四川省江安县某硫铁矿区周边农田土壤重金属来源解析及污染评价

为全面了解四川省江安县某硫铁矿区对周边农田土壤的影响,系统采集207个表层土壤样品和10个背景土壤样品,对pH值和重金属含量进行测定,采用多元统计方法解析重金属的主要来源,并对土壤重金属污染指数评价、潜在生态风险进行研究。结果表明:研究区农田土壤重金属背景值受矿区影响普遍高于全国、四川省土壤背景值,存在不同程度的累积现象;多元统计分析结果显示Cr、Ni、Cu和Cd来源相似,主要受硫铁矿区工业活动影响;Hg和As主要来源于成土母质;Zn可能受人为活动和自然因素双重影响;研究区土壤Cd污染最严重,均值为1.55 mg·kg~(-1),超标率高达99.03%,Cu次之,超标率为37.20%,整体以中度污染为主;背景参比值的选取显著影响潜在风险评价结果,以研究区土壤背景值作为参比时,79.71%采样点存在中等生态风险,主要是Cd和Hg的风险较高。研究表明,硫铁矿区工业活动导致周边农田镉污染严重,本研究为后续耕地土壤污染防治提供科学依据。

Source identification and pollution assessment of heavy metals in farmland soils around a pyrite mining area in Jiang'an County, Sichuan Province, China

To investigate the comprehensive influence of a pyrite mine on farmland soils in Jiang''an county, Sichuan Province, 207 surface soil samples and 10 background samples were collected to determine pH values and heavy metal concentrations. A multivariate analysis was applied to identify the potential sources of heavy metals. Pollution index assessment and potential ecological risk were also analyzed. The following results were obtained:background heavy metal content in the studied farmland soils was higher than the background values nationwide and Sichuan Province owing to the influence of the mining area, indicating the enrichment of heavy metals in the soil to different degrees; multivariate analysis results showed similar sources for Cr, Ni, Cu, and Cd, which was related to the industrial activity of the pyrite mining area; Hg and As were mainly affected by the parent soil materials; and Zn might originate from two sources; Cd seriously polluted the studied farmland soils with an average content of 1.55 mg·kg^-1 and the percentage of exceeding standard accounted for 99.03%, followed by Cu (37.20%); the study area was at a moderate pollution level as a whole; and the potential ecological risk assessment was significantly influenced by the background reference values; when the background content of heavy metals in the studied area was selected as the reference value, 79.71% of the samples were at the mild potential ecological risk level, which was mainly attributed to Cd and Hg. Therefore, the industrial activity of the pyrite mining area led to severe Cd pollution in the surrounding farmland soil and the present study showed the potential to provide a scientific basis for the prevention of subsequent pollution.