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Chloramines as an important photochemical source of chlorine atoms in the urban atmosphere

Wang, Chen ; Liggio, John ; Wentzell, Jeremy J B ; Jorga, Spiro ; Folkerson, Andrew ; Abbatt, Jonathan P D

Proceedings of the National Academy of Sciences - PNAS, 2023-07, Vol.120 (30), p.e2220889120-e2220889120 [Periódico revisado por pares]

United States: National Academy of Sciences

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  • Título:
    Chloramines as an important photochemical source of chlorine atoms in the urban atmosphere
  • Autor: Wang, Chen ; Liggio, John ; Wentzell, Jeremy J B ; Jorga, Spiro ; Folkerson, Andrew ; Abbatt, Jonathan P D
  • Assuntos: Atmosphere ; Boundary layers ; Central business districts ; Chlorine ; Mixing ratio ; Monochloramine ; Night ; Nitrogen oxides ; Organic compounds ; Ozone ; Particulate matter ; Photochemicals ; Photochemistry ; Photolysis ; Physical Sciences ; Summer ; Sunrise ; Urban areas ; Urban atmosphere ; Winter
  • É parte de: Proceedings of the National Academy of Sciences - PNAS, 2023-07, Vol.120 (30), p.e2220889120-e2220889120
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
    Edited by Steven S. Brown, National Oceanic and Atmospheric Administration, Boulder, CO; received December 14, 2022; accepted June 10, 2023 by Editorial Board Member Akkihebbal R. Ravishankara
  • Descrição: Monochloramine, dichloramine and trichloramine (NH Cl, NHCl , NCl ) are measured in the ambient atmosphere, in downtown Toronto in summer (median 39, 15 and 2.8 ppt) and winter (median 11, 7.3 and 0.7 ppt). NCl and NHCl were also measured in summer (median 1.3 and 14 ppt) from a suburban Toronto location. Measurements at two locations demonstrate prevalence of chloramines in an urban atmosphere. At both sites, NCl exhibits a strong diel pattern with maximum values during the night, and photolytic loss with sunrise. At the downtown site, a strong positive correlation between NH Cl and NHCl in the summer night indicates a common source, with daily average peak mixing ratios approaching 500 and 250 ppt, respectively. As a previously unidentified source of chlorine (Cl) atoms, we demonstrate that NCl photolysis contributes 49 to 82% of the total local summertime Cl production rate at different times during the day with an average noontime peak of 3.8 × 10 atoms/cm /s, with smaller contributions from ClNO and Cl . Photolysis of NH Cl and NHCl may augment this Cl production rate. Our measurements also demonstrate a daytime enhancement of chloroacetone in both the summer and winter, demonstrating the importance of Cl photochemistry. The results suggest that chloramines are an important source of Cl atoms in urban areas, with potential impacts on the abundance of organic compounds, ozone, nitrogen oxides, and particulate matter. Future studies should explore the vertical gradients of chloramines and their contribution to Cl production throughout the boundary layer.
  • Editor: United States: National Academy of Sciences
  • Idioma: Inglês
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