EVIDENCE FOR HETEROGENEOUS SO2 OXIDATION IN LJUBLJANA, YUGOSLAVIA

The results of analyses of 24-h wintertime aerosol samples collected during the 1981/82 and 1983/84 sampling periods demonstrate that the highest sulfate formation is observed during periods of high relative humidity and persistent subzero temperatures. Such conditions are conducive to formation of liquid water droplets. The existence of an aqueous mechanism is corroborated by the observed aerosol chloride loss during high sulfate episodes and by the fact that most aerosol sulfate is corroborated by the observed aerosol chloride loss during high sulfate episodes and by the fact that most aerosol sulfate is confined to a particle size range between 0. 3 and 2 mu m. Soot particles are found in the same size range, indicating the association of aerosol sulfate with combustion products. Under favorable meteorological conditions, up to 20% of the SO//2 may be oxidized to sulfate by heterogeneous mechanisms in winter.