北京某道路外侧土壤重金属形态特征与污染评价

选取北京城区某主干道两侧土壤样品作为研究对象,测定其中Cr、Ni、Cu、Zn、Cd和Pb等重金属之总量,利用修正的BCR提取法分析各种重金属存在的形态。结果显示:Cr、Ni、Cu、Zn、Cd和Pb总量平均值分别超过北京地区背景值的1.51、3.84、1.78、2.33、13.92和1.32倍;Cr、Ni、Cu、Zn和Cd元素各形态分布情况为:残渣态>氧化态>酸提取态>还原态>水溶态;而Pb为残渣态>氧化态>还原态>酸提取态>水溶态。采用4种不同评价方法对研究区域土壤重金属污染现状进行评价。结果显示,基于总量评价方法中的地累积法得到的污染顺序为Cd>Ni>Zn>Cu>Cr>Pb,而潜在生态评价法得到的潜在污染顺序为:Cd>Ni>Cu>Pb>Cr>Zn;基于形态学的评价方法中RAC风险评价法得到生物可利用性顺序为:Ni>Cd>Zn>Cu>Pb>Cr;而次生相与原生相比值法得出:生物潜在可利用性依次是:Pb>Ni>Zn>Cd>Cu>Cr。

Heavy Metal Speciation of Soil Sample Collected from Either Side of a Thoroughfare in Beijing and Heavy Metal Pollution Evaluation

Heavy metals including Cr,Ni,Cu,Zn,Cd and Pb contained in soil samples collected from a thoroughfare of Beijing were analyzed and a modified BCR extraction technique was used to analyze the chemical species of these heavy metals.The analytic results revealed that compared with the background value of the heavy metals of the area,concentrations of above six metals in soil were higher as a whole.As to the speciation,situations of the heavy metals existing in soil were studied which involved mainly residual form and others including oxidizable,reducible,water-soluble and acetic-acid-extractable forms.Additionally,four different methods were used in evaluation of heavy metal pollution in a comprehensive way,i.e.,index of Geo-accumulation(Igeo),potential ecological index(PER),risk assessment code(RAC),and ratio of secondary phase and primary phase(RSP).