An analytical model of bubble-facilitated vapor intrusion

Enze Ma; You-Kuan Zhang; Xiuyu Liang; Jinzhong Yang; Yuqing Zhao; Xinyue Liu

doi:10.1016/j.watres.2019.114992

An analytical model of bubble-facilitated vapor intrusion

Water Res. 2019 Nov 15:165:114992. doi: 10.1016/j.watres.2019.114992. Epub 2019 Aug 17.

Authors

Enze Ma¹, You-Kuan Zhang¹, Xiuyu Liang², Jinzhong Yang³, Yuqing Zhao¹, Xinyue Liu¹

Affiliations

¹ Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, PR China; State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, PR China; Shenzhen Municipal Engineering Lab of Environmental IoT Technologies, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, PR China.
² Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, PR China; State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, PR China; Shenzhen Municipal Engineering Lab of Environmental IoT Technologies, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, PR China. Electronic address: liangxy@sustech.edu.cn.
³ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China.

PMID: 31446295
DOI: 10.1016/j.watres.2019.114992

Abstract

Mass transfer from nonaqueous phase liquid (NAPL) to entrapped air induced by a fluctuating water table commonly occurs in residual NAPL zones in aquifers. Gas bubble expansion and vertical migration due to interphase mass transfer could facilitate the upward transport of volatile organic compounds (VOCs) in the aquifer and result in higher mass fluxes into a building relative to those of diffusion-limited (D-L) VOC transport. However, the current vapor intrusion models have not considered bubble migration. In this study, an analytical solution of bubble-facilitated (B-F) VOC transport in the unsaturated-saturated zone was developed. The analytical solution was tested by a numerical solution using the finite-difference method. Sensitivity analyses of model parameters were implemented to understand the VOC transport behaviors. The effects of bubble migration on vapor intrusion pathway completion time (t_c) and the attenuation factor (AF) were investigated by comparison with the D-L VOC transport model. The results indicate that the D-L model significantly overestimates the t_c and underestimates the AF because the model neglects the impacts of bubble migration. Therefore, one may make an inappropriate decision and set up an inappropriate response action schedule if using the D-L model to assess the risk of bubble-facilitated vapor intrusion. The analytical solution was applied to a laboratory experiment. The analytical model managed to interpret the laboratory experiment data, showing that the mass flux of B-F VOC transport is two orders of magnitude higher than that of D-L VOC transport.

Keywords: Analytical model; Bubble-facilitated transport; Vapor intrusion; Volatile organic chemical.

MeSH terms

Diffusion
Gases*
Models, Theoretical
Volatile Organic Compounds*

Substances

Gases
Volatile Organic Compounds