Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin : the effect of local biogenic emissions
Seco Guix, Roger (Centre de Recerca Ecològica i Aplicacions Forestals)
Peñuelas, Josep (Centre de Recerca Ecològica i Aplicacions Forestals)
Filella Cubells, Iolanda (Centre de Recerca Ecològica i Aplicacions Forestals)
Llusià Benet, Joan (Centre de Recerca Ecològica i Aplicacions Forestals)
Molowny-Horas, Roberto (Centre de Recerca Ecològica i Aplicacions Forestals)
Schallhart, S. (Innsbruck University. Institut fur Ionenphysik und Angewandte Physik)
Metzger, A. (Innsbruck University. Ionicon Analytik)
Muller, M. (Innsbruck University. Institut fur Ionenphysik und Angewandte Physik)
Hansel, A. (Innsbruck University. Institut fur Ionenphysik und Angewandte Physik)

Data: 2011
Resum: Atmospheric volatile organic compounds (VOCs) are involved in ozone and aerosol generation, thus having implications for air quality and climate. VOCs and their emissions by vegetation also have important ecological roles as they can protect plants from stresses and act as communication cues between plants and between plants and animals. In spite of these key environmental and biological roles, the reports on seasonal and daily VOC mixing ratios in the literature for Mediterranean natural environments are scarce. We conducted seasonal (winter and summer) measurements of VOC mixing ratios in an elevated (720 m a. s. l. ) holm oak Mediterranean forest site near the metropolitan area of Barcelona (NE Iberian Peninsula). Methanol was the most abundant compound among all the VOCs measured in both seasons. While aromatic VOCs showed almost no seasonal variability, short-chain oxygenated VOCs presented higher mixing ratios in summer, presumably due to greater emission by vegetation and increased photochemistry, both enhanced by the high temperatures and solar radiation in summer. Isoprenoid VOCs showed the biggest seasonal change in mixing ratios: they increased by one order of magnitude in summer, as a result of the vegetation’s greater physiological activity and emission rates. The maximum diurnal concentrations of ozone increased in summer too, most likely due to more intense photochemical activity and the higher levels of VOCs in the air. The daily variation of VOC mixing ratios was mainly governed by the wind regime of the mountain, as the majority of the VOC species analyzed followed a very similar diel cycle. Mountain and sea breezes that develop after sunrise advect polluted air masses to the mountain. These polluted air masses had previously passed over the urban and industrial areas surrounding the Barcelona metropolitan area, where they were enriched in NOx and in VOCs of biotic and abiotic origin. Moreover, these polluted air masses receive additional biogenic VOCs emitted in the local valley by the vegetation, thus enhancing O3 formation in this forested site. The only VOC species that showed a somewhat different daily pattern were monoterpenes because of their local biogenic emission. Isoprene also followed in part the daily pattern of monoterpenes, but only in summer when its biotic sources were stronger. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources.
Nota: Número d'acord de subvenció MINECO/CGL2010-17172
Nota: Número d'acord de subvenció MICINN/CSD2008-00040
Nota: Número d'acord de subvenció MICINN/CGL2007-30502-E/CLI
Nota: Número d'acord de subvenció MINECO/CGL2006-04025/BOS
Nota: Número d'acord de subvenció MINECO/FPI-BES-2005-6989
Nota: Número d'acord de subvenció AGAUR/2009/SGR-458
Drets: Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original. Creative Commons
Llengua: Anglès
Document: article ; recerca ; publishedVersion
Publicat a: Atmospheric chemistry and physics, Vol. 11, issue 24 (Des. 2011) , p. 13161-13179, ISSN 1680-7316



19 p, 4.5 MB

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Documents de recerca > Documents dels grups de recerca de la UAB > Centres i grups de recerca (producció científica) > Ciències > CREAF (Centre de Recerca Ecològica i d'Aplicacions Forestals)
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