赣南某钨矿区土壤重金属污染生态风险评价

Ecological risk assessment of heavy metals pollution in a tungsten mine soil in south of Jiangxi Province

对赣南某钨矿区及周边农田土壤重金属的污染进行调查,分析了2个尾矿堆积区及17个农田采样区土壤中重金属Pb、Cr、Mn、Zn、Cu和Cd的总量和形态,采用潜在生态危害指数法和RAC风险评价法对研究区域土壤重金属的生态风险进行评价.结果表明,尾矿堆积区尾砂中6种重金属远远超过江西省土壤背景值和国家土壤环境质量二级标准,土壤重金属浓度水平分布表现为尾矿堆积区>尾矿附近农田土壤>矿区周边农田土壤.形态分析结果显示矿区农田土壤中6种重金属主要以可还原态、可氧化态和残渣态存在,尾矿附近农田土壤重金属Pb、Mn、Zn和Cd酸溶态占比均大于10%,具有较强的生物有效性.潜在生态危害指数评价表明研究区域表层(0—20 cm)和中层(20—40 cm)土壤存在极强的重金属生态危害,Cd是土壤重金属潜在生态风险主要的贡献因子.RAC风险评价结果表明,尾矿附近农田0—40 cm土壤中Zn和Cd存在的生态风险较大,而矿区周边农田0—40 cm土壤中Cd和Mn存在的生态风险相对较大.综合基于重金属总量分析的潜在生态风险指数和基于重金属有效态的RAC评价结果,Cd、Zn和Mn的污染是研究区域土壤污染风险控制需要关注的重点.

The ecological risk of 6 heavy metals （Pb, Cr, Mn, Cu, Zn, and Cd） of contaminated soil was evaluated in a tungsten mine area located in Gannan area, Jiangxi province, China. Soil samples were collected from 2 tailings disposal sites and 17 farmland sites in the survey area. Contents and species of 6 heavy metals were analyzed, and ecological risk was assessment with the methods of potential ecological risk index and risk assessment code （RAC）. The results indicate the contents of all 6 heavy metals in tailings disposal area were much higher than the background values of Jiangxi province soils and the secondary standard of soil environmental quality. The concentrations of heavy metals in different areas followed tailings sites〉 farmland sites nearby the tailings〉 farmland sites surrounding mining areas. According to the results of speciation analysis, the acid-soluble fractions of Pb, Mn, Zn, and Cd were over than 10% in all the farmland sites nearby the tailings, which would lead to high bioavailability. The potential ecological risk assessment showed that there were extremely high ecological risks in the top soils （0—20 cm） and 20—40 cm soils of the study area, and Cd was the main contribution factor. According to the analysis of RAC, the ecological risk of Zn and Cd dominated in 0—40 cm soils of farmland nearby the tailing, while the ecological risks of Cd and Mn were relatively high in 0—40 soils of farmland surrounding the mining area. Combined with the two assessment results, Cd, Zn and Mn pose higher potential biological risk than Pb, Cu and Cr in the study area.