Reactive Uptake of Hydroperoxymethyl Thioformate to Sodium Chloride and Sodium Iodide Aerosol Particles

The oxidation products of dimethyl sulfide (DMS) contribute to the production and growth of cloud condensation nuclei (CCN) in the marine boundary layer. Recent work demonstrates that DMS is oxidized by OH radicals to the stable intermediate hydroperoxymethyl thioformate (HPMTF), which is both globally ubiquitous and efficiently lost to multiphase processes in the marine atmosphere. At present, there are no experimental measurements of the reactive uptake of HPMTF to aerosol particles, limiting model implementation of multiphase HPMTF chemistry. Using an entrained aerosol flow reactor combined with chemical ionization mass spectrometry (CIMS), we measured the reactive uptake coefficient (γ) of HPMTF to dry sodium chloride (NaCl), wet NaCl, and wet sodium iodide (NaI) particles to be (1.9 ± 1.3) × 10^-4, (1.6 ± 0.6) × 10^-3, and (9.2 ± 2.3) × 10^-1, respectively. While we did not directly measure the condensed-phase products of HPMTF reactive uptake in this experiment, the ionization products observed in the CIMS instrument provide mechanistic insight on the reaction mechanism of HPMTF with halides.