Source Remediation Challenges

Abriola, Linda M.; Christ, John A.; Pennell, Kurt D.; Ramsburg, C. Andrew

doi:10.1007/978-1-4614-2239-6_10

Cited by 9 publications

(12 citation statements)

References 153 publications

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“…The threshold between ganglia and pooled DNAPL in this work ( S N = 0.2) was referred to previous literature values (e.g., Christ et al., 2010; Gerhard & Kueper, 2003; Stonestrom & Rubin, 1989). Such simplification allowed the analysis to focus on the relative spatial distribution of ganglia and pooled DNAPL instead of the exact S N values (Abriola et al., 2012). This strategy significantly reduced the uncertainty of the unknowns and made the reconstruction problem more tractable.…”

Section: Inversion Methodologymentioning

confidence: 99%

Hydrogeophysical Characterization of Nonstationary DNAPL Source Zones by Integrating a Convolutional Variational Autoencoder and Ensemble Smoother

Kang

Kokkinaki

Kitanidis

et al. 2021

Water Resources Research

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Detailed characterization of dense nonaqueous phase liquid (DNAPL) source zone architecture (SZA) is essential for designing efficient remediation strategies. However, it is difficult to characterize a highly irregular and localized SZA, because traditional drilling investigations provide limited information. With limited data, the estimation accuracy of traditional geostatistical methods is strongly affected by the parameterization of the prior description of the SZA. To improve characterization performance, we parameterized the DNAPL saturation field using a physics‐based approach. We trained a convolutional variational autoencoder (CVAE) using data from multiphase modeling that captures the physics of DNAPL infiltration. The trained CVAE network was used in SZA inversion to obtain an improved prior DNAPL saturation field, instead of the typical stationary prior covariances. We then integrated the CVAE network into an iterative ensemble smoother (ES), to formulate a joint inversion framework. To overcome difficulties from limited/sparse data, we incorporated hydrogeological and geophysical datasets in the proposed inversion framework. To evaluate the performance of our method, we conducted numerical experiments in a hypothetical heterogeneous aquifer with an intricate SZA. The results show that the CVAE was an effective and efficient parameterization method which can capture the DNAPL infiltration patterns better than a Gaussian prior. The improved prior, combined with multisource datasets, can result in better resolution, and overall improved SZA characterization. In contrast to the standard ES method, the proposed framework reconstructed the SZA more accurately. We also demonstrated that DNAPL depletion behavior and dissolved concentration profiles can be predicted accurately using the estimated SZA.

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Section: Inversion Methodologymentioning

confidence: 99%

Hydrogeophysical Characterization of Nonstationary DNAPL Source Zones by Integrating a Convolutional Variational Autoencoder and Ensemble Smoother

Kang

Kokkinaki

Kitanidis

et al. 2021

Water Resources Research

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“…A great challenge in understanding and predicting groundwater flow and the movement and fate of substances in the subsurface is accurate estimation of heterogeneity at needed scales of resolution. Complexity of hydrogeology or heterogeneity of hydraulic conductivity ( K ) has been cited almost universally among main reasons for failure or poor performance of groundwater remediation and monitoring systems (National Research Council [NRC] , ; Illman and Alvarez ; Anderson and McCray ; Leeson and Stroo ; Abriola et al ). Commonly used methods such as slug tests, flowmeter tests, and direct push tests or analysis of borehole samples (e.g., grain size analysis and sample permeameter tests) provide highly resolved estimates, but are one‐dimensional (1D) and cannot resolve important details of the continuous, 3D heterogeneous nature of the subsurface (e.g., continuity or discontinuity of high‐ K and low‐ K bodies), which are necessary for predicting transport and for remediation method selection, design, and operation (Anderson ; Butler ; NRC , ; Bohling et al ; Castagna and Bellin ; Brauchler et al ).…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Tomography: Continuity and Discontinuity of High‐K and Low‐K Zones

Hochstetler¹,

Barrash

Leven

et al. 2015

Groundwater

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Hydraulic tomography is an emerging field and modeling method that provides a continuous hydraulic conductivity (K) distribution for an investigated region. Characterization approaches that rely on interpolation between one-dimensional (1D) profiles have limited ability to accurately identify high-K channels, juxtapositions of lenses with high K contrast, and breaches in layers or channels between such profiles. However, locating these features is especially important for groundwater flow and transport modeling, and for design and operation of in situ remediation in complex hydrogeologic environments. We use transient hydraulic tomography to estimate 3D K in a volume of 15-m diameter by 20-m saturated thickness in a highly heterogeneous unconfined alluvial (clay to sand-and-gravel) aquifer with a K range of approximately seven orders of magnitude at an active industrial site in Assemini, Sardinia, Italy. A modified Levenberg-Marquardt algorithm was used for geostatistical inversion to deal with the nonlinear nature of the highly heterogeneous system. The imaging results are validated with pumping tests not used in the tomographic inversion. These tests were conducted from three of five clusters of continuous multichannel tubing (CMTs) installed for observation in the tomographic testing. Locations of high-K continuity and discontinuity, juxtaposition of very high-K and very low-K lenses, and low-K "plugs" are evident in regions of the investigated volume where they likely would not have been identified with interpolation from 1D profiles at the positions of the pumping well and five CMT clusters. Quality assessment methods identified a suspect high-K feature between the tested volume and a lateral boundary of the model.

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“…Many remediation strategies endeavor to remove subsurface NAPL in order to reduce NAPL mass flux, contaminant plume concentrations, and plume longevity. However, subsurface heterogeneity and complex NAPL distributions make complete NAPL removal challenging [ Abriola et al ., ]. NAPL remediation efforts may involve accelerating NAPL mass transfer through soil venting, air sparging, biodegradation, and/or pumping and treating, as well as physical removal of the NAPL phase by enhancing mobilization and capture [ National Research Council , ].…”

Section: The Organic Napl Sourcementioning

confidence: 99%

Organic contaminant transport and fate in the subsurface: Evolution of knowledge and understanding

Essaid

Bekins

Cozzarelli

2015

Water Resources Research

155

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Toxic organic contaminants may enter the subsurface as slightly soluble and volatile nonaqueous phase liquids (NAPLs) or as dissolved solutes resulting in contaminant plumes emanating from the source zone. A large body of research published in Water Resources Research has been devoted to characterizing and understanding processes controlling the transport and fate of these organic contaminants and the effectiveness of natural attenuation, bioremediation, and other remedial technologies. These contributions include studies of NAPL flow, entrapment, and interphase mass transfer that have advanced from the analysis of simple systems with uniform properties and equilibrium contaminant phase partitioning to complex systems with pore-scale and macroscale heterogeneity and rate-limited interphase mass transfer. Understanding of the fate of dissolved organic plumes has advanced from when biodegradation was thought to require oxygen to recognition of the importance of anaerobic biodegradation, multiple redox zones, microbial enzyme kinetics, and mixing of organic contaminants and electron acceptors at plume fringes. Challenges remain in understanding the impacts of physical, chemical, biological, and hydrogeological heterogeneity, pore-scale interactions, and mixing on the fate of organic contaminants. Further effort is needed to successfully incorporate these processes into field-scale predictions of transport and fate. Regulations have greatly reduced the frequency of new point-source contamination problems; however, remediation at many legacy plumes remains challenging. A number of fields of current relevance are benefiting from research advances from point-source contaminant research. These include geologic carbon sequestration, nonpoint-source contamination, aquifer storage and recovery, the fate of contaminants from oil and gas development, and enhanced bioremediation.

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Source Remediation Challenges

Cited by 9 publications

References 153 publications

Hydrogeophysical Characterization of Nonstationary DNAPL Source Zones by Integrating a Convolutional Variational Autoencoder and Ensemble Smoother

Hydrogeophysical Characterization of Nonstationary DNAPL Source Zones by Integrating a Convolutional Variational Autoencoder and Ensemble Smoother

Hydraulic Tomography: Continuity and Discontinuity of High‐K and Low‐K Zones

Organic contaminant transport and fate in the subsurface: Evolution of knowledge and understanding

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