SAND CLAMS OF GANZIRRI MARINE COASTAL LAGOON IN MESSINA (ITALY). EXTRACTION AND ICP-MS ANALYSIS.

Abstract

This paper studies the possible forms or phases of heavy metals in sediments of a marine coastal lagoon, called Ganzirri, located in the Sicilian coast of the Messina’s strait by using sequential extraction. To reduce the extraction time of the Tessier method, the last step of speciation was carried out by mineralization in a microwave oven. Here we report the results of the distribution of As, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Se, Tl, V and Zn, in four fractions of sediments samples and the concentration of the same metals in clams. This study looked at three bivalve mollusc species, Tapes decussates, Chamelea gallina and Cardium edule, raised in the sediment considered and discussed the relationships between sediments and clams of same place. The metals were analyzed by means ICP-MS. To compare the total metals content at the different sampling sites, the metal pollution index (MPI) was used. The values ranged from 1.5 to 3.0. Generally, the metal content in the labile fraction of sediments is rather low and representing from 1.4 to 2.0% of the sum of four fractions. In all the sediments investigated in the present study, Fe-Mn oxides play a major role in binding As, Cu, Mo, Ni and Zn sometimes reaching about 80% of the total metals. Most of the metals (Be, Co, Tl, V, Zn) occur in the form of sulphur and/or of organic complexes that can strongly influence their mobility and availability in the environment and to a minor extent are bound to carbonates and Fe and Mn oxides. The concentrations of most of the metals in the three species of bivalves studied not vary notably depending on the location of the sampling sites and on different species. The values of MPI, calculated for tissues, range from 0.31 to 0.44. The concentrations of metals in the three species of clam from Ganzirri coastal lagoon of Southern Italy are lower than similar studies accomplished in other regions of the world consequently they may be used as baseline values.