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| Titel |
Ozone fumigation under dark/light conditions of Norway Spruce (Picea Abies) and Scots Pine (Pinus Sylvestris) |
| VerfasserIn |
Eva Canaval, Werner Jud, Armin Hansel |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111180
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| Publikation (Nr.) |
 EGU/EGU2015-11267.pdf |
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| Zusammenfassung |
| Norway Spruce (Picea abies) and Scots Pine (Pinus sylvestris) represent dominating tree
species in the northern hemisphere. Thus, the understanding of their ozone sensitivity in the
light of the expected increasing ozone levels in the future is of great importance. In our
experiments we investigated the emissions of volatile organic compounds (VOCs) of 3-4 year
old Norway Spruce and Scots Pine seedlings under ozone fumigation (50-150 ppbv) and
dark/light conditions.
For the experiments the plants were placed in a setup with inert materials including a glass
cuvette equipped with a turbulent air inlet and sensors for monitoring a large range of
meteorological parameters. Typical conditions were 20-25°C and a relative humidity of 70-90
% for both plant species. A fast gas exchange rate was used to minimize reactions of ozone in
the gas phase. A Switchable-Reagent-Ion-Time-of-Flight-MS (SRI-ToF-MS) was used to
analyze the VOCs at the cuvette outlet in real-time during changing ozone and light levels.
The use of H3O+ and NO+ as reagent ions allows the separation of certain isomers (e.g.
aldehydes and ketones) due to different reaction pathways depending on the functional
groups of the molecules.
Within the Picea abies experiments the ozone loss, defined as the difference of the ozone
concentration between cuvette inlet and outlet, remained nearly constant at the
transition from dark to light. This indicates that a major part of the supplied ozone
is depleted non-stomatally. In contrast the ozone loss increased by 50 % at the
transition from dark to light conditions within Pinus sylvestris experiments. In this
case the stomata represent the dominant loss channel. Since maximally 0.1% of
the ozone loss could be explained by gas phase reactions with monoterpenes and
sesquiterpenes, we suggest that ozone reactions on the surface of Picea abies represent
the major sink in this case and lead to an light-independent ozone loss. This is
supported by the fact that we detected a broad range of unidentified oxygenated
ozonolysis products and their fragments, whose amount exceed by far the detected
loss of BVOCs under ozone exposure. However, the observed products are not
attributable to neither green leaf volatiles nor to other known volatile precursors.
Furthermore Picea abies emits a smaller amount of ozone induced green leaf volatiles than
Pinus sylvestris. Based on this results we can explain the higher ozone tolerance of
Picea abies, which has been observed before. A likely reason for the differences in
stomatal and surface ozone loss on the investigated plants are differences in the
amount and kind of unsaturated semi-volatile compounds on the needle surface. |
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