Chemical composition of urban aerosols in Toulouse, France during CAPITOUL experiment.

Ambient PM10 and PM2.5 aerosols were monitored in Toulouse from March 2004 to February 2005 (Extensive Observed Period (EOP)) as part of the research project CAPITOUL (Canopy and Aerosol Particles Interaction in TOulouse Urban Layer). Concentrations of 8 major ions (Na⁺, NH₄ ⁺, K⁺, Mg⁺², Ca⁺², Cl⁻, NO₃ ⁻, SO₄ ²⁻), 15 metal elements (Al, Ba, Cd, Ce, Cr, Cu, Fe, La, Mn, Ni, Pb, Sr, Th, Ti, Zn), and carbonaceous aerosols [TC, POM and EC (total carbon, organic carbon and elemental carbon, respectively)] were measured in a total of 52 samples of each size. Inter-seasonal variations were analyzed. Weekly PM2.5 and PM10 total mass concentrations (major ions + carbon + metal elements) were 4.4–18.0 µg m⁻³ and 6.5–23.5 µg m⁻³, with an annual average concentration of 11.0 ± 3.6 µg m⁻³ and 13.2 ± 4.3 µg m⁻³, respectively. The highest concentration for sulfate was found in summer and fall, whereas the highest NO₃ ⁻ concentration was observed in winter. This study is strengthened by Kruskal–Wallis and Mann–Whitney statistical tests. On average, carbonaceous species constitute between 49% and 75% of the monthly concentration registered, POM concentration always remaining higher (ratio more than 51%) than EC in both size ranges. The average OC/EC ratios were 2.70 ± 0.81 and 2.70 ± 0.60 for PM2.5 and PM10, respectively. Secondary organic carbon concentrations were significantly higher in the warmer seasons reaching in summer average ratios of 65.9% and 64.5% of the total OC concentration for PM2.5 and PM10, respectively. Secondary organic carbon was produced in the fine fraction of the aerosol. Metal elements analysis and enrichment factor calculations show that traffic emissions were the major influence on the chemical composition of the urban aerosol. A receptor modeling study was conducted using Principal Component Factor Analysis followed by multi-linear regression analysis in order to provide quantitative insights into the sources of specific chemical components in PM10. [ABSTRACT FROM AUTHOR]