Importance of Advection-Driven Soil Vapor Intrusion: Effects of Atmospheric and Indoor Pressure Variations

Abstract The vapor intrusion (VI) of volatile organic compounds (VOCs) is a major concern due to their acute and chronic toxicities to indoor human. VI could be more problematic by pressure-driven advection and this could be particularly notable in residential areas. This study introduces a numerica...
Ausführliche Beschreibung

Abstract The vapor intrusion (VI) of volatile organic compounds (VOCs) is a major concern due to their acute and chronic toxicities to indoor human. VI could be more problematic by pressure-driven advection and this could be particularly notable in residential areas. This study introduces a numerical model designed to simulate the transport of VOCs by diffusion as well as advection in unsaturated zone. The model is validated with analytical models suggesting its ability to simulate complex VI scenarios with high fidelity. Using the developed model, several VI scenarios are investigated by considering the episodic changes of atmospheric pressure as well as ventilation system induced indoor pressure changes in an TCE contaminated site. The model simulation shows that relatively lower atmospheric pressures compare to those in indoor environment facilitate TCE migration to the atmosphere leading to less TCE intrusion into indoor environment. This is the case when the indoor pressure is greater than those in atmosphere. On the other hand, when the indoor pressure in building is lower than those in atmosphere and when the pressure in atmosphere is higher than those in indoor, more TCE is intruded inside the indoor of building through the subsurface building cracks leading to the increased TCE levels and human exposure risks. This work not only advances our understanding of VI dynamics but also provides a robust tool for predicting indoor VOC concentrations under varying environmental conditions, especially when pressure driven advection becomes an important transport process in unsaturated zone. Ausführliche Beschreibung