广西某赤泥堆场周边土壤重金属污染风险

Risk Analysis of Heavy Metal Contamination in Farmland Soil Around a Bauxite Residue Disposal Area in Guangxi

为考察广西典型赤泥堆场周边农田土壤重金属污染环境风险,采集194个表层土壤样品,运用内梅罗综合指数法、Harkanson潜在生态危害指数法分析重金属污染状况,利用空间插值法、主成分分析法等对8种重金属元素进行源解析.结果表明,除V、Cu,其他元素的平均含量均超过广西区背景值,Cr、Ni、Zn、As、Pb、Co平均含量超过广西区土壤背景值倍数,分别为1.69、1.35、2.45、11.83、4.17、1.95,其中As为首要污染物;农田土壤呈现出"中度"生态风险,As的贡献率高达68%.8种重金属空间分布特征整体有一定相似之处,均在赤泥库东北方向和西南方向浓度较高,而在东南方向整体浓度较低,并非下风向的西北方向,仅Cr在西北角出现明显富集,可能受到赤泥库影响.农田重金属污染源不同,As污染主要受人为因素影响,V、Ni、Cu、Zn、Pb、Co主要受到自然成土母质的影响,Cr同时受到成土母质和人为因素的影响.

Bauxite residue disposal areas（ BRDA） appear to result in the heavy metal pollution of the farm fields surrounding them. In total,194 topsoil samples were collected from the fields surrounding a BRDA in Guangxi in order to comprehensively understand the pollutant characteristics. These characteristics and their ecological risks were assessed by the Nemerow and Harkanson indices,whilst the sources and correlations of eight heavy metals（ V,Cr,Ni,Cu,Zn,As,Pb,and Co） were analyzed by means of the spatial interpolation method,correlation analysis,and principal component analysis（ PCA）. The results demonstrated that the surrounding fields were seriously polluted by heavy metals. Ninety-two percent of samples were polluted,including 36% that showed serious pollution,and As was the dominant contaminant. The ecological risk results showed that the risks of the surrounding fields were medium,and As was responsible for 68% of this. Spatial interpolation suggested that concentrations of heavy metals in the northeastward and southwestward areas were higher,however the southeastward areas were lower. Multivariate statistics indicated that the possible source of As contaminant was different to those of V,Ni,Zn,Pb,and Co; As was primarily influenced by anthropogenic contamination,including atmospheric sedimentation,and agricultural fertilization. Cr was affected by both soil parent material and atmospheric sedimentation,whereas V,Ni,Zn,Pb,And Co levels were mainly affected by soil parent material.