Isotopic composition of atmospheric nitrate in the marine and polar boundary layer

• Main Author: Morin, Samuel
• 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), Université Paris-Est, Michel Legrand, Joël Savarino
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2008
• Subjects: Stable isotopes; Atmospheric nitrate; Isotope anomaly; Oxygen; Nitrogen; Isotopes stables; Nitrate atmosphérique; Ozone; Anomalie isotopique; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Antarc*; Antarctic
• Online Access: https://theses.hal.science/tel-00326229; https://theses.hal.science/tel-00326229v2/document; https://theses.hal.science/tel-00326229v2/file/2008PEST0249_0_1.pdf

Atmospheric nitrogen oxides (NOx=NO+NO2) are central to the chemistry of the environment, as they play a pivotal role in the cycling of reactive nitrogen and the oxidative capacity of the atmosphere. The stable isotopes of atmospheric nitrate (in the form of particulate NO?3 or gaseous HNO3), their main ultimate sinks, provide insights in chemical budget of NOx : its nitrogen isotopes are almost conservative tracers of their sources, whereas NOx sinks are revealed by its triple oxygen isotopic composition. The long-awaited challenge of measuring all three stable isotope ratios of nitrate (17O/16O, 18O/16O and 15N/14N) in a single sample at sub-micromolar levels has been resolved. The newly developed method makes use of denitrifying bacteria to quantitatively convert nitrate to a stable species (N2O), whose isotope ratios are measured using an automated gas chromatography/isotope ratio mass spectrometry analytical system. Dual measurements of d15N and the isotope anomaly (?17O=d17O-0.52×d18O) of atmospheric nitrate samples collected in the Arctic, the Antarctic and in the marine boundary layer of the Atlantic Ocean, have been used to derive the chemical budget of NOx and atmospheric nitrate in these remote regions. Main results from oxygen isotope measurements pertain to the identification of seasonal and latitudinal shifts in NOx oxidative pathways in these environments (including the role of halogen oxides chemistry in polar regions during springtime), as a function of particle sizes. Nitrogen isotopes are found to provide strong constraints on the budget of reactive nitrogen in polar regions, due to the strong fractionation associated with snowpack photochemical loss of nitrate and its conversion to NOx Les oxydes d’azote atmosphériques (NOx=NO+NO2) sont des composés clefs en chimie de l’environnement, jouant un rôle central pour la capacité oxydante de l’atmosphère et le cycle de l’azote. La composition isotopique du nitrate atmosphérique (NO?3 particulaire et HNO3 gazeux), constituant leur puits ultime, ...