Evaluation and Technical Control of Soil Contamination by Heavy Metals

城市土壤中有毒重金属的分布和迁移是评价其对人类健康、农业和生态系统影响的重要内容。本研究的目的由四个部分组成。第一个是通过调查城市垃圾焚烧厂和科比市周围表层土壤中的元素浓度，确定化学沉降物中的显著元素。二是提出了非饱和土中重金属动态行为的评价方法。三是提出了控制土壤水分和污染物在土壤中运动的方法--斜坡式粗土挡墙。四是提出了选择合适的土壤污染技术控制方法的指南。得到了以下一些有价值的结果。(1)对大地震后城市垃圾焚烧厂附近和科比市周边土壤中元素的垂直分布进行了测定。通过INAA、ICP-AES等分析手段，认为Zn、Sb、Br是垃圾焚烧产生的化学沉降物，Cr、Co、Ni、Cu、Zn、As、Cd、Sb、Pb可能是坂神淡路大地震后大火产生的化学沉降物。(2)采用非饱和土柱实验研究了土壤含水量对钴吸附-解吸反应的影响。钴在砂土和粉土中的分配系数在一定含水量下均存在极小值。(3)模型试验和60 cm-480 cm（宽）尺度的数值试验结果表明，倾斜粗土挡墙有效地控制了土壤水分的向下运动。在60 cm-480 cm（宽）尺度的模型和数值试验中，该屏障的可用性主要取决于规模、降雨强度及其持续时间。

Distribution and migration of toxic heavy metals, which have been added into urban soil, are of great interest to assess its effect on the human health, agriculture, and ecosystems. The purposes of this study are consist of four parts. The first is to identify notable elements as chemical fallout by surveying concentrations of elements in surface soil around municipal solid waste incineration plant and Kobe City. The second is to propose the method to evaluate dynamic behavior of heavy metal in unsaturated soil. The third is to propose the method for control the soil water and contaminant movement in soil, named sloped coarse-soil barrier. The fourth is to propose a guideline for selecting an appropriate technical control method of soil contamination. Some valuable results were obtained as follows.(1) The vertical distribution of elements were measured in the soils sampled in the vicinity of municipal solid waste incinerators plant and around Kobe City damaged by great earthquake. elements concentrations were determined by INAA,ICP-AES.From these measurement, it was suggested that Zn, Sb, and Br were notable elements as chemical fallout derived from the municipal solid waste incinerators plant, and Cr, Co, Ni, Cu, Zn, As, Cd, Sb, Pb were possibly added to surface soil derived from big fires after Hanshin-Awaji Great Earthquake.(2) Unsaturated soil column experiments were carried out to evaluate the effects of water content on the sorption-desorption reaction of cobalt by soil. The estimated distribution coefficients of cobalt have minimum value at a certain water content for both sand and silt.(3) From model and numerical experiments of 60cm-480cm (width) scale, it was indicated that downward soil water movement was effectively controlled by sloped coarse-soil barrier. at model and numerical experiments of 60cm-480cm (width) scale. The availability of this barrier mainly depends on the scale, rainfall intensity, and its duration.