珠江口沉积物中重金属分布、形态特征及风险分析

为了解珠江口沉积物中重金属的污染现状及潜在生态危害,于2012年5月在珠江口海域采集29个站位表层沉积物,对6种重金属(Cr、Cu、Zn、As、Cd、Pb)的含量、形态特征、影响因素以及潜在生态风险进行了研究。本研究采用改进BCR提取法分析重金属赋存形态,并运用酸提取态百分含量风险评估法对重金属潜在生态风险进行评价。结果表明,珠江口沉积物中重金属总量呈现西北向东南逐渐减小的分布特征,西岸的浓度普遍高于东岸区域,重金属含量高值区主要分布于虎门、磨刀门、鸡啼门附近,陆源人为污染影响明显;重金属赋存形态中Cr、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,各重金属非残渣态所占比例以Cd最高,表明Cd的迁移性最强;以酸提取态百分含量为依据进行的珠江口沉积物重金属的风险评价,结果显示虽然Cd的绝对含量不高,但其潜在危害等级为高风险,其余重金属为中-低-无风险等级。

Distribution,speciation and risk assessment of trace metals in surface sediment of the Zhujiang estuary

29 surficial sediment samples were collected in the Zhujiang estuary and its adjacent area in May, 2012, in order to study the total content, speciation and ecological risk assessment of six trace metals (Cr, Cu, Zn, As, Cd, Pb) in the surficial sediment samples. The modified BCR method was used to identify the chemical forms and the acid extractable fraction of trace metals was used to assess potential ecological risk. In general, total content of six trace metals decreased gradually from the northwest to the southeast, with higher values in western coast areas, which received terrestrial inputs and under strong anthropogenic activities. The BCR results showed that Cr, Cu, Zn and As were mainly present in residual form, Pb was present in reducible form and Cd was present in acid-soluble form, respectively. The proportion of non-residential form was highest in Cd, which indicated the mobility of Cd was high. The risk assessment of the six trace metals indicated that Cr, Cu, Pb, Zn and As were all at low pollution level while the pollution level of Cd was relatively high, which was accordant with the BCR result.