ZVI-Clay remediation of a chlorinated solvent source zone, Skuldelev, Denmark: 2. Groundwater contaminant mass discharge reduction

Fjordbøge, Annika Sidelmann; Lange, Ida Vedel; Bjerg, Poul Løgstrup; Binning, Philip John; Riis, Charlotte; Kjeldsen, Peter

doi:10.1016/j.jconhyd.2012.08.009

Cited by 15 publications

(7 citation statements)

References 42 publications

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“…The further degradation of TCE can occur by biotic and abiotic sequential hydrogenolysis, resulting in the production of cDCE, VC, and ethane − (Figure ). Transformation of TCE to chloroacetylenes via β-elimination mediated by zerovalent iron in the source zone can likely be excluded as previous studies demonstrated that this process is of minor importance for ZVI-bentonite mixed source zones. − For CT, hydrogenolysis can take place, resulting in the formation of CF and DCM and revealing that CF can be a parent as well as a daughter compound at the site (Figure ). Hydrogenolysis of CT can be mediated abiotically by reduced iron bearing minerals , and biotically by co-metabolic reduction under anoxic conditions. , The degradation of CF by hydrogenolysis typically occurs biotically except for high-pH (∼12) conditions, under which abiotic hydrogenolysis of CF also can also take place …”

Section: Materials and Methodsmentioning

confidence: 99%

Identification of Degradation Pathways of Chlorohydrocarbons in Saturated Low-Permeability Sediments Using Compound-Specific Isotope Analysis

Wanner

Parker

Chapman

et al. 2018

Environ. Sci. Technol.

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This study aims to investigate whether compound-specific carbon isotope analysis (CSIA) can be used to differentiate the degradation pathways of chlorohydrocarbons in saturated low-permeability sediments. For that purpose, a site was selected, where a complex mixture of chlorohydrocarbons contaminated an aquifer-aquitard system. Almost 50 years after contaminant releases, high-resolution concentration, CSIA, and microbial profiles were determined. The CSIA profiles showed that in the aquitard cis-dichloroethene (cDCE), first considered as a degradation product of trichloroethene (TCE), is produced by the dichloroelimination of 1,1,2,2-tetrachloroethane (TeCA). In contrast, TeCA degrades to TCE via dehydrohalogenation in the aquifer, indicating that the aquifer-aquitard interface separates two different degradation pathways for TeCA. Moreover, the CSIA profiles showed that chloroform (CF) is degraded to dichloromethane (DCM) via hydrogenolysis in the aquitard and, to a minor degree, produced by the degradation of carbon tetrachloride (CT). Several microorganisms capable of degrading chlorohydrocarbons were detected in the aquitard, suggesting that aquitard degradation is microbially mediated. Furthermore, numerical simulations reproduced the aquitard concentration and CSIA profiles well, which allowed the determination of degradation rates for each transformation pathway. This improves the prediction of contaminant fate in the aquitard and potential magnitude of impacts on the adjacent aquifer due to back-diffusion.

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Section: Materials and Methodsmentioning

confidence: 99%

Identification of Degradation Pathways of Chlorohydrocarbons in Saturated Low-Permeability Sediments Using Compound-Specific Isotope Analysis

Wanner

Parker

Chapman

et al. 2018

Environ. Sci. Technol.

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“…The amendment can include clay to reduce the k of the resulting homogeneous mixture, and thereby decrease contaminant flux from the treated area and increase the residence time of the amendment in the treated area (Olson and Sale 2015). Several cases have been reported by researchers exploring the use of soil-mixing techniques (Olson et al 2012;Fjordbøge et al 2012aFjordbøge et al , 2012bKakarla et al 2017). While these case studies did not explicitly address back diffusion from secondary sources, they nonetheless serve as examples of how the technology may be used to do so.…”

Section: Soil Mixingmentioning

confidence: 99%

“…Another case study of soil mixing to a depth of ~8 m bgs was reported by Fjordbøge et al (2012aFjordbøge et al ( , 2012b. They used ZVI-Clay mixing to address PCE DNAPL contamination at a site in Skuldelev, Denmark.…”

Section: Soil Mixingmentioning

confidence: 99%

“…The geology of the site consists of quaternary deposits of alternating layers of sand and clay till, underlain by limestone. Fjordbøge et al (2012a) reported >99% PCE source mass reduction within a year following ZVI‐Clay mixing, and Fjordbøge et al (2012b) reported a down‐gradient PCE mass discharge reduction of 76% over a monitoring period of 1.6 years. Kakarla et al (2017) reported that clean‐up goals were met after 1 day of soil mixing at the Kearsarge Metallurgical Corporation (KMC) Superfund Site in Conway, New Hampshire.…”

Section: Literature Reviewmentioning

confidence: 99%

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Strategies for Managing Risk due to Back Diffusion

Brooks¹,

Yarney²,

Huang³

2021

Groundwater Monitoring Rem

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Back diffusion of contaminants from secondary sources may hamper site remediation if it is not properly addressed in the remedial design. A review of all reported technologies and strategies that have been or could be applied to address plume persistence due to back diffusion as published in the peer‐reviewed literature is provided. We classify these into four major categories. The first category consists of those approaches that do not include active measures to specifically address contamination in the low permeable zones (LPZs) and can therefore be considered passive LPZ management approaches. A disadvantage of these approaches is the long duration that may be required to meet acceptable endpoints; however, this allows degradation to potentially play a significant part even at modest rates. The remaining three categories all use approaches to specifically address contaminants in the LPZ. The second category consists of strategies that promote contaminant destruction through the forward diffusion of amendments into the LPZ. A variety of laboratory tests indicate concentration or flux reductions range from no improvement, to reductions as high as four orders‐of‐magnitude depending on the evaluation metric. The third category consists of strategies that alter physical characteristics of the secondary source, and includes viscosity modification, fracturing, and soil mixing. Each of these offer unique advantages and are often used to deliver one or more amendments for contaminant treatment. The final category consists of thermal and electrokinetic remediation, both less susceptible to permeability contrast limitations. However, they are not routinely used for secondary‐source treatment.

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“…In groundwater management, contaminant mass discharge (CMD) is becoming an important and commonly applied metric for evaluating the risk that contaminants pose to downgradient receptors such as groundwater resources, abstraction wells for water supply and surface water (Anderson, 2021; Balbarini et al., 2018; Ciriello & de Barros, 2020; Koch & Nowak, 2015; Pollicino et al., 2021; Rønde et al., 2017). The approach has also shown benefits for monitoring the effect and long term performance of remedial action at contaminated sites (Annable et al., 2008; Fjordboge et al., 2012; Haluska et al., 2019; ITRC, 2017; Mateas et al., 2017). CMD is defined as the mass per time of contaminant passing through a control plane, downstream of the contaminant source zone, perpendicular to the groundwater flow direction (Troldborg et al., 2010).…”

Section: Introductionmentioning

confidence: 99%

Assessing Contaminant Mass Discharge Uncertainty With Application of Hydraulic Conductivities Derived From Geoelectrical Cross‐Borehole Induced Polarization and Other Methods

Thalund-Hansen

Troldborg

Levy

et al. 2023

Water Resources Research

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A new methodology was developed to support contaminant mass discharge (CMD)‐based risk assessment of groundwater contamination downgradient of point source zones. Geoelectrical cross‐borehole induced polarization (IP) data were collected at a site undergoing in situ remediation of chlorinated solvents for determining 2D hydraulic conductivity (K) distributions with an inversion model resolution of 0.15 m (vertically) x 0.50 m (horizontally) in three control planes from 10‐20 m depth. Additionally, 18 slug tests and 31 grain size distribution analyses (GSA) from the control planes, were used for K‐estimation. The geometric means and variance of the IP, slug test, and GSA derived K‐estimates were consistent with previously studied sandy aquifers. Furthermore, the vertical variation in K between two geological settings, a sandy till and a meltwater sand formation, was clearly identified by the IP K‐estimates. The vertical variation was backed up by hydraulic profiling tool (HPT) measurements. Random realizations of CMD were simulated based on the cross‐borehole IP derived K‐values. For comparison, the CMD was also estimated with a geostatistical conditional simulation approach, using the data from slug tests and GSAs. The high IP resolution captured the small scale variations in K across the transects and led to CMD predictions with a narrow uncertainty interval, whereas slug test and GSA either under‐ or overestimated the magnitude of the areas with the highest CMD. Applying the geophysical cross‐borehole method for estimating K‐distributions in addition to traditional methods would improve CMD‐based risk assessment and evaluation of remediation performance at contaminated sites.This article is protected by copyright. All rights reserved.

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ZVI-Clay remediation of a chlorinated solvent source zone, Skuldelev, Denmark: 2. Groundwater contaminant mass discharge reduction

Cited by 15 publications

References 42 publications

Identification of Degradation Pathways of Chlorohydrocarbons in Saturated Low-Permeability Sediments Using Compound-Specific Isotope Analysis

Identification of Degradation Pathways of Chlorohydrocarbons in Saturated Low-Permeability Sediments Using Compound-Specific Isotope Analysis

Strategies for Managing Risk due to Back Diffusion

Assessing Contaminant Mass Discharge Uncertainty With Application of Hydraulic Conductivities Derived From Geoelectrical Cross‐Borehole Induced Polarization and Other Methods

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