SOURCES AND FATE OF ORGANIC CONTAMINANTS IN THE MERSEY ESTUARY - VOLATILE ORGANOHALOGEN COMPOUNDS

A study of the concentrations and distribution of a range of volatile organohalogen compounds (VOCls) in the Mersey estuary and its freshwater inputs was conducted between 1987 and 1990. The relative importance of the main freshwater inputs as sources of VOCls to the estuary have been estimated, and the Manchester Ship canal (MSC) and River Weaver have been identified as important sources. Estimated maximum VOCl inputs from the MSC and River Weaver were 43 kg day-1 chloroform; 32 kg day-1 carbon tetrachloride; 147 kg day-1 trichloroethene; 125 kg day-1 tetrachloroethene; and 12 kg day-1 bromoform. The spatial distribution of contaminants in the estuary has been investigated and the data have been interpreted by using mixing curves and a simple flux model. The concentrations of the VOCls declined seawards and it is estimated that a large proportion (80-95%) of VOCl inputs are lost from surface waters after entering the estuary, mainly by volatilisation.