Long-Term VOC Transport in a Thick Heterogeneous Vadose Zone and Perched Aquifers: Jerusalem Mountains Industrial Site

Volatile organic compounds (VOCs) from historical industrial activities can persist for decades, contaminating groundwater and the unsaturated zone, yet their transport through thick, heterogeneous vadose zones is poorly understood. This study reconstructs long-term migration of tetrachloroethylene (PCE) from a former industrial site in the Jerusalem Mountains, where leakage likely began ten years after plant commissioning and systematic monitoring started decades later. A three-dimensional numerical model of flow and transport was applied, incorporating calibrated hydraulic parameters, karstic conduits, and multiphase VOC processes including advection, dispersion, phase partitioning, volatilization, and first-order degradation kinetics. Multiple model runs explored plausible leakage scenarios under sparse historical data. Simulated PCE concentrations reproduce measurements in the vadose zone (R2 = 0.89) and deep regional aquifer (~20% normalized relative error). Results reveal pronounced preferential flows horizontally through perched aquifers and vertically along discrete faults, amplified by karstic networks. The upper vadose zone remains a persistent source, sustaining gas-phase emissions toward nearby residential areas unless targeted remediation is applied. Integrated modeling, even with limited monitoring, quantitatively reconstructs complex contaminant dynamics across saturated and unsaturated compartments, providing critical guidance for remediation. Protecting groundwater and human health requires addressing both vadose and saturated zones to prevent prolonged environmental and exposure risks.