Exploring atmospheric radon with airborne gamma-ray spectroscopy

Rn-222 is a noble radioactive gas produced along the U-238 decay chain, which is present in the majority of soils and rocks. As Rn-222 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, Rn-222 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 Rn-222 as a source of background since it affects the indirect estimate of equivalent U-238 concentration. In this work the AGRS method is used for the first time for quantifying the presence of Rn-222 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 Rn-222. The refined statistical analysis provides not only a conclusive evidence of AGRS Rn-222 detection but also a (0.96 +/- 0.07) Bq/m(3) Rn-222 concentration and a (1318 +/- 22) m atmospheric layer depth fully compatible with literature data. (C) 2017 Elsevier Ltd. All rights reserved.