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 SO42-+MeSO3- (methane sulfonate) on water surfaces. Thus, R=MeSO3-/non-sea-saltSO42- ratios would therefore gauge both the strength of DMS sources and the extent of DMSO heterogeneous oxidation if Rhet=MeSO3-/SO42- 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 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.

Biography

Agustin J Colussi is a Research Professor at California Institute of Technology, USA since 1998 and has published more than 200 papers in environmental physical chemistry.