某矿区农田土壤重金属分布特征与生态风险评价

为探明贵州六盘水某矿区周边农田土壤重金属的分布特征及污染程度,以矿区周边农田为研究对象,采集表层土壤测定Cr、Ni、Cu、Pb、Zn和As含量,分析重金属空间分布特征,评价土壤重金属污染程度及潜在生态风险,并探究其来源。结果显示,6种重金属元素含量均高于贵州省土壤重金属背景值,超标倍数依次为Cu(5.82)>Ni(2.52)>Zn(2.46)>Pb(1.81)Cr(1.51)>As(1.18),重金属分布显示矿区煤矸石山和洗选厂周边的农田土壤重金属富集较为严重。单项污染指数均值显示Cu处于重度污染水平,Ni、Zn为轻度污染水平,Pb、Cr、As为轻微污染水平;综合污染处于重度污染级别。地质累积指数法评价结果显示:Cu、Ni、Zn、Pb处于轻度污染,Cr、As表现为尚未污染水平。研究区重金属的综合潜在生态风险指数为68.02,已经达到轻度危害程度,其中Cu、Ni对综合潜在生态风险(RI)的贡献最大。多元统计分析结果显示,Zn与Pb、Zn与As以及Cu与Pb的相关性较强,表明Zn、Pb、AS、Cu的来源较相似,为第一类来源,主要源于采矿活动产生的三废;Ni、Cr分别为第二、三类来源,第二类重金属来源与汽车尾气的排放、机械损耗有关;第三类重金属主要受土壤母质影响。4种评价结果基本一致,矿区周边农田土壤重金属处于重度污染,轻度危害程度,Cu、Ni是研究区土壤影响最显著的生态风险因子,重金属主要源于采矿活动产生的三废。

Spatial Distribution Characteristics and Ecological Risk Assessment of Heavy Metals in Farmland Soil of a Mining Area

To explore distribution characteristics and pollution degree of heavy metals in farmland around a mining area in Liupanshui, Guizhou province, surface soil was collected with farmland around mining area as the research object. Contents of Cr, Ni, Cu, Pb, Zn and As are analyzed, and their spatial distribution characteristics, heavy metals pollution and potential ecological risk and their source in the study area were also studied. The results show that soil heavy metals element content in the study area are higher than soil background values of heavy metals in Guizhou province, excessive multiples of Cu (5.82) > Ni (2.52) > zinc (2.46) > Pb (1.81) Cr (1.51) > As (1.18). Heavy metal distribution shows that heavy metals accumulation is more serious in coal gangue mountain and farmland soil around the washing plant. Mean single pollution index to display level of Cu in severe pollution, Ni and Zn for light pollution level, Pb, Cr and As for slight pollution level, and comprehensive pollution situation is in the severe pollution level. The evaluation results of geological accumulation index method show that Cu, Ni, Zn and Pb are slightly polluted, while Cr and As are clean. Comprehensive potential ecological risk index of heavy metals is 68.02, which has reached the degree of mild harm, among which Cu and Ni contribute the most to comprehensive potential ecological risk (RI). The results of multivariate statistical analysis show that correlation between Zn and Pb, Zn with As and Cu with Pb is strong, indicating that sources of Zn, Pb, As and Cu are similar. As the first source, they are mainly from three wastes produced by mining activities. Ni and Cr are the second and third sources respectively. The second heavy metals source is related to automobile exhaust emission and mechanical loss. The third heavy metals source is mainly affected by soil parent material. The results of four evaluations are basically consistent. Farmland soil around mining area is severely polluted and slightly damaged. Cu and Ni are the most significant ecological risk factors affecting soil in research area, and heavy metals are mainly derived from three wastes from mining activities.