PCB CONCENTRATIONS AND CONGENER COMPOSITION IN MACROPHYTES AND SEDIMENTS IN THE ST-LAWRENCE RIVER NEAR CORNWALL, ONTARIO

PCB concentration and congener composition were examined in sediments and two species of macrophytes in the St. Lawrence River downstream of Cornwall, Ontario. Total PCBs in the macrophytes ranged from 37 to 58 5 ng/g dry weight, with biota to sediment accumulation factors ranging from 0.3 to 10. The floating-leaved species Nuphar variegatum had gen erally higher PCB concentrations than the submerged species Myriophyll um spicatum, but the latter had higher biota to sediment accumulation factors. N. variegatum also had a higher lipid content, but lipid leve ls were not a good predictor of plant PCB concentrations. Congener spe cific analysis showed congener patterns shifted between plants and sed iments; macrophytes tended to have higher levels of tetrachlorobipheny l congeners. Given that contaminant levels in plants reflect those fou nd in sediments, the high biomass of macrophytes within the river and particularly in Lake St. Francis represents an important reserve of PC Bs which may be transferred to the herbivorous and detrital food webs.