In order to predict the behaviour of toxic elements in contaminated soils, it is necessary to understand both the soluble forms of the elements in solution and the nature and amount of solid phases with which the element is associated. This information will aid in predicting the bio-availability of the toxic element and will also help in describing its fate in both terrestrial and aquatic ecosystems. A site-specific soil adsorption model was developed that would estimate the amounts of soluble Cu and Ni in representative acidic soils from Sudbury, Ontario, a historical mining region of Canada. Binding constants for Cu and Ni with organic matter and clay were determined experimentally while the binding constants for the dissolved species and with iron oxides were taken from available literature values. The models were validated by comparing determined values of dissolved Cu and Ni with those predicted by the adsorption models. The models fit all the data well, except for some soils where the fit was not as good at pH values above approximately 6.0. The models were tested by investigating Ni and Cu concentrations in a number of plant bio-receptors from the Sudbury area and correlating these concentrations against three alternative ways of estimating the metal concentrations in the soils - the total concentration as determined in an aqua-regia extract (Total soil Cu and Ni); the soluble concentration at pH 2 (Bio-accessible soil Cu and Ni); and the concentration of soluble Cu and Ni as estimated by the soil adsorption models (Modeled soil Cu and Ni). Naturally occurring plant sample were taken from transects around three smelters. The regression coefficients for the pooled Ni and Cu concentrations in these plant samples showed a consistent improvement from Total soil Cu and Ni to Bio-accessible soil Cu and Ni to Modeled soil copper. A range of garden vegetables were also sampled and Ni concentrations compared with the three methods of measuring soil Ni. Results were similar to those for the naturally occurring plant samples for Ni. These results indicated that the soil adsorption models represent a significant improvement over the concentrations measured by aqua-regia digestion in predicting metal uptake in a range of vegetative species sampled from the Sudbury area.