A self-consistent, multivariate method for the determination of gas-phase rate coefficients, applied to reactions of atmospheric VOCs and the hydroxyl radical
A self-consistent, multivariate method for the determination of gas-phase rate coefficients, applied to reactions of atmospheric VOCs and the hydroxyl radical
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DOI：
10.5194/acp-18-4039-2018
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发表时间：
2017-10
影响因子：
6.3
通讯作者：
J. Shaw;R. Lidster;D. Cryer;N. Ramírez;Fiona C. Whiting;Graham A Boustead;L. Whalley;T. Ingham;A. Rickard;R. Dunmore;D. Heard;A. Lewis;L. Carpenter;J. Hamilton;T. Dillon
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文献类型：
--
作者：
J. Shaw;R. Lidster;D. Cryer;N. Ramírez;Fiona C. Whiting;Graham A Boustead;L. Whalley;T. Ingham;A. Rickard;R. Dunmore;D. Heard;A. Lewis;L. Carpenter;J. Hamilton;T. Dillon
摘要。气相速率系数是理解大气化学的基础，但对流层中观测到的数千种挥发性有机化合物（VOCs）的氧化反应尚无实验数据。本文报道了一种新的实验方法，用于同时研究多种不同VOCs与日间大气中最重要的自由基氧化剂OH之间的反应。该技术基于既定的相对速率概念，但具有更高的目标VOCs吞吐量的优势。通过对每次实验中多个VOCs进行评价，并通过测量每种VOC与OH反应后的耗损量，可以推导出OH + VOC的反应速率系数。在受控的实验室条件下进行的实验结果与现有文献中关于19种挥发性有机化合物在合成气体混合物中与OH反应的结果一致。该方法首次用于确定羟基与2,3-二甲基戊烯反应的速率系数；K = 5.7（±0.3）× 10−11 cm3分子−1 s−1。此外，在文献中，另外七种挥发性有机化合物只有两个或更少的单个OH速率系数测量值。这项工作的结果与这些测量结果很好地吻合。在323（±10）K的高温下，使用类似的数据集确定了12种芳香、5种烷烃、5种烯烃和3种单萜化合物VOC + OH反应的新OH速率系数。在约克大学使用环境空气进行的OH相对反应性实验中，观察到大量不同的挥发性有机化合物，其中23种被确定。由于检测限和完全解析峰的困难，仅从这些环境空气样品中获得了19个OH速率系数，其中包括10个先前在T = 323（±10）K升高的反应温度下无法获得数据的反应。
Abstract. Gas-phase rate coefficients are fundamental to understanding atmospheric chemistry, yet experimental data are not available for the oxidation reactions of many of the thousands of volatile organic compounds (VOCs) observed in the troposphere. Here, a new experimental method is reported for the simultaneous study of reactions between multiple different VOCs and OH, the most important daytime atmospheric radical oxidant. This technique is based upon established relative rate concepts but has the advantage of a much higher throughput of target VOCs. By evaluating multiple VOCs in each experiment, and through measurement of the depletion in each VOC after reaction with OH, the OH + VOC reaction rate coefficients can be derived. Results from experiments conducted under controlled laboratory conditions were in good agreement with the available literature for the reaction of 19 VOCs, prepared in synthetic gas mixtures, with OH. This approach was used to determine a rate coefficient for the reaction of OH with 2,3-dimethylpent-1-ene for the first time; k = 5.7 (±0.3) × 10−11 cm3 molecule−1 s−1. In addition, a further seven VOCs had only two, or fewer, individual OH rate coefficient measurements available in the literature. The results from this work were in good agreement with those measurements. A similar dataset, at an elevated temperature of 323 (±10) K, was used to determine new OH rate coefficients for 12 aromatic, 5 alkane, 5 alkene and 3 monoterpene VOC + OH reactions. In OH relative reactivity experiments that used ambient air at the University of York, a large number of different VOCs were observed, of which 23 were positively identified. Due to difficulties with detection limits and fully resolving peaks, only 19 OH rate coefficients were derived from these ambient air samples, including 10 reactions for which data were previously unavailable at the elevated reaction temperature of T = 323 (±10) K.