Nighttime NOx loss and ClNO2 formation in the residual layer of a polluted region: Insights from field measurements and an iterative box model.
Nighttime NOx loss and ClNO2 formation in the residual layer of a polluted region: Insights from field measurements and an iterative box model.
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DOI：
10.1016/j.scitotenv.2017.11.352
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
H. Yun;Tao Wang;Weihao Wang;Y. J. Tham;Qinyi Li;Zhe Wang;S. Poon
中科院分区：
文献类型：
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作者：
H. Yun;Tao Wang;Weihao Wang;Y. J. Tham;Qinyi Li;Zhe Wang;S. Poon
五氧化二氮（N2 O 5）与气溶胶的非均相反应是污染边界层中氮氧化物（NOx）的重要汇，而硝酰氯（ClNO 2）的生成对大气氧化能力有重要影响。然而，N2 O 5的非均相损失和ClNO 2的形成仍然没有得到很好的量化，特别是在中国。在先前的一项研究中，我们在香港一个高海拔地区测量了几个气团中的ClNO 2和N2 O 5浓度，并发现了有史以来最高的水平。本研究采用迭代箱模型调查五N2 O 5/ClNO 2载货夜。我们首先估计了N2 O 5吸收系数和ClNO 2产量，然后计算了N2 O 5非均相反应对NOx损失的相对重要性和整个夜晚累积的ClNO 2产量。平均吸收系数为0.004 ± 0.003，平均产率为0.42 ± 0.26。随着气团的老化，累积的ClNO 2达到6.0 ppbv，表明珠江三角洲污染空气中产生了大量的ClNO 2。ClNO 2形成（N2 O 5 + Cl−）、N2 O 5水解（N2 O 5 + H2O）和NO3与挥发性有机化合物的反应（NO3+ VOCs）分别消耗了五个晚上产生的NO3的23%、27%和47%。大气中的NO有很大一部分（70% ± 10%）在夜间通过NO3与VOCs的反应（~ 40%）和N2 O 5的非均匀损失（~ 60%）被去除。
The heterogeneous reaction of dinitrogen pentoxide (N2O5) on aerosols is an important sink of nitrogen oxides (NOx) in the polluted boundary layer, and the production of nitryl chloride (ClNO2) can have significant effects on the atmospheric oxidative capacity. However, the heterogeneous loss of N2O5and the formation of ClNO2are still not well quantified, especially in China. In a previous study, we measured ClNO2and N2O5concentrations in several air masses at a high-elevation site in Hong Kong, and found the highest levels ever reported at one night. The present study employed an iterative box model to investigate five N2O5/ClNO2-laden nights. We first estimated the N2O5uptake coefficient and ClNO2yield and then calculated the relative importance of N2O5heterogeneous reactions to NOxloss and the accumulated ClNO2production over the entire night. The average uptake coefficient was 0.004 ± 0.003, and the average yield was 0.42 ± 0.26. As the air masses aged, the accumulated ClNO2reached up to 6.0 ppbv, indicating significant production of ClNO2in the polluted air from the Pearl River Delta. ClNO2formation (N2O5+ Cl−), N2O5hydrolysis (N2O5+ H2O), and NO3reactions with volatile organic compounds (NO3+ VOCs) consumed 23%, 27%, and 47% of the produced NO3, respectively, as the average for five nights. A significant portion of the NOxin the air masses (70% ± 10%) was removed during the night via NO3reactions with VOCs (~ 40%) and N2O5heterogeneous loss (~ 60%).