Introduction: Emissions from a variety of air particulate sources have resulted in atmospheric pollution that, in turn, has produced serious problems, causing irreversible reactions in the environment and hence is posing a major threat to our very existence. Aim: Identify monthly variations of particulate matter mass concentrations in air, the contribution of each size fraction (coarse and fine) to PM10 levels, and the contributions from natural and anthropogenic sources. Methodology: PM10 ambient air particulates in two size fractions being the coarse (PM10-2.5) and fine (PM2.5) were sampled. Heavy metals and carbonaceous compounds [organic carbon (OC) and elemental carbon (EC)] concentrations were determined. Enrichment factor (EF) was used to identify species of crustal and non-crustal origin in ambient air particulates. The identified elements were used to develop fingerprints for a number of particulate sources. Results: The mean coarse and fine particulate levels obtained were 89.2 g/m3 and 21.6 g/m3 respectively. The maximum and minimum levels occurred in February (dry season) and July (rainy season) respectively. Soil dust was found to be the major source of particulates in the two size fractions (coarse and fine). The sulphur contents in Harmattan (cold dry winds) dust in the dry season was found to be predominantly in the coarse fraction. EF was used to identify species of crustal and non–crustal origin in ambient air particulates. The Enrichment Factor values for the elements Cr, Cu, Zn, Pb and Br showed that they were mostly from anthropogenic sources. Conclusion: This study emphasizes the significant impact of seasonal variations on particulate levels. The problem with air quality is seen to be greatest during the Harmattan when cold dry winds blow soil dust particulates across West Africa.
Francis G. Ofosu
National Nuclear Research Institute, Ghana Atomic Energy Commission, Accra, Ghana.
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