Unexpected air pollution with marked emission reductions during the COVID-19 outbreak in China
Abstract
The absence of motor vehicle traffic and suspended manufacturing during the coronavirus disease 2019 (COVID-19) pandemic in China enabled assessment of the efficiency of air pollution mitigation. Up to 90% reduction of certain emissions during the city-lockdown period can be identified from satellite and ground-based observations. Unexpectedly, extreme particulate matter levels simultaneously occurred in northern China. Our synergistic observation analyses and model simulations show that anomalously high humidity promoted aerosol heterogeneous chemistry, along with stagnant airflow and uninterrupted emissions from power plants and petrochemical facilities, contributing to severe haze formation. Also, because of nonlinear production chemistry and titration of ozone in winter, reduced nitrogen oxides resulted in ozone enhancement in urban areas, further increasing the atmospheric oxidizing capacity and facilitating secondary aerosol formation.
Additional Information
© 2020 The Authors. This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/. This license does not apply to figures/photos/artwork or other content included in the article that is credited to a third party; obtain authorization from the rights holder before using such material. Received for publication March 16, 2020. Accepted for publication June 9, 2020. We are grateful to Chao Liu and Alexei Lyapustin for helpful discussions on the satellite products, and Yuxuan Wang and Yuanlong Huang for chemistry analysis. Y.W. and Y.L.Y. acknowledge the support of the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Additional support was provided by the NSF AGS-1700727 grant. G.L. and L.L. acknowledge the National Key R&D Plan Grant 2017YFC0210000 and the Strategic Priority Research Program of Chinese Academy of Sciences Grant XDB40030203. Author contributions: Y.W. conceived and designed the research. T.L., Y.W., and Y.L.Y. performed the data analyses and produced the figures. L.L, Y.W., and G.L. performed and analyzed the WRF-Chem simulations. J.Y. and L.L. obtained the ground-based pollution data. Y.W. and J.H.S wrote the paper. All authors contributed to the scientific discussions and preparation of the manuscript. The authors declare no competing interests. Data and materials availability: All data are available in the manuscript or the supplementary materials.Attached Files
Published - 702.full.pdf
Supplemental Material - abb7431_Le_SM.pdf
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Additional details
- Eprint ID
- 103957
- DOI
- 10.1126/science.abb7431
- Resolver ID
- CaltechAUTHORS:20200622-104138262
- NASA/JPL/Caltech
- NSF
- AGS-1700727
- National Key Research and Development Program of China
- 2017YFC0210000
- Chinese Academy of Sciences
- XDB40030203
- Created
-
2020-06-22Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department, COVID-19, Division of Geological and Planetary Sciences (GPS)