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Mitigating NOx emissions does not help alleviate wintertime particulate pollution in Beijing-Tianjin-Hebei (BTH), China
  • +14
  • Xia Li,
  • Naifang Bei,
  • Bo Hu,
  • Yuan Wang,
  • Suixin Liu,
  • Jiarui Wu,
  • Yuepeng Pan,
  • Tianxue Wen,
  • Zirui Liu,
  • Lang Liu,
  • Ruonan Wang,
  • Min Zuo,
  • Zhenxing Shen,
  • Junji Cao,
  • Xuexi Tie,
  • Luisa T. Molina,
  • Guohui Li
Xia Li
Institute of Earth Environment, Chinese Academy of Sciences
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Naifang Bei
Xi'an Jiaotong University
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Bo Hu
Institute of atmospheric physics, Chinese academy of sciences
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Yuan Wang
California Institute of Technology
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Suixin Liu
Institute of Earth Environment
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Jiarui Wu
Institute of Earth Environment, Chinese Academy of Sciences
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Yuepeng Pan
Institute of Atmospheric Physics, Chinese Academy of Sciences
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Tianxue Wen
Institute of Atmospheric Physics, Chinese Academy of Sciences
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Zirui Liu
Institute of Atmospheric Physics, Chinese Academy of Sciences
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Lang Liu
Institute of Earth Environment, Chinese Academy of Sciences
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Ruonan Wang
Institute of Earth Environment, Chinese acdemy of sciences
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Min Zuo
Institute of Earth Environment, Chinese Academy of Sciences
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Zhenxing Shen
Department of Environmental Science and Engineering, Xi⿿an Jiaotong University, China
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Junji Cao
Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences
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Xuexi Tie
Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
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Luisa T. Molina
Molina Center for Energy and the Environment
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Guohui Li
Institute of Earth Environment, Chinese Academy of Sciences

Corresponding Author:ligh@ieecas.cn

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Abstract

Stringent mitigation measures have reduced wintertime PM2.5 concentrations by 42.2% from 2013 to 2018 in the BTH. The observed nitrate aerosols have not exhibited a significant decreasing trend and constituted a major fraction (about 20%) of the total PM2.5, although the surface-measured NO2 level has decreased by over 20%. It still remains elusive about contributions of nitrogen oxides (NOx) emissions mitigation to the nitrate and PM2.5 level. The WRF-Chem model simulations of a persistent haze episode in January 2019 in the BTH reveal that NOx emissions mitigation does not help lower wintertime nitrate and PM2.5 concentrations under current conditions in the BTH, because the substantial O3 increase induced by NOx mitigation offsets the HNO3 loss and enhances sulfate and secondary organic aerosols formation. Our results are further consolidated by occurrence of the severe PM pollution in the BTH during the COVID-19 outbreak with a significant reduction of NO2.