PCB Concentrations and Congener Composition in Macrophytes and Sediments in the St. Lawrence River near Cornwall, Ontario

Abstract

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 585 ng/g dry weight, with biota to sediment accumulation factors ranging from 0.3 to 10. The floating-leaved species Nuphar variegatum had generally higher PCB concentrations than the submerged species Myriophyllum spicatum, but the latter had higher biota to sediment accumulation factors. N. variegatum also had a higher lipid content, but lipid levels were not a good predictor of plant PCB concentrations. Congener specific analysis showed congener patterns shifted between plants and sediments; macrophytes tended to have higher levels of tetrachlorobiphenyl congeners. Given that contaminant levels in plants reflect those found in the sediments, the high biomass of macrophytes within the river and particularly in Lake St. Francis represents an important reserve of PCBs which may be transferred to the herbivorous and detrital food webs.