Enhanced remediation of contaminated aquifers by circulating flow field: Laboratory sandbox with quantitative analysis

Soil and groundwater contamination are escalating due to anthropogenic activities, necessitating cost-effective remediation technologies. This study integrates laboratory experiments and numerical simulations to investigate extraction-injection circulation enhancing remediation agent transport in heterogeneous aquifers. A 2D irregular heterogeneous sandbox model was developed, with high-precision flow field inversion via hydraulic tomography using 20 tests ( R 2 > 0.89). Extraction-injection experiments varied well positions, injection modes, and agent concentrations. Remediation agent migration and distribution under flow were monitored through 36 sampling ports. Based on the advection-dispersion equation, the spatiotemporal agent distribution agreed with measurements ( R 2 > 0.71), validating reliability. Numerical modeling revealed that extraction-injection well elevation differences and pumping rates influence migration efficiency. Empirical equations quantified relationships between these factors and temporal/spatial agent distribution at extraction wells. This work elucidates recirculation-enhanced transport mechanisms, bridging high-precision groundwater modeling with remediation optimization. The findings provide a theoretical framework for designing efficient remediation systems at contaminated sites.