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@PHDTHESIS{Karl:41885,
      author       = {Karl, Matthias},
      title        = {{M}odellierung atmosphärisch-chemischer {R}eaktionen in
                      der {T}ageslicht-{A}tmosphären-{S}imulationskammer},
      volume       = {4140},
      issn         = {0944-2952},
      school       = {Univ. Münster},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-41885, Juel-4140},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {215 S.},
      year         = {2004},
      note         = {Record converted from VDB: 12.11.2012; Münster, Univ.,
                      Diss., 2004},
      abstract     = {The abundance of the higly reactive hydroxyl radical (OH
                      radical) in the troposphere (lower 10 kilometers of the
                      atmosphere) is of great importance for the removal of both
                      naturally occurring trace gases and those brought in by
                      human activities. Ozone (O$_{3}$) is formed in a complex
                      reaction sequence during the OH-induced degradation of
                      volatile organic compounds (VOC) involving nitrogen oxides
                      (NO$_{x}$, NO$_{x}$ = NO + NO$_{2}$) and solar radiation.
                      Elevated levels of ozone mixing ratios in the planetary
                      boundary layer (lower up to two kilometers of the
                      troposphere) represent a serious hazard for human health and
                      vegetation. Isoprene, a volatile organic compound released
                      by vegetation, plays an important role in the formation of
                      ozone. Its high reactivity towards the OH radical in
                      conjunction with its large global emission rate renders
                      isoprene a compound of outstanding importance in the
                      atmosphere. Formaldehyde (HCHO) is a major product from
                      isoprene oxidation and represents a substantial source for
                      HOx radicals (combined OH radicals and hydrogen peroxy
                      radicals (HO$_{2}$)). The atmosphere simulation chamber
                      SAPHIR provides the opportunity to investigate different air
                      masses with defined chemical compositions under conditions
                      (sun light, temperature and pressure) comparable to the
                      atmosphere. An important advantage of SAPHIR is the
                      possibility to study kinetic parameters (for example rate
                      constants) from the gas-phase oxidation of VOC at
                      tropospheric mixing ratios of reactants. The method of
                      sensitivity analysis is employed to develop an experimental
                      design for chamber experiments exploring rate constants in
                      SAPHIR. Chamber sources for gaseous nitrous acid (HONO) and
                      HCHO can have a strong impact on gas-phase chemistry.
                      Parameterisations for these chamber sources were derived
                      from the measured temporal increase of the respective
                      compounds. Time dependent concentration profiles of HCHO
                      from chamber experiments investigating the photochemical
                      removal of HCHO were analysed. Analysis of the chemical
                      balance of HCHO supplied evidence for the correctness of the
                      spectralradiometric method used for the determination of
                      photolysis frequencies of HCHO. The rate constant of HCHO
                      with the OH radical, determined in this work, is within the
                      error limits of the actually recommended value. Based on a
                      current chemical sheme for the degradation of isoprene,
                      which embodies recent kinetic data and reaction pathways, a
                      detailed pattern for the treatment of the isoprene oxidation
                      products methacrolein (MACR) and methyl vinyl ketone (MVK)
                      was developed. In experiments investigating the OH-induced
                      and O$_{3}$-induced oxidation, rate constants were
                      determined for the initial steps, using measured
                      concentrations of isoprene, OH and O$_{3}$. The determined
                      values are in accordance with literature values. In
                      comparison with literature values of OH-induced oxidation of
                      isoprene in the presence of NO$_{x}$, higher product yields
                      were derived for MACR and MVK, while the rate constants of
                      their OH-reactions were lower for about 20 \%. The
                      tropospheric relevance of these results was investigated
                      using a photochemical scenario which represents a polluted
                      air mass over a close-to-the-city forest area. It was
                      concluded that MACR and MVK provide an important sink for OH
                      radicals.},
      cin          = {ICG-II},
      cid          = {I:(DE-Juel1)VDB48},
      pnm          = {Chemie und Dynamik der Geo-Biosphäre},
      pid          = {G:(DE-Juel1)FUEK257},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/41885},
}