低渗透石化污染场地多相抽提修复效率的数值模拟

借助TOUGH3/TMVOC软件对华北地区某典型污染场地进行模型概化，模拟再现了挥发性有机化合物（VOCs）在层状低渗透性介质中的运移和分布特征；同时，设置了不同情景的多相抽提方案，分析了渗透率对多相抽提技术（MPE）去除效率的影响.结果表明，VOCs在该介质中主要以非水相液体（NAPL）相形式存在，且NAPL相饱和度最大值位于泄漏点以下的含水层；对于不同深度的分层抽提情景，当最大抽提深度为-9.25m时，介质中质量分数最大的NAPL相VOCs能够被有效去除，总有机物去除率达89.8%.同时，多相抽提作用能促进吸附相VOCs解吸，降低介质中吸附相VOCs含量；抽提结束一段时间后，介质中残留的液相、吸附相VOCs含量增加，成为潜在的地下水二次污染源.当层状介质渗透率整体降低时，MPE技术去除效率随之降低，且低渗透层中残留的NAPL相VOCs难以抽出，导致总有机物去除率降低.

A numerical simulation study on remediation efficiency of Multi-Phase Extraction (MPE) in petrochemical contaminated sites of low permeability

This paper utilized the software TOUGH3/TMVOC to build a conceptual model of a typical contaminated site in North China, and simulated the transport and distribution of Volatile Organic Chemicals (VOCs) in layered low-permeability strata. In addition, simulation scenarios under diffident conditions were set up to understand the effect of the permeability in the medium to efficiency of multi-phase extraction (MPE). VOCs mainly occurred in form of non-aqueous phase liquid (NAPL), and the maximum saturation of NAPL was located in the aquifer underneath the leakage position. When the maximum depth of extraction well was -8.75m, VOCs in NAPL phase could be effectively removed, which occupied the maximum mass fraction in the medium, and the total organic matter removal rate reached 89.8%. Besides, multi-phase extraction wells promoted the desorption of adsorption phase VOCs, and reduced the content of adsorbed VOCs in the medium effectively. After a period of extraction, the contents of residual VOCs in liquid and adsorption phase increased, which could become a potential secondary pollution source to groundwater. With the decreasing of the permeability in layered medium, the efficiency of MPE was reduced, and the residual VOCs in NAPL phase were difficult to extract in low permeability layer, which resulted in the decreasing of total organic removal rates.