Browsing by Author "Mutama, Peter M."

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    Spatial-Temporal Assessment of Changes in Aerosol Optical Properties Pre, during, and Post COVID-19 Lockdowns over Kenya, East Africa
    (Open Access Library Journal, 2024-04-26) Mutama, Peter M.; Makokha, John Wanjala; Kelonye, Festus Beru; Khamala, Geoffrey W.
    In reference to the contribution of natural and anthropogenic activities to pollution levels over Kenya, investigation of the changes in aerosol optical properties during COVID-19 lockdowns was assessed. To achieve its objective the present study used aerosol Optical Depth (AOD), Angstrom exponent (AE) and Single Scattering Albedo (SSA) from Ozone Monitoring Instrument (OMI) and Moderate-resolution Imaging Spectroradiometer (MODIS) satellite sensors, to analyze the variations in aerosol properties for pre, during and post COVID-19 pandemic. This was achieved by doing a phase wise analysis of the spatial-temporal variation over Kenya during the lockdown phase. A comparison to reference period was done for the pre-lockdown, during lockdown and post lockdown phases. 24-hour mean value data retrieval over Kenya was obtained from the Modern-Era Retrospective analysis for Research and Applications (MERRA-2) model from 1st April to 30th June 2019 - 2021. It was evident that the emissions into the atmosphere over Kenya did not reduce relatively during the COVID-19 lockdowns. The spatial-temporal variability of the pollutants (AOD, AE AND SSA) did not depict a significant deviation from the normal in the lockdown phase as compared to the same season in the previous one year and a year after lockdowns. This was because of the migration of aerosols from regional sources, dominance of natural sources such as geothermal activities and low stringent levels on lockdown protocols. However meteorological factors have had great influence on the variability and seasonality of the aerosol optical properties over the sampled region, with the March-April-May (wet season) recording lower values of AOD and June-July-August (dry season) registering the highest values of AOD. In summary lockdowns did not alter values of aerosol optical properties over Kenya due to limited control of anthropogenic emissions. The findings of this proposed study can be utilized by the scientific community and regulators to strengthen the emergency response to check on high pollution in Kenya until cleaner technologies are put in place.
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    Spatial-Temporal Assessment of Gaseous and Particulate Matter Pollutants during COVID-19 Lockdown over Kenya, East Africa
    (Voice of the Publisher, 2025-09-16) Mutama, Peter M.; Makokha, John Wanjala; Kelonye, Festus B.; Khamala, Geoffrey W.
    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.