化工污染场地土壤不饱和区典型氯代烃化合物的垂向分布特征

化工污染场地风险评估与修复是我国目前面临的重要环境问题.选取某化工厂遗留场地的不同功能区为研究对象,通过分析第1层(回填土层)、第2层(砂质粉土或黏质粉土层)和第3层(粉质黏土层)土壤样品中的1,2-二氯乙烷(1,2-DCA)质量分数,查明了1,2-DCA在土壤不饱和区的垂向分布特征.结果表明:回填土层1,2-DCA质量分数相对最小,而第2层砂质粉土或黏质粉土层到第3层粉质黏土层的质量分数变化呈增大或减小2种规律,土壤质地、渗透系数、土壤有机质含量和土壤夹层性质等可能是影响1,2-DCA质量分数垂向分布的因素.聚类分析结果表明,1,2一DCA 质量分数相对变化与土壤层序结构有一定的相关性.1,2-DCA质量分数在其生产车间周围土壤不饱和区的污染水平远大于其他功能区;第2层土壤污染最严重;第3层土壤可能受层问潜水影响,1,2-DCA随水流自两向东方向上迁移,在1,2一DCA生产车间东部第3层土壤中达到高质量分数.本研究工作可为场地采样布点的优化、风险识别与污染修复提供科学依据.

VERTICAL DISTRIBUTION OF TYPICAL CHLORINATED HYDROCARBONS IN THE VADOSE ZONE OF A CHEMICALLY CONTAMINATED SITE

Risk assessment and remediation of chemically contaminated soil is an urgent environmental problem in China. Concentration of 1,2-dichloroethane (1,2-DCA) in the first layers (artificially filled layers), the second layers (sand silt or clay silt layers) and the third layers (silt clay layers) were analyzed to gorge its vertical distribution in unsaturated soil, especially focusing on different functional regions of a former chemical manufacturing field. Data showed that 1,2-DCA concentration was lowest in the filling layers. 1, 2-DCA concentration either increased or decreased from the second sand silt or clay silt layers to the third silt clay layers. Soil texture, permeability coefficient, organic matter contents, properties of soil interlayer are factors affecting 1,2-DCA soil distribution. Cluster analysis showed that relative 1,2-DCA concentration changes may be correlated with soil layer sequences. 1,2-DCA concentration in unsaturated soil layers around 1,2-DCA production plant were much higher than in other functional regions; soil pollution was most serious in the second layers. High 1,2-DCA concentration in the third layers in the eastern side of 1,2-DCA production plant may be related to 1,2-DCA transfer from west to east across the plant with inter-strata phreatic water flow. This work offers basic indication in regards to optimizing distribution design of sampling points, risk identification and remediation.