Na-montmorillonite, MINSORB code (2-site protolysis no electrostatics surface complexation and cation exchange model developed and incorporated into MINEQL); citation in [BB99a]; fixed parameters: Zn and Mn sorption parameters and inventories (Zn 1E-3mol/kg, Mn 4E-4mol/kg); selectivity coefficient (I=0) for cation exchange Na-Ni=3.1