Integrating Spectral Induced Polarization With Reactive Transport Modeling to Quantify Nitrate Remediation Capacity of ZVI-AC Permeable Reactive Barriers

Monitoring removal performance of permeable reactive barriers (PRBs) for groundwater nitrate remediation and distinguishing remediation mechanism contributions remains a key challenge. Based on flow-through column experiments, this study integrated spectral induced polarization (SIP) monitoring with reactive transport modeling to investigate the dynamics of (Formula presented.) removal by zero-valent iron (ZVI) and activated carbon (AC) mixtures. SIP parameters link material changes to (Formula presented.) removal performance. The strong correlation between normalized chargeability and cumulative removal capacity of (Formula presented.) constrained reactive transport model errors, with average relative errors of 12.5% and 21% for predicted (Formula presented.) breakthrough concentrations. The presence of Ca²⁺ and (Formula presented.) in solution promoted the corrosion of ZVI and the total (Formula presented.) -N removal capacity increased from 6.61 to 9.05 mg/g. The remediation enhancement is concentrated primarily in the proximal sections near the contaminant injection point. The reaction term exhibits a substantially increase compared to the adsorption term. Conversely, remediation performance declines in distal sections. This finding highlights the important contribution of regulatory ions to the reaction term and emphasizes the necessity of rational proportioning of remediation materials in different PRB sections for enhanced material utilization efficiency. Transport models calibrated via SIP robustly quantify spatial heterogeneity in adsorption and reaction processes, exhibiting significant potential to guide the design of PRBs.