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@PHDTHESIS{Frber:1033616,
      author       = {Färber, Michelle},
      title        = {{I}nvestigation of current and future anthropogenic
                      chemical regimes in simulation chamber experiments},
      volume       = {657},
      school       = {Köln},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2024-06496},
      isbn         = {978-3-95806-809-4},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {225},
      year         = {2025},
      note         = {Dissertation, Köln, 2024},
      abstract     = {Air pollution is a societal challenge, affecting millions
                      of people world-wide living in urban conglomerates. In
                      cities, emissions are mostly from anthropogenic activities
                      such as traffic, industry, cooking, and use of volatile care
                      products. These emissions are not only hazardous for human
                      health, they also undergo chemical degradation driven by
                      oxidants, forming secondary pollutants such as ozone (O3)
                      and particles. Main tropospheric oxidants are the hydroxyl
                      radical (OH), dominating oxidation processes during the day,
                      the nitrate radical (NO3), predominantly available during
                      the night, and ozone. In the reaction chain of the
                      atmospheric oxidation of volatile organic compounds (VOCs),
                      peroxy (RO2) and hydroperoxy (HO2) radicals are formed,
                      which oxidise nitric oxide (NO) to nitrogen dioxide (NO2),
                      the latter being the main tropospheric source of ozone
                      following its photolysis. Understanding atmospheric
                      oxidation processes is crucial for mitigating air pollution
                      and tackling current and future air quality challenges. In
                      many different field studies, performed in or close to urban
                      areas, measured HO2 and/or RO2 radical concentrations could
                      not be reproduced by chemical model calculations, which
                      represent the current understanding of the atmospheric
                      chemistry. Even though chemical models carry uncertainties,
                      the observed discrepancies in particular for RO2 radicals
                      often exceeded a factor of three, making air quality
                      prediction challenging. Data collected during field
                      campaigns are very valuable in highlighting where our gap of
                      knowledge for atmospheric chemical processes lies.
                      Laboratory studies and experiments in atmospheric simulation
                      chambers can then focus on investigating such processes in a
                      confined and controlled environment. In this thesis, first
                      the performance and comparability of several different
                      atmospheric simulation chambers were studied. Oxidation
                      experiments of -pinene were performed in nine different
                      simulation chambers, which are part of the EUROCHAMP-2020
                      consortium. Chamber effects, such as the release of small
                      oxygenated compounds from the chamber wall or the loss of
                      trace gases or particles on the chamber wall were
                      characterised. Furthermore, yields of pinonaldehyde,
                      formaldehyde, and acetone, which are products from the
                      oxidation of -pinene by OH, could be derived for experiments
                      in five different chambers. A high variability of the yields
                      of pinonaldehyde and formaldehyde was observed, which is
                      also reflected in the available data from the literature. In
                      contrast, obtained acetone yields agree within the combined
                      uncertainties for the different chambers and within the
                      uncertainties with reported literature values. Overall,
                      well-characterised simulation chambers offer a great
                      opportunity to investigate atmospheric chemistry in a
                      controlled environment. The goal is to simplify the
                      complexity of field studies while still keeping the
                      conditions comparable to the real atmosphere. The main part
                      of the thesis is on the investigation of the daytime and
                      nighttime oxidation of anthropogenic VOCs in the atmospheric
                      simulation chamber SAPHIR at Forschungszentrum Jülich,
                      Germany. Measured trace gas and radical concentrations were
                      compared to zerodimensional box model calculations, based on
                      the Master Chemical Mechanism (MCM) and complemented by an
                      updated ozonolysis scheme for alkenes, and by
                      state-of-the-art peroxy and alkoxy chemistry from
                      structure-activity relationships (SAR). Photooxidation
                      experiments were performed for a variety of anthropogenic
                      VOCs at different levels of NO, mimicking current (high NO)
                      and future (low NO) chemical regimes. The VOCs investigated
                      were chosen according to their alkoxy chemistry, forming HO2
                      either in a single-step reaction (propane, propene,
                      trans-2-hexene) or in a multi-step reaction involving the
                      regeneration of RO2 (iso-pentane, n-hexane), which results
                      in a different number of ozone molecules produced per
                      oxidised VOC molecule. A comparison between measured trace
                      gases and radicals with results from the the MCM showed
                      overall a good agreement (within 17 $\%)$ for most VOCs. An
                      improved agreement of HO2 and RO2 radical concentrations, in
                      experiments with n-hexane, was found for the MCM
                      complemented by SAR, assuming a factor of 1:4 higher organic
                      nitrate yields for first-generation RO2 and RO2
                      isomerisation reactions. HO2/RO2 ratios were derived from
                      measured and modelled radical concentrations, showing a 20
                      $\%$ smaller ratio for the VOCs forming HO2 in a multi-step
                      reaction compared to VOCs forming HO2 in a single-step
                      reaction. The production of odd oxygen (Ox = O3 + NO2) was
                      calculated from modelled radical concentrations and from
                      measured Ox for 3 < NO < 6 ppbv and for NO < 1 ppbv, where
                      the Ox formation could additionally be determined from
                      measured radical concentrations. Overall, a good agreement
                      was found for the different approaches. In agreement with
                      the observations of the HO2/RO2 ratio, a 20 $\%$ higher Ox
                      production was observed for species, regenerating another
                      RO2 radical before eventually forming HO2. Overall, the
                      model-measurement discrepancies of the Ox production rates,
                      as found in urban areas, were not observed in the performed
                      chamber experiments. The nighttime oxidation of cis-2-butene
                      and trans-2-hexene was tested in the presence of NO2 at
                      different temperatures (from 3 C to 32 C). At low
                      temperatures, time profiles of measured RO2 radical
                      concentrations were significantly delayed and lower peak
                      concentrations were reached than observed in the modelled
                      RO2 radical time series. The model-measurement agreement
                      could be significantly improved by including the formation
                      of non-acyl peroxynitrates (RO2NO2) from the reaction of RO2
                      with NO2 in the chemical model for all formed non-acyl
                      peroxy radicals. The formation of non-acyl RO2NO2, with the
                      exception of methyl peroxynitrate, is not implemented in
                      commonly used chemical mechanisms, such as the MCM, as it is
                      thought to be negligible due to the short lifetime of alkyl
                      (non-acyl) RO2NO2 of less than 1 s at 298 K. This study
                      suggests that at 10 C, 60 $\%$ of RO2 radicals are stored as
                      corresponding peroxynitrates in the presence of only few
                      ppbv of NO2, which may impact ambient RO2 and NOx (= NO+NO2)
                      concentrations. In addition, a recent model study found an
                      increase of NOx of up to 25 $\%$ on the ground, when
                      including the formation of non-acyl RO2NO2. This suggests
                      that these reactions should be included in chemical
                      mechanisms for a better representation of the underlying
                      chemistry.},
      cin          = {ICE-3},
      cid          = {I:(DE-Juel1)ICE-3-20101013},
      pnm          = {2111 - Air Quality (POF4-211)},
      pid          = {G:(DE-HGF)POF4-2111},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      doi          = {10.34734/FZJ-2024-06496},
      url          = {https://juser.fz-juelich.de/record/1033616},
}