河池市某废弃冶炼厂周边农田土壤重金属污染特征及风险评价

为了解河池市某废弃冶炼厂周围农田土壤重金属的分布特征及潜在风险，研究了该区域不同深度土壤中5种重金属（Cd、Pb、Cr、Cu、Zn）以及主要农作物的污染状况，采用多元统计分析、改进的内梅罗指数法、潜在生态危害指数法结合GIS插值进行土壤污染调查及生态风险评价。结果表明:土壤中Cd、Pb、Cr、Cu、Zn的平均含量均高于广西土壤环境背景值，其中Cd、Pb的富集情况较为明显，其含量分别高于GB 15618-2018《土壤环境质量农用地土壤污染风险管控标准（试行）》中的风险筛选值11.5，3.3倍。研究区土壤重金属含量空间分布呈现以毗邻冶炼厂的重污染区为中心，并向四周辐射的趋势，其中冶炼厂西北和东南方向含量较高。分析研究区土壤剖面重金属含量可知，Pb只有表层土壤含量超过土壤污染风险筛选值，Zn、Cr和Cu则不同深度土壤中的含量均低于风险筛选值，而Cd在各土层深度中的含量均超过农用地土壤污染风险管制值，表明该地区Cd污染严重，应重视土壤污染对农作物的生态风险及对地下水的潜在威胁。研究区主要农作物玉米、甘蔗中Pb、Cd、Cr的平均含量分别为GB 2762-2017《食品安全国家标准食品中污染物限量》中标准限值的21.87，18.48，7.34倍和7.97，3.73，6.25倍，超标率为100%。

POLLUTION ASSESSMENT OF HEAVY METALS IN FARMLAND SOILS AROUND AN ABANDONED SMELTER IN HECHI,CHINA

In order to understand the distribution characteristics and potential risks of heavy metals in farmland soil around an abandoned smelter in Hechi, the pollution status of five heavy metals (Cd, Pb, Cr, Cu, Zn) and main crops in different depths in the region were studied. The soil pollution investigation and ecological risk assessment were carried out by using multivariate statistical analysis, improved Nemerow index method, latent hazard index method and GIS interpolation. The results showed that the average contents of Cd, Pb, Cr, Cu, Zn in soil were higher than the background values of soil environment in Guangxi. The accumulation of Cd and Pb were more obvious, and their contents were 11.5 and 3.3 times higher than the limiting values listed in Soil Environmental Quality Risk Control Standard for Agricultural Land (GB 15618-2018), respectively. The spatial distribution of soil heavy metal content in the study area showed a trend of centered by the adjacent to the smelter, and radiated to the surrounding area. The content of heavy metals in the northwest and southeast of the smelter was higher. According to the analysis of heavy metal content in the soil profile of the study area, only Pb in the surface soil exceeded the screening value of soil pollution risk, the content of Zn, Cr and Cu in different depths of soil was lower than the risk screening value, while the content of Cd in each soil layer exceeded the risk control value of agricultural land, indicating that Cd pollution was serious in this area. Therefore, we should pay more attention to the ecological risk of soil pollution to crops and groundwater. The average contents of Pb, Cd and Cr in corn and sugarcane in the study area were 21.87, 18.48, 7.34 times and 7.97, 3.73 and 6.25 times of the standard limits in the Food Safety National Standard:Contaminants Limits in Food (GB 2762-2017), respectively, with the exceeding rate of 100%.