Concentration and partitioning of Hg, Cr and Pb in sediments of dredge and disposal sites of the northern Adriatic Sea

A field survey was carried out in 1991 in order to determine the textural and some chemical characteristics of the sediments of dredge and disposal sites in the northern Adriatic Sea. Grain size, concentrations and partitioning of Hg, Cr and Pb in the Ravenna harbour sediments and disposal site in the early stage of dumping are reported. The harbour entrance sediments have a heterogeneous grain size. Mercury seems to be the major contaminant in the inner harbour samples. In the silty clay sediments of the offshore zone a gradient increasing from the coast eastwards is evident for clay and trace metals. In both zones, sequential extractions performed on harbour and offshore samples showed a prevalent association of chromium in the residual fraction and an approximately balanced partitioning of lead between the carbonate, oxide and residual fractions. Mercury proved to be associated mainly with the sulphidic-organic and residual fractions. This leads us to affirm that the dumping of the materials dredged from the Ravenna harbour should not produce a general increase in the surficial concentrations of the considered metals in the disposal area.