Seasonal variation and source areas of airborne lead-210 at Ny-Alesund in the High Arctic

High-volume aerosol particle samples were collected onto glass-fibre filters at Mount Zeppelin Global Atmosphere Watch station, Ny-Alesund, Svalbard, in 2001-05. The filters were assayed for lead-210 ((210)Pb) by measuring the alpha particles of its in-grown daughter nuclide polonium-210 ((210)Po). The observed (210)Pb activity concentrations at Mount Zeppelin vary between <4 and 1060 mu Bq m(-3), with an arithmetic mean of 130 mu Bq m(-3) and a median of 74 mu Bq m-3. The lowest (210)Pb activity concentrations are found during summer and the highest are found in winter. This variation is caused by seasonal differences in the mixing conditions of the troposphere, the level of precipitation and the speed of atmospheric chemistry induced by solar radiation. The performed source area analysis, which is based on air mass back trajectories, indicated that in summer, (210)Pb can be used as a tracer for air masses coming into contact with land areas within the past 5 days. In winter this cannot be performed because of the accumulation of (210)Pb-carrying aerosol particles into the Arctic atmosphere during the Arctic night. But even in winter a low (210)Pb activity concentration indicates that the associated air mass has had little if any contact with land areas.