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Sci Total Environ. 2016 Sep 15;565:1-7. doi: 10.1016/j.scitotenv.2016.04.131. Epub 2016 May 4.

Thermo-diffusional radon waves in soils.

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Portland Community College, 12000 SW 49th Ave, Portland, OR 97219, USA. Electronic address:
Saratov State University, 83 Astrakhanskay Street, Saratov 410012, Russian Federation.


A new theoretical framework for diurnal and seasonal oscillations of the concentration of radon in soil and open air is proposed. The theory is based on the existing temperature waves in soils and thermo-diffusional gas flux in porous media. As soil is a non-isothermal porous medium, usually possessing a large fraction of microscopic pores belonging to Knudsen's free molecular field, a thermo-diffusional gas flow in soil has to arise. The radon mass transfer equation in soil for sinusoidal temperature oscillations at the soil-atmosphere boundary is solved, which reveals that radon concentration behaves as a damped harmonic wave. The amplitude of radon concentration oscillations and phase shift between radon concentration oscillations and soil temperature depend on the radon diffusion coefficient in soil, rate of radon production, soil thermal conductivity, average soil temperature, decay constant, and heat of radon transfer. Primarily numerical calculations are presented and comparisons with experimental data are shown.


Atmosphere; Radon; Radon oscillations; Temperature waves; Thermo-transpiration

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