On-line measurements of sulfur dioxide at the 3 km level over central Europe (Sonnblick observatory, Austria) and statistical trajectory source analysis
Journal- or magazine-article
Tscherwenka, W and Seibert, P and Kasper, A and Puxbaum, H
Continuous sulfur dioxide (SO 2 ) measurements were performed at the Sonnblick Observatory (SBO), Austria (3106 m a.s.l.) for several weeks during summer, autumn and spring 1995/96. The average SO 2 concentration was 0.30 μ g m -3 standard temperature and pressure (STP; 273 K, 1013 hPa) (105 pptv), the median 0.10 μ g m -3 STP (35 pptv). For 80% of the time sulfur dioxide concentrations were at “clean levels” (<0.30 μ g m -3 ) interrupted by “episodes” lasting up to two days. During the episodes SO 2 levels rose generally above 0.5 μ g m -3 and reached up to 8.0 μ g m -3 in spring. Sulfur dioxide concentrations showed a strong seasonal variation with very low concentrations during summer and fall (means 0.11 and 0.17 μ g m -3 ) and elevated concentrations during spring (mean 0.70 μ g m -3 ). An analysis of the diurnal variation indicated that upslope winds are not responsible for the elevated SO 2 levels observed during SO 2 episodes; rather cloud transport appears to be the predominant process for lifting SO 2 from the boundary layer to the mid troposphere. For air and cloud transport across Western European countries hydrogen peroxide (H 2 O 2 ) is apparently in excess and most SO 2 is removed by oxidation leading to “clean conditions”. For the less frequent air and cloud transport from the East and Southeast SO 2 appears to be in excess leading to the “SO 2 episodes” at the 3 km level. These results are substantiated by in-cloud observations of elevated levels of SO 2 at SBO ( Brantner et al., 1994 ) and trajectory statistics for the SO 2 data set from SBO and analysis of the meteorological conditions during transport.
Alps ; Long-Range Transport ; Mid Troposphere ; Pollution Episodes ; Sonnblick Observatory ; Sulfur Dioxide ; Trajectories ; Trajectory Statistics