Abstract:

The ecological risk assessment of trace heavy metals in Daya Bay is investigated based on the surficial sediments collected in 2011. The analyzed trace heavy metals include Cr, Ni, Cu, Pb, Zn, Cd, and As. The modified BCR method was used to identify the chemical forms and the potential sources. Results show that the content of trace heavy metals is distributed as bends, with high content in Dapeng, Yaling and Fanhe Bay, descend from the shore to bay by varying degrees. The BCR sequential extraction identifies the speciation of the main trace metals. Cr,Ni,Cu,Zn,As are present in the residual form, Pb is present in reducible form and Cd is present in acid-soluble form. The ratio of heavy metals in nonresidual form with descending order is Pb(78.83%), Cd(78.65%),Cu(48.54%), Zn(48.10%), Ni(38.31%), Cr(28.43%), and As(27.76%). The ratio of Pb content is the highest, meaning the highest mobility of Pb. The source analysis shows the pollutants are mainly from natural weathering and secondly from industrial wastewater and aquaculture wastewater. The risk assessment of the seven trace heavy metals shows Cr,Ni,Cu,Pb,Zn, As are at low pollution level, but the Cd is at the highest pollution level.

Key words: trace heavy metal, speciation, controlling factor, risk assessment, Daya Bay