潜水面方向变化对LNAPL迁移过程的影响模拟研究OA

Light non-aqueous phase liquids(LNAPLs)are typical persistent pollutants in subsurface environments,and their migration mechanisms within the water-gas-NAPL multiphase system represent a core scientific challenge for targeted prevention and control of groundwater contamination.The migration process of LNAPLs in the aquifer is usually controlled by the dynamic changes of the groundwater level.The fluctuation of the dynamic water level in the unconfined aquifer may significantly affect the migration and release of LNAPLs.However,the multiphase flow redistribution mechanism under the influence of the regional water table still needs further exploration.Therefore,in response to the above scientific issues,a method based on multi-point continuous water level data was employed to quantify the process of changes in the direction of the water table.Groundwater dynamics and multiphase flow theory were integrated by constructing a multi-field and multi-phase flow coupled model including water phase,gas phase,LNAPL phase,flow field and chemical field,so as to evaluate how the variation of the direction of the water table affects the migration and distribution of LNAPLs,systematically revealing the control mechanisms by which the dynamic evolution of the groundwater table morphology governs LNAPLs migration and transformation.The results show that:① The variation in the direction of the water table affects the migration trajectory of LNAPLs,and there is a positive correlation between LNAPL migration and the direction of the water table.If the direction of the water table becomes gentler(morphological slowing),the migration speed of LNAPLs will slow down,with the migration rate of LNAPL decreasing by 38.2%.② If the direction of the water table becomes steeper(morphological steeper),the migration speed of LNAPLs will increase.③ The variation in the direction of the water table affects the change in LNAPL saturation.If the direction of the water table becomes gentler,the change in LNAPL saturation is relatively small;If the direction of the water table becomes steeper,the change in LNAPL saturation is relatively large.④ The variation in the direction of the water table affects the change in the temperature field.Under the variation of the water table,the mixing of the lower and upper water bodies will make the water temperature near the water table more uniform.The temperature gradient decreased from an initial 0.35℃/m to 0.18℃/m.⑤ The variation in the direction of the water table affects the distribution of the dissolved and volatile phases of LNAPLs.With the change of the water table,the change rates of the dissolved and volatile phases of LNAPLs become slower,the rate of change of the dissolved phase concentration decreased by 42%,and the volatilization flux dropped from 0.15 d-1 to 0.09 d-1.This study aims to reveal the impact of the variation in the direction of the water table on the migration of LNAPLs in contaminated sites.