This work presents a model of activity coefficients and a database for ionic equilibria of Cu2+, Zn2+, and Cd2+ in (H+, Na+, K+, Mg2+, Ca2+)(OH-, Cl-, NO-, ClO-, HSO-, SO2-, HCO-, CO2-) aqueous media valid up to 6-12 m ionic strength. The activity coefficient of a dissolved species is represented by empirical equation ln gamma(i) = -(A gamma/2)z(i)(2)(I - I exp(-8I(0.5)))(1/3) + Sigma b(ij)m(j), where A(gamma) is Debye-Huckel constant (1.17 at 25 degrees C), gamma(i) and z(i) are activity coefficient and charge of a dissolved species i, I is molal ionic strength, b(ij) is model parameter, and m(j) is molal concentration of dissolved species. The model is applicable to the modeling of ionic equilibria, as well as to simulation of solubility of salts in mixed electrolyte solutions. (c) 2005 Elsevier Inc. All rights reserved.