Exploring atmospheric radon with airborne gamma-ray spectroscopy

\(^{222}\)Rn is a noble radioactive gas produced along the \(^{238}\)U decay chain, which is present in the majority of soils and rocks. As \(^{222}\)Rn is the most relevant source of natural background radiation, understanding its distribution in the environment is of great concern for investigating the health impacts of low-level radioactivity and for supporting regulation of human exposure to ionizing radiation in modern society. At the same time, \(^{222}\)Rn is a widespread atmospheric tracer whose spatial distribution is generally used as a proxy for climate and pollution studies. Airborne gamma-ray spectroscopy (AGRS) always treated \(^{222}\)Rn as a source of background since it affects the indirect estimate of equivalent \(^{238}\)U concentration. In this work the AGRS method is used for the first time for quantifying the presence of \(^{222}\)Rn in the atmosphere and assessing its vertical profile. High statistics radiometric data acquired during an offshore survey are fitted as a superposition of a constant component due to the experimental setup background radioactivity plus a height dependent contribution due to cosmic radiation and atmospheric \(^{222}\)Rn. The refined statistical analysis provides not only a conclusive evidence of AGRS \(^{222}\)Rn detection but also a (0.96 \(\pm\) 0.07) Bq/m\(^{3}\) \(^{222}\)Rn concentration and a (1318 \(\pm\) 22) m atmospheric layer depth fully compatible with literature data.