THE PHOTOCHEMICAL CONVERSION OF SO2 TO SULFURIC-ACID AND PARTICULATE SULFUR IN THE PRESENCE OF BIOGENIC HYDROCARBON TRACES

Photochemical degradation processes of biogenic organic hydrocarbons are of great interest in the discussion of forest decline. The impact of SO2 on the photodegradation of the hydrocarbon α-pinene in the presence of an NOx photosmog leading to the formation of aerosols and to a conversion of SO2 to sulfuric and other sulfur compounds is the scope of this project. The yield of these products is dependent on the presence of humidity. Under dry conditions, the main product is H2SO4 and 1/3 of the consumed SO2 is recovered in the airborne aerosols. In the presence of 60% relative humidity sulfurous particles are the almost exclusive product with a yield of 50%. The nature of the sulfur aerosols is yet unknown. From ion chromatography the formation of sulfate is supported.