竺山湖及太湖西沿岸北段的重金属分布特征及其生态风险评价

对竺山湖及太湖西沿岸北段底泥沉积物中6种重金属Cd、As、Cr、Hg、Pb和Cu的质量比进行分析,结果表明,底泥沉积物中Cd、As、Cr、Hg、Pb和Cu的平均质量比分别为1.23 mg/kg、10.28 mg/kg、82.98 mg/kg、0.074 mg/kg、35.27 mg/kg和33.9 mg/kg,分别是各自背景值的4.6倍、1.1倍、1.0倍、0.7倍、2.2倍和1.8倍;底泥沉积物中重金属的垂向分布特点是:随底泥沉积物深度的增加,重金属质量比逐渐降低,并在底泥沉积物50 cm深处表现出明显的重金属质量比降低拐点。利用潜在生态风险指数法对竺山湖及太湖西沿岸北段的重金属生态风险进行评价,结果表明,该区域重金属生态风险值范围为34～444,平均值为117,太湖西沿岸大浦口区域的生态风险较大,Cd是生态风险的主要贡献元素。建议对竺山湖以及太湖西沿岸区大浦口区域Cd的污染进行必要的疏浚控制,疏浚深度在底泥50 cm深处,以有效去除该区域的Cd污染。

Distribution of heavy metals in sediments of Zhushan Lake and northern segment of western shore of Taihu Lake and its ecological risk assessment

The concentrations of six heavy metals, Cd, As, Cr, Hg, Pb, and Cu, in sediments of Zhushan Lake and the northern segment of the western shore of Taihu Lake were analyzed. The results show that the average concentrations of Cd, As, Cr, Hg, Pb, and Cu were 1.23 mg/kg, 10.28 mg/kg, 82. 98 mg/kg, 0. 074 mg/kg, 35.27 mg,/kg, and 33.9 mg/kg, which were 4. 6 times, 1.1 times, 1.0 times, 0. 7 times, 2.2 times, and 1.8 times their background values, respectively. The concentrations of heavy metals in the sediments decreased with the increase of the sediment depth and had a significant decreasing tendency at a depth of 50 cm. The potential ecological risk index method was used to evaluate the ecological risk of heavy metals in sediments of Zhushan Lake and the northern segment of the western shore of Taihu Lake. The results show that the RI index of the study area ranged from 34 to 444, with an average value of 117, the ecological risk in the Dapukou area on the western shore of Taihu Lake was high, and Cd was the main element contributing to the ecological risk. It is suggested that the Cd pollution in the Dapukou area and Zhushan Lake should be controlled by dredging, and the dredging depth should be kept at 50 cm for effective removal of Cd pollution.