About the seminar:

Atmospheric gaseous sulfuric acid, an important aerosol precursor, and other S(VI) compounds affect cloud radiative properties and thus Earth’s climate. Dimethyl sulfide (DMS) produced by marine microbes, especially in sea ice habitats, is the largest biogenic source of atmospheric sulfur and oxidizes through gas-phase reactions to H2SO4(g) or multiphase reactions to other S(VI) compounds that grow preexisting atmospheric particles. Methanesulfinic acid (CH3SOOH; MSIA) is a key intermediate in DMS oxidation at low temperatures. However, large-scale models disagree on whether reaction with OH(g), OH(aq), or O3(aq) is the main chemical sink of MSIA. Moreover, these results are based on insufficient measurements of k_(MSIA/MSI-(aq) + O3(aq)) across atmospherically relevant conditions. The most recent kinetics measurements observed the rate of reaction in microdroplets, in which kinetics depend on interfacial transport timescales and surface reactions whereas well-mixed, beaker-scale kinetics depend only on the bulk reaction rate coefficient. In this presentation, we motivate significance and uncertainties in DMS multiphase oxidative fate over polar oceans. To constrain these atmospheric multiphase kinetics based on laboratory bulk kinetics and multiphase experiments, we motivate the use of multiphase kinetic models which explicitly represent physical transport and chemical elementary steps in surface and bulk volumes of microdroplets.