Abstract：
Contamination from light non-aqueous phase liquids (LNAPLs) and their derivatives, arising from exploration, production, and transportation, has become a prevalent pollution source. This poses direct threats to human health. However, conventional investigative methods face limitations when applied to studying the extent and migration process of LNAPL contamination, as well as the redistribution of LNAPL during groundwater level fluctuations. Conventional methods lack the ability to rapidly, efficiently, and in real-time acquire information about contaminated areas. Therefore, this study utilizes time-lapse electrical resistivity tomography to investigate the migration mechanism of LNAPL under unsaturated conditions, constant groundwater levels, and groundwater level reductions. A relationship between resistivity and water and oil contents was established and used for inverse calculation of LNAPL content via resistivity inversion. Time-lapse electrical resistivity tomography revealed LNAPL migration in a \"concave\" shape across three conditions. Groundwater presence notably slowed migration, hindering downward movement and leading to a floating oil band. A robust mathematical model was established to derive the relationship between resistivity and water and oil contents. Finally, LNAPL distribution under unsaturated conditions was inversely obtained from resistivity data, showing highest content at the top leak point, obstructed area, and bottom of soil column. Consequently, time-lapse electrical resistivity tomography demonstrates a notable capacity to characterize the LNAPL migration process. This technique constitutes an effective geophysical method for monitoring and describing the characteristics of LNAPL migration. Its significance lies in enhancing our understanding of remediation for LNAPL-induced groundwater and land contamination.
摘要：
轻质非水相液体（LNAPLs）及其衍生物的污染，源于探索，生产,和交通,已成为普遍的污染源。这对人类健康构成直接威胁。然而,传统的调查方法在应用于研究LNAPL污染的程度和迁移过程时面临局限性，以及地下水位波动期间LNAPL的重新分配。常规方法缺乏快速，高效,并实时获取受污染地区的信息。因此,这项研究利用延时电阻率层析成像来研究LNAPL在不饱和条件下的迁移机制，恒定的地下水位，和地下水位下降。建立了电阻率与水和油含量之间的关系，并通过电阻率反演将其用于LNAPL含量的反计算。延时电阻率层析成像显示LNAPL在三种情况下以“凹”形迁移。地下水的存在显著减缓了迁移，阻碍向下运动并导致浮动油带。建立了稳健的数学模型，推导了电阻率与水和油含量之间的关系。最后,从电阻率数据反向获得不饱和条件下的LNAPL分布，在最高泄漏点显示最高含量，受阻区域,和土柱的底部。因此,延时电阻率层析成像显示出表征LNAPL迁移过程的显着能力。该技术构成了监测和描述LNAPL迁移特征的有效地球物理方法。其意义在于增强我们对LNAPL引起的地下水和土地污染的修复的理解。
