Spatiotemporal Dynamics of Atmospheric fine Particulate Matter (PM2.5) Over Addis Ababa, Ethiopia
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Date
2024-11
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Addis Ababa University
Abstract
Air pollution affects health, environment, and property globally; however, posing challenges in developing countries due to weak regulations and reusing secondhand factories for investments. Like other cities in the developing countries, Addis Ababa is facing air pollution problem due to rapid industrialization, ineffective transport system, and rapid growth in traffic volumes with increasing population. Hence, the aim of this study was to investigate spatiotemporal dynamics of atmospheric fine particulate matter (PM2.5) in Addis Ababa using available PurpleAir (PA) sensors in the city. Measurements from seven PA sensors (Aratkilo, Entoto, Jacros, BLH, ECA, RepiWtE, and Skyline) were processed using R and Python programming. The analysis has shown that the diurnal mean value of PM2.5 was peak during morning and early night at each PA monitoring locations. This could be attributed to traffic congestions due to people hurrying to their working place and home for respectively peak and temperature variation with minimum temperature at the early morning and night and maximum at midday. Fluctuations of PM2.5 concentrations show clear variability’s and daily patterns in the week with increasing from Monday to Friday and decreasing in the weekend. Moreover, about 75% of the daily PM2.5 are also above WHO guideline in all PA monitoring locations. Seasonal analyses have shown that the PM2.5 data have a maximum value during June to September (Kiremt season) and minimum during October to January (Bega) at each monitoring stations. In the Kiremt season, 87.5 % of the existing daily concentrations of PM2.5 were above WHO guideline in all monitoring stations. The concentrations of PM2.5 during Belg and Bega seasons were relatively lower than during Kiremt season. However, in these seasons about 75% of PM2.5 concentrations above WHO guideline. On average, the 2022 annual mean of PM2.5 was 5.5 μg/m³ and in 2023 it was 6.5 μg/m³, exceeding WHO standards by a value of 0.5 μg/m³ and 1.5 μg/m³ respectively. There is a significant difference among the daily mean PM2.5 concentrations at PA stations with a P-value of 0.01 (alpha=0.05). Relatively, BLH and RepiWtE sites had the highest PM2.5 levels, while Entoto recorded the lowest. The number of AQ sensors, more apportionment study, shift to clean energy, use diversify renewables energy, reduce waste, set standards and improve public transportation emissions are advisable in the future to cut pollution.
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Keywords
Addis Ababa, Air Pollution, Air Quality, PM2.5, Purpleair