Physically simulating the effect of lateral vapor source-building separation on soil vapor intrusion: Influences of surface pavements and soil heterogeneity

Abstract

The soil gas concentration attenuation in lateral diffusive transport determines the influence area of a contamination plume in soil vapor intrusion, a major exposure pathway of volatile chemicals at contaminated sites. In this study, we utilize both physical and mathematical models to investigate the roles of soil geology heterogeneities and impermeable surface pavements in determining the attenuation of contaminant soil gas concentration. The results indicate that the attenuation of soil gas concentration with lateral diffusion is observed to be the most significant if with a low-permeability soil layer at the bottom and a high-permeability layer on top, followed by the cases with the uniform soil properties, and the lateral attenuation is the least significant in cases with a high-permeability soil layer at the bottom and a low-permeability soil layer on top, regardless of the surface coverage. Compared to soil heterogeneity, the influences of surface conditions are less significant, and the capping effect of surface cover can only play a role in determining shallow soil gas concentration profiles. At last, the physical experimental results were used to examine a previously developed analytical vapor intrusion model including the influences of layering and surface conditions