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

Abstract

High-volume aerosol particle samples were collected onto glass-fibre filters at Mount Zeppelin Global Atmosphere Watch station, Ny-Ålesund, Svalbard, in 2001–05. The filters were assayed for lead-210 (210Pb) by measuring the alpha particles of its in-grown daughter nuclide polonium-210 (210Po). The observed 210Pb activity concentrations at Mount Zeppelin vary between <4 and 1060 mBq m-3, with an arithmetic mean of 130 mBq m-3 and a median of 74 mBq m-3. The lowest 210Pb 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, 210Pb 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 210Pb-carrying aerosol particles into the Arctic atmosphere during the Arctic night. But even in winter a low 210Pb activity concentration indicates that the associated air mass has had little if any contact with land areas.