Fraunhofer-Institut für Atmosphärische Umweltforschung IFU

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  • Publication
    Biosphere-atmosphere exchange of ammonia
    ( 1997)
    Sutton, M.A.
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    Wyers, G.P.
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    Meixner, F.X.
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    Schjorring, J.K.
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    Kesselmeier, J.
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    Kramm, G.
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    Duyzer, J.H.
    Substantial progress has been made in the last eight years in the understanding and quantification of ammonia exchange between the atmosphere and biosphere. Much of the work has been linked to the joint EC/EUROTRAC subproject BIATEX (BIosphere ATmosphere EXchange), which has served as the main European forum for work in this area. In the mid-1980s there was still much confusion and uncertainty over the rate and direction of ammonia fluxes with different ecosystems; although the results of isolated studies were available, there was no clear overview of the key factors affecting ammonia fluxes. Work since that time has highlighted the dominant effects of ecosystem type and management, as well as humidity and wetness, on ammonia exchange. Ammonia is a key component of plant metabolism, so that ammonia emission may occur from plants in relation to nitrogen nutrition and plant growth stage. In contrast, ammonia is highly soluble and may be efficiently captured by leaf cuticles and surface w etness allowing large deposition velocities. The consequence is that ammonia exchange is bi-directional over agricultural ecosystems, though for most semi-natural ecosystems dry deposition dominates, being a significant component of the total atmospheric nitrogen input. The work within BIATEX has focused in more detail on the processes controlling these differences and, using the results of both micrometeorological and controlled environment measurements, has developed new models that are able to provide the synthesis necessary to predict ammonia fluxes. Long term and regional estimates of ammonia net exchange are still uncertain, though the models developed now provide the necessary framework to guide future measurements.
  • Publication
    Atmosphere - Surface exchange of nitrogen oxides and ozone
    ( 1997)
    Fowler, D.
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    Meixner, F.X.
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    Duyzer, J.H.
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    Kramm, G.
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    Granat, L.
  • Publication
    Measurements of vertical fluxes of nitrogen oxides
    ( 1992)
    Meixner, F.X.
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    Böswald, F.
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    Eiblmeier, K.
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    Kramm, G.
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    Leimbach, S.
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    Ludwig, J.
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    Müller, H.
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    Nestlen, M.
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    Weber, P.
  • Publication
    Surface fluxes of NO and NO2 by a dynamic chamber technique - labortory studies on wheat
    ( 1992)
    Ludwig, J.
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    Weber, P.
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    Meixner, F.X.
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    Rennenberg, H.
  • Publication
    Measurements of vertical fluxes of nitrogen oxides
    ( 1991)
    Meixner, F.X.
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    Böswald, F.
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    Eiblmeier, K.
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    Kramm, G.
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    Ludwig, J.
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    Müller, H.
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    Nestlen, M.
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    Terrey, B.
    ;
    Weber, P.
  • Publication
    Die Entwicklung des Chemilumineszenzverfahrens zur Bestimmung atmosphärischer SO2-Spuren
    ( 1989)
    Jaeschke, W.
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    Obenland, H.
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    Meixner, F.X.
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    Berresheim, H.
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    Ockelmann, G.
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    Beltz, N.
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    Herrmann, J.
    ;
    Haunold, W.
    Zur Bestimmung der SO2-Konzentration in unmittelbarer Nähe anthropogener Emissionen können kommerziell erhältliche Geräte eingesetzt werden, die kontinuierlich arbeiten und auf dem Prinzip der Flammenphotometrie oder Fluoreszenz beruhen. Ihre Nachweisgrenze liegt im allgemeinen bei einem SO2-Mischungsverhältnis von 10 hoch 9, also im ppb-Bereich. Für eine eingehende Erforschung der Ausbreitung und Verteilung des SO2 in Regionen, die nicht unmittelbar durch den Menschen belastet sind, wie abgelegene Landstriche, maritime Bereiche oder die obere Troposphere und untere Stratosphäre, reicht die Empfindlichkeit herkömmlicher Geräte jedoch nicht aus. Hier liegen Mischungsverhältnisse im ppt-Bereich (10 hoch minus 12) vor, die nur mit eigens hierfür entwickelten feldgängigen Meßtechniken erfaßt werden können. Die notwendige Steigerung der Empfindlichkeiten versucht man durch die Anwendung von Anreicherungstechniken zu erreichen, indem man die Probeluft solange durch ein absorbierendes Medium leitet, bis soviel von der zu analysierenden Substanz angereichert ist, daß die Nachweisgrenze der anschließend angewendeten Analysenmethode mit Sicherheit überschritten wird.
  • Publication
    Development of automated chemical sensors for dry deposition measurement by the gradient method
    ( 1989)
    Meixner, F.X.
    ;
    Possanzini, M.
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    Slanina, J.
    The central aim of the project is the development of new and/or the improvement of already existing chemical sensors for dry deposition measurements of nitrogen compounds in the field by a micrometeorological (gradient) method. For this specific application chemical sensors must fulfill the following requirements: - relative precision of concentration measurements smaller than 5%, - sensitivity smaller than 1 ppbv, - sampling intervals smaller than 2 h, - avoidance of artifact formation during sampling and interferences against other nitrogen containing constituents. Some of these requirements can be best realized by automatization of the corresponding techniques as far as possible. Within this project, the development/improvement of chemical sensors is limited to the - automated rotating annular denuder technique, - non-automated classicval (differentiaail) denuder techniques, and - automated "thermodenuder" technique. Priority is given to the measurement of HNO2, NH3, and HNO3. The d etermination of NO and NO2 is envisaged, while the measurement of H202, HCI, CH20 and SO2 is a "by-product" of the techniques. The developed techniques are verified during several field campaigns which include the intercomparison of the techniques, the test of their monitoring capacity, and finally the application to a micrometeorological method to determine dry deposiotion fluxes.
  • Publication
    Spurenstoffe und Klima
    ( 1987)
    Müller, H.
    ;
    Seiler, W.
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    Meixner, F.X.
  • Publication
    Measurement of the two dimensional distribution of atmospheric trace gases during the STRATOZ III flight
    ( 1985)
    Meixner, F.X.
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    Rudolph, J.
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    Vierkorn-Rudolph, B.
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    Khedim, A.