Advancing hydrogeophysics for monitoring matrix-mediated geochemical reactions in natural and anthropogenic porous media

Spectral Induced Polarization (SIP) is a non-invasive geophysical method that can characterize electrochemical processes at the mineral-fluid interfaces. Although the SIP method is increasingly utilized in hydrogeophysics, thus far, we have only a limited mechanistic interpretation of SIP signatures in reference to geochemical reactions. In this thesis, I further Investigate natural and anthropogenic processes of geochemical remediation relevant to contaminant remediation and landfill management. I focus on understanding how SIP responses can be interpreted in reference to changes in the electrical double layer (EDL) that result from (1) redox-dependent heavy metal immobilization, (2) ion exchange, and (3) mineral dissolution processes taking place in natural and engineered porous media. To address this topic, I conducted a series of controlled flow-through column experiments that integrated SIP monitoring with geochemical analysis and reactive transport modeling. This approach provides a foundation for connecting variations in SIP measurements, particularly the real and imaginary conductivity, with quantifiable geochemical changes. Using three different experimental systems, I examine how SIP can be utilized as a mechanistic diagnostic method and as a proxy for process-based monitoring in contaminated environments. These three studies demonstrate that SIP not only yields bulk electrical properties, but it can function as a hydrogeophysical tool that is sensitive to target geochemical processes and able to resolve underlying mechanisms of subsurface reactions. I recommend future research efforts focus on scaling the applicability of SIP monitoring for heterogeneous field environments. This Thesis advance the application of hydrogeophysics by showing that SIP can provide real time, non-invasive measurements of geochemical processes in contaminated porous media.