MAGNITUDE AND DISTRIBUTION OF ANTHROPOGENIC CONTAMINANTS IN SALT-MARSH SEDIMENTS OF THE ESSEX COAST, UK .2. SELECTED METALS AND METALLOIDS

Total concentrations of selected metals and metalloids; As, Ca, Cd, Cu, Cr, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Se and Zn were determined in the sediments of five salt marsh sites along the Essex coast of the UK. A fairly ubiquitous degree of metal and metalloid contamination was found within the sediments of all the salt marshes investigated. The extent of contamination by individual metal species was dependent upon the nature of the site-specific inputs. The enrichment of industrially derived metals, such as Hg and Cd, for example, occurred at sites adjacent to urban areas; Two Tree Island (situated on the outer Thames Estuary) and to a lesser extent South Woodham Ferrers (situated on the River Crouch). Lead concentrations were elevated at all five sites inferring that a significant input was derived from a common generic source, such as atmospheric deposition. The distribution of metals and metalloids within individual salt marsh sites was dependent upon a number of factors including sediment type, the hydrological regime, the presence of vegetation, redox potential and organic matter content.