AMT Atmospheric Measurement Techniques AMT Atmos. Meas. Tech. 1867-8548 Copernicus Publications Göttingen, Germany 10.5194/amt-3-723-2010 Comparison of one- and two-filter detectors for atmospheric <sup>222</sup>Rn measurements under various meteorological conditions Xia Y. 1 Sartorius H. 2 Schlosser C. 2 Stöhlker U. 2 Conen F. 1 Zahorowski W. 3 Institute of Environmental Geosciences, University of Basel, Bernoullistrasse 30, 4056 Basel, Switzerland Federal Office for Radiation Protection (BfS) , Willy-Brandt-Str. 5, 38226 Salzgitter, Germany Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia 28 06 2010 3 3 723 731 Copyright: © 2010 Y. Xia et al. 2010 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://amt.copernicus.org/articles/3/723/2010/amt-3-723-2010.html The full text article is available as a PDF file from https://amt.copernicus.org/articles/3/723/2010/amt-3-723-2010.pdf

Parallel monitoring of <sup>222</sup>Rn and its short-lived progeny (<sup>218</sup>Po and <sup>214</sup>Pb) were carried out from November 2007 to April 2008 close to the top of the Schauinsland mountain, partly covered with forest, in South-West Germany. Samples were aspired from the same location at 2.5 m above ground level. We measured <sup>222</sup>Rn with a dual flow loop, two-filter detector and its short-lived progeny with a one-filter detector. A reference sector for events, facing a steep valley and dominated by pasture, was used to minimize differences between <sup>222</sup>Rn and progeny-derived <sup>222</sup>Rn activity concentrations. In the two major wind sectors covered by forest to a distance between 60 m and 80 m towards the station progeny-derived <sup>222</sup>Rn activity concentration was on average equal to 87% (without precipitation) and 74% (with precipitation) of <sup>222</sup>Rn activity concentration. The observations show that most of the time both detector types follow the same pattern. Still, there is no single disequilibrium factor that could be used to exactly transform short-lived progeny to <sup>222</sup>Rn activity concentration under all meteorological conditions.

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