南京市某闭库尾矿库区土壤重金属赋存形态及生态风险评价

Soil heavy metal occurrence forms and ecological risk assessment of a tailing pond in Nanjing

通过采集该尾矿库区的表层土壤样品,分析检测样品中重金属元素As、Pb、Cd、Cr、Cu和Zn的总量及其不同形态含量,运用潜在生态风险指数法、风险评估编码法、次生相与原生相比值法以及蚯蚓回避行为试验来分析该矿区土壤的生态风险。结果表明:1)重金属As、Cd和Cu的含量最小值均超过南京地区土壤元素背景值,且平均值分别是南京地区土壤元素背景值的3.5倍、6.7倍和9.3倍;2)潜在生态风险指数统计结果显示轻微、中等、较强和强潜在生态风险所占比例分别为14.29%、50%、28.57%和7.14%,闭库尾矿库区整体呈中等生态风险;3)6种重金属的RAC值均大于1%,存在一定风险,综合RAC与RSP来看,Cd具有极高的释放风险,是最主要的风险因子;4)强潜在生态风险点位的土壤中蚯蚓回避率达到100%,该污染土壤不适合蚯蚓生存,生态风险较高,其余点位蚯蚓回避率均小于80%,生态风险较低。

By collecting the surface soil samples of the tailings reservoir area,detecting and analyzing the total amount of heavy metals As,Pb,Cd,Cr,Cu and Zn and their different chemical forms in the samples,and the ecological risk of the soil in the mining area was analyzed by using the potential ecological risk index method,the risk assessment coding method,the secondary phase and primary comparison value method and the earthworm avoidance behavior test.The results indicated that:1)Minimum concentrations of As,Cd and Cu exceeded the background values of soil elements in Nanjing area,and the average values of the them were 3.5,6.7 and 9.3 times of the background values of soil elements in Nanjing area,respectively;2)The statistical results of potential ecological risk index show that the proportion of slight,medium,a little strong and strong potential ecological risks are 14.29%,50%,28.57%and 7.14%,respectively;3)The RAC values of the six heavy metals are all higher than 1%,and there is a certain risk,from the perspective of RAC and RSP,Cd has a very high risk of release and is the most important risk factor;4)The avoidance rate of earthworms in the soil with strong potential ecological risk points reached 100%,the polluted soil was not suitable for the survival of earthworms and the ecological risk was high,the avoidance rate of earthworms at other sites was less than 80%,and the ecological risk was low.