快速城市化地区土壤重金属污染物的分布——以昆山市为例

Distribution of Heavy Metals in Soils of Fast-Urbanizing Regions—With Kunshan as a Case Study.

以昆山市为例,探讨了快速城市化地区土壤重金属污染物分布特征。结果表明,以背景值上限值为评价指标,昆山市农田土壤100个样点中Zn、Cu、Pb、Hg、As、Cd和Cr超标率均在20%左右,N i超标率为4%,说明部分土壤已有外源污染物进入。以GB 15618—1995土壤环境质量标准第二级标准值衡量,Hg、Cd和Cr(旱地)、Zn超标率分别达5%、4%、3%、2%,Cd含量有的高达5.74 mg.kg-1。不同土属土壤重金属间的相关性有一定差别,这与其母质差异有关。认为昆山市土壤污染的防治应立足于防重于治的基本方针。同时,对Cd、Hg点源污染比较严重的区域应大力加强污染治理,并对污染土壤进行修复。

Distribution characteristics of heavy metals in soils of fast-urbanizing regions are discussed with Kunshan as a case for study. Results indicate that with the upper limits of the background values as indices for evaluation, about 25% , 24% ,22% ,21% ,18% ,18% ,14% and 4% of the 100 soil samples collected from farmland in Kunshan were exceeding the upper limit of soil content of Zn, Cu, Pb, Hg, As, Cd, Cr and Ni, respectively, suggesting external contaminants are entering the fields. According to norms of Grade 11 of GB 15618-1995 “Standard for Soil Environment Quality” ,about 5%, 4%,3% and 2% of the soil samples exceeded the limits of soil contents of Hg, Cd, Cr （dry land） and Zn, respectively. The maximum Cd content in the soil samples even reached up to 5.74 mg · kg^-1. Correlations between heavy metals varied with the soil parent material. It is held that for control of soil pollution, it is essential to give priority to prevention rather than remediation. At the same time, pollution control should be intensified in areas heavy with Cd and Hg point pollution sources, and measures taken to remediate the polluted soil.