Probing the Fate of Highly Oxygenated Molecules in Atmospheric Aerosols
XUAN ZHANG, University of California Merced
Abstract Number: 443
Working Group: Aerosol Chemistry
Abstract
Highly oxygenated molecules (HOMs) originating from biogenic emissions constitute a widespread source of organic aerosols in the pristine atmosphere. Yet, the fate of HOMs upon forming new particles remain unclear. Here we present a comprehensive dataset tracking the trajectory and ultimate fate of a diverse array of HOMs in α-pinene and limonene SOA under a range of atmospheric relevant conditions. What sets this study apart from prior research is the focus on the individual behaviors of SOA-bound HOMs upon the completion of gas-phase chemistry. The observed dynamics of HOMs therefore speak directly to their particle-phase reactivity and reflect the strength of condensed-phase chemistry, if any, in altering the HOMs molecular composition. The category of HOMs is correspondingly extended to all highly oxygenated molecules that play a role in the formation and growth of SOA particles, covering the original group produced from the gas-phase autoxidation pathway, as well as those potentially resulting from a concerted gas- and particle-phase chemistry. Another highlight of this study lies in the experimental setup that mimics ambient aerosols as a mixture of sulfate, organics, and liquid water. Under such settings, individual HOMs produced through gas phase autoxidation either nucleate or condense onto existing sulfate seeds, and the impact of various environmental conditions (dark vs. photolytic and dry vs. hydrous) on the HOMs fate was explored. Temporal profiles of isomer-resolved HOMs monomers and dimers were obtained using the particle into liquid sampler coupled with an iodometry-assisted liquid chromatography mass spectrometer. These time series unveil a striking diversity in the fate of individual HOMs species, and even isomers of identical molecular exhibit distinct behaviors such as rapid decay and steady growth. The observed dynamics of SOA-bound HOMs underscore the diverse pathways that contribute to their initial formation and continually modify their composition and lifetimes in atmospheric aerosols.