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| Titel |
Seasonal cycles of biogenic volatile organic compound fluxes and concentrations in a California citrus orchard |
| VerfasserIn |
S. Fares, J.-H. Park, D. R. Gentner, R. Weber, E. Ormeño, J. Karlik, A. H. Goldstein |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 20 ; Nr. 12, no. 20 (2012-10-29), S.9865-9880 |
| Datensatznummer |
250011540
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| Publikation (Nr.) |
 copernicus.org/acp-12-9865-2012.pdf |
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| Zusammenfassung |
| Orange trees are widely cultivated in Mediterranean climatic regions where
they are an important agricultural crop. Citrus have been characterized as
emitters of volatile organic compounds (VOC) in chamber studies under
controlled environmental conditions, but an extensive characterization at
field scale has never been performed using modern measurement methods, and is
particularly needed considering the complex interactions between the orchards
and the polluted atmosphere in which Citrus is often cultivated. For one
year, in a Valencia orange orchard in Exeter, California, we measured fluxes
using PTRMS (Proton Transfer Reaction Mass Spectrometer) and eddy covariance
for the most abundant VOC typically emitted from citrus vegetation: methanol,
acetone, and isoprenoids. Concentration gradients of additional oxygenated
and aromatic compounds from the ground level to above the canopy were also
measured. In order to characterize concentrations of speciated biogenic VOC
(BVOC) in leaves, we analyzed leaf content by GC-MS (Gas Chromatography –
Mass Spectrometery) regularly throughout the year. We also characterized in
more detail concentrations of speciated BVOC in the air above the orchard by
in-situ GC-MS during a few weeks in spring flowering and summer periods. Here
we report concentrations and fluxes of the main VOC species emitted by the
orchard, discuss how fluxes measured in the field relate to previous studies
made with plant enclosures, and describe how VOC content in leaves and
emissions change during the year in response to phenological and
environmental parameters. The orchard was a source of monoterpenes and
oxygenated VOC. The highest emissions were observed during the springtime
flowering period, with mid-day fluxes above 2 nmol m−2 s−1 for
methanol and up to 1 nmol m−2 s−1 for acetone and monoterpenes.
During hot summer days emissions were not as high as we expected considering
the known dependence of biogenic emissions on temperature. We provide
evidence that thickening of leaf cuticle wax content limited gaseous
emissions during the summer. |
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