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 organic 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 same source of pollution in the following order of importance: the sewage outfall, the industrial zone and the Axios River. The concentration of these metals increased with decreasing mean grain size, suggesting their association with the fine fraction of the sediments, the clays and the organic matter. Cadmium was more loosely correlated with the metals 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 ultramafic rocks being responsible for their enrichment. This was more apparent in the case of Ni, which was more enriched in the coarser and better sorted sediments, near the delta of the River Aliakmon.