Atmospheric Chemistry and Physics
The multiphase chemistry of glyoxal is a source of secondary organic aerosol (SOA), including its light-absorbing product imidazole-2-carboxaldehyde (IC). IC is a photosensitizer that can contribute to additional aerosol ageing and growth when its excited triplet state oxidizes hydrocarbons (reactive uptake) via H-transfer chemistry. We have conducted a series of photochemical coated-wall flow tube (CWFT) experiments using films of IC and citric acid (CA), an organic proxy and H donor in the condensed phase. The formation rate of gas-phase HO2 radicals (PHO2) was measured indirectly by converting gas-phase NO into NO2. We report on experiments that relied on measurements of NO2 formation, NO loss and HONO formation. PHO2 was found to be a linear function of (1) the [IC]×[CA] concentration product and (2) the photon actinic flux. Additionally, (3) a more complex function of relative humidity (25%
Palacios, Laura González; Arroyo, Pablo Corral; Aregahegn, Kifle Z.; Steimer, Sarah S.; Bartles-Rausch, Thorsten; Nozière, Barbara; George, Christian; Ammann, Markus; and Volkamer, Rainer, "Heterogeneous photochemistry of imidazole-2-carboxaldehyde: HO2 radical formation and aerosol growth" (2016). Chemistry & Biochemistry Faculty Contributions. 62.