Aerosol Characterization for Minna, Nigeria by EDXRF Technique and Source Attribution by PCFA and CMB Multivariate Statistical Techniques
Abstract
The ambient aerosols sampled gravimetrically in Minna during a dry season were analyzed using an ED-XRF system. Principal Component Factor Analysis (PCFA) and Chemical Mass Balance (CMB) statistical techniques were used to infer source of the aerosols and their contributions.
The average aerosols concentrations at the city centre and residential areas were respectively 288 - 483 μg/m3 (pre-harmattan) and 100 – 111 μg/m3 (pre-harmattan, but 362 -1200 μg/m3 during harmattan). Al, Si, S, K, P, Ca, Ti, Fe, Cu, Zn, V, As, Sr, Pb, Cr, Mn, Co, and Br were detected but only Zn and Pb were highly/moderately enriched. Computed elemental ratios of Pb/Zn and Pb/Br from the samples indicated high vehicular transportation contributions in the commercial areas. However K/Fe ratios showed high wood/biomass burning contributions during the daytime. The inter-elemental correlation showed significant (r2 > 0.5) associations between (Al, Si, Fe, Mn, and S), (K, Ti, and Zn), (Pb, P, and Cu), and (Br, Ca, Cu and P), indicating a complex source interactions. Loadings from the PCFA were: Factor 1 suggesting soil source; Factor 2 suggesting automobile source; Factor 3 suggesting harmattan and entrained soil from vehicular dust remobilization. A spread of wood burning influence over Factors 2 and 3 was noted. The CMB analysis provided mass contributions from Factors 1 to 3 to be 52, 28 and 21 % respectively. The study showed insignificant contribution of local industries to the observed aerosol composition in the city. Salient air quality management options for the city airshed were however discussed.
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