Exploring atmospheric radon with airborne gamma-ray spectroscopy

222Rn is a noble radioactive gas produced along the238U decay chain, which is present in the majority of soils and rocks. As222Rn 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,222Rn 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 treated222Rn as a source of background since it affects the indirect estimate of equivalent238U concentration. In this work the AGRS method is used for the first time for quantifying the presence of222Rn 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 atmospheric222Rn. The refined statistical analysis provides not only a conclusive evidence of AGRS222Rn detection but also a (0.96 ± 0.07) Bq/m3 222Rn concentration and a (1318 ± 22) m atmospheric layer depth fully compatible with literature data