Total Arsenic in Sediments from the Western North Sea and the Humber Estuary

In previous surveys of North Sea sediments, arsenic has often been omitted from the range of metals analysed. In this study we analysed archived samples from these earlier surveys and combined the data with recent results for the Dogger Bank, to examine the distribution of total arsenic in sediments from the western North Sea and Humber Estuary. Historically, the Humber has been subjected to a large point discharge of arsenic from an industrial source, and so there is interest in investigating the extent of contamination in the area. Normalization of arsenic concentrations to those of the clay analogues aluminium or rubidium did not prove to be statistically appropriate for the whole of the surveyed area. However, normalization to iron (representing iron (oxy-)hydroxide coatings with which arsenate has a high affinity) did show strong relationships for sediments from the whole of the region studied. This procedure showed elevated arsenic concentrations to be present in sediments from the outer Thames and off north east Norfolk, while those from the Humber were close to their predicted value. The Humber receives a large amount of iron from industrial discharges, providing a possible source of material for iron (oxy-)hydroxides. Although arsenical waste disposal could explain the high arsenic concentrations in sediments from the outer Thames, the causes for those off north east Norfolk are as yet unclear