Numerical analysis of vapor intrusion from the ground into buildings in the presence of lateral sources of pollution

Abstract Various screening-level and analytical models have been proposed in order to evaluate Vapor Intrusion (VI) and provide assessment tools for exposure risk in indoor environments. However, many in situ investigations show important differences between predicted and measured indoor concentrations generally associated with inappropriate conceptual modelling, incomplete VI process or by ignoring critical parameters in the evaluations. In this study, a numerical model is developed to better understand how polluted site characteristics as source position, soil properties, building pressure and type of construction may affect VI process from non-degrading chemicals. The results confirm that source location plays a critical role on VI compared to soil properties and building features. Increasing lateral distance from a building decreases indoor concentration about 5 orders of magnitude when the source is shallow and 2 to 3 orders of magnitude for deeper sources. However, despite the main influence of the position of the source, soil properties and building characteristics impacts are not insignificant: building pressure (−4 Pa) may increase VI by a factor of 2 compared to building at atmospheric pressure, slab on grade construction types increase vapor attenuation of 80% compare to a bare ground configuration and permeable soils may allow vapors to migrate more easily to the building by generating an indoor concentration up to 10 times higher compared to impermeable soils. Current VI models including lateral separation, generally adopted in polluted site engineering, are unable to consider those influencing parameters, especially building features, and thus need to be extended to improve the management of contaminated land before building constructions.