Managing the remediation strategy of contaminated megasites using field-scale calibration of geo-electrical imaging with chemical monitoring
(2024) In Science of the Total Environment 920.- Abstract
Groundwater contamination is a threat to drinking water resources and ecosystems. Remediation by injection of chemical reagents into the aquifer may be preferred to excavation to reduce cost and environmental footprint. Yet, successful remediation requires complete contact between contamination and reagents. Subsurface heterogeneities are often responsible for diffusion into low-permeable zones, which may inhibit this contact. Monitoring the spatial distribution of injected reagents over time is crucial to achieve complete interaction. Source zone contamination at megasites is particularly challenging to remediate and monitor due to the massive scale and mixture of contaminants. Source zone remediation at Kærgård Plantation megasite... (More)
Groundwater contamination is a threat to drinking water resources and ecosystems. Remediation by injection of chemical reagents into the aquifer may be preferred to excavation to reduce cost and environmental footprint. Yet, successful remediation requires complete contact between contamination and reagents. Subsurface heterogeneities are often responsible for diffusion into low-permeable zones, which may inhibit this contact. Monitoring the spatial distribution of injected reagents over time is crucial to achieve complete interaction. Source zone contamination at megasites is particularly challenging to remediate and monitor due to the massive scale and mixture of contaminants. Source zone remediation at Kærgård Plantation megasite (Denmark) is monitored here, with a new methodology, using high-resolution cross-borehole electrical resistivity tomography (XB-ERT) imaging calibrated by chemical analyses on groundwater samples. At this site, high levels of toxic non-aqueous phase liquids (NAPL) are targeted by in-situ chemical oxidation using activated persulfate. It may take numerous injection points with extensive injection campaigns to distribute reagents, which requires an understanding of how reagent may transport within the aquifer. A geophysical (XB-ERT) monitoring network of unprecedented size was installed to identify untreated zones and help manage the remediation strategy. The combination of spatially continuous geophysical information with discrete but precise chemical information, allowed detailed monitoring of sulfate distribution, produced during persulfate activation. Untreated zones identified in the first remediation campaign were resolved in the second campaign. The monitoring allowed adjusting the number of injection screens and the injection strategy from one campaign to the next, which resulted in better persulfate distribution and contaminant degradation in the second campaign. Furthermore, geophysical transects repeated over the timespan of a remediation campaign allowed high-resolution time-lapse imaging of reagent transport, which could in the future improve the predictability of transport models, compared to only using on a-priori assumptions of the hydraulic conductivity field.
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- author
- Lévy, Léa LU ; Bording, Thue S. ; Fiandaca, Gianluca ; Christiansen, Anders Vest ; Madsen, Line M. ; Bennedsen, Lars F. ; Jørgensen, Torben Højbjerg ; MacKinnon, Leah and Christensen, Jørgen F.
- organization
- publishing date
- 2024-04-10
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Chemical oxidation, Cross-borehole, Electrical resistivity, Groundwater remediation, Persulfate
- in
- Science of the Total Environment
- volume
- 920
- article number
- 171013
- publisher
- Elsevier
- external identifiers
-
- pmid:38369154
- scopus:85185406115
- ISSN
- 0048-9697
- DOI
- 10.1016/j.scitotenv.2024.171013
- language
- English
- LU publication?
- yes
- additional info
- Funding Information: We thank staff members for extensive help during fieldwork: Frederik Christensen, Rune Kraghede, Andy Kass and Christian Nedergaard at the Hydrogeophysics Group, as well as Rasmus Thalund-Hansen at DTU. We also thank Pradip Maurya for fruitful discussions related to 3D inversion and data acquisition and Jesper Pedersen for project coordination. We finally thank Dan Glaser for insightful comments on the first version of the manuscript. Funds from the Region Syddanmark (Denmark) and the Faculty of Engineering at Lund University (Sweden) supported this research. Publisher Copyright: © 2024 The Authors
- id
- 146a2b5e-789a-4bb1-83a3-24ead5c7c3b0
- date added to LUP
- 2024-03-11 11:27:32
- date last changed
- 2024-04-23 16:22:12
@article{146a2b5e-789a-4bb1-83a3-24ead5c7c3b0,
abstract = {{<p>Groundwater contamination is a threat to drinking water resources and ecosystems. Remediation by injection of chemical reagents into the aquifer may be preferred to excavation to reduce cost and environmental footprint. Yet, successful remediation requires complete contact between contamination and reagents. Subsurface heterogeneities are often responsible for diffusion into low-permeable zones, which may inhibit this contact. Monitoring the spatial distribution of injected reagents over time is crucial to achieve complete interaction. Source zone contamination at megasites is particularly challenging to remediate and monitor due to the massive scale and mixture of contaminants. Source zone remediation at Kærgård Plantation megasite (Denmark) is monitored here, with a new methodology, using high-resolution cross-borehole electrical resistivity tomography (XB-ERT) imaging calibrated by chemical analyses on groundwater samples. At this site, high levels of toxic non-aqueous phase liquids (NAPL) are targeted by in-situ chemical oxidation using activated persulfate. It may take numerous injection points with extensive injection campaigns to distribute reagents, which requires an understanding of how reagent may transport within the aquifer. A geophysical (XB-ERT) monitoring network of unprecedented size was installed to identify untreated zones and help manage the remediation strategy. The combination of spatially continuous geophysical information with discrete but precise chemical information, allowed detailed monitoring of sulfate distribution, produced during persulfate activation. Untreated zones identified in the first remediation campaign were resolved in the second campaign. The monitoring allowed adjusting the number of injection screens and the injection strategy from one campaign to the next, which resulted in better persulfate distribution and contaminant degradation in the second campaign. Furthermore, geophysical transects repeated over the timespan of a remediation campaign allowed high-resolution time-lapse imaging of reagent transport, which could in the future improve the predictability of transport models, compared to only using on a-priori assumptions of the hydraulic conductivity field.</p>}},
author = {{Lévy, Léa and Bording, Thue S. and Fiandaca, Gianluca and Christiansen, Anders Vest and Madsen, Line M. and Bennedsen, Lars F. and Jørgensen, Torben Højbjerg and MacKinnon, Leah and Christensen, Jørgen F.}},
issn = {{0048-9697}},
keywords = {{Chemical oxidation; Cross-borehole; Electrical resistivity; Groundwater remediation; Persulfate}},
language = {{eng}},
month = {{04}},
publisher = {{Elsevier}},
series = {{Science of the Total Environment}},
title = {{Managing the remediation strategy of contaminated megasites using field-scale calibration of geo-electrical imaging with chemical monitoring}},
url = {{http://dx.doi.org/10.1016/j.scitotenv.2024.171013}},
doi = {{10.1016/j.scitotenv.2024.171013}},
volume = {{920}},
year = {{2024}},
}