Enhancing Solute Mass‐Transfer in Low‐Permeability Zones in Heterogeneous Porous Media Combining Advective and Electrokinetic Transport

Abstract The spatially variable distribution of hydraulic conductivity in heterogeneous subsurface formations controls groundwater flow and solute transport. While the presence of more permeable zones facilitates rapid advective transport, contaminants often accumulate within low‐permeability zones. The latter, in turn, serve as long‐term pollution sources due to slow diffusive mass‐transfer (i.e., back‐diffusion), complicating remediation and water management efforts. Electrokinetic (EK) techniques have emerged as promising tools to enhance contaminant transport in low‐permeability materials by leveraging mass‐transfer processes (i.e., electromigration and electroosmosis) induced by the application of an electric field in the subsurface. This study aims to investigate the suitability and effectiveness of EK transport in heterogeneous subsurface systems where low‐permeability zones, in which advective transport is hampered, are embedded within an otherwise more permeable matrix where advection plays a key role in solute transport. We perform process‐based numerical simulations to investigate EK‐enhanced mass transfer in simplified heterogeneous configurations. Successively, we systematically explore scenarios associated with increased degree of complexity, focusing on the effects of different types of physical heterogeneity, including uniform and spatially variable porosity and tortuosity distributions. Our findings suggest that combining advective and EK transport can enhance delivery of charged solutes in heterogeneous porous media, resulting in more than double mass transfer in low‐permeability inclusions compared to corresponding scenarios relying exclusively on advective‐diffusive transport within the same domain and time frame.