Numerical study of the building pressure cycling method for evaluating vapor intrusion from groundwater contamination
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RESEARCH ARTICLE
Numerical study of the building pressure cycling method for evaluating vapor intrusion from groundwater contamination Yanqiu Liu 1 & Jun Man 2,3 & Yue Wang 2,3 & Yuting Xiao 2,3 & Wei Tang 2,3 & Qiang Chen 4 & Yijun Yao 2,3 Received: 4 February 2020 / Accepted: 15 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Vapor intrusion (VI) risk assessments determine the cleanup level of groundwater in the absence of ingestion. In recent VI investigations, the building pressure cycling (BPC) method has been applied to help minimize ambiguity caused by temporal variability of indoor air samples that are important to risk assessments, and, consequently, determine groundwater cleanup level accurately. In this study, we use a three-dimensional numerical model to examine the dynamic migration of VOCs from groundwater after the application of BPC. First, we validated the numerical model with field measurements. Then, the verified model is used to investigate the effects of site-specific features in determining the performance of BPC operation. At last, we summarize past field applications of BPC to examine the simulated results. Our study indicates that the BPC-induced indoor depressurization can increase the building loading rate in the first 2–3 h, which would then drop to 2–3 times of that with natural conditions in most cases of groundwater contamination. In some cases involving a strong source, e.g., a vapor source above the capillary fringe or a groundwater source with sandy soil above the groundwater level, the normalized building loading rates can be maintained as high as 4–9 without decrease after the first 2–3 h. Significantly higher increase in building loading rate may indicate a potential presence of a preferential pathway between the groundwater contamination and concerned building. Keywords Contaminated groundwater source . Chlorinated solvent vapor intrusion . Building pressure cycling method . Three-dimensional numerical model . Risk assessment . Soil texture
Introduction Vapor intrusion (VI) refers to the migration of volatile organic compounds (VOCs) from contaminant sources into the building of interest, mainly through the joint effects of
Responsible Editor: Philippe Garrigues * Yijun Yao [email protected] 1
College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
2
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
3
University of Chinese Academy of Sciences, Beijing 100049, China
4
State Environmental Protection Key Laboratory of Soil Environmental Management and Pollution Control, Ministry of Ecology and Environment, Nanjing Institute of Environmental Sciences, Nanjing 210042, China
diffusion, advection, and biodegradation (Nazaroff et al. 1987; US EPA 2017). For most sites, contaminated groundwater is a much more common VI source than other forms, such as soil and free nonaqueous phase liquid (NAPL) in unsaturated porou
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