Atmospheric OH reactivities in the Pearl River Delta – China in summer 2006: measurement and model results
Atmospheric OH reactivities in the Pearl River Delta – China in summer 2006: measurement and model results
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DOI：
10.5194/acp-10-11243-2010
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发表时间：
2009-08
影响因子：
6.3
通讯作者：
S. Lou;F. Holland;F. Rohrer;K. Lu;B. Bohn;T. Brauers;Chih-Chung Chang-;H. Fuchs;R. Häseler;
中科院分区：
文献类型：
--
作者：
S. Lou;F. Holland;F. Rohrer;K. Lu;B. Bohn;T. Brauers;Chih-Chung Chang-;H. Fuchs;R. Häseler;
抽象的。2006年夏天，在人口稠密的珠江三角洲(珠江三角洲)南部中国的一个农村地区，用一台新开发的仪器测量了大气总氢氧反应性(KOH)作为倒数OH寿命。部署的技术LP-LIF使用激光闪光光解(LP)产生人工OH，并使用激光诱导荧光(LIF)测量环境空气样品中随时间变化的OH衰变。在珠江三角洲观测到的反应性范围从10 S−1到120 S−1，表明化学反应物的负荷很大。KOH具有明显的日变化特征，黎明时平均最大值为50 S−1，中午最小值为20 S−1。从测量的微量气体计算的反应性与测量的KOH的比较表明，白天和晚上缺少的反应性大约是原来的2倍。测量的痕量气体的反应性在夜间主要受人为污染物(如CO、NOx、低碳烯和芳香烃)的影响，而在白天则受到当地异戊二烯生物排放的强烈影响。由测量参数初始化的盒子模型计算很好地再现了观察到的OH反应性，并表明缺失的反应性是由未测量的二级化学产物(主要是醛和酮)造成的，这些产物是由碳氢化合物氧化形成的。总体而言，KOH以有机化合物为主，下午有机化合物的贡献率最高为85%。本文论证了直接测量反应性的有效性，强调了在大气化学研究中直接测量含氧有机物的必要性，并讨论了OVOC反应性模型的不确定性。
Abstract. Total atmospheric OH reactivities (kOH) have been measured as reciprocal OH lifetimes by a newly developed instrument at a rural site in the densely populated Pearl River Delta (PRD) in Southern China in summer 2006. The deployed technique, LP-LIF, uses laser flash photolysis (LP) for artificial OH generation and laser-induced fluorescence (LIF) to measure the time-dependent OH decay in samples of ambient air. The reactivities observed at PRD covered a range from 10 s−1 to 120 s−1, indicating a large load of chemical reactants. On average, kOH exhibited a pronounced diurnal profile with a mean maximum value of 50 s−1 at daybreak and a mean minimum value of 20 s−1 at noon. The comparison of reactivities calculated from measured trace gases with measured kOH reveals a missing reactivity of about a factor of 2 at day and night. The reactivity explained by measured trace gases was dominated by anthropogenic pollutants (e.g., CO, NOx, light alkenes and aromatic hydrocarbons) at night, while it was strongly influenced by local, biogenic emissions of isoprene during the day. Box model calculations initialized by measured parameters reproduce the observed OH reactivity well and suggest that the missing reactivity is contributed by unmeasured, secondary chemistry products (mainly aldehydes and ketones) that were photochemically formed by hydrocarbon oxidation. Overall, kOH was dominated by organic compounds, which had a maximum contribution of 85% in the afternoon. The paper demonstrates the usefulness of direct reactivity measurements, emphasizes the need for direct measurements of oxygenated organic compounds in atmospheric chemistry studies, and discusses uncertainties of the modelling of OVOC reactivities.