Distributions and ecological assessment of heavy metals of Chengdao Oilfield sea areas

Based on the data of environmental survey obtained from Chengdao Oilfield sea areas in 2009,the distributions patterns of heavy metals in the seawater and surface sediments were analyzed.Environmental quality and ecological risk assessment of heavy metals in the investigated sea areas were also carried out.The results were summarized as follows.Overall,the contents of seven heavy metals in the seawater and surface sediments were low in the investigated sea areas.They were below the second degree of Sea Water Quality Standard and the first degree of Standard for Marine Sediments Quality respectively.In addition to Zn,Hg in the seawater and Cu in the surface sediments,the distributions patterns of heavy metals were almost the same.The total contents of heavy metals were slightly higher in the offshore than the other areas.The result of environmental quality assessment showed that the contents of heavy metals in the seawater belong to the grade of green and the contents of heavy metals in the surface sediments belong to the grade of less green.The pollution level of the surface sediments was worse than the seawater.The ecological risk assessment of heavy metals indicates that the surface sediments had low to medium potential for biological toxicity effect.The values of As,Cu,Pb and Cr indicate they occasionally had adverse biological toxicity effect at some stations.The ecological risk intensity caused by different metals was: AsCr ZnPbCuHgCd.