Keller, Alejandro

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Keller
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Alejandro
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Keller, Alejandro

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2017 - 201912020 - 20221
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  • Vorschaubild nicht verfügbar
    Publikation
    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 [in: Aerosol Science and Technology]
    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
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    Publikation
    Characterizing particulate emissions from wood burning appliances including secondary organic aerosol formation potential
    (Elsevier, 31.08.2017) Keller, Alejandro; Burtscher, Heinz [in: Journal of Aerosol Science]
    Biomass burning is a major contributor to environmental particulate matter pollution and should therefore be contemplated by emission control legislation. However, policy decisions for improving air quality by imposing emission limits are only as good as the selected metric. We discuss an approach that incorporates recent scientific results and is compatible with type-approval testing and field measurements. We include potential secondary organic aerosol (SOA) by aging emissions in an oxidation flow reactor. Quantification is done by particle-bound total carbon analysis. Total carbon is the fraction relevant to combustion quality and a better marker for toxicity than total particulate matter, which also includes salts and ashes. The data is complemented by on-line size distribution measurements. We exemplify our approach by showing measurements performed on a variety of appliances. Our measurements suggest that non-methane hydrocarbons (NMHC) species with very low volatility are responsible for most of the SOA. Condensing and precipitating this fraction significantly reduces SOA potential but has no noticeable impact on total NMHC. Thus, key precursors of SOA may be a much smaller subset than previously thought. Targeting this fraction could be a straightforward SOA mitigation strategy. These results could not have been derived using the current standard emission control metrics.
    01A - Beitrag in wissenschaftlicher Zeitschrift