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@ARTICLE{Kaminski:830478,
      author       = {Kaminski, Martin and Fuchs, Hendrik and Acir, Ismail-Hakki
                      and Bohn, Birger and Brauers, Theo and Dorn, Hans-Peter and
                      Häseler, Rolf and Hofzumahaus, Andreas and Li, Xin and
                      Lutz, Anna and Nehr, Sascha and Rohrer, Franz and Tillmann,
                      Ralf and Vereecken, Luc and Wegener, Robert and Wahner,
                      Andreas},
      title        = {{I}nvestigation of the β-pinene photooxidation by {OH} in
                      the atmosphere simulation chamber {SAPHIR}},
      journal      = {Atmospheric chemistry and physics},
      volume       = {17},
      number       = {11},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2017-04019},
      pages        = {6631 - 6650},
      year         = {2017},
      abstract     = {Besides isoprene, monoterpenes are the non-methane volatile
                      organic compounds (VOCs) with the highest global emission
                      rates. Due to their high reactivity towards OH, monoterpenes
                      can dominate the radical chemistry of the atmosphere in
                      forested areas. In the present study the photochemical
                      degradation mechanism of β-pinene was investigated in the
                      Jülich atmosphere simulation chamber SAPHIR (Simulation of
                      Atmospheric PHotochemistry In a large Reaction Chamber). One
                      focus of this study is on the OH budget in the degradation
                      process. Therefore, the SAPHIR chamber was equipped with
                      instrumentation to measure radicals (OH, HO2, RO2), the
                      total OH reactivity, important OH precursors (O3, HONO,
                      HCHO), the parent VOC β-pinene, its main oxidation
                      products, acetone and nopinone and photolysis frequencies.
                      All experiments were carried out under low-NO conditions
                      ( ≤  300 ppt) and at atmospheric β-pinene
                      concentrations ( ≤  5 ppb) with and without
                      addition of ozone. For the investigation of the OH budget,
                      the OH production and destruction rates were calculated from
                      measured quantities. Within the limits of accuracy of the
                      instruments, the OH budget was balanced in all β-pinene
                      oxidation experiments. However, even though the OH budget
                      was closed, simulation results from the Master Chemical
                      Mechanism (MCM) 3.2 showed that the OH production and
                      destruction rates were underestimated by the model. The
                      measured OH and HO2 concentrations were underestimated by up
                      to a factor of 2, whereas the total OH reactivity was
                      slightly overestimated because the model predicted a
                      nopinone mixing ratio which was 3 times higher than
                      measured. A new, theory-derived, first-generation product
                      distribution by Vereecken and Peeters (2012) was able to
                      reproduce the measured nopinone time series and the total OH
                      reactivity. Nevertheless, the measured OH and HO2
                      concentrations remained underestimated by the numerical
                      simulations. These observations together with the fact that
                      the measured OH budget was closed suggest the existence of
                      unaccounted sources of HO2. Although the mechanism of
                      additional HO2 formation could not be resolved, our model
                      studies suggest that an activated alkoxy radical
                      intermediate proposed in the model of Vereecken and Peeters
                      (2012) generates HO2 in a new pathway, whose importance has
                      been underestimated so far. The proposed reaction path
                      involves unimolecular rearrangement and decomposition
                      reactions and photolysis of dicarbonyl products, yielding
                      additional HO2 and CO. Further experiments and quantum
                      chemical calculations have to be made to completely unravel
                      the pathway of HO2 formation.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243)},
      pid          = {G:(DE-HGF)POF3-243},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000402958000003},
      doi          = {10.5194/acp-17-6631-2017},
      url          = {https://juser.fz-juelich.de/record/830478},
}