The Distribution of Trace Metal Pollutants within Intertidal Sediments of the Tamar Estuary, Sw England

Concentrations of trace metal pollutants are frequently reported from intertidal sediments (e.g. Bryan and Langston, 1992; French, 1993; Lindsay and Bell, 1997; Pirrie et al., 1997, 2000) and as these areas are often sites of intense human and animal activity, the level of contaminants are of particular interest with respect to environmental health (Rae, 1997; Clark, 1997). When trace metals are released into the water column they can be transferred rapidly to the sediment phase either by adsorption onto suspended particulate matter followed by sedimentation (Turner et al., 1993; Lindsay and Bell, 1997) or directly incorporated within the sediment as particles. Contaminants may subsequently be concentrated in specific areas, remote from their point of introduction (McLaren and Little, 1987), as a result of sediment transport and the mixing capabilities of the waters within the estuary. Studies of the distribution of sediment borne pollutants can therefore be used as an indication of the mixing ability of the system and in the identification of sources of pollutant input (French, 1993). This study carried out in the Tamar Estuary of SW England, aims to describe the downstream dispersal and possible controls upon the distribution of selected trace metal pollutants within the intertidal sediments of the estuary. The mineralized district of SW England was one of the world’s greatest mining areas, renowned for tin, copper and arsenic production and hence the mining history is likely to have had a huge effect on the local environmental geochemistry. Previous studies relating to the distribution of metals within the intertidal sediments of the Tamar Estuary (e.g. Bryan and Langston, 1992; Lindsay and Bell, 1997) have shown that certain metals such as As, Cu, Pb and Zn are enriched within the sediments. A number of more detailed analyses regarding trace metal distribution within the Tamar estuary have been undertaken by Knox et al. (1981), Morris et al. (1982; 1986) and Ackroyd et al. (1986, 1987), particularly focussing upon dissolved and suspended particulate material. The studies of Morris et al. (1986) and Ackroyd et al. (1987) also examined the trace metal concentrations (including Fe, Cu, Cd and Zn) of surficial sediments from the middle and upper parts of the Tamar Estuary. They suggested that there was substantial internal metal recycling within the estuary and the distribution of metals was also THE DISTRIBUTION OF TRACE METAL POLLUTANTS WITHIN INTERTIDAL SEDIMENTS OF THE TAMAR ESTUARY, SW ENGLAND