Abstract
Abstract. The use of the noble gas radon (222Rn) as a tracer for different research studies, for example observation-based estimation of greenhouse gas (GHG) fluxes, has led to the need of high-quality 222Rn activity concentration observations with high spatial and temporal resolution. So far a robust metrology chain for these measurements is not yet available. A portable direct atmospheric radon monitor (ARMON), based on electrostatic collection of 218Po, is now running at Spanish stations. This monitor has not yet been compared with other 222Rn and 222Rn progeny monitors commonly used at atmospheric stations. A 3-month intercomparison campaign of atmospheric 222Rn and 222Rn progeny monitors based on different measurement techniques was realized during the fall and winter of 2016–2017 to evaluate (i) calibration and correction factors between monitors necessary to harmonize the atmospheric radon observations and (ii) the dependence of each monitor's response in relation to the sampling height and meteorological and atmospheric aerosol conditions. Results of this study have shown the following. (i) All monitors were able to reproduce the atmospheric radon variability on a daily basis. (ii) Linear regression fits between the monitors exhibited slopes, representing the correction factors, between 0.62 and 1.17 and offsets ranging between −0.85 and −0.23 Bq m−3 when sampling 2 m above ground level (a.g.l.). Corresponding results at 100 m a.g.l. exhibited slopes of 0.94 and 1.03 with offsets of −0.13 and 0.01 Bq m−3, respectively. (iii) No influence of atmospheric temperature and relative humidity on monitor responses was observed for unsaturated conditions at 100 m a.g.l., whereas slight influences (order of 10−2) of ambient temperature were observed at 2 m a.g.l. (iv) Changes in the ratio between 222Rn progeny and 222Rn monitor responses were observed under very low atmospheric aerosol concentrations. Results also show that the new ARMON could be useful at atmospheric radon monitoring stations with space restrictions or as a mobile reference instrument to calibrate in situ 222Rn progeny monitors and fixed radon monitors. In the near future a long-term comparison study between ARMON, HRM, and ANSTO monitors would be useful to better evaluate (i) the uncertainties of radon measurements in the range of a few hundred millibecquerels per cubic meter to a few becquerels per cubic meter and (ii) the response time correction of the ANSTO monitor for representing fast changes in the ambient radon concentrations.
Highlights
Over continents, the natural radioactive noble gas radon (222Rn) is continuously generated within the soil from the decay of radium (226Ra) (Nazaroff and Nero, 1988), and it can escape into the atmosphere by diffusion, depending on soil characteristics and meteorological conditions (Grossi et al, 2011; López-Coto et al, 2013; Karstens et al, 2015)
Results show that the new ARMON could be useful at atmospheric radon monitoring stations with space restrictions or as a mobile reference instrument to calibrate in situ 222Rn progeny monitors and fixed radon monitors
In recent decades the atmospheric scientific community has been addressing different research topics using 222Rn as a tracer. Examples of such applications include the improvement of inverse transport models (Hirao et al, 2010), the improvement of chemical transport models (Jacob and Prather, 1990; Chambers et al, 2019a), the study of atmospheric transport and mixing processes within the planetary boundary layer (Zahorowski et al, 2004; Galmarini, 2006; Baskaran, 2011; Chambers et al, 2011, 2016, 2019b; Williams et al, 2011, 2013; Vogel et al, 2013; Vargas et al, 2015; Baskaran, 2016), the experimental estimation of greenhouse gas (GHG) fluxes (Levin et al, 1999, 2011; Vogel et al, 2012; Wada et al, 2013; Grossi et al, 2018), and others listed in Grossi et al (2016)
Summary
In recent decades the atmospheric scientific community has been addressing different research topics using 222Rn as a tracer Examples of such applications include the improvement of inverse transport models (Hirao et al, 2010), the improvement of chemical transport models (Jacob and Prather, 1990; Chambers et al, 2019a), the study of atmospheric transport and mixing processes within the planetary boundary layer (Zahorowski et al, 2004; Galmarini, 2006; Baskaran, 2011; Chambers et al, 2011, 2016, 2019b; Williams et al, 2011, 2013; Vogel et al, 2013; Vargas et al, 2015; Baskaran, 2016), the experimental estimation of greenhouse gas (GHG) fluxes (Levin et al, 1999, 2011; Vogel et al, 2012; Wada et al, 2013; Grossi et al, 2018), and others listed in Grossi et al (2016). This type of instrument performs a direct measurement of 222Rn and 220Rn (thoron) activity concentrations using the already existent method based on the electrostatic deposition of 218Po and 216Po, respectively (Hopke, 1989; Tositti et al, 2002; Grossi et al, 2012)
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