Atmospheric organic compounds are known to participate in complex photochemical reactions that affect chemical composition and important properties of aerosol particles. This presentation will discuss our on-going and recently published work on the mechanisms of condensed-phase photochemical processes in cloud droplets, which are characterized by low concentrations of solutes, and in aerosol particles, which can have highly viscous organic phases and aqueous phases with high concentrations of inorganic salts. We prepare model secondary organic aerosol (SOA) and expose the entire mixture of SOA compounds to simulated solar radiation under different experimental conditions: (a) extracted in water to mimic cloud droplets; (b) extracted in a concentrated salt solutions at different pH to mimic aerosol liquid water; (c) directly on the SOA collection substrate to mimic organic-rich phase in aerosol particles. The chemical composition of SOA is compared before and after irradiation with liquid chromatography and mass spectrometry methods. We observe that lifetimes of SOA compounds with respect to photodegradation depend strongly on the sample matrix in which SOA compounds are exposed to sunlight. In our control experiments carried out in darkness, we observe small changes in the composition of SOA in non-acidified salt solutions but extensive changes under highly acidic conditions.

Condensed-phase photochemical and dark aging processes in secondary organic aerosol

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.