[Zurück]

L. Felgitsch, M. Mayr, T.M. Seifried, P. Winkler, D. G. Schmale III, H. Grothe:
"Birch Trees as Sources of Ice Nucleating Macromolecules";
Vortrag: ATMOCHEMBIO, Clermont-Ferrand; 19.06.2017 - 21.06.2017.

Atmospheric ice nucleation is an important process in nature and climate with a direct influence on the radiation balance of our planet via ice cloud formation. Many substances have been found to show ice nucleation activity, however the relevance of the different substances is still under discussion. A major group of ice nuclei (IN) are of biological origin. IN have been found in a vast range of life forms, including bacteria, fungi, insects, plants, and mammals. Thus, IN are easily accessible and widespread in nature. Further, biological IN trigger the highest freezing temperatures observed in heterogeneous ice nucleation.

Recent findings from our working group have shown that birch pollen release ice nuclei in the macromolecular size range [1]. Particles of this size exhibit a high atmospheric lifespan and a tendency to agglomerate or become attached to other particles. They are available for cloud formation processes and their number is orders of magnitude higher than the original pollen grains. Further, we found a high resistance towards oxidation, indicating that those IN will stay active for a long time if they become airborne.

We are able to show that tissues throughout a birch tree may act as a huge source of IN. Macromolecular IN have been found in primary and secondary wood as well as on leaves, bark and in the trunk. We found IN to be directly extractable from the tissue surface, making them easily available for the surrounding environment. Analysis of the trunk showed a concentration gradient with highest concentrations in the outermost layers.


Acknowledgements
The authors would like to thank the TU Wien, the FWF -Austrian Science Fund (Project No P 26040), and the FFG - Austrian Research Promotion Agency (Project No 850689) for financial support.

References
[1] B. Pummer, H. Bauer, J. Bernardi, S. Bleicher, H. Grothe, Atmos. Chem. Phys., 2012, 12, 2541 - 2550.

ice nucleation, birch