LNAPL source zone delineation using soil gases in a heterogeneous silty-sand aquifer

Cohen, Grégory; Jousse, Florie; Luze, Nicolas; Höhener, Patrick; Atteia, Olivier

doi:10.1016/j.jconhyd.2016.06.001

Cited by 15 publications

(6 citation statements)

References 38 publications

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“…At a contaminated site, 222 Rn activities may therefore vary from one location to another not only because of NAPL distribution in the subsurface, but also as a function of physical and chemical soil heterogeneity (Hohener and Surbeck, 2004). Unlike previous contributions, Cohen et al (2016) did not observe any correlation between LNAPL abundance and 222 Rn activities in soil gas due to vadose zone heterogeneities. Höhener and Surbeck (2004) conducted a lysimeter experiment and analytical modelling to assess the applicability of the 222 Rn method in heterogeneous soils.…”

Section: Introductioncontrasting

confidence: 55%

Laboratory-scale experimental and modelling investigations of 222Rn profiles in chemically heterogeneous LNAPL contaminated vadose zones

Cohen

Bernachot

et al. 2019

Science of The Total Environment

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The potential of LNAPL delineation by 222 Rn soil-gas monitoring in a chemically heterogeneous vadose zone was investigated in this study based on laboratory (batch and columns) experiments and numerical modeling. An enhanced version of the MIN3P reactive transport code was used to simulate Rn transport in both uncontaminated and NAPL-contaminated vadose zones and results were validated against analytical solutions and laboratory experiments. Results show that 222 Rn activity profiles are mainly controlled by porous media 222 Rn production, vadose zone fluid saturations and especially the type and distribution of NAPL in contaminated areas. The results also show that decreases in 222 Rn activity and variations in activity gradients provide evidence for the presence and saturation of NAPL. This study demonstrates that LNAPL delineation via 222 Rn gas surveys at contaminated sites works best, if gas measurements extend as deep as possible and include regions where 222 Rn activity decreases due to elevated NAPL. In addition, collection and analysis of depth-discrete gas samples allows the characterization of vertical NAPL distribution based on the 222 Rn activity gradient. The determination of 222 Rn production in the unsaturated zone, as well as water capillary pressure curves are of key importance in enabling the discrimination of an uncontaminated from a NAPL-contaminated area.

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Section: Introductioncontrasting

confidence: 55%

Laboratory-scale experimental and modelling investigations of 222Rn profiles in chemically heterogeneous LNAPL contaminated vadose zones

Cohen

Bernachot

et al. 2019

Science of The Total Environment

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“…An overview of Rn applications as an environmental tracer in hydrogeological and geological investigations is provided by Sukanya et al [51]. One of the applications briefly discussed is the use of Rn as an environmental tracer for the assessment of NAPL contamination [22] in both the saturated [18,24,28,30,[52][53][54] and vadose zone [19,21,23,26,29,[55][56][57][58][59][60], due to its tendency to preferentially partition into organic phases. To implement and use Rn as a tracer for environmental applications, it is crucial to comprehend the mechanisms of its production and behavior in the subsurface.…”

Section: Radonmentioning

confidence: 99%

“…Theoretical and practical aspects of the Rn deficit technique were studied through laboratory experiments [20,53,55,57,60,110], modeling approaches [18,21,59,60,109], and field experiences [19,25,26,29,30,54,56,59,[114][115][116]. This section presents an overview of the technique's utilization in soil gas, especially from a field perspective.…”

Section: Applications Of the Rn Deficit Techniquementioning

confidence: 99%

“…Although the soil gas Rn activity concentration was primarily influenced by the possible path of a fault and a lithologic discontinuity, the characterization of the background emission in each lithologic unit allowed for the identification of areas that may be impacted by LNAPL. Cohen et al [59] compared the performance of multiple in situ gas measurements over soil coring for defining LNAPL source zones in the subsurface characterized by limited diffusion potential due to the presence of fine-grained soils. They used a network of gas probes at a depth of approximately 1 m and analyzed VOCs, O 2 , CO 2 , CH 4 , and Rn, comparing the results to independent LNAPL analysis by coring at the site.…”

Section: Soil Gas Applications Using Active Samplingmentioning

confidence: 99%

“…Different authors [19,24,26,59,112,117] highlighted that Rn activity concentrations in the field may be affected by the geochemical, lithological, granulometric, and mineralogical characteristics of the soil. This may be due to the uneven distribution of 226 Ra, from which Rn originates, in the soil, and to variations in the emanation mechanism based on soil characteristics.…”

Section: Conclusion Limitations and Future Researchmentioning

confidence: 99%

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Assessing Light Non-Aqueous Phase Liquids in the Subsurface Using the Soil Gas Rn Deficit Technique: A Literature Overview of Field Studies

Cecconi,

Verginelli,

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2024

Sustainability

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222Radon (Rn) was proposed in the late 1990s as a naturally occurring tracer for light non-aqueous phase liquids (LNAPLs) in the subsurface, due to its preferential partitioning behavior in the non-aqueous phase, resulting in a reduction in Rn activities in areas with LNAPLs in the subsurface compared to unimpacted areas (Rn deficit). The Rn deficit technique emerged as a cost-effective, non-invasive, and sustainable method to rapidly identify and quantify LNAPLs, for the characterization and monitoring of contaminated sites. This paper presents an overview of the technique and its field applications, with a specific focus on the use of the method in the vadose zone based on soil gas Rn measurements. Although various configurations have shown favorable outcomes, limitations persist in the application of the soil gas Rn deficit technique. Deep LNAPL contamination, soil matrix heterogeneity, and temporal variations in Rn emissions pose challenges to quantitative evaluations of LNAPL contamination. Recognizing these factors is crucial for site-specific assessments. This review aims to highlight both the strengths and limitations of the method, providing insights into potential areas for future research while acknowledging the positive outcomes achieved in different configurations over the past decades.

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Applicability of radon emanometry in lithologically discontinuous sites contaminated by organic chemicals

Miguel

Barrio-Parra

Elío

et al. 2018

Environ Sci Pollut Res

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The applicability of radon (Rn) measurements to delineate non-aqueous phase liquids (NAPL) contamination in subsoil is discussed at a site with lithological discontinuities through a blind test. Three alpha spectroscopy monitors were used to measure radon in soil air in a 25,000-m area, following a regular sampling design with a 20-m grid. Repeatability and reproducibility of the results were assessed by means of duplicate measurements in six sampling positions. Furthermore, three points not affected by oil spills were sampled to estimate radon background concentration in soil air. Data histograms, Q-Q plots, variograms, and cluster analysis allowed to recognize two data populations, associated with the possible path of a fault and a lithological discontinuity. Even though the concentration of radon in soil air was dominated by this discontinuity, the characterization of the background emanation in each lithological unit allowed to distinguish areas potentially affected by NAPL, thus justifying the application of radon emanometry as a screening technique for the delineation of NAPL plumes in sites with lithological discontinuities.

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LNAPL source zone delineation using soil gases in a heterogeneous silty-sand aquifer

Cited by 15 publications

References 38 publications

Laboratory-scale experimental and modelling investigations of 222Rn profiles in chemically heterogeneous LNAPL contaminated vadose zones

Laboratory-scale experimental and modelling investigations of 222Rn profiles in chemically heterogeneous LNAPL contaminated vadose zones

Assessing Light Non-Aqueous Phase Liquids in the Subsurface Using the Soil Gas Rn Deficit Technique: A Literature Overview of Field Studies

Applicability of radon emanometry in lithologically discontinuous sites contaminated by organic chemicals

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