Gas phase oxidation mechanisms of unsaturated aldehydes initiated by ozone

ELIZABETH GAONA COLMÁN, MARÍA B. BLANCO, IAN BARNES AND MARIANO A. TERUEL

San Francisco

Simposio; Atmospheric Chemical Mechanisms; 2014

Aldehydes can be released to the atmosphere by biogenic and anthropogenic sources playing an important role in the atmospheric chemistry due to the contribution to the ozone or radical formation by photolysis or reactions with OH and NO3 radicals, O3 molecules. The O3 -initiated atmospheric degradation of unsaturated VOCs in polluted areas is expected to result in the formation of mainly acids, aldehydes, anhydrides and other dicarbonyls compounds which will be subject to further reaction with atmospheric oxidants. Thus, the high reactivity of these unsaturated compounds and also their primary products formed implies that they will be contributors to the photochemical smog and SOA formation in the atmosphere, if are emitted in large quantities. In this work, we report a product study of the gas-phase reactions of O3 molecules with biogenic volatile organic compounds: trans-2-heptenal, trans-2-octenal and trans-2-nonenal. The reactions have been investigated at 298 K and 760 Torr of synthetic air using a big photoreactor coupled with in situ FTIR spectroscopy. The products were identified and quantified using infrared spectra references. The major reactions products observed were: glioxal and pentanal for the reaction of trans-2-heptenal with O3. Glyoxal and hexanal were observed in the reaction of O3 with trans-2-octenal and glyoxal and heptanal were determined as products for the reaction of trans-2-nonenal with O3. The results are discussed and used to postulate the atmospheric chemical mechanisms of these reactions in the atmosphere.