珠江口外内陆架表层沉积物重金属元素形态特征、控制因素及生态风险分析

Speciation,Source Analysis and Risk Assessment of Heavy Metals in Superficoal Sediment of Inner Continental Shelf Near the Pearl River Estuary

2011年对珠江口外内陆架海域22个点位表层沉积物中主要的重金属Cr、Ni、Cu、Pb、Zn、Cd和As含量、形态特征、来源控制因素以及潜在生态风险进行了研究。采用了BCR提取法分析各种重金属赋存形态,并依据各种重金属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:珠江口外内陆架沉积物重金属分布特征为由陆向海的方向,随着水深增大而逐渐降低。重金属赋存形态中Cr、Ni、Cu、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,Zn主要存在于残渣态与可还原态。各重金属非残渣态比重Cd最高,Cr最低,表明Cd的迁移性最强。各元素非残渣态在平面上的分布与总量分布模式相关性较好,因此,珠江口外内陆架海域通过总量来确定区域重金属污染情况在一定程度上是可靠的。重金属元素与黏土含量、可还原态Fe、Mn含量普遍具有较好的相关性。珠江口外内陆架的重金属来源比较复杂,主要来源于附近大陆的物质输入。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,发现研究区各元素综合风险评价除Cd为高风险外,Cr元素综合风险评价为无风险;其余为中一低风险等级。

Research on the contents of heavy metals,such as Cr,Ni,Cu,Pb,Zn,Cd,As,and their distribution characteristics,source control analysis in the superficial sediments of 22 sampling sites（sampled in 2011） in the inner continental shelf near the Pearl River Estuary（study area）,were conducted.The distribution characters of the specific chemical forms,sources and environmental assessments of these heavy metals were analyzed with the method of modified BCR,factorial analysis and risk assessment evaluation.Results show the contents of heavy metals decreases from land to sea as the water depth increase.As the results of modified BCR sequential extraction showed in the area,Cr,Ni,Cu,As appear mainly as the residual form,Pb appears mainly as reducible form,Cd appears mainly in acid-soluble form,Zn appears mainly in residual form and acid-soluble form,while Cd content was the highest,Cr content was the lowest in the proportion of non-residual form,furthermore the superficial distribution of non-residual forms of metals were consistent with that of total contents.It was proved some reliability to other extent methods by employing the total contents of heavy metals to determine the pollution degrees in this area.Generally better correlation between the contents of heavy metals and clay,reducible Fe,Mn,were representation.The source analysis showed the pollutants were mainly the input of near the mainland.The potential ecological risk of these seven kinds of heavy metals was evaluated by using the risk assessment code.It shows that Cr,Ni,Cu,Pb,Zn,As,were at present low pollution level,however,the pollution level of Cd was high.