In order to identify the source apportionment of particulate matter PM 10 and PM 2.5 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 4 2-, NO 3 -, Cl -) and cations (Ca 2+ , Mg 2+ , K + , NH 4 + ) 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 10 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 10 and PM 2.5 were studied, PM 10 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 2.5 fraction. In all the sites, PM 10 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.

Cette étude évalue la pollution urbaine en O 3 , NO x et SO 2 et les interactions locales avec les paramètres météorologiques de la capitale Tunis (Tunisie) entre 2003 et 2014. Elle permet d'établir des cartes de la distribution de la pollution gazeuse puis, par une approche statistique d'étude de la corrélation et d' Analyse en Composantes Principales (ACP), d'établir les interactions existant entre les paramètres météorologiques et les concentrations en ozone et oxydes d'azote. Des concentrations élevées en ozone sont observées sur la zone d'étude (66-130 ppbv), et leur distribution opposée à celle des concentrations en oxydes d'azote et dioxyde de soufre, même si les valeurs de ces derniers ne dépassent pas les normes (respectivement 51-178 ppbv et 1,8-4,4 ppbv). La matrice de corrélation ainsi que l' ACP ont permis de constater une forte corrélation entre l'ozone, la température et l'intensité des radiations solaire, d'une part, et l'humidité relative de l'air et la concentration en monoxyde d'azote, d'autre part, ces deux groupes étant anti-corrélés. Les concentrations en dioxyde d'azote apparaissent ici indépendantes des phénomènes photochimiques et très peu corrélées aux autres paramètres. Mots-cléspollution urbaine, ozone, oxyde d'azote, dioxyde de soufre, acp. AbstractAssessment of urban pollution by O 3 , NO x and SO 2 and local interactions with weather parameters is conducted in the capital Tunis (Tunisia) between 2003 and 2014. It established the distribution maps of the gaseous pollution and highlights the interactions between ozone and nitrogen oxide concentrations as well as meteorological parameters by a statistical approach using correlation studies and principal component analysis (PCA). Quite high ozone concentrations are reported in the study area (66-130 ppbv) and their distribution is the opposite of nitrogen oxides and sulphur dioxide's (respectively 51-178 ppbv et 1,8-4,4 ppbv). The correlation matrix and the PCA show a high correlation between ozone, temperature and the intensity of solar radiations on one side, and relative air humidity and nitrogen monoxide on the other side. These two groups are anti-correlated. Nitrogen dioxide concentrations seem to be independent of the photochemistry with a limited correlation to the other parameters.