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

Yao, Yijun; Wu, Yun; Tang, Mengling; Wang, Yue; Wang, Jianjin; Suuberg, Eric M.; Jiang, Lin; Liu, Jing

doi:10.1016/j.jhazmat.2015.05.024

Cited by 20 publications

(7 citation statements)

References 34 publications

(36 reference statements)

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“…The full 3‐D finite element model applied here was COMSOL Multiphysics and has been presented in previous publications (Bozkurt et al, 2009; Pennell et al, 2009; Yao et al, 2011, 2013, 2015). The simulations were performed for a steady‐state scenario assuming nonbiodegradable contaminants.…”

Section: Methodsmentioning

confidence: 99%

Investigating the Role of Soil Texture in Vapor Intrusion from Groundwater Sources

et al. 2017

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Soil texture is believed to play a significant role in the migration of subsurface volatile chemicals into buildings at contaminated sites, an exposure process known as vapor intrusion (VI). In this study, we investigated the role of soil texture in determining the attenuation of contaminant soil gas concentration from groundwater source to receptor building. We performed soil column experiments, numerical simulations, and statistical analysis of the USEPA’s VI database. The soil column experiments were conducted with commercial sand and soils with sand and sandy loam textures. Measured one-dimensional soil gas concentration profiles were compared with numerical predictions. Good agreement between experiments and model results supports the use of the classical multiphase chemical transport equation for simulating contaminant vapor transport from groundwater through the vadose zone. A full three-dimensional numerical model was then used to simulate typical VI scenarios with groundwater sources. Results indicate that, although soil particle texture can play a role in determining subslab-to-indoor air concentration attenuation, there is no obvious relationship between soil particle size and groundwater source-to-subslab except in the case of a shallow contaminant source. This conclusion is consistent with results reported in USEPA’s VI database, in which variation in soil particle size does not affect source-to-subslab attenuation factors but does influence subslab-to-indoor air concentration attenuation factors by an average of about 0.4 order of magnitude. This finding suggests that an appropriate focus of VI site investigation should include the shallow soil beneath the building foundation.

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Section: Methodsmentioning

confidence: 99%

Investigating the Role of Soil Texture in Vapor Intrusion from Groundwater Sources

et al. 2017

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“…1, and the parameters used in the simulation are listed in Table 1. More details of the numerical model can be found in our previous studies (Yao et al, 2011, 2012, 2013, 2014, 2015, 2017).…”

Section: Methodsmentioning

confidence: 99%

Investigating the Role of Soil Texture in Petroleum Vapor Intrusion

et al. 2018

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In this work we investigate the role of soil texture in petroleum vapor intrusion (PVI) by performing numerical modeling, analytical calculations, and statistical analysis of the USEPA's PVI database. Numerical simulations were conducted for three kinds of soil (sand, sandy loam, and clay), and the results indicate that the maximum attenuations of vapor concentrations from source to indoor air were observed when the clay soil is below the building. In the anaerobic zone, the normalized soil gas concentration profiles were observed to be similar and independent of soil type, whereas in the aerobic zone, a more significant attenuation was observed in finer grained soils. Such a finding is consistent with the statistical results of the USEPA's PVI database, which indicate that in the near‐source zone, the soil gas concentration in coarse‐grained soil tends to be lower than that in fine‐grained soil, possibly caused by a weaker source due to mass loss by volatilization, whereas at a distance away from the source, the measured soil gas concentrations in fine‐grained soils become much lower because of aerobic biodegradation with a shorter diffusive reaction length. Thus, 3 and 5 m are proposed as soil‐type‐dependent vertical screening distances for fine and coarse‐grained soils, respectively. It should be noted that the validity of these screening distances is examined only for relatively homogeneous soils, and they may not be applicable for cases involving layered soil systems, where the availability of O2 in the subfoundation should be evaluated with subslab or multidepth samples to confirm the presence of aerobic biodegradation. Core Ideas Soil type determines attenuation caused by biodegradation. The simulations matched the statistical results. Soil‐type‐dependent screen distances were proposed.

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“…Due to such complexity, a full 3‐D finite element model is used to study the influences of such a preferential pathway on both of these measures. The 3‐D numerical model applied here was developed with COMSOL Multiphysics and has been presented in previous publications (Bozkurt et al, 2009; Pennell et al, 2009; Yao et al, 2011, 2012, 2013a, 2013b, 2013c, 2015, 2017a, 2017b). The numerical model includes two modules, Darcy's law and chemical transport in porous media.…”

Section: Methodsmentioning

confidence: 99%

Three‐Dimensional Simulation of Land Drains as a Preferential Pathway for Vapor Intrusion into Buildings

Yao

Mao

et al. 2017

J of Env Quality

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Preferential pathways can be significant vapor intrusion (VI) contributors, causing potentially higher inhalation risk to residents of affected buildings than that arising through traditional intrusion pathways. To assess land drains as a preferential pathway, a three-dimensional model, validated using data from a 4-yr field study, was used to study the roles of subfoundation soil permeability on soil gas flow and indoor depressurization. Results indicated that it is almost impossible for an indirect preferential pathway like a land drain ending in subfoundation soils with a permeability <10−11 m2 to affect indoor air quality if the land drain connects to a source with the same vapor concentration as that of the groundwater source beneath the building. An equation was developed to estimate the threshold permeability. We also found that even after the preferential pathway was identified using indoor depressurization (also known as controlled pressure method [CPM]) and then turned off, the influence of the preferential pathway and indoor depressurization on indoor concentration might last for months, although it may not be significant (i.e., may not exceed one order of magnitude, in this study). In the absence of such a preferential VI pathway, CPM may actually reduce indoor air concentrations of contaminants below those present under natural indoor pressure conditions, due to the emission rate limit determined by the upward diffusion rate from the vapor source. Our study highlights the role of measuring subfoundation soil permeability to soil gas flow in site investigations and warns practitioners about the possible mischaracterization of indoor air concentration after applying CPM in the absence of a preferential pathway.

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

Cited by 20 publications

References 34 publications

Investigating the Role of Soil Texture in Vapor Intrusion from Groundwater Sources

Investigating the Role of Soil Texture in Vapor Intrusion from Groundwater Sources

Investigating the Role of Soil Texture in Petroleum Vapor Intrusion

Three‐Dimensional Simulation of Land Drains as a Preferential Pathway for Vapor Intrusion into Buildings

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