Seasonal variation of particulate lipophilic organic compounds at nonurban sites in Europe

Atmospheric aerosol samples, collected continuously during a sampling period longer than 1 year at six rural and background sites representing oceanic, rural and continental environments across Europe, were extracted, fractionated and analyzed by gas chromatography/mass spectrometry. The detailed organic speciation of the aerosol samples enabled the choice of some key compounds to assess the contribution of different sources. Lipophilic molecular markers were identified, including vehicle exhaust constituents, meat smoke tracers, phytosterols of higher photosynthetic plants and wood smoke components, especially from coniferous vegetation. The lowest concentrations and a quasi absence of seasonal cycle were observed at the oceanic background site of Azores. The highest values and a greater number of compounds were registered at the two continental lower-level sites. Aveiro (a rural site close to the small coastal Portuguese city of Aveiro) and K-puszta (Hungarian plains) both presented a seasonal variation with winter maxima attributable to a sizable contribution of wood-burning and meat-cooking sources. At the mountain sites (Puy de Dome, Schauinsland and the high alpine summit of Sonnblick), concentrations maximized during summer as a result of the decoupling of the lower layers from the midtroposphere with wintry weather and the influence of boundary layer air masses during the warm season.