Quantifying Reagent Spreading by Cross-Borehole Electrical Tomography to Assess Performance of Groundwater Remediation

Abstract

In situ remediation of contaminated groundwater often relies on the installation of a treatment zone (TZ) degrading the contamination. Zero-valent-iron (ZVI) is a type of reagent used for this purpose. Adequate delivery of ZVI in the whole target volume is particularly challenging and requires monitoring with high spatial resolution. We present a monitoring tool for imaging the dynamic spreading of ZVI and its associated ionic cloud, using cross-borehole time-lapse electrical resistivity tomography (ERT). This tool works in urban areas and is particularly suitable for achieving the required spatial resolution at the scale of the target volume. Groundwater and sediment samples show a consistent spatial and temporal distribution of the remediation cloud with cross-borehole ERT. Yet, the 2D anomalies observed with cross-borehole ERT provide a more spatially complete and rapid image of the remediation cloud distribution than if based solely on monitoring screens. At the study site, ZVI injection leads to uneven spreading, clearly documented by cross-borehole ERT monitoring. The benefit of hydraulic conductivity (K) mapping by cross-borehole induced polarization (IP) to understand unexpected injection paths (upstream leakage, spreading in preferred pathways) is investigated. A 2D, IP-based, continuous, and coherent K-distribution is obtained that compares well with estimations by grain size analyses from the TZ. However, the IP-based K-field fails at predicting injection paths, suggesting the creation of pathways during the high-pressure injection of ZVI. Cross-borehole time-lapse ERT is the most promising geophysical tool for performance assessment of in situ remediation involving reagents with conductivity contrast.

• author: Lévy, L. ; Thalund-Hansen, R. ; Bording, T. ; Fiandaca, G. ; Christiansen, A. V. ; Rügge, K. ; Tuxen, N. ; Hag, M. and Bjerg, P. L.
• organization: LTH Profile Area: The Energy Transition; Engineering Geology
• publishing date: 2022-09
• type: Contribution to journal
• publication status: published
• subject: Geophysical Engineering
• keywords: cross-borehole, electrical resistivity, groundwater remediation, monitoring
• in: Water Resources Research
• volume: 58
• issue: 9
• article number: e2022WR032218
• pages: 23 pages
• publisher: American Geophysical Union (AGU)
• external identifiers: scopus:85138815288
• ISSN: 0043-1397
• DOI: 10.1029/2022WR032218
• language: English
• LU publication?: yes
• additional info: Funding Information: We thank Niklas Marcel Christensen, Jie Zhang, and Vidhi Rathore, M.Sc. students at DTU Environment, for laboratory analysis of Provect-IR® content and collection of sediment core samples from the TZ area, as well as Sinh Hy Nguyen, laboratory technician at DTU Environment, for assisting with laboratory analysis of Provect-IR® contents and grain size distributions. We also thank Lærke Brabæk Ildvedsen, Morten Dreyer, and Torben Højbjerg Jørgensen at COWI for their contributions to field work and discussion on the data. We thank Pradip Maurya and Anders Kühl, at Aarhus University, for many fruitful discussions and help with IP data processing, as well as Karen Engell Dalsgaard for final proofreading. We finally thank Dimitrios Ntarlagiannis, two other anonymous reviewers as well as Associate Editor Sander Huisman for the tremendous reviewing and editing work that has helped greatly improve the quality of the manuscript. This project received funding from the Capital Region of Denmark and Lawyer Thorbergs Foundation. Funding Information: We thank Niklas Marcel Christensen, Jie Zhang, and Vidhi Rathore, M.Sc. students at DTU Environment, for laboratory analysis of Provect‐IR content and collection of sediment core samples from the TZ area, as well as Sinh Hy Nguyen, laboratory technician at DTU Environment, for assisting with laboratory analysis of Provect‐IR contents and grain size distributions. We also thank Lærke Brabæk Ildvedsen, Morten Dreyer, and Torben Højbjerg Jørgensen at COWI for their contributions to field work and discussion on the data. We thank Pradip Maurya and Anders Kühl, at Aarhus University, for many fruitful discussions and help with IP data processing, as well as Karen Engell Dalsgaard for final proofreading. We finally thank Dimitrios Ntarlagiannis, two other anonymous reviewers as well as Associate Editor Sander Huisman for the tremendous reviewing and editing work that has helped greatly improve the quality of the manuscript. This project received funding from the Capital Region of Denmark and Lawyer Thorbergs Foundation. ® ® Publisher Copyright: © 2022. The Authors.
• id: 7f38bb7d-e53a-443f-b781-263f9231b0bb
• date added to LUP: 2022-10-12 09:53:42
• date last changed: 2023-11-06 22:46:03