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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 13 | Copyright
Atmos. Chem. Phys., 18, 9705-9721, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 10 Jul 2018

Research article | 10 Jul 2018

Efficient N2O5 uptake and NO3 oxidation in the outflow of urban Beijing

Haichao Wang1, Keding Lu1, Song Guo1, Zhijun Wu1, Dongjie Shang1, Zhaofeng Tan1, Yujue Wang1, Michael Le Breton2, Shengrong Lou3, Mingjin Tang4, Yusheng Wu1, Wenfei Zhu3, Jing Zheng1, Limin Zeng1, Mattias Hallquist2, Min Hu1, and Yuanhang Zhang1,5 Haichao Wang et al.
  • 1State Key Joint Laboratory or Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
  • 2Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
  • 3Shanghai Academy of Environmental Sciences, Shanghai, China
  • 4State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
  • 5CAS Center for Excellence in Regional Atmospheric Environment, Chinese Academy of Sciences, Xiamen, China

Abstract. Nocturnal reactive nitrogen compounds play an important role in regional air pollution. Here we present the measurements of dinitrogen pentoxide (N2O5) associated with nitryl chloride (ClNO2) and particulate nitrate (pNO3) at a suburban site of Beijing in the summer of 2016. High levels of N2O5 and ClNO2 were observed in the outflow of the urban Beijing air masses, with 1min average maxima of 937 and 2900pptv, respectively. The N2O5 uptake coefficients, γ, and ClNO2 yield, f, were experimentally determined from the observed parameters. The N2O5 uptake coefficient ranged from 0.012 to 0.055, with an average of 0.034±0.018, which is in the upper range of previous field studies reported in North America and Europe but is a moderate value in the North China Plain (NCP), which reflects efficient N2O5 heterogeneous processes in Beijing. The ClNO2 yield exhibited high variability, with a range of 0.50 to unity and an average of 0.73±0.25. The concentration of the nitrate radical (NO3) was calculated assuming that the thermal equilibrium between NO3 and N2O5 was maintained. In NOx-rich air masses, the oxidation of nocturnal biogenic volatile organic compounds (BVOCs) was dominated by NO3 rather than O3. The production rate of organic nitrate (ON) via NO3+BVOCs was significant, with an average of 0.10±0.07ppbv h−1. We highlight the importance of NO3 oxidation of VOCs in the formation of ON and subsequent secondary organic aerosols in summer in Beijing.

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Short summary
N2O5, ClNO2, and particulate nitrate were measured simultaneously in Beijing, China, in 2016. The elevated N2O5 uptake coefficient and ClNO2 yield were determined, which suggest fast N2O5 uptake in Beijing. We highlight that the NO3 oxidation in nocturnal VOC degradation is efficient, with fast formation of organic nitrates. More studies are needed to investigate NO3–N2O5 chemistry and its contribution to secondary organic aerosol formation.
N2O5, ClNO2, and particulate nitrate were measured simultaneously in Beijing, China, in 2016....