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This textbook develops the basic ideas of transport models in hydrogeology, including diffusion-dispersion processes, advection, and adsorption or reaction. The book serves as an excellent text or supplementary reading in courses in applied mathematics, contaminant hydrology, ground water modeling, or hydrogeology.
This tutorial provides the application of the coupling interface OGS#IPhreeqc (open-source scientific software) to model reactive mass transport processes in environmental subsurface systems. It contains general information regarding reactive transport modeling and step-by-step model set-up with OGS#IPhreeqc and related components such as GINA and ParaView. Benchmark examples (1D to 2D) are presented in detail. The book is intended primarily for graduate students and applied scientists who deal with reactive transport modeling. It also gives valuable information to the professional geoscientists wishing to advance their knowledge in numerical simulation, with the focus on the fate and transport of nitrate. It is the third volume in a series that represents the further application of computational modeling in hydrological science.
To understand hydrochemistry and to analyze natural as well as man-made impacts on aquatic systems, hydrogeochemical models have been used since the 1960’s and more frequently in recent times. Numerical groundwater flow, transport, and geochemical models are important tools besides classical deterministic and analytical approaches. Solving complex linear or non-linear systems of equations, commonly with hundreds of unknown parameters, is a routine task for a PC. Modeling hydrogeochemical processes requires a detailed and accurate water analysis, as well as thermodynamic and kinetic data as input. Thermodynamic data, such as complex formation constants and solubility-products, are often provided as databases within the respective programs. However, the description of surface-controlled reactions (sorption, cation exchange, surface complexation) and kinetically controlled reactions requires additional input data. Unlike groundwater flow and transport models, thermodynamic models, in principal, do not need any calibration. However, considering surface-controlled or kinetically controlled reaction models might be subject to calibration. Typical problems for the application of geochemical models are: • speciation • determination of saturation indices • adjustment of equilibria/disequilibria for minerals or gases • mixing of different waters • modeling the effects of temperature • stoichiometric reactions (e.g. titration) • reactions with solids, fluids, and gaseous phases (in open and closed systems) • sorption (cation exchange, surface complexation) • inverse modeling • kinetically controlled reactions • reactive transport Hydrogeochemical models depend on the quality of the chemical analysis, the boundary conditions presumed by the program, theoretical concepts (e.g.

Groundwater Monitoring and Management Through Hydrogeochemical Modeling Approach: Approaches and Advancements of Analytical Techniques in Hydrogeochemistry; Basics of Hydrogeochemical Modeling; 3. An Overview on NETPATH Geochemical Modeling- A Case Study from Coastal Aquifer of Pondicherry; 4. Speciation of Ions in Groundwater and its Applications; 5. Understanding the Groundwater and Surface Water Interactions Through Hydrogeochemical and Multivariate Statistical Modeling Approach; 6. Statistical Methods for Characterization of Water Quality Variables in Hydrogeochemical Studies; 7. Applications of Overla Analysis Using Geographical Information System in Water Research; 8. Biogeochemical Modeling Of the Aquatic Ecosystems; 9. Contaminant Transport Modeling in Groundwater Management; 10. Rock Water Interaction in Groundwater and Using Geochemical Modelling

S. Chidambaram

Published: 2010

Total Pages: 142


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At least two distinct kinds of hydrogeochemical models have evolved historically for use in analyzing contaminant transport, but each has important limitations. One kind, focusing on organic contaminants, treats biodegradation reactions as parts of relatively simple kinetic reaction networks with no or limited coupling to aqueous and surface complexation and mineral dissolution/precipitation reactions. A second kind, evolving out of the speciation and reaction path codes, is capable of handling a comprehensive suite of multicomponent complexation (aqueous and surface) and mineral precipitation and dissolution reactions, but has not been able to treat reaction networks characterized by partial redox disequilibrium and multiple kinetic pathways. More recently, various investigators have begun to consider biodegradation reactions in the context of comprehensive equilibrium and kinetic reaction networks (e.g. Hunter et al. 1998, Mayer 1999). Here we explore two examples of multiple equilibrium and kinetic reaction pathways using the reactive transport code GIMRT98 (Steefel, in prep.): (1) a computational example involving the generation of acid mine drainage due to oxidation of pyrite, and (2) a computational/field example where the rates of chlorinated VOC degradation are linked to the rates of major redox processes occurring in organic-rich wetland sediments overlying a contaminated aerobic aquifer.
An application of geochemical modeling to environmental problems, illustrated with case studies of real-world environmental investigations.
This book covers theoretical aspects of the physical processes, derivation of the governing equations and their solutions. It focusses on hydraulics, hydrology, and contaminant transport, including implementation of computer codes with practical examples. Python-based computer codes for all the solution approaches are provided for better understanding and easy implementation. The mathematical models are demonstrated through applications and the results are analyzed through data tables, plots, and comparison with analytical and experimental data. The concepts are used to solve practical applications like surface and ground water flow, flood routing, crop water requirement and irrigation scheduling. Combines the area of computational hydraulics, hydrology, and water resources engineering with Python Gives deep description of the basic equations and the numerical solutions of both 1D and 2D problems including the numerical codes Includes step-by-step translation of numerical algorithms in computer codes with focus on learners and practitioners Demonstration of theory, mathematical models through practical applications Analysis of each example through data tables, plots, and correlation with reality This book is aimed at senior undergraduates and graduate students in Civil Engineering, Coastal Engineering, Hydrology, and Water Resources Engineering.
1. General Significance of Geochemical Models of Hydrothermal Systems,- 2. Concepts, Classification and Chemistry of Geothermal Systems,- 3.Theory of Chemical Modeling,- 4. Specific Features of Coupled Fluid Flow and Chemical Reaction,- 5. Fossil Hydrothermal Systems,- 6. Recent Hydrothermal Systems,- 7. Reservoir Management.
PHREEQC version 3 is a computer program written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC implements several types of aqueous models: two ion-association aqueous models (the Lawrence Livermore National Laboratory model and WATEQ4F), a Pitzer specific-ion-interaction aqueous model, and the SIT (Specific ion Interaction Theory) aqueous model. Using any of these aqueous models, PHREEQC has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and one-dimensional (1D) transport calculations with reversible and irreversible reactions, which include aqueous, mineral, gas, solid-solution, surface-complexation, and ion-exchange equilibria, and specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and pressure and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters within specified compositional uncertainty limits.
This report presents the development of a hydrogeochemical transport model for multicomponent systems. The model is designed for applications to proper hydrological setting, accommodation of complete suite of geochemical equilibrium processes, easy extension to deal with chemical kinetics, and least constraints of computer resources. The hydrological environment to which the model can be applied is the heterogeneous, anisotropic, saturated-unsaturated subsurface media under either transient or steady state flow conditions. The geochemical equilibrium processes included in the model are aqueous complexation, adsorption-desorption, ion exchange, precipitation-dissolution, redox, and acid-base reactions. To achieve the inclusion of the full complement of these geochemical processes, total analytical concentrations of all chemical components are chosen as the primary dependent variables in the hydrological transport equations. Attendant benefits of this choice are to make the extension of the model to deal with kinetics of adsorption-desorption, ion exchange, precipitation-dissolution, and redox relatively easy. To make the negative concentrations during the iteration between the hydrological transport and geochemical equilibrium least likely, an implicit form of transport equations are proposed. To alleviate severe constraints of computer resources in terms of central processing unit (CPU) time and CPU memory, various optional numerical schemes are incorporated in the model. The model consists of a hydrological transport module and geochemical equilibrium module. Both modules were thoroughly tested in code consistency and were found to yield plausible results. The model is verified with ten examples. 79 refs., 21 figs., 17 tabs.