Chemosphere, Vol. 29, No. 3, pp. 591-610, 1994 Pergamon Copyright O 1994 Elsevier Science Ltd 0045-6535(94)00191-X Printed in Great Britain. All tights reserved 0045-6535/94 $7.00+0.00 CONCENTRATIONS AND SOURCES OF PCBS AND ORGANOCHLORINE PESTICIDES IN THE ST. LAWRENCE RIVER (CANADA) AND ITS TRIBUTARIES Bernadette Qu0merais, Claire Lemieux, Ken R. Lum Ecotoxicology and Ecosystems Branch, St. Lawrence Centre, Environment Canada, 1001 Pierre Dupuy, Longueuil, Qu6bec, J4K 1A1, Canada Fax number: (514) 928 4264 (Received in Germany22 April 1994; accepted 24 May 1994) ABSTRACT Polychlorinated biphenyls and some organochlorlna pesticides were analyzed in St. Lawrence River water and suspended particulate matter samples collected In 1991. A Lagrangianapproachwas used as the sampling method in order to evaluate the relative Importanceof the major contaminant sources along the River, viz. the Great Lakes, Ottawa River, tributaries and Industries. PCBs appear to be the major organochlodnecontaminant In the River with a mean concentration of ca. 1.00 ng/L. Chlordane Is quite Importantwith a mean concentration of 0.32 ng/L. However, haxachiorobenzene (HCB) and hexachlorocyclohoxanes (BHCs) have much smaller concentrations,0.01 and 0.06 ng/L respectively.The situation for PCBs has Improved as their concentrations have decreased slightly since the late eighties. BHCs showed a similar trend during the same period, In contrast, HCB and chlordane concentrations have remained relatively constant since 1986. Fluxes of each organonhiodne compound in general tend to Increase from Cornwall to Qu(Jbec. However, differences in behavlour were observed depending on the contaminant. Seasonal trends were also evident. However, In general, the transport of hydrophobiccontaminants Is closely linked to the fluxes of suspended particulate matter. BHC on the other hand being quite hydrophllic behaves differently. Finally, the relative importance of each source varies according to the contaminant. INTRODUCTION Polychlorinatedbiphenyls, and organochiorine pesticides are contaminants of interest because they are ubiquitous and persist in the environment. Most of these compounds have been found in all major environmental compartments and in pristine environments. For example, PCBs have been found in polar regions (Tanabe, 1988), and in open ocean waters at concentrations ranging from 0.04 to 8 ng/L (Tanabe and Tatsukawa, 1986). Moreover, PCBs and some organochlorine pesticides, such as c¢-and 7-HCH, have been found in a wide range of atmospheric samples (Atlas and Giam, 1981; Ngabe and Bidleman, 1992; Reid et el., 1991; Chevreuil et al., 1989). They are widespread in surficial waters of North America, especially in the Great Lakes (Stevens and Neilson, 1989; Kelly et al., 1991) and the St. Lawrence River (Sylvestre, 1987; Germain and Janson, 1984; Langlois and Sloterdijk, 1988; Kaiser et al., 1990). The use of PCBs has been restricted in Canada since 1980 and chlordane has been restricted since December 1985 (CCREM, 1987). Most of these compounds tend to bioaccumulatein living organisms (Shaw and Connell, 1986, Van Der Oost et el., 1988, Granier and Chevreuil, 1992, Metcalfe and Chanton, 1990). The St. Lawrence River is 1200 km long and drains more than 1.3 million krr~. The major sources of contaminants for this river are the Great Lakes, the Ottawa River, industrial and municipal activities along the River and its tributaries. This study was carried out as a part of the St. Lawrence River Action Plan, a major objective of which is to reduce by 90% the toxic liquid effluents from the principal industria.1 plants discharging to the St. Lawrence Rivew. The aim of this paper is to evaluate the relative importance of the major sources of 13 PCB congeners and some organochlorine pesticides in the St. Lawrence River using a mass balance approach. 59!