Preprints
https://doi.org/10.5194/acp-2020-821
https://doi.org/10.5194/acp-2020-821

  17 Aug 2020

17 Aug 2020

Review status: a revised version of this preprint is currently under review for the journal ACP.

Quantitative assessment of changes in surface particulate matter concentrations over China during the COVID-19 pandemic and their implications for Chinese economic activity

Hyun Cheol Kim1,2, Soontae Kim3, Mark Cohen1, Changhan Bae4, Dasom Lee5, Rick Saylor1, Minah Bae3, Eunhye Kim3, Byeong-Uk Kim6, Jin-Ho Yoon5, and Ariel Stein1 Hyun Cheol Kim et al.
  • 1Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD, USA
  • 2Cooperative Institute for Satellite Earth System Studies, University of Maryland, College Park, MD, USA
  • 3Department of Environmental and Safety Engineering, Ajou University, Suwon, South Korea
  • 4National Air Emission Inventory and Research Center, Sejong, South Korea
  • 5School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju, South Korea
  • 6Georgia Environmental Protection Division, Atlanta, GA, USA

Abstract. Sixty days after the lockdown of Hubei province, where the coronavirus was first reported, China's true recovery from the pandemic remained an outstanding question. This study investigates how human activity changed during this period using observations of surface pollutants. By combining surface data with a three-dimensional chemistry model, the impacts of meteorological variations and variations in yearly emissions control are minimized, demonstrating how pollutant levels over China changed before and after the Lunar New Year from 2017 to 2020. The results show that the reduction in NO2 concentrations, an indicator of emissions in the transportation sector, was clearly deeper and longer in 2020 than in normal years, and started to recover after February 15. By contrast, PM2.5 emissions had not yet recovered by the end of March, showing a reduction around 30 % compared with normal years. SO2 emissions had not affected significantly by the pandemic. Additional model study using a top-down emissions adjustment still confirms a reduction around 25 % in unknown surface PM2.5 emissions over the same period, even after realistically updating SO2 and NOx emissions. This evidence suggests that different economic sectors in China may be recovering at different rates, with the fastest recovery in transportation and a slower recovery likely in agriculture. The apparent difference between the recovery timelines of NO2 and PM2.5 implies that monitoring a single pollutant alone (e.g. NOx emissions) is insufficient to draw conclusions on the overall recovery of the Chinese economy.

Hyun Cheol Kim et al.

 
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Status: final response (author comments only)
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Hyun Cheol Kim et al.

Hyun Cheol Kim et al.

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Latest update: 11 Apr 2021
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Short summary
Global outbreaks of COVID-19 offer rare opportunities of natural experiments in emission control and corresponding responses of tropospheric chemistry. This study's novel approach investigates (1) isolating pandemic's impact from natural and anthropogenic variations, (2) emission-adjustment to reproduce real-time emissions (3) brute-force modeling to investigate Chinese economic activities. Results provide characteristics of the region's chemistry and emissions.
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