VARIATIONS IN NO2 CONCENTRATIONS BEFORE, DURING, AND AFTER THE COVID-19 LOCKDOWN IN THE WILAYA OF ALGIERS

Unplanned urbanization and industrialization are among the leading causes of air pollution in urban environments, with significant economic, social, and environmental consequences, posing threats to human health. Atmospheric pollution has been the subject of multiple studies worldwide, especially in developed countries. However, developing countries, including Algeria, face difficulties in taking appropriate measures to preserve air quality due to the lack of sufficient monitoring data. To address this problem, satellite remote sensing technology has been used to monitor the spatio-temporal evolution of pollutant emissions. This study focused on identifying high-pollution areas in the wilaya (province) of Algiers, characterized by intense urbanization and increasing economic and industrial activities. The impact of reductions in anthropogenic emissions during the Covid-19 pandemic lockdown on air quality was also examined. For this purpose, variations in NO2 concentrations in Algiers before, during, and after the lockdown were analyzed using Google Earth Engine (GEE) and data from the TROPOMI tropospheric monitoring instrument. The study focused on 11 selected sites across the wilaya, revealing that the highest NO2 concentrations were observed in densely populated and industrial areas such as Oued Smar, El Harrach, and Baraki, where heavy traffic combines with significant industrial activity. Reductions in NO2 levels were observed across the wilaya during the lockdown, attributed to the considerable decrease in mobility and industrial activities during the Covid- 19 pandemic.