Influence of Soil Moisture on Soil Gas Vapor Concentration for Vapor Intrusion

Shen, Rui; Pennell, Kelly G.; Suuberg, Eric M.

doi:10.1089/ees.2013.0133

Cited by 50 publications

(35 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Again, in uniform soil, the contaminant vapor profile does not depend upon soil diffusivity in any case. On the other hand, previous studies [36-37] have shown that the c ss profile is sensitive to the vertical moisture content variation in the soil. This includes a critical role of the capillary fringe above the groundwater, which acts as a very significant vapor diffusion barrier.…”

Section: Resultsmentioning

confidence: 89%

Vapor intrusion attenuation factors relative to subslab and source, reconsidered in light of background data

Yao

Suuberg

et al. 2015

Journal of Hazardous Materials

Self Cite

View full text Add to dashboard Cite

The basis upon which recommended attenuation factors for vapor intrusion (VI) have been derived are reconsidered. By making a fitting curve to the plot showing the dependence of observed indoor air concentration (cin) on subslab concentration (css) for residences in EPA database, an analytical equation is obtained to identify the relationship among cin, css and the averaged background level. The new relationship indicates that subslab measurements may serve as a useful guide only if css is above 500 μg / m3. Otherwise, cin is independent of css, with a distribution in good agreements with other studies of background levels. Therefore, employing this screening value (500 μg / m3), new contaminant concentration attenuation factors are proposed for VI, and the values for groundwater-to-indoor and subslab-to-indoor air concentration attenuation factors are 0.004 and 0.02, respectively. The former is applied to examining the reported temporal variations of cin obtained during a long-term monitoring study. The results show that using this new groundwater-to-indoor air concentration attenuation factor also provides a reasonably conservative estimate of cin.

show abstract

Section: Resultsmentioning

confidence: 89%

Vapor intrusion attenuation factors relative to subslab and source, reconsidered in light of background data

Yao

Suuberg

et al. 2015

Journal of Hazardous Materials

Self Cite

View full text Add to dashboard Cite

show abstract

“…This observation also supports the observations reported herein where soil moisture is thought to have retarded VOC transport, trapping higher concentrations beneath highly resistive soil layers. Modeling efforts by Shen et al 2012, 2013a, 2013b, and Moradi et al 2015 also emphasize the importance of soil moisture when evaluating vapor intrusion exposure risks.…”

Section: Resultsmentioning

confidence: 99%

Field data and numerical modeling: A multiple lines of evidence approach for assessing vapor intrusion exposure risks

Pennell

McClean

Suuberg

et al. 2016

Science of The Total Environment

Self Cite

View full text Add to dashboard Cite

USEPA recommends a multiple lines of evidence approach to make informed decisions at vapor intrusion sites because the vapor intrusion pathway is notoriously difficult to characterize. Our study uses this approach by incorporating groundwater, soil gas, indoor air field measurements and numerical models to evaluate vapor intrusion exposure risks in a Metro-Boston neighborhood known to exhibit lower than anticipated indoor air concentrations based on groundwater concentrations. We collected and evaluated five rounds of field sampling data over the period of one year. Field data results show a steep gradient in soil gas concentrations near the groundwater surface; however as the depth decreases, soil gas concentration gradients also decrease. Together, the field data and the numerical model results suggest that a subsurface feature is limiting vapor transport into indoor air spaces at the study site and that groundwater concentrations are not appropriate indicators of vapor intrusion exposure risks in this neighborhood. This research also reveals the importance of including relevant physical models when evaluating vapor intrusion exposure risks using the multiple lines of evidence approach. Overall, the findings provide insight about how the multiple lines of evidence approach can be used to inform decisions by using field data collected using regulatory-relevant sampling techniques, and a well-established 3-D vapor intrusion model.

show abstract

“…The development, validation and applications of the 3-D finite element model examined here were already presented in former studies [18–20, 28–33]. In the present study, the model is applied only in a steady-state mode for non-degradable contaminants.…”

Section: Methodsmentioning

confidence: 99%

“…The open ground surface is taken to be at atmospheric reference pressure and is a sink of zero contaminant concentration. A negative pressure of -5 Pa and a contaminant flux equation is assigned at the crack, the same as in the former studies [28–33]. The detailed parameters are shown in Table 1.…”

Section: Methodsmentioning

confidence: 99%

“…In EPA’s spreadsheet version of the Johnson-Ettinger (J-E) model, the van Genuchten parameters for 12 kinds of soil type (SCS soils) are provided so that they can be chosen to apply in a multilayer system [27]. Even in scenarios involving single type of soil, the spatial variability of moisture content due to capillary fringe and rainfall events could also affect the distribution of the effective diffusivity of soil gas [28–30]. …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evaluation of site-specific lateral inclusion zone for vapor intrusion based on an analytical approach

Yao

Tang

et al. 2015

Journal of Hazardous Materials

Self Cite

View full text Add to dashboard Cite

In 2002, U.S. EPA proposed a general buffer zone of approximately 100 feet (30 m) laterally to determine which buildings to include in vapor intrusion (VI) investigations. However, this screening distance can be threatened by factors such as extensive surface pavements. Under such circumstances, EPA recommended investigating soil vapor migration distance on a site-specific basis. To serve this purpose, we present an analytical model (AAMLPH) as an alternative to estimate lateral VI screening distances at chlorinated compound-contaminated sites. Based on a previously introduced model (AAML), AAMLPH is developed by considering the effects of impervious surface cover and soil geology heterogeneities, providing predictions consistent with the three-dimensional (3-D) numerical simulated results. By employing risk-based and contribution-based screening levels of subslab concentrations (50 and 500 µg/m3, respectively) and source-to-subslab attenuation factor (0.001 and 0.01, respectively), AAMLPH suggests that buildings greater than 30 m from a plume “boundary” can still be affected by VI in the presence of any two of the three factors, which are high source vapor concentration, shallow source and significant surface cover. This finding justifies the concern that EPA has expressed about the application of the 30 m lateral separation distance in the presence of physical barriers (e.g., asphalt covers or ice) at the ground surface.

show abstract

Influence of Soil Moisture on Soil Gas Vapor Concentration for Vapor Intrusion

Cited by 50 publications

References 48 publications

Vapor intrusion attenuation factors relative to subslab and source, reconsidered in light of background data

Vapor intrusion attenuation factors relative to subslab and source, reconsidered in light of background data

Field data and numerical modeling: A multiple lines of evidence approach for assessing vapor intrusion exposure risks

Evaluation of site-specific lateral inclusion zone for vapor intrusion based on an analytical approach

Contact Info

Product

Resources

About