Investigation of desert dust contribution to source apportionment of PM10 and PM2.5 from a southern Mediterranean coast

In order to identify the source apportionment of particulate matter PM<inf>10</inf> and PM<inf>2.5</inf> in the southern Mediterranean coast of Tunis (Tunisia), three different sites characterized respectively by traffic, industries and being an urban background area are studied. The chemical characterization included a gravimetric determination of atmospheric particles mass concentration, measurements of the major anions (SO<inf>4</inf>^2-, NO <inf>3</inf>^-, Cl^-) and cations (Ca²⁺ , Mg ²⁺ , K ⁺ , NH <inf>4</inf>⁺) concentrations in the aerosol samples by ion chromatography and analysis of 18 elements by energy dispersion X-ray fluorescence. Aerosol ion balance of various PM<inf>10</inf> constituents are used to identify possible sources of the particulate matters. Thanks to these analysis, the particulate masses were reconstructed from the main possible constituents: crustal matter, primary and secondary pollutants, marine aerosols and organic matter. Wherever PM<inf>10</inf> and PM<inf>2.5</inf> were studied, PM<inf>10</inf> crustal elements and sea salt aerosols were mainly associated with the coarse fraction whereas primary and secondary anthropogenic pollutants as well as organic matter rather compose PM<inf>2.5</inf> fraction. In all the sites, PM<inf>10</inf> mass was mainly composed of crustal matter (41-50%) and poorly of sea salt (3-4%). And so aerosols chemical composition is heavily affected by dust winds from Sahara desert, with some contribution of local traffic and industries and only a slight direct impact of the nearby Mediterranean sea.