Organic matter is a ubiquitous component of atmospheric aerosols. Inorganic aerosols may acquire an organic component via in situ interactions with volatile organic compounds (VOCs), a family of processes known as secondary organic aerosol (SOA) formation. SOA formation is one of the greatest sources of uncertainty in estimations of aerosol forcing on climate.
Carbonyl-containing VOCs have recently attracted much attention as potential SOA precursors. SOA formation by these species occurs via their uptake into the aqueous phase of an aerosol particle or cloud droplet, followed by aqueous-phase chemistry leading to the formation of low-volatility oligomer products. We have built on our recent studies of glyoxal and methylglyoxal oligomerization in aqueous aerosol mimics by investigating glyoxal-methylglyoxal cross reactions as well as the chemistry of formaldehyde and acetaldehyde in the presence of ammonium salts and amino acids. We find that aerosol surface tension depression and the formation of light-absorbing organics, or “brown carbon” is typical for these systems. These properties are important for determining the climate effects of aerosol particles and their roles in atmospheric chemistry. Approaches for modeling these processes in atmospheric aerosols will be discussed.