Radon Daughter Activity Size Distributions

1 January 1984

journal article
Published by Oxford University Press (OUP) in Radiation Protection Dosimetry

Vol. 7 (1-4) , 147-150
https://doi.org/10.1093/oxfordjournals.rpd.a082980

Abstract

The size distributions of radon and thoron daughters have been measured in buildings and in the open air. Because of the low radioactivity concentration a high volume cascade impactor was used. The cascade impactor data were evaluated by means of an improved computer programme taking into account the effect of interstage losses on the measured precipitation values of the impactor. The size distributions found for the shortlived radon daughters, ²¹⁴Pb, ²¹⁴Bi, and thoron daughter, ²¹²Pb, were unimodal log-normal. There was no significant difference between activity size distributions of the short lived radon decay products and the thoron daughter ²¹²Pb. The activity median aerodynamic diameter (AMAD) measured in different buildings and at different days ranged from 0.07 µm to 0.29 µm with a mean value of 0.18 µm for the radon and thoron daughters in dwellings with low room ventilation. The mean value of the geometric standard deviation was s_g = 3.50. The size distributions in the open air are shifted significantly to larger particle sizes with a mean AMAD of 0.39 µm (range: 0.20 to 0.54 µm) and a mean standard deviation of s_g = 2.31.

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