Concentrations of dissolved and suspended particulate Cd, Cu, Mn, Ni, Pb and Zn in surface waters around the coasts of England and Wales and in adjacent seas

Abstract

Trace metal concentrations in British coastal waters were determined during the summers of 1991 and 1992. The measured concentrations of Cd, Cu, Ni, Pb and Zn are in general agreement with those previously reported in the literature. Higher offshore dissolved Mn concentrations (mean = 1·2 μg l −1) are attributed to summertime increases in benthic Mn fluxes to the water column. Concentrations of all determinands were generally higher in the Irish Sea and North Sea than in the English Channel. This reflects the larger riverine component of the North and Irish Seas, and the stronger influence of North Atlantic water in the English Channel. Elevated dissolved and suspended particulate Pb concentrations in the Dogger Bank region are tentatively attributed to atmospheric inputs, and reduced removal by the lower concentrations of suspended particulate matter at these stations. Of the six major estuaries sampled, the Tweed was regarded as a reference site since it has a sparsely populated catchment area with little industry. Dissolved Mn concentrations in the Tweed were generally lower than those in the other estuaries, although the highest suspended particulate Mn (6600 μg g −1) and Ni (69 μg g −1) concentrations were found there. These high particulate concentrations are attributed to the oxidation of Mn(II) and the subsequent scavenging of Ni by the newly precipitated Mn-oxyhydroxides. Highest suspended particulate Cd (6·1 μg g −1), Cu (200 μg g −1), Pb (650 μg g −1) and Zn (1400 μg g −1), and dissolved Pb (1·1 μg g −1) and Zn (25 μg l −1) concentrations were observed in the Tyne. The Tees had the highest dissolved Cu (10 μg l −1) concentration, while the Humber and Mersey had the highest dissolved Cd (220 ng l −1) and Ni concentrations (9·4 μg l −1), respectively. The high concentrations are attributed to anthropogenic inputs.