Geochemical Factors Affecting Trace Element Mobility

Abstract

The mobility of trace elements in soil reflects the chemical reactivity of the elements in the soil matrix. The result is that trace‐element mobility is both specie and site dependent. An overview of selected geochemical factors that influence the concentration of trace elements in the soil solution is presented. Factors affecting both cationic and anionic trace‐element mobility are given in the context of multiphase equilibria. Chemical processes such as ion exchange, adsorption, solid‐phase formation, and redox are considered and related to control of trace‐element concentration in solution and hence their mobility in soil. The limitations inherent in the use of a thermodynamic database for determining partition functions used in solute transport modeling are emphasized. The importance of microbially mediated biomethylation of trace elements such as Pb, Hg, Cd, and Se is discussed.