% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Berresheim:172737,
      author       = {Berresheim, H. and Adam, M. and Monahan, C. and O'Dowd, C.
                      and Plane, J. M. C. and Bohn, B. and Rohrer, F.},
      title        = {{M}issing {SO}2 oxidant in the coastal atmosphere? -
                      observations from high-resolution measurements of {OH} and
                      atmospheric sulfur compounds},
      journal      = {Atmospheric chemistry and physics},
      volume       = {14},
      number       = {22},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2014-06181},
      pages        = {12209 - 12223},
      year         = {2014},
      abstract     = {Diurnal and seasonal variations of gaseous sulfuric acid
                      (H2SO4) and methane sulfonic acid (MSA) were measured in NE
                      Atlantic air at the Mace Head atmospheric research station
                      during the years 2010 and 2011. The measurements utilized
                      selected-ion chemical ionization mass spectrometry (SI/CIMS)
                      with a detection limit for both compounds of 4.3 × 104
                      cm−3 at 5 min signal integration. The H2SO4 and MSA
                      gas-phase concentrations were analyzed in conjunction with
                      the condensational sink for both compounds derived from 3 nm
                      to 10 μm (aerodynamic diameter) aerosol size distributions.
                      Accommodation coefficients of 1.0 for H2SO4 and 0.12 for MSA
                      were assumed, leading to estimated atmospheric lifetimes on
                      the order of 7 and 25 min, respectively. With the SI/CIMS
                      instrument in OH measurement mode alternating between OH
                      signal and background (non-OH) signal, evidence was obtained
                      for the presence of one or more unknown oxidants of SO2 in
                      addition to OH. Depending on the nature of the oxidant(s),
                      its ambient concentration may be enhanced in the CIMS inlet
                      system by additional production. The apparent unknown SO2
                      oxidant was additionally confirmed by direct measurements of
                      SO2 in conjunction with calculated H2SO4 concentrations. The
                      calculated H2SO4 concentrations were consistently lower than
                      the measured concentrations by a factor of 4.7 ± 2.4 when
                      considering the oxidation of SO2 by OH as the only source of
                      H2SO4. Both the OH and the background signal were also
                      observed to increase significantly during daytime aerosol
                      nucleation events, independent of the ozone photolysis
                      frequency, J(O1D), and were followed by peaks in both H2SO4
                      and MSA concentrations. This suggests a strong relation
                      between the unknown oxidant(s), OH chemistry, and the
                      atmospheric photolysis and photooxidation of biogenic iodine
                      compounds. As to the identity of the atmospheric SO2
                      oxidant(s), we have been able to exclude ClO, BrO, IO, and
                      OIO as possible candidates based on {ab initio}
                      calculations. $Never\-theless,$ IO could contribute
                      significantly to the observed CIMS background signal. A
                      detailed analysis of this CIMS background signal in context
                      with recently published kinetic data currently suggests that
                      Criegee intermediates (CIs) produced from ozonolysis of
                      alkenes play no significant role for SO2 oxidation in the
                      marine atmosphere at Mace Head. On the other hand, SO2
                      oxidation by small CIs such as CH2OO produced photolytically
                      or possibly in the photochemical degradation of methane is
                      consistent with our observations. In addition, H2SO4
                      formation from dimethyl sulfide oxidation via SO3 as an
                      intermediate instead of SO2 also appears to be a viable
                      explanation. Both pathways need to be further explored.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {233 - Trace gas and aerosol processes in the troposphere
                      (POF2-233)},
      pid          = {G:(DE-HGF)POF2-233},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000345290700014},
      doi          = {10.5194/acp-14-12209-2014},
      url          = {https://juser.fz-juelich.de/record/172737},
}