EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Changes in surface level NO2 in the UK during the COVID-19 pandemic compared to predicted 2020 concentrations and the impact on O3.

Rhianna Evans1, James Lee1,2, and Will Drysdale1,2
Rhianna Evans et al.
  • 1University of York, Chemistry, United Kingdom of Great Britain – England, Scotland, Wales (
  • 2National Centre for Atmospheric Science, University of York

Governments worldwide have used non pharmaceutical interventions known as lockdowns to contain the spread of the coronavirus pandemic, leading to a mass reduction in road traffic and international travel as working from home becomes the new normal. As a result, primary emissions of nitrogen oxides are expected to have largely decreased. A study of the UK’s first lockdown (Lee et al. 2020) used historical averages, taken between 2015 and 2019, as a baseline for comparison. This method is simplistic however does not fully account for the year to year meteorological variation. The UK’s first national lockdown was announced on 23rd March 2020 extending to 31st May 2020 and by mid-April traffic was reduced by 70% compared to normal according to the Department for Transport. We examined NO2 and O3, measured by the UK’s Automatic Urban and Rural Network for the year 2020 consisting of 65 urban traffic and 61 urban background sites, for the lockdown period from 2000 to 2020. Between 2000 and 2019 NO2 decreased by an average of 0.88 and 0.49 μg m-3 per year at urban traffic and urban background sites respectively. In 2020, the lockdown caused a 20 μg m-3 decrease in NO2 at urban traffic sites, an equivalent of 26 years at the previous rate.

To improve on the previous method, we have constructed random forest models to simulate business as usual NO2 and O3 concentrations at AURN sites in 9 cities, allowing changes in meteorology to be fully accounted for. These simulations were then compared to lockdown measurements in 2020. We observed an average 55% decrease in NO2 however O3 concentrations were elevated with an average 29% increase. The total oxidant, Ox, (sum of NO2 and O3) experienced marginal change (< 1%) indicating the changes in NO2 and O3 were largely due to photochemical repartitioning. This has highlighted the importance of O3 in urban locations in a future low NOx environment in the UK when electric vehicle fleets are adopted. 


Lee et al., Atmos. Chem. Phys., 2020, 20, 15743 – 15759

How to cite: Evans, R., Lee, J., and Drysdale, W.: Changes in surface level NO2 in the UK during the COVID-19 pandemic compared to predicted 2020 concentrations and the impact on O3., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8359,, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.