广西某有色金属矿区土壤重金属地球化学基线值的确定及其污染评价

Determination of heavy metals geochemical baseline and their pollution assessment in soils of a nonferrous metal mining area in Guangxi

以广西某有色金属矿区4251个表层(0~20 cm)土壤样品中As、Cd、Cu、Cr、Hg、Ni、Pb和Zn等8种重金属为研究对象,运用累积频率曲线法确定了各重金属的地球化学基线值(以下简称基线值);以基线值为标准,采用单因子污染指数法和内梅罗综合污染指数法,评估了重金属的污染特征。结果表明:除Ni以外,其余重金属基线值均高于中国土壤元素背景值。土壤中主要污染重金属为Cd、As、Cu、Pb和Zn,其中Cd有34.3%的采样点达重度污染等级。As和Cu同源性较高,与矿石开采等人类活动相关;Cd、Pb和Zn污染受人为因素和自然来源的共同作用影响;Hg、Cr和Ni则主要为自然来源。

A total of 4251 surface(0-20 cm)soil samples were collected from a nonferrous metal mining area in Guangxi.The geochemical baseline values of As,Cd,Cu,Cr,Hg,Ni,Pb and Zn were determined with cumulative frequency curve method.The pollution degree of heavy metals were evaluated using single factor pollution index and Nemero index.The results showed that only the geochemical baseline value of Ni was lower than the background value of China,while the other heavy metals’geochemical baseline values were higher than background values of China.Cd,As,Cu,Pb and Zn were the main pollution heavy metals in the surface soils,among which 34.3%of samples of Cd reached the heavy pollution degree.As and Cu had high homology and were related to human activities such as ore mining;Cd,Pb and Zn pollution were affected by the combined effects of human factors and natural sources;Hg,Cr and Ni were mainly derived from natural sources.