MODELING THE PATHWAYS OF TOXIC CONTAMINANTS IN THE ST. CLAIR-DETROIT RIVER SYSTEM USING THE TOXFATE MODEL: THE FATE OF PERCHLOROETHYLENE.

Perchloroethylene (PERC) is a heavier-than-water soluble and volatile solvent used primarily in the dry cleaning business. Black puddles (popularly known as the 'blob'), containing several contaminants including PERC, were reported in the St. Clair River bottom sediments downstream from Sarnia in 1984 and in 1985. The TOXFATE model is used to predict the fate of PERC and the relative importance of volatilization in relation to water transport. Simulations show that in the St. Clair-Detroit River system about 82% (78-87% under a variety of temperature and wind conditions) of the PERC loading is volatilized, about 17% (12-21%) of loading enters Lake Erie (more in winter, less in summer) and only about 1% remains in the system. The residence half life of PERC being transported in the water from Sarnia to Lake Erie is 350-400 hours and the half life of PERC being volatilized is 80-85 hours.