European 222Rn flux map for atmospheric tracer applications

Rn is commonly used as a natural tracer for validating climate models. Generally, a constant and homogenous 222 Rn source term ofatom cm−2 s−1 is assumed as a standard, sometimes reduced in northern latitudes. A tendency to overestimate measured 222 Rn concentrations by simulations with this standard assumption has often been found. To improve current models of atmospheric chemistry and transport a better source term for 222 Rn than currently used is necessary. This work aimed to establish a method for mapping the 222 Rn source term by using a commonly measured proxy, the terrestrial γdose rate. A relatively stable fraction (≈20%) of the total terrestrial GDR originates from the 238 U decay chain, of which 222 Rn is a member. In this study a regression model could be established by simultaneous measurements of 222 Rn flux and terrestrial GDR at locations in Switzerland and Germany. This model was validated on a regional scale by measurements in Finland and Hungary, at locations covering wide ranges of γ-dose rates. The predictions were within the error margin of measurements, and therefore considered to suffice to produce regional means of 222 Rn flux by using γ-dose rate as a proxy. To be able to develop a 222 Rn flux map for Europe, a base map for the γ-dose rate was necessary. For this instance, we used the large number of national γ-dose rate measurements, established after the nuclear reactor accident in Chernobyl in 1986. These data are composite values of terrestrial, cosmic and anthropogenic contributions and instrument background (self-effect). We extracted the terrestrial part of the total γ-dose rate provided by the EUropean Radiological Data Exchange Platform (EURDEP), which continuously udates and stores the data. Subsequently we produced annual, seasonal and weekly γ-dose rate maps for Europe (European Union, Norway, former Yugoslavia and Switzerland) with geostatistical methods. The regression model was then used to transform the terrestrial γ-dose rate maps into 222 Rn flux maps, using also additional information (organic/mineral soil, bare rock surface). Spatially and temporally resolved 222 Rn source maps for the European Continent resulted, with a spatial resolution of 0.5◦ x 0.5◦ . Previously made studies could be confirmed, and even more information was available now: modeled 222 Rn flux ranged from 0.03 to 1.76 atom cm−2 s−1 , with a coefficient of variation of 51% and half of the values were between 0.40 and 0.70 atom cm−2 s−1 . The weekly 222 Rn flux maps were applied in a simulation with the atmospheric transport model TM5, as well as the standard assumption ofatom cm−2 s−1 (with 0.5 atom cm−2 s−1 between 60◦ N and 70◦ N). The results from TM5 showed that our spatially resolved 222 Rn source term can improve predictions of atmospheric 222 Rn concentrations. In a case study in Gif-sur-Yvette (France) one week of 222 Rn concentrations were observed. The air mass trajectories turned (a) from areas with large (0.61 atom cm−2 s−1 ) to (b) areas with small (0.30 atom cm−2 s−1 ) 222 Rn fluxes. The standard assumption overpredicted atmospheric concentrations by (a) 70% and (b) 260%, while the simulation based on the new inventory followed the observation closely. On the basis of our approach we also produced 222Rn flux maps for the United States of America and the Russian Federation territory, which are still preliminary and await verification

Analysis of environmental influences in nuclear half-life measurements exhibiting time-dependent decay rates

In a recent series of papers evidence has been presented for correlations between solar activity and nuclear decay rates. This includes an apparent correlation between Earth-Sun distance and data taken at Brookhaven National Laboratory (BNL), and at the Physikalisch-Technische Bundesanstalt (PTB). Although these correlations could arise from a direct interaction between the decaying nuclei and some particles or fields emanating from the Sun, they could also represent an "environmental" effect arising from a seasonal variation of the sensitivities of the BNL and PTB detectors due to changes in temperature, relative humidity, background radiation, etc. In this paper, we present a detailed analysis of the responses of the detectors actually used in the BNL and PTB experiments, and show that sensitivities to seasonal variations in the respective detectors are likely too small to produce the observed fluctuations

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

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

European 222Rn inventory for applied atmospheric studies

International audienc

Inter-calibration of gamma dose rate detectors on the European scale

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

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

International audience222Rn 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

Mapping Terrestrial Gamma-dose Rate in Europe Based on Routine Monitoring Data

After the nuclear reactor accident in Chernobyl in 1986, most countries of the European Union (EU) established monitoring networks measuring outdoor γ-dose rates for early warning. The data is composite values γ-dose rate due to terrestrial, cosmic and artificial radiation sources, and in most cases also include some instrument background. While EURDEP is mainly designed for exchanging and stocking data during radiological emergencies, the data it is storing in its database may potentially contain valuable information about spatio-temporal variations of the 222Rn source term which can be used for the validation of atmospheric transport models and other atmospheric tracer applications. The use of γ-dose rates as a proxy for outdoor radon concentrations is indeed possible if one can extract the terrestrial γ-dose rate contribution from the values reported in EURDEP. It is the purpose of this paper to discuss the preparation of the terrestrial γ-dose rates using EURDEP data and to present seasonal maps of terrestrial γ-dose rates in Europe. Such maps could be used for the preparation of 222Rn source term which can be used for the validation of atmospheric transport models as well as for exploring variations in soil moisture content, an important parameter in flood prediction. These applications are the focus of the ongoing studies, but beyond the scope of this paper. In this paper, we show how the terrestrial γ-dose rate can be derived from the emergency monitoring data and two seasonal maps of γ-dose rates at the European scale are produced using geostatistics.JRC.H.4-Transport and air qualit