Hochschule für Technik und Umwelt FHNW

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2004 - 20063

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Autor:in: search.filters.author.Dommen, JosefThema: search.filters.subject.660 - Technische Chemie

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  • Kein Vorschaubild vorhanden
    Publikation
    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
  • Kein Vorschaubild vorhanden
    Publikation
    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
  • Vorschaubild
    Publikation
    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