Heterogeneous Reaction of Glyoxal on Sulfuric Acid

Organic carbonyls and α-dicarbonyls are relevant molecules in atmospheric chemistry due to their role in the formation of Secondary Organic Aerosols (SOA). Glyoxal in particular has been extensively studied due to its role in SOA formation, presence in the particulate phase, high volatility, and formation as consequence of the oxidation-driven ring fragmentation of aromatic precursors and the oxidation of isoprene. However, the current understanding regarding the specific role of glyoxal in the formation mechanisms of SOA is still limited. In these work, the heterogeneous reaction of glyoxal on sulfuric acid has been investigated at various temperatures and acid concentrations.. All experiments were conducted utilizing a low pressure fast flow reactor coupled to an Ion Drift Chemical Ionization Mass Spectrometer (ID-CIMS) to measure the uptake coefficient (γ) of glyoxal by sulfuric acid. The uptake coefficient values of glyoxal by sulfuric acid range from 1x10-2 to 1x10-3 decreasing with increasing acid concentration. This concentration trend suggests that glyoxal uptake by sulfuric acid is a hydration-driven process, and not an acid-catalyzed mechanism. Furthermore, experimental results at varied temperatures suggest that there exists a temperature effect on the uptake coefficient (γ) values as results at warmer temperatures show increasing partial reversible uptake behavior for the higher acid concentration solutions. Therefore, lower temperatures and lower acidities promote higher uptake coefficient (γ) values. Thus, the obtained results offer new insight into the roles and effects of aerosol hygroscopicity and acidity and the interaction of glyoxal and sulfuric acid during SOA formation.