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| Titel |
Annual cycle of volatile organic compound exchange between a boreal pine forest and the atmosphere |
| VerfasserIn |
P. Rantala, J. Aalto, R. Taipale, T. M. Ruuskanen, J. Rinne |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 19 ; Nr. 12, no. 19 (2015-10-09), S.5753-5770 |
| Datensatznummer |
250118119
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| Publikation (Nr.) |
 copernicus.org/bg-12-5753-2015.pdf |
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| Zusammenfassung |
| Long-term flux measurements of volatile organic compounds (VOC) over boreal
forests are rare, although the forests are known to emit considerable amounts
of VOCs into the atmosphere. Thus, we measured fluxes of several VOCs and
oxygenated VOCs over a Scots-pine-dominated boreal forest semi-continuously
between May 2010 and December 2013. The VOC profiles were obtained with a
proton transfer reaction mass spectrometry, and the fluxes were calculated
using vertical concentration profiles and the surface layer profile method
connected to the Monin-Obukhov similarity theory. In total fluxes that
differed significantly from zero on a monthly basis were observed for 13 out
of 27 measured masses. Monoterpenes had the highest net emission in all seasons
and statistically significant positive fluxes were detected from March until
October. Other important compounds emitted were methanol, ethanol+formic
acid, acetone and isoprene+methylbutenol. Oxygenated VOCs showed also deposition fluxes
that were statistically different from zero. Isoprene+methylbutenol and
monoterpene fluxes followed well the traditional isoprene algorithm and the
hybrid algorithm, respectively. Emission potentials of monoterpenes were
largest in late spring and autumn which was possibly driven by growth processes
and decaying of soil litter, respectively. Conversely, largest emission
potentials of isoprene+methylbutenol were found in July. Thus, we concluded
that most of the emissions of m/z 69 at the site consisted of isoprene
that originated from broadleaved trees. Methanol had deposition fluxes
especially before sunrise. This can be connected to water films on surfaces.
Based on this assumption, we were able to build an empirical algorithm for
bi-directional methanol exchange that described both emission term and
deposition term. Methanol emissions were highest in May and June and
deposition level increased towards autumn, probably as a result of increasing
relative humidity levels leading to predominance of deposition. |
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