污染地块巨厚含水层典型DNAPLs运移模拟及安全利用深度评估

江苏省南部地区历史遗留化工污染地块同时存在巨厚含水层（厚度＞30 m）和DNAPL类污染物，故导致再开发利用时调查和治理深度难以确定。利用UTChem 模型构建地块二维地下水DNAPLs迁移模型，对巨厚含水层底板上典型DNAPLs（氯仿、1,2-二氯乙烷、四氯化碳、四氯乙烯）随时间推移的迁移扩散情况进行了模拟，并对影响其扩散范围的因素进行了探讨，基于模拟研究结果对此类地块安全利用深度进行了分析。模拟研究表明，不存在抽水井的情况下，经过70 a，含水层底板上4种典型DNAPLs（氯仿、1,2-二氯乙烷、四氯化碳、四氯乙烯）污染羽迁移范围有限，其自底板垂直向上最大迁移距离分别为16.70、16.90、15.20、7.90 m，向下游迁移距离分别为332.12、337.77、322.10、243.40 m。在存在抽水井的情况下，抽水井会显著影响DNAPLs污染羽的迁移范围。影响DNAPLs污染物迁移扩散范围的主要因素为污染物溶解度、密度、黏度、弥散度及渗透系数。本研究结果可为典型化工类型退役地块的风险管控和安全利用提供参考。

Transport Simulation of Typical DNAPLs in Deep Aquifer and Safe Utilization Depth Evaluation of Polluted Plot

There are a large number of chemical pollution sites left over by history in the areas along the river and near the sea in southern Jiangsu. There are huge thick aquifers and DNAPL pollutants in the area where these sites are located. The depth of investigation and treatment during their redevelopment and utilization has always been a prominent problem perplexing the safe utilization of the plots as construction land. In this study, UTChem model was used to build a 2D groundwater DNAPLs transport model. Transport of 4 typical DNAPLs on very thick aquifer floor (chloroform, 1,2-dichloroethane, carbon tetrachloride and tetrachloroethylene) over time were simulated, and the factors affecting its diffusion range were discussed. Based on the simulation results, suggestions and factors that should be considered for the safe utilization depth of such sites are put forward. The research showed that, the migration of four typical DNAPLs (chloroform, 1,2-dichloroethane, carbon tetrachloride and tetrachloroethylene) plumes on the aquifer floor was limited after 70 a under no pumping wells condition. The maximum migration distances from the floor vertically upward were 16.70, 16.90, 15.20 and 7.90 m respectively, and the migration distances to the downstream were 332.12, 337.77, 322.10 and 243.40 m respectively; under pumping condition, the pumping wells will significantly affect the migration range of DNAPLs pollution plume. The main factors affecting the migration and diffusion range of DNAPLs were the solubility, density, viscosity, dispersion and permeability coefficient of pollutants. The results of this study can provide a scientific basis for the risk control and safe utilization of typical chemical decommissioned plots.