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Source apportionment and seasonal variation of PM2.5 in a Sub-Saharan African city: Nairobi, Kenya

Gaita, Samuel Mwaniki; Boman, Johan; Gatari, Michael J; Pettersson, Jan B. C. and Janhäll, Sara (2014) In Atmospheric Chemistry and Physics 14. p.9977-9991
Abstract
Sources of airborne particulate matter and their seasonal variation in urban areas in Sub-Saharan Africa are poorly understood due to lack of long-term measurement data. In view of this, filter samples of airborne particulate matter (particle diameter ?2.5 ?m, PM2.5) were collected between May 2008 and April 2010 at two sites (urban background site and suburban site) within the Nairobi metropolitan area. A total of 780 samples were collected and analyzed for particulate mass, black carbon (BC) and 13 trace elements. The average PM2.5 concentration at the urban background site was 21±9.5 ?g m?3, whereas the concentration at the suburban site was 13±7.3 ?g m?3. The daily PM2.5 concentrations exceeded 25 ?g m?3 (the World Health Organization... (More)
Sources of airborne particulate matter and their seasonal variation in urban areas in Sub-Saharan Africa are poorly understood due to lack of long-term measurement data. In view of this, filter samples of airborne particulate matter (particle diameter ?2.5 ?m, PM2.5) were collected between May 2008 and April 2010 at two sites (urban background site and suburban site) within the Nairobi metropolitan area. A total of 780 samples were collected and analyzed for particulate mass, black carbon (BC) and 13 trace elements. The average PM2.5 concentration at the urban background site was 21±9.5 ?g m?3, whereas the concentration at the suburban site was 13±7.3 ?g m?3. The daily PM2.5 concentrations exceeded 25 ?g m?3 (the World Health Organization 24 h guideline value) on 29% of the days at the urban background site and 7% of the days at the suburban site. At both sites, BC, Fe, S and Cl accounted for approximately 80% of all detected elements. Positive matrix factorization analysis identified five source factors that contribute to PM2.5 in Nairobi, namely traffic, mineral dust, industry, combustion and a mixed factor (composed of biomass burning, secondary aerosol and aged sea salt). Mineral dust and traffic factors were related to approximately 74% of PM2.5. The identified source factors exhibited seasonal variation, apart from the traffic factor, which was prominently consistent throughout the sampling period. Weekly variations were observed in all factors, with weekdays having higher concentrations than weekends. The results provide information that can be exploited for policy formulation and mitigation strategies to control air pollution in Sub-Saharan African cities. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
PM2.5, source profiles, urban air quality, Sub-Sahara Africa
in
Atmospheric Chemistry and Physics
volume
14
pages
9977 - 9991
publisher
Copernicus Gesellschaft Mbh
external identifiers
  • scopus:84907221420
ISSN
1680-7324
DOI
10.5194/acp-14-9977-2014
project
MERGE
language
English
LU publication?
no
id
fd21c972-5cd1-4557-8e56-74b2519b36bf (old id 7515759)
date added to LUP
2015-07-08 14:15:44
date last changed
2017-11-12 04:08:55
@article{fd21c972-5cd1-4557-8e56-74b2519b36bf,
  abstract     = {Sources of airborne particulate matter and their seasonal variation in urban areas in Sub-Saharan Africa are poorly understood due to lack of long-term measurement data. In view of this, filter samples of airborne particulate matter (particle diameter ?2.5 ?m, PM2.5) were collected between May 2008 and April 2010 at two sites (urban background site and suburban site) within the Nairobi metropolitan area. A total of 780 samples were collected and analyzed for particulate mass, black carbon (BC) and 13 trace elements. The average PM2.5 concentration at the urban background site was 21±9.5 ?g m?3, whereas the concentration at the suburban site was 13±7.3 ?g m?3. The daily PM2.5 concentrations exceeded 25 ?g m?3 (the World Health Organization 24 h guideline value) on 29% of the days at the urban background site and 7% of the days at the suburban site. At both sites, BC, Fe, S and Cl accounted for approximately 80% of all detected elements. Positive matrix factorization analysis identified five source factors that contribute to PM2.5 in Nairobi, namely traffic, mineral dust, industry, combustion and a mixed factor (composed of biomass burning, secondary aerosol and aged sea salt). Mineral dust and traffic factors were related to approximately 74% of PM2.5. The identified source factors exhibited seasonal variation, apart from the traffic factor, which was prominently consistent throughout the sampling period. Weekly variations were observed in all factors, with weekdays having higher concentrations than weekends. The results provide information that can be exploited for policy formulation and mitigation strategies to control air pollution in Sub-Saharan African cities.},
  author       = {Gaita, Samuel Mwaniki and Boman, Johan and Gatari, Michael J and Pettersson, Jan B. C. and Janhäll, Sara},
  issn         = {1680-7324},
  keyword      = {PM2.5,source profiles,urban air quality,Sub-Sahara Africa},
  language     = {eng},
  pages        = {9977--9991},
  publisher    = {Copernicus Gesellschaft Mbh},
  series       = {Atmospheric Chemistry and Physics},
  title        = {Source apportionment and seasonal variation of PM2.5 in a Sub-Saharan African city: Nairobi, Kenya},
  url          = {http://dx.doi.org/10.5194/acp-14-9977-2014},
  volume       = {14},
  year         = {2014},
}