1. Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Science and Engineering, Nanjing University, Nanjing 210023, China;
2. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing 210029, China
The experiment of remediating PCE with surfactant (Tween 80) was carried out in two-dimensional sandbox filled with quartz sand, and the removal processes of NAPL phase under different source zone architectures (SZA) were monitored via image analysis technology. Considering the lack of experimental data on dissolved phase NAPL concentration, numerical simulation using UTCHEM software was further performed to understand the mass transfer process between NAPL phase and aqueous phase, and the effects of surfactant concentration and injection rate on the DNAPL remediation efficiency were investigated. Results from Sandbox experiments and numerical simulations confirmed that:subsurface heterogeneity largely governs the DNAPL SZA, resulting discrepancies in ganglia-to-pool (GTP) ratio. Due to the larger contact area of discrete ganglia with surfactant, DNAPL ganglia is preferentially removed. The higher the initial GTP ratio, the higher the remediation rate and the remediate efficiency of DNAPL; Though the DNAPL remediation rate could be increased by increasing the surfactant concentration or the injection rate, the surfactant remediate efficiency was reduced significantly by 93% over the course of the test. The linear driving force dissolution model can effectively simulate the process of surfactant remediation for DNAPL. Numerical simulation is an important quantitative tool for the assessment of SEAR in the field DNAPL-contaminated sites.
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