Elemental and Clay Mineralogical Compositions of Dustfall in the Lower Benue valley of Nigeria
Although the phenomenon of harmattan dustfall in Nigeria has covered many centuries, information as to the total elemental compositions and the type of clay mineralogy in the dust are very scanty. This study was carried out in the Lower Benue Valley (Latitude 7.250N – 8.250N and Longitude 8.000E – 8.500E) to investigate quantitatively, the total elemental compositions as well as to determine the clay mineralogy of the harmattan dust falling in the area. The study involved the collection of both dust and soil samples in 3 locations in the area, and the analysis of the samples using Xray florescence for elemental compositions and chemical means of clay mineralogy determination. The results indicated that harmattan dust had higher contents of Si, Fe, Mn, Sr, Zn, S, Ni, Co, Rb, Pb and Nb than the native soils. Although\ the concentration of some of these trace elements (Mn=280mgkg-1; Zr=750mgkg-1; Zn=50mgkg-1; Ni=80mgkg-1; Pb=30mgkg-1 in the native soils are currently below toxic levels, their continuous deposit into the soils through dust import may result into nutrient imbalance and possible toxicities with time. The presence of 2:1 clay minerals in the dust is however beneficial to the native soils because of the higher CEC and fertility as well as good structural development associated with these minerals.
Keywords: Elemental composition; Clay mineralogy; Dustfall; Lower Benue Valley