Peer Reviewed: Remediating Chlorinated Solvent Source Zones

Stroo, Hans F.; Unger, Marvin; Ward, C. H.; Kavanaugh, Michael C.; Vogel, Catherine M.; Leeson, Andrea; Marqusee, Jeffrey A.; Smith, Bradley

doi:10.1021/es032488k

Cited by 178 publications

(119 citation statements)

References 17 publications

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Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

“…An early effort to quantify the relationship between contaminant mass flux reduction and mass removal, and the resultant reduction in risk, was presented by Freeze and McWhorter (1997). The specific relationship between mass flux reduction and mass removal has since been examined and discussed in a number of studies , Rao et al, 2002, Rao and Jawitz, 2003Stroo et al, 2003;Brooks et al, 2004; Jayanti and Pope, 2004;Lemke et al, 2004;Parker and Park, 2004;Phelan et al, 2004;Soga et al, 2004;Jawitz et al, 2005; NRC, 2005;Fure et al, 2006;Lemke and Abriola, 2006;Brusseau et al, 2007Brusseau et al, , 2008.Three simplified, prototypical relationships between mass flux reduction and mass removal, representative of systems for which the source zone is undergoing continuous water flushing, which are useful for comparative discussion are presented in Figure 1a. These relationships can be readily developed by employing a simple limiting-case analysis of the temporal contaminant-elution/mass-removal function for immiscible-liquid systems (as shown in Figure 1b), from which the mass-flux-reduction/mass-removal relationship can be Figure 1a represents the relationship for a system for which the flushing process (mass-transfer and displacement) is relatively ideal, wherein immiscible-liquid dissolution and other mass-transfer processes are under equilibrium conditions and all contaminant mass is accessible to flowing groundwater.…”

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confidence: 99%

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Relationship between mass-flux reduction and source-zone mass removal: Analysis of field data

DiFilippo

Brusseau

2008

Journal of Contaminant Hydrology

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The magnitude of contaminant mass flux reduction associated with a specific amount of contaminant mass removed is a key consideration for evaluating the effectiveness of a source-zone remediation effort. Thus, there is great interest in characterizing, estimating, and predicting relationships between mass flux reduction and mass removal. Published data collected for several field studies were examined to evaluate relationships between mass flux reduction and sourcezone mass removal. The studies analyzed herein represent a variety of source-zone architectures, immiscible-liquid compositions, and implemented remediation technologies. There are two general approaches to characterizing the mass-flux-reduction/mass-removal relationship, end-point analysis and time-continuous analysis. End-point analysis, based on comparing masses and mass fluxes measured before and after a source-zone remediation effort, was conducted for 21 remediation projects. Mass removals were greater than 60% for all but three of the studies. Mass flux reductions ranging from slightly less than to slightly greater than one-to-one were observed for the majority of the sites. However, these single-snapshot characterizations are limited in that the antecedent behavior is indeterminate. Time-continuous analysis, based on continuous monitoring of mass removal and mass flux, was performed for two sites, both for which data were obtained under water-flushing conditions. The reductions in mass flux were significantly different for the two sites (90% vs. ~8%) for similar mass removals (~40%). These results illustrate the dependence of the mass-flux-reduction/mass-removal relationship on source-zone architecture and associated mass-transfer processes. Minimal mass flux reduction was observed for a system wherein mass removal was relatively efficient (ideal mass transfer and displacement). Conversely, a significant degree of mass flux reduction was observed for a site wherein mass removal was inefficient (nonideal mass transfer and displacement). The mass-flux-reduction/mass-removal relationship for the latter site exhibited a multi-step behavior, which cannot be predicted using some of the available simple estimation functions. KeywordsMass Flux; DNAPL; Source Zone; Remediation INTRODUCTIONThe contamination of groundwater by hazardous organic chemicals and the associated risks to human health and the environment are issues of great importance. One of the most critical issues associated with hazardous waste sites is the potential presence of immiscible-liquid contamination in the subsurface. Immiscible liquids, such as chlorinated solvents, creosote, NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript coal tars, and fuels, once introduced into the subsurface become entrapped, and serve as long-term sources of contamination. The presence of immiscible-liquid contamination at a site can greatly impact the costs and time required for site remediation. It is widely acknowledged that cleaning up sites contaminated with denser-tha...

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Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

mentioning

confidence: 99%

Relationship between mass-flux reduction and source-zone mass removal: Analysis of field data

DiFilippo

Brusseau

2008

Journal of Contaminant Hydrology

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“…Source removal is an implicitrequired step in virtually all regulatory paradigms. Overview papers (e.g., Stroo et al, 2003 andRao, 2003) describe this issue and its particular significance for chlorinated organics. Falta et al (2005a and2005b) tackled this important challenge using carefully developed and well documented models.…”

Section: Case Study 6-4 Determining the Value Of Source Removalmentioning

confidence: 99%

Mass Balance: a Key to Advancing Monitored and Enhanced Attenuation for Chlorinated Solvents

Looney¹,

Vangelas²,

Adams³

et al. 2006

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Sections 7 and 8 summarize the evaluation in terms of research and development directions and broad goals.Section 9 provides the references for the report.Finally, the appendices provide supplemental information and mathematical derivations to support Sections 4 and 6. The appendices are intended to provide sufficient detail to allow interested readers to better follow and replicate the evaluation and to facilitate technical review and discussion.The process of systematically disassembling and then reassembling a "contaminant plume" -in terms of loading and attenuation capacity -provided useful insights and promising directions to specifically improve implementation of natural attenuation, and generally improve environmental management and legacy management decision-making. source zone aqueous concentration at time zero, mass/volume C (x,y,z,t) concentration at a specific target location and specified time, mass/volume LIST OF TABLES LIST OF CASE STUDIESCase LIST OF ACRONYMS KEY DEFINITIONS Enhancement, Enhanced AttenuationAn enhancement is any type of intervention in a contaminated system that decreases contaminant loading or increases the magnitude of attenuation by natural processes beyond that which occurs without intervention. Enhanced attenuation is the result of applying an enhancement that sustainably manipulates a natural attenuation process leading to an overall reduction in mass flux of contaminants. Integrated Mass Flux (iMF), Loading, DischargeThe integrated mass flux is the total quantity of a migrating substance that moves through a planar transect that is within the system of interest and oriented perpendicular to the direction of movement. If the transect is at the entry point to the system the integrated mass flux is the loading. If the transect is at the exit point from the system, the integrated mass flux is the discharge. Note that these terms have units of mass per time (e.g., Kg/yr, g/day or the like) and they represent an extension of the traditional engineering definition of flux (e.g., Kg/yr/m 2 ) in which the transect area is accounted for to allow mass balance calculation of plume or system scale behavior.Monitored Natural Attenuation "'Monitored natural attenuation' …refers to the reliance on natural attenuation processes (within the context of a carefully controlled and monitored clean-up approach) to achieve sitespecific remedial objectives within a time frame that is reasonable compared to that offered by other more active methods. The 'natural attenuation processes' that are at work in such a remediation approach include a variety of physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater." (EPA, 1999; pg. 3) Attenuation Capacity (A c )The attenuation capacity is the general term that describes the amount of a contaminant that can be assimilated and attenuated within an identified subsurface system volume. It is the compos...

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“…Winter et al, 1998;Stroo et al, 2003;Guilbeault et al, 2005). In Denmark this is a major problem because almost all drinking water comes directly from groundwater (Henriksen et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

An integrated model for assessing the risk of TCE groundwater contamination to human receptors and surface water ecosystems

McKnight

Funder

Rasmussen³

et al. 2010

Ecological Engineering

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a b s t r a c tThe practical implementation of the European Water Framework Directive has resulted in an increased focus on the hyporheic zone. In this paper, an integrated model was developed for evaluating the impact of point sources in groundwater on human health and surface water ecosystems. This was accomplished by coupling the system dynamics-based decision support system CARO-PLUS to the aquatic ecosystem model AQUATOX using an analytical volatilization model for the stream. The model was applied to a case study where a trichloroethylene (TCE)-contaminated groundwater plume is discharging to a stream. The TCE source will not be depleted for many decades; however, measured and predicted TCE concentrations in surface water were found to be below human health risk management targets. Volatilization rapidly attenuates TCE concentrations in surface water. Thus, only a 30-m stream reach fails to meet surface water quality criteria. An ecological risk assessment found that the TCE contamination did not impact the stream ecosystem. Uncertainty assessment revealed hydraulic conductivity to be the most important site-specific parameter. These results indicate that contaminant plumes with g L −1 concentrations of TCE entering surface water systems may not pose a significant risk.

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Peer Reviewed: Remediating Chlorinated Solvent Source Zones

Cited by 178 publications

References 17 publications

Relationship between mass-flux reduction and source-zone mass removal: Analysis of field data

Relationship between mass-flux reduction and source-zone mass removal: Analysis of field data

Mass Balance: a Key to Advancing Monitored and Enhanced Attenuation for Chlorinated Solvents

An integrated model for assessing the risk of TCE groundwater contamination to human receptors and surface water ecosystems

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