Articles | Volume 16, issue 18
Research article
26 Sep 2016
Research article |  | 26 Sep 2016

Seasonal variability and source apportionment of volatile organic compounds (VOCs) in the Paris megacity (France)

Alexia Baudic, Valérie Gros, Stéphane Sauvage, Nadine Locoge, Olivier Sanchez, Roland Sarda-Estève, Cerise Kalogridis, Jean-Eudes Petit, Nicolas Bonnaire, Dominique Baisnée, Olivier Favez, Alexandre Albinet, Jean Sciare, and Bernard Bonsang

Abstract. Within the framework of air quality studies at the megacity scale, highly time-resolved volatile organic compound (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. This 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, hence with 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 evaporative sources, 10 %), with the remaining emissions from natural gas and background (23 %), solvent 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).

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Short summary
This article presents ambient air VOC measurements performed in Paris during the MEGAPOLI and FRANCIPOL campaigns (2010). For the first time, we report (O)VOC concentration levels, their temporal variations and their main emission sources. The originality of this study stands in using near-field observations to help strengthen the identification of apportioned sources derived from PMF. An important finding of this work is the high contribution of the wood burning source (50 %) in winter.
Final-revised paper