The heterogeneous reactions between gas phase glyoxal and aerosols of glycine, , as well as with a mixture of glycine and ammonium sulfate (AS) at a molar ratio of 1:100, were studied in terms of their optical, physical and chemical properties. The reactions occur over a wide range of relative humidities, from ~30% up to 90%, and occur before before deliquescence. The product aerosols exhibit substantial growth in both geometric size and optical extinction cross sections. All aerosol types show a trend of increasing relative physical and optical growth with decreasing seed aerosol size, as well as with decreasing RH values from 90% to ~50%. For the mixture of glycine-AS 1:100, there is a clear enhancement of the optical and physical growth, exceeding those of both AS and glycine, suggesting a synergistic effect. Aerosol mass spectrometer analyses show that the main products of all the studied reactions are glyoxal oligomers. In addition, the formation of imidazoles, C-N compounds with absorption peaks at ?~=300nm, is observed for all reactions and enhanced by the addition of glycine. The fraction of absorbing substances in the reacted aerosol increases with increasing RH. The results suggest that these reactions are possibly important in low RH regions, plausibly due to the reaction occurring in a few interfacial monolayers of water well before deliquescence.

Role of interfacial water in the heterogeneous uptake of glyoxal by mixed glycine and ammonium sulfate aerosols

243rd National Meeting (2012)

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