SO2 oxidation products other than H2SO4 as a trigger of new particle formation – Part 1: Laboratory investigations
1Leibniz-Institut für Troposphärenforschung e.V., Leipzig, Germany
2University of Kuopio, Kuopio, Finland
3University of Helsinki, Helsinki, Finland
Abstract. Mechanistic investigations of atmospheric H2SO4 particle formation have been performed in a laboratory study taking either H2SO4 from a liquid reservoir or using the gas-phase reaction of OH radicals with SO2. Applying both approaches for H2SO4 generation simultaneously we found that H2SO4 evaporated from the liquid reservoir acts considerably less effective for the process of particle formation and growth than the products originating from the reaction of OH radicals with SO2. Furthermore, for NOx concentrations >5×1011 molecule cm−3 the formation of new particles from the reaction of OH radicals with SO2 is inhibited. This suggests that substances other than H2SO4 (likely products from sulphur-containing peroxy radicals) trigger lower tropospheric new particle formation and growth. The currently accepted mechanism for SO2 gas-phase oxidation does not consider the formation of such substances making a revision necessary.