Partitioning of 222Rn entry into a structure surrounded by soil.

This paper describes the entry rate of 222Rn into a basement structure surrounded by a sandy clay loam soil. The highest indoor radon concentrations occurred when the rate of entry was lowest. Data from in-situ measurements were used to identify the entry pathways and also the origins of the radon during periods when the entry rate was low. Results indicated that 25% of the radon entered through the floor-wall joint and 75% through the floor and walls. About 30% of the radon originated in the concrete. Diffusion was the primary transport mechanism. However, radon entry through the floor-wall joint was a combination of diffusion and a convective flow between the subslab region and the interior of the structure.