Polycyclic aromatic hydrocarbons in the atmosphere of two French alpine valleys: Temporal trends and examination of sources

Nicolas Marchand (1) , Jean-Luc Besombes (1) , N. Chevron (1) , P. Masclet (1) , G. Aymoz (2) , J. L. Jaffrezo (2)

1 LCME - Laboratoire de Chimie Moléculaire et Environnement
2 LGGE - Laboratoire de glaciologie et géophysique de l'environnement

Alpine valleys represent some of the most important crossroads for international heavy duty traffic in Europe, but impact of this traffic on air quality is not well-known due to a lack of data in these complex systems. As part of the program "Pollution des Vallées Alpines'' (POVA), we performed two sampling surveys of PAHs in two sensitive valleys: the Chamonix and the Maurienne Valleys, between France and Italy. Sampling campaigns were performed during summer 2000 and winter 2001, both periods taking place during the closure of the "Tunnel du Mont-Blanc''. The objectives of this paper are first to describe the relations between PAH concentrations, external parameters (sampling site localization, meteorological parameters, sources), and the aerosol characteristics, including its carbonaceous fraction (OC and EC). The second objective is to study the capacity of the PAH profiles to accurately discriminate the different emissions sources. Temporal evolution of relative concentration of individual PAH (CHR), and PAH groups (BghiP+COR and BbF+BkF) are studied in order to discriminate wood combustion, gasoline, and diesel emissions, respectively. The results show that during both seasons the total particulate PAH concentrations were higher in the valley of Chamonix, despite the stopping of the international traffic through the Chamonix valley. Seasonal cycles, with higher concentrations in winter are also stronger in this valley. During winter, particulate PAH concentration can reach very high levels (155 ng.m^-3) in this valley during cold anticyclonic periods. Sources examination shows the impact of heavy duty traffic in the Maurienne valley and of gasoline vehicles in the Chamonix Valley during summer. During winter, Chamonix is characterized by the strong influences wood combustion in residential fireplaces, even if temporal evolution of specific PAH ratios are uneasy to interpret. Information on sources given by PAH profiles can only be considered as qualitative.

Domaines: Océan, Atmosphère

Nicolas Marchand, Jean-Luc Besombes, N. Chevron, P. Masclet, G. Aymoz, et al.. Polycyclic aromatic hydrocarbons in the atmosphere of two French alpine valleys: Temporal trends and examination of sources. Atmospheric Chemistry and Physics Discussions, 2004, 4 (1), pp.887-921. ⟨hal-00327843⟩