Numerical simulation oflight non-aqueous phase liquids remediation in the unsaturated zone with single fractures

For the study of the spatial and temporal distribution of oil pollutants in unsaturated zones, it is difficult to quantitatively analyze the migration mechanism in laboratory and field tests are costly and damages the foundation. Numerical simulation, as a widely used and mature method, can be used to analyze the movement of oil pollutants in unsaturated zones. In order to examine the spatial and temporal distribution law of LNAPL (light non-aqueous phase liquids) in the unsaturated zone with single fractures during the single-well extraction and in-situ flushing remediation, in this paper a numerical model is established to analyze the effect under different conditions. The results show that LNAPL preferentially flows into fractures when injected, and preferentially flows out of the fractures when the injection is stopped. The single well extraction remediation simulation show that the larger the extraction flow, the higher the remediation efficiency. The in-situ flushing technology can effectively replenish groundwater and prevent new environmental problems. The injection wells play the role of “flushing” and diluting pollutants. Under the optimal scheme, the remediation area reaches 96%, the remediation rate reaches 75%, and the LNAPL saturation is controlled at 0.05. The comparative analysis indicates that the water injection wells have the best effect when placed on the upper boundary of the pollutant, and can effectively “flush” the pollutants and carry them to the extraction well and to the land surface. The research conclusions provide a scientific theoretical basis and effective assessment methods for the remediation of soil and groundwater contaminated by light oil.