Abstract:
Subterranean networks of cavities and fissures can present circulatory systems facilitating convective and advective transport of radon-bearing air. Evidence points to aerostatic pressure differentials being the principal driving force for subterranean transport of radon in some hilly limestone terrains of the southern Appalachians; differences between the underground and outside air temperatures, and the concomitant differences in air density, appear to be the dominant factor in producing the differences in aerostatic pressure. Examples are presented of houses experiencing elevated indoor levels as a consequence of being built on top of and apparently communicating with such subterranean systems. The location of a house near the upper or lower end of a subterranean circulatory system can result in amplification of indoor radon levels in winter or summer, respectively. These phenomena have been studied in and around houses located in the hilly karst areas of Huntsville, AL, and Oak Ridge, TN