Source apportionment analyses for fine (PM2.5) and coarse (PM2.5e10) mode particulate matter (PM) measured in an urban area in southwestern Nigeria

Özet

To determine the influence of regional and local sources of the fine and coarse fractions of airborneparticulate matter (PM), samples were collected in 2006, 2007, 2010, and 2013 covering the 2 majorseasons (wet and dry) at multiple locations in Ile-Ife, Nigeria. A total of 216 samples for each of the PM2.5and PM2.5e10 were collected on polycarbonate filters using low volume Gent samplers. Elements andblack carbon was measured using x-ray fluorescence (XRF) spectrometry and optical transmissometry,respectively. The average mass concentration for the PM2.5 and PM2.5e10 at Obafemi Awolowo University(OAU) in 2006, 2007, and 2010 exceeded the annual National Ambient Air Quality Standards (NAAQS) of15 and 60 mg/m3 for PM2.5 and PM2.5e10, respectively. At the Obafemi Awolowo University TeachingHospital Complex (OAUTHC) sites, the PM2.5 and PM2.5e10 mass fractions also exceeded the NAAQSstandards except at the urban background site. Positive matrix factorization (PMF) was used to identifyand apportion the PM sources for the combined data from these sampling sites. Four sources each wereidentified for both PM2.5 and PM2.5e10. The sources are soil (44%), savannah burning (26%), scrap processing(18%) and vehicular emissions (12%) for PM2.5 and soil plus biomass burning (71%), sea salt (22%),scrap processing (5%) and vehicle emissions (tire wear) (2%) for PM2.5e10. Most of the PM mass originatedfrom anthropogenic contributions. The highest contributions were associated with northwesterly windfrom the urbanized areas of Ile-Ife.