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AuthorTitleYearJournal/ProceedingsReftypeDOI/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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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 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}
}
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}
}
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}
}
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}
}
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 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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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&#xa0;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}
}
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&#xa0;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}
}
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}
}
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&#xa0;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&#xa0;a) are observed in the groundwater fluctuation zone in a thin layer, which is from 1–2&#xa0;m-thick in the lower parts and 10–15&#xa0;m-thick in the upper parts of the catchments. Below this thin layer, the groundwater apparent age is high (between 10 and 25&#xa0;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&#xa0;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&#8211;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}
}
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}
}
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}
}
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}
}
Barger, G.L. and Thom, H.C.S. Evaluation of Drought Hazard 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}
}
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}
}
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}
}
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 &#8220;equivalent&#8221; 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 &#8220;effective&#8221; 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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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&#xa0;=&#xa0;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}
}
Bateman, H. and of Technology Bateman Manuscript Project, C.I. Tables of integral transforms: Based, in part, on notes left by Harry Bateman 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 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 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}
}
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}
}
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}
}
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−&#xa0;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&#xa0;±&#xa0;6.2 mg L−&#xa0;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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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&#xa0;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&#xa0;±&#xa0;0.17&#xa0;mM&#xa0;d−1) compared to the circumneutral pH soil (0.43&#xa0;±&#xa0;0.31&#xa0;mM&#xa0;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}
}
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}
}
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&#xa0;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 &lt;1&#xa0;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&#xa0;km inland), but mixing is limited where the conduit is entirely filled with fresh water (sites &gt;4&#xa0;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&#xa0;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}
}
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&#xa0;m and length of 5.2&#xa0;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&#xa0;m to 0.9&#xa0;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&#xa0;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}
}
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}
}
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}
}
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}
}
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}
}
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&#8722;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 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&#xa0;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&#xa0;=&#xa0;5.9) to the hydrophilic (pKow&#xa0;=&#xa0;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&#xa0;years for a stack height of 2&#xa0;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 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&#xa0;&lt;&#xa0;α&#xa0;⩽&#xa0;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&#xa0;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 &gt;10 pore-volumes. When there was biodegradation in the soil column, &gt;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 &gt; 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&#xa0;cm) with a saturated hydraulic conductivity, K0, of 0.2&#xa0;cm/s and a lower layer with a K0 of 0.12&#xa0;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}
}
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}
}
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}
}
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}
}
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&#xa0;km2) headwater catchments that represent a range of suburban development (high density residential, medium density residential, and undeveloped) within the Croton River basin, 70&#xa0;km north of New York City. Precipitation, stream discharge, and groundwater levels were monitored at 10–30&#xa0;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 1999 , pp. -  book  
BibTeX:
@book{Bury1999,
  author = {Bury, Karl V.},
  title = {Statistical Distributions in Engineering},
  publisher = {Cambridge University Press},
  year = {1999},
  pages = {--}
}
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}
}
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 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}
}
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/}
}
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}
}
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&#xa0;mg&#xa0;kg−1 dry weight, decreasing in order of inoculated-manual turned compost (IMTC)&#xa0;&gt;&#xa0;manual turned compost (MTC)&#xa0;&gt;&#xa0;continuous aerated compost (CAC)&#xa0;&gt;&#xa0;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}
}
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}
}
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}
}
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}
}
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&#xa0;&lt;&#xa0;102) the use of herringbone structures does not have an impact on the RTD, however at high Peclet numbers (Pe&#xa0;&gt;&#xa0;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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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 &gt; phenanthrene &gt; 3-2-methylphenanthrenes &gt; intermediate chain length n-alkanes &gt; longer chain length n-alkanes &gt; 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 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, &#981;R, 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&#xa0;°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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
De Waele, J., Gutiérrez, F., Parise, M. and Plan, L. Geomorphology and natural hazards in karst areas: A review 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}
}
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}
}
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}
}
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&#xa0;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&#xa0;μg&#xa0;P&#xa0;L−1) was reduced to a mean of 10&#xa0;μg&#xa0;P&#xa0;L−1 at the raceway outflow and 8&#xa0;μg&#xa0;P&#xa0;L−1 exiting the limerock filters. Total P removal for the entire system was 0.32&#xa0;g&#xa0;m−2 per year, or 46% of the inflow TP load, and uptake rates (k values) were 24 and 32&#xa0;m per year for the raceway and the raceway/limerock filter system, respectively. Most TP removal occurred within the first 3&#xa0;m of the raceways at an HRT of 1.3&#xa0;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&#xa0;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 (&gt;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&#xa0;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&#xa0;μg&#xa0;L−1 were reduced to 15 and 17&#xa0;μg&#xa0;L−1 in the muck and LR mesocosms, respectively. Mesocosm P loading rates (mean&#xa0;=&#xa0;1.75&#xa0;g&#xa0;m−2&#xa0;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}
}
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&#xa0;+&#xa0;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}
}
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}
}
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}
}
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&#xa0;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&#xa0;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&#xa0;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}
}
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&#xa0;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&#xa0;μg/L) was reduced consistently to near the detection limit (2&#xa0;μg/L) in the 3.5- and 7.0-day HRT treatments, and to a mean of 9&#xa0;μg/L in the 1.5-day HRT treatment. The mean inflow TP concentration (107&#xa0;μg/L) was reduced to 52, 29 and 23&#xa0;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&#xa0;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&#xa0;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&#xa0;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&#xa0;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&#xa0;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&#xa0;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&#xa0;mg&#xa0;l−1 (0.33 and 1.0&#xa0;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}
}
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}
}
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}
}
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}
}
Divine, C.E. and McDonnell, J.J. The future of applied tracers in hydrogeology 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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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&#xa0;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}
}
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}
}
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 &gt; 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 &#8220;natural state&#8221; 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 &#8220;signal.&#8221; 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&#xa0;m3&#xa0;day−1 (12&#xa0;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&#xa0;km (13&#xa0;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 &gt;&#xa0;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&#xa0;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&#xa0;×&#xa0;10−9, 3.7&#xa0;×&#xa0;10−9 and 1.0&#xa0;×&#xa0;10−8&#xa0;m&#xa0;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&#xa0;×&#xa0;10−9 and 9.8&#xa0;×&#xa0;10−9&#xa0;m&#xa0;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 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 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&#xa0;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 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 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}
}
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}
}
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}
}
Embry, I. Social Sustainability and the Pursuit of Design in Engineering 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&#xa0;=&#xa0;−34.7‰, 1σ&#xa0;=&#xa0;3.6) consistent with chemolithoautotrophic carbon fixation from a dissolved inorganic carbon reservoir (cave water, mean δ13C&#xa0;=&#xa0;−7.4‰ for two springs, n&#xa0;=&#xa0;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&#xa0;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&#xa0;μL&#xa0;s−1 to 1&#xa0;ml&#xa0;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}
}
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}
}
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&#xa0;−&#xa0;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}
}
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 (&lt;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 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&#xa0;=&#xa0;0.00129&#xa0;·&#xa0;Eff&#xa0;−&#xa0;0.0300, R2&#xa0;=&#xa0;0.992) and modified (β2&#xa0;=&#xa0;0.000547&#xa0;·&#xa0; Eff&#xa0;−&#xa0;0.0169, R2&#xa0;=&#xa0;0.979) tubes exhibited a similar and linear relationship.Under the conditions investigated (38&#xa0;&lt;&#xa0;Re&#xa0;&lt;&#xa0;10,000, 4&#xa0;&lt;&#xa0;Pr&#xa0;&lt;&#xa0;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)&#xa0;+&#xa0;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&#xa0;=&#xa0;0.995&#xa0;·&#xa0;ts&#xa0;R2&#xa0;=&#xa0;0.64, error&#xa0;&lt;&#xa0;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 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}
}
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&#xa0;m upstream from the main spring and 48&#xa0;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&#xa0;=&#xa0;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&#xa0;=&#xa0;1.8&#xa0;×&#xa0;106&#xa0;pfu/mL) and H40/1 (Co&#xa0;=&#xa0;5.9&#xa0;×&#xa0;106&#xa0;pfu/mL) could reach sampling points 10&#xa0;m below ground less than 30&#xa0;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&#xa0;=&#xa0;2.3&#xa0;×&#xa0;104&#xa0;pfu/mL) and H40/1 (Co&#xa0;=&#xa0;1.3&#xa0;×&#xa0;105&#xa0;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 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 experime