Application of a fugacity model for assessing chemical fate in ecodistricts of southern Ontario

A fugacity model that was developed to assess the chemical fate of organic chemicals in regions of Canada has been incorporated into the RAISON (Regional Analysis by Intelligent Systems ON a microcomputer) expert system and has been modified and applied to ecodistricts of southern Ontario, Canada. The model is used to estimate a selected chemical's distribution between four bulk compartments (air, water, soil, and sediment) and four subcompartments (groundwater, coastal water, plants and animals). Polychlorinated biphenyls (PCBs), mirex, dieldrin, and hexachlorobenzene (HCB) were the chemicals considered in the application of the modelling system. Steady state concentrations predicted by the model were compared with available observed data for the ecodistricts. Considering the large degree of lumping required for ecodistrict parameters, the model predicts concentrations within the compartments that are reasonable estimates, especially considering the fact that concentrations between the compartments vary over as much as 10 orders of magnitude.