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Original Articles

Estimating the Asian radon flux density and its latitudinal gradient in winter using ground-based radon observations at Sado Island

, , , , &
Pages 732-746 | Received 08 Apr 2009, Accepted 21 Jul 2009, Published online: 18 Jan 2017
 

Abstract

Terrestrial radon-222 flux density for the Asian continent, integrated over distances of 4500 km, is estimated in two 20. latitudinal bands centred on 48.8.N and 63.2.N. The evaluation is based on three years of wintertime radon measurements at Sado Island, Japan, together with meteorological and trajectory information. A selection of 18% of observations are suitable for evaluation of an analytical expression for the continental surface flux. Various meteorological assumptions are discussed; it is found that there is a substantial effect of increased complexity of the formulation on the flux estimates obtained. The distribution of spatially integrated radon flux over the Asian landmass is reported for the first time. Expressed as geometric means and 1±-ranges, estimated fluxes are 14.1 mBq m.2 s.1 (1±-range: 18 mBq m-2 s-1) and 8.4 mBq m-2 s-1 (1±-range: 10 mBq m-2 s-1) for the lower and higher latitude bands. These results constitute an annual minimum in flux densities for these regions, and are higher than previously reported. The existence of a latitudinal gradient in the continental radon source function is confirmed; the present estimate for Asia (-0.39 mBq m-2 s-1 per degree of latitude) is in agreement with the northern hemisphere terrestrial radon flux gradient proposed previously.