210Pb, 210Po and 7Be in oceanic air from the North Pole to the Antarctic

During the Swedish expedition SWEDARP, 1988-89 air filter samples were collected from Sweden to the Antarctic. In as similar way air filters were collected at the SWEDARCTIC expedition 1991, from Sweden to the North Pole. The samples were analysed for 7Be, 210Po and 210Pb. Our data for 7Be show maximal concentrations between 45 deg. N and 45 deg. S, (2600-5100 μBq m-3), and minima in the Arctic and Antarctic regions, 300-1100 μBq m-3 and 500-1400 μBq m-3 respectively. The data show the strong convection of air close to the Equator bringing 7Be to surface-level from the upper troposphere or even stratosphere. 210Pb and 210Po being the daughter products of 222Rn depend on the sources of aerosols from the continents. The activity ratio 210Po/210Pb reflects the residence time in the troposphere. Our data show maximal concentrations in the equatorial regions, 60-150 μBq m-3 for 210Po and 350-600 μBq m-3 for 210Pb. The corresponding values for 210Po in the polar regions, Arctic and Antarctic, are 5-80 μBq m-3 and 3-15 μBq m-3 respectively and for 210Pb, 6-100 and 4-45 μBq m-3. The activity ratio, 210Po/210Pb, between 45 deg. N and S are about 0.2-0.3 while they are as high as 0.7-1.1 in the Arctic and Antarctic regions. This shows that only small particles with long residence time reach the polar regions. The long residence time in the polar regions is due to low precipitation and low particle load. (author)