DISTRIBUTION AND FATE OF CHLOROPHENOLS IN THE ST-LAWRENCE-RIVER BASIN, CANADA

Chlorophenols were analyzed in suspended particulate matter samples fr om the St. Lawrence River and its tributaries. A Lagrangian approach w as used as the sampling method in order to discriminate various source s along the River. Four transects were sampled in spring, summer and a utumn. In addition, more intensive sampling was carried out at two of the four transects between March and November 1991 in order to study t he seasonal pattern of chlorophenol transport. Only 2,3,4,6-tetrachlor ophenol and pentachlorophenol were detected in almost ali samples. Ave rage concentrations were similar in the St. Lawrence River and its tri butaries at 16 ng/g for tetrachlorophenol and 46 ng/g for pentachlorop henol. Concentrations and fluxes were highest in autumn for both compo unds ostensibly due to their use as wood preservatives. Fluxes tended to increase from Cornwall to Quebec city and reflected a seasonal tren d. The relative importance of the major sources of chlorophenols in th is river system was calculated using a simple mass balance model. The Great Lakes and Quebec tributaries account for 25 % and 30 % respectiv ely, industries were a negligible source and diffuse sources were foun d to be the greatest at ca. 44 %.