Characterization and source apportionment of airborne particulate loadings at various receptor site-classes of Lagos Mega-City, Nigeria

This study has shown that the coarse particle fraction is the most dominant in the Residential and Heavy Traffic sampling sites with an average PM _2.5/PM₁₀ ratio of between 0.31 and 0.40 while the contributions from the two particle fractions are almost the same in the marine and Industrial sites with an average PM_2.5/PM₁₀ ratio of 0.49. A significant difference was observed between particulate loads on weekdays and a weekend in the sampling sites accepts at the Victoria Island. The mean PM_2.5/PM₁₀ ratio for the entire sampling campaign is 0.41±0.13 which is a clear indication that vehicular emission is not the principal source of pollutants at the sampling sites. The contributing sources in the four site-classes are similar but with varying degrees of contributions. Common sources identified for the classes are traffic-related, traffic emission, sea-salt and industrial emission. At the residential and traffic site-classes, the mean value of Br/Zn for PM2.5 is 2.0 and 2.1 respectively. This is a clear indicator of the fact that traffic emission is a prominent contributor to the fine PM fraction in these sites.