Abstract
Measurements of the 222Rn activity concentration profile in the soil and the 222Rn flux in West-Germany are presented. The spatial pattern of the 222Rn flux depends more on soil type than on the 226Ra activity of the soil material. The average 222Rn flux from sandy soils is 1000—2000 dpm m-2 h-1 and 4000—6000 dpm m-2 h-1 from loamy and clayey soils. Weekly 222Rn flux measurements during a period of 1 year at a sandy site show no significant temporal variations. At a clayey site, the 222Rn flux tends to be higher in summer than in winter. The permeability coefficient PRn, obtained from simultaneous 222Rn flux and concentration profile measurements in various soils, can be expressed as a function of the soil parameters total porosity ε0, soil moisture F, tortuosity k and the molecular diffusion coefficient D0 of 222Rn in air: P = D0((ε-F)/k - const.). The flux of any other gas into or out of the soil can thus be calculated from its measured concentration profile in the soil and from the 222Rn permeability coefficient, replacing the molecular diffusion coefficient of 222Rn by that of the specific gas under consideration. As an example, this method of flux determination is demonstrated for the soil CO2 flux to the atmosphere and for the flux of atmospheric CH4 into the soil.