The responsible use of our Nation's ground-water resources requires an ability to predict changes in water quality as a result of human impacts. Prediction of chemical quality in the ground-water environment depends on a detailed understanding of both chemical and hydrologic processes. To determine the spatial and temporal variability of ground-water quality, it is necessary to identify reactions occurring in the system, to define their kinetic and thermodynamic properties, and to determine how the configuration of the hydrologic regime influences ground-water quality. The objectives of this project are to: (1) identify chemical reactions in ground-water systems using observed chemical and isotopic composition of dissolved solutes and minerals, (2) develop geochemical models to aid in interpretation of chemical and isotopic data from ground- water systems, (3) develop tools for age-dating groundwaters, (4) determine rates of chemical reactions in ground-water systems from field hydrochemical data and modeled water ages, (5) conduct laboratory experiment to obtain thermodynamic data for mineral- water systems for use in geochemical models, (6) obtain laboratory kinetic data on rates of mineral dissolution and precipitation for comparison with field rates, and (7) study the fundamental mechanisms of mineral dissolution and precipitation as they apply to pure phases and to solid-solution minerals. For information related to tools for age-dating ground-water, see the Reston Chlorofluorocarbon Laboratory
