Total PCBs in Liverpool Bay sediments

The concentrations of 55 congeners of PCBs were determined in < 500 μm particles of 66 superficial sediment samples from Liverpool Bay. Total PCBs were significantly (p < 0.001) correlated with the amount of fine particles (r2 = 0.81) and with the organic carbon content (r2 = 0.80). The mean, maximum and minimum total PCB values were 3938, 37,880 and 82 pg g−1, respectively. The highest PCB concentrations were found in muddy deposits, particularly near the River Mersey in the Burbo Bight area, where concentrations were above 13,000 pg g−1. Values lower than 350 pg g−1 were found in the sandy southern area towards the North Wales coast. Organic carbon normalization was used for grain size correction. The distribution of carbon-normalized values, however, was similar to the distribution of values without normalization. This observation indicates that PCBs were particularly enriched in muddy deposits, where sewage and dredged-spoil particles, derived from dumping activities, are more likely to be deposited. As in the case of mercury, which has been extensively studied in the past, the main source of PCBs to Liverpool Bay seems to be the River Mersey. PCB concentrations in Liverpool Bay sediments are similar to those from other industrialised areas, but are much lower than the most contaminated sediments reported in the literature, such as those from the estuaries of the Hudson and Acushnet rivers