Sulfur Dioxide Accelerates the Heterogeneous Oxidation Rate of Organic Aerosol by Hydroxyl Radicals

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• 作者：Nicole K. Richards-Henderson ; Allen H. Goldstein ; Kevin R. Wilson
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：April 5, 2016
• 年：2016
• 卷：50
• 期：7
• 页码：3554-3561
• 全文大小：401K
• ISSN：1520-5851

文摘

There remains considerable uncertainty in how anthropogenic gas phase emissions alter the oxidative aging of organic aerosols in the troposphere. Here we observe a 10–20 fold acceleration in the effective heterogeneous OH oxidation rate of organic aerosol in the presence of SO₂. This acceleration originates from the radical chain reactions propagated by alkoxy radicals, which are formed efficiently inside the particle by the reaction of peroxy radicals with SO₂. As the OH approaches atmospheric concentrations, the radical chain length increases, transforming the aerosol at rates predicted to be up to 10 times the OH-aerosol collision frequency. Model predictions, constrained by experiments over orders of magnitude changes in [OH] and [SO₂], suggest that in polluted regions the heterogeneous processing of organic aerosols by OH ([SO₂] ≥ 40 ppb) occur on similar time scales as analogous gas-phase oxidation reactions. These results provide evidence for a previously unidentified mechanism by which organic aerosol oxidation is enhanced by anthropogenic gas phase emissions.