Ozone pollution in the North China Plain spreading into the late-winter haze season

Ke Li; Daniel J Jacob; Hong Liao; Yulu Qiu; Lu Shen; Shixian Zhai; Kelvin H Bates; Melissa P Sulprizio; Shaojie Song; Xiao Lu; Qiang Zhang; Bo Zheng; Yuli Zhang; Jinqiang Zhang; Hyun Chul Lee; Su Keun Kuk

doi:10.1073/pnas.2015797118

Ozone pollution in the North China Plain spreading into the late-winter haze season

Proc Natl Acad Sci U S A. 2021 Mar 9;118(10):e2015797118. doi: 10.1073/pnas.2015797118.

Authors

Ke Li^{1

2}, Daniel J Jacob³, Hong Liao⁴, Yulu Qiu⁵, Lu Shen², Shixian Zhai², Kelvin H Bates², Melissa P Sulprizio², Shaojie Song², Xiao Lu², Qiang Zhang⁶, Bo Zheng⁷, Yuli Zhang⁸, Jinqiang Zhang⁸, Hyun Chul Lee⁹, Su Keun Kuk⁹

Affiliations

¹ Harvard-NUIST Joint Laboratory for Air Quality and Climate, Nanjing University of Information Science and Technology, 210044 Nanjing, China.
² John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138.
³ John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; djacob@fas.harvard.edu hongliao@nuist.edu.cn.
⁴ Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, 210044 Nanjing, China; djacob@fas.harvard.edu hongliao@nuist.edu.cn.
⁵ Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, Beijing 100089, China.
⁶ Department of Earth System Science, Tsinghua University, 100084 Beijing, China.
⁷ Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
⁸ Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
⁹ Samsung Advance Institute of Technology, Suwon-si, Gyeonggi-do, 16678, Republic of Korea.

Abstract

Surface ozone is a severe air pollution problem in the North China Plain, which is home to 300 million people. Ozone concentrations are highest in summer, driven by fast photochemical production of hydrogen oxide radicals (HO_x) that can overcome the radical titration caused by high emissions of nitrogen oxides (NO_x) from fuel combustion. Ozone has been very low during winter haze (particulate) pollution episodes. However, the abrupt decrease of NO_x emissions following the COVID-19 lockdown in January 2020 reveals a switch to fast ozone production during winter haze episodes with maximum daily 8-h average (MDA8) ozone concentrations of 60 to 70 parts per billion. We reproduce this switch with the GEOS-Chem model, where the fast production of ozone is driven by HO_x radicals from photolysis of formaldehyde, overcoming radical titration from the decreased NO_x emissions. Formaldehyde is produced by oxidation of reactive volatile organic compounds (VOCs), which have very high emissions in the North China Plain. This remarkable switch to an ozone-producing regime in January-February following the lockdown illustrates a more general tendency from 2013 to 2019 of increasing winter-spring ozone in the North China Plain and increasing association of high ozone with winter haze events, as pollution control efforts have targeted NO_x emissions (30% decrease) while VOC emissions have remained constant. Decreasing VOC emissions would avoid further spreading of severe ozone pollution events into the winter-spring season.

Keywords: China; air quality; emission control; haze season; wintertime ozone.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Air Pollution / analysis*
COVID-19
China
Crops, Agricultural
Environmental Monitoring
Environmental Pollution
Humans
Nitrogen Oxides / chemistry
Ozone / analysis*
Pandemics
Particulate Matter / analysis*
Public Health
Seasons*
Volatile Organic Compounds*

Substances

Nitrogen Oxides
Particulate Matter
Volatile Organic Compounds
Ozone