Trace metal accumulation in different grain size fractions of the sediments from a semi-enclosed bay heavily contaminated by urban and industrial wastewaters

Cluster analysis was applied to identify granulometric similarities between sediment samples from a heavily contaminated semi-enclosed bay (the Kastel a Bay in the Middle Adriatic). Concentrations of Mn, Cr, Pb, Cd and organic matter were determined in four grain-size fractions (A, > 300 mu m; B, 54- 300 mu m; C, 20-54 mu m; and D, < 20 mu m) of the sediment samples. The fin est sediment fractions (C and D) contained the highest concentrations of Cr , Pb and organic matter. The concentrations of these metals were generally four times greater than in coarse grained-fractions. Cadmium is also accumu lated in less extent in fine-grain fractions, while Mn distribution was qui te irregular. The vertical distribution of the studied trace metals shows P b enrichment in upper sediment layers, while Cd concentration was increased only in the samples from the most polluted part of the Bay. This indicates anthropogenic origins of these metals. Principal Component Analysis was us ed to interpret the variations of trace metals and organic matter concentra tions in the sediment samples. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.