Impact of Covid-19 lockdown on air quality in the Poland, Eastern Europe.

The first case of COVID-19 in Poland was registered on 4 March 2020. Governmental measures significantly restricted social and economic activities. This study investigates the impact on air quality resulting from the preventive measures taken by the government to manage Covid-19. The study was carried out with use of aerosol optical depth (AOD) retrieved from Moderate Resolution Imaging Spectrometer (MODIS) satellite and tropospheric column NO observed by Ozone Monitoring Instrument (OMI). Concentrations of atmospheric pollutants (PM, PM, NO and SO) retrieved from ground-based air quality stations, located in five large cities of the country, were also used for quantitative assessment of air quality change. Ground-based and satellite data demonstrated the reduction of pollutants in the period of lockdown as compared to the same periods in 2018 and 2019. In particular, AOD data shows reductions of aerosol concentrations in the air column in April and May of approximately by -23% and -18% as compared to 2018-2019. The greatest contraction was for PM in April and May with reductions of -11.1% to -26.4% and from -8.7 to -21.1% respectively. For PM the reductions were from -8.6% to -33.9% and from -8.5% to -31.5% as compared to the same months in 2019. The results showed that restrictions imposed to prevent the spread of COVID-19 significantly improved Poland's air quality.