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 rec ipient of waste from heavy industries, including shipbuilding, textile manu facturing, paper production, and military base operations. It is also the f ocus of the Glasgow conurbation, and receives discharges of sewage sludge. From these activities organic contaminants have entered the Clyde, The le,e ls of PCBs in the Clyde area were determined in a survey of surface sedimen ts from 95 sites analysed for 22 chlorinated biphenyl (CB) congeners, As ex pected, areas of high total organic carbon or fine grain sediment contained high le, els of PCBs, However, one sandy site with low organic carbon cont ained the highest levels of contamination (1,822 mu g kg(-1)). Further inve stigation 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 mater residence times. The influence of the Clyd e Estuary on PCB levels in the Gareloch was investigated using Principal Co mponent Analysis (PCA), Similar distribution patterns were observed for the undisturbed intertidal estuarine samples and the Gareloch samples, while s ediments from the main dredged channel had a different distribution which p robably reflects historical inputs to the area. (C) 1999 Elsevier Science L td. All rights reserved.