Photochemical Aging of α-pinene and β-pinene Secondary Organic Aerosol formed from Nitrate Radical Oxidation

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• 作者：Theodora Nah ; Javier Sanchez ; Christopher M. Boyd ; Nga Lee Ng
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：January 5, 2016
• 年：2016
• 卷：50
• 期：1
• 页码：222-231
• 全文大小：510K
• ISSN：1520-5851

文摘

The nitrate radical (NO₃) is the dominant nighttime oxidant in most urban and rural environments and reacts rapidly with biogenic volatile organic compounds to form secondary organic aerosol (SOA) and organic nitrates (ON). Here, we study the formation of SOA and ON from the NO₃ oxidation of two monoterpenes (α-pinene and β-pinene) and investigate how they evolve during photochemical aging. High SOA mass loadings are produced in the NO₃+β-pinene reaction, during which we detected 41 highly oxygenated gas- and particle-phase ON possessing 4 to 9 oxygen atoms. The fraction of particle-phase ON in the β-pinene SOA remains fairly constant during photochemical aging. In contrast to the NO₃+β-pinene reaction, low SOA mass loadings are produced during the NO₃+α-pinene reaction, during which only 5 highly oxygenated gas- and particle-phase ON are detected. The majority of the particle-phase ON evaporates from the α-pinene SOA during photochemical aging, thus exhibiting a drastically different behavior from that of β-pinene SOA. Our results indicate that nighttime ON formed by NO₃+monoterpene chemistry can serve as either permanent or temporary NO_x sinks depending on the monoterpene precursor.