南京城市边缘带化工园区土壤重金属污染评价

为揭示城市边缘带强烈人为活动对土壤环境质量的影响,以南京化工园附近20km^2区域为研究区,网格化精确布点,采集表层土壤样品共计54个,并对其重金属Cu、Zn、Pb、Cr、Cd、Hg、As含量进行了测定分析.结果表明,研究区表层土壤中除Hg外的其它6种重金属含量均未超过国家二级标准;Hg是本区表层土壤重金属污染的主要因子.另外,应用地统计学的克里格方法对研究区内表层土壤污染的空间变异特征进行了分析,并讨论了研究区域的潜在污染源及其污染途径.结果表明,研究区内局部土壤重金属污染主要由蔬菜土壤高强度利用及农化产品投入所致,同时不排除污染水灌溉的影响.

Assessment of soil heavy metals pollution in the chemical industrial areas of Nanjing peri-urban zone

To investigate influences of intensive human activities on soil environment dynamics in the pefi-urban zone, it was conducted in an area of 20km^2 in the vicinity of the Nanjing Chemical Industrial Park. Totally 54 samples of topsoil were collected in an aerophoto-based gtidding design and the concentrations of heavy metals Cu, Zn, Pb, Cr, Cd, Hg and As in the soils sampled were analyzed. First of all, the results of statistical analysis indicated that concentrations of the heavy metals detected in the studied soils did not exceed the safety values of national soil quality criteria with the exception of Hg. Although the concentrations of a few metals in the some sampled sites slightly exceeded their average background values, the spatial variations of the concentrations of those metals, however, paralleled the pedo-gnochemistry of the study area. Hg concentration in the soils from 37% of the sampled sites was higher than environmental safety criteria according to the national soil quality standard, suggesting that Hg might be considered as a dominant element causing soil heavy metal pollution in the area. Furthermore, the spatial variability of soil pollution in terms of heavy metals was investigated by combining pollution evaluating with geastatisfical methods, and potential sources and possible entrance paths of heavy metal pollutants in those plots with measurable pollution were discussed. It was preliminarily concluded that intensive application of metalcontaining agrochemicals during long-term vegetable planting was the major cause leading soil heavy metal pollution. The possibility, however, that irrigation by contaminated surface water and land application of organic composts derived from a variety of wastes and sludge also significantly contributed to soil heavy metal pollution in some cases, could not be excluded.