Reactive Uptake and Photo-Fenton Oxidation of Glycolaldehyde in Aerosol Liquid Water

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• 作者：T. B. Nguyen ; M. M. Coggon ; R. C. Flagan ; J. H. Seinfeld
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：May 7, 2013
• 年：2013
• 卷：47
• 期：9
• 页码：4307-4316
• 全文大小：510K
• 年卷期：v.47,no.9(May 7, 2013)
• ISSN：1520-5851

文摘

The reactive uptake and aqueous oxidation of glycolaldehyde were examined in a photochemical flow reactor using hydrated ammonium sulfate (AS) seed aerosols at RH = 80%. The glycolaldehyde that partitioned into the aerosol liquid water was oxidized via two mechanisms that may produce aqueous OH: hydrogen peroxide photolysis (H₂O₂ + h谓) and the photo-Fenton reaction (Fe _(II) + H₂O₂ + h谓). The uptake of 80 (卤10) ppb glycolaldehyde produced 2鈥? wt % organic aerosol mass in the dark (k_H* = (2.09鈥?.17) 脳 10⁶ M atm^鈥?), and the presence of an OH source increased the aqueous uptake by a factor of 4. Although the uptake was similar in both OH-aging mechanisms, photo-Fenton significantly increased the degree of oxidation (O/C = 0.9) of the aerosols compared to H₂O₂ photolysis (O/C = 0.5). Aerosol organics oxidized by photo-Fenton and H₂O₂ photolysis resemble ambient 鈥渁ged鈥?and 鈥渇resh鈥?OA, respectively, after the equivalent of 2 h atmospheric aging. No uptake or changes in particle composition occurred on dry seed aerosol. This work illustrates that photo-Fenton chemistry efficiently forms highly oxidized organic mass in aerosol liquid water, providing a possible mechanism to bridge the gap between bulk-phase experiments and ambient particles.