忻州市灌区土壤重金属污染评价及分布特征分析

Evaluation and Distribution Characteristics of Heavy Metal Pollution in Soil of Xinzhou Irrigation District

以忻府区某典型污灌区农田土壤为研究对象,对重金属污染进行了风险评价且对土壤剖面的重金属含量和形态进行了分析,以期为污灌区重金属污染土壤的修复、环境治理及科学灌溉等提供参考依据。结果表明:长期污水灌溉已导致农田土壤表层土壤中的Cu、Zn、Ni、Cr、Pb、Cd、Hg、As含量相对背景值不同程度的累积,分别是土壤背景值的1.21、0.71、1.23、1.73、1.38、4.62、3.59、1.00倍,只有Zn的平均含量低于土壤的背景值。以国家土壤环境质量标准二级限量值作为污染评价阈值,在25个采样点中,2个采样点的土壤综合污染指数高于0.7,属警戒水平,其它均属于安全水平。8种重金属元素中,表层土壤中的Cu、Zn、Cd、As含量最高,Cr、Hg在80~100 cm含量最高,Ni、Pb在不同土壤中无明显差异。Cr、Zn主要以残渣态形式存在,Cu、Ni、Cd、As主要以残渣态和有机结合态存在,Pb主要以铁锰氧化物结合态和有机结合态存在,Hg以残渣态和可交换态为主,Hg的迁移风险大。

In a typical sewage irrigation area,Xinfu District,the risk assessment of heavy metal pollution was carried out and the content and morphology of heavy metals in the soil profile were analyzed,in order to provide reference for the remediation,environmental control and scientific irrigation of heavy metal contaminated soil in sewage irrigation area.The results showed that long-term sewage irrigation has caused Cu,Zn,Ni,Cr,Pb,Cd,Hg and As to accumulate to varying degrees relative to the background valuein the surface soil of the farmland,which were 1.21,0.71,1.23,1.73,1.38,4.62,3.59,1.00 times,only the average content of Zn was lower than the background value of the soil.Taking the second-level limit value of the national soil environmental quality standard as the pollution evaluation threshold,of the 25 sampling spots,the comprehensive soil pollution index of 2 sampling points was higher than 0.7,which was a warning level,and the others were all safe levels.Among the eight heavy metal elements,the top soil had the highest contents of Cu,Zn,Cd and As,the highest contents of Cr and Hg were between 80 cm and 100 cm,and there was no significant difference between Ni and Pb in different soils.Cr and Zn mainly exist in the form of residue,Cu,Ni,Cd,As mainly exist in the form of residue and organic matter,Pb mainly exists in the form of iron manganese oxide and organic matter,and Hg exists in the form of residue and exchangeable.Mainly,the risk of Hg migration was high.