To understand hydrochemistry and to analyze natural as well as man-made impacts on aquatic systems, hydrogeochemical models have been used since the 1960as 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: ac speciation ac determination of saturation indices ac adjustment of equilibria/disequilibria for minerals or gases ac mixing of different waters ac modeling the effects of temperature ac stoichiometric reactions (e.g. titration) ac reactions with solids, fluids, and gaseous phases (in open and closed systems) ac sorption (cation exchange, surface complexation) ac inverse modeling ac kinetically controlled reactions ac reactive transport Hydrogeochemical models depend on the quality of the chemical analysis, the boundary conditions presumed by the program, theoretical concepts (e.g.Presentation in predominance diagrams The presentation of the predominant species for each redox system is called stability (or better) predominance diagram (also called EH-pH or pE-pH diagrams). Predominance diagrams are extremelyanbsp;...
|Author||:||Broder J. Merkel, Britta Planer-Friedrich|
|Publisher||:||Springer Science & Business Media - 2008-05-30|