Abstract
Information from elemental and mass composition of size-fractionated airborne particle matter (PM) provides insightful knowledge about their impact on human health, meteorology and climate. To attain insight into the nature of sizefractionated PM from a typical African city, samples were collected from an urban background site in Nairobi, Kenya, during the months of August and September in 2007. PM samples ranging in size from 0.06 to 16 µm aerodynamic diameter were collected on pre-weighed polycarbonate filters with 0.4 µm pore size using a nine-stage cascade impactor. Particles less than 0.06 µm were collected on a backup filter. A total of 170 samples were collected and analysed for trace elements using the Proton Induced X-Ray Emission (PIXE) technique. The analysis showed that Si, Fe and S dominated in all size ranges and displayed unimodal mass-size distribution whereas K, Cu, Zn and Pb, depicted bimodal mass-size distribution highlighting the multiplicity of their sources. To estimate human exposure to PM, deposition fractions of both the coarse and fine PM in the human respiratory system were calculated. The deposited concentration was found to be highest in the head airways region compared to the tracheobronchial and pulmonary regions.
Highlights
The impact of airborne particulate matter (PM) on human health, climate and meteorological phenomena is poorly understood in Africa (Petkova et al, 2013)
The particle matter (PM) concentration data from this study has been utilized in calculation of deposition fractions of PM
The obtained fractions give estimated mass deposited in the head airways, tracheobronchial and pulmonary regions of human respiratory system
Summary
The impact of airborne particulate matter (PM) on human health, climate and meteorological phenomena is poorly understood in Africa (Petkova et al, 2013). Lack of air pollution information from African countries, limits the knowledge on how exposure to air pollutants affects public health, especially with regard to PM (Gulis et al, 2004, Ngo et al, 2015). This is relevant as the exposure risk and eventual negative effects of PM on human health is influenced by particle sizes and chemical composition (Milford and Davidson, 1985, Dockery and Pope, 1994, Montoya et al, 2004, Pope and Dockery, 2006, Heal et al, 2012). The objectives of this study were to obtain a size distribution of PM and elemental concentrations in a typical African city and to determine the deposition
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