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European Rn-222 flux map for atmospheric tracer applications
English title
European Rn-222 flux map for atmospheric tracer applications
Applicant
Conen Franz
Number
105123
Funding scheme
Project funding
Research institution
Departement für Geowissenschaften Universität Basel
Institution of higher education
University of Basel - BS
Main discipline
Climatology. Atmospherical Chemistry, Aeronomy
Start/End
01.12.2004 - 30.11.2007
Approved amount
176'856.00
Show all
Keywords (4)
Atmospheric tracer; Radon-222; Soil efflux; Variability
Lay Summary (English)
Lead
Lay summary
Rn-222 is commonly used as a natural tracer for validating climate models. Generally, a constant and homogenous Rn-222 source term of 1 atom cm-2 s-1 is assumed as a standard, sometimes reduced in northern latitudes. A tendency to overestimate measured Rn-222 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 Rn-222 than currently used is necessary. This work aimed to establish a method for mapping the Rn-222 source term by using a commonly measured proxy, the terrestrial ?-dose (GDR) rate. A relatively stable fraction (~20%) of the total terrestrial GDR originates from the U-238 decay chain, of which Rn-222 is a member. In this study a regression model could be established by simultaneous measurements of Rn-222 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 ?-dose rates. The predictions were within the error margin of measurements, and therefore considered to suffice to produce regional means of Rn-222 flux by using ?-dose rate as a proxy. To be able to develop a Rn-222 flux map for Europe, a base map for the ?-dose rate was necessary. For this instance, we used the large number of national ?-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 ?-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 ?-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 ?-dose rate maps into Rn-222 flux maps, using also additional information (organic/mineral soil, bare rock surface). Spatially and temporally resolved Rn-222 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 Rn-222 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 Rn-222 flux maps were applied in a simulation with the atmospheric transport model TM5, as well as the standard assumption of 1 atom 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 Rn-222 source term can improve predictions of atmospheric Rn-222 concentrations. In a case study in Gif-sur-Yvette (France) one week of Rn-222 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) Rn-222 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 Rn-222 flux maps for the United States of America and the Russian Federation territory, which are still preliminary and await verification.
Direct link to Lay Summary
Last update: 21.02.2013
Responsible applicant and co-applicants
Name
Institute
Conen Franz
Institut für Umweltgeowissenschaften Universität Basel
Leuenberger Markus
Klima und Umweltphysik Physikalisches Institut Universität Bern
Employees
Name
Institute
Szegvary Thomas
Joint Research Centre Environmental Institute
Associated projects
Number
Title
Start
Funding scheme
117622
Improving the verification of non-CO2 greenhouse gas emissions in Europe by the Rn-222 tracer method
01.02.2008
Project funding
-