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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
09 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
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, Wenfei Zhu3, Shengrong Lou3, Mingjin Tang4, Yusheng Wu1, Jing Zheng1, Limin Zeng1, Mattias Hallquist2, Min Hu1, and Yuanhang Zhang1,5 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 are important for understanding regional air pollution. Here we present the measurements of dinitrogen pentoxide (N2O5) associated with nitryl chloride (ClNO2) and particulate nitrate (pNO3) in 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 1-min average maxima of 937 pptv and 2.9 ppbv, 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 nighttime nitrate radical (NO3) was calculated assuming that the thermal equilibrium between NO3 and N2O5 was maintained. In NO2-rich air masses, the oxidation of nocturnal biogenic volatile organic compounds (BVOCs) was dominated by NO3 rather than O2. The production rate of organic nitrates (ONs) via NO2+BVOCs was significant, with an average of 0.11 ± 0.09 ppbv h−1. We highlight the importance of NO2 oxidation of VOCs in the formation of ONs and subsequent secondary organic aerosols in summer in Beijing. The capacities of BVOCs oxidation and ONs formation are maximized and independent of NOx under a high NOx/BVOCs ratio condition (>10), which indicates that the initial reduction of the NOx emission cannot help reduce the nocturnal formation of ONs.

Citation: Wang, H., Lu, K., Guo, S., Wu, Z., Shang, D., Tan, Z., Wang, Y., Le Breton, M., Zhu, W., Lou, S., Tang, M., Wu, Y., Zheng, J., Zeng, L., Hallquist, M., Hu, M., and Zhang, Y.: Efficient N2O5 Uptake and NO3 Oxidation in the Outflow of Urban Beijing, Atmos. Chem. Phys. Discuss.,, in review, 2018.
Haichao Wang et al.
Haichao Wang et al.
Haichao Wang et al.


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Short summary
N2O5, ClNO2 and particulate nitrate were measured simultaneously in Beijing, China. High levels of N2O5 and ClNO2 were observed, and elevated N2O5 uptake coefficient and ClNO2 yield were determined, which suggest fast N2O5 uptake in Beijing. We highlight the NO3 oxidation in nocturnal VOCs degradation is efficient with fast formation of organic nitrates, its contribution to secondary organic aerosol formation is required in future studies.
N2O5, ClNO2 and particulate nitrate were measured simultaneously in Beijing, China. High levels...