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- PublikationRelating hygroscopicity and composition of organic aerosol particulate matter(Copernicus, 10.02.2011) Duplissy, Jonathan; DeCarlo, Peter F.; Dommen, Josef; Alfarra, M. Rami; Metzger, Axel; Barmpadimos, Iakovos; Prevot, Andre S.H.; Weingartner, Ernest; Tritscher, Torsten; Gysel, Martin; Aiken, Allison C.; Jimenez, Jose L; Canagaratna, Manjula R.; Worsnop, Douglas R.; Collins, Don R.; Tomlinson, Jason; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]A hygroscopicity tandem differential mobility analyzer (HTDMA) was used to measure the water uptake (hygroscopicity) of secondary organic aerosol (SOA) formed during the chemical and photochemical oxidation of several organic precursors in a smog chamber. Electron ionization mass spectra of the non-refractory submicron aerosol were simultaneously determined with an aerosol mass spectrometer (AMS), and correlations between the two different signals were investigated. SOA hygroscopicity was found to strongly correlate with the relative abundance of the ion signal m/z 44 expressed as a fraction of total organic signal (f44). m/z 44 is due mostly to the ion fragment CO2+ for all types of SOA systems studied, and has been previously shown to strongly correlate with organic O/C for ambient and chamber OA. The analysis was also performed on ambient OA from two field experiments at the remote site Jungfraujoch, and the megacity Mexico City, where similar results were found. A simple empirical linear relation between the hygroscopicity of OA at subsaturated RH, as given by the hygroscopic growth factor (GF) or "ϰorg" parameter, and f44 was determined and is given by ϰorg = 2.2 × f44 − 0.13. This approximation can be further verified and refined as the database for AMS and HTDMA measurements is constantly being expanded around the world. The use of this approximation could introduce an important simplification in the parameterization of hygroscopicity of OA in atmospheric models, since f44 is correlated with the photochemical age of an air mass.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationRelating cloud condensation nuclei activity and oxidation level of α-pinene secondary organic aerosols(Wiley, 30.11.2011) Frosch, Mia; Bilde, Merete; DeCarlo, Peter F.; Jurányi, Zsófia; Tritscher, Torsten; Dommen, Josef; Donahue, Neil M.; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs [in: Journal of Geophysical Research: Atmospheres]During a series of smog chamber experiments, the effects of chemical and photochemical aging on the ability of organic aerosols generated from ozonolysis of α-pinene to act as cloud condensation nuclei (CCN) were investigated. In particular, the study focused on the relation between oxygenation and the CCN-derived single hygroscopicity parameter κ for different experimental conditions: varying precursor concentrations (10–40 ppb), different OH sources (photolysis of HONO either with or without the addition of NO or ozonolysis of tetramethylethylene), and exposure to light. Oxygenation was described by the contribution of the aerosol mass spectrometer (AMS) mass fragment m/z 44 to the total organic signal (f44) and the oxygen to carbon molar ratio (O/C), likewise determined with AMS. CCN activity, described by the hygroscopicity parameter κ, was determined with a CCN counter. It was found that f44 increases with decreasing precursor concentration and with chemical aging, whereas neither of these affects CCN activity. Overall, κ is largely independent of O/C in the range 0.3 < O/C < 0.6 (0.07 < f44 < 0.12), although an empirical unweighted least squares fit was determined: κ = (0.071 ± 0.02) · (O/C) + (0.0785 ± 0.009) for particles with diameter in the range 59–200 nm. Growth kinetics of activating secondary organic aerosols were found to be comparable to those of ammonium sulfate and were not influenced by chemical aging.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationSubarctic atmospheric aerosol composition: 2. Hygroscopic growth properties(Wiley, 10.07.2009) Herich, Hanna; Kammermann, Lukas; Friedman, Beth; Gross, Deborah S.; Weingartner, Ernest; Lohmann, Ulrike; Spichtinger, Peter; Gysel, Martin; Baltensperger, Urs; Cziczo, Daniel J. [in: Journal of Geophysical Research: Atmospheres]Subarctic aerosols were sampled during July 2007 at the Abisko Scientific Research Station Stordalen site in northern Sweden with an instrument setup consisting of a custom‐built Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) connected in series to a single particle mass spectrometer. Aerosol chemical composition in the form of bipolar single particle mass spectra was determined as a function of hygroscopic growth both in situ and in real time. The HTDMA was deployed at a relative humidity of 82%, and particles with a dry mobility diameter of 260 nm were selected. Aerosols from two distinct air masses were analyzed during the sampling period. Sea salt aerosols were found to be the dominant particle group with the highest hygroscopicity. High intensities of sodium and related peaks in the mass spectra were identified as exclusive markers for large hygroscopic growth. Particles from biomass combustion were found to be the least hygroscopic aerosol category. Species normally considered soluble (e.g., sulfates and nitrates) were found in particles ranging from high to low hygroscopicity. Furthermore, the signal intensities of the peaks related to these species did not correlate with hygroscopicity.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationSingle particle characterization of black carbon aerosols at a tropospheric alpine site in Switzerland(Copernicus, 09.08.2010) Liu, D.; Flynn, Michael; Gysel, Martin; Targino, Admir Créso; Crawford, Ian; Bower, Keith; Choularton, Thomas; Jurányi, Zsófia; Steinbacher, Martin; Hüglin, Christoph; Curtius, Joachim; Kampus, M.; Petzold, Andreas; Weingartner, Ernest; Baltensperger, Urs; Coe, Hugh [in: Atmospheric Chemistry and Physics]The refractory black carbon (rBC) mass, size distribution (190–720 nm) and mixing state in sub-micron aerosols were characterized from late February to March 2007 using a single particle incandescence method at the high alpine research station Jungfraujoch (JFJ), Switzerland (46.33° N, 7.59° E, 3580 m a.s.l.). JFJ is a ground based location, which is at times exposed to continental free tropospheric air. A median mass absorption coefficient (MAC) of 10.2±3.2 m2 g−1 at λ=630 nm was derived by comparing single particle incandescence measurements of black carbon mass with continuous measurements of absorption coefficient. This value is comparable with other estimates at this location. The aerosols measured at the site were mostly well mixed and aged during transportation via the free troposphere. Pollutant sources were traced by air mass back trajectories, trace gases concentrations and the mass loading of rBC. In southeasterly wind directions, mixed or convective weather types provided the potential to vent polluted boundary layer air from the southern Alpine area and industrial northern Italy, delivering enhanced rBC mass loading and CN concentrations to the JFJ. The aerosol loadings at this site were also significantly influenced by precipitation, which led to the removal of rBC from the atmosphere. Precipitation events were shown to remove about 65% of the rBC mass from the free tropospheric background reducing the mean loading from 13±5 ng m−3 to 6±2 ng m−3(corrected to standard temperature and pressure). Overall, 40±15% of the observed rBC particles within the detectable size range were mixed with large amounts of non-refractory materials present as a thick coating. The growth of particle size into the accumulation mode was positively linked with the degree of rBC mixing, suggesting the important role of condensable materials in increasing particle size and leading to enhanced internal mixing of these materials with rBC. It is the first time that BC mass, size distribution and mixing state are reported in the free troposphere over Europe. These ground based measurements also provide the first temporal study of rBC in the European free troposphere quantitatively measured by single particle methods. At the present time there is only limited information of BC and its mixing state in the free troposphere, especially above Europe. The results reported in this paper provide an important constraint on modelled representation of BC.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationChanges of hygroscopicity and morphology during ageing of diesel soot(Institute of Physics Publishing, 2011) Tritscher, Torsten; Jurányi, Zsófia; Martin, Maria; Chirico, Roberto; Gysel, Martin; Heringa, Maarten F.; DeCarlo, Peter F.; Sierau, Berko; Prévôt, André S. H.; Weingartner, Ernest; Baltensperger, Urs [in: Environmental Research Letters]01A - Beitrag in wissenschaftlicher Zeitschrift