703 research outputs found
Birch Trees - Sources of Biological Ice Nuclei
No full textDr. Hinrich Grothe is an Associate Professor with tenure in the Institute of Materials Chemistry at TU Wien, Austria. Dr. Grothe was trained in chemistry at the Leibnitz University of Hannover, Germany, where he earned a PhD in low-temperature chemistry.
Dr. Grothe's current research interests involve understanding ice nucleation in clouds triggered by biological particles such as pollen, bacteria, and fungi. He is also interested in aerosol chemistry and cloud glaciation processes. Dr. Grothe has been studying ice nuclei on birch pollen. He has shown that these ice nuclei can be washed-off from the grain surface and can be dispersed independently. Moreover, these nucleation macromolecules appear to be abundant on leaves, primary wood, and secondary wood.
Dr. Grothe is an important contributor to the European Geosciences Union (EGU) where he is the science officer of the section Atmospheric Chemistry & Aerosols. Each year, he organizes a session at the EGU General Assembly on atmospheric ice nucleation. He also has organized a number of workshops for early career professionals about the microphysics of ice clouds. His ultimate goal is to find nature's perfect ice nucleus
Morphologien von Partikeln in der Polaren Stratosphäre
No full textDie Morphologien von Aerosolpartikeln haben einen wichtigen Einfluss auf deren Extinktionsspektrum. Die Kenntnis dieser Spektren ist essentiell für die Identifizierung und Strukturaufklärung der Partikel. Dies gilt in besonderem Maße für Polar Stratosphärische Wolkenpartikel, die mit satellitengestützten optischen Methoden untersucht werden. In den hier vorgestellten Laborexperimenten wurden Proben präpariert, deren Phasenzusammensetzung aus Vergleichsexperimenten bereits bekannt war [1-4]. Diese Kryoproben wurden mittels einer Kryo-Transferkammer in ein environmental scanning electron microscope (ESEM) eingebracht und wurden in Temperaturabhängigkeit beobachtet. Der Vorteil dieser Technik besteht darin, dass bei Drücken bis 5 mbar gearbeitet werden kann und so eine Dehydratation der Probe vermieden wird. Für die Hydratphasen Salpetersäuretrihydrat, Salpetersäuredihydrat und deren Mischungen wurden die Morphologien bestimmt [5] und unter Zuhilfenahme der entsprechenden optischen Konstanten wurden die passenden Extinktionsspektren berechnet [6].
[1] Tizek, H.; Knözinger, E.; Grothe, H. "X-ray diffraction studies on nitric acid dihydrate" Phys. Chem. Chem. Phys., 2002 , 4, 5128-5134.
[2] Grothe, H.; Lund Myhre, C.E.; Tizek, H. "Vibrational Spectra of Nitric Acid Dihydrate (NAD)" Vibr. Spectr. 2004, 34, 55-62.
[3] Tizek, H.; Knözinger, E.; Grothe, H. "Formation and Phase Distribution of Nitric Acid Hydrates in the Mole Fraction Range xHNO3 < 0.25: a combined XRD and IR study" Phys. Chem. Chem. Phys. 2004, 6, 972-979.
[4] H. Grothe, C.E. Lund Myhre and C. J. Nielsen "Low-frequency Raman Spectra of Nitric Acid Hydrates" J. Phys. Chem. A 2006, 110, 1, 171-176.
[5] H. Grothe, H. Tizek, D. Waller and D. J. Stokes, The crystallization kinetics and morphology of nitric acid trihydrate, Phys. Chem. Chem. Phys. 2006, 8, 2232-2239.
[6] H. Grothe, H. Tizek and I. K. Ortega "Metastable Nitric Acid Hydrates - Possible Constituents of Polar Stratospheric Clouds?" Faraday Discussion 2007, 137, in print
Investigations of Surface Chemistry on Carbonaceous Particles
No full textThe relevance of carbonaceous particles in atmospheric science is increasing. Reasons
for that are their contribution to the urban aerosol, their toxicological importance and
their impact on the global radiation balance. Particle emissions like soot or secondary
organic aerosols like HULIS (humic like substances) are currently a major topic in atmospheric
research. Physical chemistry provides surface analytical methods for these
particles [1,2,3,4], to understand their relevance as part of the atmospheric gas phase
chemistry.
For these surface investigations Diffuse-Reflectance-Infrared-Fourier-Transform-
Spectroscopy (DRIFTS), Temperature-Programmed-Surface-Reaction-Spectroscopy
using a mass spectrometer (TPSR-MS), Temperature-Programmed-Desorption-Mass-
Spectroscopy (TPD-MS) and Electron-Paramagnetic-Resonance (EPR) Spectroscopy
were applied. All of these methods were used to characterize humic substances and
soot. DRIFTS provides detailed information about formation and transformation of
functional surface groups monitoring the characteristic vibration modes. TPD-MS
shows the thermal stability of these groups and TPSR-MS follows up the reaction behaviour
of these particles with gases of atmospheric relevance. Radicals on the surface
could be studied by EPR Spectroscopy. The combination of these four spectroscopic
methods allowed a detailed understanding of heterogeneous reactions with carbonaceous
surfaces at a molecular level. Investigations were done on i) the heterogeneous
reaction with nitrogen oxides and ii) with reactive halogen compounds. Stability and
reactivity of new formed functional groups could be assigned. Single heterogeneous
reaction mechanism could be clarified.
[1] Muckenhuber H., Grothe H., The heterogeneous reaction between soot and NO2
at elevated temperature, Carbon 44 (2006) 546.
[2] Sadezky A., Muckenhuber H., Grothe H., Niessner R., Pöschl U., Raman microspectroscopy
of soot and related carbonaceous materials: Spectral analysis and
structural information, Carbon 43 (2005) 1731.
[3] Muckenhuber H., Grothe H., The reaction between soot and NO2 - investigation
of functional groups using TPD-MS, Topics in Catalysis 30/31 (2004) 287.
[4] Muckenhuber H., Grothe H., A DRIFTS study of the heterogeneous reaction of
NO2 with carbonaceous materials at elevated temperature, Carbon 45 (2007) 321
Biological Ice Nucleation in the Atmosphere and the Biosphere
No full textFrom the thermodynamic point of view, ice and snow can form already at temperatures slightly below its melting point, i.e. below zero degrees Celsius. Actually, ultrapure, liquid water can be supercooled down to minus forty degrees Celsius without freezing. The reason is a kinetic activation barrier, which hinders the phase transition. However, water impurities, e.g. biological material or organic particles, can lower this activation barrier and can thus catalyze the phase transition. This process is called heterogeneous ice nucleation and it plays an important role in many biological, meteorological and technical processes, e.g. in the formation of atmospheric ice clouds [1].
The most effective ice nucleus is ice itself, since it provides the own hexagonal structure, on which water molecules from the liquid phase can be oriented to form further ice phase. The most effective heterogeneous ice nucleus is the bacterium pseudomonas syringae. The reason is a protein at its outer cell membrane, which exhibits a hexagonal, ice-like structure. Furthermore, many other bacteria, fungal spores, and pollens carry also very effective ice nuclei, many of which in fact are macromolecules.
Macromolecular ice nuclei have for a long time been neglected by atmospheric scientists. However, plants are known by biologists to produce macromolecular ice nuclei as a part of their low-temperature survival strategy. In the past, it has been shown by us that birch pollen exhibit ice nucleation active macromolecules at their surface [2, 3]. These molecules can be washed off from the pollen grains and nucleate ice independently. Only very recently, we found the same ice nuclei also on secondary and primary wood and on leafs of birch trees. The question remains if these biological ice nuclei can be dispersed through the atmosphere and can impact cloud glaciation processes.
[1] T. Bartels-Rausch, V. Bergeron, J. Cartwright, R. Escribano, J. Finney, H. Grothe, P. Gutierrez, J. Haapala, W. Kuhs, J. Pettersson, S. Price, C. Sainz-Dıaz, D Stokes, G. Strazzulla, E. Thomson, H. Trinks, and N. Uras-Aytemiz, Rev. Mod. Phys. 84 (2012)885.
[2] B.G. Pummer, H. Bauer, J. Bernardi, S. Bleicher, and H. Grothe, Atm. Chem. Phys., 12 (2012) 2541.
[3] B.G. Pummer, C. Budke, S. Augustin-Bauditz, D. Niedermeier, L. Felgitsch, C. Kampf, R. Huber, K. Liedl, T. Loerting, T. Moschen, M. Schauperl, M. Tollinger, C. Morris, H. Wex, H. Grothe, U. Pöschl, T. Koop, and J. Fröhlich-Nowoisky, Atm. Chem. Phys. 15 (2015) 4077
Biological Ice Nucleation in the Atmosphere and the Biosphere
No full textFrom the thermodynamic point of view, ice and snow can form already at temperatures slightly below its melting point, i.e. below zero degrees Celsius. Actually, ultrapure, liquid water can be supercooled down to minus forty degrees Celsius without freezing. The reason is a kinetic activation barrier, which hinders the phase transition. However, water impurities, e.g. biological material or organic particles, can lower the activation barrier and can thus catalyze the phase transition. This process is called heterogeneous ice nucleation and it plays an important role in many biological, meteorological and technical processes, e.g. in the formation of atmospheric ice clouds. The most effective ice nucleus is ice itself, since it provides the own hexagonal structure, on which water molecules from the liquid phase can be oriented in order to form further ice phase. The most effective heterogeneous ice nucleus is the bacterium Pseudomonas Syringae. The reason is a protein at its outer cell membrane, which exhibits a hexagonal, icelike structure. Furthermore, fungal spores, pollen, and carbonaceous particles are also very effective ice nuclei [1, 2]. In many cases, the physical and chemical reasons for the ice nucleation activity are understood only rudimentary. Thus, the search for the perfect ice nucleus is still an open issue [3].The talk will explain the fundamentals of heterogeneous ice nucleation and will give examples from the field and the laboratory.
[1] B.G. Pummer, H. Bauer, J. Bernardi, S. Bleicher, and H. Grothe, Atm. Chem. Phys., 12 2541 (2012).
[2] B.G. Pummer, C. Budke, S. Augustin-Bauditz, D. Niedermeier, L. Felgitsch, C. Kampf, R. Huber, K. Liedl, T. Loerting, T. Moschen, M. Schauperl, M. Tollinger, C. Morris, H. Wex, H. Grothe, U. Pöschl, T. Koop, and J. Fröhlich-Nowoisky, Atm. Chem. Phys. 15 4077 (2015).
[3] T. Bartels-Rausch, V. Bergeron, J. Cartwright, R. Escribano, J. Finney, H. Grothe, P. Gutierrez, J. Haapala, W. Kuhs, J. Pettersson, S. Price, C. Sainz-Diaz, D Stokes, G. Strazzulla, E. Thomson, H. Trinks, and N. Uras-Aytemiz, Rev. Mod. Phys. 84 885 (2012)
Birch Trees - Sources of Ice Nucleating Macromolecules
No full textPredictive understanding of atmospheric ice nucleation presents one of the grand challenges in atmospheric sciences. In the last years airborne biological particles have been investigated for their ice nucleation ability and potential explanation of observed ice crystal number concentrations and cloud glaciation. Hinrich studies experimentally biological materials as potential ice nucleating particles. His group discovered that water in contact with airborne pollen can retain efficient ice nucleating macromolecules representing a new kind of ice nuclei that could be ubiquitous in the atmosphere, previously not considered
Spectroscopic Studies on Nitric Acid Hydrates
No full textMixtures of nitric acid hydrates and water ice are important constituents of solid Cirrus cloud particles. Due to the phase diagram only hexagonal ice and nitric acid trihydrate
should have a reasonable thermodynamic stability and are commonly observed. However, a number of metastable modifications might also exist: NAD, -NAT, and cubic ice. The persistence of these metastable compounds remains uncertain and has not
been proofed yet. In the laboratory we have developed a model procedure in order to prepare and investigate
all hydrates and ice mixtures. The investigation methods are X-ray diffraction [1, 2], FTIR spectroscopy [3], Raman spectroscopy [4, 5] and Environmental SEM [6, 7]. Only recently, we have also applied Inelastic Neutron Scattering. The aim was to verify the phase composition by diffraction and to collect the spectroscopic data,
which are needed for interpretation of field measurements and aerosol chamber experiments. Here, the morphology of the particles has to be considered, since it can have an important impact on the respective extinction spectra.
[1] H. Tizek, E. Knözinger, H. Grothe, PCCP 4 (2002), 5128.
[2] H. Tizek, E. Knözinger, H. Grothe, PCCP 6 (2004), 972.
[3] H. Grothe, C.E. Lund Myhre, H. Tizek, Vibr. Spectr. 34 (2004), 55.
[4] H. Grothe, C.E. Lund Myhre, C.J. Nielsen, JPC A 110 (2006), 110, 171.
[5] R. Escribano, D. Fernández-Torre, V. Herrero, B. Martín-Llorente, B. Maté, I.
Ortega, H. Grothe, Vibr. Spectr. 43 (2007), 254.
[6] H. Grothe, H. Tizek, D Waller, D Stokes, PCCP 8 (2006), 2232.
[7] H. Grothe, H. Tizek and I. K. Ortega, Faraday Discussion 137 (2008) 223
Biological Ice Nucleation
No full textBiological Ice Nucleation
Magdalena Bichler a, Laura Felgitsch a, Verena Seidl-Seiboth b, Hinrich Grothe a
a
Institute of Materials Chemistry,
Vienna University of Technology,
Getreidemarkt 9/BC/01, 1060 Wien
b
Institute of Chemical Engineering,
Vienna University of Technology,
Gumpendorferstraße 1a, 1060 Wien
According to Huffman et al. [1] a burst of biological ice nuclei (IN)can be found over woodlands during and after rain events. The origin of these particles can be e.g. bacteria(e.g.
Pseudomonas syringae), fungi (e.g. Fusarium acuminatum spores), and(decayed) plant litter. Previous investigations in our group [2] showed that both pollen and pollen washing water from plants originating from the northern timberline show ice nucleation activity. These facts suggest that other parts of the plants might also act as IN due to their cold protection and cold tolerance mechanisms. We extended our investigation to other parts of the plants and further biological materials such as both waterinteracting and structural polysaccharides, like pectin and chitin, as well as chemical modifications of these polysaccharides.
Of particular interest concerning plant parts are berries, such as sea buckthorn and blackcurrant. We examined the ice nucleation activity of both juices of berries found near the northern timberline and extracts of these berries.
____
[1] Huffman et al., Atmos. Chem. Phys., 13, 6151-6164, 2013
[2] Pummer et al., Atmos. Chem. Phys., 12, 2541-2550, 201
The Surface Chemistry of Soot and its Impact on Atmospheric Processes
No full textSoot particles are ubiquitous in the Earth's troposphere and are defined as solid primary, carbonaceous products from an incomplete combustion process of natural or anthropogenic origin. It is reported that graphite-like carbon particles could catalyze the phase transition from liquid water into ice crystals even though they are naturally hydrophobic. Soot may become partially hydrated by oxidation or by deposition of water- soluble species present in air, such as sulphuric acid and nitric acid and therefore may increase the ice nucleation activity (INA). Current laboratory studies of the INA of soot gave contradictory results indicating that soot particles might be too complicated to be adequately described in its full complexity regarding heterogeneous ice nucleation. An adequate parameterization of particles' surface properties as well as the time dependence of the ice nucleation process is still under discussion. Graphene and their modifications offer due to their characteristics simplified model systems. Theoretical calculations of graphene revealed the impact of e.g. hydrophobicity and crystallinity on the INA. In this work we are presenting investigations of the INA of different types of graphene and graphene oxides as well as of chemically treated soot particles. Immersion drop freezing experiments as well as comprehensive analytic analyses like X-ray photoelectron-, Raman spectroscopy [1] and transmission electron microscopy were performed.
[1] A. Sadezky, H. Muckenhuber, H. Grothe, R. Niessner, U. Pöschl, Carbon 43 (2005) 1731
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