Chemical properties of Arctic aerosol particles collected at the Zeppelin station during the aerosol transition period in May and June of 2004

Single particle analysis was performed on samples taken at the Zeppelin Station, Svalbard, during the ASTAR campaign, 2004. Thirteen samples were selected to representatively cover the campaign period and different weather conditions. This particular period also covers the transition from an accumulation mode dominated size distribution in spring to an Aitken mode dominated aerosol size distribution in summer. Altogether, 1353 particles were analysed and their elemental composition documented. Another 1225 were counted but not characterized chemically. The samples were compared with respect to chemical composition, aerosol size, shape and airmass origin. The comparison showed that the samples taken before the aerosol size transition were dominated by spherical 'organic like' particles in the submicrometre range, with an Eurasian influence. The samples taken after the size transition showed a more complex character and the source origin was the Arctic basin. In this period, an increase of both marine aerosol groups as well as groups of continental origin became more pronounced. This apparent contradiction may have its explanation in cloud scavenging processes, removing the hygroscopic particles from the old continental air, leaving the more hydrophobic particles, at the same time, as the ocean source will provide a more maritime character.