ASSESSMENT OF CHEMICAL FATE IN THE ENVIRONMENT USING EVALUATIVE, REGIONAL AND LOCAL-SCALE MODELS - ILLUSTRATIVE APPLICATION TO CHLOROBENZENE AND LINEAR ALKYLBENZENE SULFONATES

Evaluation of chemical fate in the environment has been suggested to b e best accomplished using a five-stage process in which a sequence of increasing site-specific multimedia mass balance models is applied. Th is approach is illustrated for chlorobenzene and linear alkylbenzene s ulfonates (LAS). The first two stages involve classifying the chemical and quantifying the emissions into each environmental compartment. In the third stage, the characteristics of the chemical are determined u sing the evaluative equilibrium criterion model, which is capable of t reating a variety of chemicals including those that are involatile and insoluble in water. This evaluation is conducted in three steps using levels I, II, and III versions of the model, which introduce increasi ng complexity and more realistic representations of the environment. I n the fourth stage, ChemCAN, which is a level III model for specific r egions of Canada, is used to predict the chemical's fate in southern O ntario. The final stage is to apply local environmental models to pred ict environmental exposure concentrations. For chlorobenzene, the loca l model was the SoilFug model, which predicts the fate of agrochemical s, and for LAS the WW-TREAT, GRiDS, and POUT models were used to predi ct the fate of LAS in a sewage treatment plant and in riverine receivi ng waters. It is concluded that this systematic approach provides a co mprehensive assessment of chemical fate, revealing the broad character istics of chemical behavior and quantifying the likely local and regio nal exposure levels.