Abstract. 222 Rn is commonly used as a natural tracer for validating climate models. To improve such models a better source term for 222 Rn 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 222 Rn 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 238 U decay series, of which 222 Rn is a member. Accordingly, spatial variation in terrestrial GDR was found to describe almost 60% of the spatial variation in 222 Rn flux. Furthermore, temporal variation in GDR and 222 Rn was found to be correlated. Increasing soil moisture reduces gas diffusivity and the rate of 222 Rn flux but it also decreases GDR through increased shielding of photons. Prediction of 222 Rn flux through GDR for individual measurement points is imprecise but un-biased. Verification of larger scale prediction showed that estimates of mean 222 Rn fluxes were not significantly different from the measured mean values.
Abstract. 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.
Abstract.A project to compare the response of different detector types was started in 1996 at the Schauinsland mountain (1200 m above sea level) close to Freiburg, Germany, where the German office for radiation protection (BfS) runs a trace analysis laboratory since about 50 years. The aim of this inter-calibration experiment is to compare different gamma dose rate detector types over long periods and under rather unfavorable climatic conditions. This allows to characterise different probe types under environmental conditions and it complements the EURADOS inter-comparison exercises, which a carried out every 2 to 3 years. Both projects dealing with the harmonization of gamma dose rate data in the EU are used to derive terrestrial dose rate from the raw data. Using interpolation techniques provided by INTAMAP seasonal maps of the terrestrial dose rate could be generated. It is shown, that this information can be used for the calibration of satellite based soil moisture methods as well for the calculation of radon emission maps on the European scale, which are of interest for the research community, since Radon is used as a passive tracer in atmospheric research to examine transport processes on synoptic time scales.
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