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508670 
Journal Article 
Radon decay product aerosols in ambient air 
Papastefanou, C 
2009 
Yes 
Aerosol and Air Quality Research
ISSN: 1680-8584
EISSN: 2071-1409 
9 
4 
385-393 
English 
WOS:000270892800001 
The aerodynamic size distributions of radon decay product aerosols, i.e. Pb-214, Pb-212, and Pb-210 were measured using low-pressure (LPI) as well as conventional low-volume 1-ACFM and high-volume (HVI) cascade impactors. The activity size distribution of Pb-214 and Pb-212 was largely associated with submicron aerosols in the accumulation mode (0.08 to 2.0 mu m). The activity median aerodynamic diameter "AMAD" varied from 0.10 to 0.37 mu m (average 0.16 mu m) for Pb-214-aerosols and from 0.07 to 0.25 mu m (average 0.12 mu m) for Pb-212-aerosols. The geometric standard deviation, sigma(g) averaged 2.86 and 2.97, respectively. The AMAD of Pb-210-aerosols varied from 0.28 to 0.49 mu m (average 0.37 mu m) and the geometric standard deviation, sg varied from 1.6 to 2.1 (average 1.9). The activity size distribution of Pb-214-aerosols showed a small shift to larger particle sizes relative to Pb-212-aerosols. The larger median size of Pb-214-aerosols was attributed to alpha-recoil depletion of smaller aerosol particles following the decay of the aerosol-associated Po-218. Subsequent Pb-214 condensation on all aerosol particles effectively enriches larger-sized aerosols. Pb-212 does not undergo this recoil-driven redistribution. Even considering recoil following Po-214 alpha-decay, the average Pb-210-labeled aerosol grows by a factor of two during its atmospheric lifetime. Early morning and afternoon measurements indicated that similar size associations of Pb-214 occur, despite humidity differences and the potential for fresh particle production in the afternoon. In estimating lifetimes of radon decay product aerosols in ambient air, a mean residence time of about 8 days could be applied to aerosol particles in the lower atmosphere below precipitation cloud levels. 
Radon; Decay products; Pb-214; Pb-212; Pb-210; Radioactive aerosols; Cascade impactors; 1-ACFM; AMAD; Residence time; activity size distributions; mean residence time; pb-210; atmosphere; po-210; progeny; ratio; lead-210; bi-210; be-7