大亚湾表层沉积物重金属元素形态特征、控制因素及风险评价分析

为了解大亚湾表层沉积物中重金属的污染状况，对大亚湾海域23个点位表层沉积物中7种重金属元素（Cr、Ni、Cu、Pb、Zn、Cd、As）的质量分数、形态特征、来源控制因素以及潜在生态风险进行了研究。采用优化BCR提取法分析重金属元素赋存形态，并依据各种重金属元素的形态特征与沉积物基质属性进行了相关因子分析，了解其分布的控制因素。结果表明：大亚湾沉积物重金属元素呈现环带状分布特征，从岸向湾内逐渐减小；重金属元素质量分数的高值区主要分布于大鹏澳、哑铃湾及范和港附近；重金属元素赋存形态中Cr、Ni、Cu、Zn、As主要以残渣态存在，Pb主要以可还原态存在，Cd主要以酸提取态存在；7种重金属元素各自非残渣态所占比率从大到小为Pb(78.83%)、Cd(78.65%)、Cu(48.54%)、Zn(48.10%)、Ni(38.31%)、Cr(28.43%)、As(27.76%)，即Pb最高，As最低，表明Pb的迁移性最强；通过因子分析，大亚湾重金属主要为沿岸自然风化产物的输入，其次为工业废水及养殖污水。运用酸提取态风险评估法对重金属元素潜在生态风险进行评价，发现研究区所选重金属元素综合风险评价Cd为高风险，其余重金属为中-低风险等级。

Chemical Form,Control Factor and Risk Assessment of Trace Heavy Metals in Superficial Sediment of Daya Bay

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.