Evaluation on potential ecological risk of the heavy metals in the surface sediments of the Changjiang (Yangtze) estuary and its adjacent coastal area

Based on the contents of elements(Cd,Cr,Cu,Pb,Zn,Al,As,Ca,Sr,ect) and clay in the surface sediments of Yangtze estuary and the surrounding area in 2006,using Hakanson ecological risk index method,we analyzed the contamination degree of heavy metals in the surface sediment,evaluated the environmental quality status of surface sediments,and defied the potential ecological risk of surface sediments.We found that there was a good quality status in surface sediments of Yangtze estuary and its adjacent area,and the order of contamination content in sediments was AsCrCdZnCuPb.In addition,the potential ecological risk of heavy metals was also low;and the order of potential ecological risk index was CdAs Cu Cr Pb Zn.Geographically,the relative high value of contamination degree and potential ecological risk were seen in the mud area outside Hangzhou bay and southeast of Yangtze estuary.Among the heavy metals,Cd showed a value of contamination degree and potential ecological risk that were significantly higher than other elements,probably because Cd were more affected by the concentration of suspended particular matter,the content of organic matter and salinity than other elements.Compared with the data of 2003,the potential ecological risk of heavy metals and high value of potential ecological risk index were not significant changed.