PM_2.5 and PM₁₀ during COVID-19 lockdown in Kuwait: Mixed effect of dust and meteorological covariates

This study investigated the impact of COVID-19 lockdown on particulate matter concentrations, specifically PM_2.5 and PM₁₀, in Kuwait. We studied the variations in PM_2.5 and PM₁₀ between the lockdown in 2020 with the corresponding periods of the years 2017-2019, and also investigated the differences in PM variations between the 'curfew' and 'non curfew' hours. We applied mixed-effect regression to investigate the factors that dictate PM variability (i.e., dust and meteorological covariates), and also processed satellite-based aerosol optical depths (AOD) to determine the spatial variability in aerosol loads. The results showed low PM_2.5 concentration during the lockdown (33 microg/m³) compared to the corresponding previous three years (2017-2019); however, the PM₁₀ concentration (122.5 microg/m³) increased relative to 2017 (116.6 microg/m³), and 2019 (92.8 microg/m³). After removing the 'dust effects', both PM_2.5 and PM₁₀ levels dropped by 18% and 31%, respectively. The mixed-effect regression model showed that high temperature and high wind speed were the main contributors to high PM_2.5 and PM₁₀, respectively, in addition to the dust haze and blowing dust. This study highlights that the reductions of anthropogenic source emissions are overwhelmed by dust events and adverse meteorology in arid regions, and that the lockdown did not reduce the high concentrations of PM in Kuwait.