[A-HW17] Near Surface Investigation and Modeling for Groundwater Resources Assessment and Conservation

[AHW17-P08] Study on Hydraulic Properties Evolution Caused by Pore-Clogging from ISCO using Time-Lapsed Hydraulic Tomography.

*Bing Shine Ke¹, Jui-Pin Tsai¹ (1.National Taiwan University, Taiwan)

Keywords:In-situ Chemical Oxidation (ISCO), Hydraulic Tomography, Pore Clogging/Unclogging, Hydraulic Conductivity

In-situ chemical oxidation (ISCO) is a widely applied technique for soil and groundwater remediation, with Fenton's reagent being a common oxidant used. However, during the remediation process, the precipitation of iron induced by Fenton's reagent can lead to pore clogging, resulting in a decrease in the hydraulic conductivity (K) field and altering the flow field, which affects the effectiveness of ISCO. To address the pore clogging issue, we propose the injection of organic acids to dissolve the iron precipitates. This method not only resolves the pore clogging issue but also complements the biological ISCO. Given the limited research in this area, we conducted sandbox experiments to simulate the injection of Fenton's reagent and used time-lapsed Hydraulic Tomography (HT) to quantify the evolution of the hydraulic conductivity (K) field. Additionally, based on the changes in K values, sand and water samples were analyzed using Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) and Ion Chromatography (IC) to measure iron content, establishing the feasibility of HT. The results show that near the injection sites, K values first increase and then decrease, consistent with pore clogging and unclogging phenomena. The total iron concentration analyzed by ICP-OES and IC corresponded to the precipitation and dissolution of iron. In flow field simulations, areas with significant decreases in K values showed a decrease in the average velocity on streamlines and changes in flow direction, as well as the change in particle transport distance. This study integrates hydraulic–geochemical approaches, using time-lapsed HT to quantify the impact of chemical reactions on the hydraulic properties of groundwater, allowing for a more precise understanding of the dynamic changes in the K field and flow field.