Datensatz

Zusammenfassung

Trace gases containing sulfur enhance the formation and growth of atmospheric aerosol particles thus indirectly affecting the Earths climate. Sulfur dioxide is a central constituent of the atmospheric sulfur cycle. It is directly emitted into the atmosphere from natural as well as from anthropogenic sources, but also originates from the oxidation of other sulfur-containing compounds. Aircraft-based measurements in the troposphere over southern Brazil in altitudes from 0.7 to 13km showed isolated layers of SO2-rich air in the free troposphere containing comparable amounts of sulfur dioxide as observed near the ground. Model calculations imply long-range transport of sulfur dioxide from copper smelters or volcanoes located in the Andes. Convection may play an important role for vertical transport into the upper troposphere. In the atmosphere sulfur dioxide is converted into sulfuric acid within a couple of days. This also happens in the exhaust of Diesel engines when oxidation catalysts are employed for the oxidation of soot, leading to the emission of sulfuric acid. As sulfuric acid is an aerosol precursor this results in an enhanced nanoparticle concentration in the exhaust plume. Aerosol particles of a few nanometers in size are able to penetrate into the human lung representing a potential health risk. Measurements in the exhaust of a Diesel passenger car and measurements on a heavy-duty engine on a test bench confirmed that the use of particulate filters in combination with oxidation catalysts does indeed induce an enhancement of sulfuric acid in the exhaust.