An approach to characterization of sources of urban airborne particles through heavy metal speciation

Abstract

Airborne particles, collected in an urban atmosphere, influenced by surrounding farm areas (Seville), were analyzed by speciation for ten heavy metals. The use of a sequential extraction procedure allowed the subdivision of the total content of each metal into four different fractions. Statistical multivariate analysis was performed on the fractions and the main sources of metal contamination were characterized. The results show that soil aerosols make the largest contribution to pollution with Fe and Al as the most abundant metals acting as markers for this source. In addition, the close correlation between Pb and Cu suggests that these are mainly pollutants generated by traffic. The other metals permitted identification of an industrial source but always in association with a soil source. From the percentage distribution of species, we found that Fe and Al are found in the carbonate or oxide fraction (40%) and in the residual metal fraction (40%). While Pb and Cu mainly appear as oxides and carbonates (50% and 40%, respectively), Cd prevails in soluble or exchangeable form (55%).