上海农田土壤重金属的环境质量评价

对上海市农田土壤中Cu、Zn、Pb、Cd、Cr、Hg、As进行测定分析,利用不同的评价方法和标准来评价土壤重金属的环境质量状况,并在GIS软件支持下,通过空间插值分析了研究区重金属含量的空间分布特征.结果发现,除As外,各重金属平均含量均高于其背景含量;Cu、Zn、Cd、Cr、Hg和As的浓度均有个别地方的含量超过了国家<土壤环境质量标准>(GB 15618-1995)二级标准限值;从土壤重金属空间分布来看,农田质量整体尚好,土壤优良率为71.4%,合格率为94.9%,不合格率为5.1%;土壤质量受到各种重金属不同程度的影响,存在显著的空间分异,而Zn、Cd、Hg的污染是引起上海地区土壤质量下降的主要原因;各级土壤以城镇建设用地为中心,圈层状分布特征明显,随着上海地区城镇化空间扩展的推进与土地利用方式的变化,可能会导致新污染区的出现与土壤质量的下降.

Evaluation on Environmental Quality of Heavy Metals in Agricultural Soils of Shanghai

Contents of heavy metals (Cu, Zn, Pb, Cd, Cr, Hg and As) in agricultural surface soils from Shanghai were analyzed. Different evaluation methods and assessment standards of heavy metals were also used for comparison. In addition, inverse distance interpolation (IDW) method was also applied to study the spatial variability of heavy metals pollution, based on GIS. The results show that mean concentrations of heavy metals in soils all exceeded their corresponding natural-background values, except for As. Compared mean concentrations of heavy metals with the National Standard, the soils were not contaminated. All the determined heavy metals excluding Pb in some regions, however, exceeded the critical values of national soil quality standard. Additionally, it is indicated that most of cropland soils were good, and the ratio of good soil, certified soil and disqualified soil were 71.4%, 94.9% and 5.1%, respectively. Most of the disqualified soils, which distributed in Jiading and Pudong, however, have been urbanized and covered with buildings and factories. Moreover, the soil quality was influenced by different heavy metals at different levels, thus the regional differentiation of soil pollution was obvious. Zn, Cd and Hg were the dominant elements causing soil heavy metal pollution in the study area. Furthermore, it was found there was a close relationship between the urban distribution and heavy metal pollution of the soils. Therefore, it is concluded that with the expanding of urbanization, a new polluted area may appear.