Behavior of 222 Rn, 220 Rn and their progenies along a daily cycle for different meteorological situations: Implications on atmospheric aerosol residence times and Rn daughters' equilibrium factors.

The correct assessment of the radiological hazard from radon and daughters, external and internal doses, residence times and equilibrium factors, implies the need to properly determine ²²² Rn (radon), ²²⁰ Rn (thoron) and their respective short-lived progenies ( ²¹⁴ Pb and ²¹⁴ Bi, and ²¹² Pb and ²¹² Bi, respectively), where the precise measurements of both progenies are quite complex due to their very short half-lives. In addition, it is important to study the temporal behavior of all these radionuclides along daily cycles. Therefore, the aim of this study was to analyze the temporal evolution of radon, thoron and their progenies, and of their activity ratios along daily cycles for two different meteorological situations (synoptic and mesoscale processes). Radon and thoron were measured using a radon monitoring system, while their respective progenies were collected onto atmospheric filters using an ASS-500 sampler, and then measured by gamma-ray spectrometry. Furthermore, the different relationships between the concentrations of radionuclides and the different meteorological variables of interest (temperature, ABL height, and speed and direction of the wind) were found. Finally, the atmospheric aerosol residence times and Rn daughters' equilibrium factors were estimated for each sampling carried out along the two daily cycles, finding results consistent with previous studies.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)