Background: Air samples collected on three different urban sites in East of France (Strasbourg, Besançon, and Spicheren), from April 2006 to January 2007, were characterized to measure the concentrations of polycyclic aromatic hydrocarbons (PAHs) in the particulate phase (PM(10)) and to examine their seasonal variation, diurnal variations, and emission sources.
Results: The average concentrations of ΣPAHs were 12.6, 9.5, and 8.9 ng m(-3) for the Strasbourg, Besançon, and Spicheren sites, respectively. Strong seasonal variations of individual PAH concentrations were found at the three sampling sites, with higher levels in the winter that gradually decreased to the lowest levels in the summer. The diurnal variations of PAH concentrations in summer presented highest concentrations during the morning (04:00-10:00) and the evening (16:00-22:00) times, indicating the important contribution from vehicle emissions, in the three sampling sites. Furthermore, the ratio of BaP/BeP suggests that the photochemical degradation of PAHs can suppress their concentrations in the midday/afternoon (10:00-16:00), time interval of highest global irradiance. In winter, concentrations of PAH were highest during the evening (16:00-22:00) time, suggesting that domestic heating can potentially be an important source for particulate PAH, for the three sampling sites.
Conclusion: Diagnostic ratios were used to identify potential sources of PAHs. Results showed that vehicle emissions may be the major source of PAHs, especially in summer, with a prevalent contribution of diesel engines rather than gasoline engines at the three sites studied, independently of the seasons.