title: "Sizing" Heterogeneous Chemistry in the Conversion of Gaseous Dimethyl Sulfide to Atmospheric Particles.
abstract: The oxidation of biogenic dimethyl sulfide (DMS) emissions is a global source of cloud condensation nuclei. The amounts of the nucleating H2SO4(g) species produced in such process, however, remain uncertain. Hydrophobic DMS is mostly oxidized in the gas phase into H2SO4(g) + DMSO(g) (dimethyl sulfoxide), whereas water-soluble DMSO is oxidized into H2SO4(g) in the gas phase and into SO4(2-) + MeSO3(-) (methanesulfonate) on water surfaces. R = MeSO3(-)/(non-sea-salt SO4(2-)) ratios would therefore gauge both the strength of DMS sources and the extent of DMSO heterogeneous oxidation if Rhet = MeSO3(-)/SO4(2-) for DMSO(aq) + ·OH(g) were known. Here, we report that Rhet = 2.7, a value obtained from online electrospray mass spectra of DMSO(aq) + ·OH(g) reaction products that quantifies the MeSO3(-) produced in DMSO heterogeneous oxidation on aqueous aerosols for the first time. On this basis, the inverse R dependence on particle radius in size-segregated aerosol collected over Syowa station and Southern oceans is shown to be consistent with the competition between DMSO gas-phase oxidation and its mass accommodation followed by oxidation on aqueous droplets. Geographical R variations are thus associated with variable contributions of the heterogeneous pathway to DMSO atmospheric oxidation, which increase with the specific surface area of local aerosols.
authors.affiliation: The Hakubi Center for Advanced Research, Kyoto University , Kyoto 606-8302, Japan.|Research Institute for Sustainable Humanosphere, Kyoto University , Uji 611-0011, Japan.|PRESTO, Japan Science and Technology Agency , Kawaguchi 332-0012, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Enami
authors.affiliation: Faculty of Environmental Earth Science, Hokkaido University , Sapporo 060-0610, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Sakamoto
authors.affiliation: Department of Earth Science System, Fukuoka University , Fukuoka 814-0180, Japan.
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Hara
authors.affiliation: Graduate School of Environmental Studies, Nagoya University , Nagoya 464-8601, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Osada
authors.affiliation: Linde Center for Global Environmental Science, California Institute of Technology , California 91125, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hoffmann
authors.affiliation: Linde Center for Global Environmental Science, California Institute of Technology , California 91125, United States.
authors.forename: Agustín J
authors.initials: AJ
authors.lastname: Colussi
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D000393:Air Pollutants / Q000737:chemistry*; D000864:Antarctic Regions; D005740:Gases / Q000737:chemistry*; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D013440:Sulfides / Q000737:chemistry*
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D005740:Gases; D013440:Sulfides; C004784:dimethyl sulfide