The distribution of trace metal pollutants within intertidal sediments of the Tamar Estuary, SW England

The Tamar Estuary is a partially mixed, flood dominant estuary, the middle and lower parts of which are flanked by extensive intertidal flats and salt marsh deposits. The southern part of the Tamar valley is highly mineralised with tin, copper and arsenic production during the 19(th) century. Consequently, the mining history is likely to have had a huge effect on the local environmental geochemistry. In this study the concentration of selected trace elements (As, Cu, Ph and Zn) from intertidal sediments from the Tamar Estuary have been measured in order to examine the downstream distribution pattern in relation to historical sources of pollution. The results show highest concentrations in the middle parts of the estuary and notably a distinct absence ofelevated concentrations immediately adjacent to mine sites. This pattern is consistent with the dominance of down estuary transport of sediment during winter. A decrease in concentration of metals seawards from the head of the estuary is thought to be a response to physical transport processes and the input of sediments derived from offshore.