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Puzzling haze events in China during the coronavirus (COVID-19) shutdown.

  • Chang Y Yale-NUIST Center on Atmospheric Environment Nanjing University of Information Science & Technology Nanjing China.
  • Huang RJ State Key Laboratory of Loess and Quaternary Geology, Center for Excellence in Quaternary Science and Global Change, and Key Laboratory of Aerosol Chemistry & Physics, Institute of Earth and Environment Chinese Academy of Sciences Xi'an China.
  • Ge X School of Environmental Science and Engineering Nanjing University of Information Science & Technology Nanjing China.
  • Huang X School of Environmental Science and Engineering Nanjing University of Information Science & Technology Nanjing China.
  • Hu J School of Environmental Science and Engineering Nanjing University of Information Science & Technology Nanjing China.
  • Duan Y Shanghai Environmental Monitoring Center Shanghai China.
  • Zou Z Department of Environmental Science & Engineering Fudan University Shanghai China.
  • Liu X College of Resources & Environmental Sciences China Agricultural University Beijing China.
  • Lehmann MF Department of Environmental Sciences University of Basel Basel Switzerland.
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  • 2020-08-25
Published in:
  • Geophysical research letters. - 2020
COVID‐19
Emission Reduction
Fine Particle
Haze
Novel Coronavirus
English It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH-20), when China was in an unprecedented state of shutdown to contain the coronavirus (COVID-19) outbreak, than in 2019 (NYH-19). We performed a comprehensive measurement and modeling analysis of the aerosol chemistry and physics at multiple sites in China (mainly in Shanghai) before, during, and after NYH-19 and NYH-20. Much higher secondary aerosol fraction in PM2.5 were observed during NYH-20 (73%) than during NYH-19 (59%). During NYH-20, PM2.5 levels correlated significantly with the oxidation ratio of nitrogen (r 2 = 0.77, p < 0.01), and aged particles from northern China were found to impede atmospheric new particle formation and growth in Shanghai. A markedly enhanced efficiency of nitrate aerosol formation was observed along the transport pathways during NYH-20, despite the overall low atmospheric NO2 levels.
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https://sonar.ch/global/documents/50061
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