生态修复后某矿区下游农田土壤金属污染特征与风险评价

Characteristics and Risk Assessment of Soil Metal Pollution in Farmland Downstream of Mining Area After Ecological Restoration

为研究广东省某矿区开展生态修复多年后下游农田土壤的金属污染状况,选取该矿区下游某村周边农田土壤及灌溉水渠作为研究对象,对该区域采集了40个土壤表层样本和8个水体样本,利用Arcgis软件对农田土壤样品中As、Cu、Cd、Pb、Zn、Mn和Fe_(2)O_(3)的质量分数进行克里金空间插值,解析该区域农田土壤金属的空间分布特征;采用综合污染指数法和潜在生态风险指数法对该区域耕作层土壤中As、Cu、Cd、Pb、Zn和Mn进行风险评价。结果表明,40个土壤样品中As、Cd、Cu、Zn和Pb的超标率分别为77.5%、70%、87.5%、27.5%和67.5%,说明调查区域农田土壤污染属于多金属复合污染,且对农作物的生产和安全产生巨大的威胁。部分土壤样品中As、Pb和Cd含量超过了中国农用地土壤污染风险管制值,需采取严格管控措施。通过分析土壤金属的空间分布,发现土壤金属含量超标点位主要位于灌溉口与受污染河流周边,且含量与离灌溉口距离成反比。结合目前灌溉水样中的金属均未超标的情况,得出该区域农田土壤污染是由该矿区生态环境修复前所产生的含金属灌溉水导致土壤中金属的积累引起的。土壤中金属的综合污染指数平均值为1.89,属于轻微污染;潜在生态风险指数平均值为277.63,潜在生态风险程度为中。调查区的农田土壤存在系统性风险,应当加强土壤环境监测与修复。

To investigate the metal pollution status of downstream farmland soils after ecological restoration for several years in a mining area in Guangdong Province,a study was conducted on the farmland soils and irrigation channels surrounding a village downstream of the mining area.A total of 40 topsoil samples and 8 water samples were collected in the region.The mass fractions of As,Cu,Cd,Pb,Zn,Mn,and Fe_(2)O_(3) in the farmland soils were analyzed using ArcGIS software and Kriging spatial interpolation to determine their spatial distribution characteristics.The risk of As,Cu,Cd,Pb,Zn,and Mn in the topsoil was evaluated using the comprehensive pollution index method and potential ecological risk index method.The results revealed that the exceedance rates of As,Cd,Cu,Zn,and Pb in the 40 soil samples were 77.5%,70%,87.5%,27.5%,and 67.5%,respectively,indicating that the farmland soil pollution in the surveyed area was a multi-metal composite pollution,posing a significant threat to crop production and safety.Some soil samples exceeded the risk control values for As,Pb,and Cd in Chinese agricultural soils,necessitating strict control measures.The analysis of soil metal spatial distribution indicated that the locations with excessive metal concentrations were mainly near irrigation outlets and contaminated rivers,with concentrations inversely proportional to the distance from the irrigation outlets.Considering that the metal concentrations in the irrigation water samples were within acceptable limits,it could be concluded that the farmland soil pollution in the area resulted from the accumulation of metals in the soil due to the irrigation with metal-contaminated water before the ecological restoration of the mining area.The average comprehensive pollution index of metals in the soil was 1.89,indicating slight pollution,and the average potential ecological risk index was 277.63,indicating a moderate potential ecological risk.These findings highlighted the systematic risks in the farmland soils of the surveyed area,emphasizing the need for enhanced soil environmental monitoring and remediation measures.