HR: 1340h
AN: H43C-0384    [Abstracts]
TI: Geochemical Modeling of Soils: A Soil-Component Approach
AU: * Lee, L
EM: rclee@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center MS 973, Denver, CO 80225 United States
AB: Quantitative modeling of pedological processes begins by placing measured soil properties within a framework that allows the identification and testing of geochemical and biological mechanisms. For example, mass-balance interpretations of pedogenesis describe gains and losses of chemical elements in a manner that can implicate specific mineral reactions and biological processes. Soil-component modeling is an extension of the mass-balance interpretation of pedogenesis that describes observed gains and losses in chemical elements, ion-exchange capacity, and soil volume with hypothesized sets of soil components such as minerals and soil organic matter. These models are calculated using mole-balance equations for mineral components, associated equations for ion-exchange capacities and volumes of minerals and soil organic matter, and equations that account for the uncertainties of all analytical data. The GRex computer program was written to evaluate these relations and identify combinations of minerals and organic matter that can simultaneously account for the observed chemical and physical properties of a single soil or net-change in properties between two related soils. The power of this approach is that many alternative scenarios of mineral and organic matter assemblages can be quickly defined that may provide insight into the geochemical mechanisms of pedogenesis, or suggest additional field and laboratory work. Examples of this modeling method, as applied to data on soils from sites along a marine terrace chronosequence in Oregon and a basalt climosequence on the island of Hawaii, will be shown.
DE: 1886 Weathering (1625)
DE: 1010 Chemical evolution
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting