The Biogeochemistry of Polychlorinated Biphenyls (PCBs) in the Clyde: Distribution and Source Evaluation

The River Clyde, on the West coast of Scotland, has a long history as a recipient of waste from heavy industries, including shipbuilding, textile manufacturing, paper production, and military base operations. It is also the focus of the Glasgow conurbation, and receives discharges of sewage sludge. From these activities organic contaminants have entered the Clyde. The levels of PCBs in the Clyde area were determined in a survey of surface sediments from 95 sites analysed for 22 chlorinated biphenyl (CB) congeners. As expected, areas of high total organic carbon or fine grain sediment contained high levels of PCBs. However, one sandy site with low organic carbon contained the highest levels of contamination (1, 822 μg kg−1). Further investigation at this site is ongoing to establish geochemical controls on the distribution. Elsewhere, the distribution patterns of homologue groups and of CB 153 normalised data both showed similar congener patterns in areas of co-varying salinities and water residence times. The influence of the Clyde Estuary on PCB levels in the Gareloch was investigated using Principal Component Analysis (PCA). Similar distribution patterns were observed for the undisturbed intertidal estuarine samples and the Gareloch samples, while sediments from the main dredged channel had a different distribution which probably reflects historical inputs to the area.