攀枝花煤矿区周围农田重金属污染特征及风险分析

本研究以四川省攀枝花市几大煤矿区周围农田为研究对象,采集表层煤矿区附近的24个农田土壤表层样,利用三酸消解法提取并测定土壤样品中Ni、Cu、Zn、As、Cd、Pb六种重金属元素的总量,同时利用0.1 mol/L氯化钙和0.5 mol/L磷酸二氢钾浸提并测定Ni、Cu、Zn、Cd、Pb、As有效态含量。采用内梅罗综合污染指数法、地累积指数法和生态风险指数法分析研究区农田重金属污染状况及其环境风险。结果表明所有煤矿区周边农田土壤中Ni、Cu、Zn、As、Cd、Pb的平均含量高于四川省土壤背景值,其中部分点位As、Cd和Zn超过国家农田土壤重金属风险管控标准,点位超标率分别为8.3%、41.7%和25%;Cd和Pb具有较高生物有效性,生物有效性系数分别为35.29%和20.10%;相关性分析结果表明Cd、Zn、As和Pb两两间存在互为显著相关,农田中这四种元素主要来源于煤矿开采和加工。三种评价结果均表明煤矿区附近农田中Cd处于显著污染水平,是农田土壤污染风险的主要贡献因子;花山矿区周围的农田是四大矿区中重金属污染最为严重的,需引起相关部门重视或采取一定的土壤污染风险管控措施。

Characteristics and Risk Analysis of Heavy Metal Pollution in Farmland around Panzhihua Coal Mining Area

In order to reveal the contamination status of coal mining activities, twenty four surface soil samples were collected from the farmland surrounding the Panzhihua coal mining area, Sichuan Province, and the total concentration of six heavy metals (Ni, Cu, Zn, As, Cd and Pb) in soil samples were determined with a digestion of three acid mix, and the bioavailability of these elements were extracted by 0.1 mol/L calcium chloride and 0.5 mol/L monopotassium phosphate. The contamination status and the environmental risks in the study area was assessed with Nemerow composite index method, geo-accumulation index method, and potential ecological risk index method. The results show that the average content of Ni, Cu, Zn, As, Cd and Pb in the farmland soil around the mining area are higher than the soil background value of Sichuan Province and there is a phenomenon of accumulation of heavy metals; the concentration of As, Cd and Zn in some sampling sites were over the Soil Environmental Quality Risk Control Standard of China, the over-standard rate were 8.3%, 41.7% and 25%, respectively. The results of bioavailability indicated Cd and Pb have the highest values, 35.29% and 20.10%, respectively. Correlation analysis showed that Cd, As, Zn and Pb have a close relationship with each other, indicating they may source from the coal mining and processing. The results of three risk assessment methods indicated that Cd was at a high or strong pollution level which is the main cause of the farmland contamination. Nemerow comprehensive pollution index showed that the farmlands near Huashan Coal Mine was the site suffering the most serious heavy metal pollution and such scenario need be highly concerned by local government and some measurements should be done to control the heavy metals pollution in farmlands.