USGS: Partitioning of Solutes between Solid and Aqueous Phases
Partitioning of Solutes between Solid and Aqueous Phases
When solutes are introduced into a ground water system, or into surface waters, physicochemical reactions may occur between the dissolved solutes and native solid materials. Detailed knowledge of the chemical reactions that occur at solid surfaces is required to assess the impact of such inputs on water quality. In addition, the geochemical cycling of some trace elements may be controlled by the distribution between solid and aqueous phases. A fundamental understanding of the surface chemistry reactions is needed to incorporate a mathematical description of these processes into chemical equilibrium and solute transport models. Objectives of this project are to study the adsorption behavior of inorganic and organic solutes on particulate materials that are important in natural systems, including aluminosilicate minerals, colloids (such as hydrous oxides of aluminum, silicon, iron, or manganese), and solids of biogenic origin; to derive stability constants for the partitioning of solutes between a particular solid surface and the aqueous phase and understand the mechanisms of surface bonding from a theoretical perspective, including electrical double layer theory; and to generate a surface-stability-constant data base which is compatible with existing computer models of chemical equilibrium and which could be used in the field evaluation of solute-transport models.