Radon migration

The dimensionless group Pep is essentially the ratio of the rate of convective transport to the rate of diffusive transport. Similarly, Nr describes the relative importance of radioactive decay to convective flow as a method of removing radon from the soil pores. In the case of Pep >>1/ diffusion can be neglected and the first term in equation (1) drops out. If in addition Nr >>1, then radioactive decay can be neglected as a removal term. If Pep 1, then diffusive radon migration dominates, and the second term in equation (1) can be neglected. 

Tanner, A.B., Radon Migration in the Ground a Supplementary Review, in Proc. Natural Radiation Environment III. Conf-780422, (Gesell, T.F., and Lowder, W.M., eds.) pp. 5-56, U.S. Dept, of Commerce, National Technical Information Service, Springfield VA, (1980). 

Tanner, A.B. (1964) Radon migration in the ground a review. In The Natural Radiation Environment, ed. J.A.S. Adams W.M. Lowder, University of Chicago Press, pp. 161-90. 

Radon-222, with a half-life of 4 days, is produced in rocks and soil that contain even minute amounts of uranium-238. Because it is a gas, radon migrates readily from the soil into the surrounding air. It seeps into houses and other buildings through openings around pipes, and through cracks in basement floors and walls. 

Membrane banners are applied to the exterior of the foundation and also beneath the floor slab during construction. Materials used for the membrane barriers range from coextruded poly olefin to polyvinyl chloride to foil sheets with many other materials in between. All membrane barriers must have the edges sealed to prevent radon from migrating around the edges and back into the building. 

The second approach is to investigate both experimentally and theoretically the influence of soils at a localized level, on the scale of an individual house, for example. Production and transport of radon in soils and migration of radon into houses depend upon local soil conditions, and results of these studies will improve our basic understanding of the physical processes involved. This in turn will aid in the systematic development of more effective entry identification and mitigation techniques to prevent or reduce radon entry into dwellings. 

Factors Influencing Production and Migration of Radon in Soils... 

Figure 1. Schematic illustration of factors influencing the production and migration of radon in soils and into buildings. Geochemical processes affect the radium concentration in the soil. The emanating fraction is principally dependent upon soil moisture (1 0) and the size distribution of the soil grains (d). Diffusion of radon through the soil is affected primarily by soil porosity ( ) and moisture content, while convective flow of radon-bearing soil gas depends mainly upon the air permeability (k) of the soil and the pressure gradient (VP) established by the building.

Factors influencing the production and migration of radon in soils have been examined, and various sources of geographic data have been discussed. Two significant soil characteristics include air permeability and, less importantly, radium concentration. While there are, at present, few opportunities to compare the larger-scale data with on-site field measurements, those comparisons that have been made for both surface radium concentrations and air permeability of soils show a reasonable correspondence. Further comparisons between the aerial radiometric data and surface measurements are needed. Additional work and experience with SCS information on soils will improve the confidence in the permeability estimates, as will comparisons between the estimated permeabilities and actual air permeability measurements performed in the field. 

Fleischer, R. L. and A. Mogro-Campero, Mapping of Integrated Radon Emanation for Detection of Long-Distance Migration of Gases Within the Earth Techniques and Principles,. 1. Geophvs. Res. 83(B7) 3539-3549 (1977). 

Fleischer, R.L. and Mogro-Campero, A., 1978. Mapping of integrated radon emanation for deteetion of long-distance migration of gases within the Earth techniques and prineiples. J. Geophys. Res., 83 3539-3549. 

Mogro-Campero, A. and Fleischer, R.L., 1976. Subterrestrial fluid convection a hypothesis for longdistance migration of radon within the earth. Earth Planet. Sci. Lett., 34 321-325. 

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