Geochemical behaviour of the aerosol sampled in a suburban zone of Sfax City (Tunisia)
This work examines the geochemistry of the soluble elements (Ca2+, Mg2+, Fe2+ + Fe3+, Na+, K+, NH4+, Cl−, NO3−, SO42− and PO43−) present in the aerosol collected from a suburban site in Sfax City (Tunisia), which is frequently subjected to the urban plume. The descriptive study showed the influence of enrichment sources and meteorological factors. Complementary statistical approaches based on principal component analysis and multiple linear regression showed that the sampled aerosol has three different origins: crustal, marine and anthropogenic. The corresponding components are respectively made of (Ca2+, Mg2+, Fe2+ + Fe3+, K+ and PO43−), (Cl− and Na+) and (SO42−, NH4+ and NO3−). The contribution of the first two components is shown to depend on seasonal effects caused by two antagonistic circulations of continental and marine winds. The contribution of the anthropogenic component (SO42−, NH4+ and NO3−) is shown to be related to the effect of dominant north-easterly winds, which carry the pollution of Sfax City to the study site. Statistical approaches related to the behaviour of these anthropogenic compounds, in the presence of secondary aerosol precursors (SO2, NO2), proved their dependence on gas/particle conversion processes, especially those of neutralisation.
Keywords: aerosols, air pollution, air quality, urban pollution, Sfax, Tunisia, suburban sites, principal component analysis, PCA, linear regression, fine particles