某铅锌矿区农田重金属分布特征及其风险评价

Spatial distribution and risk assessment of heavy metal pollution in farmland soil of a lead-zinc mining area

为进一步探讨铅锌矿开采和冶炼地区农田重金属污染的分布特征和污染途径,以会泽县者海镇铅锌矿区周边农田土壤为研究对象,共布设496个采样点,测定表层土壤中重金属(Cd、Hg、Pb、Cu、Zn)的含量.利用自然邻点法对表层土壤中重金属含量进行插值拟合,以空间三维模型研究该地区农田土壤重金属污染特征,运用单因子指数、综合污染指数和潜在生态风险指数法对重金属污染程度进行评价,采用相关分析、主成分分析和聚类分析识别污染途径.结果表明:Cd、Hg、Pb、Cu和Zn的含量平均值(mg/kg)分别是云南省背景值的33.05、5.83、12.02、4.89和16.33倍;Cd、Hg、Pb、Zn含量空间分布表现为西北部浓度最高,且中部高于东西两侧,而Cu与此相反;单因子指数评价结果显示99.8%的土样达到Cd重度污染,其次是Cu(82.06%)、Zn(62.50%);综合污染指数表明,研究区均处于重度污染程度,西北部尤为严重;综合生态风险评价表明,中部风险高两边低,Cd的贡献率最大占61%;相关分析结果显示,Zn、Cd、Pb、Hg之间呈显著正相关性(P<0.01),表明其污染途径相近;主成分分析和聚类分析表明,Cd、Hg、Pb、Zn污染途径主要与人类活动有关,Cu主要受自然因素影响,因此对该地区土壤重金属的修复和治理应综合考虑人为因素和自然因素的影响.

The purpose of this study was to further investigate the general distribution of heavy metal in farmland soilsand to identify the possible sources of heavy metals pollution from a lead-zinc mining and smelting area in Zhehai, a townof Huize County. A total of 496topsoil samples were collected and the concentrations of Cd, Hg, Pb, Cu and Zn weredetermined in all the soil samples. The concentrations of heavy metals in surface soil were interpolated using the NaturalNeighbor Interpolation method and three-dimensional models were created to study spatial characteristics of heavy metalpollution in the cropland soils. The degrees of heavy metals pollution were evaluated by using Single Pollution index （PI）,Nemero Synthesis Pollution index （NPI） and Potential Ecological Risk index （PER）. Principle Component Analysis andCluster Analysis were used to identify pollution sources. The results showed that the concentrations （mg/kg） of Cd, Hg, Pb,Cu and Zn were 33.05, 5.83, 12.02, 4.89 and 16.33times as compared to soil background values of Yunnan Province,respectively. Spatial distribution of Cd, Hg, Pb and Zn in the cropland soils illustrated that the most seriously pollutedregion was in the northwest, meanwhile the center was more severe than the other two sides. The concentration of Cu,however, was showed a contrast trend. The results of PI showed that 99.8% of the amount of the soil samples wascontaminated by Cd, which reached the heavy pollution level, and was followed by Cu （82.06%） and Zn （62.50%）. NPI indicated that the whole study area belonged to heavy pollution degree, and especially in the northwest was the mostsevere region. PER demonstrated that high risk appeared in the middle while low risk could be found on both sides, whichCd made the greatest contribution to with a ratio of 61%. Correlation analysis revealed that Zn, Cd, Pb and Hg werepositively correlated with each other （P〈0.01）, indicating that these four pollutants might come from the same source. Theresults of Principal Component Analysis and Cluster Analysis showed that Cd, Hg, Pb and Zn were mainly affected by themining activities, while Cu was mostly affected by natural factors. Therefore, in order to recover the soil from heavy metalpollution, the impact of both anthropogenic and natural sources should be taken into accounts.