The impact of monoaromatic hydrocarbons on OH reactivity in the coastal UK boundary layer and free troposphere
The impact of monoaromatic hydrocarbons on OH reactivity in the coastal UK boundary layer and free troposphere
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DOI：
10.5194/acp-14-6677-2014
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发表时间：
2013-12
影响因子：
6.3
通讯作者：
R. Lidster;J. Hamilton;James D. Lee;A. Lewis;J. Hopkins;S. Punjabi;A. Rickard;J. Young
中科院分区：
文献类型：
--
作者：
R. Lidster;J. Hamilton;James D. Lee;A. Lewis;J. Hopkins;S. Punjabi;A. Rickard;J. Young
抽象的。与羟基自由基(OH)的反应是大气中几乎所有挥发性有机化合物(VOCs)的主要去除机制；然而，很难将测量的OH反应性与已知的汇进行协调。未溶解的高相对分子质量VOCs对OH汇有贡献，其中单芳烃可能是一个重要的亚类。发展了一种基于全二维气相色谱-飞行时间质谱仪(GC×GC-TOFMS)的方法，扩大了从全空气样品中分离出较大VOCs的程度。该技术表现出极好的灵敏度、分辨率和与已建立的气相色谱-火焰电离(GC-FID)方法的良好一致性，适用于在两种仪器上都能分析的化合物。对英国东海岸海洋边界层和自由对流层内的挥发性有机化合物进行了测量，使用的是2011年冬季从五架飞机上收集的样本。除了简单的芳烃、苯、甲苯、乙苯、Σ间二甲苯和对二甲苯外，还定量了10种具有不同烷基取代基的单芳烃化合物。这些额外的化合物随后被纳入在英国农村和郊区的两个现场发生的大气化学的约束箱模式模拟中，以评估这些较大的单芳烃物种对羟基反应性的潜在影响；它们被计算为对整个模型的羟基损失率额外贡献2-6%，提供了最大额外的羟基沉约0.9S−1。
Abstract. Reaction with the hydroxyl radical (OH) is the dominant removal mechanism for virtually all volatile organic compounds (VOCs) in the atmosphere; however, it can be difficult to reconcile measured OH reactivity with known sinks. Unresolved higher molecular weight VOCs contribute to OH sinks, of which monoaromatics are potentially an important sub-class. A method based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS) has been developed that extends the degree with which larger VOCs can be individually speciated from whole air samples (WAS). The technique showed excellent sensitivity, resolution and good agreement with an established gas chromatography–flame ionisation (GC-FID) method, for compounds amenable to analysis on both instruments. Measurements have been made of VOCs within the UK east coast marine boundary layer and free troposphere, using samples collected from five aircraft flights in winter 2011. Ten monoaromatic compounds with an array of different alkyl ring substituents have been quantified, in addition to the simple aromatics, benzene, toluene, ethyl benzene and Σm- and p-xylene. These additional compounds were then included in constrained box model simulations of atmospheric chemistry occurring at two UK rural and suburban field sites in order to assess the potential impact of these larger monoaromatics species on OH reactivity; they have been calculated to contribute an additional 2–6% to the overall modelled OH loss rate, providing a maximum additional OH sink of ~0.9 s−1.