东平湖底泥重金属形态分析及污染现状评价

Speciation analysis and the pollution assessment of heavy metals in sediments of Dongping Lake

采集了东平湖13个主要监测点的底泥,测定、分析了东平湖底泥中的部分重金属质量比及形态分布,并对底泥重金属污染现状进行评价。结果显示,底泥中4种重金属Zn、Cu、Pb、Cd的质量比分别为84.55～161.82 mg/kg、12.77～30.68mg/kg、30.64～69.26 mg/kg、3.51～16.98 mg/kg。运用潜在生态危害评价对底泥中重金属的质量比进行评价,结果表明,Cd污染最严重,13个采样点的潜在生态危害系数均高于320,属于极强生态危害;Cu、Zn、Pb的潜在生态危害系数均低于40,属于轻微生态危害。4种金属污染由大到小的顺序为Cd、Pb、Cu、Zn。东平湖底泥中Cu、Zn、Pb的形态以残渣态为主,因而重金属在底泥中的稳定性高,Cd酸溶态含量较高,容易释放到水体,造成二次污染。

This paper takes Dongping Lake as a case study for its decisive functions in establishing the South-to-North Water Transfer Project. In this paper, we have set up 13 monitoring points at the coast and middle areas of the lake through the Global Positioning System. For our research goal, we have collected sediment sludge from the above said 13 monitoring points, and made systematic analysis of the concentrations and its organic and inorganic substance distributions, such as those of Cu, Zn, Pb and Cd by using acid digestion and sequential extraction methods, respectively. The pollution of heavy metals in the sediments was evaluated through potential ecological risk assessment. The ingredients of the four heavy metals in the sediments were found at the concentration of Zn being 84.55-161.82 mg/kg, Cu being 12.77-30.68 mg/kg, Pb being 30.64-69.26 mg/kg and Cd being 3.51-16.98 mg/kg, respectively. The average content and the monitored data of Zn, Pb and Cd all exceeded the local soil background values. As to the Cu, its actual monitoring data only exceeded the background value. According to the environmental soil quality standard （GB 15618—1995）, Cu meets the first class standard, whereas Zn and Pb come to the second class rate （6.5Pb〉Cu〉Zn. The results obtained have thus indicated that Cu, Zn and Pb mainly exist in the residual species, and, as a result, their existence in the sediments proves to be highly stable. In addition, since Cd is mainly associated with the acid extractable fraction easily to get released from the water, it may lead to the secondary pollution.