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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-1217
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
11 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Large particulate nitrate formation from N2O5 uptake in a chemically reactive layer aloft during winter time in Beijing
Haichao Wang1, Keding Lu1, Xiaorui Chen1, Qindan Zhu1,a, Zhijun Wu1, Yusheng Wu1, and Kang Sun2 1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
2China National Environmental Monitoring Centre, Beijing, China
anow at: the Department of Chemistry, University of California, Berkeley, CA 94720, USA
Abstract. Particulate nitrate (pNO3) is a dominant component of secondary aerosols in urban areas. Therefore, it is critical to explore its formation mechanism to assist with the planning of haze abatement strategies. Simultaneous ground-based and tower-based measurements were conducted during a winter heavy haze episode in urban Beijing, China. We found pNO3 formation via N2O5 heterogeneous uptake was negligible at ground level, due to the presence of high NO concentrations limiting the production of N2O5. In contrast, the contribution from N2O5 uptake was larger at higher altitudes (e.g., > 150 m), which was supported by the observed large total oxidant (NO2 + O3) missing aloft compared with ground level. The nighttime integrated production potential of pNO3 for the higher altitude air mass overhead urban Beijing was estimated to be 50 μg m−3, and enhanced the surface pNO3 significantly with 28 μg m−3 after nocturnal boundary layer broken in the next morning. In this case, the oxidation of NOX to nitrate was maximized once N2O5 uptake coefficient over 0.0017, since N2O5 uptake dominated the fate of NO3 and N2O5 with the presence of large aerosol surface concentrations. These results highlight that pNO3 formation via N2O5 heterogeneous hydrolysis at higher altitude air masses aloft could be an important source for haze formation in the urban airshed during winter time. Accurately describing the formation and development of reactive air masses aloft is a critical task for improving current chemical transport models.

Citation: Wang, H., Lu, K., Chen, X., Zhu, Q., Wu, Z., Wu, Y., and Sun, K.: Large particulate nitrate formation from N2O5 uptake in a chemically reactive layer aloft during winter time in Beijing, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-1217, in review, 2018.
Haichao Wang et al.
Haichao Wang et al.
Haichao Wang et al.

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Short summary
Based on the ground-based and tower-based observation and modeling in urban Beijing, we found N2O5 heterogeneous uptake was negligible at the ground level, but very active at high altitude and has large particulate nitrate formation potential during polluted episodes. The results highlight that particulate nitrate formation via N2O5 heterogeneous hydrolysis could be an important mechanism for winter haze episodes in a chemically reactive layer overhead urban Beijing.
Based on the ground-based and tower-based observation and modeling in urban Beijing, we found...
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