Hochschule für Technik und Umwelt FHNW
Dauerhafte URI für den Bereichhttps://irf.fhnw.ch/handle/11654/35
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11 Ergebnisse
Bereich: Suchergebnisse
Publikation Development of a waveguide-based interferometer for the measurement of trace substances(Zenodo, 07.11.2023) Weingartner, Ernest; Bilal, Jonas; Steigmeier, Peter; Jundt, Gregor; Häusler, Samuel; Lenner, Miklós; Flöry, Nikolaus; Bittner, Matthias; Betschon, FelixPhotonic integration on a chip has the potential to develop new low-cost, high-performance sensing devices. A proof of concept of the sensing capabilities of a waveguide-based photothermal interferometer for the measurement of traces of light-absorbing substances (soot particles, gases) has been achieved. The measurement principle can also be extended to a wide range of other applications such as refractive index measurements, or vibration/distance sensors. A unique feature is that the waveguide technology allows for a passive operation of the interferometer, i.e., no quadrature point control is required.04B - Beitrag KonferenzschriftPublikation A novel measurement system for unattended, in situ characterization of carbonaceous aerosols(Copernicus, 22.12.2023) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Weingartner, ErnestCarbonaceous aerosol is a relevant constituent of the atmosphere in terms of climate and health impacts. Nevertheless, measuring this component poses many challenges. There is currently no simple and sensitive commercial technique that can reliably capture its totality in an unattended manner, with minimal user intervention, for extended periods of time. To address this issue we have developed the fast thermal carbon totalizator (FATCAT). Our system captures an aerosol sample on a rigid metallic filter and subsequently analyses it by rapidly heating the filter directly, through induction, to a temperature around 800°C. The carbon in the filter is oxidized and quantified as CO2 in order to establish the total carbon (TC) content of the sample. The metallic filter is robust, which solves filter displacement or leakage problems, and does not require a frequent replacement like other measurement techniques. The limit of detection of our system using the 3σ criterion is TC =0.19 µg-C (micrograms of carbon). This translates to an average ambient concentration of TC =0.32 µg-C m^−3 and TC =0.16 µg-C m^−3 for sampling interval of 1 or 2 h respectively using a sampling flow rate of 10 L min^−1. We present a series of measurements using a controlled, well-defined propane flame aerosol as well as wood-burning emissions using two different wood-burning stoves. Furthermore, we complement these measurements by coating the particles with secondary organic matter by means of an oxidation flow reactor. Our device shows a good correlation (correlation coefficient, R^2>0.99) with well-established techniques, like mass measurements by means of a tapered element oscillating microbalance and TC measurements by means of thermal–optical transmittance analysis. Furthermore, the homogeneous fast-heating of the filter produces fast thermograms. This is a new feature that, to our knowledge, is exclusive of our system. The fast thermograms contain information regarding the volatility and refractoriness of the sample without imposing an artificial fraction separation like other measurement methods. Different aerosol components, like wood-burning emissions, soot from the propane flame and secondary organic matter, create diverse identifiable patterns.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Waveguide based passively demodulated photothermal interferometer for light absorption measurements of trace substances(Optica Publishing Group, 2023) Visser, Bradley; Bilal, Jonas; Flöry, Nikolaus; Wipf, Manuela; Steigmeier, Peter; Rüggeberg, Tobias; Betschon, Felix; Weingartner, Ernest01A - Beitrag in wissenschaftlicher ZeitschriftPublikation A single-beam photothermal interferometer for in situ measurements of aerosol light absorption(Copernicus, 2020) Visser, Bradley; Röhrbein, Jannis; Steigmeier, Peter; Drinovec, Luka; Močnik, Griša; Weingartner, ErnestWe have developed a novel single-beam photothermal interferometer and present here its application for the measurement of aerosol light absorption. The use of only a single laser beam allows for a compact optical set-up and significantly easier alignment compared to standard dual-beam photothermal interferometers, making it ideal for field measurements. Due to a unique configuration of the reference interferometer arm, light absorption by aerosols can be determined directly – even in the presence of light-absorbing gases. The instrument can be calibrated directly with light-absorbing gases, such as NO2, and can be used to calibrate other light absorption instruments. The detection limits (1σ) for absorption for 10 and 60 s averaging times were determined to be 14.6 and 7.4 Mm−1, respectively, which for a mass absorption cross section of 10 m2 g−1 leads to equivalent black carbon concentration detection limits of 1460 and 740 ng m−3, respectively. The detection limit could be reduced further by improvements to the isolation of the instrument and the signal detection and processing schemes employed.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation 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, Markus06 - PräsentationPublikation 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 - Präsentation