Hochschule für Technik und Umwelt FHNW
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Publikation A 17 month climatology of the cloud condensation nuclei number concentration at the high alpine site Jungfraujoch(Wiley, 24.05.2011) Jurányi, Zsófia; Gysel, Martin; Weingartner, Ernest; Bukowiecki, Nicolas; Kammermann, Lorenz; Baltensperger, UrsBetween May 2008 and September 2009 the cloud condensation nuclei (CCN) number concentration, NCCN, was measured at the high alpine site Jungfraujoch, which is located in the free troposphere most of the time. Measurements at 10 different supersaturations (0.12%–1.18%) were made using a CCN counter (CCNC). The monthly median NCCN values show a distinct seasonal variability with ∼5–12 times higher values in summer than in winter. The major part of this variation can be explained by the seasonal amplitude of total aerosol number concentration (∼4.5 times higher values in summer), but it is further amplified (factor of ∼1.1–2.6) by a shift of the particle number size distribution toward slightly larger sizes in summer. In contrast to the extensive properties, the monthly median of the critical dry diameter, above which the aerosols activate as CCN, does not show a seasonal cycle (relative standard deviations of the monthly median critical dry diameters at the different supersaturations are 4–9%) or substantial variability (relative standard deviations of individual data points at the different supersaturations are less than 18–37%). The mean CCN-derived hygroscopicity of the aerosol corresponds to a value of the hygroscopicity parameter κ of 0.20 (assuming a surface tension of pure water) with moderate supersaturation dependence. NCCN can be reliably predicted throughout the measurement period with knowledge of the above-mentioned averaged κ value and highly time-resolved (∼5 min) particle number size distribution data. The predicted NCCN was within 0.74 to 1.29 times the measured value during 80% of the time (94,499 data points in total at 10 different supersaturations).01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Aerosol and trace gas vehicle emission factors measured in a tunnel using an Aerosol Mass Spectrometer and other on-line instrumentation(Elsevier, 04/2011) Chirico, Roberto; Prevot, Andre S.H.; DeCarlo, Peter F.; Heringa, Maarten F.; Richter, Rene; Weingartner, Ernest; Baltensperger, UrsIn this study we present measurements of gas and aerosol phase composition for a mixed vehicle fleet in the Gubrist tunnel (Switzerland) in June 2008. PM1 composition measurements were made with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS) and a Multi Angle Absorption Photometer (MAAP). Gas-phase measurements of CO, CO2, NOx and total hydrocarbons (THC) were performed with standard instrumentation. Weekdays had a characteristic diurnal pattern with 2 peaks in concentrations for all traffic related species corresponding to high vehicle density (∼300 ± 30 vehicles per 5 min) in the morning rush hour between 06:00 and 09:00 and in the afternoon rush hours from approximately 15:30 to 18:30. The emission factors (EF) of OA were heavily influenced by the OA mass loading. To exclude this partitioning effect, only organic aerosol mass concentrations from 60 μg m−3 to 90 μg m−3 were considered and for these conditions the EF(OA) value for HDV was 33.7 ± 2.3 mg km−1 for a temperature inside the tunnel of 20–25 °C. This value is not directly applicable to ambient conditions because it is derived from OA mass concentrations that are roughly a factor of 10 higher than typical ambient concentrations. An even higher EF(OA)HDV value of 47.4 ± 1.6 mg km−1 was obtained when the linear fit was applied to all data points including OA concentrations up to 120 μg m−3. Similar to the increasing EF, the OA/BC ratio in the tunnel was also affected by the organic loading and it increased by a factor of ∼3 over the OA range 10–120 μg m−3. This means that also the OA emission factors at ambient concentrations of around 5–10 μg m−3 would be 2–3 times lower than the emission factor given above. For OA concentrations lower than 40 μg m−3 the OA/BC mass ratio was below 1, while at an OA concentration of 100–120 μg m−3 the OA/BC ratio was ∼1.5. The AMS mass spectra (MS) acquired in the tunnel were highly correlated with the primary organic aerosol (POA) MS from a EURO 3 diesel vehicle with a speed similar to the average tunnel speed.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation 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, Konstantina06 - PräsentationPublikation Employment of novel tools for the continuous characterization of the carbonaceous fraction in ambient aerosol(13.09.2021) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Weingartner, Ernest06 - PräsentationPublikation Performance of the new continuous carbonaceous aerosol measurement system FATCAT during long term unattended measurement campaigns(23.06.2021) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Weingartner, Ernest06 - PräsentationPublikation High resolution unattended particle-bound total carbon measurements and source identification at the Jungfraujoch global GAW station(2021) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Weingartner, Ernest06 - PräsentationPublikation High resolution unattended particle-bound total carbon measurements and source identification at the Jungfraujoch global GAW station(18.05.2021) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Weingartner, ErnestTotal aerosol carbonaceous mass (TC) is a major constituent of atmospheric fine aerosol not yet continuously monitored with adequate time resolution. Adding a TC measurement to existing measurement programs is crucial for comprehensive interpretation of the impact of aerosols. To fill this gap, we developed the “fast thermal carbon totalizator” (FATCAT) for long-term unsupervised monitoring of TC. FATCAT has been deployed since 2019 at diverse sites including the Jungfraujoch global GAW station (JFJ). FATCAT collects particles on a metallic filter, and subsequently heats it to 800°C under an oxidizing atmosphere. The limit of detection is LoD=0.2 µg of carbon (µg-C). At the reduced atmospheric pressure of the JFJ, which limits the sampling flow, this corresponds to TC=0.3 µg-C/m3 using a time resolution of two hours. We discuss our experience during the first two year of continuous TC measurements and the possibility of using our instrument to distinguish carbonaceous aerosol from different source using fast, 50 seconds, thermograms. This unique feature allows us to identify source specific fingerprints. Several high TC episodes during September 2020 at JFJ show the typical pattern for biomass combustion. Back trajectories attribute them to long-range transported emissions from Californian wildfires. Graphitic carbon from, e.g., local fossil fuel combustion evolves at higher temperatures. The data collected at the JFJ is already the longest produced TC dataset for this site without instrument related interruptions. The dataset generated by our instrument and post-analysis data products represent an improvement to the available measurement inventory. It can serve as quality control for other measurement systems. Prominently, measurements of eBC via MAAP or Aethalometer and organic mass using ToF-ACSM. TC data can be used in parallel to these devices as a quality check, and to warrant carbon mass closure and reduce systematic biases.06 - PräsentationPublikation 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, KonstantinaWe 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
