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| Titel |
Emissions of isoprenoids and oxygenated biogenic volatile organic compounds from a New England mixed forest |
| VerfasserIn |
K. A. McKinney, B. H. Lee, A. Vasta, T. V. Pho, J. W. Munger |
| 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 ; 11, no. 10 ; Nr. 11, no. 10 (2011-05-24), S.4807-4831 |
| Datensatznummer |
250009758
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| Publikation (Nr.) |
 copernicus.org/acp-11-4807-2011.pdf |
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| Zusammenfassung |
| Fluxes of biogenic volatile organic compounds, including isoprene,
monoterpenes, and oxygenated VOCs measured above a mixed forest canopy in
central Massachusetts during the 2005 and 2007 growing seasons are reported.
Mixing ratios were measured using proton transfer reaction mass spectrometry
(PTR-MS) and fluxes computed by the disjunct eddy covariance technique.
Isoprene was by far the predominant BVOC emitted at this site, with summer
mid-day average fluxes of 5.3 and 4.4 mg m−2 hr−1 in 2005 and 2007,
respectively. In comparison, mid-day average fluxes of monoterpenes were
0.21 and 0.15 mg m−2 hr−1 in each of these years. On short times
scales (days), the diel pattern in emission rate compared well with a
standard emission algorithm for isoprene. The general shape of the seasonal
cycle and the observed decrease in isoprene emission rate in early September
was, however, not well captured by the model. Monoterpene emission rates
exhibited dependence on light as well as temperature, as determined from the
improved fit to the observations obtained by including a light-dependent
term in the model. The mid-day average flux of methanol from the canopy was
0.14 mg m−2 hr−1 in 2005 and 0.19 mg m−2 hr−1 in 2007, but
the maximum flux was observed in spring (29 May 2007), when the flux reached
1.0 mg m−2 hr−1. This observation is consistent with enhanced
methanol production during leaf expansion. Summer mid-day fluxes of acetone
were 0.15 mg m−2 hr−1 during a short period in 2005, but only 0.03
mg m−2 h−1 averaged over 2007. Episodes of negative fluxes of
oxygenated VOCs, particularly acetone, were observed periodically,
especially in 2007. Thus, deposition within the canopy could help explain
the low season-averaged flux of acetone in 2007. Fluxes of species of
biogenic origin at mass-to-charge ($m/z$) ratios of 73
(0.05 mg m−2 hr−1 in 2005; 0.03 mg m−2 hr−1 in 2007) and 153
(5 μg m−2 hr−1 in 2007), possibly corresponding to methyl ethyl ketone and an
oxygenated terpene or methyl salicylate, respectively, were also observed. |
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