Groundwater contamination by constituents of hydrocarbon fluids may occur from the earth’s surface or subsurface. Key sources of contamination include spills and leakages from oilwells, underground storage tanks (USTs), and oil transport-tankers. These light non-aqueous phase liquid (LNAPL) contaminants pollute the soil and its continuous migration, may even end up contaminating aquifer systems. This highlights the need to understand the fate and migration behavior of LNAPL contaminants in the subsurface, especially in the unsaturated zone – with a view to limiting the contaminants transport. This study presents a numerical approach for describing and predicting the fate of LNAPL contaminant-transport in the subsurface. Multiphase flow concept was adopted, where two LNAPL phases – oil, and gas – were mainly considered. Diesel and crude oil are the hydrocarbon contaminants used, while unconsolidated sand was used as the porous matrix. Two contaminant flow scenarios were simulated experimentally — surface and subsurface imbibition. Mass balance equations and constitutive functions from the several important phenomena that influence LNAPL contaminant flow, in the subsurface, are discussed. Extended Darcy’s law in combination with van Genuchten model were applied in the 2D numerical model description for mass balance equation and constitutive relationship, respectively. The numerical simulation was executed using COMSOL Multiphysics® v. 5.5. The numerical simulation results showed a good correlation with the experimental results, and suggest that exposure time, fluid viscosity, density, contaminant supply, amount released, and the hydraulic properties of the porous matrix, are the most important parameters in LNAPL contaminant subsurface migration. This study thereby concludes that if the fluid thermodynamic properties and the hydraulic properties of the porous matrix are known, the numerical model can accurately predict the migration behavior of hydrocarbon contaminants. In that way, it becomes possible to effectively track oil-spills and leakages propagating into the vicinity of groundwater table and freshwater aquifer. The study outcome is useful in designing and implementing efficient hydrocarbon contamination remediation approaches and saving time by taking the right action.

烃类流体成分对地下水的污染可能发生在地球的表面或地下。污染的主要来源包括油井，地下储罐（USTs）和石油运输油轮的溢出和泄漏。这些轻质非水相液体（LNAPL）污染物污染了土壤，土壤不断迁移，甚至可能污染含水层系统。这突出了需要了解LNAPL污染物在地下，特别是在非饱和带中的命运和迁移行为，以限制污染物的运输。这项研究提出了一种数值方法，用于描述和预测LNAPL在地下的污染物运移的命运。采用了多相流概念，其中主要考虑了油和气两个LNAPL相。柴油和原油是所用的碳氢化合物污染物，而未固结的砂被用作多孔基质。通过实验模拟了两种污染物流情景-地面和地下吸收。讨论了影响LNAPL污染物在地下流动的几种重要现象的质量平衡方程和本构函数。在二维数值模型描述中，将扩展达西定律与van Genuchten模型相结合分别用于质量平衡方程和本构关系。数值模拟是使用COMSOLMultiphysics®v。5.5执行的。数值模拟结果与实验结果具有良好的相关性，并表明暴露时间，流体粘度，密度，污染物供应，释放量，多孔基质的水力学特性是LNAPL污染物地下迁移的最重要参数。因此，该研究得出的结论是，如果已知多孔基质的流体热力学性质和水硬性质，则该数值模型可以准确预测烃类污染物的迁移行为。这样，可以有效地跟踪传播到地下水位和淡水含水层附近的溢油和泄漏。该研究结果可用于设计和实施有效的碳氢化合物污染修复方法，并通过采取正确的措施节省时间。因此，该研究得出的结论是，如果已知多孔基质的流体热力学性质和水硬性质，则该数值模型可以准确预测烃类污染物的迁移行为。这样，可以有效地跟踪传播到地下水位和淡水含水层附近的溢油和泄漏。该研究结果可用于设计和实施有效的碳氢化合物污染修复方法，并通过采取正确的措施节省时间。因此，该研究得出的结论是，如果已知多孔基质的流体热力学性质和水硬性质，则该数值模型可以准确预测烃类污染物的迁移行为。这样，可以有效地跟踪传播到地下水位和淡水含水层附近的溢油和泄漏。该研究结果可用于设计和实施有效的碳氢化合物污染修复方法，并通过采取正确的措施节省时间。