GEOCHEMICAL AND SEDIMENTOLOGICAL PATTERNS IN THE THERMAIKOS GULF, NORTH-WEST AEGEAN SEA, FORMED FROM A MULTISOURCE OF ELEMENTS

Surface sediment samples from Thermaikos Gulf were analysed for organi c carbon, Cd, Pb, Cr, Cu, Zn, Mn, Ni, Co and Fe and were subjected to grain size analysis. The results showed that Pb, Cu and Zn had the sam e source of pollution in the following order of importance: the sewage outfall, the industrial zone and the Aries River. The concentration o f these metals increased with decreasing mean grain size, suggesting t heir association with the fine fraction of the sediments, the clays an d the organic matter. Cadmium was more loosely correlated with the met als of the previous group, being derived from the community activities and also from the weathering of land-based ophiolitic rocks. Iron, Cr , Ni, Co and Mn are of natural origin, the weathering of mafic and ult ramafic rocks being responsible for their enrichment. This was more ap parent in the case of Ni, which was more enriched in the coarser and b etter sorted sediments, near the delta of the River Aliakmon.