Behavior of Radon Progeny near Outdoor Surfaces in Contrasting Terrains

Federal legislation expresses a long-term goal of reducing indoor radon to levels comparable to those outdoors. A thorough understanding of the behavior of radon and its progeny in the outdoor environment is therefore important We report near-surface measurements of radon, attached-to-aerosol progeny, and unattachcd-toaerosol progeny in the contrasting environments of the forested hill country of Oak Ridge, TN and the desert sands of White Sands National Monument, NM. Vertical progeny gradients are greater at White Sands due to a smoother terrain, and dose levels tend to be lower due to lower radon flux from the gypsum sand. Both sites show a significant diurnal variation of dose rate with a maximum occurring usually in the early morning. Correlation of dose rate variation with radon variation is surprisingly small suggesting the importance of other factors such as progeny deposition and aerosol concentration in controlling outdoor dose.