Metal equilibria in contaminated soil

Chemical Modeling of Trace Metal Equilibria in Contaminated Soil Solutions Using the Computer Program GEOCHEM... 

Mattigod, S. V. and Sposito, G. Chemical modeling of trace metal equilibria in contaminated soil solutions using the computer program GEOCHEM, j[n Jenne, E.A., ed., "Chemical Modeling in Aqueous Systems. Speciation, Sorption, Solubiliiy, and Kinetics." Amer. Chem. Soc., 1978 (This volume). 

The equilibrium equations that normally have to be considered in the EKR modeling of a soil contaminated by heavy metals can be classified into one of the following categories complex formation reactions, precipitation of the metal hydroxides or of other species, ion exchange reactions, surface complexation reactions, etc. Anyway, the autoionization of water always has to be considered and the precipitation of carbonates, together with the carbonate-bicarbonate equilibrium, should normally also be considered. However, the above equations have only considered the species in aqueous phase, so if a species precipitates, a new master species has to be included in this equilibrium system, whose concentration would be the amount of the precipitated species per unit volume of water. This additional degree of freedom is constrained by the solubility product constant of the precipitate (KO, because the new solid phase is in equilibrium with the aqueous phase. If there exists Np precipitated species, the pure-phase equilibria can be represented with the following equation ... 

---