Heavy Metal Pollution of the Surface Sediments in Niyang River,Tibet

Heavy metal pollution in the sediment is an important factor affecting river ecosystem. The surface sediments were collected from Niyang River to study the pollution of five kinds of heavy metals,namely Cu,Zn,Cd,Pb,Cr. The results showed that except for Cd,the most of heavy metal contents were lower than the soil background values. Enrichment factor（ EF） values revealed that Cd,Cu,Zn,Pb and Cr in the whole were less than 1. 5; and the orders of the average E_rⁱ for the studied metals were less than 40. The mean RI values showed less than 70. Heavy metal pollution has not occurred in Niyang River and has low ecological risk,but the anthropogenic emissions of heavy metal Cd in this basin do exist.