Gysel, Martin
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Martin Gysel
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- PublikationThe influence of small aerosol particles on the properties of water and ice clouds(Royal Society of Chemistry, 09.08.2008) Choularton, Thomas W.; Bower, Keith N.; Weingartner, Ernest; Crawford, Ian; Coe, Hugh; Gallagher, Martin W.; Flynn, Michael; Crosier, Jonathan; Connolly, Paul; Targino, Admir Créso; Alfarra, M. Rami; Baltensperger, Urs; Sjögren, Staffan; Verheggen, Bart; Cozic, Julie; Gysel, Martin [in: Faraday Discussions]In this paper, results are presented of the influence of small organic- and soot-containing particles on the formation of water and ice clouds. There is strong evidence that these particles have grown from nano particle seeds produced by the combustion of oil products. Two series of field experiments are selected to represent the observations made. The first is the CLoud-Aerosol Characterisation Experiment (CLACE) series of experiments performed at a high Alpine site (Jungfraujoch), where cloud was in contact with the ground and the measuring station. Both water and ice clouds were examined at different times of the year. The second series of experiments is the CLOud Processing of regional Air Pollution advecting over land and sea (CLOPAP) series, where ageing pollution aerosol from UK cities was observed, from an airborne platform, to interact with warm stratocumulus cloud in a cloud-capped atmospheric boundary layer. Combining the results it is shown that aged pollution aerosol consists of an internal mixture of organics, sulfate, nitrate and ammonium, the organic component is dominated by highly oxidized secondary material. The relative contributions and absolute loadings of the components vary with location and season. However, these aerosols act as Cloud Condensation Nuclei (CCN) and much of the organic material, along with the other species, is incorporated into cloud droplets. In ice and mixed phase cloud, it is observed that very sharp transitions (extending over just a few metres) are present between highly glaciated regions and regions consisting of supercooled water. This is a unique finding; however, aircraft observations in cumulus suggest that this kind of structure may be found in these cloud types too. It is suggested that this sharp transition is caused by ice nucleation initiated by oxidised organic aerosol coated with sulfate in more polluted regions of cloud, sometimes enhanced by secondary ice particle production in these regions.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationHygroscopic growth and water uptake kinetics of two-phase aerosol particles consisting of ammonium sulfate, adipic and humic acid mixtures(Elsevier, 02/2007) Sjögren, Staffan; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs; Cubison, Michael J.; Coe, Hugh; Zardini, Alessandro A.; Marcolli, Claudia; Krieger, Ulrich K.; Peter, Thomas [in: Journal of Aerosol Science]The hygroscopic growth of solid aerosol particles consisting of mixtures of ammonium sulfate and either adipic acid or Aldrich humic acid sodium salt was characterized with a hygroscopicity tandem differential mobility analyzer and an electrodynamic balance. In particular, the time required for the aerosol particle phase and the surrounding water vapor to reach equilibrium at high relative humidity (RH) was investigated. Depending on the chemical composition of the particles, residence times of > 40 s were required to reach equilibrium at 85% RH, yielding up to a 7% reduction in the measured hygroscopic growth factors from measurements at 4 s residence time compared to measurements at equilibrium. We suggest that the solid organic compound, when present as the dominant component, encloses the water-soluble inorganic salt in veins and cavities, resulting in the observed slow water uptake. Comparison with predictions from the Zdanovskii-Stokes-Robinson relation shows enhanced water uptake of the mixed particles. This is explained with the presence of the salt solution in veins resulting in a negative curvature of the solution meniscus at the opening of the vein. In conclusion, it is important for studies of mixtures of water soluble compounds with insoluble material to allow for sufficient residence time at the specified humidity to reach equilibrium before the hygroscopicity measurements.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationSecondary organic aerosols from anthropogenic and biogenic precursors(Royal Society of Chemistry, 2005) Baltensperger, Urs; Kalberer, Markus; Dommen, Josef; Paulsen, Dwane; Alfarra, M. Rami; Coe, Hugh; Fisseha, Rebeka; Gascho, Astrid; Gysel, Martin; Nyeki, Stephan; Sax, Mirjam; Steinbacher, Martin; Prévôt, André S.H.; Sjögren, Staffan; Weingartner, Ernest; Zenobi, Renato [in: Faraday Discussions]Secondary organic aerosol (SOA) formation from the photooxidation of an anthropogenic (1,3,5-trimethylbenzene) and a biogenic (α-pinene) precursor was investigated at the new PSI smog chamber. The chemistry of the gas phase was followed by proton transfer reaction mass spectrometry, while the aerosol chemistry was investigated with aerosol mass spectrometry, ion chromatography, laser desorption ionization mass spectrometry, and infrared spectroscopy, along with volatility and hygroscopicity studies. Evidence for oligomer formation for SOA from both precursors was given by an increasing abundance of compounds with a high molecular weight (up to 1000 Da) and by an increasing thermal stability with increasing aging time. The results were compared to data obtained from ambient aerosol samples, revealing a number of similar features.01A - Beitrag in wissenschaftlicher Zeitschrift