TOTAL CONTENTS AND SEQUENTIAL EXTRACTIONS OF MERCURY, CADMIUM, AND LEAD IN COASTAL SEDIMENTS

Samples of sediments collected along Italian coasts were analysed for mercury, cadmium, and lead contents by means of atomic absorption spectrometry methods. Determinations of iron and organic carbon were also performed. In addition, selective extractions were applied to the samples in order to evaluate the presence of the elements investigated in different chemical fractions. The mean values of total metals, expressed on the basis of dry weight, were 0.23+/-0.41 mg kg-1 for Hg, 0.16+/-0.12 mg kg-1 for Cd, and 41.1+/-37.3 mg kg-1 for Pb. In general, the levels of metals found in the stations where there was not much shipping activity were quite low and typical of unpolluted coastal sediments, whereas the highest concentrations noted were in the stations placed inside harbours. The procedure of selective extractions evidenced high percentages of metals in the residual fraction. For lead and cadmium, the concentrations obtained through leaching showed the anomaly/background contrast better than the total concentrations.