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@ARTICLE{Tan:857600,
      author       = {Tan, Zhaofeng and Lu, Keding and Hofzumahaus, Andreas and
                      Fuchs, Hendrik and Bohn, Birger and Holland, Frank and Liu,
                      Yuhan and Rohrer, Franz and Shao, Min and Sun, Kang and Wu,
                      Yusheng and Zeng, Limin and Zhang, Yinsong and Zou, Qi and
                      Kiendler-Scharr, Astrid and Wahner, Andreas and Zhang,
                      Yuanhang},
      title        = {{E}xperimental budgets of {OH}, ${HO}\<sub\>2\</sub\>$ and
                      ${RO}\<sub\>2\</sub\>$ radicals and implications for ozone
                      formation in the {P}earl {R}iver {D}elta in {C}hina 2014},
      journal      = {Atmospheric chemistry and physics / Discussions Discussions
                      [...]},
      volume       = {acp-2018-801},
      issn         = {1680-7375},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2018-06585},
      pages        = {1 - 28},
      year         = {2018},
      abstract     = {Hydroxyl (OH) and peroxy radicals (HO2, RO2) were measured
                      in the Pearl River Delta which is one of the most polluted
                      areas in China, in autumn 2014. The radical observations
                      were complemented by measurements of OH reactivity (inverse
                      OH lifetime) and a comprehensive set of trace gases
                      including CO, NOx and VOCs. OH reactivity was in the range
                      between 15s−1 and 80s−1, of which about $50\%$ was
                      unexplained by the measured OH reactants. In the three weeks
                      of the campaign, maximum median radical concentrations were
                      4.5×106cm−3 for OH at noon, and 3×108cm−3 and
                      2.0×108cm−3 for HO2 and RO2, respectively, in the early
                      afternoon. The completeness of the daytime radical
                      measurements made it possible to carry out experimental
                      budget analyses for all radicals (OH, HO2, and RO2) and
                      their sum (ROx). The maximum loss rates for OH, HO2, and RO2
                      reached values between 10ppbv/h and 15ppbv/h during daytime.
                      The largest fraction of this can be attributed to radical
                      interconveresio reactions while the real loss rate of ROx
                      remained below 3ppbv/h. Within experimental uncertainties,
                      the destruction rates of HO2 and the sum of OH, HO2, and RO2
                      are balanced by their respective production rates. In case
                      of RO2, the budget can only be closed when the missing OH
                      reactivity is attributed to unmeasured VOCs. Thus, the
                      existence of unmeasured VOCs is directly confirmed by RO2
                      measurements. Although the closure of the RO2 budget is
                      greatly improved by the additional unmeasured VOCs, a
                      significant imbalance in the afternoon remains indicating a
                      missing RO2 sink. In case of OH, the destruction in the
                      morning is compensated by the quantified OH sources from
                      photolysis (HONO, O3), ozonolysis of alkenes and OH
                      recycling (HO2+NO). In the afternoon, however, the OH budget
                      indicates a missing OH source of (4–6)ppbv/h. The diurnal
                      variation of the missing OH source shows a similar pattern
                      as that of the missing RO2 sink so that both largely
                      compensate each other in the ROx budget. These observations
                      suggest the existence of a chemical mechanism that converts
                      RO2 to OH without the involvement of NO. The photochemical
                      net ozone production rate calculated from the reaction of
                      HO2 and RO2 with NO yields a daily integrated amount of
                      102ppbv ozone with daily integrated ROx primary sources
                      being 22ppbv in this campaign. This value can be attributed
                      to the oxidation of measured $(18\%)$ and unmeasured
                      $(60\%)$ hydrocarbons, formaldehyde $(14\%)$ and CO $(8\%).$
                      An even larger integrated net ozone production of 140ppbv
                      would be calculated from the oxidation rate of VOCs with OH,
                      if HO2 and all RO2 radicals would react with NO. However,
                      the unknown RO2 loss (evident in the RO2 budget) causes
                      $30\%$ less ozone production than would be expected from the
                      VOC oxidation rate.},
      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},
      doi          = {10.5194/acp-2018-801},
      url          = {https://juser.fz-juelich.de/record/857600},
}