Abstract
Various vapour intrusion (VI) models have been proposed in order to predict indoor concentration of Volatile Organic Compounds (VOCs) in buildings. However, these models tend to be conservative, and overestimate or underestimate vapour flux emissions due to several assumptions. Particularly, most of these VI models only consider an infinite uniform contaminated groundwater as the principal source of VOCs in the soil, and lateral pollution source in the vadose zone are disregarded. It has been shown that ignoring the lateral source position may lead to uncertainties on the estimations. In this paper, a numerical model is developed in order to better understand the relationship between the lateral source position in the soil, including both a source in the vadose zone and a source located at the groundwater level, and the resulting indoor air concentration. Results show that source position plays a significant role on vapour intrusion attenuation. In fact, indoor concentration of VOCs decreases with increasing lateral separation. Finally, it is shown that considering the source position can significantly improve the quality of VI predictions.
Highlights
Volatile Organic Compounds (VOCs) can migrate from the subsurface into buildings by the difference in concentrations and air pressure between the subsurface contaminated areas and the indoor spaces [1]
Vapour intrusion (VI) occurs essentially through the cracks and/or openings existing in the building foundation and may cause human health problems associated with the exposure of VOCs in the indoor environments [1]
The main objective of this work is to propose a numerical study to better understand the relationship between the lateral source position in the soil, including both a source in the vadose zone and a source located at the groundwater level, and the resulting indoor air concentration
Summary
VOCs can migrate from the subsurface (contaminated groundwater or soil) into buildings (vapour intrusion) by the difference in concentrations (diffusion) and air pressure between the subsurface contaminated areas and the indoor spaces (advection) [1]. Numerical models are useful for their capacity to capture precise characteristics of VI scenarios, but a significant computational effort is required and measured parameters from the studied site are needed For this reason, analytical screening tools are much more used in practice. The atmosphere, having a much larger area than vapour intrusion pathways, serves as a much more important sink than the foundation porosity and cracks [12] In this context, the main objective of this work is to propose a numerical study to better understand the relationship between the lateral source position in the soil, including both a source in the vadose zone (unsaturated zone from the top of the ground surface to the water table) and a source located at the groundwater level, and the resulting indoor air concentration
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