| Popis: |
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 ( |
