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Environ Toxicol Chem

Title:		Sensitivity analysis on parameters and processes affecting vapor intrusion risk
Author(s):		Picone S; Valstar J; van Gaans P; Grotenhuis T; Rijnaarts H;
Address:		"Wageningen University, Subdepartment of Environmental Technology, Wageningen, The Netherlands. sara.picone@wur.nl"
Journal Title:		Environ Toxicol Chem
Year:		2012
Volume:		20120330
Issue:		5
Page Number:		1042 - 1052
DOI:		10.1002/etc.1798
ISSN/ISBN:		1552-8618 (Electronic) 0730-7268 (Linking)
Abstract:		"A one-dimensional numerical model was developed and used to identify the key processes controlling vapor intrusion risks by means of a sensitivity analysis. The model simulates the fate of a dissolved volatile organic compound present below the ventilated crawl space of a house. In contrast to the vast majority of previous studies, this model accounts for vertical variation of soil water saturation and includes aerobic biodegradation. The attenuation factor (ratio between concentration in the crawl space and source concentration) and the characteristic time to approach maximum concentrations were calculated and compared for a variety of scenarios. These concepts allow an understanding of controlling mechanisms and aid in the identification of critical parameters to be collected for field situations. The relative distance of the source to the nearest gas-filled pores of the unsaturated zone is the most critical parameter because diffusive contaminant transport is significantly slower in water-filled pores than in gas-filled pores. Therefore, attenuation factors decrease and characteristic times increase with increasing relative distance of the contaminant dissolved source to the nearest gas diffusion front. Aerobic biodegradation may decrease the attenuation factor by up to three orders of magnitude. Moreover, the occurrence of water table oscillations is of importance. Dynamic processes leading to a retreating water table increase the attenuation factor by two orders of magnitude because of the enhanced gas phase diffusion"
Keywords:		"Biodegradation, Environmental Diffusion Gases/analysis *Groundwater Housing *Models, Chemical Risk Soil/*analysis Volatile Organic Compounds/*analysis;"
Notes:		"MedlinePicone, Sara Valstar, Johan van Gaans, Pauline Grotenhuis, Tim Rijnaarts, Huub eng Research Support, Non-U.S. Gov't 2012/03/07 Environ Toxicol Chem. 2012 May; 31(5):1042-52. doi: 10.1002/etc.1798. Epub 2012 Mar 30"