Multi-elemental analysis and source apportionment of urban aerosols in a low density residential area: A case study of Ikoyi Lagos Nigeria

Abstract

Concentrations of size segregated aerosols (PM_2.5-10 and PM_2.5 ) were measured daily at a receptor site located in Ikoyi, Lagos, between August to September, 2007 in order to investigate the chemical compositions and sources. Size-segregated fractions were collected using a double staged 'Gent' stack filter unit sampler. Elemental characterization was carried out by Particle Induced X-ray Emission (PIXE) technique in an external ion beam analysis set-up. Data matrix of 35 by 23 species (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br, Rb, Sr, Zr, and Pb) were obtained in each fraction and their elemental concentrations were assessed. Data obtained from the elemental analysis of both  fractions were further subjected to Pearson correlation and Principal Component Analysis (PCA) for source apportionment and identification. Pearson inter-elemental correlations indicated that some elements could have common source origins or similar chemical properties. Source apportionment results by PCA resolved five sources (Soil dust, 31 %; Sea spray, 23 %; Heavy oil combustion, 14 %; Industrial, 13 %; Physical construction, 6 %) and six sources (Traffic, 20 %; Soil dust, 19 %; Non-ferrous smelting, 12 %; Heavy oil combustion, 10 %; Biomass burning, 9 %; Sea spray, 6 % ) for PM_2.5-10 and PM_2.5 samples respectively. The study concluded that  anthropogenic (traffic, industrial, and biomass burning)emission sources posed great hazard to Ikoyi receptors.

Keywords: Atmospheric, Compositions, Emissions, Ion Beam, Particulates, PIXE