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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/acp-2020-838
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2020-838
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  18 Aug 2020

18 Aug 2020

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A revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

UK surface NO2 levels dropped by 42 % during the COVID-19 lockdown: impact on surface O3

James D. Lee1, Will S. Drysdale1, Doug P. Finch2, Shona E. Wilde1, and Paul I. Palmer2 James D. Lee et al.
  • 1National Centre for Atmospheric Science, Department of Chemistry, University of York, York, UK
  • 2School of GeoSciences, University of Edinburgh, Edinburgh, UK

Abstract. We report changes in surface nitrogen dioxide (NO2) across the UK during the COVID-19 pandemic when large and rapid emission reductions accompanied a nationwide lockdown (23rd March–31st May, 2020, inclusively), and compare them with values from an equivalent period over the previous five years. Data are from the Automatic Urban and Rural Network (AURN) that form the basis of checking nationwide compliance with ambient air quality directives. We calculate that NO2 reduced by 42 % on average across all 126 urban AURN sites, with a slightly larger (48 %) reduction at sites close to the roadside (urban traffic). We also find that ozone (O3) increased by 11 % on average across the urban background network during the lockdown period. Total oxidant levels (Ox = NO2 + O3) increased only slightly on average (3 %), suggesting the majority of this change can be attributed to photochemical repartitioning due to the reduction in NOx. Generally, we find larger, positive Ox changes in southern UK cities which we attribute to increased UV radiation and temperature in 2020 compared to previous years. The net effect of the NO2 and O3 changes is a sharp decrease in exceedances of the NO2 air quality objective limit for the UK, with only one exceedance in London in 2020 up until the end of May. Concurrent increases in O3 exceedances in London emphasize the potential for O3 to become an air pollutant of concern as NOx emissions are reduced in the next 10–20 years.

James D. Lee et al.

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Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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James D. Lee et al.

James D. Lee et al.

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Short summary
Efforts to prevent the COVID-19 virus spreading across the globe have included travel restrictions and the closure of workplaces, leading to a significant drop in emissions of primary air pollutants. This provides for a unique opportunity to examine how air pollutant concentrations respond to an abrupt and prolonged reduction. We examine how NO2 and O3 have been affected at several urban measurement sites in the UK. We look at the change in NO2 compared to previous years and the effect on O3.
Efforts to prevent the COVID-19 virus spreading across the globe have included travel...
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