title: Kinetics of heterogeneous reactions of HO2 radical at ambient concentration levels with (NH4)2SO4 and NaCl aerosol particles.
abstract: The HO2 uptake coefficient (gamma) for inorganic submicrometer wet and dry aerosol particles ((NH4)2SO4 and NaCl) under ambient conditions (760 Torr and 296 +/- 2 K) was measured using an aerosol flow tube (AFT) coupled with a chemical conversion/laser-induced fluorescence (CC/LIF) technique. The CC/LIF technique enabled experiments to be performed at almost the same HO2 radical concentration as that in the atmosphere. HO2 radicals were injected into the AFT through a vertically movable Pyrex tube. Injector position-dependent profiles of LIF intensity were measured as a function of aerosol concentration. Measured gamma values for dry aerosols of (NH4)2SO4 were 0.04 +/- 0.02 and 0.05 +/- 0.02 at 20% and 45% relative humidity (RH), respectively, while those of NaCl were <0.01 and 0.02 +/- 0.01 at 20% and 53% RH, respectively. For wet (NH4)2SO4 aerosols, measured gamma values were 0.11 +/- 0.03, 0.15 +/- 0.03, 0.17 +/- 0.04, and 0.19 +/- 0.04, at 45%, 55%, 65%, and 75% RH, respectively, whereas for wet NaCl aerosols the values were 0.11 +/- 0.03, 0.09 +/- 0.02, and 0.10 +/- 0.02 for 53%, 63%, and 75% RH, respectively. Wet (NH4)2SO4 and NaCl aerosols doped with CuSO4 showed gamma values of 0.53 +/- 0.12 and 0.65 +/- 0.17, respectively. These results suggest that compositions, RH, and phase for aerosol particles are significant to HO2 uptake. Potential HO2 loss processes and their atmospheric contributions are discussed.
authors.affiliation: Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohoma, Kanagawa 236-0001, Japan. taketani@ jamstec.go.jp
authors.forename: Fumikazu
authors.initials: F
authors.lastname: Taketani
authors.forename: Yugo
authors.initials: Y
authors.lastname: Kanaya
authors.forename: Hajime
authors.initials: H
authors.lastname: Akimoto
mesh_terms: D000336:Aerosols / Q000737:chemistry; D000645:Ammonium Sulfate / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D017382:Reactive Oxygen Species / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry*
chemical_list: D000336:Aerosols; D005609:Free Radicals; D017382:Reactive Oxygen Species; D012965:Sodium Chloride; D000645:Ammonium Sulfate