苏南典型村镇河网区沉积物重金属与营养盐污染评价

Assessment of Heavy Metal and Nutrient Pollution in Surface Sediments from Rural River Network in Southern Jiangsu Province, China

采集江苏省常熟市某镇34个河网表层沉积物样品,分析了其中全氮(TN)、全磷(TP)、有机质(OM)以及重金属元素As、Cd、Cr、Cu、Hg、Ni、Pb、Zn,同时对沉积物重金属和营养盐的污染特征和来源进行了研究。结果表明:杨园镇河网表层沉积物重金属As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的平均含量分别为15.7、6.11、162、124、0.55、86.3、72.5、370 mg·kg-1,分别是江苏省土壤背景值的1.6、46.9、2.1、5.5、1.9、3.2、2.8、5.9倍,TN、TP平均含量分别为2541、1299 mg·kg-1,河网区沉积物重金属Cd、氮磷污染严重且空间分布差异明显。采用地累积指数和沉积物质量基准评价了河网表层沉积物重金属污染及相应生物毒性效应,表明Cd的污染程度最强,并且发生生物毒性效应的几率很高。采用有机指数和有机氮评价河网沉积物有机碳氮污染状况,有机指数平均为0.98,处于Ⅳ级,有机碳污染严重;有机氮平均为0.24%,处于Ⅳ级,有机氮污染严重。相关性分析和因子分析表明沉积物中重金属和营养盐主要来自工业废水和生活污水的排放,建议通过优化产业布局、强化源头防治和深化污水处理以防控和削减该地区水体重金属危害。

River sediments could accumulate heavy metals and nutrients from and then release into water, causing water pollution. An investigation was performed to assess the pollution status and sources of heavy metals（As, Cd, Cr, Cu, Hg, Ni, Pb and Zn）, and nutrients [total nitrogen （TN）, total phosphorus （TP） and organic matter（ OM ）] in 34 surface sediment samples collected from rural rivers in Southern Jiangsu Province, China. The mean concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in surface sediments were 15.7, 6.11, 162, 124, 0.55, 86.3, 72.5 mg·kg-1 and 370 mg·kg-1, which were 1.6, 46.9, 2.1, 5.5, 1.9, 3.2, 2.8 times and 5.9 times higher than their background values in the soils of Jiangsu Province, respectively. TN and TP were averagely 2.54 g ·kg-1 and 1.30 g ·kg-1, respectively. The Index of Geoaccumulation showed that Cd was the most serious pollutant. Organic index and organic nitrogen of sediments were 0.98 and 0.24%, respectively, both falling into the level Ⅳ, implying their pollution. The discharges of domestic sewage and industrial wastewater were identified as major pollutant sources. The present results suggest that heavy metal and nutrient pollution have become an environmental issue in the studied area and immediate remediation measures should be implemented.