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@ARTICLE{Priestley:894242,
      author       = {Priestley, Michael and Bannan, Thomas J. and Le Breton,
                      Michael and Worrall, Stephen D. and Kang, Sungah and
                      Pullinen, Iida and Schmitt, Sebastian and Tillmann, Ralf and
                      Kleist, Einhard and Zhao, Defeng and Wildt, Jürgen and
                      Garmash, Olga and Mehra, Archit and Bacak, Asan and
                      Shallcross, Dudley E. and Kiendler-Scharr, Astrid and
                      Hallquist, Åsa M. and Ehn, Mikael and Coe, Hugh and
                      Percival, Carl J. and Hallquist, Mattias and Mentel, Thomas
                      F. and McFiggans, Gordon},
      title        = {{C}hemical characterisation of benzene oxidation products
                      under high- and $low-{NO}\<sub\>\<i\>x\</i\>\</sub\>$
                      conditions using chemical ionisation mass spectrometry},
      journal      = {Atmospheric chemistry and physics},
      volume       = {21},
      number       = {5},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-03122},
      pages        = {3473 - 3490},
      year         = {2021},
      abstract     = {Aromatic hydrocarbons are a class of volatile organic
                      compounds associated with anthropogenic activity and make up
                      a significant fraction of urban volatile organic compound
                      (VOC) emissions that contribute to the formation of
                      secondary organic aerosol (SOA). Benzene is one of the most
                      abundant species emitted from vehicles, biomass burning and
                      industry. An iodide time-of-flight chemical ionisation mass
                      spectrometer (ToF-CIMS) and nitrate ToF-CIMS were deployed
                      at the Jülich Plant Atmosphere Chamber as part of a series
                      of experiments examining benzene oxidation by OH under high-
                      and low-NOx conditions, where a range of organic oxidation
                      products were detected. The nitrate scheme detects many
                      oxidation products with high masses, ranging from
                      intermediate volatile organic compounds (IVOCs) to extremely
                      low volatile organic compounds (ELVOCs), including C12
                      dimers. In comparison, very few species with C≥6 and O≥8
                      were detected with the iodide scheme, which detected many
                      more IVOCs and semi-volatile organic compounds (SVOCs) but
                      very few ELVOCs and low volatile organic compounds (LVOCs).
                      A total of 132 and 195 CHO and CHON oxidation products are
                      detected by the iodide ToF-CIMS in the low- and high-NOx
                      experiments respectively. Ring-breaking products make up the
                      dominant fraction of detected signal and 21 and 26 of the
                      products listed in the Master Chemical Mechanism (MCM) were
                      detected. The time series of highly oxidised (O≥6) and
                      ring-retaining oxidation products (C6 and double-bond
                      equivalent = 4) equilibrate quickly, characterised by a
                      square form profile, compared to MCM and ring-breaking
                      products which increase throughout oxidation, exhibiting
                      sawtooth profiles. Under low-NOx conditions, all CHO
                      formulae attributed to radical termination reactions of
                      first-generation benzene products, and first-generation
                      auto-oxidation products are observed. Several N-containing
                      species that are either first-generation benzene products or
                      first-generation auto-oxidation products are also observed
                      under high-NOx conditions. Hierarchical cluster analysis
                      finds four clusters, of which two describe photo-oxidation.
                      Cluster 2 shows a negative dependency on the NO2/NOx ratio,
                      indicating it is sensitive to NO concentration and thus
                      likely to contain NO addition products and alkoxy-derived
                      termination products. This cluster has the highest average
                      carbon oxidation state (OSC¯¯¯¯¯¯¯) and the lowest
                      average carbon number. Where nitrogen is present in a
                      cluster member of cluster 2, the oxygen number is even, as
                      expected for alkoxy-derived products. In contrast, cluster 1
                      shows no dependency on the NO2/NOx ratio and so is likely to
                      contain more NO2 addition and peroxy-derived termination
                      products. This cluster contains fewer fragmented species, as
                      the average carbon number is higher and OSC¯¯¯¯¯¯¯
                      lower than cluster 2, and more species with an odd number of
                      oxygen atoms. This suggests that clustering of time series
                      which have features pertaining to distinct chemical regimes,
                      for example, NO2/NOx perturbations, coupled with a priori
                      knowledge, can provide insight into identification of
                      potential functionality.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {2111 - Air Quality (POF4-211)},
      pid          = {G:(DE-HGF)POF4-2111},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000626739700004},
      doi          = {10.5194/acp-21-3473-2021},
      url          = {https://juser.fz-juelich.de/record/894242},
}