CONTRASTING BEHAVIOR OF ARSENIC AND MERCURY IN LIVERPOOL BAY SEDIMENTS

Arsenic, mercury, aluminium, iron and manganese concentrations were determined in surface sediments from the Liverpool Bay area. Hg/Al ratios suggest an overall two-fold enrichment of Hg compared to average shale values resulting from natural lithogenic inputs. The River Mersey is the main source of Hg; however, sewage sludge and dredged spoil disposal activities produce areas containing up to six times the projected natural levels. Arsenic is enriched by a factor of 2·3 compared to average shale. As/Al ratios suggest an enrichment of arsenic in the disposal area; however, arsenic concentrations in sewage sludge show that disposal activities are not responsible for the overall enrichment in the bay. Very high arsenic concentrations have been reported for sediments in freshwater and estuarine sediments from North Wales. As/Fe values in this study increase towards the Welsh coast indicating that the overall arsenic enrichment in Liverpool Bay sediments may derive from natural inputs from the mineralized areas of North Wales. © 1992 Academic Press Limited.