沉积物重金属污染评价方法比较——以潭江为例

重金属通常被认为是反映水环境质量的重要指标,而沉积物作为污染物的重要宿体则是水环境的基本组成部分。为对潭江流域沉积物重金属污染状况进行分析和评价,在潭江干流由上游至下游的近河口处共计15个采样点进行表层沉积物采样。对采得样品采用ICP-AES和原子吸收等方法进行测定。根据对15个表层沉积物样品的重金属含量检测后得到的数据,分别采用潜在生态风险评价方法、地累积指数法和沉积物质量控制基准对沉积物重金属污染状况和生态风险进行评价,得出的结果表明:潭江流域表层沉积物中Cd和Pb生态风险很高,Cu在部分采样点风险较高,As的污染风险一般,Cr和Zn的污染风险较低。通过潭江实例比较这3种评价方法,结合潭江实例,得出的结论认为潜在生态风险评价方法考虑较综合但主观性强,地累积法简便但具有局限性,沉积物基准与实践结合紧密但尚无普适基准。因此,对沉积物中重金属的生态风险评价需要用多种方法进行综合比较以减少误差提高准确度。

Evaluation of Heavy Metal Pollution in River Sediment:A Comparative Case Study in Tanjiang River

Sediment of a water body as the carrier of heavy metal was studied in Tanjiang River,which geologically belongs to the Pearl River Delta.Samples of top sediment were taken and collected from a total of 15 loci of the river downstream from the source in November 2010,and the concentrations of heavy metals were analyzed by using ICP-AES and AA.Three different methods were used to evaluate the status and ecological risk of heavy metal pollution,including methods of the potential ecological risk index,geological accumulation index and sediment quality guideline(SQGs).Results of the evaluation revealed that sediment contamination of Cd and Pb had resulted in a very high ecological risk as a whole,while risk of Cu was high in some places,and risk of Cr and Zn low.The comparison indicated that the potential ecological risk index was a comprehensive method but with some drawbacks of subjectivity;geological accumulation index was very simple in use but only quasi-quantitative result could be obtained;and as to SQGs,being practicable though,there wasn’t yet a guideline that could be universally observed.So,to get a accurate result in assessing heavy metal pollution,it had better use different evaluation methods.