Non-methane hydrocarbon variability in Athens during wintertime: the role of traffic and heating

Anastasia Panopoulou (1, 2, 3) , Eleni Liakakou (2) , Valérie Gros (4, 5) , Stéphane Sauvage (6) , Nadine Locoge (7) , Bernard Bonsang (4, 5) , Basil Psiloglou (2) , Evangelos Gerasopoulos (2) , Nikolaos Mihalopoulos (8, 1)

1 UOC - University of Crete [Heraklion]
2 NOA - National Observatory of Athens
3 CERI EE - IMT Nord Europe - Centre for Energy and Environment
4 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
5 CAE - Chimie Atmosphérique Expérimentale
6 LEFE - Laboratoire Ecologie Fonctionnelle et Environnement
7 CERI MP - IMT Nord Europe - Centre for Materials and Processes
8 IERSD - Institute for Environmental Research and Sustainable Development

Non-methane hydrocarbons (NMHCs) play an important role in atmospheric chemistry, contributing to ozone and secondary organic aerosol formation. They can also serve as tracers for various emission sources such as traffic, solvents, heating and vegetation. The current work presents, for the first time to our knowledge, time-resolved data of NMHCs, from two to six carbon atoms, for a period of 5 months (mid-October 2015 to mid-February 2016) in the "greater Athens area" (GAA), Greece. The measured NMHC levels are among the highest reported in the literature for the Mediterranean area during winter months, and the majority of the compounds demonstrate a remarkable day-today variability. Their levels increase by up to factor of 4 from autumn (October-November) to winter (December-February). Mi-croscale meteorological conditions, especially wind speed in combination with the planetary boundary layer (PBL) height, seem to contribute significantly to the variability of NMHC levels, with an increase of up to a factor of 10 under low wind speed (< 3 m s −1) conditions; this reflects the impact of local sources rather than long-range transport. All NMHCs demonstrated a pronounced bimodal, diurnal pattern with a morning peak followed by a second peak before midnight. The amplitude of both peaks gradually increased towards winter, in comparison to autumn, by a factor of 3 to 6 and closely followed that of carbon monoxide (CO), which indicates a contribution from sources other than traffic, e.g., domestic heating (fuel or wood burning). By comparing the NMHC diurnal variability with that of black carbon (BC), its fractions associated with wood burning (BC wb) and fossil fuel combustion (BC ff), and with source profiles we conclude that the morning peak is attributed to traffic while the night peak is mainly attributed to heating. With respect to the night peak, the selected tracers and source profiles clearly indicate a contribution from both traffic and domestic heating (fos-sil fuel and wood burning). NMHCs slopes versus BC wb are similar when compared with those versus BC ff (slight difference for ethylene), which indicates that NMHCs are most likely equally produced by wood and oil fossil fuel burning.

Mots clés: ChArMEx

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

Anastasia Panopoulou, Eleni Liakakou, Valérie Gros, Stéphane Sauvage, Nadine Locoge, et al.. Non-methane hydrocarbon variability in Athens during wintertime: the role of traffic and heating. Atmospheric Chemistry and Physics, 2018, 18 (21), pp.16139-16154. ⟨10.5194/acp-18-16139-2018⟩. ⟨hal-02400827⟩