Exploring atmospheric radon with airborne gamma-ray spectroscopy

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²²²Rn is a noble radioactive gas produced along the ²³⁸U decay chain, which is present in the majority of soils and rocks. As ²²²Rn 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 treated ²²²Rn as a source of background since it affects the indirect estimate of equivalent ²³⁸U concentration. In this work the AGRS method is used for the first time for quantifying the presence of ²²²Rn 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 ²²²Rn. The refined statistical analysis provides not only a conclusive evidence of AGRS ²²²Rn 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.