Potential ecological risk assessment of heavy metals in the sediments of Changjiang River Estuary and its adjacent sea area

According to the monitoring data on Changjiang River Estuary and its adjacent sea areas' sediments in October 2007 and June 2009,heavy metals(Cu,Pb,Zn,Cd,Cr,As,Hg) and TOC in the sediments of those areas were studied.The method of Potential Ecological Risk Index techniques presented by Hakanson was used to assess the potential ecological risk of heavy metals.The average contents of Cu,Pb,Zn,Cd,Cr,As,Hg were 37.43×10-6,36.85×10-6,93.48×10-6,0.17×10-6,72.91×10-6,10.60×10-6 and 0.043×10-6 respectively.In general,the distribution of heavy metals show that it was high in Changjiang River Estuary and Hangzhou Bay,but lower at the outer continental shelf waters.Overall,the contents of heavy metals were higher in the south sea areas than those in the north sea areas.The sequences of the heavy metals pollution index of the studied metals were CuCr ZnPbAsCdHg,Cu and Cr were the main pollution factors;the order of potential ecological risk were CdHgCuAsPbCrZn,Cd,Hg and Cu were the main potential ecological risk factors.Thus,it can be seen that just parts of the study area were polluted by the heavy metals.They were also low potential ecological risk with the potential ecological risk indeices less than 150.