Non-uniform tropospheric NO2 level changes in European Union caused by governmental COVID-19 restrictions and geography

Anthropogenic pressures that have been reduced by the COVID-19 measures have had spatially and temporally differentiated impact on the atmospheric environment. We investigated the relationship between NO2 level data and COVID-19 restrictions with a focus on 27 European Union member states. Nationally, the NO2 level change was an average of -10 % in 2020/2019, while the 2021/2020 increase averaged + 11.4 %. The direction of these changes is clear, but magnitude varies considerably by geographical area. A significant proportion of the population was affected by the year-on-year changes in emissions. The severity of the restrictions did not play a relevant role in the extent of emission changes, but measures themselves had an impact on the overall reduction in NO2 levels in 2020. In many regions, the reduction in stringency of 2021 restrictions has led to a recurrent deterioration in ambient air quality, with NO2 levels reaching, and in some cases exceeding, previous levels.