An assessment of the heavy metal pollution of two tidal marshes on the north-west coast of Ireland

An assessment of heavy metal concentrations was performed on two sheltered littoral locations on the north-west coast of Ireland, encompassing the tidal flat, eroded tidal marsh edge and backmarsh/supratidal settings. Both sites possess catchments devoid of major industries, allowing an indication of regional pollution levels to be approximated. Profiles of heavy metal concentrations were interpreted by considering diagenetic effects, with conclusions supported by grain size and organic carbon determinations. An increase in heavy metal concentrations landwards was observed, resultant upon increased organic components in the sediment and a dominance of metal-humic complexes. Concentrations of lead, copper, zinc, chromium and manganese were found to be relatively low for both sites, although an increase in anthropogenic input in recent sediments was implied. Both sites were also dated radiometrically. The dates calculated helped to show that the tidal marshes of north-western Ireland have not yet been anthropogenically modified to the point of toxicity.