Atmospheric in situ gamma-ray spectrometry for precipitation investigation

Abstract

AbstractThe underwater gamma-ray spectrometer GeoMAREA was utilized for in situ continuous monitoring of radon progenies in the atmosphere near the city of Anavyssos, Attica, Greece, during the period from 1 November 2017 until 1 April 2018. The acquired spectra before and during rainfalls were used to derive rainwater’s spectra revealing that the major contributors to the observed photo-peaks are the progenies of 222Rn (214Pb, 214Bi). The total counting rate of the spectra and the counting rate of the net areas of 352 keV and 609 keV photo-peaks (214Pb and 214Bi, respectively) proved to be effective parameters for rainfall identification and investigation. Statistical analysis did not reveal a significant association between radon progenies and temperature, pressure, humidity and dew point during rainfalls or dry meteorological conditions. However, preferable wind directions for rainwater rich in radon progenies revealed the impact of the atmospheric masses trajectories before a precipitation event. According to HYSPLIT modelling of selected rainfall events, air masses that pass over terrestrial areas at low altitudes (< 1500 m above ground level) 48 h before the event result in rainwater enriched in radon progenies. On contrary, air masses that pass before an event over terrestrial areas at higher altitudes (> 3000 m above ground level) result in rainwater of low radon progenies concentration. Overall, the method was considered promising for continuous in situ measurements of radon progenies in the atmosphere and may extend the use of radon as a tracer for studies related to climate investigation.