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Proc Natl Acad Sci U S A

Title:		Ozone pollution in the North China Plain spreading into the late-winter haze season
Author(s):		Li K; Jacob DJ; Liao H; Qiu Y; Shen L; Zhai S; Bates KH; Sulprizio MP; Song S; Lu X; Zhang Q; Zheng B; Zhang Y; Zhang J; Lee HC; Kuk SK;
Address:		"Harvard-NUIST Joint Laboratory for Air Quality and Climate, Nanjing University of Information Science and Technology, 210044 Nanjing, China. John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138. John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; djacob@fas.harvard.edu hongliao@nuist.edu.cn. 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. Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, Beijing 100089, China. Department of Earth System Science, Tsinghua University, 100084 Beijing, China. Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China. Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Samsung Advance Institute of Technology, Suwon-si, Gyeonggi-do, 16678, Republic of Korea"
Journal Title:		Proc Natl Acad Sci U S A
Year:		2021
Volume:		118
Issue:		10
Page Number:		-
DOI:		10.1073/pnas.2015797118
ISSN/ISBN:		1091-6490 (Electronic) 0027-8424 (Print) 0027-8424 (Linking)
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:		"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 air qual;"
Notes:		"MedlineLi, Ke Jacob, Daniel J Liao, Hong Qiu, Yulu Shen, Lu Zhai, Shixian Bates, Kelvin H Sulprizio, Melissa P Song, Shaojie Lu, Xiao Zhang, Qiang Zheng, Bo Zhang, Yuli Zhang, Jinqiang Lee, Hyun Chul Kuk, Su Keun eng Research Support, Non-U.S. Gov't 2021/03/03 Proc Natl Acad Sci U S A. 2021 Mar 9; 118(10):e2015797118. doi: 10.1073/pnas.2015797118"