SO2 oxidation products other than H2SO4 as a trigger of new particle formation. Part 1: Laboratory investigations
Mechanistic investigations of atmospheric H2SO4 particle formation\nhave been performed in a laboratory study taking either H2SO4 from\na liquid reservoir or using the gas-phase reaction of OH radicals\nwith SO2. Applying both approaches for H2SO4 generation simultaneously\nit was found that H2SO4 evaporated from the liquid reservoir acts\nconsiderably less effective for the process of particle formation\nand growth than the products originating from the reaction of OH\nradicals with SO2. Furthermore, for NOx concentrations >5�1011 molecule\ncm-3 the formation of new particles from the reaction of OH radicals\nwith SO2 is inhibited. This suggests that substances other than H2SO4\n(potentially products from sulphur-containing peroxy radicals) trigger\nlower tropospheric new particle formation and growth. The currently\naccepted mechanism for SO2 gas-phase oxidation does not consider\nthe formation of such substances. The analysis of new particle formation\nfor different reaction conditions in our experiment suggests that\na contribution of impurities to the nucleation process is unlikely.