湘潭县农田土壤重金属污染及生态风险评价

为探讨湘潭县农田土壤重金属的污染特征及潜在生态风险,以湘潭县农田土壤为研究对象,分析了土壤中As、Hg、Zn、Pb、Cu、Cr、Cd、Ni 8种重金属元素含量和污染特征,并利用潜在生态危害指数法评价了该区域农田中土壤重金属的综合潜在生态风险。结果表明:8种重金属中Cd含量平均值高于风险筛选值,低于风险管制值,其他7种重金属含量的平均值均低于风险筛选值,且Cd和Hg累积程度较高,其最小值分别是背景值的1.53倍和1.04倍。在单项污染风险评价中,超过90%的样本Cr、As、Hg、Pb含量小于风险筛选值,90.4%的样本Cd含量大于风险筛选值,且Cd含量高的区域主要分布在东部地区,没有Cr、As、Hg、Pb和Cd含量大于风险管制值的样本;综合污染风险评价结果显示92%的样本可能存在食用农产品不符合质量安全标准等的土壤污染风险。综合潜在生态风险系数的平均值为314.9,处于强潜在生态风险水平。通过以上分析说明,该区农田土壤重金属整体呈现出高生态风险状态,这种现象主要是由该区农田土壤中Cd的污染程度比较高造成的。

Heavy metal pollution and potential ecological risk assessment in farmland soils located in Xiangtan County in Hunan Province,China

To characterize the pollution and potential ecological risk from heavy metals in soil of farmland in Xiangtan County, eight heavy metals(As, Hg, Zn, Pb, Cu, Cr, Cd, and Ni)were analyzed and evaluated, using the Potential Ecological Hazard Index. Based on the Soil Environmental Quality Risk Control Standards for Soil Contamination of Agricultural Land(GB 15618-2018), we found that only Cd concentration(mean value)exceeded the risk screening value(RSV)among all the soil heavy metals in the study region. Cd and Hg showed high accumulation, and the minimum Cd and Hg concentration was 1.53 times and 1.04 times that of the local background values, respectively. With regards to single index evaluations, the proportion of samples with concentrations of Cr, As, Hg and Pb lower than the RSV was more than 90%. In most samples, Cd concentration was higher than RSV. The high Cd concentration occured in the eastern region. No samples with heavy metals concentrations higher than the risk intervention value(RIV)were found. The results of this comprehensive evaluation indicate that 92% of the samples may have soil pollution risks, and edible agricultural products may not be meeting quality and safety standards. The soil pollution in this county should be attributed to Cd pollution. Furthermore, the average of the potential ecological risk factor is 314.9 in this area, which indicates a high level of potential risk, mainly due to the high levels of Cd contamination.