太湖和辽河沉积物重金属质量基准及生态风险评估

摘要

以太湖、辽河的表层沉积物为研究对象,运用相平衡分配法(EqP)初步探讨了两流域沉积物中4种重金属(Cd,Cu,Pb,Zn)的沉积物质量基准(CSQC)推荐值,并对两流域沉积物中的重金属进行了生态风险评估.根据美国国家环境保护局(US EPA)基于水生生物对重金属的最终慢性毒理水平的淡水水质基准,制定了太湖及辽河4种重金属(Cd,Cu,Pb和Zn)的沉积物质量基准推荐值分别为6.42,55.3,20.6和201.5 mg/kg及5.42,52.8,18.9和177.7 mg/kg.通过与不同国家及地区制定的CSQC值进行比较,推算出4种重金属的CSQC值大都接近所有数据的中间值.从沉积物固相和间隙水相2个不同的角度对沉积物中重金属进行的生态风险评估表明,两流域的大部分区域同步可提取重金属(SEM)与酸可挥发性硫化物(AVS)含量的差值大于0,而Σi[CTi]/[CSQC,i]值与Σi[CIW,i]/[CCCi]值均大于1,说明在整体上两流域沉积物中的重金属存一定的生态风险.由于未考虑各金属元素之间的拮抗或协同等作用以及底栖生物敏感性的问题,所使用的生态风险方法在评价生态风险方面可能会相对有所偏差.%The Equilibrium Partitioning (EqP) approach was used to preliminarily discuss the sediment quality criteria (SQC)recommended values of four heavy metals-cadmium (Cd) , copper (Cu), lead (Ph), and zinc (Zn) -for surface sediments from Taihu Lake and Liao River. Ecological risk assessment of the heavy metals in sediments from the two basins was conducted. The SQCs for the heavy metals were calculated using the US EPA fresh water quality criteria, which are based on aquatic toxicity of the final chronic level of heavy metals. The calculated SQCs of Cd, Cu, Pb and Zn of the two basins are, respectively, 6.42, 55.3,20. 6 and 201.5 mg/kg(Taihu Lake basin), and 5.42, 52. 8, 18.9 and 177.7 mg/kg (Liao River basin). These values were compared with those of different countries and regions, and it was found that the SQCs obtained in this study were close to the median values in the referenced data. Sediment ecological risk assessment of heavy metals was conducted based on sediment solid phase and interstitial water phase, respectively. SEM-AVSvalues of most areas in the two basins were ＞ 0, and the ∑ i [ CTi ］/［ CSOC.i ] and ∑i [ Clw,i] ［ CCCi ] values were all ＞ 1.This suggests that there exist some ecological risks from heavy metals in the sediments from the two basins on the whole.Without considering the antagonistic or synergistic effects between different metal elements and sensitivity of benthic organisms, the approach of ecological risk assessment used in this paper may be relatively biased.