title: The atmospheric photolysis of o-tolualdehyde.
abstract: The photolysis of o-tolualdehyde by natural sunlight has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. The photolysis rate coefficient was measured directly under different solar flux levels, with values in the range j(o-tolualdehyde) = (1.62-2.15) × 10(-4) s(-1) observed, yielding an average value of j(o-tolualdehyde)/j(NO(2)) = (2.53 ± 0.25) × 10(-2). The estimated photolysis lifetime is 1-2 h, confirming that direct photolysis by sunlight is the major atmospheric degradation pathway for o-tolualdehyde. Published UV absorption cross-section data were used to derive an effective quantum yield (290-400 nm) close to unity, within experimental error. Possible reaction pathways for the formation of the major photolysis products, benzocyclobutenol (tentatively identified) and o-phthalaldehyde, are proposed. Appreciable yields (5-13%) of secondary organic aerosol (SOA) were observed at EUPHORE and also during supplementary experiments performed in an indoor chamber using an artificial light source. Off-line analysis by gas chromatography-mass spectrometry allowed identification of o-phthalaldehyde, phthalide, phthalic anhydride, o-toluic acid, and phthalaldehydic acid in the particle phase.
authors: Department of Chemistry and Environmental Research Institute, University College Cork, Cork, Ireland.
authors: Grainne M
authors: GM
authors: Clifford
authors: Aurélie
authors: A
authors: Hadj-Aïssa
authors: Robert M
authors: RM
authors: Healy
authors: Abdelwahid
authors: A
authors: Mellouki
authors: Amalia
authors: A
authors: Muñoz
authors: Klaus
authors: K
authors: Wirtz
authors: Montserrat
authors: M
authors: Martín Reviejo
authors: Esther
authors: E
authors: Borrás
authors: John C
authors: JC
authors: Wenger
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D001547:Benzaldehydes / Q000737:chemistry*; D010782:Photolysis; D013030:Spain; D013472:Sunlight
chemical_list: D001547:Benzaldehydes; C093384:2-methylbenzaldehyde