Air Quality Improvements During the COVID-19 Lockdown in Central Europe: Separation of Emission Reduction and Meteorological Impacts

Abstract

Corona lockdown measures caused unprecedented emission reductions in many parts of the world. However, this does not linearly translate into improved air quality, since meteorological conditions also have a significant impact on air pollutant concentration patterns. This study disentangles effects of emission reduction and the meteorological situation on the concentrations of air pollutants with a focus on elemental carbon (EC) in Central Europe during the first major lockdown in spring 2020. European emission data for 2016 was updated for 2020 by extrapolating previous emission trends for each country and sector for 2020. Lockdown emission reductions were approximated with daily adjustment factors for the sectors traffic (road, air, and ship), public power and industry and for almost all countries based on mobility data, energy consumption and industrial productivity data. Chemistry transport model results focus on traffic related emissions and show significant reductions between 20% and 55% for NO2 concentrations during strongest lockdown measures between mid of March and mid of April. PM2.5 concentration reductions were less strong compared to NO2, only up to 15% in large parts of Europe. Elemental carbon (EC) was reduced by up to 20% in southern Germany and France. Exceptionally low EC concentrations, as observed in April in Northern Central Europe, were not an effect of lockdown measures. They were caused by advection of clean air from Scandinavia. To investigate this further, EC concentrations as well as lockdown emission reductions of EC were also calculated with meteorological data for the same spring period in 2016 and 2018. It could be seen that meteorological effects resulted in modified effects of the lockdown on EC concentration changes, particularly in Denmark and northern Germany in April 2020.