Tracking river plumes with volatile halocarbon contaminants: The St. Clair river-lake St. Clair example

Abstract The concentrations of seven widespread, volatile, halocarbon contaminants–tetrachloroethylene (C2Cl4), carbon tetrachloride (CCl4), 1,1,1-trichloroethane (C2H3Cl3), trichloroethylene (C2HCl3), chloroform (CHCl3), bromodichloromethane (CHBrCl2) and Freon 12 (CCl2F2)–were determined in the lower reaches of the St. Clair River and throughout Lake St. Clair. The results indicate large inputs of carbon tetrachloride and tetrachloroethylene and smaller loadings of chloroform, 1,1,1-trichloroethane and trichloroethylene from the St. Clair River, particularly the South Channel, Bassett Channel and Chenal Ecarte, to Lake St. Clair. In total, daily loadings of more than 100 kg are indicated, resulting in a lake burden of approximately 1,000 kg of these halocarbons. The plumes of contaminated river water, particularly for carbon tetrachloride and tetrachloroethylene, extend approximately 15 km into the shallow, well-mixed lake. At that range, the halocarbon levels generally drop to near-background concentrations, suggesting significant removal of the waterborne contaminants through volatilization.