Atmospheric Polycyclic Aromatic Hydrocarbons (PAHs) in Two French Alpine Valleys
Résumé
In Europe, Alpine valleys represent one of the most important crossroads for heavy traffic. The vehicle impact on air quality is not well-known due to a lack of data in valley systems. Besides a health toxicity concern, the study of atmospheric polycyclic aromatic hydrocarbons (PAHs) is of geo-chemical interest because they are emitted mainly by combustion processes. This class of compounds is also particularly interesting for the study of the potential impact of heavy duty traffic on air pollution. PAHs are therefore actually regarded as priority pollutants of our air environment. As part of the program "Pollution des Vallées Alpines” (POVA), we performed two sampling surveys of PAHs in two sensitive valleys: the valley of Chamonix and the valley of Maurienne. In each valley, two sites were instrumented for atmospheric PAH sampling, and for others pollutant monitoring such as NOx, ozone, and particulate matter (PM10). The first sampling campaign was performed in summer 2000 and the second in winter 2001 both periods occurring during the corresponding closure of the Mont Blanc tunnel. During both seasons the total particulate PAH concentrations were higher in the valley of Chamonix despite the stop of international traffic through the Chamonix Valley. In summer, the average total PAH concentration was nearly twice as high in the Chamonix Valley (1.3 ng m−3) than in Maurienne Valley (0.8 ng m−3). In winter the difference between the two valleys is larger since the average PAH concentrations reached 48 ng m−3 and 18 ng m−3 in Chamonix and Maurienne Valley, respectively. In addition PAH total concentration reached very high levels (155 ng m−3) in the valley of Chamonix especially during anticyclonic periods. This very sharp increase of the PAH concentrations can be connected to an increase of the emissions in winter.