Environment Research Institute, Shandong University, Ji'nan, Shandong, China.
Environment Research Institute, Shandong University, Ji'nan, Shandong, China.
Sci Total Environ. 2018 Jan 15;612:1114-1122. doi: 10.1016/j.scitotenv.2017.08.310. Epub 2017 Sep 8.
Atmospheric oxidizing capacity (AOC), dominated by the hydroxyl radical (OH), is an important index of the self-cleaning capacity of atmosphere and plays a vital role in the tropospheric chemistry. To better understand the key processes governing the chemistry of rural atmosphere of southern China, we analyzed the oxidation capacity and radical chemistry at a regional background site in Hong Kong from 23 August to 22 December 2012, which covered the summer, autumn and winter seasons. A chemical box model built on the latest Master Chemical Mechanism (v3.3) was used to elucidate the OH reactivity and sources of RO radicals (RO=OH+HO+RO). The AOC showed a clear seasonal pattern with stronger intensity in late summer compared to autumn and winter. Reactions with NO (30%) and oxygenated volatile organic compounds (OVOCs) (31%) together dominated the OH loss in summer, while reactions with CO (38% in autumn and 39% in winter) and OVOCs (34% in autumn and 25% in winter) made larger contributions in autumn and winter. Photolysis of O (36%-47%) presented the major RO source during all three seasons. The second largest ROx source was HONO photolysis (25%) in summer compared to HCHO photolysis in autumn (20%) and winter (21%). Besides, photolysis of other OVOCs was another important primary source of ROx radicals with average contributions of 14%, 13% and 20% for the summer, autumn and winter cases, respectively. Overall, the present study evaluates the oxidizing capacity of the rural atmosphere of South China and elucidates the varying characteristics of photochemical processes in different air masses.
大气氧化能力（AOC），主要由羟基自由基（OH）主导，是大气自净能力的一个重要指标，在对流层化学中起着至关重要的作用。为了更好地了解中国南方农村大气化学的关键过程，我们分析了 2012 年 8 月 23 日至 12 月 22 日期间香港一个区域背景站点的氧化能力和自由基化学，该时段涵盖了夏季、秋季和冬季。我们使用建立在最新主化学机制（v3.3）上的化学箱模型来阐明 OH 反应性和 RO 自由基（RO=OH+HO+RO）的来源。AOC 呈现出明显的季节性模式，夏季比秋季和冬季强度更大。在夏季，与 NO（30%）和含氧挥发性有机化合物（OVOCs）（31%）的反应共同主导了 OH 的消耗，而在秋季（CO 占 38%，OVOCs 占 34%）和冬季（CO 占 39%，OVOCs 占 25%），CO 和 OVOCs 的反应贡献更大。在所有三个季节中，O（36%-47%）的光解都是主要的 RO 源。夏季第二大 ROx 源是 HONO 光解（占 25%），而秋季是 HCHO 光解（占 20%），冬季是 HCHO 光解（占 21%）。此外，其他 OVOCs 的光解也是 ROx 自由基的另一个重要初级源，夏季、秋季和冬季的平均贡献分别为 14%、13%和 20%。总的来说，本研究评估了中国南方农村大气的氧化能力，并阐明了不同气团中光化学反应的变化特征。
