Aerosol particle size distribution of atmospheric lead-210 in northern Finland

Size-segregated aerosol samples were collected with a high-volume 6-stage cascade impactor at Sodankyla, Finland, 100 km north of the Arctic Circle. The Pb-210 content of the samples were determined with radiochemical separation of in-grown Po-210 followed by alpha spectrometry. Most of the Pb-210 activity was incorporated in accumulation mode aerosol particles. The activity median aerodynamic diameter (AMAD) ranged from 0.53 mu m to 0.98 mu m 38-61 per cent of Pb-210 activity was found to be associated with aerosol particles smaller than 0.69 mu m. A slight downward tendency of Pb-210 activity median aerodynamic diameter was observed as a function of increasing Pb-210 activity concentration. This is related to the continental origin of airborne Pb-210 on one hand, and various aerosol particle growth processes on the other hand. Also a clear tendency towards a higher Be-7/Pb-210 activity ratio as a function of increasing aerosol particle diameter was observed. This, in turn, reflects the different origin of (210)pb, exhalation of Rn-222 from the soil into the air, and Be-7, formation by cosmic radiation in the upper troposphere and the stratosphere. (C) 2017 Elsevier Ltd. All rights reserved.