Characterizing the automatic radon flux Transfer Standard system Autoflux: laboratory calibration and field experiments

Abstract

Abstract. High-quality, long-term measurements of terrestrial trace gas emissions are important for investigations of atmospheric, geophysical and biological processes to help mitigate climate change, protect the environment, and the health of citizens. High-frequency terrestrial fluxes of the radioactive noble gas 222Rn, in particular, are useful for validating radon flux maps, used to evaluate the performance of regional atmospheric models, to improve greenhouse gas emission inventories (by the Radon Tracer Method) and to determine Radon Priority Areas for radiation protection goals. A new automatic radon flux system (the Autoflux) was developed as a Transfer Standard (TS) to assist with establishing a traceability chain for field-based radon flux measurements. The operational characteristics and features of the system were optimized based on a literature review of existing flux measurement systems. To characterize and calibrate the Autoflux a bespoke radon Exhalation Bed (EB) facility was also constructed with the intended purpose of providing a constant radon emanation under a specific set of controlled laboratory conditions. The calibrated Autoflux was then used to transfer the derived calibration to a second continuous radon flux system under laboratory conditions, both instruments were then tested in the field and compared with modeled fluxes. This paper presents: i) a literature review of state-of-the-art radon flux systems and EB facilities; ii) the design, characterization and calibration of a reference radon EB facility; iii) the design, characterization and calibration of the Autoflux system; iv) the calibration of a second radon flux system (INTE_Flux) using the EB and Autoflux, with a total uncertainty of 9 % (k=1) for an average radon flux of ~1800 mBq m−2 s−1 under controlled laboratory conditions; and iv) an example application of the calibrated TS and INTE_Flux systems for in situ radon flux measurements which are then compared with simulated radon fluxes. Calibration of the TS under different environmental conditions and at lower reference fluxes will be the subject of a separate future investigation.

Characterizing the automatic radon flux transfer standard system Autoflux: laboratory calibration and field experiments

“…Code and data availability. The data and the codes from this study are available from the corresponding author and at the following link: https://github.com/ClauGro/GRL_Data (last access: 30 May 2023; https://doi.org/10.5281/zenodo.7331337, Grossi, 2022). Scripts of the software R v. 3.6.2 (with RStudio) and Python v. 3.8 (with Spyder) were used and are also shared in the GitHub repository.…”