THE INFLUENCES OF DIFFUSION AND ADVECTIVE FLOW ON THE DISTRIBUTION OFRADON ACTIVITY WITHIN USEPAS SOIL CHAMBER

The U.S. Environmental Protection Agency's (EPA's) soil chamber was de signed to study the production and transport of radon and other potent ial indoor air pollutants originating in the soil. This paper presents an analysis of steady-state diffusion in the soil for two different c onditions of moisture. The model accounts for multiphase emanation and transport. When the position dependence of the moisture profile was t aken into account, the model and measurements agreed well (average dev iations of 5% - 13%). Non-steady-state measurements are also discussed . Diffusion plays an important role in radon transport even for this r elatively high permeability (3 x 10(-11) m(2)) soil. The implication i s that diffusion plays an important role in transporting radon to a po int near the building shell even though the entry mechanism by which r adon penetrates the shell may primarily be advective flow. Copyright ( C) 1996 Elsevier Science Ltd.