Browsing by Author "Silvestre, Armando J. D."
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- Characterisation of carbonaceous aerosols from the Azorean island of TerceiraPublication . Alves, Célia A.; Oliveira, Tiago S.; Pio, Casimiro; Silvestre, Armando J. D.; Fialho, Paulo; Barata, Filipe; Legrand, MichelAerosol samples were collected from 2002 to 2003 in Terceira, one of the islands of the Azores archipelago in the north-eastern Atlantic. The atmospheric samples have been analysed for its carbonaceous content and for lipid class compounds. The major constituents that comprise plant wax are n-alkanes (C23–C33, with and odd-to-even carbon predominance and carbon maxima at 29 or 31), n-alkanols (C22–C30, even-to-odd) and n-alkanoic acids (C22–C30, even-to-odd), with minor amounts of n-alkanals and polycyclic biomarkers, such as phytosterols. Some alkanedioic acids and phthalates were also detected. The occurrence of short-chain homologues may indicate an additional marine source, probably introduced into the atmosphere via sea spray. Changes in the composition of the homologous series derived from terrestrial plants throughout the observation period may be related to alterations in the regional sources and transport pathways. These terrestrial lipids contributed up to 47% of the total compound mass, while the marine input was estimated to be inferior to 19%, both of them being more representative in summer. Biomass burning sources represented approximately 1% of the total inputs to the organic aerosol for the most part of the year, excepting during the spring, when it contributed to 10%. Petroleum products and plasticizers presented higher contributions (up to 19%) during the winter months. Secondary constituents resulting from oxidation during transport varied from 14% to 37% of the apportioned organic mass. The fraction derived from soil resuspension accounted for 2–16%.
- Seasonal variation of particulate lipophilic organic compounds at nonurban sites in EuropePublication . Oliveira, Tiago S.; Pio, Casimiro; Alves, Célia A.; Silvestre, Armando J. D.; Evtyugina, M.; Afonso, Joana; Fialho, Paulo; Legrand, Michel; Puxbaum, Hans; Gelencsér, AndrásAtmospheric 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 Dôme, 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.