The Atmospheric Photolysis of o-Tolualdehyde

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• 作者：Grainne M. Clifford ; Aur茅lie Hadj-A茂ssa ; Robert M. Healy ; Abdelwahid Mellouki ; Amalia Mu帽oz ; Klaus Wirtz ; Montserrat Mart铆n Reviejo ; Esther Borr谩s ; John C. Wenger
• 刊名：Environmental Science & Technology
• 出版年：2011
• 出版时间：November 15, 2011
• 年：2011
• 卷：45
• 期：22
• 页码：9649-9657
• 全文大小：929K
• 年卷期：v.45,no.22(November 15, 2011)
• ISSN：1520-5851

文摘

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鈥?.15) 脳 10^鈥? s^鈥? observed, yielding an average value of j(o-tolualdehyde)/j(NO₂) = (2.53 卤 0.25) 脳 10^鈥?. The estimated photolysis lifetime is 1鈥? 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鈥?00 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鈥?3%) 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鈥搈ass spectrometry allowed identification of o-phthalaldehyde, phthalide, phthalic anhydride, o-toluic acid, and phthalaldehydic acid in the particle phase.