LAUSR

This study investigates with Sentinel-5P data the magnitude of the change in the concentration of air pollutants (NO2, HCHO, SO2, O3, CO, and aerosol index) in the air of ten cities and urban areas of the French region of Grand Est as a result of the first lockdown imposed between 17 March 2020 - 11 May 2020. The results have shown that the air quality in the urban environments of Grand Est has improved significantly compared to the situation in 2019 in the same period without lockdown. NO2, O3, aerosol index and CO are the ones that were most reduced with an average of -33.98%, -5.94%, -26.82% and -0.66%, respectively (observed maximum decreases was -54.7%, -7.7%, -13.1%, and -5.3%, respectively). The largest decrease has occurred in the EPCI areas of Eurometropole de Strasbourg, CA Colmar and CA Mulhouse Alsace. It has also been seen that the greatest decreases in air pollution first occurred in land cover classes close to cities and then secondly in the built-up urban areas. In this study, a global depollution index called ACI (Atmospheric Clearance Index) has also been developed which involves several parameters of air pollution and quantitatively shows depollution–permanence of the contamination levels. In addition, the correlation between the novel ACI and other population and economic development indices has been studied. The results indicated that there is a negative and statistically significant correlation between ACI and population density, GDP, gross value added at basic prices, number of employees, and active enterprises.