Air Quality Study to Analyze PM2.5 Sources and their Possible Mitigation pathways in Nairobi
- 1Université Paris Cité, France (ezekielwaiguru24@gmail.com)
- 2Laboratoire Interuniversitaire des Systèmes Atmosphèriques (LISA), UMR CNRS 7583, Universitè Paris Est Crèteil et Universitè de Paris, Institut Pierre Simon Laplace, Crèteil, France
- 3OSU-Efluve, Observatoire Sciences de l’Univers-Enveloppes Fluides de la Ville à l’Exobiologie, Université Paris-Est-Créteil, CNRS UMS 3563, Ecole Nationale des Ponts et Chaussés, Université de Paris, France
- 5Lamont Doherty Earth Observation of Columbia University
- 6University of Nairobi Institute of Nuclear Science and Technology
- 7Innovations for Poverty Action (IPA), Nairobi, Kenya
- 8Kenyatta University Department of Environmental Planning and Management
- 9Carnegie Mellon University, Pittsburgh
- 10Monash University
- 11Columbia University Department of Chemical Engineering
Anthropogenic activities in cities can be major sources of fine particulate matter which contribute significantly to increased mortality and disease. In rapidly developing cities of eastern Africa, lack of routine air pollution measurements have hampered formulation of actionable air quality policies. This study integrates ground-based observations of low-cost sensors (LCS) and regional chemical transport modelling (CHIMERE, https://www.lmd.polytechnique.fr/chimere/) to quantify spatial-temporal variability of PM2.5 and NO2 concentrations, primary/secondary aerosol loading, local versus regional pollution share, and contribution of key economic sectors. Prior to deployment, LCS PM2.5 mass concentrations were calibrated with a reference instrument (BAM-1020), while LCS NO2 measurements could only be normalized internally. Between June-December 2021 period, sensors were deployed at urban background site (IPA, and UoN), urban traffic sites (KUCC, BuruBuru, and Marurui), and a peri-urban site (Ngong). BuruBuru and Marurui are in addition exposed to nearby residential emissions. Daily average PM2.5 varied from 26.3 to 27.6 µg/𝑚3 at traffic sites, 17.8 to 21.7 µg/𝑚3 at urban background sites, while it was 20.3 µg/𝑚3 at peri-urban site. PM2.5 and NO2 diurnal patterns mimicked daily traffic cycle with constantly higher evening peaks compared to morning peaks indicating residential emissions. A link of “large pollution” events with PM2.5 concentrations above 50 µg/m3 and low wind speeds (<4 m/s) was made evident and points to local sources. Preliminary modelling results of a nested CHIMERE run over Eastern Africa down to 2 km horizontal resolution show satisfying results when compared to measurements. They point to a strong urban source of fine particle pollution, with the strongest mass contribution of primary organic aerosol. Analysis of final model output will help to better understand air quality dynamics in Nairobi and ultimately help evaluation of possible future emission mitigation scenarios.
How to cite: Nyaga, E. W., Beekmann, M., R., S., Giordano, M. R., Ward, S., Westervelt, D., Gatari, M., Njeru, M., Mungai, J., Opinde, G., Mwendwa, T., Presto, A., Tjernstrom, E., and v. McNeill, F.: Air Quality Study to Analyze PM2.5 Sources and their Possible Mitigation pathways in Nairobi, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10315, https://doi.org/10.5194/egusphere-egu23-10315, 2023.
