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@ARTICLE{Cho:999168,
      author       = {Cho, Changmin and Fuchs, Hendrik and Hofzumahaus, Andreas
                      and Holland, Frank and Bloss, William J. and Bohn, Birger
                      and Dorn, Hans-Peter and Glowania, Marvin and Hohaus,
                      Thorsten and Liu, Lu and Monks, Paul S. and Niether, Doreen
                      and Rohrer, Franz and Sommariva, Roberto and Tan, Zhaofeng
                      and Tillmann, Ralf and Kiendler-Scharr, Astrid and Wahner,
                      Andreas and Novelli, Anna},
      title        = {{E}xperimental chemical budgets of {OH}, {HO} 2 , and {RO}
                      2 radicals in rural air in western {G}ermany during the
                      {JULIAC} campaign 2019},
      journal      = {Atmospheric chemistry and physics},
      volume       = {23},
      number       = {3},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2023-01202},
      pages        = {2003 - 2033},
      year         = {2023},
      abstract     = {Photochemical processes in ambient air were studied using
                      the atmospheric simulation chamber SAPHIR at
                      Forschungszentrum Jülich, Germany. Ambient air was
                      continuously drawn into the chamber through a 50 m high
                      inlet line and passed through the chamber for 1 month in
                      each season throughout 2019. The residence time of the air
                      inside the chamber was about 1 h. As the research center
                      is surrounded by a mixed deciduous forest and is located
                      close to the city Jülich, the sampled air was influenced by
                      both anthropogenic and biogenic emissions. Measurements of
                      hydroxyl (OH), hydroperoxyl (HO2), and organic peroxy (RO2)
                      radicals were achieved by a laser-induced fluorescence
                      instrument. The radical measurements together with
                      measurements of OH reactivity (kOH, the inverse of the OH
                      lifetime) and a comprehensive set of trace gas
                      concentrations and aerosol properties allowed for the
                      investigation of the seasonal and diurnal variation of
                      radical production and destruction pathways. In spring and
                      summer periods, median OH concentrations reached
                      6 × 106 cm−3 at noon, and median concentrations of
                      both HO2 and RO2 radicals were 3 × 108 cm−3. The
                      measured OH reactivity was between 4 and 18 s−1 in both
                      seasons. The total reaction rate of peroxy radicals with NO
                      was found to be consistent with production rates of odd
                      oxygen (Ox= NO2 + O3) determined from NO2 and O3
                      concentration measurements. The chemical budgets of radicals
                      were analyzed for the spring and summer seasons, when peroxy
                      radical concentrations were above the detection limit. For
                      most conditions, the concentrations of radicals were mainly
                      sustained by the regeneration of OH via reactions of HO2 and
                      RO2 radicals with nitric oxide (NO). The median diurnal
                      profiles of the total radical production and destruction
                      rates showed maxima between 3 and 6 ppbv h−1 for OH,
                      HO2, and RO2. Total ROX (OH, HO2, and RO2) initiation and
                      termination rates were below 3 ppbv h−1. The highest
                      OH radical turnover rate of 13 ppbv h−1 was observed
                      during a high-temperature (max. 40 ∘C) period in August.
                      In this period, the highest HO2, RO2, and ROX turnover rates
                      were around 11, 10, and 4 ppbv h−1, respectively. When
                      NO mixing ratios were between 1 and 3 ppbv, OH and HO2
                      production and destruction rates were balanced, but
                      unexplained RO2 and ROX production reactions with median
                      rates of 2 and 0.4 ppbv h−1, respectively, were
                      required to balance their destruction. For NO mixing ratios
                      above 3 ppbv, the peroxy radical reaction rates with NO
                      were highly uncertain due to the low peroxy radical
                      concentrations close to the limit of NO interferences in the
                      HO2 and RO2 measurements. For NO mixing ratios below
                      1 ppbv, a missing source for OH and a missing sink for HO2
                      were found with maximum rates of 3.0 and 2.0 ppbv h−1,
                      respectively. The missing OH source likely consisted of a
                      combination of a missing inter-radical HO2 to OH conversion
                      reaction (up to 2 ppbv h−1) and a missing primary
                      radical source (0.5–1.4 ppbv h−1). The dataset
                      collected in this campaign allowed analyzing the potential
                      impact of OH regeneration from RO2 isomerization reactions
                      from isoprene, HO2 uptake on aerosol, and RO2 production
                      from chlorine chemistry on radical production and
                      destruction rates. These processes were negligible for the
                      chemical conditions encountered in this study.},
      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:000931124700001},
      doi          = {10.5194/acp-23-2003-2023},
      url          = {https://juser.fz-juelich.de/record/999168},
}