ABSTRACT
The processes that control metal mobilities include not only dissolution/ precipitation but also redox reactions, complexation with ligands, sorption/ desorption by solids, and biotransformation, Reeder et al. 2006. The water saturation states of various metals with respect to various solids can be calculated by use of programs like MINTEQA2 (US EPA), PHREEQC, Parkhurst and Appelo 1999, or the Geochemists Workbench, Bethke 2002. The phases of interest, however, may lack the necessary thermodynamic stability data or they may be complicated by being a solid solution. Metal solubility can be significantly enhanced through complex formation with various organic or inorganic ligands. An example is that of the affinity of UO22+ for dissolved CO3=. The solubility of UO22+ in equilibrium with schoepite* at a pH of 7.0 is 3.4 μM. With 1 μM dissolved CO2 the solubility increases to 56 μM.
