Atmospheric pollutants response to the emission reduction and meteorology during the COVID-19 lockdown in the north of Africa (Morocco)

Climate and air quality change due to COVID-19 lockdown (LCD) are extremely concerned subjects of several research recently. The contribution of meteorological factors and emission reduction to air pollution change over the north of Morocco has been investigated in this study using the framework generalized additive models, that have been proved to be a robust technique for the environmental data sets, focusing on main atmospheric pollutants in the region including ozone (O(3)), nitrogen dioxide (NO(2)), sulfur dioxide (SO(2)), particulate matter (PM(2.5) and PM(10)), secondary inorganic aerosols (SIA), nom-methane volatile organic compounds and carbon monoxide (CO) from the regional air pollution dataset of the Copernicus Atmosphere Monitoring Service. Our results, indicate that secondary air pollutants (PM(2.5), PM(10) and O(3)) are more influenced by metrological factors and the other air pollutants reported by this study (NO(2) and SO(2)). We show a negative effect for PBHL, total precipitation and NW10M on PM (PM(2.5) and PM(10)), this meteorological parameters contribute to decrease in PM(2.5) by 9, 2 and 9% respectively, before LCD and 8, 1 and 5% respectively during LCD. However, a positive marginal effect was found for SAT, Irradiance and RH that contribute to increase PM(2.5) by 9, 12 and 18% respectively, before LCD and 17, 54 and 34% respectively during LCD. We found also that meteorological factors contribute to O(3), PM(2.5), PM(10) and SIA average mass concentration by 22, 5, 3 and 34% before LCD and by 28, 19, 5 and 42% during LCD respectively. The increase in meteorological factors marginal effect during LCD shows the contribution of photochemical oxidation to air pollution due to increase in atmospheric oxidant (O(3) and OH radical) during LCD, which can explain the response of PM to emission reduction. This study indicates that PM (PM(2.5), PM(10)) has more controlled by SO(2) due to the formation of sulfate particles especially under high oxidants level. The positive correlation between westward wind at 10 m (WW10M), Northward Wind at 10 m (NW10M) and PM indicates the implication of sea salt particles transported from Mediterranean Sea and Atlantic Ocean. The Ozone mass concentration shows a positive trend with Irradiance, Total and SAT during LCD; because temperature and irradiance enhance tropospheric ozone formation via photochemical reaction.This study shows the contribution of atmospheric oxidation capacity to air pollution change. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00477-022-02224-z.