Characterization of Aerosol Physical and Optical Properties at the Observatoire Pérenne de l'Environnement (OPE) Site

Antoine Farah (1) , Paolo Villani (1) , Clémence Rose (1) , Sébastien Conil (2) , Laurent Langrene (2) , Paolo Laj (3) , Karine Sellegri (1)

1 LaMP - Laboratoire de Météorologie Physique
2 ANDRA - Agence Nationale pour la Gestion des Déchets Radioactifs
3 IGE - Institut des Géosciences de l’Environnement

The Observatoire Pérenne de l'Environnement (OPE) station is a rural background site located in NorthEastern France. Besides emissions from agricultural activities, the site is located far from local emissions but at an even distance from the intense emission zones of Western Germany to the northeast and the Paris area to the southwest. In the paper, we report and analyze almost six years of measurements (1 May 2012 to 31 December 2018) of the optical and physical properties of aerosol particles. Based on aerosol optical and physical measurements combined with air mass back-trajectories, we investigate the dependence of these properties on air mass type. Two distinct equivalent black carbon (EBC) sources-origins-fossil fuel (FF) and biomass burning (BB)-were identified. FF was the dominant source of EBC (>70%) but showed a very marked seasonal variation. BB fraction is found higher during the cold seasons in the order of 35% (0.1 µg m −3) against 17% (0.05 µg m −3) during the warm seasons. The highest EBC and N 0.54-1.15 (particles whose diameter ranged from 0.54 to 1.15 µm) median concentrations were observed during the night time and during the cold seasons compared to the warmer seasons, indicating primary sources trapped within a thin boundary layer (BL). A different behavior is found for N 10-550 (particles whose diameter ranged from 10 to 550 nm) and coarse mode particles (N 1.15-4.5 , i.e., particles whose diameter ranged from 1.15 to 4.5 µm) median concentrations, which were observed during the warm seasons compared to the cold seasons, indicating rather biogenic secondary sources for the smaller particles, and potentially primary biogenic sources for the coarse mode particles. The scattering and absorption coefficients and single scattering albedo (SSA) show the same seasonal variations like the ones of N 0.54-1.15 concentrations, indicating that particles larger than 500 nm seemed to contribute the most to the optical properties of the aerosol.

Mots clés: particle size distributions (PSDs); aerosol light absorption and scattering; EBC source apportionment; long-range transport

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]; Océan, Atmosphère

Antoine Farah, Paolo Villani, Clémence Rose, Sébastien Conil, Laurent Langrene, et al.. Characterization of Aerosol Physical and Optical Properties at the Observatoire Pérenne de l'Environnement (OPE) Site. Atmosphere, 2020, 11 (2), pp.172. ⟨10.3390/atmos11020172⟩. ⟨hal-02499126⟩