阳澄湖表层沉积物中氮磷及重金属的空间分布特征及污染评价

为了解阳澄湖表层沉积物中氮磷及重金属的空间分布和污染特征,对全湖开展了大范围调查,基于综合污染指数、地积累指数法和潜在生态风险指数法对沉积物污染风险进行评价.结果表明:阳澄湖表层沉积物中w(TN)、w(TP)平均值分别为3 433、379 mg/kg,湖区氮磷污染严重且空间差异明显,w(TN)高值区位于阳澄东湖,w(TP)高值区位于阳澄西湖；综合污染指数评价结果显示,整个阳澄湖TN均为重度污染状态,TP除阳澄西湖外大部分区域处于轻度污染状态.阳澄湖表层沉积物中w(Cu)、w(Zn)、w(Pb)、w(Cr)、w(Cd)、w(As)、w(Hg)、w(Ni)的平均值分别为35.0、141、12.6、62.6、0.36、27.5、0.145、47.6 mg/kg,分别是江苏省土壤重金属环境背景值的1.50、2.17、0.57、0.83、4.22、2.93、5.78、1.45倍,阳澄西湖的重金属含量要高于阳澄中湖和阳澄东湖.地积累指数法和潜在生态风险指数法评价结果均表明,Hg和Cd是主要的生态风险贡献因子,二者生态风险指数平均值分别为231.23、126.63.相关分析结果表明,阳澄湖表层沉积物中Cu、Zn、Pb、Cr、Cd、Hg和Ni的质量分数显著相关,说明其具有相似的来源,结合水系结构和周边企业分布,推测其主要来自于相城区和常熟市的工业企业. 

Spatial Distribution and Pollution Assessment of Nitrogen,Phosphorus and Heavy Metals in Surface Sediments of Lake Yangcheng, Jiangsu Province, China

Abstract: Lake Yangcheng, the third largest freshwater lake in Lake Taihu plain, is a drinking water source for Suzhou City. The lake is also important for aquaculture, flood control, tourism and recreation. However, rapid urbanization and economic development have caused serious deterioration of water quality in the past decades. Ninety-five surface sediment samples were collected in May 2015 to characterize the spatial patterns of pollutants (i.e., nitrogen, phosphorus and heavy metals) in surface sediments. The contents of total nitrogen (TN), total phosphorus (TP) and heavy metals (Cu, Zn, Pb, Cr, Cd, As, Hg, Ni) were analyzed, and risk of sediment contamination was evaluated using integrated pollution index, geo-accumulation index and potential ecological risk index. The results showed that the average contents of TN and TP were 3433 and 379 mg/kg, respectively, indicating a serious situation in the lake. Spatially, relatively high content of TN was recorded in the eastern part of the lake, while relatively high content of TP was found in the western part of the lake. Integrated pollution index showed that TN was severely polluted in the whole lake, and TP was slightly polluted in most areas except for the western part. The average contents of Cu, Zn, Pb, Cr, Cd, As, Hg and Ni in the surface sediments were 35.0,1, 12.6,2.6,0.36,7.5,0.145 and 47.6 mg/kg, which were 1.50,2.17,0.57,0.83,4.22,2.93,5.78 and 1.45 times higher than the background values, respectively. The contents of heavy metals in the surface sediments of the western part were higher than other areas. Both the results of geo-accumulation index and the potential ecological risk assessment indicated that Hg and Cd were the main pollutants and led to high potential ecological risk, which reached serious ecological risk level (231.23,6.63). The contents of Cu, Zn, Pb, Cr, Cd, Hg and Ni were highly positively correlated with each other, indicating that these metals had the same sources of pollution, which might originate from the industrial enterprises of Xiangcheng District and Changshu City according to the water drainage structure and surrounding enterprise distribution.