Cu, Zn and Sn Vertical Distribution in Sediment Cores from the Elefsis Gulf (Attiki-Greece)

Elefsis Gulf, on the coasts of Attiki, in Greece, is characterised by its rather enclosed type, the presence of heavy industries located at its northeastern coast (like refineries, shipyards, iron and steel industries) and the use of its ports for the transportation of raw material and products. Previous research has shown that both industrial and marine transport activities, during the past six decades, have contaminated the gulf environment with various pollutants including metals. The respective sedimentation rate was calculated to approximately 0.5-0.8 cm/year. The present work is aiming to evaluate Cu, Zn and Sn vertical and fractional distribution in Elefsis Gulf sediments. For this purpose, sediment cores were collected from four sites along the north coast of the gulf. After lyophilization and sieving, the samples were treated applying the sequential extraction analytical procedure of Tessier et al. (with a few modifications) for the partitioning of the elements among the various geochemical fractions. Metal concentrations were measured using atomic absorption spectroscopy. The results showed that most of the non-residual Cu is associated with the organic/sulphides fraction, as Cu exhibits a strong affinity for the organic matter while it can also be present in sulphide minerals. In general, significant Zn percentage is associated with the exchangeable fraction (12%-32% of the total), indicating biological availability and anthropogenic input. As expected, considerable Zn is bound to ferromanganese oxides (21%-41% of the total) due to their scavenging ability for trace metals. The four non-residual fractions of Zn show a downcore decrease. More than 79% of the total Sn occurs in the residual fraction. However, the four non-residual fractions of Sn exhibit enrichment at 10-20 cm sediment core depth. Concluding, Elefsis Gulf sediments correspond to a significant pollution level while the recent ones may act as secondary pollution sources, implying therefore th- e need for an environmentally sound management scheme.