Abstract. Within the framework of air quality studies at the megacity scale, highly time-resolved volatile organic compounds (C2–C8) measurements were performed in downtown Paris (urban background sites) from January to November 2010. This unique dataset included non-methane hydrocarbons (NMHCs) and aromatic/oxygenated species (OVOCs) measured by a GC-FID (Gas Chromatograph with a Flame Ionization Detector) and a PTR-MS (Proton Transfer Reaction – Mass Spectrometer), respectively. The current study presents the seasonal variability of atmospheric VOCs being monitored in the French megacity and their various associated emission sources. Clear seasonal and diurnal patterns differed from one VOC to another as the result of their different origins and the influence of environmental parameters (solar radiation, temperature). Source Apportionment (SA) was comprehensively conducted using a multivariate mathematical receptor modeling. The United States Environmental Protection Agency's Positive Matrix Factorization tool (US EPA, PMF) was used to apportion and quantify ambient VOC concentrations into six different sources. The modeled source profiles were identified from near-field observations (measurements from three distinct emission sources: inside a highway tunnel, at a fireplace and from a domestic gas flue, with hence a specific focus on road-traffic, wood burning activities and natural gas emissions) and hydrocarbon profiles reported in the literature. The reconstructed VOC sources were cross-validated using independent tracers such as inorganic gases (NO, NO2, CO), black carbon (BC) and meteorological data (temperature). The largest contributors to the predicted VOC concentrations were traffic-related activities (including motor vehicle exhaust, 15 % of the total mass on the annual average, and gasoline evaporation, 10 %), with the remaining emissions from natural gas and background (23 %), solvents use (20 %), wood burning (18 %) and a biogenic source (15 %). An important finding of this work is the significant contribution from wood burning, especially in winter, where it could represent up to ~ 50 % of the total mass of VOCs. Biogenic emissions also surprisingly contributed up to ~ 30 % in summer (due to the dominating weight of OVOCs in this source). Finally, the mixed natural gas and background source exhibited a high contribution in spring (35 %, when continental air influences were observed) and in autumn (23 %, for home heating consumption).
Assessment of the impact of the traffic situation in urban area on the amount of volatile organic compounds getting into the cabin of the car on the road
