Auflistung nach Autor:in "Kalberer, Markus"

Gerade angezeigt 1 - 15 von 15

A compact and portable deposition chamber to study nanoparticles in air-exposed tissue
(Mary Ann Liebert, 2013) Mertes, Peter; Praplan, Arnaud P.; Künzi, Lisa; Dommen, Josef; Baltensperger, Urs; Geiser, Marianne; Weingartner, Ernest; Ricka, Jaroslav; Fierz, Martin; Kalberer, Markus
01A - Beitrag in wissenschaftlicher Zeitschrift
Changes of fatty acid aerosol hygroscopicity induced by ozonolysis under humid conditions
(Copernicus, 18.08.2008) Vesna, O.; Sjögren, Staffan; Weingartner, Ernest; Samburova, Vera; Kalberer, Markus; Gäggeler, Heinz W.; Ammann, Markus
Unsaturated fatty acids are important constituents of the organic fraction of atmospheric aerosols originating from biogenic or combustion sources. Oxidative processing of these may change their interaction with water and thus affect their effect on climate. The ozonolysis of oleic and arachidonic acid aerosol particles was studied under humid conditions in a flow reactor at ozone exposures close to atmospheric levels, at concentrations between 0.5 and 2 ppm. While oleic acid is a widely used proxy for such studies, arachidonic acid represents polyunsaturated fatty acids, which may decompose into hygroscopic products. The hygroscopic (diameter) growth factor at 93% relative humidity (RH) of the oxidized arachidonic particles increased up to 1.09 with increasing RH during the ozonolysis. In contrast, the growth factor of oleic acid was very low (1.03 at 93% RH) and was almost invariant to the ozonolysis conditions, so that oleic acid is not a good model to observe oxidation induced changes of hygroscopicity under atmospheric conditions. We show for arachidonic acid particles that the hygroscopic changes induced by humidity during ozonolysis are accompanied by about a doubling of the ratio of carboxylic acid protons to aliphatic protons. We suggest that, under humid conditions, the reaction of water with the Criegee intermediates might open a pathway for the formation of smaller acids that lead to more significant changes in hygroscopicity. Thus the effect of water to provide a competing pathway during ozonolysis observed in this study should be motivation to include water, which is ubiquitously present in and around atmospheric particles, in future studies related to aerosol particle aging.
01A - Beitrag in wissenschaftlicher Zeitschrift
Condensation nuclei (CN) and ultrafine CN in the free troposphere to 12 km. A case study over the Jungfraujoch High‐Alpine research station
(Wiley, 15.09.1999) Nyeki, Stephan; Kalberer, Markus; Lugauer, Matthias; Weingartner, Ernest; Petzold, Andreas; Schröder, Franz; Colbeck, Ian; Baltensperger, Urs
Condensation nuclei (CN) were measured in the free troposphere (FT) above the Jungfraujoch (JFJ) high-alpine research station (3454 m; Switzerland) from 4.5 to 12 km asl in a case study on July 30, 1997. Vertical profiles of CN concentration for d ≥ 5 nm (N≥5), d ≥ 15 nm (N≥15 15) were measured, and indicated that ultrafine CN (UCN; 5 ≤ d ≤ 15 nm; N5-15) exhibited a distinct increase with altitude. Some evidence for near-constant values of d(logCN)/dz within discrete layers was found, which generally coincided with different airmasses as delineated by changes in the lapse rate dθ/dz at ∼ 5.5, 6.4, 9.0 and 10.6 km asl. In addition, CN concentration was mapped over a 40 × 75 km horizontal domain at 8.0 km asl centered above the JFJ. A pronounced variation in N≥5,N≥15 and specific humidity, but not in UCN, exhibited quasi-stationary 2-D features and was attributed to the chance encounter of a mountain wave. The case study provides further evidence that the upper FT may be a source of new particles.
01A - Beitrag in wissenschaftlicher Zeitschrift
Convective boundary layer evolution to 4 km asl over High‐alpine terrain. Airborne lidar observations in the Alps
(Wiley, 01.03.2000) Nyeki, Stephan; Kalberer, Markus; Colbeck, Ian; De Wekker, Stephan; Furger, Markus; Gäggeler, Heinz W.; Koßmann, Meinolf; Lugauer, Matthias; Steyn, Douw; Weingartner, Ernest; Wirth, Martin; Baltensperger, Urs
Mountain ranges have important influences on the structure and composition of the convective boundary layer (CBL) and free troposphere (FT). Evolution of the summer CBL, measured over the European Alps using airborne lidar, was clearly observed to attain a near-uniform height up to 4.2 km asl by early afternoon. A climatology of in-situ high-alpine aerosol measurements suggests that such substantial growth, corresponding to ∼ 0.3 of the mid-latitude tropopause height, often occurs during summer months. Subsequent nocturnal collapse of the CBL was estimated to result in the venting of ∼ 0.8 ± 0.3 (SO4 4) Gg/day into a FT residual layer, leeward of the Alps.
01A - Beitrag in wissenschaftlicher Zeitschrift
Heterogeneous chemical processing of 13NO2 by monodisperse carbon aerosols at very low concentrations
(American Chemical Society, 19.09.1996) Kalberer, Markus; Tabor, K.; Ammann, Markus; Parrat, Yves; Weingartner, Ernest; Piguet, D.; Rössler, E.; Jost, Dieter T.; Türler, Andreas; Gäggeler, Heinz W.; Baltensperger, Urs
The heterogeneous reaction of NO2 with different carbon aerosol particles was investigated in situ. The NO2 was labeled with the β+-emitter 13N (half-life 10.0 min) which allowed application of NO2 at very low concentrations. The carbon aerosol was either produced by a spark discharge generator using graphite electrodes or by a brush generator resuspending commercial soot material. Monodisperse size cuts between 50- and 490-nm diameter were selected and mixed with the 13NO2. After a defined reaction time, the different reaction products were separated by means of selective traps and detected on-line by γ-spectrometry. A sticking coefficient for chemisorption of NO2 between 0.3 × 10ˉ⁴ and 4.0 × 10ˉ⁴ and a rate constant for the reduction of adsorbed NO2 to NO(g) between 4.0 × 10 ˉ⁴ and 9.4 × 10 ˉ⁴ /s were determined for both aerosols. The sticking coefficient obtained in this study in situ with aerosol particles is 2 orders of magnitudes smaller than the uptake coefficient recently reported with bulk carbon material.
01A - Beitrag in wissenschaftlicher Zeitschrift
Identification of organic acids in secondary organic aerosol and the corresponding gas phase from chamber experiments
(American Chemical Society, 15.10.2004) Fisseha, Rebeka; Dommen, Josef; Sax, Mirjam; Paulsen, Dwane; Kalberer, Markus; Maurer, Rolf; Höfler, Frank; Weingartner, Ernest; Baltensperger, Urs
Organic acids in the gas and aerosol phase from photooxidation of 1,3,5-trimethylbenzene in the presence of 300 ppb propene and 300 ppb NOx in smog chamber experiments were determined using a wet effluent diffusion denuder/aerosol collector coupled to ion chromatography (IC) with conductivity detection. Behind the IC, the samples were collected using a fraction collector, for identification of unresolved/unidentified organic acids with IC-mass spectrometry (MS). In total, 20 organic acids were found with MS of which 10 were identified. The organic acids identified offline by IC-MS were then further quantified based on the online IC data. The identification was additionally confirmed with gas chromatography-mass spectrometry. At the maximum aerosol concentration, organic acids comprised 20-45% of the total aerosol mass. The method has a detection limit of 10-100 ng/m3 for the identified carboxylic acids.
01A - Beitrag in wissenschaftlicher Zeitschrift
Identification of polymers as major components of atmospheric organic aerosols
(Springer, 2004) Kalberer, Markus; Paulsen, Dwane; Sax, Mirjam; Steinbacher, Martin; Dommen, Josef; Prévôt, André S.H.; Fisseha, Rebeka; Weingartner, Ernest; Frankevich, Vladimir; Zenobi, Renato; Baltensperger, Urs
Results from photooxidation of aromatic compounds in a reaction chamber show that a substantial fraction of the organic aerosol mass is composed of polymers. This polymerization results from reactions of carbonyls and their hydrates. After aging for more than 20 hours, about 50% of the particle mass consists of polymers with a molecular mass up to 1000 daltons. This results in a lower volatility of this secondary organic aerosol and a higher aerosol yield than a model using vapor pressures of individual organic species would predict.
01A - Beitrag in wissenschaftlicher Zeitschrift
Laboratory observation of oligomers in the aerosol from isoprene/NOₓ photooxidation
(Wiley, 2006) Dommen, Josef; Metzger, Axel; Duplissy, Jonathan; Kalberer, Markus; Alfarra, M. Rami; Gascho, Astrid; Weingartner, Ernest; Prévôt, André S.H.; Verheggen, Bart; Baltensperger, Urs
Compounds assigned to be oxidation products of isoprene (2-methyl-1,3-butadiene) have recently been observed in ambient aerosols, suggesting that isoprene might play an important role in secondary organic aerosol (SOA) formation due to its large global source strength. SOA yields from photooxidation of isoprene and NOₓ in a chamber agree fairly well with previous data. Matrix assisted laser desorption/ionization mass spectrometry showed the formation of high molecular weight compounds over the course of 15-hour experiments. Concurrently, the volatility of the SOA decreased markedly as observed by a tandem differential mobility analyzer. The volume fraction remaining of SOA at 150°C increased steadily from 5 to 25% during the same experiments. These observations are attributed to oligomerization reactions occurring in the aerosol phase. Under dry conditions a lower volatility was observed.
01A - Beitrag in wissenschaftlicher Zeitschrift
Online gas and aerosol measurement of water soluble carboxylic acids in Zurich
(Wiley, 2006) Fisseha, Rebeka; Dommen, Josef; Gäggeler, Kathrin; Weingartner, Ernest; Samburova, Vera; Kalberer, Markus; Baltensperger, Urs
We discuss the diurnal and seasonal variability of low molecular weight organic acids in Zurich city on the basis of online quasi‐continuous measurement in the gas and aerosol phase using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to ion chromatography. The measurements were performed during August–September 2002 and March 2003. Acetic acid exhibited the highest concentration in the gas phase during all the measurement periods, followed by formic acid. Oxalic acid was predominantly found in the aerosol phase and often below the detection limit in the gas phase. In addition, filter samples were analyzed using ion chromatography–mass spectrometry (IC‐MS) to provide more information on organic acids in the aerosol phase. From the offline IC‐MS measurements, 20 monocarboxylic, dicarboxylic, and tricarboxylic acids were determined. In addition, more than 20 different masses were detected with the MS; however, identification of the organic acids was not possible. The sum of the carboxylic acids contributed on average 2% to the water soluble organic carbon (WSOC). The fraction of dicarboxylic acids to the WSOC was higher in summer compared to winter suggesting that dicarboxylic acids are mainly a result of photochemical reactions in summer whereas in winter they mainly result from primary sources.
01A - Beitrag in wissenschaftlicher Zeitschrift
The organic coating unit, an all-in-one system for reproducible generation of secondary organic aerosol
(22.06.2022) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Kalbermatter, Daniel; Hammer, Tobias; Vasilatou, Konstantina; Wolfer, Kate; Resch, Julian; Kalberer, Markus
06 - Präsentation
The organic coating unit, an all-in-one system for reproducible generation of secondary organic aerosol
(06.09.2022) Keller, Alejandro; Kalbermatter, Daniel; Specht, Patrick; Steigmeier, Peter; Wolfer, Katherin; Resch, Julian; Kalberer, Markus; Hammer, Tobias; Vasilatou, Konstantina
06 - Präsentation
The organic coating unit, an all-in-one system for reproducible generation of secondary organic matter aerosol
(Taylor & Francis, 18.08.2022) Keller, Alejandro; Kalbermatter, Daniel M.; Wolfer, Kate; Specht, Patrick; Steigmeier, Peter; Resch, Julian; Kalberer, Markus; Hammer, Tobias; Vasilatou, Konstantina
We report on a novel automated oxidation flow reactor to generate a wide variety of organic aerosol samples. The instrument is equipped with a humidifier, a dosing system for volatile organic precursors and an oxidation flow reactor (OFR) for generation of secondary organic matter (SOM). The instrument, known as organic coating unit (OCU), can produce homogeneously nucleated SOM particles or, used in combination with a standard combustion generator (e.g., a diffusion flame soot generator or any other seed particle), particles coated with a controlled amount of SOM. The physical and chemical properties of the generated particles can be controlled in a simple manner by selecting through a touch-screen target values for parameters, such as organic gaseous precursor concentration, humidity, and UV (ultraviolet) light intensity. Parameters and measured quantities are automatically stored in text files for easy export and analysis. Furthermore, we provide stable operation conditions and characterize the physicochemical properties of the generated aerosols with an array of methods, including transmission electron microscopy (TEM), thermal-optical analysis and liquid chromatography coupled with mass spectrometry (LC-MS). This all-in-one instrument is robust, compact, portable, and user-friendly, making it ideal for laboratory or field-based aerosol studies.
01A - Beitrag in wissenschaftlicher Zeitschrift
Seasonal and diurnal characteristics of water soluble inorganic compounds in the gas and aerosol phase in the Zurich area
(Copernicus, 2006) Fisseha, Rebeka; Dommen, Josef; Gutzwiller, Lukas; Weingartner, Ernest; Gysel, Martin; Emmenegger, C.; Kalberer, Markus; Baltensperger, Urs
Gas and aerosol samples were taken using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to ion chromatography (IC) in the city of Zurich, Switzerland from August to September 2002 and in March 2003. Major water soluble inorganic ions; nitrate, sulfate, and nitrite were analyzed online with a time resolution of two hours for the gas and aerosol phase. The fraction of water soluble inorganic anions in PM10 varied from 15% in August to about 38% in March. Seasonal and diurnal variations of nitrate in the gas and aerosol phase were observed with more than 50% of the total nitrate in the gas phase during August and more than 80% of nitrate in the aerosol phase during March exceeding the concentration of sulfate by a factor of 2. Aerosol sulfate, on the other hand, did not show significant variability with season. However, in the gas phase, the SO2 concentration was 6.5 times higher in winter than in summer. Nitrous acid (HONO) also showed a diurnal variation in both the gas and aerosol phase with the lowest concentration (0.2–0.6 µg/m³) in the afternoon. The primary pollutants, NO, CO and SO2 mixing ratios were often at their highest between 04:00–10:00 local time due to the build up of fresh vehicle emission under a nocturnal inversion.
01A - Beitrag in wissenschaftlicher Zeitschrift
Secondary organic aerosol formation by irradiation of 1,3,5-trimethylbenzene−NOₓ-H2O in a new reaction chamber for atmospheric chemistry and physics
(American Chemical Society, 12.03.2005) Paulsen, Dwane; Dommen, Josef; Kalberer, Markus; Prévôt, André S.H.; Richter, René; Sax, Mirjam; Steinbacher, Martin; Weingartner, Ernest; Baltensperger, Urs
A new environmental reaction smog chamber was built to simulate particle formation and growth similar to that expected in the atmosphere. The organic material is formed from nucleation of photooxidized organic compounds. The chamber is a 27 m³ fluorinated ethylene propylene (FEP) bag suspended in a temperature-controlled enclosure. Four xenon arc lamps (16 kW total) are used to irradiate primary gas components for experiments lasting up to 24 h. Experiments using irradiations of 1,3,5-trimethylbenzene−NOₓ−H2O at similar input concentrations without seed particles were used to determine particle number and volume concentration wall loss rates of 0.209 ± 0.018 and 0.139 ± 0.070 1/h, respectively. The particle formation was compared with and without propene.
01A - Beitrag in wissenschaftlicher Zeitschrift
Secondary 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
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