Measurement and calculation of OH reactivity at a United Kingdom coastal site
Measurement and calculation of OH reactivity at a United Kingdom coastal site
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DOI：
10.1007/s10874-010-9171-0
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发表时间：
2009-09
影响因子：
2
通讯作者：
James D. Lee;J. Young;K. Read;J. Hamilton;J. Hopkins;A. Lewis;B. Bandy;J. Davey;Peter M. Edwards;T. Ingham;Daniel E. Self;Shona C. Smith;M. Pilling;D. Heard
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文献类型：
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作者：
James D. Lee;J. Young;K. Read;J. Hamilton;J. Hopkins;A. Lewis;B. Bandy;J. Davey;Peter M. Edwards;T. Ingham;Daniel E. Self;Shona C. Smith;M. Pilling;D. Heard
2004 年 5 月，在英国诺福克北部海岸的韦伯恩大气观测站对 OH 反应性进行了测量。作为 TORCH-2 现场活动的一部分，还同时测量了多种支持物质，从而可以对 OH 氧化化学进行详细研究。测量是在各种气团中进行的，其中最常见的 3 种空气是来自大西洋的空气，从英国大陆上空以西南方向到达现场，而更清洁的北风空气则源自远北海或北极，经过北海并从北/东北方向到达现场。在活动期间的 6 天中进行了直接 OH 反应性测量，并受到研究期间流行的 3 个气团中的 2 个的影响。测得的平均、最小和最大 OH 反应性分别为：4.9、1.3 和 9.7。将测得的 OH 反应性与关键 OH 汇（例如 NO2 和 CO）进行比较，观察到总体呈正相关。然后使用测量的全系列 OH 汇物种（包括 >30 NMHC）及其与 OH 反应的伪一级速率常数计算 OH 反应性 (k')。在大部分测量周期内，测量值和计算值 k' 之间存在显着差异，平均值 k'meas-k'calc= 1.9 s-1，表明存在未测量的 OH 汇。使用包含主化学机理子集的零维盒模型来更准确地计算 OH 反应性。同时测量的痕量物质被用作模型的输入，它们的氧化降解通过包含约 5,000 种物质的化学机制进行描述。模型产生的额外 OH 汇物种导致 k'meas 和 k'calc 之间的一致性得到改善，但整个测量期间的平均缺失 OH 反应性仍保持在 1.4 s-1。人们对这种缺失反应性的来源进行了推测，包括参考研究表明，标准仪器可能无法测量大量潜在的高分子量芳香族物质。
Measurements of OH reactivity were made at the Weybourne Atmospheric Observatory on the North Norfolk coast, UK in May 2004. A wide range of supporting species was also measured concurrently as part of the TORCH-2 field campaign, allowing a detailed study of the OH oxidation chemistry to be carried out. Measurements were made in a variety of air masses, with the 3 most prevalent being air from the Atlantic that arrived at the site from over mainland UK in a South Westerly direction, and much cleaner Northerly air that originated over the far North Sea or Arctic, passed over the North Sea and arrived at the site from a North/North Easterly direction. Direct OH reactivity measurements were made on 6 days during the campaign and with influence of 2 of the 3 air masses prevalent during the study period. The average, minimum and maximum measured OH reactivity are: 4.9, 1.3 and 9.7 respectively. The measured OH reactivity was compared to key OH sinks such as NO2and CO and a general positive correlation was observed. OH reactivity (k′) was then calculated using the full range of OH sinks species that were measured (including >30 NMHCs) and their pseudo first order rate constants for reaction with OH. For much of the measurement period there is a significant difference between the measured and calculatedk′, with an average value ofk′meas-k′calc= 1.9 s-1, indicative of unmeasured OH sinks. A zero-dimensional box model containing a subset of the Master Chemical Mechanism was used to calculate the OH reactivity more accurately. The simultaneously measured trace species were used as inputs to the model and their oxidative degradation was described by a chemical mechanism containing ~5,000 species. The extra OH sinks species produced by the model, resulted in an improvement in the agreement betweenk′measandk′calc, however the averaged missing OH reactivity across the entire measurement period remained at 1.4 s-1. Speculation is made as to the source of this missing reactivity, including reference to studies showing that a potentially large number of high molecular weight aromatic species could be unmeasured by standard instrumentation.