed during dye-tracing recovery tests in the Norville aquifer system (chalk), France. Karst-conduit flow and transport parameters were assessed using two different interpretative methods: the linear graphical method and the Chatwin method (implemented in the Qtracer2 program). The linear graphical method was used to model the observed tailing effects, which was explained by a second smaller delayed breakthrough curve. By comparing the results of tracer-test interpretation for the two methods, it was possible to relate the area of this second curve to the importance of turbulent flow in spring discharge. The more turbulent the flow, the less important the contribution of the second breakthrough curve and the tailing effect. The observed tailing could possibly be controlled by hydrodynamics to a greater extent than usually expected, the tailing effects being mostly attributed to diffusion phenomena. Tailing effects were expected to increase with discharge and the piezometric level, which would have resulted in overpressure in conduits, fissure flooding, etc. Instead, breakthrough tailing tended to disappear with increasing aquifer discharge, which would support the hypothesis of there being mostly hydrodynamic-controlled tailing effects instead of matrix- or fissure-diffusion. | |||||
BibTeX:
@article{Massei2006,
author = {Massei, N. and Wang, H. and Field, M. and Dupont, J. and Bakalowicz, M. and Rodet, J.},
title = {Interpreting tracer breakthrough tailing in a conduit-dominated karstic aquifer},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {6},
pages = {849--858},
url = {http://dx.doi.org/10.1007/s10040-005-0010-3}
}
|
|||||
| Massoudieh, A., Mathew, A. and Ginn, T.R. | Column and batch reactive transport experiment parameter estimation using a genetic algorithm | 2008 | Computers & Geosciences Vol. 34(1), pp. 24-34 |
article | URL |
| Abstract: This paper focuses on the application of a genetic algorithm (GA) in estimating the fate and transport parameters of a reacting solute from the column and batch experiments involving a saturated porous medium. A program is developed using C++ to model the column and batch data using kinetically controlled one- or two-site sorption models including linear and/or nonlinear forms. The objective of the algorithm is to minimize the sum of squared differences between the measured and modeled solute concentration data associated with column effluent (i.e., “breakthrough curves”). The GA is capable of estimating transport and reactions parameters such as forward and reverse reaction rates and parameters of the nonlinear reaction models, from a given set of measured data. Further simulations have been performed to estimate the appropriate configurations of the GA, which assist the method in estimating the fate and transport parameters more efficiently. It is shown that a wide range of the GA parameters can lead to convergence to appropriate estimations. The results obtained from this study show that the capability of GAs to fit the column and batch experiment data is promising. | |||||
BibTeX:
@article{Massoudieh2008,
author = {Massoudieh, Arash and Mathew, Ann and Ginn, Timothy R.},
title = {Column and batch reactive transport experiment parameter estimation using a genetic algorithm},
journal = {Computers & Geosciences},
year = {2008},
volume = {34},
number = {1},
pages = {24--34},
url = {http://www.sciencedirect.com/science/article/pii/S0098300407001161}
}
|
|||||
| Mastrocicco, M., Colombani, N., Cavazzini, A. and Pasti, L. | A green and fast chromatographic method for determining organic compound mobility in soils | 2009 | Journal of Chromatography A Vol. 1216(40), pp. 6802-6809 |
article | URL |
| Abstract: Soil leaching column chromatography (SLCC) employing totally aqueous mobile phases has been used for the estimation of retardation factors (R) of heterocyclic compounds and heteroatom-substituted aryl derivatives Aniline, Aniside, Cresol, Hydroquinone, p-Nitroaniline, Phenol, Phenylenediamine, Piridine, Sulfanilamide, Sulfathiazole, Sulfamethoxazole, Metolachlor and Toluene in soils with low fraction of organic carbon. Small columns (0.39 cm × 10 cm i.d.) were packed with soils of different compositions (alluvial sediment, coarse sand and standard Eurosoil4 mixed with quartz). The theory of linear chromatography was employed to correlate statistical peak moments to R. Rs estimated through SLCC were compared with those derived from water–organic carbon partitioning coefficient reported in the literature. The adsorption isotherm of Metolachlor was measured by frontal analysis on a small column packed with alluvial sediment. The approach proposed for measuring the adsorption isotherm requires small amounts of chemicals and soils and does not need fraction collection nor detector calibration. The information obtained by SLCC experiments was used to predict the elution of Metolachlor and Phenol on a large column (8.9 cm × 100 cm i.d.) packed with alluvial sediment. The method used in this work, not making use of any chemical solvents, respects the fundamental concepts of green chemistry. | |||||
BibTeX:
@article{Mastrocicco2009,
author = {Mastrocicco, Micòl and Colombani, Nicolò and Cavazzini, Alberto and Pasti, Luisa},
title = {A green and fast chromatographic method for determining organic compound mobility in soils},
journal = {Journal of Chromatography A},
year = {2009},
volume = {1216},
number = {40},
pages = {6802--6809},
url = {http://www.sciencedirect.com/science/article/pii/S0021967309011807}
}
|
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| Mastrocicco, M., Prommer, H., Pasti, L., Palpacelli, S. and Colombani, N. | Evaluation of saline tracer performance during electrical conductivity groundwater monitoring | 2011 | Journal of Contaminant Hydrology Vol. 123(3-4), pp. 157-166 |
article | URL |
| Abstract: Saline solutions are the most commonly used hydrological tracers, because they can be easily and economically monitored by in situ instrumentation such as electrical conductivity (EC) loggers in wells or by geoelectrical measurements. Unfortunately, these low-cost techniques only provide information on the total concentration of ions in solution, i.e., they cannot resolve the ionic composition of the aqueous solution. This limitation can introduce a bias in the estimation of aquifer parameters where sorption phenomena between saline tracers and sediments become relevant. In general, only selected anions such as Cl− and Br− are recognised to be transported unretarded and they are referred to as conservative tracers or mobile anions. However, cations within the saline tracer may interact with the soil matrix through a range of processes such as ion exchange, surface complexation and via physical mass-transfer phenomena. Heterogeneous reactions with minerals or mineral surfaces may not be negligible where aquifers are composed of fine alluvial sediments. The focus of the present study was to examine and to quantify the bias between the aquifer parameters estimated during model-based interpretation of experimental data of EC measurements of saline tracer relative to the aquifer parameters found by specific measurements (i.e. via ionic chromatography, IC) of truly conservative species. To accomplish this, column displacement experiments with alluvial aquifer materials collected from the Po lowlands (Italy) were performed under water saturated conditions. The behaviour of six selected, commonly used saline tracers (i.e., LiCl, KCl, and NaCl; LiBr, KBr, and NaBr) was studied and the data analysed by inverse modelling. The results demonstrate that the use of EC as a tracer can lead to an erroneous parameterisation of the investigated porous media, if the reactions between solute and matrix are neglected. In general, errors were significant except for KCl and KBr, which is due to the weak interaction between dissolved K+ and the sediment material. The study shows that laboratory scale pre-investigations can help with tracer selection and to optimise the concentration range targeted for in situ multilevel monitoring by unspecific geoelectrical instrumentation. | |||||
BibTeX:
@article{Mastrocicco2011,
author = {Mastrocicco, Micòl and Prommer, Henning and Pasti, Luisa and Palpacelli, Stefano and Colombani, Nicolò},
title = {Evaluation of saline tracer performance during electrical conductivity groundwater monitoring},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {123},
number = {3-4},
pages = {157--166},
url = {http://www.sciencedirect.com/science/article/pii/S0169772211000040}
}
|
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| Matheron, G. and De Marsily, G. | Is transport in porous media always diffusive? A counterexample | 1980 | Water Resources Research Vol. 16(5), pp. 901-917 |
article | URL |
| Abstract: For the special case of a stratified porous medium with flow parallel to the bedding it is shown that the transport of solute cannot, in general, be represented by the usual convection-diffusion equation, even for large time. The necessary conditions for the appearance of a Fickian diffusive process are discussed and compared with previous work done by Gelhar et al. (1979) and Marie et al. (1967). It is shown, however, that when the flow is not exactly parallel to the stratification, diffusive behavior is much more likely to appear. The need for further work on the mechanism of transport in porous media is then emphasized. | |||||
BibTeX:
@article{Matheron1980,
author = {Matheron, G. and De Marsily, G.},
title = {Is transport in porous media always diffusive? A counterexample},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1980},
volume = {16},
number = {5},
pages = {901--917},
url = {http://dx.doi.org/10.1029/WR016i005p00901}
}
|
|||||
| Matić, N., Maldini, K., Cuculić, V. and Frančišković-Bilinski, S. | Investigations of karstic springs of the Biokovo Mt from the Dinaric karst of Croatia | 2012 | Chemie der Erde - Geochemistry Vol. 72(2), pp. 179-190 |
article | URL |
| Abstract: Ten gravity springs from the slopes of the Biokovo Mt, Adriatic coast of Croatia were investigated. Three of them are included in the regional water supply system. The aim of this study was to investigate hydrogeological and geochemical characteristics of watershed, presenting one of the most typical karstic areas in the world. | |||||
BibTeX:
@article{Matic2012,
author = {Matić, Natalija and Maldini, Krešimir and Cuculić, Vlado and Frančišković-Bilinski, Stanislav},
title = {Investigations of karstic springs of the Biokovo Mt from the Dinaric karst of Croatia},
journal = {Chemie der Erde - Geochemistry},
year = {2012},
volume = {72},
number = {2},
pages = {179--190},
url = {http://www.sciencedirect.com/science/article/pii/S0009281911000572}
}
|
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| Maurice, L., Atkinson, T., Barker, J., Bloomfield, J., Farrant, A. and Williams, A. | Karstic behaviour of groundwater in the English Chalk | 2006 | Journal of Hydrology Vol. 330(1-2)Hydro-ecological functioning of the Pang and Lambourn catchments, UK Results from the Lowland Catchment Research (LOCAR) initiative, pp. 63-70 |
article | URL |
| Abstract: Although the Chalk is only weakly karstified, tracer testing from stream sinks has demonstrated groundwater flow velocities comparable to those observed in highly karstic aquifers. Field survey of surface karst features in the catchments of the Pang and Lambourn rivers in southern England demonstrates the importance of overlying and adjacent Palaeogene strata in the development of karst features. Tracer techniques employed within the catchments enable further characterisation of the range and connectivity of solutional voids in this area of the Chalk, and allow assessment of the relative importance of different mechanisms of contaminant attenuation. Quantitative tracer test results suggest that groundwater flow may be through a complex combination of small conduits, typically 10–1000 mm in diameter, and more laterally extensive fissures with apertures of 1–50 mm. Evidence of connectivity between conduits and fissures suggest that in areas of the Chalk with rapid groundwater flow, fissures supplying abstraction boreholes may be connected to karst conduit networks with low potential for contaminant attenuation. | |||||
BibTeX:
@article{Maurice2006,
author = {Maurice, L.D. and Atkinson, T.C. and Barker, J.A. and Bloomfield, J.P. and Farrant, A.R. and Williams, A.T.},
title = {Karstic behaviour of groundwater in the English Chalk},
booktitle = {Hydro-ecological functioning of the Pang and Lambourn catchments, UK Results from the Lowland Catchment Research (LOCAR) initiative},
journal = {Journal of Hydrology},
year = {2006},
volume = {330},
number = {1-2},
pages = {63--70},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406001922}
}
|
|||||
| Maurice, L., Atkinson, T., Barker, J., Williams, A. and Gallagher, A. | The nature and distribution of flowing features in a weakly karstified porous limestone aquifer | Journal of Hydrology(0), pp. - | article | URL | |
| Abstract: The nature and distribution of flowing features in boreholes in an area of approximately 400 km2 in a weakly karstic porous limestone aquifer (the Chalk) was investigated using Single Borehole Dilution Tests (SBDTs) and borehole imaging. 120 flowing features identified from SBDTs in 24 boreholes have densities which decrease from ∼ 0.3 m-1 near the water table to ∼ 0.07 m-1 at depths of more than 40 m below the water table; the average density is 0.20 m-1. There is some evidence of regional lithological control and borehole imaging of 3 boreholes indicated that most flowing features are associated with marls, hardgrounds and flints that may be developed at a more local scale. | |||||
BibTeX:
@article{Maurice,
author = {Maurice, L. and Atkinson, T.C. and Barker, J.A. and Williams, A.T. and Gallagher, A.},
title = {The nature and distribution of flowing features in a weakly karstified porous limestone aquifer},
journal = {Journal of Hydrology},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411008353}
}
|
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| Maurice, L., Atkinson, T., Williams, A., Barker, J. and Farrant, A. | Catchment scale tracer testing from karstic features in a porous limestone | 2010 | Journal of Hydrology Vol. 389(1-2), pp. 31-41 |
article | URL |
| Abstract: Tracer testing was undertaken from sinking streams feeding the Chalk, a porous limestone aquifer characterised by frequent small-scale surface karst features. The objective was to investigate the nature and extent of sub-surface karstic development in the aquifer. Previous tracer testing has demonstrated rapid flow combined with low attenuation of tracer. In this study, at two sites rapid groundwater flow was combined with very high attenuation and at two other sites no tracer was detected at springs within the likely catchment area of the stream sinks tested, suggesting that tracer was totally attenuated along the flowpath. It is proposed that the networks beneath stream sinks in the Chalk and other mildly karstic aquifers distribute recharge into multiple enlarged fractures that divide and become smaller at each division whereas the networks around springs have a predominantly tributary topology that concentrates flow into a few relatively large cavities, a morphology with similarities to that of the early stages of karstification. Tracer attenuation is controlled by the degree to which the two networks are directly connected. In the first state, there is no direct linkage and flow between the two networks is via primary fractures in which tracer attenuation is extreme. The second state is at a percolation threshold in which a single direct link joins the two networks. A very small proportion of tracer reaches the spring rapidly but overall attenuation is very high. In the third state, the recharge and discharge networks are integrated therefore a large fraction of tracer reaches the spring and peak concentrations are relatively high. Despite the large number of stream sinks that recharge the Chalk aquifer, these results suggest that sub-surface conduit development may not always be continuous, with flow down smaller fissures and fractures causing high attenuation of solutes and particulates providing a degree of protection to groundwater outlets that is not seen in more highly karstic aquifers. Bacteriophage tracers that can be detected at very large dilutions (1015) are recommended for investigating groundwater pathways where attenuation may be high. | |||||
BibTeX:
@article{Maurice2010,
author = {Maurice, L. and Atkinson, T.C. and Williams, A.T. and Barker, J.A. and Farrant, A.R.},
title = {Catchment scale tracer testing from karstic features in a porous limestone},
journal = {Journal of Hydrology},
year = {2010},
volume = {389},
number = {1-2},
pages = {31--41},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410002957}
}
|
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| Maxwell, R.M., Welty, C. and Tompson, A.F. | Streamline-based simulation of virus transport resulting from long term artificial recharge in a heterogeneous aquifer | 2003 | Advances in Water Resources Vol. 26(10), pp. 1075-1096 |
article | URL |
| Abstract: The likelihood for viruses, protozoan oocysts, and other human pathogens to enter groundwater, and in particular, sensitive or vulnerable water supplies, has increased as the numbers of anthropogenic sources such as septic systems, leaking sewers, animal farming operations, and artificial recharge of treated wastewater have proliferated. In this paper, we utilize a detailed numerical model of groundwater flow in a region encompassing a large artificial groundwater recharge operation in Orange County, California to evaluate the potential for transport of viruses and protozoan oocysts in such a system, as dictated by a transport model that includes colloid filtration and microbial inactivation components. The purpose of the model is not oriented towards the analysis of any perceived or real microbial contamination, but rather is directed at understanding the influence of aquifer heterogeneity within the modeled system. The transport model is based upon a novel representation of geologic heterogeneity, a high-resolution flow simulator, and an efficient streamline-based transport algorithm. Example virus transport simulations illustrate a large degree of variability in virus breakthrough across water supply pumping wells, with shallower wells providing less than two orders of magnitude of virus removal, and deeper wells indicating many orders of magnitude of virus removal. Simulation results also show variability among pathogens modeled, with Cryptosporidium parvum filtered to a much greater degree than other pathogens. Comparison to transport of an abiotic colloid and a conservative chemical tracer are provided to illustrate the influence of filtration and inactivation on the transport process. The results emphasize the need for improved microbial transport models in realistic aquifer systems, more reliable virus characterization methods and monitoring networks, and their ultimate integration into a broader epidemiological and regulatory framework for aquifer management. | |||||
BibTeX:
@article{Maxwell2003,
author = {Maxwell, Reed M. and Welty, Claire and Tompson, Andrew F.B.},
title = {Streamline-based simulation of virus transport resulting from long term artificial recharge in a heterogeneous aquifer},
journal = {Advances in Water Resources},
year = {2003},
volume = {26},
number = {10},
pages = {1075--1096},
url = {http://www.sciencedirect.com/science/article/pii/S0309170803000745}
}
|
|||||
| Mayes, W., Batty, L., Younger, P., Jarvis, A., Kõiv, M., Vohla, C. and Mander, U. | Wetland treatment at extremes of pH: A review | 2009 | Science of The Total Environment Vol. 407(13)Thematic Papers: Selected papers from the 2007 Wetland Pollutant Dynamics and Control Symposium, pp. 3944-3957 |
article | URL |
| Abstract: Constructed wetlands are an established treatment technology for a diverse range of polluted effluents. There is a long history of using wetlands as a unit process in treating acid mine drainage, while recent research has highlighted the potential for wetlands to buffer highly alkaline (pH > 12) drainage. This paper reviews recent evidence on this topic, looking at wetlands treating acidic mine drainage, and highly alkaline leachates associated with drainage from lime-rich industrial by-products or where such residues are used as filter media in constructed wetlands for wastewater treatment. The limiting factors to the success of wetlands treating highly acidic waters are discussed with regard to design practice for the emerging application of wetlands to treat highly alkaline industrial discharges. While empirically derived guidelines (with area-adjusted contaminant removal rates typically quoted at 10 g Fe m2/day for influent waters pH > 5.5; and 3.5–7 g acidity/m2/day for pH > 4 to < 5.5) for informing sizing of mine drainage treatment wetlands have generally been proved robust (probably due to conservatism), such data exhibit large variability within and between sites. Key areas highlighted for future research efforts include: (1) wider collation of mine drainage wetland performance data in regionalised datasets to improve empirically-derived design guidelines and (2) obtaining an improved understanding of nature of the extremophile microbial communities, microbially-mediated pollutant attenuation and rhizospheral processes in wetlands at extremes of pH. An enhanced knowledge of these (through multi-scale laboratory and field studies), will inform engineering design of treatment wetlands and assist in the move from the empirically-derived conservative sizing estimates that currently prevail to process-based optimal design guidance that could reduce costs and enhance the performance and longevity of wetlands for treating acidic and highly alkaline drainage waters. | |||||
BibTeX:
@article{Mayes2009,
author = {Mayes, W.M. and Batty, L.C. and Younger, P.L. and Jarvis, A.P. and Kõiv, M. and Vohla, C. and Mander, U.},
title = {Wetland treatment at extremes of pH: A review},
booktitle = {Thematic Papers: Selected papers from the 2007 Wetland Pollutant Dynamics and Control Symposium},
journal = {Science of The Total Environment},
year = {2009},
volume = {407},
number = {13},
pages = {3944--3957},
url = {http://www.sciencedirect.com/science/article/pii/S0048969708006980}
}
|
|||||
| Mazurek, M., Alt-Epping, P., Bath, A., Gimmi, T., Niklaus Waber, H., Buschaert, S., Cannière, P.D., Craen, M.D., Gautschi, A., Savoye, S., Vinsot, A., Wemaere, I. and Wouters, L. | Natural tracer profiles across argillaceous formations | 2011 | Applied Geochemistry Vol. 26(7), pp. 1035-1064 |
article | URL |
| Abstract: Argillaceous formations generally act as aquitards because of their low hydraulic conductivities. This property, together with the large retention capacity of clays for cationic contaminants, has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste. In several countries, programmes are under way to characterise the detailed transport properties of such formations at depth. In this context, the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large-scale and long-term transport behaviour of these formations. Here, tracer-profile data, obtained by various methods of pore-water extraction for nine sites in central Europe, are compiled. Data at each site comprise some or all of the conservative tracers: anions (Cl−, Br−), water isotopes (δ18O, δ2H) and noble gases (mainly He). Based on a careful evaluation of the palaeo-hydrogeological evolution at each site, model scenarios are derived for initial and boundary pore-water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites, using transport parameters derived from laboratory or in situ tests. The comprehensive results from this project have been reported in Mazurek et al. (2009). Here the results for three sites are presented in detail, but the conclusions are based on model interpretations of the entire data set. In essentially all cases, the shapes of the profiles can be explained by diffusion acting as the dominant transport process over periods of several thousands to several millions of years and at the length scales of the profiles. Transport by advection has a negligible influence on the observed profiles at most sites, as can be shown by estimating the maximum advection velocities that still give acceptable fits of the model with the data. The advantages and disadvantages of different conservative tracers are also assessed. The anion Cl− is well suited as a natural tracer in aquitards, because its concentration varies considerably in environmental waters. It can easily be measured, although the uncertainty regarding the fraction of the pore space that is accessible to anions in clays remains an issue. The stable water isotopes are also well suited, but they are more difficult to measure and their values generally exhibit a smaller relative range of variation. Chlorine isotopes (δ37Cl) and He are more difficult to interpret because initial and boundary conditions cannot easily be constrained by independent evidence. It is also shown that the existence of perturbing events such as the activation of aquifers due to uplift and erosion, leading to relatively sharp changes of boundary conditions, can be considered as a pre-requisite to obtain well-interpretable tracer signatures. On the other hand, gradual changes of boundary conditions are more difficult to parameterise and so may preclude a clear interpretation. | |||||
BibTeX:
@article{Mazurek2011,
author = {Mazurek, Martin and Alt-Epping, Peter and Bath, Adrian and Gimmi, Thomas and Niklaus Waber, H. and Buschaert, Stéphane and Cannière, Pierre De and Craen, Mieke De and Gautschi, Andreas and Savoye, Sébastien and Vinsot, Agnès and Wemaere, Isabelle and Wouters, Laurent},
title = {Natural tracer profiles across argillaceous formations},
journal = {Applied Geochemistry},
year = {2011},
volume = {26},
number = {7},
pages = {1035--1064},
url = {http://www.sciencedirect.com/science/article/pii/S0883292711002095}
}
|
|||||
| Mazzia, A., Manzini, G. and Putti, M. | Bad behavior of Godunov mixed methods for strongly anisotropic advection–dispersion equations | 2011 | Journal of Computational Physics Vol. 230(23), pp. 8410-8426 |
article | URL |
| Abstract: We study the performance of Godunov mixed methods, which combine a mixed-hybrid finite element solver and a Godunov-like shock-capturing solver, for the numerical treatment of the advection–dispersion equation with strong anisotropic tensor coefficients. It turns out that a mesh locking phenomenon may cause ill-conditioning and reduce the accuracy of the numerical approximation especially on coarse meshes. This problem may be partially alleviated by substituting the mixed-hybrid finite element solver used in the discretization of the dispersive (diffusive) term with a linear Galerkin finite element solver, which does not display such a strong ill conditioning. To illustrate the different mechanisms that come into play, we investigate the spectral properties of such numerical discretizations when applied to a strongly anisotropic diffusive term on a small regular mesh. A thorough comparison of the stiffness matrix eigenvalues reveals that the accuracy loss of the Godunov mixed method is a structural feature of the mixed-hybrid method. In fact, the varied response of the two methods is due to the different way the smallest and largest eigenvalues of the dispersion (diffusion) tensor influence the diagonal and off-diagonal terms of the final stiffness matrix. One and two dimensional test cases support our findings. | |||||
BibTeX:
@article{Mazzia2011,
author = {Mazzia, Annamaria and Manzini, Gianmarco and Putti, Mario},
title = {Bad behavior of Godunov mixed methods for strongly anisotropic advection–dispersion equations},
journal = {Journal of Computational Physics},
year = {2011},
volume = {230},
number = {23},
pages = {8410--8426},
url = {http://www.sciencedirect.com/science/article/pii/S0021999111004499}
}
|
|||||
| Małloszewski, P. and Zuber, A. | On the calibration and validation of mathematical models for the interpretation of tracer experiments in groundwater | 1992 | Advances in Water Resources Vol. 15(1)Validation of Geo-hydrological Models Part 1, pp. 47-62 |
article | URL |
| Abstract: Calibration and validation processes of mathematical models applied to the interpretation of tracer experiments in groundwater are reviewed and exemplified by a number of case studies. Definitions of basic terms related to those processes are given and adapted to specific problems of groundwater tracing. The calibration procedures commonly used are often ambiguous, due to the interplay of parameters, and then a proper validation is unavailable. The number of fitting parameters may sometimes be reduced by using information available from independent observations, or by calibration of a multi-tracer experiment. Even if a unique calibration is achieved, an ideal validation process is usually impossible or uneconomical to perform. Therefore, indirect validation methods must be used. A satisfactory agreement of the values of parameters obtained by calibration with those known from independent observations may be regarded as an indirect validation. Direct or indirect validation is often obtained only with respect to some parameters and in such cases it should be regarded as a partial validation only. | |||||
BibTeX:
@article{Malloszewski1992,
author = {Małloszewski, P. and Zuber, A.},
title = {On the calibration and validation of mathematical models for the interpretation of tracer experiments in groundwater},
booktitle = {Validation of Geo-hydrological Models Part 1},
journal = {Advances in Water Resources},
year = {1992},
volume = {15},
number = {1},
pages = {47--62},
url = {http://www.sciencedirect.com/science/article/pii/030917089290031V}
}
|
|||||
| Małoszewski, P., Wachniew, P. and Czupryński, P. | Study of hydraulic parameters in heterogeneous gravel beds: Constructed wetland in Nowa Słupia (Poland) | 2006 | Journal of Hydrology Vol. 331(3-4), pp. 630-642 |
article | URL |
| Abstract: Combined use of tracers and mathematical modelling for evaluation of hydraulic characteristics of constructed wetlands is presented for the subsurface-flow system with Phragmites australis in Nowa Słupia (Poland). Instantaneously injected bromide and tritium tracers were used to obtain residence time distributions of wastewaters in three parallel inhomogeneous gravel cells of the wetland. The multi flow dispersion model, which assumes the existence of several flow-paths with different hydraulic properties was developed using the respective parallel combination of analytical solutions of the one-dimensional advection–dispersion equation. The model was used successfully to fit the experimental tracer breakthrough curves. Different flow components were identified and wastewater volumes, water-saturated porosity, mean wastewater travel times, longitudinal dispersivities as well as hydraulic conductivity of wetland cells were derived from model parameters. The variation in flow components and apparent hydraulic characteristics among wetland cells relate to the improper design and maintenance of the wetland. The single fissure dispersion model, which assumes possible diffusion of tracers into the zones with stagnant water during convective-dispersive flow through the mobile zone is adopted to the research conditions and used to model the TBC-s for one cell. The results show that this model can be calibrated with the satisfactory accuracy in that cell but yields unacceptable values of some parameters. | |||||
BibTeX:
@article{Maloszewski2006,
author = {Małoszewski, Piotr and Wachniew, Przemysław and Czupryński, Piotr},
title = {Study of hydraulic parameters in heterogeneous gravel beds: Constructed wetland in Nowa Słupia (Poland)},
journal = {Journal of Hydrology},
year = {2006},
volume = {331},
number = {3-4},
pages = {630--642},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406003222}
}
|
|||||
| Małoszewski, P. and Zuber, A. | Determining the turnover time of groundwater systems with the aid of environmental tracers: 1. Models and their applicability | 1982 | Journal of Hydrology Vol. 57(3-4), pp. 207-231 |
article | URL |
| Abstract: Three new lumped-parameter models have been developed for the interpretation of environmental radioisotope data in groundwater systems. Two of these models combine other simpler models, i.e. the piston flow model is combined either with the exponential model (exponential distribution of transit times) or with the linear model (linear distribution of transit times). The third model is based on a new solution to the dispersion equation which more adequately represents the real systems than the conventional solution generally applied so far. | |||||
BibTeX:
@article{Maloszewski1982,
author = {Małoszewski, P. and Zuber, A.},
title = {Determining the turnover time of groundwater systems with the aid of environmental tracers: 1. Models and their applicability},
journal = {Journal of Hydrology},
year = {1982},
volume = {57},
number = {3-4},
pages = {207--231},
url = {http://www.sciencedirect.com/science/article/pii/0022169482901470}
}
|
|||||
| McDonald, J.B. and Xu, Y.J. | A generalization of the beta distribution with applications | 1995 | Journal of Econometrics Vol. 66(1–2), pp. 133-152 |
article | URL |
| Abstract: This paper introduces a five-parameter beta distribution (GB) which nests the generalized beta and gamma distributions and includes more than thirty distributions as limiting or special cases. The generalized beta leads to an exponential generalized beta (EGB) distribution which includes generalized forms of the logistics, exponential, Gompertz and Gumbell distributions, and the normal as special cases. The EGB family of distributiosn provides the basis for partially adaptive estimation of econometric models with possibly skewed and leptokurtic error distributions. Applications of the models to investigating the distribution of income, stock returns and in regression analysis are considered. | |||||
BibTeX:
@article{McDonald1995,
author = {McDonald, James B. and Xu, Yexiao J.},
title = {A generalization of the beta distribution with applications},
journal = {Journal of Econometrics},
year = {1995},
volume = {66},
number = {1–2},
pages = {133--152},
url = {http://www.sciencedirect.com/science/article/pii/0304407694016124}
}
|
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| McGuire, K.J. and McDonnell, J.J. | A review and evaluation of catchment transit time modeling | 2006 | Journal of Hydrology Vol. 330(3-4), pp. 543-563 |
article | URL |
| Abstract: Transit time is a fundamental catchment descriptor that reveals information about storage, flow pathways and source of water in a single characteristic. Given the importance of transit time, little guidance exists for the application of transit time modeling in complex catchment systems. This paper presents an evaluation and review of the transit time literature in the context of catchments and water transit time estimation. It is motivated by new and emerging interests in transit time estimation in catchment hydrology and the need to distinguish approaches and assumptions in groundwater applications from catchment applications. The review is focused on lumped parameter transit time modeling for water draining catchments and provides a critical analysis of unresolved issues when applied at the catchment-scale. These issues include: (1) input characterization, (2) recharge estimation, (3) data record length problems, (4) stream sampling issues, (5) selection of transit time distributions, and (6) model evaluation. The intent is to promote new advances in catchment hydrology by clarifying and formalizing the assumptions, limitations, and methodologies in applying transit time models to catchments. | |||||
BibTeX:
@article{McGuire2006,
author = {McGuire, Kevin J. and McDonnell, Jeffrey J.},
title = {A review and evaluation of catchment transit time modeling},
journal = {Journal of Hydrology},
year = {2006},
volume = {330},
number = {3-4},
pages = {543--563},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406002150}
}
|
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| McMillan, H., Krueger, T. and Freer, J. | Benchmarking observational uncertainties for hydrology: rainfall, river discharge and water quality | 2012 | Hydrological Processes, pp. n/a-n/a | article | URL |
| Abstract: This review and commentary sets out the need for authoritative and concise information on the expected error distributions and magnitudes in observational data. We discuss the necessary components of a benchmark of dominant data uncertainties and the recent developments in hydrology which increase the need for such guidance. We initiate the creation of a catalogue of accessible information on characteristics of data uncertainty for the key hydrological variables of rainfall, river discharge and water quality (suspended solids, phosphorus and nitrogen). This includes demonstration of how uncertainties can be quantified, summarizing current knowledge and the standard quantitative results available. In particular, synthesis of results from multiple studies allows conclusions to be drawn on factors which control the magnitude of data uncertainty and hence improves provision of prior guidance on those uncertainties. Rainfall uncertainties were found to be driven by spatial scale, whereas river discharge uncertainty was dominated by flow condition and gauging method. Water quality variables presented a more complex picture with many component errors. For all variables, it was easy to find examples where relative error magnitudes exceeded 40%. We consider how data uncertainties impact on the interpretation of catchment dynamics, model regionalization and model evaluation. In closing the review, we make recommendations for future research priorities in quantifying data uncertainty and highlight the need for an improved ‘culture of engagement’ with observational uncertainties. | |||||
BibTeX:
@article{McMillan2012,
author = {McMillan, Hilary and Krueger, Tobias and Freer, Jim},
title = {Benchmarking observational uncertainties for hydrology: rainfall, river discharge and water quality},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {2012},
pages = {n/a--n/a},
url = {http://dx.doi.org/10.1002/hyp.9384}
}
|
|||||
| McNamara, J.P., Tetzlaff, D., Bishop, K., Soulsby, C., Seyfried, M., Peters, N.E., Aulenbach, B.T. and Hooper, R. | Storage as a Metric of Catchment Comparison | 2011 | Hydrological Processes Vol. 25(21), pp. 3364-3371 |
article | URL |
| Abstract: The volume of water stored within a catchment, and its partitioning among groundwater, soil moisture, snowpack, vegetation, and surface water are the variables that ultimately characterize the state of the hydrologic system. Accordingly, storage may provide useful metrics for catchment comparison. Unfortunately, measuring and predicting the amount of water present in a catchment is seldom done; tracking the dynamics of these stores is even rarer. Storage moderates fluxes and exerts critical controls on a wide range of hydrologic and biologic functions of a catchment. While understanding runoff generation and other processes by which catchments release water will always be central to hydrologic science, it is equally essential to understand how catchments retain water. We have initiated a catchment comparison exercise to begin assessing the value of viewing catchments from the storage perspective. The exercise is based on existing data from five watersheds, no common experimental design, and no integrated modelling efforts. Rather, storage was estimated independently for each site. This briefing presents some initial results of the exercise, poses questions about the definitions and importance of storage and the storage perspective, and suggests future directions for ongoing activities. | |||||
BibTeX:
@article{McNamara2011,
author = {McNamara, James P. and Tetzlaff, Doerthe and Bishop, Kevin and Soulsby, Chris and Seyfried, Mark and Peters, Norman E. and Aulenbach, Brent T. and Hooper, Richard},
title = {Storage as a Metric of Catchment Comparison},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2011},
volume = {25},
number = {21},
pages = {3364--3371},
url = {http://dx.doi.org/10.1002/hyp.8113}
}
|
|||||
| Measures, C. | GEOTRACES – An international study of the global marine biogeochemical cycles of trace elements and their isotopes | 2007 | Chemie der Erde - Geochemistry Vol. 67(2), pp. 85-131 |
article | URL |
| Abstract: Trace elements serve important roles as regulators of ocean processes including marine ecosystem dynamics and carbon cycling. The role of iron, for instance, is well known as a limiting micronutrient in the surface ocean. Several other trace elements also play crucial roles in ecosystem function and their supply therefore controls the structure, and possibly the productivity, of marine ecosystems. Understanding the biogeochemical cycling of these micronutrients requires knowledge of their diverse sources and sinks, as well as their transport and chemical form in the ocean. | |||||
BibTeX:
@article{Measures2007,
author = {Measures, Chris},
title = {GEOTRACES – An international study of the global marine biogeochemical cycles of trace elements and their isotopes},
journal = {Chemie der Erde - Geochemistry},
year = {2007},
volume = {67},
number = {2},
pages = {85--131},
url = {http://www.sciencedirect.com/science/article/pii/S0009281907000050}
}
|
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| Megharaj, M., Ramakrishnan, B., Venkateswarlu, K., Sethunathan, N. and Naidu, R. | Bioremediation approaches for organic pollutants: A critical perspective | 2011 | Environment International Vol. 37(8), pp. 1362-1375 |
article | URL |
| Abstract: Due to human activities to a greater extent and natural processes to some extent, a large number of organic chemical substances such as petroleum hydrocarbons, halogenated and nitroaromatic compounds, phthalate esters, solvents and pesticides pollute the soil and aquatic environments. Remediation of these polluted sites following the conventional engineering approaches based on physicochemical methods is both technically and economically challenging. Bioremediation that involves the capabilities of microorganisms in the removal of pollutants is the most promising, relatively efficient and cost-effective technology. However, the current bioremediation approaches suffer from a number of limitations which include the poor capabilities of microbial communities in the field, lesser bioavailability of contaminants on spatial and temporal scales, and absence of bench-mark values for efficacy testing of bioremediation for their widespread application in the field. The restoration of all natural functions of some polluted soils remains impractical and, hence, the application of the principle of function-directed remediation may be sufficient to minimize the risks of persistence and spreading of pollutants. This review selectively examines and provides a critical view on the knowledge gaps and limitations in field application strategies, approaches such as composting, electrobioremediation and microbe-assisted phytoremediation, and the use of probes and assays for monitoring and testing the efficacy of bioremediation of polluted sites. | |||||
BibTeX:
@article{Megharaj2011,
author = {Megharaj, Mallavarapu and Ramakrishnan, Balasubramanian and Venkateswarlu, Kadiyala and Sethunathan, Nambrattil and Naidu, Ravi},
title = {Bioremediation approaches for organic pollutants: A critical perspective},
journal = {Environment International},
year = {2011},
volume = {37},
number = {8},
pages = {1362--1375},
url = {http://www.sciencedirect.com/science/article/pii/S0160412011001681}
}
|
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| Mehler, R. and Ostrowski, M.W. | Comparison of the efficiency of best stormwater management practices in urban drainage systems | 1999 | Water Science and Technology Vol. 39(9), pp. 269-276 |
article | URL |
| Abstract: Increasingly extended and alternative methods for urban stormwater management have been discussed in Germany and elsewhere. Without question an economically and ecologically sound combination of central and decentral measures will be a concept of the future. Yet, at present the introduction of approaches other than traditional combined sewer systems is restricted due to missing planning tools and technologies. Adding a number of frequently used Best Stormwater Management Practices (BSMP's) has widely extended the applicability of an existing stormwater water balance and pollution load model. | |||||
BibTeX:
@article{Mehler1999,
author = {Mehler, R. and Ostrowski, M. W.},
title = {Comparison of the efficiency of best stormwater management practices in urban drainage systems},
journal = {Water Science and Technology},
year = {1999},
volume = {39},
number = {9},
pages = {269--276},
url = {http://www.iwaponline.com/wst/03909/wst039090269.htm}
}
|
|||||
| Meier, P.G., Hong, W.-H. and Deininger, R.A. | Application of tracer techniques to continuous-flow toxicity testing | 1987 | Water Research Vol. 21(10), pp. 1259-1264 |
article | URL |
| Abstract: Frequent toxicant analyses are essential for good quality data in long-term continuous-flow tests. Due to the time consuming and costly chemical analyses, exposure levels are measured at best on a daily basis. These infrequent determinations may not detect variability in toxicant concentrations that could result in test failures. To minimize repetitive testing and improve data quality, a dye tracer method was evaluated. Rhodamine WT was selected as a toxicant tracer because of easy detectability, low toxicity to aquatic organisms, and negligible transformation in the aquatic environment. | |||||
BibTeX:
@article{Meier1987,
author = {Meier, Peter G. and Hong, Wuk-Hee and Deininger, Rolf A.},
title = {Application of tracer techniques to continuous-flow toxicity testing},
journal = {Water Research},
year = {1987},
volume = {21},
number = {10},
pages = {1259--1264},
url = {http://www.sciencedirect.com/science/article/pii/0043135487901783}
}
|
|||||
| Meiman, J., Groves, C. and Herstein, S. | In-Cave Dye Tracing and Drainage Basin Divides in the Mammoth Cave Karst Aquifer, Kentucky | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 179-185 | inproceedings | URL |
| Abstract: Karst ground-water basin divides are generally depicted as two-dimensional lines on maps, but they are better considered as three-dimensional surfaces within the subsurface. Dye traces are necessary to map out these surfaces and to locate conduits inaccessible to cave surveyors, and are indispensable for understanding the geometry of the complex networks of flow paths through the aquifer. A key reason why the Mammoth Cave System is the world's longest known cave is that its passages extend over several major ground-water basins. The divides between these basins define the drainage system geometry and precise location of them is critical for understanding and protecting the cave and its remarkable aquatic ecosystem. In 1999 we initiated a long-term program of dye tracing within the Mammoth Cave System to more precisely locate the divides and to understand their increasingly apparent complexities. In this paper we report on results of some of the more interesting dye injections of the program. Although the Mammoth Cave Karst Aquifer is perhaps the best understood conduit flow network in the world (with over 700 traces), we have found that much more work is needed to provide the level of understanding necessary for protection and conservation. The first reason is a matter of scale and resolution: with the current distribution of traces that define the ground-water basins, many regional basin divides are only approximately defined. In areas where this condition exists in combination with potential threats to ground-water quality (primarily urban and transportation areas) additional tracing is needed to know the flow paths of individual recharge points. A second reason for additional traces is to increase our understanding of the plumbing of active conduits through the karst aquifer. While this type of dye tracing is logistically demanding, requiring visits to in-cave dye recovery locations, it is adding a new level of detail to our understanding of the nature of the karst aquifer. |
|||||
BibTeX:
@inproceedings{Meiman2001,
author = {Meiman, Joe and Groves, Chris and Herstein, Shannon},
title = {In-Cave Dye Tracing and Drainage Basin Divides in the Mammoth Cave Karst Aquifer, Kentucky},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {179--185},
url = {http://water.usgs.gov/ogw/karst/kigconference/jm_incavedye.htm}
}
|
|||||
| Mellander, P.-E., Jordan, P., Wall, D.P., Melland, A.R., Meehan, R., Kelly, C. and Shortle, G. | Delivery and impact bypass in a karst aquifer with high phosphorus source and pathway potential | 2012 | Water Research Vol. 46(7), pp. 2225-2236 |
article | URL |
| Abstract: Conduit and other karstic flows to aquifers, connecting agricultural soils and farming activities, are considered to be the main hydrological mechanisms that transfer phosphorus from the land surface to the groundwater body of a karstified aquifer. In this study, soil source and pathway components of the phosphorus (P) transfer continuum were defined at a high spatial resolution; field-by-field soil P status and mapping of all surface karst features was undertaken in a > 30 km2 spring contributing zone. Additionally, P delivery and water discharge was monitored in the emergent spring at a sub-hourly basis for over 12 months. Despite moderate to intensive agriculture, varying soil P status with a high proportion of elevated soil P concentrations and a high karstic connectivity potential, background P concentrations in the emergent groundwater were low and indicative of being insufficient to increase the surface water P status of receiving surface waters. However, episodic P transfers via the conduit system increased the P concentrations in the spring during storm events (but not >0.035 mg total reactive P L−1) and this process is similar to other catchments where the predominant transfer is via episodic, surface flow pathways; but with high buffering potential over karst due to delayed and attenuated runoff. These data suggest that the current definitions of risk and vulnerability for P delivery to receiving surface waters should be re-evaluated as high source risk need not necessarily result in a water quality impact. Also, inclusion of conduit flows from sparse water quality data in these systems may over-emphasise their influence on the overall status of the groundwater body. | |||||
BibTeX:
@article{Mellander2012,
author = {Mellander, Per-Erik and Jordan, Phil and Wall, David P. and Melland, Alice R. and Meehan, Robert and Kelly, Coran and Shortle, Ger},
title = {Delivery and impact bypass in a karst aquifer with high phosphorus source and pathway potential},
journal = {Water Research},
year = {2012},
volume = {46},
number = {7},
pages = {2225--2236},
url = {http://www.sciencedirect.com/science/article/pii/S0043135412000802}
}
|
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| Merks, R., Hoekstra, A. and Sloot, P. | The Moment Propagation Method for Advection–Diffusion in the Lattice Boltzmann Method: Validation and Péclet Number Limits | 2002 | Journal of Computational Physics Vol. 183(2), pp. 563-576 |
article | URL |
| Abstract: We numerically validate the moment propagation method for advection–diffusion in a lattice Boltzmann simulation against the analytic Taylor–Aris prediction for dispersion in a three-dimensional Poiseuille flow. Good agreement between simulation and theory is found, with relative errors smaller than 2%. The Péclet number limits on the moment propagation method are studied, and maximum parameter values are obtained. We show that a modification of the moment propagation method allows advection–diffusion simulations with higher Péclet numbers, in particular in the low Reynolds number limit. | |||||
BibTeX:
@article{Merks2002,
author = {Merks, R.M.H. and Hoekstra, A.G. and Sloot, P.M.A.},
title = {The Moment Propagation Method for Advection–Diffusion in the Lattice Boltzmann Method: Validation and Péclet Number Limits},
journal = {Journal of Computational Physics},
year = {2002},
volume = {183},
number = {2},
pages = {563--576},
url = {http://www.sciencedirect.com/science/article/pii/S0021999102972098}
}
|
|||||
| Merritt, W., Letcher, R. and Jakeman, A. | A review of erosion and sediment transport models | 2003 | Environmental Modelling & Software Vol. 18(8-9)The Modelling of Hydrologic Systems, pp. 761-799 |
article | URL |
| Abstract: Information on sediment and nutrient export from catchments and about related erosive processes is required by catchment managers and decision-makers. Many models exist for the consideration of these processes. However, these models differ greatly in terms of their complexity, their inputs and requirements, the processes they represent and the manner in which these processes are represented, the scale of their intended use and the types of output information they provide. This paper reviews several different erosion and sediment and sediment-associated nutrient transport models with regard to these factors. The review of models is limited to those models with explicit considerations of either the sediment generation or transport process. | |||||
BibTeX:
@article{Merritt2003,
author = {Merritt, W.S. and Letcher, R.A. and Jakeman, A.J.},
title = {A review of erosion and sediment transport models},
booktitle = {The Modelling of Hydrologic Systems},
journal = {Environmental Modelling & Software},
year = {2003},
volume = {18},
number = {8-9},
pages = {761--799},
url = {http://www.sciencedirect.com/science/article/pii/S1364815203000781}
}
|
|||||
| Meyer, J.F.C. and Diniz, G.L. | Pollutant dispersion in wetland systems: Mathematical modelling and numerical simulation | 2007 | Ecological Modelling Vol. 200(3-4), pp. 360-370 |
article | URL |
| Abstract: In this paper we present and justify an original use of a diffusive-advective partial differential equation model, its discretization procedures and resulting numerical simulations for the dispersal of pollutants in an air–water system, with distinct behaviours in water and in air. The authors believe that the relevance of the developed work lies in its potential use in practical environmental assessment processes for the definition of both preventive and clean-up strategies. | |||||
BibTeX:
@article{Meyer2007,
author = {Meyer, João Frederico C.A. and Diniz, Geraldo L.},
title = {Pollutant dispersion in wetland systems: Mathematical modelling and numerical simulation},
journal = {Ecological Modelling},
year = {2007},
volume = {200},
number = {3-4},
pages = {360--370},
url = {http://www.sciencedirect.com/science/article/pii/S0304380006003814}
}
|
|||||
| Michael W., R. | On model equations for particle dispersion in inhomogeneous turbulence | 2005 | International Journal of Multiphase Flow Vol. 31(1), pp. 93-114 |
article | URL |
| Abstract: Comparisons are made between the Advection–Diffusion Equation (ADE) approach for particle transport and the two-fluid model approach based on the PDF method. In principle, the ADE approach offers a much simpler way of calculating the inertial deposition of particles in a turbulent boundary layer than that based on the PDF approach. However the ADE equations that have recently been used are only strictly valid for a simple Gaussian process when particle inertia is small. Using a prescribed, but in general non-Gaussian random particle velocity field, it is shown that the net particle mass flux contains a drift term in addition to that from the mean velocity of the particle velocity field, associated with the compressibility of the velocity field. Furthermore the diffusive flux in general depends not only upon the gradient of the mean concentration (true only for a Gaussian random flow field) but also upon higher order derivatives whose relative contribution depends on diffusion coefficients Dijk… etc. These coefficients depend upon the statistical moments associated with random displacements and compressibility of the particle flow field along particle trajectories which in turn depend upon particle inertia. In contrast the PDF approach offers the advantage of using a simple gradient (Gaussian) approximation in particle phase space which can lead to a non-Gaussian spatial dispersion process when particle inertia is important. Conditions based on the particle mean free path are derived for which a simple ADE is appropriate. Some of the features of particle transport in an inhomogeneous turbulent flow are illustrated by examining particle dispersion in a random flow field composed of pairs of counter rotating vortices which has an rms velocity which increase linearly from a stagnation point. | |||||
BibTeX:
@article{MichaelW.2005,
author = {Michael W., Reeks},
title = {On model equations for particle dispersion in inhomogeneous turbulence},
journal = {International Journal of Multiphase Flow},
year = {2005},
volume = {31},
number = {1},
pages = {93--114},
url = {http://www.sciencedirect.com/science/article/pii/S030193220400120X}
}
|
|||||
| Michael, M. | On the timescales characterizing groundwater discharge at springs | 1999 | Journal of Hydrology Vol. 219(1-2), pp. 56-69 |
article | URL |
| Abstract: In some regions, measurements made at springs can be used to study regional hydrogeologic processes, and determine hydraulic and transport properties of aquifers. Here, input–output models, spectral analysis, and time series analysis are used to identify three different timescales characterizing discharge at springs. First, the “hydraulic time scale” depends on the transmissivity of the aquifer and relates long term changes in discharge to long term changes in recharge. The hydraulic time scale will describe, for example, the secular decrease in discharge during a period of drought. A second hydraulic time scale, referred to as the “time lag”, measures the time lag between groundwater recharge (in the studied examples, recharge is snowmelt during the springtime) and the time of peak discharge at the spring. Finally, the “age” or mean residence time of groundwater represents the transport time of tracers and the volume of water in the aquifers. As examples, large discharge springs (typically several m3/s) in the Oregon and California Cascades are studied. These springs are associated with volcanic-hosted fracture-flow systems. | |||||
BibTeX:
@article{Michael1999,
author = {Michael, Manga},
title = {On the timescales characterizing groundwater discharge at springs},
journal = {Journal of Hydrology},
year = {1999},
volume = {219},
number = {1-2},
pages = {56--69},
url = {http://www.sciencedirect.com/science/article/pii/S002216949900044X}
}
|
|||||
| Mikac, I., Fiket, Ž., Terzić, S., Barešić, J., Mikac, N. and Ahel, M. | Chemical indicators of anthropogenic impacts in sediments of the pristine karst lakes | 2011 | Chemosphere Vol. 84(8), pp. 1140-1149 |
article | URL |
| Abstract: The anthropogenic impact on the pristine karst lakes was investigated using combination of specific parameters, including multielemental analysis of major inorganic constituents (Al, K, Fe) and trace metals (Li, Ag, Cd, Sn, Pb, Bi, Cr, Co, Ni, Cu, Zn and Sb), polycyclic aromatic hydrocarbons (PAHs) and anionic surfactants of linear alkylbenzene sulfonate (LAS) type. The study was performed in the Plitvice Lakes National Park, situated in a sparsely populated area of the northwestern Dinarides, central Croatia. Dated cores of recent sediments from the two biggest lakes, Lake Prosce and Lake Kozjak, were analysed for the selected contaminants using highly specific methods, involving inductively coupled plasma mass spectrometry (ICP/MS), gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The concentration of inorganic constituents reflected primarily the geological background of the area as well as geomorphological and geochemical characteristics of the Plitvice Lakes. Due to the higher terrigenous input, the concentration of all elements was significantly higher in the Lake Prosce. The concentration of toxic metals was relatively low in both lakes, except for Cd (>1 mg kg−1) and Pb (up to 40 mg kg−1). The vertical profiles of these metals suggested that elevated concentrations of Cd were of natural origin, derived from the erosion of the Jurassic dolomite bedrock, while Pb was predominately of recent anthropogenic origin. A similar distribution pattern, suggesting the same prevailing mechanism of input, was observed for pyrolytic PAHs. The characteristic diagnostic PAH ratios revealed that higher PAHs prevailingly originated from the combustion of biomass and fossil fuels. LAS, which represent highly specific indicators of untreated wastewaters, were found in rather high concentrations in the recent sediment layers (up to 4.7 mg kg−1), suggesting that contaminated household and hotel wastewaters reach the Lakes, very probably by leaking through the porous karst rocks. | |||||
BibTeX:
@article{Mikac2011,
author = {Mikac, I. and Fiket, Ž. and Terzić, S. and Barešić, J. and Mikac, N. and Ahel, M.},
title = {Chemical indicators of anthropogenic impacts in sediments of the pristine karst lakes},
journal = {Chemosphere},
year = {2011},
volume = {84},
number = {8},
pages = {1140--1149},
url = {http://www.sciencedirect.com/science/article/pii/S0045653511004188}
}
|
|||||
| Mikutta, R., Mikutta, C., Kalbitz, K., Scheel, T., Kaiser, K. and Jahn, R. | Biodegradation of forest floor organic matter bound to minerals via different binding mechanisms | 2007 | Geochimica et Cosmochimica Acta Vol. 71(10), pp. 2569-2590 |
article | URL |
| Abstract: Mineral-associated organic matter (OM) represents a large reservoir of organic carbon (OC) in natural environments. The factors controlling the extent of the mineral-mediated OC stabilization, however, are poorly understood. The protection of OM against biodegradation upon sorption to mineral phases is assumed to result from the formation of strong bonds that limit desorption. To test this, we studied the biodegradation of OM bound to goethite (α-FeOOH), pyrophyllite, and vermiculite via specific mechanisms as estimated from OC uptake in different background electrolytes and operationally defined as ‘ligand exchange’, ‘Ca2+ bridging’, and ‘van der Waals forces’. Organic matter extracted from an Oa forest floor horizon under Norway spruce (Picea abies (L.) Karst) was reacted with minerals at dissolved OC concentrations of ∼5–130 mg/L at pH 4. Goethite retained up to 30.1 mg OC/g predominantly by ‘ligand exchange’; pyrophyllite sorbed maximally 12.5 mg OC/g, largely via ‘van der Waals forces’ and ‘Ca2+ bridging’, while sorption of OM to vermiculite was 7.3 mg OC/g, mainly due to the formation of ‘Ca2+ bridges’. Aromatic OM components were selectively sorbed by all minerals (goethite ≫ phyllosilicates). The sorption of OM was strongly hysteretic with the desorption into 0.01 M NaCl being larger for OM held by ‘Ca2+ bridges’ and ‘van der Waals forces’ than by ‘ligand exchange’. Incubation experiments under aerobic conditions (initial pH 4; 90 days) revealed that OM mainly bound to minerals by ‘ligand exchange’ was more resistant against mineralization than OM held by non-columbic interactions (‘van der Waals forces’). Calcium bridges enhanced the stability of sorbed OM, especially for vermiculite, but less than the binding via ‘ligand exchange’. Combined evidence suggests that the extent and rate of mineralization of mineral-associated OM are governed by desorption. The intrinsic stability of sorbed OM as related to the presence of resistant, lignin-derived aromatic components appears less decisive for the sorptive stabilization of OM than the involved binding mechanisms. In a given environment, the type of minerals present and the solution chemistry determine the operating binding mechanisms, thereby the extent of OM sorption and desorption, and thus ultimately the bioavailability of mineral-associated OM. | |||||
BibTeX:
@article{Mikutta2007,
author = {Mikutta, Robert and Mikutta, Christian and Kalbitz, Karsten and Scheel, Thorsten and Kaiser, Klaus and Jahn, Reinhold},
title = {Biodegradation of forest floor organic matter bound to minerals via different binding mechanisms},
journal = {Geochimica et Cosmochimica Acta},
year = {2007},
volume = {71},
number = {10},
pages = {2569--2590},
url = {http://www.sciencedirect.com/science/article/pii/S001670370700124X}
}
|
|||||
| Miller, C.T., Christakos, G., Imhoff, P.T., McBride, J.F., Pedit, J.A. and Trangenstein, J.A. | Multiphase flow and transport modeling in heterogeneous porous media: challenges and approaches | 1998 | Advances in Water Resources Vol. 21(2)Multiphase Flow and Chemical Transport, pp. 77-120 |
article | URL |
| Abstract: We review the current status of modeling multiphase systems, including balance equation formulation, constitutive relations for both pressure-saturation-conductivity and interphase mass transfer, and stochastic and computational issues. We discuss weaknesses and inconsistencies of current approaches based on theoretical, computational, and experimental evidence. Where possible, we suggest new or evolving approaches. | |||||
BibTeX:
@article{Miller1998,
author = {Miller, Cass T. and Christakos, George and Imhoff, Paul T. and McBride, John F. and Pedit, Joseph A. and Trangenstein, John A.},
title = {Multiphase flow and transport modeling in heterogeneous porous media: challenges and approaches},
booktitle = {Multiphase Flow and Chemical Transport},
journal = {Advances in Water Resources},
year = {1998},
volume = {21},
number = {2},
pages = {77--120},
url = {http://www.sciencedirect.com/science/article/pii/S030917089600036X}
}
|
|||||
| Mimi, Z.A. and Assi, A. | Intrinsic vulnerability, hazard and risk mapping for karst aquifers: A case study | 2009 | Journal of Hydrology Vol. 364(3-4), pp. 298-310 |
article | URL |
| Abstract: Groundwater from karst aquifers is among the most important resources of drinking water supply of the worldwide population. The European COST action 620 proposed a comprehensive approach to karst groundwater protection, comprising methods of intrinsic and specific vulnerability mapping, hazard and risk mapping. This paper presents the first application of all components of this European approach to the groundwater underlying the Ramallah district, a karst hydrogeology system in Palestine. The vulnerability maps which were developed can assist in the implementation of groundwater management strategies to prevent degradation of groundwater quality. Large areas in the case study area can be classified as low or very low risk area corresponding to the pollution sources due to the absence of hazards and also due to low vulnerabilities. These areas could consequently be interesting for future development as they are preferable in view of ground water protection. | |||||
BibTeX:
@article{Mimi2009,
author = {Mimi, Ziad A. and Assi, Amjad},
title = {Intrinsic vulnerability, hazard and risk mapping for karst aquifers: A case study},
journal = {Journal of Hydrology},
year = {2009},
volume = {364},
number = {3-4},
pages = {298--310},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408005489}
}
|
|||||
| Minye, L. | A method for computing the degree of mixing in steady continuous flow systems | 2011 | Chemical Engineering Science Vol. 66(13), pp. 3045-3048 |
article | URL |
| Abstract: The degree of mixing was first proposed by Danckwerts and further discussed by Zwietering more than 50 years ago to measure mixing performance of a continuous flow system. Although the measure has been widely discussed in mixing literature, there has never been a method to compute its value for a general continuous flow. In this paper, a method is developed to compute this measure for a general steady continuous flow system for the first time. The method is based on the recently developed mean age theory. The governing equations for the mean age and higher moments of age are also derived for different types of tracer introduction other than pulse input in the current mean age theory. | |||||
BibTeX:
@article{Minye2011,
author = {Minye, Liu},
title = {A method for computing the degree of mixing in steady continuous flow systems},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {13},
pages = {3045--3048},
url = {http://www.sciencedirect.com/science/article/pii/S0009250911002211}
}
|
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| Miralles-Wilhelm, F. and Gelhar, L.W. | Stochastic analysis of oxygen-limited biodegradation in heterogeneous aquifers with transient microbial dynamics | 2000 | Journal of Contaminant Hydrology Vol. 42(1), pp. 69-97 |
article | URL |
| Abstract: A stochastic theory of multiple species transport and transformation is developed for the problem of oxygen-limited biodegradation of contaminants in aquifers, considering the presence of transient microbial growth dynamics. The theory incorporates the effects of physical, chemical and microbiological heterogeneities into a stochastic analysis of the coupled transport/transformation equations for a system consisting of a contaminant, an oxidizer, i.e., dissolved oxygen, and active biomass in heterogeneous and anisotropic aquifers. The developed theory is used to quantify the effects of mean concentrations on the field scale coefficients of decay, retardation and macrodispersion, and to evaluate the assumption of a steady-state biomass, previously reported in the literature. A comparison between the steady state assumption [Miralles-Wilhelm, F., Gelhar, L.W., Kapoor, V., 1997. Stochastic analysis of oxygen-limited biodegration in three dimensionally in heterogeneous aquifers. Water Resources Research, 33 (6)] and this work for hypothesized field conditions shows that the effects of transient microbial growth on the effective retardation factor and macrodispersivities are minor, while the effects are modest for the effective decay rate. Transient microbial growth dynamics are found to occur over most contaminant and dissolved oxygen mean concentration ranges, and therefore a transient mean balance equation for biomass should be included in modeling efforts directed at quantifying oxygen-limited biodegradation at field scales. As in previous research, the effective decay rate is found to be less than the mean, which results in a larger field scale contaminant half-life in a heterogenous aquifer, compared to that in a homogeneous aquifer. | |||||
BibTeX:
@article{Miralles-Wilhelm2000,
author = {Miralles-Wilhelm, Fernando and Gelhar, Lynn W.},
title = {Stochastic analysis of oxygen-limited biodegradation in heterogeneous aquifers with transient microbial dynamics},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {42},
number = {1},
pages = {69--97},
url = {http://www.sciencedirect.com/science/article/pii/S0169772299000704}
}
|
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| Mitra, A. | Minimum absolute deviation estimation in regression analysis | 1987 | Computers & Industrial Engineering Vol. 12(1), pp. 67-76 |
article | URL |
| Abstract: The use of ordinary least squares estimators (OLS) in regression analysis is widespread. The OLS estimates are, however, very sensitive to the presence of large disturbances. As an alternative to the OLS estimator, the minimum absolute deviation estimator (MAD) is studied. The purpose of this study is, first, to determine the effect of error distributions, with progressively heavier tails starting from the normal distribution and ending with the Cauchy distribution, on the performance of the MAD estimates and the OLS estimates. This provides a framework for when to choose the MAD estimator over the OLS estimator. Second, the effect of some of the other parameters in regression analysis, namely, the unknown parameter vector, the multicollinearity between the independent variables, and the size of the sample on the relative performance of the MAD and OLS estimators is investigated. Some guidelines regarding the choice of the MAD estimator in regression analysis are provided. | |||||
BibTeX:
@article{Mitra1987,
author = {Mitra, Amitava},
title = {Minimum absolute deviation estimation in regression analysis},
journal = {Computers & Industrial Engineering},
year = {1987},
volume = {12},
number = {1},
pages = {67--76},
url = {http://www.sciencedirect.com/science/article/pii/0360835287900258}
}
|
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| Mitsutani, K., Grace, J. and Lim, C. | Residence time distribution of particles in a continuous liquid–solid classifier | 2005 | Chemical Engineering Science Vol. 60(10), pp. 2703-2713 |
article | URL |
| Abstract: Experiments were carried out in a continuous classification column of diameter 191 mm and height 1.47 m with water as the liquid and glass beads as the particles. Initial experiments were carried out with narrowly sized particles and somewhat larger tracer particles which could be separated by screening. The main experiments involved a wide distribution of particle sizes, with injected pulses of tracer particles of slightly higher density separated from samples using an organic liquid of intermediate density. The results show that the mixing behaviour is intermediate between plug flow and perfect mixing. Increasing the discharge rate of underflow product stream decreased both the mean residence time and the degree of classification significantly. At relatively low voidage, small particles settled more quickly and large particles more slowly than predicted on the basis of the approach proposed by Lockett and Al-Habbooby (Trans. Inst. Chem. Eng. 51(1973) 281–292) where each particle fraction is assumed to travel as if it were alone in a suspension of the overall solids concentration. | |||||
BibTeX:
@article{Mitsutani2005,
author = {Mitsutani, K. and Grace, J.R. and Lim, C.J.},
title = {Residence time distribution of particles in a continuous liquid–solid classifier},
journal = {Chemical Engineering Science},
year = {2005},
volume = {60},
number = {10},
pages = {2703--2713},
url = {http://www.sciencedirect.com/science/article/pii/S0009250904009212}
}
|
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| Modarres, R., Nayak, T.K. and Gastwirth, J.L. | Estimation of upper quantiles under model and parameter uncertainty | 2002 | Computational Statistics & Data Analysis Vol. 39(4), pp. 529-554 |
article | URL |
| Abstract: In this paper we assess accuracy of some commonly used estimators of upper quantiles of a right skewed distribution under both parameter and model uncertainty. In particular, for each of log-normal, log-logistic, and log-double exponential distributions, we study the bias and mean squared error of the maximum likelihood estimator (MLE) of the upper quantiles under both the correct and incorrect model specifications. We also consider two data dependent or adaptive estimators. The first (tail-exponential) is based on fitting an exponential distribution to the highest 10–20 percent of the data. The second selects the best fitting likelihood-based model and uses the MLE obtained from that model. The simulation results provide some practical guidance concerning the estimation of the upper quantiles when one is uncertain about the underlying model. We found that the consequences of assuming log-normality when the true distribution is log-logistic or log-double exponential are not severe in moderate sample sizes. For extreme quantiles, no estimator was reliable in small samples. For large sample sizes the selection estimator performs fairly well. For small sample sizes the tail-exponential method is a good alternative. Presenting it and the MLE for the log-normal enables one to assess the potential effects of model uncertainty. | |||||
BibTeX:
@article{Modarres2002,
author = {Modarres, Reza and Nayak, Tapan K. and Gastwirth, Joseph L.},
title = {Estimation of upper quantiles under model and parameter uncertainty},
journal = {Computational Statistics & Data Analysis},
year = {2002},
volume = {39},
number = {4},
pages = {529--554},
url = {http://www.sciencedirect.com/science/article/pii/S0167947301000949}
}
|
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| Mohamed, M., Hatfield, K., Hassan, A. and Klammler, H. | Stochastic evaluation of subsurface contaminant discharges under physical, chemical, and biological heterogeneities | 2010 | Advances in Water Resources Vol. 33(7), pp. 801-812 |
article | URL |
| Abstract: A finite element 2D Monte Carlo approach is used to evaluate the sensitivity of groundwater contaminant discharges to a Damkohler number ω and spatial variability in aquifer hydraulic conductivity, initial microbial biomass concentrations, and electron acceptor/donor concentrations. Bioattenuation is most sensitive to spatial variations in incipient biomass and critical electron donors/acceptors for ω ≥ 1 (i.e., when pore-water residence times are high compared to the time needed for microbial growth or contaminant attenuation). Under these conditions, critical reaction processes can become substrate-limited at multiple locations throughout the aquifer; which in turn increases expected contaminant discharges and their uncertainties at monitored transects. For ω ≤ 0.2, contaminant discharge is not sensitive to incipient biomass variations. Physical heterogeneities expedite plume arrival and delay departure at transects and in turn attenuate peak discharges but do not affect cumulative contaminant discharges. Physical heterogeneities do, however, induce transect mass discharge variances that are bimodal functions of time; the first peak beings consistently higher. A simple stream tube model is invoked to explain the occurrence of peaks in contaminant discharge variance. | |||||
BibTeX:
@article{Mohamed2010,
author = {Mohamed, M. and Hatfield, K. and Hassan, A. and Klammler, H.},
title = {Stochastic evaluation of subsurface contaminant discharges under physical, chemical, and biological heterogeneities},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {7},
pages = {801--812},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810000825}
}
|
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| Mohamed, M., Hatfield, K. and Perminova, I. | Evaluation of Monod kinetic parameters in the subsurface using moment analysis: Theory and numerical testing | 2007 | Advances in Water Resources Vol. 30(9), pp. 2034-2050 |
article | URL |
| Abstract: The spatial moments of a contaminant plume undergoing bio-attenuation are coupled to the moments of microbial populations effecting that attenuation. In this paper, a scalable inverse method is developed for estimating field-scale Monod parameters such as the maximum microbial growth rate (μmax), the contaminant half saturation coefficient (Ks), and the contaminant yield coefficient (Ys). The method uses spatial moments that characterize the distribution of dissolved contaminant and active microbial biomass in the aquifer. A finite element model is used to generate hypothetical field-scale data to test the method under both homogeneous and heterogeneous aquifer conditions. Two general cases are examined. In the first, Monod parameters are estimated where it is assumed a microbial population comprised of a single bacterial species is attenuating one contaminant (e.g., an electron donor and an electron acceptor). In a second case, contaminant attenuation is attributed to a microbial consortium comprised of two microbial species, and Monod parameters for both species are estimated. Results indicate the inverse method is only slightly sensitive to aquifer heterogeneity and that estimation errors decrease as the sampling time interval decreases with respect to the groundwater travel time between sample locations. Optimum conditions for applying the scalable inverse method in both space and time are investigated under both homogeneous and heterogeneous aquifer conditions. | |||||
BibTeX:
@article{Mohamed2007,
author = {Mohamed, M. and Hatfield, K. and Perminova, I.V.},
title = {Evaluation of Monod kinetic parameters in the subsurface using moment analysis: Theory and numerical testing},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {9},
pages = {2034--2050},
url = {http://www.sciencedirect.com/science/article/pii/S0309170807000723}
}
|
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| Molinero, J., Raposo, J.R., Galíndez, J.M., Arcos, D. and Guimerá, J. | Coupled hydrogeological and reactive transport modelling of the Simpevarp area (Sweden) | 2008 | Applied Geochemistry Vol. 23(7)High-level radioactive waste disposal in Sweden: Hydrogeochemical characterisation and modelling of two potential sites, pp. 1957-1981 |
article | URL |
| Abstract: The Simpevarp area is one of the alternative sites being considered for the deep geological disposal of high level radioactive waste in Sweden. In this paper, a coupled regional groundwater flow and reactive solute transport model of the Simpevarp area is presented that integrates current hydrogeological and hydrochemical data of the area. The model simulates the current hydrochemical pattern of the groundwater system in the area. To that aim, a conceptual hydrochemical model was developed in order to represent the dominant chemical processes. Groundwater flow conditions were reproduced by taking into account fluid-density-dependent groundwater flow and regional hydrogeologic boundary conditions. Reactive solute transport calculations were performed on the basis of the velocity field so obtained. The model was calibrated and sensitivity analyses were carried out in order to investigate the effects of heterogeneities of hydraulic conductivity in the subsurface medium. Results provided by the reactive transport model are in good agreement with much of the measured hydrochemical data. This paper emphasizes the appropriateness of the use of reactive solute transport models when water-rock interaction reactions are involved, and demonstrates what powerful tools they are for the interpretation of hydrogeological and hydrochemical data from site geological repository characterization programs, by providing a qualitative framework for data analysis and testing of conceptual assumptions in a process-oriented approach. | |||||
BibTeX:
@article{Molinero2008,
author = {Molinero, Jorge and Raposo, Juan R. and Galíndez, Juan M. and Arcos, David and Guimerá, Jordi},
title = {Coupled hydrogeological and reactive transport modelling of the Simpevarp area (Sweden)},
booktitle = {High-level radioactive waste disposal in Sweden: Hydrogeochemical characterisation and modelling of two potential sites},
journal = {Applied Geochemistry},
year = {2008},
volume = {23},
number = {7},
pages = {1957--1981},
url = {http://www.sciencedirect.com/science/article/pii/S088329270800084X}
}
|
|||||
| Molson, J. and Frind, E. | On the use of mean groundwater age, life expectancy and capture probability for defining aquifer vulnerability and time-of-travel zones for source water protection | 2012 | Journal of Contaminant Hydrology Vol. 127(1-4)GQ10: Groundwater Quality Management in a Rapidly Changing World, pp. 76-87 |
article | URL |
| Abstract: Protection and sustainability of water supply wells requires the assessment of vulnerability to contamination and the delineation of well capture zones. Capture zones, or more generally, time-of-travel zones corresponding to specific contaminant travel times, are most commonly delineated using advective particle tracking. More recently, the capture probability approach has been used in which a probability of capture of P = 1 is assigned to the well and the growth of a probability-of-capture plume is tracked backward in time using an advective–dispersive transport model. This approach accounts for uncertainty due to local-scale heterogeneities through the use of macrodispersion. In this paper, we develop an alternative approach to capture zone delineation by applying the concept of mean life expectancy E (time remaining before being captured by the well), and we show how life expectancy E is related to capture probability P. Either approach can be used to delineate time-of-travel zones corresponding to specific travel times, as well as the ultimate capture zone. The related concept of mean groundwater age A (time since recharge) can also be applied in the context of defining the vulnerability of a pumped aquifer. In the same way as capture probability, mean life expectancy and groundwater age account for local-scale uncertainty or unresolved heterogeneities through macrodispersion, which standard particle tracking neglects. The approach is tested on 2D and 3D idealized systems, as well as on several watershed-scale well fields within the Regional Municipality of Waterloo, Ontario, Canada. | |||||
BibTeX:
@article{Molson2012,
author = {Molson, J.W. and Frind, E.O.},
title = {On the use of mean groundwater age, life expectancy and capture probability for defining aquifer vulnerability and time-of-travel zones for source water protection},
booktitle = {GQ10: Groundwater Quality Management in a Rapidly Changing World},
journal = {Journal of Contaminant Hydrology},
year = {2012},
volume = {127},
number = {1--4},
pages = {76--87},
url = {http://www.sciencedirect.com/science/article/pii/S0169772211000611}
}
|
|||||
| Molson, J., Frind, E., Van Stempvoort, D. and Lesage, S. | Humic acid enhanced remediation of an emplaced diesel source in groundwater: 2. Numerical model development and application | 2002 | Journal of Contaminant Hydrology Vol. 54(3-4), pp. 277-305 |
article | URL |
| Abstract: A pilot scale experiment for humic acid-enhanced remediation of diesel fuel, described in Part 1 of this series, is numerically simulated in three dimensions. Groundwater flow, enhanced solubilization of the diesel source, and reactive transport of the dissolved contaminants and humic acid carrier are solved with a finite element Galerkin approach. The model (BIONAPL) is calibrated by comparing observed and simulated concentrations of seven diesel fuel components (BTEX and methyl-, dimethyl- and trimethylnaphthalene) over a 1500-day monitoring period. Data from supporting bench scale tests were used to estimate contaminant-carrier binding coefficients and to simulate two-site sorption of the carrier to the aquifer sand. The model accurately reproduced the humic acid-induced 10-fold increase in apparent solubility of trimethylnaphthalene. Solubility increases on the order of 2–5 were simulated for methylnaphthalene and dimethylnaphthalene, respectively. Under the experimental and simulated conditions, the residual 500-ml diesel source was almost completely dissolved and degraded within 5 years. Without humic acid flushing, the simulations show complete source dissolution would take about six times longer. | |||||
BibTeX:
@article{Molson2002,
author = {Molson, J.W. and Frind, E.O. and Van Stempvoort, D.R. and Lesage, S.},
title = {Humic acid enhanced remediation of an emplaced diesel source in groundwater: 2. Numerical model development and application},
journal = {Journal of Contaminant Hydrology},
year = {2002},
volume = {54},
number = {3-4},
pages = {277--305},
url = {http://www.sciencedirect.com/science/article/pii/S0169772201001814}
}
|
|||||
| Moltyaner, G. | Mixing cup and through-the-wall measurements in field-scale tracer tests and their related scales of averaging | 1987 | Journal of Hydrology Vol. 89(3-4), pp. 281-302 |
article | URL |
| Abstract: Methods and scales of averaging associated with the sampling devices used in field-tracer experiments are critically important in the assessment of dispersive properties of aquifers. In this paper the importance is illustrated on the basis of experimental data obtained from two naturalgradient dispersion tests performed at Chalk River, Ontario. | |||||
BibTeX:
@article{Moltyaner1987,
author = {Moltyaner, G.L.},
title = {Mixing cup and through-the-wall measurements in field-scale tracer tests and their related scales of averaging},
journal = {Journal of Hydrology},
year = {1987},
volume = {89},
number = {3-4},
pages = {281--302},
url = {http://www.sciencedirect.com/science/article/pii/0022169487901831}
}
|
|||||
| Mondesir, S. and Byl, T.D. | Bacteria Induced Dissolution of Limestone in Fuel-Contaminated Karst Wells | 2005 | U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160, pp. 192 | inproceedings | URL |
| Abstract: Karst landscapes are formed in water-soluble geologic formations, such as limestone, in which disso- lution processes have enlarged water-transmitting openings. Approximately 20 percent of the United States is underlain by carbonate rocks and is classified as karst, and 40 percent of the United States east of the Mis- sissippi River is underlain by karst aquifers. Karst ground-water systems are extremely vulnerable to con- tamination. Many organic contaminants such as fuels can stimulate bacteria biodegradation and the production of carbon dioxide (CO2). The increased respiration by bacteria in contaminated karsts aquifers can lead to a significant increase in CO2 production and formation of carbonic acid. A quantitative study was conducted to determine the effect of elevated concentrations of carbonic acid due to bacteria action on limestone dissolution. Sealed flasks were set up that contained 250 milliliters of distilled water, limestone fragments of known size and weight, and varying concentrations of CO2. The flasks with elevated CO2 concentration had a 3-fold increase in the rate of calcium carbonate dissolution. Water with elevated CO2 concentrations had a slightly lower pH than water with the lower CO2 concentra- tions, but the difference in pH was not statistically significant at the 0.05 confidence level. Further tests were done to determine if these lab results applied to field conditions. Water samples were collected from wells completed in karst aquifers. The CO2 concentrations in water samples collected from fuel-contami- nated wells were higher than in samples collected from wells with no fuel contamination. Also, the dis- solved calcium was usually two or three times greater in the fuel-contaminated wells. The results have implications for redesigning geochemical models that predict conduit enlargement when fuel contaminants are present in karst aquifers. | |||||
BibTeX:
@inproceedings{Mondesir2005,
author = {Mondesir, Serge and Byl, T. D.},
title = {Bacteria Induced Dissolution of Limestone in Fuel-Contaminated Karst Wells},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2005},
pages = {192},
url = {pubs.usgs.gov/sir/2005/5160/index.html}
}
|
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| Mongelli, F. and Pagliarulo, P. | Influence of water recharge on heat transfer in a semi-infinite aquifer | 1997 | Geothermics Vol. 26(3), pp. 365-378 |
article | URL |
| Abstract: A simple model is proposed for the temperature field within an unconfined semi-infinite thick aquifer, with groundwater flowing parallel to the terrestrial heat flow in the recharge zone, and perpendicular to heat flow in the other parts of the aquifer. The results enable evaluation of the extent of the influence of the recharge zone, once the thermal and hydrological parameters are known. Beyond this zone, where thermal equilibrium between water and rock is reached, water temperature reaches the constant highest value, and water movement cannot be revealed by temperature measurements. Moreover, over,on the basis of the range of influence of the recharge zone, the regional water pore velocity can be inferred. | |||||
BibTeX:
@article{Mongelli1997,
author = {Mongelli, Francesco and Pagliarulo, Pietro},
title = {Influence of water recharge on heat transfer in a semi-infinite aquifer},
journal = {Geothermics},
year = {1997},
volume = {26},
number = {3},
pages = {365--378},
url = {http://www.sciencedirect.com/science/article/pii/S037565059600048X}
}
|
|||||
| Mooley, D.A. | Gamma Distribution Probability Model for Asian Summer Monsoon Monthly Rainfall | 1973 | Monthly Weather Review Vol. 101(2), pp. 160-176 |
article | URL |
| Abstract: Using data from 39 well-distributed and long-record stations over the area, we found gamma distribution to be the most suitable probability model from among the Pearsonian models that show good fit to monthly rainfall in the Asian summer monsoon. We show that the monthly rainfall distribution is not Gaussian and the simple square-root, cube-root, and logarithmic transformations are of limited utility for normalizing the rainfall distribution. A Craig type chart indicates that the rainfall distribution is a Type I distribution or a special or limiting case of this distribution; these distributions are fitted to monthly rainfall, and the goodness-of-fit is tested by the chi-square test. The gamma distribution (Pearson's Type III), which is a limiting case of Type I distribution and next, to the Gaussian distribution in simplicity, gives a good fit to monthly rainfall at all the stations in each of the summer monsoon months; the Kolmogorov-Smirnov test and the variance ratio test confirm this good fit. The Type I distribution shows good fit to June rainfall at 26 stations, July rainfall at 31 stations, August rainfall at 24 stations, and September rainfall at 23 stations. Type IX, a special case of Type I, shows good fit to June rainfall at four stations, July rainfall at two stations, August rainfall at four stations, and September rainfall at three stations. In cases where the gamma and other Pearsonian distributions show good fit, the gamma distribution is found to be the most suitable. The spatial distribution of the scale and shape parameters of the gamma distribution applied to monthly rainfall over the area is examined and the chief features of the distribution are indicated and explained. Deciles of the mixed gamma distribution applied to monthly rainfall are tabulated; these can be used to obtain the monthly rainfall probabilities required by any user. |
|||||
BibTeX:
@article{Mooley1973,
author = {Mooley, Diwakar A.},
title = {Gamma Distribution Probability Model for Asian Summer Monsoon Monthly Rainfall},
journal = {Monthly Weather Review},
publisher = {American Meteorological Society},
year = {1973},
volume = {101},
number = {2},
pages = {160--176},
url = {http://dx.doi.org/10.1175/1520-0493(1973)101<0160:GDPMFA>2.3.CO;2}
}
|
|||||
| Moon, H., Chang, I.S., Jang, J.K. and Kim, B.H. | Residence time distribution in microbial fuel cell and its influence on COD removal with electricity generation | 2005 | Biochemical Engineering Journal Vol. 27(1), pp. 59-65 |
article | URL |
| Abstract: The liquid flow characteristics in a microbial fuel cell (MFC) were determined using a residence time distribution (RTD) test, and its effects on the performance of the MFC were investigated in terms of electricity generation and chemical oxygen demand (COD) removal. A membrane-less MFC was used with two different anode structures; normal graphite felt disk (“Normal” MFC) and perforated graphite felt disk (“Perforated” MFC). The RTD results showed that there exists nonideal flows such as channeling and tailing in the “Normal” MFC and the flow characteristics were much better in the “Perforated” MFC with the improved electricity generation. COD removal rate was similar between the MFCs. These results show that the flow characterization is an important area of study for the optimization of an MFC. | |||||
BibTeX:
@article{Moon2005,
author = {Moon, Hyunsoo and Chang, In Seop and Jang, Jae Kyung and Kim, Byung Hong},
title = {Residence time distribution in microbial fuel cell and its influence on COD removal with electricity generation},
journal = {Biochemical Engineering Journal},
year = {2005},
volume = {27},
number = {1},
pages = {59--65},
url = {http://www.sciencedirect.com/science/article/pii/S1369703X05000513}
}
|
|||||
| Moon, Y. and Yao, T. | A robust mean absolute deviation model for portfolio optimization | 2011 | Computers & Operations Research Vol. 38(9), pp. 1251-1258 |
article | URL |
| Abstract: In this paper we develop a robust model for portfolio optimization. The purpose is to consider parameter uncertainty by controlling the impact of estimation errors on the portfolio strategy performance. We construct a simple robust mean absolute deviation (RMAD) model which leads to a linear program and reduces computational complexity of existing robust portfolio optimization methods. This paper tests the robust strategies on real market data and discusses performance of the robust optimization model empirically based on financial elasticity, standard deviation, and market condition such as growth, steady state, and decline in trend. Our study shows that the proposed robust optimization generally outperforms a nominal mean absolute deviation model. We also suggest precautions against use of robust optimization under certain circumstances. | |||||
BibTeX:
@article{Moon2011,
author = {Moon, Yongma and Yao, Tao},
title = {A robust mean absolute deviation model for portfolio optimization},
journal = {Computers & Operations Research},
year = {2011},
volume = {38},
number = {9},
pages = {1251--1258},
url = {http://www.sciencedirect.com/science/article/pii/S0305054810002492}
}
|
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| Moore, M., Schulz, R., Cooper, C., Smith Jr., S. and Rodgers Jr., J. | Mitigation of chlorpyrifos runoff using constructed wetlands | 2002 | Chemosphere Vol. 46(6), pp. 827-835 |
article | URL |
| Abstract: Constructed wetlands have been proposed as a potential best management practice (BMP) to mitigate effects of pesticide-associated agricultural runoff. Wetland mesocosms (14 m×59–73 m) were amended with chlorpyrifos to simulate a storm runoff event at concentrations of 73, 147 and 733 μg/l. Water, sediment and plant samples collected weekly for 12 weeks indicated that chlorpyrifos rapidly sorbed to sediment and plant material, with approximately 47–65% of measured chlorpyrifos mass retained within the first 30–36 m of wetland mesocosms. Of the measured mass, approximately 55% and 25% were retained by sediments and plants, respectively. A field-scale evaluation of a constructed wetland's mitigation capability was performed in the Lourens River watershed of Cape Town, South Africa. Results indicate that the wetland was able to retain and considerably decrease the concentration (and hence toxicity) of chlorpyrifos and suspended sediment entering the receiving waterbody (Lourens River). This research provides fundamental answers concerning constructed wetland capabilities that are necessary for constructing field-scale systems within agricultural watersheds. | |||||
BibTeX:
@article{Moore2002,
author = {Moore, M.T and Schulz, R and Cooper, C.M and Smith Jr., S and Rodgers Jr., J.H},
title = {Mitigation of chlorpyrifos runoff using constructed wetlands},
journal = {Chemosphere},
year = {2002},
volume = {46},
number = {6},
pages = {827--835},
url = {http://www.sciencedirect.com/science/article/pii/S0045653501001898}
}
|
|||||
| Moore, P.J., Martin, J.B. and Screaton, E.J. | Geochemical and statistical evidence of recharge, mixing, and controls on spring discharge in an eogenetic karst aquifer | 2009 | Journal of Hydrology Vol. 376(3-4), pp. 443-455 |
article | URL |
| Abstract: Information about sources of recharge, distributions of flow paths, and the extent of water–rock reactions in karst aquifers commonly result from monitoring spring chemistry and discharge. To investigate the relationship between spring characteristics and the complexities of karst aquifers, we couple variations in surface- and groundwater chemistry to physical conditions including river stage, precipitation, and evapotranspiration (ET) within a sink-rise system through a 6-km portion of the Upper Floridan aquifer (UFA) in north-central Florida. Principal component analysis (PCA) of time series major-element compositions suggests that at least three sources of water affect spring discharge, including allogenic recharge into a swallet, diffuse recharge through a thin vadose zone, and water upwelling from deep within the aquifer. The deep-water source exerts the strongest influence on water chemistry by providing a majority of Na+, Mg2+, K+, Cl−, and SO 4 2 - to the system. Anomalously high temperature at one of several monitoring wells reflects vertical flow of about 1 m/year. Mass-balance calculations suggest diffuse recharge and deep-water upwelling can provide up to 50% of the spring discharge; however, their contributions depend on head gradients between the conduit and surrounding aquifer matrix, which are influenced by variations in precipitation, ET, and river stage. Our results indicate that upwelling from deep flow paths may provide significant contributions of water to spring discharge, and that monitoring only springs limits interpretations of karst systems by masking critical components of the aquifer, such as water sources and flow paths. These results also suggest the matrix in eogenetic aquifers is a major pathway for flow even in a system dominated by conduits. | |||||
BibTeX:
@article{Moore2009,
author = {Moore, Paul J. and Martin, Jonathan B. and Screaton, Elizabeth J.},
title = {Geochemical and statistical evidence of recharge, mixing, and controls on spring discharge in an eogenetic karst aquifer},
journal = {Journal of Hydrology},
year = {2009},
volume = {376},
number = {3-4},
pages = {443--455},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409004545}
}
|
|||||
| Moore, P.J., Martin, J.B., Screaton, E.J. and Neuhoff, P.S. | Conduit enlargement in an eogenetic karst aquifer | 2010 | Journal of Hydrology Vol. 393(3-4), pp. 143-155 |
article | URL |
| Abstract: Most concepts of conduit development have focused on telogenetic karst aquifers, where low matrix permeability focuses flow and dissolution along joints, fractures, and bedding planes. However, conduits also exist in eogenetic karst aquifers, despite high matrix permeability which accounts for a significant component of flow. This study investigates dissolution within a 6-km long conduit system in the eogenetic Upper Floridan aquifer of north-central Florida that begins with a continuous source of allogenic recharge at the Santa Fe River Sink and discharges from a first-magnitude spring at the Santa Fe River Rise. Three sources of water to the conduit include the allogenic recharge, diffuse recharge through epikarst, and mineralized water upwelling from depth. Results of sampling and inverse modeling using PHREEQC suggest that dissolution within the conduit is episodic, occurring only during 30% of 16 sampling times between March 2003 and April 2007. During low flow conditions, carbonate saturated water flows from the matrix to the conduit, restricting contact between undersaturated allogenic water with the conduit wall. When gradients reverse during high flow conditions, undersaturated allogenic recharge enters the matrix. During these limited periods, estimates of dissolution within the conduit suggest wall retreat averages about 4 × 10−6 m/day, in agreement with upper estimates of maximum wall retreat for telogenetic karst. Because dissolution is episodic, time-averaged dissolution rates in the sink-rise system results in a wall retreat rate of about 7 × 10−7 m/day, which is at the lower end of wall retreat for telogenetic karst. Because of the high permeability matrix, conduits in eogenetic karst thus enlarge not just at the walls of fractures or pre-existing conduits such as those in telogenetic karst, but also may produce a friable halo surrounding the conduits that may be removed by additional mechanical processes. These observations stress the importance of matrix permeability in eogenetic karst and suggest new concepts may be necessary to describe how conduits develop within these porous rocks. | |||||
BibTeX:
@article{Moore2010,
author = {Moore, Paul J. and Martin, Jonathan B. and Screaton, Elizabeth J. and Neuhoff, Philip S.},
title = {Conduit enlargement in an eogenetic karst aquifer},
journal = {Journal of Hydrology},
year = {2010},
volume = {393},
number = {3-4},
pages = {143--155},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410005160}
}
|
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| Moore, T.L., Hunt, W.F., Burchell, M.R. and Hathaway, J.M. | Organic nitrogen exports from urban stormwater wetlands in North Carolina | 2011 | Ecological Engineering Vol. 37(4), pp. 589-594 |
article | URL |
| Abstract: Effluent organic nitrogen concentrations from seven constructed stormwater wetlands in North Carolina were examined to compare background organic nitrogen (ON) concentrations and the fraction of organic nitrogen relative to total nitrogen discharged. Seasonal influences on organic nitrogen concentrations were also examined. The median ON concentration from the stormwater wetlands was 0.78 mg l−1, and despite differences in wetland design and influent ON characteristics, outlet ON concentrations from all but one wetland were not significantly different. ON export from all stormwater wetlands was significantly less than untreated runoff entering the wetlands (p = 0.002). In addition, median organic:total nitrogen (ON:TN) ratios from stormwater wetlands (0.75) were significantly greater than from untreated urban runoff (0.66), comparing more closely to ON:TN ratios collected from a naturally occurring wetland and reported in the literature for natural landscapes. Seasonal differences in organic nitrogen concentrations were identified with significantly lower concentrations during the winter. Though stormwater wetlands will not (and perhaps should not be expected to) completely remove total nitrogen loads from runoff, these results suggest constructed wetlands can play a role in restoring the balance between organic and inorganic nitrogen forms closer to that of an undisturbed landscape. The presence of background organic nitrogen concentrations from stormwater wetlands similar to those from a naturally occurring wetland highlights the importance of choosing appropriate metrics (e.g., effluent concentrations) when assessing treatment performance. | |||||
BibTeX:
@article{Moore2011,
author = {Moore, Trisha L.C. and Hunt, William F. and Burchell, Michael R. and Hathaway, Jon M.},
title = {Organic nitrogen exports from urban stormwater wetlands in North Carolina},
journal = {Ecological Engineering},
year = {2011},
volume = {37},
number = {4},
pages = {589--594},
url = {http://www.sciencedirect.com/science/article/pii/S0925857410003502}
}
|
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| Moral, F., Cruz-Sanjulián, J. and Olías, M. | Geochemical evolution of groundwater in the carbonate aquifers of Sierra de Segura (Betic Cordillera, southern Spain) | 2008 | Journal of Hydrology Vol. 360(1-4), pp. 281-296 |
article | URL |
| Abstract: Sierra de Segura (Betic Cordillera), with a total area of over 3000 km2, is the source of the two principal rivers in southern Spain, the Guadalquivir and the Segura. Due to the orographic effect of these mountains, precipitations are considerably more abundant than in nearby lowland areas, where the climate is semi-arid. Sierra de Segura is constituted of Mesozoic and Cenozoic sedimentary rocks, among which there are thick limestone–dolomitic formations which have given rise to extensive outcrops of permeable materials. In geomorphological terms, there is a large plateau intensively karstified that constitutes the main recharge area. Discharge takes place via a large number of springs, of which the 50 most important add up to a mean spring flow of about 13,500 l/s. The active geochemical processes in aquifers of Sierra de Segura, with their corresponding time sequence, are: dissolution of CO2, dissolution of calcite, incongruent dissolution of dolomite, dedolomitization, exsolution of CO2, and precipitation of calcite. More evolved water has higher temperature, magnesium content and Mg/Ca ratio; therefore, these parameters can be utilised as indicators of the degree of hydrochemical evolution. In addition, a good correlation between water temperature and magnesium concentration (or Mg/Ca ratio) indicates that an increase in temperature accelerates the kinetics of the dissolution of dolomite. Finally, the distribution of the temperatures in the vadose zone, determined by atmospheric thermal gradient, implies an apparent stratification of the predominant hydrochemical processes and of the groundwater physical and chemical characteristics. | |||||
BibTeX:
@article{Moral2008,
author = {Moral, F. and Cruz-Sanjulián, J.J. and Olías, M.},
title = {Geochemical evolution of groundwater in the carbonate aquifers of Sierra de Segura (Betic Cordillera, southern Spain)},
journal = {Journal of Hydrology},
year = {2008},
volume = {360},
number = {1-4},
pages = {281--296},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408003272}
}
|
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| Morales, T., Fdez. de Valderrama, I., Uriarte, J.A., Antigüedad, I. and Olazar, M. | Predicting travel times and transport characterization in karst conduits by analyzing tracer-breakthrough curves | 2007 | Journal of Hydrology Vol. 334(1-2), pp. 183-198 |
article | URL |
| Abstract: This paper analyzes data obtained in 26 tracer tests carried out in 11 karstic connections following solutional conduits in karst aquifers in the Basque Country. These conduits are preferential drainage pathways in these aquifers and so they confer a marked anisotropy and high vulnerability to them. Consequently, their consideration in protection and management studies and projects is a priority. The connections studied cover a wide hydrogeological spectrum (a wide range of sizes, slopes, geomorphic and hydrologic types) and the tests have been carried out at different hydrodynamic states. It is noteworthy that they all follow a similar trend, which has allowed for the development of a statistical approximation for the treatment of the whole information. Relationships have been established involving velocity, solute time of arrival, attenuation of peak concentration and time of passage of tracer cloud. These relationships are a valuable tool for management and supporting decision-making and allow for making estimates in connections in which the information available was scarce. This information is especially useful, given that the complexity of transport in karst conduits gives way to important deviations between real data (empirical observations) and the data obtained by simple approaches based on the Fickian-type diffusion equation. |
|||||
BibTeX:
@article{Morales2007,
author = {Morales, Tomás and Fdez. de Valderrama, Iñigo and Uriarte, Jesús A. and Antigüedad, Iñaki and Olazar, Martín},
title = {Predicting travel times and transport characterization in karst conduits by analyzing tracer-breakthrough curves},
journal = {Journal of Hydrology},
year = {2007},
volume = {334},
number = {1-2},
pages = {183--198},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406005397}
}
|
|||||
| Morales, T., Uriarte, J.A., Olazar, M., Antigüedad, I. and Angulo, B. | Solute transport modelling in karst conduits with slow zones during different hydrologic conditions | 2010 | Journal of Hydrology Vol. 390(3-4), pp. 182-189 |
article | URL |
| Abstract: Eight tracer tests conducted under different flow conditions in two well-developed karst connections in the Santa Eufemia–Ereñozar karst unit (Basque Country, northern Spain) are considered for transport characterization. Lithium tracer was injected as an impulse release for obtaining well-defined tracer breakthrough curves (TBCs). In order to simulate curve evolution and obtain transport characteristic parameters, two approaches have been applied: a standard analytical solution and a new numerical one that accounts for transient storage processes. The numerical model simulates the effect of localized variations in conduit geometry that give way to dead zones or slow zones in the transport process. This model fits the experimental curves well and explains their tails mainly by diversion processes from the main flow line towards stagnant zones. An increase in dispersion coefficient values is observed in both conduits as flow rates and average flow velocities increase. Stagnation and tracer transient retention processes, which may be quantified by means of the numerical solution, are more important as circulating flow rates decrease and travel times increase. The diversion processes in the two connections follow a similar evolution, with significant changes in the magnitude of the retentions registered depending on the hydrodynamic state of the traced system. Consequently, there is a clear hydrodynamic-controlled tailing effect. | |||||
BibTeX:
@article{Morales2010,
author = {Morales, Tomás and Uriarte, Jesus A. and Olazar, Martín and Antigüedad, Iñaki and Angulo, Bárbara},
title = {Solute transport modelling in karst conduits with slow zones during different hydrologic conditions},
journal = {Journal of Hydrology},
year = {2010},
volume = {390},
number = {3-4},
pages = {182-189},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410004099}
}
|
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| Morales-Juberías, T., Olazar, M., Arandes, J.M., Zafra, P., Antigüedad, I. and Basauri, F. | Application of a solute transport model under variable velocity conditions in a conduit flow aquifer: Olalde karst system, Basque Country, Spain | 1997 | Environmental Geology Vol. 30(3), pp. 143-151 |
article | URL |
| Abstract: A model based on numerical solutions, which allows for solving the dispersion equation under variable recharge and velocity conditions, is developed to simulate solute transport in conduit flow aquifers during flow recession periods. As an example, the evolution of a tracer in the little known karst conduit that links the sinking stream of Oma valley to the Olalde spring is investigated in the karstic region of Santa Eufemia-Ereozar (Basque Country, Spain). The model, with different hypothetical structures, allows for obtaining series of tracer breakthrough curves, which are fitted to experimental data using an optimization algorithm. These results, although they can be used to simulate the tracer evolution between the two points considered, do not allow for determining the internal structure and spatial disposition of contributions in the aquifer. | |||||
BibTeX:
@article{Morales-Juberias1997,
author = {Morales-Juberías, Tomás and Olazar, Martín and Arandes, Jose María and Zafra, Pedro and Antigüedad, Iñaki and Basauri, Félix},
title = {Application of a solute transport model under variable velocity conditions in a conduit flow aquifer: Olalde karst system, Basque Country, Spain},
journal = {Environmental Geology},
publisher = {Springer Berlin / Heidelberg},
year = {1997},
volume = {30},
number = {3},
pages = {143--151},
url = {http://dx.doi.org/10.1007/s002540050141}
}
|
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| Morris, C.E., Bardin, M., Berge, O., Frey-Klett, P., Fromin, N., Girardin, H., Guinebretière, M.-H., Lebaron, P., Thiéry, J.M. and Troussellier, M. | Microbial Biodiversity: Approaches to Experimental Design and Hypothesis Testing in Primary Scientific Literature from 1975 to 1999 | 2002 | Microbiology and Molecular Biology Reviews Vol. 66(4), pp. 592-616 |
article | URL |
| Abstract: Research interest in microbial biodiversity over the past 25 years has increased markedly as microbiologists have become interested in the significance of biodiversity for ecological processes and as the industrial, medical, and agricultural applications of this diversity have evolved. One major challenge for studies of microbial habitats is how to account for the diversity of extremely large and heterogeneous populations with samples that represent only a very small fraction of these populations. This review presents an analysis of the way in which the field of microbial biodiversity has exploited sampling, experimental design, and the process of hypothesis testing to meet this challenge. This review is based on a systematic analysis of 753 publications randomly sampled from the primary scientific literature from 1975 to 1999 concerning the microbial biodiversity of eight habitats related to water, soil, plants, and food. These publications illustrate a dominant and growing interest in questions concerning the effect of specific environmental factors on microbial biodiversity, the spatial and temporal heterogeneity of this biodiversity, and quantitative measures of population structure for most of the habitats covered here. Nevertheless, our analysis reveals that descriptions of sampling strategies or other information concerning the representativeness of the sample are often missing from publications, that there is very limited use of statistical tests of hypotheses, and that only a very few publications report the results of multiple independent tests of hypotheses. Examples are cited of different approaches and constraints to experimental design and hypothesis testing in studies of microbial biodiversity. To prompt a more rigorous approach to unambiguous evaluation of the impact of microbial biodiversity on ecological processes, we present guidelines for reporting information about experimental design, sampling strategies, and analyses of results in publications concerning microbial biodiversity. | |||||
BibTeX:
@article{Morris2002,
author = {Morris, Cindy E. and Bardin, Marc and Berge, Odile and Frey-Klett, Pascale and Fromin, Nathalie and Girardin, Hélène and Guinebretière, Marie-Hélène and Lebaron, Philippe and Thiéry, Jean M. and Troussellier, Marc},
title = {Microbial Biodiversity: Approaches to Experimental Design and Hypothesis Testing in Primary Scientific Literature from 1975 to 1999},
journal = {Microbiology and Molecular Biology Reviews},
year = {2002},
volume = {66},
number = {4},
pages = {592--616},
url = {http://mmbr.asm.org/content/66/4/592.abstract}
}
|
|||||
| Morris, P.J. and Waddington, J.M. | Groundwater residence time distributions in peatlands: Implications for peat decomposition and accumulation | 2011 | Water Resources Research Vol. 47(2), pp. W02511- |
article | URL |
| Abstract: Peat soils consist of poorly decomposed plant detritus, preserved by low decay rates, and deep peat deposits are globally significant stores in the carbon cycle. High water tables and low soil temperatures are commonly held to be the primary reasons for low peat decay rates. However, recent studies suggest a thermodynamic limit to peat decay, whereby the slow turnover of peat soil pore water may lead to high concentrations of phenols and dissolved inorganic carbon. In sufficient concentrations, these chemicals may slow or even halt microbial respiration, providing a negative feedback to peat decay. We document the analysis of a simple, one-dimensional theoretical model of peatland pore water residence time distributions (RTDs). The model suggests that broader, thicker peatlands may be more resilient to rapid decay caused by climate change because of slow pore water turnover in deep layers. Even shallow peat deposits may also be resilient to rapid decay if rainfall rates are low. However, the model suggests that even thick peatlands may be vulnerable to rapid decay under prolonged high rainfall rates, which may act to flush pore water with fresh rainwater. We also used the model to illustrate a particular limitation of the diplotelmic (i.e., acrotelm and catotelm) model of peatland structure. Model peatlands of contrasting hydraulic structure exhibited identical water tables but contrasting RTDs. These scenarios would be treated identically by diplotelmic models, although the thermodynamic limit suggests contrasting decay regimes. We therefore conclude that the diplotelmic model be discarded in favor of model schemes that consider continuous variation in peat properties and processes. | |||||
BibTeX:
@article{Morris2011,
author = {Morris, P. J. and Waddington, J. M.},
title = {Groundwater residence time distributions in peatlands: Implications for peat decomposition and accumulation},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2011},
volume = {47},
number = {2},
pages = {W02511--},
url = {http://dx.doi.org/10.1029/2010WR009492}
}
|
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| Moss, J.A., Nocker, A. and Snyder, R.A. | Microbial Characteristics of a Submerged Karst Cave System in Northern Florida | 2011 | Geomicrobiology Journal Vol. 28(8)Geomicrobiology Journal, pp. 719-731 |
article | URL |
| Abstract: Karst aquifer systems contain submerged caves that act as conduits for subterranean water flow and are subject to rapid surface recharge at points such as sink holes and submerging streams. We examined the microbial communities in six conduits of the Northern Florida Wakulla Springs cave system and in several hydrologically connected surface sinks. Culturable bacteria were assessed using both oligotrophic and copiotrophic media, and specific media for Enterococcus and Escherichia coli. Culture independent methods included using 16S rRNA PCR amplified DNA for T-RFLP analysis and development of clone libraries for sequencing. Pronounced seasonality was found in all microbiological parameters suggesting responsiveness to surface conditions from recharge of the groundwater despite near constant groundwater temperature. Other differences may reflect the character of the drainage areas feeding different conduits and flow rates and flow reversals that affected residence time in cave conduits. In a region of groundwater flow divide, elevated numbers of a plate counts, flocculent material, and a sulfide smell were reflected in T-RFLP pattern differences. Sequence data from five selected sampling locations revealed the presence of Enterobacter and Klebsiella sequences in surface waters, but not in conduits. One conduit contained a high percentage of sequences with close homology to the archaeal species Thermococcalles archaeon. Other cave-specific sequences were found that do not match previously characterized bacteria. Overall, the data suggest both temporal and spatial differences in the microbial communities within the extensive cave system conduits feeding the spring vent, reflecting both drainage area influences and undocumented subterranean microbial diversity. Karst aquifer systems contain submerged caves that act as conduits for subterranean water flow and are subject to rapid surface recharge at points such as sink holes and submerging streams. We examined the microbial communities in six conduits of the Northern Florida Wakulla Springs cave system and in several hydrologically connected surface sinks. Culturable bacteria were assessed using both oligotrophic and copiotrophic media, and specific media for Enterococcus and Escherichia coli. Culture independent methods included using 16S rRNA PCR amplified DNA for T-RFLP analysis and development of clone libraries for sequencing. Pronounced seasonality was found in all microbiological parameters suggesting responsiveness to surface conditions from recharge of the groundwater despite near constant groundwater temperature. Other differences may reflect the character of the drainage areas feeding different conduits and flow rates and flow reversals that affected residence time in cave conduits. In a region of groundwater flow divide, elevated numbers of a plate counts, flocculent material, and a sulfide smell were reflected in T-RFLP pattern differences. Sequence data from five selected sampling locations revealed the presence of Enterobacter and Klebsiella sequences in surface waters, but not in conduits. One conduit contained a high percentage of sequences with close homology to the archaeal species Thermococcalles archaeon. Other cave-specific sequences were found that do not match previously characterized bacteria. Overall, the data suggest both temporal and spatial differences in the microbial communities within the extensive cave system conduits feeding the spring vent, reflecting both drainage area influences and undocumented subterranean microbial diversity. |
|||||
BibTeX:
@article{Moss2011,
author = {Moss, Joseph A. and Nocker, Andreas and Snyder, Richard A.},
title = {Microbial Characteristics of a Submerged Karst Cave System in Northern Florida},
booktitle = {Geomicrobiology Journal},
journal = {Geomicrobiology Journal},
publisher = {Taylor & Francis},
year = {2011},
volume = {28},
number = {8},
pages = {719--731},
url = {http://dx.doi.org/10.1080/01490451.2010.517235}
}
|
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| Moussu, F., Oudin, L., Plagnes, V., Mangin, A. and Bendjoudi, H. | A multi-objective calibration framework for rainfall–discharge models applied to karst systems | 2011 | Journal of Hydrology Vol. 400(3-4), pp. 364-376 |
article | URL |
| Abstract: This paper assesses the potential of several calibration strategies to meet two objectives: good discharge simulations and the ability to reproduce one functional characteristic. Indeed, although classical rainfall–discharge models are often calibrated based on their efficiency in simulating discharge time series, this does not warrant an optimal representation of certain of the system’s hydrodynamic properties, since these properties are used for water management purposes. Therefore, this paper investigates the trade-off between two objectives: (i) good discharge simulations in terms of the least mean square errors and (ii) the ability to reproduce the autocorrelation function of the discharge time series. For this purpose, we applied two rainfall–discharge models on the Baget karst system, an extensively studied system located in the French Pyrenees. The results show that a single-objective calibration based on the classical Nash and Sutcliffe efficiency (NSE) coefficient gives relatively satisfying modelling results, but the autocorrelation function is systematically overestimated. The proposed multi-objective approach improves the ability of the model to mimic the autocorrelation function without greatly altering the model’s NSE efficiency. Last, the multi-objective framework reduces parameter uncertainty and increases the robustness of the two rainfall–discharge models. | |||||
BibTeX:
@article{Moussu2011,
author = {Moussu, François and Oudin, Ludovic and Plagnes, Valérie and Mangin, Alain and Bendjoudi, Hocine},
title = {A multi-objective calibration framework for rainfall–discharge models applied to karst systems},
journal = {Journal of Hydrology},
year = {2011},
volume = {400},
number = {3-4},
pages = {364--376},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411000722}
}
|
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| Mudarra, M. and Andreo, B. | Relative importance of the saturated and the unsaturated zones in the hydrogeological functioning of karst aquifers: The case of Alta Cadena (Southern Spain) | 2011 | Journal of Hydrology Vol. 397(3-4), pp. 263-280 |
article | URL |
| Abstract: From analysis of the hydrodynamic and hydrochemical responses of karst springs, it is possible to know the behaviour of the aquifers they drain. This manuscript aims to contribute to the characterization of infiltration process, and to determine the relative importance of the saturated zone and of the unsaturated zone in the hydrogeological functioning of carbonate aquifers, using natural hydrochemical tracers. Thus, chemical components together with temperature and electrical conductivity (both punctual and continuous records) have been monitored in three springs which drain Alta Cadena carbonate aquifer, Southern Spain. An evaluation of the percentage of the electrical conductivity frequency peaks determined for each of the three springs is linked to the chemical parameters that comprise the conductivity signal. One of these springs responds rapidly to precipitation (conduit flow system), due to the existence of a high degree of karstification in the unsaturated zone and in the saturated zone, both of which play a similar role in the functioning of the spring. Another spring responds to precipitation with small increases in water flow, somewhat lagged, because the aquifer has a low degree of karstification, even in the unsaturated zone, which seems to influence its functioning more strongly than does the saturated zone. The third spring drains a sector of the aquifer with a moderately developed degree of karstification, one that is intermediate between the other two, in which both the unsaturated zone and the saturated zone participate in the functioning of the spring, but with the latter zone having a stronger influence. These three springs show different hydrogeological functioning although they are in similar geological and climatic contexts, which show the heterogeneity of karst media and the importance of an adequate investigation for groundwater management and protection in karst areas. | |||||
BibTeX:
@article{Mudarra2011,
author = {Mudarra, M. and Andreo, B.},
title = {Relative importance of the saturated and the unsaturated zones in the hydrogeological functioning of karst aquifers: The case of Alta Cadena (Southern Spain)},
journal = {Journal of Hydrology},
year = {2011},
volume = {397},
number = {3-4},
pages = {263--280},
url = {http://www.sciencedirect.com/science/article/pii/S002216941000747X}
}
|
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| Mudarra, M., Andreo, B. and Baker, A. | Characterisation of dissolved organic matter in karst spring waters using intrinsic fluorescence: Relationship with infiltration processes | 2011 | Science of The Total Environment Vol. 409(18), pp. 3448-3462 |
article | URL |
| Abstract: From analysis of spectrophotometric properties of dissolved organic matter (OM) and the hydrochemical responses of some karst springs under different hydrologic conditions, an assessment of the origin and transfer pathway of OM present in karst spring waters, from soil and epikarst toward the spring, has been conducted for three karst aquifers in southern Spain: Alta Cadena, Sierra de Enmedio and Los Tajos. Intrinsic fluorescence (excitation–emission matrices or EEMs), together with major water chemistry (electrical conductivity, temperature, alkalinity, Cl−, Mg+ 2) and PCO2 along with natural hydrochemical tracers (TOC and NO3−), have been monitored in 19 springs which drain the three karst aquifers examined in this study. The spring water EEM spectra indicate that fulvic acid-like substances, produced in the soil as a consequence of the decomposition of OM, are the dominant fluorophores, although some of the OM appears to originate from in situ microbiological activity but could be indicative of contamination present in recharge waters from livestock. During each recharge event, TOC and NO3− concentrations increased and variations in fluorescence intensities of peaks attributed to fulvic acid-like compounds were observed. In areas with minimal soil development, spatial and temporal variations in the fluorescence intensity of fulvic acid-like substances and other fluorophores derived from microbiological activity, together with other hydrochemical parameters, provide insights into the hydrogeological functioning of karst aquifers and the infiltration velocity of water from soil and facilitate assessment of contamination vulnerability in these aquifers. | |||||
BibTeX:
@article{Mudarra2011a,
author = {Mudarra, M. and Andreo, B. and Baker, A.},
title = {Characterisation of dissolved organic matter in karst spring waters using intrinsic fluorescence: Relationship with infiltration processes},
journal = {Science of The Total Environment},
year = {2011},
volume = {409},
number = {18},
pages = {3448--3462},
url = {http://www.sciencedirect.com/science/article/pii/S0048969711005298}
}
|
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| Mudholkar, G.S., Asubonteng, K.O. and Hutson, A.D. | Transformation of the bathtub failure rate data in reliability for using Weibull-model analysis | 2009 | Statistical Methodology Vol. 6(6), pp. 622-633 |
article | URL |
| Abstract: All statistical methods involve basic model assumptions, which if violated render results of the analysis dubious. A solution to such a contingency is to seek an appropriate model or to modify the customary model by introducing additional parameters. Both of these approaches are in general cumbersome and demand uncommon expertise. An alternative is to transform the data to achieve compatibility with a well understood and convenient customary model with readily available software. The well-known example is the Box–Cox data transformation developed in order to make the normal theory linear model usable even when the assumptions of normality and homoscedasticity are not met. | |||||
BibTeX:
@article{Mudholkar2009,
author = {Mudholkar, Govind S. and Asubonteng, Kobby O. and Hutson, Alan D.},
title = {Transformation of the bathtub failure rate data in reliability for using Weibull-model analysis},
journal = {Statistical Methodology},
year = {2009},
volume = {6},
number = {6},
pages = {622--633},
url = {http://www.sciencedirect.com/science/article/pii/S1572312709000434}
}
|
|||||
| Mudholkar, G.S. and Tian, L. | An entropy characterization of the inverse Gaussian distribution and related goodness-of-fit test | 2002 | Journal of Statistical Planning and Inference Vol. 102(2), pp. 211-221 |
article | URL |
| Abstract: The inverse Gaussian family is widely used for modeling positively skewed measurements. In this note, we present an entropy characterization of the inverse Gaussian family and use it to construct a goodness-of-fit test for ascertaining appropriateness of such models. This test is consistent against all alternatives without a singular component and has good power properties. | |||||
BibTeX:
@article{Mudholkar2002,
author = {Mudholkar, Govind S and Tian, Lili},
title = {An entropy characterization of the inverse Gaussian distribution and related goodness-of-fit test},
journal = {Journal of Statistical Planning and Inference},
year = {2002},
volume = {102},
number = {2},
pages = {211--221},
url = {http://www.sciencedirect.com/science/article/pii/S0378375801000994}
}
|
|||||
| Mull, D.S., Liebermann, T.D., Smoot, J.L. and Woosley Jr., L.H. | Application of dye-tracing techniques for determining solute-transport characteristics of ground water in karst terranes [BibTeX] |
1988 | , pp. 103-103 | manual | |
BibTeX:
@manual{Mull1988,
author = {Mull, D. S. and Liebermann, T. D. and Smoot, J. L. and Woosley, Jr., L. H.},
title = {Application of dye-tracing techniques for determining solute-transport characteristics of ground water in karst terranes},
year = {1988},
pages = {103--103},
note = {EPA 904/6-88-001}
}
|
|||||
| Mulligan, C.N. and Yong, R.N. | Natural attenuation of contaminated soils | 2004 | Environment International Vol. 30(4), pp. 587-601 |
article | URL |
| Abstract: Natural attenuation is increasing in use as a low cost means of remediating contaminated soil and groundwater. Modelling of contaminant migration plays a key role in evaluating natural attenuation as a remediation option and in ensuring that there will be no adverse impact on humans and the environment. During natural attenuation, the contamination must be characterized thoroughly and monitored through the process. In this paper, attenuation mechanisms for both organic and inorganic contaminants, use of models and protocols, role of monitoring and field case studies will be reviewed. | |||||
BibTeX:
@article{Mulligan2004,
author = {Mulligan, Catherine N. and Yong, Raymond N.},
title = {Natural attenuation of contaminated soils},
journal = {Environment International},
year = {2004},
volume = {30},
number = {4},
pages = {587--601},
url = {http://www.sciencedirect.com/science/article/pii/S0160412003002332}
}
|
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| Musgrove, M., Stern, L. and Banner, J. | Springwater geochemistry at Honey Creek State Natural Area, central Texas: Implications for surface water and groundwater interaction in a karst aquifer | 2010 | Journal of Hydrology Vol. 388(1-2), pp. 144-156 |
article | URL |
| Abstract: A two and a half year study of two adjacent watersheds at the Honey Creek State Natural Area (HCSNA) in central Texas was undertaken to evaluate spatial and temporal variations in springwater geochemistry, geochemical evolution processes, and potential effects of brush control on karst watershed hydrology. The watersheds are geologically and geomorphologically similar, and each has springs discharging into Honey Creek, a tributary to the Guadalupe River. Springwater geochemistry is considered in a regional context of aquifer components including soil water, cave dripwater, springwater, and phreatic groundwater. Isotopic and trace element variability allows us to identify both vadose and phreatic groundwater contributions to surface water in Honey Creek. Spatial and temporal geochemical data for six springs reveal systematic differences between the two watersheds. Springwater Sr isotope values lie between values for the limestone bedrock and soils at HCSNA, reflecting a balance between these two primary sources of Sr. Sr isotope values for springs within each watershed are consistent with differences between soil compositions. At some of the springs, consistent temporal variability in springwater geochemistry (Sr isotopes, Mg/Ca, and Sr/Ca values) appears to reflect changes in climatic and hydrologic parameters (rainfall/recharge) that affect watershed processes. Springwater geochemistry was unaffected by brush removal at the scale of the HCSNA study. Results of this study build on previous regional studies to provide insight into watershed hydrology and regional hydrologic processes, including connections between surface water, vadose groundwater, and phreatic groundwater. | |||||
BibTeX:
@article{Musgrove2010,
author = {Musgrove, M. and Stern, L.A. and Banner, J.L.},
title = {Springwater geochemistry at Honey Creek State Natural Area, central Texas: Implications for surface water and groundwater interaction in a karst aquifer},
journal = {Journal of Hydrology},
year = {2010},
volume = {388},
number = {1-2},
pages = {144--156},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410002350}
}
|
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| Mushrush, G.W., Wynne, J.H., Field, M.S., Beal, E.J., Hardy, D.R. and Hughes, J.M. | A Model Study Using Fluorescein as a Fluorescent Probe for Hydrocarbon Contaminated Groundwater | 2001 | Energy Sources Vol. 23(2), pp. 137-142 |
article | DOI URL |
| Abstract: The quantity of gasoline and middle distillate fuels in transit and storage makes these fuels the most common hydrocarbon contaminants in groundwater. Groundwater can be contaminated by hydrocarbons from surface spills, transportation accidents, leaking above ground storage tanks, leaking underground service station tanks, and leaking interstate pipelines. Groundwater flows can be tracked by many methods, but fluorescence detection of dyes is both simple and easy. Fluorescein is a dye that has been successfully used for tracing groundwater flow. This dye is easily detectable at the 10-11 M concentration and is relatively nontoxic. Results from this study showed that gasoline-contaminated water does not reduce the fluorescence intensity of fluorescein, but that a like amount of middle distillate does diminish the fluorescence intensity of fluorescein. The quantity of gasoline and middle distillate fuels in transit and storage makes these fuels the most common hydrocarbon contaminants in groundwater. Groundwater can be contaminated by hydrocarbons from surface spills, transportation accidents, leaking above ground storage tanks, leaking underground service station tanks, and leaking interstate pipelines. Groundwater flows can be tracked by many methods, but fluorescence detection of dyes is both simple and easy. Fluorescein is a dye that has been successfully used for tracing groundwater flow. This dye is easily detectable at the 10-11 M concentration and is relatively nontoxic. Results from this study showed that gasoline-contaminated water does not reduce the fluorescence intensity of fluorescein, but that a like amount of middle distillate does diminish the fluorescence intensity of fluorescein. |
|||||
BibTeX:
@article{Mushrush2001,
author = {Mushrush, George W. and Wynne, James H. and Field, Malcom S. and Beal, Erna J. and Hardy, Dennis R. and Hughes, Janet M.},
title = {A Model Study Using Fluorescein as a Fluorescent Probe for Hydrocarbon Contaminated Groundwater},
journal = {Energy Sources},
publisher = {Taylor & Francis},
year = {2001},
volume = {23},
number = {2},
pages = {137--142},
url = {http://dx.doi.org/10.1080/00908310151092317},
doi = {http://dx.doi.org/10.1080/00908310151092317}
}
|
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| Mustafa, A., Scholz, M., Harrington, R. and Carroll, P. | Long-term performance of a representative integrated constructed wetland treating farmyard runoff | 2009 | Ecological Engineering Vol. 35(5), pp. 779-790 |
article | URL |
| Abstract: The integrated constructed wetland (ICW) system studied in this research paper was constructed as part of a series of 15 wetland systems to improve the water quality of an entire catchment area (Annestown Stream watershed, Ireland) dominated by farming activities. The studied ICW comprised four cells and was used for the treatment of farmyard dirty water from a dairy farm near Dunhill (Ireland). The performance of this system was evaluated through physical, chemical and microbiological parameters collected for 7 years. The removal efficiencies were relatively good if compared to the international literature: biochemical oxygen demand (97.6%), chemical oxygen demand (94.9%), suspended solids (93.7%), ammonia-nitrogen (99%), nitrate-nitrogen (74%) and molybdate reactive phosphorus (91.8%). A molecular microbiological analysis of sediment samples collected from the site indicated that the number of denitrifying bacteria detected in the ICW system was higher than the number of ammonia-oxidizing bacteria. The monitored nutrient concentrations in groundwater and surface waters indicated that this ICW system did not pollute the receiving waters. The results showed that ICW are likely to be efficient in removing nutrients from farmyard runoff rich in nitrogen and phosphorus. | |||||
BibTeX:
@article{Mustafa2009,
author = {Mustafa, Atif and Scholz, Miklas and Harrington, Rory and Carroll, Paul},
title = {Long-term performance of a representative integrated constructed wetland treating farmyard runoff},
journal = {Ecological Engineering},
year = {2009},
volume = {35},
number = {5},
pages = {779--790},
url = {http://www.sciencedirect.com/science/article/pii/S0925857408003029}
}
|
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| Nadarajah, S. and Gupta, A.K. | Some bivariate gamma distributions | 2006 | Applied Mathematics Letters Vol. 19(8), pp. 767-774 |
article | URL |
| Abstract: We introduce two new bivariate gamma distributions based on a characterizing property involving products of gamma and beta random variables. We derive various representations for their joint densities, product moments, conditional densities and conditional moments. Some of these representations involve special functions such as the complementary incomplete gamma and Whittaker functions. We also discuss ways to construct multivariate generalizations. | |||||
BibTeX:
@article{Nadarajah2006,
author = {Nadarajah, Saralees and Gupta, Arjun K.},
title = {Some bivariate gamma distributions},
journal = {Applied Mathematics Letters},
year = {2006},
volume = {19},
number = {8},
pages = {767--774},
url = {http://www.sciencedirect.com/science/article/pii/S089396590500337X}
}
|
|||||
| Nadarajah, S. and Kotz, S. | A note on the correlated gamma distribution of Loáiciga and Leipnik | 2007 | Advances in Water Resources Vol. 30(4), pp. 1053-1055 |
article | URL |
| Abstract: The recent paper by Loáiciga and Leipnik [Loáiciga HA, Leipnik RB. Correlated gamma variables in the analysis of microbial densities in water. Adv Water Resour 2005;28:329–35] introduced a novel bivariate gamma distribution and studied its ratio distribution with application to hydrological sciences. In this note, we derive the corresponding distributions of the sum and the product. We also derive a powerful mixture representation of the bivariate gamma distribution unnoticed by Loáiciga and Leipnik. | |||||
BibTeX:
@article{Nadarajah2007,
author = {Nadarajah, Saralees and Kotz, Samuel},
title = {A note on the correlated gamma distribution of Loáiciga and Leipnik},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {4},
pages = {1053--1055},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001138}
}
|
|||||
| Nadarajah, S. and Zografos, K. | Formulas for Rényi information and related measures for univariate distributions | 2003 | Information Sciences Vol. 155(1-2), pp. 119-138 |
article | URL |
| Abstract: In a recent paper Song [J. Stat. Plan. Infer. 93 (2001) 51] considered Rényi information of order λ and established its connection to the loglikelihood. From this relation an intrinsic distribution measure was proposed and analytic expressions of this measure and Rényi information were derived for some standard continuous distributions. In this paper, we derive analytical formulas for Rényi and Shannon entropies, as well as, for Song’s measure for 26 flexible families of univariate continuous distributions. We believe that the results presented here will serve as an important reference for scientists and engineers in many areas. | |||||
BibTeX:
@article{Nadarajah2003,
author = {Nadarajah, S. and Zografos, K.},
title = {Formulas for Rényi information and related measures for univariate distributions},
journal = {Information Sciences},
year = {2003},
volume = {155},
number = {1-2},
pages = {119--138},
url = {http://www.sciencedirect.com/science/article/pii/S0020025503001567}
}
|
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| Nagase, A. and Dunnett, N. | Amount of water runoff from different vegetation types on extensive green roofs: Effects of plant species, diversity and plant structure | 2012 | Landscape and Urban Planning Vol. 104(3-4), pp. 356-363 |
article | URL |
| Abstract: Increased stormwater runoff from impervious surfaces is a major concern in urban areas and green roofs are increasingly used as an innovative means of stormwater management. However, there are very few studies on how different vegetation types affect the amount of water runoff. This paper describes an experiment that investigates the influence of plant species and plant diversity on the amount of water runoff from a simulated green roof. Twelve species were selected from the three major taxonomic and functional plant groups that are commonly used for extensive green roofs (forbs, sedum and grasses). Four species were chosen from each group and planted in combinations of increasing diversity and complexity: monocultures, four-species mixtures and twelve-species mixtures. The results showed that there was a significant difference in amount of water runoff between vegetation types; grasses were the most effective for reducing water runoff, followed by forbs and sedum. It was also shown that the size and structure of plants significantly influenced the amount of water runoff. Plant species with taller height, larger diameter, and larger shoot and root biomass were more effective in reducing water runoff from simulated green roofs than plant species with shorter height, smaller diameter, and smaller shoot and root biomass. The amount of water runoff from Sedum spp. was higher than that from bare ground. Species richness did not affect the amount of water runoff in this study. | |||||
BibTeX:
@article{Nagase2012,
author = {Nagase, Ayako and Dunnett, Nigel},
title = {Amount of water runoff from different vegetation types on extensive green roofs: Effects of plant species, diversity and plant structure},
journal = {Landscape and Urban Planning},
year = {2012},
volume = {104},
number = {3--4},
pages = {356--363},
url = {http://www.sciencedirect.com/science/article/pii/S0169204611003239}
}
|
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| Nair, V.V. and Thampi, S.G. | A triple continuum one-dimensional transport model for colloid facilitated contaminant migration in sets of parallel fractures with fracture skin | 2011 | Colloids and Surfaces A: Physicochemical and Engineering Aspects Vol. 373(1-3), pp. 74-81 |
article | URL |
| Abstract: A triple continuum one-dimensional transport model is developed to analyse colloid facilitated contaminant transport in fractured geological formations. The model accounts for contaminant transport in the fracture, reversible deposition onto fracture surfaces and onto the colloids, diffusion into the rock formation and irreversible deposition of colloids onto the fracture surfaces. Sorption of the contaminant onto the fracture surfaces and onto suspended and deposited colloids are assumed to follow the linear equilibrium assumption (LEA); whereas the irreversible deposition of colloids onto the fracture skin surface is assumed to be governed by the linear kinetic sorption isotherms. The resulting coupled contaminant transport equations are solved using a numerical model employing fully implicit finite difference method based formulation. Results clearly demonstrate that the presence of the fracture skin significantly influences colloid facilitated contaminant migration in fractured formations. Fracture skin porosity and fracture skin diffusion coefficient are demonstrated to be the critical fracture skin properties that affect colloid facilitated contaminant migration in fractures. The impact of different colloid parameters on contaminant transport is investigated. The distribution coefficient for contaminant sorption onto the suspended colloids is found to be the most significant colloid related parameter influencing contaminant migration in fractured formation with fracture skin. | |||||
BibTeX:
@article{Nair2011,
author = {Nair, Vinish V. and Thampi, Santosh G.},
title = {A triple continuum one-dimensional transport model for colloid facilitated contaminant migration in sets of parallel fractures with fracture skin},
journal = {Colloids and Surfaces A: Physicochemical and Engineering Aspects},
year = {2011},
volume = {373},
number = {1-3},
pages = {74--81},
url = {http://www.sciencedirect.com/science/article/pii/S0927775710006011}
}
|
|||||
| Najib, K., Jourde, H. and Pistre, S. | A methodology for extreme groundwater surge predetermination in carbonate aquifers: Groundwater flood frequency analysis | 2008 | Journal of Hydrology Vol. 352(1-2), pp. 1-15 |
article | URL |
| Abstract: The present paper introduces a methodology devoted to groundwater flooding hazard assessment. It focuses on groundwater floodings due to water table rises that are induced by heavy rainfall events. This special kind of flooding can cause devastating damages, particularly in fractured and karstified carbonate aquifers. Indeed, hydrodynamic conditions prevailing in these heterogeneous formations can involve strong groundwater surges. The developed methodology shows how flood frequency analysis methods can be applied in groundwater flood frequency analysis. Actually, it consists in estimating the T-year hydraulic head that characterizes the T-year groundwater surge, given a return period T. It also aims at defining the rainfall events likely to cause such extreme groundwater surges. This methodology was applied within the framework of a building construction project in a karstic Mediterranean aquifer located in Southern France. The present paper is designated to be a first contribution to groundwater flood frequency analysis. This new field of research has to be further developed in order to put forward consensus guidelines for hydrogeologists and decision-makers as in flood frequency analysis. | |||||
BibTeX:
@article{Najib2008,
author = {Najib, K. and Jourde, H. and Pistre, S.},
title = {A methodology for extreme groundwater surge predetermination in carbonate aquifers: Groundwater flood frequency analysis},
journal = {Journal of Hydrology},
year = {2008},
volume = {352},
number = {1-2},
pages = {1--15},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407007238}
}
|
|||||
| Namkoong, W., Hwang, E.-Y., Park, J.-S. and Choi, J.-Y. | Bioremediation of diesel-contaminated soil with composting | 2002 | Environmental Pollution Vol. 119(1), pp. 23-31 |
article | URL |
| Abstract: The major objective of this research was to find the appropriate mix ratio of organic amendments for enhancing diesel oil degradation during contaminated soil composting. Sewage sludge or compost was added as an amendment for supplementing organic matter for composting of contaminated soil. The ratios of contaminated soil to organic amendments were 1:0.1, 1:0.3, 1:0.5, and 1:1 as wet weight basis. Target contaminant of this research was diesel oil, which was spiked at 10,000 mg/kg sample on a dry weight basis. The degradation of diesel oil was significantly enhanced by the addition of these organic amendments relative to straight soil. Degradation rates of total petroleum hydrocarbons (TPH) and n-alkanes were the greatest at the ratio of 1:0.5 of contaminated soil to organic amendments on wet weight basis. Preferential degradation of n-alkanes over TPH was observed regardless of the kind and the amount of organic amendments. The first order degradation constant of n-alkanes was about twice TPH degradation constant. Normal alkanes could be divided in two groups (C10–C15 versus C16–C20) based on the first order kinetic constant. Volatilization loss of TPH was only about 2% of initial TPH. Normal alkanes lost by volatilization were mainly by the compounds of C10 to C16. High correlations (r=0.80–0.86) were found among TPH degradation rate, amount of CO2 evolved, and dehydrogenase activity. | |||||
BibTeX:
@article{Namkoong2002,
author = {Namkoong, Wan and Hwang, Eui-Young and Park, Joon-Seok and Choi, Jung-Young},
title = {Bioremediation of diesel-contaminated soil with composting},
journal = {Environmental Pollution},
year = {2002},
volume = {119},
number = {1},
pages = {23--31},
url = {http://www.sciencedirect.com/science/article/pii/S0269749101003281}
}
|
|||||
| Nanbakhsh, H., Kazemi-Yazdi, S. and Scholz, M. | Design comparison of experimental storm water detention systems treating concentrated road runoff | 2007 | Science of The Total Environment Vol. 380(1-3)Contaminants in Natural and Constructed Wetlands: Pollutant Dynamics and Control Wetland Pollution and Control Special Issue, pp. 220-228 |
article | URL |
| Abstract: The aim was to assess the treatment efficiencies of experimental storm water detention (extended storage) systems based on the Atlantis Water Management Limited detention cells receiving concentrated runoff that has been primarily treated by filtration with different inert aggregates. Randomly collected gully pot liquor was used in stead of road runoff. To test for a ‘worst case scenario’, the experimental system received higher volumes and pollutant concentrations in comparison to real detention systems under real (frequently longer but diluted) runoff events. Gravel (6 and 20 mm), sand (1.5 mm), Ecosoil (inert 2 mm aggregate provided by Atlantis Water Management Limited), block paving and turf were tested in terms of their influence on the water quality. Concentrations of five-day at 20 °C ATU biochemical oxygen demand (BOD) in contrast to suspended solids (SS) were frequently reduced to below international secondary wastewater treatment standards. The denitrification process was not completed. This resulted in higher outflow than inflow nitrate-nitrogen concentrations. An analysis of variance indicated that some systems were similar in terms of most of their treatment performance variables including BOD and SS. It follows that there is no advantage in using additional aggregates with high adsorption capacities in the primary treatment stage. | |||||
BibTeX:
@article{Nanbakhsh2007,
author = {Nanbakhsh, Hassan and Kazemi-Yazdi, Sara and Scholz, Miklas},
title = {Design comparison of experimental storm water detention systems treating concentrated road runoff},
booktitle = {Contaminants in Natural and Constructed Wetlands: Pollutant Dynamics and Control Wetland Pollution and Control Special Issue},
journal = {Science of The Total Environment},
year = {2007},
volume = {380},
number = {1-3},
pages = {220--228},
url = {http://www.sciencedirect.com/science/article/pii/S0048969706008138}
}
|
|||||
| Neal, C., Reynolds, B., Rowland, P., Norris, D., Kirchner, J.W., Neal, M., Sleep, D., Lawlor, A., Woods, C., Thacker, S., Guyatt, H., Vincent, C., Hockenhull, K., Wickham, H., Harman, S. and Armstrong, L. | High-frequency water quality time series in precipitation and streamflow: From fragmentary signals to scientific challenge | Science of The Total Environment(0), pp. - | article | URL | |
| Abstract: Eighteen months of 7-hourly analyses of rainfall and stream water chemistry are presented, spanning a wide range of chemical determinands and building on over 20 years of weekly records for the moorland headwaters of the river Severn. The high-frequency time series data show that hydrochemical responses to major hydrological and biological drivers of short-term variability in rainfall and rivers are not captured by conventional low-frequency monitoring programmes. A wealth of flow related, flow independent, diurnal, seasonal and annual fluctuations indicate a cacophony of interactions within the catchment and stream. The complexity of the chemical dynamics is visually obvious, although there appears to be no clear way of translating this complexity into a simple algorithm. The work provides a proof of concept for the complex structure of catchment functioning revealed by extensive high-frequency measurements coupled with high analytical sensitivity and reproducibility. It provides new insights into hydrogeochemical functioning and a novel resource for catchment modelling. | |||||
BibTeX:
@article{Neal,
author = {Neal, Colin and Reynolds, Brian and Rowland, Philip and Norris, David and Kirchner, James W. and Neal, Margaret and Sleep, Darren and Lawlor, Alan and Woods, Clive and Thacker, Sarah and Guyatt, Hayley and Vincent, Colin and Hockenhull, Kathryn and Wickham, Heather and Harman, Sarah and Armstrong, Linda},
title = {High-frequency water quality time series in precipitation and streamflow: From fragmentary signals to scientific challenge},
journal = {Science of The Total Environment},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0048969711013751}
}
|
|||||
| Neretnieks, I. | A stochastic multi-channel model for solute transport—analysis of tracer tests in fractured rock | 2002 | Journal of Contaminant Hydrology Vol. 55(3–4), pp. 175-211 |
article | URL |
| Abstract: Some of the basic assumptions of the advection–dispersion model (AD-model) are revisited. This model assumes a continuous mixing along the flowpath similar to Fickian diffusion. This implies that there is a constant dispersion length irrespective of observation distance. This is contrary to most field observations. The properties of an alternative model based on the assumption that individual water packages can retain their identity over long distances are investigated. The latter model is called the multi-channel model (MCh-model). Inherent in the latter model is that if the waters in the different pathways are collected and mixed, the “dispersion length” is proportional to distance. The conditions for when non-mixing between adjacent streams can be assumed are explored. | |||||
BibTeX:
@article{Neretnieks2002,
author = {Neretnieks, Ivars},
title = {A stochastic multi-channel model for solute transport—analysis of tracer tests in fractured rock},
journal = {Journal of Contaminant Hydrology},
year = {2002},
volume = {55},
number = {3–4},
pages = {175--211},
url = {http://www.sciencedirect.com/science/article/pii/S0169772201001954}
}
|
|||||
| Neretnieks, I. and Moreno, L. | Prediction of some in situ tracer tests with sorbing tracers using independent data | 2003 | Journal of Contaminant Hydrology Vol. 61(1–4)8th Internation Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 01, pp. 351-360 |
article | URL |
| Abstract: Some recent converging tracer tests with sorbing tracers at the Äspö Hard Rock Laboratory in Sweden, the TRUE tests, have been predicted using only laboratory data and hydraulic data from borehole measurements. No model parameters were adjusted to obtain a better fit with the experiments. The independent data were fracture frequency and transmissivity data obtained in the field and laboratory data on sorption and matrix diffusion. | |||||
BibTeX:
@article{Neretnieks2003,
author = {Neretnieks, Ivars and Moreno, Luis},
title = {Prediction of some in situ tracer tests with sorbing tracers using independent data},
booktitle = {8th Internation Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 01},
journal = {Journal of Contaminant Hydrology},
year = {2003},
volume = {61},
number = {1–4},
pages = {351--360},
url = {http://www.sciencedirect.com/science/article/pii/S0169772202001237}
}
|
|||||
| Neukum, C. and Azzam, R. | Quantitative assessment of intrinsic groundwater vulnerability to contamination using numerical simulations | 2009 | Science of The Total Environment Vol. 408(2), pp. 245-254 |
article | URL |
| Abstract: Intrinsic vulnerability assessment to groundwater contamination is part of groundwater management in many areas of the world. However, popular assessment methods estimate vulnerability only qualitatively. To enhance vulnerability assessment, an approach for quantitative vulnerability assessment using numerical simulation of water flow and solute transport with transient boundary conditions and new vulnerability indicators are presented in this work. Based on a conceptual model of the unsaturated underground with distinct hydrogeological layers and site specific hydrological characteristics the numerical simulations of water flow and solute transport are applied on each hydrogeological layer with standardized conditions separately. Analysis of the simulation results reveals functional relationships between layer thickness, groundwater recharge and transit time. Based on the first, second and third quartiles of solute mass breakthrough at the lower boundary of the unsaturated zone, and the solute dilution, four vulnerability indicators are extracted. The indicator transit time t50 is the time were 50% of solute mass breakthrough passes the groundwater table. Dilution is referred as maximum solute concentration Cmax in the percolation water when entering the groundwater table in relation to the injected mass or solute concentration C0 at the ground surface. Duration of solute breakthrough is defined as the time period between 25% and 75% (t25%–t75%) of total solute mass breakthrough at the groundwater table. The temporal shape of the breakthrough curve is expressed with the quotient (t25%–t50%) / (t25%–t75%). Results from an application of this new quantitative vulnerability assessment approach, its advantages and disadvantages, and potential benefits for future groundwater management strategies are discussed. | |||||
BibTeX:
@article{Neukum2009,
author = {Neukum, Christoph and Azzam, Rafig},
title = {Quantitative assessment of intrinsic groundwater vulnerability to contamination using numerical simulations},
journal = {Science of The Total Environment},
year = {2009},
volume = {408},
number = {2},
pages = {245--254},
url = {http://www.sciencedirect.com/science/article/pii/S0048969709009097}
}
|
|||||
| Nguyen, K.T. and Papavassiliou, D.V. | Flow effects on the kinetics of a second-order reaction | 2008 | Chemical Engineering Journal Vol. 140(1-3), pp. 370-380 |
article | URL |
| Abstract: Flow effects on the kinetics of an isothermal, equimolar, second-order reaction taking place in a channel were investigated using a Lagrangian numerical method. The reactants were released instantaneously from the two opposite walls of the channel into fully developed turbulent or laminar flow. The overall conversion, the residence time and reactor length required to achieve 80% conversion, and the effective reaction rate coefficient were calculated. A correlation of the efficiency ratio, defined as the effective rate coefficient divided by the reaction rate constant, with the flow parameters was found. | |||||
BibTeX:
@article{Nguyen2008,
author = {Nguyen, Kien T. and Papavassiliou, Dimitrios V.},
title = {Flow effects on the kinetics of a second-order reaction},
journal = {Chemical Engineering Journal},
year = {2008},
volume = {140},
number = {1-3},
pages = {370--380},
url = {http://www.sciencedirect.com/science/article/pii/S1385894707006699}
}
|
|||||
| Nguyet, V. and Goldscheider, N. | Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam | 2006 | Hydrogeology Journal Vol. 14(7), pp. 1147-1159 |
article | URL |
| Abstract: The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas. | |||||
BibTeX:
@article{Nguyet2006,
author = {Nguyet, Vu and Goldscheider, Nico},
title = {Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {7},
pages = {1147--1159},
url = {http://dx.doi.org/10.1007/s10040-006-0038-z}
}
|
|||||
| Ni, X. and Gough, P. | On the discussion of the dimensionless groups governing oscillatory flow in a baffled tube [BibTeX] |
1997 | Chemical Engineering Science Vol. 52(18), pp. 3209-3212 |
article | URL |
BibTeX:
@article{Ni1997,
author = {Ni, X. and Gough, P.},
title = {On the discussion of the dimensionless groups governing oscillatory flow in a baffled tube},
journal = {Chemical Engineering Science},
year = {1997},
volume = {52},
number = {18},
pages = {3209--3212},
url = {http://www.sciencedirect.com/science/article/pii/S0009250997001048}
}
|
|||||
| Niemi, A.J. | Residence time distributions of variable flow processes | 1977 | The International Journal of Applied Radiation and Isotopes Vol. 28(10–11), pp. 855-860 |
article | URL |
| Abstract: Tracer response functions can be interpreted and used under conditions of variable flow, if they are presented in terms of an integrated flow variable and if the flow patterns are not affected by changes of flow rate. | |||||
BibTeX:
@article{Niemi1977,
author = {Niemi, Antti J.},
title = {Residence time distributions of variable flow processes},
journal = {The International Journal of Applied Radiation and Isotopes},
year = {1977},
volume = {28},
number = {10–11},
pages = {855--860},
url = {http://www.sciencedirect.com/science/article/pii/0020708X77900266}
}
|
|||||
| Noiriel, C., Luquot, L., Madé, B., Raimbault, L., Gouze, P. and van der Lee, J. | Changes in reactive surface area during limestone dissolution: An experimental and modelling study | 2009 | Chemical Geology Vol. 265(1-2)CO2 geological storage: Integrating geochemical, hydrodynamical, mechanical and biological processes from the pore to the reservoir scale, pp. 160-170 |
article | URL |
| Abstract: This study explores the dynamics of porosity and reactive surface area changes during porous limestone dissolution by CO2-rich water. The Sr and Ca concentrations in both the rock and the outlet solution are used to evaluate the reactive surface area changes of the two rock-forming calcites, i.e. micrite grains and sparite crystals, which have different trace element signatures. The geometric surface area measured with X-ray microtomography decreases slightly whereas the reactive surface area increases continuously with increasing porosity from 20.3 to 30.2%. Surprisingly, changes in reactive surface areas are very different between the two calcites. The reactive surface area changes in the micrite are parabolic while the reactive surface area of sparite increases greatly. The numerical model HYTEC is used to model the change in reactive surface areas during the experiment. Different geometrical models are tested. The model based on spherical-grain dissolution and spherical-pore growth fails to reproduce the experimental results, while the sugar-lump model provides reasonable agreement with the experiment. | |||||
BibTeX:
@article{Noiriel2009,
author = {Noiriel, Catherine and Luquot, Linda and Madé, Benoît and Raimbault, Louis and Gouze, Philippe and van der Lee, Jan},
title = {Changes in reactive surface area during limestone dissolution: An experimental and modelling study},
booktitle = {CO2 geological storage: Integrating geochemical, hydrodynamical, mechanical and biological processes from the pore to the reservoir scale},
journal = {Chemical Geology},
year = {2009},
volume = {265},
number = {1-2},
pages = {160--170},
url = {http://www.sciencedirect.com/science/article/pii/S0009254109000643}
}
|
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| Nolan, B.T., Healy, R.W., Taber, P.E., Perkins, K., Hitt, K.J. and Wolock, D.M. | Factors influencing ground-water recharge in the eastern United States | 2007 | Journal of Hydrology Vol. 332(1-2), pp. 187-205 |
article | URL |
| Abstract: Ground-water recharge estimates for selected locations in the eastern half of the United States were obtained by Darcian and chloride-tracer methods and compared using statistical analyses. Recharge estimates derived from unsaturated-zone (RUZC) and saturated-zone (RSZC) chloride mass balance methods are less variable (interquartile ranges or IQRs are 9.5 and 16.1 cm/yr, respectively) and more strongly correlated with climatic, hydrologic, land use, and sediment variables than Darcian estimates (IQR = 22.8 cm/yr). The unit-gradient Darcian estimates are a nonlinear function of moisture content and also reflect the uncertainty of pedotransfer functions used to estimate hydraulic parameters. Significance level is <0.001 for nearly all explanatory variables having correlations with RUZC of <−0.3 or >0.3. Estimates of RSZC were evaluated using analysis of variance, multiple comparison tests, and an exploratory nonlinear regression (NLR) model. Recharge generally is greater in coastal plain surficial aquifers, fractured crystalline rocks, and carbonate rocks, or in areas with high sand content. Westernmost portions of the study area have low recharge, receive somewhat less precipitation, and contain fine-grained sediment. The NLR model simulates water input to the land surface followed by transport to ground water, depending on factors that either promote or inhibit water infiltration. The model explains a moderate amount of variation in the data set (coefficient of determination = 0.61). Model sensitivity analysis indicates that mean annual runoff, air temperature, and precipitation, and an index of ground-water exfiltration potential most influence estimates of recharge at sampled sites in the region. Soil characteristics and land use have less influence on the recharge estimates, but nonetheless are significant in the NLR model. | |||||
BibTeX:
@article{Nolan2007,
author = {Nolan, Bernard T. and Healy, Richard W. and Taber, Patrick E. and Perkins, Kimberlie and Hitt, Kerie J. and Wolock, David M.},
title = {Factors influencing ground-water recharge in the eastern United States},
journal = {Journal of Hydrology},
year = {2007},
volume = {332},
number = {1-2},
pages = {187--205},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406003465}
}
|
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| O'Reilly, A.M., Chang, N.-B. and Wanielista, M.P. | Cyclic biogeochemical processes and nitrogen fate beneath a subtropical stormwater infiltration basin | 2012 | Journal of Contaminant Hydrology Vol. 133(0), pp. 53-75 |
article | URL |
| Abstract: A stormwater infiltration basin in north–central Florida, USA, was monitored from 2007 through 2008 to identify subsurface biogeochemical processes, with emphasis on N cycling, under the highly variable hydrologic conditions common in humid, subtropical climates. Cyclic variations in biogeochemical processes generally coincided with wet and dry hydrologic conditions. Oxidizing conditions in the subsurface persisted for about one month or less at the beginning of wet periods with dissolved O2 and NO3− showing similar temporal patterns. Reducing conditions in the subsurface evolved during prolonged flooding of the basin. At about the same time O2 and NO3− reduction concluded, Mn, Fe and SO42 − reduction began, with the onset of methanogenesis one month later. Reducing conditions persisted up to six months, continuing into subsequent dry periods until the next major oxidizing infiltration event. Evidence of denitrification in shallow groundwater at the site is supported by median NO3−–N less than 0.016 mg L− 1, excess N2 up to 3 mg L− 1 progressively enriched in δ15N during prolonged basin flooding, and isotopically heavy δ15N and δ18O of NO3− (up to 25‰ and 15‰, respectively). Isotopic enrichment of newly infiltrated stormwater suggests denitrification was partially completed within two days. Soil and water chemistry data suggest that a biogeochemically active zone exists in the upper 1.4 m of soil, where organic carbon was the likely electron donor supplied by organic matter in soil solids or dissolved in infiltrating stormwater. The cyclic nature of reducing conditions effectively controlled the N cycle, switching N fate beneath the basin from NO3− leaching to reduction in the shallow saturated zone. Results can inform design of functionalized soil amendments that could replace the native soil in a stormwater infiltration basin and mitigate potential NO3− leaching to groundwater by replicating the biogeochemical conditions under the observed basin. | |||||
BibTeX:
@article{O'Reilly2012,
author = {O'Reilly, Andrew M. and Chang, Ni-Bin and Wanielista, Martin P.},
title = {Cyclic biogeochemical processes and nitrogen fate beneath a subtropical stormwater infiltration basin},
journal = {Journal of Contaminant Hydrology},
year = {2012},
volume = {133},
number = {0},
pages = {53--75},
url = {http://www.sciencedirect.com/science/article/pii/S0169772212000423}
}
|
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| Oates, P.M., Castenson, C., Harvey, C.F., Polz, M. and Culligan, P. | Illuminating reactive microbial transport in saturated porous media: Demonstration of a visualization method and conceptual transport model | 2005 | Journal of Contaminant Hydrology Vol. 77(4), pp. 233-245 |
article | URL |
| Abstract: We demonstrate a method to study reactive microbial transport in saturated translucent porous media using the bacteria Pseudomonas fluorescens 5RL genetically engineered to carry a plasmid with bioluminescence genes inducible by salicylate. Induced bacteria were injected into a cryolite grain filled chamber saturated with a sterile non-growth-promoting (phosphorus limited) chemical mixture containing salicylate as an aromatic hydrocarbon analogue. The amount of light produced by the bacteria serves as an estimator of the relative efficiency of aerobic biodegradation since bioluminescence is dependent on both salicylate and oxygen but only consumes oxygen. Bioluminescence was captured with a digital camera and analyzed to study the evolving spatial pattern of the bulk oxygen consuming reactions. As fluid flow transported the bacteria through the chamber, bioluminescence was observed to initially increase until an oxygen depletion zone developed behind the advective front. Bacterial transport was modeled with the advection dispersion equation and oxygen concentration was modeled assuming bacterial consumption via Monod kinetics with consideration of additional effects of rate-limited mass transfer from residual gas bubbles. Consistent with previous measurements, bioluminescence was considered proportional to oxygen consumed. Using the observed bioluminescence, model parameters were fit that were consistent with literature values and produced results in good agreement with the experimental data. These findings demonstrate potential for using this method to investigate the complex spatial and temporal dynamics of reactive microbial transport in saturated porous media. | |||||
BibTeX:
@article{Oates2005,
author = {Oates, Peter M. and Castenson, Catherine and Harvey, Charles F. and Polz, Martin and Culligan, Patricia},
title = {Illuminating reactive microbial transport in saturated porous media: Demonstration of a visualization method and conceptual transport model},
journal = {Journal of Contaminant Hydrology},
year = {2005},
volume = {77},
number = {4},
pages = {233--245},
url = {http://www.sciencedirect.com/science/article/pii/S0169772204001950}
}
|
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| Olaf A., C. | Choice of dispersion coefficients in reactive transport calculations on smoothed fields | 2002 | Journal of Contaminant Hydrology Vol. 58(3-4), pp. 261-282 |
article | URL |
| Abstract: Local dispersion dominates the mixing of compounds that are introduced separately into the subsurface and do not partition into any other than the aqueous phase. Thus, reactions between these compounds are controlled by dispersive mixing if they are not limited by kinetics. I quantify longitudinal dispersive mixing by the longitudinal effective dispersion coefficient of a conservative tracer introduced by a point-like injection [Water Resources Research 36 (12) (2000) 3591–3604]. In the upscaling of mixing-controlled reactive transport, I apply the mean velocity and the effective dispersion coefficient to the macroscopic transport calculations, whereas the reactive parameters on the macro-scale are identical to those on the local scale. The applicability of the approach is demonstrated for the transport of compounds undergoing a second-order irreversible bimolecular reaction. Ten realizations of a two-dimensional heterogeneous log-conductivity field are considered. Using the effective dispersion parameters, the overall mass balance is met in the ensemble average, whereas solute spreading is underestimated. I assess the lack of spreading by the difference between the expected macrodispersion and effective dispersion coefficients. I extend the approach to simulations on log-conductivity fields obtained by kriging of regularly spaced conductivity measurements. These fields contain the large-scale features of the true fields but do not resolve the small-scale variability. For the calculations on the kriged fields, the corresponding conditional covariance is substituted into the analytical expressions of effective dispersion, yielding a correction effective dispersion coefficient. The comparison between simulations on the fully resolved fields and on the kriged fields indicates that the approach is valid for wide plumes meeting the ergodicity condition. The high variability of mixing on small scales unresolved by kriging, however, leads to severe uncertainty when mixing-controlled reactions are predicted for narrow plumes. | |||||
BibTeX:
@article{OlafA.2002,
author = {Olaf A., Cirpka},
title = {Choice of dispersion coefficients in reactive transport calculations on smoothed fields},
journal = {Journal of Contaminant Hydrology},
year = {2002},
volume = {58},
number = {3-4},
pages = {261--282},
url = {http://www.sciencedirect.com/science/article/pii/S0169772202000396}
}
|
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| Ole, S. | Research, practice, uncertainty and responsibility | 2006 | The Journal of Mathematical Behavior Vol. 25(4), pp. 267-284 |
article | URL |
| Abstract: Three issues concerning the relationship between research and practice are addressed. (1) A certain ‘prototype mathematics classroom’ seems to dominate the research field, which in many cases seems selective with respect to what practices to address. I suggest challenging the dominance of the discourse created around the prototype mathematics classroom. (2) I find it important to broaden the school-centred discourse on mathematics education and to address the very different out-of-school practices that include mathematics. Many of these practices are relevant for interpreting what is taking place in a school context. That brings us to (3) socio-political issues of mathematics education. When the different school-sites for learning mathematics as well as the many different practices that include mathematics are related, we enter the socio-political dimension of mathematics education. | |||||
BibTeX:
@article{Ole2006a,
author = {Ole, Skovsmose},
title = {Research, practice, uncertainty and responsibility},
journal = {The Journal of Mathematical Behavior},
year = {2006},
volume = {25},
number = {4},
pages = {267--284},
url = {http://www.sciencedirect.com/science/article/pii/S0732312306000484}
}
|
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| de Oliveira, C.R. | Is Dirichlet the physical boundary condition for the one-dimensional hydrogen atom? | 2010 | Physics Letters A Vol. 374(28), pp. 2805-2808 |
article | URL |
| Abstract: It is argued that Dirichlet is the physical boundary condition at the origin for the one-dimensional hydrogen atom: The three-dimensional hydrogen atom is confined to a tube, and the limit as the diameter of the tube cross section goes to zero is taken. It is shown that the energy expectations are finite only in case of Dirichlet boundary condition. | |||||
BibTeX:
@article{deOliveira2010,
author = {de Oliveira, César R.},
title = {Is Dirichlet the physical boundary condition for the one-dimensional hydrogen atom?},
journal = {Physics Letters A},
year = {2010},
volume = {374},
number = {28},
pages = {2805--2808},
url = {http://www.sciencedirect.com/science/article/pii/S0375960110005463}
}
|
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| Olsson, Å. and Grathwohl, P. | Transverse dispersion of non-reactive tracers in porous media: A new nonlinear relationship to predict dispersion coefficients | 2007 | Journal of Contaminant Hydrology Vol. 92(3-4), pp. 149-161 |
article | URL |
| Abstract: Assessing the potential of natural attenuation in groundwater relies on the ability to predict and quantify the processes that occur in contaminant plumes. Transverse dispersion is a significant mass transfer mechanism for mixing of electron acceptors and donors and thus may control the lengths of steady state plumes. | |||||
BibTeX:
@article{Olsson2007,
author = {Olsson, Åsa and Grathwohl, Peter},
title = {Transverse dispersion of non-reactive tracers in porous media: A new nonlinear relationship to predict dispersion coefficients},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {92},
number = {3-4},
pages = {149--161},
url = {http://www.sciencedirect.com/science/article/pii/S0169772206001744}
}
|
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| Onac, B.P., Wynn, J.G. and Sumrall, J.B. | Tracing the sources of cave sulfates: a unique case from Cerna Valley, Romania | 2011 | Chemical Geology Vol. 288(3-4), pp. 105-114 |
article | URL |
| Abstract: In order to reliably distinguish between different genetic processes of cave sulfate formation and to quantify the role of thermo-mineral waters on mineral deposition and cave morphology, it is critical to understand sulfur (S) sources and S transformations during hydrological and speleogenetic processes. Previous work has shown that sulfuric acid speleogenesis (SAS) often produces sulfate deposits with 34S-depleted isotopic signatures compared to those of the original source of S in sulfate rocks. However, 34S-depleted isotopic composition of S-bearing minerals alone does not provide enough information to clearly distinguish SAS from other speleogenetic processes driven by carbonic acid, geothermal heat, or other processes. The isotopic composition (δ18O and δ34S) of sulfate minerals (mainly gypsum) from seven caves of the Cerna Valley (Romania) defines three distinct populations, and demonstrates that the δ34S values of SAS-precipitated cave sulfates depend not only on the source of the S, but also on the H2S:SO42− ratio during aqueous S species reactions and mineral precipitation. Population 1 includes sulfates that are characterized by relatively low δ34S values (− 19.4 to − 27.9‰) with δ18O values between 0.2 and 4.3‰ that are consistent with oxidation of dissolved sulfide produced during methane-limited thermochemical sulfate reduction (TSR) that presently characterizes the chemistry of springs in the upper Cerna Valley. Population 2 of cave sulfates has 34S-enriched δ34S values (14.3 to 19.4‰) and more 18O-depleted δ18O values (from − 1.8 to − 10.0‰). These values argue for oxidation of dissolved sulfide produced during sulfate-limited TSR that presently characterizes the chemistry of springs further downstream in the Cerna Valley. The δ18O values of cave sulfates from Population 1 are consistent with oxidation under more oxic aqueous conditions than those of Population 2. δ34S values of cave sulfates within Population 3 (δ34S: 5.8 to 6.5‰) may be consistent with several scenarios (i.e., pyrite oxidation, oxidation of dissolved sulfide produced during methane-limited TSR coupled with O2-limited oxidation during SAS). However, comparatively 18O-enriched δ18OSO4 values (11.9 to 13.9‰) suggest the majority of this sulfate O was derived from atmospheric O2 in gas-phase oxidation prior to hydration. Thus, the combined use of oxygen- and sulfur-isotope systematics of sulfate minerals precipitated in a variety of cave settings along Cerna Valley may serve as an example of how more complex cave systems can be deconvoluted to allow for more complete recognition of the range of processes and parameters that may be involved in SAS. | |||||
BibTeX:
@article{Onac2011,
author = {Onac, Bogdan P. and Wynn, Jonathan G. and Sumrall, Jonathan B.},
title = {Tracing the sources of cave sulfates: a unique case from Cerna Valley, Romania},
journal = {Chemical Geology},
year = {2011},
volume = {288},
number = {3-4},
pages = {105--114},
url = {http://www.sciencedirect.com/science/article/pii/S0009254111002804}
}
|
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| Onea, A., Wörner, M. and Cacuci, D.G. | A qualitative computational study of mass transfer in upward bubble train flow through square and rectangular mini-channels | 2009 | Chemical Engineering Science Vol. 64(7), pp. 1416-1435 |
article | URL |
| Abstract: In this paper we present a new method for numerical simulation of conjugate mass transfer of a dilute species with resistance in both phases and an arbitrary equilibrium distribution coefficient. The method is based on the volume-of-fluid technique and accounts for the concentration jump at the interface by transforming the discontinuous physical concentration field into a continuous numerical one. The method is validated by several test problems and is used to investigate the mass transfer in upward bubble train flow within square and rectangular channels. Computations are performed for a single flow unit cell and a channel hydraulic diameter of 2 mm. The simulations consider the transfer of a dilute species from the dispersed gas into the continuous liquid phase. Optionally, the mass transfer is accompanied by a first-order homogeneous chemical reaction in the liquid phase or a first-order heterogeneous reaction at the channel walls. The results of this numerical study are qualitative in nature. First, because periodic boundary conditions in axial direction are not only used for the velocity field but also for the concentration field and second, because the species diffusivity in the liquid phase is arbitrarily increased so that the liquid phase Schmidt number is 0.8 and the thickness of the concentration and momentum boundary layer is similar. Two different equilibrium distribution coefficients are considered, one where the mass transfer is from high to low concentration, and one where it is vice versa. The numerical study focuses on the influence of the unit cell length, liquid slug length and channel aspect ratio on mass transfer. It is found that for the exposure times investigated the liquid film between the bubble and the wall is saturated and the mass transfer occurs by the major part through the bubble front and rear so that short unit cells are more efficient for mass transfer. Similar observations are made for the homogeneous reaction and for the heterogeneous reaction when the reaction is slow. In case of a fast heterogeneous reaction and when the main resistance to mass transfer is in the gas phase, it appears that for square channels long unit cells are more efficient, while large aspect ratio rectangular channels are more efficient than square channels, suggesting that for these conditions they might be more appropriate for use in monolithic catalysts. | |||||
BibTeX:
@article{Onea2009,
author = {Onea, Alexandru and Wörner, Martin and Cacuci, Dan G.},
title = {A qualitative computational study of mass transfer in upward bubble train flow through square and rectangular mini-channels},
journal = {Chemical Engineering Science},
year = {2009},
volume = {64},
number = {7},
pages = {1416--1435},
url = {http://www.sciencedirect.com/science/article/pii/S0009250908006295}
}
|
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| Orban, P., Brouyère, S., Batlle-Aguilar, J., Couturier, J., Goderniaux, P., Leroy, M., Maloszewski, P. and Dassargues, A. | Regional transport modelling for nitrate trend assessment and forecasting in a chalk aquifer | 2010 | Journal of Contaminant Hydrology Vol. 118(1-2), pp. 79-93 |
article | URL |
| Abstract: Regional degradation of groundwater resources by nitrate has become one of the main challenges for water managers worldwide. Regulations have been defined to reverse observed nitrate trends in groundwater bodies, such as the Water Framework Directive and the Groundwater Daughter Directive in the European Union. In such a context, one of the main challenges remains to develop efficient approaches for groundwater quality assessment at regional scale, including quantitative numerical modelling, as a decision support for groundwater management. A new approach combining the use of environmental tracers and the innovative ‘Hybrid Finite Element Mixing Cell’ (HFEMC) modelling technique is developed to study and forecast the groundwater quality at the regional scale, with an application to a regional chalk aquifer in the Geer basin in Belgium. Tritium data and nitrate time series are used to produce a conceptual model for regional groundwater flow and contaminant transport in the combined unsaturated and saturated zones of the chalk aquifer. This shows that the spatial distribution of the contamination in the Geer basin is essentially linked to the hydrodynamic conditions prevailing in the basin, more precisely to groundwater age and mixing and not to the spatial patterns of land use or local hydrodispersive processes. A three-dimensional regional scale groundwater flow and solute transport model is developed. It is able to reproduce the spatial patterns of tritium and nitrate and the observed nitrate trends in the chalk aquifer and it is used to predict the evolution of nitrate concentrations in the basin. The modelling application shows that the global inertia of groundwater quality is strong in the basin and trend reversal is not expected to occur before the 2015 deadline fixed by the European Water Framework Directive. The expected time required for trend reversal ranges between 5 and more than 50 years, depending on the location in the basin and the expected reduction in nitrate application. To reach a good chemical status, nitrate concentrations in the infiltrating water should be reduced as soon as possible below 50 mg/l; however, even in that case, more than 50 years is needed to fully reverse upward trends. | |||||
BibTeX:
@article{Orban2010,
author = {Orban, Philippe and Brouyère, Serge and Batlle-Aguilar, Jordi and Couturier, Julie and Goderniaux, Pascal and Leroy, Mathieu and Maloszewski, Piotr and Dassargues, Alain},
title = {Regional transport modelling for nitrate trend assessment and forecasting in a chalk aquifer},
journal = {Journal of Contaminant Hydrology},
year = {2010},
volume = {118},
number = {1-2},
pages = {79--93},
url = {http://www.sciencedirect.com/science/article/pii/S016977221000104X}
}
|
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| Ottino, J. | Mixing and chemical reactions a tutorial | 1994 | Chemical Engineering Science Vol. 49(24, Part A)Chemical Reaction Engineering: Science & Technology Thirteenth International Symposium On Chemical Reaction Engineering, pp. 4005-4027 |
article | URL |
| Abstract: The objective of this paper is to complement previous reviews focusing on somewhat more classical aspects of mixing in the content of chemical reaction engineering and to provide additional fluid mechanical perspective by highlighting recent developments. Coverage is restricted to frameworks capable of accommodating a visual and physical description of fluid flow and associated spatial inhomogeneities that might ultimately lead to predictions in a variety of situations, in both laminar and turbulent flows. It is argued that the treatment of laminar or viscous mixing is in good shape. This has been spurred by theoretical developments based on chaos theory and increased computational resources, as well as by advances in fluid mechanics and a host of new experimental results; in this case a body of theory fulfills the double role of producing basic understanding leading to prediction. By contrast, the picture in turbulent mixing is still less sharply defined and no accepted paradigm fulfills both the role of understanding and engineering prediction. Typical flows undergo transitions and are, in general, far from homogeneous, involving coexistence of regions of active and poor mixing; current statistical approaches are not fully equipped to deal with these situations. The difficulty lies in the case of moderate and fast reactions. If reactions are diffusion controlled, chemistry is controlled by the smallest scales. Important processes occur within striations, and straightforward averaging, in general, does not work; coarse graining results in loss of interface and computing the rate of reaction cannot be accomplished without some sort of subgrid model based on the physics of the problem. A lamellar model provides a simple picture that frequently leads to accurate predictions and indicates when mixing effects are important. Noteworthy among recent developments are the observations of lamellar structures at Kolmogorov scales in highly turbulent flows and the establishment of the kinematical connection between chaos and mixing. Remarkably, the smallest scales in turbulent flows and chaotic flows appear to be described by identical statistics. Illustrations are provided throughout. | |||||
BibTeX:
@article{Ottino1994,
author = {Ottino, J.M.},
title = {Mixing and chemical reactions a tutorial},
booktitle = {Chemical Reaction Engineering: Science & Technology Thirteenth International Symposium On Chemical Reaction Engineering},
journal = {Chemical Engineering Science},
year = {1994},
volume = {49},
number = {24, Part A},
pages = {4005--4027},
url = {http://www.sciencedirect.com/science/article/pii/S0009250905800041}
}
|
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| Ovaysi, S. and Piri, M. | Pore-scale modeling of dispersion in disordered porous media | 2011 | Journal of Contaminant Hydrology Vol. 124(1–4), pp. 68-81 |
article | URL |
| Abstract: We employ a direct pore-level model of incompressible flow that uses the modified moving particle semi-implicit (MMPS) method. The model is capable of simulating both unsteady- and steady-state flow directly in microtomography images of naturally-occurring porous media. We further develop this model to simulate solute transport in disordered porous media. The governing equations of flow and transport at the pore level, i.e., Navier–Stokes and convection–diffusion, are solved directly in the pore space mapped by microtomography techniques. Three naturally-occurring sandstones are studied in this work. We verify the accuracy of the model by comparing the computed longitudinal dispersion coefficients against the experimental data for a wide range of Peclet numbers, i.e., 5 × 10− 2 < Pe < 1 × 106. Solutions of full Navier–Stokes enable us to examine the impact of inertial forces at the very high Peclet numbers. We show that inclusion of the inertial forces improves the agreement between the computed dispersion coefficients with their experimental counterparts. We then investigate the impact of pore-space topology on the pre-asymptotic and asymptotic dispersion regimes by comparing solute dispersion in the three sandstones that possess different topological features. We illustrate how grain size and homogeneity of the two sandstones dictate the threshold and magnitude of the asymptotic regime. | |||||
BibTeX:
@article{Ovaysi2011,
author = {Ovaysi, Saeed and Piri, Mohammad},
title = {Pore-scale modeling of dispersion in disordered porous media},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {124},
number = {1–4},
pages = {68--81},
url = {http://www.sciencedirect.com/science/article/pii/S0169772211000180}
}
|
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| Ozyurt, N.N. and Bayari, C.S. | LUMPED Unsteady: a Visual Basic® code of unsteady-state lumped-parameter models for mean residence time analyses of groundwater systems | 2005 | Computers & Geosciences Vol. 31(3), pp. 329-341 |
article | URL |
| Abstract: A Microsoft® Visual Basic 6.0 (Microsoft Corporation, 1987–1998) code of 9 lumped-parameter models of unsteady flow is presented for the analysis of mean residence time in aquifers. Groundwater flow systems obeying plug and well-mixed flow models and their combinations in parallel or serial connection can be simulated by the code. Models can use tritium, tritiugenic He-3, oxygen-18, deuterium, krypton-85, chlorofluorocarbons (CFC-11, CFC-12 and CFC-113) and sulfur hexafluoride (SF6) as the environmental tracers. The executable code runs under all 32-bit Windows operating systems. Details of the code are explained and its limitations are indicated. | |||||
BibTeX:
@article{Ozyurt2005,
author = {Ozyurt, N. Nur and Bayari, C. Serdar},
title = {LUMPED Unsteady: a Visual Basic® code of unsteady-state lumped-parameter models for mean residence time analyses of groundwater systems},
journal = {Computers & Geosciences},
year = {2005},
volume = {31},
number = {3},
pages = {329--341},
url = {http://www.sciencedirect.com/science/article/pii/S0098300404002067}
}
|
|||||
| P.V., D. | Continuous flow systems. Distribution of residence times: P. V. Danckwerts, Chem. Engng Sci. 2: 1–13, 1953 | 1995 | Chemical Engineering Science Vol. 50(24)Frontiers of Chemical Engineering Science, pp. 3855- |
article | URL |
| Abstract: When material flows through a vessel or a chemical plant at constant rate, some of it spends more and some less than the average residence time in the system. If the system is, for instance, a blender, a chemical reactor or a drier, this spread of residence times may have an important effect on the performance of the plant. This paper describes methods for the quantitative description and measurement of residence-time distributions, and their use in calculating the performance of chemical plant items. | |||||
BibTeX:
@article{P.V.1995,
author = {P.V., Danckwerts},
title = {Continuous flow systems. Distribution of residence times: P. V. Danckwerts, Chem. Engng Sci. 2: 1–13, 1953},
booktitle = {Frontiers of Chemical Engineering Science},
journal = {Chemical Engineering Science},
year = {1995},
volume = {50},
number = {24},
pages = {3855--},
url = {http://www.sciencedirect.com/science/article/pii/0009250996818100}
}
|
|||||
| Pacheco, J.R., Ping Chen, K. and Hayes, M.A. | Rapid and efficient mixing in a slip-driven three-dimensional flow in a rectangular channel | 2006 | Fluid Dynamics Research Vol. 38(8), pp. 503-521 |
article | URL |
| Abstract: A method for generating mixing in an electroosmotic flow of an electrolytic solution in a three-dimensional channel is proposed. When the width-to-height aspect ratio of the channel cross-section is large, mixing of a blob of a solute in a slip-driven three-dimensional flow in a rectangular channel can be used to model and assess the effectiveness of this method. It is demonstrated through numerical simulations that under certain operating conditions, rapid and efficient mixing can be achieved. Future investigation will include the solution of the exact equations and experimentation. | |||||
BibTeX:
@article{Pacheco2006,
author = {Pacheco, J. Rafael and Ping Chen, Kang and Hayes, Mark A.},
title = {Rapid and efficient mixing in a slip-driven three-dimensional flow in a rectangular channel},
journal = {Fluid Dynamics Research},
year = {2006},
volume = {38},
number = {8},
pages = {503--521},
url = {http://www.sciencedirect.com/science/article/pii/S0169598306000402}
}
|
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| Page, D., Dillon, P., Mueller, J. and Bartkow, M. | Quantification of herbicide removal in a constructed wetland using passive samplers and composite water quality monitoring | 2010 | Chemosphere Vol. 81(3), pp. 394-399 |
article | URL |
| Abstract: Constructed wetlands used as treatment for urban stormwater have the potential to improve water quality. This study aimed to estimate the removal of selected herbicides in stormwater by a constructed wetland using composite water quality monitoring and passive samplers. For the four week duration of the study the wetland was effective in reducing the concentrations of diuron, simazine and atrazine. Mean estimated concentrations over a 28 d period were 192, 70 and 5 ng L−1 at the inlet and 94, 30 and 2 ng L−1 at the outlet for diuron, simazine and atrazine, respectively. Concentrations of these herbicides generally halved as a result of passage through the constructed wetland with a design hydraulic retention time of 7 d. Simple ratios of the inlet and outlet herbicide concentrations as well as hydraulic load-based methods of measuring the wetland’s removal efficiency resulted in a range of estimations 33–51% for diuron and 20–60% for simazine. Due to their lower detection limits, the use of passive samplers provides a more efficient technique than conventional sampling for assessment of stormwater wetland treatment. | |||||
BibTeX:
@article{Page2010,
author = {Page, Declan and Dillon, Peter and Mueller, Jochen and Bartkow, Michael},
title = {Quantification of herbicide removal in a constructed wetland using passive samplers and composite water quality monitoring},
journal = {Chemosphere},
year = {2010},
volume = {81},
number = {3},
pages = {394--399},
url = {http://www.sciencedirect.com/science/article/pii/S0045653510007691}
}
|
|||||
| Painter Ph.D. P.E., R. and Byl Ph.D., T. | Assessment of the Impact of a Multidisciplinary Research Program on Student Outcomes | 2012 | Proceedings of the American Society for Engineering Education (ASEE) 119th Annual Conference and Exposition, San Antonio, Texas, USA, June 10 - 13, 2012 | article | |
| Abstract: The Tennessee State University (TSU) Environmental Engineering research program provides financial assistance to students at the undergraduate and graduate level. The program requires students to present the results of environmental research and projects at local, regional or national poster competitions. This paper provides a description of student involvement in the Environmental Engineering research program at TSU. An assessment of the program’s impact on student outcomes based on their performance at local and regional poster competitions is also presented. | |||||
BibTeX:
@article{Painter2005,
author = {Painter, Ph.D. P.E., Roger and Byl, Ph.D., Thomas},
title = {Assessment of the Impact of a Multidisciplinary Research Program on Student Outcomes},
booktitle = {Proceedings of the American Society for Engineering Education (ASEE) 119th Annual Conference and Exposition, San Antonio, Texas, USA, June 10 - 13, 2012},
year = {2012}
}
|
|||||
| Painter, R. | Engineering Ethics, Environmental Justice and Environmental Impact Analysis: A Synergistic Approach to Improving Student Learning | 2012 | Proceedings of the American Society for Engineering Education (ASEE) 119th Annual Conference and Exposition, San Antonio, Texas, USA, June 10 - 13, 2012 | inproceedings | |
| Abstract: Engineering ethics is being taught to Environmental Engineering students at Tennessee State University (TSU) in context with the broader aspects of environmental justice issues. The content regarding engineering ethics and environmental justice issues is presented in case studies as part of a required environmental engineering course titled Environmental Impact Analysis. The case studies also present the implementation of Environmental Impact Analysis (EIA) via the National Environmental Policy Act (NEPA). Executive Order 12898, “Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations”, was accompanied by specific guidance from the president regarding recognizing the importance of procedures under NEPA for identifying and addressing environmental justice concerns. In this regard case studies that facilitate the interpretation of NEPA naturally extend to engineering ethics and environmental justice issues. Traditionally, engineering ethics have been taught only in terms of micro-ethics – the individual ethical decision-making of the engineering professional. However engineers are more and more expected to be moral agents responsible for helping to develop solutions to societal ethical problems. Unfortunately, macroethics problems don’t fit neatly into traditional engineering education and the unavoidable fact that there are no concise “right answer” that can be imposed by the individual engineer challenges the typical engineering student’s worldview. In this regard we need to change the way engineers think about ethics and a change in pedagogy is needed. Furthermore, an element of critical pedagogy is indicated to correct the worldview of engineers regarding ethics. Critical reflection is key to significant shifts of frames of reference. In this context the goal of encouraging students to view engineering ethics through the lens of environmental justice issues is motivated by transformation learning theory. During the first half of the semester lectures covered NEPA and EIA in the conventional manner and research papers were assigned for EIA case studies. Beginning at midterm the relationship of environmental justice issues to NEPA and EIA were introduced and subsequent case study assignments also involved environmental justice issues. For these case studies, the student’s role played the various stakeholders on both sides of the case study issues. Anecdotally the impact of the intervention was immediately reflected by an increased level of class participation and discussion of ethical dilemmas posed by the case studies. To assess the impact on student outcomes regarding engineering ethics a survey was administered at the end of the semester regarding the engineering ethics content of the student’s previous technical engineering courses. For comparison purposes the survey included several questions similar to questions from a survey at Stanford University over a three year period. Relative to the Stanford results, the survey indicated a dramatic increase in the interest and awareness of the EIA course students regarding the role of engineering ethics in society. The survey results excluding the impact of the EIA course are very similar to the Stanford results and indicate that almost all the students expect to face ethical issues during their careers, but less than one-third say they have discussed an ethical issue in any of their technical engineering courses. | |||||
BibTeX:
@inproceedings{Painter2012b,
author = {Painter, Roger},
title = {Engineering Ethics, Environmental Justice and Environmental Impact Analysis: A Synergistic Approach to Improving Student Learning},
booktitle = {Proceedings of the American Society for Engineering Education (ASEE) 119th Annual Conference and Exposition, San Antonio, Texas, USA, June 10 - 13, 2012},
year = {2012}
}
|
|||||
| Painter, R., Byl, T., Sharpe, L., Kheder, A. and Harris, J. | The Role of Attached and Free-Living Bacteria in Biodegradation in Karst Aquifers | 2011 | Water Vol. 3(4), pp. 1139-1148 |
article | URL |
| Abstract: Natural attenuation of groundwater contamination occurs at some level for all aquifers impacted with organic contaminants. The issues regarding natural attenuation are whether it takes place at a sufficient rate to be protective of human health and the environment. Implementation of a Monitored Natural Attenuation (MNA) remedial alternative for groundwater requires parties responsible for the contamination to demonstrate to regulators and the public that MNA is protective at a given site. Analysis of MNA for remediation of karst aquifers is hampered by a lack of understanding of biodegradation in karst environments. The lack of studies examining biodegradation in karst aquifers may in large part be due to the widespread perception that contaminants are rapidly flushed out of karst aquifers resulting in insufficient residence times for contaminants to biodegrade. In highly developed and well-connected conduit systems, the rate of contaminant migration is perceived to be much faster than the rate of biodegradation. This perception of contaminant transport is largely incorrect. Tracer studies for karst aquifers often indicate that these aquifers are characterized by diverse flow regimes and storage capabilities. Additionally, it is also believed that if bioremediation in bedrock aquifers is dependent upon contact between surface-attached bacteria and contaminants, then bioremediation would be limited by the low surface-area-to-volume ratio (SA/V) of karst aquifers. A quantitative basis, however, for accepting or rejecting the assumption that attached bacteria dominate the biodegradation process in karst conduits has not been shown. The objective of this research was to determine if free-living karst bacteria from contributed as much to toluene biodegradation as attached bacteria. This is an important area of research. Research indicates bacteria are both attached and free-living in karst aquifers and it is unrealistic to think that only the attached bacteria facilitate biodegradation. The groundwater use in all tests was taken from a karst aquifer know to be impacted by BTEX. The resulting first-order rate constants were computed to be 0.014 per hour for the open system and 0.0155 per hour for the packed reactor system. Biodegradation of toluene in flow-through laboratory karst systems of varying SA/V indicated that the observed biodegradation of toluene was attributable to free-living karst bacteria and not limited by low SA/V in karst. This was evidenced by the fact that the systems with five-fold variation in SA/V were shown to have observed pseudo first order reaction rate constants that differed by only 7.0%. If attached bacteria were primarily responsible for biodegradation and limiting, a proportional difference in the observed rates relative to the difference in surface area would be expected. | |||||
BibTeX:
@article{Painter2011,
author = {Painter, Roger and Byl, Tom and Sharpe, Lonnie and Kheder, Ahmad and Harris, Justin},
title = {The Role of Attached and Free-Living Bacteria in Biodegradation in Karst Aquifers},
journal = {Water},
year = {2011},
volume = {3},
number = {4},
pages = {1139--1148},
url = {http://www.mdpi.com/2073-4441/3/4/1139/}
}
|
|||||
| Painter, R., Byl, T., Sharpe, L. and Patterson, T. | Determining the Rate of Biodegradation in Fuel Impacted Karst Aquifers | 2012 | Proceedings of the 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety, Houston, Texas, USA, April 1 - 5, 2012 | inproceedings | URL |
| Abstract: Hydrologic and geologic characteristics of fractured rock aquifers have been described as not being suited for natural bioremediation because of small microbial populations. It is also widely perceived that karst groundwater often has insufficient residence time for biodegradation to occur. It is perhaps due to these perceptions that less research has been conducted for quantitative modeling of karst as compared to consolidated aquifers. Modeling biodegradation in karst is in the domain of non-ideal chemical reaction kinetics. For all non-ideal flow reactors, the concentration response to an input of tracer must lie between the limiting cases of completely mixed flow and purely plug flow. The residence time distribution function (RTD) for tracer molecules in a single karst conduit or a complex system of conduits is a probability density function which can be interpreted to define the probability that contaminant molecules present at the influent at time equals zero will arrive at the effluent after a particular amount of time. In this work, the biodegradation rate of a contaminant (toluene) in raw karst groundwater from a BTEX impacted site in central Kentucky was quantitatively measured in microcosm studies and the extent of biodegradation of toluene in the same groundwater was measured for a complex flow system. Data from conservative tracer studies and for toluene biodegradation were used in conjunction with the advection dispersion equation to investigate the biodegradation rate. Results indicated that the biodegradation of toluene in karst groundwater is a volumetric reaction which can be described by pseudo first order reaction kinetics. The values of the rate constant (k') obtained from the dispersion-like model ranged from 0.017 (hr)-1 to 0.0210 (hr)-1 compared to 0.0186 (hr)-1 for the microcosm experiments. This corresponds to a half life of less than two days for toluene and has major implications to issues regarding natural attenuation of fuel impacted sites. | |||||
BibTeX:
@inproceedings{Painter2012c,
author = {Painter, Roger and Byl, Tom and Sharpe, Lonnie and Patterson, Tony},
title = {Determining the Rate of Biodegradation in Fuel Impacted Karst Aquifers},
booktitle = {Proceedings of the 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety, Houston, Texas, USA, April 1 - 5, 2012},
year = {2012},
url = {http://aiche.confex.com/aiche/s12/webprogrampreliminary/Paper243120.html}
}
|
|||||
| Painter, R., Byl, T., Sharpe, L., Watson, V. and Patterson, T. | A Residence Time Distribution Approach to Biodegradation in Fuel Impacted Karst Aquifers | 2012 | Journal of Civil & Environmental Engineering Vol. 2(4) |
article | URL |
| Abstract: It is widely perceived that karst groundwater often has insufficient residence time for significant biodegradation of contaminants to occur. It is perhaps due to these perceptions that less research has been conducted for quantitative modeling of biodegradation in karst as compared to consolidated aquifers. Modeling biodegradation in karst is in the domain of non-ideal chemical reaction kinetics. The residence time distribution function (RTD) for tracer molecules in a single karst conduit or a complex system of conduits is a probability density function which can be interpreted to define the probability that contaminant molecules present at the influent at time equals zero will arrive at the effluent after a particular amount of time. To demonstrate this methodology the biodegradation rate of a contaminant (toluene) in raw karst groundwater from a BTEX impacted site in central Kentucky was quantitatively measured in batch microcosm studies and the extent of biodegradation of toluene in the same groundwater was measured for a complex flow system. The values of the pseudo first order rate constant (k’) obtained ranged from 0.017 (hr)-1 to 0.0210 (hr)-1 compared to 0.0186 (hr)-1 for the microcosm experiments. The close agreement between the values of k’ obtained from the static microcosms and the ADE model indicate that the model adequately describes the RTD for modeling biodegradation in karst aquifers. The values of k’ obtained correspond to a half-life of less than two days for toluene and this has major implications to issues regarding natural attenuation of fuel impacted karst sites. | |||||
BibTeX:
@article{Painter2012,
author = {Painter, Roger and Byl, Tom and Sharpe, Lonnie and Watson, Valetta and Patterson, Tony},
title = {A Residence Time Distribution Approach to Biodegradation in Fuel Impacted Karst Aquifers},
journal = {Journal of Civil & Environmental Engineering},
publisher = {OMICS Group},
year = {2012},
volume = {2},
number = {4},
url = {http://www.omicsgroup.org/journals/2165-784X/2165-784X-2-121.php?aid=7137}
}
|
|||||
| Painter, R., Byl, T., Sharpe, L., Watson, V. and Patterson, T. | A Residence Time Distribution Approach to Biodegradation in Fuel Impacted Karst Aquifers | 2012 | Journal of Civil & Environmental Engineering Vol. 2(5), pp. - |
article | DOI URL |
| Abstract: It is widely perceived that karst groundwater often has insufficient residence time for significant biodegradation of contaminants to occur. It is perhaps due to these perceptions that less research has been conducted for quantitative modeling of biodegradation in karst as compared to consolidated aquifers. Modeling biodegradation in karst is in the domain of non-ideal chemical reaction kinetics. The residence time distribution function (RTD) for tracer molecules in a single karst conduit or a complex system of conduits is a probability density function which can be interpreted to define the probability that contaminant molecules present at the influent at time equals zero will arrive at the effluent after a particular amount of time. To demonstrate this methodology the biodegradation rate of a contaminant (toluene) in raw karst groundwater from a BTEX impacted site in central Kentucky was quantitatively measured in batch microcosm studies and the extent of biodegradation of toluene in the same groundwater was measured for a complex flow system. The values of the pseudo first order rate constant (k’) obtained ranged from 0.017 (hr)-1 to 0.0210 (hr)-1 compared to 0.0186 (hr)-1 for the microcosm experiments. The close agreement between the values of k’ obtained from the static microcosms and the ADE model indicate that the model adequately describes the RTD for modeling biodegradation in karst aquifers. The values of k’ obtained correspond to a half-life of less than two days for toluene and this has major implications to issues regarding natural attenuation of fuel impacted karst sites. | |||||
BibTeX:
@article{Painter2012a,
author = {Painter, Roger and Byl, Tom and Sharpe, Lonnie and Watson, Valetta and Patterson, Tony},
title = {A Residence Time Distribution Approach to Biodegradation in Fuel Impacted Karst Aquifers},
journal = {Journal of Civil & Environmental Engineering},
publisher = {OMICS Publishing Group},
year = {2012},
volume = {2},
number = {5},
pages = {--},
url = {http://www.omicsgroup.org/journals/2165-784X/2165-784X-2-121.php?%20aid=7137},
doi = {http://dx.doi.org/10.4172/2165-784X.1000121}
}
|
|||||
| Painter, R., Byl, T. and Watson, V. | Residence Time Distribution Derived from Independent Gamma Distributions of Tracer Travel Distance and Linear Velocity | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 75 | inproceedings | URL |
| Abstract: The advection dispersion equation (ADE) is widely used as a predictor of residence time distributions (RTDs) for tracer breakthrough curves for karst systems. Solutions of the ADE for tracer breakthrough studies with near plug flow behavior are characteristically Gaussian in appearance. However, very few, if any, quantitative tracer studies result in tracer concentrations that are normally distributed about the mean residence time. While the symmetry of Gaussian breakthrough curves often correctly predicts finite tracer concentrations at zero time, it generally does not accurately predict actual tracer breakthrough curves, which invariably are characterized by relatively long tails. This suggests that a different conceptual approach may be appropriate for describing these systems in easily visualized terms. The objective of this project was to develop a more descriptive approach of tracer break-through data based on the gamma probability density function. The tracer travel distance and tracer linear velocity were assumed to be randomly distributed variables with gamma distributions. The RTD for tracer breakthrough curves was derived from the individual distributions of tracer travel distance and linear velocity. This approach was compared and contrasted with the traditional approach based on the ADE for modeling tracer break-through data at a karst site, as well as, modeling the rate of biodegradation of toluene in laboratory karst aquifers. | |||||
BibTeX:
@inproceedings{Painter2008,
author = {Painter, Roger and Byl, Tom and Watson, Valetta},
title = {Residence Time Distribution Derived from Independent Gamma Distributions of Tracer Travel Distance and Linear Velocity},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {75},
url = {http://pubs.usgs.gov/sir/2008/5023/30painter.htm}
}
|
|||||
| Painter, R. and King, L. | The Role of Environmental Justice Issues in Environmental Engineering Ethics | 2005 | American Society for Engineering Education (ASEE) Annual Conference, Conference Proceedings 2005 | inproceedings | |
| Abstract: The engineering accreditation agency, ABET regards engineering ethics as an important component of engineering education. ABET’s Criterion 3(f ) states that “Engineering Programs must demonstrate their graduates have an understanding of professional and ethical responsibilities.” Limitations on credit hours in engineering programs often preclude ethics being taught in a separate course and engineering faculty must include ethics topics in traditional engineering courses. Teaching engineering ethics to environmental engineering students in the context of solid and hazardous waste management classes poses unique challenges and opportunities for instructors. The role of environmental engineers in designing and especially in selecting sites for solid and hazardous waste facilities necessitates an engineering ethics education that addresses environmental justice issues. The author has successfully used case studies and hypothetical scenarios to teach engineering ethics in solid and hazardous waste management classes. These studies address environmental justice issues and current regulatory/social conditions with an emphasis on how these issues impact environmental engineers. | |||||
BibTeX:
@inproceedings{Painter2005b,
author = {Painter, Roger and King, Lashun},
title = {The Role of Environmental Justice Issues in Environmental Engineering Ethics},
booktitle = {American Society for Engineering Education (ASEE) Annual Conference, Conference Proceedings 2005},
publisher = {American Society for Engineering Education (ASEE)},
year = {2005}
}
|
|||||
| Painter, R., Watson, V. and Kheder, A. | Robust Statistical Analysis for MSW Characterization Studies | 2011 | Journal of Civil & Environmental Engineering Vol. 1(1), pp. 102-102 |
article | URL |
| Abstract: Tennessee State University conducted a pilot municipal solid waste study for Tennessee Department of Environment at two Tennessee municipal solid waste disposal facilities. A major goal for the pilot study was to develop and demonstrate statistical analysis methodologies to be used in a future statewide municipal solid waste study. In municipal solid waste studies the costs of sorting and weighing a sufficient number of samples to obtain reasonably precise estimates is prohibitive for some waste constituents. This issue regarding the number of municipal solid waste samples was addressed using a real-time iterative analysis that involved simultaneous tracking of the mean, trimmed mean, and median of the sample populations. Sampling was terminated for a particular waste category based on observation of dimensioning incremental improvement in 90 percent confidence intervals for the mean and median. This approach was adopted to take advantage of the robustness of efficiency of the mean for waste categories with near normal distribution and the robustness of validity of the median for grossly non-normally distributed categories. The trimmed mean was included in the analysis as an intermediate estimator to the mean and median with regard to loss of sample information. The convergence of the three estimators for nearly normal data and the trimmed mean intermediate relationship to the mean and median provided excellent field guidance regarding the tradeoff between precision and sampling cost. This approach also provides the option of making statistical inference on the median for grossly non-normal waste subcategories when additional sampling to designate the mean is not an option. | |||||
BibTeX:
@article{PainterR.2011,
author = {Painter, Roger and Watson, Valetta and Kheder, Ahmad},
title = {Robust Statistical Analysis for MSW Characterization Studies},
journal = {Journal of Civil & Environmental Engineering},
year = {2011},
volume = {1},
number = {1},
pages = {102--102},
url = {http://www.omicsgroup.org/journals/2165-784X/2165-784X-1-102.php?aid=3073}
}
|
|||||
| Painter, R.D., Kochary, S. and Byl, T. | Free-Living Bacteria or Attached Bacteria: Which Contributes More to Bioremediation? | 2005 | U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160, pp. 180-187 | inproceedings | URL |
| Abstract: Researchers have implied that natural bioremediation in karst or fractured rock is unlikely to occur because of the lack of bacteria biofilm in karst aquifers. Hydrologic and geologic characteristics of fractured rock aquifers have been described as not being suited for natural bioremediation because of small microbial populations. If bioremediation in bedrock aquifers is dependent upon contact between surface-attached bac- teria and contaminants, then bioremediation would be limited by the low surface area to volume ratio (SA/V) of karst aquifers. A quantitative basis, however, for accepting or rejecting the assumption that attached bacteria dominate the biodegradation process in karst conduits has not been shown. The objective of this research was to determine if free-living karst bacteria contributed as much to toluene biodegradation as attached bacteria. Two flow-through reactor systems were established to test the different biodegradation rates. Each reactor system consisted of four 1.24-liter cylinders connected together with glass tubing for a total open volume of approximately 5 liters. The second reactor system was similar to the open system except the cylinders were filled with acid-washed, circular glass spheres that increased surface area to vol- ume ratio approximately fivefold compared to the open system. Rhodamine dye was used to calculate the different residence-time distributions in each system. A sterile control study established that less than 3 per- cent of the toluene was lost to abiotic processes. Next, raw water from a karst aquifer containing live, indig- enous bacteria was pumped through each system for 5 days to establish a biofilm on the glass surfaces. Colonization of the surface was confirmed by microscope visualization before toluene was added to the sys- tems. The resulting first-order rate constants were computed to be 0.014 per hour for the open system and 0.0155 per hour for the packed reactor system. If surface-attached bacteria were the main contributors to the biodegradation process and the SA/V ratio was increased fivefold, a significantly higher biodegradation rate should have occurred in the packed reactor. The results of this study indicate that the free-living bacteria indigenous to a karst aquifer contribute as much to the toluene biodegradation process as attached bacteria. | |||||
BibTeX:
@inproceedings{Painter2005a,
author = {Painter, Roger D. and Kochary, Shawkat and Byl, T.D.},
title = {Free-Living Bacteria or Attached Bacteria: Which Contributes More to Bioremediation?},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Rapid City, South Dakota, September 12-15, 2005: U.S. Geological Survey Scientific Investigations Report 2005-5160},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2005},
pages = {180--187},
url = {pubs.usgs.gov/sir/2005/5160/index.html}
}
|
|||||
| Pal, D. | Effect of chemical reaction on the dispersion of a solute in a porous medium | 1999 | Applied Mathematical Modelling Vol. 23(7), pp. 557-566 |
article | URL |
| Abstract: A mathematical model is presented in this paper which describes the dispersion of a chemically active solute in the laminar flow in a sparsely packed porous medium. The validity of time-dependent dispersion coefficient is widened by using a generalized dispersion coefficient. The effect of porous parameter and chemical reaction on the dispersion coefficient is studied. The exact solution for the mean concentration distribution of a chemically active solute is obtained as a function of downwind distance and time. Results are also obtained for pure convection. | |||||
BibTeX:
@article{Pal1999,
author = {Pal, Dulal},
title = {Effect of chemical reaction on the dispersion of a solute in a porous medium},
journal = {Applied Mathematical Modelling},
year = {1999},
volume = {23},
number = {7},
pages = {557--566},
url = {http://www.sciencedirect.com/science/article/pii/S0307904X98100999}
}
|
|||||
| Palakodeti, R.C., LeBoeuf, E.J. and Clarke, J.H. | Tool for assessment of process importance at the groundwater/surface water interface | 2009 | Journal of Environmental Management Vol. 91(1), pp. 87-101 |
article | URL |
| Abstract: The groundwater/surface water interface (GWSWI) represents an important transition zone between groundwater and surface water environments that potentially changes the nature and flux of contaminants exchanged between the two systems. Identifying dominant and rate-limiting contaminant transformation processes is critically important for estimating contaminant fluxes and compositional changes across the GWSWI. A new, user-friendly, spreadsheet- and Visual Basic-based analytical screening tool that assists in evaluating the dominance of controlling kinetic processes across the GWSWI is presented. Based on contaminant properties, first-order processes that may play a significant role in solute transport/transformation are evaluated in terms of a ratio of process importance (Pi) that relates the process rate to the rate of fluid transfer. Besides possessing several useful compilations of contaminant and process data, the screening tool also includes 1-D analytical models that assist users in evaluating contaminant transport across the GWSWI. The tool currently applies to 29 organics and 10 inorganics of interest within the context of the GWSWI. Application of the new screening tool is demonstrated through an evaluation of natural attenuation at a site with trichloroethylene and 1,1,2,2-tetrachloroethane contaminated groundwater discharging into wetlands. | |||||
BibTeX:
@article{Palakodeti2009,
author = {Palakodeti, Ravi C. and LeBoeuf, Eugene J. and Clarke, James H.},
title = {Tool for assessment of process importance at the groundwater/surface water interface},
journal = {Journal of Environmental Management},
year = {2009},
volume = {91},
number = {1},
pages = {87--101},
url = {http://www.sciencedirect.com/science/article/pii/S0301479709002382}
}
|
|||||
| Palmer, A.N. | Distinction between epigenic and hypogenic maze caves | 2011 | Geomorphology Vol. 134(1-2)Geomorphology and Natural Hazards in Karst Areas, pp. 9-22 |
article | URL |
| Abstract: Certain caves formed by dissolution of bedrock have maze patterns composed of closed loops in which many intersecting fractures or pores have enlarged simultaneously. Their origin can be epigenic (by shallow circulation of meteoric groundwater) or hypogenic (by rising groundwater or production of deep-seated solutional aggressiveness). Epigenic mazes form by diffuse infiltration through a permeable insoluble caprock or by floodwater supplied by sinking streams. Most hypogenic caves involve deep sources of aggressiveness. Transverse hypogenic cave origin is a recently proposed concept in which groundwater of mainly meteoric origin rises across strata in the distal portions of large flow systems, to form mazes in soluble rock sandwiched between permeable but insoluble strata. The distinction between maze types is debated and is usually based on examination of diagnostic cave features and relation of caves to their regional setting. In this paper, the principles of mass transfer are applied to clarify the limits of each model, to show how cave origin is related to groundwater discharge, dissolution rate, and time. The results show that diffuse infiltration and floodwater can each form maze caves at geologically feasible rates (typically within 500 ka). Transverse hypogenic mazes in limestone, to enlarge significantly within 1 Ma, require an unusually high permeability of the non-carbonate beds (generally ≥ 10−4 cm/s), large discharge, and calcite saturation no greater than 90%, which is rare in deep diffuse flow in sedimentary rocks. Deep sources of aggressiveness are usually required. The origin of caves by transverse hypogenic flow is much more favorable in evaporite rocks than in carbonate rocks. | |||||
BibTeX:
@article{Palmer2011,
author = {Palmer, Arthur N.},
title = {Distinction between epigenic and hypogenic maze caves},
booktitle = {Geomorphology and Natural Hazards in Karst Areas},
journal = {Geomorphology},
year = {2011},
volume = {134},
number = {1-2},
pages = {9--22},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X11001498}
}
|
|||||
| Pan, J.-B., Lee, C.-C., Lee, C.-H., Yeh, H.-F. and Lin, H.-I. | Application of fracture network model with crack permeability tensor on flow and transport in fractured rock | 2010 | Engineering Geology Vol. 116(1-2), pp. 166-177 |
article | URL |
| Abstract: Very efficient and practical models that use a crack tensor in terms of fracture geometry parameters for field rock mass are proposed. A framework of the crack tensor approach combined with the identifying fracture-controlled characteristics was successively used in a hypothetical hydro-geological field for determining the dynamics of flow and transport of nuclides in fractured rock. | |||||
BibTeX:
@article{Pan2010,
author = {Pan, Jian-Bang and Lee, Chen-Chang and Lee, Cheng-Haw and Yeh, Hsin-Fu and Lin, Hung-I},
title = {Application of fracture network model with crack permeability tensor on flow and transport in fractured rock},
journal = {Engineering Geology},
year = {2010},
volume = {116},
number = {1-2},
pages = {166--177},
url = {http://www.sciencedirect.com/science/article/pii/S0013795210001614}
}
|
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| Panday, S., Wu, Y., Huyakorn, P., Wade, S. and Saleem, Z. | A composite numerical model for assessing subsurface transport of oily wastes and chemical constituents | 1997 | Journal of Contaminant Hydrology Vol. 25(1-2), pp. 39-62 |
article | URL |
| Abstract: Subsurface fate and transport models are utilized to predict concentrations of chemicals leaching from wastes into downgradient receptor wells. The contaminant concentrations in groundwater provide a measure of the risk to human health and the environment. The level of potential risk is currently used by the U.S. Environmental Protection Agency to determine whether management of the wastes should conform to hazardous waste management standards. It is important that the transport and fate of contaminants is simulated realistically. Most models in common use are inappropriate for simulating the migration of wastes containing significant fractions of nonaqueous-phase liquids (NAPLs). The migration of NAPL and its dissolved constituents may not be reliably predicted using conventional aqueous-phase transport simulations. To overcome this deficiency, an efficient and robust regulatory assessment model incorporating multiphase flow and transport in the unsaturated and saturated zones of the subsurface environment has been developed. The proposed composite model takes into account all of the major transport processes including infiltration and ambient flow of NAPL, entrapment of residual NAPL, adsorption, volatilization, degradation, dissolution of chemical constituents, and transport by advection and hydrodynamic dispersion. Conceptually, the subsurface is treated as a composite unsaturated zone-saturated zone system. The composite simulator consists of three major interconnected computational modules representing the following components of the migration pathway: (1) vertical multiphase flow and transport in the unsaturated zone; (2) areal movement of the free-product lens in the saturated zone with vertical equilibrium; and (3) three-dimensional aqueous-phase transport of dissolved chemicals in ambient groundwater. Such a composite model configuration promotes computational efficiency and robustness (desirable for regulatory assessment applications). Two examples are presented to demonstrate the model verification and a site application. Simulation results obtained using the composite modeling approach are compared with a rigorous numerical solution and field observations of crude oil saturations and plume concentrations of total dissolved organic carbon at a spill site in Minnesota, U.S.A. These comparisons demonstrate the ability of the present model to provide realistic depiction of field-scale situations. | |||||
BibTeX:
@article{Panday1997,
author = {Panday, S. and Wu, Y.S. and Huyakorn, P.S. and Wade, S.C. and Saleem, Z.A.},
title = {A composite numerical model for assessing subsurface transport of oily wastes and chemical constituents},
journal = {Journal of Contaminant Hydrology},
year = {1997},
volume = {25},
number = {1-2},
pages = {39--62},
url = {http://www.sciencedirect.com/science/article/pii/S0169772296000228}
}
|
|||||
| Pandey, G. and Nguyen, V.-T.-V. | A comparative study of regression based methods in regional flood frequency analysis | 1999 | Journal of Hydrology Vol. 225(1–2), pp. 92-101 |
article | URL |
| Abstract: Reliable estimates of flow statistics are needed for water resources management and flood forecasting purposes. However, the location of gaging station seldom coincides with the site of interest, or the available record becomes too short to make meaningful statistical inferences. Thus regional regression models, such as power-form model of Thomas and Benson (Thomas, D.M., Benson, M.A., 1970. Generalization of streamflow characteristics from drainage-basin characteristics, US Geological Survey, Water Supply Paper, 1975), which relate regional physiographic characteristics to streamflow statistics are developed to estimate the streamflow statistics where data are needed but not available. Depending upon the postulated model type and nature of the data, there are several ways of estimating model parameters. This paper compares the performances of nine methods of estimating parameters of the power-form model that expresses flood quantile as a function of basin area. The performance of each method is assessed based upon its quantile prediction ability from an ungaged site in the region. A jacknife procedure is used to simulate the ungaged site condition in the region. Based upon a case study using the hydrologic and physiographic data from Quebec, Canada, nonlinear models outperformed the log-linearized (or linear) models. Despite the differences in the parameter estimation techniques and suitability for different data type, the quantile prediction abilities of all of the linear models were not different from each other. Most of the linear models had higher bias and higher root mean squared error and they under-predicted floods from large basins. | |||||
BibTeX:
@article{Pandey1999,
author = {Pandey, G.R. and Nguyen, V.-T.-V.},
title = {A comparative study of regression based methods in regional flood frequency analysis},
journal = {Journal of Hydrology},
year = {1999},
volume = {225},
number = {1–2},
pages = {92--101},
url = {http://www.sciencedirect.com/science/article/pii/S0022169499001353}
}
|
|||||
| Pang, W.-K., Hou, S.-H., Yu, B.W. and Li, K.W.K. | A simulation based approach to the parameter estimation for the three-parameter gamma distribution | 2004 | European Journal of Operational Research Vol. 155(3)Traffic and Transportation Systems Analysis, pp. 675-682 |
article | URL |
| Abstract: The gamma distribution is one of the commonly used statistical distribution in reliability. While maximum likelihood has traditionally been the main method for estimation of gamma parameters, Hirose has proposed a continuation method to parameter estimation for the three-parameter gamma distribution. In this paper, we propose to apply Markov chain Monte Carlo techniques to carry out a Bayesian estimation procedure using Hirose’s simulated data as well as two real data sets. The method is indeed flexible and inference for any quantity of interest is readily available. | |||||
BibTeX:
@article{Pang2004,
author = {Pang, Wan-Kai and Hou, Shui-Hung and Yu, Bosco W.T and Li, Ken W. K},
title = {A simulation based approach to the parameter estimation for the three-parameter gamma distribution},
booktitle = {Traffic and Transportation Systems Analysis},
journal = {European Journal of Operational Research},
year = {2004},
volume = {155},
number = {3},
pages = {675--682},
url = {http://www.sciencedirect.com/science/article/pii/S0377221702008834}
}
|
|||||
| Pang, W.-K., Leung, P.-K., Huang, W.-K. and Liu, W. | On interval estimation of the coefficient of variation for the three-parameter Weibull, lognormal and gamma distribution: A simulation-based approach | 2005 | European Journal of Operational Research Vol. 164(2), pp. 367-377 |
article | URL |
| Abstract: The coefficient of variation (CV) of a population is defined as the ratio of the population standard deviation to the population mean. It is regarded as a measure of stability or uncertainty, and can indicate the relative dispersion of data in the population to the population mean. CV is a dimensionless measure of scatter or dispersion and is readily interpretable, as opposed to other commonly used measures such as standard deviation, mean absolute deviation or error factor, which are only interpretable for the lognormal distribution. CV is often estimated by the ratio of the sample standard deviation to the sample mean, called the sample CV. Even for the normal distribution, the exact distribution of the sample CV is difficult to obtain, and hence it is difficult to draw inferences regarding the population CV in the frequentist frame. Different methods of estimating the sample standard deviation as well as the sample mean result in different shapes of the sampling distribution of the sample CV, from which inferences about the population CV can be made. In this paper we propose a simulation-based Bayesian approach to tackle this problem. A set of real data is used to generate the sampling distribution of the CV under the assumption that the data follow the three-parameter Gamma distribution. A probability interval is then constructed. The method also applies easily to lognormal and Weibull distributions. | |||||
BibTeX:
@article{Pang2005,
author = {Pang, Wan-Kai and Leung, Ping-Kei and Huang, Wei-Kwang and Liu, Wei},
title = {On interval estimation of the coefficient of variation for the three-parameter Weibull, lognormal and gamma distribution: A simulation-based approach},
journal = {European Journal of Operational Research},
year = {2005},
volume = {164},
number = {2},
pages = {367--377},
url = {http://www.sciencedirect.com/science/article/pii/S0377221703008956}
}
|
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| Panno, S., Hackley, K., Hwang, H. and Kelly, W. | Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators | 2001 | Chemical Geology Vol. 179(1-4)Hydrochemistry of Springs, pp. 113-128 |
article | URL |
| Abstract: The sources of nitrate (NO3−) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO3− concentrations in excess of the USEPA's drinking water standard of 10 mg N/l. Relative to background levels, the NO3− concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter have contributed additional NO3− to groundwater in the shallow karst aquifer. This information, and the dominance of agriculture in the study area, suggest that agrichemical contributions may be significant. To test this hypothesis, water samples from 10 relatively large karst springs were collected during four different seasons and analyzed for inorganic constituents, dissolved organic carbon, atrazine, and δ15N and δ18O of the NO3− ions. The isotopic data were most definitive and suggested that the sources of NO3− in spring water are dominated by N-fertilizer with some possible influence of atmospheric NO3− and, to a much lesser extent, human and/or animal waste. Differences in the isotopic composition of NO3− and some of the chemical characteristics were observed during the four consecutive seasons in which spring water samples were collected. Isotopic values for δ15N and δ18O of the NO3− ranged from 3.2‰ to 19.1‰ and from 7.2‰ to 18.7‰, respectively. The trend of δ15N and δ18O data for NO3− also indicated that a significant degree of denitrification is occurring in the shallow karst hydrologic system (within the soil zone, the epikarst and the shallow karst aquifer) prior to discharging to springs. | |||||
BibTeX:
@article{Panno2001,
author = {Panno, S.V and Hackley, K.C and Hwang, H.H and Kelly, W.R},
title = {Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators},
booktitle = {Hydrochemistry of Springs},
journal = {Chemical Geology},
year = {2001},
volume = {179},
number = {1-4},
pages = {113--128},
url = {http://www.sciencedirect.com/science/article/pii/S0009254101003187}
}
|
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| Panno, S.V., Curry, B., Wang, H., Hackley, K.C., Liu, C.-L., Lundstrom, C. and Zhou, J. | Climate change in southern Illinois, USA, based on the age and δ13C of organic matter in cave sediments | 2004 | Quaternary Research Vol. 61(3), pp. 301-313 |
article | URL |
| Abstract: Matrix-supported diamicton and uniform to laminated, silty, fine-grained sediment deposited from about 42,500 to 27,600 cal yr B.P. under slackwater conditions nearly filled two caves in southwestern Illinois. At some point, most of the sediment was flushed from the caves and from about 22,700 to 4000 cal yr B.P., floods deposited a drape of sandy and silty sediment on remnant slackwater successions, cobbly alluvium, and bedrock (especially from 7700 to 4000 cal yr B.P.). Clay mineral analyses of the slackwater cave sediment reveal a provenance of chiefly Petersburg Silt, a smectite- and illite-rich proglacial lacustrine unit present in the overlying Illinois Episode glacial succession. Today, remnants of the ancient subterranean slackwater deposits nearly fill several secondary passages and, in at least two locations, cover a cobble-mantled strath terrace 1.3 to 1.5 m above active stream channels. Slumping and sinkhole formation appear to have been important mechanisms for deposition of the ancient subterranean deposits. Slumping of these surficial deposits and associated vegetation can occur along the flanks of sinkholes (in addition to sinkhole formation) and enter caves; however, the finer organics, some of them comminuted during transport into the caves, become part of the cave alluvium. This finer organic fraction is the modern analog of the humified organic matter disseminated in slackwater sediment dated in this investigation by radiocarbon methods. Twenty-four 14C ages on humified organic matter provide chronologic control. The δ13C values of the organic matter reflect the proportion of C4-type to C3-type vegetation growing in and around swallets and sinkholes at the time of redeposition. Drought-tolerant C4-type vegetation was more prevalent relative to C3-type vegetation from 42,500 to 31,200 cal yr B.P. compared to conditions from 28,800 cal yr B.P. to the present. The δ13C values are consistent with the results from other investigations of speleothems and organic matter from loessial paleosols. | |||||
BibTeX:
@article{Panno2004,
author = {Panno, Samuel V and Curry, B.Brandon and Wang, Hong and Hackley, Keith C and Liu, Chao-Li and Lundstrom, Craig and Zhou, Juanzuo},
title = {Climate change in southern Illinois, USA, based on the age and δ13C of organic matter in cave sediments},
journal = {Quaternary Research},
year = {2004},
volume = {61},
number = {3},
pages = {301--313},
url = {http://www.sciencedirect.com/science/article/pii/S0033589404000249}
}
|
|||||
| Pant, P. and Pant, S. | A review: Advances in microbial remediation of trichloroethylene (TCE) [BibTeX] |
2010 | Journal of Environmental Sciences Vol. 22(1), pp. 116-126 |
article | DOI URL |
BibTeX:
@article{Pant2010,
author = {Pant, Prabhakar and Pant, Sudhakar},
title = {A review: Advances in microbial remediation of trichloroethylene (TCE)},
journal = {Journal of Environmental Sciences},
year = {2010},
volume = {22},
number = {1},
pages = {116--126},
url = {http://www.sciencedirect.com/science/article/pii/S1001074209600826},
doi = {http://dx.doi.org/10.1016/s1001-0742(09)60082-6}
}
|
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| Pareek, V.K., Sharma, R., Cooper, C.G. and Adesina, A.A. | Solids Residence Time Distribution in a Three-Phase Bubble Column Reactor: An Artificial Neural Network Analysis | 2008 | The Open Chemical Engineering Journal Vol. 2, pp. 73-78 |
article | DOI URL |
| Abstract: Residence time distribution (RTD) study of solids in a three-phase pilot-scale bubble column photoreactor has been carried out in order to provide data for the development of an artificial neural network model usable for process optimisation. The experimental data indicated that the RTD of solids was a complex nonlinear function of gas and liquid velocities as well as the contacting pattern (co-current and countercurrent flow of gas and liquid). In this study, the solid particle RTD data were modeled using feed forward artificial neural networks (ANN). The networks were trained with 250-sets of input-output patterns using back-propagation algorithm. The trained networks were tested using 50-sets of RTD data previously unknown to the networks. Out of several configurations, a 3-layered network with 6-neurons in its hidden layer yielded optimal results with respect to the validation data. The optimal model and empirical data exhibited good agreement with a correlation coefficient of 0.995. | |||||
BibTeX:
@article{Pareek2008,
author = {Pareek, V. K. and Sharma, R. and Cooper, C. G. and Adesina, A. A.},
title = {Solids Residence Time Distribution in a Three-Phase Bubble Column Reactor: An Artificial Neural Network Analysis},
journal = {The Open Chemical Engineering Journal},
publisher = {Bentham Open},
year = {2008},
volume = {2},
pages = {73--78},
url = {http://www.benthamscience.com/open/tocengj/articles/V002/73TOCENGJ.htm},
doi = {http://dx.doi.org/10.2174/1874123100802010073}
}
|
|||||
| Parise, M., De Waele, J. and Gutiérrez, F. | Engineering and environmental problems in karst — An introduction [BibTeX] |
2008 | Engineering Geology Vol. 99(3-4)Engineering and environmental problems in karst Natural and Anthropogenic Hazards in Karst Areas, pp. 91-94 |
article | URL |
BibTeX:
@article{Parise2008,
author = {Parise, Mario and De Waele, Jo and Gutiérrez, Francisco},
title = {Engineering and environmental problems in karst — An introduction},
booktitle = {Engineering and environmental problems in karst Natural and Anthropogenic Hazards in Karst Areas},
journal = {Engineering Geology},
year = {2008},
volume = {99},
number = {3-4},
pages = {91--94},
url = {http://www.sciencedirect.com/science/article/pii/S0013795208000288}
}
|
|||||
| Park, D., Levenspiel, O. and Fitzgerald, T.J. | Plume model for large particle fluidized-bed combustors | 1981 | Fuel Vol. 60(4), pp. 295-306 |
article | URL |
| Abstract: A model is proposed to represent the underfeed, fluidized coal combustor. Its assumptions are described and its mathematical representation developed. This model accounts for the possible rapid release of volatiles near the feed ports, particle reaction and shrinkage in the bed, elutriation of unburned fines and afterburning of volatiles above the bed. Design charts are then presented to predict the carbon efficiency of the combustor as well as the temperature jump above the bed in terms of the type of coal used, the number of feed ports in the bed, percentage excess air, gas velocity and the amount of secondary air needed to introduce the coal. As a special case, this model also represents the fluidized combustor with an overfeed of large coal particles or any combination of overfeed of large particles and underfeed of fines. | |||||
BibTeX:
@article{Park1981,
author = {Park, Dalkeun and Levenspiel, Octave and Fitzgerald, T. J.},
title = {Plume model for large particle fluidized-bed combustors},
journal = {Fuel},
year = {1981},
volume = {60},
number = {4},
pages = {295--306},
url = {http://www.sciencedirect.com/science/article/pii/0016236181901988}
}
|
|||||
| Park, D. and Roesner, L.A. | Evaluation of pollutant loads from stormwater BMPs to receiving water using load frequency curves with uncertainty analysis | Water Research(0), pp. - | article | URL | |
| Abstract: This study examined pollutant loads released to receiving water from a typical urban watershed in the Los Angeles (LA) Basin of California by applying a best management practice (BMP) performance model that includes uncertainty. This BMP performance model uses the k-C* model and incorporates uncertainty analysis and the first-order second-moment (FOSM) method to assess the effectiveness of BMPs for removing stormwater pollutants. Uncertainties were considered for the influent event mean concentration (EMC) and the aerial removal rate constant of the k-C* model. The storage treatment overflow and runoff model (STORM) was used to simulate the flow volume from watershed, the bypass flow volume and the flow volume that passes through the BMP. Detention basins and total suspended solids (TSS) were chosen as representatives of stormwater BMP and pollutant, respectively. This paper applies load frequency curves (LFCs), which replace the exceedance percentage with an exceedance frequency as an alternative to load duration curves (LDCs), to evaluate the effectiveness of BMPs. An evaluation method based on uncertainty analysis is suggested because it applies a water quality standard exceedance based on frequency and magnitude. As a result, the incorporation of uncertainty in the estimates of pollutant loads can assist stormwater managers in determining the degree of total daily maximum load (TMDL) compliance that could be expected from a given BMP in a watershed. | |||||
BibTeX:
@article{Park,
author = {Park, Daeryong and Roesner, Larry A.},
title = {Evaluation of pollutant loads from stormwater BMPs to receiving water using load frequency curves with uncertainty analysis},
journal = {Water Research},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0043135412002783}
}
|
|||||
| Park, E. and Parker, J. | Evaluation of an upscaled model for DNAPL dissolution kinetics in heterogeneous aquifers | 2005 | Advances in Water Resources Vol. 28(12), pp. 1280-1291 |
article | URL |
| Abstract: Estimates of contaminant fluxes from DNAPL sources as a function of time and DNAPL mass reduction are important to assess the long-term sustainability and costs of monitored natural attenuation and to determine the benefits of partial source removal. We investigate the accuracy of the upscaled mass transfer function (MTF) proposed by Parker and Park [Parker JC, Park E. Modeling field-scale dense nonaqueous phase liquid dissolution kinetics in heterogeneous aquifers. WRR 2004;40:W05109] to describe field-scale dissolved phase fluxes from DNAPL sources for a range of scenarios generated using high-resolution 3-D numerical simulations of DNAPL infiltration and long-term dissolved phase transport. The results indicate the upscaled MTF is capable of accurately describing field-scale DNAPL dissolution rates as a function of time. For finger-dominated source regions, an empirical mass depletion exponent in the MTF takes on values greater than one which results in predicted mass flux rates that decrease continuously with diminishing DNAPL mass over time. Lens-dominated regions exhibit depletion exponents less than one, which results in more step-function like mass flux versus time behavior. Mass fluxes from DNAPL sources exhibiting both lens- and finger-dominated subregions were less accurately described by the simple MTF, but were well described by a dual-continuum model of the same form for each subregion. The practicality of calibrating a dual-continuum model will likely depend on the feasibility of obtaining spatially resolved field measurements of contaminant fluxes or concentrations associated with the subregions using multilevel sampling or some other means. | |||||
BibTeX:
@article{Park2005,
author = {Park, E. and Parker, J.C.},
title = {Evaluation of an upscaled model for DNAPL dissolution kinetics in heterogeneous aquifers},
journal = {Advances in Water Resources},
year = {2005},
volume = {28},
number = {12},
pages = {1280--1291},
url = {http://www.sciencedirect.com/science/article/pii/S0309170805000916}
}
|
|||||
| Park, S., Lee, K., Park, I. and Ha, S. | Effect of the aggregation level of surface runoff fields and sewer network for a SWMM simulation | 2008 | Desalination Vol. 226(1-3)10th IWA International Specialized Conference on Diffuse Pollution and Sustainable Basin Management 18–22 September 2006, Istanbul, Turkey 10th IWA International Specialized Conference on Diffuse Pollution and Sustainable Basin Management, pp. 328-337 |
article | URL |
| Abstract: The partitioning level of a catchment in storm water runoff modelling becomes an issue if the calculated results from the different number of subcatchments show the same performance. This study aims to identify the proper processing level of spatial resolution for the SWMM model application in an urban area. Using GIS overlaying technique, the division of subcatchments as a hydrologic similarity unit (HSU) is achieved with a comprehensive consideration of surface slope conditions, flow directions of storm sewers, and current land cover situation. Three surface-sewer alternatives are made on the basis of three different levels of surface divisions as well as the number of sewer connections and used as runoff simulation fields for the application of SWMM. As the result, it is found that the effect of a spatial resolution on the surface runoff results is not significant. On the other hand, the accumulated pollution load from a unit subcatchment, which is built by aggregation of several unit subcatchments consisting of various land cover conditions, is reduced through the deterioration of surface spatial resolution. Although overall runoff pattern and accumulated runoff are slightly affected by spatial resolution, the simulated runoff from sewer outlet shows slight difference at the peak appearance time. | |||||
BibTeX:
@article{Park2008,
author = {Park, S.Y. and Lee, K.W. and Park, I.H. and Ha, S.R.},
title = {Effect of the aggregation level of surface runoff fields and sewer network for a SWMM simulation},
booktitle = {10th IWA International Specialized Conference on Diffuse Pollution and Sustainable Basin Management 18–22 September 2006, Istanbul, Turkey 10th IWA International Specialized Conference on Diffuse Pollution and Sustainable Basin Management},
journal = {Desalination},
year = {2008},
volume = {226},
number = {1-3},
pages = {328--337},
url = {http://www.sciencedirect.com/science/article/pii/S0011916408001653}
}
|
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| Pasquale, V., Verdoya, M. and Chiozzi, P. | Groundwater flow analysis using different geothermal constraints: The case study of Acqui Terme area, northwestern Italy | 2011 | Journal of Volcanology and Geothermal Research Vol. 199(1-2), pp. 38-46 |
article | URL |
| Abstract: We review some analytical techniques that use underground thermal data as tracers of groundwater flow. These techniques allow the evaluation of the Darcy velocity in shallow aquifers of mid-low permeability and the evaluation of heat gain/loss by conduction in deeper aquifers. Examples of application are then given for the Acqui Terme hydrothermal system, located in the Tertiary Piedmont Basin (northwestern Italy). The analysis of borehole temperatures allowed the inference of the hydraulic features of the sedimentary cover of the hydrothermal system. The results show the presence of a relatively weak flow, with upward and horizontal components, only in conglomerates occurring at the base of the marly impermeable cover. The analysis of the heat transported in the deep parts of the hydrothermal system was approached by splitting the water path into different sections, each with given shape, slope and hydraulic properties. The recharge area is situated in the upland, south of the discharge area. Meteoric water initially descends and then flows horizontally within the fractured metamorphic basement of the basin, heating by conduction. Finally, from a reservoir positioned at intermediate depths, hot water reaches rapidly the surface through a sub-vertical fault. This scheme of deep water flow is constrained by the regional surface heat flow and the local geothermal gradient, and it is consistent with data of rock–water equilibrium temperature. | |||||
BibTeX:
@article{Pasquale2011,
author = {Pasquale, Vincenzo and Verdoya, Massimo and Chiozzi, Paolo},
title = {Groundwater flow analysis using different geothermal constraints: The case study of Acqui Terme area, northwestern Italy},
journal = {Journal of Volcanology and Geothermal Research},
year = {2011},
volume = {199},
number = {1-2},
pages = {38--46},
url = {http://www.sciencedirect.com/science/article/pii/S0377027310003136}
}
|
|||||
| Patel, V.R., Ein-Mozaffari, F. and Upreti, S.R. | Effect of time delays in characterizing the continuous mixing of non-Newtonian fluids in stirred-tank reactors | 2011 | Chemical Engineering Research and Design Vol. 89(10), pp. 1919-1928 |
article | URL |
| Abstract: Aqueous xanthan gum solutions are pseudoplastic fluids possessing yield stress. Their continuous mixing is an extremely complicated phenomenon exhibiting non idealities such as channeling, recirculation and dead zones within the stirred-tank reactors. To characterize the continuous mixing of xanthan gum solutions, three dynamic models were utilized: (1) a dynamic model with 2 time delays in discrete time domain, (2) a dynamic model with two time delays in continuous time domain, and (3) a simplified dynamic model with a single time delay in discrete time domain. A hybrid genetic algorithm was employed to estimate the model parameters through the experimental input–output dynamic data. The extents of channeling and fully mixed volume were used to compare the performances of these three models. The dynamic model parameters exerting strong influence on the response predicted by the dynamic model were identified. It was observed that the models with 2 time delays gave a better match with the experimental results. | |||||
BibTeX:
@article{Patel2011,
author = {Patel, Vishalkumar R. and Ein-Mozaffari, Farhad and Upreti, Simant R.},
title = {Effect of time delays in characterizing the continuous mixing of non-Newtonian fluids in stirred-tank reactors},
journal = {Chemical Engineering Research and Design},
year = {2011},
volume = {89},
number = {10},
pages = {1919--1928},
url = {http://www.sciencedirect.com/science/article/pii/S0263876211000499}
}
|
|||||
| Patricia, K. | Engineering, a civilising influence? [BibTeX] |
2010 | Futures Vol. 42(10), pp. 1110-1118 |
article | DOI URL |
BibTeX:
@article{Patricia2010,
author = {Patricia, Kelly},
title = {Engineering, a civilising influence?},
journal = {Futures},
year = {2010},
volume = {42},
number = {10},
pages = {1110--1118},
url = {http://www.sciencedirect.com/science/article/pii/S0016328710001813},
doi = {http://dx.doi.org/10.1016/j.futures.2010.08.011}
}
|
|||||
| Patricia, K. | Letter from the oasis: Helping engineering students to become sustainability professionals [BibTeX] |
2006 | Futures Vol. 38(6), pp. 696-707 |
article | DOI URL |
BibTeX:
@article{Patricia2006,
author = {Patricia, Kelly},
title = {Letter from the oasis: Helping engineering students to become sustainability professionals},
journal = {Futures},
year = {2006},
volume = {38},
number = {6},
pages = {696--707},
url = {http://www.sciencedirect.com/science/article/pii/S0016328705001758},
doi = {http://dx.doi.org/10.1016/j.futures.2005.10.005}
}
|
|||||
| Paul, S. and Mazumder, B. | Effects of nonlinear chemical reactions on the transport coefficients associated with steady and oscillatory flows through a tube | 2011 | International Journal of Heat and Mass Transfer Vol. 54(1–3), pp. 75-85 |
article | URL |
| Abstract: The paper concerns with the determination of effective transport coefficients associated with the oscillatory flow through a tube where a solute undergoes nonlinear chemical reactions both within the fluid and at the boundary. Method of homogenization, a multiple-scale method of averaging, is adopted to derive the transport equation that contains advection, diffusion and reaction. The resultant equation shows how the transport coefficients are influenced by the rate and degree of the nonlinear chemical reaction. Two different nonlinear reactions are considered at the bulk flow and the boundary. The reactions at the boundary may be reversible and irreversible in nature. Several facts are established from the model by fixing the rate or degree of the nonlinear reactions. Results demonstrate that the reaction at the boundary is more influential than the bulk-flow reaction in determining the transport coefficients. Also fluid-phase reaction coefficient diminishes as the nonlinearity increases, whereas the trend is opposite for the nonlinear wall-phase reaction coefficient. Different controlling parameters are found to play significant role on the transport coefficients when the ratio of wall-phase concentration to the fluid-phase concentration is low. | |||||
BibTeX:
@article{Paul2011,
author = {Paul, Suvadip and Mazumder, B.S.},
title = {Effects of nonlinear chemical reactions on the transport coefficients associated with steady and oscillatory flows through a tube},
journal = {International Journal of Heat and Mass Transfer},
year = {2011},
volume = {54},
number = {1–3},
pages = {75--85},
url = {http://www.sciencedirect.com/science/article/pii/S0017931010005624}
}
|
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| Paul, S. and Mazumder, B. | Transport of reactive solutes in unsteady annular flow subject to wall reactions | 2009 | European Journal of Mechanics - B/Fluids Vol. 28(3), pp. 411-419 |
article | URL |
| Abstract: The present paper concerns with the dispersion process in steady and oscillatory flows through an annular pipe in presence of reversible and irreversible reactions at the wall. Method of homogenization, a multiple-scale method of averaging, is adopted for deriving the effective transport equations. The main objective is to look into the effect of aspect ratio of the annular pipe on the dispersion coefficient due to the combined effect of axial convection and radial diffusion in steady and oscillatory flows along the annulus, subject to the kinetic reversible phase exchange and irreversible absorption at the outer wall. Results demonstrate that upto a certain critical value of aspect ratio, dispersion coefficient increases with increase of aspect ratio when the wall is retentive, though the wall inertness may lead to decrease of dispersion coefficient with increase of aspect ratio. The results would be useful to the medical practitioners working in the domain of catheterized artery. | |||||
BibTeX:
@article{Paul2009,
author = {Paul, Suvadip and Mazumder, B.S.},
title = {Transport of reactive solutes in unsteady annular flow subject to wall reactions},
journal = {European Journal of Mechanics - B/Fluids},
year = {2009},
volume = {28},
number = {3},
pages = {411--419},
url = {http://www.sciencedirect.com/science/article/pii/S099775460800099X}
}
|
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| Payn, R.A., Gooseff, M.N., Benson, D.A., Cirpka, O.A., Zarnetske, J.P., Bowden, W.B., McNamara, J.P. and Bradford, J.H. | Comparison of instantaneous and constant-rate stream tracer experiments through non-parametric analysis of residence time distributions | 2008 | Water Resources Research Vol. 44(6), pp. W06404- |
article | URL |
| Abstract: Artificial tracers are frequently employed to characterize solute residence times in stream systems and infer the nature of water retention. When the duration of tracer application is different between experiments, tracer breakthrough curves at downstream locations are difficult to compare directly. We explore methods for deriving stream solute residence time distributions (RTD) from tracer test data, allowing direct, non-parametric comparison of results from experiments of different durations. Paired short- and long-duration field experiments were performed using instantaneous and constant-rate tracer releases, respectively. The experiments were conducted in two study reaches that were morphologically distinct in channel structure and substrate size. Frequency- and time domain deconvolution techniques were used to derive RTDs from the resulting tracer concentrations. Comparisons of results between experiments of different duration demonstrated few differences in hydrologic retention characteristics inferred from short- and long-term tracer tests. Because non-parametric RTD analysis does not presume any shape of the distribution, it is useful for comparisons across tracer experiments with variable inputs and for validations of fundamental transport model assumptions. | |||||
BibTeX:
@article{Payn2008,
author = {Payn, Robert A. and Gooseff, Michael N. and Benson, David A. and Cirpka, Olaf A. and Zarnetske, Jay P. and Bowden, W. Breck and McNamara, James P. and Bradford, John H.},
title = {Comparison of instantaneous and constant-rate stream tracer experiments through non-parametric analysis of residence time distributions},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2008},
volume = {44},
number = {6},
pages = {W06404--},
url = {http://dx.doi.org/10.1029/2007WR006274}
}
|
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| Pažanin, I. | Modeling of solute dispersion in a circular pipe filled with micropolar fluid | Mathematical and Computer Modelling(0), pp. - | article | URL | |
| Abstract: In this paper we study the transport of a reactive solute through a thin (or long) cylindrical pipe filled with micropolar fluid. We suppose that the solute particles undergo a first-order chemical reaction at the lateral boundary of the pipe. The effective model for solute concentration is derived by means of a formal asymptotic analysis with respect to the pipe’s thickness. The asymptotic approximation is built, showing explicitly the effects of fluid microstructure and chemical reaction on the solute dispersion. | |||||
BibTeX:
@article{Pazanin,
author = {Pažanin, Igor},
title = {Modeling of solute dispersion in a circular pipe filled with micropolar fluid},
journal = {Mathematical and Computer Modelling},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0895717711008053}
}
|
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| Peggy, J. | The supervision of environmental risk: The case of HCB waste or Botany/Randwick? | 2009 | Journal of Environmental Management Vol. 90(4)Toxic Risk and Governance: The Case of Hexachlorobenzene, pp. 1576-1582 |
article | URL |
| Abstract: The governance activities of capital and the state include attempts to control the timing and spacing of social activities such as the production of environmental risks and settlement of different social groups. The supervisory activities that have shaped the environmental and social history of the Botany/Randwick area are identified here, to examine how the HCB waste risk developed in that community. The analysis shows that multiple environmental risks and an ethnically diverse, working class community have been brought together in space to create environmental injustice. Analysing the governance of one environmental risk like hexachlorobenzene (HCB) waste may not increase understanding about communities facing multiple environmental risks or the supervisory processes that lead to the unfair accumulation of risks for particular places or social groups. Lessons from the environmental justice movement suggest that reframing problems like HCB waste management at Botany/Randwick as distributive justice issues may contribute to governance arrangements that better manage multiple risks and pollution sources in space affecting marginalised communities. | |||||
BibTeX:
@article{Peggy2009a,
author = {Peggy, James},
title = {The supervision of environmental risk: The case of HCB waste or Botany/Randwick?},
booktitle = {Toxic Risk and Governance: The Case of Hexachlorobenzene},
journal = {Journal of Environmental Management},
year = {2009},
volume = {90},
number = {4},
pages = {1576--1582},
url = {http://www.sciencedirect.com/science/article/pii/S0301479708001795}
}
|
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| Peixoto, F.C. and de Medeiros, J.L. | Modelling and parameter estimation in reactive continuous mixtures: the catalytic cracking of alkanes - part I | 1999 | Brazilian Journal of Chemical Engineering Vol. 16(1), pp. 65-81 |
article | URL |
| Abstract: Fragmentation kinetics is employed to model a continuous reactive mixture. An explicit solution is found and experimental data on the catalytic cracking of a mixture of alkanes are used for deactivation and kinetic parameter estimation. | |||||
BibTeX:
@article{Peixoto1999a,
author = {Peixoto, F. C. and de Medeiros, J. L.},
title = {Modelling and parameter estimation in reactive continuous mixtures: the catalytic cracking of alkanes - part I},
journal = {Brazilian Journal of Chemical Engineering},
publisher = {scielo},
year = {1999},
volume = {16},
number = {1},
pages = {65--81},
url = {http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66321999000100007&lng=en&nrm=iso&tlng=en}
}
|
|||||
| Peixoto, F.C. and de Medeiros, J.L. | Modelling and parameter estimation in reactive continuous mixtures: the catalytic cracking of alkanes - part II | 1999 | Brazilian Journal of Chemical Engineering Vol. 16(3), pp. 229-236 |
article | URL |
| Abstract: Fragmentation kinetics is employed to model a continuous reactive mixture of alkanes under catalytic cracking conditions. Standard moment analysis techniques are employed, and a dynamic system for the time evolution of moments of the mixture's dimensionless concentration distribution function (DCDF) is found. The time behavior of the DCDF is recovered with successive estimations of scaled gamma distributions using the moments time data. | |||||
BibTeX:
@article{Peixoto1999b,
author = {Peixoto, F. C. and de Medeiros, J. L.},
title = {Modelling and parameter estimation in reactive continuous mixtures: the catalytic cracking of alkanes - part II},
journal = {Brazilian Journal of Chemical Engineering},
publisher = {scielo},
year = {1999},
volume = {16},
number = {3},
pages = {229--236},
url = {http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66321999000300002&lng=en&nrm=iso&tlng=en}
}
|
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| Perrin, J., Jeannin, P.-Y. and Cornaton, F. | The role of tributary mixing in chemical variations at a karst spring, Milandre, Switzerland | 2007 | Journal of Hydrology Vol. 332(1-2), pp. 158-173 |
article | URL |
| Abstract: Solute concentration variations during flood events were investigated in a karst aquifer of the Swiss Jura. Observations were made at the spring, and at the three main subterraneous tributaries feeding the spring. A simple transient flow and transport numerical model was able to reproduce chemographs and hydrographs observed at the spring, as a result of a mixing of the concentration and discharge of the respective tributaries. Sensitivity analysis carried out with the model showed that it is possible to produce chemical variations at the spring even if all tributaries have constant (but different for each of them) solute concentrations. This process is called tributary mixing. The good match between observed and modelled curves indicate that, in the phreatic zone, tributary mixing is probably an important process that shapes spring chemographs. Chemical reactions and other mixing components (e.g. from low permeability volumes) have a limited influence. | |||||
BibTeX:
@article{Perrin2007,
author = {Perrin, J. and Jeannin, P.-Y. and Cornaton, F.},
title = {The role of tributary mixing in chemical variations at a karst spring, Milandre, Switzerland},
journal = {Journal of Hydrology},
year = {2007},
volume = {332},
number = {1-2},
pages = {158--173},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406003428}
}
|
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| Perrin, J., Jeannin, P.-Y. and Zwahlen, F. | Epikarst storage in a karst aquifer: a conceptual model based on isotopic data, Milandre test site, Switzerland | 2003 | Journal of Hydrology Vol. 279(1-4), pp. 106-124 |
article | URL |
| Abstract: The Milandre test site is a karst aquifer characterized by diffuse infiltration, a well developed conduit network, and several tributaries feeding an underground river. Field data include discharge rate measurements, stable isotopes, weekly rainfall and spring-water isotope sampling, and detailed isotope sampling during three flood events. Flood sampling was carried out at several tributaries corresponding to conduit flow, vadose flow and seepage flow. Weekly sampling showed a strong buffering of the rainfall isotopic signal at the spring. This attenuation suggests an important mixing reservoir in the system. Flood events showed highly peaking hydraulic responses but buffered rain isotope responses. These results indicate that the soil and epikarst sub-systems have an important storage capacity. A conceptual model of flow and transport in the soil and epikarst zone is proposed: Soil plays an important role in mixing due to the presence of capillary water storage. Consequently dampened concentrations reach the epikarst despite a rapid hydraulic response. The epikarst acts as the storage element and distributes water as either a base flow component or a quick flow component. When recharge exceeds a given threshold, excess infiltrated water bypasses the soil and epikarst and reaches the saturated zone as fresh flow. Based on this model, the significance of phreatic storage is thought to be limited, at least in Milandre test site. Hence the saturated zone is seen mainly as a transmissive zone through its well developed conduit network. | |||||
BibTeX:
@article{Perrin2003,
author = {Perrin, Jérôme and Jeannin, Pierre-Yves and Zwahlen, François},
title = {Epikarst storage in a karst aquifer: a conceptual model based on isotopic data, Milandre test site, Switzerland},
journal = {Journal of Hydrology},
year = {2003},
volume = {279},
number = {1-4},
pages = {106--124},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403001719}
}
|
|||||
| Perrin, J. and Luetscher, M. | Inference of the structure of karst conduits using quantitative tracer tests and geological information: example of the Swiss Jura | 2008 | Hydrogeology Journal Vol. 16(5), pp. 951-967 |
article | URL |
| Abstract: Karst aquifers are known for being particularly heterogeneous with highly transmissive conduits embedded in low permeability volumes of rock matrix. Artificial tracer experiments have been carried out in a complex karst aquifer of the folded Jura Mountains in Switzerland with the aim of deciphering the conduit organisation. It is shown that tracer experiments with multiple injection points under different flow conditions can lead to useful information on the conduits’ structure. This information has been combined with data from structural geology, spring hydrology, and speleological observations. A conceptual model of the conduit network shows that a detailed inference of the conduit organisation can be reached: geology controls conduit location and orientation; spring hydrology, including temporary springs, constrains conduit elevations and relative hydraulic heads in the aquifer subsystems; and tracer tests identify major flow paths and outlets of the system and dilution caused by non-traced tributaries, as well as the presence of secondary flow routes. This understanding of the Aubonne aquifer structure has important implications for the future management of the groundwater resource. Similar approaches coupling geological information, spring hydrology, and multi-tracer tests under various flow conditions may help to characterise the structure of the conduit network in karst aquifers. | |||||
BibTeX:
@article{Perrin2008,
author = {Perrin, Jérôme and Luetscher, Marc},
title = {Inference of the structure of karst conduits using quantitative tracer tests and geological information: example of the Swiss Jura},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2008},
volume = {16},
number = {5},
pages = {951--967},
url = {http://dx.doi.org/10.1007/s10040-008-0281-6}
}
|
|||||
| Personné, J.-C., Poty, F., Mahler, B. and Drogue, C. | Colonization by Aerobic Bacteria in Karst: Laboratory and In Situ Experiments | 2004 | Ground Water Vol. 42(4), pp. 526-533 |
article | URL |
| Abstract: Experiments were carried out to investigate the potential for bacterial colonization of different substrates in karst aquifers and the nature of the colonizing bacteria. Laboratory batch experiments were performed using limestone and PVC as substrates, a natural bacterial isolate and a known laboratory strain (Escherichia coli [E. coli]) as inocula, and karst ground water and a synthetic formula as growth media. In parallel, fragments of limestone and granite were submerged in boreholes penetrating two karst aquifers for more than one year; the boreholes are periodically contaminated by enteric bacteria from waste water. Once a month, rock samples were removed and the colonizing bacteria quantified and identified. The batch experiments demonstrated that the natural isolate and E. coli both readily colonized limestone surfaces using karst ground water as the growth medium. In contrast, bacterial colonization of both the limestone and granite substrates, when submerged in the karst, was less intense. More than 300 bacterial strains were isolated over the period sampled, but no temporal pattern in colonization was seen as far as strain, and colonization by E. coli was notably absent, although strains of Salmonella and Citrobacter were each observed once. Samples suspended in boreholes penetrating highly fractured zones were less densely colonized than those in the borehole penetrating a less fractured zone. The results suggest that contamination of karst aquifers by enteric bacteria is unlikely to be persistent. We hypothesize that this may be a result of the high flow velocities found in karst conduits, and of predation of colonizing bacteria by autochthonous zooplankton. | |||||
BibTeX:
@article{Personne2004,
author = {Personné, J.-C. and Poty, F. and Mahler, B.J. and Drogue, C.},
title = {Colonization by Aerobic Bacteria in Karst: Laboratory and In Situ Experiments},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {2004},
volume = {42},
number = {4},
pages = {526--533},
url = {http://dx.doi.org/10.1111/j.1745-6584.2004.tb02621.x}
}
|
|||||
| Personné J.-C., P.F.M.B. and Drogue, C. | Colonization by Aerobic Bacteria in Karst: Laboratory and In Situ Experiments. [BibTeX] |
2005 | Ground Water Vol. 42 |
article | |
BibTeX:
@article{Personne2005,
author = {Personné, J.-C., Poty F. Mahler B. and Drogue, C.},
title = {Colonization by Aerobic Bacteria in Karst: Laboratory and In Situ Experiments.},
journal = {Ground Water},
year = {2005},
volume = {42}
}
|
|||||
| Persson, J., Somes, N.L.G. and Wong, T.H.F. | Hydraulics Efficiency of Constructed Wetlands and Ponds | 1999 | Water Science and Technology Vol. 40(3), pp. 291-289 |
article | URL |
| Abstract: Constructed ponds and wetlands are widely used in urban design to serve a number of functions including stormwater management. The design of constructed wetlands for stormwater management involves a number of multi-disciplinary inputs. Fundamental to their sustainable operation are the proper control of the hydrologic regime of the wetland and optimal flow hydrodynamics within the wetland. Many ofthe problems encountered in constructed wetlands can be minimised or avoided by good engineering design principles. Poor wetland hydrodynamics are often identified as a major contributor to wetland management problems. Ponds and wetlands with a high hydraulic efficiency are expected to promote full utilisation ofthe available detention storage and near plug flow conditions. The shape and layout of urban ponds and wetlands are often varied to suit the landscape and to satisfy aesthetic requirements as an urban water feature. These can be achieved while maintaining an effective stormwater treatment outcome if steps are taken to ensure that the hydrodynamic behaviour of the system is not severely compromised. A consistent measure is required to allow the effects of design features to be evaluated against this criterion. This paper introduces a new measure for hydraulic efficiency that combines existing measures of flow uniformity and effective volume. Case studies are presented on the use of this measure to assess the effects of different pond and wetland shapes, locations of inlet and outlet, botanical layouts and basin morphology on the flow hydrodynamics. | |||||
BibTeX:
@article{Persson1999,
author = {Persson, J. and Somes, N. L. G. and Wong, T. H. F.},
title = {Hydraulics Efficiency of Constructed Wetlands and Ponds},
journal = {Water Science and Technology},
year = {1999},
volume = {40},
number = {3},
pages = {291--289},
url = {http://www.iwaponline.com/wst/04003/wst040030291.htm}
}
|
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| Petavy, F., Ruban, V., Conil, P. and Viau, J.Y. | Attrition efficiency in the decontamination of stormwater sediments | 2009 | Applied Geochemistry Vol. 24(1), pp. 153-161 |
article | URL |
| Abstract: The purpose of this research is to propose a laboratory method based on attrition and sieving for the treatment of runoff water sediments in the aim of developing a pilot unit. The attrition process serves to remove fine particles and pollutants from the surface of coarse stormwater sediment particles. In all cases, the efficiency of pollutant removal is dependent upon various parameters, including cutoff threshold, residence time, solid density, temperature and impeller speed. This article presents the optimization of these various parameters along with method efficiency; for this work, several sediments have been tested. The results indicate that an attrition scrubber may be effectively used to remediate contaminated sediment and that reuse is definitely possible. A model of the method will also be proposed to study the behavior of fine particles and pollutants. | |||||
BibTeX:
@article{Petavy2009,
author = {Petavy, François and Ruban, Veronique and Conil, Pierre and Viau, Jean Yves},
title = {Attrition efficiency in the decontamination of stormwater sediments},
journal = {Applied Geochemistry},
year = {2009},
volume = {24},
number = {1},
pages = {153--161},
url = {http://www.sciencedirect.com/science/article/pii/S0883292708004083}
}
|
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| Petera, J., Strzelecki, W., Agrawal, D. and Weatherley, L. | Charged droplet and particle-mixing studies in liquid–liquid systems in the presence of non-linear electrical fields | 2005 | Chemical Engineering Science Vol. 60(1), pp. 135-149 |
article | URL |
| Abstract: This paper is concerned with the mixing and residence time distribution behaviour of an experimental electrically enhanced column contactor in which electrically charged drops of water were fed into an organic liquid phase of sunflower oil across which a non-linear electrical field was maintained. The effects of electrical field strength upon mixing in the continuous phase were determined and a significant increase in mixing was observed as the field strength was increased. A quantitative theoretical development describing the observed behaviour is also presented. The mixing is described by simultaneous consideration of the movement of the drop phase and the continuous liquid phase. The drop motion, after formation at the charged nozzle and during the subsequent trajectory motion under the influence of the non-linear electric field, is analysed. The interaction between the drop motion and the velocity field of the continuous phase is thus described. The paper describes theoretical prediction of the interactions between charged drops and the electrodes. These interactions can exert a strong influence on the overall residence time of drops passing through the column, and potentially on the velocity profile of the continuous phase. Description of both sets of interactions is used to predict mixing patterns in the continuous phase as a function of applied field strength. The predicted mixing patterns are compared with experimentally recorded images of tracer movement in the continuous phase obtained under the same conditions. The calculated patterns compare favourably with those measured by experiment. The modelling methodology was used afterwards with success for predicting the residence time distribution in the form of the normalised concentration (proportional to the exit function) versus time. | |||||
BibTeX:
@article{Petera2005,
author = {Petera, J. and Strzelecki, W. and Agrawal, D. and Weatherley, L.R.},
title = {Charged droplet and particle-mixing studies in liquid–liquid systems in the presence of non-linear electrical fields},
journal = {Chemical Engineering Science},
year = {2005},
volume = {60},
number = {1},
pages = {135--149},
url = {http://www.sciencedirect.com/science/article/pii/S0009250904005068}
}
|
|||||
| Peterson, E.W. and Wicks, C.M. | Assessing the importance of conduit geometry and physical parameters in karst systems using the storm water management model (SWMM) | 2006 | Journal of Hydrology Vol. 329(1-2), pp. 294-305 |
article | URL |
| Abstract: Questions about the importance of conduit geometry and about the values of hydraulic parameters in controlling ground-water flow and solute transport through karstic aquifers have remained largely speculative. One goal of this project was to assess the role that the conduit geometry and the hydraulic parameters have on controlling transport dynamics within karstic aquifers. The storm water management model (SWMM) was applied to the Devil’s Icebox–Connor’s Cave System in central Missouri, USA. Simulations with incremental changes to conduit geometry or hydraulic parameters were performed with the output compared to a calibrated baseline model. Ten percent changes in the length or width of a conduit produced statistically significant different fluid flow responses. The model exhibited minimal sensitivity to slope and infiltration rates; however, slight changes in Manning’s roughness coefficient can highly alter the simulated output. | |||||
BibTeX:
@article{Peterson2006,
author = {Peterson, Eric W. and Wicks, Carol M.},
title = {Assessing the importance of conduit geometry and physical parameters in karst systems using the storm water management model (SWMM)},
journal = {Journal of Hydrology},
year = {2006},
volume = {329},
number = {1-2},
pages = {294--305},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406000990}
}
|
|||||
| Peterson, E.W. and Wicks, C.M. | Fluid and Solute Transport from a Conduit to the Matrix in a Carbonate Aquifer System | 2005 | Mathematical Geology Vol. 37(8), pp. 851-867 |
article | URL |
| Abstract: Within carbonate systems, the working hypothesis suggests that when a conduit is flooded fluid and solute migrate from the conduit into the matrix. This flux of fluid and solute into the matrix creates a reservoir that can be slowly released once the flooding recedes. Although hypothesized, these fluxes have never been measured. To quantify the distance that a fluid and solute would move into a matrix, the fluxes of fluid and solute from a conduit into a matrix were simulated for nine different carbonate aquifer systems. Two independent numerical approaches were used to simulate (1) fluid flux into the matrix and (2) solute flux into the matrix during a flooding event. When flooding occurs within the conduit, the volume of water transported into and stored in the matrix with a high porosity and high hydraulic conductivity (Floridan Aquifer) was less than 0.34 m 3 along a 1 m length of conduit, resulting in a penetration depth of 7.2×10 −2 m into the matrix. In a low porosity and low hydraulic conductivity matrix (Ozark Plateau), the volume of water transported into and stored in the matrix was less than 6.85×10 −5 m 3 along a 1 m length of conduit, resulting in a penetration depth of 2.0×10 −4 m into the matrix. Simulated solute flow shows that less than 0.1% of the solute moves in to the matrix. The two approaches demonstrate that during high flow conditions fluid and solute are forced through the conduits, with very little moving into the carbonate matrix. Once the fluid and solute enter a conduit and are moving, they will remain in the conduit until they are discharged at an outlet. Thus, a carbonate matrix does not become a reservoir for solute and fluid during a high-flow event. | |||||
BibTeX:
@article{Peterson2005,
author = {Peterson, Eric W. and Wicks, Carol M.},
title = {Fluid and Solute Transport from a Conduit to the Matrix in a Carbonate Aquifer System},
journal = {Mathematical Geology},
publisher = {Springer Netherlands},
year = {2005},
volume = {37},
number = {8},
pages = {851--867},
url = {http://dx.doi.org/10.1007/s11004-005-9211-5}
}
|
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| Petrova, S., Kirova, H., Syrakov, D. and Prodanova, M. | Some fast variants of TRAP scheme for solving advection equation — comparison with other schemes | 2008 | Computers & Mathematics with Applications Vol. 55(10)Advanced Numerical Algorithms for Large-Scale Computations, pp. 2363-2380 |
article | URL |
| Abstract: The advection scheme TRAP was elaborated for the Bulgarian three-dimensional PC-oriented Eulerian air pollution model. The TRAP scheme uses polynomial fit of concentration profile as the BOTT scheme but differs from it in calculating fluxes. Instead of integrating the polynomial fit over the neighboring grid values as in the BOTT scheme, the flux area is supposed to be trapezoidal and is determined as a product of the Courant number and a single value of the approximation polynomial referring the middle of the passed distance. The obtained scheme is explicit, positively definite and conservative with limited numerical dispersion and good transport ability. Displaying the same properties as the BOTT scheme, the TRAP scheme turns out to be several times faster. | |||||
BibTeX:
@article{Petrova2008,
author = {Petrova, Silvia and Kirova, Hristina and Syrakov, Dimiter and Prodanova, Maria},
title = {Some fast variants of TRAP scheme for solving advection equation — comparison with other schemes},
booktitle = {Advanced Numerical Algorithms for Large-Scale Computations},
journal = {Computers & Mathematics with Applications},
year = {2008},
volume = {55},
number = {10},
pages = {2363--2380},
url = {http://www.sciencedirect.com/science/article/pii/S0898122107007304}
}
|
|||||
| Petrunic, B., MacQuarrie, K. and Al, T. | Reductive dissolution of Mn oxides in river-recharged aquifers: a laboratory column study | 2005 | Journal of Hydrology Vol. 301(1-4), pp. 163-181 |
article | URL |
| Abstract: River-recharged aquifers are developed for drinking water supplies in many parts of the world. Often, however, dissolved organic carbon (DOC) present in the infiltrating river water causes biogeochemical reactions to occur in the adjacent aquifer that create elevated Mn and Fe. Mn concentrations in groundwater from some of the production wells installed in the aquifer at Fredericton, New Brunswick exceed the Canadian Drinking Water Guideline of 9.1×10−4 mmol/l by up to 5.5×10−2 mmol/l. It has previously been hypothesized that the influx of DOC from the Saint John River is causing bacterially mediated reductive dissolution of Mn oxides in the aquifer system, leading to elevated aqueous Mn concentrations. Previous work was limited to the collection of water samples from production wells and several observation wells installed in the glacial outwash aquifer. The objective of this study was to investigate the biogeochemical controls on Mn concentrations using sand-filled columns. One column was inoculated with bacteria while a second column was treated with ethanol in order to decrease the microbial population initially present in the system. Both columns received the same influent solution that contained acetate as a source of DOC. The results of the experiments suggested that the two main controls on Mn concentrations in the columns were microbially mediated reductive dissolution of Mn oxides and cation exchange. The conceptual model that was developed based on the experimental data was supported by the results obtained using a one-dimensional reactive-transport model. The reductive dissolution of Mn oxides in the aquifer sands could be adequately simulated using dual-Monod kinetics. Similar trends are observed in the experimental data and field data collected from Production Well 5, located in the Fredericton Aquifer. From the experiments, it is evident that cation-exchange reactions may be an important geochemical control on Mn concentrations during the initial stages of pumping; however, the reductive dissolution of Mn oxides may represent a long-term source of Mn in the drinking water supply. | |||||
BibTeX:
@article{Petrunic2005,
author = {Petrunic, B.M. and MacQuarrie, K.T.B. and Al, T.A.},
title = {Reductive dissolution of Mn oxides in river-recharged aquifers: a laboratory column study},
journal = {Journal of Hydrology},
year = {2005},
volume = {301},
number = {1-4},
pages = {163--181},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404003129}
}
|
|||||
| Pham-Gia, T. and Hung, T.L. | The mean and median absolute deviations | 2001 | Mathematical and Computer Modelling Vol. 34(7–8), pp. 921-936 |
article | URL |
| Abstract: In this article, we present a survey of important results related to the mean and median absolute deviations of a distribution, both denoted by MAD in the statistical modelling literature and hence creating some confusion. Some up-to-date published results, and some original ones of our own, are also included, along with discussions on several controversial issues. | |||||
BibTeX:
@article{Pham-Gia2001,
author = {Pham-Gia, T. and Hung, T. L.},
title = {The mean and median absolute deviations},
journal = {Mathematical and Computer Modelling},
year = {2001},
volume = {34},
number = {7–8},
pages = {921--936},
url = {http://www.sciencedirect.com/science/article/pii/S0895717701001091}
}
|
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| Phanikumar, M.S. and McGuire, J.T. | A multi-species reactive transport model to estimate biogeochemical rates based on single-well push–pull test data | 2010 | Computers & Geosciences Vol. 36(8), pp. 997-1004 |
article | URL |
| Abstract: Push–pull tests are a popular technique to investigate various aquifer properties and microbial reaction kinetics in situ. Most previous studies have interpreted push–pull test data using approximate analytical solutions to estimate (generally first-order) reaction rate coefficients. Though useful, these analytical solutions may not be able to describe important complexities in rate data. This paper reports the development of a multi-species, radial coordinate numerical model (PPTEST) that includes the effects of sorption, reaction lag time and arbitrary reaction order kinetics to estimate rates in the presence of mixing interfaces such as those created between injected “push” water and native aquifer water. The model has the ability to describe an arbitrary number of species and user-defined reaction rate expressions including Monod/Michelis–Menten kinetics. The FORTRAN code uses a finite-difference numerical model based on the advection-dispersion-reaction equation and was developed to describe the radial flow and transport during a push–pull test. The accuracy of the numerical solutions was assessed by comparing numerical results with analytical solutions and field data available in the literature. The model described the observed breakthrough data for tracers (chloride and iodide-131) and reactive components (sulfate and strontium-85) well and was found to be useful for testing hypotheses related to the complex set of processes operating near mixing interfaces. | |||||
BibTeX:
@article{Phanikumar2010,
author = {Phanikumar, Mantha S. and McGuire, Jennifer T.},
title = {A multi-species reactive transport model to estimate biogeochemical rates based on single-well push–pull test data},
journal = {Computers & Geosciences},
year = {2010},
volume = {36},
number = {8},
pages = {997--1004},
url = {http://www.sciencedirect.com/science/article/pii/S0098300410001214}
}
|
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| Phelan Jr., F.R. and Bauer, B.J. | Simulation of nanotube separation in field-flow fractionation (FFF) | 2007 | Chemical Engineering Science Vol. 62(17), pp. 4620-4635 |
article | URL |
| Abstract: A Brownian dynamics simulation based on a prolate spheroid particle model has been developed to model the separation of nanotubes in cross flow driven, field-flow fractionation (FFF). The particle motions are governed by stochastic forms of a linear momentum balance with orientation dependent drag and diffusion coefficients, and the Jeffrey equation with rotational diffusion. The simulation shows that nanotube scale particles would be expected to elute by a normal mode mechanism up to aspect ratios of about 1000, based on a particle diameter of 1 nm. Separation of nanotubes of different length is governed by the value of the retention variable for each component in agreement with theory. Elution profiles and average velocity through the device as a function of particle size, and the flow rates in the throughput and cross-flow directions are examined. The simulation shows that clean separations between components of different size is achieved when the ratio of the retention values is greater than 2. | |||||
BibTeX:
@article{PhelanJr.2007,
author = {Phelan, Jr., Frederick R. and Bauer, Barry J.},
title = {Simulation of nanotube separation in field-flow fractionation (FFF)},
journal = {Chemical Engineering Science},
year = {2007},
volume = {62},
number = {17},
pages = {4620--4635},
url = {http://www.sciencedirect.com/science/article/pii/S0009250907003387}
}
|
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| Pitt, R., Clark, S. and Field, R. | Groundwater contamination potential from stormwater infiltration practices | 1999 | Urban Water Vol. 1(3), pp. 217-236 |
article | URL |
| Abstract: The potential effects of stormwater on groundwater quality was estimated based on the likely presence of problem constituents in the stormwater, their mobility through soils, the type of treatment received before infiltration, and the infiltration method used. The constituents of most concern include chloride, certain pesticides (lindane and chlordane), organic toxicants (1,3-dichlorobenzene, pyrene and fluoranthene), pathogens, and some heavy metals (nickel and zinc). Reported instances of groundwater contamination associated with stormwater was rare in residential areas where infiltration occurred through surface soils (except for chloride), but was more common (especially for toxicants) in commercial and industrial areas where subsurface infiltration was used. | |||||
BibTeX:
@article{Pitt1999,
author = {Pitt, Robert and Clark, Shirley and Field, Richard},
title = {Groundwater contamination potential from stormwater infiltration practices},
journal = {Urban Water},
year = {1999},
volume = {1},
number = {3},
pages = {217--236},
url = {http://www.sciencedirect.com/science/article/pii/S146207589900014X}
}
|
|||||
| Piver, W.T. | Contamination and Restoration of Groundwater Aquifers | 1993 | Environmental Health Perspectives Vol. 100, pp. 237-247 |
article | URL |
| Abstract: Humans are exposed to chemicals in contaminated groundwaters that are used as sources of drinking water. Chemicals contaminate groundwater resources as a result of waste disposal methods for toxic chemicals, overuse of agricultural chemicals, and leakage of chemicals into the subsurface from buried tanks used to hold fluid chemicals and fuels. In the process, both the solid portions of the subsurface and the groundwaters that flow through these porous structures have become contaminated. Restoring these aquifers and minimizing human exposure to the parent chemicals and their degradation products will require the identification of suitable biomarkers of human exposure; better understandings of how exposure can be related to disease outcome; better understandings of mechanisms of transport of pollutants in the heterogeneous structures of the subsurface; and field testing and evaluation of methods proposed to restore and cleanup contaminated aquifers. In this review, progress in these many different but related activities is presented. | |||||
BibTeX:
@article{Piver1993,
author = {Piver, Warren T.},
title = {Contamination and Restoration of Groundwater Aquifers},
journal = {Environmental Health Perspectives},
publisher = {Brogan & Partners},
year = {1993},
volume = {100},
pages = {237--247},
url = {http://www.jstor.org/stable/3431530}
}
|
|||||
| Piver, W.T., Jacobs, T.L. and Medina Miguel A., J. | Evaluation of Health Risks for Contaminated Aquifers | 1997 | Environmental Health Perspectives Vol. 105, pp. 127-143 |
article | URL |
| Abstract: This review focuses on progress in the development of transport models for heterogeneous contaminated aquifers, the use of predicted contaminant concentrations in groundwater for risk assessment for heterogeneous human populations, and the evaluation of aquifer remediation technologies. Major limitations and areas for continuing research for all methods presented in this review are identified. | |||||
BibTeX:
@article{Piver1997,
author = {Piver, Warren T. and Jacobs, Timothy L. and Medina, Miguel A., Jr.},
title = {Evaluation of Health Risks for Contaminated Aquifers},
journal = {Environmental Health Perspectives},
publisher = {Brogan & Partners},
year = {1997},
volume = {105},
pages = {127--143},
url = {http://www.jstor.org/stable/3433402}
}
|
|||||
| Plaza, C., Xing, B., Fernández, J.M., Senesi, N. and Polo, A. | Binding of polycyclic aromatic hydrocarbons by humic acids formed during composting | 2009 | Environmental Pollution Vol. 157(1), pp. 257-263 |
article | URL |
| Abstract: Binding of two model polycyclic aromatic hydrocarbons (PAHs), phenanthrene and pyrene, by humic acids (HAs) isolated from an organic substrate at different stages of composting and a soil was investigated using a batch fluorescence quenching method and the modified Freundlich model. With respect to soil HA, the organic substrate HA fractions were characterized by larger binding affinities for both phenanthrene and pyrene. Further, isotherm deviation from linearity was larger for soil HA than for organic substrate HAs, indicating a larger heterogeneity of binding sites in the former. The composting process decreased the binding affinity and increased the heterogeneity of binding sites of HAs. The changes undergone by the HA fraction during composting may be expected to contribute to facilitate microbial accessibility to PAHs. The results obtained also suggest that bioremediation of PAH-contaminated soils with matured compost, rather than with fresh organic amendments, may result in faster and more effective cleanup. | |||||
BibTeX:
@article{Plaza2009,
author = {Plaza, César and Xing, Baoshan and Fernández, José M. and Senesi, Nicola and Polo, Alfredo},
title = {Binding of polycyclic aromatic hydrocarbons by humic acids formed during composting},
journal = {Environmental Pollution},
year = {2009},
volume = {157},
number = {1},
pages = {257--263},
url = {http://www.sciencedirect.com/science/article/pii/S0269749108003758}
}
|
|||||
| Plugatyr, A. and Svishchev, I.M. | Residence time distribution measurements and flow modeling in a supercritical water oxidation reactor: Application of transfer function concept | 2008 | The Journal of Supercritical Fluids Vol. 44(1), pp. 31-39 |
article | URL |
| Abstract: Residence time distribution (RTD) measurements are carried out in a flow-through tubular supercritical water oxidation (SCWO) reactor using ex situ pulse response experiments. The experiments are performed from ambient to supercritical water conditions with a volumetric flow rate fixed at 1 ml/min. The transfer function concept is used to interpret tracer information and to elucidate hydrodynamic flow patterns inside the “hot zone” of the reactor vessel. The experimental RTD curves are modeled by an axially dispersed plug flow. At supercritical conditions, the studied tubular SCWO reactor can be characterized as a mixed flow system (with Péclet numbers of 1.4-2). The results also indicate the presence of fast preferential fluid flow in the reactor below 573 K and 10 MPa. | |||||
BibTeX:
@article{Plugatyr2008,
author = {Plugatyr, Andriy and Svishchev, Igor M.},
title = {Residence time distribution measurements and flow modeling in a supercritical water oxidation reactor: Application of transfer function concept},
journal = {The Journal of Supercritical Fluids},
year = {2008},
volume = {44},
number = {1},
pages = {31--39},
url = {http://www.sciencedirect.com/science/article/pii/S0896844607003609}
}
|
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| Polk, J.S., van Beynen, P. and Wynn, J. | An isotopic calibration study of precipitation, cave dripwater, and climate in west-central Florida | 2011 | Hydrological Processes, pp. n/a-n/a | article | URL |
| Abstract: A calibration study of oxygen and hydrogen isotopic composition from precipitation and cave dripwater was conducted in west-central Florida at Legend Cave during 2007–2008. This study was performed to better understand how modern precipitation patterns can be discerned through examination of cave dripwater and speleothem calcite for paleoclimate reconstruction. The ‘amount effect’ was shown to be a dominant control on the oxygen isotopic composition of precipitation for the study area. A meteoric water line with a slope of 6·7 suggests evaporative effects occur either during precipitation or subsequent hydrological processes. However, δ18O values of cave dripwater averaged near the mean annual amount-weighted average of precipitation, suggesting that the isotopic composition of dripwater tracks the long-term average of rainfall. An observed weak seasonal influence occurred in the d-excess values, with summer precipitation being more enriched due to increased evaporative effects. Comparison of precipitation δ18O values to synoptic weather data shows the dominant amount effect influence occurs due to strong convective storms producing highly 18O-depleted rainfall at greater amounts during the year. Constant δ18O values of the dripwater indicate that paleoclimate reconstructions using speleothems from this area would record changes in annual to interannual shifts in precipitation amount above the cave. Copyright © 2011 John Wiley & Sons, Ltd. | |||||
BibTeX:
@article{Polk2011,
author = {Polk, Jason S. and van Beynen, Philip and Wynn, Jonathan},
title = {An isotopic calibration study of precipitation, cave dripwater, and climate in west-central Florida},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2011},
pages = {n/a--n/a},
url = {http://dx.doi.org/10.1002/hyp.8169}
}
|
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| Pontier, H., Williams, J. and May, E. | Progressive changes in water and sediment quality in a wetland system for control of highway runoff | 2004 | Science of The Total Environment Vol. 319(1-3), pp. 215-224 |
article | URL |
| Abstract: Innovative wetland based systems were designed and installed on the Newbury Bypass, Berkshire, England to provide flow balancing and pollution control for road runoff. The systems were monitored over 18 months to evaluate performance, pollutant removal processes and offer improved design and operation codes for this new application of wetlands. Water quality, sediment accumulation rates, and metal concentrations in size-fractionated, settling solids and deposited sediments were determined in parts of the system to provide information on spatial and temporal variability. The results presented here show that over the long term, there were progressive changes in parts of the system for BOD and COD and for metal concentrations in the sediment fractions, which occurred with linear (or semi log-linear) rates, despite variability in flow rates, retention times and in pollutant loading to the system. Future work will continue monitoring to increase the data set, examine possible processes contributing to the regression constants, and test the potential use of the regressions in system modelling. Attempts at modelling road runoff treatment using wetlands must allow for progressions, since the systems can only be effective if they retain removed metals in the sediment sink. | |||||
BibTeX:
@article{Pontier2004,
author = {Pontier, H and Williams, J.B and May, E},
title = {Progressive changes in water and sediment quality in a wetland system for control of highway runoff},
journal = {Science of The Total Environment},
year = {2004},
volume = {319},
number = {1--3},
pages = {215--224},
url = {http://www.sciencedirect.com/science/article/pii/S0048969703004108}
}
|
|||||
| Popescu, R., Deodatis, G. and Nobahar, A. | Effects of random heterogeneity of soil properties on bearing capacity | 2005 | Probabilistic Engineering Mechanics Vol. 20(4), pp. 324-341 |
article | URL |
| Abstract: This study examines the effect of random heterogeneity of soil properties on bearing capacity. The stochastic soil property considered is the undrained shear strength and two major sources of uncertainty are identified with it: inherent spatial variability (modeled as a non-Gaussian, homogeneous stochastic field) and uncertainty in the estimation of its expected value (modeled as a random variable). The two sources of uncertainty are treated separately, before being eventually combined. A Monte Carlo simulation approach is followed in combination with non-linear finite element analysis. It is demonstrated that the inherent spatial variability of soil shear strength can drastically modify the basic form of the failure mechanism in this bearing capacity problem. Consequently, there is no ‘average’ failure mechanism (surface) in this problem, leading to the conclusion that Monte Carlo simulation is the only methodology capable of providing a solution to this geomechanics problem. It is further demonstrated that this behavior of the failure mechanism translates into a substantial reduction in the ultimate bearing capacity (in an average sense), compared to the corresponding deterministic (homogeneous soil) case. In addition, differential settlements are computed in the stochastic analysis, something impossible in a deterministic analysis of a symmetric problem. A parametric study is performed using fragility curves to investigate the effects of various probabilistic parameters involved in the problem. It is found that the coefficient of variation and the marginal probability distribution of the soil's shear strength (both controlling the amount of loose pockets in the soil mass) are the two most important parameters in reducing the bearing capacity (in an average sense) and producing substantial differential settlements in heterogeneous soils (compared to homogeneous soils). A technique is finally introduced for determining ‘overall’ fragility curves that account for both inherent soil spatial variability and uncertainty in the expected value of soil strength. Based on such ‘overall’ fragility curves obtained at failure (ultimate bearing capacity), nominal values of the bearing capacity of a heterogeneous soil deposit corresponding to an exceedance probability of 5% are established for a range of probabilistic characteristics. | |||||
BibTeX:
@article{Popescu2005,
author = {Popescu, Radu and Deodatis, George and Nobahar, Arash},
title = {Effects of random heterogeneity of soil properties on bearing capacity},
journal = {Probabilistic Engineering Mechanics},
year = {2005},
volume = {20},
number = {4},
pages = {324--341},
url = {http://www.sciencedirect.com/science/article/pii/S0266892005000184}
}
|
|||||
| Price, T. and Probert, D. | Role of constructed wetlands in environmentally-sustainable developments | 1997 | Applied Energy Vol. 57(2-3)Water Thrift, pp. 129-174 |
article | URL |
| Abstract: Whilst discounting the likely, frequent widespread use of natural wetlands for liquid-effluent treatment within the UK, a brief history of the global development of constructed wetlands is given. The designs and types of flora and fauna used within UK-based constructed wetlands, are discussed. Then, a case study of the constructed wetlands used at the Wildfowl and Wetlands Trust, Gloucestershire, UK, highlights how constructed wetlands can be used successfully for decontaminating liquid effluent within the UK. | |||||
BibTeX:
@article{Price1997,
author = {Price, Trevor and Probert, Douglas},
title = {Role of constructed wetlands in environmentally-sustainable developments},
booktitle = {Water Thrift},
journal = {Applied Energy},
year = {1997},
volume = {57},
number = {2-3},
pages = {129--174},
url = {http://www.sciencedirect.com/science/article/pii/S0306261997000329}
}
|
|||||
| Prinzhofer, A., Girard, J.P., Buschaert, S., Huiban, Y. and Noirez, S. | Chemical and isotopic characterization of hydrocarbon gas traces in porewater of very low permeability rocks: The example of the Callovo-Oxfordian argillites of the eastern part of the Paris Basin | 2009 | Chemical Geology Vol. 260(3-4), pp. 269-277 |
article | URL |
| Abstract: A methodology has been developed to determine chemical and carbon isotopic compositions of trace amounts of hydrocarbon gas compounds (methane, ethane, propane, iso- and normal-butane) present as dissolved compounds in the porewater of the low permeability Callovo-Oxfordian argillites in eastern Paris Basin, France. Results indicate that the studied hydrocarbons contain significant amounts of ethane, butane and propane, in addition to methane. Carbon isotopic compositions reflect primarily thermogenic origin (thermal cracking of organic matter), and lack of any significant biodegradation. Because temperature did not exceed 50 °C in the studied argillites, investigated hydrocarbons must have originated in hotter/deeper organic-bearing formations, possibly Stephanian coals. Data supports the predominance of high maturity thermogenic gas in the upper part of the Callovo-Oxfordian, and low maturity thermogenic gas mixed with minor bacterially produced methane in the lower part of the formation. A mixing between three end-member gases models quite well the data: one thermogenic gas with a low maturity (42% methane, with a δ13C of − 53‰), a gas with higher maturity (55% methane, with a δ13C of − 47‰) and a bacterial gas (99.45% methane, with a δ13C of − 80‰). This study illustrates that migration of hydrocarbon gases can take place in rocks with very low permeability and porosity, such as compacted mudrocks, given enough time. It further suggests that the studied fluid migration and transfer in aquitards would help characterization and understanding of fluid movements in sedimentary basins, as a complement to studies focused on water aquifers and hydrocarbon reservoirs. Chemical and isotopic composition of dissolved hydrocarbons in porewater can be used as natural tracers of fluid circulation in sedimentary basins, in addition to more conventional tracers. | |||||
BibTeX:
@article{Prinzhofer2009,
author = {Prinzhofer, Alain and Girard, Jean Pierre and Buschaert, Stéphane and Huiban, Yvon and Noirez, Sonia},
title = {Chemical and isotopic characterization of hydrocarbon gas traces in porewater of very low permeability rocks: The example of the Callovo-Oxfordian argillites of the eastern part of the Paris Basin},
journal = {Chemical Geology},
year = {2009},
volume = {260},
number = {3-4},
pages = {269--277},
url = {http://www.sciencedirect.com/science/article/pii/S0009254108005925}
}
|
|||||
| Project, B.M., Bateman, H., Erdélyi, A. and of Naval Research, U.S.O. | Tables of integral transforms. Based, in part, on notes left by Harry Bateman, [BibTeX] |
1954 | , pp. - | book | |
BibTeX:
@book{Project1954,
author = {Bateman Manuscript Project and Bateman, Harry and Erdélyi, Arthur and United States Office of Naval Research},
title = {Tables of integral transforms. Based, in part, on notes left by Harry Bateman,},
publisher = {McGraw-Hill},
year = {1954},
pages = {--}
}
|
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| Pronk, M., Goldscheider, N. and Zopfi, J. | Microbial communities in karst groundwater and their potential use for biomonitoring | 2009 | Hydrogeology Journal Vol. 17(1), pp. 37-48 |
article | URL |
| Abstract: The structure, diversity and dynamics of microbial communities from a swallow hole draining agricultural land and two connected karst springs (Switzerland) were studied using molecular microbiological methods and related to hydrological and physicochemical parameters. Storm responses and an annual hydrological cycle were monitored to determine the short- and long-term variability, respectively, of bacterial communities. Statistical analysis of bacterial genetic fingerprints (16S rDNA PCR-DGGE) of spring water samples revealed several clusters that corresponded well with different levels of the allochthonous swallow hole contribution. Microbial communities in spring water samples highly affected by the swallow hole showed low similarities among them, reflecting the high temporal variability of the bacterial communities infiltrating at the swallow hole. Conversely, high similarities among samples with low allochthonous contribution provided evidence for a stable autochthonous endokarst microbial community. Three spring samples, representative for low, medium and high swallow hole contribution, were analysed by cloning/sequencing in order to identify the major bacterial groups in the communities. The autochthonous endokarst microbial community was mainly characterized of δ-Proteobacteria , Acidobacteria and Nitrospira species. A high percentage of unknown sequences suggested further that many karst aquifer bacteria are still undiscovered. Finally, the potential use of groundwater biomonitoring using microbial communities is discussed. | |||||
BibTeX:
@article{Pronk2009a,
author = {Pronk, Michiel and Goldscheider, Nico and Zopfi, Jakob},
title = {Microbial communities in karst groundwater and their potential use for biomonitoring},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {37--48},
url = {http://dx.doi.org/10.1007/s10040-008-0350-x}
}
|
|||||
| Pronk, M., Goldscheider, N. and Zopfi, J. | Particle-Size Distribution As Indicator for Fecal Bacteria Contamination of Drinking Water from Karst Springs | 2007 | Environmental Science & Technology Vol. 41(24), pp. 8400-8405 |
article | DOI URL |
| Abstract: Continuous monitoring of particle-size distribution (PSD), total organic carbon (TOC), turbidity, discharge and physicochemical parameters, together with analyses of fecal indicator bacteria, particularly Escherichia coli, made it possible to better understand the processes governing pathogen transport in karst groundwater and to establish PSD as indicator for possible microbial contamination of drinking water from karst springs. In the study area near Yverdon-les-Bains, Switzerland, tracer tests proved connection between a sinking stream draining agricultural land and several springs, 4.8?6.3 km away. Tracing and monitoring results demonstrate that (i) suspended particles (turbidity) in the spring water either originate from remobilization of sediments inside the aquifer (autochthonous) or from the sinking stream and land surface (allochthonous); (ii) allochthonous turbidity coincides with increased E. coli and TOC levels; (iii) PSD makes it possible to distinguish the two types of turbidity; (iv) a relative increase of finer particles (0.9?10 µm) indicates allochthonous turbidity and thus possible fecal contamination. The method permits to optimize water treatment and identify periods when the spring water must be rejected. Findings from other test sites confirm the feasibility of this approach. Continuous monitoring of particle-size distribution (PSD), total organic carbon (TOC), turbidity, discharge and physicochemical parameters, together with analyses of fecal indicator bacteria, particularly Escherichia coli, made it possible to better understand the processes governing pathogen transport in karst groundwater and to establish PSD as indicator for possible microbial contamination of drinking water from karst springs. In the study area near Yverdon-les-Bains, Switzerland, tracer tests proved connection between a sinking stream draining agricultural land and several springs, 4.8?6.3 km away. Tracing and monitoring results demonstrate that (i) suspended particles (turbidity) in the spring water either originate from remobilization of sediments inside the aquifer (autochthonous) or from the sinking stream and land surface (allochthonous); (ii) allochthonous turbidity coincides with increased E. coli and TOC levels; (iii) PSD makes it possible to distinguish the two types of turbidity; (iv) a relative increase of finer particles (0.9?10 µm) indicates allochthonous turbidity and thus possible fecal contamination. The method permits to optimize water treatment and identify periods when the spring water must be rejected. Findings from other test sites confirm the feasibility of this approach. |
|||||
BibTeX:
@article{Pronk2007,
author = {Pronk, Michiel and Goldscheider, Nico and Zopfi, Jakob},
title = {Particle-Size Distribution As Indicator for Fecal Bacteria Contamination of Drinking Water from Karst Springs},
journal = {Environmental Science & Technology},
publisher = {American Chemical Society},
year = {2007},
volume = {41},
number = {24},
pages = {8400--8405},
url = {http://dx.doi.org/10.1021/es071976f},
doi = {http://dx.doi.org/10.1021/es071976f}
}
|
|||||
| Pronk, M., Goldscheider, N. and Zopfi, J. | Dynamics and interaction of organic carbon, turbidity and bacteria in a karst aquifer system | 2006 | Hydrogeology Journal Vol. 14(4), pp. 473-484 |
article | URL |
| Abstract: The dynamics of organic carbon (OC), turbidity, faecal indicator bacteria and physicochemical parameters was studied in a karst system near Yverdon, Switzerland. Online measurements and sampling were done at a swallow hole draining an agricultural surface (the input), and two groups of springs (the outputs) that often show bacterial contamination. A fluorescent tracer that was injected into the swallow hole during low-flow conditions first arrived at the springs 10–12 days after injection; the total recovery rate was 29%. Previous tracer tests during high-flow conditions gave shorter travel times. After a major rainfall event, a primary turbidity peak was observed at the springs. It coincides with the rising limb of the hydrograph, indicating remobilisation of autochthonous particles from the aquifer. A secondary turbidity peak occurs several days later, suggesting the arrival of allochthonous particles from the swallow hole. Wider peaks of OC and bacteria were observed simultaneously. Applying methods from molecular microbiology (PCR-DGGE) allowed characterisation of the bacterial communities at the swallow hole and the springs. The results demonstrate that the swallow hole is an important source of groundwater contamination, while its contribution to aquifer recharge is insignificant. OC appears to be a better indicator for bacterial contamination than turbidity. | |||||
BibTeX:
@article{Pronk2006,
author = {Pronk, Michiel and Goldscheider, Nico and Zopfi, Jakob},
title = {Dynamics and interaction of organic carbon, turbidity and bacteria in a karst aquifer system},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {4},
pages = {473--484},
url = {http://dx.doi.org/10.1007/s10040-005-0454-5}
}
|
|||||
| Pronk, M., Goldscheider, N., Zopfi, J. and Zwahlen, F. | Percolation and Particle Transport in the Unsaturated Zone of a Karst Aquifer | 2009 | Ground Water Vol. 47(3), pp. 361-369 |
article | URL |
| Abstract: Recharge and contamination of karst aquifers often occur via the unsaturated zone, but the functioning of this zone has not yet been fully understood. Therefore, irrigation and tracer experiments, along with monitoring of rainfall events, were used to examine water percolation and the transport of solutes, particles, and fecal bacteria between the land surface and a water outlet into a shallow cave. Monitored parameters included discharge, electrical conductivity, temperature, organic carbon, turbidity, particle-size distribution (PSD), fecal indicator bacteria, chloride, bromide, and uranine. Percolation following rainfall or irrigation can be subdivided into a lag phase (no response at the outlet), a piston-flow phase (release of epikarst storage water by pressure transfer), and a mixed-flow phase (increasing contribution of freshly infiltrated water), starting between 20 min and a few hours after the start of recharge event. Concerning particle and bacteria transport, results demonstrate that (1) a first turbidity signal occurs during increasing discharge due to remobilization of particles from fractures (pulse-through turbidity); (2) a second turbidity signal is caused by direct particle transfer from the soil (flow-through turbidity), often accompanied by high levels of fecal indicator bacteria, up to 17,000 Escherichia coli/100 mL; and (3) PSD allows differentiation between the two types of turbidity. A relative increase of fine particles (0.9 to 1.5 μm) coincides with microbial contamination. These findings help quantify water storage and percolation in the epikarst and better understand contaminant transport and attenuation. The use of PSD as “early-warning parameter” for microbial contamination in karst water is confirmed. | |||||
BibTeX:
@article{Pronk2009,
author = {Pronk, Michiel and Goldscheider, Nico and Zopfi, Jakob and Zwahlen, François},
title = {Percolation and Particle Transport in the Unsaturated Zone of a Karst Aquifer},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2009},
volume = {47},
number = {3},
pages = {361--369},
url = {http://dx.doi.org/10.1111/j.1745-6584.2008.00509.x}
}
|
|||||
| Pronk, M., Goldscheider, N., Zwahlen, F. and Zopfi, J. | Dynamics of Microbial Communities in Karst Groundwater - a Case Study from Yverdon-les-Bains, Switzerland. [BibTeX] |
2007 | XXXV International Association of Hydrogeologists (IAH) Congress, Groundwater and Ecosystems, 17-21 September 2007 | inproceedings | |
BibTeX:
@inproceedings{Goldscheider2007,
author = {Pronk, M and Goldscheider, N and Zwahlen, F and Zopfi, J},
title = {Dynamics of Microbial Communities in Karst Groundwater - a Case Study from Yverdon-les-Bains, Switzerland.},
booktitle = {XXXV International Association of Hydrogeologists (IAH) Congress, Groundwater and Ecosystems, 17-21 September 2007},
year = {2007}
}
|
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| Ptak, T., Piepenbrink, M. and Martac, E. | Tracer tests for the investigation of heterogeneous porous media and stochastic modelling of flow and transport—a review of some recent developments | 2004 | Journal of Hydrology Vol. 294(1-3)Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media, pp. 122-163 |
article | URL |
| Abstract: In heterogeneous porous aquifers, simulations and predictions of groundwater flow and solute (contaminant) transport require detailed knowledge of aquifer parameters and their spatial distribution. In most cases this information cannot easily be obtained at acceptable expenses. In general, subsurface investigation techniques are applied only at borehole locations, and the parameter values measured have to be regionalized in order to obtain continuous parameter fields. Geophysical measurements very often yield unsatisfactory results due to resolution, detection range and parameterisation problems. In such situations tracer tests offer the possibility to efficiently investigate the aquifer between the wells and to characterize the relevant aquifer properties based on effective parameter values. Tracer tests can be performed at laboratory and field-scales with depth integrated (two-dimensional) or multilevel (three-dimensional) set-ups, and under natural or forced hydraulic gradient conditions. Both non-reactive and reactive tracer compounds can be used. This contribution covers and gives examples on the following topics: depth integrated and three-dimensional natural and forced gradient tracer test methods together with their fields of application at different transport scales, novel tracer compounds and applications, high resolution multilevel–multitracer methods and high resolution multilevel–multitracer equipment, as well as approaches to evaluate tracer experiments and to quantify tracer transport. In this way the paper shows some recent trends in tracer based subsurface investigation and emphasizes the advantages and importance of modern tracer testing. | |||||
BibTeX:
@article{Ptak2004,
author = {Ptak, Thomas and Piepenbrink, Matthias and Martac, Eugeniu},
title = {Tracer tests for the investigation of heterogeneous porous media and stochastic modelling of flow and transport—a review of some recent developments},
booktitle = {Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media},
journal = {Journal of Hydrology},
year = {2004},
volume = {294},
number = {1-3},
pages = {122--163},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404001027}
}
|
|||||
| Ptak, T., Piepenbrink, M. and Martac, E. | Tracer tests for the investigation of heterogeneous porous media and stochastic modelling of flow and transport—a review of some recent developments | 2004 | Journal of Hydrology Vol. 294(1-3)Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media, pp. 122-163 |
article | URL |
| Abstract: In heterogeneous porous aquifers, simulations and predictions of groundwater flow and solute (contaminant) transport require detailed knowledge of aquifer parameters and their spatial distribution. In most cases this information cannot easily be obtained at acceptable expenses. In general, subsurface investigation techniques are applied only at borehole locations, and the parameter values measured have to be regionalized in order to obtain continuous parameter fields. Geophysical measurements very often yield unsatisfactory results due to resolution, detection range and parameterisation problems. In such situations tracer tests offer the possibility to efficiently investigate the aquifer between the wells and to characterize the relevant aquifer properties based on effective parameter values. Tracer tests can be performed at laboratory and field-scales with depth integrated (two-dimensional) or multilevel (three-dimensional) set-ups, and under natural or forced hydraulic gradient conditions. Both non-reactive and reactive tracer compounds can be used. This contribution covers and gives examples on the following topics: depth integrated and three-dimensional natural and forced gradient tracer test methods together with their fields of application at different transport scales, novel tracer compounds and applications, high resolution multilevel–multitracer methods and high resolution multilevel–multitracer equipment, as well as approaches to evaluate tracer experiments and to quantify tracer transport. In this way the paper shows some recent trends in tracer based subsurface investigation and emphasizes the advantages and importance of modern tracer testing. | |||||
BibTeX:
@article{Ptak2004a,
author = {Ptak, Thomas and Piepenbrink, Matthias and Martac, Eugeniu},
title = {Tracer tests for the investigation of heterogeneous porous media and stochastic modelling of flow and transport—a review of some recent developments},
booktitle = {Stochastic Models of Flow and Transport in Multiple-scale Heterogeneous Porous Media},
journal = {Journal of Hydrology},
year = {2004},
volume = {294},
number = {1-3},
pages = {122--163},
url = {http://www.sciencedirect.com/science/article/pii/S0022169404001027}
}
|
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| Ptak, T. and Schmid, G. | Dual-tracer transport experiments in a physically and chemically heterogeneous porous aquifer: effective transport parameters and spatial variability | 1996 | Journal of Hydrology Vol. 183(1-2), pp. 117-138 |
article | URL |
| Abstract: In order to investigate the effects of reactive transport processes within a heterogeneous porous aquifer, two small-scale forced gradient tracer tests were conducted at the ‘Horkheimer Insel’ field site. During the experiments, two fluorescent tracers were injected simultaneously in the same fully penetrating groundwater monitoring well, located approximately 10 m from the pumping well. Fluoresceine and Rhodamine WT were used to represent the classes of practically non-sorbing and sorbing solutes, respectively. Multilevel breakthrough curves with a temporal resolution of 1 min were measured for both tracers at different depths within the pumping well using fibre-optic fluorimeters. This paper presents the tracer test design, the fibre-optic fluorimetry instrumentation, the experimental results and the interpretation of the measured multilevel breakthrough curves in terms of temporal moments and effective transport parameters. Significant sorption of Rhodamine WT is apparent from the effective retardation factors. Furthermore, an enhanced tailing of Rhodamine WT breakthrough curves is observed, which is possibly caused by a variability of aquifer sorption properties. The determined effective parameters are spatially variable, suggesting that a complex numerical flow and transport modelling approach within a stochastic framework will be needed to adequately describe the transport behaviour observed in the two experiments. Therefore, the tracer test results will serve in future work for the validation of numerical stochastic transport simulations taking into account the spatial variability of hydraulic conductivity and sorption-related aquifer properties. | |||||
BibTeX:
@article{Ptak1996,
author = {Ptak, T. and Schmid, G.},
title = {Dual-tracer transport experiments in a physically and chemically heterogeneous porous aquifer: effective transport parameters and spatial variability},
journal = {Journal of Hydrology},
year = {1996},
volume = {183},
number = {1-2},
pages = {117--138},
url = {http://www.sciencedirect.com/science/article/pii/S0022169496800370}
}
|
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| Ptak, T. and Teutsch, G. | Forced and natural gradient tracer tests in a highly heterogeneous porous aquifer: instrumentation and measurements | 1994 | Journal of Hydrology Vol. 159(1-4), pp. 79-104 |
article | URL |
| Abstract: At the Horkheimer Insel experimental field site, several short to intermediate distance forced and natural gradient tracer tests with depth-integrated and multilevel sampling were conducted to characterize the aquifer transport properties. Compared with other test sites, the aquifer at the Horkheimer Insel is highly heterogeneous and highly conductive. Hence, new tracer measurement techniques had to be developed. This paper presents some of the instrumentation developed together with measurements and their initial interpretation. The results demonstrate that for contaminant transport predictions in highly heterogeneous and highly conductive aquifers, investigation techniques with a high resolution in time and space are needed. The aquifer heterogeneity is evident from the spatial variability of peak concentration, transport velocity and longitudinal macrodispersivity values obtained from the tracer tests. Furthermore, the tracer test results indicate that at the observation scale investigated, a complex numerical flow and transport model is needed to describe adequately mass transport within the heterogeneous aquifer. | |||||
BibTeX:
@article{Ptak1994a,
author = {Ptak, T. and Teutsch, G.},
title = {Forced and natural gradient tracer tests in a highly heterogeneous porous aquifer: instrumentation and measurements},
journal = {Journal of Hydrology},
year = {1994},
volume = {159},
number = {1-4},
pages = {79--104},
url = {http://www.sciencedirect.com/science/article/pii/002216949490250X}
}
|
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| Puaux, J., Bozga, G. and Ainser, A. | Residence time distribution in a corotating twin-screw extruder | 2000 | Chemical Engineering Science Vol. 55(9), pp. 1641-1651 |
article | URL |
| Abstract: A modeling study for the polymer flow and mixing in a corotating twin-screw extruder is presented. The residence time distribution (RTD) in a fully intermeshing corotating twin-screw extruder was measured, using iron powder as tracer, and an LDPE as flow material. Pulse-type input signal experiments were performed in different working conditions. To fit the experimental data obtained on two different screw profiles, the one- and two-parameter flow models described in literature were tested. The best fitting of the experimental RTD curves was obtained by using a delayed tanks in series model with internal recirculation, or a delayed axial dispersion model. This is consistent with the physical characteristics of the flow in a fully intermeshing corotating twin-screw extruder. | |||||
BibTeX:
@article{Puaux2000,
author = {Puaux, J.P and Bozga, G and Ainser, A},
title = {Residence time distribution in a corotating twin-screw extruder},
journal = {Chemical Engineering Science},
year = {2000},
volume = {55},
number = {9},
pages = {1641--1651},
url = {http://www.sciencedirect.com/science/article/pii/S0009250999004303}
}
|
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| Purnomo, A.S., Mori, T., Kamei, I., Nishii, T. and Kondo, R. | Application of mushroom waste medium from Pleurotus ostreatus for bioremediation of DDT-contaminated soil | 2010 | International Biodeterioration & Biodegradation Vol. 64(5), pp. 397-402 |
article | URL |
| Abstract: The ability of spent mushroom waste (SMW) from Pleurotus ostreatus to degrade 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT) was investigated. DDT was degraded by 48% during a 28 d incubation and 5.1% of the DDT was mineralized during a 56 d incubation by SMW from P. ostreatus. The degradation potential in artificial DDT-contaminated soil was also investigated. The SMW from P. ostreatus degraded the DDT by 40% and 80% during a 28 d incubation in sterilized (SL) and un-sterilized (USL) soils, respectively. [U-14C]DDT was mineralized by 5.1% and 8.0% during a 56 d incubation in SL and USL soils, respectively. These results indicate that SMW from P. ostreatus is a medium which can be potentially used for bioremediation in DDT-contaminated environments. | |||||
BibTeX:
@article{Purnomo2010,
author = {Purnomo, Adi Setyo and Mori, Toshio and Kamei, Ichiro and Nishii, Takafumi and Kondo, Ryuichiro},
title = {Application of mushroom waste medium from Pleurotus ostreatus for bioremediation of DDT-contaminated soil},
journal = {International Biodeterioration & Biodegradation},
year = {2010},
volume = {64},
number = {5},
pages = {397--402},
url = {http://www.sciencedirect.com/science/article/pii/S0964830510000624}
}
|
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| Qafoku, N.P., Zhong, L., Thompson, C.J., Liu, C., Arey, B.W., Mitroshkov, A. and Riley, R.G. | Physical control on CCl4 and CHCl3 desorption from artificially contaminated and aged sediments with supercritical carbon dioxide | 2009 | Chemosphere Vol. 74(4), pp. 494-500 |
article | URL |
| Abstract: The long-term interactions of carbon tetrachloride (CCl4) and chloroform (CHCl3) with sediments that are low in organic matter (OM) are not well studied. In this study, CCl4 and CHCl3 were mixed with supercritical carbon dioxide (CO2) and loaded onto columns packed with two sediments with low OM and different textures, to establish contamination and achieve expedited artificial aging. The columns were subsequently leached with a simulated groundwater under hydraulically saturated conditions. Scanning electron microscopy was used to inspect the morphology of sediment single particles, determine the degree of particle association in aggregates and qualitatively estimate porosity and the possible diffusional pathways that might affect the overall contaminant desorption rates. Results demonstrated that most of contaminant inventories were rapidly released in the first pore volume of effluent, although a small portion of contaminants’ total mass exhibited time-dependent desorption. The calculated Kd values of CCl4 or CHCl3 partition were negligibly small. Both contaminants had similar transport behavior which was simulated well with a distributed (multiple)-rate (DR) statistical model. The model accounted for the apparent contaminant mass transfer through diffusional pathways of different lengths, towards the advective pores. The distribution of contaminant mass between equilibrium and kinetic fractions, the distribution of the individual rate constants, and the average rate constants calculated with the parameters of the γ-distribution function (β and η) of the DR model, were sediment (texture) dependent. This indicated that contaminant desorption during the late stage of leaching was driven by concentration gradients (i.e., diffusion) within sediment matrix porosity. | |||||
BibTeX:
@article{Qafoku2009,
author = {Qafoku, Nikolla P. and Zhong, Lirong and Thompson, Christopher J. and Liu, Chongxuan and Arey, Bruce W. and Mitroshkov, Alex and Riley, Robert G.},
title = {Physical control on CCl4 and CHCl3 desorption from artificially contaminated and aged sediments with supercritical carbon dioxide},
journal = {Chemosphere},
year = {2009},
volume = {74},
number = {4},
pages = {494--500},
url = {http://www.sciencedirect.com/science/article/pii/S0045653508012770}
}
|
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| Qian, J., Zhan, H., Luo, S. and Zhao, W. | Experimental evidence of scale-dependent hydraulic conductivity for fully developed turbulent flow in a single fracture | 2007 | Journal of Hydrology Vol. 339(3-4), pp. 206-215 |
article | URL |
| Abstract: This study uses laboratory experiments to investigate scale dependent hydraulic conductivity of fully developed turbulent flow in a single fracture under different fracture surface roughness, fracture apertures, and hydraulic gradients. The hydraulic conductivity for fully developed turbulent flow is defined as K = V2/J, where V and J are absolute values of the flow velocity and the hydraulic gradient, respectively. Three different surface roughness (fine, medium, and coarse), three different fracture apertures (1.0 mm, 2.0 mm, and 2.5 mm), and five different hydraulic gradients have been tested. Experimental evidence shows that K values generally increase with scale in a linear fashion. Surface roughness and fracture apertures appear to have the most significant influence upon the scale-dependency of K, which is less sensitive to hydraulic gradients. In general, a higher hydraulic gradient will lead to a lower K value at a given scale. The scale-dependency of K might be a manifestation of two-dimensional torturous flow within a rough surface fracture. | |||||
BibTeX:
@article{Qian2007,
author = {Qian, Jiazhong and Zhan, Hongbin and Luo, Shaohe and Zhao, Weidong},
title = {Experimental evidence of scale-dependent hydraulic conductivity for fully developed turbulent flow in a single fracture},
journal = {Journal of Hydrology},
year = {2007},
volume = {339},
number = {3-4},
pages = {206--215},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407001928}
}
|
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| Qian, J., Zhan, H., Zhao, W. and Sun, F. | Experimental study of turbulent unconfined groundwater flow in a single fracture | 2005 | Journal of Hydrology Vol. 311(1-4), pp. 134-142 |
article | URL |
| Abstract: Laboratory experiments have been carried out to study groundwater flow in a single fracture under the conditions of different surface roughness and apertures. We found that the gradient of the Reynolds number versus the average velocity in a single fracture was almost independent of the change of fracture surface roughness, and it decreased when the aperture decreased under the same surface roughness. The experimental results showed that the average flow velocity (V) could be approximated by an empirical exponential function of the hydraulic gradient (I), and the power index of the exponential function was close to 0.5 when the hydraulic gradient is around 0.003 to 0.02. Such a V–I relationship indicated a non-Darcian turbulent flow in the fracture even though the Reynolds number was relatively low (between 333.26 and 1413.62). This finding supports the claims of non-Darcian flow observed in fractures by many recent studies under relatively fast flow condition but disagreed with the Darcian flow and local cubic law assumptions used in some previous studies. | |||||
BibTeX:
@article{Qian2005,
author = {Qian, Jiazhong and Zhan, Hongbin and Zhao, Weidong and Sun, Fenggen},
title = {Experimental study of turbulent unconfined groundwater flow in a single fracture},
journal = {Journal of Hydrology},
year = {2005},
volume = {311},
number = {1-4},
pages = {134--142},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405000168}
}
|
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| Quinn, J.J., Tomasko, D. and Kuiper, J.A. | Modeling complex flow in a karst aquifer | 2006 | Sedimentary Geology Vol. 184(3-4)Heterogeneity in Sedimentary Aquifers: Challenges for Characterization and Flow Modeling Geological Society of America Annual Meeting “GeoScience Horizons 2003”, pp. 343-351 |
article | URL |
| Abstract: Carbonate aquifers typically have complex groundwater flow patterns that result from depositional heterogeneities and post-lithification fracturing and karstification. Various sources of information may be used to build a conceptual understanding of flow in the system, including drilling data, well tests, geophysical surveys, tracer tests, and spring gaging. These data were assembled to model flow numerically in Germany's Malm Formation, at a site where water disappears from the beds of ephemeral stream valleys, flows through conduit systems, and discharges to springs along surface water features. Modeling was performed by using a finite-difference approach, with drain networks, representing the conduit component of flow, laced throughout the porous medium along paths inferred on the basis of site data. This approach represents an improvement over other karst models that attempt to represent a conduit by a single, specialized model node at the spring location or by assigning a computationally problematic extremely high permeability to a zone. By handling the conduit portion of this mixed-flow system with drains, a realistic, interpretive flow model was created for this intricate aquifer. | |||||
BibTeX:
@article{Quinn2011,
author = {Quinn, John J. and Tomasko, David and Kuiper, James A.},
title = {Modeling complex flow in a karst aquifer},
booktitle = {Heterogeneity in Sedimentary Aquifers: Challenges for Characterization and Flow Modeling Geological Society of America Annual Meeting “GeoScience Horizons 2003”},
journal = {Sedimentary Geology},
year = {2006},
volume = {184},
number = {3-4},
pages = {343--351},
url = {http://www.sciencedirect.com/science/article/pii/S0037073805003805}
}
|
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| Raeisi, E., Groves, C. and Meiman, J. | Effects of partial and full pipe flow on hydrochemographs of Logsdon river, Mammoth Cave Kentucky USA | 2007 | Journal of Hydrology Vol. 337(1-2), pp. 1-10 |
article | URL |
| Abstract: Summary Logsdon River, within Kentucky’s Mammoth Cave System, drains the 25 km2 Cave City groundwater basin. Temperature, specific conductance, stage, and velocity were measured at the river’s downstream end within the cave with 2-min resolution for one year beginning on May 5, 1995. New interpretation of these data show relationships to the conduit’s geometry and fluid transport behavior. The 37 observed storm hydrographs/chemographs are classified into two groups: open channel flow and pipe flow (conduit filled). In the 16 pipe flow events Logsdon River exceeded the capacity of its conduit, raising the water table above the conduit ceiling with some storm water thus temporarily stored within the aquifer adjacent to the conduit. Pipe flow events were characterized by depression of specific conductance (spC) before peak discharge, a peak in spC at peak discharge, and a second depression in spC after peak discharge. The first spC minimum represents the maximum concentration of passing storm water and the second is interpreted as the result of recent storm water draining back into the conduit, having been temporarily stored in the aquifer adjacent to the conduit. Mean velocity decreases in the transition from partial to full pipe flow due to increased head loss at full pipe flow compared to nearly full pipe flow. | |||||
BibTeX:
@article{Raeisi2007,
author = {Raeisi, Ezzat and Groves, Chris and Meiman, Joe},
title = {Effects of partial and full pipe flow on hydrochemographs of Logsdon river, Mammoth Cave Kentucky USA},
journal = {Journal of Hydrology},
year = {2007},
volume = {337},
number = {1-2},
pages = {1--10},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406006238}
}
|
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| Rafał, P. | Suitability of the selected statistical distributions for fitting diameter data in distinguished development stages and phases of near-natural mixed forests in the Świętokrzyski National Park (Poland) | 2006 | Forest Ecology and Management Vol. 236(2-3), pp. 393-402 |
article | URL |
| Abstract: The purpose of this study is to evaluate goodness of fit of empirical and theoretical DBH distributions in near-natural forests with fir (Abies alba Mill.) and beech (Fagus sylvatica L.) representing different development stages and phases. | |||||
BibTeX:
@article{Rafal2006,
author = {Rafał, Podlaski},
title = {Suitability of the selected statistical distributions for fitting diameter data in distinguished development stages and phases of near-natural mixed forests in the Świętokrzyski National Park (Poland)},
journal = {Forest Ecology and Management},
year = {2006},
volume = {236},
number = {2-3},
pages = {393--402},
url = {http://www.sciencedirect.com/science/article/pii/S0378112706009157}
}
|
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| Rahimian, S.K., Rayman, S. and White, R.E. | Comparison of single particle and equivalent circuit analog models for a lithium-ion cell | 2011 | Journal of Power Sources Vol. 196(20), pp. 8450-8462 |
article | URL |
| Abstract: The physics-based single particle (SP) model was compared to the semi-empirical equivalent circuit analog (ECA) model to predict the cell voltage under constant current charge and discharge for different sets of Li-ion cell data. The parameters of the models were estimated for each set of data using nonlinear least squares regression. In order to enhance the probability of finding the global optima, a combination of the trust region method with a genetic algorithm was applied to minimize the objective function (the sum of squared residuals). Several statistical quantities such as sum of the squared errors, adjusted R2, root mean squared error, confidence intervals of the parameters, and prediction bounds were included to compare the models. A significance test (t test) on the parameters and the analysis of the variances (F and χ2 tests) were also performed to discriminate between the goodness of the fit obtained from the two models. The statistical results indicate that the SP model superiorly predicts all sets of data compared to the ECA model, while the computation times of both models are on the same order of magnitude. | |||||
BibTeX:
@article{Rahimian2011,
author = {Rahimian, Saeed Khaleghi and Rayman, Sean and White, Ralph E.},
title = {Comparison of single particle and equivalent circuit analog models for a lithium-ion cell},
journal = {Journal of Power Sources},
year = {2011},
volume = {196},
number = {20},
pages = {8450--8462},
url = {http://www.sciencedirect.com/science/article/pii/S0378775311011190}
}
|
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| Raines, M.A. and Dewers, T.A. | Mixed transport/reaction control of gypsum dissolution kinetics in aqueous solutions and initiation of gypsum karst | 1997 | Chemical Geology Vol. 140(1-2), pp. 29-48 |
article | URL |
| Abstract: Experiments with gypsum in aqueous solutions at 25°C, low ionic strengths, and a range of saturation states indicate a mixed surface reaction and diffusional transport control of gypsum dissolution kinetics. Dissolution rates were determined in a mixed flow/rotating disc reactor operating under steady-state conditions, in which polished gypsum discs were rotated at constant speed and reactant solutions were continuously fed into the reactor. Rates increase with velocity of spin under laminar conditions (low rates of spin), but increase asymptotically to a constant rate as turbulent conditions develop with increasing spin velocity, experiencing a small jump in magnitude across the laminar–turbulent transition. A linear dependence of rates on the square root of spin velocity in the laminar regime is consistent with rates being limited by transport through a hydrodynamic boundary layer. The increase in rate with onset of turbulence accompanies a near discontinuous drop in hydrodynamic boundary layer thickness across the transition. A relative independence of rates on spinning velocity in the turbulent regime plus a nonlinear dependence of rates on saturation state are factors consistent with surface reaction control. Together these behaviors implicate a `mixed' transport and reaction control of gypsum dissolution kinetics. A rate law which combines both kinetic mechanisms and can reproduce experimental results under laminar flow conditions is proposed as follows:R=kt1−Ω±b+ζ1−1+2(1−Ω±bζ1/2where kt is the rate coefficient for transport control, and Ω±b is the mean ionic saturation state of the bulk fluid. The dimensionless parameter ζ(=D m±eq/2δk+ where m±eq=mean ionic molal equilibrium concentration, D is the diffusion coefficient through the hydrodynamic boundary layer, δ equals the boundary layer thickness and k+ is the rate constant for surface reaction control) indicates which process, transport or surface reaction, dominates, and is sensitive to the hydrodynamic conditions in the reactor. For the range of conditions used in our experiments, ζ varies from about 1.4 to 4.5. | |||||
BibTeX:
@article{Raines1997,
author = {Raines, Michael A and Dewers, Thomas A},
title = {Mixed transport/reaction control of gypsum dissolution kinetics in aqueous solutions and initiation of gypsum karst},
journal = {Chemical Geology},
year = {1997},
volume = {140},
number = {1-2},
pages = {29--48},
url = {http://www.sciencedirect.com/science/article/pii/S0009254197000181}
}
|
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| Rajaie, E. and Sohrabi, M. | Application of the Monte Carlo technique in simulation of flow and modeling the residence time distribution in a continuous two impinging liquid–liquid streams contactor | 2008 | Chemical Engineering Journal Vol. 143(1-3), pp. 249-256 |
article | URL |
| Abstract: In the present study, a stochastic model for the residence time distribution (RTD) in a coaxial counter current liquid–liquid impinging streams system has been developed. | |||||
BibTeX:
@article{Rajaie2008,
author = {Rajaie, Ehsan and Sohrabi, Morteza},
title = {Application of the Monte Carlo technique in simulation of flow and modeling the residence time distribution in a continuous two impinging liquid–liquid streams contactor},
journal = {Chemical Engineering Journal},
year = {2008},
volume = {143},
number = {1-3},
pages = {249--256},
url = {http://www.sciencedirect.com/science/article/pii/S1385894708002167}
}
|
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| Ramalingam, S. | Goodness-of-fit test for length-biased data with discussion on prevalence, sensitivity and specificity of the length bias | 1995 | Journal of Statistical Planning and Inference Vol. 48(3), pp. 277-290 |
article | URL |
| Abstract: Due to reasons like absence of a proper sampling frame or inaccessibility to population units, data in statistical studies are sometimes contaminated by a phenomenon called length bias (LB). In this article, an asymptotic test statistic is derived to examine the homogeneity of a length biased sample from the Mean Exponential Family (MEF), a new class of distributions introduced by Shanmugam (J. Statist. Plann. Inference 23 (1989) 227–291). Expressions for the test statistic are obtained for length biased binomial, Poisson, negative binomial, beta, gamma, normal, Pareto, Laplace, and Raleigh distributions as special cases. The results are illustrated. One among several advantages in our approach is the ability to quantify the specificity and sensitivity of LB and their instrinsic relations. | |||||
BibTeX:
@article{Ramalingam1995,
author = {Ramalingam, Shanmugam},
title = {Goodness-of-fit test for length-biased data with discussion on prevalence, sensitivity and specificity of the length bias},
journal = {Journal of Statistical Planning and Inference},
year = {1995},
volume = {48},
number = {3},
pages = {277--290},
url = {http://www.sciencedirect.com/science/article/pii/037837589500007V}
}
|
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| Rammohan, A., Kemoun, A., Al-Dahhan, M. and Dudukovic, M. | A Lagrangian description of flows in stirred tanks via computer-automated radioactive particle tracking (CARPT) | 2001 | Chemical Engineering Science Vol. 56(8), pp. 2629-2639 |
article | URL |
| Abstract: In this study, computer-automated radioactive particle tracking (CARPT) is implemented for the first time in the characterization of flows in stirred tanks. Both the experimental technique and the experimental set-up are discussed. The CARPT technique is seen to capture qualitatively most of the important flow phenomena observed in stirred tank flows, like the two recirculating loops above and below the impeller and the dead zones at the bottom of the tank. The CARPT data is also used to extract “Sojourn” time distributions in different zones of the reactor. These distributions are used to partially quantify the observed dead and active zones in the tank. | |||||
BibTeX:
@article{Rammohan2001,
author = {Rammohan, A.R and Kemoun, A and Al-Dahhan, M.H and Dudukovic, M.P},
title = {A Lagrangian description of flows in stirred tanks via computer-automated radioactive particle tracking (CARPT)},
journal = {Chemical Engineering Science},
year = {2001},
volume = {56},
number = {8},
pages = {2629--2639},
url = {http://www.sciencedirect.com/science/article/pii/S0009250900005376}
}
|
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| Rangaiah, G.P. and Krishnaswamy, P.R. | Application of Time Domain Curve-Fitting to Parameter Estimation in RTD Models | 1990 | Journal of Chemical Engineering of Japan Vol. 23(2), pp. 124-130 |
article | URL |
| Abstract: Parameters in residence time distribution (RTD) models are commonly estimated by least-squares curve-fit in the time domain. Two procedures suggested in the literature for this purpose involve (i) fixing τ (the mean residence time) as equal to μ (first moment of the experimental response) prior to curve-fitting and (ii) estimating τ along with other model parameters by curve-fitting. In this work these two procedures, i.e., curve-fitting with and without the constraint τ = μ, are compared. Four models in conjunction with eight sets of RTD data are considered. The results indicate that consistently better results are obtained when the constraint τ = μ is relaxed prior to curve-fitting. This is particularly so for models with fewer parameters like the dispersion model. | |||||
BibTeX:
@article{Rangaiah1990,
author = {Rangaiah, G. P. and Krishnaswamy, P. R.},
title = {Application of Time Domain Curve-Fitting to Parameter Estimation in RTD Models},
journal = {Journal of Chemical Engineering of Japan},
publisher = {The Society of Chemical Engineers, Japan},
year = {1990},
volume = {23},
number = {2},
pages = {124--130},
url = {https://www.jstage.jst.go.jp/article/jcej/23/2/23_2_124/_article}
}
|
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| Rao, A.M., McCarthy, M.J., Gardner, W.S. and Jahnke, R.A. | Respiration and denitrification in permeable continental shelf deposits on the South Atlantic Bight: Rates of carbon and nitrogen cycling from sediment column experiments | 2007 | Continental Shelf Research Vol. 27(13), pp. 1801-1819 |
article | URL |
| Abstract: Nitrogen (N) cycling and respiration rates were measured in sediment columns packed with southeastern United States continental shelf sands, with high permeability (4.66×10−11 m2) and low organic carbon (0.05%) and nitrogen (0.008%). To simulate porewater advection, natural shelf seawater was pumped through columns of different lengths to achieve fluid residence times of approximately 3, 6, and 12 h. Experiments were conducted seasonally at in situ temperature. Fluid flow was uniform in nearly all columns, with minimal dead zones and channeling. Significant respiration (O2 consumption and ∑CO2 production) occurred in all columns, with highest respiration rates in summer. Most (78–100%) remineralized N was released as N2 in the majority of cases, including columns with oxic porewater throughout, with only a small fraction released as NO3− from some oxic columns. A rate of 0.84–4.83×1010 mol N yr−1, equivalent to 1.06–6.09×10−6 mmol N cm−2 h−1, was calculated for benthic N2 production in the South Atlantic Bight, which can account for a large fraction of new N inputs to this shelf region. Metal and sulfate reduction occurred in long residence time columns with anoxic outflow in summer and fall, when respiration rates were highest. Because permeable sediments dominate continental shelves, N2 production in high permeability coastal sediments may play an important role in the global N cycle. | |||||
BibTeX:
@article{Rao2007,
author = {Rao, Alexandra M.F. and McCarthy, Mark J. and Gardner, Wayne S. and Jahnke, Richard A.},
title = {Respiration and denitrification in permeable continental shelf deposits on the South Atlantic Bight: Rates of carbon and nitrogen cycling from sediment column experiments},
journal = {Continental Shelf Research},
year = {2007},
volume = {27},
number = {13},
pages = {1801--1819},
url = {http://www.sciencedirect.com/science/article/pii/S0278434307000830}
}
|
|||||
| Rao, D. and Edwards, L.L. | Mixing effects in stirred tank reactors: a comparison of models | 1973 | Chemical Engineering Science Vol. 28(5), pp. 1179-1192 |
article | URL |
| Abstract: The Two-Environment Model of Ng and Rippin and the Monte Carlo residual life time model of Kattan and Adler developed for studying the effect of arbitrary residence time distribution and intermediate degrees of segregation on chemical reactor performance were shown to be equivalent from the point of view of a physical argument and a comparison of conversions obtained for a second order chemical reaction with mixed feed. Conversions with mixed feed were compared for a single CSTR and a reactor with a 2-CSTR residence time distribution using identical values of the micro-mixing parameter for both of the models. | |||||
BibTeX:
@article{Rao1973,
author = {Rao, D.P. and Edwards, Louis L.},
title = {Mixing effects in stirred tank reactors: a comparison of models},
journal = {Chemical Engineering Science},
year = {1973},
volume = {28},
number = {5},
pages = {1179--1192},
url = {http://www.sciencedirect.com/science/article/pii/0009250973850274}
}
|
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| Ravbar, N., Engelhardt, I. and Goldscheider, N. | Anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries: the case of the Podstenjšek spring, Slovenia | 2011 | Hydrological Processes Vol. 25(13), pp. 2130-2140 |
article | URL |
| Abstract: Anomalous behaviour of specific electrical conductivity (SEC) was observed at a karst spring in Slovenia during 26 high-flow events in an 18-month monitoring period. A conceptual model explaining this anomalous SEC variability is presented and reproduced by numerical modelling, and the practical relevance for source protection zoning is discussed. After storm rainfall, discharge increases rapidly, which is typical for karst springs. SEC displays a first maximum during the rising limb of the spring hydrograph, followed by a minimum indicating the arrival of freshly infiltrated water, often confirmed by increased levels of total organic carbon (TOC). The anomalous behaviour starts after this SEC minimum, when SEC rises again and remains elevated during the entire high-flow period, typically 20–40 µS/cm above the baseflow value. This is explained by variable catchment boundaries: When the water level in the aquifer rises, the catchment expands, incorporating zones of groundwater with higher SEC, caused by higher unsaturated zone thickness and subtle lithologic changes. This conceptual model has been checked by numerical investigations. A generalized finite-difference model including high-conductivity cells representing the conduit network (“discrete-continuum approach”) was set up to simulate the observed behaviour of the karst system. The model reproduces the shifting groundwater divide and the nearly simultaneous increase of discharge and SEC during high-flow periods. The observed behaviour is relevant for groundwater source protection zoning, which requires reliable delineation of catchment areas. Anomalous behaviour of SEC can point to variable catchment boundaries that can be checked by tracer tests during different hydrologic conditions. Copyright © 2011 John Wiley & Sons, Ltd. | |||||
BibTeX:
@article{Ravbar2011,
author = {Ravbar, Nataša and Engelhardt, Irina and Goldscheider, Nico},
title = {Anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries: the case of the Podstenjšek spring, Slovenia},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2011},
volume = {25},
number = {13},
pages = {2130--2140},
url = {http://dx.doi.org/10.1002/hyp.7966}
}
|
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| Ravbar, N., Petrič, M. and Kogovšek, J. | The Characteristics of Groundwater Flow in Karst Aquifers During Long Lasting Low Flow Conditions, Example from SW Slovenia | 2010 | Advances in Research in Karst Media, pp. 131-136 | incollection | DOI URL |
| Abstract: As it is expected that global warming will induce changes in hydrological regimes, the presented study has been conducted to understand how karst groundwater resources may be affected during long-term dry periods. A multi-tracer test with three injection points aimed at identifying the dynamics of underground drainage through a well-developed system of karst channels and through vadose zone. Results show low apparent dominant flow velocities (through well developed karst conduits between 5.9 and 22.8 m/h, through vadose zone 3.6 m/h), multiple peaked and extended breakthrough curves. These findings are relevant for groundwater quality monitoring, protection and management, as they infer that contaminant transport in karst, at least in the studied area, may be retarded and long-lasting. | |||||
BibTeX:
@incollection{Ravbar2010,
author = {Ravbar, N. and Petrič, M. and Kogovšek, J.},
title = {The Characteristics of Groundwater Flow in Karst Aquifers During Long Lasting Low Flow Conditions, Example from SW Slovenia},
booktitle = {Advances in Research in Karst Media},
publisher = {Springer Berlin Heidelberg},
year = {2010},
pages = {131--136},
url = {http://dx.doi.org/10.1007/978-3-642-12486-0_20},
doi = {http://dx.doi.org/10.1007/978-3-642-12486-0}
}
|
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| Rawatlal, R. and Starzak, M. | Unsteady-state residence-time distribution in perfectly mixed vessels | 2003 | AIChE Journal Vol. 49(2), pp. 471-484 |
article | URL |
| Abstract: While addressing some difficulties in the modeling of unsteady-state residence-time distribution (RTD), the care of perfectly mixed systems was considered. By an extension of the boundary condition domain, the traditional unfeasible concept of fresh and original populations was discarded to achieve a solution valid for all the fluid elements in a single vessel. This result enabled the development of the unsteady-state RTD for N vessels in series in the form of a joint probability density function. The relationship between the joint RTD and the combined RTD was also established. Numerical simulations were performed under various time varying flow patterns. The proposed solution can be applied to RTD-based models of chemical reactors operating under unsteady-state conditions. Potential applications in polymer reaction engineering are briefly outlined. | |||||
BibTeX:
@article{Rawatlal2003,
author = {Rawatlal, Randhir and Starzak, Maciej},
title = {Unsteady-state residence-time distribution in perfectly mixed vessels},
journal = {AIChE Journal},
publisher = {Wiley Subscription Services, Inc., A Wiley Company},
year = {2003},
volume = {49},
number = {2},
pages = {471--484},
url = {http://dx.doi.org/10.1002/aic.690490217}
}
|
|||||
| Ray, K., Painter, R. and Byl, T. | Ammonia Oxidation by Bacteria Collected from a Karst-Bedrock Well | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 72 | inproceedings | URL |
| Abstract: Elevated ammonia concentrations in groundwater pose health and environmental problems. In karst systems where water can enter directly through sinkholes or disappearing streams without any filtration, ammonia contamination can be exacerbated. The rate of ammonia oxidation by nitrifying bacteria in karst systems is not known. The objective of this study was to characterize the aerobic and anaerobic rate of NH3 oxidation using bacteria indigenous to a karst aquifer in Middle Tennessee. Static batch reactors using indigenous karst bacteria collected from a spring established a first-order rate of NH3-oxidation (k) = 0.0209 per day. Because this rate appeared to be slow, in a follow-up experiment, the effect of supplements and surface area were investigated. It was found that, in a flow-through karst system, a 500% increase in surface area to volume (SA/V) ratio increased the k value 54%. Addition of 1 g of lactate/L further increased the k value almost 10-fold. Because NH3-oxidizing bacteria are autotrophs (CO2 fixing), it is hypothesized the lactate stimulated the growth of symbiotic bacteria that significantly enhanced the activity of NH3-oxidizing bacteria. Anaerobic NH3 oxidation was also investigated using data collected in 2002 from an anaerobic karst site in northern Tennessee with high levels of NH3. The tracer and ammonia data were entered into the RTDB model and yielded a calculated ammonia oxidation k of 0.0168/day. The observation of ammonia biotransformation at an anaerobic site is circumstantial evidence that the anaerobic ammonia oxidation pathway called anammox was active. Additional research, however, is needed to confirm if the anammox pathway was responsible for the observed anaerobic removal of NH3. | |||||
BibTeX:
@inproceedings{Ray2008,
author = {Ray, Kelly and Painter, Roger and Byl, Tom},
title = {Ammonia Oxidation by Bacteria Collected from a Karst-Bedrock Well},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {72},
url = {http://pubs.usgs.gov/sir/2008/5023/27ray.htm}
}
|
|||||
| Rechard, R.P. and Tierney, M.S. | Assignment of probability distributions for parameters in the 1996 performance assessment for the Waste Isolation Pilot Plant. Part 1: description of process | 2005 | Reliability Engineering & System Safety Vol. 88(1), pp. 1-32 |
article | URL |
| Abstract: A managed process was used to consistently and traceably develop probability distributions for parameters representing epistemic uncertainty in four preliminary and the final 1996 performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP). The key to the success of the process was the use of a three-member team consisting of a Parameter Task Leader, PA Analyst, and Subject Matter Expert. This team, in turn, relied upon a series of guidelines for selecting distribution types. The primary function of the guidelines was not to constrain the actual process of developing a parameter distribution but rather to establish a series of well-defined steps where recognized methods would be consistently applied to all parameters. An important guideline was to use a small set of distributions satisfying the maximum entropy formalism. Another important guideline was the consistent use of the log transform for parameters with large ranges (i.e. maximum/minimum>103). A parameter development team assigned 67 probability density functions (PDFs) in the 1989 PA and 236 PDFs in the 1996 PA using these and other guidelines described. | |||||
BibTeX:
@article{Rechard2005,
author = {Rechard, Rob P. and Tierney, Martin S.},
title = {Assignment of probability distributions for parameters in the 1996 performance assessment for the Waste Isolation Pilot Plant. Part 1: description of process},
journal = {Reliability Engineering & System Safety},
year = {2005},
volume = {88},
number = {1},
pages = {1--32},
url = {http://www.sciencedirect.com/science/article/pii/S0951832004001486}
}
|
|||||
| Rector, T.J., Garland, J.L. and Starr, S.O. | Dispersion characteristics of a rotating hollow fiber membrane bioreactor: Effects of module packing density and rotational frequency | 2006 | Journal of Membrane Science Vol. 278(1-2), pp. 144-150 |
article | URL |
| Abstract: The coupling of biological reactor with membrane dissolution processes has gained increasing attention in the wastewater treatment community because of their effective delivery of gaseous products and high treatment efficiencies. Turbulent flow may be an important factor for optimizing performance of these systems, both by reducing plug-flow conditions and associated axial gradients within the reactor and increasing mass transfer across the biofilm attached to membrane fibers. While turbulence is typically enhanced via increased flow velocity, rotation of the membranes themselves is an alternative mechanism for increasing turbulence that might eliminate problems associated with high flow (e.g., increased shear, mal-distribution of fluid flow). The effects of variable rotational frequencies (0, 5, 10 and 20 rpm) and membrane module packing densities (62, 82, 92%) on residence time distributions (RTD) curves of a bromide tracer were investigated to assess the potential for membrane rotation as a means of increasing turbulence. The resulting RTD curves were compared to a dispersive plug-flow model to determine the Peclet numbers (Pe) and subsequent axial dispersion coefficients. These finding indicated that increased dispersion is observed with increasing rotational frequency, with the effects of module packing density on dispersion characteristics decreasing with increased rotation. This study demonstrated that module rotation can cause turbulent flow prompting enhanced dispersion and allowing for low operational flow rates and reduction of mass transfer constraints associated with membrane bioreactors (MBR). | |||||
BibTeX:
@article{Rector2006,
author = {Rector, Tony J. and Garland, Jay L. and Starr, Stanley O.},
title = {Dispersion characteristics of a rotating hollow fiber membrane bioreactor: Effects of module packing density and rotational frequency},
journal = {Journal of Membrane Science},
year = {2006},
volume = {278},
number = {1-2},
pages = {144--150},
url = {http://www.sciencedirect.com/science/article/pii/S037673880500801X}
}
|
|||||
| Reed, T.M., Todd McFarland, J., Fryar, A.E., Fogle, A.W. and Taraba, J.L. | Sediment discharges during storm flow from proximal urban and rural karst springs, central Kentucky, USA | 2010 | Journal of Hydrology Vol. 383(3-4), pp. 280-290 |
article | URL |
| Abstract: Summary Since the mid-1990s, various studies have addressed the timing of sediment transport to karst springs during storm flow or the composition and provenance of sediment discharged from springs. However, relatively few studies have focused on the flow thresholds at which sediment is mobilized or total sediment yields across various time scales. We examined each of these topics for a mainly urban spring (Blue Hole) and a rural spring (SP-2) in the Inner Bluegrass region of central Kentucky (USA). Suspended sediment consisted mostly of quartz silt and sand, with lesser amounts of calcite and organic matter. Total suspended sediment (TSS) values measured during storm flow were greater at SP-2 than at Blue Hole. By aggregating data from four storms during 2 years, we found that median suspended-sediment size jumped as Q exceeded ∼0.5 m3/s for both springs. At Blue Hole, TSS tended to vary with Q and capacity approached 1 g/L, but no systematic relationship between TSS and Q was evident at SP-2. Sediment fluxes from the Blue Hole basin were ∼2 orders of magnitude greater for storms in March (2002 and 2004) than September (2002 and 2003). In contrast, sediment fluxes from the SP-2 basin were of similar magnitude in September 2003 and March 2004. The overall range of area-normalized fluxes for both springs, 9.16 × 10−3–4.45 × 102 kg/(ha h), overlaps values reported for farm plots and a stream in the Inner Bluegrass region and for other spring basins in the eastern USA and western Europe. Sediment compositions, sizes, and responses to storms in the basins may differ because of land use (e.g., the extent of impervious cover in the Blue Hole basin), basin size (larger for Blue Hole), conduit architecture, which appears to be more complex in the Blue Hole basin, and the impoundment of SP-2, which may have promoted decadal-scale storage of sediment upgradient. | |||||
BibTeX:
@article{Reed2010,
author = {Reed, Thomas M. and Todd McFarland, J. and Fryar, Alan E. and Fogle, Alex W. and Taraba, Joseph L.},
title = {Sediment discharges during storm flow from proximal urban and rural karst springs, central Kentucky, USA},
journal = {Journal of Hydrology},
year = {2010},
volume = {383},
number = {3-4},
pages = {280--290},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409008373}
}
|
|||||
| Refsgaard, J.C., Christensen, S., Sonnenborg, T.O., Seifert, D., Højberg, A.L. and Troldborg, L. | Review of strategies for handling geological uncertainty in groundwater flow and transport modeling | 2012 | Advances in Water Resources Vol. 36(0)Special Issue on Uncertainty Quantification and Risk Assessment, pp. 36-50 |
article | URL |
| Abstract: The geologically related uncertainty in groundwater modeling originates from two main sources: geological structures and hydraulic parameter values within these structures. Within a geological structural element the parameter values will always exhibit local scale heterogeneity, which can be accounted for, but is often neglected, in assessments of prediction uncertainties. Strategies for assessing prediction uncertainty due to geologically related uncertainty may be divided into three main categories, accounting for uncertainty due to: (a) the geological structure; (b) effective model parameters; and (c) model parameters including local scale heterogeneity. The most common methodologies for uncertainty assessments within each of these categories, such as multiple modeling, Monte Carlo analysis, regression analysis and moment equation approach, are briefly described with emphasis on their key characteristics. Based on reviews of previous studies, assessments are made on the relative importance of the three uncertainty categories for different types of model predictions. Furthermore, the strengths, limitations and interactions of these methodologies are discussed and conclusions are made with respect to identifying key subjects for which further research is needed. When all sources of uncertainty are analyzed by exploring model parameter and local scale heterogeneity uncertainty for several plausible geological model structures the joint uncertainties can be assessed by use of model averaging techniques, such as Bayesian Model Averaging (BMA). General challenge in model averaging with respect to choosing mutually exclusive and collectively exhaustive choice models, as well as to assign weights when models are used beyond their calibration base, are discussed. | |||||
BibTeX:
@article{Refsgaard2012,
author = {Refsgaard, Jens Christian and Christensen, Steen and Sonnenborg, Torben O. and Seifert, Dorte and Højberg, Anker Lajer and Troldborg, Lars},
title = {Review of strategies for handling geological uncertainty in groundwater flow and transport modeling},
booktitle = {Special Issue on Uncertainty Quantification and Risk Assessment},
journal = {Advances in Water Resources},
year = {2012},
volume = {36},
number = {0},
pages = {36--50},
url = {http://www.sciencedirect.com/science/article/pii/S0309170811000625}
}
|
|||||
| Reimann, T. and Hill, M.E. | MODFLOW-CFP: A New Conduit Flow Process for MODFLOW–2005 [BibTeX] |
2009 | Ground Water Vol. 47(3), pp. 321-325 |
article | URL |
BibTeX:
@article{Reimann2009,
author = {Reimann, Thomas and Hill, Melissa E.},
title = {MODFLOW-CFP: A New Conduit Flow Process for MODFLOW–2005},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2009},
volume = {47},
number = {3},
pages = {321--325},
url = {http://dx.doi.org/10.1111/j.1745-6584.2009.00561.x}
}
|
|||||
| Reinelt, L.E. and Horner, R.R. | Pollutant removal from stormwater runoff by palustrine wetlands based on comprehensive budgets | 1995 | Ecological Engineering Vol. 4(2)Restoration and Creation of Wetlands - Scientific Basis and Measuring Success, pp. 77-97 |
article | URL |
| Abstract: Comprehensive budgets of total suspended solids (TSS), total phosphorus (TP), total zinc (the most prevalent metal in urban runoff), and fecal coliforms (FC) were developed for two palustrine freshwater wetlands in Washington, USA. These budgets were based on input (inflow, precipitation, groundwater) and output (outflow, evaporation). One wetland received runoff from a primarily urbanized watershed (187 ha), whereas the other watershed (87 ha) was mostly rural and forested. Annual loadings to the urban wetland for TSS, TP, and zinc were 107, 0.63 and 0.43 kg ha−1 yr−1, respectively, based on watershed area. Corresponding loadings to the nonurban wetland were 30, 0.62 and 0.08 kg ha−1 yr−1. High TP input from groundwater at the nonurban wetland (82% of the TP input) resulted in overall loadings comparable to the urban wetland. Fecal coliform loadings were 4.2 · 1010 and 1.4 · 109 organisms ha−1 yr−1 for the urban and nonuran wetlands, respectively. Mean annual removal percentages (over the two-year study period) for TSS, TP, zinc, and FC were estimated at 14, 8, 31, and 49%, respectively in the urban wetland (2 ha). Corresponding removal rates in the nonurban wetland (1.5 ha) were 56, 82, 23, and 29%, respectively. Pollutant removal was influenced by season, flow conditions, residence time, pollutant source (surface versus groundwater), and pollutant state (solid versus dissolved). Results for the nonurban wetland showed that groundwater inputs were significant for TP loadings and removal. | |||||
BibTeX:
@article{Reinelt1995,
author = {Reinelt, Lorin E. and Horner, Richard R.},
title = {Pollutant removal from stormwater runoff by palustrine wetlands based on comprehensive budgets},
booktitle = {Restoration and Creation of Wetlands - Scientific Basis and Measuring Success},
journal = {Ecological Engineering},
year = {1995},
volume = {4},
number = {2},
pages = {77--97},
url = {http://www.sciencedirect.com/science/article/pii/092585749400002M}
}
|
|||||
| Reitan, T. and Petersen-Øverleir, A. | Bayesian methods for estimating multi-segment discharge rating curves | 2009 | Stochastic Environmental Research and Risk Assessment Vol. 23(5), pp. 627-642 |
article | URL |
| Abstract: This study explores Bayesian methods for handling compound stage-discharge relationships, a problem which arises in many natural rivers. It is assumed: (1) the stage-discharge relationship in each rating curve segment is a power-law with a location parameter, or zero-plane displacement; (2) the segment transitions are abrupt and continuous; and (3) multiplicative measurement errors are of equal variance. The rating curve fitting procedure is then formulated as a piecewise regression problem where the number of segments and the associated changepoints are assumed unknown. Procedures are developed for describing both global and site-specific prior distributions for all rating curve parameters, including the changepoints. Estimation and uncertainty analysis is evaluated using Markov chain Monte Carlo simulation (MCMC) techniques. The first model explored accounts for parameter and model uncertainties in the interpolated area, i.e. within the range of available stage-discharge measurements. A second model is constructed in an attempt to include the uncertainty in extrapolation, which is necessary when the rating curve is used to estimate discharges beyond the highest or lowest measurement. This is done by assuming that the rate of changepoints both inside and outside the measured area follows a Poisson process. The theory is applied to actual data from Norwegian gauging stations. The MCMC solutions give results that appear sensible and useful for inferential purposes, though the latter model needs further efforts in order to obtain a more efficient simulation scheme. | |||||
BibTeX:
@article{Reitan2009,
author = {Reitan, Trond and Petersen-Øverleir, Asgeir},
title = {Bayesian methods for estimating multi-segment discharge rating curves},
journal = {Stochastic Environmental Research and Risk Assessment},
publisher = {Springer-Verlag},
year = {2009},
volume = {23},
number = {5},
pages = {627--642},
url = {http://dx.doi.org/10.1007/s00477-008-0248-0}
}
|
|||||
| Rejesus, R.M. and Hornbaker, R.H. | Economic and environmental evaluation of alternative pollution-reducing nitrogen management practices in central Illinois | 1999 | Agriculture, Ecosystems & Environment Vol. 75(1-2), pp. 41-53 |
article | URL |
| Abstract: Nitrogen fertilizer application from production agriculture is likely the largest contributor to non-point source nitrate pollution in the United States. This type of pollution from the agricultural sector is an important policy issue because it may cause serious environmental and health risks to society. There have been studies that examined the different effects of nitrogen timing and rate practices, but none has yet compared the economic and environmental effects of these practices to site-specific management (SSM) precision technology. This paper examines the economic and environmental impacts of alternative nitrogen management practices, including SSM, within the Lake Decatur watershed of central Illinois. Thus, this study provides evidence on how different nitrogen management practices perform in terms of their effect on water quality and profitability. Data for the analysis were derived from the Environmental Policy Integrated Climate (EPIC) agronomic simulation model due to unavailability of actual on-site data. The analysis revealed that SSM of nitrogen fertilizer has great potential in reducing the mean and variability of nitrate pollution in the watershed while improving profitability of producers, relative to the current practice in the watershed. The management practice where fertilizer is applied during the spring at 140 kg ha−1 provides reduction in mean and variability of nitrate pollution comparable to that of SSM. However, SSM technology substantially reduces the variability of net returns compared to the other management practices analyzed. Hence, SSM of nitrogen fertilizer has the potential to reduce nitrate pollution while reducing economic variability and maintaining profitability. | |||||
BibTeX:
@article{Rejesus1999,
author = {Rejesus, Roderick M. and Hornbaker, Robert H.},
title = {Economic and environmental evaluation of alternative pollution-reducing nitrogen management practices in central Illinois},
journal = {Agriculture, Ecosystems & Environment},
year = {1999},
volume = {75},
number = {1-2},
pages = {41--53},
url = {http://www.sciencedirect.com/science/article/pii/S0167880999000584}
}
|
|||||
| Ren, J.-J. and He, B. | Estimation and goodness-of-fit for the Cox model with various types of censored data | 2011 | Journal of Statistical Planning and Inference Vol. 141(2), pp. 961-971 |
article | URL |
| Abstract: The currently existing estimation methods and goodness-of-fit tests for the Cox model mainly deal with right censored data, but they do not have direct extension to other complicated types of censored data, such as doubly censored data, interval censored data, partly interval-censored data, bivariate right censored data, etc. In this article, we apply the empirical likelihood approach to the Cox model with complete sample, derive the semiparametric maximum likelihood estimators (SPMLE) for the Cox regression parameter and the baseline distribution function, and establish the asymptotic consistency of the SPMLE. Via the functional plug-in method, these results are extended in a unified approach to doubly censored data, partly interval-censored data, and bivariate data under univariate or bivariate right censoring. For these types of censored data mentioned, the estimation procedures developed here naturally lead to Kolmogorov–Smirnov goodness-of-fit tests for the Cox model. Some simulation results are presented. | |||||
BibTeX:
@article{Ren2011,
author = {Ren, Jian-Jian and He, Bin},
title = {Estimation and goodness-of-fit for the Cox model with various types of censored data},
journal = {Journal of Statistical Planning and Inference},
year = {2011},
volume = {141},
number = {2},
pages = {961--971},
url = {http://www.sciencedirect.com/science/article/pii/S0378375810004179}
}
|
|||||
| Renate D, K. | Passion and politics in women's studies in the nineties [BibTeX] |
1991 | Women's Studies International Forum Vol. 14(3), pp. 125-134 |
article | DOI URL |
BibTeX:
@article{RenateD1991,
author = {Renate D, Klein},
title = {Passion and politics in women's studies in the nineties},
journal = {Women's Studies International Forum},
year = {1991},
volume = {14},
number = {3},
pages = {125--134},
url = {http://www.sciencedirect.com/science/article/pii/027753959190104P},
doi = {http://dx.doi.org/10.1016/0277-5395(91)90104-p}
}
|
|||||
| Rietkerk, M., Brovkin, V., van Bodegom, P.M., Claussen, M., Dekker, S.C., Dijkstra, H.A., Goryachkin, S.V., Kabat, P., Nes, E.H.v., Neutel, A.M., Nicholson, S.E., Nobre, C., Petoukhov, V., Provenzale, A., Scheffer, M. and Seneviratne, S.I. | Local ecosystem feedbacks and critical transitions in the climate | 2009 | Biogeosciences Discuss. Vol. 6(5), pp. 10121-10136 |
article | DOI URL |
| Abstract: Global and regional climate models, such as those used in IPCC assessments, are the best tools available for climate predictions. Such models typically account for large-scale land-atmosphere feedbacks. However, these models omit local vegetationenvironment 5 feedbacks that are crucial for critical transitions in ecosystems. Here, we reveal the hypothesis that, if the balance of feedbacks is positive at all scales, local vegetation-environment feedbacks may trigger a cascade of amplifying effects, propagating from local to large scale, possibly leading to critical transitions in the largescale climate. We call for linking local ecosystem feedbacks with large-scale land10 atmosphere feedbacks in global and regional climate models in order to yield climate predictions that we are more confident about. | |||||
BibTeX:
@article{Rietkerk2009,
author = {Rietkerk, M. and Brovkin, V. and van Bodegom, P. M. and Claussen, M. and Dekker, S. C. and Dijkstra, H. A. and Goryachkin, S. V. and Kabat, P. and Nes, E. H. van and Neutel, A. M. and Nicholson, S. E. and Nobre, C. and Petoukhov, V. and Provenzale, A. and Scheffer, M. and Seneviratne, S. I.},
title = {Local ecosystem feedbacks and critical transitions in the climate},
journal = {Biogeosciences Discuss.},
publisher = {Copernicus Publications},
year = {2009},
volume = {6},
number = {5},
pages = {10121--10136},
url = {http://www.biogeosciences-discuss.net/6/10121/2009/bgd-6-10121-2009.html},
doi = {http://dx.doi.org/10.5194/bgd-6-10121-2009}
}
|
|||||
| Rivett, M.O., Buss, S.R., Morgan, P., Smith, J.W. and Bemment, C.D. | Nitrate attenuation in groundwater: A review of biogeochemical controlling processes | 2008 | Water Research Vol. 42(16), pp. 4215-4232 |
article | URL |
| Abstract: Biogeochemical processes controlling nitrate attenuation in aquifers are critically reviewed. An understanding of the fate of nitrate in groundwater is vital for managing risks associated with nitrate pollution, and to safeguard groundwater supplies and groundwater-dependent surface waters. Denitrification is focused upon as the dominant nitrate attenuation process in groundwater. As denitrifying bacteria are essentially ubiquitous in the subsurface, the critical limiting factors are oxygen and electron donor concentration and availability. Variability in other environmental conditions such as nitrate concentration, nutrient availability, pH, temperature, presence of toxins and microbial acclimation appears to be less important, exerting only secondary influences on denitrification rates. Other nitrate depletion mechanisms such as dissimilatory nitrate reduction to ammonium and assimilation of nitrate into microbial biomass are unlikely to be important in most subsurface settings relative to denitrification. Further research is recommended to improve current understanding on the influence of organic carbon, sulphur and iron electron donors, physical restrictions on microbial activity in dual porosity aquifers, influences of environmental condition (e.g. pH in poorly buffered environments and salinity in coastal or salinized soil settings), co-contaminant influences (particularly the contrasting inhibitory and electron donor influences of pesticides) and improved quantification of denitrification rates in the laboratory and field. | |||||
BibTeX:
@article{Rivett2008,
author = {Rivett, Michael O. and Buss, Stephen R. and Morgan, Philip and Smith, Jonathan W.N. and Bemment, Chrystina D.},
title = {Nitrate attenuation in groundwater: A review of biogeochemical controlling processes},
journal = {Water Research},
year = {2008},
volume = {42},
number = {16},
pages = {4215--4232},
url = {http://www.sciencedirect.com/science/article/pii/S0043135408002984}
}
|
|||||
| Robert H., K. | Detention and mixing in free water wetlands | 1994 | Ecological Engineering Vol. 3(4), pp. 345-380 |
article | URL |
| Abstract: Mixing was studied in free water surface wetland receiving pumped river water, by measurement of the non-interacting tracer lithium. The flow pattern was found to be intermediate between plug flow and well-mixed. The nominal detention time, calculated from volume aand flow, was 50% larger than the mean tracer detention time. The peak time was found to be one-half the tracer detention time. Three models were constructed: plug flow with dispersion, tanks in series, and a series-parallel network of tanks. All proved capable of fitting the exit tracer concentration curves but the network model provided a better fit to internal measurements. Pumping frequency was high enough to allow use of an average flowrate. The degree of mixing, as characterized by the variance of the exit tracer response curve, was comparable to that found by other researchers for wetlands, ponds and rivers. | |||||
BibTeX:
@article{RobertH.1994,
author = {Robert H., Kadlec},
title = {Detention and mixing in free water wetlands},
journal = {Ecological Engineering},
year = {1994},
volume = {3},
number = {4},
pages = {345--380},
url = {http://www.sciencedirect.com/science/article/pii/0925857494000077}
}
|
|||||
| Robert W, W. | Environmental injustice in America and its politics of scale [BibTeX] |
1999 | Political Geography Vol. 18(1), pp. 49-73 |
article | DOI URL |
BibTeX:
@article{RobertW1999,
author = {Robert W, Williams},
title = {Environmental injustice in America and its politics of scale},
journal = {Political Geography},
year = {1999},
volume = {18},
number = {1},
pages = {49--73},
url = {http://www.sciencedirect.com/science/article/pii/S0962629898000766},
doi = {http://dx.doi.org/10.1016/s0962-6298(98)00076-6}
}
|
|||||
| Robert W, W. | The contested terrain of environmental justice research: community as unit of analysis [BibTeX] |
1999 | The Social Science Journal Vol. 36(2), pp. 313-328 |
article | DOI URL |
BibTeX:
@article{RobertW1999a,
author = {Robert W, Williams},
title = {The contested terrain of environmental justice research: community as unit of analysis},
journal = {The Social Science Journal},
year = {1999},
volume = {36},
number = {2},
pages = {313--328},
url = {http://www.sciencedirect.com/science/article/pii/S0362331999000087},
doi = {http://dx.doi.org/10.1016/s0362-3319(99)00008-7}
}
|
|||||
| Roberts, G.W., Larson, K.B. and Spaeth, E.E. | The interpretation of mean transit time measurements for multiphase tissue systems | 1973 | Journal of Theoretical Biology Vol. 39(2), pp. 447-475 |
article | URL |
| Abstract: A model-independent proof of the central-volume principle for multiphase tissue systems is presented. This derivation emphasizes the transport processes which occur within the system, and the physical constraints which the system must satisfy for valid application of the principle. These constraints include: (i) the fluid flowing into the system must be equivalentlylabelled; (ii) the system under study must be part of a larger system which has no diffusive inlets or outlets. The derivation shows that the definition of the volume of distribution and the choice of appropriate partition coefficients for evaluation of this quantity, are independent of any assumption concerning tracer equilibrium between phases as a whole. A less restrictive definition of equivalent labelling also results from the proof. | |||||
BibTeX:
@article{Roberts1973,
author = {Roberts, George W. and Larson, Kenneth B. and Spaeth, Edmund E.},
title = {The interpretation of mean transit time measurements for multiphase tissue systems},
journal = {Journal of Theoretical Biology},
year = {1973},
volume = {39},
number = {2},
pages = {447--475},
url = {http://www.sciencedirect.com/science/article/pii/0022519373901112}
}
|
|||||
| Robinson, B.A. and Viswanathan, H.S. | Application of the theory of micromixing to groundwater reactive transport models | 2003 | Water Resources Research Vol. 39(11), pp. 1313- |
article | URL |
| Abstract: This study extends and applies the theory of micromixing, first introduced in the chemical reaction engineering literature, to the topic of reactive transport in porous media. For all but the simplest linear kinetic and sorption models the fate and transport of a reactive solute depends on the residence times and the details of small-scale mixing. The latter phenomenon, also called micromixing, is important because it brings into close proximity chemical species that react, and it controls the local concentrations in a flowing system. Solutes with reaction rates or sorption isotherms that depend on species concentration will therefore be affected by micromixing. Two models for micromixing are introduced, the minimum and maximum mixedness models, that provide bounds on the extent of reaction or retardation behavior within the constraints imposed by the residence time distribution (RTD) of a conservative solute in the same flow system. These mixing models prescribe the latest or earliest permissible mixing of parcels of fluid of different residence times, which in turn bounds the degree of reaction of a reactive solute for nonlinear rate laws or sorption isotherms. Simulation results using the bounding models show that micromixing effects are most important for nonlinear reaction curves, solute pulses of short duration, and systems with broad RTD curves. Use of these models is a straightforward and practical way to investigate the importance of a phenomenon for which data are seldom available and whose impact on groundwater reactive transport models has heretofore not been studied in a systematic, bounding manner. | |||||
BibTeX:
@article{Robinson2003,
author = {Robinson, Bruce A. and Viswanathan, Hari S.},
title = {Application of the theory of micromixing to groundwater reactive transport models},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2003},
volume = {39},
number = {11},
pages = {1313--},
url = {http://dx.doi.org/10.1029/2003WR002368}
}
|
|||||
| Robinson, B.A., Viswanathan, H.S. and Valocchi, A.J. | Efficient numerical techniques for modeling multicomponent ground-water transport based upon simultaneous solution of strongly coupled subsets of chemical components | 2000 | Advances in Water Resources Vol. 23(4), pp. 307-324 |
article | URL |
| Abstract: An iterative solution technique for reactive transport problems is developed, which we call the selective coupling method, that represents a versatile alternative to traditional uncoupled iterative techniques and the fully coupled global implicit method. The chemical formulation studied allows a combination of equilibrium and kinetic reactions, and therefore is a more versatile model formulation than a purely equilibrium-based system. However, this is a very challenging system for obtaining an efficient numerical solution. Techniques that sequentially compute the concentrations of aqueous components possibly ignore important derivatives in the Jacobian matrix of the full system of equations. The selective coupling method developed here allows only the strongly coupled components to be solved together, and the transport iteration consists of solving groups of components simultaneously. We also develop a method denoted as coupled normalization to reduce the computational work and memory requirements for particular types of reactive transport problems. These approaches can result in computational savings relative to the global implicit method by achieving a similar iteration count while reducing the cpu time per iteration. More importantly, the memory requirements of the selective coupling technique are controlled by the maximum number of coupled components, rather than by the total number of components. For complex aqueous chemical systems and grids with a large number of nodes, memory efficiency is the characteristic that makes the selective coupling method particularly attractive relative to the global implicit method. A series of example cases illustrate the efficiency of the new approach. These test problems are also used to address the implementation issues surrounding the most efficient strategy for coupling the aqueous components when carrying out the chemical transport iteration. In-depth knowledge of the behavior of the chemical system is required to select an appropriate solution strategy. | |||||
BibTeX:
@article{Robinson2000,
author = {Robinson, Bruce A. and Viswanathan, Hari S. and Valocchi, Albert J.},
title = {Efficient numerical techniques for modeling multicomponent ground-water transport based upon simultaneous solution of strongly coupled subsets of chemical components},
journal = {Advances in Water Resources},
year = {2000},
volume = {23},
number = {4},
pages = {307--324},
url = {http://www.sciencedirect.com/science/article/pii/S0309170899000342}
}
|
|||||
| Rodney O., F. | On the relationship between Lagrangian micromixing models and computational fluid dynamics | 1998 | Chemical Engineering and Processing: Process Intensification Vol. 37(6), pp. 521-535 |
article | URL |
| Abstract: The relationship between Lagrangian micromixing models, which are widely employed in chemical reaction engineering, and Eulerian computational fluid dynamic (CFD) models based on the Reynolds-averaged species conservation equation is explored. A general modeling methodology which combines the strengths of both approaches is developed in the form of a multi-environment CFD micromixing model. The formulation is shown to be equivalent to a presumed multi-scalar probability density function (PDF) approach. The four-environment generalized mixing model (GMM) model originally proposed by Villermaux and Falk (Villermaux and Falk, Chem. Eng. Sci. 49 (5127) (1994)) is used to illustrate the methodology by applying it to model a series-parallel reaction in a tubular reactor. | |||||
BibTeX:
@article{RodneyO.1998,
author = {Rodney O., Fox},
title = {On the relationship between Lagrangian micromixing models and computational fluid dynamics},
journal = {Chemical Engineering and Processing: Process Intensification},
year = {1998},
volume = {37},
number = {6},
pages = {521--535},
url = {http://www.sciencedirect.com/science/article/pii/S0255270198000592}
}
|
|||||
| Rodrigues, A.E. and Minceva, M. | Modelling and simulation in chemical engineering: Tools for process innovation | 2005 | Computers & Chemical Engineering Vol. 29(6)Selected Papers Presented at the 14th European Symposium on Computer Aided Process Engineering ESCAPE-14 The 14th European Symposium on Computer Aided Process Engineering, pp. 1167-1183 |
article | URL |
| Abstract: The Chemical Engineering Science movement has served well in solving problems from micro to macro scales. Ultimately, as Professor R. Sargent pointed out, it would be better if translated in “Scientific Engineering”. | |||||
BibTeX:
@article{Rodrigues2005,
author = {Rodrigues, Alirio E. and Minceva, Mirjana},
title = {Modelling and simulation in chemical engineering: Tools for process innovation},
booktitle = {Selected Papers Presented at the 14th European Symposium on Computer Aided Process Engineering ESCAPE-14 The 14th European Symposium on Computer Aided Process Engineering},
journal = {Computers & Chemical Engineering},
year = {2005},
volume = {29},
number = {6},
pages = {1167--1183},
url = {http://www.sciencedirect.com/science/article/pii/S0098135405000098}
}
|
|||||
| Rodrigues, M.E., Costa, A.R., Henriques, M., Azeredo, J. and Oliveira, R. | Wave characterization for mammalian cell culture: residence time distribution | 2012 | New Biotechnology Vol. 29(3), pp. 402-408 |
article | URL |
| Abstract: The high dose requirements of biopharmaceutical products led to the development of mammalian cell culture technologies that increase biomanufacturing capacity. The disposable Wave bioreactor is one of the most promising technologies, providing ease of operation and no cross-contamination, and using an innovative undulation movement that ensures good mixing and oxygen transfer without cell damage. However, its recentness demands further characterization. This study evaluated the residence time distribution (RTD) in Wave, allowing the characterization of mixing and flow and the comparison with ideal models and a Stirred tank reactor (STR) used for mammalian cell culture. RTD was determined using methylene blue with pulse input methodology, at three flow rates common in mammalian cell culture (3.3 × 10−5 m3/h, 7.9 × 10−5 m3/h, and 1.25 × 10−4 m3/h) and one typical of microbial culture (5 × 10−3 m3/h). Samples were taken periodically and the absorbance read at 660 nm. It was observed that Wave behavior diverted from ideal models, but was similar to STR. Therefore, the deviations are not related to the particular Wave rocking mechanism, but could be associated with the inadequacy of these reactors to operate in continuous mode or to a possible inability of the theoretical models to properly describe the behavior of reactors designed for mammalian cell culture. Thus, the development of new theoretical models could better characterize the performance of these reactors. | |||||
BibTeX:
@article{Rodrigues2012,
author = {Rodrigues, Maria Elisa and Costa, Ana Rita and Henriques, Mariana and Azeredo, Joana and Oliveira, Rosário},
title = {Wave characterization for mammalian cell culture: residence time distribution},
journal = {New Biotechnology},
year = {2012},
volume = {29},
number = {3},
pages = {402--408},
url = {http://www.sciencedirect.com/science/article/pii/S1871678411002263}
}
|
|||||
| Romanov, D., Gabrovsek, F. and Dreybrodt, W. | The impact of hydrochemical boundary conditions on the evolution of limestone karst aquifers | 2003 | Journal of Hydrology Vol. 276(1-4), pp. 240-253 |
article | URL |
| Abstract: The early evolution of karst aquifers depends on a manifold of initial and boundary conditions such as geological setting, hydrologic properties of the initial aquifer, and petrologic properties of the rock. When all water entering at various inputs into the aquifer has equal chemical composition with respect to the system H2O–CO2–CaCO3 early evolution under conditions of constant head exhibits breakthrough (BT) behaviour. If the chemical compositions of the input waters are different, deep in the aquifer where the saturated solutions mix renewed aggressiveness occurs, and additional dissolutional widening of fractures by mixing corrosion (MC) changes the hydrologic properties of the aquifer. To study the impact of MC on the evolution of karst we have modelled a simple karst aquifer consisting of a confined limestone bed, with two symmetrically located inputs at constant head and open flow conditions along the entire width at base level. To calculate dissolutional widening of the fractures the well-known dissolution kinetics of limestone was used, which is linear up to 90% of saturation with respect to calcite and then switches to a nonlinear fourth order rate law. First, two extremes are modelled: (a) Both inputs receive aggressive water of equal chemical composition with [Ca2+]=0.75[Ca2+]eq. In this case two channels migrate downstream with that from one input more competitive and reaching base level first, causing BT. (b) Water at both inputs is saturated with respect to calcite, but in equilibrium with different partial pressures of CO2. Therefore, dissolution widening can occur only where these waters mix. A central channel starts to grow extending down-head until base level is reached. Flow rates through the aquifer first rise and become constant after the channel has reached base level. In the following runs these two extreme modes of karstification are combined. The waters entering have different chemical compositions and therefore different equilibrium concentrations [Ca2+]eq. This allows MC to be active. They are also undersaturated with the inflowing solutions at concentration [Ca2+]in=f[Ca2+]eq where f is the ratio of saturation. In comparison to the extreme limit (a) the action of MC now creates permeability where the solutions mix and diverts the evolution of conduits into this region. Finally one conduit reaches base level and causes BT. This behaviour is found for f=0.7, 0.9, and 0.96. | |||||
BibTeX:
@article{Romanov2003,
author = {Romanov, Douchko and Gabrovsek, Franci and Dreybrodt, Wolfgang},
title = {The impact of hydrochemical boundary conditions on the evolution of limestone karst aquifers},
journal = {Journal of Hydrology},
year = {2003},
volume = {276},
number = {1-4},
pages = {240--253},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403000581}
}
|
|||||
| Romanov, D., Kaufmann, G. and Hiller, T. | Karstification of aquifers interspersed with non-soluble rocks: From basic principles towards case studies | 2010 | Engineering Geology Vol. 116(3-4), pp. 261-273 |
article | URL |
| Abstract: We have developed a numerical model able to describe the karstification of aquifers in fractured rocks containing soluble (limestone or gypsum) and insoluble layers. When water is flowing along fractures crossing the soluble layers, it is able to dissolve the material there, to increase the aperture width of the conduit, and consequently to increase the local hydraulic conductivity. Depending on the thickness and the distribution of these layers, the dissolution can be active only for limited periods, or during the whole evolution time. Fractures located in insoluble layers do not change at all. We are interested in the integral effect of these local processes and study four simplified scenarios of karstification along a prominent wide conduit crossing a fractured limestone block. We keep the initial and the boundary conditions the same for all scenarios and vary only in the amount and the distribution of the soluble material. We demonstrate that aquifers in 100% limestone, without any insoluble layers, develop along areas with high hydraulic conductivities and high hydraulic gradients, creating channel like pathways. On the other hand aquifers containing soluble layers with limited thickness develop faster and exhibit diffuse patterns determined by the chemical properties of the rock. | |||||
BibTeX:
@article{Romanov2010,
author = {Romanov, Douchko and Kaufmann, Georg and Hiller, Thomas},
title = {Karstification of aquifers interspersed with non-soluble rocks: From basic principles towards case studies},
journal = {Engineering Geology},
year = {2010},
volume = {116},
number = {3-4},
pages = {261--273},
url = {http://www.sciencedirect.com/science/article/pii/S0013795210001845}
}
|
|||||
| Rone, T.R. | Engaged Education: Experiential Learning, Intensive Field Experiences, and Social Change [BibTeX] |
2010 | International Encyclopedia of Education, 8-Volume Set, pp. 711-718 | inbook | DOI URL |
BibTeX:
@inbook{Rone2010,
author = {Rone, Tracy R.},
title = {Engaged Education: Experiential Learning, Intensive Field Experiences, and Social Change},
booktitle = {International Encyclopedia of Education, 8-Volume Set},
publisher = {Elsevier},
year = {2010},
pages = {711--718},
edition = {Third},
url = {http://www.sciencedirect.com/science/article/pii/B9780080448947016559},
doi = {http://dx.doi.org/10.1016/b978-0-08-044894-7.01655-9}
}
|
|||||
| Ronkanen, A.-K. and Kløve, B. | Hydraulics and flow modelling of water treatment wetlands constructed on peatlands in Northern Finland | 2008 | Water Research Vol. 42(14), pp. 3826-3836 |
article | URL |
| Abstract: In this study, we evaluated flow structure, effective flow area (Aeff) and effective porosity (θeff) in three peatlands using the stable isotope 18O/16O ratio and tracer tests. We also applied the readily available groundwater modelling MODFLOW code for wetland flow modelling and simulated in one study site how the hydraulic performance of the wetland will be improved by changing the design of the distribution ditch. Preferential flow paths occurred in all three studied wetlands and Aeff varied from 40% to 90% of total wetland area while θeff was 0.75–0.99. Constructed flow models accurately simulated the hydraulic head across wetlands (r2 = 0.95–0.99). Similarities between the flow models and the stable isotope distributions observed in this study suggest possibilities in using MODFLOW to design peatlands. The improvement of the inlet ditch configuration (ditch length/wetland width > 0.45) can prevent or reduce short-circuiting and dead zones in peatlands treating wastewater. | |||||
BibTeX:
@article{Ronkanen2008,
author = {Ronkanen, Anna-Kaisa and Kløve, Bjørn},
title = {Hydraulics and flow modelling of water treatment wetlands constructed on peatlands in Northern Finland},
journal = {Water Research},
year = {2008},
volume = {42},
number = {14},
pages = {3826--3836},
url = {http://www.sciencedirect.com/science/article/pii/S0043135408002224}
}
|
|||||
| Ronkanen, A.-K. and Kløve, B. | Use of stabile isotopes and tracers to detect preferential flow patterns in a peatland treating municipal wastewater | 2007 | Journal of Hydrology Vol. 347(3–4), pp. 418-429 |
article | URL |
| Abstract: The understanding of flow processes is one of the key elements in evaluating treatment efficiency in constructed wetlands. This study use a new method based on analysis of stabile oxygen and hydrogen isotope distributions in surface water in order to find water flow pathways in a treatment system established on a natural peatland in Ruka, Finland. The 18O/16O distributions of surface water samples were analysed in three field campaigns (2002, 2004, and 2005) and 2H/1H distribution in one field campaign (2002). Two conventional tracer (KBr and KI) tests and a tracer (NaCl) test in ground water tubes were conducted to study residence times and soil water flow characteristics. Online registration of electrical conductivity and temperature were used to analyse the NaCl experiment. The results showed clear spatial differences in 18O/16O distributions that were similar in each field campaign. Both 18O/16O and 2H/1H also varied clearly with depth until 40 cm. The results indicate that a strong preferential pathway exists in the wetland and that the water flows mainly in the top of peat layer. The observed flow path was the reason for the varying NH4-N distribution showing that a large potential area for nutrient removal is not used. The results show that the isotope method can be used to evaluate the water flow structure in peatlands and determinate the active flow area for wastewater purification. Along with the traditional tracer test the method can be used to estimate the active flow volume. A modification to the potential residence time equation is proposed by including active flow area, flow depth and an effective porosity. | |||||
BibTeX:
@article{Ronkanen2007,
author = {Ronkanen, Anna-Kaisa and Kløve, Bjørn},
title = {Use of stabile isotopes and tracers to detect preferential flow patterns in a peatland treating municipal wastewater},
journal = {Journal of Hydrology},
year = {2007},
volume = {347},
number = {3–4},
pages = {418--429},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407005306}
}
|
|||||
| Ross, S.M. | Introduction to Probability Models [BibTeX] |
1997 | , pp. - | book | |
BibTeX:
@book{Ross1997,
author = {Ross, Sheldon M.},
title = {Introduction to Probability Models},
publisher = {Academic Press},
year = {1997},
pages = {--},
edition = {Sixth}
}
|
|||||
| Royaee, S.J. and Sohrabi, M. | Comprehensive Study on Wastewater Treatment Using Photo-Impinging Streams Reactor: Residence Time Distribution and Reactor Modeling | 2012 | Industrial & Engineering Chemistry Research Vol. 51(11), pp. 4152-4160 |
article | URL |
| Abstract: A photo impinging streams reactor was employed to study the degradation of phenol in aqueous solutions applying titanium dioxide nanoparticles as the reaction catalyst. The central composite experimental design method was applied to determine the pertinent operating parameters of such a process. These were phenol concentration, catalyst loading, pH of the slurry, and the feed flow rate. Residence time distribution (RTD) of the slurry phase within the reactor was measured using the impulse tracer method. A compartment model consisting of a number of mixed and plug flow regions was assigned to describe the flow pattern in the reactor. On the basis of such an arrangement and applying the Markov chains discrete time formulation, a three parameters model was derived for the RTD. The parameters of the theoretical RTD model were evaluated by comparing the latter with those determined experimentally. The RTD expression was applied in conjunction with the phenol degradation kinetic model to predict the apparent rate coefficient for such a reaction. The higher values observed for the apparent rate coefficient in impinging streams reactor than those available in the literature may be explained by the mass transfer limitations affecting the conventional reactors performance. A photo impinging streams reactor was employed to study the degradation of phenol in aqueous solutions applying titanium dioxide nanoparticles as the reaction catalyst. The central composite experimental design method was applied to determine the pertinent operating parameters of such a process. These were phenol concentration, catalyst loading, pH of the slurry, and the feed flow rate. Residence time distribution (RTD) of the slurry phase within the reactor was measured using the impulse tracer method. A compartment model consisting of a number of mixed and plug flow regions was assigned to describe the flow pattern in the reactor. On the basis of such an arrangement and applying the Markov chains discrete time formulation, a three parameters model was derived for the RTD. The parameters of the theoretical RTD model were evaluated by comparing the latter with those determined experimentally. The RTD expression was applied in conjunction with the phenol degradation kinetic model to predict the apparent rate coefficient for such a reaction. The higher values observed for the apparent rate coefficient in impinging streams reactor than those available in the literature may be explained by the mass transfer limitations affecting the conventional reactors performance. |
|||||
BibTeX:
@article{Royaee2012,
author = {Royaee, Sayed Javid and Sohrabi, Morteza},
title = {Comprehensive Study on Wastewater Treatment Using Photo-Impinging Streams Reactor: Residence Time Distribution and Reactor Modeling},
journal = {Industrial & Engineering Chemistry Research},
publisher = {American Chemical Society},
year = {2012},
volume = {51},
number = {11},
pages = {4152--4160},
url = {http://dx.doi.org/10.1021/ie201384s}
}
|
|||||
| Roychoudhury, A.N., Viollier, E. and Van Cappellen, P. | A plug flow-through reactor for studying biogeochemical reactions in undisturbed aquatic sediments | 1998 | Applied Geochemistry Vol. 13(2), pp. 269-280 |
article | URL |
| Abstract: A slow flow, plug-through reactor was developed for measuring equilibrium and kinetic parameters of biogeochemical reactions on intact sections of sediment cores. The experimental approach was designed to preserve the structural, geochemical and microbiological integrity of the sediment sections and, hence, retrieve reaction parameters that apply to in-situ conditions. | |||||
BibTeX:
@article{Roychoudhury1998,
author = {Roychoudhury, A. N. and Viollier, E. and Van Cappellen, P.},
title = {A plug flow-through reactor for studying biogeochemical reactions in undisturbed aquatic sediments},
journal = {Applied Geochemistry},
year = {1998},
volume = {13},
number = {2},
pages = {269--280},
url = {http://www.sciencedirect.com/science/article/pii/S0883292797000644}
}
|
|||||
| Rozos, E. and Koutsoyiannis, D. | A multicell karstic aquifer model with alternative flow equations | 2006 | Journal of Hydrology Vol. 325(1-4), pp. 340-355 |
article | URL |
| Abstract: A multicell groundwater model was constructed to investigate the potential improvement in the modelling of karstic aquifers by using a mixed equation suitable for both the free surface and pressure flow conditions in karstic conduits. To estimate the model parameters the shuffled complex evolution (SCE) optimisation method was used. This ensured a fast and objective model calibration. The model was applied to two real-world karstic aquifers and it became clear that in case of absence of water level measurements, the use of the mixed equation did not improved the performance. In cases where both spring discharge and water level measurements were available, the use of the mixed equation proved to be advantageous in reproducing the features of the observed time series especially of the water level. | |||||
BibTeX:
@article{Rozos2006,
author = {Rozos, Evangelos and Koutsoyiannis, Demetris},
title = {A multicell karstic aquifer model with alternative flow equations},
journal = {Journal of Hydrology},
year = {2006},
volume = {325},
number = {1-4},
pages = {340--355},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405005512}
}
|
|||||
| Rubin, H., Dveyrin, D., Birkhölzer, J. and Rouvé, G. | Advection and dispersion of contaminant in a permeable medium embedding fractures in which advection velocity is comparatively slow | 1997 | Journal of Hydrology Vol. 199(1-2), pp. 135-162 |
article | URL |
| Abstract: This paper concerns the advective migration of an aqueous contaminant in a fractured permeable formation. Calculation and analysis refer to fractures in which advection velocity is comparatively small. The slow advective velocity is created by some local cavities or almost vertical orientation of the fractures. It is shown that the advective contaminant transport is characterized by two dimensionless parameters: (1) the ratio between the permeable block and fracture flow rates, termed the ‘mobility number’; (2) the ratio between the longitudinal advection velocity of the permeable block flow and that of the fracture flow, termed the ‘advection velocity ratio’. | |||||
BibTeX:
@article{Rubin1997,
author = {Rubin, Hillel and Dveyrin, Dmitry and Birkhölzer, Jens and Rouvé, Gerhard},
title = {Advection and dispersion of contaminant in a permeable medium embedding fractures in which advection velocity is comparatively slow},
journal = {Journal of Hydrology},
year = {1997},
volume = {199},
number = {1-2},
pages = {135--162},
url = {http://www.sciencedirect.com/science/article/pii/S0022169496032581}
}
|
|||||
| Rubin, H., Jansen, D., Forkel, C. and Köngeter, J. | Simulation of contaminant transport in fractured permeable formations by multiporosity modeling | 1999 | Journal of Hydrology Vol. 223(3-4), pp. 107-130 |
article | URL |
| Abstract: This paper concerns contaminant transport in aquifers comprising fractured porous formations. It is considered that the aquifer subject to contamination is composed of macro-blocks, which embed two sets of macro-fractures. Each macro-block incorporates numerous micro-blocks of low permeability, which embed micro-fractures. Therefore, the basic conceptual model, used in this study, is a triple-porosity two-dimensional model. | |||||
BibTeX:
@article{Rubin1999,
author = {Rubin, H. and Jansen, D. and Forkel, C. and Köngeter, J.},
title = {Simulation of contaminant transport in fractured permeable formations by multiporosity modeling},
journal = {Journal of Hydrology},
year = {1999},
volume = {223},
number = {3-4},
pages = {107--130},
url = {http://www.sciencedirect.com/science/article/pii/S0022169499000980}
}
|
|||||
| Rubin, H., Soliman, A., Birkhölzer, J. and Rouve, G. | Transport of a tracer slug in a fractured permeable formation | 1996 | Journal of Hydrology Vol. 176(1-4), pp. 153-180 |
article | URL |
| Abstract: This paper concerns the migration of a tracer slug injected into a fractured permeable formation. Basic transport processes are formulated. Dimensionless parameters governing transport phenomena in the domain are identified, and their effects are determined. A simplified conceptual model is employed for the quantitative evaluation of the physical phenomena associated with tracer migration in the domain. The analytical approach applied in this study provides some basic characteristics concerning the build-up and decay of tracer breakthrough curves. Characteristics of fracture networks incorporating a large number of fracture sectors are evaluated using a numerical finite difference scheme. | |||||
BibTeX:
@article{Rubin1996,
author = {Rubin, H. and Soliman, A.M. and Birkhölzer, J. and Rouve, G.},
title = {Transport of a tracer slug in a fractured permeable formation},
journal = {Journal of Hydrology},
year = {1996},
volume = {176},
number = {1-4},
pages = {153--180},
url = {http://www.sciencedirect.com/science/article/pii/0022169495027750}
}
|
|||||
| Rudolf, M., Wolter, H.-J. and Zimmermann, H. | A linear model for tracking error minimization | 1999 | Journal of Banking & Finance Vol. 23(1), pp. 85-103 |
article | URL |
| Abstract: This article investigates four models for minimizing the tracking error between the returns of a portfolio and a benchmark. Due to linear performance fees of fund managers, we can argue that linear deviations give a more accurate description of the investors’ risk attitude than squared deviations. All models have in common that absolute deviations are minimized instead of squared deviations as is the case for traditional optimization models. Linear programs are formulated to derive explicit solutions. The models are applied to a portfolio containing six national stock market indexes (USA, Japan, UK, Germany, France, Switzerland) and the tracking error with respect to the MSCI (Morgan Stanley Capital International Index) world stock market index is minimized. The results are compared to those of a quadratic tracking error optimization technique. The portfolio weights of the optimized portfolio and its risk/return properties are different across the models which implies that optimization models should be targeted to the specific investment objective. Finally, it is shown that linear tracking error optimization is equivalent to expected utility maximization and lower partial moment minimization. | |||||
BibTeX:
@article{Rudolf1999,
author = {Rudolf, Markus and Wolter, Hans-Jürgen and Zimmermann, Heinz},
title = {A linear model for tracking error minimization},
journal = {Journal of Banking & Finance},
year = {1999},
volume = {23},
number = {1},
pages = {85--103},
url = {http://www.sciencedirect.com/science/article/pii/S0378426698000764}
}
|
|||||
| Rueda, F., Moreno-Ostos, E. and Armengol, J. | The residence time of river water in reservoirs | 2006 | Ecological Modelling Vol. 191(2), pp. 260-274 |
article | URL |
| Abstract: The average length of time water remains within the boundaries of an aquatic system is one of the key parameters controlling the system's biogeochemical behavior. This time scale, which is generally referred to as the hydraulic residence time, provides a first order description of multiple and complex processes that create transport. This manuscript reviews the procedures to estimate transport time scales in reservoirs and explores, through the analysis of numerical simulations, the links between these time scales and the underlying hydrodynamic processes in a reservoir in North-Eastern Spain. The mean residence time scales undergo dramatic variations in time and in general, are comparable to the time scales of the systems’ variability itself, such as those associated with seasonal changes in stratification, allowing complex patterns of intermittent mixing events to determine residence time scales. We demonstrate that the temporal variations of mean residence times occur not only at seasonal time scales, but also at shorter scales. The time scales are closely related to mixing and transport processes occurring within the reservoir, at the inflow sections and at the watershed. | |||||
BibTeX:
@article{Rueda2006,
author = {Rueda, Francisco and Moreno-Ostos, Enrique and Armengol, Joan},
title = {The residence time of river water in reservoirs},
journal = {Ecological Modelling},
year = {2006},
volume = {191},
number = {2},
pages = {260--274},
url = {http://www.sciencedirect.com/science/article/pii/S0304380005002760}
}
|
|||||
| Ruehl, C., Fisher, A., Hatch, C., Huertos, M.L., Stemler, G. and Shennan, C. | Differential gauging and tracer tests resolve seepage fluxes in a strongly-losing stream | 2006 | Journal of Hydrology Vol. 330(1-2)Hydro-ecological functioning of the Pang and Lambourn catchments, UK Results from the Lowland Catchment Research (LOCAR) initiative, pp. 235-248 |
article | URL |
| Abstract: The Pajaro River, central coastal California, consistently loses 0.2–0.4 m3/s of discharge along an 11.42-km experimental reach late in the water year, when discharge is ⩽4.5 m3/s. Channel loss occurs throughout this reach, but is greatest in magnitude near the bottom of the reach. Water isotopic data and other observations suggest that channel loss results mainly from streambed seepage, as opposed to evapotranspiration. If it occurs throughout the year, the channel loss along this short stream reach could contribute 6–13 × 106 m3 of annual aquifer recharge, or ∼20–40% of current sustainable basin yield. We performed a series of tracer injections along this reach to determine if hydrologic exchange occurs within this strongly-losing stream. We found that during periods of high channel loss, there were also comparable storage exchange fluxes and lateral inflow of tracer-free water. Within upper and lower parts of the experimental reach, storage exchange fluxes are about 10 times greater than lateral inflow. The former are associated with the movement of water between the main channel and surface or subsurface storage zones. In this system, it is likely that the latter are primarily associated with spatially- or temporally-long subsurface flow paths within the shallow streambed, as opposed to inflow of ground water from deeper in the basin. Along both upper and lower parts of the experimental reach, lateral inflow tends to increase as channel discharge decreases. In contrast, storage exchange fluxes increase with decreasing discharge along the upper parts of the reach, but decrease with decreasing discharge along the lower parts. Gauging and tracer test results suggest that subsurface storage exchange and loss may occur simultaneously, and that the lateral inflow of tracer-free water can be caused by long-scale subsurface flow as well as ground water making its first appearance in the channel. | |||||
BibTeX:
@article{Ruehl2006,
author = {Ruehl, C. and Fisher, A.T. and Hatch, C. and Huertos, M. Los and Stemler, G. and Shennan, C.},
title = {Differential gauging and tracer tests resolve seepage fluxes in a strongly-losing stream},
booktitle = {Hydro-ecological functioning of the Pang and Lambourn catchments, UK Results from the Lowland Catchment Research (LOCAR) initiative},
journal = {Journal of Hydrology},
year = {2006},
volume = {330},
number = {1-2},
pages = {235--248},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406001697}
}
|
|||||
| Rufo, M.J., Pérez, C.J. and Martín, J. | Local parametric sensitivity for mixture models of lifetime distributions | 2009 | Reliability Engineering & System Safety Vol. 94(7)Special Issue on Sensitivity Analysis, pp. 1238-1244 |
article | URL |
| Abstract: Mixture models are receiving considerable significance in the last years. Practical situations in reliability and survival analysis may be addressed by using mixture models. When making inferences on them, besides the estimates of the parameters, a sensitivity analysis is necessary. In this paper, a general technique to estimate local prior sensitivities in finite mixtures of distributions from natural exponential families having quadratic variance function (NEF-QVF) is proposed. Those families include some distributions of wide use in reliability theory. An advantage of this method is that it allows a direct implementation of the sensitivity measure estimates and their errors. In addition, the samples that are drawn to estimate the parameters in the mixture model are re-used to estimate the sensitivity measures and their errors. An illustrative application based on insulating fluid failure data is shown. | |||||
BibTeX:
@article{Rufo2009,
author = {Rufo, M. J. and Pérez, C. J. and Martín, J.},
title = {Local parametric sensitivity for mixture models of lifetime distributions},
booktitle = {Special Issue on Sensitivity Analysis},
journal = {Reliability Engineering & System Safety},
year = {2009},
volume = {94},
number = {7},
pages = {1238--1244},
url = {http://www.sciencedirect.com/science/article/pii/S0951832008001531}
}
|
|||||
| Rumschitzki, D. and Liu, K. | Zwietering's maximum-mixedness reactor and the continuously stirred tank reactor | 1994 | Chemical Engineering Science Vol. 49(23), pp. 3883-3886 |
article | URL |
| Abstract: It is shown by means of examples that the concentration in a steady state Zwietering maximum-mixedness reactor, even with an exponential residence time density and certain limit conditions at infinite future life, does not have to be uniform as in a CSTR. Some points on Shinnar paradoxes are clarified by examining a minimal definition of a CSTR and relating it to Zwietering reactors. | |||||
BibTeX:
@article{Rumschitzki1994,
author = {Rumschitzki, David and Liu, Ke},
title = {Zwietering's maximum-mixedness reactor and the continuously stirred tank reactor},
journal = {Chemical Engineering Science},
year = {1994},
volume = {49},
number = {23},
pages = {3883--3886},
url = {http://www.sciencedirect.com/science/article/pii/0009250994002037}
}
|
|||||
| Runes, H.B., Jenkins, J.J., Moore, J.A., Bottomley, P.J. and Wilson, B.D. | Treatment of atrazine in nursery irrigation runoff by a constructed wetland | 2003 | Water Research Vol. 37(3), pp. 539-550 |
article | URL |
| Abstract: To investigate the treatment capability of a surface flow wetland at a container nursery near Portland, Oregon, atrazine was introduced during simulated runoff events. Treatment efficiency was evaluated as the percent atrazine recovered (as percent of applied) in the water column at the wetland's outlet. Atrazine treatment efficiency at the outlet of the constructed wetland during a 7-d period ranged from 18–24% in 1998 (experiments 1–3) and 16–17% in 1999 (experiments 4 and 5). Changes in total flow, or frequency and intensity of runoff events did not affect treatment. For experiment 6 in 1999, where the amount, frequency, and duration of runoff events exceeded all other experiments, treatment was compromised. For all experiments, deethylatrazine (DEA) and deisopropylatrazine (DIA) accounted for 13–21% of the initial application. Hydroxyatrazine (HA) was rarely detected in the water. Organic carbon adsorption coefficients (Koc) were determined from batch equilibrium sorption isotherms with wetland sediment, and they decreased in the order of HA>DIA>atrazine>DEA. Static water–sediment column experiments indicated that sorption is an important mechanism for atrazine loss from water passing through the constructed wetland. The results of the MPN assay indicated the existence in the wetland of a low-density population of microorganisms with the potential to mineralize atrazine's ethyl side chain. | |||||
BibTeX:
@article{Runes2003,
author = {Runes, Heather B and Jenkins, Jeffrey J and Moore, James A and Bottomley, Peter J and Wilson, Bruce D},
title = {Treatment of atrazine in nursery irrigation runoff by a constructed wetland},
journal = {Water Research},
year = {2003},
volume = {37},
number = {3},
pages = {539--550},
url = {http://www.sciencedirect.com/science/article/pii/S004313540200310X}
}
|
|||||
| Runkel, R.L. and Chapra, S.C. | An efficient numerical solution of the transient storage equations for solute transport in small streams | 1993 | Water Resources Research Vol. 29(1), pp. 211-215 |
article | URL |
| Abstract: Several investigators have proposed solute transport models that incorporate the effects of transient storage. Transient storage occurs in small streams when portions of the transported solute become isolated in zones of water that are immobile relative to water in the main channel (e.g., pools, gravel beds). Transient storage is modeled by adding a storage term to the advection-dispersion equation describing conservation of mass for the main channel. In addition, a separate mass balance equation is written for the storage zone. Although numerous applications of the transient storage equations may be found in the literature, little attention has been paid to the numerical aspects of the approach. Of particular interest is the coupled nature of the equations describing mass conservation for the main channel and the storage zone. In the work described herein, an implicit finite difference technique is developed that allows for a decoupling of the governing differential equations. This decoupling method may be applied to other sets of coupled equations such as those describing sediment-water interactions for toxic contaminants. For the case at hand, decoupling leads to a 50% reduction in simulation run time. Computational costs may be further reduced through efficient application of the Thomas algorithm. These techniques may be easily incorporated into existing codes and new applications in which simulation run time is of concern. | |||||
BibTeX:
@article{Runkel1993,
author = {Runkel, Robert L. and Chapra, Steven C.},
title = {An efficient numerical solution of the transient storage equations for solute transport in small streams},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1993},
volume = {29},
number = {1},
pages = {211--215},
url = {http://dx.doi.org/10.1029/92WR02217}
}
|
|||||
| Russell, M.J. and MacLean, V.L. | Management issues in a Tasmanian tourist cave: Potential microclimatic impacts of cave modifications | 2008 | Journal of Environmental Management Vol. 87(3), pp. 474-483 |
article | URL |
| Abstract: Caves can be difficult to navigate and often require physical modification to allow easy access for visitors. Single entrance caves double the access impact of each visitor. Visitors in tourist caves have direct physical effects such as the introduction of concrete and steel structures; transport of mud, dust, and nutrients; installation of lights and the exhalation of water vapour and carbon dioxide into the air. Indirect physical effects include alteration of the microclimate, both through physical modifications that change the ventilation regime and through the presence of visitors leading to changes in temperature, humidity and CO2 within the cave environment. Anthropomorphic changes to cave physical environments to aid access or to reduce backtracking can have adverse effects on the internal microclimate of cave systems with subsequent changes to the cave environment affecting the quality of decorations and cave art and the diversity of cave fauna. Although often stated that caves operate at or near a constant temperature, closer examination indicates that cave temperatures are neither static nor constant. The degree of variation depends largely on the structure and physical characteristics of the cave. Air temperature and humidity gradients between the inside and outside cave environment can result in air density differences, which create airflow, which will in turn affect the cave microclimate. As part of the development of a management framework for King Solomons Cave, Tasmania, a study of the microclimate was carried out on behalf of Tasmanian Parks and Wildlife Service. Analysis of the variables showed significant differences in air temperature within each site and between sites. These differences range from 4 °C variation at one site to 0 °C at another site. The data were used to model potential airflow between the cave and the external environment. Results indicate that part of the cave is dominated by airflow between the chimney and the cave entrance leading to microclimatic fluctuations, while stable climatic conditions occur at the end of the cave. Future management strategies that propose a passage from the chamber to the surface via the current end zone would create a potential for airflow induced microclimatic change, leading to a change in both the temperature and moisture regimes, necessitating the construction of an airtight double door system. | |||||
BibTeX:
@article{Russell2008,
author = {Russell, Mick J. and MacLean, Victoria L.},
title = {Management issues in a Tasmanian tourist cave: Potential microclimatic impacts of cave modifications},
journal = {Journal of Environmental Management},
year = {2008},
volume = {87},
number = {3},
pages = {474--483},
url = {http://www.sciencedirect.com/science/article/pii/S0301479707000370}
}
|
|||||
| Russell, T.F. and Celia, M.A. | An overview of research on Eulerian–Lagrangian localized adjoint methods (ELLAM) | 2002 | Advances in Water Resources Vol. 25(8-12), pp. 1215-1231 |
article | URL |
| Abstract: For problems of convection–diffusion type, Eulerian–Lagrangian localized adjoint methods provide a methodology that maintains the accuracy and efficiency of Eulerian–Lagrangian methods, while also conserving mass and systematically treating any type of boundary condition. In groundwater hydrology, this framework is useful for solute transport, as well as vadose-zone transport, multiphase transport, and reactive flows. The formulation was originated around 1990 by the authors, Herrera and Ewing, in a paper that appeared in Advances in Water Resources [Adv. Water Resour. 13 (1990) 187]. This paper reviews the progress in the development, analysis, and application of these methods since 1990, and suggests topics for future work. | |||||
BibTeX:
@article{Russell2002,
author = {Russell, Thomas F. and Celia, Michael A.},
title = {An overview of research on Eulerian–Lagrangian localized adjoint methods (ELLAM)},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {8-12},
pages = {1215--1231},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802001045}
}
|
|||||
| Russo, A., Johnson, G., Schnaar, G. and Brusseau, M. | Nonideal transport of contaminants in heterogeneous porous media: 8. Characterizing and modeling asymptotic contaminant-elution tailing for several soils and aquifer sediments | 2010 | Chemosphere Vol. 81(3), pp. 366-371 |
article | URL |
| Abstract: Miscible-displacement experiments were conducted to characterize long-term, low-concentration elution tailing associated with sorption/desorption processes. A variety of soils and aquifer sediments, representing a range of particle-size distributions and organic-carbon contents, were employed, and trichloroethene (TCE) was used as the model organic compound. Trichloroethene transport exhibited extensive elution tailing for all media, with several hundred to several thousand pore volumes of water flushing required to reach the detection limit. The elution tailing was more extensive for the media with higher organic-carbon contents and associated retardation factors. However, when normalized by retardation, the extent of tailing did not correlate directly to organic-carbon content. These latter results suggest that differences in the geochemical nature of organic carbon (e.g., composition, structure) among the various media influenced observed behavior. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous-distribution function was used to successfully simulate trichloroethene transport, including the extensive elution tailing. | |||||
BibTeX:
@article{Russo2010,
author = {Russo, A. and Johnson, G.R. and Schnaar, G. and Brusseau, M.L.},
title = {Nonideal transport of contaminants in heterogeneous porous media: 8. Characterizing and modeling asymptotic contaminant-elution tailing for several soils and aquifer sediments},
journal = {Chemosphere},
year = {2010},
volume = {81},
number = {3},
pages = {366--371},
url = {http://www.sciencedirect.com/science/article/pii/S004565351000799X}
}
|
|||||
| Ruzicka, M. | On dimensionless numbers | 2008 | Chemical Engineering Research and Design Vol. 86(8), pp. 835-868 |
article | URL |
| Abstract: The goal is to provide a little review on dimensionless numbers, commonly encountered in chemical engineering. Both their sources are considered: dimensional analysis and scaling of governing equations with boundary conditions. The numbers produced by scaling of equation are presented for transport of momentum, heat and mass. Momentum transport is considered in both single-phase and multi-phase flows. The numbers obtained are assigned the physical meaning, and their mutual relations are highlighted. Certain drawbacks of building correlations based on dimensionless numbers are pointed out. | |||||
BibTeX:
@article{Ruzicka2008,
author = {Ruzicka, M.C.},
title = {On dimensionless numbers},
journal = {Chemical Engineering Research and Design},
year = {2008},
volume = {86},
number = {8},
pages = {835--868},
url = {http://www.sciencedirect.com/science/article/pii/S0263876208000725}
}
|
|||||
| Ryan, E.M., Tartakovsky, A.M. and Amon, C. | Pore-scale modeling of competitive adsorption in porous media | 2011 | Journal of Contaminant Hydrology Vol. 120-121(0)Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media, pp. 56-78 |
article | URL |
| Abstract: In this paper we present a smoothed particle hydrodynamics (SPH) pore-scale multicomponent reactive transport model with competitive adsorption. SPH is a Lagrangian, particle based modeling method which uses the particles as interpolation points to discretize and solve flow and transport equations. The theory and details of the SPH pore-scale model are presented along with a novel method for handling surface reactions, the continuum surface reaction (CSR) model. The numerical accuracy of the CSR model is validated with analytical and finite difference solutions, and the effects of spatial and temporal resolution on the accuracy of the model are also discussed. The pore-scale model is used to study competitive adsorption for different Damköhler and Peclet numbers in a binary system where a plume of species B is introduced into a system which initially contains species A. The pore-scale model results are compared with a Darcy-scale model to investigate the accuracy of a Darcy-scale reactive transport model for a wide range of Damköhler and Peclet numbers. The comparison shows that the Darcy model over estimates the mass fraction of aqueous and adsorbed species B and underestimates the mass fractions of species A. The Darcy-scale model also predicts faster transport of species A and B through the system than the pore-scale model. The overestimation of the advective velocity and the extent of reactions by the Darcy-scale model are due to incomplete pore-scale mixing. As the degree of the solute mixing decreases with increasing Peclet and Damköhler numbers, so does the accuracy of the Darcy-scale model. | |||||
BibTeX:
@article{Ryan2011,
author = {Ryan, Emily M. and Tartakovsky, Alexandre M. and Amon, Cristina},
title = {Pore-scale modeling of competitive adsorption in porous media},
booktitle = {Reactive Transport in the Subsurface: Mixing, Spreading and Reaction in Heterogeneous Media},
journal = {Journal of Contaminant Hydrology},
year = {2011},
volume = {120-121},
number = {0},
pages = {56--78},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210000707}
}
|
|||||
| Ryan, M. and Meiman, J. | An Examination of Short-Term Variations in Water Quality at a Karst Spring in Kentucky | 1996 | Ground Water Vol. 34(1), pp. 23-30 |
article | URL |
| Abstract: Water quality at many karst springs undergoes very high amplitude but relatively brief degradation following influxes of runoff. Accurately recording transient variations requires more rigorous sampling strategies than traditional methods. A pilot study to determine the usefulness of high-frequency, flow-dependent sampling strategies, combined with coincidental quantitative dye tracer tests, was implemented in the Big Spring Ground-Water Basin in Mammoth Cave National Park, Kentucky. Data recorded following two separate runoff events showed that the concentrations of two nonpoint source pollutants, fecal coliform bacteria and suspended sediment, greatly exceeded prerunoff event values for very short periods of time. A phreatic conduit segment, calculated at 17 million liters in volume, instantaneously propagated head changes, caused by direct runoff entering the aquifer, from the ground-water inputs to Big Spring. A significant delay between the initial increases in discharge and the arrival of direct runoff, as indicated by a steady decrease in specific conductance, represented the time required to displace this volume of phreatic water. The delay showed that sampling a karst spring only during peak discharge would be an unreliable sampling method. Runoff from two different subcatchments was tagged with tracer dye and the timing of the passage of the resultant dye clouds through Big Spring were compared to water quality variations. Distinct lag times between the arrival of direct runoff at Big Spring and the bacteria and suspended sediment waveforms were shown through the concurrent quantitative tracer tests to be related to the areal distribution of land-cover type within the basin. | |||||
BibTeX:
@article{Ryan1996,
author = {Ryan, Martin and Meiman, Joe},
title = {An Examination of Short-Term Variations in Water Quality at a Karst Spring in Kentucky},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {1996},
volume = {34},
number = {1},
pages = {23--30},
url = {http://dx.doi.org/10.1111/j.1745-6584.1996.tb01861.x}
}
|
|||||
| Ryckelynck, T., Le Borgne, F., Egermann, P., Brefort, B. and Salignac, A.-L. | Numerical modeling of solute dispersion through vertical well and aquifer under oscillating pressure | 2010 | Journal of Petroleum Science and Engineering Vol. 72(1–2), pp. 56-63 |
article | URL |
| Abstract: The dispersion issue of a solute in a pulsating flow through a tube is the topic of different studies both in chemical engineering and biomechanics. In hydrogeology and for aquifer gas storages, oscillations of water in piezometers and control-wells can exhibit amplitude of several tens of meters within annual cycles. Owing to water–air interface in wells, the effective dispersion coefficients defined by Taylor (1953, 1954), Aris (1956, 1960), and later Watson (1983) are not suitable. To address this issue, the phenomena are numerically modeled. Results allow to adapt the expression of the Taylor's effective dispersion coefficient by introducing an effective velocity. In a second step, the coupling between the well model and an aquifer model, provides the downhole solute propagation. For a 450 m deep well with interface oscillations of 80 m, it is shown that 35 years are needed to reach a solute concentration at the strainers equal to 10−3 times the concentration at the interface, which is constant. The goal of this study was to investigate a non-expensive and easy to implement technique in order to introduce a tracer from a control-well using the energy related to the air/water oscillating interface. The introduction of such tracer in the storage aquifer is useful to understand the dispersion phenomena at the edge of the gas saturated area. | |||||
BibTeX:
@article{Ryckelynck2010,
author = {Ryckelynck, Thomas and Le Borgne, François and Egermann, Patrick and Brefort, Bernadette and Salignac, Anne-Lise},
title = {Numerical modeling of solute dispersion through vertical well and aquifer under oscillating pressure},
journal = {Journal of Petroleum Science and Engineering},
year = {2010},
volume = {72},
number = {1–2},
pages = {56--63},
url = {http://www.sciencedirect.com/science/article/pii/S0920410510000483}
}
|
|||||
| Rzonca, B. | Carbonate aquifers with hydraulically non-active matrix: A case study from Poland | 2008 | Journal of Hydrology Vol. 355(1–4), pp. 202-213 |
article | URL |
| Abstract: Summary The Devonian carbonate (karst) rocks of the Holy Cross Mountains (Góry Świętokrzyskie) in Poland, which constitute a major water supply for the region, are the subject of the presented study. Using standard laboratory methods, the matrix hydrogeological properties (open porosity, permeability and specific yield) of the limestones and dolomites were determined. The test results showed very low open porosities of the samples, as well as an extremely low permeability. The specific yield in all the cases was zero. There was a very slight correlation between the permeability (represented by the hydraulic conductivity) and the open porosity for limestones – and no correlation for dolomites. The measured parameters do not depend on the structure of the rock matrix (classified as pelite, sparite or crystalline) nor does the occurrence of fractures. Differences in open porosity (but not in hydraulic conductivity) were observed between the samples from different structural units. | |||||
BibTeX:
@article{Rzonca2008,
author = {Rzonca, Bartłomiej},
title = {Carbonate aquifers with hydraulically non-active matrix: A case study from Poland},
journal = {Journal of Hydrology},
year = {2008},
volume = {355},
number = {1–4},
pages = {202--213},
url = {http://www.sciencedirect.com/science/article/pii/S0022169408001534}
}
|
|||||
| Sagias, N.C. and Tombras, G.S. | On the cascaded Weibull fading channel model | 2007 | Journal of the Franklin Institute Vol. 344(1), pp. 1-11 |
article | URL |
| Abstract: A new stochastic fading channel model called cascaded Weibull fading is introduced and the associated capacity is derived in closed form. This model is generated by the product of independent, but not necessarily identically distributed, Weibull random variables (RVs). By quantifying the convergence rate of the central limit theorem as pertaining to the multiplication of Weibull distributed RVs, the statistical basis of the lognormal distribution is investigated. By performing Kolmogorov–Smirnov tests, the null hypothesis for this product to be approximated by the lognormal distribution is studied. Another null hypothesis is also examined for this product to be approximated by a Weibull distribution with properly adjusted statistical parameters. | |||||
BibTeX:
@article{Sagias2007,
author = {Sagias, Nikos C. and Tombras, George S.},
title = {On the cascaded Weibull fading channel model},
journal = {Journal of the Franklin Institute},
year = {2007},
volume = {344},
number = {1},
pages = {1--11},
url = {http://www.sciencedirect.com/science/article/pii/S0016003206001049}
}
|
|||||
| Sakuraba, C.S., Ronconi, D.P. and Sourd, F. | Scheduling in a two-machine flowshop for the minimization of the mean absolute deviation from a common due date | 2009 | Computers & Operations Research Vol. 36(1)Part Special Issue: Operations Research Approaches for Disaster Recovery Planning, pp. 60-72 |
article | URL |
| Abstract: This paper addresses the minimization of the mean absolute deviation from a common due date in a two-machine flowshop scheduling problem. We present heuristics that use an algorithm, based on proposed properties, which obtains an optimal schedule for a given job sequence. A new set of benchmark problems is presented with the purpose of evaluating the heuristics. Computational experiments show that the developed heuristics outperform results found in the literature for problems up to 500 jobs. | |||||
BibTeX:
@article{S.Sakuraba2009,
author = {Sakuraba, Celso S. and Ronconi, Débora P. and Sourd, Francis},
title = {Scheduling in a two-machine flowshop for the minimization of the mean absolute deviation from a common due date},
booktitle = {Part Special Issue: Operations Research Approaches for Disaster Recovery Planning},
journal = {Computers & Operations Research},
year = {2009},
volume = {36},
number = {1},
pages = {60--72},
url = {http://www.sciencedirect.com/science/article/pii/S0305054807001335}
}
|
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| Salehin, M., Packman, A.I. and Wörman, A. | Comparison of transient storage in vegetated and unvegetated reaches of a small agricultural stream in Sweden: seasonal variation and anthropogenic manipulation | 2003 | Advances in Water Resources Vol. 26(9)Modeling Hyporheic Zone Processes, pp. 951-964 |
article | URL |
| Abstract: In this work, we compare solute transport and hyporheic exchange in vegetated and unvegetated reaches of Säva Brook, an agricultural stream in Sweden subject to extreme variations in channel vegetation and morphology due to both natural seasonal effects and anthropogenic manipulation. A solute injection experiment was conducted in September, 2001 (late summer), at which time there was extensive in-channel vegetation in upstream reaches but none in downstream reaches due to channel excavation by farmers. Experimental results are interpreted using both the advective storage path model and the transient storage model. Results from the vegetated and excavated reaches of the stream are compared both with each other and with the results of a previous experiment conducted in April, 1998 (early spring), when the stream was not excavated but there was only minimal vegetation present in the area due to natural seasonal effects. Results from the two injection experiments are compared by using scaled parameters that appropriately include the effects of stream velocity and depth on hyporheic exchange. This analysis indicates that the variation of solute storage time in all non-excavated agricultural reaches is attributable to differences in stream flow depth, velocity, and the hydraulic conductivity of the streambed sediments. Mixing in vegetated reaches is characterized by rapid exchange and considerable lag of the mean solute peak relative to the mean channel velocity. In addition, excavation altered the stream channel geometry so as to increase the storage time of solutes and reduce the effective exchange rate. This work indicates the need to consider the effect of specific processes when analyzing hyporheic exchange using tracer-injection methods, and supports the use of model frameworks with the potential to explicitly include different formulations for various hyporheic and dead zone transport processes. | |||||
BibTeX:
@article{Salehin2003,
author = {Salehin, Mashfiqus and Packman, Aaron I. and Wörman, Anders},
title = {Comparison of transient storage in vegetated and unvegetated reaches of a small agricultural stream in Sweden: seasonal variation and anthropogenic manipulation},
booktitle = {Modeling Hyporheic Zone Processes},
journal = {Advances in Water Resources},
year = {2003},
volume = {26},
number = {9},
pages = {951--964},
url = {http://www.sciencedirect.com/science/article/pii/S0309170803000848}
}
|
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| Salengke, S. and Sastry, S. | Residence time distribution of cylindrical particles in a curved section of a holding tube: the effect of particle concentration and bend radius of curvature | 1996 | Journal of Food Engineering Vol. 27(2), pp. 159-176 |
article | URL |
| Abstract: The residence time and the residence time distribution (RTD) of model food particles (cylindrical, diameter and length = 0.02 m, density = 1130 kg/m3) in the curved section of a transparent holding tube have been investigated. Variables included in the study were particle concentration (20%, 30% and 40%) and bend radius of curvature (0.089, 0.22 and 0.28 m). The results show that the means of the normalized residence time tend to increase as either particle concentration or bend radius of curvature increased. However, there was no clear tendency of the effect of the experimental variables on the standard deviation of the normalized residence time. Empirical correlations between the means and the standard deviations of the normalized residence time and particle Froude number, particle concentration, and the ratio of bend radius of curvature to tube diameter are presented. | |||||
BibTeX:
@article{Salengke1996,
author = {Salengke, S. and Sastry, S.K.},
title = {Residence time distribution of cylindrical particles in a curved section of a holding tube: the effect of particle concentration and bend radius of curvature},
journal = {Journal of Food Engineering},
year = {1996},
volume = {27},
number = {2},
pages = {159--176},
url = {http://www.sciencedirect.com/science/article/pii/0260877494000913}
}
|
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| Salvadori, G. and De Michele, C. | Statistical characterization of temporal structure of storms | 2006 | Advances in Water Resources Vol. 29(6), pp. 827-842 |
article | URL |
| Abstract: The authors present a statistical procedure to estimate the probability distributions of storm characteristics. The approach uses recent advances in stochastic hydrological modeling. The temporal dynamics of rainfall are modeled via a reward alternating renewal process that describes wet and dry phases of storms. In particular, the wet phase is modeled as a rectangular pulse process with dependent random duration and intensity; the global dependence structure is described using multidimensional copulas. The marginal distributions are described by Generalized Pareto laws. The authors derive both the storm volume statistics and the rainfall volume distribution within a fixed temporal window preceding a storm. Based on these results, they calculate the antecedent moisture conditions. The paper includes a thorough discussion of the validity of the assumptions and approximations introduced, and an application to actual rainfall data. The models presented here have important implications for improved design procedures of water resources and hydrologic systems. | |||||
BibTeX:
@article{Salvadori2006,
author = {Salvadori, G. and De Michele, C.},
title = {Statistical characterization of temporal structure of storms},
journal = {Advances in Water Resources},
year = {2006},
volume = {29},
number = {6},
pages = {827--842},
url = {http://www.sciencedirect.com/science/article/pii/S030917080500196X}
}
|
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| Salvadori, G. and De Michele, C. | Frequency analysis via copulas: Theoretical aspects and applications to hydrological events | 2004 | Water Resources Research Vol. 40(12), pp. W12511- |
article | URL |
| Abstract: In this paper we provide a general theoretical framework exploiting copulas for studying the return periods of hydrological events; in particular, we consider events depending upon the joint behavior of two nonindependent random variables, an approach which can easily be generalized to the multivariate case. We show that using copulas may greatly simplify the calculations and may even yield analytical expressions for the isolines of the return periods, both in the unconditional and in the conditional case. In addition, we show how a new probability distribution may be associated with the return period of specific events and introduce the definitions of sub-, super-, and critical events as well as those of primary and secondary return periods. An illustration of the techniques proposed is provided by analyzing some case studies already examined in literature. | |||||
BibTeX:
@article{Salvadori2004,
author = {Salvadori, G. and De Michele, C.},
title = {Frequency analysis via copulas: Theoretical aspects and applications to hydrological events},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2004},
volume = {40},
number = {12},
pages = {W12511--},
url = {http://dx.doi.org/10.1029/2004WR003133}
}
|
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| Salvati, R. and Sasowsky, I.D. | Development of collapse sinkholes in areas of groundwater discharge | 2002 | Journal of Hydrology Vol. 264(1-4), pp. 1-11 |
article | URL |
| Abstract: Collapse sinkholes are found in groundwater recharge zones throughout the world. They cause substantial loss of property each year, and occasional fatalities. In such settings, the formation of these features occurs through the downward migration of regolith into karst voids. The presence of a void in the bedrock, and sufficient seepage pressure or gravitative force in the regolith, is required for their creation. We investigated the development of cover collapse sinkholes in an unusual setting, areas of groundwater discharge rather than recharge. Upward hydraulic gradients and the likelihood of groundwater saturated with respect to calcite are difficult to reconcile with standard models for collapse development. Short flowpaths or renewed groundwater aggressivity towards calcite (via mischungskorrosion, thermally driven circulation, or deep-seated gaseous sources) are hypothetical mechanisms that could generate the subsurface voids that are needed to allow cover collapse development in discharge areas. For the two field sites in central Italy that we investigated, calculated carbon dioxide partial pressures in springs ranged from 7.38×10−2 to 7.29×10−1 atm. This indicates that deep-seated gaseous sources are most likely the mechanism allowing the development of the sinkholes. Groundwater is recharged in surrounding limestone massifs. The water moves through the carbonates and becomes saturated with calcite. As it circulates deeply in to the adjacent valleys, it mixes with deep-seated waters and gaseous fluxes from major fault systems, acquiring renewed aggressivity towards calcite. Finally, the water ascends into confined aquifers in the valley fill, and dissolves carbonate material present within, leading to surface collapse. | |||||
BibTeX:
@article{Salvati2002,
author = {Salvati, Roberto and Sasowsky, Ira D},
title = {Development of collapse sinkholes in areas of groundwater discharge},
journal = {Journal of Hydrology},
year = {2002},
volume = {264},
number = {1-4},
pages = {1--11},
url = {http://www.sciencedirect.com/science/article/pii/S0022169402000628}
}
|
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| Sanchez-Moral, S., Portillo, M., Janices, I., Cuezva, S., Fernández-Cortés, A., Cañaveras, J. and Gonzalez, J. | The role of microorganisms in the formation of calcitic moonmilk deposits and speleothems in Altamira Cave | 2012 | Geomorphology Vol. 139--140(0), pp. 285-292 |
article | URL |
| Abstract: Bacteria are able to induce carbonate precipitation although the participation of microbial or chemical processes in speleothem formation remains a matter of debate. In this study, the origin of carbonate depositions such as moonmilk, an unconsolidated microcrystalline formation with high water content, and the consolidation of carbonate precipitates into hard speleothems were analyzed. The utilized methods included measurements of the composition of stable isotopes in these precipitates, fluorimetric determinations of RNA/DNA ratios and respirometric estimations in Altamira Cave. Results from isotope composition showed increases of the δ18O and δ13C ratios from moonmilk in the very first stages of formation toward large speleothems. Estimates of RNA/DNA ratios suggested an inactivation of microorganisms from incipient moonmilk toward consolidated deposits of calcium carbonate. Respiratory activity of microorganisms also showed a significant decrease in samples with accumulated calcite. These results suggest that bacterial activity induces the conditions required for calcium carbonate precipitation, initiating the first stages of deposition. Progressive accumulation of carbonate leads towards a less favorable environment for the development of bacteria. On consolidated speleothems, the importance of bacteria in carbonate deposition decreases and chemical processes gain importance in the deposition of carbonates. | |||||
BibTeX:
@article{Sanchez-Moral2012,
author = {Sanchez-Moral, S. and Portillo, M.C. and Janices, I. and Cuezva, S. and Fernández-Cortés, A. and Cañaveras, J.C. and Gonzalez, J.M.},
title = {The role of microorganisms in the formation of calcitic moonmilk deposits and speleothems in Altamira Cave},
journal = {Geomorphology},
year = {2012},
volume = {139--140},
number = {0},
pages = {285--292},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X11005563}
}
|
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| Sanchez-Vila, X. and Bolster, D. | An analytical approach to transient homovalent cation exchange problems | 2009 | Journal of Hydrology Vol. 378(3-4), pp. 281-289 |
article | URL |
| Abstract: Cation exchange in groundwater is one of the dominant surface reactions that occurs in nature and it carries with it many important environmental implications. The mass transfer of cation exchanging pollutants in groundwater can be described by a series of coupled partial differential equations, involving both aqueous and adsorbed species. The resulting system is mathematically challenging due to the complex nonlinearities that arise, which in turn complicates analytical approaches. While some analytical solutions for simplified problems exist, these typically lack the mechanisms that allow the waters to change their global chemical signature (in terms of total cations present in aqueous form) over time. We propose a methodology to solve the problem of exchanging two homovalent cations by deriving the driving equation for one of the aqueous species. This equation incorporates explicitly a retardation factor and a decay term, both with parameters that can vary in space and time. While the full solution can only be obtained numerically, we provide a solution in terms of a perturbative approach, where the leading terms can be obtained explicitly. The resulting solution provides physical explanations for the possible existence of non-monotonic concentrations for a range of parameters governing cation exchange processes. | |||||
BibTeX:
@article{Sanchez-Vila2009,
author = {Sanchez-Vila, Xavier and Bolster, Diogo},
title = {An analytical approach to transient homovalent cation exchange problems},
journal = {Journal of Hydrology},
year = {2009},
volume = {378},
number = {3-4},
pages = {281--289},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409006076}
}
|
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| Sanders, B.F., Arega, F. and Sutula, M. | Modeling the dry-weather tidal cycling of fecal indicator bacteria in surface waters of an intertidal wetland | 2005 | Water Research Vol. 39(14), pp. 3394-3408 |
article | URL |
| Abstract: Recreational water quality at beaches in California and elsewhere is often poor near the outlets of rivers, estuaries, and lagoons. This condition has prompted interest in the role of wetlands in modulating surface water concentrations of fecal indicator bacteria (FIB), the basis of water quality standards internationally. A model was developed and applied to predict the dry-weather tidal cycling of FIB in Talbert Marsh, an estuarine, intertidal wetland in Huntington Beach, California, in response to loads from urban runoff, bird feces, and resuspended sediments. The model predicts the advection, dispersion and die-off of total coliform, Escherichia coli, and enterococci using a depth-integrated formulation. We find that urban runoff and resuspension of contaminated wetland sediments are responsible for surface water concentrations of FIB in the wetland. Model predictions show that urban runoff controls surface water concentrations at inland sites and sediment resuspension controls surface water concentrations near the mouth. Direct wash-off of bird feces into the surface water is not a significant contributor, although bird feces can contribute to the sediment bacteria load. The key parameters needed to accurately predict FIB concentrations, using a validated hydrodynamic model, are: the load due to urban runoff, sediment erodibility parameters, and sediment concentrations and surface water die-off rates of enteric bacteria. In the present study, literature values for sediment erodibility and water column die-off rates are used and average concentrations of FIB are predicted within 1/2 log unit of measurements. Total coliform are predicted more accurately than E. coli or enterococci, both in terms of magnitude and tidal variability. Since wetland-dependent animals are natural sources of FIB, and FIB survive for long periods of time and may multiply in wetland sediments, these results highlight limitations of FIB as indicators of human fecal pollution in and near wetlands. | |||||
BibTeX:
@article{Sanders2005,
author = {Sanders, Brett F. and Arega, Feleke and Sutula, Martha},
title = {Modeling the dry-weather tidal cycling of fecal indicator bacteria in surface waters of an intertidal wetland},
journal = {Water Research},
year = {2005},
volume = {39},
number = {14},
pages = {3394--3408},
url = {http://www.sciencedirect.com/science/article/pii/S0043135405003064}
}
|
|||||
| Sanford, W. | Calibration of models using groundwater age [BibTeX] |
2011 | Hydrogeology Journal Vol. 19(1), pp. 13-16 |
article | URL |
BibTeX:
@article{Sanford2011a,
author = {Sanford, Ward},
title = {Calibration of models using groundwater age},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {19},
number = {1},
pages = {13--16},
url = {http://dx.doi.org/10.1007/s10040-010-0637-6}
}
|
|||||
| Sansalone, J.J. and Kim, J.-Y. | Suspended particle destabilization in retained urban stormwater as a function of coagulant dosage and redox conditions | 2008 | Water Research Vol. 42(4–5), pp. 909-922 |
article | URL |
| Abstract: Source area runoff entrains a hetero-disperse particle size distribution (PSD). When retained for clarification, larger sediment and settleable particles are mainly influenced by gravitational forces, while the suspended particles, in particular the clay-size particles, are subject to coagulation phenomena. Such phenomena occur in untreated runoff as well as runoff treated with a coagulant, albeit to differing rates and extents. Runoff PSDs and water chemistry indices including zeta potential (ξ) are potentially modified during inter-event stormwater retention in best management practices (BMPs). This study examined ξ of clay-size particles (<2 μm) in retained runoff, captured from an instrumented watershed, subject to batch coagulation and variable redox conditions. Separate parallel tests were also conducted with wastewater. Significant turbidity, particle mass (measured as total suspended solids (TSS)) and volume concentration (as total volume concentration (TVC)) reduction generated by alum and ferric chloride consistently occurred at a ξ in the range of −15 to about −10 mV. Alum addition produced a charge reversal at dosing above 60 mg/L (18×10−5 M) while ferric chloride did not reverse charge. With respect to turbidity and TSS reductions, alum outperformed ferric chloride, without the need for pH control. While ξ illustrated no clear trend during aerobic retention, anoxic retention resulted in a trend for ξ approaching the isoelectric point. The decrease in negative ξ towards the isoelectric point appears to be a result of the coupled pH depression under reductive conditions and an increase in conductivity. Results have significant implications for BMPs that retain runoff between events. | |||||
BibTeX:
@article{Sansalone2008,
author = {Sansalone, John J. and Kim, Jong-Yeop},
title = {Suspended particle destabilization in retained urban stormwater as a function of coagulant dosage and redox conditions},
journal = {Water Research},
year = {2008},
volume = {42},
number = {4–5},
pages = {909--922},
url = {http://www.sciencedirect.com/science/article/pii/S0043135407005830}
}
|
|||||
| Santos, V. and Dantas, C. | Transit time and RTD measurements by radioactive tracer to assess the riser flow pattern | 2004 | Powder Technology Vol. 140(1–2), pp. 116-121 |
article | URL |
| Abstract: Transit time measurements with radioactive tracers in a model riser were examined by a nondispersive tracer (60Co) encapsulated in a sphere. The flow dispersion of a CH3 82Br gaseous tracer was measured and compared with a normal distribution. The curve of the tracer concentration C(t) versus time was shown and evaluated for form and peak area. The transit time was measured by means of three methods, i.e., electronic watch recording, maximum point and center of mass. Signals were collected by two gamma detectors coupled to an electronic watch and multichannel analyzer. The measuring arrangement was positioned on the riser, operating under ambient conditions. A better precision was obtained by the center of mass measurements as seen in the comparison of statistical deviations. In applying the RTD method, the mean transit time, variance and asymmetry of the tracer distribution as a function of time were calculated. Experimental uncertainties occurring from tracer injection are avoided by taking the first detector peak as the time reference (t=0). The RTD method allows the further evaluation of the flow pattern. Steady laminar flow and plug-flow can be characterized. | |||||
BibTeX:
@article{Santos2004,
author = {Santos, V.A. and Dantas, C.C.},
title = {Transit time and RTD measurements by radioactive tracer to assess the riser flow pattern},
journal = {Powder Technology},
year = {2004},
volume = {140},
number = {1–2},
pages = {116--121},
url = {http://www.sciencedirect.com/science/article/pii/S0032591004000269}
}
|
|||||
| Saralees, N. | Products, and ratios for a bivariate gamma distribution | 2005 | Applied Mathematics and Computation Vol. 171(1), pp. 581-595 |
article | URL |
| Abstract: We derive the distributions of P = XY and W = X/(X + Y) and the corresponding moment properties when X and Y follow a bivariate gamma distribution. The expressions turn out to involve several special functions. We also provide extensive tabulations of the percentage points associated with the two distributions. These tables—obtained using intensive computing power—will be of use to practitioners of the bivariate gamma distribution. | |||||
BibTeX:
@article{Saralees2005,
author = {Saralees, Nadarajah},
title = {Products, and ratios for a bivariate gamma distribution},
journal = {Applied Mathematics and Computation},
year = {2005},
volume = {171},
number = {1},
pages = {581--595},
url = {http://www.sciencedirect.com/science/article/pii/S0096300305001189}
}
|
|||||
| Sarathai, Y., Koottatep, T. and Morel, A. | Hydraulic characteristics of an anaerobic baffled reactor as onsite wastewater treatment system | 2010 | Journal of Environmental Sciences Vol. 22(9), pp. 1319-1326 |
article | URL |
| Abstract: Abstract The feasibility of using anaerobic baffled reactor (ABR) as onsite wastewater treatment system was discussed. The ABR consisted of one sedimentation chamber and three up-flow chambers in series was experimented under different peak flow factors (PFF of 1 to 6), superficial gas velocities (between 0.6 and 3.1 cm/hr) and hydraulic retention times (HRT) (24, 36 and 48 hr). Residence time distribution (RTD) analyses were carried out to investigate the hydraulic characteristics of the ABR. It was found that the PFF resulted in hydraulic dead space. The dead space did not exceed 13% at PFF of 1, 2 and 4 while there was 2-fold increase (26%) at PFF of 6. Superficial gas velocities did not result in more (biological) dead space. The mixing pattern of ABR tended to be a completely-mixed reactor when PFF increased. Superficial gas velocities did not affect mixing pattern. The effects of PFF on mixing pattern could be minimized by higher HRT (48 hr). The tank-in-series (TIS) model (N = 4) was suitable to describe the hydraulic behaviour of the studied system. The HRT of 48 hr was able to maintain the mixing pattern under different flow patterns, introducing satisfactory hydraulic efficiency. Chemical oxygen demand (COD) and total suspended solids (TSS) removals under all flow patterns were achieved more than 85% and 90%, respectively. The standard deviation of effluent COD and TSS concentration did not exceed 15 mg/L. | |||||
BibTeX:
@article{Sarathai2010,
author = {Sarathai, Yuttachai and Koottatep, Thammarat and Morel, Antoine},
title = {Hydraulic characteristics of an anaerobic baffled reactor as onsite wastewater treatment system},
journal = {Journal of Environmental Sciences},
year = {2010},
volume = {22},
number = {9},
pages = {1319--1326},
url = {http://www.sciencedirect.com/science/article/pii/S1001074209602576}
}
|
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| Saravanathamizhan, R., Paranthaman, R., Balasubramanian, N. and Basha, C.A. | Residence time distribution in continuous stirred tank electrochemical reactor | 2008 | Chemical Engineering Journal Vol. 142(2), pp. 209-216 |
article | URL |
| Abstract: The aim of the present investigation is to study the electrolyte flow characteristics in a continuous stirred tank electrochemical reactor (CSTER) using residence time distribution (RTD). The flow behavior of electrolyte has been experimented using pulse tracer technique and the residence time distribution curves at various operating conditions are critically analyzed. A three-parameter model has been developed to explain the flow characteristic of electrolyte in a continuous stirred tank electrochemical reactor and the model simulations are validated with the experimental observations. | |||||
BibTeX:
@article{Saravanathamizhan2008,
author = {Saravanathamizhan, R. and Paranthaman, R. and Balasubramanian, N. and Basha, C. Ahmed},
title = {Residence time distribution in continuous stirred tank electrochemical reactor},
journal = {Chemical Engineering Journal},
year = {2008},
volume = {142},
number = {2},
pages = {209--216},
url = {http://www.sciencedirect.com/science/article/pii/S1385894708001356}
}
|
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| Savoy, L., Surbeck, H. and Hunkeler, D. | Radon and CO2 as natural tracers to investigate the recharge dynamics of karst aquifers | 2011 | Journal of Hydrology Vol. 406(3-4), pp. 148-157 |
article | URL |
| Abstract: This study investigated the use of radon (222Rn), a radioactive isotope with a half-life of 3.8 days, and CO2 as natural tracers to evaluate the recharge dynamics of karst aquifer under varying hydrological conditions. Dissolved 222Rn and carbon dioxide (CO2) were measured continuously in an underground stream of the Milandre test site, Switzerland. Estimated soil water 222Rn activities were higher than baseflow 222Rn activities, indicating elevated 222Rn production in the soil zone compared to limestone, consistent with a 226Ra enrichment in the soil zone compared to limestone. During small flood events, 222Rn activities did not vary while an immediate increase of the CO2 concentration was observed. During medium and large flood events, an immediate CO2 increase and a delayed 222Rn activity increase to up to 4.9 Bq/L and 11 Bq/L, respectively occurred. The detection of elevated 222Rn activities during medium and large flood events indicate that soil water participates to the flood event. A soil origin of the 222Rn is consistent with its delayed increase compared to discharge reflecting the travel time of 222Rn from the soil to the saturated zone of the system via the epikarst. A three-component mixing model suggested that soil water may contribute 4–6% of the discharge during medium flood events and 25–43% during large flood events. For small flood events, the water must have resided at least 25 days below the soil zone to explain the background 222Rn activities, taking into account the half-life of 222Rn (3.8 days). In contrast to 222Rn, the CO2 increase occurred simultaneously with the discharge increase. This observation as well as the CO2 increase during small flood events, suggests that the elevated CO2 level is not due to the arrival of soil water as for 222Rn. A possible explanation for the CO2 trend is that baseflow water in the stream has lower CO2 levels due to gas loss compared to water stored in low permeability zones. During flood event, the stored water is more rapidly mobilised than during baseflow with less time for gas loss. The study demonstrates that 222Rn and CO2 provides value information on the dynamics of groundwater recharge of karst aquifer, which can be of high interest when evaluating the vulnerability of such systems to contamination. | |||||
BibTeX:
@article{Savoy2011,
author = {Savoy, Ludovic and Surbeck, Heinz and Hunkeler, Daniel},
title = {Radon and CO2 as natural tracers to investigate the recharge dynamics of karst aquifers},
journal = {Journal of Hydrology},
year = {2011},
volume = {406},
number = {3-4},
pages = {148--157},
url = {http://www.sciencedirect.com/science/article/pii/S0022169411003490}
}
|
|||||
| Sawyer, A.H. and Cardenas, M.B. | Hyporheic flow and residence time distributions in heterogeneous cross-bedded sediment | 2009 | Water Resources Research Vol. 45(8), pp. W08406- |
article | URL |
| Abstract: The permeability heterogeneity of cross-bedded sediment increases path lengths of river-groundwater mixing (hyporheic exchange) in riverbeds and modifies the distribution of residence times. For two case studies, we numerically simulated fluid flow and solute transport through immobile bed forms composed of heterogeneous sediment and equivalent homogeneous sediment in order to clarify how cross-bedded permeability structures impact hyporheic exchange. The two permeability fields are from the cross-bedded Massillon Sandstone and modern climbing ripple deposits of the Brazos River (Texas). In both cases, permeability heterogeneity creates long hyporheic exchange paths but only slightly increases the depth of exchange relative to equivalent homogeneous sediment. In the Massillon example, permeability heterogeneity increases the proportion of long hyporheic residence times (>3 days). In the Brazos example, permeability heterogeneity increases the proportion of short residence times (<17 h). We attribute the different responses in residence time distributions to differences in permeability patterns near the sediment-water interface. The tails of residence time distributions extend for tens of years and conform to a power law in both heterogeneous and homogeneous sediment. Current–bed form interactions are responsible for the long tails, as opposed to permeability heterogeneity. | |||||
BibTeX:
@article{Sawyer2009,
author = {Sawyer, Audrey Hucks and Cardenas, M. Bayani},
title = {Hyporheic flow and residence time distributions in heterogeneous cross-bedded sediment},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2009},
volume = {45},
number = {8},
pages = {W08406--},
url = {http://dx.doi.org/10.1029/2008WR007632}
}
|
|||||
| Sayara, T., Sarrà, M. and Sánchez, A. | Effects of compost stability and contaminant concentration on the bioremediation of PAHs-contaminated soil through composting | 2010 | Journal of Hazardous Materials Vol. 179(1-3), pp. 999-1006 |
article | URL |
| Abstract: The objective of this study was to investigate the effect of two factors: the stability degree (0.37–4.55 mg O2 g−1 Organic Matter h−1) of different composts derived from the organic fraction of municipal solid wastes and the concentration of a complex mixture of PAHs including flourene, phenanthrene, anthracene, flouranthene, pyrene and benzo(a)anthracene in the bioremediation of soil. The two factors were systematically studied applying central composite design methodology. The obtained results demonstrated that compost stability degree was particularly important during the first stage of the process. Stable composts enhanced the levels of degradation in soil–compost mixture and a degradation rate of 92% was achieved in this period, but only 40% was degraded with the least stable compost. The PAHs concentration was also important during the process, since the degradation rates increased with the increase in the PAHs concentration. Moreover, all the individual PAHs demonstrated a notable decrease in their concentrations after the incubation period, but pyrene was degraded to lower levels in some treatments compared to others PAHs. | |||||
BibTeX:
@article{Sayara2010,
author = {Sayara, Tahseen and Sarrà, Montserrat and Sánchez, Antoni},
title = {Effects of compost stability and contaminant concentration on the bioremediation of PAHs-contaminated soil through composting},
journal = {Journal of Hazardous Materials},
year = {2010},
volume = {179},
number = {1--3},
pages = {999--1006},
url = {http://www.sciencedirect.com/science/article/pii/S0304389410004103}
}
|
|||||
| Sayara, T., Sarrà, M. and Sánchez, A. | Preliminary screening of co-substrates for bioremediation of pyrene-contaminated soil through composting | 2009 | Journal of Hazardous Materials Vol. 172(2-3), pp. 1695-1698 |
article | URL |
| Abstract: The feasibility of using different organic amendments of different origin and properties in the bioremediation of pyrene-contaminated soil by means of composting has been tested. The selected pyrene concentration was 1 g of pyrene per kg of dry soil. The organic amendments used include: raw organic fraction of municipal solid wastes (OFMSW), industrial compost from OFMSW composting (COFMSW), compost derived from home composting of OFMSW (HCOFMSW), anaerobically digested sludge (ADS), non-digested activated sludge (NDS) and centrifuged non-digested activated sludge (CNDS). The degradation rate was related to the amendment properties that directly affected the composting process. Raw OFMSW was not capable to enhance pyrene degradation in comparison to control, but stable HCOFMSW exhibited the highest removal rate (69%). The amendments stability and the temperatures reached as a consequence influenced the process, and thermophilic temperatures showed an inhibition effect on the microbial activity related to pyrene degradation. Some of the tested wastes need to be further investigated to find inexpensive organic amendments for soil bioremediation. | |||||
BibTeX:
@article{Sayara2009,
author = {Sayara, Tahseen and Sarrà, Montserrat and Sánchez, Antoni},
title = {Preliminary screening of co-substrates for bioremediation of pyrene-contaminated soil through composting},
journal = {Journal of Hazardous Materials},
year = {2009},
volume = {172},
number = {2--3},
pages = {1695--1698},
url = {http://www.sciencedirect.com/science/article/pii/S0304389409012606}
}
|
|||||
| Scanlon, B. | Relationships between groundwater contamination and major-ion chemistry in a karst aquifer | 1990 | Journal of Hydrology Vol. 119(1-4), pp. 271-291 |
article | URL |
| Abstract: Groundwater contamination was examined within a rural setting of the Inner Bluegrass Karst Region of central Kentucky where potential contaminant sources include soil-organic matter, organic and inorganic fertilizer, and septic-tank effluent. To evaluate controls on groundwater contamination, data on nitrate concentrations and indicator bacteria in water from wells and springs were compared with physical and chemical attributes of the groundwater system. Bacterial densities greater than the recommended limit were found in all springs and approximately half of the wells, whereas nitrate concentrations >45 mg l−1 were restricted to 20% of the springs and 10% of the wells. Nitrate concentrations varied markedly in closely spaced wells and springs, which indicates that land use is not the primary control on groundwater contamination. | |||||
BibTeX:
@article{Scanlon1990,
author = {Scanlon, B.R.},
title = {Relationships between groundwater contamination and major-ion chemistry in a karst aquifer},
journal = {Journal of Hydrology},
year = {1990},
volume = {119},
number = {1-4},
pages = {271--291},
url = {http://www.sciencedirect.com/science/article/pii/0022169490900472}
}
|
|||||
| Scanlon, B.R., Mace, R.E., Barrett, M.E. and Smith, B. | Can we simulate regional groundwater flow in a karst system using equivalent porous media models? Case study, Barton Springs Edwards aquifer, USA | 2003 | Journal of Hydrology Vol. 276(1-4), pp. 137-158 |
article | URL |
| Abstract: Various approaches can be used to simulate groundwater flow in karst systems, including equivalent porous media distributed parameter, lumped parameter, and dual porosity approaches, as well as discrete fracture or conduit approaches. The purpose of this study was to evaluate two different equivalent porous media approaches: lumped and distributed parameter, for simulating regional groundwater flow in a karst aquifer and to evaluate the adequacy of these approaches. The models were applied to the Barton Springs Edwards aquifer, Texas. Unique aspects of this study include availability of detailed information on recharge from stream-loss studies and on synoptic water levels, long-term continuous water level monitoring in wells throughout the aquifer, and spring discharge data to compare with simulation results. The MODFLOW code was used for the distributed parameter model. Estimation of hydraulic conductivity distribution was optimized by using a combination of trial and error and automated inverse methods. The lumped parameter model consists of five cells representing each of the watersheds contributing recharge to the aquifer. Transient simulations were conducted using both distributed and lumped parameter models for a 10-yr period (1989–1998). Both distributed and lumped parameter models fairly accurately simulated the temporal variability in spring discharge; therefore, if the objective of the model is to simulate spring discharge, either distributed or lumped parameter approaches can be used. The distributed parameter model generally reproduced the potentiometric surface at different times. The impact of the amount of pumping on a regional scale on spring discharge can be evaluated using a lumped parameter model; however, more detailed evaluation of the effect of pumping on groundwater levels and spring discharge requires a distributed parameter modeling approach. Sensitivity analyses indicated that spring discharge was much more sensitive to variations in recharge than pumpage, indicating that aquifer management should consider enhanced recharge, in addition to conservation measures, to maintain spring flow. This study shows the ability of equivalent porous media models to simulate regional groundwater flow in a highly karstified aquifer, which is important for water resources and groundwater management. | |||||
BibTeX:
@article{Scanlon2003,
author = {Scanlon, Bridget R and Mace, Robert E and Barrett, Michael E and Smith, Brian},
title = {Can we simulate regional groundwater flow in a karst system using equivalent porous media models? Case study, Barton Springs Edwards aquifer, USA},
journal = {Journal of Hydrology},
year = {2003},
volume = {276},
number = {1-4},
pages = {137--158},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403000647}
}
|
|||||
| Schaefli, B., Talamba, D.B. and Musy, A. | Quantifying hydrological modeling errors through a mixture of normal distributions | 2007 | Journal of Hydrology Vol. 332(3-4), pp. 303-315 |
article | URL |
| Abstract: Summary Bayesian inference of posterior parameter distributions has become widely used in hydrological modeling to estimate the associated modeling uncertainty. The classical underlying statistical model assumes a Gaussian modeling error with zero mean and a given variance. For hydrological modeling residuals, this assumption however rarely holds; the present paper proposes the use of a mixture of normal distributions as a simple solution to overcome this problem in parameter inference studies. The hydrological and the statistical model parameters are inferred using a Markov chain Monte Carlo method known as the Metropolis–Hastings algorithm. The proposed methodology is illustrated for a rainfall-runoff model applied to a highly glacierized alpine catchment. The associated total modeling error is modeled using a mixture of two normal distributions, the mixture components referring respectively to the low and the high flow discharge regime. The obtained results show that the use of a finite mixture model constitutes a promising solution to model hydrological modeling errors in parameter inference studies and could give additional insights into the model behavior. | |||||
BibTeX:
@article{Schaefli2007,
author = {Schaefli, Bettina and Talamba, Daniela Balin and Musy, André},
title = {Quantifying hydrological modeling errors through a mixture of normal distributions},
journal = {Journal of Hydrology},
year = {2007},
volume = {332},
number = {3-4},
pages = {303--315},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406003635}
}
|
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| Schäfer, D., Schäfer, W. and Kinzelbach, W. | Simulation of reactive processes related to biodegradation in aquifers: 2. Model application to a column study on organic carbon degradation | 1998 | Journal of Contaminant Hydrology Vol. 31(1-2), pp. 187-209 |
article | URL |
| Abstract: The reactive transport model TBC (Transport, Biochemistry, and Chemistry) was applied to a laboratory column study on microbial organic carbon degradation by von Gunten and Zobrist [von Gunten, U., Zobrist, J., 1993. Biogeochemical changes in groundwater-infiltration systems: column studies, Geochim. Cosmochim. Acta, 57 (1993) 3895–3906]. Five microbial groups were considered in the model: facultatively aerobic bacteria or denitrifiers, fermenters, and sulfate-, manganese-, and iron-reducers. By simulating their growth, subsequent consumption of organic carbon and electron acceptors, and production of metabolic products, it was possible to reproduce the observed transient concentration changes of the reactive species. Inhibition and availability of electron acceptors and/or organic carbon governed the transient growth behaviour of the different microbial groups. With the model the much slower growth of sulfate reducers compared to that of facultatively aerobic or denitrifying bacteria could be reproduced. To be able to reproduce the observed spatial sequence of different microbial groups a maximum microbial capacity had to be introduced. It restricts total microbial density in the porous material. Without this restriction the excessive organic substrate supply would have caused the microbial activity to be exclusively located at the immediate vicinity of the column inlet. The distribution of facultatively aerobic or denitrifying organisms and sulfate reducers in the column was determined by the exchange coefficient for the electron acceptor between pore water and biophase. The exchange of sulfate seemed to be much slower than that of O2 and NO3−. The growth of manganese and iron reducers was limited by the availability of the solid electron acceptors Fe(III) and Mn(IV). The testing of two hypotheses concerning the interaction of iron and sulfide in the column suggests that the formation of elemental sulfur during abiotic reductive iron dissolution is an important sink for sulfide. The TBC model has proven to be complex enough to grasp the important reactive processes. The model provides a temporally and spatially resolved quantification of microbial degradation activity. It has shown to be a useful tool in testing alternative hypotheses on processes which could not directly be identified from the observed concentration data. | |||||
BibTeX:
@article{Schaefer1998,
author = {Schäfer, Dirk and Schäfer, Wolfgang and Kinzelbach, Wolfgang},
title = {Simulation of reactive processes related to biodegradation in aquifers: 2. Model application to a column study on organic carbon degradation},
journal = {Journal of Contaminant Hydrology},
year = {1998},
volume = {31},
number = {1-2},
pages = {187--209},
url = {http://www.sciencedirect.com/science/article/pii/S0169772297000612}
}
|
|||||
| Schäfer, T., Huber, F., Seher, H., Missana, T., Alonso, U., Kumke, M., Eidner, S., Claret, F. and Enzmann, F. | Nanoparticles and their influence on radionuclide mobility in deep geological formations | 2012 | Applied Geochemistry Vol. 27(2)Fundamental processes of radionuclide migration in the geosphere, pp. 390-403 |
article | URL |
| Abstract: This article gives an overview of the current status of knowledge concerning the role of nanoparticles (inorganic and organic) in deep geological host rocks and the potential influence of these nanoparticles on radionuclide migration in far-field systems. The manuscript is not intended to be a full review paper or overview paper concerning nanoparticles, here the intention is to refer to recent publications but to highlight the progress made in the 6th framework project IP FUNMIG (Fundamental processes of radionuclide migration) and the open literature over the past 5 a concerning the process understanding of nanoparticle related issues in the three host rock formations investigated, namely: claystones, crystalline rocks and salt rock overburden. The results show inter alia that the inorganic nanoparticle concentration in deep groundwaters of advection dominated systems rarely exceeds 1 mg L−1 and is expected to be in the ng L−1 range in diffusion controlled systems. For organic nanoparticles DOC concentrations up to tens of milligrams in diffusion-controlled indurated clays with molecular sizes mostly <500 Da have been found. Fulvic acid type organics have been identified in crystalline environments and plastic Clay formations (Boom Clay) with molecular sizes ⩽300 kDa. Additional sources of inorganic nanoparticles from the repository near-field (compacted bentonite) were identified and the initial erosion rates were determined. The results indicate under stagnant conditions ∼38 mg cm−2 a−1 for bi-distilled water, ∼20 mg cm−2 a−1 for glacial melt water (Grimsel groundwater) and very low rates ∼0.02 mg cm−2 a−1 for 5 mM CaCl2 contact water. The low critical coagulation concentration (CCC) indicative for purely diffusion controlled coagulation of 1 mM L−1 Ca2+ found in bentonite nanoparticle stability analysis matches the low nanoparticle mobilization from compacted bentonite found in these systems. | |||||
BibTeX:
@article{Schaefer2012,
author = {Schäfer, Thorsten and Huber, Florian and Seher, Holger and Missana, Tiziana and Alonso, Ursula and Kumke, Michael and Eidner, Sascha and Claret, Francis and Enzmann, Frieder},
title = {Nanoparticles and their influence on radionuclide mobility in deep geological formations},
booktitle = {Fundamental processes of radionuclide migration in the geosphere},
journal = {Applied Geochemistry},
year = {2012},
volume = {27},
number = {2},
pages = {390--403},
url = {http://www.sciencedirect.com/science/article/pii/S0883292711003994}
}
|
|||||
| Schäfer, W. and Kinzelbach, W. | Transport of reactive species in heterogeneous porous media | 1996 | Journal of Hydrology Vol. 183(1-2), pp. 151-168 |
article | URL |
| Abstract: In order to be able to extrapolate reactive pollutant transport behaviour from the laboratory experiment in the aquifer field scale it is necessary to combine the deterministic laboratory results with the stochastics of the field situation to produce effective macroscopic properties. For simple linear adsorption standard methods can be applied to arrive at effective retardation and dispersion parameters. Effective time-scales for chemical reactions such as adsorption and degradation may no longer be determined by the time-scales of processes on the molecular scale only but also by rate-limiting steps arising from the variable accessibility of reactive parts of the medium. For a bacterial degradation reaction it is suggested that an exchange coefficient between mobile water and reactive phase can parametrize subscale processes. The coefficient depends on the degree of heterogeneity of the medium. | |||||
BibTeX:
@article{Schaefer1996,
author = {Schäfer, W. and Kinzelbach, W.K.H.},
title = {Transport of reactive species in heterogeneous porous media},
journal = {Journal of Hydrology},
year = {1996},
volume = {183},
number = {1-2},
pages = {151--168},
url = {http://www.sciencedirect.com/science/article/pii/S0022169496800394}
}
|
|||||
| Scheibe, T. and Yabusaki, S. | Scaling of flow and transport behavior in heterogeneous groundwater systems | 1998 | Advances in Water Resources Vol. 22(3), pp. 223-238 |
article | URL |
| Abstract: Three-dimensional numerical simulations using a detailed synthetic hydraulic conductivity field developed from geological considerations provide insight into the scaling of subsurface flow and transport processes. Flow and advective transport in the highly resolved heterogeneous field were modeled using massively parallel computers, providing a realistic baseline for evaluation of the impacts of parameter scaling. Upscaling of hydraulic conductivity was performed at a variety of scales using a flexible power law averaging technique. A series of tests were performed to determine the effects of varying the scaling exponent on a number of metrics of flow and transport behavior. Flow and transport simulation on high-performance computers and three-dimensional scientific visualization combine to form a powerful tool for gaining insight into the behavior of complex heterogeneous systems. | |||||
BibTeX:
@article{Scheibe1998,
author = {Scheibe, Timothy and Yabusaki, Steven},
title = {Scaling of flow and transport behavior in heterogeneous groundwater systems},
journal = {Advances in Water Resources},
year = {1998},
volume = {22},
number = {3},
pages = {223--238},
url = {http://www.sciencedirect.com/science/article/pii/S0309170898000141}
}
|
|||||
| Scheibe, T.D., Dong, H. and Xie, Y. | Correlation between bacterial attachment rate coefficients and hydraulic conductivity and its effect on field-scale bacterial transport | 2007 | Advances in Water Resources Vol. 30(6-7)Biological processes in porous media: From the pore scale to the field, pp. 1571-1582 |
article | URL |
| Abstract: It has been widely observed in field experiments that the apparent rate of bacterial attachment, particularly as parameterized by the collision efficiency in filtration-based models, decreases with transport distance (i.e., exhibits scale-dependency). This effect has previously been attributed to microbial heterogeneity; that is, variability in cell–surface properties within a single monoclonal population. We demonstrate that this effect could also be interpreted as a field-scale manifestation of local-scale correlation between physical heterogeneity (hydraulic conductivity variability) and reaction heterogeneity (attachment rate coefficient variability). A field-scale model of bacterial transport developed for the South Oyster field research site located near Oyster, Virginia, and observations from field experiments performed at that site, are used as the basis for this study. Three-dimensional Monte Carlo simulations of bacterial transport were performed under four alternative scenarios: (1) homogeneous hydraulic conductivity (K) and attachment rate coefficient (Kf); (2) heterogeneous K, homogeneous Kf; (3) heterogeneous K and Kf with local correlation based on empirical and theoretical relationships; and (4) heterogeneous K and Kf without local correlation. The results of the 3D simulations were analyzed using 1D model approximations following conventional methods of field data analysis. An apparent decrease with transport distance of effective collision efficiency was observed only in the case where the local properties were both heterogeneous and correlated. This effect was observed despite the fact that the local collision efficiency was specified as a constant in the 3D model, and can therefore be interpreted as a scale effect associated with the local correlated heterogeneity as manifested at the field scale. | |||||
BibTeX:
@article{Scheibe2007,
author = {Scheibe, Timothy D. and Dong, Hailiang and Xie, YuLong},
title = {Correlation between bacterial attachment rate coefficients and hydraulic conductivity and its effect on field-scale bacterial transport},
booktitle = {Biological processes in porous media: From the pore scale to the field},
journal = {Advances in Water Resources},
year = {2007},
volume = {30},
number = {6--7},
pages = {1571--1582},
url = {http://www.sciencedirect.com/science/article/pii/S0309170806001357}
}
|
|||||
| Scherr, F.F., Sarmah, A.K., Di, H.J. and Cameron, K.C. | Modeling Degradation and Metabolite Formation Kinetics of Estrone-3-sulfate in Agricultural Soils | 2008 | Environmental Science & Technology Vol. 42(22), pp. 8388-8394 |
article | DOI URL |
| Abstract: Data from microcosm studies of estrone-3-sulfate aerobic degradation in pasture soils is used to derive degradation end-points for parent compound and metabolite, testing two kinetic models. Data from microcosm studies of estrone-3-sulfate aerobic degradation in pasture soils is used to derive degradation end-points for parent compound and metabolite, testing two kinetic models. |
|||||
BibTeX:
@article{Scherr2008,
author = {Scherr, Frank F. and Sarmah, Ajit K. and Di, Hong J. and Cameron, Keith C.},
title = {Modeling Degradation and Metabolite Formation Kinetics of Estrone-3-sulfate in Agricultural Soils},
journal = {Environmental Science & Technology},
publisher = {American Chemical Society},
year = {2008},
volume = {42},
number = {22},
pages = {8388--8394},
url = {http://dx.doi.org/10.1021/es801850a},
doi = {http://dx.doi.org/10.1021/es801850a}
}
|
|||||
| Schijven, J.F., Hassanizadeh, S.M. and de Bruin, R.H. | Two-site kinetic modeling of bacteriophages transport through columns of saturated dune sand | 2002 | Journal of Contaminant Hydrology Vol. 57(3-4), pp. 259-279 |
article | URL |
| Abstract: Breakthrough curves, on a semi-log scale, from tests in porous media with block-input of viruses, bacteria, protozoa and colloidal particles often exhibit a typical skewness: a rather slowly rising limb and a smooth transition of a declining limb to a very long tail. One-site kinetic models fail to fit the rising and declining limbs together with the tail satisfactorily. Inclusion of an equilibrium adsorption site does not seem to improve simulation results. This was encountered in the simulation of breakthrough curves from a recent field study on the removal of bacteriophages MS2 and PRD1 by passage through dune sand. In the present study, results of laboratory experiments for the study of this issue are presented. Breakthrough curves of salt and bacteriophages MS2, PRD1, and φX174 in 1D column experiments have been measured. One- and two-site kinetic models have been applied to fit and predict breakthrough curves from column experiments. The two-site model fitted all breakthrough curves very satisfactorily, accounting for the skewness of the rising limb as well as for the smooth transition of the declining limb to the tail of the breakthrough curve. The one-site model does not follow the curvature of the breakthrough tail, leading to an overestimation of the inactivation rate coefficient for attached viruses. Interaction with kinetic site 1 is characterized by relatively fast attachment and slow detachment, whereas attachment to and detachment from kinetic site 2 is fast. Inactivation of viruses and interaction with kinetic site 2 provide only a minor contribution to removal. Virus removal is mainly determined by the attachment to site 1. Bacteriophage φX174 attached more than MS2 and PRD1, which can be explained by the greater electrostatic repulsion that MS2 and PRD1 experience compared to the less negatively charged φX174. | |||||
BibTeX:
@article{Schijven2002,
author = {Schijven, Jack F. and Hassanizadeh, S. Majid and de Bruin, Ria H.A.M.},
title = {Two-site kinetic modeling of bacteriophages transport through columns of saturated dune sand},
journal = {Journal of Contaminant Hydrology},
year = {2002},
volume = {57},
number = {3-4},
pages = {259--279},
url = {http://www.sciencedirect.com/science/article/pii/S0169772201002157}
}
|
|||||
| Schilling, K.E. and Helmers, M. | Tile drainage as karst: Conduit flow and diffuse flow in a tile-drained watershed | 2008 | Journal of Hydrology Vol. 349(3-4), pp. 291-301 |
article | URL |
| Abstract: Summary The similarity of tiled-drained watersheds to karst drainage basins can be used to improve understanding of watershed-scale nutrient losses from subsurface tile drainage networks. In this study, short-term variations in discharge and chemistry were examined from a tile outlet collecting subsurface tile flow from a 963 ha agricultural watershed. Study objectives were to apply analytical techniques from karst springs to tile discharge to evaluate water sources and estimate the loads of agricultural pollutants discharged from the tile with conduit, intermediate and diffuse flow regimes. A two-member mixing model using nitrate, chloride and specific conductance was used to distinguish rainwater versus groundwater inputs. Results indicated that groundwater comprised 75% of the discharge for a three-day storm period and rainwater was primarily concentrated during the hydrograph peak. A contrasting pattern of solute concentrations and export loads was observed in tile flow. During base flow periods, tile flow consisted of diffuse flow from groundwater sources and contained elevated levels of nitrate, chloride and specific conductance. During storm events, suspended solids and pollutants adhered to soil surfaces (phosphorus, ammonium and organic nitrogen) were concentrated and discharged during the rapid, conduit flow portion of the hydrograph. During a three-day period, conduit flow occurred for 5.6% of the time but accounted for 16.5% of the total flow. Nitrate and chloride were delivered primarily with diffuse flow (more than 70%), whereas 80–94% of total suspended sediment, phosphorus and ammonium were exported with conduit and intermediate flow regimes. Understanding the water sources contributing to tile drainage and the manner by which pollutant discharge occurs from these systems (conduit, intermediate or diffuse flow) may be useful for designing, implementing and evaluating non-point source reduction strategies in tile-drained landscapes. | |||||
BibTeX:
@article{Schilling2008,
author = {Schilling, Keith E. and Helmers, Matthew},
title = {Tile drainage as karst: Conduit flow and diffuse flow in a tile-drained watershed},
journal = {Journal of Hydrology},
year = {2008},
volume = {349},
number = {3-4},
pages = {291--301},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407006713}
}
|
|||||
| Schmidt, L.D. | The Engineering of Chemical Reactions [BibTeX] |
1998 | , pp. - | book | |
BibTeX:
@book{Schmidt1998,
author = {Schmidt, Lanny D.},
title = {The Engineering of Chemical Reactions},
publisher = {Oxford University Press},
year = {1998},
pages = {--}
}
|
|||||
| Scholes, L., Shutes, R., Revitt, D., Forshaw, M. and Purchase, D. | The treatment of metals in urban runoff by constructed wetlands | 1998 | Science of The Total Environment Vol. 214(1-3), pp. 211-219 |
article | URL |
| Abstract: The use of constructed wetlands for the treatment of domestic wastewater is now well established in the UK and their ability to treat a range of industrial wastewaters is now being investigated. However, their ability to treat urban runoff is relatively untested despite the fact that this application could have important environmental and operational benefits, in both industrial and developing countries. In response to this, the Environment Agency have developed constructed wetland treatment systems at two selected sites in south-east England, both of which receive large volumes of urban runoff. The sites are located at Brentwood and Dagenham and were completed in April 1995. Water and sediment samples have been collected at bi-monthly intervals at each site since October 1995 and analysed for a range of parameters including the total concentrations of six trace metals — cadmium, copper, nickel, chromium, lead and zinc. Similar analysis has been carried out on plants collected from both sites in the spring of 1997. Results show a wide variation in pollutant levels, reflecting the highly variable quality characteristics of urban runoff. Mean removal efficiencies of metals in the water vary between sites in dry weather conditions, with maximum removal efficiencies being recorded at the Dagenham wetland during a storm event. Analysis of plant tissues indicates that the reeds bioaccumulate trace metals and that metal uptake is greatest in the roots. Sediment metal concentrations are typical of a site receiving urban runoff. At both sites the highest sediment concentrations are consistently recorded in samples collected from the settlement tanks. | |||||
BibTeX:
@article{Scholes1998,
author = {Scholes, L and Shutes, R.B.E and Revitt, D.M and Forshaw, M and Purchase, D},
title = {The treatment of metals in urban runoff by constructed wetlands},
journal = {Science of The Total Environment},
year = {1998},
volume = {214},
number = {1--3},
pages = {211--219},
url = {http://www.sciencedirect.com/science/article/pii/S0048969798000722}
}
|
|||||
| Scholz, M. | Case study: design, operation, maintenance and water quality management of sustainable storm water ponds for roof runoff | 2004 | Bioresource Technology Vol. 95(3), pp. 269-279 |
article | URL |
| Abstract: The purpose of this case study was to optimise design, operation and maintenance guidelines, and to assess the water treatment potential of a storm water pond system after 15 months of operation. The system was based on a combined silt trap, attenuation pond and vegetated infiltration basin. This combination was used as the basis for construction of a roof water runoff system from a single domestic property. United Kingdom Building Research Establishment and Construction Industry Research and Information Association, and German Association for Water, Wastewater and Waste design guidelines were tested. These design guidelines failed because they did not consider local conditions. The infiltration function for the infiltration basin was logarithmic. Algal control techniques were successfully applied, and treatment of rainwater runoff from roofs was found to be largely unnecessary for recycling (e.g., watering plants). However, seasonal and diurnal variations of biochemical oxygen demand, dissolved oxygen and pH were recorded. | |||||
BibTeX:
@article{Scholz2004,
author = {Scholz, Miklas},
title = {Case study: design, operation, maintenance and water quality management of sustainable storm water ponds for roof runoff},
journal = {Bioresource Technology},
year = {2004},
volume = {95},
number = {3},
pages = {269--279},
url = {http://www.sciencedirect.com/science/article/pii/S0960852404000823}
}
|
|||||
| Scholz, M., Harrington, R., Carroll, P. and Mustafa, A. | Monitoring of nutrient removal within integrated constructed wetlands (ICW) | 2010 | Desalination Vol. 250(1), pp. 356-360 |
article | URL |
| Abstract: The aim of the project was to assess the nutrient removal within integrated constructed wetlands (ICW). The study was based on twelve free-water surface ICW treating farmyard runoff in Ireland. | |||||
BibTeX:
@article{Scholz2010,
author = {Scholz, Miklas and Harrington, Rory and Carroll, Paul and Mustafa, Atif},
title = {Monitoring of nutrient removal within integrated constructed wetlands (ICW)},
journal = {Desalination},
year = {2010},
volume = {250},
number = {1},
pages = {356--360},
url = {http://www.sciencedirect.com/science/article/pii/S0011916409010881}
}
|
|||||
| Schroth, M., Istok, J. and Haggerty, R. | In situ evaluation of solute retardation using single-well push–pull tests | 2000 | Advances in Water Resources Vol. 24(1), pp. 105-117 |
article | URL |
| Abstract: More efficient methods are needed for the in situ evaluation of solute sorption to aquifer sediments. The objective of this study was to develop a simplified method for estimating retardation factors for injected solutes from “push–pull” test extraction phase breakthrough curves (BTCs). Sensitivity analyses based on numerical simulations were used to evaluate the method performance for a variety of test conditions. Simulations were conducted for varying retardation factors, aquifer parameters and injection phase durations, for tests performed under nonideal transport conditions such as nonlinear equilibrium and linear nonequilibrium sorption, and for a test performed in a physically heterogeneous aquifer. Predicted retardation factors showed errors ⩽14% in tests performed under ideal transport conditions (physically homogeneous aquifer with spatially uniform dispersivity that does not vary from solute to solute, spatially uniform linear equilibrium sorption). The method performed more poorly for solutes with large retardation factors (R>20) and for tests conducted under nonideal transport conditions, and is expected to perform poorly in aquifers with highly heterogeneous sorption. In an example application, we used the method to estimate the distribution coefficient for 85Sr using data from a field test performed by Pickens JF, Jackson RE, Inch KJ, Merritt WF. (Water Resour Res 1981;17:529–44). Reasonable agreement was found between distribution coefficients obtained using the simplified method of estimation and those obtained by Pickens et al. (1981). | |||||
BibTeX:
@article{Schroth2000,
author = {Schroth, M.H and Istok, J.D and Haggerty, R},
title = {In situ evaluation of solute retardation using single-well push–pull tests},
journal = {Advances in Water Resources},
year = {2000},
volume = {24},
number = {1},
pages = {105--117},
url = {http://www.sciencedirect.com/science/article/pii/S0309170800000233}
}
|
|||||
| Schuller, P., Ellies, A. and Kirchner, G. | Vertical migration of fallout 137Cs in agricultural soils from Southern Chile | 1997 | Science of The Total Environment Vol. 193(3), pp. 197-205 |
article | URL |
| Abstract: Total inventories and depth distributions of atomic weapons testing fallout 137Cs were determined at four sites in Chile. Cesium inventories are always higher than previously estimated for the Southern Hemisphere and depend on annual rainfall. From the measured depth distributions cesium migration rates of < 0.5 cm/year were calculated. Modeling the 137Cs transport by the convection-dispersion equation yielded a better accordance with the measured depth distributions than the application of a compartmental model. | |||||
BibTeX:
@article{Schuller1997,
author = {Schuller, Paulina and Ellies, Achim and Kirchner, Gerald},
title = {Vertical migration of fallout 137Cs in agricultural soils from Southern Chile},
journal = {Science of The Total Environment},
year = {1997},
volume = {193},
number = {3},
pages = {197--205},
url = {http://www.sciencedirect.com/science/article/pii/S0048969796053387}
}
|
|||||
| Schwarz, K., Gocht, T. and Grathwohl, P. | Transport of polycyclic aromatic hydrocarbons in highly vulnerable karst systems | 2011 | Environmental Pollution Vol. 159(1), pp. 133-139 |
article | URL |
| Abstract: Fluxes of polycyclic aromatic hydrocarbons (PAHs) were investigated along the route of transport in a south German karst system. Atmospheric deposition, seepage water in caves and spring water at the outlet of the catchment were monitored continuously over 1.5 years allowing the establishment of an input/output mass balance at the catchment scale. The results reveal that, even in the highly vulnerable karst catchment, PAHs are effectively retained in the soils. Only during high discharge events, such as snowmelt in spring, increasing PAH concentrations at the outlet of the catchment indicates a mobilization of the pollutants. These events are typically correlated with increasing particle concentrations. Based on our results, we conclude that particle-facilitated transport is the dominating cause of PAH mobilization. In summary, PAHs accumulate over time in soils and only occasionally high discharge events cause a short concentration pulse to be flushed through the karst system. | |||||
BibTeX:
@article{Schwarz2011a,
author = {Schwarz, Kerstin and Gocht, Tilman and Grathwohl, Peter},
title = {Transport of polycyclic aromatic hydrocarbons in highly vulnerable karst systems},
journal = {Environmental Pollution},
year = {2011},
volume = {159},
number = {1},
pages = {133--139},
url = {http://www.sciencedirect.com/science/article/pii/S0269749110004318}
}
|
|||||
| Schwientek, M., Maloszewski, P. and Einsiedl, F. | Effect of the unsaturated zone thickness on the distribution of water mean transit times in a porous aquifer | 2009 | Journal of Hydrology Vol. 373(3-4), pp. 516-526 |
article | URL |
| Abstract: Summary The mean transit time of groundwater is commonly expected to increase gradually with increasing depth below water table. The present study provides evidence that the theoretical distribution of transit times may be significantly altered depending on the thickness of the unsaturated zone. An unconfined porous groundwater system formed by Tertiary sediments (Test Field Scheyern close to Munich in southern Germany) is overlain by an unsaturated zone with variable thickness between 4 and 60 m. Between 1992 and 2007 the groundwater system has been repeatedly sampled for tritium contents at different depths using two high-resolved wells. Modelled tritium concentrations by using a lumped parameter approach yielded depth profiles of mean transit times of tracer. In one well the profile was characterized by two local transit time maxima, each of approximately 100 years. A moving particle approach (MPA) developed in this study was used on the streamlines between the recharge zones linked to different sampling depths in the well. This suggested that the observed transit time in the profile was mainly governed by variable travel distances of the tracer through the unsaturated zone at the points of recharge. This finding was confirmed at a second multi-level well of the test site. The lumped parameter modelling of chlorofluorocarbon data yielded lower transit times as compared to those obtained from tritium data. This effect was explained by the different behaviour of tritium and chlorofluorocarbons in the unsaturated zone. The study clearly shows that the impact of a variable thickness of the unsaturated zone may overweigh the effect of local heterogeneities. Such transit time distributions of water in porous aquifers as observed in the present study can only be achieved with the help of environmental tracer data. | |||||
BibTeX:
@article{Schwientek2009,
author = {Schwientek, M. and Maloszewski, P. and Einsiedl, F.},
title = {Effect of the unsaturated zone thickness on the distribution of water mean transit times in a porous aquifer},
journal = {Journal of Hydrology},
year = {2009},
volume = {373},
number = {3-4},
pages = {516--526},
url = {http://www.sciencedirect.com/science/article/pii/S0022169409003151}
}
|
|||||
| Seagren, E.A., Rittmann, B.E. and Valocchi, A.J. | An experimental investigation of NAPL pool dissolution enhancement by flushing | 1999 | Journal of Contaminant Hydrology Vol. 37(1-2), pp. 111-137 |
article | URL |
| Abstract: Experiments coupled with mathematical modeling are used to further elucidate the quantification of NAPL pool dissolution and its enhancement by water flushing. The experiments were performed using glass bead-packed column reactors with small pools of neat toluene or a toluene in dodecane mixture (toluene mole fraction, Xtol≈0.02 or 0.09). Experimental quasi-steady-state toluene dissolution fluxes were determined by a mass-balance approach. The results of these experiments are used to quantify the impact of flushing on the NAPL pool dissolution flux, J, for wide ranges of two of the key controlling parameters—equilibrium concentration, CS, and average pore water velocity, vx. In addition, the experimental dissolution flux data are used to evaluate predictions made using independently obtained model parameters and analytical mathematical models incorporating the two basic approaches used for mathematically describing the interphase distribution of NAPLs: the local equilibrium (LE) approach; and the mass transfer limited, or nonequilibrium (NE) approach. The data from the experiments with a neat toluene pool demonstrate the expected trend of increasing J as vx increased from approximately 2 to 30 m/day. The LE model and the NE model with an average mass transfer coefficient, kl=4.76 m/day, were able to describe the neat toluene pool data for vx<18 m/day reasonably well. However, for vx>18 m/day, the NE model with kl=4.76 m/day provides a better description of the data, suggesting that the equilibrium boundary condition may become invalid for very high velocities. The experiments with the binary toluene in dodecane pools also show the expected trend of increasing J with increasing vx. The LE model describes the binary pool data reasonably well for the entire range of vx studied (approximately 0.1 to 10 m/day), and the NE model predictions with the average kl=4.76 m/day determined in the neat-pool studies do not deviate significantly from the LE model in this vx range, although small deviations occur for >10 m/day. | |||||
BibTeX:
@article{Seagren1999,
author = {Seagren, Eric A. and Rittmann, Bruce E. and Valocchi, Albert J.},
title = {An experimental investigation of NAPL pool dissolution enhancement by flushing},
journal = {Journal of Contaminant Hydrology},
year = {1999},
volume = {37},
number = {1-2},
pages = {111--137},
url = {http://www.sciencedirect.com/science/article/pii/S0169772298001570}
}
|
|||||
| Seely, J.F., Birkes, D. and Lee, Y. | Characterizing Sums of Squares by Their Distributions | 1997 | The American Statistician Vol. 51(1), pp. 55-58 |
article | URL |
| Abstract: In a linear model under normality it is shown that the error sum of squares is characterized by its distribution. Two proofs are presented, one using the almost-sure uniqueness of uniformly minimum variance unbiased estimators and the other using linear algebra. Two illustrations of how this characterization can be used are given. | |||||
BibTeX:
@article{Seely1997a,
author = {Seely, Justus F. and Birkes, David and Lee, Youngjo},
title = {Characterizing Sums of Squares by Their Distributions},
journal = {The American Statistician},
publisher = {American Statistical Association},
year = {1997},
volume = {51},
number = {1},
pages = {55--58},
url = {http://www.jstor.org/stable/2684696}
}
|
|||||
| Sefidpour, A. and Bouguila, N. | Spatial color image segmentation based on finite non-Gaussian mixture models | 2012 | Expert Systems with Applications Vol. 39(10), pp. 8993-9001 |
article | URL |
| Abstract: Finite mixture models are one of the most widely and commonly used probabilistic techniques for image segmentation. Although the most well known and commonly used distribution when considering mixture models is the Gaussian, it is certainly not the best approximation for image segmentation and other related image processing problems. In this paper, we propose and investigate the use of several other mixture models based namely on Dirichlet, generalized Dirichlet and Beta–Liouville distributions, which offer more flexibility in data modeling, for image segmentation. A maximum likelihood (ML) based algorithm is applied for estimating the resulted segmentation model’s parameters. Spatial information is also employed for figuring out the number of regions in an image and several color spaces are investigated and compared. The experimental results show that the proposed segmentation framework yields good overall performance, on various color scenes, that is better than comparable techniques. | |||||
BibTeX:
@article{Sefidpour2012,
author = {Sefidpour, Ali and Bouguila, Nizar},
title = {Spatial color image segmentation based on finite non-Gaussian mixture models},
journal = {Expert Systems with Applications},
year = {2012},
volume = {39},
number = {10},
pages = {8993--9001},
url = {http://www.sciencedirect.com/science/article/pii/S0957417412002680}
}
|
|||||
| Seifert, D. and Engesgaard, P. | Use of tracer tests to investigate changes in flow and transport properties due to bioclogging of porous media | 2007 | Journal of Contaminant Hydrology Vol. 93(1-4), pp. 58-71 |
article | URL |
| Abstract: Tracer tests were conducted in three laboratory columns to study changes in the hydraulic properties of a porous medium due to bioclogging. About 30 breakthrough curves (BTCs) for each column were obtained. The BTCs were analyzed using analytical equilibrium and dual-porosity models, and estimates of the hydrodynamic dispersion and mass transfer coefficients were obtained by curve fitting. The change in transport properties developed in three stages: an initial phase (I) with no significant changes in transport properties, phase II with growth of biomass near the inlet of the columns causing changes in dispersivity, and phase III with added growth of micro-colonies deeper in the columns causing mass transfer of solutes from the water phase to the biophase. Tracer transport changed from being uniform to more non-uniform with increase in mass transfer of the tracer between the mobile phase and the immobile biomass. An increase in the bulk dispersivity value of up to one order of magnitude was observed. Numerical simulations suggest that local dispersivity values may be as much as 40 times higher in the more severe clogged areas inside the column. The bulk hydraulic conductivities of the columns decreased by up to three orders of magnitude. The hydraulic conductivity and dispersivity parameters were almost recovered after disinfection of the columns. Different models relating the changes of the hydraulic conductivity to the changes in the mobile porosity due to bioclogging were reviewed, and the micro-colony relation of Thullner et al. [Thullner, M., Zeyer, J., Kinzelbach, W., 2002. Influence of microbial growth on hydraulic properties of pore networks, Transport in Porous Media, 49, 99–122.] was found to best describe the relation between the bulk hydraulic parameters. | |||||
BibTeX:
@article{Seifert2007,
author = {Seifert, Dorte and Engesgaard, Peter},
title = {Use of tracer tests to investigate changes in flow and transport properties due to bioclogging of porous media},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {93},
number = {1-4},
pages = {58--71},
url = {http://www.sciencedirect.com/science/article/pii/S0169772207000204}
}
|
|||||
| Semple, K.T., Reid, B.J. and Fermor, T.R. | Impact of composting strategies on the treatment of soils contaminated with organic pollutants | 2001 | Environmental Pollution Vol. 112(2), pp. 269-283 |
article | URL |
| Abstract: Chemical pollution of the environment has become a major source of concern. Studies on degradation of organic compounds have shown that some microorganisms are extremely versatile at catabolizing recalcitrant molecules. By harnessing this catabolic potential, it is possible to bioremediate some chemically contaminated environmental systems. Composting matrices and composts are rich sources of xenobiotic-degrading microorganisms including bacteria, actinomycetes and lignolytic fungi, which can degrade pollutants to innocuous compounds such as carbon dioxide and water. These microorganisms can also biotransform pollutants into less toxic substances and/or lock up pollutants within the organic matrix, thereby reducing pollutant bioavailability. The success or failure of a composting/compost remediation strategy depends however on a number of factors, the most important of which are pollutant bioavailability and biodegradability. This review discusses the interactions of pollutants with soils; look critically at the clean up of soils contaminated with a variety of pollutants using various composting strategies and assess the feasibility of using composting technologies to bioremediate contaminated soil. | |||||
BibTeX:
@article{Semple2001,
author = {Semple, K. T. and Reid, B. J. and Fermor, T. R.},
title = {Impact of composting strategies on the treatment of soils contaminated with organic pollutants},
journal = {Environmental Pollution},
year = {2001},
volume = {112},
number = {2},
pages = {269--283},
url = {http://www.sciencedirect.com/science/article/pii/S0269749100000993}
}
|
|||||
| Semyon V., T. | Numerical solution of problems on unbounded domains. A review | 1998 | Applied Numerical Mathematics Vol. 27(4)Special Issue on Absorbing Boundary Conditions, pp. 465-532 |
article | URL |
| Abstract: While numerically solving a problem initially formulated on an unbounded domain, one typically truncates this domain, which necessitates setting the artificial boundary conditions (ABCs) at the newly formed external boundary. The issue of setting the ABCs appears most significant in many areas of scientific computing, for example, in problems originating from acoustics, electrodynamics, solid mechanics, and fluid dynamics. In particular, in computational fluid dynamics (where external problems represent a wide class of important formulations) the proper treatment of external boundaries may have a profound impact on the overall quality and performance of numerical algorithms and interpretation of the results. | |||||
BibTeX:
@article{SemyonV.1998,
author = {Semyon V., Tsynkov},
title = {Numerical solution of problems on unbounded domains. A review},
booktitle = {Special Issue on Absorbing Boundary Conditions},
journal = {Applied Numerical Mathematics},
year = {1998},
volume = {27},
number = {4},
pages = {465--532},
url = {http://www.sciencedirect.com/science/article/pii/S0168927498000257}
}
|
|||||
| Sepulveda, N. | Comparisons Among Ground-Water Flow Models and Analysis of Discrepancies in Simulated Transmissivities of the Upper Floridan Aquifer in Ground-Water Flow Model Overlap Areas | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 58-67 | inproceedings | URL |
| Abstract: Discrepancies in simulated transmissivities of the Upper Floridan aquifer were identified in the overlap areas of seven ground-water flow models in southwest and west-central Florida. Discrepancies in transmissivity are generally the result of uncertainty and spatial variability in other aquifer properties. All ground-water flow models were used to simulate the potentiometric surface of the Upper Floridan aquifer for approximated steady-state conditions from August 1993 through July 1994 using the time-independent hydraulic properties assigned to the models. Specified-head and general-head boundary data used to generate boundary conditions appropriate to these models were obtained from the estimated annual average heads for the steady-state period. Water-use data and the approximated surficial aquifer system water table were updated to reflect conditions during the approximated steady-state period. Simulated heads at control points, vertical leakage rates to the Upper Floridan aquifer, and spring flows were used to analyze the discrepancies in transmissivities in model overlap areas. Factors causing transmissivity discrepancies in model overlap areas include differences among directly applied recharge rates, differences among model simulated vertical leakance values assigned to the overlaying confining unit resulting in varying leakage rates to the Upper Floridan aquifer, differences in heads and conductances used in general-head boundary cells, and differences in transmissivities assigned in the vicinity of springs. Additional factors include the grid resolution and algorithm used to approximate the heads of the surficial aquifer system when these are used as a source/sink layer. | |||||
BibTeX:
@inproceedings{Sepulveda2001,
author = {Sepulveda, Nicasio},
title = {Comparisons Among Ground-Water Flow Models and Analysis of Discrepancies in Simulated Transmissivities of the Upper Floridan Aquifer in Ground-Water Flow Model Overlap Areas},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {58--67},
url = {http://water.usgs.gov/ogw/karst/kigconference/ns_comparisons.htm}
}
|
|||||
| Servan-Camas, B. and Tsai, F.T.-C. | Saltwater intrusion modeling in heterogeneous confined aquifers using two-relaxation-time lattice Boltzmann method | 2009 | Advances in Water Resources Vol. 32(4), pp. 620-631 |
article | URL |
| Abstract: This study develops a lattice Boltzmann method (LBM) with a two-relaxation-time collision operator (LTRT) to solve saltwater intrusion problems. A directional-speed-of-sound (DSS) technique is introduced to take into account the hydraulic conductivity heterogeneity and discontinuity, as well as the velocity-dependent dispersion coefficient. The forcing terms in the LTRT model are customized in order to recover the density-dependent groundwater flow and mass transport equations. Using the LTRT with the squared DSS achieves at least second-order accuracy. The LTRT results are verified with Henry’s analytical solution as well as compared with several numerical examples and modified Henry problems that consider heterogeneous hydraulic conductivity and velocity-dependent dispersion. The numerical results show good agreement with the Henry analytical solution and with the numerical solutions obtained by other numerical methods. | |||||
BibTeX:
@article{Servan-Camas2009,
author = {Servan-Camas, Borja and Tsai, Frank T.-C.},
title = {Saltwater intrusion modeling in heterogeneous confined aquifers using two-relaxation-time lattice Boltzmann method},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {4},
pages = {620--631},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809000220}
}
|
|||||
| Servan-Camas, B. and Tsai, F.T.-C. | Lattice Boltzmann method with two relaxation times for advection–diffusion equation: Third order analysis and stability analysis | 2008 | Advances in Water Resources Vol. 31(8), pp. 1113-1126 |
article | URL |
| Abstract: The objectives of this study are to investigate the third order accuracy and linear stability of the lattice Boltzmann method (LBM) with the two-relaxation-time collision operator (LTRT) for the advection–diffusion equation (ADE) and compare the LTRT model with the single-relaxation-time (LBGK) model. While the LBGK has been used extensively, the LTRT appears to be a more flexible model because it uses two relaxation times. The extra relaxation time can be used to improve solution accuracy and/or stability. This study conducts a third order Chapman–Enskog expansion on the LTRT to recover the macroscopic differential equations up to the third order. The dependency of third order terms on the relaxation times is obtained for different types of equilibrium distribution functions (EDFs) and lattices. By selecting proper relaxation times, the numerical dispersion can be significantly reduced. Furthermore, to improve solution accuracy, this study introduces pseudo-velocities to develop new EDFs to reduce the second order numerical diffusion. This study also derives stability domains based on the lattice Peclet number and Courant number for different types of lattices, EDFs and different values of relaxation times, while conducting linear stability analysis on the LTRT. Numerical examples demonstrate the improvement of the LTRT solution accuracy and stability by selecting proper relaxation times, lattice Peclet number and Courant number. | |||||
BibTeX:
@article{Servan-Camas2008,
author = {Servan-Camas, Borja and Tsai, Frank T.-C.},
title = {Lattice Boltzmann method with two relaxation times for advection–diffusion equation: Third order analysis and stability analysis},
journal = {Advances in Water Resources},
year = {2008},
volume = {31},
number = {8},
pages = {1113--1126},
url = {http://www.sciencedirect.com/science/article/pii/S0309170808000833}
}
|
|||||
| Setlhogile, T., Arntzen, J., Mabiza, C. and Mano, R. | Economic valuation of selected direct and indirect use values of the Makgadikgadi wetland system, Botswana | 2011 | Physics and Chemistry of the Earth, Parts A/B/C Vol. 36(14â15)11th WaterNet/WARFSA/GWP-SA Symposium: IWRM for National and Regional Integration through Science, Policy and Practice, pp. 1071-1077 |
article | URL |
| Abstract: Economic valuation of wetlands aims to investigate public preferences for changes in the state of the wetland and the natural resources it constitutes in monetary terms. It provides a means of quantifying the direct and indirect benefits that people derive from wetlands. In addition, it informs management planning and practice about resource options, optimal allocation and also provides information for conservation of the resource. The Makgadikgadi wetland is a unique system that mostly consists of dry pans during most of the year. This study aimed at estimating the value of groundwater recharge and community-based natural resource management (CBNRM) activities within the Makgadikgadi wetland and how these goods and services contribute to the local and national economy. The study used the Total Economic Valuation approach, which considers both the direct and indirect use values of the resource. In essence, the study concentrated on one direct use value (use of resources through CBNRM) and one indirect use value (groundwater recharge). With regard to CBNRM, three community-based organisations (CBOs) were selected for the study and static and dynamic costâbenefit models for these CBOs were developed. The groundwater recharge value was largely determined through desktop review and interviews with stakeholders. The results indicate a small positive contribution of CBOs towards the economy of Botswana and a high potential for communities to derive substantial benefits from the projects because currently benefits realised by communities are limited. CBOs involved in joint venture partnerships with tourism and hunting enterprises benefit more from utilising the wetlandâs resources. Groundwater recharge often occurs in areas away from the physical location of the wetland and may not be easily attributable to the wetland. However, the study assessed the value taking into consideration the various sectors which rely on the groundwater resource. The groundwater recharge value is significant (BWP 9â10 million) but lower when compared with the value generated by the Okavango delta (BWP 16 million). Given future increases in water demands, groundwater abstraction will exceed recharge, thus hampering the availability of the resource for the future generations and maintenance of the environment. | |||||
BibTeX:
@article{Setlhogile2011,
author = {Setlhogile, Tshepo and Arntzen, Jaap and Mabiza, Collin and Mano, Reneth},
title = {Economic valuation of selected direct and indirect use values of the Makgadikgadi wetland system, Botswana},
booktitle = {11th WaterNet/WARFSA/GWP-SA Symposium: IWRM for National and Regional Integration through Science, Policy and Practice},
journal = {Physics and Chemistry of the Earth, Parts A/B/C},
year = {2011},
volume = {36},
number = {14â15},
pages = {1071--1077},
url = {http://www.sciencedirect.com/science/article/pii/S1474706511001975}
}
|
|||||
| Shapiro, A. | The challenge of interpreting environmental tracer concentrations in fractured rock and carbonate aquifers [BibTeX] |
2011 | Hydrogeology Journal Vol. 19(1), pp. 9-12 |
article | URL |
BibTeX:
@article{Shapiro2011,
author = {Shapiro, Allen},
title = {The challenge of interpreting environmental tracer concentrations in fractured rock and carbonate aquifers},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {19},
number = {1},
pages = {9--12},
url = {http://dx.doi.org/10.1007/s10040-010-0678-x}
}
|
|||||
| Shapiro, S.D., Busenberg, E., Focazio, M.J. and Plummer, L. | Historical trends in occurrence and atmospheric inputs of halogenated volatile organic compounds in untreated ground water used as a source of drinking water | 2004 | Science of The Total Environment Vol. 321(1-3), pp. 201-217 |
article | URL |
| Abstract: Analyses of samples of untreated ground water from 413 community-, non-community- (such as restaurants), and domestic-supply wells throughout the US were used to determine the frequency of detection of halogenated volatile organic compounds (VOCs) in drinking-water sources. The VOC data were compiled from archived chromatograms of samples analyzed originally for chlorofluorocarbons (CFCs) by purge-and-trap gas chromatography with an electron-capture detector (GC-ECD). Concentrations of the VOCs could not be ascertained because standards were not routinely analyzed for VOCs other than trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113). Nevertheless, the peak areas associated with the elution times of other VOCs on the chromatograms can be classified qualitatively to assess concentrations at a detection limit on the order of parts per quadrillion. Three or more VOCs were detected in 100% (percent) of the chromatograms, and 77.2% of the samples contained 10 or more VOCs. The maximum number of VOCs detected in any sample was 24. Modeled ground-water residence times, determined from concentrations of CFC-12, were used to assess historical trends in the cumulative occurrence of all VOCs detected in this analysis, as well as the occurrence of individual VOCs, such as CFC-11, carbon tetrachloride (CCl4), chloroform and tetrachloroethene (PCE). The detection frequency for all of the VOCs detected has remained relatively constant from approximately 1940 to 2000; however, the magnitude of the peak areas on the chromatograms for the VOCs in the water samples has increased from 1940 to 2000. For CFC-11, CCl4, chloroform and PCE, small peaks decrease from 1940 to 2000, and large peaks increase from 1940 to 2000. The increase in peak areas on the chromatograms from analyses of more recently recharged water is consistent with reported increases in atmospheric concentrations of the VOCs. Approximately 44% and 6.7% of the CCl4 and PCE detections, respectively, in pre-1940 water, and 68% and 62% of the CCl4 and PCE detections, respectively, in water recharged in 2000 exceed solubility equilibrium with average atmospheric concentrations. These exceedences can be attributed to local atmospheric enrichment or direct contaminant input to ground-water flow systems. The detection of VOCs at concentrations indicative of atmospheric sources in 100% of the samples indicates that untreated drinking water from ground-water sources in the US recharged within the past 60 years has been affected by anthropogenic activity. Additional inputs from a variety of sources such as spills, underground injections and leaking landfills or storage tanks increasingly are providing additional sources of contamination to ground water used as drinking-water sources. | |||||
BibTeX:
@article{Shapiro2004,
author = {Shapiro, Stephanie Dunkle and Busenberg, Eurybiades and Focazio, Michael J. and Plummer, L.Niel},
title = {Historical trends in occurrence and atmospheric inputs of halogenated volatile organic compounds in untreated ground water used as a source of drinking water},
journal = {Science of The Total Environment},
year = {2004},
volume = {321},
number = {1-3},
pages = {201--217},
url = {http://www.sciencedirect.com/science/article/pii/S0048969703005096}
}
|
|||||
| Sharma, M. and McBean, E. | A methodology for solid waste characterization based on diminishing marginal returns | 2007 | Waste Management Vol. 27(3), pp. 337-344 |
article | URL |
| Abstract: A methodology is developed for estimating the number of waste sorts for characterizing solid wastes into categories based on diminishing minimum incremental information. Convergence in the square of the coefficient of variation with successive waste sorts is used to indicate cost-efficient termination of sampling at substantially reduced numbers of sorts in comparison with existing methodologies. These findings indicate that the numbers of waste sorts beyond that determined using the proposed methodology do not add substantial marginal gains in information and/or reduction in the confidence interval of the estimate. The methodology is demonstrated using waste composition analyses from the Greater Vancouver Regional District where 22 waste sorts are examined. The proposed methodology is simple, and the number of waste sorts can be estimated with a hand-held calculator and utilized in the field. | |||||
BibTeX:
@article{Sharma2007,
author = {Sharma, Mukesh and McBean, Edward},
title = {A methodology for solid waste characterization based on diminishing marginal returns},
journal = {Waste Management},
year = {2007},
volume = {27},
number = {3},
pages = {337--344},
url = {http://www.sciencedirect.com/science/article/pii/S0956053X06000596}
}
|
|||||
| Sharmin, R., Ioannidis, M.A. and Legge, R.L. | Surfactant-enhanced dissolution under conditions of surfactant partitioning between water and NAPL: Micromodel experiments and modeling implications | 2002 | Vol. 47Computational Methods in Water Resources Proceedings of the XIVth International Conference on Computational Methods in Water Resources (CMWR XIV), pp. 875-882 |
incollection | URL |
| Abstract: The effect of surfactant partitioning between the NAPL and aqueous phases on NAPL dissolution is investigated. Dissolution experiments are conducted in a 2D transparent glass micromodel using aqueous solutions of a non-ionic surfactant (Triton X-100) to dissolve residual perchloroethylene (PCE), trapped in the form of ganglia. The dissolution experiments are conducted at different flow rates of the flushing solution and contrasted to experiments using clean water. The concentration of dissolved PCE in the effluent is measured and the evolution of PCE ganglia size distribution directly observed. Solubility and interfacial tension measurements complement these experiments. Surfactant partitioning into the NAPL is observed to drastically retard the dissolution of PCE during the initial stages. Numerical simulations confirm that the kinetics of surfactant transfer from the aqueous phase into the NAPL must be taken into account to predict the dissolution behavior. | |||||
BibTeX:
@incollection{Sharmin2002,
author = {Sharmin, R. and Ioannidis, M. A. and Legge, R. L.},
title = {Surfactant-enhanced dissolution under conditions of surfactant partitioning between water and NAPL: Micromodel experiments and modeling implications},
booktitle = {Computational Methods in Water Resources Proceedings of the XIVth International Conference on Computational Methods in Water Resources (CMWR XIV)},
publisher = {Elsevier},
year = {2002},
volume = {47},
pages = {875--882},
url = {http://www.sciencedirect.com/science/article/pii/S0167564802801538}
}
|
|||||
| Sharmin, R., Ioannidis, M.A. and Legge, R.L. | Effect of nonionic surfactant partitioning on the dissolution kinetics of residual perchloroethylene in a model porous medium | 2006 | Journal of Contaminant Hydrology Vol. 82(1-2), pp. 145-164 |
article | URL |
| Abstract: At concentrations above the critical micelle concentration, surfactants can significantly enhance the solubilization of residual nonaqueous phase liquids (NAPL) and, for this reason, are the focus of research on surfactant-enhanced aquifer remediation (SEAR). As a consequence of their amphiphilic nature, surfactants may also partition to various extents between the organic and aqueous phases, thereby affecting SEAR performance. We report here on the observation and analysis of the effect of surfactant partitioning on the dissolution kinetics of residual perchloroethylene (PCE) by aqueous solutions (1000 mg/L) of the non-ionic surfactant Triton X-100 in a model porous medium. For this fluid system, batch equilibration experiments showed that the surfactant partitions strongly into the NAPL (NAPL–water partition coefficient equal to 12.5). Dynamic interfacial tension (IFT) measurements were employed to study surfactant diffusion and interfacial adsorption. The dynamic IFT measurements were consistent with partitioning of the surfactant between the two liquid phases. PCE dissolution experiments, conducted in a transparent glass micromodel using an aqueous surfactant solution, were contrasted to experiments using clean water. Surfactant partitioning was observed to delay significantly the onset of micellar solubilization of PCE, an observation reproduced by a numerical model. This effect is attributed to the reduction of surfactant concentration in the immediate vicinity of the NAPL–water interface, which accompanies transport of the surfactant into the NAPL. Accordingly, it is suggested that both the rate and the extent of diffusion of the surfactant into the NAPL affect the onset of and the driving force for micellar solubilization. While many surfactants do not readily partition in NAPL, this possibility must be considered when selecting non-ionic surfactants for the enhanced solubilization of residual chlorinated solvents in porous media. | |||||
BibTeX:
@article{Sharmin2006,
author = {Sharmin, Rumana and Ioannidis, Marios A. and Legge, Raymond L.},
title = {Effect of nonionic surfactant partitioning on the dissolution kinetics of residual perchloroethylene in a model porous medium},
journal = {Journal of Contaminant Hydrology},
year = {2006},
volume = {82},
number = {1-2},
pages = {145--164},
url = {http://www.sciencedirect.com/science/article/pii/S0169772205001725}
}
|
|||||
| Sheldon, N.D. and Tabor, N.J. | Quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols | 2009 | Earth-Science Reviews Vol. 95(1-2), pp. 1-52 |
article | URL |
| Abstract: Paleosols (fossil soils) are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows. Until recently, paleosols were studied using primarily qualitative methods. In recent years, paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor. Some of this change has been a result of applying existing techniques to new materials, but many of the innovations have been the result of applying new techniques to new materials, including thermodynamic modeling of soil formation, isotope geochemistry, and applications of empirical relationships derived from modern soils. A variety of semi-quantitative and quantitative tools has been developed to examine past weathering and pedogenesis, and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed. Though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions, proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the Earth's surface, in direct contact with the atmospheric and climatic conditions at the time of their formation. Paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance, weathering intensity, mean annual precipitation and temperature during pedogenesis, nutrient fluxes into and out of the paleosols, the atmospheric composition of important gases including CO2 and O2, the moisture balance during pedogenesis, the soil gas composition, reconstructed vegetative covering, and paleo-altitude. | |||||
BibTeX:
@article{Sheldon2009,
author = {Sheldon, Nathan D. and Tabor, Neil J.},
title = {Quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols},
journal = {Earth-Science Reviews},
year = {2009},
volume = {95},
number = {1-2},
pages = {1--52},
url = {http://www.sciencedirect.com/science/article/pii/S001282520900052X}
}
|
|||||
| Shen, C. and Phanikumar, M.S. | An efficient space-fractional dispersion approximation for stream solute transport modeling | 2009 | Advances in Water Resources Vol. 32(10), pp. 1482-1494 |
article | URL |
| Abstract: The success of transient storage (TS) modeling for natural streams depends, in part, on the ability to describe the dispersion process accurately. Evidence based on stream tracer data shows that solute transport processes often do not follow the classical second-order dispersion model (e.g., early breakthrough and faster than Fickian travel times were observed). While models based on space-fractional dispersion are a promising alternative, different definitions of fractional derivatives exist in the literature. Unlike integer-order derivatives, fractional derivatives represent convolutions of concentration with long-range spatial correlation and numerical approximations can produce dense matrices. Therefore issues of both accuracy and computational efficiency need to be examined to successfully identify model parameters for natural streams. In this paper, we first compare the performance of several numerical approaches for solving the space-fractional dispersion equation. We examine three different numerical approaches to approximate the space-fractional derivatives including: (a) a fully-implicit scheme based on the shifted Grünwald–Letnikov (GL) approximation (b) a three-point implicit representation based on the GL formula and (c) a three-point implicit scheme based on mass conservation and the Caputo definition of the fractional derivative. We then use an operator-splitting technique to evaluate a TS model based on space-fractional dispersion (the FSTS model) and test the model against analytical solutions and stream tracer data. A sequence acceleration method (Richardson extrapolation) significantly improves the performance of all schemes examined. Results indicate that the fully-implicit GL method with Richardson extrapolation produces the most accurate solutions while the three-point implicit GL scheme has a stringent time-step restriction to produce acceptable solutions. The three-point implicit scheme based on the Caputo derivative produces accurate solutions in a fraction of the time taken by the fully-implicit GL method and represents the best trade-off between accuracy and computational efficiency for practical applications. The scheme is suitable for parameter estimation and is used to successfully describe tracer data in a natural stream. | |||||
BibTeX:
@article{Shen2009,
author = {Shen, Chaopeng and Phanikumar, Mantha S.},
title = {An efficient space-fractional dispersion approximation for stream solute transport modeling},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {10},
pages = {1482--1494},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809001031}
}
|
|||||
| Shevenell, L. and McCarthy, J.F. | Effects of precipitation events on colloids in a karst aquifer | 2002 | Journal of Hydrology Vol. 255(1-4), pp. 50-68 |
article | URL |
| Abstract: The effects of precipitation events on colloid mobilization were evaluated during several storms from six wells in a karstic aquifer at the Oak Ridge Y-12 Plant in eastern Tennessee (USA). Turbidity increases and rapidly recedes following rain events. Although the magnitude of the turbidity increases are relatively small (≤4.78 NTU), the increased turbidity suggests transient increases in colloid abundance during storm versus non-storm periods. During the larger storms (>19 mm), the increased turbidity is associated with increases in pH, total organic carbon (TOC) and temperature, and with decreases in dissolved oxygen (DO). These larger storms result in flushing of a greater proportion of higher pH, TOC (and lower DO) soil or matrix waters into the fractures and conduits than occurs during smaller storms. Smaller storms also result in increases in turbidity, but show increases in DO and decreases in pH reflecting less influence on the water chemistry from the longer residence time epikarst or and matrix waters, and greater impact from the more dilute, newly recharged waters. Due to the complexity of karst flow and temporal variations in flow and chemistry, controls on turbidity are not consistent through time and space at the wells. During smaller storms, recharge by lower ionic strength waters may promote colloid release and thus contribute to observed increases in turbidity. During larger storms, elevated turbidity may be more related to pH increases resulting from greater influx of matrix and soil waters into fractures and conduits. Chemical factors alone cannot account for the changes in turbidity observed during the various storms. Because of the complicated nature of flow and particle transport in karst aquifers, the presence of colloids during precipitation events is dictated by a complex interplay of chemical reactions and the effects of physical perturbations due to increased flow through the conduits and fractures. Simple trends in water quality parameters could not be identified, and broad generalizations cannot easily be made in karst settings, and some of the expected correlations between chemical parameters during the storms were not observed in this work. | |||||
BibTeX:
@article{Shevenell2002,
author = {Shevenell, Lisa and McCarthy, John F.},
title = {Effects of precipitation events on colloids in a karst aquifer},
journal = {Journal of Hydrology},
year = {2002},
volume = {255},
number = {1-4},
pages = {50--68},
url = {http://www.sciencedirect.com/science/article/pii/S0022169401005108}
}
|
|||||
| Shiau, L.-D. and Lu, T.-S. | Modeling the nonideal mixing behavior in a continuous-stirred crystallizer | 2006 | Computers & Chemical Engineering Vol. 30(6–7), pp. 970-977 |
article | URL |
| Abstract: A two-parameter model, termed as a two-MSMPR-crystallizers-with-interchange model, is proposed in this paper to predict the overall performances of a nonideal, continuous-stirred crystallizer. The model equations, including the population balance equations and the mass balance equations, are solved simultaneously to predict the resulting crystal size distribution (CSD) for power law growth and nucleation kinetics. The effects of nonhomogeneous mixing, in terms of the two parameters, α and β, on the weight-average size, the coefficient of variation and the production rate of the resulting crystals are studied. | |||||
BibTeX:
@article{Shiau2006,
author = {Shiau, Lie-Ding and Lu, Tsan-Sheng},
title = {Modeling the nonideal mixing behavior in a continuous-stirred crystallizer},
journal = {Computers & Chemical Engineering},
year = {2006},
volume = {30},
number = {6–7},
pages = {970--977},
url = {http://www.sciencedirect.com/science/article/pii/S0098135406000160}
}
|
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| Shilling, F.M., London, J.K. and Liévanos, R.S. | Marginalization by collaboration: Environmental justice as a third party in and beyond CALFED [BibTeX] |
2009 | Environmental Science & Policy Vol. 12(6), pp. 694-709 |
article | DOI URL |
BibTeX:
@article{Shilling2009,
author = {Shilling, Fraser M. and London, Jonathan K. and Liévanos, Raoul S.},
title = {Marginalization by collaboration: Environmental justice as a third party in and beyond CALFED},
journal = {Environmental Science & Policy},
year = {2009},
volume = {12},
number = {6},
pages = {694--709},
url = {http://www.sciencedirect.com/science/article/pii/S1462901109000471},
doi = {http://dx.doi.org/10.1016/j.envsci.2009.03.003}
}
|
|||||
| Shilling, F.M., London, J.K. and Liévanos, R.S. | Marginalization by collaboration: Environmental justice as a third party in and beyond CALFED | 2009 | Environmental Science & Policy Vol. 12(6)Collaborative Governance and Adaptive Management: California's CALFED Water Program, pp. 694-709 |
article | URL |
| Abstract: Governance and planning of ecosystem and water management within the California Bay-Delta, a critical component of California's water economy, have been characterized by a range of innovations in collaboration and conflict resolution. Despite legal mandates to incorporate environmental justice, the California Bay-Delta Authority's (CBDA) policy-development process and the subsequent Delta Vision process have systematically marginalized the role of environmental justice in California's water policy. We suggest that environmental justice in Bay-Delta planning can be understood as a “third party” with a tenuous seat at the CALFED water management table. As such environmental justice is a useful lens through which to assess the state's broader commitments and capacities relative to equity as a planning principal and outcome. We interpret the fate of environmental justice within Bay-Delta planning as indicative of the inherent tensions between systems based on increasing market dominance and state legitimation and the values of environmental justice based on distributive, procedural, and cognitive justice. We construct a model of marginalization and environmental injustice in collaborative planning to illustrate these tensions. We draw upon experiences of members of the Environmental Justice Sub-Committee of CBDA's Bay Delta Public Advisory Committee, as well as interviews with other key environmental justice interests, and a comprehensive review of internal and public CBDA documents relating to the environmental justice program including budgets and program plans, and ethnographic field work. We conclude that by learning from the mistakes of Bay-Delta planning, a positive model of collaborative, environmental justice-based planning for water and ecosystem management is possible. | |||||
BibTeX:
@article{Shilling2009a,
author = {Shilling, Fraser M. and London, Jonathan K. and Liévanos, Raoul S.},
title = {Marginalization by collaboration: Environmental justice as a third party in and beyond CALFED},
booktitle = {Collaborative Governance and Adaptive Management: California's CALFED Water Program},
journal = {Environmental Science & Policy},
year = {2009},
volume = {12},
number = {6},
pages = {694--709},
url = {http://www.sciencedirect.com/science/article/pii/S1462901109000471}
}
|
|||||
| Shinnar, R. and Naor, P. | Residence time distributions in systems with internal reflux | 1967 | Chemical Engineering Science Vol. 22(10), pp. 1369-1381 |
article | URL |
| Abstract: A general method for calculating residence time distributions for systems with internal reflux is described. The method allows the derivation of the Laplace transform of any system composed of mixed vessels with both forward and backward flow between them. In particular, the properties of a linear cascade of mixed vessels with forward and backward flow between the vessels is discussed. | |||||
BibTeX:
@article{Shinnar1967,
author = {Shinnar, Reuel and Naor, Pinhas},
title = {Residence time distributions in systems with internal reflux},
journal = {Chemical Engineering Science},
year = {1967},
volume = {22},
number = {10},
pages = {1369--1381},
url = {http://www.sciencedirect.com/science/article/pii/0009250967800277}
}
|
|||||
| Shoemaker, W.B. and Kuniansky, E.L. | Effects of Turbulence on Hydraulic Heads and Parameter Sensitivities in Preferential Ground-Water Flow Layers | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 89-90 | inproceedings | URL |
| Abstract: The U.S. Geological Survey created a Conduit Flow Process (CFP) (Shoemaker and others, 2008) for the Modular Finite-Difference Ground-Water Flow Model, MODFLOW-2005. An application of the CFP on the Biscayne aquifer in southern Florida is described that examines (1) the potential for turbulent groundwater flow, and (2) the effects of turbulent flow on hydraulic heads and parameter sensitivities. Turbulent flow was spatially extensive (Figure 1) in preferential groundwater flow layers with mean void diameters equal to about 3.5 centimeters, groundwater temperature equal to about 25 degrees Celsius, and critical Reynolds numbers less than about 400. Turbulence either increased or decreased simulated heads from laminar altitudes. Specifically, head differences from laminar altitudes ranged from about -18 to +27 centimeters, and were explained by the magnitude of net flow to the finite-difference model cell. Turbulence also influenced the sensitivities of model parameters. Specifically, the composite-scaled sensitivities of horizontal hydraulic conductivities decrease by as much as 70% when turbulence is removed. Resultant hydraulic head and sensitivity differences due to turbulent groundwater flow highlight potential errors in models which assume laminar flow in an equivalent porous-media having uniformly distributed void spaces. | |||||
BibTeX:
@inproceedings{Shoemaker2008,
author = {Shoemaker, W. Barclay and Kuniansky, Eve L.},
title = {Effects of Turbulence on Hydraulic Heads and Parameter Sensitivities in Preferential Ground-Water Flow Layers},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {89--90},
url = {http://pubs.usgs.gov/sir/2008/5023/34shoemaker.htm}
}
|
|||||
| Shofner, G.A., Mills, H.H. and Duke, J.E. | A simple map index of karstification and its relationship to sinkhole and cave distribution in Tennessee | 2001 | Journal of Cave and Karst Studies Vol. 63(2), pp. 67-75 |
article | URL |
| Abstract: We here introduce a readily determined index of surface karstification, termed “sinkhole” index, based on the mean spacing of closed contours in a given area. The index shows a high correlation with total sinkhole area and a moderate correlation with total volume. The index was measured in 5056 blocks with dimensions of 2.5’ of latitude by 2.5’ of longitude, covering much of Tennessee. A new map showing the distribution of this index in the state is similar to one previously published karst map of Tennessee, but shows the variation of karstification in a more detailed manner. The sinkhole index was also used to compare the distribution of sinkholes and caves in Tennessee, using cave data compiled by the Tennessee Cave Survey. Maps of the sinkhole index and the number and total length of caves in each 2.5’ x 2.5’ block show strong regional similarities. However, there are dramatic exceptions. In addition, using blocks as the basic unit of analysis, the correlation coefficients between the sinkhole index and the two measures of cave abundance are low, generally explaining less than 10% of the variance. Thus, although similar geologic conditions appear to favor both sinkhole development and cave formation, the actual processes involved in the development of these two types of features seem to be only weakly related. | |||||
BibTeX:
@article{Shofner2001,
author = {Shofner, Gregory A. and Mills, Hugh H. and Duke, Jason E.},
title = {A simple map index of karstification and its relationship to sinkhole and cave distribution in Tennessee},
journal = {Journal of Cave and Karst Studies},
year = {2001},
volume = {63},
number = {2},
pages = {67--75},
url = {http://www.caves.org/pub/journal/JCKS/PDF/V63/v63n2-Shofner.htm}
}
|
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| Shore, H. and Benson-Karhi, D. | Modeling Temperature-Dependent Properties of Oxygen, Argon, and Nitrogen via Response Modeling Methodology (RMM) and Comparison with Acceptable Models | 2010 | Industrial & Engineering Chemistry Research Vol. 49(19), pp. 9469-9485 |
article | DOI URL |
| Abstract: In a recent paper, temperature-dependent properties of water were modeled via response modeling methodology (RMM), and the resultant models were compared to models obtained by TableCurve2D (a dedicated software for relational modeling), and to ?Acceptable models?, recommended by DIPPR (a widely used database for constant and temperature-dependent physical properties). In this paper, we extend the comparison to oxygen, argon and nitrogen. Model comparison has been conducted for 10 temperature-dependent physical and thermodynamic properties. Detailed results are reported in this paper. Summary tables, which rank the various models in terms of goodness-of-fit and stability over all properties, are provided. The three variations of the RMM model (two-, three-, and four-parameter models) compare favorably with other models, often with more parameters, in terms of both goodness-of-fit and stability. The unique desirable properties of RMM models are discussed. In a recent paper, temperature-dependent properties of water were modeled via response modeling methodology (RMM), and the resultant models were compared to models obtained by TableCurve2D (a dedicated software for relational modeling), and to ?Acceptable models?, recommended by DIPPR (a widely used database for constant and temperature-dependent physical properties). In this paper, we extend the comparison to oxygen, argon and nitrogen. Model comparison has been conducted for 10 temperature-dependent physical and thermodynamic properties. Detailed results are reported in this paper. Summary tables, which rank the various models in terms of goodness-of-fit and stability over all properties, are provided. The three variations of the RMM model (two-, three-, and four-parameter models) compare favorably with other models, often with more parameters, in terms of both goodness-of-fit and stability. The unique desirable properties of RMM models are discussed. |
|||||
BibTeX:
@article{Shore2010a,
author = {Shore, Haim and Benson-Karhi, Diamanta},
title = {Modeling Temperature-Dependent Properties of Oxygen, Argon, and Nitrogen via Response Modeling Methodology (RMM) and Comparison with Acceptable Models},
journal = {Industrial & Engineering Chemistry Research},
publisher = {American Chemical Society},
year = {2010},
volume = {49},
number = {19},
pages = {9469--9485},
url = {http://dx.doi.org/10.1021/ie100981y},
doi = {http://dx.doi.org/10.1021/ie100981y}
}
|
|||||
| Shutes, R. | Artificial wetlands and water quality improvement | 2001 | Environment International Vol. 26(5-6)Environmental Geochemistry in the Tropics and Subtropics, pp. 441-447 |
article | URL |
| Abstract: This paper illustrates the role of plants to assist the treatment of water pollution in man-made wetlands in tropical and temperate climates. It also considers the potential for environmental education of these wetland systems. The management and natural treatment of pollution is described in the Mai Po Marshes, Hong Kong and a wetland in London which is also an important site for birds. The design of the Putrajaya Lake and Wetland system in Malaysia is compared with a constructed wetland and lake for the treatment of urban surface runoff in a new residential development in the United Kingdom. The benefits of these natural systems are discussed in the context of the global trend for introducing sustainable methods of environmental management and low cost pollution treatment systems. | |||||
BibTeX:
@article{Shutes2001,
author = {Shutes, R.B.E},
title = {Artificial wetlands and water quality improvement},
booktitle = {Environmental Geochemistry in the Tropics and Subtropics},
journal = {Environment International},
year = {2001},
volume = {26},
number = {5--6},
pages = {441--447},
url = {http://www.sciencedirect.com/science/article/pii/S0160412001000253}
}
|
|||||
| da Silva Ferreira, C., Bolfarine, H. and Lachos, V.H. | Skew scale mixtures of normal distributions: Properties and estimation | 2011 | Statistical Methodology Vol. 8(2), pp. 154-171 |
article | URL |
| Abstract: Scale mixtures of normal distributions are often used as a challenging class for statistical procedures for symmetrical data. In this article, we have defined a skewed version of these distributions and we have derived several of its probabilistic and inferential properties. The main virtue of the members of this family of distributions is that they are easy to simulate from and they also supply genuine EM algorithms for maximum likelihood estimation. For univariate skewed responses, the EM-type algorithm has been discussed with emphasis on the skew- t , skew-slash, skew-contaminated normal and skew-exponential power distributions. Some simplifying and unifying results are also noted with the Fisher information matrix, which is derived analytically for some members of this class. Results obtained from simulated and real data sets are reported, illustrating the usefulness of the proposed methodology. The main conclusion in reanalyzing a data set previously studied is that the models so far entertained are clearly not the most adequate ones. | |||||
BibTeX:
@article{SilvaFerreira2011,
author = {da Silva Ferreira, Clécio and Bolfarine, Heleno and Lachos, Víctor H.},
title = {Skew scale mixtures of normal distributions: Properties and estimation},
journal = {Statistical Methodology},
year = {2011},
volume = {8},
number = {2},
pages = {154--171},
url = {http://www.sciencedirect.com/science/article/pii/S1572312710000948}
}
|
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| Simcik, M., Ruzicka, M., Mota, A. and Teixeira, J. | Smart RTD for multiphase flow systems | Chemical Engineering Research and Design(0), pp. - | article | URL | |
| Abstract: A relatively new concept is presented for evaluation of the fluid age distribution a = a(x,t) within the interior of an apparatus. In the standard RTD approach, the tracer study is performed and the residence time distribution is obtained. In the new approach denoted as SRTD, the fluid age is considered as the field quantity and the governing equation is formulated for its spatio-temporal distribution within the flow domain. There are only few studies devoted to this alternative approach, which typically concern only the single-phase flow systems. In this contribution we investigate its applicability also to multiphase systems. In the case of a bubble column, both the RTD and SRTD concepts are employed and discussed. The results are calculated numerically and compared with the experimental observations. | |||||
BibTeX:
@article{Simcik,
author = {Simcik, M. and Ruzicka, M.C. and Mota, A. and Teixeira, J.A.},
title = {Smart RTD for multiphase flow systems},
journal = {Chemical Engineering Research and Design},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0263876212001268}
}
|
|||||
| Simos G., M. | Goodness-of-fit tests and minimum distance estimation via optimal transformation to uniformity | 2009 | Journal of Statistical Planning and Inference Vol. 139(2), pp. 100-108 |
article | URL |
| Abstract: A unified approach of parameter-estimation and goodness-of-fit testing is proposed. The new procedures may be applied to arbitrary laws with continuous distribution function. Specifically, both the method of estimation and the goodness-of-fit test are based on the idea of optimally transforming the original data to the uniform distribution, the criterion of optimality being an L2-type distance between the empirical characteristic function of the transformed data, and the characteristic function of the uniform ( 0 , 1 ) distribution. Theoretical properties of the new estimators and tests are studied and some connections with classical statistics, moment-based procedures and non-parametric methods are investigated. Comparison with standard procedures via Monte Carlo is also included, along with a real-data application. | |||||
BibTeX:
@article{SimosG.2009,
author = {Simos G., Meintanis},
title = {Goodness-of-fit tests and minimum distance estimation via optimal transformation to uniformity},
journal = {Journal of Statistical Planning and Inference},
year = {2009},
volume = {139},
number = {2},
pages = {100--108},
url = {http://www.sciencedirect.com/science/article/pii/S0378375808001511}
}
|
|||||
| Simos G., M. | A new approach of goodness-of-fit testing for exponentiated laws applied to the generalized Rayleigh distribution | 2008 | Computational Statistics & Data Analysis Vol. 52(5), pp. 2496-2503 |
article | URL |
| Abstract: Goodness-of-fit statistics are considered which are appropriate for generalized families of distributions, resulting from exponentiation. The tests employ a variation of the data determined by the cumulative distribution function of the corresponding non-generalized distribution. The resulting test, which makes use of the Mellin transform of the transformed data, is shown to be consistent. Simulation results for the case of the generalized Rayleigh distribution show that the proposed test compares well with standard methods based on the empirical distribution function. | |||||
BibTeX:
@article{SimosG.2008,
author = {Simos G., Meintanis},
title = {A new approach of goodness-of-fit testing for exponentiated laws applied to the generalized Rayleigh distribution},
journal = {Computational Statistics & Data Analysis},
year = {2008},
volume = {52},
number = {5},
pages = {2496--2503},
url = {http://www.sciencedirect.com/science/article/pii/S0167947307003283}
}
|
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| Simpkins, W. and Bradbury, K. | Groundwater flow, velocity, and age in a thick, fine-grained till unit in southeastern Wisconsin | 1992 | Journal of Hydrology Vol. 132(1-4), pp. 283-319 |
article | URL |
| Abstract: Piezometer nests were installed at study sites in each of five north-south-trending end moraines of the late Pleistocene Oak Creek Formation in southeastern Wisconsin. The formation is composed primarily of a fine-grained glacial diamicton (till) and laterally continuous and discontinuous, coarse-grained lake and meltwater stream sediment. It overlies the Silurian dolomite aquifer, which is a source of drinking water to rural areas. The average vertical linear velocity and age of ground water in the Oak Creek Formation were estimated by three methods: Darcy's Law, environmental isotopes including 3H, δ2H, δ18O, and 14C (dissolved inorganic carbon), and solute transport modeling of 18O. The F-1 and Metro sites in the Tinley moraine showed excellent agreement among the three estimates of vertical velocity and showed the lowest velocity values (0.3–0.5 cm year−1 downward), which suggests that diffusion controls vertical mass transport at these sites. Although the extrapolated maximum age of ground water is 35 000 years, ground water below 75 m at these sites is probably not older than 15 000 years, which is the maximum age of the formation. Estimates of velocity showed less agreement at study sites in the Lake Border moraine system to the east and ranged from about 0.2 to 20.7 cm year−1; maximum groundwater age could range from 213 to 6000 years. Higher and more variable velocities, perhaps owing to thinner and more heterogeneous sediment in these areas, suggest that diffusion may not dominate vertical mass transport. Heterogeneity and fractures may also promote the development of groundwater flow systems dominated by lateral flow. Because of the uncertainty about the nature of groundwater flow, velocity, and age in the formation east of the Tinley moraine, future waste-disposal activity in southeastern Wisconsin should be confined to the thickest parts of the Tinley moraine near the present F-1 and Metro sites. | |||||
BibTeX:
@article{Simpkins1992,
author = {Simpkins, W.W. and Bradbury, K.R.},
title = {Groundwater flow, velocity, and age in a thick, fine-grained till unit in southeastern Wisconsin},
journal = {Journal of Hydrology},
year = {1992},
volume = {132},
number = {1-4},
pages = {283--319},
url = {http://www.sciencedirect.com/science/article/pii/002216949290183V}
}
|
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| Singh, S. | Time Base as an Invertible Function of the Parameters of Gamma Unit Hydrograph | 2009 | Journal of Irrigation and Drainage Engineering Vol. 135(6), pp. 802-805 |
article | URL |
| Abstract: Analytical but approximate invertible equations for time base of gamma unit hydrographs or unit kernel hydrograph (UKH), which are applicable to all catchments, are derived in terms of the parameters of the unit hydrograph. The time base has been linked to the time to peak and lag time for the gamma UKH. The gamma UKH is redefined taking the time base and time to peak as parameters, as these parameters are physically more conceivable than the conventional parameters. The widely used National Resource Conservation Service empirical equations for the time base are found not applicable to all catchments. The proposed equations can also be used for determining the conventional parameters from the known values of the time base and time to peak or lag time. Using the proposed equations for time to peak and time base, the gamma UKH is fitted to few published storm events considering the time base as a parameter. | |||||
BibTeX:
@article{Singh2009,
author = {Singh, S.},
title = {Time Base as an Invertible Function of the Parameters of Gamma Unit Hydrograph},
journal = {Journal of Irrigation and Drainage Engineering},
publisher = {American Society of Civil Engineers},
year = {2009},
volume = {135},
number = {6},
pages = {802--805},
url = {http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29IR.1943-4774.0000105}
}
|
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| Singh, S. | Use of Gamma Distribution/Nash Model Further Simplified for Runoff Modeling | 2007 | Journal of Hydrologic Engineering Vol. 12(2), pp. 222-224 |
article | URL |
| Abstract: The use of the gamma distribution as instantaneous unit hydrograph (IUH) for modeling runoff is simple and reasonably accurate. A simplified procedure was proposed for modeling runoff using the gamma IUH, in which the incomplete gamma function was computed indirectly, but the gamma function was computed. A further simplified procedure for runoff modeling using a gamma IUH or Nash model’s IUH is proposed. This procedure does not require computation of either the gamma function or incomplete gamma function. | |||||
BibTeX:
@article{Singh2007,
author = {Singh, S.},
title = {Use of Gamma Distribution/Nash Model Further Simplified for Runoff Modeling},
journal = {Journal of Hydrologic Engineering},
publisher = {American Society of Civil Engineers},
year = {2007},
volume = {12},
number = {2},
pages = {222--224},
url = {http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291084-0699%282007%2912%3A2%28222%29}
}
|
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| Singh, S.K. | Simplified Use of Gamma-Distribution/Nash Model for Runoff Modeling | 2004 | Journal of Hydrologic Engineering Vol. 9(3), pp. 240-243 |
article | URL |
| Abstract: A simple method is suggested for computing the direct runoff hydrograph resulting from a complex storm using a two-parameter gamma distribution as the instantaneous unit hydrograph. The computation of the incomplete gamma function is accomplished indirectly, which requires evaluations of only simple functions that can be performed on a scientific calculator. In place of “unit hydrograph,” a “unit kernel” approach is suggested, which reduces the computational effort when dealing with any selected sampling interval because it implicitly accounts for the sampling interval. The use of the unit kernel renders the S-curve invariant with the sampling interval, as opposed to the conventional procedure. The new procedure enhances the applicability of the two-parameter gamma distribution or the Nash model for rainfall-runoff modeling, as the calculations can be performed using a spreadsheet, such as an Excel spreadsheet. Application of the new procedure on published data sets shows that the direct runoff obtained is almost the same as computed using either tabulated or computer-obtained values of the incomplete gamma function. | |||||
BibTeX:
@article{Singh2004,
author = {Singh, Sushil K.},
title = {Simplified Use of Gamma-Distribution/Nash Model for Runoff Modeling},
journal = {Journal of Hydrologic Engineering},
publisher = {American Society of Civil Engineers (ASCE)},
year = {2004},
volume = {9},
number = {3},
pages = {240--243},
url = {http://dx.doi.org/10.1061/(ASCE)1084-0699(2004)9:3(240)}
}
|
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| Sinreich, M., Flynn, R. and Zopfi, J. | Use of particulate surrogates for assessing microbial mobility in subsurface ecosystems | 2009 | Hydrogeology Journal Vol. 17(1), pp. 49-59 |
article | URL |
| Abstract: Mass fluxes from the ground surface can play a vital role in influencing groundwater ecosystems. Rates of delivery may influence intact ecosystem composition, while fluxes of substances associated with anthropogenic activity may critically alter the functioning of associated microbial assemblages. Field-based tracing experiments offer a valuable means of understanding mass transport rates and mechanisms, particularly in complex heterogeneous epikarst systems overlying vulnerable fissured aquifers. A short-term tracer experiment monitoring solute and particle tracer concentrations after they passed through a 10-m-thick sequence of limestone, capped by a thin soil, revealed rapid travel times and variable attenuation rates for the substances employed. Results demonstrated that particle tracers have shorter average travel times and can reach the subsurface in higher concentrations and over shorter times than non-reactive solutes. High recovery rates for the bacterial tracer Ralstonia eutropha H16 contrasted strongly with those of similarly sized fluorescent polystyrene microspheres, highlighting the importance of physico-chemical surface characteristics of particle tracers. Complementary laboratory batch experiments examined the role played by organic and inorganic soil/rock surfaces on particle tracer attenuation. Findings suggest that biofilms may significantly promote transport of particulate material below ground, i.e., the delivery of allochthonous microorganisms to karst groundwater. | |||||
BibTeX:
@article{Sinreich2009,
author = {Sinreich, Michael and Flynn, Raymond and Zopfi, Jakob},
title = {Use of particulate surrogates for assessing microbial mobility in subsurface ecosystems},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {49--59},
url = {http://dx.doi.org/10.1007/s10040-008-0362-6}
}
|
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| Skalbeck, J., Reed, D., Hunt, R. and Lambert, J. | Relating groundwater to seasonal wetlands in southeastern Wisconsin, USA | 2009 | Hydrogeology Journal Vol. 17(1), pp. 215-228 |
article | URL |
| Abstract: Historically, drier types of wetlands have been difficult to characterize and are not well researched. Nonetheless, they are considered to reflect the precipitation history with little, if any, regard for possible relation to groundwater. Two seasonal coastal wetland types (wet prairie, sedge meadow) were investigated during three growing seasons at three sites in the Lake Michigan Basin, Wisconsin, USA. The six seasonal wetlands were characterized using standard soil and vegetation techniques and groundwater measurements from the shallow and deep systems. They all met wetland hydrology criteria (e.g., water within 30 cm of land surface for 5% of the growing season) during the early portion of the growing season despite the lack of appreciable regional groundwater discharge into the wetland root zones. Although root-zone duration analyses did not fit a lognormal distribution previously noted in groundwater-dominated wetlands, they were able to discriminate between the plant communities and showed that wet prairie communities had shorter durations of continuous soil saturation than sedge meadow communities. These results demonstrate that the relative rates of groundwater outflows can be important for wetland hydrology and resulting wetland type. Thus, regional stresses to the shallow groundwater system such as pumping or low Great Lake levels can be expected to affect even drier wetland types. | |||||
BibTeX:
@article{Skalbeck2009,
author = {Skalbeck, John and Reed, Donald and Hunt, Randall and Lambert, Jamie},
title = {Relating groundwater to seasonal wetlands in southeastern Wisconsin, USA},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {215--228},
url = {http://dx.doi.org/10.1007/s10040-008-0345-7}
}
|
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| Smart, C.C. | Artificial Tracer Techniques for the Determination of the Structure of Conduit Aquifers | 1988 | Ground Water Vol. 26(4), pp. 445-453 |
article | URL |
| Abstract: Fluorescent dye tracer technology now permits accurate determination of tracer breakthrough curves in karst hydrology. Such data may be evaluated in terms of hydraulic processes of dispersion, divergence, convergence, dilution, and storage. The breakthrough curve reflects the character of ground-water flow and the structure of the ground-water conduit network, so that within constraints of regional geology, geomorphology, and hydrology, it is possible to interpret tracer breakthrough curves to produce a structural model of a karst aquifer. Such structural models provide a basis for further field investigations and rational computer modeling. An example of such an approach is taken from a series of tracer tests on the Castleguard karst aquifer, Alberta, Canada, an alpine karst with rapid conduit flow, and a strongly seasonal flow regime. A dimensionless recovery index is developed to identify the relationship between springs, and this shows that the behavior and configuration of the active aquifer vary dramatically with discharge. | |||||
BibTeX:
@article{Smart1988,
author = {Smart, C. C.},
title = {Artificial Tracer Techniques for the Determination of the Structure of Conduit Aquifers},
journal = {Ground Water},
publisher = {Blackwell Publishing Ltd},
year = {1988},
volume = {26},
number = {4},
pages = {445--453},
url = {http://dx.doi.org/10.1111/j.1745-6584.1988.tb00411.x}
}
|
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| Smith, J.S. and Valsaraj, K.T. | Reusable adsorbents for dilute solution separation. 2. Model development and residence time distribution characterization for a laboratory adsorption column | 1998 | Separation and Purification Technology Vol. 13(2), pp. 147-159 |
article | URL |
| Abstract: A general mathematical model was derived that describes the process of adsolubilization, i.e. the adsorption of hydrophobic organic compounds (HOCS) onto a packed bed of surfactant-modified alumina. Analytic solutions of the limiting forms of the model were presented for the case where a constant surfactant loading was maintained (i.e. continuous supply of make-up surfactant). Under this condition, classical concentration (C/C°) profiles and breakthrough curves resulted. However, when the surfactant loading was not maintained constant (i.e. no supply of make-up surfactant), numerical solutions showed that the synergistic equilibrium between the HOC and the bound surfactant results in concentration pulses (C/C0 ⪢ 1) in the HOC profile. It was suggested that the latter mode of operation might be a simple means of concentrating dilute solutions. To demonstrate the adsolubilization process, a laboratory adsorber column was fabricated for continuous operation. Residence time distribution (RTD) experiments were conducted to determine the dependence of the axial dispersion coefficient (an important model parameter) upon the fluid velocity. This information will be valuable when comparing model predictions with experimental data collected in Part III of this series. | |||||
BibTeX:
@article{Smith1998,
author = {Smith, Jeffrey S and Valsaraj, Kalliat T},
title = {Reusable adsorbents for dilute solution separation. 2. Model development and residence time distribution characterization for a laboratory adsorption column},
journal = {Separation and Purification Technology},
year = {1998},
volume = {13},
number = {2},
pages = {147--159},
url = {http://www.sciencedirect.com/science/article/pii/S138358669700066X}
}
|
|||||
| Smith, L.C., Elliot, D. and James, A. | Characterisation of mixing patterns in an anaerobic digester by means of tracer curve analysis | 1993 | Ecological Modelling Vol. 69(3-4), pp. 267-285 |
article | URL |
| Abstract: A range of methods for analysing tracer response curves was evaluated for determing mixing patterns in a pilot-scale contact process anaerobic digester. The methods considered included point indices, analytical models such as the dispersion model, and combined models describing different hydraulic zones. In addition, a computer simulation model was developed to quantify the mixing zones and the interaction between them. The methods were compared for (i) ease of use, (ii) accuracy, (iii) consistency, and (iv) application over a wide range of operating conditions. | |||||
BibTeX:
@article{Smith1993,
author = {Smith, Lynn C. and Elliot, D.J. and James, A.},
title = {Characterisation of mixing patterns in an anaerobic digester by means of tracer curve analysis},
journal = {Ecological Modelling},
year = {1993},
volume = {69},
number = {3-4},
pages = {267--285},
url = {http://www.sciencedirect.com/science/article/pii/030438009390030V}
}
|
|||||
| Soetaert, K. and Meysman, F. | Reactive transport in aquatic ecosystems: Rapid model prototyping in the open source software R | 2012 | Environmental Modelling & Software Vol. 32(0), pp. 49-60 |
article | URL |
| Abstract: The concentrations of many natural compounds are altered by chemical and biological transformations, and physical processes such as adsorption and transport. Their fate can be predicted using reactive transport models that describe reaction and advective and dispersive movement of these components in their natural environment. | |||||
BibTeX:
@article{Soetaert2012,
author = {Soetaert, Karline and Meysman, Filip},
title = {Reactive transport in aquatic ecosystems: Rapid model prototyping in the open source software R},
journal = {Environmental Modelling & Software},
year = {2012},
volume = {32},
number = {0},
pages = {49--60},
url = {http://www.sciencedirect.com/science/article/pii/S1364815211001940}
}
|
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| Somes, N., Fabian, J. and Wong, T. | Tracking pollutant detention in constructed stormwater wetlands | 2000 | Urban Water Vol. 2(1), pp. 29-37 |
article | URL |
| Abstract: The detention of stormwater in constructed ponds and wetlands is a widely adopted means of improving the quality of stormwater. The effectiveness of these detention systems in the removal of suspended solids and associated pollutants from stormwater is related to a number of factors, many of which are influenced by the detention period of pollutants. Stormwater detention systems operate over a wide range of hydrodynamic and pollutant loading conditions owing to the stochastic characteristics of stormwater quantity and quality. Stormwater pollutant detention periods vary according to the system hydrology (e.g. inflow characteristics and antecedent storage conditions) and the characteristics of the pollutographs. This paper presents a methodology and two case studies of a research project directed at tracking pollutant detention in basins controlled by two different outlet structures and a range of inflow characteristics. The results of the simulations provide an interesting insight on the influence of the types of outlet structures and stormwater inflow characteristics on the distribution of pollutant detention times. | |||||
BibTeX:
@article{Somes2000,
author = {Somes, N.L.G and Fabian, J and Wong, T.H.F},
title = {Tracking pollutant detention in constructed stormwater wetlands},
journal = {Urban Water},
year = {2000},
volume = {2},
number = {1},
pages = {29--37},
url = {http://www.sciencedirect.com/science/article/pii/S1462075800000376}
}
|
|||||
| Somes, N.L., Bishop, W.A. and Wong, T.H. | Numerical simulation of wetland hydrodynamics | 1999 | Environment International Vol. 25(6–7)International Congress on Modelling and Simulation, pp. 773-779 |
article | URL |
| Abstract: This paper describes the numerical simulation of flow hydrodynamics within a wetland. Using data collected from a field-based investigation of wetland hydrodynamics in the Monash University Research Wetland, a two-dimensional model was developed and calibrated. MIKE 21, a two-dimensional depth averaged model developed by the Danish Hydraulic Institute was used to undertake the simulations. Field observation found that hydraulic roughness, as reflected in the different zones of vegetation, and the relationship between water depth and vegetation, were the factors that controlled flow within the wetland. However, calibration of the model found eddy viscosity was the key calibration parameter due to the flow within the wetland being dominated by inertia rather than friction. | |||||
BibTeX:
@article{Somes1999,
author = {Somes, Nicholas L.G. and Bishop, Warwick A. and Wong, Tony H.F.},
title = {Numerical simulation of wetland hydrodynamics},
booktitle = {International Congress on Modelling and Simulation},
journal = {Environment International},
year = {1999},
volume = {25},
number = {6–7},
pages = {773--779},
url = {http://www.sciencedirect.com/science/article/pii/S0160412099000586}
}
|
|||||
| Soulsby, C., Malcolm, R., Helliwell, R., Ferrier, R.C. and Jenkins, A. | Isotope hydrology of the Allt a' Mharcaidh catchment, Cairngorms, Scotland: implications for hydrological pathways and residence times | 2000 | Hydrological Processes Vol. 14(4), pp. 747-762 |
article | URL |
| Abstract: The hydrology of oxygen-18 (18O) isotopes was monitored between 1995 and 1998 in the Allt a' Mharcaidh catchment in the Cairngorm Mountains, Scotland. Precipitation (mean δ18O=−7·69‰) exhibited strong seasonal variation in δ18O values over the study period, ranging from −2·47‰ in the summer to −20·93‰ in the winter months. As expected, such variation was substantially damped in stream waters, which had a mean and range of δ18O of −9·56‰ and −8·45 to −10·44‰, respectively. Despite this, oxygen-18 proved a useful tracer and streamwater δ18O variations could be explained in terms of a two-component mixing model, involving a seasonally variable δ18O signature in storm runoff, mixing with groundwater characterized by relatively stable δ18O levels. Variations in soil water δ18O implied the routing of depleted spring snowmelt and enriched summer rainfall into streamwaters, probably by near-surface hydrological pathways in peaty soils. The relatively stable isotope composition of baseflows is consistent with effective mixing processes in shallow aquifers at the catchment scale. Examination of the seasonal variation in δ18O levels in various catchment waters provided a first approximation of mean residence times in the major hydrological stores. Preliminary estimates are 0·2–0·8 years for near-surface soil water that contributes to storm runoff and 2 and >5 years for shallow and deeper groundwater, respectively. These 18O data sets provide further evidence that the influence of groundwater on the hydrology and hydrochemistry of upland catchments has been underestimated. | |||||
BibTeX:
@article{Soulsby2000,
author = {Soulsby, C. and Malcolm, R. and Helliwell, R. and Ferrier, R. C. and Jenkins, A.},
title = {Isotope hydrology of the Allt a' Mharcaidh catchment, Cairngorms, Scotland: implications for hydrological pathways and residence times},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2000},
volume = {14},
number = {4},
pages = {747--762},
url = {http://dx.doi.org/10.1002/(SICI)1099-1085(200003)14:4<747::AID-HYP970>3.0.CO;2-0}
}
|
|||||
| Soulsby, C., Piegat, K., Seibert, J. and Tetzlaff, D. | Catchment-scale estimates of flow path partitioning and water storage based on transit time and runoff modelling | 2011 | Hydrological Processes Vol. 25(25), pp. 3960-3976 |
article | URL |
| Abstract: Tracer-derived mean transit times (MTT) and rainfall–runoff modelling were used to explore stream flow generation in 14 Scottish catchments. Both approaches conceptualise the partitioning, storage, and release of water at the catchment scale. The study catchments were predominantly upland and ranged from 0.5 to 1800 km2. Lumped convolution integral models using tracer input–output relationships generally provided well-constrained MTT estimates using a gamma function as the transit time distribution. These ranged from 60 days to >10 years and are mainly controlled by catchment soil cover and drainage density. The HBV model was calibrated using upper and lower storage layers to conceptualise rapidly responding near-surface flow paths and slower groundwater contributions to runoff. Calibrated parameters that regulate groundwater recharge and partitioning between the two storages were reasonably well-identified and correlations with MTTs. The most clearly identified parameters and those with the strongest correlations with MTT and landscape controls (particularly soil cover) were the recession coefficients which control the release of water from the upper and lower storage layers. There was also strong correlation between the ‘dynamic’ storage estimated by HBV and the ‘total’ catchment storage inferred by tracer damping, although the latter was usually two orders of magnitude greater. This is explained by the different storages estimated: while the ‘total’ storage inferred by tracers also includes the passive storage involved in mixing, the model estimates ‘dynamic’ storage from water balance considerations. The former can be interpreted as relating to total porosity, whereas the latter rather corresponds to the drainable porosity. As MTTs for Scottish the uplands can be estimated from catchment characteristics, landscape analysis can be used to constrain sensitive model parameters when modelling in ungauged basins. Furthermore, the ‘dynamic’ storage inferred by HBV may also be used to provide a first approximation of minimum total catchment storage. | |||||
BibTeX:
@article{Soulsby2011,
author = {Soulsby, C. and Piegat, K. and Seibert, J. and Tetzlaff, D.},
title = {Catchment-scale estimates of flow path partitioning and water storage based on transit time and runoff modelling},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {2011},
volume = {25},
number = {25},
pages = {3960--3976},
url = {http://dx.doi.org/10.1002/hyp.8324}
}
|
|||||
| Soulsby, C., Rodgers, P., Smart, R., Dawson, J. and Dunn, S. | A tracer-based assessment of hydrological pathways at different spatial scales in a mesoscale Scottish catchment | 2003 | Hydrological Processes Vol. 17(4), pp. 759-777 |
article | URL |
| Abstract: Geochemically based hydrograph separation techniques were used in a preliminary assessment to infer how runoff processes change with landscape characteristics and spatial scale (1–233 km2) within a mesoscale catchment in upland Scotland. A two-component end-member mixing analysis (EMMA) used Gran alkalinity as an assumed conservative tracer. Analysis indicated that, at all scales investigated, acidic overland flow and shallow subsurface storm flows from the peaty soils covering the catchment headwaters dominated storm runoff generation. The estimated groundwater contribution to annual runoff varied from 30% in the smallest (ca 1 km2) peat-dominated headwater catchment with limited groundwater storage, to >60% in larger catchments (>30 km2) with greater coverage of more freely draining soils and more extensive aquifers in alluvium and other drift. This simple approach offers a useful, integrated conceptualization of the hydrological functioning in a mesoscale catchment, which can be tested and further refined by focused modelling and process-based research. However, even as it stands, the simple conceptualization of system behaviour will have significant utility as a tool for communicating hydrological issues in a range of planning and management decisions. | |||||
BibTeX:
@article{Soulsby2003,
author = {Soulsby, C. and Rodgers, P. and Smart, R. and Dawson, J. and Dunn, S.},
title = {A tracer-based assessment of hydrological pathways at different spatial scales in a mesoscale Scottish catchment},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2003},
volume = {17},
number = {4},
pages = {759--777},
url = {http://dx.doi.org/10.1002/hyp.1163}
}
|
|||||
| Soulsby, C., Tetzlaff, D. and Hrachowitz, M. | Are transit times useful process-based tools for flow prediction and classification in ungauged basins in montane regions? | 2010 | Hydrological Processes Vol. 24(12), pp. 1685-1696 |
article | URL |
| Abstract: Transit times are being increasingly explored as process-based tools for conceptualizing hydrological function at a range of scales. Despite this, little effort has been made to relate transit times to conventional hydrometric flow statistics. Rather, the identification of the appropriate transit time distribution (TTD) for a hydrological system and the derivation of metrics such as the mean transit time (MTT) have required quantitative assessment of input–output relationships for conservative tracers using lumped parameter models. This has allowed the main landscape controls to be identified and has facilitated the prediction of MTTs in ungauged basins in particular geomorphic provinces, though relationships with streamflow measures have been unexamined. We used estimated MTTs (with uncertainty) for 16 experimental catchments (0·5–690 km2 in area) with contrasting geologic, topographic, pedologic and climatic characteristics in Scotland. The MTT was highly variable ranging from 60 days to ca > 1500 days, reflecting differences in catchment soil cover, geomorphic properties and precipitation. The MTT was closely correlated with key hydrometric design statistics such as the mean annual flood (MAF) and percentiles of high (Q5) and low (Q95) flows. Analysis of MTT estimates, in conjunction with geographic information system (GIS)-based assessment of landscape controls, showed that MTT could be predicted to within 30% for ungauged basins from catchment soil cover and drainage density. Furthermore, hydrometric design statistics for ungauged basins could also be forecast from MTT predictions with median relative errors of 14, 11 and 28% for the MAF, Q5 and Q95 respectively. We suggest that MTTs—predicted from mapped landscape characteristics—can be useful diagnostic metrics for ungauged montane basins, as well as a useful similarity index for process-based catchment classification. This is important as montane headwaters are often critical, but data-poor environments influencing the quantity, quality and ecology of downstream flows. | |||||
BibTeX:
@article{Soulsby2010,
author = {Soulsby, C. and Tetzlaff, D. and Hrachowitz, M.},
title = {Are transit times useful process-based tools for flow prediction and classification in ungauged basins in montane regions?},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {12},
pages = {1685--1696},
url = {http://dx.doi.org/10.1002/hyp.7578}
}
|
|||||
| Soulsby, C., Tetzlaff, D., Rodgers, P., Dunn, S. and Waldron, S. | Runoff processes, stream water residence times and controlling landscape characteristics in a mesoscale catchment: An initial evaluation | 2006 | Journal of Hydrology Vol. 325(1–4), pp. 197-221 |
article | URL |
| Abstract: Tracer studies, using Gran alkalinity and δ18O, in nested sub-basins of the 230 km2 Feshie catchment in the Cairngorm mountains, Scotland, were used to characterise hydrology in terms of groundwater contributions to annual runoff and mean residence times. Relationships between these fundamental hydrological descriptors and catchment characteristics were explored with the use of a GIS. Catchment soil distribution—mapped by the UK's Hydrology Of Soil Type (HOST) digital data base—exerted the strongest influence on flow path partitioning and mean residence times. Smallest groundwater contributions (∼30–40%) and shortest residence times (∼2–5 months) were observed in catchments dominated by peat and/or shallow alpine soils and bedrock. Longer residence times (∼12–15 months) and greater groundwater contributions (∼45–55%) were observed in catchments dominated by more freely draining podzolic, sub-alpine and alluvial soils. These different subcatchment responses were integrated to give intermediate residence times (∼6 months) at the catchment outfall. The influence of catchment topography and scale appeared to be largely mediated by their influence on soil cover and distribution. The study illustrates the potential utility of integrating digital landscape analysis with tracer studies to understand the hydrological functioning of mesoscale catchments. | |||||
BibTeX:
@article{Soulsby2006,
author = {Soulsby, C. and Tetzlaff, D. and Rodgers, P. and Dunn, S. and Waldron, S.},
title = {Runoff processes, stream water residence times and controlling landscape characteristics in a mesoscale catchment: An initial evaluation},
journal = {Journal of Hydrology},
year = {2006},
volume = {325},
number = {1–4},
pages = {197--221},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405005433}
}
|
|||||
| Sowman, M., Fuggle, R. and Preston, G. | A review of the evolution of environmental evaluation procedures in South Africa | 1995 | Environmental Impact Assessment Review Vol. 15(1), pp. 45-67 |
article | URL |
| Abstract: In 1989, the Council for the Environment, an advisory committee to the Minister of Environment Affairs, published a document outlining an environmental evaluation procedure appropriate to South Africa's circumstances. This procedure, termed integrated environmental management (IEM), is designed to ensure that the environmental impacts and implications of proposals (including policies, programs, plans, and projects) are investigated and adequately considered in the planning and decision-making process. This article provides an historical perspective on the events that contributed to the development of IEM, as well as some insights into the socioeconomic and political factors that influenced the form of evaluation eventually recommended for South Africa. A description and appraisal of the IEM procedure is then presented. | |||||
BibTeX:
@article{Sowman199,
author = {Sowman, Merle and Fuggle, Richard and Preston, Guy},
title = {A review of the evolution of environmental evaluation procedures in South Africa},
journal = {Environmental Impact Assessment Review},
year = {1995},
volume = {15},
number = {1},
pages = {45--67},
url = {http://www.sciencedirect.com/science/article/pii/019592559400004K}
}
|
|||||
| Speed, M., Tetzlaff, D., Soulsby, C., Hrachowitz, M. and Waldron, S. | Isotopic and geochemical tracers reveal similarities in transit times in contrasting mesoscale catchments | 2010 | Hydrological Processes Vol. 24(9), pp. 1211-1224 |
article | URL |
| Abstract: There is a need for more isotopic tracer studies at the mesoscale to extend our understanding of catchment transit times and their associated controls beyond smaller experimental sites (typically < 10 km2). This paper, therefore, examines the isotope hydrology of six mesoscale (101–102 km2) sub-catchments of the 2000 km2 basin of the River Dee in northern Scotland. All the catchments were upland in character (mean altitude > 400 m) with similar suites of soil coverage (predominantly regosols, gleys, peats and podzols), although the relative distribution varied, as did the presence of other landscape features such as aquifers in Quaternary drifts and lakes. Input–output relationships of δ18O in precipitation and runoff revealed contrasting responses and differential damping which were broadly consistent with catchment characteristics. The mean transit times (MTTs) were estimated using a convolution integral with a Gamma distribution as the transfer function. These varied from 528 days in the most responsive catchments to > 800 days in catchments where the tracer signature was most damped. Shorter MTTs were found in sub-catchments with a higher percentage cover of responsive soils (i.e. regosols, gleys and peats), whilst sub-catchments with longest MTTs had a higher coverage of free-draining podzolic and alluvial soils, as well as significant amount of stored water either in fluvio-glacial aquifers or large lakes. The MTT of all six catchments had the same order of magnitude; this contrasts with studies in the Scottish Highlands with smaller (<10 km2) catchments where MTT has been shown to vary between 60 and 1200 days. | |||||
BibTeX:
@article{Speed2010,
author = {Speed, M. and Tetzlaff, D. and Soulsby, C. and Hrachowitz, M. and Waldron, S.},
title = {Isotopic and geochemical tracers reveal similarities in transit times in contrasting mesoscale catchments},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {9},
pages = {1211--1224},
url = {http://dx.doi.org/10.1002/hyp.7593}
}
|
|||||
| Spielman, L.A. and Levenspiel, O. | A Monte Carlo treatment for reacting and coalescing dispersed phase systems | 1965 | Chemical Engineering Science Vol. 20(3), pp. 247-254 |
article | URL |
| Abstract: The Monte Carlo method of digital computer simulation is used to study the influence of coalescence on the progress of reactions occurring in the dispersed phase of two-phase systems in backmix reactors. Three different types of chemical reaction of both one and two reactants are studied and performance charts are prepared and discussed. It is shown that depending on the system, coalescence can either increase or decrease the extent of conversion of reactants. The Monte Carlo method, because of its simplicity, is found to be especially suited to studying discrete systems of this type since analytical solution is not yet possible and other numerical methods are very cumbersome. Possible extensions are discussed and the possibility of using the dispersed phase model for studying mixing and reaction in homogeneous systems is pointed out. | |||||
BibTeX:
@article{Spielman1965,
author = {Spielman, L. A. and Levenspiel, O.},
title = {A Monte Carlo treatment for reacting and coalescing dispersed phase systems},
journal = {Chemical Engineering Science},
year = {1965},
volume = {20},
number = {3},
pages = {247--254},
url = {http://www.sciencedirect.com/science/article/pii/0009250965800355}
}
|
|||||
| Sposito, G. | Chaotic solute advection by unsteady groundwater flow | 2006 | Water Resources Research Vol. 42(6), pp. W06D03- |
article | URL |
| Abstract: Solute mixing in fluids is enhanced significantly by chaotic advection, the phenomenon in which fluid pathlines completely fill the spatial domain explored by a laminar flow. Steady groundwater flows are, in general, not well conditioned for this phenomenon because Darcy's law confines them spatially to nonintersecting stream surfaces. Unsteady groundwater flows, however, may, in principle, induce chaotic solute advection if their time dependence is periodic and produces frequent reorientation of pathlines, an effect connected closely to the development of high solute mixing efficiencies. In this paper, a simple, two-dimensional model groundwater system is studied theoretically to evaluate the possibility of inducing chaotic solute advection in the flow field near a recirculation well whose pumping behavior is time periodic. In the vernacular of dynamical systems theory the model studied is an example of a Hamiltonian system, thus allowing a mathematical formulation that facilitates consideration of whether chaotic advection can occur. When the model system is driven time periodically by alternate operation of the production and injection components of the recirculation well, numerical simulations of the fluid pathlines indicate that regions of chaotic solute advection will, indeed, develop in the flow field near the well, with expected major improvement in plume spreading. | |||||
BibTeX:
@article{Sposito2006,
author = {Sposito, Garrison},
title = {Chaotic solute advection by unsteady groundwater flow},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2006},
volume = {42},
number = {6},
pages = {W06D03--},
url = {http://dx.doi.org/10.1029/2005WR004518}
}
|
|||||
| Sposito, G., Jury, W.A. and Gupta, V.K. | Fundamental Problems in the Stochastic Convection-Dispersion Model of Solute Transport in Aquifers and Field Soils | 1986 | Water Resources Research Vol. 22(1), pp. 77-88 |
article | URL |
| Abstract: The stochastic convection-dispersion equation (CDE) and its application to field scale subsurface solute transport are investigated with respect to their physical and mathematical foundations. It is shown that even the best-developed stochastic CDE models involve physical approximations and mathematical assumptions which stand in need of much more rigorous theoretical study and detailed field experimentation. The stochastic convection-dispersion model does not yet resolve clearly the mathematical conditions necessary in order to relate the mean solute concentration calculated with a field scale stochastic CDE to measured values of the solute concentration determined in a single field experiment. The “scale effect” in respect to solute dispersion coefficients has been studied only under conditions in which results of little predictive value can be obtained. Without the clarification of these and other fundamental issues raised in the present paper, it seems prudent to conclude that additional theoretical research on field scale solute dispersion is needed and that the stochastic convection-dispersion model does not yet warrant unqualified use as a quantitative predictive tool in the management of solute movement in aquifers and field soils. | |||||
BibTeX:
@article{Sposito1986,
author = {Sposito, Garrison and Jury, William A. and Gupta, Vijay K.},
title = {Fundamental Problems in the Stochastic Convection-Dispersion Model of Solute Transport in Aquifers and Field Soils},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1986},
volume = {22},
number = {1},
pages = {77--88},
url = {http://dx.doi.org/10.1029/WR022i001p00077}
}
|
|||||
| Sposito, G., White, R.E., Darrah, P.R. and Jury, W.A. | A Transfer Function Model of Solute Transport Through Soil: 3. The Convection-Dispersion Equation | 1986 | Water Resources Research Vol. 22(2), pp. 255-262 |
article | URL |
| Abstract: The two-component convection-dispersion equation (CDE) model is developed as a special case of the transfer function model (TFM) of solute transport. It is shown that the two-component CDE model can be reformulated as an integral equation for the “fast” solute component which has the same form and interpretation as the TFM integral equation specialized to (1) steady water flow conditions and (2) solute input or loss restricted to the entrance or exit surface of a soil unit. The travel time probability density function (pdf) for a solute according to the two-component CDE model then is calculated analytically as a Laplace transform. Numerical inversion of the transformed pdf is carried out for several different sets of values of the four adjustable parameters in the CDE model. The effects of convection, dispersion, and linear sorption processes, as well as the influence of the “slow” solute component, are illustrated by the numerically simulated travel time pdf. It is suggested that the fractional transport volume is the most significant physical parameter in the model in terms of impact on the shape of the travel time pdf. | |||||
BibTeX:
@article{Sposito1986a,
author = {Sposito, Garrison and White, Robert E. and Darrah, Peter R. and Jury, William A.},
title = {A Transfer Function Model of Solute Transport Through Soil: 3. The Convection-Dispersion Equation},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {1986},
volume = {22},
number = {2},
pages = {255--262},
url = {http://dx.doi.org/10.1029/WR022i002p00255}
}
|
|||||
| Springer, M.D. | The algebra of random variables [BibTeX] |
1979 | , pp. - | book | |
BibTeX:
@book{Springer1979,
author = {Springer, Melvin Dale},
title = {The algebra of random variables},
publisher = {John Wiley & Sons, Inc.},
year = {1979},
pages = {--}
}
|
|||||
| Srinivasamoorthy, K., Vijayaraghavan, K., Vasanthavigar, M., Rajivgandhi, R. and Sarma, V. | Integrated techniques to identify groundwater vulnerability to pollution in a highly industrialized terrain, Tamilnadu, India | 2011 | Environmental Monitoring and Assessment Vol. 182(1), pp. 47-60 |
article | URL |
| Abstract: Investigation has been made to identify groundwater vulnerability to pollution by using geoelectric and hydrochemical investigations in an important industrial town Mettur located in Tamilnadu state of India. Schlumberger vertical electric soundings were carried out in 23 locations and groundwater samples collected from bore wells in the same locations. The resistivity value with <20 Ωm up to a depth of 36 m indicate contamination of groundwater in areas influenced by sewages from industries, domestic and agricultural practices in the central and southern part of the study area. The calculated specific conductance was noted higher than EC in central and southern part of the study area with low resistivity indicating the contaminated nature of groundwater. Concentrations of Ca, Na, Mg and K along with Cl, HCO 3 , SO 4 and NO 3 were higher in certain locations when compared with WHO and ISI standards. The facies concept demarcated four groups based on the nature of groundwater contamination. The trace elements Fe and Pb were higher in locations confined to industrial zones and Zn and Cu were within the prescribed limit in all the samples. | |||||
BibTeX:
@article{Srinivasamoorthy2011,
author = {Srinivasamoorthy, Krishnaraj and Vijayaraghavan, K. and Vasanthavigar, Murugesan and Rajivgandhi, R. and Sarma, V.},
title = {Integrated techniques to identify groundwater vulnerability to pollution in a highly industrialized terrain, Tamilnadu, India},
journal = {Environmental Monitoring and Assessment},
publisher = {Springer Netherlands},
year = {2011},
volume = {182},
number = {1},
pages = {47--60},
url = {http://dx.doi.org/10.1007/s10661-010-1857-x}
}
|
|||||
| Srinivasan, G., Tartakovsky, D., Dentz, M., Viswanathan, H., Berkowitz, B. and Robinson, B. | Random walk particle tracking simulations of non-Fickian transport in heterogeneous media | 2010 | Journal of Computational Physics Vol. 229(11), pp. 4304-4314 |
article | URL |
| Abstract: Derivations of continuum nonlocal models of non-Fickian (anomalous) transport require assumptions that might limit their applicability. We present a particle-based algorithm, which obviates the need for many of these assumptions by allowing stochastic processes that represent spatial and temporal random increments to be correlated in space and time, be stationary or non-stationary, and to have arbitrary distributions. The approach treats a particle trajectory as a subordinated stochastic process that is described by a set of Langevin equations, which represent a continuous time random walk (CTRW). Convolution-based particle tracking (CBPT) is used to increase the computational efficiency and accuracy of these particle-based simulations. The combined CTRW–CBPT approach enables one to convert any particle tracking legacy code into a simulator capable of handling non-Fickian transport. | |||||
BibTeX:
@article{Srinivasan2010,
author = {Srinivasan, G. and Tartakovsky, D.M. and Dentz, M. and Viswanathan, H. and Berkowitz, B. and Robinson, B.A.},
title = {Random walk particle tracking simulations of non-Fickian transport in heterogeneous media},
journal = {Journal of Computational Physics},
year = {2010},
volume = {229},
number = {11},
pages = {4304--4314},
url = {http://www.sciencedirect.com/science/article/pii/S0021999110000872}
}
|
|||||
| Srivastava, R. and Brusseau, M. | Nonideal transport of reactive solutes in heterogeneous porous media: 1. Numerical model development and moments analysis | 1996 | Journal of Contaminant Hydrology Vol. 24(2), pp. 117-143 |
article | URL |
| Abstract: The transport of reactive solutes at the field scale is characteristically nonideal, and this nonideality is often caused by more than one factor. In these cases, mathematical models that explicitly account for multiple factors are necessary for proper simulation of transport and for accurate analysis of causative factors. The purpose of this paper is to present a mathematical model for simulating the transport of reactive solute in heterogeneous porous media. We have taken a multi-scale, multi-factor approach that explicitly accounts for such factors as hydraulic-conductivity variability, structured porous media, rate-limited diffusive mass transfer, and nonlinear, rate-limited, spatially variable sorption. The influence of these factors on the displacement and spreading of solute plumes and on mass flux is illustrated with a series of two-dimensional (vertical) simulations. | |||||
BibTeX:
@article{Srivastava1996,
author = {Srivastava, R. and Brusseau, M.L.},
title = {Nonideal transport of reactive solutes in heterogeneous porous media: 1. Numerical model development and moments analysis},
journal = {Journal of Contaminant Hydrology},
year = {1996},
volume = {24},
number = {2},
pages = {117--143},
url = {http://www.sciencedirect.com/science/article/pii/S0169772296000393}
}
|
|||||
| Sriyaraj, K. and Shutes, R. | An assessment of the impact of motorway runoff on a pond, wetland and stream | 2001 | Environment International Vol. 26(5-6)Environmental Geochemistry in the Tropics and Subtropics, pp. 433-439 |
article | URL |
| Abstract: The impact of soil filtered runoff from a section of the M25 outer London motorway (constructed in 1981) on a pond, wetland and stream in a nature reserve was investigated by monitoring water, sediment. The tissues of the emergent plants Typha latifolia and Glyceria maxima collected from the pond were analysed for the heavy metals, Cd, Pb, Cu and Zn. Macroinvertebrates were monitored in the stream and biotic indices applied to the data. The plant tissue concentrations for Typha and Glyceria show decreasing metal concentrations from root to rhizome to leaf. This trend has previously been reported for Typha exposed to runoff although the tissue concentrations are lower in this study with the exception of Cd in root tissue. The Biological Monitoring Working Party (BMWP) score and Average Score Per Taxon (ASPT) for the stream at sites above and below the pond outlet are lower than the scores recorded by the Environment Agency for England and Wales at an upstream site above the Pond/Wetland. The sites have an Overall Quality Index of ‘moderate water quality’, and there is no evidence of a deterioration of biologically assessed water quality between them. The results of the study show the long-term impact on sediment of filtered road runoff discharges to a natural wetland and pond located in a nature reserve. The use of natural wetlands for the discharge of road runoff is inadvisable. Constructed wetlands in combination with other structures including settlement trenches and ponds should be considered as an alternative treatment option. | |||||
BibTeX:
@article{Sriyaraj2001,
author = {Sriyaraj, K and Shutes, R.B.E},
title = {An assessment of the impact of motorway runoff on a pond, wetland and stream},
booktitle = {Environmental Geochemistry in the Tropics and Subtropics},
journal = {Environment International},
year = {2001},
volume = {26},
number = {5--6},
pages = {433--439},
url = {http://www.sciencedirect.com/science/article/pii/S0160412001000241}
}
|
|||||
| Stagge, J.H., Davis, A.P., Jamil, E. and Kim, H. | Performance of grass swales for improving water quality from highway runoff | Water Research(0), pp. - | article | URL | |
| Abstract: The performance of grass swales for treating highway runoff was evaluated using an experimental design that allowed for influent and effluent flow and pollutant concentration measurements to be taken at specific intervals through each storm event. Two common swale design alternatives, pre-treatment grass filter strips and vegetated check dams, were compared during 45 storm events over 4.5 years. All swale alternatives significantly removed total suspended solids and all metals evaluated: lead, copper, zinc, and cadmium. The probability of instantaneous concentrations exceeding 30 mg/L TSS was decreased from 41–56% in the untreated runoff to 1–19% via swale treatment. Nutrient treatment was variable, with generally positive removal except for seasonal events with large pulses of release from the swales. Nitrite was the only consistently removed nutrient constituent. Chloride concentrations were higher in swale discharges in nearly every measurement, suggesting accumulation during the winter and release throughout the year. Sedimentation and filtration within the grass layer are the primary mechanisms of pollutant treatment; correspondingly, particles and particulate-bound pollutants show the greatest removal via swales. Inclusion of filter strips or check dams had minimal effects on water quality. | |||||
BibTeX:
@article{Stagge,
author = {Stagge, James H. and Davis, Allen P. and Jamil, Eliea and Kim, Hunho},
title = {Performance of grass swales for improving water quality from highway runoff},
journal = {Water Research},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0043135412001406}
}
|
|||||
| Stephen E., S. | The importance of the third dimension on transport through saturated porous media: case study based on transport of particles | 1996 | Journal of Hydrology Vol. 179(1-4), pp. 181-195 |
article | URL |
| Abstract: The present study involves transport experiments in a three-dimensional, heterogeneous porous medium. Latex particles and chloride are utilized as tracers in an artificially constructed porous medium consisting of a heterogeneous mixture of glass beads. Data collected include chloride breakthrough, particle breakthrough, and particle concentrations remaining within the medium (determined through destructive sampling at the end of the experiment). The chloride breakthrough curve showed substantial dispersion, an indication of mixing among a number of different flow lines (the mixing occurred in the outflow reservoir). The outflow counts of latex particles showed that particles were successfully transported across the length of the medium. The destructive samples showed a complex distribution of particles remaining within the medium which was correlated with the structure of the medium, particularly with the high-permeability pathways. Comparison of the results from this experiment with results from previously published results from two-dimensional media demonstrate that the successful transport of particles across the medium is a direct result of connectivity of high-permeability paths in the third dimension. This observation is consistent both with the distribution of trapped particles and with numerical analysis of the flow field. | |||||
BibTeX:
@article{StephenE.1996,
author = {Stephen E., Silliman},
title = {The importance of the third dimension on transport through saturated porous media: case study based on transport of particles},
journal = {Journal of Hydrology},
year = {1996},
volume = {179},
number = {1-4},
pages = {181--195},
url = {http://www.sciencedirect.com/science/article/pii/0022169495028382}
}
|
|||||
| Steppe, K., De Pauw, D.J. and Lemeur, R. | Validation of a dynamic stem diameter variation model and the resulting seasonal changes in calibrated parameter values | 2008 | Ecological Modelling Vol. 218(3–4), pp. 247-259 |
article | URL |
| Abstract: Validation of ecological models is not a straightforward task and much controversy exists in the published literature on the exact definition. A lot of approaches have been suggested, without one being clearly superior. In this paper, we use the earlier published dynamic ‘RCGro’ tree water flow and storage model as an illustrative example to address some model validation issues. We show that the model fails validation when confronted with a data set not used during model building and calibration. We apply and discuss therefore several validation criteria, including visual comparison between model output and measured data using both time series and scatter plots, calculation of the slope, the intercept and the R2 statistic of the regression line, computation of the model efficiency, and visual analysis of the residual errors. We then investigate Rykiel's [Rykiel Jr., E.J., 1996. Testing ecological models: the meaning of validation. Ecol. Model. 90, 229–244] suggestion to re-calibrate the model in order to deal with validation failures. Using three different data sets representing spring, summer and late summer growth of beech (Fagus sylvatica L.) and oak (Quercus robur L.), we show that model re-calibration is necessary to successfully pass both the visual and the quantitative validation tests. Recalibration caused the values of some of the hydraulic parameters to change (C(stem) and C(crown)) as well as parameters related to radial stem growth (β and ϕ). From these changes, information regarding the overall seasonal behaviour could be derived (e.g., cessation of growth). Additionally, it was shown that general conclusions about the differences between beech and oak (e.g., a higher hydraulic capacitance and a lower hydraulic xylem resistance for oak compared to beech) remained valid across the seasons as well. We finally demonstrate that the recalibrated model parameter values are not transferable across the growing season and underscore the need for caution when applying a model or application developed for one temporal or spatial situation to another. | |||||
BibTeX:
@article{Steppe2008,
author = {Steppe, Kathy and De Pauw, Dirk J.W. and Lemeur, Raoul},
title = {Validation of a dynamic stem diameter variation model and the resulting seasonal changes in calibrated parameter values},
journal = {Ecological Modelling},
year = {2008},
volume = {218},
number = {3–4},
pages = {247--259},
url = {http://www.sciencedirect.com/science/article/pii/S0304380008003475}
}
|
|||||
| Steven S, C. | Environmental justice: the role of epidemiology in protecting unempowered communities from environmental hazards [BibTeX] |
1996 | Science of The Total Environment Vol. 184(1-2), pp. 67-76 |
article | DOI URL |
BibTeX:
@article{StevenS1996,
author = {Steven S, Coughlin},
title = {Environmental justice: the role of epidemiology in protecting unempowered communities from environmental hazards},
journal = {Science of The Total Environment},
year = {1996},
volume = {184},
number = {1-2},
pages = {67--76},
url = {http://www.sciencedirect.com/science/article/pii/0048969795049908},
doi = {http://dx.doi.org/10.1016/0048-9697(95)04990-8}
}
|
|||||
| Stewart, M.K., Morgenstern, U., McDonnell, J.J. and Pfister, L. | The ‘hidden streamflow’ challenge in catchment hydrology: a call to action for stream water transit time analysis [BibTeX] |
2012 | Hydrological Processes Vol. 26(13), pp. 2061-2066 |
article | URL |
BibTeX:
@article{Stewart2012,
author = {Stewart, M. K. and Morgenstern, U. and McDonnell, J. J. and Pfister, L.},
title = {The ‘hidden streamflow’ challenge in catchment hydrology: a call to action for stream water transit time analysis},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd},
year = {2012},
volume = {26},
number = {13},
pages = {2061--2066},
url = {http://dx.doi.org/10.1002/hyp.9262}
}
|
|||||
| Stringfield, V. and LeGrand, H. | Hydrology of carbonate rock terranes — A review: With special reference to the United States | 1969 | Journal of Hydrology Vol. 8(4), pp. 377-417 |
article | URL |
| Abstract: Limestone and other carbonate rocks are characterized by many unusual features and extreme conditions, either involving the hydrologic system within them or wrought by hydrologic conditions on them or through them. Perhaps there could be little agreement as to what is typical or average for the many features of carbonate rocks, as indicated by the following conditions: bare rock and thin soils are common, but so are thick soils; very highly permeable limestones are common, but so are poorly permeable ones; and rugged karst topographic features with underlying solution caverns are common, but so are flat, nearly featureless topographic conditions. Some conditions of carbonate terranes are suitable to man's needs and interests, such as the use of some permeable aquifers for water supply and the exploitation of caves for tourist attractions. On the other hand, many problems may exist, including: permeability too low for adequate water supply or so high that the aquifer retains too little water for use during periods of fair weather, soils too thin for growing of crops and for adequate filtration of wastes near the ground surface, instability of the ground for buildings and foundations in sinkhole areas, and unusually rugged topography. Some of the many variable conditions are readily observable, but others can be determined only by careful geologic and hydrologic studies. | |||||
BibTeX:
@article{Stringfield1969,
author = {Stringfield, V.T. and LeGrand, H.E.},
title = {Hydrology of carbonate rock terranes — A review: With special reference to the United States},
journal = {Journal of Hydrology},
year = {1969},
volume = {8},
number = {4},
pages = {377--417},
url = {http://www.sciencedirect.com/science/article/pii/0022169469901000}
}
|
|||||
| Stueber, A.M. and Criss, R.E. | Origin and transport of dissolved chemicals in a karst watershed, Southwestern Illinois | 2005 | JAWRA Journal of the American Water Resources Association Vol. 41(2), pp. 267-290 |
article | URL |
| Abstract: An extensive base of water quality information emphasizing the effects of land use and hydrology was obtained in the karstified Fountain Creek watershed of southwestern Illinois to help resolve local water quality issues. Agrichemicals dominate the loads of most water quality constituents in the streams and shallow karstic ground water. Only calcium (Ca), magnesium (Mg), Aluminum (A1), and sulfate (SO4) ions are predominantly derived from bedrock or soils, while agrichemicals contribute most of the sodium (Na), potassium (K), chlorine (Cl), nitrate (NO3), fluorine (F), phosphorus (P), and atrazine. Concentrations of individual ions correlate with discharge variations in karst springs and surface streams; highly soluble ions supplied by diffuse ground water are diluted by high flows, while less soluble ions increase with flow as they are mobilized from fields to karst conduits under storm conditions. Treated wastewater containing detergent residues dominates the boron load of streams and provides important subordinate loads of several other constituents, including atrazine derived from the Mississippi River via the public water supply. Average surface water concentrations at the watershed outlet closely approximate a 92:8 mixture of karst ground water and treated wastewater, demonstrating the dominance of ground water contributions to streams. Therefore the karst aquifer and watershed streams form a single water quality system that is also affected by wastewater effluent. | |||||
BibTeX:
@article{Stueber2005,
author = {Stueber, Alan M. and Criss, Robert E.},
title = {Origin and transport of dissolved chemicals in a karst watershed, Southwestern Illinois},
journal = {JAWRA Journal of the American Water Resources Association},
publisher = {Blackwell Publishing Ltd},
year = {2005},
volume = {41},
number = {2},
pages = {267--290},
url = {http://dx.doi.org/10.1111/j.1752-1688.2005.tb03734.x}
}
|
|||||
| Su, L.-H. and Tien, Y.-Y. | Minimizing mean absolute deviation of completion time about a common due window subject to maximum tardiness for a single machine | 2011 | International Journal of Production Economics Vol. 134(1)Enterprise risk management in operations, pp. 196-203 |
article | URL |
| Abstract: This study deals with the problem of scheduling jobs on a single machine to minimize the mean absolute deviation of the job completion time about a large common due window subject to the maximum tardiness constraint. Using the well-known three-field notation, the problem is identified as MAD/large DueWindow/Tmax. The common due window is set to be large enough to allow idle time prior to the beginning of a schedule to investigate the effect of the Tmax constraint. Penalties arise if a job is completed outside the due window. A branch and bound algorithm and a heuristic are proposed. Many properties of the solutions and precedence relationships are identified. Our computational results reveal that the branch and bound algorithm is capable of solving problems of up to 50 jobs and the heuristic algorithm yields approximate solutions that are very close to the exact solution. | |||||
BibTeX:
@article{Su2011,
author = {Su, Ling-Huey and Tien, Yi-Yu},
title = {Minimizing mean absolute deviation of completion time about a common due window subject to maximum tardiness for a single machine},
booktitle = {Enterprise risk management in operations},
journal = {International Journal of Production Economics},
year = {2011},
volume = {134},
number = {1},
pages = {196--203},
url = {http://www.sciencedirect.com/science/article/pii/S0925527311002829}
}
|
|||||
| Suh, K.-S., Kim, K.-C., Park, G.-H., Jung, S.-H. and Lee, J.-L. | Numerical analysis of a pollutant dispersion in subsurface soil | 2011 | Mathematical and Computer Modelling Vol. 54(11-12), pp. 3197-3203 |
article | URL |
| Abstract: A hydraulic scale model was used in a laboratory experiment for the purpose of understanding the characteristics of a pollutant dispersion in subsurface soil. The experimental site was an area near a radioactive waste repository in the Republic of Korea. The hydraulic scale model was designed and manufactured in geometric similarity to the actual site. The tracer 99mTc which has a short half-life was injected instantaneously into the soil. Numerical simulations were performed to compare the measured radioisotope data and to investigate the overall dispersion patterns. The calculated concentrations are in good agreement with a time series of the measured concentrations at the midpoint of the detection lines. | |||||
BibTeX:
@article{Suh2011,
author = {Suh, Kyung-Suk and Kim, Ki-Chul and Park, Geon-Hyeong and Jung, Sung-Hee and Lee, Jung-Lyul},
title = {Numerical analysis of a pollutant dispersion in subsurface soil},
journal = {Mathematical and Computer Modelling},
year = {2011},
volume = {54},
number = {11-12},
pages = {3197--3203},
url = {http://www.sciencedirect.com/science/article/pii/S0895717711004961}
}
|
|||||
| Sukop, M., Anwar, S., Lee, J., Cunningham, K. and Langevin, C. | Modeling Ground-water Flow and Solute Transport in Karst with Lattice Boltzmann Methods | 2008 | U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, pp. 77-86 | inproceedings | URL |
| Abstract: Lattice Boltzmann Methods (LBMs) are relatively new and have not yet been widely applied to ground-water systems. LBMs are particularly attractive for numerical modeling of flow and solute transport in karst aquifers because they are able to: . Simulate inertial flows . Incorporate complex wall and conduit geometries . Solve adjacent Darcian and Navier-Stokes flow regimes . Solve the appropriate advection-diffusion equation in conduit zones characterized by laminar or eddy flow and solve a linked anisotropic advection-dispersion equation in porous media zones with Darcian flow Examples are provided for each of these capabilities. |
|||||
BibTeX:
@inproceedings{Sukop2008,
author = {Sukop, M.C. and Anwar, S. and Lee, J.S. and Cunningham, K.J. and Langevin, C.D.},
title = {Modeling Ground-water Flow and Solute Transport in Karst with Lattice Boltzmann Methods},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023},
publisher = {U.S. Geological Survey Karst Interest Group and National Cave and Karst Research Institute and Hoffman Environmental Research Center and Center for Cave and Karst Studies at Western Kentucky University},
year = {2008},
pages = {77--86},
url = {http://pubs.usgs.gov/sir/2008/5023/32sukop.htm}
}
|
|||||
| Sürücü, B. and Sazak, H.S. | Monitoring reliability for a three-parameter Weibull distribution | 2009 | Reliability Engineering & System Safety Vol. 94(2), pp. 503-508 |
article | URL |
| Abstract: Control charts are widely used to monitor production processes in the manufacturing industry and are also useful for monitoring reliability. A method to monitor reliability has recently been proposed when the distributions of inter-failure times are exponential and Weibull with known parameters. This method has also been extended to monitor the cumulative time elapsed between a fixed number of failures for the exponential distribution. In this paper, we consider a three-parameter Weibull distribution to model inter-failure times, use a robust estimation technique to estimate the unknown parameters, and extend the proposed method to monitor the cumulative time elapsed between r failures using the three-parameter Weibull distribution. Since the distribution of the sum of independent Weibull random variates is not known (except in specific cases with known parameters), we give two useful moment approximations to be able to apply their scheme. We show how effective the approximations are and the usefulness of the method in detecting a possible instability during production. | |||||
BibTeX:
@article{Sueruecue2009,
author = {Sürücü, Barış and Sazak, Hakan S.},
title = {Monitoring reliability for a three-parameter Weibull distribution},
journal = {Reliability Engineering & System Safety},
year = {2009},
volume = {94},
number = {2},
pages = {503--508},
url = {http://www.sciencedirect.com/science/article/pii/S0951832008001737}
}
|
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| Sze, M.F.F. and McKay, G. | Enhanced mitigation of para-chlorophenol using stratified activated carbon adsorption columns | 2012 | Water Research Vol. 46(3), pp. 700-710 |
article | URL |
| Abstract: The adsorptive removal of toxic para-chlorophenol using activated carbon adsorption columns is a proven effective engineering process. This paper examined the possibility to stratify an adsorbent bed into layers, in order to enhance the adsorption process performance in terms of increased column service time and adsorbent bed saturation. Four different types of fixed-bed adsorption columns are used and compared under the same operating conditions, but with the variation of column geometry and activated carbon particle size stratification. The Type 3 column – a cylindrical column with particle stratification packing, is found to be the most efficient choice, as the extent of column service time and adsorbent bed saturation are the largest. This could eventually decrease the frequency of adsorbent replacement/regeneration and hence reduce the operating cost of the fixed-bed adsorption process. The Homogeneous Surface Diffusion Model (HSDM) was applied successfully to describe the dynamic adsorption of para-chlorophenol onto Filtrasorb 400 (F400) activated carbon in different types of columns. The Redlich-Peterson isotherm model equation, an experimentally derived external mass transfer correlation and a constant surface diffusivity are used in the HSDM. The optimised surface diffusivity of para-chlorophenol is found to be 1.20E-8 cm2/s, which is in good agreement with other phenolics/F400 carbon diffusing systems in literature. | |||||
BibTeX:
@article{Sze2012,
author = {Sze, Michael Fan Fu and McKay, Gordon},
title = {Enhanced mitigation of para-chlorophenol using stratified activated carbon adsorption columns},
journal = {Water Research},
year = {2012},
volume = {46},
number = {3},
pages = {700--710},
url = {http://www.sciencedirect.com/science/article/pii/S0043135411007238}
}
|
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| Szecsody, J.E. and Bales, R.C. | Sorption kinetics of low-molecular-weight hydrophobic organic compounds on surface-modified silica | 1989 | Journal of Contaminant Hydrology Vol. 4(2), pp. 181-203 |
article | URL |
| Abstract: The rate of sorption and desorption of substituted benzenes was investigated in a series of batch and column experiments using surface-modified silica of known chemical composition. Porous silicas with patchy surface coatings of aliphatic-chain groups (C1, C8 and C18) and an aliphatic chain terminating in a phenyl group were prepared; these were less hydrophobic and more easily wetted by water than similar, commercially available, chromatography materials. The surfaces were chosen to represent important functional groups found in soil and aquifer materials. Batch desorption of p-nitrobenzene, nitrotoluene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, and 1,2,4,5-tetrachlorobenzene required up to 100 hours to reach equilibrium. Slow sorption and desorption of 1,4-dichlorobenzene in column experiments was evidenced by tailing in breakthrough curves. Results were interpreted considering three possible rate-limiting steps: diffusion through immobile liquid, diffusion through a bound organic phase, and slow chemical binding and release. Diffusion through immobile fluid caused some but not all of the observed slow sorption, as evidenced by experiments with different particle size and pore size (toruosity). Desorption on C8- and C18- modified silicas was at least one order of magnitude faster than on phenyl and C1 surfaces, illustrating the importance of the nature of the surface organic phase. Simple diffusion through the bound organic phase is not an adequate explanation for the behavior, due to the small distances. Slow binding and release at strong sites for sorption of 1,4-dichlorobenzene on the phenyl-polymer-modified silica apparently caused most of the observed tailing. First-order rate coefficients observed for all modified surfaces were in the range of 10−4-10−1 s−1. As equilibrium is reached within hours, slow sorption is observed at the laboratory scale, but local equilibrium applies to most field situations. | |||||
BibTeX:
@article{Szecsody1989,
author = {Szecsody, James E. and Bales, Roger C.},
title = {Sorption kinetics of low-molecular-weight hydrophobic organic compounds on surface-modified silica},
journal = {Journal of Contaminant Hydrology},
year = {1989},
volume = {4},
number = {2},
pages = {181--203},
url = {http://www.sciencedirect.com/science/article/pii/016977228990020X}
}
|
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| Szeftel, P., (Dan) Moore, R. and Weiler, M. | Influence of distributed flow losses and gains on the estimation of transient storage parameters from stream tracer experiments | 2011 | Journal of Hydrology Vol. 396(3-4), pp. 277-291 |
article | URL |
| Abstract: Interactions between mobile stream water and transient storage zones have been the subject of careful attention for decades. However, few studies have considered explicitly the influence of water exchange between the channel and neighbouring hydrological units when modelling transient storage processes, especially the lateral inflow coming from hillslope contributions and outflow to a deep aquifer or to hyporheic flow paths extending beyond the study reach. The objective of this study was to explore the influence of different conceptualizations of these hydrologic exchanges on the estimation of transient storage parameters. Slug injections of sodium chloride (NaCl) were carried out in eight contiguous reaches in the Cotton Creek Experimental Watershed (CCEW), located in south-east British Columbia. Resulting breakthrough curves were subsequently analysed using a Transient Storage Model (TSM) in an inverse modelling framework. We estimated solute transport parameters using three distinct, hypothetical spatial patterns of lateral inflow and outflow, all based on variations of the same five-parameter model structure. We compared optimized parameter values to those resulting from a distinct four-parameter model structure meant to represent the standard application of the TSM, in which only lateral inflow was implemented for net gaining reaches or only lateral outflow for net losing reaches. In the five-parameter model, solute mass was stored predominantly in the transient storage zone and slowly released back to the stream. Conversely, solute mass was predominantly removed from the stream via flow losses in the four-parameter model structure. This led to contrasting estimates of solute transport parameters and subsequent interpretation of solute transport dynamics. Differences in parameter estimates across variations of the five-parameter model structure were small yet statistically significant, except for the transient storage exchange rate coefficient α, for which unique determination was problematic. We also based our analysis on F med 200 , the fraction of median transport time due to transient storage. Differences across configurations in F med 200 estimates were consistent but small when compared to the variability of F med 200 among reaches. Optimized parameter values were influenced dominantly by the model structure (four versus five parameters) and then by the conceptualization of spatial arrangement of lateral fluxes along the reach for a set model structure. When boundary conditions are poorly defined, the information contained in the stream tracer breakthrough curve is insufficient to identify a single, unambiguous model structure representing solute transport simulations. Investigating lateral fluxes prior to conducting a study on transient storage processes is necessary, as assuming a certain spatial organization of these fluxes might set ill-defined bases for inter-reach comparisons. Given the difficulty in quantifying the spatial patterns and magnitudes of lateral inputs and outputs, we recommend small-scale laboratory tracer experiments with well-defined and variable boundary conditions as a complement to field studies to provide new insights into stream solute dynamics. | |||||
BibTeX:
@article{Szeftel2011,
author = {Szeftel, Pascal and (Dan) Moore, R.D. and Weiler, Markus},
title = {Influence of distributed flow losses and gains on the estimation of transient storage parameters from stream tracer experiments},
journal = {Journal of Hydrology},
year = {2011},
volume = {396},
number = {3-4},
pages = {277--291},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410007146}
}
|
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| Taghavy, A., Costanza, J., Pennell, K.D. and Abriola, L.M. | Effectiveness of nanoscale zero-valent iron for treatment of a PCE–DNAPL source zone | 2010 | Journal of Contaminant Hydrology Vol. 118(3-4)Manufactured Nanomaterials in Subsurface Systems, pp. 128-142 |
article | URL |
| Abstract: Nanoscale zero-valent iron (nZVI) has received considerable attention as a potential in situ remediation technology for treating chlorinated solvent source zones. Experimental and mathematical modeling studies were conducted to investigate the performance of nZVI in the transformation of tetrachloroethene (PCE) entrapped as a dense nonaqueous phase liquid (DNAPL). Injection of a 60 g/L suspension of nZVI into a column containing 20–30 mesh Ottawa sand and PCE–DNAPL at a residual saturation of 5.5% resulted in a uniform distribution of nZVI and minimal displacement of PCE. Subsequent flushing with 267 pore volumes of water containing 3 mM CaCl2 at a Darcy velocity of 0.75 m/day resulted in steady-state effluent concentrations of PCE near the solubility limit (ca. 200 mg/L) and production of dissolved-phase ethene (10–30 mg/L). Over the duration of the experiment, approximately 30% of the initial PCE–DNAPL mass reacted to form ethene, 50% was eluted as dissolved-phase PCE, and 20% remained in the column as PCE–DNAPL. To further explore the implications of the nZVI column results, a multiphase transport model was developed that incorporated rate-limited PCE–DNAPL dissolution and reactions with nZVI. Using a fitted pseudo first-order transformation rate coefficient of 1.42 1/h, the model accurately captured observed trends in effluent concentrations of PCE and ethene and overall mass balance. A model sensitivity study reveals a strong dependence of treatment effectiveness on system characteristics. The sensitivity analysis suggests that an increase in the extent of PCE transformation is facilitated by decreasing flow rate, emplacement of nZVI down-gradient of the DNAPL source zone, and decreasing length of the DNAPL source zone. These findings indicate that, although emplacement of high concentrations of nZVI within a PCE–DNAPL source zone can result in substantial transformation of the parent compound, careful attention to design parameters (e.g. flow rate, location and amount nZVI delivered) will be required to achieve complete conversion to benign reaction products. | |||||
BibTeX:
@article{Taghavy2010,
author = {Taghavy, Amir and Costanza, Jed and Pennell, Kurt D. and Abriola, Linda M.},
title = {Effectiveness of nanoscale zero-valent iron for treatment of a PCE–DNAPL source zone},
booktitle = {Manufactured Nanomaterials in Subsurface Systems},
journal = {Journal of Contaminant Hydrology},
year = {2010},
volume = {118},
number = {3-4},
pages = {128--142},
url = {http://www.sciencedirect.com/science/article/pii/S0169772210001063}
}
|
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| Talei, A., Chua, L.H.C. and Quek, C. | A novel application of a neuro-fuzzy computational technique in event-based rainfall–runoff modeling | 2010 | Expert Systems with Applications Vol. 37(12), pp. 7456-7468 |
article | URL |
| Abstract: Intelligent computing tools based on fuzzy logic and Artificial Neural Networks (ANN) have been successfully applied in various problems with superior performances. A new approach of combining these two powerful AI tools, known as neuro-fuzzy systems, has increasingly attracted scientists in different fields. Although many studies have been carried out using this approach in pattern recognition and signal processing, few studies have been undertaken to evaluate their performances in hydrologic modeling, specifically rainfall–runoff (R–R) modeling. This study presents an application of an Adaptive Network-based Fuzzy Inference System (ANFIS), as a neuro-fuzzy-computational technique, in event-based R–R modeling in order to evaluate the capabilities of this method for a sub-catchment of Kranji basin in Singapore. Approximately two years of rainfall and runoff data which from 66 separate rainfall events were analyzed in this study. Two different approaches in the selection criteria for calibration events were adopted and the performance of an ANFIS R–R model was compared against an established physically-based model called Storm Water Management Model (SWMM) in R–R modeling. The results of this study show that the selected neuro-fuzzy-computational technique (ANFIS) is comparable to SWMM in event-based R–R modeling. In addition, ANFIS is found to be better at peak flow estimation compared to SWMM. This study demonstrates the promising potential of neuro-fuzzy-computationally inspired hybrid tools in R–R modeling and analysis. | |||||
BibTeX:
@article{Talei2010,
author = {Talei, Amin and Chua, Lloyd Hock Chye and Quek, Chai},
title = {A novel application of a neuro-fuzzy computational technique in event-based rainfall–runoff modeling},
journal = {Expert Systems with Applications},
year = {2010},
volume = {37},
number = {12},
pages = {7456--7468},
url = {http://www.sciencedirect.com/science/article/pii/S0957417410002861}
}
|
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| Tamburo, E., Aiuppa, A., Marini, L. and Valenza, M. | Modelling groundwater processes in a carbonate catchment: A case study from the Madonie area (Northern Sicily) | 2011 | Applied Geochemistry Vol. 26(7), pp. 1274-1287 |
article | URL |
| Abstract: This study reports on the results of a hydrogeochemical survey carried out in the Madonie area, a carbonate massif located in Palermo Province, Northern Sicily. The large dataset (226 collected sites) is used to highlight the processes controlling the distribution of dissolved chemicals in groundwaters; and, more importantly, to develop a general model (based on reaction-path modelling, and using the EQ3/6 code) of rock–water reactions in a carbonate environment. The investigated groundwater samples have conductivity between 31.7 and 8220 μS/cm; their total dissolved solids (TDS) content is higher near the coast area, where the seawater contribution becomes important. Calcium and HCO 3 - excess concentrations in groundwaters, with respect to the meteoric water–seawater mixing line, suggest that water–rock interactions in carbonate aquifers play a major role on water chemistry. Using the dataset, reaction-path modelling is used to simulate the evolution of groundwaters upon interaction with carbonate rocks. Model simulations are performed in time mode, taking into account the mineralogical composition of Madonie carbonate rocks, and the different dissolution rates of each dissolving mineral. The model results of reaction path calculations are in fair agreement with analytical data for natural waters, demonstrating the likelihood of model assumptions, and supporting further the relevance of carbonate dissolution in determining the chemistry of fluids in the investigated area. The developed model is useful for low-temperature weathering of carbonate mineral in general, and is thus likely to apply in a variety of geological contexts. | |||||
BibTeX:
@article{Tamburo2011,
author = {Tamburo, E. and Aiuppa, A. and Marini, L. and Valenza, M.},
title = {Modelling groundwater processes in a carbonate catchment: A case study from the Madonie area (Northern Sicily)},
journal = {Applied Geochemistry},
year = {2011},
volume = {26},
number = {7},
pages = {1274--1287},
url = {http://www.sciencedirect.com/science/article/pii/S0883292711002551}
}
|
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| Tanner, C.C., Kadlec, R.H., Gibbs, M.M., Sukias, J.P. and Nguyen, M. | Nitrogen processing gradients in subsurface-flow treatment wetlands—influence of wastewater characteristics | 2002 | Ecological Engineering Vol. 18(4), pp. 499-520 |
article | URL |
| Abstract: Nitrification, an aerobic microbial process, is generally considered to be the rate-limiting step for N removal in subsurface-flow (SSF) constructed wetlands treating organic wastewaters. SSF wetland nitrogen (N) processing gradients were investigated using cascade mesocosms comprised of five planted (Schoenoplectus tabernaemontani), gravel-filled tanks operated in series, in order to determine the effects of organic substrate availability (measured as chemical oxygen demand, COD) and partial pre-nitrification on rates of N removal. Duplicate sets of cascades supplied with 23 mm d−1 of four different organic wastewaters provided COD:N ratios of ∼2–15 (<1–30 in individual tanks) and a range of N species balances (34–88% ammoniacal-N, NH4-N; <1–40% oxidised N, NOx-N). Mass balances for organic N (Org-N), NH4-N and NOx-N, and COD removal were calculated for each tank of the cascades. Concurrent measurements were made of plant growth and N uptake, sediment N accumulation and selected biogeochemical indicators (redox potential, pH, and CO2 and CH4 emissions). Using a simplified model of sequential N transformations and sinks, average net rates of N mineralisation ranged from 0.22 to 0.53 g m−2 d−1, nitrification from 0.56 to 2.15 g m−2 d−1, denitrification from 0.47 to 1.99 g m−2 d−1 (60–84% of measured N removal) and plant assimilation from 0.28 to 0.47 g m−2 d−1 in the cascade tanks. Nitrification and denitrification occurred concurrently with COD removal, even in the upstream stages of cascades receiving the higher-strength wastewaters. Surprisingly, neither net areal nitrification rates, nor first order nitrification rate constants (kA) were correlated with COD removal rates (as a measure of heterotrophic oxygen demand). Nitrification rates were correlated with average NH4-N concentrations in the cascade tanks, and were closely paralleled by net denitrification rates. Although kA for N mineralisation, nitrification and total N removal were highest for the partially pre-nitrified wastewater tested, considerably higher areal mass removals were achieved in the cascades receiving more concentrated ammonium-rich wastewaters. The oxygen demand required to support full nitrification of ammonia and mineralised Org-N in the cascades (without accounting for competitive heterotrophic oxygen demand) was in the upper range of that expected to be able to be supplied through surficial and plant-mediated oxygen transfer. Implications for understanding the nature of coupled nitrification–denitrification and COD removal in SSF treatment wetlands are discussed. | |||||
BibTeX:
@article{Tanner2002,
author = {Tanner, Chris C. and Kadlec, Robert H. and Gibbs, Max M. and Sukias, James P.S. and Nguyen, M.Long},
title = {Nitrogen processing gradients in subsurface-flow treatment wetlands—influence of wastewater characteristics},
journal = {Ecological Engineering},
year = {2002},
volume = {18},
number = {4},
pages = {499--520},
url = {http://www.sciencedirect.com/science/article/pii/S0925857402000113}
}
|
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| Tanveer, S. | Singularities in the Classical Rayleigh-Taylor Flow: Formation and Subsequent Motion | 1993 | Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences Vol. 441(1913), pp. 501-525 |
article | DOI URL |
| Abstract: This paper is concerned with the creation and subsequent motion of singularities of solution to classical Rayleigh-Taylor flow (two-dimensional inviscid, incompressible fluid over a vacuum). For a specific set of initial conditions, we give analytical evidence to suggest the instantaneous formation of one or more singularity(ies) at specific point(s) in the unphysical plane, whose locations depend sensitively to small changes in initial conditions in the physical domain. One-half power singularities are created in accordance with an earlier conjecture; however, depending on initial conditions, other forms of singularities are also possible. For a specific initial condition, we follow a numerical procedure in the unphysical plane to compute the motion of a one-half singularity. This computation confirms our previous conjecture that the approach of a one-half singularity towards the physical domain corresponds to the development of a spike at the physical interface. Under some assumptions that appear to be consistent with numerical calculations, we present analytical evidence to suggest that a singularity of the one-half type cannot impinge the physical domain in finite time. | |||||
BibTeX:
@article{Tanveer1993,
author = {Tanveer, S.},
title = {Singularities in the Classical Rayleigh-Taylor Flow: Formation and Subsequent Motion},
journal = {Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences},
year = {1993},
volume = {441},
number = {1913},
pages = {501--525},
url = {http://rspa.royalsocietypublishing.org/content/441/1913/501.abstract},
doi = {http://dx.doi.org/10.1098/rspa.1993.0076}
}
|
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| Taylor, C.J. and Greene, E.A. | Quantitative Approaches in Characterizing Karst Aquifers | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 164-166 | inproceedings | URL |
| Abstract: Karst aquifers are an important ground-water resource and are highly vulnerable to contamination due to relatively fast transport and limited attenuation processes. Quantitative understanding of karst hydrologic functions is integral to managing water resources and developing protection or remediation strategies. However, traditional methods of aquifer characterization and testing, based on Darcian approaches, provide misleading or inadequate quantitative data when applied to karst settings. This difficulty is partly a problem of scale (volume of aquifer tested), and partly a problem of the complex nature of the typical karst aquifer system. Early approaches to studying karst concentrated on describing geomorphic features and their hydrologic functions, or understanding singular elements of karst flow dynamics, such as spring discharge, or hydraulic properties of solutional conduits. However, proper understanding of karst aquifers requires a systems approach in which the hydrologic function of each primary component-vadose zone, epikarst, and conduit network-is considered separately and as an integrated part of the whole system. The major difficulty facing the hydrologist is that karst aquifers typically exhibit dual ground-water flow regimes, that is, fast (conduit-dominated) flow and slow (diffuse) flow. In selecting investigative techniques to characterize properties of a karst aquifer, it is therefore important to determine how the data obtained by a particular test method are influenced by the fast-flow regime, slow-flow regime, or both. With this point in mind, several quantitative methods that are particularly useful in investigating the hydraulic parameters of the karst aquifer system are briefly discussed here. Quantitative water-tracing tests, conducted with fluorescent dyes, are among the most useful types of field methods that can be employed in the investigation of a karst aquifer. A common misconception is that dye-tracing methods are too expensive, difficult, or unreliable, to use in many karst investigations. This is simply not the case. Like any other type of aquifer-testing technique, dye-tracing tests require careful planning and implementation, and a proper understanding of the applicability and limitations of the techniques and the data. One great advantage is that tracer tests can be designed and implemented to any field scale, and another is that the movement of the dye tracer almost exactly replicates the movement of water (and many dissolved solutes) through the aquifer. Quantitative water-tracing tests require careful measurement of dye concentration at frequent sampling intervals and discharge through the sampled part of the aquifer, usually a spring. It is advisable that qualitative, or point-to-point tracer tests, using passive dye detectors and less frequent sampling, be conducted first to delineate ground-water flow paths, ensure that all potential dye-resurgence sites are known and sampled, aid in selecting the proper sampling frequency and duration, and assess the possible interference of ambient fluorescent solutes with detection and measurement of the tracer dye. The use of dye-tracing tests to delineate ground- water flowpaths and basin boundaries in karst aquifers is demonstrated by Bayless, Taylor, and Hopkins (1994) and Taylor and McCombs (1998). The principal tool for analysis of quantitative water-tracing tests conducted with fluorescent dyes is the dye hydrograph, a specialized tracer breakthrough curve. The time of travel of the dye, indicated by the first detection of dye at concentrations above background fluorescence levels, provides a direct measurement of average ground-water velocity. The shape of the dye-hydrograph curve provides an indication of the dispersion of the dye as it migrates through the aquifer (Greene, 1999). For example, multiple peaks on a dye hydrograph may indicate splitting of the dye along multiple flow paths (conduits), or intermittent flushing of dye from hydraulic dead zones. Dye hydrograph analysis is particularly useful in contaminant transport investigations, because the tracer dye can be used as a surrogate pollutant. Estimates of peak contaminant concentration, persistence at concentrations that exceed quality criteria (such as maximum contaminant level, or MCL), and contaminant loading can be easily calculated for karst springs (Mull and others, 1988). Data obtained from quantitative dye-tracing tests can also be used to calculate a variety of parameters related to the geometry and hydraulic properties of any type of conduit network system. A good demonstration of the application of these techniques was presented by Fountain (1993) in a study of subglacial conduit networks. Examples of physical properties that can be calculated include conduit diameter, surface area, and hydraulic depth (assuming open-channel flow conditions). Estimates of fluid dynamic parameters that can be determined include the Peclet number, Reynolds number, Froude number, and hydraulic head loss. A summary of these methods and a software program that greatly facilitates the calculations involved in dye-hydrograph analysis was recently published by Field (1999). Traditional aquifer tests can be used to estimate rates of ground-water movement and hydraulic properties such as transmissivity and storativity if special consideration is given to the dual-flow nature of karst aquifers while interpreting the aquifer test data. Recognition must be given to the fact that the framework of the karst aquifer is composed of integrated networks of fractures and solutional conduits of different sizes and interconnection. The aquifer test data represents a measurement of the composite hydraulic response of families of fractures and solutional conduits having different hydraulic characteristics (Streltsova, 1988). The larger solutional openings act collectively as the initial source of water being pumped during an aquifer test. Typically, these larger solutional openings are hydraulically connected to smaller, more diffuse sets of fractures in the aquifer. As the pumping continues, the fluid pressure in the larger solutional openings is reduced, resulting in hydraulic gradients which allow water in the diffuse fractures to provide recharge to the larger solutional openings. Thus, in describing the hydraulic properties of the karst aquifer, four physical parameters must be described: T, the transmissivity of the solutional openings; S, the storativity of the solutional openings; Sf, the storativity of the network of diffuse fractures; and b, the rate of fluid exchange between the network of fractures and the solutional openings (Greene, Shapiro, and Carter, 1999). As a tool for simulation of flow and transport in karst aquifers, numerical models are frequently used. At present, great difficulties exist in accurately simulating karst flow systems at the local or subregional scale because of the difficulty in developing numerical models that realistically represent boundary conditions for conduit networks. Nevertheless, numerical models are among the best quantitative tools for gaining a better understanding of the functioning of individual karst hydrology components and for predicting how the system works as a whole. The two most common types of approaches can be classified as either a black box (or lumped parameter) approach or a distributed parameter approach. The black box approach uses techniques such as recession analysis and transfer/kernel functions to simulate karst aquifers. Several examples are shown where recession analysis is used to estimate regional hydraulic parameters and the volume of available ground-water resources. In addition, we demonstrate the use of kernel functions to interpret and simulate karst responses to precipitation. The limitations of the black box (or lumped parameter) model approach become apparent when a known heterogeneity that has a physical basis needs to be modeled. Tracer- test results (velocity, breakthrough times) often show that slow-flow or fast-flow dominates different parts of the aquifer, for example, as ground water moves from the epikarst to the conduit network. Each of these aquifer components represents a particular heterogeneity that cannot be ignored in the modeling process. Thus, a distributed parameter model approach is used to incorporate known heterogeneities determined from field data. The three major distributed parameter approaches to describing flow include; 1) equivalent porous media, 2) discrete fracture, and 3) double porosity or double continuum approach. Examples are shown and each type of model is discussed. |
|||||
BibTeX:
@inproceedings{Taylor2001b,
author = {Taylor, Charles J. and Greene, Earl A.},
title = {Quantitative Approaches in Characterizing Karst Aquifers},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {164--166},
url = {http://water.usgs.gov/ogw/karst/kigconference/cjt_quantitative.htm}
}
|
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| Taylor, G. | Dispersion of Soluble Matter in Solvent Flowing Slowly through a Tube | 1953 | Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences Vol. 219(1137), pp. 186-203 |
article | URL |
| Abstract: When a soluble substance is introduced into a fluid flowing slowly through a small-bore tube it spreads out under the combined action of molecular diffusion and the variation of velocity over the cross-section. It is shown analytically that the distribution of concentration produced in this way is centred on a point which moves with the mean speed of flow and is symmetrical about it in spite of the asymmetry of the flow. The dispersion along the tube is governed by a virtual coefficient of diffusivity which can be calculated from observed distributions of concentration. Since the analysis relates the longitudinal diffusivity to the coefficient of molecular diffusion, observations of concentration along a tube provide a new method for measuring diffusion coefficients. The coefficient so obtained was found, with potassium permanganate, to agree with that measured in other ways. The results may be useful to physiologists who may wish to know how a soluble salt is dispersed in blood streams. | |||||
BibTeX:
@article{Taylor1953,
author = {Taylor, Geoffrey},
title = {Dispersion of Soluble Matter in Solvent Flowing Slowly through a Tube},
journal = {Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences},
year = {1953},
volume = {219},
number = {1137},
pages = {186--203},
url = {http://rspa.royalsocietypublishing.org/content/219/1137/186.abstract}
}
|
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| Taylor, G.D., Fletcher, T.D., Wong, T.H., Breen, P.F. and Duncan, H.P. | Nitrogen composition in urban runoff—implications for stormwater management | 2005 | Water Research Vol. 39(10), pp. 1982-1989 |
article | URL |
| Abstract: A study was conducted to characterise the composition of nitrogen in urban stormwater in Melbourne, Australia, during baseflows and storm events, and to compare the results with international data. Nitrogen in Melbourne stormwater was predominantly dissolved (∼80%), with ammonia the least-abundant form (∼11%). Concentrations of nitrogen species did not vary significantly between baseflow and storms, although the proportion of nitrogen in particulate form was higher during storm events ( p = 0.04 ). | |||||
BibTeX:
@article{Taylor2005,
author = {Taylor, Geoff D. and Fletcher, Tim D. and Wong, Tony H.F. and Breen, Peter F. and Duncan, Hugh P.},
title = {Nitrogen composition in urban runoff—implications for stormwater management},
journal = {Water Research},
year = {2005},
volume = {39},
number = {10},
pages = {1982--1989},
url = {http://www.sciencedirect.com/science/article/pii/S0043135405001016}
}
|
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| Taylor, G.I. | The Air Wave Surrounding an Expanding Sphere [BibTeX] |
1946 | Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences Vol. 186(1006), pp. 273-292 |
article | DOI URL |
BibTeX:
@article{Taylor1946,
author = {Taylor, G. I.},
title = {The Air Wave Surrounding an Expanding Sphere},
journal = {Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences},
year = {1946},
volume = {186},
number = {1006},
pages = {273--292},
url = {http://rspa.royalsocietypublishing.org/content/186/1006/273.short},
doi = {http://dx.doi.org/10.1098/rspa.1946.0044}
}
|
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| Taylor, T.P., Pennell, K.D., Abriola, L.M. and Dane, J.H. | Surfactant enhanced recovery of tetrachloroethylene from a porous medium containing low permeability lenses: 1. Experimental studies | 2001 | Journal of Contaminant Hydrology Vol. 48(3-4), pp. 325-350 |
article | URL |
| Abstract: A matrix of batch, column and two-dimensional (2-D) box experiments was conducted to investigate the coupled effects of rate-limited solubilization and layering on the entrapment and subsequent recovery of a representative dense NAPL, tetrachloroethylene (PCE), during surfactant flushing. Batch experiments were performed to determine the equilibrium solubilization capacity of the surfactant, polyoxyethylene (20) sorbitan monooleate (Tween 80), and to measure fluid viscosity, density and interfacial tension. Results of one-dimensional column studies indicated that micellar solubilization of residual PCE was rate-limited at Darcy velocities ranging from 0.8 to 8.2 cm/h and during periods of flow interruption. Effluent concentration data were used to develop effective mass transfer coefficient (Ke) expressions that were dependent upon the Darcy velocity and duration of flow interruption. To simulate subsurface heterogeneity, 2-D boxes were packed with layers of F-70 Ottawa sand and Wurtsmith aquifer material within 20–30 mesh Ottawa sand. A 4% Tween 80 solution was then flushed through PCE-contaminated boxes at several flow velocities, with periods of flow interruption. Effluent concentration data and visual observations indicated that both rate-limited solubilization and pooling of PCE above the fine layers reduced PCE recovery to levels below those anticipated from batch and column measurements. These experimental results demonstrate the potential impact of both mass transfer limitations and subsurface layering on the recovery of PCE during surfactant enhanced aquifer remediation. | |||||
BibTeX:
@article{Taylor2001a,
author = {Taylor, Tammy P. and Pennell, Kurt D. and Abriola, Linda M. and Dane, Jacob H.},
title = {Surfactant enhanced recovery of tetrachloroethylene from a porous medium containing low permeability lenses: 1. Experimental studies},
journal = {Journal of Contaminant Hydrology},
year = {2001},
volume = {48},
number = {3-4},
pages = {325--350},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200001856}
}
|
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| Tchobanoglous, G., Burton, F.L. and Stensel, H.D. | Wastewater Engineering: Treatment and Reuse [BibTeX] |
2003 | , pp. - | book | |
BibTeX:
@book{Tchobanoglous2003,
author = {Tchobanoglous, George and Burton, Franklin L. and Stensel, H. David},
title = {Wastewater Engineering: Treatment and Reuse},
publisher = {McGraw-Hill},
year = {2003},
pages = {--},
edition = {Fourth},
note = {Metcalf & Eddy, Inc.}
}
|
|||||
| of Technology Bateman Manuscript Project, C.I., Bateman, H., Erdélyi, A. and of Naval Research, U.S.O. | Tables of integral transforms [BibTeX] |
1954 | , pp. - | book | |
BibTeX:
@book{Technology.BatemanManuscriptProject.1954,
author = {California Institute of Technology Bateman Manuscript Project and Bateman, Harry and Erdélyi, Arthur and United States Office of Naval Research},
title = {Tables of integral transforms},
publisher = {McGraw-Hill},
year = {1954},
pages = {--}
}
|
|||||
| Tenney, C., Lastoskie, C. and Dybas, M. | A reactor model for pulsed pumping groundwater remediation | 2004 | Water Research Vol. 38(18), pp. 3869-3880 |
article | URL |
| Abstract: A hybrid in situ bioremediation/pulsed pumping strategy has been developed to cost effectively remediate a carbon tetrachloride plume in Schoolcraft, Michigan. The pulsed pumping system uses a line of alternating injection and extraction wells perpendicular to the direction of natural groundwater flow. The wells pump periodically to clean the recirculation zone between adjacent wells. During the pump-off phase, natural groundwater flow brings new contaminant into the recirculation zone. The wells are pumped again prior to breakthrough of contaminant from the recirculation zone. | |||||
BibTeX:
@article{Tenney2004,
author = {Tenney, C.M. and Lastoskie, C.M. and Dybas, M.J.},
title = {A reactor model for pulsed pumping groundwater remediation},
journal = {Water Research},
year = {2004},
volume = {38},
number = {18},
pages = {3869--3880},
url = {http://www.sciencedirect.com/science/article/pii/S0043135404003501}
}
|
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| Terzakis, S., Fountoulakis, M., Georgaki, I., Albantakis, D., Sabathianakis, I., Karathanasis, A., Kalogerakis, N. and Manios, T. | Constructed wetlands treating highway runoff in the central Mediterranean region | 2008 | Chemosphere Vol. 72(2), pp. 141-149 |
article | URL |
| Abstract: Two free water surface (FWS) and two subsurface flow (SSF) pilot-size constructed wetlands treating highway runoff (HRO) were monitored over a period of two years (September 2005–August 2007). One FWS and one SSF were designed with a hydraulic retention time (HRT) of 12 h, named FWS12 and SSF12, respectively, with each one capable of treating a maximum HRO of 12.6 m3 d−1. The other couple, named FWS24 and SSF24, respectively, was designed with an HRT of 24 h, with each receiving a maximum HRO of 6.3 m3 d−1. The influent flowed from a highway section with a total surface 2752 m2 on the island of Crete, Greece, in the heart of the South-Central Mediterranean region. Influent and effluent were monitored for COD, TSS, total N (TN), NO 3 - and total P (TP) concentrations. Furthermore, removal efficiencies were examined for heavy metals (Cu, Ni, Pb, Zn) for both years, while polycyclic aromatic compounds (PAHs) were examined for the period between September 2006 and August 2007. The influent had a two-year average COD value of 101 mg l−1, whereas the mean values for TSS, TN, N – NO 3 - and TP were 203, 4.30, 1.25 and 4.17 mg l−1, respectively. For Cu, Ni, Pb and Zn the respective two-year mean influent concentrations were 56, 114, 49 and 250 μg l−1. Mean concentration of total PAHs in runoff (∑PAHs, 16 compounds) were 12.01 μg l−1. The performance among the four beds was not significantly different according to ANOVA analysis followed by Tukey test (at p < 0.05) for almost all the above physicochemical parameters, suggesting that all systems performed in a similar way. All studied systems, achieved a mean of two-year removal efficiencies of 47% for COD, 89% for TSS, 49% for TN, 58% for N – NO 3 - , 60% for TP, 47% for Cu, 23% for Ni, 33% for Pb, 61% for Zn and 59% for ∑PAHs (16 compounds). | |||||
BibTeX:
@article{Terzakis2008,
author = {Terzakis, S. and Fountoulakis, M.S. and Georgaki, I. and Albantakis, D. and Sabathianakis, I. and Karathanasis, A.D. and Kalogerakis, N. and Manios, T.},
title = {Constructed wetlands treating highway runoff in the central Mediterranean region},
journal = {Chemosphere},
year = {2008},
volume = {72},
number = {2},
pages = {141--149},
url = {http://www.sciencedirect.com/science/article/pii/S0045653508001768}
}
|
|||||
| Testu, A., Didierjean, S., Maillet, D., Moyne, C., Metzger, T. and Niass, T. | Thermal dispersion for water or air flow through a bed of glass beads | 2007 | International Journal of Heat and Mass Transfer Vol. 50(7-8), pp. 1469-1484 |
article | URL |
| Abstract: The one-temperature model for thermal dispersion in a porous medium is based on the notion of an average ‘enthalpic’ temperature, solution of an energy equation of the convection–diffusion type. It requires the determination of thermal dispersion coefficients. The functional form of the correlations that relate them to dimensionless groups is established as well as the limits of this model. An experimental bench has been built to measure these coefficients for water or air flow through a bed of glass beads. They are estimated through a Bayesian inversion of several local temperature measurements, with uncertainty on their location, and with the use of the analytical solution of a corresponding model. Results are presented in terms of variation of these two coefficients with the Reynolds or Péclet numbers and with the nature of the fluid and corresponding correlations are given. | |||||
BibTeX:
@article{Testu2007,
author = {Testu, A. and Didierjean, S. and Maillet, D. and Moyne, C. and Metzger, T. and Niass, T.},
title = {Thermal dispersion for water or air flow through a bed of glass beads},
journal = {International Journal of Heat and Mass Transfer},
year = {2007},
volume = {50},
number = {7-8},
pages = {1469--1484},
url = {http://www.sciencedirect.com/science/article/pii/S0017931006005096}
}
|
|||||
| Tetsuro, H. | The role of dewatering in the progressive deformation of a sandy accretionary wedge: constraints from direct imagings of fluid flow and void structure | 2005 | Tectonophysics Vol. 397(3-4), pp. 261-280 |
article | URL |
| Abstract: Geological investigation of the deformation structures and sedimentary setting of the Emi Group, a Miocene sand-rich accretionary complex, central Japan, revealed a six stage-structural evolution during shallow level accretion in a subduction zone. The early deformation (stage 1) is characterized by independent particulate flow in layer parallel faults, scaly cleavages and web structures, and upward dewatering in dish-and-pillar structures and breccia injections, while later deformation (stages 2–6) involve mappable scale folding, meso- to macro-scopic thrusts and web structures with cataclastic flow. Based on microscopic analyses of these structures, the early faulting with independent particulate flow (stage 1 deformation) is associated with dilatancy and preferred orientation of void space, whereas the later faulting with cataclastic flow (stage 2 deformation) occurs with compaction and crude preferred orientation. The former features imply more permeable fluid migration pathways, supported by the permeability measurements and direct imaging of fluid flow by X-ray CT. On the other hand, the later fault zone has lower permeability and porosity than intact rock, and plays as fluid sealing. Thus, in the early stage (stages 1), fluid flow occurs as focused flow through dilatant fault zones with independent particulate flow or fluid migration by upward dewatering forming dish-and-pillar structures and breccia injections, whereas no evidence of fluid flow is recognized at the later stages (stages 2–6). Namely the fault zones focus fluid flow during primary accretion in shallow levels, and the fluid flow is strongly controlled by the deformation mechanism. Furthermore, the change of the deformation mechanism could be effected by progressive increment of the confining pressure, accompanied with accretion and lithification in the accretionary prism. In the shallow, dilatant-faulting regime where the deformation mechanism is independent particulate flow, focused flow dominates, whereas in the deep, cataclastic regime distributed flow may play a main conduit rather than the focused flow. | |||||
BibTeX:
@article{Tetsuro2005,
author = {Tetsuro, Hirono},
title = {The role of dewatering in the progressive deformation of a sandy accretionary wedge: constraints from direct imagings of fluid flow and void structure},
journal = {Tectonophysics},
year = {2005},
volume = {397},
number = {3-4},
pages = {261--280},
url = {http://www.sciencedirect.com/science/article/pii/S0040195104004937}
}
|
|||||
| Tetzlaff, D., Brewer, M.J., Malcolm, I.A. and Soulsby, C. | Storm flow and baseflow response to reduced acid deposition—using Bayesian compositional analysis in hydrograph separation with changing end members | 2010 | Hydrological Processes Vol. 24(16), pp. 2300-2312 |
article | URL |
| Abstract: In this paper, we present the analysis of long-term (since 1989) hydrochemical data from two small (ca 1 km2) catchments in Central Scotland. Both catchments have experienced marked reductions in acid deposition. Time-series analysis of stream water alkalinity, although systematically changing as a result of recovery from acidification, was used to conceptualize how the composition and contribution of different hydrological sources responded over the study period. Nonlinear curve fitting methods allowed the temporal changes in concentration–discharge relationships to be sufficiently well described to assess the impact of reduced acid deposition on storm flow and baseflow hydrochemistry. A Bayesian compositional analysis was applied to facilitate chemically based hydrograph separation. This allowed temporal variation over longer time periods in catchment-scale hydrological source contributions (specifically groundwater) to be estimated. Although these showed no systematic trend, they did differ between the two catchments, most likely as a result of small, but significant differences in the riparian soil cover. Understanding such changes to high and low flows over time is of paramount importance as such flow extremes have the most relevance to applied problems, particularly those related to environmental change. | |||||
BibTeX:
@article{Tetzlaff2010,
author = {Tetzlaff, D. and Brewer, M. J. and Malcolm, I. A. and Soulsby, C.},
title = {Storm flow and baseflow response to reduced acid deposition—using Bayesian compositional analysis in hydrograph separation with changing end members},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {16},
pages = {2300--2312},
url = {http://dx.doi.org/10.1002/hyp.7679}
}
|
|||||
| Tetzlaff, D., Seibert, J. and Soulsby, C. | Inter-catchment comparison to assess the influence of topography and soils on catchment transit times in a geomorphic province; the Cairngorm mountains, Scotland | 2009 | Hydrological Processes Vol. 23(13), pp. 1874-1886 |
article | URL |
| Abstract: A quantitative, process relevant analysis of ten mesoscale (ca 10–90 km2) catchments in the Cairngorm mountains, Scotland was carried out using 10-m digital terrain models (DTMs). This analysis produced a range of topographic indices that described differences in the landscape organisation of the catchments in a way that helped explain contrasts in their hydrology. Mean transit time (MTT)—derived from isotopic tracer data—was used as a metric that characterised differences in the hydrological function of the ten catchments. Some topographic indices exhibited significant correlations with MTT. Most notably, the ratio of the median flow path length to the median flow path gradient was negatively correlated with MTT, whilst the median upslope area was positively correlated. However, the relationships exhibited significant scatter which precluded their use as a predictive tool that could be applied to ungauged basins in this region. In contrast, maps of soil hydrological properties could be used to differentiate hydrologically responsive soils (which are dominated by overland flow and shallow sub-surface storm flow) from free draining soils (that facilitate deeper sub-surface flows). MTT was negatively correlated with the coverage of responsive soils in catchments. This relationship provided a much better basis for predicting MTT in ungauged catchments in this geomorphic province. In the Cairngorms, the extensive cover of various glacial drift deposits appears to be a first order control on soil distributions and strongly influences the porosity and permeability of the sub-surface. These catchment characteristics result in soil cover being a much more discerning indicator of hydrological function than topography alone. The study highlights the potential of quantitative landscape analysis in catchment comparison and the need for caution in extrapolating relationships between landscape controls and metrics of hydrological function beyond specific geomorphic provinces. | |||||
BibTeX:
@article{Tetzlaff2009,
author = {Tetzlaff, D. and Seibert, J. and Soulsby, C.},
title = {Inter-catchment comparison to assess the influence of topography and soils on catchment transit times in a geomorphic province; the Cairngorm mountains, Scotland},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2009},
volume = {23},
number = {13},
pages = {1874--1886},
url = {http://dx.doi.org/10.1002/hyp.7318}
}
|
|||||
| Tetzlaff, D., Soulsby, C., Waldron, S., Malcolm, I.A., Bacon, P.J., Dunn, S.M., Lilly, A. and Youngson, A.F. | Conceptualization of runoff processes using a geographical information system and tracers in a nested mesoscale catchment | 2007 | Hydrological Processes Vol. 21(10), pp. 1289-1307 |
article | URL |
| Abstract: Tracer investigations were combined with a geographical information system (GIS) analysis of the 31 km2 Girnock catchment (Cairngorm Mountains, Scotland) in order to understand hydrological functioning by identifying dominant runoff sources and estimating mean residence times. The catchment has a complex geology, soil cover and topography. Gran alkalinity was used to demonstrate that catchment geology has a dominant influence on baseflow chemistry, but flow paths originating in acidic horizons in the upper soil profiles controlled stormflow alkalinity. Chemically based hydrograph separations at the catchment scale indicated that ∼30% of annual runoff was derived from groundwater sources. Similar contributions (23–36%) were estimated for virtually all major sub-basins. δ18O of precipitation (mean: − 9·4‰; range: − 16·1 to − 5·0‰) and stream waters (mean: − 9·1‰; range: − 11·6 to − 7·4‰) were used to assess mean catchment and sub-basin residence times, which were in the order ∼4–6 months. GIS analysis showed that these tracer-based diagnostic features of catchment functioning were consistent with the landscape organization of the catchment. Soil and HOST (Hydrology of Soil Type) maps indicated that the catchment and individual sub-basins were dominated by hydrologically responsive soils, such as peats (Histosol), peaty gleys (Histic Gleysols) and rankers (Umbric Leptosols and Histosols). Soil cover (in combination with a topographic index) predicted extensive areas of saturation that probably expand during hydrological events, thus providing a high degree of hydrological connectivity between catchment hillslopes and stream channel network. This was validated by aerial photographic interpretation and groundtruthing. These characteristics of hydrological functioning (i.e. dominance of responsive hydrological pathways and short residence times) dictate that the catchment is sensitive to land use change impacts on the quality and quantity of streamflows. It is suggested that such conceptualization of hydrological functioning using tracer-validated GIS analysis can play an important role in the sustainable management of river basins. | |||||
BibTeX:
@article{Tetzlaff2007,
author = {Tetzlaff, D. and Soulsby, C. and Waldron, S. and Malcolm, I. A. and Bacon, P. J. and Dunn, S. M. and Lilly, A. and Youngson, A. F.},
title = {Conceptualization of runoff processes using a geographical information system and tracers in a nested mesoscale catchment},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2007},
volume = {21},
number = {10},
pages = {1289--1307},
url = {http://dx.doi.org/10.1002/hyp.6309}
}
|
|||||
| Thanos, A.M., Galtier, P.A. and Papayannakos, N.G. | Liquid flow non-idealities and hold-up in a pilot scale packed bed reactor with cocurrent gas-liquid upflow | 1996 | Chemical Engineering Science Vol. 51(11)Chemical Reaction Engineering: From Fundamentals to Commercial Plants and Products, pp. 2709-2714 |
article | URL |
| Abstract: Residence time distribution (R.T.D.) experiments were carried out in a pilot scale upflow reactor. Feeds with properties similar to the properties of feeds at reaction conditions were used. The Piston-Dispersion model is used to describe the liquid flow non-idealities. The effect of velocity and particle dimensions on the Peclet number and liquid hold-up are discussed. Predicted deviations of the performance of a typical pilot hydrotreater from that of an ideal plug flow reactor are presented. | |||||
BibTeX:
@article{Thanos1996,
author = {Thanos, A. M. and Galtier, P. A. and Papayannakos, N. G.},
title = {Liquid flow non-idealities and hold-up in a pilot scale packed bed reactor with cocurrent gas-liquid upflow},
booktitle = {Chemical Reaction Engineering: From Fundamentals to Commercial Plants and Products},
journal = {Chemical Engineering Science},
year = {1996},
volume = {51},
number = {11},
pages = {2709--2714},
url = {http://www.sciencedirect.com/science/article/pii/0009250996001406}
}
|
|||||
| Theodoropoulou, M., Karoutsos, V., Kaspiris, C. and Tsakiroglou, C. | A new visualization technique for the study of solute dispersion in model porous media | 2003 | Journal of Hydrology Vol. 274(1–4), pp. 176-197 |
article | URL |
| Abstract: A new technique of high resolution is developed to perform visualization experiments of the hydrodynamic dispersion of pollutants in transparent glass-etched pore networks, which are regarded as representative models of natural porous media and single fractures. The technique is based on the continuous detection of the sharp colour changes caused on an aqueous solution, as the solute concentration varies, because of the strong sensitivity of a system of indicators to pH. Image analysis is used for the transformation of the spatial distribution of colour intensity to solute concentration profiles. Unidirectional miscible displacement and single source-solute transport experiments are used to identify and quantify the transient and steady-state solute dispersion regimes in a pore network, and estimate the longitudinal and transverse dispersion coefficients as functions of Peclet number. The dispersion coefficients are estimated by fitting the spatial/temporal distribution of solute concentration over various regions of the network to analytic solutions of the convection–dispersion equation, obtained by using a flux-type boundary condition at solute sources. The experimental technique and the method of analysis of its results may be proved very useful for model validation, sensitivity analysis of dispersion coefficients with respect to pore space parameters, and identification of liquid pollutant dispersion regimes in underground aquifers. | |||||
BibTeX:
@article{Theodoropoulou2003,
author = {Theodoropoulou, M.A. and Karoutsos, V. and Kaspiris, C. and Tsakiroglou, C.D.},
title = {A new visualization technique for the study of solute dispersion in model porous media},
journal = {Journal of Hydrology},
year = {2003},
volume = {274},
number = {1–4},
pages = {176--197},
url = {http://www.sciencedirect.com/science/article/pii/S0022169402004213}
}
|
|||||
| Thirupathi, G., Krishnamoorthy, C. and Pushpavanam, S. | Adsorption characteristics of inorganic salts and detergents on sand beds | 2007 | Chemical Engineering Journal Vol. 125(3), pp. 177-186 |
article | URL |
| Abstract: Experiments were carried out to study the adsorption of two inorganic salts and a commercial detergent on sand. Adsorption isotherms were obtained from batch experiments by measuring the bulk concentration of the feed and that of the liquid after the equilibration period. Langmuir isotherm was found to predict the experimental observations accurately. Column experiments were performed to obtain the breakthrough curves for these inorganic salts and detergents. Two different modes of operation are discussed: (1) straight through mode and (2) recycle mode. The latter can be used for studying features of expensive chemicals in a cost effective manner. The experimental setup was designed so that by switching the valves, the same column can be utilized to study both modes. A convective-dispersion equation is used to describe the continuous operation and the effective dispersivity, D is estimated from the experimental breakthrough curves using an optimization technique. The optimized dispersivity, D is calculated so that the theoretical predictions match the experimental breakthrough curves. In our studies, we find that the behavior of the recycle mode is sensitive to the parameter, D. Hence, the dispersion coefficient is obtained using the recycle mode data. The results of the adsorption study described here can be used in scale up to the field level. | |||||
BibTeX:
@article{Thirupathi2007,
author = {Thirupathi, G. and Krishnamoorthy, C.P. and Pushpavanam, S.},
title = {Adsorption characteristics of inorganic salts and detergents on sand beds},
journal = {Chemical Engineering Journal},
year = {2007},
volume = {125},
number = {3},
pages = {177--186},
url = {http://www.sciencedirect.com/science/article/pii/S1385894706003391}
}
|
|||||
| Thom, H.C.S. | A Note On The Gamma Distribution | 1958 | Monthly Weather Review Vol. 86(4), pp. 117-122 |
article | URL |
| Abstract: The general properties of the gamma distribution, which has several applications in meteorology, are discussed. A short review of the general properties of good statistical estimators is given. This is applied to the gamma distribution to show that the maximum likelihood estimators are jointly sufficient. A new, simple approximation of the likelihood solutions is given, and the efficiency of the fitting procedure is computed. | |||||
BibTeX:
@article{Thom1958,
author = {Thom, H. C. S.},
title = {A Note On The Gamma Distribution},
journal = {Monthly Weather Review},
publisher = {American Meteorological Society},
year = {1958},
volume = {86},
number = {4},
pages = {117--122},
url = {http://dx.doi.org/10.1175/1520-0493(1958)086<0117:ANOTGD>2.0.CO;2}
}
|
|||||
| Thrailkill, J. | Flow in a limestone aquifer as determined from water tracing and water levels in wells | 1985 | Journal of Hydrology Vol. 78(1-2), pp. 123-136 |
article | URL |
| Abstract: The Inner Bluegrass Karst Region of central Kentucky, U.S.A., is a fluviokarst underlain by flat-lying slightly argillaceous limestones (Ordovician). Water tracing and field observations have shown the aquifer to be divisible into groundwater basins and intervening interbasin areas. Flow in groundwater basins is in a dendritic system of solution conduits at depths as great as 35 m beneath the surface which often passes beneath surface divides to emerge at low-level springs, in contrast to interbasin areas in which the flow is shallow and generally parallels surface slopes. The availability of relatively dense water-level data in an area in which a number of water traces had been conducted allowed a comparison between the configuration of the potentiometric surface and water tracing data. | |||||
BibTeX:
@article{Thrailkill1985,
author = {Thrailkill, John},
title = {Flow in a limestone aquifer as determined from water tracing and water levels in wells},
journal = {Journal of Hydrology},
year = {1985},
volume = {78},
number = {1-2},
pages = {123--136},
url = {http://www.sciencedirect.com/science/article/pii/002216948590157X}
}
|
|||||
| Thrailkill, J., Sullivan, S.B. and Gouzie, D.R. | Flow parameters in a shallow conduit-flow carbonate aquifer, Inner Bluegrass Karst Region, Kentucky, USA | 1991 | Journal of Hydrology Vol. 129(1-4), pp. 87-108 |
article | URL |
| Abstract: In the carbonate aquifers which underlie most karst terrains, groundwater flow is through a dendritic system of solution conduits. In such aquifers, termed shallow conduit-flow aquifers, the methods used to model granular and fracture aquifers are not generally applicable. Investigations were conducted in the Inner Bluegrass Karst Region of central Kentucky with the objective of developing methods of modeling shallow conduit-flow aquifers as well as obtaining quantitative information on a specific portion of the aquifer to assist in its management for water supply purposes. | |||||
BibTeX:
@article{Thrailkill1991,
author = {Thrailkill, John and Sullivan, Stephen B. and Gouzie, Douglas R.},
title = {Flow parameters in a shallow conduit-flow carbonate aquifer, Inner Bluegrass Karst Region, Kentucky, USA},
journal = {Journal of Hydrology},
year = {1991},
volume = {129},
number = {1-4},
pages = {87--108},
url = {http://www.sciencedirect.com/science/article/pii/002216949190046K}
}
|
|||||
| Thullner, M., Centler, F., Richnow, H.-H. and Fischer, A. | Quantification of organic pollutant degradation in contaminated aquifers using compound specific stable isotope analysis – Review of recent developments | Organic Geochemistry(0), pp. - | article | URL | |
| Abstract: Compound specific stable isotope analysis (CSIA) has been established as a viable tool for proving, characterizing and assessing degradation of organic pollutants within contaminated aquifers. The fractionation of stable isotopes during contaminant degradation leads to observable shifts in stable isotope ratios which can serve as an indicator for in situ pollutant degradation and allow for a quantitative assessment by means of the so-called Rayleigh (distillation) equation. | |||||
BibTeX:
@article{Thullner,
author = {Thullner, Martin and Centler, Florian and Richnow, Hans-Hermann and Fischer, Anko},
title = {Quantification of organic pollutant degradation in contaminated aquifers using compound specific stable isotope analysis – Review of recent developments},
journal = {Organic Geochemistry},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0146638011002944}
}
|
|||||
| Thurston, K. | Lead and petroleum hydrocarbon changes in an urban wetland receiving stormwater runoff | 1999 | Ecological Engineering Vol. 12(3-4), pp. 387-399 |
article | URL |
| Abstract: The hydrology and water quality of an urban wetland receiving stormwater runoff from a municipal maintenance garage were measured during the summer of 1993 to evaluate the wetland’s water quality enhancement function. Surface water accounted for half of the inflow and more than 80% of the outflow. Stormwater runoff and dry period water samples were analyzed for total lead and total petroleum hydrocarbons. Lead and petroleum were present at higher levels in stormwater runoff samples than in the weekly samples. Average mass loadings of these constituents were higher at the wetland inlet than at the outlet. Levels of lead and petroleum hydrocarbons in sediments were higher near the inlet than elsewhere on the site. Hydrologic and analytical data together suggest that sedimentation was the primary mechanism actively reducing water column concentrations of lead and petroleum hydrocarbons introduced to the wetland via stormwater runoff. | |||||
BibTeX:
@article{Thurston1999,
author = {Thurston, KerryA},
title = {Lead and petroleum hydrocarbon changes in an urban wetland receiving stormwater runoff},
journal = {Ecological Engineering},
year = {1999},
volume = {12},
number = {3--4},
pages = {387--399},
url = {http://www.sciencedirect.com/science/article/pii/S0925857498001165}
}
|
|||||
| Tian, Y.Q., Wang, D., Chen, R.F. and Huang, W. | Using modeled runoff to study DOC dynamics in stream and river flow: A case study of an urban watershed southeast of Boston, Massachusetts | 2012 | Ecological Engineering Vol. 42(0), pp. 212-222 |
article | URL |
| Abstract: The origin, function, and fate of dissolved organic carbon (DOC) in stream flow are not well-understood. This study explores the environmental factors controlling the spatial and temporal variation of DOC in terrestrial ecosystems of a watershed southeast of Boston, Massachusetts. Our hypothesis is that environmental factors: stream flow, land cover type, vegetation density, and drainage area are significant in estimating DOC export from an urban watershed. The hypothesized environmental factors were statistically correlated to the variation of the sampled in-stream DOC concentrations at annual, seasonal, and daily scales. For the purpose of scaling up to a large watershed that lacks dense gauged hydrological data or for projection of future scenarios, we examined the effectiveness of using simulated stream flow for studying terrestrial DOC dynamics. Our results demonstrated that all hypothesized environmental factors except vegetation density were particularly strong predictors in watersheds with a large proportion of developed (urban) area. The resulting linear model is able to explain about 76% (R2 = 0.76) and 64% (R2 = 0.64) of the variance of in-stream DOC concentrations at seasonal and annual scales respectively. Results suggest that more frequent DOC sampling than once each month is required to establish the quantitative relationship between simulated stream flows from a Soil Water Assessment Tool (SWAT) and in-stream DOC concentrations at daily scale. Using a hydrological model is effective for studying the impacts of climate and human activities on DOC export to aquatic ecosystems at appropriate scales. | |||||
BibTeX:
@article{Tian2012,
author = {Tian, Yong Q. and Wang, Dawei and Chen, Robert F. and Huang, Wei},
title = {Using modeled runoff to study DOC dynamics in stream and river flow: A case study of an urban watershed southeast of Boston, Massachusetts},
journal = {Ecological Engineering},
year = {2012},
volume = {42},
number = {0},
pages = {212--222},
url = {http://www.sciencedirect.com/science/article/pii/S0925857412000390}
}
|
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| Tice, J.D., Lyon, A.D. and Ismagilov, R.F. | Effects of viscosity on droplet formation and mixing in microfluidic channels | 2004 | Analytica Chimica Acta Vol. 507(1)Microfluidics and Lab - On - a - Chip, pp. 73-77 |
article | URL |
| Abstract: This paper characterizes the conditions required to form nanoliter-sized droplets (plugs) of viscous aqueous reagents in flows of immiscible carrier fluid within microfluidic channels. For both non-viscous (viscosity of 2.0 mPa s) and viscous (viscosity of 18 mPa s) aqueous solutions, plugs formed reliably in a flow of water-immiscible carrier fluid for Capillary number less than 0.01, although plugs were able to form at higher Capillary numbers at lower ratios of the aqueous phase flow rate to the flow rate of the carrier fluid (in all the experiments performed, the Reynolds number was less than 1). The paper also shows that combining viscous and non-viscous reagents can enhance mixing in droplets moving through straight microchannels by providing a nearly ideal initial distribution of reagents within each droplet. The study should facilitate the use of this droplet-based microfluidic platform for investigation of protein crystallization, kinetics, and assays. | |||||
BibTeX:
@article{Tice2004,
author = {Tice, Joshua D. and Lyon, Adam D. and Ismagilov, Rustem F.},
title = {Effects of viscosity on droplet formation and mixing in microfluidic channels},
booktitle = {Microfluidics and Lab - On - a - Chip},
journal = {Analytica Chimica Acta},
year = {2004},
volume = {507},
number = {1},
pages = {73--77},
url = {http://www.sciencedirect.com/science/article/pii/S0003267003014934}
}
|
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| Tilley, D.R. and Brown, M.T. | Dynamic emergy accounting for assessing the environmental benefits of subtropical wetland stormwater management systems | 2006 | Ecological Modelling Vol. 192(3–4), pp. 327-361 |
article | URL |
| Abstract: An eco-hydrological model of a subtropical urbanizing watershed in south Florida, USA was developed to simulate solar emergy using H.T. Odum's energy systems language as programmed in an iconographic simulation software (i.e., Extend®) to provide dynamic valuation of a wetland stormwater management system (WSMS). The solar emergy (i.e., ultimate amount of solar energy required to produce another form of energy) and emdollar (EM$, value an energy flow contributes to an economy based on its proportion of total emergy flow) values of watershed transpiration (a measure of productivity), surface discharge and change in landscape water storage were quantified for various ratios of wetland to upland areas, valuing wetlands in EM$ ha−1 y−1. Simulation results indicated that integrating a WSMS into the watershed increased landscape productivity, decreased surface discharge and increased surface water storage. The eco-hydrological value of watershed productivity was 367 EM$ ha−1 y−1 when 10% of the watershed was wetland, which was an increase of 65 EM$ ha−1 y−1 (based on Florida's emergy-to-dollar ratio in 1985, 2 × 1012 sej $−1). The annual contribution of this extra ecological productivity to public welfare was 12 million EM$, which was estimated from the product of eco-hydrological value and local emergy investment ratio of south Dade County (18:1). Average emdollar value of water saved per unit of wetland was 343 EM$ ha−1 y−1. Dynamic emergy accounting provided distributions of solar transformities of hydrologic variables as opposed to more commonly used point estimates. Our work advances the temporal dynamic principles of emergy accounting by demonstrating how solar emergy may be continuously tracked through an ecosystem to estimate the value of nature's life-support services. | |||||
BibTeX:
@article{Tilley2006,
author = {Tilley, David Rogers and Brown, Mark T.},
title = {Dynamic emergy accounting for assessing the environmental benefits of subtropical wetland stormwater management systems},
journal = {Ecological Modelling},
year = {2006},
volume = {192},
number = {3–4},
pages = {327--361},
url = {http://www.sciencedirect.com/science/article/pii/S0304380005003728}
}
|
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| Tilley, D.R. and Brown, M.T. | Wetland networks for stormwater management in subtropical urban watersheds | 1998 | Ecological Engineering Vol. 10(2), pp. 131-158 |
article | URL |
| Abstract: A quantitative method suitable for planning wetland stormwater treatment at the regional, multibasin scale was developed based on simple zero order kinetics (uptake rates) and average nutrient loading conditions. The method was applied to urbanized watersheds south of Miami, FL and yielded a hierarchically organized network of wetlands for processing stormwaters. Coastal watersheds in Dade county, FL, varying in intensity of development from heavily urbanized to almost completely undeveloped and ranging in size from 38 600 ha to 700 ha were analyzed. Watersheds were divided into three spatial scales: basin (>1000 ha), sub-basin (1000–100 ha) and neighborhood (100–10 ha). The methods used to calculate wetland area were based on: (1) reducing nutrient and sediment concentrations to background levels of the receiving water body (Biscayne Bay); and (2) retaining storm runoff to attenuate pulses of freshwater discharge. At each spatial scale, the wetland area needed to treat nitrogen, phosphorus, suspended sediment, biological oxygen demand and the water quantity was calculated. The constituent requiring the largest treatment area determined the amount of wetland area necessary. Results indicated that at the neighborhood scale, phosphorus runoff, generated by a 5-year 24-h design storm, required the largest wetland treatment area, needing between 2.3 and 10.8% of total basin area. At the sub-basin scale, the loading of total suspended solids, derived from land use specific criteria, needed the largest treatment area, ranging from 0.2 to 4.5% of basin area. The basin scale treatment, based on retaining drainage canal discharge for at least 72 h, needed between 0.1 and 2.5% of basin area. This methodology is useful for feasibility analysis and leads to design principles for planning basin-scale, stormwater management systems in urbanized watersheds. | |||||
BibTeX:
@article{Tilley1998,
author = {Tilley, David R. and Brown, Mark T.},
title = {Wetland networks for stormwater management in subtropical urban watersheds},
journal = {Ecological Engineering},
year = {1998},
volume = {10},
number = {2},
pages = {131--158},
url = {http://www.sciencedirect.com/science/article/pii/S092585749800010X}
}
|
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| Tipping, R.G., Runkel, A.C., Alexander Jr., E.C., Alexander, S.C. and Green, J.A. | Evidence for hydraulic heterogeneity and anisotropy in the mostly carbonate Prairie du Chien Group, southeastern Minnesota, USA | 2006 | Sedimentary Geology Vol. 184(3-4)Heterogeneity in Sedimentary Aquifers: Challenges for Characterization and Flow Modeling Geological Society of America Annual Meeting “GeoScience Horizons 2003”, pp. 305-330 |
article | URL |
| Abstract: In southeastern Minnesota, Paleozoic bedrock aquifers have typically been represented in groundwater flow simulations as isotropic, porous media. To obtain a more accurate hydrogeologic characterization of the Ordovician Prairie du Chien Group, a new approach was tested, combining detailed geologic observations, particularly of secondary porosity, with hydraulic data. Lithologic observations of the depositional and erosional history of the carbonate-dominated bedrock unit constrained characterization of both primary (matrix) and secondary porosity from outcrops and core. Hydrostratigraphic data include outcrop and core observations along with core plug permeability tests. Hydrogeologic data include discrete interval aquifer tests, borehole geophysics, water chemistry and isotope data, and dye trace studies. Results indicate that the Prairie du Chien Group can be subdivided into the Shakopee aquifer at the top, consisting of interbedded dolostone, sandstone and shale, and the underlying Oneota confining unit consisting of thickly bedded dolostone. The boundary between these two hydrogeologic units does not correspond to lithostratigraphic boundaries, as commonly presumed. Groundwater flow in the Shakopee aquifer is primarily through secondary porosity features, most commonly solution-enlarged bedding planes and sub-horizontal and vertical fractures. Regional scale preferential development of cavernous porosity and permeability along specific stratigraphic intervals that correspond to paleokarst were also identified, along with a general depiction of the distribution of vertical and horizontal fractures. The combination of outcrop and core investigations, along with borehole geophysics, discrete interval aquifer tests, water chemistry and isotope data and dye trace studies show that the Prairie du Chien Group is best represented hydrogeologically as heterogeneous and anisotropic. Furthermore, heterogeneity and anisotropy within the Prairie du Chien Group is mappable at a regional scale (> 15,000 km2). | |||||
BibTeX:
@article{Tipping2006,
author = {Tipping, Robert G. and Runkel, Anthony C. and Alexander Jr., E. Calvin and Alexander, Scott C. and Green, Jeffery A.},
title = {Evidence for hydraulic heterogeneity and anisotropy in the mostly carbonate Prairie du Chien Group, southeastern Minnesota, USA},
booktitle = {Heterogeneity in Sedimentary Aquifers: Challenges for Characterization and Flow Modeling Geological Society of America Annual Meeting “GeoScience Horizons 2003”},
journal = {Sedimentary Geology},
year = {2006},
volume = {184},
number = {3-4},
pages = {305--330},
url = {http://www.sciencedirect.com/science/article/pii/S0037073805003787}
}
|
|||||
| Toran, L. and Roman, E. | CO2 outgassing in a combined fracture and conduit karst aquifer near Lititz Spring, Pennsylvania | 2006 | Geological Society of America Special Papers Vol. 404, pp. 275-282 |
article | DOI URL |
| Abstract: Lititz Spring in southeastern Pennsylvania and a nearby domestic well were sampled for 9 months. Although both locations are connected to conduits (as evidenced by a tracer test), most of the year they were saturated with respect to calcite, which is more typical of matrix flow. Geochemical modeling (PHREEQC) was used to explain this apparent paradox and to infer changes in matrix and conduit contribution to flow. The saturation index varied from 0.5 to 0 most of the year, with a few samples in springtime dropping below saturation. The log Pco2 value varied from −2.5 to −1.7. Lower log Pco2 values (closer to the atmospheric value of −3.5) were observed when the solutions were at or above saturation with respect to calcite. In contrast, samples collected in the springtime had high Pco2, low saturation indices, and high water levels. Geochemical modeling showed that when outgassing occurs from a water with initially high Pco2, the saturation index of calcite increases. In the Lititz Spring area, the recharge water travels through the soil zone, where it picks up CO2 from soil gas, and excess CO2 subsequently is outgassed when this recharge water reaches the conduit. At times of high water level (pipe full), recharge with excess CO2 enters the system but the outgassing does not occur. Instead the recharge causes dilution, reducing the calcite saturation index. Understanding the temporal and spatial variation in matrix and conduit flow in karst aquifers benefited here by geochemical modeling and calculation of Pco2 values. | |||||
BibTeX:
@article{Toran2006,
author = {Toran, Laura and Roman, Eric},
title = {CO2 outgassing in a combined fracture and conduit karst aquifer near Lititz Spring, Pennsylvania},
journal = {Geological Society of America Special Papers},
year = {2006},
volume = {404},
pages = {275--282},
url = {http://specialpapers.gsapubs.org/content/404/275.abstract},
doi = {http://dx.doi.org/10.1130/2006.2404(23}
}
|
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| Torres, A.P. and Oliveira, F.A.R. | Residence time distribution studies in continuous thermal processing of liquid foods: a review | 1998 | Journal of Food Engineering Vol. 36(1), pp. 1-30 |
article | URL |
| Abstract: This paper presents a review on residence time distribution (RTD) studies in continuous thermal processing of liquid foods. The theoretical basis of the Danckwerts analysis is summarized, as well as the most important flow models, with special emphasis on tubular systems. Methods for experimental determination, modelling and estimation of RTD are critically described. While main design objectives in continuous thermal processes may be guaranteed by a proper minimum residence or holding time, process optimization requires the knowledge of the residence time distribution. Both concepts are reviewed and discussed. A significant scatter was noticed among published results and the need for a systematic work is clear. It was concluded that future research should focus on studies at pasteurization/sterilization temperatures, as well as on studies conducted with real food products or model food systems with non-Newtonian flow behaviour. Furthermore, information relating RTD to processing conditions would be a useful tool for process optimization. | |||||
BibTeX:
@article{Torres1998b,
author = {Torres, A. Pinheiro and Oliveira, F. A. R.},
title = {Residence time distribution studies in continuous thermal processing of liquid foods: a review},
journal = {Journal of Food Engineering},
year = {1998},
volume = {36},
number = {1},
pages = {1--30},
url = {http://www.sciencedirect.com/science/article/pii/S0260877498000375}
}
|
|||||
| Torres, A.P. and Oliveira, F.A.R. | Residence time distribution of liquids in a continuous tubular thermal processing system part II: Relating hold tube efficiency to processing conditions | 1998 | Journal of Food Engineering Vol. 35(2), pp. 165-175 |
article | URL |
| Abstract: The concept of efficiency of a holding tube is essential to guarantee the safety of continuously processed fluid foods. A good prediction of efficiency allows a better control of the processing conditions, guaranteeing product safety while decreasing product quality losses due to overprocessing. Different published methods were compared to data obtained in this work and to reported data, to assess their ability to predict tube efficiency in a range of Reynolds number (Re) covering laminar, transient and turbulent flow. Furthermore, a model assuming dispersed plug flow and a power-law relation between Peclet number (Pe) and Re was developed and evaluated. Published models were shown to be, in general, conservative for both laminar and turbulent flow, but often overpredicted the experimental efficiency in the zone of 2100 <Re < 4000. Deviations between predicted and experimental values were very considerable (errors from −25% to 90%). The model proposed has proved to be conservative over the whole range, but more accurate (errors up to 15%). | |||||
BibTeX:
@article{Torres1998c,
author = {Torres, A. Pinheiro and Oliveira, F. A. R.},
title = {Residence time distribution of liquids in a continuous tubular thermal processing system part II: Relating hold tube efficiency to processing conditions},
journal = {Journal of Food Engineering},
year = {1998},
volume = {35},
number = {2},
pages = {165--175},
url = {http://www.sciencedirect.com/science/article/pii/S0260877498000089}
}
|
|||||
| Torres, A.P., Oliveira, F.A.R. and Fortuna, S.P. | Residence time distribution of liquids in a continuous tubular thermal processing system part I: Relating RTD to processing conditions | 1998 | Journal of Food Engineering Vol. 35(2), pp. 147-163 |
article | URL |
| Abstract: A systematic experimental study on residence time distribution (RTD) in tubular flow was performed, covering a wide range of processing conditions. The flow of water in various sections of a tubular continuous thermal processing system was analysed using the classical Danckwerts approach. Methylene blue was used as tracer and different constant temperatures (25–80 °C) and flow rates (80–380 l/ h) were tested. These conditions yielded mean residence times up to 6 min and Reynolds numbers between 1350 and 9700. Various models were fitted to the experimental data, and the dispersion model showed to yield the best fit. Peak analysis led to both accurate and precise as well as conservative parameters, when compared to other methods of parameter estimation. Results revealed that fluid dispersion in tubular flow (Peclet number) can be related to processing conditions (Reynolds number) by a power law model. Results were compared to published correlations. | |||||
BibTeX:
@article{Torres1998a,
author = {Torres, A. Pinheiro and Oliveira, F. A. R. and Fortuna, S. P.},
title = {Residence time distribution of liquids in a continuous tubular thermal processing system part I: Relating RTD to processing conditions},
journal = {Journal of Food Engineering},
year = {1998},
volume = {35},
number = {2},
pages = {147--163},
url = {http://www.sciencedirect.com/science/article/pii/S0260877498000077}
}
|
|||||
| Torsten, Z. | Capability of convection–dispersion transport models to predict transient water and solute movement in undisturbed soil columns | 1998 | Journal of Contaminant Hydrology Vol. 30(1-2), pp. 101-128 |
article | URL |
| Abstract: The capability of the convection–dispersion model coupled with the Richards equation to predict transient transport of water and solutes in porous media is studied in a laboratory soil column. The solutes used are 3H2O as a conservative tracer and 14C-labeled dibutylphthalate (DBP) as a sorbing solute. To account for multiple nonideal transport processes, a model was developed that may consider hysteresis of the water retention curve, sorption nonequilibrium (sorption kinetics and sorption hysteresis) and mobile and immobile water domains during solute transport. The model parameters were determined independently from the transient experiments, but on the same soil column to avoid uncertainty in transferring results from one sample to another. The hydraulic properties of the soil column were estimated by a multistep outflow experiment using inverse modeling. Transport parameters were estimated form breakthrough curves of 3H2O measured under steady-state flow conditions. The sorption parameters of DBP were determined using batch techniques. Matrix potentials in the soil could not be predicted using a simple hysteresis model. Whereas the prediction of the tracer transport was satisfactory, it was not successful for DBP, inspite taking all nonequilibrium processes into account. DBP showed an early breakthrough and fluctuations in the outflow concentrations, which were induced by changes in the hydraulic boundary conditions. These fluctuations are caused by exchange processes during redistribution. The results suggest that models based on equilibrium assumptions may not always be suitable to predict the observed transport patterns. A calibration of the multinonequilibrium convective–dispersive model with the measured data, however, was possible. | |||||
BibTeX:
@article{Torsten1998,
author = {Torsten, Zurmühl},
title = {Capability of convection–dispersion transport models to predict transient water and solute movement in undisturbed soil columns},
journal = {Journal of Contaminant Hydrology},
year = {1998},
volume = {30},
number = {1-2},
pages = {101--128},
url = {http://www.sciencedirect.com/science/article/pii/S016977229700034X}
}
|
|||||
| Toth, D. and Katz, B. | Mixing of shallow and deep groundwater as indicated by the chemistry and age of karstic springs | 2006 | Hydrogeology Journal Vol. 14(6), pp. 1060-1080 |
article | URL |
| Abstract: Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca–HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquifer water with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium-3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge. | |||||
BibTeX:
@article{Toth2006,
author = {Toth, David and Katz, Brian},
title = {Mixing of shallow and deep groundwater as indicated by the chemistry and age of karstic springs},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {6},
pages = {1060--1080},
url = {http://dx.doi.org/10.1007/s10040-006-0099-z}
}
|
|||||
| Trachsel, F., Günther, A., Khan, S. and Jensen, K.F. | Measurement of residence time distribution in microfluidic systems | 2005 | Chemical Engineering Science Vol. 60(21), pp. 5729-5737 |
article | URL |
| Abstract: We present a method for measuring the residence time distribution (RTD) in microfluidic systems. A piezoelectrically actuated sample injector releases approximately 100 nl of tracer liquid into a microchannel of rectangular cross section. The spreading of the tracer pulse in pressure-driven microflows is monitored with fluorescence microscopy measurements. Residence time distributions are determined for single-phase liquid and segmented gas–liquid microflows, with the RTD being significantly narrower for the latter case. The selected flow conditions are relevant to synthesis in microreactors with residence times up to several minutes. | |||||
BibTeX:
@article{Trachsel2005,
author = {Trachsel, Franz and Günther, Axel and Khan, Saif and Jensen, Klavs F.},
title = {Measurement of residence time distribution in microfluidic systems},
journal = {Chemical Engineering Science},
year = {2005},
volume = {60},
number = {21},
pages = {5729--5737},
url = {http://www.sciencedirect.com/science/article/pii/S0009250905002964}
}
|
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| Trefry, M., Svensson, T. and Davis, G. | Hypoaigic influences on groundwater flux to a seasonally saline river | 2007 | Journal of Hydrology Vol. 335(3-4), pp. 330-353 |
article | URL |
| Abstract: Hypoaigic zones are aquifer volumes close to and beneath the shores of saline surface water bodies, and are characterized by the presence of time-dependent natural convection and chemical stratification. When transient and cyclic processes are involved there is significant potential for complex flow and reaction in the near-shore aquifer, presenting a unique challenge to pollutant risk assessment methodologies. This work considers the nature of some hypoaigic processes generated by the seasonally saline Canning River of Western Australia near a site contaminated by petroleum hydrocarbons. A dissolved hydrocarbon plume migrates within the shallow superficial aquifer to the nearby bank of the Canning River. Beneath the river bank a zone of complex fluid mixing is established by seasonal and tidal influences. Understanding this complexity and the subsequent ramifications for local biogeochemical conditions is critical to inferring the potential for degradation of advecting contaminants. A range of modelling approaches throws light on the overall topographic controls of discharge to the river, on the saline convection processes operating under the river bank, on the potential for fluid mixing, and on the various important time scales in the system. Saline distributions simulated within the aquifer hypoaigic zone are in at least qualitative agreement with previous field measurements at the site and are strongly affected by seasonal influences. Groundwater seepage velocities at the shoreline are found to be positively correlated with river salinity. Calculations of fluid age distributions throughout the system show sensitivity to dispersivity values; however, maximum fluid ages under the river appear to be diffusion limited to a few decades. The saline convection cell in the aquifer defines a zone of strong dispersive dilution of aged (many decades) deep aquifer fluids with relatively young (several months) riverine fluids. Seasonal recharge and river salinity cycles induce regular perturbations to the convection cell, yielding intra-annual variations of 50% in seepage velocity and almost 30% in wedge penetration distance at the plume location. | |||||
BibTeX:
@article{Trefry2007,
author = {Trefry, M.G. and Svensson, T.J.A. and Davis, G.B.},
title = {Hypoaigic influences on groundwater flux to a seasonally saline river},
journal = {Journal of Hydrology},
year = {2007},
volume = {335},
number = {3-4},
pages = {330--353},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406006330}
}
|
|||||
| Trefry, M.G., Lester, D.R., Metcalfe, G., Ord, A. and Regenauer-Lieb, K. | Toward enhanced subsurface intervention methods using chaotic advection | 2012 | Journal of Contaminant Hydrology Vol. 127(1-4)GQ10: Groundwater Quality Management in a Rapidly Changing World, pp. 15-29 |
article | URL |
| Abstract: Many intervention activities in the terrestrial subsurface involve the need to recover/emplace distributions of scalar quantities (e.g. dissolved phase concentrations or heat) from/in volumes of saturated porous media. These scalars can be targeted by pump-and-treat methods or by amendment technologies. Application examples include in-situ leaching for metals, recovery of dissolved contaminant plumes, or utilizing heat energy in geothermal reservoirs. While conventional pumping methods work reasonably well, costs associated with maintaining pumping schedules are high and improvements in efficiency would be welcome. In this paper we discuss how transient switching of the pressure at different wells can intimately control subsurface flow, generating a range of “programmed” flows with various beneficial characteristics. Some programs produce chaotic flows which accelerate mixing, while others create encapsulating flows which can isolate fluid zones for lengthy periods. In a simplified model of an aquifer subject to balanced pumping, chaotic flow topologies have been predicted theoretically and verified experimentally using Hele–Shaw cells. Here, a survey of the key characteristics of chaotic advection is presented. Mathematical methods are used to show how these characteristics may translate into practical situations involving regional flows and heterogeneity. The results are robust to perturbations, and withstand significant aquifer heterogeneity. It is proposed that chaotic advection may form the basis of new efficient technologies for groundwater interventions. | |||||
BibTeX:
@article{Trefry2012,
author = {Trefry, Michael G. and Lester, Daniel R. and Metcalfe, Guy and Ord, Alison and Regenauer-Lieb, Klaus},
title = {Toward enhanced subsurface intervention methods using chaotic advection},
booktitle = {GQ10: Groundwater Quality Management in a Rapidly Changing World},
journal = {Journal of Contaminant Hydrology},
year = {2012},
volume = {127},
number = {1-4},
pages = {15--29},
url = {http://www.sciencedirect.com/science/article/pii/S0169772211000489}
}
|
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| Trinchero, P., Sánchez-Vila, X. and Fernàndez-Garcia, D. | Point-to-point connectivity, an abstract concept or a key issue for risk assessment studies? | 2008 | Advances in Water Resources Vol. 31(12), pp. 1742-1753 |
article | URL |
| Abstract: Connectivity of high/low-permeability areas has been recognized to significantly impact groundwater flow and solute transport. The task of defining a rigorous quantitative measure of connectivity for continuous variables has failed so far, and thus there exist a suite of connectivity indicators which are dependent on the specific hydrodynamic processes and the interpretation method. Amongst the many existing indicators, we concentrate on those characterizing connectivity between the points involved in a hydraulic or tracer test. The flow connectivity indicator used here is based on the time elapsed for hydraulic response in a pumping test (e.g., the storage coefficient estimated by the Cooper–Jacob method, S est ). Regarding transport, we select the estimated porosity from the breakthrough curve ( ϕ est ) . According to Knudby and Carrera [Knudby C, Carrera J. On the relationship between indicators of geostatistical, flow and transport connectivity. Adv Water Resour 2005;28(4):405–21] these two indicators measure connectivity differently, and are poorly correlated. Here, we use perturbation theory to analytically investigate the intrinsic relationship between S est and ϕ est . We find that ϕ est can be expressed as a weighted line integral along the particle trajectory involving two parameters: the transmissivity point values, T, and the estimated values of S est along the particle path. The weighting function is linear with the distance from the pumping well, thus the influence of the weighting function is maximum at the injection area, whereas the hydraulic information close to the pumping well becomes redundant (null weight). The relative importance of these two factors is explored using numerical simulations in a given synthetic aquifer and tested against intermediate-scale laboratory tracer experiments. We conclude that the degree of connectivity between two points of an aquifer (point-to-point connectivity) is a key issue for risk assessment studies aimed at predicting the travel time of a potential contaminant. | |||||
BibTeX:
@article{Trinchero2008,
author = {Trinchero, Paolo and Sánchez-Vila, Xavier and Fernàndez-Garcia, Daniel},
title = {Point-to-point connectivity, an abstract concept or a key issue for risk assessment studies?},
journal = {Advances in Water Resources},
year = {2008},
volume = {31},
number = {12},
pages = {1742--1753},
url = {http://www.sciencedirect.com/science/article/pii/S0309170808001565}
}
|
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| Tromp, K., Lima, A.T., Barendregt, A. and Verhoeven, J.T. | Retention of heavy metals and poly-aromatic hydrocarbons from road water in a constructed wetland and the effect of de-icing | 2012 | Journal of Hazardous Materials Vol. 203--204(0), pp. 290-298 |
article | URL |
| Abstract: A full-scale remediation facility including a detention basin and a wetland was tested for retention of heavy metals and Poly-Aromatic Hydrocarbons (PAHs) from water drained from a motorway in The Netherlands. The facility consisted of a detention basin, a vertical-flow reed bed and a final groundwater infiltration bed. Water samples were taken of road water, detention basin influent and wetland effluent. By using automated sampling, we were able to obtain reliable concentration averages per 4-week period during 18 months. The system retained the PAHs very well, with retention efficiencies of 90–95%. While environmental standards for these substances were surpassed in the road water, this was never the case after passage through the system. For the metals the situation was more complicated. All metals studied (Cu, Zn, Pb, Cd and Ni) had concentrations frequently surpassing environmental standards in the road water. After passage through the system, most metal concentrations were lower than the standards, except for Cu and Zn. There was a dramatic effect of de-icing salts on the concentrations of Cu, Zn, Cd and Ni, in the effluent leaving the system. For Cu, the concentrations even became higher than they had ever been in the road water. It is advised to let the road water bypass the facility during de-icing periods. | |||||
BibTeX:
@article{Tromp2012,
author = {Tromp, Karin and Lima, Ana T. and Barendregt, Arjan and Verhoeven, Jos T.A.},
title = {Retention of heavy metals and poly-aromatic hydrocarbons from road water in a constructed wetland and the effect of de-icing},
journal = {Journal of Hazardous Materials},
year = {2012},
volume = {203--204},
number = {0},
pages = {290--298},
url = {http://www.sciencedirect.com/science/article/pii/S0304389411015160}
}
|
|||||
| Tsang, C.-F., Gelhar, L., de Marsily, G. and Andersson, J. | Solute transport in heterogeneous media: A discussion of technical issues coupling site characterization and predictive assessment | 1994 | Advances in Water Resources Vol. 17(4), pp. 259-264 |
article | URL |
| Abstract: Long-term predictive evaluation of solute transport and transformation in geologic media is a critical element in the performance assessment of nuclear waste geologic repositories and in the environmental restoration or control of contaminated sites that is facing many countries today. Since the geologic media are heterogeneous and their details can never be known deterministically, long-term prediction of flow and transport in such systems requires new thinking. Thus, it is no longer possible to consider site characterization and predictive modeling calculations to be separate activities; rather they are highly coupled. This paper presents a discussion of the coupling and proposes a framework of technical issues that need to be studied. | |||||
BibTeX:
@article{Tsang1994,
author = {Tsang, Chin-Fu and Gelhar, Lynn and de Marsily, Ghislain and Andersson, Johan},
title = {Solute transport in heterogeneous media: A discussion of technical issues coupling site characterization and predictive assessment},
journal = {Advances in Water Resources},
year = {1994},
volume = {17},
number = {4},
pages = {259--264},
url = {http://www.sciencedirect.com/science/article/pii/0309170894900051}
}
|
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| Tsang, D.C.W. and Lo, I.M.C. | Competitive Cu and Cd Sorption and Transport in Soils: A Combined Batch Kinetics, Column, and Sequential Extraction Study | 2006 | Environ. Sci. Technol. Vol. 40(21)Environmental Science & Technology, pp. 6655-6661 |
article | URL |
| Abstract: The competitive effect influenced the transport behavior of Cu and Cd contrastingly in soils, as illustrated by the experimental findings obtained from column, batch kinetics, and sequential extraction tests. Of particular interest, Cd transport behavior changed from nonequilibrium in a single-metal system to equilibrium in a binary-metal system, whereas Cu exhibited a slightly greater degree of nonequilibrium transport under competition. The equilibrium time of specific sorption (?7 days) was found to be much longer than that of nonspecific sorption (?30 min). While there was a competitive effect on nonspecific sorption for both Cu and Cd, the majority of rate-limited specific sorption of Cd on oxide and organic matter fractions (contributing to ?20% of total sorption) was dramatically displaced by Cu. Such a strong suppression of specific sorption of Cd by the presence of Cu resulted in a shorter equilibrium time of overall sorption, which probably accounts for its equilibrium transport. In contrast, the competitive effect on rate-limited sorption and transport behavior of Cu was less significant. This study demonstrated a correlation between the competitive effect of Cu and Cd on their nonspecific and specific sorption and the corresponding significance of rate-limited sorption and nonequilibrium transport behavior. The competitive effect influenced the transport behavior of Cu and Cd contrastingly in soils, as illustrated by the experimental findings obtained from column, batch kinetics, and sequential extraction tests. Of particular interest, Cd transport behavior changed from nonequilibrium in a single-metal system to equilibrium in a binary-metal system, whereas Cu exhibited a slightly greater degree of nonequilibrium transport under competition. The equilibrium time of specific sorption (?7 days) was found to be much longer than that of nonspecific sorption (?30 min). While there was a competitive effect on nonspecific sorption for both Cu and Cd, the majority of rate-limited specific sorption of Cd on oxide and organic matter fractions (contributing to ?20% of total sorption) was dramatically displaced by Cu. Such a strong suppression of specific sorption of Cd by the presence of Cu resulted in a shorter equilibrium time of overall sorption, which probably accounts for its equilibrium transport. In contrast, the competitive effect on rate-limited sorption and transport behavior of Cu was less significant. This study demonstrated a correlation between the competitive effect of Cu and Cd on their nonspecific and specific sorption and the corresponding significance of rate-limited sorption and nonequilibrium transport behavior. |
|||||
BibTeX:
@article{Tsang2006,
author = {Tsang, Daniel C. W. and Lo, Irene M. C.},
title = {Competitive Cu and Cd Sorption and Transport in Soils: A Combined Batch Kinetics, Column, and Sequential Extraction Study},
booktitle = {Environmental Science & Technology},
journal = {Environ. Sci. Technol.},
publisher = {American Chemical Society},
year = {2006},
volume = {40},
number = {21},
pages = {6655--6661},
url = {http://dx.doi.org/10.1021/es060625i}
}
|
|||||
| Tuccimei, P., Salvati, R., Capelli, G., Delitala, M. and Primavera, P. | Groundwater fluxes into a submerged sinkhole area, Central Italy, using radon and water chemistry | 2005 | Applied Geochemistry Vol. 20(10), pp. 1831-1847 |
article | URL |
| Abstract: The groundwater contribution into Green Lake and Black Lake (Vescovo Lakes Group), two cover collapse sinkholes in Pontina Plain (Central Italy), was estimated using water chemistry and a 222Rn budget. These data can constrain the interactions between sinkholes and deep seated fluid circulation, with a special focus on the possibility of the bedrock karst aquifer feeding the lake. The Rn budget accounted for all quantifiable surface and subsurface input and output fluxes including the flux across the sediment–water interface. The total value of groundwater discharge into Green Lake and Black Lake (∼540 ± 160 L s−1) obtained from the Rn budget is lower than, but comparable with historical data on the springs group discharge estimated in the same period of the year (800 ± 90 L s−1). Besides being an indirect test for the reliability of the Rn-budget “tool”, it confirms that both Green and Black Lake are effectively springs and not simply “water filled” sinkholes. New data on the water chemistry and the groundwater fluxes into the sinkhole area of Vescovo Lakes allows the assessment of the mechanism responsible for sinkhole formation in Pontina Plain and suggests the necessity of monitoring the changes of physical and chemical parameters of groundwater below the plain in order to mitigate the associated risk. | |||||
BibTeX:
@article{Tuccimei2005,
author = {Tuccimei, P. and Salvati, R. and Capelli, G. and Delitala, M.C. and Primavera, P.},
title = {Groundwater fluxes into a submerged sinkhole area, Central Italy, using radon and water chemistry},
journal = {Applied Geochemistry},
year = {2005},
volume = {20},
number = {10},
pages = {1831--1847},
url = {http://www.sciencedirect.com/science/article/pii/S088329270500106X}
}
|
|||||
| Turner, J.V. and Townley, L.R. | Determination of groundwater flow-through regimes of shallow lakes and wetlands from numerical analysis of stable isotope and chloride tracer distribution patterns | 2006 | Journal of Hydrology Vol. 320(3-4)Groundwater - surface water interactions in wetlands for integrated water resources management INTECOL Conference, pp. 451-483 |
article | URL |
| Abstract: A numerical model previously developed to systematically examine groundwater flow in vertical section near shallow surface water bodies such as lakes, wetlands and ponds is further developed to include simulation of the distribution patterns of hydrogeochemical and stable isotopic tracers in relation to the surface water body and the geometry of distribution patterns of the tracers in the groundwater release zone of the lake. Many different possible flow regimes are identified, however, in this paper attention is focused on flow-through water bodies, as these are the flow regimes observed in field validation. Two shallow lakes on the Swan Coastal Plain of south-west Western Australia are the subject of field studies where hydrogeochemical and stable isotopes are used to validate the flow-through groundwater flow regime predicted by the modelling confirming the validity of the approach. The flow regime transition diagrams introduced in earlier papers are extended to include consideration of the hydrogeochemical and stable isotopic indices ClL/Cl+ and (1000+δL)/(1000+δ+). These ratios are introduced as an additional two of nine non-dimensional ratios that are necessary to analyse the problem. The ratios represent the chloride and isotopic composition (ClL and δL), respectively, in the groundwater release zones of the lakes, relative to these parameters in the groundwater capture zone (Cl+ and δ+) for the lake. Field data from the case studies plotted on appropriately configured transition diagrams demonstrates the overall validity of the modelling approach and its underlying assumptions. It is concluded that isotopic and hydrogeochemical data are invaluable in interpreting the interaction between lakes or wetlands and regional aquifers as it is very difficult to make physical or hydraulic measurements in the field that allow an understanding of lake–aquifer interaction. The tools and concepts developed that are summarized in the presented transition diagrams are invaluable starting points for the consideration and analysis of other case-specific examples of groundwater–surface water interaction and will improve the scientific basis of decision-making concerning lake and wetland management and groundwater interaction by water resource and environmental managers. | |||||
BibTeX:
@article{Turner2006,
author = {Turner, Jeffrey V. and Townley, Lloyd R.},
title = {Determination of groundwater flow-through regimes of shallow lakes and wetlands from numerical analysis of stable isotope and chloride tracer distribution patterns},
booktitle = {Groundwater - surface water interactions in wetlands for integrated water resources management INTECOL Conference},
journal = {Journal of Hydrology},
year = {2006},
volume = {320},
number = {3-4},
pages = {451--483},
url = {http://www.sciencedirect.com/science/article/pii/S0022169405003616}
}
|
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| Uchida, T. and Asano, Y. | Spatial variability in the flowpath of hillslope runoff and streamflow in a meso-scale catchment | 2010 | Hydrological Processes Vol. 24(16), pp. 2277-2286 |
article | URL |
| Abstract: Recent studies have reported that not only water travelling through the soil layer but also emerging from fractured/weathered bedrock, contributes to hillslope runoff from steep wet hillslopes. Therefore, discharge is derived from a variety of hillslope sources. However, data are often lacking about how spatial variability in the water movement in bedrock on hillslopes affects hydrological behaviours in individual catchments because most previous studies have focused on single hillslopes in individual catchments. Therefore, we began by examining spatial variability in the bedrock groundwater contribution to hillslope runoff using a data set from Fudoji (central Japan), which has uniform bedrock geology, soil type and land use. We found that most hillslope runoff within the meso-scale catchment (4·27 km2) was a mixture of water flowing through the soil layer (subsurface flow) and water emerging from bedrock (groundwater flow). The depths of water sources (flowpath) that contributed to hillslope runoff varied greatly, even though the catchment had uniform bedrock geology, soil type and land use. Furthermore, we examined how bedrock groundwater affected hydrological behaviour in the catchment and found that the streamflow of first- to sixth-order streams were a mixture of water from the soil layer and bedrock groundwater, indicating that the end member of streamflow was the same as hillslope runoff in terms of the depth of flowpath. We also found that the mixing ratio of water from the soil layer and bedrock groundwater in first-order streams exhibited a significant spatial variation, but that the mixing ratio in third- to sixth-order streams did not. This indicates that depth of flowpath is a key component for describing hillslope and catchment hydrological responses. | |||||
BibTeX:
@article{Uchida2010,
author = {Uchida, Taro and Asano, Yuko},
title = {Spatial variability in the flowpath of hillslope runoff and streamflow in a meso-scale catchment},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2010},
volume = {24},
number = {16},
pages = {2277--2286},
url = {http://dx.doi.org/10.1002/hyp.7767}
}
|
|||||
| Unlu, E. and Faller, J.F. | RTD in twin-screw food extrusion | 2002 | Journal of Food Engineering Vol. 53(2), pp. 115-131 |
article | URL |
| Abstract: The geometric mean residence time (GMRT) and the RTD were measured on a twin-screw extruder using a KCl tracer and electrical conductivity measurements at the die. Extruder screw speeds (150–350 rpm) and feed rate (98.55–20.0 kg/h) were varied in a 3×3 factorial experiment with the matrix diagonal having a constant specific feeding load (SFL) of 0.057 kg/(h rpm). Feed rate had a greater effect on the mean residence time than the screw speed, with a 41% reduction in GMRT (108–64.0 s) with a 2.33-fold increase in feed rate, while screw speed had a greater influence on the normalized spreads of the RTD (mixing),with an increase in normalized spread of 21% (from 0.67 to 0.81) as screw speed increased 2.33 fold. Increasing feed rate yielded no change in normalized spread. Increasing screw speed and feed rate proportionally (constant SFL) from the minimum conditions to the maximums (a 2.33-fold increase for both) decreased the GMRT more than 50% from 123 to 56.2 s, increased the normalized spread from 0.70 to 0.82, and increased the barrel fill from 55.0% to 59.5%. Increasing feed rate increased barrel fill, die pressure, motor torque and product temperature while at the same time decreased residence time. Increasing screw speed decreased barrel fill, die pressure, motor torque and the GMRT while increasing the product temperature. Increasing feed rate and screw speed proportionally (constant SFL) yielded a slightly increasing trend for barrel fill. | |||||
BibTeX:
@article{Unlu2002,
author = {Unlu, Emine and Faller, James F.},
title = {RTD in twin-screw food extrusion},
journal = {Journal of Food Engineering},
year = {2002},
volume = {53},
number = {2},
pages = {115--131},
url = {http://www.sciencedirect.com/science/article/pii/S0260877401001480}
}
|
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| Usunoff, E., Carrera, J. and Mousavi, S. | An approach to the design of experiments for discriminating among alternative conceptual models | 1992 | Advances in Water Resources Vol. 15(3)Validation of Geo-hydrological Models, pp. 199-214 |
article | URL |
| Abstract: We contend that the main source of uncertainty in model predictions is often related to uncertainties in the conceptual model. While different approaches have been proposed for designing experiments so as to reduce the uncertainty of estimated parameters, much less attention has been devoted to the problem of experiment design for conceptual model discrimination. We propose a criterion for ensuring that a given design will indeed lead to data with sufficient discriminating capacity. This is based on finding, via automatic calibration algorithms, the minimum distance between simulations of the experiment obtained with the alternative models. If the distances thus obtained for all model pairings are large enough, then the proposed experiment can be used for effectively selecting one among those models (provided that ‘reality’ is closely reproduced by one of them). This methodology is applied to a uranium tracer test performed on unaltered granite samples at the Paul Scherrer Institute and which was part of INTRAVAL test case 1b. Using half of the data for calibrating three conceptual models shows that two of them cannot be rejected as valid representations of reality. We use the second half of data to demonstrate that they do not provide sufficient model discrimination capacity, despite the fact that existing criteria would suggest the opposite. We then proceed to propose an additional experiment for resolving the indetermination. | |||||
BibTeX:
@article{Usunoff1992,
author = {Usunoff, E. and Carrera, J. and Mousavi, S.F.},
title = {An approach to the design of experiments for discriminating among alternative conceptual models},
booktitle = {Validation of Geo-hydrological Models},
journal = {Advances in Water Resources},
year = {1992},
volume = {15},
number = {3},
pages = {199--214},
url = {http://www.sciencedirect.com/science/article/pii/030917089290024V}
}
|
|||||
| V.U, S. | Low flow hydrology: a review | 2001 | Journal of Hydrology Vol. 240(3-4), pp. 147-186 |
article | URL |
| Abstract: The paper intends to review the current status of low-flow hydrology — a discipline which deals with minimum flow in a river during the dry periods of the year. The discussion starts with the analysis of low-flow generating mechanisms operating in natural conditions and the description of anthropogenic factors which directly or indirectly affect low flows. This is followed by the review of existing methods of low-flow estimation from streamflow time-series, which include flow duration curves, frequency analysis of extreme low-flow events and continuous low-flow intervals, baseflow separation and characterisation of streamflow recessions. The paper describes the variety of low-flow characteristics (indices) and their applications. A separate section illustrates the relationships between low-flow characteristics. The paper further focuses on the techniques for low-flow estimation in ungauged river catchments, which include a regional regression approach, graphical representation of low-flow characteristics, construction of regional curves for low-flow prediction and application of time-series simulation methods. The paper presents a summary of recent international low-flow related research initiatives. Specific applications of low-flow data in river ecology studies and environmental flow management as well as the problem of changing minimum river flows as the result of climate variability are also discussed. The review is largely based on the research results reported during the last twenty years. | |||||
BibTeX:
@article{V.U2001,
author = {V.U, Smakhtin},
title = {Low flow hydrology: a review},
journal = {Journal of Hydrology},
year = {2001},
volume = {240},
number = {3-4},
pages = {147--186},
url = {http://www.sciencedirect.com/science/article/pii/S0022169400003401}
}
|
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| Valdes, D., Dupont, J.-P., Laignel, B., Ogier, S., Leboulanger, T. and Mahler, B.J. | A spatial analysis of structural controls on Karst groundwater geochemistry at a regional scale | 2007 | Journal of Hydrology Vol. 340(3-4), pp. 244-255 |
article | URL |
| Abstract: The coupled spatial investigation of the geometrical and geochemical properties of a chalk karstic aquifer provides information on the degree to which geologic structure controls aquifer functioning and groundwater quality. Major ion concentrations in the chalk aquifer of the Haute-Normandie region (France) were measured at a high spatial resolution (more than 100 sampling sites over a 6000 km2 area) and mapped. The first observation is a continuity of the geochemical properties, in spite of the karstic properties of the aquifer principal components analysis of geochemical maps revealed two types of spatial distributions: ions with an autochthonous origin (Ca2+, HCO3), and ions with a principally allochthonous origin (Cl−, Na+, NO 3 - , SO 4 2 - ). Mg2+ was categorised as both autochthonous (chalk dissolution) and allochthonous (brought in by infiltration of Tertiary deposits). To better understand the spatial distribution of the geochemistry, the aquifer geochemistry was compared to the physical properties of the aquifer, in particular aquifer thickness (representing aquifer geometry) and piezometric level (representing aquifer flow). Use of spatial correlation between the geochemical and the geometrical properties provided insight regarding the directional structure of the data and give evidence of directional relations between geochemical and geometrical properties. The degree of mineralisation (principally composed of Ca2+ and HCO 3 - ions) increased along the direction of flow, corresponding to an increase in chalk dissolution rate along the flowpath. The steepest mineralisation gradients were related to an increase in the Mg/Ca ratio, evidence of longer residence times and corresponding to zones where aquifer flow capacity is limited because of a decrease of the thickness of the flow section (anticlines or faults). These results highlight the dominant role played by the geometry and the structural context in controlling aquifer geochemistry. | |||||
BibTeX:
@article{Valdes2007,
author = {Valdes, Danièle and Dupont, Jean-Paul and Laignel, Benoît and Ogier, Sylvie and Leboulanger, Thierry and Mahler, Barbara J.},
title = {A spatial analysis of structural controls on Karst groundwater geochemistry at a regional scale},
journal = {Journal of Hydrology},
year = {2007},
volume = {340},
number = {3-4},
pages = {244--255},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407002387}
}
|
|||||
| Valdes, D., Dupont, J.-P., Massei, N., Laignel, B. and Rodet, J. | Investigation of karst hydrodynamics and organization using autocorrelations and T–ΔC curves | 2006 | Journal of Hydrology Vol. 329(3-4), pp. 432-443 |
article | URL |
| Abstract: In karst systems, rain events often result in a decrease in conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. We investigated the response to rain events at five karst outlets (three springs and two wells) discharging from the cretaceous chalk aquifer of the Haute-Normandie region, France. As the input signal (rainfall) is relatively homogeneous spatially, the differences in the responses at the sites provide information on the internal organization of the karst systems and their hydrodynamic functioning. We used autocorrelation functions and turbidity–conductivity (T–ΔC) hysteresis curves to analyze the responses. At short time scales, autocorrelation functions allow estimation of the inertia of the conduit flow system. The T–ΔC curves reflect the processes of deposition, resuspension, and direct transport of suspended solids within the karst network. The results show that: (i) a long memory effect for conductivity indicates storage of water in the karst network and deposition of suspended solids, and the transport of the dissolved phase and suspended solids is not the same; (ii) a short memory effect for conductivity indicates that transport of the dissolved phase and suspended solids is synchronous and direct. On the basis of the results at the five sites, we propose three conceptual models of hydrodynamic functioning. | |||||
BibTeX:
@article{Valdes2006,
author = {Valdes, Danièle and Dupont, Jean-Paul and Massei, Nicolas and Laignel, Benoıˆt and Rodet, Joël},
title = {Investigation of karst hydrodynamics and organization using autocorrelations and T–ΔC curves},
journal = {Journal of Hydrology},
year = {2006},
volume = {329},
number = {3-4},
pages = {432--443},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406001156}
}
|
|||||
| Vallero, D.A. | Biomedical ethics for engineers: ethics and decision making in biomedical and biosystem engineering [BibTeX] |
2007 | , pp. - | book | |
BibTeX:
@book{Vallero2007b,
author = {Vallero, Daniel A.},
title = {Biomedical ethics for engineers: ethics and decision making in biomedical and biosystem engineering},
publisher = {Elsevier/Academic Press},
year = {2007},
pages = {--}
}
|
|||||
| Vallero, D.A. | Bioethics and the Engineer [BibTeX] |
2007 | Biomedical Ethics for Engineers: Ethics and Decision Making in Biomedical and Biosystem Engineering, pp. 49-102 | inbook | DOI URL |
BibTeX:
@inbook{Vallero2007c,
author = {Vallero, Daniel A.},
title = {Bioethics and the Engineer},
booktitle = {Biomedical Ethics for Engineers: Ethics and Decision Making in Biomedical and Biosystem Engineering},
publisher = {Elsevier/Academic Press},
year = {2007},
pages = {49--102},
url = {http://www.sciencedirect.com/science/article/pii/B9780750682275500059},
doi = {http://dx.doi.org/10.1016/b978-075068227-5/50005-9}
}
|
|||||
| Vallero, D.A. | Paradigms lost: learning from environmental mistakes, mishaps, and misdeeds [BibTeX] |
2006 | , pp. - | book | |
BibTeX:
@book{Vallero2006a,
author = {Vallero, Daniel A.},
title = {Paradigms lost: learning from environmental mistakes, mishaps, and misdeeds},
publisher = {Butterworth-Heinemann},
year = {2006},
pages = {--}
}
|
|||||
| Vallero, D.A. | Just Environmental Decisions, Please [BibTeX] |
2006 | Paradigms Lost: Learning from Environmental Mistakes, Mishaps and Misdeeds, pp. 419-479 | inbook | DOI URL |
BibTeX:
@inbook{Vallero2006b,
author = {Vallero, Daniel A.},
title = {Just Environmental Decisions, Please},
booktitle = {Paradigms Lost: Learning from Environmental Mistakes, Mishaps and Misdeeds},
publisher = {Butterworth-Heinemann},
year = {2006},
pages = {419--479},
url = {http://www.sciencedirect.com/science/article/pii/B9780750678889500144},
doi = {http://dx.doi.org/10.1016/b978-075067888-9/50014-4}
}
|
|||||
| Valocchi, A.J. | Use of temporal moment analysis to study reactive solute transport in aggregated porous media | 1990 | Geoderma Vol. 46(1-3), pp. 233-247 |
article | URL |
| Abstract: The paper presents an overview of the use of temporal moment analysis as a useful alternative to more complete analytical or numerical solutions of mathematical models describing adsorbing solute transport in aggregated, saturated porous media. The goal of temporal moment analysis is to derive analytical formulas for the lower-order time moments of the solute breakthrough curve, thereby yielding significant physical insight into the behavior of solute transport models. Only the bi-continuum conceptual model and one-dimensional systems are emphasized in this paper. The transfer function approach for calculating temporal moments is described and illustrated with several examples involving diffusion into spherical aggregates, first-order mass transfer, and kinetically controlled intra-aggregate adsorption. The use of moment analysis for model comparison and sensitivity analysis is discussed; in particular, the paper shows how simplified empirical first-order mass transfer models can be utilized to approximate more complex models involving diffusion into nonuniformly sized spherical aggregates. | |||||
BibTeX:
@article{Valocchi1990,
author = {Valocchi, Albert J.},
title = {Use of temporal moment analysis to study reactive solute transport in aggregated porous media},
journal = {Geoderma},
year = {1990},
volume = {46},
number = {1-3},
pages = {233--247},
url = {http://www.sciencedirect.com/science/article/pii/0016706190900174}
}
|
|||||
| Van den Daele, G.F., Barker, J.A., Connell, L.D., Atkinson, T.C., Darling, W. and Cooper, J. | Unsaturated flow and solute transport through the Chalk: Tracer test and dual permeability modelling | 2007 | Journal of Hydrology Vol. 342(1-2), pp. 157-172 |
article | URL |
| Abstract: A tracer test was carried out in the unsaturated Chalk at the Fleam Dyke research site in Cambridgeshire, UK, to investigate the role of the Chalk fractures and matrix in unsaturated flow and solute transport. The experiment, under natural rainfall conditions, involved distributing deuterated water on a grass-covered lysimeter (a cube of volume 125 m3) and on an adjacent 4 m × 4 m field plot. Tracer migration was monitored through regular core sampling and collection of lysimeter drainage water. The presence of occasional secondary peaks in sampling of the vertical tracer profile suggested the occurrence of fracture flow, allowing some tracer to bypass the Chalk matrix. However, in the 15 months following application, none of the tracer was detected in the lysimeter drainage at 5 m depth. Modelling of the tracer results was undertaken with the 1-D numerical transient dual permeability model MACRO 5.0, initially developed for macroporous soils. Modelling results showed that MACRO 5.0 could reliably simulate transient recharge through the Chalk. The simulations suggested that fracture flow is important at the site, but that it is only initiated at 1 m depth or deeper. The extent of fracture flow appeared to be highly variable in different layers of the profile, varying between 40% and 85% of the cumulative flux, mainly depending on the saturated hydraulic conductivity of the matrix. Diffusion between the fractures and the matrix tended to equalize solute concentrations in both flow domains, although solute bypass through the fractures occurred in some Chalk strata. Besides diffusive exchange, the modelling stressed the importance of advective exchange of solutes. The results suggest that the Chalk aquifer at the Fleam Dyke site is only moderately vulnerable to pollution, even though for moderate rainfall conditions some bypass flow was possible. | |||||
BibTeX:
@article{VandenDaele2007,
author = {Van den Daele, Gerd F.A. and Barker, John A. and Connell, Luke D. and Atkinson, Tim C. and Darling, W.G. and Cooper, J.D.},
title = {Unsaturated flow and solute transport through the Chalk: Tracer test and dual permeability modelling},
journal = {Journal of Hydrology},
year = {2007},
volume = {342},
number = {1-2},
pages = {157--172},
url = {http://www.sciencedirect.com/science/article/pii/S002216940700306X}
}
|
|||||
| Van Gestel, K., Mergaert, J., Swings, J., Coosemans, J. and Ryckeboer, J. | Bioremediation of diesel oil-contaminated soil by composting with biowaste | 2003 | Environmental Pollution Vol. 125(3), pp. 361-368 |
article | URL |
| Abstract: Soil spiked with diesel oil was mixed with biowaste (vegetable, fruit and garden waste) at a 1:10 ratio (fresh weight) and composted in a monitored composting bin system for 12 weeks. Pure biowaste was composted in parallel. In order to discern the temperature effect from the additional biowaste effect on diesel degradation, one recipient with contaminated soil was hold at room temperature, while another was kept at the actual composting temperature. Measurements of composting parameters together with enumerations and identifications of microorganisms demonstrate that the addition of the contaminated soil had a minor impact on the composting process. The first-order rate constant of diesel degradation in the biowaste mixture was four times higher than in the soil at room temperature, and 1.2 times higher than in the soil at composting temperature. | |||||
BibTeX:
@article{VanGestel2003,
author = {Van Gestel, Kristin and Mergaert, Joris and Swings, Jean and Coosemans, Jozef and Ryckeboer, Jaak},
title = {Bioremediation of diesel oil-contaminated soil by composting with biowaste},
journal = {Environmental Pollution},
year = {2003},
volume = {125},
number = {3},
pages = {361--368},
url = {http://www.sciencedirect.com/science/article/pii/S026974910300109X}
}
|
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| Van Ommen, H., Hopmans, J. and Van der Zee, S. | Prediction of solute breakthrough from scaled soil physical properties | 1989 | Journal of Hydrology Vol. 105(3-4), pp. 263-273 |
article | URL |
| Abstract: Solute transport in unsaturated soil may be described with a transfer function model in which the travel time3distribution for a nonreactive solute depends on the distribution of the flow velocity (V). When the spatial variable V is described with the scaling theory of similar media, the travel time distribution follows from the scaling factor (δ) distribution. | |||||
BibTeX:
@article{VanOmmen1989b,
author = {Van Ommen, H.C. and Hopmans, J.W. and Van der Zee, S.E.A.T.M.},
title = {Prediction of solute breakthrough from scaled soil physical properties},
journal = {Journal of Hydrology},
year = {1989},
volume = {105},
number = {3-4},
pages = {263--273},
url = {http://www.sciencedirect.com/science/article/pii/002216948990108X}
}
|
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| Van Ommen, H., Van Genuchten, M., Van Der Molen, W., Dijksma, R. and Hulshof, J. | Experimental and theoretical analysis of solute transport from a diffuse source of pollution | 1989 | Journal of Hydrology Vol. 105(3-4), pp. 225-251 |
article | URL |
| Abstract: Transport processes governing soil and groundwater contamination by a diffuse (non-point) source were studied by means of a field tracer experiment in the Hupselse Beek catchment area in The Netherlands. A bromide tracer was applied to the intake area (11m × 260m) of a drain, and subsequently monitored in the unsaturated zone, as well as in the drain effluent. Data from the unsaturated zone were analyzed using both the classical convection-dispersion solute transport equation (CDE) and a regional stochastic model (RSM) which assumes lognormal distributions of the pore water velocity and the dispersion coefficient across the field. Both models described the data equally well, with the CDE model giving a somewhat better mass balance of the recovered bromide. Calculated solute fluxes leaving the unsaturated were used as input into a mixing cell type model for transport in the saturated zone. Drain effluent concentrations predicted with the coupled unsaturated-saturated transport model were compared with the observed breakthrough curve; results indicate the presence of preferential flow in the unsaturated zone. | |||||
BibTeX:
@article{VanOmmen1989,
author = {Van Ommen, H.C. and Van Genuchten, M.Th. and Van Der Molen, W.H. and Dijksma, R. and Hulshof, J.},
title = {Experimental and theoretical analysis of solute transport from a diffuse source of pollution},
journal = {Journal of Hydrology},
year = {1989},
volume = {105},
number = {3-4},
pages = {225--251},
url = {http://www.sciencedirect.com/science/article/pii/0022169489901066}
}
|
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| Van Stempvoort, D., Lesage, S., Novakowski, K., Millar, K., Brown, S. and Lawrence, J. | Humic acid enhanced remediation of an emplaced diesel source in groundwater.: 1. Laboratory-based pilot scale test | 2002 | Journal of Contaminant Hydrology Vol. 54(3-4), pp. 249-276 |
article | URL |
| Abstract: The enhanced solubility of petroleum-derived compounds in humic acid solutions is the basis for a new groundwater remediation technology. In this unique pilot-scale test, a stationary contaminant source consisting of diesel fuel was placed below the water table in a model sand aquifer (1.2×5.5×1.8-m deep) and flushed with water at a flow rate of 2 cm/h over 5 years. At 51 days, laboratory grade humic acid was added to the water and maintained at a level of approximately 0.8 g/l. The addition of humic acid had only a small impact on the aqueous transport of the BTEX components, which were rapidly dissolved from the diesel, but had a large effect on the flushing of PAHs, including methylated naphthalenes (MNs). Binding to aqueous humic acid enhanced the solubilization of MNs two- to tenfold. During aqueous transport, biodegradation of the BTEX and PAHs occurred, limiting the lateral and longitudinal extent of the diesel contaminant plume in the model aquifer. It appears that through enhanced solubilization, the overall biodegradation rate of the MNs was increased. As the various MNs were depleted from the diesel source, the MN plume shrank and then disappeared. | |||||
BibTeX:
@article{VanStempvoort2002,
author = {Van Stempvoort, D.R and Lesage, S and Novakowski, K.S and Millar, K and Brown, S and Lawrence, J.R},
title = {Humic acid enhanced remediation of an emplaced diesel source in groundwater.: 1. Laboratory-based pilot scale test},
journal = {Journal of Contaminant Hydrology},
year = {2002},
volume = {54},
number = {3-4},
pages = {249--276},
url = {http://www.sciencedirect.com/science/article/pii/S0169772201001826}
}
|
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| Vanclooster, M., Mallants, D., Diels, J. and Feyen, J. | Determining local-scale solute transport parameters using time domain reflectometry (TDR) | 1993 | Journal of Hydrology Vol. 148(1-4), pp. 93-107 |
article | URL |
| Abstract: The time domain reflectometry (TDR) technique was evaluated as a viable method for quick and accurate characterization of the solute transport parameters in controlled laboratory conditions. The method is able to measure steady-state solute breakthrough curves of inert solutes in soil columns. Transport of a solute was monitored in a column uniformly packed with a disturbed sandy material and columns filled with undisturbed soil material of three different soil horizons of a sandy soil profile. The measured solute breakthrough curves were used to assess the parameters of the classical two-parameter convection dispersion equation (CDE), in which it is assumed that the solute is completely miscible. Alternatively, a four-parameter two-region model was fitted to the data, assuming exchange between immobile and mobile water. The study reveals that transport of solutes in undisturbed sandy soil is much better described using the two-region model. In addition, it has been shown that the apparent dispersion coefficient of the CDE could be linearly related to the solute pore water velocity. | |||||
BibTeX:
@article{Vanclooster1993,
author = {Vanclooster, M. and Mallants, D. and Diels, J. and Feyen, J.},
title = {Determining local-scale solute transport parameters using time domain reflectometry (TDR)},
journal = {Journal of Hydrology},
year = {1993},
volume = {148},
number = {1-4},
pages = {93--107},
url = {http://www.sciencedirect.com/science/article/pii/0022169493902547}
}
|
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| Varziri, M.S., McAuley, K.B. and McLellan, P.J. | Approximate Maximum Likelihood Parameter Estimation for Nonlinear Dynamic Models: Application to a Laboratory-Scale Nylon Reactor Model | 2008 | Industrial & Engineering Chemistry Research Vol. 47(19), pp. 7274-7283 |
article | DOI URL |
| Abstract: In this article, parameters and states of a laboratory-scale nylon 612 reactor model (Schaffer et al. Ind. Eng. Chem. Res. 2003, 42, 2946?2959; Zheng et al. Ind. Eng. Chem. Res. 2005, 44, 2675?2686; and Campbell, D. A. Ph.D. Thesis, Department of Mathematics and Statistics, McGill University, Montreal, Quebec, Canada, 2007) are estimated using a novel approximate maximum likelihood estimation (AMLE) algorithm (Poyton et al. Comput. Chem. Eng. 2006, 30, 698?708; Varziri et al. Comput. Chem. Eng., published online, http://dx.doi.org/10.1016/j.compchemeng.2008.04.005; Varziri et al. Ind. Eng. Chem. Res. 2008, 47, 380?393; and Varziri et al. Can. J. Chem. Eng., accepted for publication). AMLE is a method for estimating the states and parameters in differential equation models with possible modeling imperfections. The nylon reactor model equations are represented by stochastic differential equations (SDEs) to account for any modeling errors or unknown process disturbances that enter the reactor system during experimental runs. In this article, we demonstrate that AMLE can address difficulties that frequently arise when estimating parameters in nonlinear continuous-time dynamic models of industrial processes. Among these difficulties are different types of measured responses with different levels of measurement noise, measurements taken at irregularly spaced sampling times, unknown initial conditions for some state variables, unmeasured state variables, and unknown disturbances that enter the process and influence its future behavior. In this article, parameters and states of a laboratory-scale nylon 612 reactor model (Schaffer et al. Ind. Eng. Chem. Res. 2003, 42, 2946?2959; Zheng et al. Ind. Eng. Chem. Res. 2005, 44, 2675?2686; and Campbell, D. A. Ph.D. Thesis, Department of Mathematics and Statistics, McGill University, Montreal, Quebec, Canada, 2007) are estimated using a novel approximate maximum likelihood estimation (AMLE) algorithm (Poyton et al. Comput. Chem. Eng. 2006, 30, 698?708; Varziri et al. Comput. Chem. Eng., published online, http://dx.doi.org/10.1016/j.compchemeng.2008.04.005; Varziri et al. Ind. Eng. Chem. Res. 2008, 47, 380?393; and Varziri et al. Can. J. Chem. Eng., accepted for publication). AMLE is a method for estimating the states and parameters in differential equation models with possible modeling imperfections. The nylon reactor model equations are represented by stochastic differential equations (SDEs) to account for any modeling errors or unknown process disturbances that enter the reactor system during experimental runs. In this article, we demonstrate that AMLE can address difficulties that frequently arise when estimating parameters in nonlinear continuous-time dynamic models of industrial processes. Among these difficulties are different types of measured responses with different levels of measurement noise, measurements taken at irregularly spaced sampling times, unknown initial conditions for some state variables, unmeasured state variables, and unknown disturbances that enter the process and influence its future behavior. |
|||||
BibTeX:
@article{Varziri2008a,
author = {Varziri, M. Saeed and McAuley, Kim B. and McLellan, P. James},
title = {Approximate Maximum Likelihood Parameter Estimation for Nonlinear Dynamic Models: Application to a Laboratory-Scale Nylon Reactor Model},
journal = {Industrial & Engineering Chemistry Research},
publisher = {American Chemical Society},
year = {2008},
volume = {47},
number = {19},
pages = {7274--7283},
url = {http://dx.doi.org/10.1021/ie800503v},
doi = {http://dx.doi.org/10.1021/ie800503v}
}
|
|||||
| Vatistas, N. and Marconi, P. | The IEM mixing model in exothermic reactions | 1992 | Chemical Engineering Science Vol. 47(7), pp. 1727-1731 |
article | URL |
| Abstract: Incomplete mixing in chemically reactive systems with highly exothermic or endothermic reactions may give rise to segregation, affecting not only the concentration but also the temperature. Its effect on the former has previously been examined using, among others, the isothermal IEM (interaction by exchange with the mean) model. Here this model has been extended to make it suitable for the study of temperature-related segregation too. The derived non-isothermal IEM model has been employed to study the effect of both concentration- and temperature-related segregation on steady-state multiplicity. | |||||
BibTeX:
@article{Vatistas1992,
author = {Vatistas, N. and Marconi, P.F.},
title = {The IEM mixing model in exothermic reactions},
journal = {Chemical Engineering Science},
year = {1992},
volume = {47},
number = {7},
pages = {1727--1731},
url = {http://www.sciencedirect.com/science/article/pii/000925099285020C}
}
|
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| Vaute, L., Drogue, C., Garrelly, L. and Ghelfenstein, M. | Relations between the structure of storage and the transport of chemical compounds in karstic aquifers | 1997 | Journal of Hydrology Vol. 199(3–4), pp. 221-238 |
article | URL |
| Abstract: Study of the movement of chemical compounds naturally present in the water, or which result from pollution, are examined according to the reservoir structure in karstic aquifers. Structure is represented by a simple geometrical model; slow flow takes place in blocks with a network of low-permeability cracks. The blocks are separated by highly permeable karstic conduits that allow rapid flow, and these form the aquifer drainage system. The karst studied covers 110 km2. It is fed by an interrupted stream draining a 35 km2 non-karstic basin, contaminated at the entry to the karst by effluents from a sewage treatment station. The underground water reappears as a resurgence with an annual average flow of approximately 1 m3 s−1, after an apparent underground course of 8 km in the karst. Several local sources of pollution (effluent from septic tanks) contaminate the underground water during its course. Sixteen measurement operations were performed at 12 water points, between the interrupted stream and the spring. Some sampling points were at drains, and others were in the low-permeability fissured blocks. Comparison at each point of the concentrations of 14 chemical compounds gave the following results: when pollutant discharge occurs in a permeable zone, movement is rapid in the drainage network formed by the karstic conduits, and does not reach the less permeable fissured blocks which are thus protected; however, if discharge is in a low-permeability zone, the flow does not allow rapid movement of the polluted water, and this increases the pollutant concentration at the discharge. This simple pattern can be upset by a reversal of the apparent piezometric gradient between a block and a conduit during floods or pumping; this may reverse flow directions and hence modify the movement of contaminants. The study made it possible to site five boreholes whose positions in the karstic structure were unknown, showing the interest of such an approach for the forecasting of the impact of potential pollution. | |||||
BibTeX:
@article{Vaute1997,
author = {Vaute, L. and Drogue, C. and Garrelly, L. and Ghelfenstein, M.},
title = {Relations between the structure of storage and the transport of chemical compounds in karstic aquifers},
journal = {Journal of Hydrology},
year = {1997},
volume = {199},
number = {3–4},
pages = {221--238},
url = {http://www.sciencedirect.com/science/article/pii/S0022169496032453}
}
|
|||||
| Veling, E. | Approximations of impulse response curves based on the generalized moving Gaussian distribution function | 2010 | Advances in Water Resources Vol. 33(5), pp. 546-561 |
article | URL |
| Abstract: We derive approximations (in time) for impulse response curves not based on the Gaussian distribution (like the well-known Edgeworth expansions), but based on other suitable distribution functions. In general, we derive the full expansion for such an approximation based on an approximative function, the derivatives and the cumulants of this approximative function and on the cumulants of the impulse response curve itself, see formula (39). Suitable distribution functions exhibit a skewed profile which offers better opportunities for approximations of typical impulse response curves than approximations based on the symmetrical Gaussian distribution. As an example of such a suitable approximative distribution function we study more in detail the Generalized Moving Gaussian distribution Z t = 1 M 0 t ν exp − α t − β / t 2 , 0 < t < ∞ , α > 0 , β > 0 , − ∞ < ν < ∞ , with the normalization M 0 = 2 β α ν + 1 / 2 exp 2 α β K ν + 1 2 α β . | |||||
BibTeX:
@article{Veling2010,
author = {Veling, E.J.M},
title = {Approximations of impulse response curves based on the generalized moving Gaussian distribution function},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {5},
pages = {546--561},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810000412}
}
|
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| Veni, G. | A geomorphological strategy for conducting environmental impact assessments in karst areas | 1999 | Geomorphology Vol. 31(1-4), pp. 151-180 |
article | URL |
| Abstract: In their efforts to protect regional groundwater supplies, governmental agencies are increasingly requiring studies of karst areas and their features. In areas where tracer tests or geophysics are not required, funded, or otherwise feasible, geomorphological methods remain as the primary tool for assessing karst. This study proposes a geomorphologically-based environmental impact assessment strategy for karst areas. While it is supported with results from a study of the karstic Edwards Aquifer recharge zone on the Camp Bullis Military Training Installation, TX, USA, it is based on the study of several karst areas and is generalized to accommodate and be fine-tuned for regional variations. Biological and other resource issues can also be assessed with this strategy. The assessment identifies environmentally sensitive features and areas, as is often required to meet regulatory directives. In karst areas with relatively small features, excavation is a key tool for accurate assessment. Although the results of this study will help to better manage karst areas, proper management must be done on a regional scale. The highly permeable nature of karst precludes adequate management solely on a feature-by-feature basis. Studies on the relationship of water quality to impervious cover show adverse environmental impacts significantly increase when impervious cover exceeds 15% of a surface watershed. The Camp Bullis study finds similar impacts in its groundwater drainage basin, supporting the argument of 15% impervious cover as a regionally effective means of also protecting karst aquifers when coupled with protection of critical areas identified by field surveys. | |||||
BibTeX:
@article{Veni1999,
author = {Veni, George},
title = {A geomorphological strategy for conducting environmental impact assessments in karst areas},
journal = {Geomorphology},
year = {1999},
volume = {31},
number = {1-4},
pages = {151--180},
url = {http://www.sciencedirect.com/science/article/pii/S0169555X9900077X}
}
|
|||||
| Ventura, J.A. and Weng, M.X. | An improved dynamic programming algorithm for the single-machine mean absolute deviation problem with a restrictive common due date | 1995 | Operations Research Letters Vol. 17(3), pp. 149-152 |
article | URL |
| Abstract: In 1991, Hall et al. showed that the problem of minimizing the mean earliness and tardiness of n jobs scheduled on a single machine around a restrictive common due date is NP-complete. They proposed a pseudo-polynomial dynamic programming algorithm, called Optcet, for identifying an optimal schedule. This paper points out that two of the three subroutines in Optcet can be eliminated and, consequently, the total computational effort can be reduced significantly. | |||||
BibTeX:
@article{Ventura1995,
author = {Ventura, Jose A. and Weng, Michael X.},
title = {An improved dynamic programming algorithm for the single-machine mean absolute deviation problem with a restrictive common due date},
journal = {Operations Research Letters},
year = {1995},
volume = {17},
number = {3},
pages = {149--152},
url = {http://www.sciencedirect.com/science/article/pii/0167637795000066}
}
|
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| Vereecken, H., Döring, U., Hardelauf, H., Jaekel, U., Hashagen, U., Neuendorf, O., Schwarze, H. and Seidemann, R. | Analysis of solute transport in a heterogeneous aquifer: the Krauthausen field experiment | 2000 | Journal of Contaminant Hydrology Vol. 45(3-4), pp. 329-358 |
article | URL |
| Abstract: A field-scale natural gradient tracer experiment with bromide, uranin and lithium was conducted in a heterogeneous aquifer at Krauthausen, Germany. The temporal and spatial evolution of the solute plumes was monitored over 398 days for bromide and 449 days for uranin and lithium. The spatial variability of basic aquifer parameters, hydraulic conductivity, and sorption parameters of the aquifer material was investigated in detail. Local Darcian velocities were measured using NH4Br82 as a radioactive tracer in 33 observation wells. Vertical and horizontal correlation lengths of hydraulic properties were determined using variogram analysis. The magnitude of the local Darcian velocities was found to be lognormally distributed. In addition, the groundwater flow direction showed a clear trend in the vertical direction. The horizontal correlation length of the magnitude of Darcian velocity agreed with the correlation length of K estimated from grain size data. Batch experiments on aquifer sediments showed that sorption of uranin and lithium could be described by a Freundlich isotherm. The Freundlich n parameter of uranin sorption showed little variation with depth. The time evolution of the bromide plume was quantified in terms of spatial moments. The longitudinal effective dispersivity estimated from spatial moment analysis was within the range of calculated effective dispersivities, taking into account the uncertainty of estimates of the lnK statistics. | |||||
BibTeX:
@article{Vereecken2000,
author = {Vereecken, H and Döring, U and Hardelauf, H and Jaekel, U and Hashagen, U and Neuendorf, O and Schwarze, H and Seidemann, R},
title = {Analysis of solute transport in a heterogeneous aquifer: the Krauthausen field experiment},
journal = {Journal of Contaminant Hydrology},
year = {2000},
volume = {45},
number = {3-4},
pages = {329--358},
url = {http://www.sciencedirect.com/science/article/pii/S0169772200001078}
}
|
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| Veresoglou, S.D., Chen, B. and Rillig, M.C. | Arbuscular mycorrhiza and soil nitrogen cycling | 2012 | Soil Biology and Biochemistry Vol. 46(0), pp. 53-62 |
article | URL |
| Abstract: Nitrogen is a major nutrient that frequently limits primary productivity in terrestrial ecosystems. Therefore, the physiological responses of plants to soil nitrogen (N) availability have been extensively investigated, and the study of the soil N-cycle has become an important component of ecosystem ecology and biogeochemistry. The bulk of the literature in these areas has, however, overlooked the fact that most plants form mycorrhizal associations, and that nutrient uptake is therefore mediated by mycorrhizal fungi. It is well established that ecto- and ericoid mycorrhizas influence N nutrition of plants, but roles of arbuscular mycorrhizas in N nutrition are less well established; perhaps even more importantly, current conceptual models ignore possible influences of arbuscular mycorrhizal (AM) fungi on N-cycling processes. We review evidence for the interaction between the AM symbiosis with microbes and processes involved in soil N-cycling. We show that to date investigations have rather poorly addressed such interactions and discuss possible reasons for this. We outline mechanisms that could potentially operate with regards to AM fungal – N-cycling interactions, discuss experimental designs aimed at studying these, and conclude by pointing out priorities for future research. | |||||
BibTeX:
@article{Veresoglou2012,
author = {Veresoglou, Stavros D. and Chen, Baodong and Rillig, Matthias C.},
title = {Arbuscular mycorrhiza and soil nitrogen cycling},
journal = {Soil Biology and Biochemistry},
year = {2012},
volume = {46},
number = {0},
pages = {53--62},
url = {http://www.sciencedirect.com/science/article/pii/S003807171100410X}
}
|
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| Verma, P., Yeates, J. and Daly, E. | A stochastic model describing the impact of daily rainfall depth distribution on the soil water balance | 2011 | Advances in Water Resources Vol. 34(8), pp. 1039-1048 |
article | URL |
| Abstract: Simplified, vertically-averaged soil moisture models have been widely used to describe and study eco-hydrological processes in water-limited ecosystems. The principal aim of these models is to understand how the main physical and biological processes linking soil, vegetation, and climate impact on the statistical properties of soil moisture. A key component of these models is the stochastic nature of daily rainfall, which is mathematically described as a compound Poisson process with daily rainfall amounts drawn from an exponential distribution. Since measurements show that the exponential distribution is often not the best candidate to fit daily rainfall, we compare the soil moisture probability density functions obtained from a soil water balance model with daily rainfall depths assumed to be distributed as exponential, mixed-exponential, and gamma. This model with different daily rainfall distributions is applied to a catchment in New South Wales, Australia, in order to show that the estimation of the seasonal statistics of soil moisture might be improved when using the distribution that better fits daily rainfall data. This study also shows that the choice of the daily rainfall distributions might considerably affect the estimation of vegetation water-stress, leakage and runoff occurrence, and the whole water balance. | |||||
BibTeX:
@article{Verma2011,
author = {Verma, Parikshit and Yeates, James and Daly, Edoardo},
title = {A stochastic model describing the impact of daily rainfall depth distribution on the soil water balance},
journal = {Advances in Water Resources},
year = {2011},
volume = {34},
number = {8},
pages = {1039--1048},
url = {http://www.sciencedirect.com/science/article/pii/S0309170811001151}
}
|
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| Vesper, D.J., Loop, C.M. and White, W.B. | Contaminant transport in karst aquifers | 2000--2001 | Theoretical and Applied Karstology Vol. 13--14(0), pp. 101-111 |
article | URL |
| Abstract: Contaminants are easily injected into karst aquifers through sinking streams, sinkholes, or through open fractures and shafts in the carbonate rock. Transport of the contaminants through the aquifer is by a variety of mechanisms depending on the physical and chemical properties of the contaminant. Contaminants consist of (1) water soluble compounds, both organic and inorganic, (2) slightly soluble organic com-pounds, less dense than water (LNAPLs), (3) slightly soluble organic compounds, more dense than water (DNAPLs), (4) pathogens, (5) metals, and (6) trash. Water soluble compounds (e.g. nitrates, cyanides, carboxylic acids, phenols) move with the water. But rather than forming a plume spreading from the input point, the contaminated water forms linear stringers migrating down the conduit system toward the discharge point. LNAPLs (e.g. petroleum hydrocarbons) float on the water table and can migrate down the water table gradient to cave streams where they tend to pond behind obstructions. DNAPLs (e.g. chlorinated hydrocarbons), in contrast, sink to the bottom of the aquifer. In the conduit system, DNAPLs pond in low spots at the bottom of the conduit and infiltrate sediment piles. Transport of both LNAPL and DNAPL is dependent on storm flow which can force LNAPL through the system as plug flow and can move DNAPLs by mobilizing the sediment piles. Pathogens (viruses, bacteria, parasites) are transported through the karstic drainage system because of the absence of filtration and retain their activity for long distances. Metals (e.g. chromium, nickel, cadmium, mercury, and lead) tend to precipitate as hydroxides and carbonates in the neutral pH, carbonate rich water of the karst aquifer. Metal transport is mainly as particulates and as metal adsorbed onto small particulates such as clays and colloids. Metal transport is also episodic. Metals migrate down the flow path under flow conditions that take small particulates into suspension. Trash is carried into karst aquifers through sinkholes and sinking streams. It is, in effect, a form of clastic sediment, and can be carried deep into the conduit system where it can act as a source term for other contaminants leached from the trash. | |||||
BibTeX:
@article{Vesper20002001,
author = {Vesper, D. J. and Loop, C. M. and White, W. B.},
title = {Contaminant transport in karst aquifers},
journal = {Theoretical and Applied Karstology},
year = {2000--2001},
volume = {13--14},
number = {0},
pages = {101--111},
url = {http://www.speleogenesis.info/journal/publication.php?id=4490}
}
|
|||||
| Vesper, D.J. and White, W.B. | Metal transport to karst springs during storm flow: an example from Fort Campbell, Kentucky/Tennessee, USA | 2003 | Journal of Hydrology Vol. 276(1-4), pp. 20-36 |
article | URL |
| Abstract: Low levels of heavy metals were investigated in a series of springs discharging from the Mississippian limestone aquifer underlying the Fort Campbell Army Base in western Kentucky/Tennessee. Springs were sampled at short time intervals through periods of storm discharge. Unfiltered samples were digested and analysed by inductively-coupled plasma mass spectrometry. Metals detected at the μg/l level included As, Cd, Cr, Ni and Pb. Metal concentrations exhibited a pronounced maximum coincident with the peak of the storm hydrograph in contrast to carbonate species (Ca, Mg) which dipped to a minimum at the peak of the storm hydrograph. Metal concentrations track with aluminium and iron suggesting that the metal transport is mainly by adsorption onto suspended particulates which are mobilized during storm flow. | |||||
BibTeX:
@article{Vesper2003,
author = {Vesper, Dorothy J and White, William B},
title = {Metal transport to karst springs during storm flow: an example from Fort Campbell, Kentucky/Tennessee, USA},
journal = {Journal of Hydrology},
year = {2003},
volume = {276},
number = {1-4},
pages = {20--36},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403000234}
}
|
|||||
| Vexler, A., Shan, G., Kim, S., Tsai, W.-M., Tian, L. and Hutson, A.D. | An empirical likelihood ratio based goodness-of-fit test for Inverse Gaussian distributions | 2011 | Journal of Statistical Planning and Inference Vol. 141(6), pp. 2128-2140 |
article | URL |
| Abstract: The Inverse Gaussian (IG) distribution is commonly introduced to model and examine right skewed data having positive support. When applying the IG model, it is critical to develop efficient goodness-of-fit tests. In this article, we propose a new test statistic for examining the IG goodness-of-fit based on approximating parametric likelihood ratios. The parametric likelihood ratio methodology is well-known to provide powerful likelihood ratio tests. In the nonparametric context, the classical empirical likelihood (EL) ratio method is often applied in order to efficiently approximate properties of parametric likelihoods, using an approach based on substituting empirical distribution functions for their population counterparts. The optimal parametric likelihood ratio approach is however based on density functions. We develop and analyze the EL ratio approach based on densities in order to test the IG model fit. We show that the proposed test is an improvement over the entropy-based goodness-of-fit test for IG presented by Mudholkar and Tian (2002). Theoretical support is obtained by proving consistency of the new test and an asymptotic proposition regarding the null distribution of the proposed test statistic. Monte Carlo simulations confirm the powerful properties of the proposed method. Real data examples demonstrate the applicability of the density-based EL ratio goodness-of-fit test for an IG assumption in practice. | |||||
BibTeX:
@article{Vexler2011,
author = {Vexler, Albert and Shan, Guogen and Kim, Seongeun and Tsai, Wan-Min and Tian, Lili and Hutson, Alan D.},
title = {An empirical likelihood ratio based goodness-of-fit test for Inverse Gaussian distributions},
journal = {Journal of Statistical Planning and Inference},
year = {2011},
volume = {141},
number = {6},
pages = {2128--2140},
url = {http://www.sciencedirect.com/science/article/pii/S0378375810005823}
}
|
|||||
| Vezzaro, L., Eriksson, E., Ledin, A. and Mikkelsen, P. | Quantification of uncertainty in modelled partitioning and removal of heavy metals (Cu, Zn) in a stormwater retention pond and a biofilter | Water Research(0), pp. - | article | URL | |
| Abstract: Strategies for reduction of micropollutant (MP) discharges from stormwater drainage systems require accurate estimation of the potential MP removal in stormwater treatment systems. However, the high uncertainty commonly affecting stormwater runoff quality modelling also influences stormwater treatment models. This study identified the major sources of uncertainty when estimating the removal of copper and zinc in a retention pond and a biofilter by using a conceptual dynamic model which estimates MP partitioning between the dissolved and particulate phases as well as environmental fate based on substance-inherent properties. The two systems differ in their main removal processes (settling and filtration/sorption, respectively) and in the time resolution of the available measurements (composite samples and pollutographs). The most sensitive model factors, identified by using Global Sensitivity Analysis (GSA), were related to the physical characteristics of the simulated systems (flow and water losses) and to the fate processes related to Total Suspended Solids (TSS). The model prediction bounds were estimated by using the Generalized Likelihood Uncertainty Estimation (GLUE) technique. Composite samples and pollutographs produced similar prediction bounds for the pond and the biofilter, suggesting a limited influence of the temporal resolution of samples on the model prediction bounds. GLUE highlighted model structural uncertainty when modelling the biofilter, due to disregard of plant-driven evapotranspiration, underestimation of sorption and neglect of oversaturation with respect to minerals/salts. The results of this study however illustrate the potential for the application of conceptual dynamic fate models base on substance-inherent properties, in combination with available datasets and statistical methods, to estimate the MP removal in different stormwater treatment systems and compare with environmental quality standards targeting the dissolved MP fraction. | |||||
BibTeX:
@article{Vezzaro,
author = {Vezzaro, L. and Eriksson, E. and Ledin, A. and Mikkelsen, P.S.},
title = {Quantification of uncertainty in modelled partitioning and removal of heavy metals (Cu, Zn) in a stormwater retention pond and a biofilter},
journal = {Water Research},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0043135411004957}
}
|
|||||
| Vezzaro, L., Eriksson, E., Ledin, A. and Mikkelsen, P.S. | Modelling the fate of organic micropollutants in stormwater ponds | 2011 | Science of The Total Environment Vol. 409(13), pp. 2597-2606 |
article | URL |
| Abstract: Urban water managers need to estimate the potential removal of organic micropollutants (MP) in stormwater treatment systems to support MP pollution control strategies. This study documents how the potential removal of organic MP in stormwater treatment systems can be quantified by using multimedia models. The fate of four different MP in a stormwater retention pond was simulated by applying two steady-state multimedia fate models (EPI Suite and SimpleBox) commonly applied in chemical risk assessment and a dynamic multimedia fate model (Stormwater Treatment Unit Model for Micro Pollutants — STUMP). The four simulated organic stormwater MP (iodopropynyl butylcarbamate — IPBC, benzene, glyphosate and pyrene) were selected according to their different urban sources and environmental fate. This ensures that the results can be extended to other relevant stormwater pollutants. All three models use substance inherent properties to calculate MP fate but differ in their ability to represent the small physical scale and high temporal variability of stormwater treatment systems. Therefore the three models generate different results. A Global Sensitivity Analysis (GSA) highlighted that settling/resuspension of particulate matter was the most sensitive process for the dynamic model. The uncertainty of the estimated MP fluxes can be reduced by calibrating the dynamic model against total suspended solids data. This reduction in uncertainty was more significant for the substances with strong tendency to sorb, i.e. glyphosate and pyrene and less significant for substances with a smaller tendency to sorb, i.e. IPBC and benzene. The results provide support to the elaboration of MP pollution control strategies by limiting the need for extensive and complex monitoring campaigns targeting the wide range of specific organic MP found in stormwater runoff. | |||||
BibTeX:
@article{Vezzaro2011,
author = {Vezzaro, Luca and Eriksson, Eva and Ledin, Anna and Mikkelsen, Peter S.},
title = {Modelling the fate of organic micropollutants in stormwater ponds},
journal = {Science of The Total Environment},
year = {2011},
volume = {409},
number = {13},
pages = {2597--2606},
url = {http://www.sciencedirect.com/science/article/pii/S0048969711002191}
}
|
|||||
| Vezzaro, L. and Mikkelsen, P.S. | Application of global sensitivity analysis and uncertainty quantification in dynamic modelling of micropollutants in stormwater runoff | 2012 | Environmental Modelling & Software Vol. 27–28(0), pp. 40-51 |
article | URL |
| Abstract: The need for estimating micropollutants fluxes in stormwater systems increases the role of stormwater quality models as support for urban water managers, although the application of such models is affected by high uncertainty. This study presents a procedure for identifying the major sources of uncertainty in a conceptual lumped dynamic stormwater runoff quality model that is used in a study catchment to estimate (i) copper loads, (ii) compliance with dissolved Cu concentration limits on stormwater discharge and (iii) the fraction of Cu loads potentially intercepted by a planned treatment facility. The analysis is based on the combination of variance-decomposition Global Sensitivity Analysis (GSA) with the Generalized Likelihood Uncertainty Estimation (GLUE) technique. The GSA-GLUE approach highlights the correlation between the model factors defining the mass of pollutant in the system and the importance of considering hydrological parameters as source of uncertainty when calculating Cu loads and concentrations due to their influence. The influence of hydrological parameters on simulated concentrations changes during rain events. Four informal likelihood measures are used to quantify model prediction bounds. The width of the uncertainty bounds depends on the likelihood measure, with the inverse variance based likelihood more suitable for covering measured pollutographs. Uncertainty for simulated concentration is higher than for Cu loads, which again shows lower uncertainty compared to studies neglecting the hydrological submodel as source of uncertainty. A combined likelihood measure ensuring both good predictions in flow and concentration is used to identify the parameter sets used for long time simulations. These results provide a basis for reliable application of models as support in the development of strategies aiming to reduce discharge of stormwater micropollutants to the aquatic environment. | |||||
BibTeX:
@article{Vezzaro2012,
author = {Vezzaro, Luca and Mikkelsen, Peter Steen},
title = {Application of global sensitivity analysis and uncertainty quantification in dynamic modelling of micropollutants in stormwater runoff},
journal = {Environmental Modelling & Software},
year = {2012},
volume = {27–28},
number = {0},
pages = {40--51},
url = {http://www.sciencedirect.com/science/article/pii/S1364815211002106}
}
|
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| Vías, J., Andreo, B., Perles, M., Carrasco, F., Vadillo, I. and Jiménez, P. | Proposed method for groundwater vulnerability mapping in carbonate (karstic) aquifers: the COP method | 2006 | Hydrogeology Journal Vol. 14(6), pp. 912-925 |
article | URL |
| Abstract: The ‘COP method’ has been developed for the assessment of intrinsic vulnerability of carbonate aquifers in the frame of the European COST Action 620. This method uses the properties of overlying layers above the water table (O factor), the concentration of flow (C factor) and precipitation (P factor) over the aquifer, as the parameters to assess the intrinsic vulnerability of groundwater. This method considers karst characteristics, such as the presence of swallow holes (C factor) and their catchment areas as well as karstic landforms, as factors which decrease the natural protection provided by overlying layers (O factor). The P factor allows for consideration of the spatial and temporal variability of precipitation, which is considered the transport agent of contamination. Two carbonate aquifers in the South of Spain, Sierra de Líbar (a conduit flow system) and Torremolinos (a diffuse flow system), have been selected for the application and validation of the method and the results have been compared with three methods widely applied in different aquifers around the world (AVI, GOD and DRASTIC). Comparisons with these methods and validation tools (hydrogeological data and tracer test) show the advantages of the COP method in the assessment of vulnerability of karstic groundwaters. | |||||
BibTeX:
@article{Vias2006,
author = {Vías, J. and Andreo, B. and Perles, M. and Carrasco, F. and Vadillo, I. and Jiménez, P.},
title = {Proposed method for groundwater vulnerability mapping in carbonate (karstic) aquifers: the COP method},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2006},
volume = {14},
number = {6},
pages = {912--925},
url = {http://dx.doi.org/10.1007/s10040-006-0023-6}
}
|
|||||
| Vicum, L., Ottiger, S., Mazzotti, M., Makowski, Ł. and Bałdyga, J. | Multi-scale modeling of a reactive mixing process in a semibatch stirred tank | 2004 | Chemical Engineering Science Vol. 59(8-9)Complex Systems and Multi-scale Methodology, pp. 1767-1781 |
article | URL |
| Abstract: In this work the influence of turbulent mixing on the course of two parallel chemical reactions (neutralization of sodium hydroxide and hydrolysis of ethyl chloroacetate) is investigated for a process carried out in a semibatch stirred tank reactor. The multi-scale nature of the process is highlighted by a time-scale analysis of controlling process mechanisms. Two reactive mixing models of different complexity, both accounting for all relevant phenomena from the micro- to the macroscale, are applied for the simulation of the process. Computational results of both models for various operating conditions are compared with experimental data, thus highlighting the strengths of the two models. | |||||
BibTeX:
@article{Vicum2004,
author = {Vicum, Lars and Ottiger, Stefan and Mazzotti, Marco and Makowski, Łukasz and Bałdyga, Jerzy},
title = {Multi-scale modeling of a reactive mixing process in a semibatch stirred tank},
booktitle = {Complex Systems and Multi-scale Methodology},
journal = {Chemical Engineering Science},
year = {2004},
volume = {59},
number = {8--9},
pages = {1767--1781},
url = {http://www.sciencedirect.com/science/article/pii/S0009250904000910}
}
|
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| Viel, J.-F., Hägi, M., Upegui, E. and Laurian, L. | Environmental justice in a French industrial region: Are polluting industrial facilities equally distributed? [BibTeX] |
2011 | Health & Place Vol. 17(1), pp. 257-262 |
article | DOI URL |
BibTeX:
@article{Viel2011,
author = {Viel, Jean-François and Hägi, Mathieu and Upegui, Erika and Laurian, Lucie},
title = {Environmental justice in a French industrial region: Are polluting industrial facilities equally distributed?},
journal = {Health & Place},
year = {2011},
volume = {17},
number = {1},
pages = {257--262},
url = {http://www.sciencedirect.com/science/article/pii/S1353829210001589},
doi = {http://dx.doi.org/10.1016/j.healthplace.2010.10.007}
}
|
|||||
| Vikhansky, A. | Numerical analysis of residence time distribution in microchannels | 2011 | Chemical Engineering Research and Design Vol. 89(3), pp. 347-351 |
article | URL |
| Abstract: This article describes a numerical approach, which allows for the analysis of the residence time distribution (RTD) in microchannels. While the traditional methods provide the RTD at the outlet of the reactor, we consider the distribution of the tracer's age across the entire flowfield. The equation for the tracer's age distribution is solved by a modified method of moments and the distribution function is calculated by a reconstruction procedure. As an example we consider a Dean vortex-based micromixer. | |||||
BibTeX:
@article{Vikhansky2011a,
author = {Vikhansky, A.},
title = {Numerical analysis of residence time distribution in microchannels},
journal = {Chemical Engineering Research and Design},
year = {2011},
volume = {89},
number = {3},
pages = {347--351},
url = {http://www.sciencedirect.com/science/article/pii/S0263876210001826}
}
|
|||||
| Vikhansky, A. | Effect of diffusion on residence time distribution in chaotic channel flow | 2008 | Chemical Engineering Science Vol. 63(7), pp. 1866-1870 |
article | URL |
| Abstract: We consider the residence time distribution (RTD) of a liquid flowing through a spatially periodic channel. It is shown that chaotic advection significantly reduces deviation of the RTD which then consist of two parts: the main pulse which does not depend on the Péclet number and a long tail which is formed in the near-boundary layer, where the advection is weak. Boundary layer approximation provides the dependence of the statistical moments of the RTD on Péclet number. It is shown that the length of the tail increases with Pe, while its mass decreases. The numerical results support the theoretical findings. | |||||
BibTeX:
@article{Vikhansky2008,
author = {Vikhansky, A.},
title = {Effect of diffusion on residence time distribution in chaotic channel flow},
journal = {Chemical Engineering Science},
year = {2008},
volume = {63},
number = {7},
pages = {1866--1870},
url = {http://www.sciencedirect.com/science/article/pii/S0009250907009128}
}
|
|||||
| Vikhansky, A. and Wang, W. | Taylor dispersion in finite-length capillaries | 2011 | Chemical Engineering Science Vol. 66(4), pp. 642-649 |
article | URL |
| Abstract: The solute transport in a core-annular geometry is studied. A Newtonian or non-Newtonian (i.e., power-law) liquid flows through the core, while the solute can exchange between the liquid and the surrounding tissue. The permeability of the phase interface depends on the nature of the solute, i.e., relatively low for lipids and macromolecules but high for ions and gases. We analyse the moment’s equations of the residence time distribution (RTD). The solution of the equation for the second moment provides the exact formula for the Taylor dispersion coefficient. Unlike previous studies using a perturbation procedure where coefficient of axial dispersion cannot be defined at low permeability, the current study gives Taylor coefficient of dispersion for any value of the permeability. It is found that the coefficient in shear-thinning fluid is lower than in the Newtonian one, although the relative importance of non-Newtonian effects decreases when other factors, e.g. inter-phase transport and solubility, become dominant. The equations for the higher moments are analysed and the general structure of the solution is obtained in the form of integrals, which can be easily evaluated numerically. When the analysis is applied to solute transport between capillaries and surrounding tissues, it is shown that the classic Taylor expression does not describe dispersion of solute, e.g. glucose and albumin, in the capillary, except in situations where the Péclet number is very low. For the range of parameters typical for microvascular circulation in tissues, the higher moments play an important role and need to be considered. | |||||
BibTeX:
@article{Shoar2011,
author = {Vikhansky, A. and Wang, W.},
title = {Taylor dispersion in finite-length capillaries},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {4},
pages = {642--649},
url = {http://www.sciencedirect.com/science/article/pii/S0009250910006810}
}
|
|||||
| Vikhansky, A. and Wang, W. | Taylor dispersion in finite-length capillaries | 2011 | Chemical Engineering Science Vol. 66(4), pp. 642-649 |
article | URL |
| Abstract: The solute transport in a core-annular geometry is studied. A Newtonian or non-Newtonian (i.e., power-law) liquid flows through the core, while the solute can exchange between the liquid and the surrounding tissue. The permeability of the phase interface depends on the nature of the solute, i.e., relatively low for lipids and macromolecules but high for ions and gases. We analyse the moment’s equations of the residence time distribution (RTD). The solution of the equation for the second moment provides the exact formula for the Taylor dispersion coefficient. Unlike previous studies using a perturbation procedure where coefficient of axial dispersion cannot be defined at low permeability, the current study gives Taylor coefficient of dispersion for any value of the permeability. It is found that the coefficient in shear-thinning fluid is lower than in the Newtonian one, although the relative importance of non-Newtonian effects decreases when other factors, e.g. inter-phase transport and solubility, become dominant. The equations for the higher moments are analysed and the general structure of the solution is obtained in the form of integrals, which can be easily evaluated numerically. When the analysis is applied to solute transport between capillaries and surrounding tissues, it is shown that the classic Taylor expression does not describe dispersion of solute, e.g. glucose and albumin, in the capillary, except in situations where the Péclet number is very low. For the range of parameters typical for microvascular circulation in tissues, the higher moments play an important role and need to be considered. | |||||
BibTeX:
@article{Vikhansky2011b,
author = {Vikhansky, A. and Wang, W.},
title = {Taylor dispersion in finite-length capillaries},
journal = {Chemical Engineering Science},
year = {2011},
volume = {66},
number = {4},
pages = {642--649},
url = {http://www.sciencedirect.com/science/article/pii/S0009250910006810}
}
|
|||||
| Villa, M., Mosqueda, F., Hurtado, S., Mantero, J., Manjón, G., Periañez, R., Vaca, F. and García-Tenorio, R. | Contamination and restoration of an estuary affected by phosphogypsum releases | 2009 | Science of The Total Environment Vol. 408(1), pp. 69-77 |
article | URL |
| Abstract: The Huelva Estuary in Huelva, Spain, has been one of the most studied environmental compartments in the past years from the point of view of naturally occurring radioactive material (NORM) releases. It has been historically affected by waste releases, enriched in radionuclides from the U-decay series, from factories located in the area devoted to the production of phosphoric acid and phosphate fertilizers. | |||||
BibTeX:
@article{Villa2009,
author = {Villa, M. and Mosqueda, F. and Hurtado, S. and Mantero, J. and Manjón, G. and Periañez, R. and Vaca, F. and García-Tenorio, R.},
title = {Contamination and restoration of an estuary affected by phosphogypsum releases},
journal = {Science of The Total Environment},
year = {2009},
volume = {408},
number = {1},
pages = {69--77},
url = {http://www.sciencedirect.com/science/article/pii/S0048969709008912}
}
|
|||||
| Villaseñor, J., Mena, J., Fernández, F.J., Gómez, R. and de Lucas, A. | Kinetics of domestic wastewater COD removal by subsurface flow constructed wetlands using different plant species in temperate period | 2011 | International Journal of Environmental Analytical Chemistry Vol. 91(7-8)International Journal of Environmental Analytical Chemistry, pp. 693-707 |
article | DOI URL |
| Abstract: The objective of this work has been to study the kinetics of domestic wastewater chemical oxygen demand (COD) removal when using constructed wetlands (CWs) with different plant species and at different water depths. Kinetic rate constants were obtained by using several kinetic models, and also combined with different hydraulic models. Synthetic wastewater was fed to five identical pilot-scale CWs, planted with different species (CW1: unplanted; CW2: Phragmites australis; CW3: Lythrum salicaria; CW4: Cladium mariscus; CW5: Iris pseudacorus). Wastewater was treated under continuous operation during 5 months. Water samples were taken along intermediate points at the wetland, and also at three different depths (top, medium depth and bottom). The COD experimental data were fitted to different kinetic models previously and extensively reported in the literature: the K-C and K-C* equations, and also the 'retardation' model. Also, the effect of the hydraulics characteristics was considered. Apart from the ideal plug flow assumption, two different flow models were used when integrating the mass balance equations: the plug flow with dispersion model and a detention time gamma distribution (DTGD) model. The more developed plants (CW3 and CW5) were the ones that caused an increase in COD removal rate compared with the unplanted wetland. Differences in COD removal rates were observed at different depths in the unplanted wetland, and the higher rate constant values were obtained near the wetlands top. On the contrary, the higher plants development in CW3 and CW5 eliminated the influence of water depth. The retardation model offered the best mathematical fitting to the experimental data. By using non ideal flow models, an increase in the rate constant values was always obtained, especially in the wetlands whose hydraulic behaviour was very far from the ideal plug flow. The rate constants values obtained using the DTGD model were higher (25-54%), compared to the values obtained if ideal flow was considered. These results could aid the design of CW, particularly in temperate periods. | |||||
BibTeX:
@article{Villasenor2011,
author = {Villaseñor, José and Mena, Javier and Fernández, Francisco J. and Gómez, Rocío and de Lucas, Antonio},
title = {Kinetics of domestic wastewater COD removal by subsurface flow constructed wetlands using different plant species in temperate period},
booktitle = {International Journal of Environmental Analytical Chemistry},
journal = {International Journal of Environmental Analytical Chemistry},
publisher = {Taylor & Francis},
year = {2011},
volume = {91},
number = {7-8},
pages = {693--707},
url = {http://dx.doi.org/10.1080/03067319.2010.497918},
doi = {http://dx.doi.org/10.1080/03067319.2010.497918}
}
|
|||||
| Villaseñor-Alva, J.A. and González-Estrada, E. | A bootstrap goodness of fit test for the generalized Pareto distribution | 2009 | Computational Statistics & Data Analysis Vol. 53(11), pp. 3835-3841 |
article | URL |
| Abstract: This paper proposes a bootstrap goodness of fit test for the Generalized Pareto distribution (GPd) with shape parameter γ . The proposed test is an intersection–union test which tests separately the cases of γ ≥ 0 and γ < 0 and rejects if both cases are rejected. If the test does not reject, then it is known whether the shape parameter γ is either positive or negative. A Monte Carlo simulation experiment was conducted to assess the power of performance of the intersection–union test. The GPd hypothesis was tested on a data set containing Mexico City’s ozone levels. 11The R code for implementing the proposed test can be obtained from the authors. | |||||
BibTeX:
@article{Villasenor-Alva2009,
author = {Villaseñor-Alva, José A. and González-Estrada, Elizabeth},
title = {A bootstrap goodness of fit test for the generalized Pareto distribution},
journal = {Computational Statistics & Data Analysis},
year = {2009},
volume = {53},
number = {11},
pages = {3835--3841},
url = {http://www.sciencedirect.com/science/article/pii/S0167947309001406}
}
|
|||||
| Villermaux, J. and Falk, L. | A generalized mixing model for initial contacting of reactive fluids | 1994 | Chemical Engineering Science Vol. 49(24, Part 2), pp. 5127-5140 |
article | URL |
| Abstract: This paper deals with the representation of phenomena occurring when a fluid stream containing reactive species comes into contact, mixes up and reacts with an excess of miscible fluid. The various steps of the mixing process are: erosion of fresh fluid, dilution of the smaller eddies into the reacting zone, invasion of this zone by incorporation of bulk fluid, and exchange or diffusion between small eroded and incorporated eddies in the reacting cloud. Material balance equations are derived both in a Lagrangian and in an Eulerian framework. It is shown that the Generalized Mixing Model (GMM) contains previously published models as special cases. | |||||
BibTeX:
@article{Villermaux1994,
author = {Villermaux, Jacques and Falk, Laurent},
title = {A generalized mixing model for initial contacting of reactive fluids},
journal = {Chemical Engineering Science},
year = {1994},
volume = {49},
number = {24, Part 2},
pages = {5127--5140},
url = {http://www.sciencedirect.com/science/article/pii/0009250994003033}
}
|
|||||
| Vincenzi, V., Gargini, A. and Goldscheider, N. | Using tracer tests and hydrological observations to evaluate effects of tunnel drainage on groundwater and surface waters in the Northern Apennines (Italy) | 2009 | Hydrogeology Journal Vol. 17(1), pp. 135-150 |
article | URL |
| Abstract: The impact of a railway tunnel on groundwater and surface waters in the Northern Apennines (Italy) was demonstrated and characterised by multi-tracer tests and hydrological observations. The 15-km-long Firenzuola tunnel crosses turbidite marls and sandstones previously not considered as aquifers. During the drilling, water inrushes occurred at fracture zones, and the tunnel still continues to drain the aquifer. The water table dropped below the level of the valleys, and gaining streams transformed into losing streams or ran completely dry, as did many springs, causing severe damage to the aquatic fauna and other elements of the ecosystem. Two multi-tracer tests, each using uranine and sulforhodamine G, were carried out in two impacted catchments in order to confirm and quantify the stream–aquifer–tunnel interrelations. The results proved connection between losing streams and numerous water inlets in the tunnel, with maximum linear distances of 1.4 km and velocities up to 135 m/d. Several of the demonstrated flowpaths pass under previous groundwater divides (mountain ridges), proving that the tunnel has completely modified the regional flow system. Water balance estimations demonstrate that the observed water losses cannot be explained by climate change but can largely be attributed to the tunnel drainage. | |||||
BibTeX:
@article{Vincenzi2009,
author = {Vincenzi, Valentina and Gargini, Alessandro and Goldscheider, Nico},
title = {Using tracer tests and hydrological observations to evaluate effects of tunnel drainage on groundwater and surface waters in the Northern Apennines (Italy)},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {1},
pages = {135--150},
url = {http://dx.doi.org/10.1007/s10040-008-0371-5}
}
|
|||||
| Vitrac, O. and Hayert, M. | Effect of the distribution of sorption sites on transport diffusivities: A contribution to the transport of medium-weight-molecules in polymeric materials | 2007 | Chemical Engineering Science Vol. 62(9), pp. 2503-2521 |
article | URL |
| Abstract: The detailed transports of both small and large molecules in heterogeneous media including either random disorder or periodic obstacles are known to decrease the value of macroscopic diffusion coefficients. This work proposes to analyze the successive displacements of medium-sized molecules in polymer materials according to the dispersion and topology of sorption sites from a modified application of the transition state theory. In absence of available information on the dispersion of rate constants between sorption macrosites for such molecules, their transport mechanisms at molecular scale is related to their sorption properties, which are more likely to be available. Simulations by kinetic Monte Carlo (KMC) techniques are presented for different distributions of occupancy values randomly allocated in space or distributed in self-similar clusters. Network structures are generated from the equilibrium occupancy on the basis of transition-state theory formulation on 2D lattice approximations. Different reconstruction strategies on 2D hexagonal lattices are examined regarding maximum likelihood principles including maximization of obstruction effects and minimization of either local or global variance of conductances between sorption sites. Effects of short time scales are assessed by comparing results obtained with networks verifying reversible and non-reversible random walks. | |||||
BibTeX:
@article{Vitrac2007,
author = {Vitrac, O. and Hayert, M.},
title = {Effect of the distribution of sorption sites on transport diffusivities: A contribution to the transport of medium-weight-molecules in polymeric materials},
journal = {Chemical Engineering Science},
year = {2007},
volume = {62},
number = {9},
pages = {2503--2521},
url = {http://www.sciencedirect.com/science/article/pii/S0009250907001339}
}
|
|||||
| Vogt, K.A., Publicover, D.A., Bloomfield, J., Perez, J.M., Vogt, D.J. and Silver, W.L. | Belowground responses as indicators of environmental change | 1993 | Environmental and Experimental Botany Vol. 33(1)The Impact of the Environment on Roots and Root Systems, pp. 189-205 |
article | URL |
| Abstract: This paper discusses when and under what circumstances belowground parameters become advantageous to monitor as sensitive, early indicators of an environment being exposed to anthropogenic stress. The following specific belowground attributes are presented as useful parameters to monitor because they are sensitive to stress and should be influenced prior to the occurrence of visible aboveground symptoms: fine root biomass and turnover, mycorrhizal biomass and species of fungi colonizing the roots, secondary defensive chemical production in roots, carbohydrate reserves in roots, and nutrient and/or trace element concentrations and ratios in roots. | |||||
BibTeX:
@article{Vogt1993,
author = {Vogt, Kristiina A. and Publicover, David A. and Bloomfield, Janine and Perez, Javier M. and Vogt, Daniel J. and Silver, Whendee L.},
title = {Belowground responses as indicators of environmental change},
booktitle = {The Impact of the Environment on Roots and Root Systems},
journal = {Environmental and Experimental Botany},
year = {1993},
volume = {33},
number = {1},
pages = {189--205},
url = {http://www.sciencedirect.com/science/article/pii/009884729390065N}
}
|
|||||
| Vrentas, J. and Vrentas, C. | Asymptotic solutions for laminar dispersion in circular tubes | 2000 | Chemical Engineering Science Vol. 55(4), pp. 849-855 |
article | URL |
| Abstract: A short-time asymptotic solution is developed for the dispersion of a passive solute in the fully developed laminar flow of a Newtonian fluid through a straight circular tube. The new solution describes the axial dependence of the average concentration both near the leading and trailing edges of the concentration distribution, and it predicts the existence of a pronounced maximum near the trailing edge. | |||||
BibTeX:
@article{Vrentas2000,
author = {Vrentas, J.S. and Vrentas, C.M.},
title = {Asymptotic solutions for laminar dispersion in circular tubes},
journal = {Chemical Engineering Science},
year = {2000},
volume = {55},
number = {4},
pages = {849--855},
url = {http://www.sciencedirect.com/science/article/pii/S0009250999003553}
}
|
|||||
| W.E., B. | Temporal moments of a tracer pulse in a perfectly parallel flow system | 2003 | Advances in Water Resources Vol. 26(6), pp. 599-607 |
article | URL |
| Abstract: Perfectly parallel groundwater transport models partition water flow into isolated one-dimensional stream tubes which maintain total spatial correlation of all properties in the direction of flow. The case is considered of the temporal moments of a conservative tracer pulse released simultaneously into N stream tubes with arbitrarily different advective–dispersive transport and steady flow speeds in each of the stream tubes. No assumptions are made about the form of the individual stream tube arrival-time distributions or about the nature of the between-stream tube variation of hydraulic conductivity and flow speeds. The tracer arrival-time distribution g(t,x) is an N-component finite-mixture distribution, with the mean and variance of each component distribution increasing in proportion to tracer travel distance x. By utilising moment relations of finite mixture distributions, it is shown (to r=4) that the rth central moment of g(t,x) is an rth order polynomial function of x or φ, where φ is mean arrival time. In particular, the variance of g(t,x) is a positive quadratic function of x or φ. This generalises the well-known quadratic variance increase for purely advective flow in parallel flow systems and allows a simple means of regression estimation of the large-distance coefficient of variation of g(t,x). The polynomial central moment relation extends to the purely advective transport case which arises as a large-distance limit of advective–dispersive transport in parallel flow models. The associated limit g(t,x) distributions are of N-modal form and maintain constant shapes independent of travel distance. The finite-mixture framework for moment evaluation is also a potentially useful device for forecasting g(t,x) distributions, which may include multimodal forms. A synthetic example illustrates g(t,x) forecasting using a mixture of normal distributions. | |||||
BibTeX:
@article{W.E.2003,
author = {W.E., Bardsley},
title = {Temporal moments of a tracer pulse in a perfectly parallel flow system},
journal = {Advances in Water Resources},
year = {2003},
volume = {26},
number = {6},
pages = {599--607},
url = {http://www.sciencedirect.com/science/article/pii/S0309170803000472}
}
|
|||||
| W.S., V. | New stochastic model for dispersion in heterogeneous porous media: 2. Gaussian plume transmission across stepwise velocity fluctuations | 2011 | Applied Mathematical Modelling Vol. 35(7), pp. 3355-3386 |
article | URL |
| Abstract: The stochastic solute dispersion model studied in the previous article, can be applied to more realistic velocity variations by approximating them as piecewise constant. This requires treatment by a boundary value formulation, which raises problems connected with entropy considerations. A method is developed to deal with these by the introduction of a specially designed compensator function into the boundary value probability integral for calculating solute concentration. Applying this even for a single velocity step yields an intractable integration, but a suitable approximation is constructed that allows it to be evaluated in analytical form. The result is that a Gaussian solute plume impinging on a velocity step is transmitted as a modulated and compressed or dilated quasi-Gaussian. Plume dispersion is encapsulated in an enhancement factor F that multiplies the diffusive, linear time, dispersion. F is also time dependent; at the time of step penetration it equals kinematical dilation, but anneals away non-linearly so that a length scale can be established over which downstream effects of a velocity step on the dispersion extends. | |||||
BibTeX:
@article{W.S.2011,
author = {W.S., Verwoerd},
title = {New stochastic model for dispersion in heterogeneous porous media: 2. Gaussian plume transmission across stepwise velocity fluctuations},
journal = {Applied Mathematical Modelling},
year = {2011},
volume = {35},
number = {7},
pages = {3355--3386},
url = {http://www.sciencedirect.com/science/article/pii/S0307904X11000291}
}
|
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| Wahi, A.K., Hogan, J.F., Ekwurzel, B., Baillie, M.N. and Eastoe, C.J. | Geochemical Quantification of Semiarid Mountain Recharge | 2008 | Ground Water Vol. 46(3), pp. 414-425 |
article | URL |
| Abstract: Analysis of a typical semiarid mountain system recharge (MSR) setting demonstrates that geochemical tracers help resolve the location, rate, and seasonality of recharge as well as ground water flowpaths and residence times. MSR is defined as the recharge at the mountain front that dominates many semiarid basins plus the often-overlooked recharge through the mountain block that may be a significant ground water resource; thus, geochemical measurements that integrate signals from all flowpaths are advantageous. Ground water fluxes determined from carbon-14 (14C) age gradients imply MSR rates between 2 × 106 and 9 × 106 m3/year in the Upper San Pedro Basin, Arizona, USA. This estimated range is within an order of magnitude of, but lower than, prior independent estimates. Stable isotopic signatures indicate that MSR has a 65% ± 25% contribution from winter precipitation and a 35% ± 25% contribution from summer precipitation. Chloride and stable isotope results confirm that transpiration is the dominant component of evapotranspiration (ET) in the basin with typical loss of more than 90% of precipitation-less runoff to ET. Such geochemical constraints can be used to further refine hydrogeologic models in similar high-elevation relief basins and can provide practical first estimates of MSR rates for basins lacking extensive prior hydrogeologic measurements. | |||||
BibTeX:
@article{Wahi2008,
author = {Wahi, Arun K. and Hogan, James F. and Ekwurzel, Brenda and Baillie, Matthew N. and Eastoe, Christopher J.},
title = {Geochemical Quantification of Semiarid Mountain Recharge},
journal = {Ground Water},
publisher = {Blackwell Publishing Inc},
year = {2008},
volume = {46},
number = {3},
pages = {414--425},
url = {http://dx.doi.org/10.1111/j.1745-6584.2007.00413.x}
}
|
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| Wahl, M.D., Brown, L.C., Soboyejo, A.O., Martin, J. and Dong, B. | Quantifying the hydraulic performance of treatment wetlands using the moment index | 2010 | Ecological Engineering Vol. 36(12), pp. 1691-1699 |
article | URL |
| Abstract: A new hydraulic index was derived according to residence time distribution theory. The approach quantifies hydraulic inefficiencies according to the juxtaposition of the hold back parameter relative to the residence time distribution. The index was evaluated for its ability to detect variation, for conformity with qualitative assessments, and for correlation to effluent pollutant fractions in order to assess its suitability as a predictor of treatment. | |||||
BibTeX:
@article{Wahl2010,
author = {Wahl, Mark D. and Brown, Larry C. and Soboyejo, Alfred O. and Martin, Jay and Dong, Bin},
title = {Quantifying the hydraulic performance of treatment wetlands using the moment index},
journal = {Ecological Engineering},
year = {2010},
volume = {36},
number = {12},
pages = {1691--1699},
url = {http://www.sciencedirect.com/science/article/pii/S0925857410002223}
}
|
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| Walker, D.J. | Modelling residence time in stormwater ponds | 1998 | Ecological Engineering Vol. 10(3), pp. 247-262 |
article | URL |
| Abstract: The removal of many stormwater pollutants in a wet pond, wetland or detention basin is dependent on residence time. Actual residence time in constructed ponds is a function of the intermittent nature of the inflows, and the flow patterns that develop in the basin during flow events. A method has been developed to allow a long-term residence time distribution to be calculated, using inflow records and the results of modelling the behaviour of the basin during inflow events of varying size. The method uses numerical models to solve the depth-averaged flow and transport equations and is demonstrated on the re-design of a wet pond in Adelaide, Australia. | |||||
BibTeX:
@article{Walker1998,
author = {Walker, David J.},
title = {Modelling residence time in stormwater ponds},
journal = {Ecological Engineering},
year = {1998},
volume = {10},
number = {3},
pages = {247--262},
url = {http://www.sciencedirect.com/science/article/pii/S0925857498000160}
}
|
|||||
| Walker, G. | Environmental justice, impact assessment and the politics of knowledge: The implications of assessing the social distribution of environmental outcomes | 2010 | Environmental Impact Assessment Review Vol. 30(5)Conflict Mediation and Social Impact Assessment, pp. 312-318 |
article | URL |
| Abstract: Claims of environmental injustice have increasingly become part of environmental conflicts, both explicitly through the work of environmental justice campaigning groups and implicitly through the arguments deployed about the rights and wrongs of a given situation. Such claims can centre on different notions of justice, including those concerned with questions of distribution and procedure. This paper focuses on distributional or outcome justice and explores what implications follow when the distributional concerns of environmental justice are included in the practice of impact assessment processes, including through social impact assessment (SIA). The current use of impact assessment methods in the UK is reviewed showing that although practices are evolving there is a little routine assessment of distributional inequalities. It is argued that whilst this should become part of established practice to ensure that inequalities are revealed and matters of justice are given a higher profile, the implications for conflict within decision making processes are not straightforward. On the one hand, there could be scope for conflict to be ameliorated by analysis of inequalities informing the debate between stakeholders, and facilitating the implementation of mitigation and compensation measures for disadvantaged groups. On the other hand, contestation over how evidence is produced and therefore what it shows, and disagreement as to the basis on which justice and injustice are to be determined, means that conflict may also be generated and sustained within what are essentially political and strategic settings. | |||||
BibTeX:
@article{Walker2010,
author = {Walker, Gordon},
title = {Environmental justice, impact assessment and the politics of knowledge: The implications of assessing the social distribution of environmental outcomes},
booktitle = {Conflict Mediation and Social Impact Assessment},
journal = {Environmental Impact Assessment Review},
year = {2010},
volume = {30},
number = {5},
pages = {312--318},
url = {http://www.sciencedirect.com/science/article/pii/S0195925510000661}
}
|
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| Waller, L.A., Smith, D., Childs, J.E. and Real, L.A. | Monte Carlo assessments of goodness-of-fit for ecological simulation models | 2003 | Ecological Modelling Vol. 164(1), pp. 49-63 |
article | URL |
| Abstract: One often develops stochastic ecologic simulation models based on local interactions between individuals or groups and bases systemic conclusions on trends summarized over multiple data sets generated from the model. In many cases, such models generate data sets (“realizations”) each violating the usual assumptions associated with traditional statistical tests of goodness-of-fit, most notably that of independent observations. Monte Carlo hypothesis tests applied to multiple realizations from such models provide appropriate goodness-of-fit tests regardless of within-model peculiarities. The Monte Carlo tests address the question “Do the observed data appear consistent with the model?” in contrast to the usual question “Does the model appear consistent with the observed data?”. In addition, such tests can make use of the same data sets used to draw systemic inference (i.e. the tests require no additional simulation runs). We illustrate the concept using Pearson’s chi-square statistic with correlated data. We also consider the behavior of a similar statistic and of “modeling efficiency” in assessing the fit of a simulation model for the spatial spread of raccoon rabies in Connecticut. | |||||
BibTeX:
@article{Waller2003,
author = {Waller, Lance A. and Smith, David and Childs, James E. and Real, Leslie A.},
title = {Monte Carlo assessments of goodness-of-fit for ecological simulation models},
journal = {Ecological Modelling},
year = {2003},
volume = {164},
number = {1},
pages = {49--63},
url = {http://www.sciencedirect.com/science/article/pii/S0304380003000115}
}
|
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| Wang, H. and Jawitz, J.W. | Hydraulic analysis of cell-network treatment wetlands | 2006 | Journal of Hydrology Vol. 330(3–4), pp. 721-734 |
article | URL |
| Abstract: When individual cells of a multiple-cell treatment wetland are hydraulically connected, the wetland has a cell-network structure. The hydraulic performance of treatment wetlands is often characterized using tracer residence time distributions (RTDs) measured between the wetland inlet and outlet, such that the wetland is considered as a single hydraulic unit, regardless of the extent of networking between individual internal cells. This work extends the single hydraulic unit approach to enable the specification of moments and RTD parameters for individual cells, or clusters of cells, within the cell-network based on inert tracer tests with injection only at the network inlet. Hydraulic performance is quantified in terms of hydraulic efficiency and travel time dimensionless variance using both the method of moments and RTD modeling. Cell-network analysis was applied to a case study from the Orlando Easterly Wetland (OEW), demonstrating the improvement in hydraulic performance of individual wetland cells following wetland restoration activities. Furthermore, cell-network analysis indicated that the location of water quality sampling station locations within the cell network can significantly affect the accuracy of pollutant removal effectiveness estimation when the individual sample station RTD does not represent the hydraulic unit RTD. At the OEW, it was determined that historical nutrient removal effectiveness estimation may be underestimated for one area and overestimated for another, and recommendations were provided for sample station locations to minimize future performance estimation errors. | |||||
BibTeX:
@article{Wang2006,
author = {Wang, Huaguo and Jawitz, James W.},
title = {Hydraulic analysis of cell-network treatment wetlands},
journal = {Journal of Hydrology},
year = {2006},
volume = {330},
number = {3–4},
pages = {721--734},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406002708}
}
|
|||||
| Wang, H. and Lacroix, M. | Interpolation techniques applied to the Eulerian-Lagrangian solution of the convection-dispersion equation in natural coordinates | 1997 | Computers & Geosciences Vol. 23(6), pp. 677-688 |
article | URL |
| Abstract: A weighted second-order (quadratic) interpolation technique is proposed to eliminate the oscillation phenomena manifested in the numerical Eulerian-Lagrangian solution of the convection-dispersion equation in natural coordinates when sharp fronts of concentration occur. Weighting is based on the interpolation of local moving points by using the known points in the fixed Eulerian grid. To increase numerical accuracy, the use of a third order (cubic) polynomial is discussed. Numerical experiments show that, in comparison with the quadratic formula, the application of this cubic interpolation technique has a number of advantages: (1) numerical oscillation is much less important or disappears; (2) the upstream spatial shift brought about by the quadratic formula disappears; and (3) stability is greater, even when the grid current number is larger than 1. The proposed numerical model is tested against two classical problems for which analytical solutions exist. The additional comparison of the numerical results obtained by the Eulerian-Lagrangian method using cubic interpolation, and those obtained by a purely Eulerian method (UWMCB), is carried out to illustrate the possibility of a real gain in precision. | |||||
BibTeX:
@article{Wang1997,
author = {Wang, H.Q. and Lacroix, M.},
title = {Interpolation techniques applied to the Eulerian-Lagrangian solution of the convection-dispersion equation in natural coordinates},
journal = {Computers & Geosciences},
year = {1997},
volume = {23},
number = {6},
pages = {677--688},
url = {http://www.sciencedirect.com/science/article/pii/S009830049700037X}
}
|
|||||
| Wang, L., Stuart, M.E., Bloomfield, J.P., Butcher, A.S., Gooddy, D.C., McKenzie, A.A., Lewis, M.A. and Williams, A.T. | Prediction of the arrival of peak nitrate concentrations at the water table at the regional scale in Great Britain | 2012 | Hydrological Processes Vol. 26(2), pp. 226-239 |
article | URL |
| Abstract: A simple process-based approach to predict regional-scale loading of nitrate at the water table was implemented in a GIS for Great Britain. This links a nitrate input function, unsaturated zone thickness, and lithologically dependent rate of nitrate unsaturated zone travel to estimate arrival time of nitrate at the water table. The nitrate input function is the loading at the base of the soil and has been validated using unsaturated zone porewater profiles. The unsaturated zone thickness uses groundwater levels based on regional-scale observations infilled by interpolated river base levels. Estimates of the rate of unsaturated zone travel are attributed from regional-scale hydrogeological mapping. The results indicate that peak nitrate loading may have already arrived at the water table for many aquifers, but that it has not where the unsaturated zone is relatively thick There are contrasting outcomes for the two main aquifers which have similar unsaturated zone velocities, the predominantly low relief Permo-Triassic sandstones, and the Chalk, which forms significant topographic features. For about 60% of the Chalk, the peak input has not yet reached the water table and will continue to arrive over the next 60 years. The methodology is readily transferable and provides a robust method for estimating peak arrival time for any diffuse conservative pollutant where an input function can be defined at a regional scale and requires only depth to groundwater and a hydrogeological classification. The methodology is extendable in that if additional information is available this can easily be incorporated into the model scheme. | |||||
BibTeX:
@article{Wang2012,
author = {Wang, L. and Stuart, M. E. and Bloomfield, J. P. and Butcher, A. S. and Gooddy, D. C. and McKenzie, A. A. and Lewis, M. A. and Williams, A. T.},
title = {Prediction of the arrival of peak nitrate concentrations at the water table at the regional scale in Great Britain},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2012},
volume = {26},
number = {2},
pages = {226--239},
url = {http://dx.doi.org/10.1002/hyp.8164}
}
|
|||||
| Wang, P.P., Zheng, C. and Gorelick, S.M. | A general approach to advective–dispersive transport with multirate mass transfer | 2005 | Advances in Water Resources Vol. 28(1), pp. 33-42 |
article | URL |
| Abstract: A numerical solution that is significantly more general than other semi-analytical solutions is presented for governing equations describing advective–dispersive transport with multirate mass transfer between mobile and immobile domains. The new solution approach is general in the sense that it does not impose any restrictive assumption on the spatial or temporal variability of advective and dispersive processes in the mobile domain. A single integro-differential equation (IDE) is developed for the concentration in the mobile domain by separating the concentration in the immobile domain from the set of two partial differential equations. The solution to the IDE requires the evaluation of a temporal integral of the concentration in the mobile domain, which is a function of the Laplace transform of the distribution of the mass transfer rate coefficient. The Laplace transform is not limited to flow fields with known constant velocities. The solutions for one- and two-dimensional examples obtained using the new approach agree with those obtained by existing semi-analytical and numerical approaches. | |||||
BibTeX:
@article{Wang2005,
author = {Wang, P. Patrick and Zheng, Chunmiao and Gorelick, Steven M.},
title = {A general approach to advective–dispersive transport with multirate mass transfer},
journal = {Advances in Water Resources},
year = {2005},
volume = {28},
number = {1},
pages = {33--42},
url = {http://www.sciencedirect.com/science/article/pii/S0309170804001642}
}
|
|||||
| Wang, Y., Ma, T. and Luo, Z. | Geostatistical and geochemical analysis of surface water leakage into groundwater on a regional scale: a case study in the Liulin karst system, northwestern China | 2001 | Journal of Hydrology Vol. 246(1-4), pp. 223-234 |
article | URL |
| Abstract: The Liulin karst system is typical of hydrogeological systems in northern China, with a group of springs as the dominant way of regional groundwater discharge. Surface water leakage into groundwater has been observed in six sections of the rivers in the study area. To extract hydrogeological information from hydrochemical data, 29 water samples were collected from the system. On a trilinear diagram, most of the groundwater samples are clustered around the surface waters, indicating the effect of leakage on their chemistry. R-mode factor analysis was made on seven variables (Na, Ca, Mg, SO4, Cl, HCO3, and NO3) of the samples and three principal factors were obtained: the F1 factor is composed of Ca, Mg and SO4 , the F2 of HCO3 and NO3, and the F3 of Na and Cl. These factors are then used as regionalized variables in ordinary Kriging for unbiased estimates of the spatial variations of their scores. Considering regional hydrogeological conditions, the hydrogeological implications of the spatial distribution of the factor scores as related to the effects of the surface leakage are discussed. To evaluate the geochemical processes, the geochemical modeling code NETPATH was employed. The modeling results show that mixing commonly occurs in the system and dolomite dissolution is more important than calcite dissolution. Dedolomitization (calcite precipitation and dolomite dissolution driven by anhydrite dissolution) is locally important, in the western flank of the system where the surface water leakage has the least effect. | |||||
BibTeX:
@article{Wang2001,
author = {Wang, Y and Ma, T and Luo, Z},
title = {Geostatistical and geochemical analysis of surface water leakage into groundwater on a regional scale: a case study in the Liulin karst system, northwestern China},
journal = {Journal of Hydrology},
year = {2001},
volume = {246},
number = {1-4},
pages = {223--234},
url = {http://www.sciencedirect.com/science/article/pii/S0022169401003766}
}
|
|||||
| Wanko, A., Tapia, G., Mosé, R. and Gregoire, C. | Adsorption distribution impact on preferential transport within horizontal flow constructed wetland (HFCW) | 2009 | Ecological Modelling Vol. 220(23), pp. 3342-3352 |
article | URL |
| Abstract: Predicting preferential water flow and solute transport in soils is in the interest of scientists and engineers in the fields of agricultural soil, forest hydrology, soil physics and wastewater treatment by constructed wetland. In artificial wetlands, any preferential pathway induces an insufficient residence time of pollutants in the soil, making an incomplete and unfinished biodegradation process, a wrong evaluation of the hydraulic residence time of the system which would hinder its management in a complete system with several entities of treatment and a non-homogeneous growth of the biofilm in the solid filter mass. This paper is a contribution in tracer experiment data analysis within a horizontal flow constructed wetland built in a storm water basin. A two-dimensional numerical model was used to simulate flow and reactive solute transport. The flow model was successfully calibrated in very dry soil conditions. The adsorption profiles used in the reactive transport modeling are those of five molecules: metolachlor, atrazine, deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA). We show that the adsorption distribution is an internal factor of soil which is responsible to the “preferential” pathway transport in a homogeneous gravel texture. The mean residence time of pollutants within the filter is strongly correlated with the average value of the adsorption coefficient. Moreover, we note a lack of significant impact of the heterogeneity of the medium on the statistical moments of breakthrough curve. It appears that a uni-modal breakthrough curve is not significant to the absence of preferential flow in the medium and at least a two-dimensional display can provide sufficient evidence on the presence or absence of preferential pathways. Finally, using a PLS regression, it is possible to perfectly discriminate the number of peaks of concentration and the asymmetry of the breakthrough curve. | |||||
BibTeX:
@article{Wanko2009,
author = {Wanko, Adrien and Tapia, Gabriela and Mosé, Robert and Gregoire, Caroline},
title = {Adsorption distribution impact on preferential transport within horizontal flow constructed wetland (HFCW)},
journal = {Ecological Modelling},
year = {2009},
volume = {220},
number = {23},
pages = {3342--3352},
url = {http://www.sciencedirect.com/science/article/pii/S0304380009005730}
}
|
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| Ward, A.S., Gooseff, M.N. and Singha, K. | Characterizing hyporheic transport processes — Interpretation of electrical geophysical data in coupled stream–hyporheic zone systems during solute tracer studies | 2010 | Advances in Water Resources Vol. 33(11)Special Issue on ground water-surface water interactions GW-SW Interactions, pp. 1320-1330 |
article | URL |
| Abstract: Quantifying hyporheic solute dynamics has been limited by our ability to assess the magnitude and extent of stream interactions with multiple domains: mobile subsurface storage (MSS, e.g., freely flowing pore water) and immobile subsurface storage (ISS, e.g., poorly connected pore water). Stream-tracer experiments coupled with solute transport modeling are frequently used to characterize lumped MSS and ISS dynamics, but are limited by the ability to sample only “mobile” water and by window of detection issues. Here, we couple simulations of near-surface electrical resistivity (ER) methods with conservative solute transport to directly compare solute transport with ER interpretations, and to determine the ability of ER to predict spatial and temporal trends of solute distribution and transport in stream–hyporheic systems. Results show that temporal moments from both ER and solute transport data are well correlated for locations where advection is not the dominant solute transport process. Mean arrival time and variance are especially well-predicted by ER interpretation, providing the potential to estimate rate-limited mass transport (i.e. diffusive) parameters from these data in a distributed domain, substantially increasing our knowledge of the fate and transport of subsurface solutes. | |||||
BibTeX:
@article{Ward2010,
author = {Ward, Adam S. and Gooseff, Michael N. and Singha, Kamini},
title = {Characterizing hyporheic transport processes — Interpretation of electrical geophysical data in coupled stream–hyporheic zone systems during solute tracer studies},
booktitle = {Special Issue on ground water-surface water interactions GW-SW Interactions},
journal = {Advances in Water Resources},
year = {2010},
volume = {33},
number = {11},
pages = {1320--1330},
url = {http://www.sciencedirect.com/science/article/pii/S0309170810001120}
}
|
|||||
| Watterson, I.G. and Dix, M.R. | Simulated changes due to global warming in daily precipitation means and extremes and their interpretation using the gamma distribution | 2003 | Journal of Geophysical Research Vol. 108(D13), pp. 4379-4399 |
article | URL |
| Abstract: The potential change in precipitation due to global warming is studied using five-member ensembles of climate simulations by the CSIRO Mark 2 atmosphere-ocean model for the period 1871–1990 and forward to 2100 under both the Special Report on Emission Scenarios (SRES) A2 (rapid CO2 increase) and B2 (moderate increase) forcing scenarios. The mean surface warming for the period 1961–1990 is 0.3 K. The warming from 1961–1990 to 2071–2100 is 3.5 K under A2, 29% more than for B2, and with a very similar spatial pattern. The daily precipitation (P) frequency distributions for January and July days in these periods are presented, focusing on the A2 case. The distributions for wet days at each point are approximated by the gamma distribution. The global mean P increase of around 6%, in both months, is related to a mean increase in the gamma's scale parameter of 18%, offset by small decreases in the shape parameter and wet day frequency. However, local changes of opposite signs also occur, especially in the tropics. Ensemble averages of 30-year extreme daily precipitation for January and July, and other months, are generally greater for 2071–2100 than for 1961–1990, with an average increase of 14%. Extreme value theory based on the monthly gamma distributions provides a good match to these values. The theory is extended to the annual case. In general, the 1961–1990 extremes peak in the subtropical rainbands in the model, where increases of 10 to 30% are common. Larger relative increases occur in polar regions, and also over northern land in January. | |||||
BibTeX:
@article{Watterson2003,
author = {Watterson, I. G. and Dix, M. R.},
title = {Simulated changes due to global warming in daily precipitation means and extremes and their interpretation using the gamma distribution},
journal = {Journal of Geophysical Research},
publisher = {American Geophysical Union (AGU)},
year = {2003},
volume = {108},
number = {D13},
pages = {4379--4399},
url = {http://dx.doi.org/10.1029/2002JD002928}
}
|
|||||
| Wayne, S. | CFD study of an evaporative trickle bed reactor: Mal-distribution and thermal runaway induced by feed disturbances | 2010 | Chemical Engineering Journal Vol. 161(1-2), pp. 257-268 |
article | URL |
| Abstract: A numerical study was carried out to investigate steady-state and transient phase distribution, evaporation, and thermal runaway in a large-scale high-pressure trickle bed reactor. A cooling recycle stream, containing reaction products and a fresh feed, was included via a closed loop calculation. It was found that, as expected, phase distribution in the catalyst bed had a substantial impact on production rate; a faulty feed distribution system can cost approximately 20% in overall steady-state product conversion. In the event that the cooling recycle stream is lost, the external reactor shell temperature can exceed its design intent. It was found that reducing the quantity of fresh reactant feed in this situation can dramatically reduce the potential for vessel damage. Thermal inertia of the catalyst particles proved to be a significant contribution to the transient energy balance. Model results are supported with a posteriori thermal excursion plant data. | |||||
BibTeX:
@article{Wayne2010,
author = {Wayne, Strasser},
title = {CFD study of an evaporative trickle bed reactor: Mal-distribution and thermal runaway induced by feed disturbances},
journal = {Chemical Engineering Journal},
year = {2010},
volume = {161},
number = {1-2},
pages = {257--268},
url = {http://www.sciencedirect.com/science/article/pii/S1385894710003918}
}
|
|||||
| Webb, A.R. | Gamma mixture models for target recognition | 2000 | Pattern Recognition Vol. 33(12), pp. 2045-2054 |
article | URL |
| Abstract: This paper considers a mixture model approach to automatic target recognition using high-resolution radar measurements. The mixture model approach is motivated from several perspectives including requirements that the target classifier is robust to uncertainty in amplitude scaling, rotation and translation of the target. Estimation of the model parameters is achieved using the expectation-maximisation (EM) algorithm. Gamma mixtures are introduced and the re-estimation equations derived. The models are applied to the classification of high-resolution radar range profiles of ships and results compared with a previously published self-organising map approach. | |||||
BibTeX:
@article{Webb2000,
author = {Webb, Andrew R.},
title = {Gamma mixture models for target recognition},
journal = {Pattern Recognition},
year = {2000},
volume = {33},
number = {12},
pages = {2045--2054},
url = {http://www.sciencedirect.com/science/article/pii/S0031320399001958}
}
|
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| Weed, D.L. and Coughlin, S.S. | New Ethics Guidelines for Epidemiology: Background and Rationale | 1999 | Annals of Epidemiology Vol. 9(5), pp. 277-280 |
article | URL |
| Abstract: In the past decade, at least four sets of ethics guidelines for epidemiologists have been prepared by various national and international organizations. None, however, have been officially adopted by the American College of Epidemiology (ACE). Recently, the ACE asked its Ethics and Standards of Practice (ESOP) Committee to produce ethics guidelines. In this paper, we explain the context and rationale for this effort, describe the purpose and content of ethics guidelines in epidemiology, and discuss their strengths and weaknesses. Three issues that are central to the mission of ACE–education, policy, and advocacy–are inadequately addressed in existing ethics guidelines. In addition, ethics guidelines are not static documents; they should reflect the changing role of epidemiologists in society, including issues arising in emerging subspecialty areas. New, more dynamic, guidelines that emphasize core values, obligations, and virtues, may help to further define and legitimize the profession of epidemiology and will provide a foundation for the discussion of specific ethical issues in the classroom and in professional practice. Guidelines however, do not provide the final word on ethical issues. Specific °cisions in particular cases require judgments made upon reflection of the core values, obligations, and virtues described in the guidelines. From our review, we conclude that a new set of guidelines is reasonable and warranted. | |||||
BibTeX:
@article{Weed1999,
author = {Weed, Douglas L. and Coughlin, Steven S.},
title = {New Ethics Guidelines for Epidemiology: Background and Rationale},
journal = {Annals of Epidemiology},
year = {1999},
volume = {9},
number = {5},
pages = {277--280},
url = {http://www.sciencedirect.com/science/article/pii/S1047279799000125}
}
|
|||||
| Wei, Q., Zhu, G., Wu, P., Cui, L., Zhang, K., Zhou, J. and Zhang, W. | Distributions of typical contaminant species in urban short-term storm runoff and their fates during rain events: A case of Xiamen City | 2010 | Journal of Environmental Sciences Vol. 22(4), pp. 533-539 |
article | URL |
| Abstract: The pollutants in urban storm runoff, which lead to an non-point source contamination of water environment around cities, are of great concerns. The distributions of typical contaminants and the variations of their species in short term storm runoff from different land surfaces in Xiamen City were investigated. The concentrations of various contaminants, including organic matter, nutrients (i.e., N and P) and heavy metals, were significantly higher in parking lot and road runoff than those in roof and lawn runoff. The early runoff samples from traffic road and parking lot contained much high total nitrogen (TN 6–19 mg/L) and total phosphorus (TP 1–3 mg/L). A large proportion (around 60%) of TN existed as total dissolved nitrogen (TDN) species in most runoff. The percentage of TDN and the percentage of total dissolved phosphorus remained relatively stable during the rain events and did not decrease as dramatically as TN and TP. In addition, only parking lot and road runoff were contaminated by heavy metals, and both Pb (25–120 μg/L) and Zn (0.1–1.2 mg/L) were major heavy metals contaminating both runoff. Soluble Pb and Zn were predominantly existed as labile complex species (50%–99%), which may be adsorbed onto the surfaces of suspended particles and could be easily released out when pH decreased. This would have the great impact to the environment. | |||||
BibTeX:
@article{Wei2010a,
author = {Wei, Qunshan and Zhu, Gefu and Wu, Peng and Cui, Li and Zhang, Kaisong and Zhou, Jingjing and Zhang, Wenru},
title = {Distributions of typical contaminant species in urban short-term storm runoff and their fates during rain events: A case of Xiamen City},
journal = {Journal of Environmental Sciences},
year = {2010},
volume = {22},
number = {4},
pages = {533--539},
url = {http://www.sciencedirect.com/science/article/pii/S1001074209601388}
}
|
|||||
| Wei, Z. and Zhang, D. | Coupled fluid-flow and geomechanics for triple-porosity/dual-permeability modeling of coalbed methane recovery | 2010 | International Journal of Rock Mechanics and Mining Sciences Vol. 47(8), pp. 1242-1253 |
article | URL |
| Abstract: A coupled fluid-flow and geomechanics model for simulating coalbed methane (CBM) recovery is presented. In the model, the fluid-flow process is simulated with a triple-porosity/dual-permeability model, and the coupling effects of effective stress and micro-pore swelling/shrinkage are modeled with the coupled fluid-flow and geomechanical deformation approach. The mathematical model is implemented with a finite volume method. First, a case without considering coupling between fluid-flow and geomechanics is simulated and compared with an existing simulator. The effects of coupled fluid-flow and geomechanics are then studied in detail with two illustrative examples. The first one is designed for testing the effective stress effect without micro-pore swelling/shrinkage effect, and the other for testing the coupling effects of the effective stress and micro-pore swelling/shrinkage on the methane production. The numerical results indicate that both the effective stress and the micro-pore shrinkage make a significant contribution to fluid-flow in CBM reservoir and to methane production. The methane production sensitivity to Young’s modulus and Langmuir sorption strain are investigated as well. Finally, we make a dynamic analysis of the coupling effects of fluid-flow process and geomechanics. | |||||
BibTeX:
@article{Wei2010,
author = {Wei, Zhijie and Zhang, Dongxiao},
title = {Coupled fluid-flow and geomechanics for triple-porosity/dual-permeability modeling of coalbed methane recovery},
journal = {International Journal of Rock Mechanics and Mining Sciences},
year = {2010},
volume = {47},
number = {8},
pages = {1242--1253},
url = {http://www.sciencedirect.com/science/article/pii/S136516091000167X}
}
|
|||||
| Weiler, M., McGlynn, B.L., McGuire, K.J. and McDonnell, J.J. | How does rainfall become runoff? A combined tracer and runoff transfer function approach | 2003 | Water Resources Research Vol. 39(11), pp. 1315- |
article | URL |
| Abstract: Hydrographs are an enticing focus for hydrologic research: they are readily available hydrological data that integrate the variety of terrestrial runoff generation processes and upstream routing. Notwithstanding, new techniques to glean information from the hydrograph are lacking. After early approaches of graphically separating streamflow components, hydrograph separations in the past two decades have focused on tracers as a more objective means to separate the storm hydrograph. These tracer-based methods provide process-based information; however, their implicit assumptions limit their applicability and explanatory power. We present a new method for isotope hydrograph separation that integrates the instantaneous unit hydrograph and embraces the temporal variability of rainfall isotopic composition (one of the largest impediments to the standard use of isotopes as tracers). Our model computes transfer functions for event water and preevent water calculated from a time-variable event water fraction. The transfer function hydrograph separation model (TRANSEP) provides coupled but constrained representations of transport and hydraulic transfer functions, overcoming limitations of other models. We illustrate the utility of TRANSEP by applying it to two rainfall events from a 17 ha catchment at Maimai in New Zealand, where 18O, rainfall, and runoff data were sampled with a high temporal resolution. We explore which runoff and tracer transfer function (exponential piston flow, gamma distribution, or two parallel linear reservoirs) gave the best results for the proposed model structure and for the example data set. Uncertainty analysis was used to determine if the parameters were identifiable and if the information available for applying TRANSEP was sufficient. The results of the best performing transfer function are considered in detail to identify model performance, illustrate individual event characteristics, and interpret runoff processes in the catchment. | |||||
BibTeX:
@article{Weiler2003,
author = {Weiler, Markus and McGlynn, Brian L. and McGuire, Kevin J. and McDonnell, Jeffrey J.},
title = {How does rainfall become runoff? A combined tracer and runoff transfer function approach},
journal = {Water Resources Research},
publisher = {American Geophysical Union (AGU)},
year = {2003},
volume = {39},
number = {11},
pages = {1315--},
url = {http://dx.doi.org/10.1029/2003WR002331}
}
|
|||||
| Weiner, R., Seagren, E., Arnosti, C. and Quintero, E. | [30] Bacterial survival in biofilms: Probes for exopolysaccharide and its hydrolysis, and measurements of intra- and interphase mass fluxes [BibTeX] |
1999 | Vol. 310Biofilms, pp. 403-426 |
incollection | URL |
BibTeX:
@incollection{Weiner1999,
author = {Weiner, Ronald and Seagren, E. and Arnosti, C. and Quintero, E.},
title = {[30] Bacterial survival in biofilms: Probes for exopolysaccharide and its hydrolysis, and measurements of intra- and interphase mass fluxes},
booktitle = {Biofilms},
publisher = {Academic Press},
year = {1999},
volume = {310},
pages = {403--426},
url = {http://www.sciencedirect.com/science/article/pii/S0076687999100326}
}
|
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| Wellman, T.P., Kauffman, L. and Clark, B. | A zonal evaluation of intrinsic susceptibility in selected principal aquifers of the United States | Journal of Hydrology(0), pp. - | article | URL | |
| Abstract: A method was developed to evaluate intrinsic groundwater susceptibility in 11 study areas across the United States. Calibrated groundwater-flow models and a variable-advection particle-tracking scheme that accounts for uncertainty were used to derive ranges of conservative solute concentration and groundwater age within spatially defined zones from solute loading to the water table. Aquifers were partitioned into six zones; four relative depth zones and two zones to represent pumping wells and surface water. Five years after solute was introduced in simulated recharge and stream leakage, normalized zone concentrations were detected at values above 10−4 in the shallowest aquifer zone, well zone, and surface-water zone for 10 of the 11 study areas. At the 125-year time scale, 9 out of the 11 study areas exhibited detectable concentrations in all zones and the majority of zones possess concentrations that are substantial relative to the source concentration (C/Co > 10−1). Thresholds defined by the time representing the earliest 1% of groundwater-transit times were used to identify fast transport pathways within the groundwater. The 1% thresholds occurred in a period of days to years for the shallow zone, days to decades for the well and surface-water zones, and years to millennia for the deeper zones. Thresholds defined by the 99th percentile of groundwater travel times were used to reflect late-time response and ranged considerably between study area (∼102 to ∼106 years), which highlights the potential for chemical constituents to persist in groundwater for long periods under a conservative state. The results of this investigation provide an instructive example of the intricate relations between climate and aquifer characteristics and their role on solute transport in groundwater. The proposed method accounts for dynamical processes in the aquifer and complements more traditional assessments of susceptibility using (apparent) mean water age. | |||||
BibTeX:
@article{Wellman,
author = {Wellman, Tristan P. and Kauffman, Leon and Clark, Brian},
title = {A zonal evaluation of intrinsic susceptibility in selected principal aquifers of the United States},
journal = {Journal of Hydrology},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S0022169412002090}
}
|
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| Welty, C. and Gelhar, L.W. | Evaluation of longitudinal dispersivity from nonuniform flow tracer tests | 1994 | Journal of Hydrology Vol. 153(1–4), pp. 71-102 |
article | URL |
| Abstract: The importance of incorporating nonuniform flow effects in determining field-scale values of long-itudinal dispersivity from tracer tests in aquifers is illustrated. We show that under conditions of Fickian dispersive flux, where a tracer has traveled at least 10 times the longitudinal dispersivity value, nonuniform flow effects account for the typical tailing exhibited by data from radial flow and doublet (two-well) tracer tests. Approximate analytical solutions for solute transport in nonuniform flow fields based on earlier general work are presented. Specific cases evaluated include pulse and step inputs in diverging radial flow, a pulse input in converging radial flow, and doublet (two-well) tests with pulse and step inputs. The additional effect of longitudinal dispersivity increasing linearly with distance for radial flow cases is examined. Also presented is an analysis of the effect of injection borehole flushing represented by an exponentially decreasing tracer input in the converging radial flow case. The solutions are applied to four sets of field data where previous analyses did not adequately address nonuniform flow effects. Some data reanalyses yield longitudinal dispersivity values which are up to a factor of three smaller than those previously reported, indicating a previous overprediction of plume dilution. We demonstrate that an understanding of the sensitivity of the mathematical solutions to tracer input conditions, nonuniform flow effects, and scale can lead to better tracer-test design. | |||||
BibTeX:
@article{Welty1994,
author = {Welty, Claire and Gelhar, Lynn W.},
title = {Evaluation of longitudinal dispersivity from nonuniform flow tracer tests},
journal = {Journal of Hydrology},
year = {1994},
volume = {153},
number = {1–4},
pages = {71--102},
url = {http://www.sciencedirect.com/science/article/pii/0022169494901872}
}
|
|||||
| Wen, C.-Y. and Fan, L.-T. | Models for flow systems and chemical reactors [BibTeX] |
1975 | Vol. 3, pp. - |
book | |
BibTeX:
@book{Wen1975,
author = {Wen, Chin-Yung and Fan, Liang-Tseng},
title = {Models for flow systems and chemical reactors},
publisher = {M Dekker},
year = {1975},
volume = {3},
pages = {--}
}
|
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| Wen, X.-H. and Gómez-Hernández, J. | Numerical modeling of macrodispersion in heterogeneous media: a comparison of multi-Gaussian and non-multi-Gaussian models | 1998 | Journal of Contaminant Hydrology Vol. 30(1-2), pp. 129-156 |
article | DOI URL |
| Abstract: The macrodispersion of an inert solute in a 2-D heterogeneous porous media is estimated numerically in a series of fields of varying heterogeneity. Four different random function (RF) models are used to model log-transmissivity (ln T) spatial variability, and for each of these models, ln T variance is varied from 0.1 to 2.0. The four RF models share the same univariate Gaussian histogram and the same isotropic covariance, but differ from one another in terms of the spatial connectivity patterns at extreme transmissivity values. More specifically, model A is a multivariate Gaussian model for which, by definition, extreme values (both high and low) are spatially uncorrelated. The other three models are non-multi-Gaussian: model B with high connectivity of high extreme values, model C with high connectivity of low extreme values, and model D with high connectivities of both high and low extreme values. Residence time distributions (RTDs) and macrodispersivities (longitudinal and transverse) are computed on ln T fields corresponding to the different RF models, for two different flow directions and at several scales. They are compared with each other, as well as with predicted values based on first-order analytical results. Numerically derived RTDs and macrodispersivities for the multi-Gaussian model are in good agreement with analytically derived values using first-order theories for log-transmissivity variance up to 2.0. The results from the non-multi-Gaussian models differ from each other and deviate largely from the multi-Gaussian results even when ln T variance is small. RTDs in non-multi-Gaussian realizations with high connectivity at high extreme values display earlier breakthrough than in multi-Gaussian realizations, whereas later breakthrough and longer tails are observed for RTDs from non-multi-Gaussian realizations with high connectivity at low extreme values. Longitudinal macrodispersivities in the non-multi-Gaussian realizations are, in general, larger than in the multi-Gaussian ones, while transverse macrodispersivities in the non-multi-Gaussian realizations can be larger or smaller than in the multi-Gaussian ones depending on the type of connectivity at extreme values. Comparing the numerical results for different flow directions, it is confirmed that macrodispersivities in multi-Gaussian realizations with isotropic spatial correlation are not flow direction-dependent. Macrodispersivities in the non-multi-Gaussian realizations, however, are flow direction-dependent although the covariance of ln T is isotropic (the same for all four models). It is important to account for high connectivities at extreme transmissivity values, a likely situation in some geological formations. Some of the discrepancies between first-order-based analytical results and field-scale tracer test data may be due to the existence of highly connected paths of extreme conductivity values. | |||||
BibTeX:
@article{Wen1998,
author = {Wen, Xian-Huan and Gómez-Hernández, J.Jaime},
title = {Numerical modeling of macrodispersion in heterogeneous media: a comparison of multi-Gaussian and non-multi-Gaussian models},
journal = {Journal of Contaminant Hydrology},
year = {1998},
volume = {30},
number = {1-2},
pages = {129--156},
url = {http://www.sciencedirect.com/science/article/pii/S0169772297000351},
doi = {http://dx.doi.org/10.1016/S0169-7722(97)00035-1}
}
|
|||||
| Wendland, E. and Himmelsbach, T. | Transport simulation with stochastic aperture for a single fracture – comparison with a laboratory experiment | 2002 | Advances in Water Resources Vol. 25(1), pp. 19-32 |
article | URL |
| Abstract: In order to investigate the migration behaviour of dissolved solutes in a fractured sedimentary host rock two laboratory experiments using pyranine as tracer were performed in a fractured sandstone block. During a first attempt, the experimental breakthrough curves were used to calibrate a three-dimensional numerical model based on the parallel plate approach. In a second approach, the natural roughness of the fracture surface was added to the model by assigning spatially variable apertures to the fracture elements. The experimental results indicate that the matrix diffusion has a decisive influence on the transport process, acting as a retardation term. The numerical investigation shows that solute migration is controlled by the mean aperture of the single fracture. If the variance of the fracture aperture, however, becomes too large the fracture flow becomes increasingly affected by channelling processes. | |||||
BibTeX:
@article{Wendland2002,
author = {Wendland, Edson and Himmelsbach, Thomas},
title = {Transport simulation with stochastic aperture for a single fracture – comparison with a laboratory experiment},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {1},
pages = {19--32},
url = {http://www.sciencedirect.com/science/article/pii/S0309170801000276}
}
|
|||||
| Wenninger, J., Uhlenbrook, S., Tilch, N. and Leibundgut, C. | Experimental evidence of fast groundwater responses in a hillslope/floodplain area in the Black Forest Mountains, Germany | 2004 | Hydrological Processes Vol. 18(17), pp. 3305-3322 |
article | URL |
| Abstract: Analysis of water flow pathways from hillslopes to streams is essential for the optimal protection of water resources as well as for ecohydrological studies. This study addresses runoff generation processes at a hillslope and near-stream shallow groundwater system in the Black Forest Mountains, southwestern Germany. The changing spatial and temporal flow patterns during differing hydrological situations were examined using a combined hydraulic and hydrochemical approach. Groundwater levels at 10 wells, discharge at a near-stream saturated area, and several natural tracers (deuterium, dissolved silica, and major anions and cations) were observed at different locations during high and low flows. The importance of the groundwater component during flood formation was clearly demonstrated: its contribution was about 80% during a double peak flood event at the saturated area. In addition, a rapid change of the shallow groundwater levels was observed along two transects of groundwater wells in the floodplain. This led to an enhanced groundwater discharge into the saturated area located at the end of one study transect. The amount of groundwater additionally activated during the event was about 30% of total discharge recorded at the outlet of the saturated area. Two alternative hypotheses are discussed to explain this phenomenon: the establishment of locally confined conditions and the development of a pressure wave (hypothesis A), or the significant change of the three-dimensional groundwater flow lines that caused a large increase of the groundwater catchment at the saturated area during the investigated event (hypothesis B). Even if the exact flow paths and mechanisms could not be clearly identified, the importance of rapid responding hillslope groundwater was undoubtedly demonstrated by a combination of tracer and hydrometric methods. | |||||
BibTeX:
@article{Wenninger2004,
author = {Wenninger, Jochen and Uhlenbrook, Stefan and Tilch, Nils and Leibundgut, Christian},
title = {Experimental evidence of fast groundwater responses in a hillslope/floodplain area in the Black Forest Mountains, Germany},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2004},
volume = {18},
number = {17},
pages = {3305--3322},
url = {http://dx.doi.org/10.1002/hyp.5686}
}
|
|||||
| Werner, T.M. and Kadlec, R.H. | Stochastic simulation of partially-mixed, event-driven treatment wetlands | 2000 | Ecological Engineering Vol. 14(3), pp. 253-267 |
article | URL |
| Abstract: Simulated rain events and runoff produce a more realistic influent to a stormwater treatment wetland than do an averaged inlet flow and concentration. Network flow models provide a more realistic prediction of a treatment wetland’s internal flows than does a plug flow or complete mixing estimation. Therefore, a combination of simulated rain events and a partial mixing model was chosen to produce realistic and descriptive predictions of treatment wetland function. The internal flow and mixing of the wetland was modeled using the network model ZDM. First-order pollutant removal was added to the hydraulic model, and the combination was calibrated to experimental nitrate data from Des Plaines River Wetland Demonstration Project wetland EWC1. Rainfall probability distributions were used in Monte Carlo simulations, and coupled with simple pollutant deposition and runoff from a watershed, to provide varying concentrations and flows into a wetland. The model was then combined with the variable rain and inlet flows produced by the Monte Carlo simulation, to provide predictions of the expected performance of a treatment wetland for nitrate reduction. The results of the simulation contain more detail than a time averaged model, which predicts only flowrate and concentration. The simulations produced such averages, but they also produced cumulative frequency distributions of anticipated exit concentrations. Using the ZDM model, an equation was developed to estimate the average conversion provided by a treatment wetland. | |||||
BibTeX:
@article{Werner2000,
author = {Werner, Timothy M. and Kadlec, Robert H.},
title = {Stochastic simulation of partially-mixed, event-driven treatment wetlands},
journal = {Ecological Engineering},
year = {2000},
volume = {14},
number = {3},
pages = {253--267},
url = {http://www.sciencedirect.com/science/article/pii/S0925857499000038}
}
|
|||||
| Werner, T.M. and Kadlec, R.H. | Wetland residence time distribution modeling | 2000 | Ecological Engineering Vol. 15(1–2), pp. 77-90 |
article | URL |
| Abstract: The non-ideal flows of constructed wetlands were modeled with a network of an infinite number of small stirred tanks distributed along a set of main plug flow channels. The stirred tanks represent zones of diminished mixing (ZDMs) because they undergo only limited exchange of water with the main channels. Based on this concept, a computer model, ZDM, was developed to reproduce the experimental wetland residence time distributions (RTDs). This non-site specific model is capable of producing realistic RTDs, and reproducing experimental RTDs determined from impulse tracer studies performed on both steady and variable flow systems. Eight experimental RTDs from the Des Plaines River site in Illinois, USA, along with 41 RTDs from the literature were used to test the flow model. It was found that tracer studies completed with more attention to detail were more readily reproduced by the model. These details include adequate flushing of previous tracer studies, use of inert tracer, adequate sampling frequency and accurate knowledge of the wetland water volume. | |||||
BibTeX:
@article{Werner2000b,
author = {Werner, Timothy M and Kadlec, Robert H},
title = {Wetland residence time distribution modeling},
journal = {Ecological Engineering},
year = {2000},
volume = {15},
number = {1–2},
pages = {77--90},
url = {http://www.sciencedirect.com/science/article/pii/S0925857499000361}
}
|
|||||
| Werner, T.M. and Kadlec, R.H. | Application of residence time distributions to stormwater treatment systems | 1996 | Ecological Engineering Vol. 7(3), pp. 213-234 |
article | URL |
| Abstract: Statistical measurements and qualitative assessments made by applying standard residence time distribution theory to non-steady-flow systems are of limited utility. A method is developed to enable non-steady-flow systems to be brought into the realm of steady-flow systems, so that residence time distribution (RTD) theory can be employed in a straight forward manner to characterize the non-ideal flows in these systems. Constructed wetland effluent concentrations resulting from impulse tracer inputs to the systems are considered. In addition to representing the concentrations with standard RTD functions, the concentrations are represented as functions of the cumulative discharge volume. This method provides the ability to easily analyze and compare data from steady and non-steady-flow systems, and thus to infer the degree of non-ideality of unsteady systems. | |||||
BibTeX:
@article{Werner1996,
author = {Werner, Timothy M. and Kadlec, Robert H.},
title = {Application of residence time distributions to stormwater treatment systems},
journal = {Ecological Engineering},
year = {1996},
volume = {7},
number = {3},
pages = {213--234},
url = {http://www.sciencedirect.com/science/article/pii/0925857496000134}
}
|
|||||
| White, W.B. | Karst hydrology: recent developments and open questions | 2002 | Engineering Geology Vol. 65(2-3)Engineering and Environmental Impacts of Karst, pp. 85-105 |
article | URL |
| Abstract: Karst aquifers are those that contain dissolution-generated conduits that permit the rapid transport of ground water, often in turbulent flow. The conduit system receives localized inputs from sinking surface streams and as storm runoff through sinkholes. The conduit system interconnects with the ground water stored in fractures and in the granular permeability of the bedrock. As a conceptual framework, the basic components of karstic aquifers seem to be generally accepted. Progress in the decade of the 1990s has focused mainly on quantifying the conceptual model. The equilibrium chemistry of the limestone and dolomite dissolution has been reliably established, and there are formal models for the kinetics of dissolution. Kinetic models have been used to calculate both fracture enlargement to protoconduits (0.01-m aperture) and the enlargement of protoconduits to the size of typical cave passages. Modeling of ground water flow in karstic aquifers has been less successful. Progress has been made in the use of water budgets, tracer studies, hydrograph analysis and chemograph analysis for the characterization of karstic aquifers. Topics on which progress is needed include (a) the construction of models that describe the complete aquifer including the interactions of all components, (b) models for clastic sediment transport within the aquifer, and (c) working out processes and mechanisms for contaminant transport in karst aquifers. An optimistic assessment at the end of the millennium is that a complete model for karstic aquifers is visible on the horizon. | |||||
BibTeX:
@article{White2002,
author = {White, William B.},
title = {Karst hydrology: recent developments and open questions},
booktitle = {Engineering and Environmental Impacts of Karst},
journal = {Engineering Geology},
year = {2002},
volume = {65},
number = {2-3},
pages = {85--105},
url = {http://www.sciencedirect.com/science/article/pii/S0013795201001168}
}
|
|||||
| White, W.B. and White, E.L. | Conduit fragmentation, cave patterns, and the localization of karst ground water basins: the Appalachians as a test case | 2000--2001 | Theoretical and Applied Karstology Vol. 13--14(0), pp. 9-23 |
article | URL |
| Abstract: Because conduit systems in maturely developed karst aquifers have a low hydraulic resistance, aquifers drain easily and karst aquifers are subdivided into well-defined ground water basins. Ground water elevations are highest at basin boundaries; lowest at the spring where the ground water is discharged. Parameters that control the type of conduit development are (1) the effective hydraulic gradient, (2) the focus of the drainage basin, and (3) the karstifiability of the bedrock. Moderate to highly effective hydraulic gradients permit the runaway process that leads to single conduit caves and well ordered branchwork systems. Low hydraulic gradients allow many alternate flow paths and thus a large degree of fuzziness in the basin boundaries. Low gradient ground water basins also tend to merge due to rising water tables during periods of high discharge. Focus is provided by geological constraints that optimize discharge at specific locations that can evolve into karst springs. Karstifiability is a measure of the bulk rate at which aquifer rocks will dissolve. Fine grained, pure limestones and shaley dolomites mark the opposite ends of the range. The cave surveys of the Appalachian Highlands provide a data base that can be used to classify the lateral arrangements of conduit systems and thus determine the relative importance of the factors defined above. | |||||
BibTeX:
@article{White20002001,
author = {White, W. B. and White, E. L.},
title = {Conduit fragmentation, cave patterns, and the localization of karst ground water basins: the Appalachians as a test case},
journal = {Theoretical and Applied Karstology},
year = {2000--2001},
volume = {13--14},
number = {0},
pages = {9--23},
url = {http://www.speleogenesis.info/journal/publication.php?id=4492}
}
|
|||||
| White, W.B. and White, E.L. | Ground water flux distribution between matrix, fractures, and conduits: constraints on modelling | 2005 | Speleogenesis and Evolution of Karst Aquifers Vol. 3(8), pp. 9-23 |
article | URL |
| Abstract: Calculations are presented to show the relative contribution of the matrix, fracture, and conduit permeability to the overall flow of ground water through a karst aquifer. The conceptual model is a cross-section spanning the full width and thickness of the aquifer. A constant, but adjustable head is assumed. The rock matrix is characterized by an adjustable hydraulic conductivity. Varying proportions of fractures and conduits of adjustable fracture apertures and conduit diameters were the calculational parameters. Calculations used Darcy’s law for matrix flow, the cube law for fracture flow, and the Darcy-Weisbach equation for conduit flow. The results show a surprising dominance of fracture flow in the early stages of aquifer development. A focusing mechanism is needed to localize the flow into a relatively small number of conduits. | |||||
BibTeX:
@article{White2005,
author = {White, W. B. and White, E. L.},
title = {Ground water flux distribution between matrix, fractures, and conduits: constraints on modelling},
journal = {Speleogenesis and Evolution of Karst Aquifers},
year = {2005},
volume = {3},
number = {8},
pages = {9--23},
url = {http://www.speleogenesis.info/journal/publication.php?id=4492}
}
|
|||||
| White, W.B. and White, E.L. | Karst Hydrology: Concepts From the Mammoth Cave Area [BibTeX] |
1989 | , pp. - | book | |
BibTeX:
@book{White1989,
author = {White, William B. and White, Elizabeth L.},
title = {Karst Hydrology: Concepts From the Mammoth Cave Area},
publisher = {Van Nostrand Reinhold},
year = {1989},
pages = {--}
}
|
|||||
| Whiteley, J. and Murray, F. | Autocatalyst-derived platinum, palladium and rhodium (PGE) in infiltration basin and wetland sediments receiving urban runoff | 2005 | Science of The Total Environment Vol. 341(1-3), pp. 199-209 |
article | URL |
| Abstract: The emission of platinum group elements (PGE) from automobile catalytic converters has led to rapid increases in Pt, Pd and Rh concentrations in roadside media. Significant quantities of the PGE may enter and accumulate in fluvial systems via road runoff. This paper examines the occurrence and spatial distribution of autocatalyst-derived PGE in surface sediments of infiltration basin and wetland sediments receiving road-runoff in Perth, Western Australia. Samples were analysed by ICP-MS following microwave digestion and cation exchange. PGE concentrations ranged between 1.5–17.2 Rh, 5.4–61.2 Pd and 9.0–103.8 ng g−1 Pt. The highest levels of PGE were generally found at basin topographic low points and these concentrations were found to be strongly related to the area of road surface drained and the traffic volume. PGE ratios in infiltration basin and wetland sediments were within the typical range of catalytic converter compositions. However, comparisons of PGE ratios between parent road dusts and infiltration basin sediments revealed a systematic shift in Pt/Pd ratios, suggesting that PGE fractionation can occur during transport through the drainage system and that a small portion of Pd in road dust may be solubilised under natural conditions. | |||||
BibTeX:
@article{Whiteley2005,
author = {Whiteley, J.D. and Murray, F.},
title = {Autocatalyst-derived platinum, palladium and rhodium (PGE) in infiltration basin and wetland sediments receiving urban runoff},
journal = {Science of The Total Environment},
year = {2005},
volume = {341},
number = {1--3},
pages = {199--209},
url = {http://www.sciencedirect.com/science/article/pii/S0048969704006710}
}
|
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| Whittaker, J. and Teutsch, G. | Numerical simulation of subsurface characterization methods: application to a natural aquifer analogue | 1999 | Advances in Water Resources Vol. 22(8), pp. 819-829 |
article | URL |
| Abstract: Information from an outcrop is used as an analogue of a natural heterogeneous aquifer in order to provide an exhaustive data set of hydraulic properties. Based on this data, two commonly used borehole based investigation methods are simulated numerically. For a scenario of sparse sampling of the aquifer, the process of regionalization of the borehole hydraulic conductivity values is simulated by application of a deterministic interpolation approach and conditioned stochastic simulations. Comparison of the cumulative distributions of particle arrival times illustrates the effects of the sparse sampling, the properties of the individual investigation methods and the regionalization methods on the ability to predict flow and transport behaviour in the real system (i.e. the exhaustive data set). | |||||
BibTeX:
@article{Whittaker1999,
author = {Whittaker, Janet and Teutsch, Georg},
title = {Numerical simulation of subsurface characterization methods: application to a natural aquifer analogue},
journal = {Advances in Water Resources},
year = {1999},
volume = {22},
number = {8},
pages = {819--829},
url = {http://www.sciencedirect.com/science/article/pii/S0309170898000566}
}
|
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| Whyte, D.C. and Kirchner, J.W. | Assessing water quality impacts and cleanup effectiveness in streams dominated by episodic mercury discharges | 2000 | Science of The Total Environment Vol. 260(1–3)Proceedings of the Fifth, pp. 1-9 |
article | URL |
| Abstract: Accurate pollutant mass budgets are needed for identifying contaminant sources and establishing cleanup goals. We monitored mercury discharges from an abandoned mine site in northern California with the objectives of: (1) estimating the mass loading of mercury from the site; (2) evaluating the factors that control the mercury discharges; (3) assessing the significance of peak flows in transporting contaminants; and (4) developing methods for measuring the effectiveness of cleanup efforts. We sampled water downstream from the mine site over a wide range of streamflows. Mercury concentrations varied over 2000-fold, from 485 to 1 040 000 ng/l, grossly exceeding the regulatory water quality objective of 12 ng/l at all times. Particulate mercury represented over 99.97% of the total mercury, and mercury concentrations were closely correlated to suspended sediment concentrations (r=0.98). Thus, we can use suspended sediment concentrations as a proxy for mercury concentrations, and calculate a continuous record of mercury flux from continuous monitoring of streamflow (using a small flume) and turbidity (using an optical backscatter sensor). Mercury fluxes inferred in this way are consistent with fluxes estimated from field samples. In January and February of 1998, our small abandoned mine site released approximately 82 kg of mercury to downstream waters. Most of the mercury was released during brief intense rainstorms. For example, in one 200-min period we recorded 3.4 cm of rain, a 2.6-fold increase in streamflow (460–1120 l/s), and an 82-fold increase in mercury flux (1.2–99 g/min). Over 75% of the total mercury flux during this 2-month period occurred in less than 10% of the total time. In systems such as this one, where contaminant transport is highly episodic, sampling programs that miss the high-flow episodes may greatly underestimate the actual water quality threat. In addition, changes in pollutant fluxes or concentrations in receiving waters may not reflect changes in pollutant sources (such as an environmental cleanup) if the stochastic forcing (e.g. intense rainstorms) varies through time. We propose that water quality trends can be more accurately measured by changes in the relationship between contaminant flux and stochastic driving factors, as expressed by contaminant rating curves. | |||||
BibTeX:
@article{Whyte2000,
author = {Whyte, Dyan C. and Kirchner, James W.},
title = {Assessing water quality impacts and cleanup effectiveness in streams dominated by episodic mercury discharges},
booktitle = {Proceedings of the Fifth},
journal = {Science of The Total Environment},
year = {2000},
volume = {260},
number = {1–3},
pages = {1--9},
url = {http://www.sciencedirect.com/science/article/pii/S0048969700005374}
}
|
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| Wilding, G.E. and Mudholkar, G.S. | A gamma goodness-of-fit test based on characteristic independence of the mean and coefficient of variation | 2008 | Journal of Statistical Planning and Inference Vol. 138(12), pp. 3813-3821 |
article | URL |
| Abstract: Characterization theorems in probability and statistics are widely appreciated for their role in clarifying the structure of the families of probability distributions. Less well known is the role characterization theorems have as a natural, logical and effective starting point for constructing goodness-of-fit tests. The characteristic independence of the mean and variance and of the mean and the third central moment of a normal sample were used, respectively, by Lin and Mudholkar [1980. A simple test for normality against asymmetric alternatives. Biometrika 67, 455–461] and by Mudholkar et al. [2002a. Independence characterizations and testing normality against skewness-kurtosis alternatives. J. Statist. Plann. Inference 104, 485–501] for developing tests of normality. The characteristic independence of the maximum likelihood estimates of the population parameters was similarly used by Mudholkar et al. [2002b. Independence characterization and inverse Gaussian goodness-of-fit. Sankhya A 63, 362–374] to develop a test of the composite inverse Gaussian hypothesis. The gamma models are extensively used for applied research in the areas of econometrics, engineering and biomedical sciences; but there are few goodness-of-fit tests available to test if the data indeed come from a gamma population. In this paper we employ Hwang and Hu's [1999. On a characterization of the gamma distribution: the independence of the sample mean and the sample coefficient of variation. Ann. Inst. Statist. Math. 51, 749–753] characterization of the gamma population in terms of the independence of sample mean and coefficient of variation for developing such a test. The asymptotic null distribution of the proposed test statistic is obtained and empirically refined for use with samples of moderate size. | |||||
BibTeX:
@article{Wilding2008,
author = {Wilding, Gregory E. and Mudholkar, Govind S.},
title = {A gamma goodness-of-fit test based on characteristic independence of the mean and coefficient of variation},
journal = {Journal of Statistical Planning and Inference},
year = {2008},
volume = {138},
number = {12},
pages = {3813--3821},
url = {http://www.sciencedirect.com/science/article/pii/S0378375808000281}
}
|
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| Williams, J.C. and Rahman, M.A. | The continuous mixing of particulate solids | 1970 | Journal of the Society of Cosmetic Chemists Vol. 21(1), pp. 3-36 |
article | URL |
| Abstract: The present state of knowledge of continuous mixing is reviewed and thexs problems of applying the concepts developed for fluid mixing to PARTICULATE SOLIDS systems are discussed. The available experimental techniques are considered and a simple method suitable for solids mixers is described. The performance of an inclined rotating drum mixer has been investigated by the delta-input response technique, using components of the same particle size but differing in other properties. It is shown that this technique, which leads to the evaluation of the variance reduction ratio, is useful in assessing the performance of a mixer, and that it can be used to establish the best operating conditions for a given system. |
|||||
BibTeX:
@article{Williams1970,
author = {Williams, J. C. and Rahman, M. A.},
title = {The continuous mixing of particulate solids},
journal = {Journal of the Society of Cosmetic Chemists},
publisher = {Society of Cosmetic Chemists of Great Britain},
year = {1970},
volume = {21},
number = {1},
pages = {3--36},
url = {http://journal.scconline.org/abstracts/cc1970/cc021n01/p00003-p00036.html}
}
|
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| Williams, P.W. | The role of the subcutaneous zone in karst hydrology | 1983 | Journal of Hydrology Vol. 61(1-3)V.T. Stringfield Symposium - Processes in Karst Hydrology, pp. 45-67 |
article | URL |
| Abstract: The subcutaneous zone is the upper weathered layer of rock beneath the soil, but above the permanently saturated (phreatic) zone. It is of particular hydrological importance in karst because of its high secondary permeability, arising from the considerable chemical solution in this zone. However, corrosional enlargement of fissures diminishes with depth; thus permeability decreases in the same direction with the result that percolation is inhibited, except down widened master joints and faults. Storage of water consequently occurs in this zone, particularly after storms. The upper surface of this suspended saturated layer in the subcutaneous zone is defined by a perched water table, which slopes towards points of rapid vertical percolation. The potential induces lateral water movement converging on the most permeable areas such as beneath dolines. Leakage from the subcutaneous store sustains slow percolation in the vadose zone. Cross-correlation of rainfall with percolation rates in caves in New Mexico, U.S.A., and New Zealand reveal response lags of 2–14 weeks with no apparent relationship to depth below the surface. Other percolation sites show no correlation with rainfall; interpreted as being a consequence of considerable friction in tight fissure networks. The recognition of storage and rapid as well as very slow percolation from the subcutaneous zone requires re-interpretation of the components of hydrographs from karst springs and of some conceptual models of karst aquifers. The importance of subcutaneous storage in sustaining baseflow discharge at some sites must be recognised, as must the contribution of subcutaneous water to flood hydrographs. Methods of estimating the volumes of subcutaneous and phreatic components of karst-spring flood hydrographs are presented. The paper concludes with a discussion of the significance of subcutaneous hydrologic processes for an understanding of karst geomorphology. The desirability of explaining karst landform evolution in terms of hydrologic processes is stressed. | |||||
BibTeX:
@article{Williams1983,
author = {Williams, Paul W.},
title = {The role of the subcutaneous zone in karst hydrology},
booktitle = {V.T. Stringfield Symposium - Processes in Karst Hydrology},
journal = {Journal of Hydrology},
year = {1983},
volume = {61},
number = {1-3},
pages = {45--67},
url = {http://www.sciencedirect.com/science/article/pii/0022169483902342}
}
|
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| Williams, S.D., Wolfe, W.J. and Farmer, J.J. | Sampling Strategies for Volatile Organic Compounds at Three Karst Springs in Tennessee | 2006 | Ground Water Monitoring & Remediation Vol. 26(1), pp. 53-62 |
article | URL |
| Abstract: The influence of different sampling strategies on characterizing volatile organic compound (VOC) concentrations and estimating VOC loads was evaluated at three karst springs in Tennessee. During a 6-month period, water samples for VOC analyses were collected weekly at all three springs and as frequently as every 20 min during storms at the two springs with variable water quality conditions. Total 6-month loads for selected VOCs were calculated, and VOC data were systematically subsampled to simulate and evaluate several potential sampling strategies. Results from the study indicate that sampling strategies for karst springs need to be developed on a site-specific basis. The use of fixed sampling intervals (as infrequently as quarterly or semiannually) produced accurate concentration and load estimates at one of the springs; however, additional sampling was needed to detect storm-related changes at a second spring located in a similar hydrogeologic setting. Continuous discharge data and high-frequency or flow-controlled sampling were needed at the third spring, which had the most variable flow and water quality conditions. The lack of continuous discharge data at the third spring would substantially affect load calculations, and the use of fixed sampling intervals would affect load calculations and the ability to detect pulses of high contaminant concentrations that might exceed toxicity levels for aquatic organisms. | |||||
BibTeX:
@article{Williams2006,
author = {Williams, Shannon D. and Wolfe, William J. and Farmer, James J.},
title = {Sampling Strategies for Volatile Organic Compounds at Three Karst Springs in Tennessee},
journal = {Ground Water Monitoring & Remediation},
publisher = {Blackwell Publishing Inc},
year = {2006},
volume = {26},
number = {1},
pages = {53--62},
url = {http://dx.doi.org/10.1111/j.1745-6592.2006.00044.x}
}
|
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| Willmott, C.J. and Matsuura, K. | On the use of dimensioned measures of error to evaluate the performance of spatial interpolators | 2006 | International Journal of Geographical Information Science Vol. 20(1), pp. 89-102 |
article | DOI URL |
| Abstract: Spatial cross‐validation and average‐error statistics are examined with respect to their abilities to evaluate alternate spatial interpolation methods. A simple cross‐validation methodology is described, and the relative abilities of three, dimensioned error statistics—the root‐mean‐square error (RMSE), the mean absolute error (MAE), and the mean bias error (MBE)—to describe average interpolator performance are examined. To illustrate our points, climatologically averaged weather‐station temperatures were obtained from the Global Historical Climatology Network (GHCN), Version 2, and then alternately interpolated spatially (gridded) using two spatial‐interpolation procedures. Substantial differences in the performance of our two spatial interpolators are evident in maps of the cross‐validation error fields, in the average‐error statistics, as well as in estimated land‐surface‐average air temperatures that differ by more than 2°C. The RMSE and its square, the mean‐square error (MSE), are of particular interest, because they are the most widely reported average‐error measures, and they tend to be misleading. It (RMSE) is an inappropriate measure of average error because it is a function of three characteristics of a set of errors, rather than of one (the average error). Our findings indicate that MAE and MBE are natural measures of average error and that (unlike RMSE) they are unambiguous. | |||||
BibTeX:
@article{Willmott2006,
author = {Willmott, C. J. and Matsuura, K.},
title = {On the use of dimensioned measures of error to evaluate the performance of spatial interpolators},
journal = {International Journal of Geographical Information Science},
publisher = {Taylor & Francis},
year = {2006},
volume = {20},
number = {1},
pages = {89--102},
url = {http://dx.doi.org/10.1080/13658810500286976},
doi = {http://dx.doi.org/10.1080/13658810500286976}
}
|
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| Willmott, C.J. and Matsuura, K. | Advantages of the mean absolute error (MAE) over the root mean square error (RMSE) in assessing average model performance | 2005 | Climate Research Vol. 30(1), pp. 79-82 |
article | DOI URL |
| Abstract: The relative abilities of 2, dimensioned statistics—the root-mean-square error (RMSE) and the mean absolute error (MAE)—to describe average model-performance error are examined. The RMSE is of special interest because it is widely reported in the climatic and environmental literature; nevertheless, it is an inappropriate and misinterpreted measure of average error. RMSE is inappropriate because it is a function of 3 characteristics of a set of errors, rather than of one (the average error). RMSE varies with the variability within the distribution of error magnitudes and with the square root of the number of errors (n1/2), as well as with the average-error magnitude (MAE). Our findings indicate that MAE is a more natural measure of average error, and (unlike RMSE) is unambiguous. Dimensioned evaluations and inter-comparisons of average model-performance error, therefore, should be based on MAE. | |||||
BibTeX:
@article{Willmott2005,
author = {Willmott, Cort J. and Matsuura, Kenji},
title = {Advantages of the mean absolute error (MAE) over the root mean square error (RMSE) in assessing average model performance},
journal = {Climate Research},
year = {2005},
volume = {30},
number = {1},
pages = {79--82},
url = {http://www.int-res.com/abstracts/cr/v30/n1/p79-82/},
doi = {http://dx.doi.org/10.3354/cr030079}
}
|
|||||
| Willmott, C.J., Matsuura, K. and Robeson, S.M. | Ambiguities inherent in sums-of-squares-based error statistics | 2009 | Atmospheric Environment Vol. 43(3), pp. 749-752 |
article | URL |
| Abstract: Commonly used sums-of-squares-based error or deviation statistics—like the standard deviation, the standard error, the coefficient of variation, and the root-mean-square error—often are misleading indicators of average error or variability. Sums-of-squares-based statistics are functions of at least two dissimilar patterns that occur within data. Both the mean of a set of error or deviation magnitudes (the average of their absolute values) and their variability influence the value of a sum-of-squares-based error measure, which confounds clear assessment of its meaning. Interpretation problems arise, according to Paul Mielke, because sums-of-squares-based statistics do not satisfy the triangle inequality. We illustrate the difficulties in interpreting and comparing these statistics using hypothetical data, and recommend the use of alternate statistics that are based on sums of error or deviation magnitudes. | |||||
BibTeX:
@article{Willmott2009,
author = {Willmott, Cort J. and Matsuura, Kenji and Robeson, Scott M.},
title = {Ambiguities inherent in sums-of-squares-based error statistics},
journal = {Atmospheric Environment},
year = {2009},
volume = {43},
number = {3},
pages = {749--752},
url = {http://www.sciencedirect.com/science/article/pii/S1352231008009564}
}
|
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| Wissmeier, L. and Barry, D. | Implementation of variably saturated flow into PHREEQC for the simulation of biogeochemical reactions in the vadose zone | 2010 | Environmental Modelling & Software Vol. 25(4), pp. 526-538 |
article | URL |
| Abstract: A software tool for the simulation of one-dimensional unsaturated flow and solute transport together with biogeochemical reactions in the vadose zone was developed by integrating a numerical solution of Richards' equation into the geochemical modelling framework PHREEQC. Unlike existing software, the new simulation tool is fully based on existing capabilities of PHREEQC without source code modifications or coupling to external software packages. Because of the direct integration, the full set of PHREEQC's geochemical reactions with connected databases for reaction constants is immediately accessible. Thus, unsaturated flow and solute transport can be simulated together with complex solution speciation, equilibrium and kinetic mineral reactions, redox reactions, ion exchange reactions and surface adsorption including diffuse double layer calculations. Liquid phase flow is solved as a result of element advection, where the Darcy flux is calculated according to Richards' equation. For accurate representation of advection-dominated transport, a total-variation-diminishing scheme was implemented. Dispersion was simulated with a standard approach; however, PHREEQC's multicomponent transport capabilities can be used to simulate species-dependent diffusion. Since liquid phase saturation is recalculated after every reaction step, biogeochemical processes that modify liquid phase saturation, such as dissolution or precipitation of hydrated minerals are considered a priori. Implementation of the numerical schemes for flow and solute transport have been described, along with examples of the extensive code verification, before illustrating more advanced application examples. These include (i) the simulation of infiltration with saturation-dependent cation exchange capacity, (ii) changes in hydraulic properties due to mineral reactions and (iii) transport of mobile organic substances with complexation of heavy metals in varying geochemical conditions. | |||||
BibTeX:
@article{Wissmeier2010,
author = {Wissmeier, L. and Barry, D.A.},
title = {Implementation of variably saturated flow into PHREEQC for the simulation of biogeochemical reactions in the vadose zone},
journal = {Environmental Modelling & Software},
year = {2010},
volume = {25},
number = {4},
pages = {526--538},
url = {http://www.sciencedirect.com/science/article/pii/S1364815209002606}
}
|
|||||
| Wolfe, W.J. and Haugh, C.J. | Preliminary Conceptual Models Of Chlorinated-Solvent Accumulation in Karst Aquifers | 2001 | U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011, pp. 157-162 | inproceedings | URL |
| Abstract: Conceptual models are needed to assist regulators and site managers in characterizing chlorinated-solvent contamination in karst settings and evaluating clean-up alternatives. Five preliminary conceptual models were developed, emphasizing accumulation sites for chlorinated DNAPL in karst aquifers. The models were developed for the karst regions of Tennessee, but are intended to be transferable to similar karst settings elsewhere.The five models of DNAPL accumulation in karst settings are: (1) trapping in regolith; (2) pooling at the top of bedrock; (3) pooling in karst conduits; (4) pooling in bedrock diffuse-flow zones; and (5) pooling in isolation from active ground-water flow. More than one conceptual model of DNAPL accumulation may be applicable to a given site depending on details of the contaminant release and geologic setting. Trapping in regolith is most likely where the regolith is thick and relatively impermeable with few large cracks and fissures. Accumulation at the top of rock is favored by flat-lying strata with few fractures or karst features near the bedrock surface. Fractures or karst features near the bedrock surface encourage migration of chlorinated DNAPL into karst conduits or diffuse-flow zones in bedrock. DNAPL can migrate through one type of bedrock aquifer into an underlying aquifer of a different type or into openings that are isolated from significant ground-water flow. |
|||||
BibTeX:
@inproceedings{Wolfe2001,
author = {Wolfe, William J. and Haugh, Connor J.},
title = {Preliminary Conceptual Models Of Chlorinated-Solvent Accumulation in Karst Aquifers},
booktitle = {U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001: USGS Water-Resources Investigations Report 01-4011},
publisher = {U.S. Geological Survey Karst Interest Group},
year = {2001},
pages = {157--162},
url = {http://water.usgs.gov/ogw/karst/kigconference/wjw_preliminaryconcept.htm}
}
|
|||||
| Wolfe, W.J. and Williams, S.D. | Soil Gas Screening for Chlorinated Solvents at Three Contaminated Karst Sites in Tennessee | 2002 | Ground Water Monitoring & Remediation Vol. 22(4), pp. 91-99 |
article | URL |
| Abstract: Soil gas was sampled using active sampling techniques and passive collectors at three sites in Tennessee to evaluate the effectiveness of these techniques for locating chlorinated solvent sources and flowpaths in karst aquifers. Actively collected soil gas samples were analyzed in the field with a portable gas chromatograph, and the passive soil gas collectors were analyzed in the lab with gas chromatography/mass spectrometry. Results of the sampling indicate that the effectiveness of both techniques is highly dependent on the distribution of the contaminants in the subsurface, the geomorphic and hydrogeologic characteristics of the site, and, in one case, on seasonal conditions. Both active and passive techniques identified areas of elevated subsurface chlorinated solvent concentrations at a landfill site where contamination remains concentrated in the regolith. Neither technique detected chlorinated solvents known to be moving in the bedrock at a manufacturing site characterized by thick regolith and an absence of surficial karst features. Passive soil gas sampling had varied success detecting flowpaths for chloroform in the bedrock at a train derailment site characterized by shallow regolith and abundant surficial karst features. At the train derailment site, delineation of the contaminant flowpath through passive soil gas sampling was stronger and more detailed under winter conditions than summer. | |||||
BibTeX:
@article{Wolfe2002,
author = {Wolfe, William J. and Williams, Shannon D.},
title = {Soil Gas Screening for Chlorinated Solvents at Three Contaminated Karst Sites in Tennessee},
journal = {Ground Water Monitoring & Remediation},
publisher = {Blackwell Publishing Ltd},
year = {2002},
volume = {22},
number = {4},
pages = {91--99},
url = {http://dx.doi.org/10.1111/j.1745-6592.2002.tb00775.x}
}
|
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| Wong, T.H., Fletcher, T.D., Duncan, H.P. and Jenkins, G.A. | Modelling urban stormwater treatment—A unified approach | 2006 | Ecological Engineering Vol. 27(1), pp. 58-70 |
article | URL |
| Abstract: To protect receiving waters from stormwater pollution, stormwater managers need to be able to predict the performance of proposed stormwater treatment measures, under variable operating conditions. This paper describes the development of a model, capable of predicting the performance of stormwater wetlands, ponds, vegetated swales, sediment basins and biofilters, with a single algorithm. The model describes two principal processes: (a) water quality behaviour and (b) hydrodynamic behaviour. | |||||
BibTeX:
@article{Wong2006,
author = {Wong, Tony H.F. and Fletcher, Tim D. and Duncan, Hugh P. and Jenkins, Graham A.},
title = {Modelling urban stormwater treatment—A unified approach},
journal = {Ecological Engineering},
year = {2006},
volume = {27},
number = {1},
pages = {58--70},
url = {http://www.sciencedirect.com/science/article/pii/S0925857405002351}
}
|
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| Wörman, A., Xu, S. and Dverstorp, B. | Kinematic analysis of solute mass flows in rock fractures with spatially random parameters | 2003 | Journal of Contaminant Hydrology Vol. 60(3-4), pp. 163-191 |
article | URL |
| Abstract: Field data of physical properties in heterogeneous crystalline bedrock, like porosity and fracture aperture, is associated with uncertainty that can have a significant impact on the analysis of solute transport in rock fractures. Solutions to the central temporal moments of the residence time probability density function (PDF) are derived in a closed form for a solute Dirac pulse. The solutions are based on a model that takes into account advection along the fracture plane, diffusion into the rock matrix and sorption kinetics in the rock matrix. The most relevant rock properties including fracture aperture and several matrix properties as well as flow velocity are assumed to be spatially random along transport pathways. The mass transport is first solved in a general form along one-dimensional pathways, but the results can be extended to multi-dimensional flows simply by substituting the expected travel time for inert water parcels. Based on data obtained with rock samples taken at Äspö Hard Rock Laboratory in Sweden, the solutions indicate that the heterogeneity of the rock properties contributes to increasing significantly both the variance and the skewness of the residence time probability density function for a pulse travelling in a fracture. The Äspö data suggests that the bias introduced in the variance of the residence time PDF by neglecting the effect of heterogeneity of the rock properties on the radionuclide migration is very large for fractures thinner than a few tenths of a millimetre. | |||||
BibTeX:
@article{Woerman2003,
author = {Wörman, Anders and Xu, Shulan and Dverstorp, Björn},
title = {Kinematic analysis of solute mass flows in rock fractures with spatially random parameters},
journal = {Journal of Contaminant Hydrology},
year = {2003},
volume = {60},
number = {3-4},
pages = {163--191},
url = {http://www.sciencedirect.com/science/article/pii/S0169772202000888}
}
|
|||||
| Wörner, M., Ghidersa, B. and Onea, A. | A model for the residence time distribution of bubble-train flow in a square mini-channel based on direct numerical simulation results | 2007 | International Journal of Heat and Fluid Flow Vol. 28(1)The International Conference on Heat Transfer and Fluid Flow in Microscale (HTFFM-05) The International Conference on Heat Transfer and Fluid Flow in Microscale, pp. 83-94 |
article | URL |
| Abstract: This paper presents an original method for evaluating the liquid phase residence time distribution in bubble-train flow using data from direct numerical simulations (DNS). The method is a particle method and relies on the uniform introduction of virtual particles in the volume occupied by the liquid phase within a single flow unit cell. The residence time distribution is obtained by statistical evaluation of the time needed by any particle to travel an axial distance equivalent to the length of the flow unit cell. Residence time curves are evaluated from DNS data of bubble-train flow in a square mini-channel for different lengths of the flow unit cell. The curves obtained are well fitted by an exponential relationship, which has been developed on basis of a two-tanks-in-series compartment model, where the first tank is a plug flow reactor and the second is a continuous stirred tank reactor. | |||||
BibTeX:
@article{Woerner2007,
author = {Wörner, Martin and Ghidersa, Bradut and Onea, Alexandru},
title = {A model for the residence time distribution of bubble-train flow in a square mini-channel based on direct numerical simulation results},
booktitle = {The International Conference on Heat Transfer and Fluid Flow in Microscale (HTFFM-05) The International Conference on Heat Transfer and Fluid Flow in Microscale},
journal = {International Journal of Heat and Fluid Flow},
year = {2007},
volume = {28},
number = {1},
pages = {83--94},
url = {http://www.sciencedirect.com/science/article/pii/S0142727X06001366}
}
|
|||||
| Worthington, S.R.H. | Diagnostic hydrogeologic characteristics of a karst aquifer (Kentucky, USA) | 2009 | Hydrogeology Journal Vol. 17(7), pp. 1665-1678 |
article | URL |
| Abstract: Laboratory experiments and numerical modeling have shown that dissolution in carbonate aquifers results in high-permeability channel networks. However, the lack of techniques to assess the extent and significance of these channel networks presents a major problem in characterizing carbonate aquifers. This problem was addressed by identifying the differences between two simulations (with and without channels) of the intensely studied limestone aquifer at Mammoth Cave (Kentucky, USA). Long-distance tracer-test results and spring discharges were used for assessing model accuracy as well as head measurements in wells. The channel simulation provided a much better calibration than the homogeneous porous-medium simulation and revealed five important differences: (1) convergent flow to large springs, (2) equipotentials forming troughs, (3) decreases in hydraulic gradient and (4) increases in hydraulic conductivity in a downgradient direction, and (5) substantial scaling effects. These five characteristics are also common in other carbonate aquifers and provide a means of identifying whether a carbonate aquifer is more similar to porous-medium or to karst-aquifer end members. | |||||
BibTeX:
@article{Worthington2009,
author = {Worthington, Stephen R. H.},
title = {Diagnostic hydrogeologic characteristics of a karst aquifer (Kentucky, USA)},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {7},
pages = {1665--1678},
url = {http://dx.doi.org/10.1007/s10040-009-0489-0}
}
|
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| Woziwodzki, S. and Jędrzejczak, Ł. | Effect of eccentricity on laminar mixing in vessel stirred by double turbine impellers | 2011 | Chemical Engineering Research and Design Vol. 89(11), pp. 2268-2278 |
article | URL |
| Abstract: Laminar mixing is often conducted in industrial processes, for example in polymerization reactors or in biotechnological processes. The laminar flow conditions caused problems of inefficient mixing due to some mixing anomalies like occurrence of the isolated mixing regions (IMR), segregation or compartmentalization phenomena. In this paper, flow visualization experiments are used to examine the size, positions and structure of the IMR regions as a function of Reynolds number and eccentricity ratio in the vessel equipped with double turbine impellers. It was found that the eccentricity brings deformation and reduction of the IMR volume. Moreover another benefit of using eccentrically located impeller systems is an improvement of axial flow. Two types of IMR regions are found: undulated IMR (UIMR) and ribbon-like IMR (RIMR). The structure of IMR depends on the eccentricity ratio defined as E/R. At the low eccentricity values the structure of single filament wrapped around core of the IMR is found. Additionally, the IMR region is inclined to the impeller plane. | |||||
BibTeX:
@article{Woziwodzki2011,
author = {Woziwodzki, Szymon and Jędrzejczak, Łukasz},
title = {Effect of eccentricity on laminar mixing in vessel stirred by double turbine impellers},
journal = {Chemical Engineering Research and Design},
year = {2011},
volume = {89},
number = {11},
pages = {2268--2278},
url = {http://www.sciencedirect.com/science/article/pii/S0263876211001407}
}
|
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| Wu, B. and Chen, Z. | An integrated physical and biological model for anaerobic lagoons | 2011 | Bioresource Technology Vol. 102(8), pp. 5032-5038 |
article | URL |
| Abstract: A computational fluid dynamics (CFD) model that integrates physical and biological processes for anaerobic lagoons is presented. In the model development, turbulence is represented using a transition k–ω model, heat conduction and solar radiation are included in the thermal model, biological oxygen demand (BOD) reduction is characterized by first-order kinetics, and methane yield rate is expressed as a linear function of temperature. A test of the model applicability is conducted in a covered lagoon digester operated under tropical climate conditions. The commercial CFD software, ANSYS-Fluent, is employed to solve the integrated model. The simulation procedures include solving fluid flow and heat transfer, predicting local resident time based on the converged flow fields, and calculating the BOD reduction and methane production. The simulated results show that monthly methane production varies insignificantly, but the time to achieve a 99% BOD reduction in January is much longer than that in July. | |||||
BibTeX:
@article{Wu2011a,
author = {Wu, Binxin and Chen, Zhenbin},
title = {An integrated physical and biological model for anaerobic lagoons},
journal = {Bioresource Technology},
year = {2011},
volume = {102},
number = {8},
pages = {5032--5038},
url = {http://www.sciencedirect.com/science/article/pii/S0960852411001489}
}
|
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| Wu, J., Hu, B.X. and Zhang, D. | Applications of nonstationary stochastic theory to solute transport in multi-scale geological media | 2003 | Journal of Hydrology Vol. 275(3-4)Studies on Water Movement and Solute Transport in Arid Regions, pp. 208-228 |
article | URL |
| Abstract: In this study, we make use of a nonstationary stochastic theory in studying solute flux through spatially nonstationary flows in porous media. The nonstationarity of flow stems from various sources, such as multi-scale, nonstationary medium features and complex hydraulic boundary conditions. These flow nonstationarities are beyond the applicable range of the ‘classical’ stochastic theory for stationary flow fields, but widely exist in natural media. In this study, the stochastic frames for flow and transport are developed through an analytical analysis while the solutions are obtained with a numerical method. This approach combines the stochastic concept with the flexibility of the numerical method in handling medium nonstationarity and boundary/initial conditions. It provides a practical way for applying stochastic theory to solute transport in complex groundwater environments. This approach is demonstrated through some synthetic cases of solute transport in multi-scale media as well as some hypothetical scenarios of solute transport in the groundwater below the Yucca Mountain project area. It is shown that the spatial variations of mean log-conductivity and correlation function significantly affect the mean and variance of solute flux. Even for a stationary medium, complex hydraulic boundary conditions may result in a nonstationary flow field. Flow nonstationarity and/or nonuniform distribution of initial plume (geometry and/or density) may lead to nonGaussian behaviors (with multiple peaks) for mean and variance of the solute flux. The calculated standard deviation of solute flux is generally larger than its mean value, which implies that real solute fluxes may significantly deviate from the mean predictions. | |||||
BibTeX:
@article{Wu2003,
author = {Wu, Jichun and Hu, Bill X. and Zhang, Dongxiao},
title = {Applications of nonstationary stochastic theory to solute transport in multi-scale geological media},
booktitle = {Studies on Water Movement and Solute Transport in Arid Regions},
journal = {Journal of Hydrology},
year = {2003},
volume = {275},
number = {3-4},
pages = {208--228},
url = {http://www.sciencedirect.com/science/article/pii/S0022169403000441}
}
|
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| Wu, J.-W., Lee, H.-M. and Lei, C.-L. | Computational testing algorithmic procedure of assessment for lifetime performance index of products with two-parameter exponential distribution | 2007 | Applied Mathematics and Computation Vol. 190(1), pp. 116-125 |
article | URL |
| Abstract: Process capability indices (PCIs) are used to measure process potential and performance. Since the lifetime of products generally may possess an exponential, gamma or Weibull distribution, etc., so under a two-parameter exponential distribution, this study constructs a maximum likelihood estimator (MLE) of the lifetime performance index based on the right type II censored sample. Then the MLE of the lifetime performance index is utilized to develop the new hypothesis testing algorithmic procedure in the condition of known L. Finally, a practical example is illustrated to employ the testing algorithmic procedure to determine whether the process is capable. | |||||
BibTeX:
@article{Wu2007,
author = {Wu, Jong-Wuu and Lee, Hsiu-Mei and Lei, Chia-Ling},
title = {Computational testing algorithmic procedure of assessment for lifetime performance index of products with two-parameter exponential distribution},
journal = {Applied Mathematics and Computation},
year = {2007},
volume = {190},
number = {1},
pages = {116--125},
url = {http://www.sciencedirect.com/science/article/pii/S0096300307000343}
}
|
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| Wu, Y.-S., Di, Y., Kang, Z. and Fakcharoenphol, P. | A multiple-continuum model for simulating single-phase and multiphase flow in naturally fractured vuggy reservoirs | 2011 | Journal of Petroleum Science and Engineering Vol. 78(1), pp. 13-22 |
article | URL |
| Abstract: The existence of vugs or cavities in naturally fractured reservoirs has long been observed. Even though these vugs are known for their large attribution to reserves of oil, natural gas, or groundwater, few quantitative investigations of fractured vuggy reservoirs have been conducted. In this paper, a multiple-continuum conceptual model is presented, based on geological data and observations of core samples from carbonate formations in China, to investigate single-phase and multiphase flow behavior in such vuggy fractured reservoirs. The conceptual model has been implemented into a three-dimensional, three-phase reservoir simulator with a generalized multiple-continuum modeling approach. The conceptual model considers fractured vuggy rock as a triple- or multiple-continuum medium, consisting of (1) highly permeable and well-connected fractures, (2) low-permeability rock matrix, and (3) various-sized vugs. The matrix system may contain a large number of small or isolated cavities, whereas vugs are larger cavities, indirectly connected to fractures through small fractures, microfractures or matrix. Similar to the conventional double-porosity model, the fracture continuum is primarily responsible for the occurrence of global flow, while vuggy and matrix continua, providing storage space, are locally connected to each other and interacting with globally connecting fractures. In addition, flow in fractured vuggy reservoirs may be further complicated by occurrence of non-Darcy's and other nonlinear flow behavior, because of large pore space and high-permeability flow channels. To account for such complicated flow regime, our model formulation includes non-Darcy flow using the multiphase extension of the Forchheimer equation as well as flow according to parallel-wall fracture and tube models, based on solutions of flow through a parallel-wall, uniform fracture and Hagen–Poiseuille tube flow. | |||||
BibTeX:
@article{Wu2011,
author = {Wu, Yu-Shu and Di, Yuan and Kang, Zhijiang and Fakcharoenphol, Perapon},
title = {A multiple-continuum model for simulating single-phase and multiphase flow in naturally fractured vuggy reservoirs},
journal = {Journal of Petroleum Science and Engineering},
year = {2011},
volume = {78},
number = {1},
pages = {13--22},
url = {http://www.sciencedirect.com/science/article/pii/S0920410511001021}
}
|
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| Wu, Y.-S., Liu, H. and Bodvarsson, G. | A triple-continuum approach for modeling flow and transport processes in fractured rock | 2004 | Journal of Contaminant Hydrology Vol. 73(1-4), pp. 145-179 |
article | URL |
| Abstract: This paper presents a triple-continuum conceptual model for simulating flow and transport processes in fractured rock. Field data collected from the unsaturated zone of Yucca Mountain, a repository site of high-level nuclear waste, show a large number of small-scale fractures. The effect of these small fractures has not been considered in previous modeling investigations within the context of a continuum approach. A new triple-continuum model (consisting of matrix, small-fracture, and large-fracture continua) has been developed to investigate the effect of these small fractures. This paper derives the model formulation and discusses the basic triple-continuum behavior of flow and transport processes under different conditions, using both analytical solutions and numerical approaches. The simulation results from the site-scale model of the unsaturated zone of Yucca Mountain indicate that these small fractures may have an important effect on radionuclide transport within the mountain. | |||||
BibTeX:
@article{Wu2004,
author = {Wu, Yu-Shu and Liu, H.H. and Bodvarsson, G.S.},
title = {A triple-continuum approach for modeling flow and transport processes in fractured rock},
journal = {Journal of Contaminant Hydrology},
year = {2004},
volume = {73},
number = {1-4},
pages = {145--179},
url = {http://www.sciencedirect.com/science/article/pii/S016977220400004X}
}
|
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| Wu, Z., Zeng, L., Chen, G., Li, Z., Shao, L., Wang, P. and Jiang, Z. | Environmental dispersion in a tidal flow through a depth-dominated wetland | Communications in Nonlinear Science and Numerical Simulation(0), pp. - | article | URL | |
| Abstract: Presented in this paper is a theoretical analysis for longitudinal evolution of mean concentration of an environmental emission into a tidal wetland flow. The velocity distribution of the periodic flow through the wetland is derived, with that for a fully developed steady wetland flow included as a special case. The zero-th, first and the growth of the second order moments of the concentration are rigorously obtained by applying Aris’s method of concentration moments to derive the environmental dispersivity. The necessary time needed for the environmental dispersivity to attain a steady oscillating status is analyzed. The effects of some characteristic parameters, especially one representing the impact of vegetation in the wetland on both velocity profile and environmental dispersivity, and another identifying the effect of flow oscillation on the environmental dispersivity, are illustrated in detail. To reflect the dispersion enhancement by the flow oscillation, a typical example is given to characterize the critical length and duration of the contaminant cloud. | |||||
BibTeX:
@article{Wu,
author = {Wu, Zi and Zeng, L. and Chen, G.Q. and Li, Z. and Shao, Ling and Wang, P. and Jiang, Z.},
title = {Environmental dispersion in a tidal flow through a depth-dominated wetland},
journal = {Communications in Nonlinear Science and Numerical Simulation},
number = {0},
pages = {--},
url = {http://www.sciencedirect.com/science/article/pii/S100757041200175X?v=s5}
}
|
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| Xu, R. and Yan, F. | Karst geology and engineering treatment in the Geheyan Project on the Qingjiang River, China | 2004 | Engineering Geology Vol. 76(1-2)Engineering Geology in China, pp. 155-164 |
article | URL |
| Abstract: The Geheyan Hydropower Project is located in a highly karstified limestone area. The Shilongdong limestone of the foundation bedrock is strongly karstified. Over 600 karst caves of different sizes were discovered in the project area, with a total volume of more than 60,000 m3. Faults parallel to the river are quite developed and karstification is intensified along the faults and their intersections. Exploration adits following the fault zones show a linear karstification ratio of 50%. Therefore, the potential karst leakage under the dam foundation and around both dam abutments is potentially problematic. Thanks to a proper investigation program and a large amount of geological investigations and analysis the karst conditions and major karst zones in the dam site had been identified before the construction commenced. Accordingly, the optimum grouting route was chosen and appropriate seepage control measures were adopted. During the construction, the pre-construction investigation results were well confirmed. Up to now, the project has been in good operation for nine years and the engineering treatment are proved to be very effective. | |||||
BibTeX:
@article{Xu2004,
author = {Xu, Ruichun and Yan, Fuzhang},
title = {Karst geology and engineering treatment in the Geheyan Project on the Qingjiang River, China},
booktitle = {Engineering Geology in China},
journal = {Engineering Geology},
year = {2004},
volume = {76},
number = {1-2},
pages = {155--164},
url = {http://www.sciencedirect.com/science/article/pii/S0013795204001346}
}
|
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| Xue, D., Botte, J., De Baets, B., Accoe, F., Nestler, A., Taylor, P., Van Cleemput, O., Berglund, M. and Boeckx, P. | Present limitations and future prospects of stable isotope methods for nitrate source identification in surface- and groundwater | 2009 | Water Research Vol. 43(5), pp. 1159-1170 |
article | URL |
| Abstract: Nitrate (NO3−) contamination of surface- and groundwater is an environmental problem in many regions of the world with intensive agriculture and high population densities. Knowledge of the sources of NO3− contamination in water is important for better management of water quality. Stable nitrogen (δ15N) and oxygen (δ18O) isotope data of NO3− have been frequently used to identify NO3− sources in water. This review summarizes typical δ15N- and δ18O-NO3− ranges of known NO3− sources, interprets constraints and future outlooks to quantify NO3− sources, and describes three analytical techniques (“ion-exchange method”, “bacterial denitrification method”, and “cadmium reduction method”) for δ15N- and δ18O-NO3− determination. Isotopic data can provide evidence for the presence of dominant NO3− sources. However, quantification, including uncertainty assessment, is lacking when multiple NO3− sources are present. Moreover, fractionation processes are often ignored, but may largely constrain the accuracy of NO3− source identification. These problems can be overcome if (1) NO3− isotopic data are combined with co-migrating discriminators of NO3− sources (e.g. 11B), which are not affected by transformation processes, (2) contributions of different NO3− sources can be quantified via linear mixing models (e.g. SIAR), and (3) precise, accurate and high throughput isotope analytical techniques become available. | |||||
BibTeX:
@article{Xue2009,
author = {Xue, Dongmei and Botte, Jorin and De Baets, Bernard and Accoe, Frederik and Nestler, Angelika and Taylor, Philip and Van Cleemput, Oswald and Berglund, Michael and Boeckx, Pascal},
title = {Present limitations and future prospects of stable isotope methods for nitrate source identification in surface- and groundwater},
journal = {Water Research},
year = {2009},
volume = {43},
number = {5},
pages = {1159--1170},
url = {http://www.sciencedirect.com/science/article/pii/S0043135408006490}
}
|
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| Yablonsky, G.S., Constales, D. and Marin, G.B. | A new approach to diagnostics of ideal and non-ideal flow patterns: I. The concept of reactive-mixing index (REMI) analysis | 2009 | Chemical Engineering Science Vol. 64(23), pp. 4875-4883 |
article | URL |
| Abstract: A new approach is proposed allowing to characterize the hydrodynamic regime in the presence of chemical reactions, through small pulse-response experiments using a reacting component as a tracer instead of inert components which are used in the traditional Danckwerts-type experiment. | |||||
BibTeX:
@article{Yablonsky2009,
author = {Yablonsky, G. S. and Constales, D. and Marin, G. B.},
title = {A new approach to diagnostics of ideal and non-ideal flow patterns: I. The concept of reactive-mixing index (REMI) analysis},
journal = {Chemical Engineering Science},
year = {2009},
volume = {64},
number = {23},
pages = {4875--4883},
url = {http://www.sciencedirect.com/science/article/pii/S0009250909005272}
}
|
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| Yager, R., Voss, C. and Southworth, S. | Comparison of alternative representations of hydraulic-conductivity anisotropy in folded fractured-sedimentary rock: modeling groundwater flow in the Shenandoah Valley (USA) | 2009 | Hydrogeology Journal Vol. 17(5), pp. 1111-1131 |
article | URL |
| Abstract: A numerical representation that explicitly represents the generalized three-dimensional anisotropy of folded fractured-sedimentary rocks in a groundwater model best reproduces the salient features of the flow system in the Shenandoah Valley, USA. This conclusion results from a comparison of four alternative representations of anisotropy in which the hydraulic-conductivity tensor represents the bedrock structure as (model A) anisotropic with variable strikes and dips, (model B) horizontally anisotropic with a uniform strike, (model C) horizontally anisotropic with variable strikes, and (model D) isotropic. Simulations using the US Geological Survey groundwater flow and transport model SUTRA are based on a representation of hydraulic conductivity that conforms to bedding planes in a three-dimensional structural model of the valley that duplicates the pattern of folded sedimentary rocks. In the most general representation, (model A), the directions of maximum and medium hydraulic conductivity conform to the strike and dip of bedding, respectively, while the minimum hydraulic-conductivity direction is perpendicular to bedding. Model A produced a physically realistic flow system that reflects the underlying bedrock structure, with a flow field that is significantly different from those produced by the other three models. | |||||
BibTeX:
@article{Yager2009,
author = {Yager, Richard and Voss, Clifford and Southworth, Scott},
title = {Comparison of alternative representations of hydraulic-conductivity anisotropy in folded fractured-sedimentary rock: modeling groundwater flow in the Shenandoah Valley (USA)},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2009},
volume = {17},
number = {5},
pages = {1111--1131},
url = {http://dx.doi.org/10.1007/s10040-008-0431-x}
}
|
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| Yagi, S. and Miyauchi, T. | On the Residence Time Curves of the Continuous Reactors | 1953 | Chemical engineering Vol. 17(10), pp. 382-386 |
article | DOI URL |
| Abstract: Such a reactor model as fulfils the eq. (2) -i.e. mean diffusivity and velocity are able to be assumed is proposed and the residence time curves of the model are mathematically solved as eq. (7)-(8)'. Based on them, we discussed various behaviours of such a reactor model. From comparisons between the model and the measurements performed by Gilliland et. al.4), 5), 6) mainly on the fluidized bed, we have concluded that the model is able to give fairly good representation to the experimental results. Based on such a quantity as U, we have discussed the characteristics on the concentration driving force of various flow reactors and concluded that the term U seems to be a representative quantity of such characteristics. |
|||||
BibTeX:
@article{Yagi1953,
author = {Yagi, Sakae and Miyauchi, Terukatsu},
title = {On the Residence Time Curves of the Continuous Reactors},
journal = {Chemical engineering},
publisher = {The Society of Chemical Engineers, Japan},
year = {1953},
volume = {17},
number = {10},
pages = {382-386},
url = {http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=kakoronbunshu1953&cdvol=17&noissue=10&startpage=382},
doi = {http://dx.doi.org/10.1252/kakoronbunshu1953.17.382}
}
|
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| Yanagimoto, T. | The conditional maximum likelihood estimator of the shape parameter in the gamma distribution | 1988 | Metrika Vol. 35(1), pp. 161-175 |
article | URL |
| Abstract: The conditional maximum likelihood estimator of the shape parameter in the gamma distribution is studied for a finite sample size in comparison with the (unconditional) maximum likelihood estimator. The former estimator is concluded to be strictly superior to the latter. The reasons for the conclusion include the undesirable behavior of the residual likelihood, the consistency and relatively less bias of the conditional maximum likelihood estimator. Simulation studies for risk comparisons also support the conclusion. | |||||
BibTeX:
@article{Yanagimoto1988,
author = {Yanagimoto, T.},
title = {The conditional maximum likelihood estimator of the shape parameter in the gamma distribution},
journal = {Metrika},
publisher = {Physica Verlag, An Imprint of Springer-Verlag GmbH},
year = {1988},
volume = {35},
number = {1},
pages = {161--175},
url = {http://dx.doi.org/10.1007/BF02613299}
}
|
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| Yang, J., Li, L. and Wang, A. | A partial correlation-based Bayesian network structure learning algorithm under linear SEM | 2011 | Knowledge-Based Systems Vol. 24(7), pp. 963-976 |
article | URL |
| Abstract: A new algorithm, the PCB (partial correlation-based) algorithm, is presented for Bayesian network structure learning. The algorithm effectively combines ideas from local learning with partial correlation techniques. It reconstructs the skeleton of a Bayesian network based on partial correlation and then performs a greedy hill-climbing search to orient the edges. Specifically, we make three contributions. First, we prove that in a linear SEM (simultaneous equation model) with uncorrelated errors, when the datasets are generated by linear SEM, subject to arbitrary distribution disturbances, we can use partial correlation as the criterion of the CI test. Second, we perform a series of experiments to find the best threshold value of the partial correlation. Finally, we show how partial correlation can be used in Bayesian network structure learning under linear SEM. The effectiveness of the method is compared with current state of the art methods on eight networks. A simulation shows that the PCB algorithm outperforms existing algorithms in both accuracy and run time. | |||||
BibTeX:
@article{Yang2011,
author = {Yang, Jing and Li, Lian and Wang, Aiguo},
title = {A partial correlation-based Bayesian network structure learning algorithm under linear SEM},
journal = {Knowledge-Based Systems},
year = {2011},
volume = {24},
number = {7},
pages = {963--976},
url = {http://www.sciencedirect.com/science/article/pii/S0950705111000712}
}
|
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| Yang, X. and Sam Mannan, M. | An uncertainty and sensitivity analysis of dynamic operational risk assessment model: A case study | 2010 | Journal of Loss Prevention in the Process Industries Vol. 23(2), pp. 300-307 |
article | URL |
| Abstract: In Dynamic Operational Risk Assessment (DORA) models, component repair time is an important parameter to characterize component state and the subsequent system-state trajectory. Specific distributions are fit to the industrial component repair time to be used as the input of Monte Carlo simulation of system-state trajectory. The objective of this study is to propose and apply statistical techniques to characterize the uncertainty and sensitivity on the distribution model selection and the associated parameters determination, in order to study how the DORA output that is the probability of operation out-of-control, can be apportioned by the distribution model selection. In this study, eight distribution fittings for each component are performed. Chi-square test, Kolmogorov–Smirnov test, and Anderson-Darling test are proposed to measure the goodness-of-fit to rank the distribution models for characterizing the component repair time distribution. Sensitivity analysis results show that the selection of distribution model among exponential distribution, gamma distribution, lognormal distribution and Weibull distribution to fit the industrial data has no significant impact on DORA results in the case study. | |||||
BibTeX:
@article{Yang2010,
author = {Yang, Xiaole and Sam Mannan, M.},
title = {An uncertainty and sensitivity analysis of dynamic operational risk assessment model: A case study},
journal = {Journal of Loss Prevention in the Process Industries},
year = {2010},
volume = {23},
number = {2},
pages = {300--307},
url = {http://www.sciencedirect.com/science/article/pii/S0950423009001855}
}
|
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| Yidana, S., Ophori, D. and Banoeng-Yakubo, B. | Irrigation Water Resource Management for Sustainable Agriculture—The Ankobra Basin, Ghana | 2007 | Journal of Irrigation and Drainage Engineering Vol. 133(6), pp. 609-615 |
article | URL |
| Abstract: Two irrigation water assessment methods, the USDA classification scheme and the soil infiltration potential, were applied to water from three different locations (Ankwaso, Dominase, and Prestea) of the Ankobra River basin in Ghana, to evaluate its effectiveness as a sustainable water resource for irrigation. The study classifies water from all three locations into the low salinity, low sodicity zone with Prestea and Ankwaso having waters of the highest sodicity and salinity, respectively. A classification scheme based on effects of the water on the hydraulic properties of soils reveals that water from all locations of the basin has the potential to affect the infiltration properties of soils, especially when applied over a long period of time. Linear regression analysis indicates a strong relationship between electrical conductivity (EC) and sodium adsorption ratio (SAR) at R2 =0.773 (n=30) for Prestea. This relationship is probably due to the fact that Na, Mg, and Ca, which are the major determinants of water SAR, are also the major contributors to the water EC at Prestea, and this is probably due to surface mining activities, which encourage the weathering of calcic and albitic feldspars. Time series analysis reveals that EC and SAR for Dominase and Prestea, respectively, have increased from 1989 to 1992. On the other hand, SAR and EC have been decreasing since 1989, for the two locations. Forecast data from the time series analyses agree well with observed data, at 0.01 level of significance. Projections were made at ten time steps ahead of 1992 using time series analysis. | |||||
BibTeX:
@article{Yidana2007,
author = {Yidana, S. and Ophori, D. and Banoeng-Yakubo, B.},
title = {Irrigation Water Resource Management for Sustainable Agriculture—The Ankobra Basin, Ghana},
journal = {Journal of Irrigation and Drainage Engineering},
publisher = {American Society of Civil Engineers},
year = {2007},
volume = {133},
number = {6},
pages = {609--615},
url = {http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9437%282007%29133%3A6%28609%29}
}
|
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| Yoshimura, K., Nakao, S., Noto, M., Inokura, Y., Urata, K., Chen, M. and Lin, P.-W. | Geochemical and stable isotope studies on natural water in the Taroko Gorge karst area, Taiwan—chemical weathering of carbonate rocks by deep source CO2 and sulfuric acid | 2001 | Chemical Geology Vol. 177(3-4), pp. 415-430 |
article | URL |
| Abstract: The geochemical cycle of CO2 and the hydrological cycle in the Taroko Gorge karst area, Taiwan, are discussed using chemical composition data of the natural water, together with stable isotope ratios of carbon and oxygen of the water and soil CO2. The soil CO2 concentration at a depth of 1 m showed seasonal variations with a maximum of 5.2% (v/v) and the minimum of 0.6% (v/v) at three different altitudes ranging from 50 to 2000 m asl. The soil temperature is the most important factor controlling the soil CO2 concentration in this area. The solubility of carbonates in groundwater can be explained by evolution under closed system conditions depending on the soil CO2 concentration measured. Unexpectedly, high δ13C values of HCO3− in groundwater were observed at some springs. There was also an equivalent relationship between the sum of the concentration of Mg2+ and Ca2+ ions and that of HCO3− and SO42− ions in their waters. These two facts suggest that some deep source CO2 and sulfuric acid derived from weathering of pyrite may take part in the chemical weathering of carbonate rocks (mainly calcareous schist) as well as the soil CO2. After the correction for the contribution of sulfuric acid, the δ13C values of HCO3− of groundwater issuing from some springs were still high, suggesting the presence of a deep source CO2 flux. Altitude isotope effects were observed for surface water and rainwater in this area and could be expressed as δ18O (‰)=−0.0024h−3.67 (h: altitude, m asl). The estimated altitudes of catchment basins of springs using this equation were over 1000–2000 m higher than those of springs. The rain falling high in the mountains is supplied with soil CO2, dissolves carbonate rocks under closed system conditions, penetrates deep underground, and comes out again from springs together with the deep source CO2 along fault crushing belts. | |||||
BibTeX:
@article{Yoshimura2001,
author = {Yoshimura, K. and Nakao, S. and Noto, M. and Inokura, Y. and Urata, K. and Chen, M. and Lin, P.-W.},
title = {Geochemical and stable isotope studies on natural water in the Taroko Gorge karst area, Taiwan—chemical weathering of carbonate rocks by deep source CO2 and sulfuric acid},
journal = {Chemical Geology},
year = {2001},
volume = {177},
number = {3-4},
pages = {415--430},
url = {http://www.sciencedirect.com/science/article/pii/S000925410000423X}
}
|
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| Young, D.F. and Ball, W.P. | Column experimental design requirements for estimating model parameters from temporal moments under nonequilibrium conditions | 2000 | Advances in Water Resources Vol. 23(5), pp. 449-460 |
article | URL |
| Abstract: Data truncation is a practical necessity of laboratory column experiments because of both time and detection-limit constraints. In this paper, we study the extent to which data truncation can affect estimates of transport modeling parameters, as derived from temporal moment calculations and in the context of solute transport experiments that are influenced by sorption and nonequilibrium partitioning among mobile and immobile phases. Our results show that, for a given amount of solute used, step changes in input conditions can give more accurate moment-derived parameters than Dirac or square-wave pulses, whereas Dirac and square-wave pulses are essentially identical in terms of accuracy of parameter estimates. By simulating data truncation for a wide range of column input and transport conditions, we provide guidance toward the experimental designs that are needed to keep parameter estimation error within specified bounds, assuming nonequilibrium conditions of transport that result from either first-order or diffusion-based rate processes. More specifically, we investigate the relationships between mass of solute added to the system, minimum solute quantification limits, experiment duration times, and accuracy of parameter estimation, all as a function of experimental conditions. | |||||
BibTeX:
@article{Young2000,
author = {Young, Dirk F and Ball, William P},
title = {Column experimental design requirements for estimating model parameters from temporal moments under nonequilibrium conditions},
journal = {Advances in Water Resources},
year = {2000},
volume = {23},
number = {5},
pages = {449--460},
url = {http://www.sciencedirect.com/science/article/pii/S0309170899000470}
}
|
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| Young, P. and Garnier, H. | Identification and estimation of continuous-time, data-based mechanistic (DBM) models for environmental systems | 2006 | Environmental Modelling & Software Vol. 21(8), pp. 1055-1072 |
article | URL |
| Abstract: Initially, the paper provides an introduction to the main aspects of existing time-domain methods for identifying linear continuous-time models from discrete-time data and shows how one of these methods has been applied to the identification and estimation of a model for the transportation and dispersion of a pollutant in a river. It then introduces a widely applicable class of new, nonlinear, State Dependent Parameter (SDP) models. Finally, the paper describes how this SDP approach has been used to identify, estimate and control a nonlinear differential equation model of global carbon cycle dynamics and global warming. | |||||
BibTeX:
@article{Young2006,
author = {Young, P.C. and Garnier, H.},
title = {Identification and estimation of continuous-time, data-based mechanistic (DBM) models for environmental systems},
journal = {Environmental Modelling & Software},
year = {2006},
volume = {21},
number = {8},
pages = {1055--1072},
url = {http://www.sciencedirect.com/science/article/pii/S1364815205000952}
}
|
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| Yu, J.-W. and Neretnieks, I. | Modelling of transport and reaction processes in a porous medium in an electrical field | 1996 | Chemical Engineering Science Vol. 51(19), pp. 4355-4368 |
article | URL |
| Abstract: A numerical model has been developed to describe the transport and reaction processes in a porous medium in an electrical field. The model discretizes the one-dimensional porous medium by a number of compartments. The governing equations are formulated by material balance over each compartment. The model describes transport processes of advection, dispersion, ionic migration and electroosmosis. Various reactions such as aqueous complexation, precipitation/dissolution, and electrochemical reactions are treated by kinetic approaches. For fast fluid-phase reactions such as complexation, local equilibrium assumption may be applied in the model, which reduces the number of primary components and hence the number of governing equations. The sorption processes occurring at the surfaces of the porous medium are at the moment treated only by a single-component linear isotherm. Numerical solution to the model gives concentration and electrical potential distributions in the porous medium at different times and gives as well the electrical current history. Modelling results for three sample cases are reported to demonstrate the application of the model. In the first sample case, the removal of copper from sand by an electrical field is simulated. The second case concerns an electrokinetic soil remediation process with cathode rinsing. The third case models the selective filtering function of the ion exchange membranes. | |||||
BibTeX:
@article{Yu1996,
author = {Yu, Ji-Wei and Neretnieks, Ivars},
title = {Modelling of transport and reaction processes in a porous medium in an electrical field},
journal = {Chemical Engineering Science},
year = {1996},
volume = {51},
number = {19},
pages = {4355--4368},
url = {http://www.sciencedirect.com/science/article/pii/0009250996002837}
}
|
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| Yu, J.-W., Tian, G.-L. and Tang, M.-L. | Statistical inference and prediction for the Weibull process with incomplete observations | 2008 | Computational Statistics & Data Analysis Vol. 52(3), pp. 1587-1603 |
article | URL |
| Abstract: In this article, statistical inference and prediction analyses for the Weibull process with incomplete observations via classical approach are studied. Specifically, observations in the early developmental phase of a testing program cannot be observed. We derive the closed-form expressions for the maximum likelihood estimates of the parameters in both the failure- and time-truncated Weibull processes. Confidence interval and hypothesis testing for the parameters of interest are considered. In addition, predictive inferences on future failures and the goodness-of-fit test of the model are developed. Two real examples from an engine system development study and a Boeing air-conditioning system development study are presented to illustrate the proposed methodologies. | |||||
BibTeX:
@article{Yu2008,
author = {Yu, Jun-Wu and Tian, Guo-Liang and Tang, Man-Lai},
title = {Statistical inference and prediction for the Weibull process with incomplete observations},
journal = {Computational Statistics & Data Analysis},
year = {2008},
volume = {52},
number = {3},
pages = {1587--1603},
url = {http://www.sciencedirect.com/science/article/pii/S0167947307002022}
}
|
|||||
| Yue, S. | A bivariate gamma distribution for use in multivariate flood frequency analysis | 2001 | Hydrological Processes Vol. 15(6), pp. 1033-1045 |
article | URL |
| Abstract: A gamma distribution is one of the most frequently selected distribution types for hydrological frequency analysis. The bivariate gamma distribution with gamma marginals may be useful for analysing multivariate hydrological events. This study investigates the applicability of a bivariate gamma model with five parameters for describing the joint probability behavior of multivariate flood events. The parameters are proposed to be estimated from the marginal distributions by the method of moments. The joint distribution, the conditional distribution, and the associated return periods are derived from marginals. The usefulness of the model is demonstrated by representing the joint probabilistic behaviour between correlated flood peak and flood volume and between correlated flood volume and flood duration in the Madawask River basin in the province of Quebec, Canada. Copyright © 2001 John Wiley & Sons, Ltd. | |||||
BibTeX:
@article{Yue2001b,
author = {Yue, Sheng},
title = {A bivariate gamma distribution for use in multivariate flood frequency analysis},
journal = {Hydrological Processes},
publisher = {John Wiley & Sons, Ltd.},
year = {2001},
volume = {15},
number = {6},
pages = {1033--1045},
url = {http://dx.doi.org/10.1002/hyp.259}
}
|
|||||
| Yue, S., Ouarda, T. and Bobée, B. | A review of bivariate gamma distributions for hydrological application | 2001 | Journal of Hydrology Vol. 246(1-4), pp. 1-18 |
article | URL |
| Abstract: A univariate gamma distribution is one of the most commonly adopted statistical distributions in hydrological frequency analysis. A bivariate gamma distribution constructed from specified gamma marginals may be useful for representing joint probabilistic properties of multivariate hydrological events such as floods and storms. This article presents a review of various bivariate gamma distribution models that are constructed from gamma marginals. Advantages and limitations of each of these models are pointed out. Applicability of a few bigamma distributions whose gamma marginal distributions have different scale and shape parameters is investigated. The dependence of these models is directly or indirectly measured via the Pearson's product-moment correlation coefficient. The scale and shape parameters of the models are estimated from their marginal distributions by the method of moments. Results indicate that these bigamma distribution models will be useful for describing the joint probability distribution of two correlated random variables with gamma marginals. | |||||
BibTeX:
@article{Yue2001a,
author = {Yue, S. and Ouarda, T.B.M.J. and Bobée, B.},
title = {A review of bivariate gamma distributions for hydrological application},
journal = {Journal of Hydrology},
year = {2001},
volume = {246},
number = {1-4},
pages = {1--18},
url = {http://www.sciencedirect.com/science/article/pii/S0022169401003742}
}
|
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| Zahraeifard, V. and Deng, Z. | Hydraulic residence time computation for constructed wetland design | 2011 | Ecological Engineering Vol. 37(12), pp. 2087-2091 |
article | URL |
| Abstract: Hydraulic residence time (HRT) is one of the key design parameters controlling the removal efficiency of contaminants and nutrients in stormwater and wastewater wetlands. The paper presents a new approach to the estimation of HRT using the variable residence time (VART) model. The VART model is employed to simulate the major processes (including advection, dispersion, and transient storage of contaminants/nutrients in vegetated zones) affecting HRT and thereby to produce a hydraulic residence time distribution (HRTD) for a design wetland. The HRTD in combination with a moment-based method is then utilized to find a mean design HRT for the design wetland. Methods for estimation of parameters governing the HRTD are proposed. The new approach to HRT computation is demonstrated through a case study for the Tres Rios Demonstration (TRD) Wetlands in Arizona, USA. Modeling results show that the design HRTs for the Hayfield wetland (H1) and the Cobble wetlands (C1 and C2) are 4.04, 4.66, and 2.65 days, respectively. The computed HRTs agree well with those reported by previous studies, confirming the efficacy of the new approach to hydraulic design of constructed wetlands. | |||||
BibTeX:
@article{Zahraeifard2011,
author = {Zahraeifard, Vahid and Deng, Zhiqiang},
title = {Hydraulic residence time computation for constructed wetland design},
journal = {Ecological Engineering},
year = {2011},
volume = {37},
number = {12},
pages = {2087--2091},
url = {http://www.sciencedirect.com/science/article/pii/S0925857411002746}
}
|
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| Žák, K., Ložek, V., Kadlec, J., Hladı́ková, J. and Cı́lek, V. | Climate-induced changes in Holocene calcareous tufa formations, Bohemian Karst, Czech Republic | 2002 | Quaternary International Vol. 91(1)Late Pleistocene and Holocene Investigations in Europe. Internati onal Conference on Past Global Changes (PAGES), pp. 137-152 |
article | URL |
| Abstract: About 70 localities where Holocene calcareous tufa is formed recently and/or was formed in the past are known in the Bohemian Karst, a small karst area located SW of Prague. All known tufa accumulations display a very similar pattern of lithological and biostratigraphic evolution, reflecting climatic changes, erosion events and biota succession. A 17 m thick tufa accumulation at Svatý Jan pod Skalou was selected and thoroughly studied as a typical, well developed representative of local tufa deposits. Tufa formation started at about 9500 BP, on a flat fluvial gravel terrace of Late Glacial/Early Holocene age. Deposition of lithologically uniform, pure hard porous tufa continued until about 6500 BP. From that time, a more unstable climate with several dry periods and erosion events produced a lithologically varied complex of loose tufa alternating with embedded soils and scree layers. Termination of the tufa deposition occurred about 2500 BP, and was followed by partial erosion connected with relocation of the spring below the tufa body. Holocene climatic changes were recorded in lithology, molluscan assemblages, and oscillations of oxygen and carbon stable isotope ratios in carbonate. The observed patterns are in good agreement with the evolution of calcareous tufa deposits throughout Central Europe. | |||||
BibTeX:
@article{Zak2002,
author = {Žák, Karel and Ložek, Vojen and Kadlec, Jaroslav and Hladı́ková, Jana and Cı́lek, Václav},
title = {Climate-induced changes in Holocene calcareous tufa formations, Bohemian Karst, Czech Republic},
booktitle = {Late Pleistocene and Holocene Investigations in Europe. Internati onal Conference on Past Global Changes (PAGES)},
journal = {Quaternary International},
year = {2002},
volume = {91},
number = {1},
pages = {137--152},
url = {http://www.sciencedirect.com/science/article/pii/S1040618201001070}
}
|
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| Zaramella, M., Marion, A. and Packman, A.I. | Applicability of the Transient Storage Model to the hyporheic exchange of metals | 2006 | Journal of Contaminant Hydrology Vol. 84(1-2), pp. 21-35 |
article | URL |
| Abstract: Stream–subsurface exchange results from a complex ensemble of transport mechanisms that require different modeling approaches. Field and laboratory experiments show that advective exchange through the underlying sediments is an important mechanism of solutes transport and storage in riverine systems. Here, Transient Storage Model parameters are obtained for reactive solute exchange driven by bedform-induced advection. Consideration of exchange induced by this single mechanism allows specific relationships between model parameters and system properties like solute reactivity to be identified. This work shows that when a simplified model like the Transient Storage Model is applied to analyze metal storage in river sediments, particular attention must be devoted to the choice of modeling parameters. | |||||
BibTeX:
@article{Zaramella2006,
author = {Zaramella, Mattia and Marion, Andrea and Packman, Aaron I.},
title = {Applicability of the Transient Storage Model to the hyporheic exchange of metals},
journal = {Journal of Contaminant Hydrology},
year = {2006},
volume = {84},
number = {1-2},
pages = {21--35},
url = {http://www.sciencedirect.com/science/article/pii/S0169772205002330}
}
|
|||||
| Zeng, L. and Chen, G. | Ecological degradation and hydraulic dispersion of contaminant in wetland | 2011 | Ecological Modelling Vol. 222(2)Wetlands in China, pp. 293-300 |
article | URL |
| Abstract: For the typical case of a pulsed contaminant emission into a free surface wetland flow, a theoretical analysis is presented in this paper for the decay of the depth-averaged concentration under the combined action of ecological degradation and hydraulic dispersion. Based on a first-order reaction model extensively employed in related ecological risk assessment and environmental hydraulic design, the effect of ecological degradation is separated from the hydraulic effect via an exponential transformation for the general formulation for contaminant transport. The speed profile of a fully developed steady flow through the wetland is obtained. A hydraulic dispersion model for the depth-averaged concentration is devised as an extension of Taylor’s classical analysis on dispersion, and corresponding hydraulic dispersivity is obtained by Aris’s method of moments. Analytical solution of depth-averaged concentration is rigorously derived and characterized. For typical pollutant constituents in wastewater emission, the evolution of contaminant cloud in the wetland flow is illustrated by critical length and duration of influenced region with contaminant concentration beyond given environmental standard level, with essential implications for ecological risk assessment and environmental management. | |||||
BibTeX:
@article{Zeng2011,
author = {Zeng, L. and Chen, G.Q.},
title = {Ecological degradation and hydraulic dispersion of contaminant in wetland},
booktitle = {Wetlands in China},
journal = {Ecological Modelling},
year = {2011},
volume = {222},
number = {2},
pages = {293--300},
url = {http://www.sciencedirect.com/science/article/pii/S0304380009007108}
}
|
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| Zeng, L., Chen, G., Tang, H. and Wu, Z. | Environmental dispersion in wetland flow | 2011 | Communications in Nonlinear Science and Numerical Simulation Vol. 16(1), pp. 206-215 |
article | URL |
| Abstract: For the typical case of a pulsed contaminant emission into a shallow wetland channel, a theoretical analysis is presented in this paper for the decay of the width-averaged mean concentration under environmental dispersion. The velocity profile of a fully developed steady flow through the wetland channel is obtained with that for the well-known plane Poiseuille flow as a special case. An environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classic analysis on dispersion, and corresponding environmental dispersivity is obtained by Aris’s method of moments and illustrated with an asymptotic time variation with stem dominated, transitional, and width-stem dominated stages. Analytical solution for the longitudinal decay of mean concentration due to environmental dispersion is rigorously derived and characterized with multiple time scales. | |||||
BibTeX:
@article{Zeng2011a,
author = {Zeng, L. and Chen, G.Q. and Tang, H.S. and Wu, Z.},
title = {Environmental dispersion in wetland flow},
journal = {Communications in Nonlinear Science and Numerical Simulation},
year = {2011},
volume = {16},
number = {1},
pages = {206--215},
url = {http://www.sciencedirect.com/science/article/pii/S1007570410001152}
}
|
|||||
| Zeng, L., Wu, Y., Ji, P., Chen, B., Zhao, Y., Chen, G. and Wu, Z. | Effect of wind on contaminant dispersion in a wetland flow dominated by free-surface effect | 2012 | Ecological Modelling Vol. 237–238(0), pp. 101-108 |
article | URL |
| Abstract: Flow and environmental dispersion are essential to ecological risk assessment and ecological restoration associated with wetlands. Presented in this paper is an analytical study for effect of wind on contaminant dispersion in a wetland flow dominated by free-surface effect. Based on the momentum transport equation generally adopted for wetland flow, the solution for velocity distribution in a free-surface wetland flow under wind is rigorously derived, with a limiting case covering the known solution of flow in the absence of wind. The thickness of inverse flow layer, maximum velocity, and its location are obtained. By use of Aris's method of concentration moments, the expression for environmental dispersivity in the free-surface wetland flow under wind is derived, and that in the absence of wind can be included as a special case. The direction and intensity of wind can influence greatly the environmental dispersivity at a stable stage. The time scale for environmental dispersivity to approach the stable stage is independent of wind. Analytical solution of mean concentration is derived and illustrated for a pulsed contaminant emission into a wetland flow dominated by free-surface effect under wind. For typical pollutant Pb, the length and duration of influence region with contaminant concentration beyond given standard level of water quality are illustrated. | |||||
BibTeX:
@article{Zeng2012,
author = {Zeng, L. and Wu, Y.H. and Ji, P. and Chen, B. and Zhao, Y.J. and Chen, G.Q. and Wu, Z.},
title = {Effect of wind on contaminant dispersion in a wetland flow dominated by free-surface effect},
journal = {Ecological Modelling},
year = {2012},
volume = {237–238},
number = {0},
pages = {101--108},
url = {http://www.sciencedirect.com/science/article/pii/S0304380012001937}
}
|
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| Zhang, F., Yeh, G.-T., Parker, J.C., Brooks, S.C., Pace, M.N., Kim, Y.-J., Jardine, P.M. and Watson, D.B. | A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions | 2007 | Journal of Contaminant Hydrology Vol. 92(1-2), pp. 10-32 |
article | URL |
| Abstract: This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss–Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M–NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions. | |||||
BibTeX:
@article{Zhang2007,
author = {Zhang, Fan and Yeh, Gour-Tsyh and Parker, Jack C. and Brooks, Scott C. and Pace, Molly N. and Kim, Young-Jin and Jardine, Philip M. and Watson, David B.},
title = {A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {92},
number = {1-2},
pages = {10--32},
url = {http://www.sciencedirect.com/science/article/pii/S0169772206002440}
}
|
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| Zhang, G.T., Wannenmacher, N., Haidert, A. and Levenspiel, O. | How to narrow the residence time distribution of fluids in laminar flow in pipes | 1990 | The Chemical Engineering Journal Vol. 45(1), pp. 43-48 |
article | URL |
| Abstract: This study tested the effectiveness of different stirrer designs and stirring rates, both continuous and reciprocating, on narrowing the residence time | |||||
BibTeX:
@article{Zhang1990,
author = {Zhang, G. T. and Wannenmacher, N. and Haidert, A. and Levenspiel, O.},
title = {How to narrow the residence time distribution of fluids in laminar flow in pipes},
journal = {The Chemical Engineering Journal},
year = {1990},
volume = {45},
number = {1},
pages = {43--48},
url = {http://www.sciencedirect.com/science/article/pii/0300946790800247}
}
|
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| Zhang, H., Tang, S. and Liang, B. | Residence time distribution in two-phase flow mini-channel reactor | 2011 | Chemical Engineering Journal Vol. 174(2-3), pp. 652-659 |
article | URL |
| Abstract: Mini-channel reactors have a high level of heat and mass transfer performance, and thus present great potential in highly exothermic reactions or those with explosion risks. Residence time distribution (RTD) and mean residence time (MRT) are important in reactor design and modelling. However, normally reported measurements of RTD and MRT were often conducted at room temperature and low pressure, significantly from actual reaction conditions. In the current work, the RTD and MRT of the two phases that flow in mini-channel reactors for both the toluene–nitrogen and cyclohexane–nitrogen systems were measured at 165 °C and 1 MPa, respectively. The RTD of the liquid phase was determined using the pulsing tracer method. The experimental data were fitted using a dispersion model. Results showed that the MRT of the liquid phase is much longer than that of the gas phase. It is preferred by the slow reactions such as the oxidation of hydrocarbons. The reaction experiments demonstrated that a longer liquid MRT is favorable for the reactions like the oxidation of hydrocarbons, which have a relatively lower reaction rate. In the plug flow zone, the MRT of the liquid phase decreased rapidly with both increasing gas and liquid flow. However, when the flow pattern shifted to the annular flow, the MRT of the liquid phase remained constant. An empirical model was developed to predict the MRTs in different flow patterns using dimensional analysis. | |||||
BibTeX:
@article{Zhang2011,
author = {Zhang, Haiguang and Tang, Shengwei and Liang, Bin},
title = {Residence time distribution in two-phase flow mini-channel reactor},
journal = {Chemical Engineering Journal},
year = {2011},
volume = {174},
number = {2-3},
pages = {652--659},
url = {http://www.sciencedirect.com/science/article/pii/S1385894711011144}
}
|
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| Zhang, J., Ma, J., Dou, L., Wu, S., Qian, X., Xie, H., Zhu, Y. and He, F. | Mass Measurement Errors of Fourier-Transform Mass Spectrometry (FTMS): Distribution, Recalibration, and Application | 2008 | Journal of Proteome Research Vol. 8(2), pp. 849-859 |
article | DOI URL |
| Abstract: On the basis of a comprehensive investigation of the precursor ion mass error distribution of the LTQ-FT platform, we developed a large MET database search and small statistical MET filter strategy named LDSF for database search MET specification and database search result validation. This approach could reshape the curve of the mass error to more closely resemble the Gaussian distribution, and significantly improve the sensitivity of the result validation procedure. On the basis of a comprehensive investigation of the precursor ion mass error distribution of the LTQ-FT platform, we developed a large MET database search and small statistical MET filter strategy named LDSF for database search MET specification and database search result validation. This approach could reshape the curve of the mass error to more closely resemble the Gaussian distribution, and significantly improve the sensitivity of the result validation procedure. |
|||||
BibTeX:
@article{Zhang2008a,
author = {Zhang, Jiyang and Ma, Jie and Dou, Lei and Wu, Songfeng and Qian, Xiaohong and Xie, Hongwei and Zhu, Yunping and He, Fuchu},
title = {Mass Measurement Errors of Fourier-Transform Mass Spectrometry (FTMS): Distribution, Recalibration, and Application},
journal = {Journal of Proteome Research},
publisher = {American Chemical Society},
year = {2008},
volume = {8},
number = {2},
pages = {849--859},
url = {http://dx.doi.org/10.1021/pr8005588},
doi = {http://dx.doi.org/10.1021/pr8005588}
}
|
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| Zhang, K. and Woodbury, A.D. | A Krylov finite element approach for multi-species contaminant transport in discretely fractured porous media | 2002 | Advances in Water Resources Vol. 25(7), pp. 705-721 |
article | URL |
| Abstract: Simulation of non-ideal transport of multi-species solutes in fractured porous media can easily introduce hundreds of thousand to millions of unknowns. In this paper, a Krylov finite element method, the Arnoldi reduction method (ARM), for solving these type problems has been introduced. The Arnoldi reduction technique uses orthogonal matrix transformations to reduce each of the aforementioned coupled systems to much smaller size. In order to speed convergence of the Arnoldi process, an eigenvalue shift in each finite element system is introduced. This approach greatly improves the diagonal dominant properties of the matrices to be solved. This property leads to great enhancement of the iterative solution and the convergence rate for Arnoldi reduction process. In addition, the use of the eigenvalue shift technique greatly relaxes the grid Peclet restrictions. Courant number criteria restrictions are also effectively removed. We utilize an ORTHOMIN procedure to carry out the equation system reductions for discrete fractured media. The proposed numerical method has been verified by comparison against analytical solutions. The developed model is highly efficient in computing time and storage space. Simulations of radioactive decay chain and trichloroethylene transport are made and compared to the Laplace transform Galerkin (LTG) method where appropriate. Examples with about one million unknowns are solved on personal computers and shown that the ARM is even more efficient than the LTG method, by allowing for similar speed increases with multi-components. Therefore, the Arnoldi approach will allow for a variety of complex, high-resolution problems to be solved on small computer platforms. | |||||
BibTeX:
@article{Zhang2002a,
author = {Zhang, Keni and Woodbury, Allan D.},
title = {A Krylov finite element approach for multi-species contaminant transport in discretely fractured porous media},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {7},
pages = {705--721},
url = {http://www.sciencedirect.com/science/article/pii/S0309170802000842}
}
|
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| Zhang, L. and Mitsch, W.J. | Modelling hydrological processes in created freshwater wetlands: an integrated system approach | 2005 | Environmental Modelling & Software Vol. 20(7), pp. 935-946 |
article | URL |
| Abstract: This study investigates hydrologic processes of four different flow-through created freshwater wetlands in Ohio, USA, by use of several versions of a simple daily mass-balance water budget model. The model includes surface inflows and outflows, precipitation, evapotranspiration, and groundwater seepage. We calibrated the daily water budget for two experimental wetlands that had pumped inflow during 1999 and validated it during 2000–2002 on the same basins. The coefficient of prediction efficiency is 0.70 and the modelled hydroperiod followed observed water depths during the calibration period well. The average retention time in the calibration year 1999 was 4.4–4.6 days. The model was applied to a 3-ha created riparian wetland that receives river flooding. Results illustrated that this wetland has developed a hydroperiod with more than sufficient flooding to ensure that it will meet the hydrologic criteria of a formal jurisdictional wetland definition in the USA. Water budget predictions for a stormwater wetland provided useful design information for hydroperiod and hydrologic dynamics prior to the construction of that system. The model was simulated for average, dry, and wet years. An integrated systems approach was developed using a STELLA 7.0 with its capabilities of dynamic interface level control (e.g. buttons and switches) features. | |||||
BibTeX:
@article{Zhang2005,
author = {Zhang, Li and Mitsch, William J.},
title = {Modelling hydrological processes in created freshwater wetlands: an integrated system approach},
journal = {Environmental Modelling & Software},
year = {2005},
volume = {20},
number = {7},
pages = {935--946},
url = {http://www.sciencedirect.com/science/article/pii/S1364815204001252}
}
|
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| Zhang, L., Zhang, J. and Zhao, Y. | Analysis of a finite element numerical solution for a nonlinear seepage flow model in a deformable dual media fractal reservoir | 2011 | Journal of Petroleum Science and Engineering Vol. 76(3-4), pp. 77-84 |
article | URL |
| Abstract: In this paper, an unsteady state flow mathematical model for a deformable dual media fractal gas reservoir in a second kind of boundary conditions is developed, with the consideration of dynamic changes in porosity and permeability as a result of pressure depletion in the system. Existence and convergence from this mathematical model are proven for a finite element discrete numerical solution in the framework of a fractal geometry theory. Then, a concise numerical solution, in the one variable linear interpolation function space, is achieved by adopting the Galerkin finite element method. | |||||
BibTeX:
@article{Zhang2011a,
author = {Zhang, Liehui and Zhang, Jinliang and Zhao, Yulong},
title = {Analysis of a finite element numerical solution for a nonlinear seepage flow model in a deformable dual media fractal reservoir},
journal = {Journal of Petroleum Science and Engineering},
year = {2011},
volume = {76},
number = {3-4},
pages = {77--84},
url = {http://www.sciencedirect.com/science/article/pii/S0920410510002688}
}
|
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| Zhang, T., Wang, T. and Wang, J. | Mathematical modeling of the residence time distribution in loop reactors | 2005 | Chemical Engineering and Processing: Process Intensification Vol. 44(11), pp. 1221-1227 |
article | URL |
| Abstract: The axial dispersion model was applied to the riser and down-comer, respectively, of an airlift loop reactor and a mathematical model was developed to describe its residence time distribution (RTD). A numerical solution was first obtained for the case where there is no gas–liquid separator. A tracer impulse was considered to flow in an infinite tube comprising alternating riser, gas–liquid separator and down-comer. The tracer concentration at a point in the reactor is the sum of all the tracer concentrations at the corresponding points in the infinite tube. Based on this model, an analytical solution was obtained for the mathematical model. The comparison between the analytical solution and experimental data shows that the model can be used to simulate the RTD in airlift loop reactors. By using the analytical solution in a loop reactor with partial recirculation, the solution with a recycle factor is obtained. A comparison with data in the literature shows that the solution with the recycle factor can be used for the RTD in a loop reactor with partial recirculation. | |||||
BibTeX:
@article{Zhang2005a,
author = {Zhang, Tongwang and Wang, Tiefeng and Wang, Jinfu},
title = {Mathematical modeling of the residence time distribution in loop reactors},
journal = {Chemical Engineering and Processing: Process Intensification},
year = {2005},
volume = {44},
number = {11},
pages = {1221--1227},
url = {http://www.sciencedirect.com/science/article/pii/S0255270105000978}
}
|
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| Zhang, T., Zhao, B. and Wang, J. | Mathematical models for macro-scale mass transfer in airlift loop reactors | 2006 | Chemical Engineering Journal Vol. 119(1), pp. 19-26 |
article | URL |
| Abstract: Inter-phase mass transfer is an important issue for design and development of airlift loop reactors of high performance in either chemical or biochemical applications. In this work, the axial dispersion in both gas and liquid phases was taken into account for modeling the macro-scale mass transfer in airlift loop reactors. Finite difference method was used to numerically solve the differential equation system of the mass transfer model. For oxygen, the numerical results showed that the solute concentration of the gas phase can be treated as constant and the flow pattern of the liquid phase as a plug flow. Based on the conclusion obtained from numerical solution, the mass transfer model was simplified and the analytical solution of the simplified model was obtained. Comparison between the numerical and analytical solutions showed that the simplification of the model was reasonable and there was almost no influence on the calculated results. Experimental measurements on the mass transfer rate were carried out to verify the mathematical model. The comparison between the experimental and calculated results showed that the mass transfer model has satisfactory prediction ability and can be used to describe the mass transfer process in airlift loop reactors. | |||||
BibTeX:
@article{Zhang2006a,
author = {Zhang, Tongwang and Zhao, Bin and Wang, Jinfu},
title = {Mathematical models for macro-scale mass transfer in airlift loop reactors},
journal = {Chemical Engineering Journal},
year = {2006},
volume = {119},
number = {1},
pages = {19--26},
url = {http://www.sciencedirect.com/science/article/pii/S1385894706000982}
}
|
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| Zhang, T.W., Wang, T.F. and Wang, J.F. | Application of Residence Time Distribution for Measuring the Fluid Velocity and Dispersion Coefficient | 2007 | Chemical Engineering & Technology Vol. 30(1), pp. 27-32 |
article | DOI URL |
| Abstract: Most studies on residence time distribution (RTD) have focused on the tail of the RTD curve, and very little attention has been paid to the effect of white noise on the measured results. The aim of this work is to study the effect of white noise on the calculated parameters with different data processing methods. The anti-disturbance abilities of the moment method and the least squares method are compared. The results show that the anti-disturbance ability of the least squares method was better than that of the moment method. As a result of peak overlapping in the RTD curve of a loop reactor, the moment method cannot be used to calculate the fluid velocity and dispersion coefficient. Experiments show that the least squares method is still applicable in a loop reactor. | |||||
BibTeX:
@article{Zhang2007a,
author = {Zhang, T. W. and Wang, T. F. and Wang, J. F.},
title = {Application of Residence Time Distribution for Measuring the Fluid Velocity and Dispersion Coefficient},
journal = {Chemical Engineering & Technology},
publisher = {WILEY-VCH Verlag},
year = {2007},
volume = {30},
number = {1},
pages = {27--32},
url = {http://dx.doi.org/10.1002/ceat.200600002},
doi = {http://dx.doi.org/10.1002/ceat.200600002}
}
|
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| Zhang, X., Bengough, A.G., Crawford, J.W. and Young, I.M. | A lattice BGK model for advection and anisotropic dispersion equation | 2002 | Advances in Water Resources Vol. 25(1), pp. 1-8 |
article | URL |
| Abstract: This paper presents a lattice Boltzmann model (LBM) for 2-D advection and anisotropic dispersion equation (AADE) based on the Bhatnagar, Gross and Krook (BGK) model. In the proposed model, the particle speed space is discretized using a rectangular lattice that has four speeds in nine directions, and the single relaxation time is assumed to be directionally dependent. To ensure that the collision is mass-invariant when the relaxation time is directionally dependent, the concentration is calculated from a weighted summation of the particle distribution functions. The proposed model was verified against benchmark problems and the finite difference solution of solute transport with spatially variable dispersion coefficients and non-uniform velocity field. The significant results are that it conserves mass perfectly and offers accurate and efficient solutions for both dispersion-dominated and advection-dominated problems. | |||||
BibTeX:
@article{Zhang2002,
author = {Zhang, Xiaoxian and Bengough, Anthony G. and Crawford, John W. and Young, Iain M.},
title = {A lattice BGK model for advection and anisotropic dispersion equation},
journal = {Advances in Water Resources},
year = {2002},
volume = {25},
number = {1},
pages = {1--8},
url = {http://www.sciencedirect.com/science/article/pii/S0309170801000471}
}
|
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| Zhang, X., Brooks, R.D. and King, M.L. | A Bayesian approach to bandwidth selection for multivariate kernel regression with an application to state-price density estimation | 2009 | Journal of Econometrics Vol. 153(1), pp. 21-32 |
article | URL |
| Abstract: This paper presents a Bayesian approach to bandwidth selection for multivariate kernel regression. A Monte Carlo study shows that under the average squared error criterion, the Bayesian bandwidth selector is comparable to the cross-validation method and clearly outperforms the bootstrapping and rule-of-thumb bandwidth selectors. The Bayesian bandwidth selector is applied to a multivariate kernel regression model that is often used to estimate the state-price density of Arrow–Debreu securities with the S&P 500 index options data and the DAX index options data. The proposed Bayesian bandwidth selector represents a data-driven solution to the problem of choosing bandwidths for the multivariate kernel regression involved in the nonparametric estimation of the state-price density pioneered by Aït-Sahalia and Lo [Aït-Sahalia, Y., Lo, A.W., 1998. Nonparametric estimation of state-price densities implicit in financial asset prices. The Journal of Finance, 53, 499, 547.] | |||||
BibTeX:
@article{Zhang2009a,
author = {Zhang, Xibin and Brooks, Robert D. and King, Maxwell L.},
title = {A Bayesian approach to bandwidth selection for multivariate kernel regression with an application to state-price density estimation},
journal = {Journal of Econometrics},
year = {2009},
volume = {153},
number = {1},
pages = {21--32},
url = {http://www.sciencedirect.com/science/article/pii/S0304407609001080}
}
|
|||||
| Zhang, X., Qi, X., Zhou, X. and Pang, H. | An in situ method to measure the longitudinal and transverse dispersion coefficients of solute transport in soil | 2006 | Journal of Hydrology Vol. 328(3-4)The ICWRER - Symposium in Dresden, Germany, pp. 614-619 |
article | URL |
| Abstract: Summary The knowledge of hydraulic conductivity and solute transport parameters of top-soil is important in a variety of fields and their measurement has been an interest in both theory and practice. In this paper we present an in situ method to measure the longitudinal and transverse dispersion coefficients of solute movement by modifying the double-ring infiltrometer into a triple-ring infiltrometer. Water flow in the apparatus is controlled in one dimension and solute movement in three dimensions. The solute transport parameters can be measured simultaneously with the hydraulic conductivity. Analytical solutions are derived to describe the solute movement, and field experiment was carried out to calculate the solute parameters in homogeneous soil using a simple method developed based on the analytical solutions. Simulating results using these estimated parameters predict the observed breakthrough curves reasonably well. | |||||
BibTeX:
@article{Zhang2006,
author = {Zhang, Xiaoxian and Qi, Xuebin and Zhou, Xinguo and Pang, Hongbin},
title = {An in situ method to measure the longitudinal and transverse dispersion coefficients of solute transport in soil},
booktitle = {The ICWRER - Symposium in Dresden, Germany},
journal = {Journal of Hydrology},
year = {2006},
volume = {328},
number = {3-4},
pages = {614--619},
url = {http://www.sciencedirect.com/science/article/pii/S0022169406000278}
}
|
|||||
| Zhang, X., Siddiqi, Z., Song, X., Mandiwana, K.L., Yousaf, M. and Lu, J. | Atmospheric dry and wet deposition of mercury in Toronto | 2012 | Atmospheric Environment Vol. 50(0), pp. 60-65 |
article | URL |
| Abstract: Atmospheric mercury (Hg) speciation and deposition are critical in understanding the cycling of mercury in the environment. To estimate the dry and wet deposition of mercury in an urban environment, concentrations of gaseous elemental mercury (GEM), gaseous oxidized inorganic mercury (GOIM), mercury associated with particles having size less than 2.5 μm (Hg(p) < 2.5) (December 2003–November 2004) and total particulate mercury (THg(p)) (June 2004–December 2004) in the atmosphere, as well as the concentrations of methyl mercury (MeHg) and total mercury (THg) in atmospheric precipitation samples (June 2005–January 2006 and September 2007–March 2008), were measured in downtown Toronto, Canada. | |||||
BibTeX:
@article{Zhang2012,
author = {Zhang, Xiaotong and Siddiqi, Zia and Song, Xinjie and Mandiwana, Khakhathi L. and Yousaf, Muhammad and Lu, Julia},
title = {Atmospheric dry and wet deposition of mercury in Toronto},
journal = {Atmospheric Environment},
year = {2012},
volume = {50},
number = {0},
pages = {60--65},
url = {http://www.sciencedirect.com/science/article/pii/S1352231012000039}
}
|
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| Zhang, Y., Benson, D.A. and Reeves, D.M. | Time and space nonlocalities underlying fractional-derivative models: Distinction and literature review of field applications | 2009 | Advances in Water Resources Vol. 32(4), pp. 561-581 |
article | URL |
| Abstract: We investigate the spatiotemporal nonlocality underlying fractional-derivative models as a possible explanation for regional-scale anomalous dispersion with heavy tails. Properties of four fractional-order advection–dispersion equation (fADE) models were analyzed and compared systematically, including the space fADEs with either maximally positive or negative skewness, the time fADE with a temporal fractional-derivative 0 < γ < 1 , and the extension of the time fADE with 1 < γ < 2 . Space fADEs describe the dependence of local concentration change on a wide range of spatial zones (i.e., the space nonlocality), while time fADEs describe dynamic mass exchange between mobile and multiple immobile phases and therefore record the temporal history of concentration “loading” (i.e., the time-nonlocality). We then applied the fADEs as models of anomalous dispersion to four extensively-studied, regional-scale, natural systems, including a hillslope composed of fractured soils, a river with simultaneous active flow zones and various dead-zones, a relatively homogeneous glaciofluvial aquifer dominated by stratified sand and gravel, and a highly heterogeneous alluvial aquifer containing both preferential flowpaths and abundant aquitards. We find that the anomalous dispersion observed at each site might not be characterized reasonably or sufficiently by previous studies. In particular, the use of the space fADE with less than maximally positive skewness implies a spatial dependence on downstream concentrations that may not be physically realistic for solute transport in watershed catchments and rivers (where the influence of dead-zones on solute transport can be described by a temporal, not spatial, fractional model). Field-scale transport studies show that large ranges of solute displacement can be described by a space nonlocal, fractional-derivative model, and long waiting times can be described efficiently by a time-nonlocal, fractional model. The unknown quantitative relationship between the nonlocal parameters and the heterogeneity, and the similarity in concentration profiles that are solutions to the different nonlocal transport models, all demonstrate the importance of distinguishing the representative nonlocality (time and/or space) for any given regional-scale anomalous dispersion process. | |||||
BibTeX:
@article{Zhang2009,
author = {Zhang, Yong and Benson, David A. and Reeves, Donald M.},
title = {Time and space nonlocalities underlying fractional-derivative models: Distinction and literature review of field applications},
journal = {Advances in Water Resources},
year = {2009},
volume = {32},
number = {4},
pages = {561--581},
url = {http://www.sciencedirect.com/science/article/pii/S0309170809000165}
}
|
|||||
| Zhang, Y. and Gable, C.W. | Two-scale modeling of solute transport in an experimental stratigraphy | 2008 | Journal of Hydrology Vol. 348(3-4), pp. 395-411 |
article | URL |
| Abstract: A high-resolution non-stationary hydraulic conductivity map is generated based on an experimental stratigraphy. A heterogenous model is created, incorporating the complete conductivity variation. A hydrostratigraphic model (HSM) is also created which divides the space into discrete lithofacies units. For each unit, an equivalent conductivity is estimated using numerical up-scaling. Under a lateral hydraulic gradient, steady-state, incompressible groundwater flow experiments are conducted in both models. Within each flow field, conservative pulse-input line-source tracer is simulated. In the heterogeneous model, the tracer exhibits both scale-dependency in the observed longitudinal macrodispersivity and persistent long tailing associated with anomalous, non-Fickian dispersion. In comparison, HSM-predicted, global mean relative error of hydraulic head is 1.5%, that of groundwater flux is 0.77%. Using (small) hydrodynamic dispersivities, the HSM closely predicts the evolution of the tracer moments. A certain degree of tailing is also predicted, as this model has captured the largest scale, between-unit velocity variations. However, detailed plume shape is not captured, nor are the arrival and tailing of the breakthrough curves. Using macrodispersivity (both unit-specific and time-dependent), the breakthrough prediction has improved, especially the solute arrival time. Both macrodispersion models also capture the development of breakthrough asymmetry as well as power-law tailing. However, the development of a steep front and multiple peak concentrations are not captured. Similar observations are also found for a continuous-source injection. Overall, for the chosen boundary condition, the advection–dispersion equation can be used by the lithofacies model to capture certain key aspects of the bulk flow and transport behaviors, although displacement mapping reveals that heterogeneity-induced dispersion is correlated both in time and space, a likely result of the correlated velocity field. | |||||
BibTeX:
@article{Zhang2008,
author = {Zhang, Ye and Gable, Carl W.},
title = {Two-scale modeling of solute transport in an experimental stratigraphy},
journal = {Journal of Hydrology},
year = {2008},
volume = {348},
number = {3-4},
pages = {395--411},
url = {http://www.sciencedirect.com/science/article/pii/S0022169407005938}
}
|
|||||
| Zhang, Y., Gable, C.W. and Sheets, B. | Equivalent hydraulic conductivity of three-dimensional heterogeneous porous media: An upscaling study based on an experimental stratigraphy | 2010 | Journal of Hydrology Vol. 388(3-4), pp. 304-320 |
article | URL |
| Abstract: A critical issue facing large scale numerical simulation models is the estimation of representative hydraulic conductivity to account for the unresolved sub-grid-scale heterogeneity. In this study, two experiment-based hydraulic conductivity models offer a test case to evaluate this parameter. Each model contains a different heterogeneity pattern with connectivity characteristics that cannot be captured by univariate and bivariate statistics. A three-dimensional numerical upscaling method was developed to compute an equivalent conductivity full tensor for each model. The equivalent conductivities were compared to direct averages of local conductivities and to an effective conductivity predicted by several analytical methods. For each model, ln K variances up to 16 were evaluated. The impact of variance on both upscaled conductivity and three fluid flow connectivity factors was assessed. Results suggest: (1) the upscaling method gave reliable results comparable to an established method which only gives the diagonal components, (2) for both aquifer models, when ln K variances are low (less than 1.0), all analytical methods evaluated are nearly equally accurate; however, when variance becomes higher, the analytical methods of Desbarats (1992) and Noetinger and Haas (1996) were found to provide robust estimates of equivalent conductivities, despite possible violation of the multiGaussian assumption, (3) fluid flow characteristics in each model were significantly impacted by increasing variance, which can result in flow channeling in the lateral direction and increasing global anisotropy ratios of the equivalent conductivity, and (4) geometric connectivity, as analyzed by a percolation cluster analysis, indicates the importance of such features in focusing flow, in addition to the effects of high variance. | |||||
BibTeX:
@article{Zhang2010,
author = {Zhang, Ye and Gable, Carl W. and Sheets, Ben},
title = {Equivalent hydraulic conductivity of three-dimensional heterogeneous porous media: An upscaling study based on an experimental stratigraphy},
journal = {Journal of Hydrology},
year = {2010},
volume = {388},
number = {3-4},
pages = {304--320},
url = {http://www.sciencedirect.com/science/article/pii/S0022169410002726}
}
|
|||||
| Zhao, W., Picard, G., Leu, G. and Singer, P. | Characterization of Single-Phase Flow Through Carbonate Rocks: Quantitative Comparison of NMR Flow Propagator Measurements with a Realistic Pore Network Model | 2010 | Transport in Porous Media Vol. 81(2), pp. 305-315 |
article | URL |
| Abstract: We report here the quantitative comparisons between the measured NMR flow propagator of a carbonate rock and the flow propagator calculated with a porous network extracted from the micro-CT image of the twin plug. We developed a numerical model based on a particle tracking algorithm in pore space. The particle tracking in throats is described using the first arrival time distribution. As pores have an important volume fraction in the sample considered, we implemented a time-delay mechanism for particle transport in the pores. We consider that the nodes have volume and there is a transport of the tracking particles inside the nodes, which leads to an “apparent” time-delay. Simulations of flow propagator show good agreement with low field NMR experiments performed on the twin plug of the sample used for pore network extraction with a single adjustable parameter (that describes the dynamics in the pores). These results lead us to a better understanding of the connection between pore structure and the behavior of NMR flow propagator in fluid-saturated rocks and are essential in interpreting the experimental data and correlating NMR parameters to petrophysical properties. | |||||
BibTeX:
@article{Zhao2010,
author = {Zhao, Weishu and Picard, Guillemette and Leu, Gabriela and Singer, Philip},
title = {Characterization of Single-Phase Flow Through Carbonate Rocks: Quantitative Comparison of NMR Flow Propagator Measurements with a Realistic Pore Network Model},
journal = {Transport in Porous Media},
publisher = {Springer Netherlands},
year = {2010},
volume = {81},
number = {2},
pages = {305--315},
url = {http://dx.doi.org/10.1007/s11242-009-9402-5}
}
|
|||||
| Zhao, X., Wallace, R.B., Hyndman, D.W., Dybas, M.J. and Voice, T.C. | Heterogeneity of chlorinated hydrocarbon sorption properties in a sandy aquifer | 2005 | Journal of Contaminant Hydrology Vol. 78(4), pp. 327-342 |
article | URL |
| Abstract: Hydraulic conductivity and sorption coefficients for chlorinated hydrocarbons (chloroform, carbon tetrachloride and tetrachloroethylene) were evaluated for 216 sediment samples collected across a 15 m transect and a 21 m depth interval in a contaminated aquifer near Schoolcraft, Michigan. Relationships between hydraulic conductivity, linear sorption partition coefficients, grain size classes, and spatial location were investigated using linear regression analysis and geostatistical techniques. Clear evidence of layering was found in sorption properties, hydraulic conductivity and grain sizes. Conductivity correlated well with grain size, as expected, but sorption varied inversely with grain size, contrary to some previous reports. No significant correlation was found between sorption properties and hydraulic conductivity. This is likely due to the unexpected presence of small amounts of highly sorptive coal-like solids, which dominate the sorption behavior but have little effect on conductivity. The results demonstrate that recent findings regarding the high sorption capacity of coal materials found in soils can exert a controlling influence on contaminant transport. Designers of in situ remediation systems should be cautioned that 1) it is not reasonable to assume that sorption capacity and hydraulic conductivity are related, 2) sorption capacity and hydraulic conductivity are critical measurements for contaminant site characterization and subsequent transport modeling, 3) estimating sorption capacity from organic carbon measurement may lead to greater errors than performing sorption isotherms, and 4) it is more important to characterize vertical heterogeneity rather than horizontal heterogeneity because both sorption and hydraulic conductivity are correlated across longer distances in the horizontal plane. | |||||
BibTeX:
@article{Zhao2005,
author = {Zhao, Xianda and Wallace, Roger B. and Hyndman, David W. and Dybas, Michael J. and Voice, Thomas C.},
title = {Heterogeneity of chlorinated hydrocarbon sorption properties in a sandy aquifer},
journal = {Journal of Contaminant Hydrology},
year = {2005},
volume = {78},
number = {4},
pages = {327--342},
url = {http://www.sciencedirect.com/science/article/pii/S0169772205000902}
}
|
|||||
| Zhou, B., Jiang, Y., Wang, Q. and Shao, M. | Chloride transport in undisturbed soil columns of the loess Plateau | 2011 | African Journal of Agricultural Research Vol. 6(20), pp. 4807-4815 |
article | URL |
| Abstract: In soils containing preferential flow paths, both water and solute can move preferentially, bypassing much of the soil matrix. The object of this study was to examine the effect of preferential solute transport in Changwu (loamy soil) soil and Ansai soil (sandy soil) containing macroporosity. Miscible displacement experiments were conducted with 5 undisturbed soil columns (19.45 cm diameter, 43.5 cm long). Breakthrough curves (BTC’s) of Chloride were measured under water-saturated steady flow conditions. The data were simulated using three conceptual models. The results show that two-flow region model described the preferential solute transport much better than the two-region model and the convection dispersion equation (CDE), especially there were humps in the tailing side. Moreover, distinct double peaks were apparent with the increase of pore water velocity in a loamy soil column. In addition, high pore water velocity and small mass transfer coefficient between the two-flow regions enhanced the development of double BTC peaks. | |||||
BibTeX:
@article{Zhou2011,
author = {Zhou, Beibei and Jiang, Yanli and Wang, Quanjiu and Shao, Ming’an},
title = {Chloride transport in undisturbed soil columns of the loess Plateau},
journal = {African Journal of Agricultural Research},
year = {2011},
volume = {6},
number = {20},
pages = {4807--4815},
url = {http://www.academicjournals.org/ajar/abstracts/abstracts/abstracts2011/26%20Sept/Zhou%20et%20al.htm}
}
|
|||||
| Zhou, B., Shao, M. and Shao, H. | Effects of rock fragments on water movement and solute transport in a Loess Plateau soil | 2009 | Comptes Rendus Geoscience Vol. 341(6), pp. 462-472 |
article | URL |
| Abstract: Calcium carbonate concretions are present in the soil of the Loess Plateau as a result of pedogenesis. The presence of these small rock fragments can have a great impact on soil bulk density, structure and water storage properties, as well as on soil water movement and solute transport processes. We studied the effects of different gravimetric rock fragment contents in a soil (Rw) (0, 10, 20, 30, 40, 50, and 60%) on infiltration, saturated hydraulic conductivity (Ks) and solute transport. Both infiltration rates and the saturated hydraulic conductivity initially decreased with increasing rock fragment content to minimum values for Rw = 40%, and then increased. The Peck–Watson and Bouwer–Rice equations predicted Ks for low rock fragment contents but failed to forecast the observed trends. Cumulative infiltration over time was described well by a power function. Solute transport processes, determined using CaCl2 as a tracer, were accurately described by both the convection–dispersion equation (CDE) and the two-region model (T-R) although the T-R model fitted the experimental data a little better than the CDE, which is possibly more convenient to use. When Rw was about 40% solute transport parameters indicated that relatively more advection occurred in this mixture where immobile regions occupied the greatest proportion of the columns. | |||||
BibTeX:
@article{Zhou2009,
author = {Zhou, Beibei and Shao, Ming’an and Shao, Hongbo},
title = {Effects of rock fragments on water movement and solute transport in a Loess Plateau soil},
journal = {Comptes Rendus Geoscience},
year = {2009},
volume = {341},
number = {6},
pages = {462--472},
url = {http://www.sciencedirect.com/science/article/pii/S1631071309000820}
}
|
|||||
| Zhou, Q., Liu, H.-H., Bodvarsson, G. and Molz, F. | Evidence of Multi-Process Matrix Diffusion in a Single Fracture from a Field Tracer Test | 2006 | Transport in Porous Media Vol. 63(3), pp. 473-487 |
article | URL |
| Abstract: Compared to values inferred from laboratory tests on matrix cores, many field tracer tests in fractured rock have shown enhanced matrix diffusion coefficient values (obtained using a single-process matrix-diffusion model with a homogeneous matrix diffusion coefficient). To investigate this phenomenon, a conceptual model of multi-process matrix diffusion in a single-fracture system was developed. In this model, three matrix diffusion processes of different diffusion rates were assumed to coexist: (1) diffusion into stagnant water and infilling materials within fractures, (2) diffusion into a degraded matrix zone, and (3) further diffusion into an intact matrix zone. The validity of the conceptual model was then demonstrated by analyzing a unique tracer test conducted using a long-time constant-concentration injection. The tracer-test analysis was conducted using a numerical model capable of tracking the multiple matrix-diffusion processes. The analysis showed that in the degraded zone, a diffusion process with an enhanced diffusion rate controlled the steep rising limb and decay-like falling limb in the observed breakthrough curve, whereas in the intact matrix zone, a process involving a lower diffusion rate affected the long-term middle platform of slowly increasing tracer concentration. The different matrix-diffusion-coefficient values revealed from the field tracer test are consistent with the variability of matrix diffusion coefficient measured for rock cores with different degrees of fracture coating at the same site. By comparing to the matrix diffusion coefficient calibrated using single-process matrix diffusion, we demonstrated that this multi-process matrix diffusion may contribute to the enhanced matrix-diffusion-coefficient values for single-fracture systems at the field scale. | |||||
BibTeX:
@article{Zhou2006,
author = {Zhou, Quanlin and Liu, Hui-Hai and Bodvarsson, Gudmundur and Molz, Fred},
title = {Evidence of Multi-Process Matrix Diffusion in a Single Fracture from a Field Tracer Test},
journal = {Transport in Porous Media},
publisher = {Springer Netherlands},
year = {2006},
volume = {63},
number = {3},
pages = {473--487},
url = {http://dx.doi.org/10.1007/s11242-005-1123-9}
}
|
|||||
| Zhou, Q., Liu, H.-H., Molz, F.J., Zhang, Y. and Bodvarsson, G.S. | Field-scale effective matrix diffusion coefficient for fractured rock: Results from literature survey | 2007 | Journal of Contaminant Hydrology Vol. 93(1-4), pp. 161-187 |
article | URL |
| Abstract: Matrix diffusion is an important mechanism for solute transport in fractured rock. We recently conducted a literature survey on the effective matrix diffusion coefficient, Dme, a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale Dme values were calculated, either directly using data reported in the literature, or by reanalyzing the corresponding field tracer tests. The reanalysis was conducted for the selected tracer tests using analytic or semi-analytic solutions for tracer transport in linear, radial, or interwell flow fields. Surveyed data show that the scale factor of the effective matrix diffusion coefficient (defined as the ratio of Dme to the lab-scale matrix diffusion coefficient, Dm, of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. | |||||
BibTeX:
@article{Zhou2007,
author = {Zhou, Quanlin and Liu, Hui-Hai and Molz, Fred J. and Zhang, Yingqi and Bodvarsson, Gudmundur S.},
title = {Field-scale effective matrix diffusion coefficient for fractured rock: Results from literature survey},
journal = {Journal of Contaminant Hydrology},
year = {2007},
volume = {93},
number = {1-4},
pages = {161--187},
url = {http://www.sciencedirect.com/science/article/pii/S0169772207000241}
}
|
|||||
| Zhou, W. and Manousiouthakis, V.I. | Non-ideal reactor network synthesis through IDEAS: Attainable region construction | 2006 | Chemical Engineering Science Vol. 61(21), pp. 6936-6945 |
article | URL |
| Abstract: The attainable region (AR) for non-ideal reactor networks is constructed for the first time using the Infinite DimEnsionAl State-space (IDEAS) framework. The axial dispersion model is used to represent a non-ideal reactor, and it is shown that the IDEAS framework and associated Shrink-wrap algorithm are applicable to this model. A case study demonstrates that the AR for a reactor network featuring non-ideal dispersion models is larger than the AR for a reactor network featuring only ideal CSTR/PFR models. | |||||
BibTeX:
@article{Zhou2006a,
author = {Zhou, Wen and Manousiouthakis, Vasilios I.},
title = {Non-ideal reactor network synthesis through IDEAS: Attainable region construction},
journal = {Chemical Engineering Science},
year = {2006},
volume = {61},
number = {21},
pages = {6936--6945},
url = {http://www.sciencedirect.com/science/article/pii/S0009250906004118}
}
|
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| Zhu, J., Currens, J.C. and Dinger, J.S. | Challenges of using electrical resistivity method to locate karst conduits—A field case in the Inner Bluegrass Region, Kentucky | 2011 | Journal of Applied Geophysics Vol. 75(3), pp. 523-530 |
article | URL |
| Abstract: Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit. | |||||
BibTeX:
@article{Zhu2011,
author = {Zhu, Junfeng and Currens, James C. and Dinger, James S.},
title = {Challenges of using electrical resistivity method to locate karst conduits—A field case in the Inner Bluegrass Region, Kentucky},
journal = {Journal of Applied Geophysics},
year = {2011},
volume = {75},
number = {3},
pages = {523--530},
url = {http://www.sciencedirect.com/science/article/pii/S0926985111001893}
}
|
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| Zhu, W. and Hirth, G. | A network model for permeability in partially molten rocks | 2003 | Earth and Planetary Science Letters Vol. 212(3-4), pp. 407-416 |
article | URL |
| Abstract: Estimation of permeability in partially molten rocks requires knowledge of the melt phase distribution at the grain-scale. The melt distribution in an isotropic two-phase (solid+melt) system under equilibrium conditions is well defined. In such a system, all of the melt channels are identical and they are either interconnected or isolated depending upon the dihedral angle and the melt fraction. A simple power-law relationship between permeability, grain size and melt fraction has been derived for such a system. However, several factors, such as non-hydrostatic stress, anisotropic interfacial energy, or the existence of a third phase, will alter this relationship. We developed a three-dimensional network model to calculate permeability as a function of melt fraction for a system with a distribution of dihedral angles. In our model, each channel is treated as a prism with a length of the grain edges. The cross-sectional area of each prism is determined by a given dihedral angle and a melt fraction. By incorporating different dihedral angles into a network model, we are able to model permeability of partially molten rocks, taking the grain-scale heterogeneity of melt distribution into account. Our results show that the permeability of a heterogeneous system can be significantly smaller than the calculated permeability of an isotropic system with the same median dihedral angle. | |||||
BibTeX:
@article{Zhu2003,
author = {Zhu, Wenlu and Hirth, Greg},
title = {A network model for permeability in partially molten rocks},
journal = {Earth and Planetary Science Letters},
year = {2003},
volume = {212},
number = {3-4},
pages = {407--416},
url = {http://www.sciencedirect.com/science/article/pii/S0012821X03002644}
}
|
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| Zimmerman, M.D., Bennett, P.C., Sharp Jr., J.M. and Choi, W.-J. | Experimental determination of sorption in fractured flow systems | 2002 | Journal of Contaminant Hydrology Vol. 58(1-2), pp. 51-77 |
article | URL |
| Abstract: Fracture “skins” are alteration zones on fracture surfaces created by a variety of biological, chemical, and physical processes. Skins increase surface area, where sorption occurs, compared to the unaltered rock matrix. This study examines the sorption of organic solutes on altered fracture surfaces in an experimental fracture-flow apparatus. Fracture skins containing abundant metal oxides, clays, and organic material from the Breathitt Formation (Kentucky, USA) were collected in a manner such that skin surface integrity was maintained. The samples were reassembled in the lab in a flow-through apparatus that simulated ∼2.7 m of a linear fracture “conduit.” A dual-tracer injection scheme was utilized with the sorbing or reactive tracer compared to a non-reactive tracer (chloride) injected simultaneously. Sorption was assessed from the ratio of the first temporal moments of the breakthrough curves and from the loss of reactive tracer mass and evaluated as a function of flow velocity and solute type. The breakthrough curves suggest dual-flow regimes in the fracture with both sorbing and non-sorbing flow fields. Significant sorption occurs for the reactive components, and sorption increased with decreasing flow rate and decreasing compound solubility. Based on moment analysis, however, there was little retardation of the center of solute mass. These data suggest that non-equilibrium sorption processes dominate and that slow desorption and boundary layer diffusion cause extensive tailing in the breakthrough curves. | |||||
BibTeX:
@article{Zimmerman2002,
author = {Zimmerman, Mitchell D and Bennett, Philip C and Sharp Jr., John M and Choi, Wan-Joo},
title = {Experimental determination of sorption in fractured flow systems},
journal = {Journal of Contaminant Hydrology},
year = {2002},
volume = {58},
number = {1-2},
pages = {51--77},
url = {http://www.sciencedirect.com/science/article/pii/S0169772202000232}
}
|
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| Ziskind, G., Shmueli, H. and Gitis, V. | An analytical solution of the convection–dispersion–reaction equation for a finite region with a pulse boundary condition | 2011 | Chemical Engineering Journal Vol. 167(1), pp. 403-408 |
article | URL |
| Abstract: Transport of particles through porous media is commonly described by the convection–dispersion–reaction equation. Although experimental studies are obviously performed in finite domains, a comparison with analytical solutions is problematic because the latter are available for semi-infinite regions or are subject to unrealistic boundary conditions. | |||||
BibTeX:
@article{Ziskind2011,
author = {Ziskind, Gennady and Shmueli, Havatzelet and Gitis, Vitaly},
title = {An analytical solution of the convection–dispersion–reaction equation for a finite region with a pulse boundary condition},
journal = {Chemical Engineering Journal},
year = {2011},
volume = {167},
number = {1},
pages = {403--408},
url = {http://www.sciencedirect.com/science/article/pii/S1385894710011435}
}
|
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| Žižek, S., Horvat, M., Gibičar, D., Fajon, V. and Toman, M.J. | Bioaccumulation of mercury in benthic communities of a river ecosystem affected by mercury mining | 2007 | Science of The Total Environment Vol. 377(2-3), pp. 407-415 |
article | URL |
| Abstract: The presence of mercury in the river Idrijca (Slovenia) is mainly due to 500 years of mercury mining in this region. In order to understand the cycling of mercury in the Idrijca ecosystem it is crucial to investigate the role of biota. This study is part of an ongoing investigation of mercury biogeochemistry in the river Idrijca, focusing on the accumulation and speciation of mercury in the lower levels of the food chain, namely filamentous algae, periphyton and macroinvertebrates. Mercury analysis and speciation in the biota and in water were performed during the spring, summer and autumn seasons at four locations on the river, representing different degrees of mercury contamination. Total (THg) and methyl mercury (MeHg) were measured. The results showed that the highest THg concentrations in biota correlate well with THg levels in sediments and water. The level of MeHg is spatially and seasonally variable, showing higher values at the most contaminated sites during the summer and autumn periods. The percentage of Hg as MeHg increases with the trophic level from water (0.1–0.8%), algae (0.5–1.3%), periphyton (1.6–8.8%) to macroinvertebrates (0.1–100%), which indicates active transformation, accumulation and magnification of mercury in the benthic organism of this heavily contaminated torrential river. | |||||
BibTeX:
@article{Zizek2007,
author = {Žižek, Suzana and Horvat, Milena and Gibičar, Darija and Fajon, Vesna and Toman, Mihael J.},
title = {Bioaccumulation of mercury in benthic communities of a river ecosystem affected by mercury mining},
journal = {Science of The Total Environment},
year = {2007},
volume = {377},
number = {2-3},
pages = {407--415},
url = {http://www.sciencedirect.com/science/article/pii/S0048969707001866}
}
|
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| Zoua, S., Ma, J. and Koussis, A.D. | Analytical solutions to non-Fickian subsurface dispersion in uniform groundwater flow | 1996 | Journal of Hydrology Vol. 179(1-4), pp. 237-258 |
article | URL |
| Abstract: Analytical solutions are obtained by the Fourier transform technique for the one-, two-, and three-dimensional transport of a conservative solute injected instantaneously in a uniform groundwater flow. These solutions account for dispersive non-linearity caused by the heterogeneity of the hydraulic properties of aquifer systems and can be used as building blocks to construct solutions by convolution (principle of superposition) for source conditions other than slug injection. The dispersivity is assumed to vary parabolically with time and is thus constant for the entire system at any given time. Two approaches for estimating time-dependent dispersion parameters are developed for two-dimensional plumes. They both require minimal field tracer test data and, therefore, represent useful tools for assessing real-world aquifer contamination sites. The first approach requires mapped plume-area measurements at two specific times after the tracer injection. The second approach requires concentration-versus-time data from two sampling wells through which the plume passes. Detailed examples and comparisons with other procedures show that the methods presented herein are sufficiently accurate and easier to use than other available methods. | |||||
BibTeX:
@article{Zoua1996,
author = {Zoua, Shimin and Ma, Jianghai and Koussis, Antonis D.},
title = {Analytical solutions to non-Fickian subsurface dispersion in uniform groundwater flow},
journal = {Journal of Hydrology},
year = {1996},
volume = {179},
number = {1-4},
pages = {237--258},
url = {http://www.sciencedirect.com/science/article/pii/0022169495028307}
}
|
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| Zuber, A. | On the interpretation of tracer data in variable flow systems | 1986 | Journal of Hydrology Vol. 86(1-2), pp. 45-57 |
article | URL |
| Abstract: A general formula for the interpretation of tracer experiments in variable flow has been derived, based on generalization of the transit (exit) time distribution of the tracer mass flux resulting from an instantaneous injection. Systems with a constant volume or a constant turnover time of the dynamic part of the system are considered. A possible difference between the turnover time and the mean transit time of tracer is allowed for in the final formulae, for cases as in groundwater in which the tracer is delayed due to molecular diffusion into stagnant water. | |||||
BibTeX:
@article{Zuber1986,
author = {Zuber, A.},
title = {On the interpretation of tracer data in variable flow systems},
journal = {Journal of Hydrology},
year = {1986},
volume = {86},
number = {1-2},
pages = {45--57},
url = {http://www.sciencedirect.com/science/article/pii/0022169486900053}
}
|
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| Zuber, A. and Motyka, J. | Matrix porosity as the most important parameter of fissured rocks for solute transport at large scales | 1994 | Journal of Hydrology Vol. 158(1-2), pp. 19-46 |
article | URL |
| Abstract: Simple considerations show that tracer and/or pollutant velocity at large scales in fissured rocks can be described by the formula vtnp ≈ (ΔHΔx)k, where vt is the mean velocity of a conservative tracer or pollutant, np is the matrix porosity, ΔHΔx is the hydraulic gradient, and k is the hydraulic conductivity. The applicability of the formula is discussed and its validity tested in several case studies in which hydraulic conductivities calculated from either pollutant transport velocity or environmental tracer ages were compared with those known or estimated from other determinations. The influence of matrix diffusion on the environmental tracer ages can also be proved independently by comparison of the rock volume (Vrock) estimated from the hydrogeologic map with that calculated from volumetric flow rate (Q), age of tracer (tt) and matrix porosity (Vrock ≈ Qttnp). | |||||
BibTeX:
@article{Zuber1994,
author = {Zuber, A. and Motyka, J.},
title = {Matrix porosity as the most important parameter of fissured rocks for solute transport at large scales},
journal = {Journal of Hydrology},
year = {1994},
volume = {158},
number = {1-2},
pages = {19--46},
url = {http://www.sciencedirect.com/science/article/pii/0022169494900442}
}
|
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| Zuber, A., Różański, K., Kania, J. and Purtschert, R. | On some methodological problems in the use of environmental tracers to estimate hydrogeologic parameters and to calibrate flow and transport models | 2011 | Hydrogeology Journal Vol. 19(1), pp. 53-69 |
article | URL |
| Abstract: Environmental tracers are used qualitatively for a better formulation of conceptual models and quantitatively for assessing groundwater ages with the aid of box models or for calibrating numerical transport models. Unfortunately, tracers often yield different ages that do not represent uniquely the water ages. Difficulties result also from different definitions of age, e.g. water age, advective age, tracer age, or radiometric tracer age, that are measured differently and depend on aquifer parameters and characteristics of particular tracers. Even the movement of an ideal tracer can be delayed with respect to the advective movement of water due to diffusion exchange between mobile and immobile water zones, which for fissured rocks or thin aquifers, may lead to significant differences between advective and tracer ages, i.e. also between advective and tracer velocities. The advective velocity is of importance in water resources considerations as being related to Darcy velocity, whereas the tracer velocity is a more useful term for the prediction of pollutant transport. When a groundwater system changes from one hydrodynamic steady state to another, environmental tracers need much more time to reach a new steady state. Several tracer studies are recalled as examples of tracer-specific effects on the estimations of groundwater age. | |||||
BibTeX:
@article{Zuber2011,
author = {Zuber, Andrzej and Różański, Kazimierz and Kania, Jarosław and Purtschert, Roland},
title = {On some methodological problems in the use of environmental tracers to estimate hydrogeologic parameters and to calibrate flow and transport models},
journal = {Hydrogeology Journal},
publisher = {Springer Berlin / Heidelberg},
year = {2011},
volume = {19},
number = {1},
pages = {53--69},
url = {http://dx.doi.org/10.1007/s10040-010-0655-4}
}
|
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| Zwietering, T. | A backmixing model describing micromixing in single-phase continuous-flow systems | 1984 | Chemical Engineering Science Vol. 39(12), pp. 1765-1778 |
article | URL |
| Abstract: A new model is presented which describes the mixing of fluids entering a continuous-flow reactor. The model contains only one parameter characterizing the micromixing rate, in a turbulent field. It pays special attention to the dilution of the entering stream of fluid by the surrounding older fluid. The dilution causes not only a change in concentration, but also a huge expansion of the stream. | |||||
BibTeX:
@article{Zwietering1984,
author = {Zwietering, Th.N.},
title = {A backmixing model describing micromixing in single-phase continuous-flow systems},
journal = {Chemical Engineering Science},
year = {1984},
volume = {39},
number = {12},
pages = {1765--1778},
url = {http://www.sciencedirect.com/science/article/pii/0009250984801128}
}
|
|||||
| Zwietering, T. | The degree of mixing in continuous flow systems | 1959 | Chemical Engineering Science Vol. 11(1), pp. 1-15 |
article | URL |
| Abstract: The concepts of Danckwerts about the degrees of mixing and segregation are extended to the case of a continuous flow system with an arbitrary but known residence time distribution. For this purpose a life-expectation distribution is defined in addition to the age distribution. Further, a condition of maximum mixedness (minimum segregation) is defined for such a system. This condition, and the condition of complete segregation introduced by Danckwerts, are two opposite extremes. When the system is a reactor in which a chemical reaction of an arbitrary order takes place, the conversion can be calculated for both cases; thus two limits are obtained between which the conversion must lie. | |||||
BibTeX:
@article{Zwietering1959,
author = {Zwietering, Th.N.},
title = {The degree of mixing in continuous flow systems},
journal = {Chemical Engineering Science},
year = {1959},
volume = {11},
number = {1},
pages = {1--15},
url = {http://www.sciencedirect.com/science/article/pii/0009250959800683}
}
|
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| Modeling of chemical kinetics and reactor design [BibTeX] |
2001 | book | URL | ||
BibTeX:
@book{Coker2001,,
title = {Modeling of chemical kinetics and reactor design},
publisher = {Gulf Professional Publishing},
year = {2001},
url = {http://www.sciencedirect.com/science/book/9780884154815}
}
|
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| Methods in karst hydrogeology [BibTeX] |
2007 | (26), pp. - | book | ||
BibTeX:
@book{Goldscheider2007a,,
title = {Methods in karst hydrogeology},
publisher = {Taylor & Francis},
year = {2007},
number = {26},
pages = {--}
}
|
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| Advances in Chemical Engineering: Mathematics in Chemical Kinetics and Engineering [BibTeX] |
2008 | Vol. 34, pp. - |
book | ||
BibTeX:
@book{Marin2008,,
title = {Advances in Chemical Engineering: Mathematics in Chemical Kinetics and Engineering},
publisher = {Academic Press},
year = {2008},
volume = {34},
pages = {--}
}
|
|||||
| Handbook of industrial mixing: science and practice [BibTeX] |
2004 | , pp. - | book | ||
BibTeX:
@book{Paul2004,,
title = {Handbook of industrial mixing: science and practice},
publisher = {Wiley-Interscience},
year = {2004},
pages = {--}
}
|
|||||
| CRC Standard Mathematical Tables [BibTeX] |
1970 | , pp. - | book | ||
BibTeX:
@book{Selby1970,,
title = {CRC Standard Mathematical Tables},
publisher = {The Chemical Rubber Co.},
year = {1970},
pages = {--},
edition = {Eighteenth}
}
|
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| Information resources in toxicology [BibTeX] |
2009 | , pp. - | book | ||
BibTeX:
@book{Wexler2009,,
title = {Information resources in toxicology},
publisher = {Academic Press},
year = {2009},
pages = {--},
edition = {Fourth}
}
|
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| CRC Standard Mathematical Tables and Formulae [BibTeX] |
1996 | , pp. - | book | ||
BibTeX:
@book{Zwillinger1996,,
title = {CRC Standard Mathematical Tables and Formulae},
publisher = {CRC Press, Inc.},
year = {1996},
pages = {--},
edition = {Thirtieth}
}
|
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| Groundwater quality reflect karst development: a case study in central-west Florid : J. Chen, G. Thomas & S. Upchurch, in: Karst geohazards: engineering and environmental problems in karst terrane. Proc. 5th conference, Gatlinburg 1995, ed B.F. Beck, (Balkema), 1995, pp 103–109 [BibTeX] |
1996 | International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts Vol. 33(2), pp. A56- |
article | URL | |
BibTeX:
@article{1996,,
title = {Groundwater quality reflect karst development: a case study in central-west Florid : J. Chen, G. Thomas & S. Upchurch, in: Karst geohazards: engineering and environmental problems in karst terrane. Proc. 5th conference, Gatlinburg 1995, ed B.F. Beck, (Balkema), 1995, pp 103–109},
journal = {International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts},
year = {1996},
volume = {33},
number = {2},
pages = {A56--},
url = {http://www.sciencedirect.com/science/article/pii/0148906296838095}
}
|
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| Activism [BibTeX] |
1984 | Public Relations Review Vol. 10(4), pp. 71-229 |
article | DOI URL | |
BibTeX:
@article{1984,,
title = {Activism},
journal = {Public Relations Review},
year = {1984},
volume = {10},
number = {4},
pages = {71--229},
url = {http://www.sciencedirect.com/science/article/pii/S0363811184800843},
doi = {http://dx.doi.org/10.1016/s0363-8111(84)80084-3}
}
|
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