Molecular Surface Chemistry on Birch Pollen

Abstract

MOLECULAR SURFACE CHEMISTRY ON BIRCH POLLEN

Laura Felgitsch1, Magdalena Bichler1, Thomas Häusler1, Victor U. Weiss2, Martina Marchetti-Deschmann2, Günter Allmaier2, Hinrich Grothe1

1 Vienna University of Technology, Institute of Materials Chemistry, Vienna, Austria 2 Vienna University of Technology, Institute of Chemical Technologies and Analytics, Vienna, Austria

Pollen grains of various species have been found to act as CCN (cloud condensation nuclei) and IN (ice nuclei), granting them the ability to influence the Earth's water cycle and the radiation balance. These properties are not exclusively bound to the pollen grains alone but to molecular compounds that can be easily washed off from their surfaces with water. Pollen themselves have not been seen as important as CCN or IN for higher altitudes due to their big size and therefore rapid sinking velocity. The surface-released substances on the other hand are able to form aerosols much smaller than the pollen grains or get attached to other aerosols leading to a longer lifespan in the atmosphere and higher reachable altitudes. Huffman et al. (2013) have determined that the IN concentration over woodlands increases significantly during and after rain, which supports the theory that the role of pollen has been underestimated. We work with various analytic methods to elucidate the structure of those molecules or aggregates and to describe the underlying principle of generation. Therefore we use instrumental analytic techniques as Nuclear Magnetic Resonance spectroscopy (NMR), Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS), and Gas-phase Electrophoretic Mobility Molecular Analysis (GEMMA). Also standard techniques as various chromatographic and electrophoretic separation techniques and solvent extraction are applied. We state here that this substance might be due to the aggregation of small molecules, with agglomerates showing a specific surface structure. Our results indicate that the substance is amphiphilic in character leading finally to micelle formation.

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