GAS-PHASE MECHANISMS OF THE OZONE INITIATED OXIDATION OF UNSATURATED ALDEHYDES

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

California

Conferencia; ATMOSPHERIC CHEMICAL MECHANISMS; 2014

Aldehydes are released to the atmosphere by biogenic and anthropogenic sources and play an important role in atmospheric chemistry due to their contribution to ozone and radical formation through photolysis or reactions with OH and NO3 radicals, and O3 molecules. The O3-initiated atmospheric degradation of unsaturated VOCs in polluted areas is expected to result in the formation of a variety of compounds including acids, aldehydes, anhydrides and dicarbonyls in the case of unsaturated aldehydes. Thus, if are emitted in large quantities the oxidation of these unsaturated compounds will be important contributors to photochemical smog and SOA formation in the atmosphere, In this work, we report a product study of the gas-phase reactions of O3 molecules with three 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 large photoreactor coupled with in situ FTIR spectroscopy for the analysis of reactants and products. The major reactions products observed were i) glyoxal and pentanal for the reaction of trans-2-heptenal with O3, ii) glyoxal and hexanal in the reaction of O3 with trans-2-octenal and iii) glyoxal and heptanal for the reaction of trans-2-nonenal with O3. The results are discussed and mechanisms are postulated for the atmospheric ozonolysis of these unsaturated biogenic compounds.