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

Alexia Baudic (1) , Valérie Gros (1, 2) , Stéphane Sauvage (3) , Nadine Locoge (4, 5) , Olivier Sanchez (6) , Roland Sarda-Estève (1, 2) , Cerise Kalogridis (7, 8) , Jean-Eudes Petit (1, 2) , Nicolas Bonnaire (1, 2) , Dominique Baisnée (1, 2) , Olivier Favez (9) , Alexandre Albinet (9) , Jean Sciare (10) , Bernard Bonsang (1, 2)

1 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
2 CAE - Chimie Atmosphérique Expérimentale
3 CERI EE - IMT Nord Europe - Centre for Energy and Environment
4 Mines Douai EMD - École des Mines de Douai
5 Université de Lille
6 HEGP - Hôpital Européen Georges Pompidou [APHP]
7 CNRS - Centre National de la Recherche Scientifique
8 UVSQ - Université de Versailles Saint-Quentin-en-Yvelines
9 INERIS - Institut National de l'Environnement Industriel et des Risques
10 CyI - Cyprus Institute

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).

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Alexia Baudic, Valérie Gros, Stéphane Sauvage, Nadine Locoge, Olivier Sanchez, et al.. Seasonal variability and source apportionment of volatile organic compounds (VOCs) in the Paris megacity (France). Atmospheric Chemistry and Physics, 2017, 16 (18), pp.11961 - 11989. ⟨10.5194/acp-16-11961-2016⟩. ⟨hal-01583966⟩