Aerosol Variability Over Nigeria with a Focus on Changes After COVID-19 Episode

Air pollution threatens human health and the environment locally and globally. Particulate matter (PM2.5) monitoring is a crucial component of air quality monitoring, particularly in urbanised and densely populated areas. The COVID-19 pandemic made it very evident that, in such a rare circumstance, the areas of extreme pollution are attracting a higher disease load. The need to check PM2.5 concentrations is more significant due to decadal volatility, seasonal variation, or even for the comeback of pollution levels after the pandemic lockdown. The present study focuses on Nigeria to understand the variability and trends of aerosols over the country. Aerosol optical depth (AOD) obtained from MODIS Terra has been analysed spatially for the periods 2010–2019 and 2021–2022 to understand the mean variations and to perform the non-parametric Mann–Kendall trend test. The study also evaluates the in-situ observations of PM2.5 concentrations at two of the most populated cities of Nigeria, Abuja and Lagos for 2021. PM2.5 concentration level extremity checks were analysed with the value of daily threshold suggested by the Government of Nigeria and World Health Organisation (WHO). The results reveal that the trend of AOD in the area over the past few years has significantly increased, and the daily time series variations are observed more during the dry season. The study suggests that there is a need to reform the existing policies to avoid highly polluted zones in Nigeria.