SOURCES AND DISTRIBUTION OF HEAVY METALS IN RIVER SEDIMENTS FROM THE SOUTHERN DRAINAGE BASIN OF THE SEA OF MARMARA, TURKEY

The Nilufer Stream draining, the industrial city of Bursa is the most polluted with generally high enrichment factors (EF > 7) for Cu, Pb, Zn, Ni and Cr close to Bursa. In this stream these metals mainly occur in the non-residual fractions indicating anthropogenic origin. The highest concentrations of these elements close to Bursa and their gradual downstream dilution supports inputs from anthropogenic sources. The Simav stream draining the Balikesir an Susurluk areas is significantly locally enriched only in Pb (EF > 6). This metal occurs mainly in the residual and the Fe-Mn oxyhdroxide phases. The site where the oxyhdroxide bound Pb is dominant is located close to Balikesir City, indicating anthropogenic inputs. The residual Pb phases in these sediments are related to natural inputs, such as the Pb-Zn mineralized zones. The Gonen and Biga streams draining into the Erdek Bay are in general characterized by high contents of Cr with EF values up to 76. The Gonen stream is also relatively enriched in Pb. Cr in the sediments occur mostly in the organic and Fe-Mn oxyhdroxide phases indicating anthropogenic sources, whereas Pb occurs mainly in the residual phase. Metals in the drainage sediments at stations located close to the Sea of Marmara (SOM) are enriched in Zn, Cr and Pb in the Kocasu River (comprising the Nilufer and Simav streams), Cr and Pb in the Gonen stream and Cr in the Biga Stream. These results suggest the main source of high Zn, Cr and Pb observed in the southern SOM surface sediments are the riverine inputs.