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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-89
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Summertime fine particulate nitrate pollution in the North China Plain: Increasing trends, formation mechanisms, and implications for control policy
Liang Wen1, Likun Xue1, Xinfeng Wang1, Caihong Xu1, Tianshu Chen1, Lingxiao Yang1, Tao Wang2, and Wenxing Wang1 1Environment Research Institute, Shandong University, Ji'nan, Shandong, China
2Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong, China
Abstract. Nitrate aerosol composes a significant fraction of fine particles and plays a key role in regional air quality and climate. To obtain a holistic understanding of the nitrate pollution and its formation mechanisms over the North China Plain (NCP) – the most industrialized and polluted region in northern China, intensive field observations were conducted at three sites during summertime in 2014–2015. The measurement sites include the downtown and downwind of Ji'nan, the capital city of Shandong Province, as well as the peak of NCP – Mt. Tai (1534 m a.s.l.), and hence cover representative urban, rural and remote areas of the region. Elevated nitrate concentrations were observed at all three sites despite distinct temporal and spatial variations. The nitrate / PM2.5 and nitrate / sulfate ratios have significantly increased in Ji'nan (2005–2015) and at Mt. Tai (from 2007 to 2014), indicating the worsening situation of regional nitrate pollution. A multi-phase chemical box model (RACM/CAPRAM) was deployed and constrained by observations to elucidate the nitrate formation mechanisms. The principal formation route is the partitioning of gaseous HNO3 to aerosol phase at daytime, whilst the nocturnal nitrate formation is dominated by the heterogeneous hydrolysis of N2O5. The daytime nitrate production in the NCP region is mainly limited by the availability of NO2 and to a lesser extent O3 and NH3, and the nighttime formation is controlled by both NO2 and O3. NH3 prompts significantly the nitrate formation at daytime but plays a slightly negative role in the nighttime. Our analyses suggest that controlling NOx and O3 is an efficient way at the moment to mitigate nitrate pollution in the NCP region, where NH3 is usually in excess in summer. This study provides observational evidence of rising trend of nitrate aerosol as well as scientific support for formulating effective control strategies for regional haze in China.
Citation: Wen, L., Xue, L., Wang, X., Xu, C., Chen, T., Yang, L., Wang, T., and Wang, W.: Summertime fine particulate nitrate pollution in the North China Plain: Increasing trends, formation mechanisms, and implications for control policy, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-89, in review, 2018.
Liang Wen et al.
Liang Wen et al.

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Short summary
We present the first piece of observational evidence of the increasing trend of fine nitrate aerosol in the North China Plain during 2005–2015. The summertime nitrate formation mechanism is dissected with a multi-phase chemical box model based on observations at three different sites. The nitrate formation is most sensitive to NO2 and to a lesser extent to O3. NH3 plays a significant role in prompting the nitrate formation, but it is usually in excess in summer in the NCP region.
We present the first piece of observational evidence of the increasing trend of fine nitrate...
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