Spatiotemporal empirical analysis of particulate matter PM 2.5 pollution and air quality index (AQI) trends in Africa using MERRA-2 reanalysis datasets (1980-2021)

• Published in: The Science of the total environment 2024-02, Vol.912, p.169027
• Main Authors: Ouma, Yashon O, Keitsile, Amantle, Lottering, Lone, Nkwae, Boipuso, Odirile, Phillimon
• Format: Article
• Language: English
• ISSN: 1879-1026

In this study, the spatial-temporal trends of PM pollution were analyzed for subregions in Africa and the entire continent from 1980 to 2021. The distributions and trends of PM were derived from the monthly concentrations of the aerosol species from MERRA-2 reanalysis datasets comprising of sulphates (SO ), organic carbon (OC), black carbon (BC), Dust2.5 and Sea Salt (SS2.5). The resulting PM trends were compared with the climate factors, socio-economic indicators, and terrain characteristics. Using the Mann-Kendall (M-K) test, the continent and its subregions showed positive trends in PM concentrations, except for western and central Africa which exhibited marginal negative trends. The M-K trends also determined Dust2.5 as the dominant contributing aerosol factor responsible for the high PM concentrations in the northern, western and central regions of Africa, while SO and OC were respectively the most significant contributors to PM in the eastern and southern Africa regions. For the climate factors, the PM trends were determined to be positively correlated with the wind speed trends, while precipitation and temperature trends exhibited low and sometimes negative correlations with PM . Socio-economically, highly populated, and bare/sparse vegetated areas showed higher PM concentrations, while vegetated areas tended to have lower PM concentrations. Topographically, low laying regions were observed to retain the deposited PM especially in the northern and western regions of Africa. The Air Quality Index (AQI) results showed that 94 % of the continent had an average PM of 12-35 μg/m hence classified as "Moderate" AQI, and the rest of the continent's PM levels was between 35 and 55 μg/m implying AQI classification of "Unhealthy for Sensitive People". Northern and western Africa regions had the highest AQI, while southern Africa had the lowest AQI. The approach and findings in this study can be used to complement the evaluation and management of air quality in Africa.