Heavy Metal Pollution in Stream Sediments of the Neka River, N Iran

The Neka River is located at 21km in east of Sari, center city of the Mazanderan province, north of Iran. 51 stream sediment samples were collected from 4 sample sites. The samples were digested by HF+HClO4+HNO3 and analyzed by AAS in laboratory of Geological Survey of Iran. The results of analysis show that the enrichment ratio and Geo-accumulation index are too high for Ag, Cd and Sn in the whole sediments of the Neka River. Zn shows very high enrichment in the sites of Boz Mil and Lajan Lateh Sofla sample sites and Pb shows very high enrichment in the site of Boz Mil. Degrees of Geo-accumulation Index are very high for Ag-Cd in the 4 sites but for Zn are high to medium and for other elements are medium. In the Neka Choob and Mola Khil sample sites, the Co and Ag are too high because of anthropogenic contamination and Fe and Ni are low relatively. In the Boz Mil and Lajan Lateh Sofla sample sites, the Pb and Ag are too high because of anthropogenic contamination and V, Ni, Cu and Zn are low relatively. Coal mining and coal deposition in the upper part of the Neka River, urban and wood industry sewage are the main sources of the pollution.