Auflistung nach Autor:in "Rubach, Florian"

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    Publikation
    Ambient and laboratory observations of organic ammonium salts in PM₁
    (Royal Society of Chemistry, 2017) Schlag, Patrick; Rubach, Florian; Mentel, Thomas F.; Reimer, David Thomas; Canonaco, Francesco; Henzing, Bas; Moerman, M.; Otjes, R.; Prévôt, André S.H.; Rohrer, Franz; Rosati, B.; Tillmann, Ralf; Weingartner, Ernest; Kiendler-Scharr, Astrid [in: Faraday Discussions]
    Ambient measurements of PM1aerosol chemical composition at Cabauw, the Netherlands, implicate higher ammonium concentrations than explained by the formation of inorganic ammonium salts. This additional particulate ammonium is called excess ammonium (eNH4). Height profiles over the Cabauw Experimental Site for Atmospheric Research (CESAR) tower, of combined ground based and airborne aerosol mass spectrometric (AMS) measurements on a Zeppelin airship show higher concentrations ofeNH4at higher altitudes compared to the ground. Through flights across the Netherlands, the Zeppelin based measurements furthermore substantiateeNH4as a regional phenomenon in the planetary boundary layer. The excess ammonium correlates with mass spectral signatures of (di-)carboxylic acids, making a heterogeneous acid–base reaction the likely process of NH3uptake. We show that this excess ammonium was neutralized by the organic fraction forming particulate organic ammonium salts. We discuss the significance of such organic ammonium salts for atmospheric aerosols and suggest that NH3emission control will have benefits for particulate matter control beyond the reduction of inorganic ammonium salts.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    Vertical profiling of aerosol hygroscopic properties in the planetary boundary layer during the PEGASOS campaigns
    (Copernicus, 2016) Rosati, Bernadette; Gysel, Martin; Rubach, Florian; Mentel, Thomas F.; Goger, Brigitta; Poulain, Laurent; Schlag, Patrick; Miettinen, Pasi; Pajunoja, Aki; Virtanen, Annele; Klein Baltink, Henk; Henzing, Bas; Größ, Johannes; Gobbi, Gian Paolo; Wiedensohler, Alfred; Kiendler-Scharr, Astrid; Decesari, Stefano; Facchini, Maria Cristina; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
    Vertical profiles of the aerosol particles hygroscopic properties, their mixing state as well as chemical composition were measured above northern Italy and the Netherlands. An aerosol mass spectrometer (AMS; for chemical composition) and a white-light humidified optical particle spectrometer (WHOPS; for hygroscopic growth) were deployed on a Zeppelin NT airship within the PEGASOS project. This allowed one to investigate the development of the different layers within the planetary boundary layer (PBL), providing a unique in situ data set for airborne aerosol particles properties in the first kilometre of the atmosphere. Profiles measured during the morning hours on 20 June 2012 in the Po Valley, Italy, showed an increased nitrate fraction at  ∼  100 m above ground level (a.g.l.) coupled with enhanced hygroscopic growth compared to  ∼  700 m a. g. l. This result was derived from both measurements of the aerosol composition and direct measurements of the hygroscopicity, yielding hygroscopicity parameters (κ) of 0.34  ±  0.12 and 0.19  ±  0.07 for 500 nm particles, at  ∼  100 and  ∼  700 m a. g. l., respectively. The difference is attributed to the structure of the PBL at this time of day which featured several independent sub-layers with different types of aerosols. Later in the day the vertical structures disappeared due to the mixing of the layers and similar aerosol particle properties were found at all probed altitudes (mean κ ≈ 0.18  ±  0.07). The aerosol properties observed at the lowest flight level (100 m a. g. l.) were consistent with parallel measurements at a ground site, both in the morning and afternoon. Overall, the aerosol particles were found to be externally mixed, with a prevailing hygroscopic fraction. The flights near Cabauw in the Netherlands in the fully mixed PBL did not feature altitude-dependent characteristics. Particles were also externally mixed and had an even larger hygroscopic fraction compared to the results in Italy. The mean κ from direct measurements was 0.28 ±  0.10, thus considerably higher than κ values measured in Italy in the fully mixed PBL.
    01A - Beitrag in wissenschaftlicher Zeitschrift