Air pollution is among the most serious environmental and public health problems worldwide, especially in low and middle-income countries like Rwanda. This study explores the spatial and temporal variations of criteria air pollutants across Rwanda from 2019 to 2023, utilizing data from 18 national air quality monitoring stations and 16 weather stations. Results reveal that PM2.5 and PM10 concentrations exceeded WHO guidelines, with the mean reaching 90 μg/m3 (PM2.5) and 127 μg/m3 (PM10), predominantly in Kigali City, Northern, and Western provinces. CO concentration peaked in the Eastern province and Kigali. In contrast, NO2 and O3 were highest in the Central and Northern provinces. Over five years, NO2 showed a slight increase trend, while CO, O3, and SO2 displayed minor declines and remained in line with WHO guidelines. Diurnal variations highlighted morning (06:00-07:00 am) and evening (06:00-09:00 pm) pollutant peaks, driven by morning rush hour traffic, domestic stoves, and industrial activities. Border stations like Bugeshi-Rubavu recorded elevated pollutant levels due to cross-border emissions from the bordering countries. Seasonal analysis revealed higher pollutant levels during dry seasons, influenced by reduced rainfall and increased anthropogenic activities. CO concentration was positively correlated with temperature during MAM (r = 0.69) due to increased biomass burning and agricultural emissions. Wind speed is negatively correlated with PM2.5 and PM10 in JJA, aiding pollutant dispersion, while PM2.5 is positively correlated with humidity in MAM (r = 0.7), linked to secondary aerosol formation. These findings underscore the urgent need to improve air quality, particularly in urban and border regions, and address Rwanda’s transboundary pollution concerns.
References
[1]
Xiao, K., Wang, Y., Wu, G., Fu, B. and Zhu, Y. (2018) Spatiotemporal Characteristics of Air Pollutants (PM10, PM2.5, SO2, NO2, O3, and CO) in the Inland Basin City of Chengdu, Southwest China. Atmosphere, 9, Article 74. https://doi.org/10.3390/atmos9020074
[2]
Smith, P., Ashmore, M.R., Black, H.I.J., Burgess, P.J., Evans, C.D., Quine, T.A., et al. (2012) REVIEW: The Role of Ecosystems and Their Management in Regulating Climate, and Soil, Water and Air Quality. JournalofAppliedEcology, 50, 812-829. https://doi.org/10.1111/1365-2664.12016
[3]
WHO (2021) Global Report on the Epidemiology of Health-Care-Associated Infections.
[4]
R Subramanian (2020) Air Pollution in Kigali, Rwanda: Spatial and Temporal Variability, Source Contributions, and the Impact of Car-Free Sundays. CleanAirJournal, 30, 1-15. https://doi.org/10.17159/caj/2020/30/2.8023
[5]
Manisalidis, I., Stavropoulou, E., Stavropoulos, A. and Bezirtzoglou, E. (2020) Environmental and Health Impacts of Air Pollution: A Review. FrontiersinPublicHealth, 8, Article 14. https://doi.org/10.3389/fpubh.2020.00014
[6]
Kalisa, W., Zhang, J., Igbawua, T., Henchiri, M., Mulinga, N., Nibagwire, D., et al. (2023) Spatial and Temporal Heterogeneity of Air Pollution in East Africa. ScienceoftheTotalEnvironment, 886, Article ID: 163734. https://doi.org/10.1016/j.scitotenv.2023.163734
[7]
Giannadaki, D., Lelieveld, J. and Pozzer, A. (2016) Implementing the US Air Quality Standard for PM2.5 Worldwide Can Prevent Millions of Premature Deaths per Year. EnvironmentalHealth, 15, Article No. 88. https://doi.org/10.1186/s12940-016-0170-8
[8]
Cohen, A.J., Brauer, M., Burnett, R., Anderson, H.R., Frostad, J., Estep, K., et al. (2017) Estimates and 25-Year Trends of the Global Burden of Disease Attributable to Ambient Air Pollution: An Analysis of Data from the Global Burden of Diseases Study 2015. TheLancet, 389, 1907-1918. https://doi.org/10.1016/s0140-6736(17)30505-6
[9]
Maji, K.J., Arora, M. and Dikshit, A.K. (2017) Burden of Disease Attributed to Ambient PM2.5 and PM10 Exposure in 190 Cities in China. EnvironmentalScienceandPollutionResearch, 24, 11559-11572. https://doi.org/10.1007/s11356-017-8575-7
[10]
REMA (2018) Inventory of Sources of Air Pollution in Rwanda Determination of Future Trends and Development of a National Air Quality Control Strategy.
[11]
MININFRA (2018) Energy Sector Strategic Plan. No. 2018/19-2023/24.
[12]
Kalisa, E., Nagato, E.G., Bizuru, E., Lee, K.C., Tang, N., Pointing, S.B., et al. (2018) Characterization and Risk Assessment of Atmospheric PM2.5 and PM10 Particulate-Bound PAHs and NPAHs in Rwanda, Central-East Africa. EnvironmentalScience&Technology, 52, 12179-12187. https://doi.org/10.1021/acs.est.8b03219
[13]
DeWitt, H.L., Gasore, J., Rupakheti, M., Potter, K.E., Prinn, R.G., Ndikubwimana, J.D.D., et al. (2019) Seasonal and Diurnal Variability in O3, Black Carbon, and CO Measured at the Rwanda Climate Observatory. AtmosphericChemistryandPhysics, 19, 2063-2078. https://doi.org/10.5194/acp-19-2063-2019
[14]
Farquharson, D., Jaramillo, P. and Samaras, C. (2018) Sustainability Implications of Electricity Outages in Sub-Saharan Africa. NatureSustainability, 1, 589-597. https://doi.org/10.1038/s41893-018-0151-8
[15]
Subramanian, R., Ellis, A., Torres-Delgado, E., Tanzer, R., Malings, C., Rivera, F., et al. (2018) Air Quality in Puerto Rico in the Aftermath of Hurricane Maria: A Case Study on the Use of Lower Cost Air Quality Monitors. ACSEarthandSpaceChemistry, 2, 1179-1186. https://doi.org/10.1021/acsearthspacechem.8b00079
[16]
Ndayisenga, J.D.D. (2022) Seasonal Variability of Ambient Ozone over Nyarugenge District in Kigali City. University of Rwanda.
[17]
Guhirwa, S. (2018) A Study on Spatial and Temporal Variability of Black Carbon in Urban and Rural Background in Rwanda. Ph.D. Thesis, University of Rwanda.
[18]
Xu, W.Y., Zhao, C.S., Ran, L., Deng, Z.Z., Liu, P.F., Ma, N., et al. (2011) Characteristics of Pollutants and Their Correlation to Meteorological Conditions at a Suburban Site in the North China Plain. AtmosphericChemistryandPhysics, 11, 4353-4369. https://doi.org/10.5194/acp-11-4353-2011
[19]
Cahoon, D.R., Stocks, B.J., Levine, J.S., Cofer, W.R. and O’Neill, K.P. (1992) Seasonal Distribution of African Savanna Fires. Nature, 359, 812-815. https://doi.org/10.1038/359812a0
[20]
Jonah, K., Wen, W., Shahid, S., Ali, M.A., Bilal, M., Habtemicheal, B.A., et al. (2021) Spatiotemporal Variability of Rainfall Trends and Influencing Factors in Rwanda. Journal of Atmospheric and Solar-Terrestrial Physics, 219, Article ID: 105631. https://doi.org/10.1016/j.jastp.2021.105631
[21]
Habineza, T. (2022) Diurnal and Seasonal Variability of Particulate Matter Concentrations over Kigali. Ph.D. Thesis, University of Rwanda.
[22]
Weatherhead, E.C., Reinsel, G.C., Tiao, G.C., Meng, X., Choi, D., Cheang, W., et al. (1998) Factors Affecting the Detection of Trends: Statistical Considerations and Applications to Environmental Data. Journal of Geophysical Research: Atmospheres, 103, 17149-17161. https://doi.org/10.1029/98jd00995
[23]
Gilbert, R.O. (1987) Statistical Methods for Environmental Pollution Monitoring. John Wiley & Sons.
[24]
Li, X., Peng, L., Yao, X., Cui, S., Hu, Y., You, C., et al. (2017) Long Short-Term Memory Neural Network for Air Pollutant Concentration Predictions: Method Development and Evaluation. Environmental Pollution, 231, 997-1004. https://doi.org/10.1016/j.envpol.2017.08.114
[25]
Nyasulu, M., Haque, M.M., Boiyo, R., Kumar, K.R. and Zhang, Y. (2020) Seasonal Climatology and Relationship between AOD and Cloud Properties Inferred from the MODIS over Malawi, Southeast Africa. Atmospheric Pollution Research, 11, 1933-1952. https://doi.org/10.1016/j.apr.2020.07.023
[26]
Nyasulu, M., Haque, M.M., Kumar, K.R., Banda, N., Ayugi, B. and Uddin, M.J. (2021) Temporal Patterns of Remote-Sensed Tropospheric Carbon Dioxide and Methane over an Urban Site in Malawi, Southeast Africa: Implications for Climate Effects. Atmospheric Pollution Research, 12, 125-135. https://doi.org/10.1016/j.apr.2021.02.005
[27]
Carslaw, D.C. (2019) The Openair Manual Open-Source Tools for Analysing Air Pollution Data. University of York and Ricardo Energy & Environment.
[28]
R Core Team (2019) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing.
[29]
Carslaw, D.C. and Ropkins, K. (2012) Openair—An R Package for Air Quality Data Analysis. Environmental Modelling & Software, 27, 52-61. https://doi.org/10.1016/j.envsoft.2011.09.008
Kalisa, E. and Nagato, E. (2017) Spatial Temporal Variability of PM2.5 in Urban Areas in Rwanda. Kanazawa International Symposium, Institute of Nature and Environmental Technology, 1.
[32]
Nsengimana, H., Bizimana, J.P. and Sezirahiga, Y. (2011) A Study on Air Pollution in Rwanda with Reference to Kigali City and Vehicular Emissions. REMA, BUTARE.
[33]
Williams, R.S., Hegglin, M.I., Kerridge, B.J., Jöckel, P., Latter, B.G. and Plummer, D.A. (2019) Characterising the Seasonal and Geographical Variability in Tropospheric Ozone, Stratospheric Influence and Recent Changes. Atmospheric Chemistry and Physics, 19, 3589-3620. https://doi.org/10.5194/acp-19-3589-2019
[34]
Nduwayezu, J.B., Ishimwe, T., Niyibizi, A. and Ngirabakunzi, B. (2015) Quantification of Air Pollution in Kigali City and Its Environmental and Socio-Economic Impact in Rwanda. American Journal of Environmental Engineering, 5, 106-119.
[35]
Opio, R., Mugume, I. and Nakatumba-Nabende, J. (2021) Understanding the Trend of NO2, SO2 and CO over East Africa from 2005 to 2020. Atmosphere, 12, Article 1283. https://doi.org/10.3390/atmos12101283
[36]
Hu, X., Zhang, Y., Jacobson, M.Z. and Chan, C.K. (2008) Coupling and Evaluating Gas/Particle Mass Transfer Treatments for Aerosol Simulation and Forecast. Journal of Geophysical Research: Atmospheres, 113, D11208. https://doi.org/10.1029/2007jd009588
[37]
Andersson, A., Kirillova, E.N., Decesari, S., DeWitt, L., Gasore, J., Potter, K.E., et al. (2020) Seasonal Source Variability of Carbonaceous Aerosols at the Rwanda Climate Observatory. Atmospheric Chemistry and Physics, 20, 4561-4573. https://doi.org/10.5194/acp-20-4561-2020
