Spatial-Temporal Assessment of Gaseous and Particulate Matter Pollutants during COVID-19 Lockdown over Kenya, East Africa

Abstract

Varied naturally occurring and anthropogenic emissions within the Kenyan territory contribute to elevation of levels of organic and inorganic, gaseous and particulate pollutant types. A study to ascertain main contributing factors to the status quo was vital. The study compares satellite-derived datasets for five main pollutant parameters, such as Black carbon (BC), Sulphur Dioxide (SO2), Nitrogen Dioxide (NO2), Carbon Monoxide (CO), and Ozone gas (O3) for three equal periods: pre-lockdown (April-June 2019), lockdown (April-June 2020) and post-lockdown (April-June 2021). The study utilized Aura/Ozone Monitoring Instrument (OMI), Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2), and MODIS (Moderate-resolution Imaging Spectroradiometer) satellite sensors to ascertain the variations in anthropogenic emissions into the atmosphere during COVID-19 lockdowns in Kenya. This was achieved by doing a phase-wise analysis of spatial-temporal variation of the fore mentioned five main pollutants over Kenya during the pre, during and post lockdown phases. The datasets obtained were manipulated using the Adobe Illustrator (2015 series) and the Grid Analysis and Display System (Grads) Version 2.2.1.oga.1 for the above-mentioned pollutants from 2019 to 2021 (April-June). It was evident that the spatial-temporal variability of the pollutants did not depict a significant reduction in the lockdown phase. This was because of the migration of aerosols from regional sources, the dominance of natural sources such as geothermal activities, and low stringent levels of lockdown protocols. However, meteorological factors had a great influence on the variability of the concentration of pollutants over the sampled region with the MAM (March-April-May), considered wet, season recording lower concentrations and JJA (June-July-August), considered a dry season, registering the highest concentrations.