Geochemical studies in several rivers and estuaries used for oyster rearing

Base-line studies have been carried out on the trace metal content of bottom sediments and waters of five estuaries and their catchment drainage, representing both contaminated and relatively uncontaminated environments. Relationships have been established between the composition of water and sediments in tributary drainage and those in the estuary. In particular, regional contamination of the hinterland with one or more of the elements As, Cd, Cu, Pb, Zn and Sn from mining and smelting activity was reflected by enhancement in estuarine muds in relation to the proportion of the catchment affected and the degree of contamination. Preliminary observations on young oysters showed that in general metal accumulation reflected the geochemical status of the estuary. These investigations have confirmed the potential use of geochemical reconnaissance maps based on stream sediment analysis as a means of focussing attention on rivers and estuaries affected by regional metal pollution.