An assessment of metal contamination in Northern Irish coastal sediments

Coastal sediments may be considered contaminated with a metal if they have undergone an increase in concentrations above background levels due to anth ropogenic inputs. The extent of contamination in Northern Irish coastal sed iments was examined by a combination of statistical and graphical analysis utilising aluminium as a grain-size proxy. Enrichment of mercury, lead, zin c and copper was commonly observed in sediments throughout the study area, whereas concentrations of nickel, chromium and iron largely reflected level s in their source rocks. Belfast Lough was the most contaminated area, and it is suggested that the metals commonly associated with industrial and dom estic discharges are more biologically available than at the other coastal sites studied. Concentrations of metals in Strangford Lough were close to o r at background concentrations and may be used as a baseline to assess the degree of enrichment in other Irish coastal sediments. The area of fine sed iments in the western Irish Sea had higher concentrations of metals than so me inshore areas that could not be accounted for by grain-size differences alone. The sources and transport mechanisms of metals to the western Irish Sea and the influence of a seasonal gyre on contaminant accumulation are di scussed.