Journal of Earth Science & Climatic Change
Open Access

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 but into SO4 2- + MeSO3- (methane sulfonate) on water surfaces. Thus, R=MeSO3-/non-sea-salt- SO42- 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, which 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 gasphase 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.

Biography

Agustín J Colussi is a Senior Research Scientist at CALTECH since 1998 and has published more than 200 papers in environmental physical chemistry.

Email: ajcoluss@caltech.edu