Rethinking Conceptual Site Models in Groundwater Remediation

Suthersan, Suthan; Potter, Scott T.; Schnobrich, Matthew; Wahlberg, Jennifer; Quinnan, Joseph; Welty, Nicklaus; Fewless, Tom

doi:10.1111/gwmr.12192

Cited by 12 publications

(8 citation statements)

References 15 publications

(13 reference statements)

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“…Fuel release sites typically have sparse monitoring networks installed for reasons other than estimation of mass discharge. Thus, the accuracy of any method to estimate GW‐NSZD rates will depend on the location and spacing of the wells relative to the lateral variations in concentrations and groundwater discharge within the contaminant plume (Mackay et al ; Suthersan et al ), a matter discussed further later.…”

Section: Conceptual Modelmentioning

confidence: 99%

Methods to Estimate Source Zone Depletion of Fuel Releases by Groundwater Flow

Mackay

Paradis

Buscheck

et al. 2018

Groundwater Monitoring Rem

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We compare two methods for estimating the natural source zone depletion (NSZD) rate at fuel release sites that occurs by groundwater flow through the source zone due to dissolution and transport of biodegradation products. Dissolution is addressed identically in both methods. The “mass budget method”, previously proposed and applied by others, estimates the petroleum hydrocarbon biodegradation rate based on dissolved electron acceptor delivery and dissolved biodegradation product removal by groundwater flow. The mass budget method relies on assumed stoichiometry for the degradation reactions and differences in concentrations of dissolved species (oxygen, nitrate, sulfate, reduced iron, reduced manganese, nonvolatile dissolved organic carbon, methane) at monitoring locations upgradient and downgradient of the source zone. We illustrate a refinement to account for degradation reactions associated with loss of reduced iron from solution. The “carbon budget method,” a simplification of approaches applied by others, addresses carbon‐containing species in solution or lost from solution (precipitated) and does not require assumptions about stoichiometry or information about electron acceptors. We apply both methods to a fuel release site with unusually detailed monitoring data and discuss applicability to more typical and less thoroughly monitored sites. The methods, as would typically be applied, yield similar results but have different constraints and uncertainties. Overall, we conclude that the carbon budget method has greater practical utility as it is simpler, requires fewer assumptions, accounts for most iron‐reducing reactions, and does not include CO2 that escapes from the saturated to the unsaturated zone.

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Section: Conceptual Modelmentioning

confidence: 99%

Methods to Estimate Source Zone Depletion of Fuel Releases by Groundwater Flow

Mackay

Paradis

Buscheck

et al. 2018

Groundwater Monitoring Rem

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“…Such difference between directly measured‐ and Darcy's law‐estimated groundwater fluxes raises the question of considering representative hydraulic gradient and conductivity. In line with Suthersan et al (), a transition has to be done from the old era of a simplified bulk averaged parameters and steady state, to a more detailed high spatial and time resolution consideration of hydrogeological processes. This emphasizes the necessity of direct in situ groundwater flux measurements, especially in heterogeneous aquifers and in surface water connected‐aquifers affected by transient groundwater flow conditions (ITRC ; Cremeans et al ).…”

Section: Discussionmentioning

confidence: 98%

Innovative Contaminant Mass Flux Monitoring in an Aquifer Subject to Tidal Effects

Jamin

Cosme²,

Briers³

et al. 2020

Groundwater Monitoring Rem

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Exposure from groundwater contamination to aquatic receptors residing in receiving surface water is dependent upon the rate of contaminated groundwater discharge. Characterization of groundwater fluxes is challenging, especially in coastal environments where tidal fluctuations result in transient groundwater flows towards these receptors. This can also be further complicated by the high spatial heterogeneity of subsurface deposits enhanced by anthropogenic influences such as the mixing of natural sediments and backfill materials, the presence of subsurface built structures such as sheet pile walls or even occurrence of other sources of contaminant discharge. In this study, the finite volume point dilution method (FVPDM) was successfully used to characterize highly transient groundwater flows and contaminant mass fluxes within a coastal groundwater flow system influenced by marked tides. FVPDM tests were undertaken continuously for more than 48 h at six groundwater monitoring wells, in order to evaluate groundwater flow dynamics during several tide cycles. Contaminant concentrations were measured simultaneously which allowed calculating contaminant mass fluxes. The study highlighted the importance of the aquifer heterogeneity, with groundwater fluxes ranging from 10−7 to 10−3 m/s. Groundwater flux monitoring enabled a significant refinement of the conceptual site model, including the fact that inversion of groundwater fluxes was not observed at high tide. Results indicated that contaminant mass fluxes were particularly higher at a specific monitoring well, by more than three orders of magnitude, than at other wells of the investigated aquifer. This study provided crucial information for optimizing further field investigations and risk mitigation measures.

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“…O LIF representa uma ferramenta eficiente para identificação semiquantitativa de hidrocarbonetos na fase móvel, trapeado ou residual em sub-superfície, como demonstrado por diversos trabalhos, incluindo Löhmannsröben & Roch (2000), Lamb (2012), Isler et al (2013), Suthersan et al (2016). As vantagens do emprego LIF incluem menor tempo de investigação, aquisição de informações de modo contínuo no intervalo de profundidade investigado e possibilitar a modificação da malha de amostragem em razão dos resultados obtidos em tempo real durante a investigação, possibilitando um diagnóstico ambiental mais consistente e conclusivo.…”

Section: Lifunclassified

Aplicação do método de fluorescência induzida por laser na caracterização de áreas contaminadas com resíduos oleosos

Krahenbuhl¹,

Teramoto

Kiang

2018

R. Águas Subter.

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A aplicação de perfilagem contínua, por meio do método de fluorescência induzida por laser (LIF), em uma área urbana com disposição pretérita de resíduos oleosos (superior a 30 anos), mostrou-se útil na delimitação tridimensional de resíduos oleosos em subsuperfície, indicando em tempo real e com baixo investimento a área passível de remediação. A comparação com dados obtidos por outras formas de investigação ambiental indica que o LIF é eficiente na detecção em campo, tanto de resíduos oleosos como de material oleoso impregnado no solo, independente do seu grau de intemperismo e da heterogeneidade na distribuição espacial. As respostas de fluorescência foram coerentes com o tipo de material encontrado, em que predominam hidrocarbonetos aromáticos policíclicos de cadeias maiores. O método foi sensível mesmo no caso de lentes delgadas de resíduos.

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Rethinking Conceptual Site Models in Groundwater Remediation

Cited by 12 publications

References 15 publications

Methods to Estimate Source Zone Depletion of Fuel Releases by Groundwater Flow

Methods to Estimate Source Zone Depletion of Fuel Releases by Groundwater Flow

Innovative Contaminant Mass Flux Monitoring in an Aquifer Subject to Tidal Effects

Aplicação do método de fluorescência induzida por laser na caracterização de áreas contaminadas com resíduos oleosos

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