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@ARTICLE{Rosanka:877782,
      author       = {Rosanka, Simon and Vu, Giang H. T. and Nguyen, Hue M. T.
                      and Pham, Tien V. and Javed, Umar and Taraborrelli, Domenico
                      and Vereecken, Luc},
      title        = {{A}tmospheric chemical loss processes of isocyanic acid
                      ({HNCO}): a combined theoretical kinetic and global
                      modelling study},
      journal      = {Atmospheric chemistry and physics},
      volume       = {20},
      number       = {11},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2020-02449},
      pages        = {6671 - 6686},
      year         = {2020},
      abstract     = {Isocyanic acid (HNCO) is a chemical constituent suspected
                      to be harmful to humans if ambient concentrations exceed
                      ∼1 ppbv. HNCO is mainly emitted by combustion processes
                      but is also inadvertently released by NOx mitigation
                      measures in flue gas treatments. With increasing biomass
                      burning and more widespread usage of catalytic converters in
                      car engines, good prediction of HNCO atmospheric levels with
                      global models is desirable. Little is known directly about
                      the chemical loss processes of HNCO, which limits the
                      implementation in global Earth system models. This study
                      aims to close this knowledge gap by combining a theoretical
                      kinetic study on the major oxidants reacting with HNCO with
                      a global modelling study. The potential energy surfaces of
                      the reactions of HNCO with OH and NO3 radicals, Cl atoms,
                      and ozone were studied using high-level
                      CCSD(T)/CBS(DTQ)//M06-2X/aug-cc-pVTZ quantum chemical
                      methodologies, followed by transition state theory (TST)
                      theoretical kinetic predictions of the rate coefficients at
                      temperatures of 200–3000 K. It was found that the
                      reactions are all slow in atmospheric conditions, with
                      k(300K)≤7×10−16 cm3molecule−1s−1, and that
                      product formation occurs predominantly by H abstraction; the
                      predictions are in good agreement with earlier experimental
                      work, where available. The reverse reactions of NCO radicals
                      with H2O, HNO3, and HCl, of importance mostly in combustion,
                      were also examined briefly.The findings are implemented into
                      the atmospheric model EMAC (ECHAM/MESSy Atmospheric
                      Chemistry) to estimate the importance of each chemical loss
                      process on a global scale. The EMAC predictions confirm that
                      the gas-phase chemical loss of HNCO is a negligible process,
                      contributing less than $1 \%$ and leaving heterogeneous
                      losses as the major sinks. The removal of HNCO by clouds and
                      precipitation contributes about $10 \%$ of the total loss,
                      while globally dry deposition is the main sink, accounting
                      for $∼90 \%.$ The global simulation also shows that due
                      to its long chemical lifetime in the free troposphere, HNCO
                      can be efficiently transported into the UTLS by deep
                      convection events. Daily-average mixing ratios of
                      ground-level HNCO are found to regularly exceed 1 ppbv in
                      regions dominated by biomass burning events, but rarely
                      exceed levels above 10 ppt in other areas of the
                      troposphere, though locally instantaneous toxic levels are
                      expected.},
      cin          = {IEK-8 / JARA-HPC},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013 / $I:(DE-82)080012_20140620$},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243) / FRONTier simulations
                      of AIR composition evolution (FRONTAIR) $(jiek81_20190501)$},
      pid          = {G:(DE-HGF)POF3-243 / $G:(DE-Juel1)jiek81_20190501$},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000538775000001},
      doi          = {10.5194/acp-20-6671-2020},
      url          = {https://juser.fz-juelich.de/record/877782},
}