lnstitut für Sensorik und Elektronik
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Publikation Coating of soot and (NH4)2SO4 particles by ozonolysis products of α-pinene(Elsevier, 10/2003) Saathoff, Harald; Naumann, Karl-Heinz; Schnaiter, Martin; Schöck, Werner; Möhler, Ottmar; Schurath, Ulrich; Weingartner, Ernest; Gysel, Martin; Baltensperger, UrsThe ozonolysis of α-pinene in a large aerosol chamber was used to generate secondary organic aerosol (SOA) mass by homogeneous nucleation, or by heterogeneous nucleation, either on soot, or on (NH4)2SO4 seed aerosols. The rate of the α-pinene + ozone reaction and the aerosol yield of ∼19% are in good agreement with literature data. The organic coating of soot particles leads to a compaction of the fractal agglomerates expressed by an increase in fractal dimension from 1.9 to 2.1 for Diesel soot, and from 2.0 to 2.3 for spark generated “Palas” soot. The dielectric coating of the soot particles with SOA layers between 2 to 11 nm gives rise to a substantial enhancement of their single scattering albedo, from about 0.2 to 0.5, and increases the effective absorption coefficients of both soot types by ca. 30%. The coating of both soot types increases the hygroscopic growth factors (HGF) to values close below the HGF measured for pure SOA material d/d0∼1:12 at 90% RH.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Properties of jet engine combustion particles during the PartEmis experiment: Hygroscopicity at subsaturated conditions(Wiley, 06.06.2003) Gysel, Martin; Nyeki, Stephan; Weingartner, Ernest; Baltensperger, Urs; Giebl, Heinrich; Hitzenberger, Regina; Petzold, Andreas; Wilson, C. W.Hygroscopic properties of combustion particles were measured online with a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) during PartEmis jet engine combustor experiments. The combustor was operated at old and modern cruise conditions with fuel sulfur contents (FSC) of 50, 410 and 1270 μg/g, and hygroscopic growth factors (HGF) of particles with different dry diameters were investigated at relative humidities RH ≤ 95%. HGFs increased strongly with increasing FSC (HGF[95% RH, 50 nm, modern cruise] = 1.01 and 1.16 for low and high FSC, respectively), and decreased with increasing particle size at fixed FSC, whereas no significant difference was detected between old and modern cruise. HGFs agreed well with a two-parameter theoretical model which provided an estimate of the sulfuric acid content of dry particles, indicating a nearly linear dependence on FSC.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Properties of jet engine combustion particles during the PartEmis experiment. Hygroscopic growth at supersaturated conditions(Wiley, 31.07.2003) Hitzenberger, Regina; Giebl, Heinrich; Petzold, Andreas; Gysel, Martin; Nyeki, Stephan; Weingartner, Ernest; Baltensperger, Urs; Wilson, C. W.During the EU Project PartEmis, the microphysical properties of aircraft combustion aerosol were investigated. This study is focused on the ability of exhaust aerosols to act as cloud condensation nuclei (CCN). The combustor was operated at two different conditions representing old and modern aircraft engine technology. CCN concentrations were measured with the University of Vienna CCN counter [Giebl et al., 2002] at supersaturations around 0.7%. The activation ratio (fraction of CCN in total aerosol) depended on the fuel sulphur content (FSC) and also on the operation conditions. CCN/CN ratios increased from 0.93 through 1.43 to 5.15*10ˉ³ (old cruise conditions) and 0.67 through 3.04 to 7.94*10ˉ³ (modern cruise conditions) when FSC increased from 50 through 410 to1270 μg/g. The activation behaviour was modelled using classical theories and with a semi-empirical model [Gysel et al., 2003] based on measured hygroscopicity of the aerosol under subsaturated conditions, which gave the best agreement.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Properties of jet engine combustion particles during the PartEmis experiment. Microphysics and Chemistry(Wiley, 15.07.2003) Petzold, Andreas; Stein, Claudia; Nyeki, Stephan; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs; Giebl, Heinrich; Hitzenberger, Regina; Döpelheuer, Andreas; Vrchoticky, Susi; Puxbaum, Hans; Johnson, M.; Hurley, Chris D.; Marsh, Richard; Wilson, Chris W.The particles emitted from an aircraft engine combustor were investigated in the European project PartEmis. Measured aerosol properties were mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, and cloud condensation nuclei (CCN) activation potential. The combustor operation conditions corresponded to modern and older engine gas path temperatures at cruise altitude, with fuel sulphur contents (FSC) of 50, 410, and 1270 μg/g. Operation conditions and FSC showed only a weak influence on the microphysical aerosol properties, except for hygroscopic and CCN properties. Particles of size D ≥ 30 nm were almost entirely internally mixed. Particles of sizes D < 20 nm showed a considerable volume fraction of compounds that volatilise at 390 K (10–15%) and 573 K (4–10%), while respective fractions decreased to <5% for particles of size D ≥ 50 nm.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Hygroscopicity of aerosol particles at low temperatures. 1. New low-temperature H-TDMA instrument. setup and first applications(American Chemical Society, 22.11.2001) Weingartner, Ernest; Gysel, Martin; Baltensperger, UrsA hygroscopicity tandem differential mobility analyzer (H-TDMA) is described that allows a fast and accurate determination of the water uptake by submicrometer aerosol particles at temperatures below 0 °C. To avoid volatilization of semivolatile particles, the humidification works without heating the gas stream, and the gas-phase composition is not changed during the analysis. The applied scanning mobility analysis allows a fast and accurate measurement of the humidogram, but care has to be taken with too high scanning velocities leading to artifacts in the particle size measurement. During a field campaign at a high-alpine site (Jungfraujoch, 3580 m above sea level), humidograms of free tropospheric particles were measured at T = −10 °C. The hygroscopic growth of these particles was characterized by monomodal growth distributions, which means that in the observed size range (dry particle diameters (Do) = 50−250 nm) the free tropospheric aerosol was to a large extent internally mixed. No distinct deliquescence was observed, indicating that the multicomponent aerosol particles are present in a liquid state even at a low relative humidity (RH) <10%. At RH 85%, average hygroscopic growth factors of 1.44, 1.49, and 1.53 were measured for Do = 50, 100, and 250 nm. The estimated soluble volume fraction of the particles in the observed size range was found to be 0.79, 0.86, and 0.91, respectively.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Hygroscopicity of aerosol particles at low temperatures. 2. Theoretical and experimental hygroscopic properties of laboratory generated aerosols(American Chemical Society, 21.11.2001) Gysel, Martin; Weingartner, Ernest; Baltensperger, UrsA Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) system has been used to measure hygroscopic growth curves and deliquescence relative humidities (DRH) of laboratory generated (NH4)2SO4, NaCl, and NaNO3 particles at temperatures T = 20 °C and −10 °C. Good agreement (better than 3.5%) between measured growth curves and Köhler theory was found using empirical temperature and concentration dependent values for water activity, solution density, and surface tension. The measured growth curves only experience a small temperature dependence in the observed temperature range. Therefore, to a first approximation, it is possible to neglect the temperature dependence of the water activity for theoretical calculations in the temperature range −10 °C < T < 25 °C. The small differences between experiment and theory, which were predominantly observed for NaCl particles, are probably caused by a small amount of water adsorbed on the “dry” crystals. It was also observed that these particles experience a significant restructuring at relative humidity RH < DRH, which was also taken into account for a comparison with theoretical curves. If salt particles are used for instrument calibration, precautions regarding the dry particle diameter have to be taken.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Hygroscopic properties of submicrometer atmospheric aerosol particles measured with H-TDMA instruments in various environments - a review(Stockholm University Press, 01.01.2008) Swietlicki, Erik; Hansson, Hans-Christen; Hämeri, Kaarle; Svenningsson, Birgitta; Massling, Andreas; McFiggans, Gordon; McMurry, Peter H.; Petäjä, Tuukka; Tunved, Peter; Gysel, Martin; Topping, David; Weingartner, Ernest; Baltensperger, Urs; Rissler, Jenny; Wiedensohler, Alfred; Kulmala, MarkkuThe hygroscopic properties play a vital role for the direct and indirect effects of aerosols on climate, as well as the health effects of particulate matter (PM) by modifying the deposition pattern of inhaled particles in the humid human respiratory tract. Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA) instruments have been used in field campaigns in various environments globally over the last 25 yr to determine the water uptake on submicrometre particles at subsaturated conditions. These investigations have yielded valuable and comprehensive information regarding the particle hygroscopic properties of the atmospheric aerosol, including state of mixing. These properties determine the equilibrium particle size at ambient relative humidities and have successfully been used to calculate the activation of particles at water vapour supersaturation. This paper summarizes the existing published H-TDMA results on the sizeresolved submicrometre aerosol particle hygroscopic properties obtained from ground-based measurements at multiple marine, rural, urban and free tropospheric measurement sites. The data is classified into groups of hygroscopic growth indicating the external mixture, and providing clues to the sources and processes controlling the aerosol. An evaluation is given on how different chemical and physical properties affect the hygroscopic growth.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Hygroscopic 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, ThomasThe 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 ZeitschriftPublikation Hygroscopic properties of water-soluble matter and humic-like organics in atmospheric fine aerosol(Copernicus, 22.01.2004) Gysel, Martin; Weingartner, Ernest; Nyeki, Stephan; Paulsen, Dwane; Baltensperger, Urs; Galambos, Ildikó; Kiss, GyulaAmbient continental-rural fine aerosol (K-puszta, Hungary, PM1.5) was sampled on quartz fibre filters in winter and summer 2001. Water-soluble matter (WSM) was extracted in MilliQ-water, and, in a second step, solid phase extraction was used to isolate the less hydrophilic fraction (ISOM) of the water-soluble organic matter (WSOM) from remaining inorganic salts and "most" hydrophilic organic matter (MHOM). This approach allowed ISOM, which constitutes the major fraction of WSOM, to be isolated from ambient aerosols and investigated in pure form. Hygroscopic properties of both WSM and ISOM extracts as well as of aquatic reference fulvic and humic acids were investigated using a Hygroscopicity Tandem Differential Mobility Analyser (H-TDMA). ISOM deliquesced between 30% and 60% relative humidity (RH), and hygroscopic growth factors at 90% RH ranged from 1.08 to 1.17. The hygroscopicity of ISOM is comparable to secondary organic aerosols obtained in smog chamber experiments, but lower than the hygroscopicity of highly soluble organic acids. The hygroscopic behaviour of investigated fulvic and humic acids had similarities to ISOM, but hygroscopic growth factors were slightly smaller and deliquescence was observed at higher RH (75-85% and 85-95% RH for fulvic acid and humic acid, respectively). These differences probably originate from larger average molecular mass and lower solubility of fulvic and humic acids. Inorganic composition data, measured ISOM hygroscopicity, and a presumed value for the hygroscopicity of the small remaining MHOM fraction were used to predict hygroscopic growth of WSM extracts. Good agreement between model prediction and measured water uptake was observed with differences (by volume) ranging from +1% to -18%. While deliquescence properties of WSM extracts were mainly determined by the inorganic salts (42-53 wt % of WSM), the WSOM accounted for a significant fraction of particulate water. At 90% RH, according to model predictions and measurements, about 80-62% of particulate water in the samples are associated with inorganic salts and about 20-38% with WSOM. The relative contributions of both distinguished WSOM fractions, ISOM and MHOM, remains uncertain since MHOM was not available in isolated form, but the results suggest that the less abundant MHOM is also important due to its presumably larger hygroscopicity.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation The effect of physical and chemical aerosol properties on warm cloud droplet activation(Copernicus, 2006) McFiggans, Gordon B.; Artaxo, Paulo; Baltensperger, Urs; Coe, Hugh; Facchini, Maria Cristina; Feingold, Graham; Fuzzi, Sandro; Gysel, Martin; Laaksonen, Ari; Lohmann, Ulrike; Mentel, Thomas F.; Murphy, Daniel M.; O'Dowd, Colin D.; Snider, Jefferson R.; Weingartner, ErnestAbstract. The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the "indirect effects" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made.01A - Beitrag in wissenschaftlicher Zeitschrift