Abstract
The absence of motor vehicle traffic and suspended manufacturing during the COVID-19 pandemic in China produced a unique experiment to assess 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 non-linear 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.
Highlights
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
Certain societal events in China with short-term stringent emission controls have been studied as natural experiments, such as the “Olympic Blue” during the 2008 Beijing Summer Olympic Games [9] and the “APEC Blue” during the 2014 Asia-Pacific Economic Cooperation (APEC) Economic Leaders’ Meetings in Beijing [10, 11]
Emission controls during these two events resulted in a 40 to 60% reduction in SO2, NO2, nonmethane volatile organic compounds (VOCs), and particulate matter (PM)
Summary
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. The key chemical and physical processes responsible for severe haze formation in China remain elusive, including exacerbated ozone levels [4, 5], pathways of secondary aerosol formation [6, 7], and emissions-meteorology interactions [8].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
