SO2 oxidation products other than H2SO4 as a trigger of new particle formation. Part 1: Laboratory investigations

T. Berndt, F. Stratmann, S. Bräsel, J. Heintzenberg, A. Laaksonen, M. Kulmala
2008 Atmospheric Chemistry and Physics  
Mechanistic investigations of atmospheric H 2 SO 4 particle formation have been performed in a laboratory study taking either H 2 SO 4 from a liquid reservoir or using the gas-phase reaction of OH radicals with SO 2 . Applying both approaches for H 2 SO 4 generation simultaneously we found that H 2 SO 4 evaporated from the liquid reservoir 5 acts considerably less effective for the process of particle formation and growth than the products originating from the reaction of OH radicals with SO 2
more » ... radicals with SO 2 . Furthermore, for NO x concentrations >5×10 11 molecule cm −3 the formation of new particles from the reaction of OH radicals with SO 2 is inhibited. This suggests that substances other than H 2 SO 4 (likely products from sulphur-containing peroxy radicals) trigger lower tro-10 pospheric new particle formation and growth. The currently accepted mechanism for SO 2 gas-phase oxidation does not consider the formation of such substances making a revision necessary. 25 situ via the reaction of OH radicals with SO 2 ("H 2 SO 4 " here stands for all products of 9762 ACPD 8, 2008 Abstract 25 Gas-phase analysis was carried out using a GC-FID (HP 5890) with a cryoenrichment unit for hydrocarbons, a humidity sensor (Vaisala), analyzers for O 3, SO 2 , 9763 ACPD 8, 2008 Abstract 20 imentally found to be 0.5±0.2 as expected from the simple reaction scheme given above. This finding confirms that OH radical concentration, and consequently the "H 2 SO 4 " concentrations, are well described by the model applied. For normally used initial reaction conditions (O 3 : ∼1.5×10 11 with a conversion <25%, furan: 6.2×10 11 9765 ACPD 8, 2008
doi:10.5194/acp-8-6365-2008 fatcat:5o3rcx4qprhklilak26je2s3qe