Characterization and Remediation of Chlorinated Volatile Organic Contaminants in the Vadose Zone

Brusseau, Mark L.; Carroll, Kenneth C.; Truex, Michael J.; Becker, David J.

doi:10.2136/vzj2012.0137

Cited by 34 publications

(25 citation statements)

References 113 publications

(169 reference statements)

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“…These two issues are typically the primary risk drivers for decisions regarding remediation of vadose-zone systems. Hence, the development and assessment of cleanup objectives for vadose-zone sources is typically based on the impact of residual mass in the vadose zone on groundwater or vapor intrusion (e.g., EPA, 2001; USACE, 2002; Carroll et al, 2012; Brusseau et al, 2013). …”

Section: Introductionmentioning

confidence: 99%

Measuring spatial variability of vapor flux to characterize vadose-zone VOC sources: Flow-cell experiments

Mainhagu

Morrison

Truex

et al. 2014

Journal of Contaminant Hydrology

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A method termed vapor-phase tomography has recently been proposed to characterize the distribution of volatile organic contaminant mass in vadose-zone source areas, and to measure associated three-dimensional distributions of local contaminant mass discharge. The method is based on measuring the spatial variability of vapor flux, and thus inherent to its effectiveness is the premise that the magnitudes and temporal variability of vapor concentrations measured at different monitoring points within the interrogated area will be a function of the geospatial positions of the points relative to the source location. A series of flow-cell experiments was conducted to evaluate this premise. A well-defined source zone was created by injection and extraction of a non-reactive gas (SF6). Spatial and temporal concentration distributions obtained from the tests were compared to simulations produced with a mathematical model describing advective and diffusive transport. Tests were conducted to characterize both areal and vertical components of the application. Decreases in concentration over time were observed for monitoring points located on the opposite side of the source zone from the local–extraction point, whereas increases were observed for monitoring points located between the local–extraction point and the source zone. The results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.

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Section: Introductionmentioning

confidence: 99%

Measuring spatial variability of vapor flux to characterize vadose-zone VOC sources: Flow-cell experiments

Mainhagu

Morrison

Truex

et al. 2014

Journal of Contaminant Hydrology

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“…High-resolution sampling of sediment cores collected from boreholes drilled within the study site (see Figure 1) was conducted to provide benchmark data for spatial distributions of contaminant concentrations (Brusseau et al, 2013). One set of cores was collected in the spring of 2012, approximately one year prior to the VPT test.…”

Section: Methodsmentioning

confidence: 99%

“…Methods based on high-resolution spatial or temporal sampling of VOCs under induced-gradient conditions have been employed recently to improve characterization of vadose-zone sources, as reviewed in Brusseau et al (2013a). For example, the vapor-phase cyclic or multi-stage contaminant mass discharge (MS-CMD) test was recently developed to measure mass discharge for vadose-zone sources under both induced-gradient and natural-gradient conditions (Brusseau et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…The vapor-phase tomography (VPT) test method was recently developed to provide three-dimensional, spatially resolved characterization of VOC concentrations and vapor flux in the vadose zone (Brusseau et al, 2011). This method involves collecting depth-specific concentration and flow-rate (or surrogate) data at multiple monitoring points during a short-term vapor extraction that is conducted at a selected location.…”

Section: Introductionmentioning

confidence: 99%

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Using vapor phase tomography to measure the spatial distribution of vapor concentrations and flux for vadose-zone VOC sources

Mainhagu

Morrison

Brusseau

2015

Journal of Contaminant Hydrology

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A test was conducted at a chlorinated-solvent contaminated site in Tucson, AZ, to evaluate the effectiveness of vapor-phase tomography (VPT) for characterizing the distribution of volatile organic contaminants (VOC) in the vadose zone. A soil vapor extraction (SVE) system has been in operation at the site since 2007. Vapor concentration and vacuum pressure were measured at four different depths in each of four monitoring wells surrounding the extraction well. The test provided a 3D characterization of local vapor concentrations under induced-gradient conditions. Permeability data obtained from analysis of borehole logs were combined with the vapor-concentration data to determine VOC mass flux within the test domain. A region of higher mass flux was identified in the deepest interval of the S-SW section of the domain, indicating the possible location of a zone with greater contaminant mass. These results are consistent with the TCE-concentration distribution obtained from sediment coring conducted at the site. In contrast, the results of a standard soil gas survey did not indicate the presence of a zone with greater contaminant mass. These results indicate that the VPT test provided a robust characterization of VOC concentration and flux distribution at the site.

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“…Nonaqueous-phase liquid (NAPL) contaminants introduced into the unsaturated zone spread as a liquid phase; however, they can also vaporize and migrate in a gaseous state. In particular, vapor (gas) plumes migrate easily in the unsaturated zone (Barber and Davis, 1991;Davis et al, 2005Davis et al, , 2009Höhener et al, 2006;Brusseau et al, 2013). When assessing the danger of groundwater contamination by downwardmigrating vapor plumes, retention effects on transport are of major interest.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on retardation of a heavy NAPL vapor in partially saturated porous media

Kleinknecht

Class

Braun

2017

Hydrol. Earth Syst. Sci.

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Abstract. Non-aqueous-phase liquid (NAPL) contaminants introduced into the unsaturated zone spread as a liquid phase; however, they can also vaporize and migrate in a gaseous state. Vapor plumes migrate easily and thus pose a potential threat to underlying aquifers. Large-scale column experiments were performed to quantify partitioning processes responsible for the retardation of carbon disulfide (CS 2 ) vapor in partially saturated porous media. The results were compared with a theoretical approach taking into account the partitioning into the aqueous phase as well as adsorption to the solid matrix and to the air-water interface. The experiments were conducted in large, vertical columns (i.d. of 0.109 m) of 2 m length packed with different porous media. A slug of CS 2 vapor and the conservative tracer argon was injected at the bottom of the column followed by a nitrogen chase. Different seepage velocities were applied to characterize the transport and to evaluate their impact on retardation. Concentrations of CS 2 and argon were measured at the top outlet of the column using two gas chromatographs. The temporal-moment analysis for step input was employed to evaluate concentration breakthrough curves and to quantify dispersion and retardation. The experiments conducted showed a pronounced retardation of CS 2 in moist porous media which increased with water saturation. The comparison with an analytical solution helped to identify the relative contributions of partitioning processes to retardation. Thus, the experiments demonstrated that migrating CS 2 vapor is retarded as a result of partitioning processes. Moreover, CS 2 dissolved in the bulk water is amenable to biodegradation. The first evidence of CS 2 decay by biodegradation was found in the experiments. The findings contribute to the understanding of vapor-plume transport in the unsaturated zone and provide valuable experimental data for the transfer to field-like conditions.

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Characterization and Remediation of Chlorinated Volatile Organic Contaminants in the Vadose Zone

Cited by 34 publications

References 113 publications

Measuring spatial variability of vapor flux to characterize vadose-zone VOC sources: Flow-cell experiments

Measuring spatial variability of vapor flux to characterize vadose-zone VOC sources: Flow-cell experiments

Using vapor phase tomography to measure the spatial distribution of vapor concentrations and flux for vadose-zone VOC sources

Experimental study on retardation of a heavy NAPL vapor in partially saturated porous media

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