[Zurück]

B. Sierau, C. Oehm, O. Möhler, I. Steinke, A. Roth, F. Freutel, J. Schneider, B. G. Pummer, H. Grothe, M. Abegglen, M. Kohn, A. Welti, O. Stetzer, U. Lohmann:
"Towards the identification of individual biological particles as ice nuclei using single particle mass spectrometry";
Vortrag: ESF-Workshop - Atmospheric Ice Nucleation, Wien (eingeladen); 06.04.2013 - 07.04.2013; in: "Workshop - Atmospheric Ice Nucleation - Book of Abstracts", (2013).

Aerosols of biological origin such as bacteria, spores and pollen are gaining increasing attention in the research field of cloud microphysics. Their ability to act as heterogeneous ice nuclei has been shown in various laboratory studies; however, their atmospheric relevance in aerosol-cloud interactions is debatable. This is partly due to the lack of understanding of the actual processes driving water and ice nucleation on biological particles (e.g. Möhler et al.,
2008), but also the challenging and unambiguous identification of these particles in the field.
This study focuses on mass spectrometric measurements of the chemical composition of laboratory generated bacterial cells and their residues, pollen, pollen fragments, and pollen washing water containing fragments of pollen and/or substances washed of from pollen that are expected to play a major role in the ice nucleating process involving pollen (Pummer et al., 2012; Augustin et al., 2012). For analysis, a TSI Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used - a type of laser ablation instrument that is regularly applied for the in-situ detection and identification of ice crystal residuals (e.g. Pratt et al., 2009). The investigated biological particles are the bacterial species Pseudomonas syringae
and Pseudomonas fluorescence, as well as birch and pine pollen and their washing waters, and Lycophyte spores. Except the Lycophyte spores, all species have been shown to be ice nucleation active.
"Fingerprints" usable for the identification of bacteria, spores and pollen by aerosol mass spectrometry are discussed and compared with mass spectra from real dust and soil samples that might have been exposed to or are internally or externally mixed with such biological
material. Moreover, the findings are referenced to ambient spectra collected by identical instruments in the field and in the lab, and also to spectra referred to as "bioaerosols" in the ESF Workshop - Atmospheric Ice Nucleation literature (e.g. Fergenson et al., 2004). The results will be put into perspective for the identification of biological particles as IN.

mass spectrometry, atmospheric aerosol, pollen