National Research Program

Chemical Models of Natural Systems

The increasing need for understanding the effects of human activity on the chemistry of natural systems requires a continually increasing degree of sophistication in the models used to describe the processes through which these effects occur. Such models include thermodynamic and (or) kinetic models of: aqueous speciation, the chemistry of dissolved gases, gaseous and aqueous diffusion, transport of constituents across interfaces, redox processes, mineral-water interactions, the chemistry of anthropogenic inputs to natural systems, and isotope effects associated with these processes. Project objectives are to (1) identify the factors influencing the reactions and transport of solutes in natural waters; (2) evaluate reactions and transport processes for volatile constituents in unsaturated zones; (3) identify processes occurring at the saturated-unsaturated interface (the capillary fringe); and (4) investigate the application of isotope effects as a tool for understanding these processes.


Thorstenson, D.C., and Parkhurst, D.L., 2004, Calculation of individual isotope equilibrium constants for geochemical reactions: Geochimica et Cosmochimica Acta, v. 68, p. 2,449-2,465. (on-line abstract)

Thorstenson, D.C., and Parkhurst, D.L, 2002, Calculation of individual isotope equilibrium constants for implementation in geochemical models: U.S. Geological Survey Water-Resources Investigations Report 02-4172, 129 p. (on-line report)

Donald C. Thorstenson
U.S. Geological Survey, P.O. Box 25046, ms413, Denver Federal Center, Lakewood, CO
Telephone: 303-236-6229

 For information on additional projects in the National Research Program, see Indexes to NRP projects and bibliographies

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