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| Titel |
Methyl halide fluxes from tropical plants under controlled radiation and temperature regimes |
| VerfasserIn |
Emanuel Blei, Yoko Yokouchi, Takuya Saito, Susumu Nozoe |
| 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 |
250108253
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| Publikation (Nr.) |
 EGU/EGU2015-7999.pdf |
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| Zusammenfassung |
| Methyl halides (CH3Cl, CH3Br, CH3I) contribute significantly to the halogen burden of the
atmosphere and have the potential to influence the stratospheric ozone layer through their
catalytic effect in the Chapman cycle. As such they have been studied over the
years, and many plants and biota have been examined for their potential to act as a
source of these gases. One of the potentially largest terrestrial sources identified
was tropical vegetation such as tropical ferns and Dipterocarp trees. Most of these
studies concentrated on the identification and quantification of such fluxes rather
than their characteristics and often the chambers used in these studies were either
opaque or only partially transparent to the full solar spectrum. Therefore it is not
certain to which degree emissions of methyl halides are innate to the plants and
how much they might vary due to radiation or temperature conditions inside the
enclosures.
In a separate development it had been proposed that UV-radiation could cause live plant
materials to be become emitters of methane even under non-anoxic conditions. As
methane is chemically very similar to methyl halides and had been proposed to be
produced from methyl-groups ubiquitously found in plant cell material there is a
relatively good chance that such a production mechanism would also apply to methyl
halides.
To test whether radiation can affect elevated emissions of methyl halides from plant
materials and to distinguish this from temperature effects caused by heat build-up in
chambers a set of controlled laboratory chamber enclosures under various radiation and
temperature regimes was conducted on four different tropical plant species (Magnolia
grandiflora, Cinnamonum camphora, Cyathea lepifera, Angiopteris lygodiifolia), the
latter two of which had previously been identified as strong methyl halide emitters.
Abscised leaf samples of these species were subjected to radiation treatments such
UV-B, UV-A and broad spectrum radiation similar to natural sunlight without the
UV–component and the emissions were compared to dark enclosures. Parallel to this
temperature effects were studied in dark enclosures as well. The presentation will discuss
the outcome of these experiments and what conclusions can be drawn from them. |
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