Chemical characterization of harmattan dust across Oyo and Minna, Nigeria

Abstract

Harmattan dust haze in Nigeria is due to annual deposition of very fine dust particles as a result of both natural and human activities. There are scanty reports on the mineralogical, elemental and heavy metal composition in the Harmattan dust blowing across the country to support the presence of minerals and elements in the Harmattan dust.The aim of this study is to assess minerals and elemental compositions of Harmattan dust variations across Oyo (7032'N, 3025'E) and Minna (9035'N, 6032'E), Nigeria. dust samples were collected using clean plastic bowls of 10 cm diameter and analysis was conducted on the samples collected at the two stations using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Fluoresence (XRF), Particle Induced X-ray Emission (PIXE)and Atomic Absorption Spectroscopy (AAS). It was observed that elements, such as K, Ca,Ti, Mn, Fe, Ni, Cu, Zn, Mo, As, Zr, Pb, V, Sr, Cr and Ce, were present in different concentrations in the samples collected. Minerals, such as Quartz [SiO2], Rutile [TiO2],Periclase [MgO], Corundum [Al2O3], Hematite [Fe2O3],Cuprite [Cu2O], [ZrO2], Litharge [PbO], Monazite [P2O5], Zincite [ZnO], Montroydite [HgO] and Lime [CaO], were present in the samples collected at each station in different proportions. The soil mass concentration of the elements was calculated and observed to be 3.5179μg m3 at Oyo and 3.4745μg m3 at Minna. It was observed that the Harmattan dusts moving across Nigeria have almost all the elements present in Harmattan dust varying from station to station as the dust is moving towards the south of the country. The study concluded that the elemental composition of the dust samples analyzed revealed that the percentage compositions of some elements are higher than the acceptable WHO standard values,which may affect human health. It is therefore recommended that adequate precautionary measures and policies should be made to help mitigate the effects of high elemental concentrations observed.