Predicting terrestrial ²²²Rn flux using gamma dose rate as a proxy

T. Szegvary (1) , M. C. Leuenberger (2) , F. Conen (1)

1 Environmental Geosciences
2 CEP - Climate and Environmental Physics [Bern]

²²²Rn is commonly used as a natural tracer for validating climate models. To improve such models a better source term for ²²²Rn than currently used is necessary. The aim of this work is to establish a method for mapping this source term by using a commonly measured proxy, the gamma dose rate (GDR). Automatic monitoring of GDR has been networked in 25 European countries by the Institute for Environment and Sustainability at the Joint Research Centre (JRC IES) in Ispra, Italy, using a common data format. We carried out simultaneous measurements of ²²²Rn flux and GDR at 63 locations in Switzerland, Germany, Finland and Hungary in order to cover a wide range of GDR. Spatial variations in GDR resulted from different radionuclide concentrations in soil forming minerals. A relatively stable fraction (20%) of the total terrestrial GDR originates from the ²³⁸U decay series, of which ²²²Rn is a member. Accordingly, spatial variation in terrestrial GDR was found to describe almost 60% of the spatial variation in ²²²Rn flux. Furthermore, temporal variation in GDR and ²²²Rn was found to be correlated. Increasing soil moisture reduces gas diffusivity and the rate of ²²²Rn flux but it also decreases GDR through increased shielding of photons. Prediction of ²²²Rn flux through GDR for individual measurement points is imprecise but un-biased. Verification of larger scale prediction showed that estimates of mean ²²²Rn fluxes were not significantly different from the measured mean values.

Domaines: Océan, Atmosphère

T. Szegvary, M. C. Leuenberger, F. Conen. Predicting terrestrial ²²²Rn flux using gamma dose rate as a proxy. Atmospheric Chemistry and Physics, 2007, 7 (11), pp.2789-2795. ⟨hal-00296241⟩