Signature of Arctic surface ozone depletion events in the isotope anomaly (∆ 17 O) of atmospheric nitrate

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Morin, S., Savarino, J., Bekki, Slimane, Gong, S., Bottenheim, J. W.
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Air Quality Research Division Toronto, Environment and Climate Change Canada (ECCC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic; Nunavut
• Online Access: https://hal.science/hal-00327970; https://hal.science/hal-00327970v2/document; https://hal.science/hal-00327970v2/file/acp-7-1451-2007.pdf; https://doi.org/10.5194/acp-7-1451-2007

International audience We report in this paper the first measurements of the isotopic anomaly of oxygen in Arctic atmospheric inorganic nitrate. Data and samples were collected at Alert, Nunavut, Canada (82°30' N, 62°19' W) in spring 2004. Focusing on the polar sunrise period, characterized by the occurrence of severe boundary layer ozone depletion events (ODEs), our data show a significant correlation between the evolution of atmospheric ozone (O 3 ) mixing ratios and ∆ 17 O in nitrate ∆ 17 O(NO - 3 )). This relationship can be expressed as: 17 O(NO - 3 )/‰=0.15 O 3 / (nmol mol -1 ) + 28.6, with R 2 =0.70 (n=12), for ∆ 17 O(NO - 3 ) ranging between 29 and 34. To quantitatively interpret this relationship, we derive from mechanisms at play in the arctic boundary layer isotopic mass-balance equations, which depend on the concentrations of reactive species and their isotopic characteristics. Changes in the relative importance of O 3 , RO 2 and BrO in the oxidation of NO x during ODEs, and the large isotopic anomalies that O 3 and BrO carry, are the driving force for the high variability in the measured ∆ 17 O(NO - 3 ). BrONO 2 hydrolysis is found to be the major source of nitrate in the arctic boundary layer, in agreement with recent modeling studies. In addition, the isotopic fingerprint of the activity of ozone in a relatively stable compound appears somewhat promising in the perspective of using the isotopic composition of nitrate embedded in polar ice-cores as a paleo-indicator of the atmospheric ozone level that may yield an indirect proxy for the oxidative power of past atmospheres.