Document Detail


A numerical investigation of vapor intrusion--the dynamic response of contaminant vapors to rainfall events.
MedLine Citation:
PMID:  22922135     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The U.S. government and various agencies have published guidelines for field investigation of vapor intrusion, most of which suggest soil gas sampling as an integral part of the investigation. Contaminant soil gas data are often relatively more stable than indoor air vapor concentration measurements, but meteorological conditions might influence soil gas values. Although a few field and numerical studies have considered some temporal effects on soil gas vapor transport, a full explanation of the contaminant vapor concentration response to rainfall events is not available. This manuscript seeks to demonstrate the effects on soil vapor transport during and after different rainfall events, by applying a coupled numerical model of fluid flow and vapor transport. Both a single rainfall event and seasonal rainfall events were modeled. For the single rainfall event models, the vapor response process could be divided into three steps: namely, infiltration, water redistribution, and establishment of a water lens atop the groundwater source. In the infiltration step, rainfall intensity was found to determine the speed of the wetting front and wash-out effect on the vapor. The passage of the wetting front led to an increase of the vapor concentration in both the infiltration and water redistribution steps and this effect is noted at soil probes located 1m below the ground surface. When the mixing of groundwater with infiltrated water was not allowed, a clean water lens accumulated above the groundwater source and led to a capping effect which can reduce diffusion rates of contaminant from the source. Seasonal rainfall with short time intervals involved superposition of the individual rainfall events. This modeling results indicated that for relatively deeper soil that the infiltration wetting front could not flood, the effects were damped out in less than a month after rain; while in the long term (years), possible formation of a water lens played a larger role in determining the vapor intrusion risk. In addition, soil organic carbon retarded the transport process, and damped the contaminant concentration fluctuations.
Authors:
Rui Shen; Kelly G Pennell; Eric M Suuberg
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2012-08-22
Journal Detail:
Title:  The Science of the total environment     Volume:  437     ISSN:  1879-1026     ISO Abbreviation:  Sci. Total Environ.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-15     Completed Date:  2013-04-11     Revised Date:  2013-10-17    
Medline Journal Info:
Nlm Unique ID:  0330500     Medline TA:  Sci Total Environ     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  110-20     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 Elsevier B.V. All rights reserved.
Affiliation:
School of Engineering, Brown University, Providence, RI 02912, USA. rui_shen@brown.edu
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MeSH Terms
Descriptor/Qualifier:
Air Pollution*
Diffusion
Groundwater / chemistry
Models, Chemical
Numerical Analysis, Computer-Assisted
Rain / chemistry*
Seasons
Soil / chemistry
Soil Pollutants / chemistry*
Volatilization
Grant Support
ID/Acronym/Agency:
P42 ES013660/ES/NIEHS NIH HHS; P42ES013660/ES/NIEHS NIH HHS
Chemical
Reg. No./Substance:
0/Soil; 0/Soil Pollutants
Comments/Corrections

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