Probing the Fate of Highly Oxygenated Molecules in Atmospheric Aerosols

This study presents a comprehensive data set tracking the trajectory of highly oxidized molecules (HOMs) produced from the ozonolysis of monoterpenes across the gas to particle conversion process. A particular focus was to examine the ultimate fate of HOMs in suspended particles after the completion of gas phase chemistry. The observed dynamics of HOMs, therefore, provides direct insights into the role of condensed-phase chemistry, if any, in modifying their molecular composition. Individual SOA-bound HOMs exhibited remarkably diverse behaviors, and even certain isomers of identical elemental composition appeared to undergo different transformations. A small group of C_8-10 and C₂₀ HOMs decayed rapidly in hydrated particles, on a time scale akin to those of organic hydroperoxides. On the other hand, a subset of C_12-20 dimers was found to continuously grow in abundance, and the presence of water substantially enhanced their growth rates. This rising trend was well captured by box model simulations that incorporate the kinetics of condensed-phase chemistry, specifically the peroxyhemiacetal formation pathway. The majority of HOMs remained structurally stable across all hydrous and photolytic conditions investigated in this study. This persistence highlights the potential of HOMs as a widespread and sustained source of cloud condensation nuclei in the atmosphere.