Pore-scale visualization of LNAPL displacement by chemical agents in heterogeneous groundwater system

The remediation of light non-aqueous phase liquids (LNAPLs) from groundwater remains a critical environmental challenge, particularly in heterogeneous aquifers. Existing remediation techniques often struggle with low-permeability zones, limiting their effectiveness. In this study, we developed and validated a microfluidic platform to simulate heterogeneous porous media and evaluate the performance of four chemical agents, including the green bio-solvent Cyrene. Cyrene demonstrated superior efficiency, achieving a 30-45 % increase in oil removal compared to conventional agents, particularly in low-permeability zones. The platform enabled real-time visualization of pore-scale displacement processes, while the gray value method quantified residual oil saturation (S_or), and results demonstrated that permeability and pore structure significantly affect displacement efficiency. These findings highlight the scalability and environmental advantages of Cyrene for groundwater remediation and provide new insights into displacement mechanisms in complex subsurface systems.