HR: 0800h
AN: A11C-0599    [Abstracts]
TI: Latitudinal variations of nitrogen and triple oxygen isotopic composition of nitrate in the marine boundary layer over the Atlantic Ocean
AU: * Morin, S
EM: samuel.morin@lgge.obs.ujf-grenoble.fr
AF: LGGE, CNRS-UJF Grenoble, Saint Martin d'Heres, 38400, France
AU: Frey, M M
EM: frey@lgge.obs.ujf-grenoble.fr
AF: LGGE, CNRS-UJF Grenoble, Saint Martin d'Heres, 38400, France
AU: Frey, M M
EM: frey@lgge.obs.ujf-grenoble.fr
AF: School of Engineering, University of California, Merced, Atwater, CA 95301, United States
AU: Grudzieu, A
EM: Amandine.Grudzieu@bvra.e.ujf-grenoble.fr
AF: LGGE, CNRS-UJF Grenoble, Saint Martin d'Heres, 38400, France
AU: Martins, J
EM: Jean.Martins@hmg.inpg.fr
AF: LTHE, CNRS-UJF Grenoble, Saint Martin d'Heres, 38400, France
AU: Savarino, J
EM: joel.savarino@lgge.obs.ujf-grenoble.fr
AF: LGGE, CNRS-UJF Grenoble, Saint Martin d'Heres, 38400, France
AB: The analysis of the isotopic composition of nitrate (NO₃^-) in various environments is a fast-growing field of investigation. Atmospheric nitrate oxygen isotopes feature the appealing potential to record a footprint of the cycling between ozone (O₃) and nitrogen oxides (NO_x), through the transmission of an isotope anomaly (Δ¹⁷O=δ¹⁷O - 0.52 ×~δ¹⁸O) borne by the ozone molecule. This discovery has lead to the idea that the isotopic composition of nitrate preserved in firn and ice of the polar ice caps could be used as a proxy of past ozone chemistry and thus provide the long-awaited link between the climate record from ice cores and the oxidative capacity of ancient atmospheres. To better constrain the relationships between nitrate oxygen isotopes and the oxidative state of the atmosphere, we have carried out a series of ship-borne measurements in the marine boundary layer (MBL) between Cape Town, Rep. South Africa (30°S) and Bremerhaven, Germany (50°N) covering a wide range of meteorological and atmospheric chemistry conditions. Onboard the R/V Polarstern, we measured surface ozone and collected size-segregated aerosols with a latitudinal resolution of 4°. Besides major ions concentrations, nitrate contained in these samples was analyzed for all stable isotopes of its constituents (namely δ¹⁵N, δ¹⁷O and δ¹⁸O), using the denitrifier technique (based on Kaiser et al., Anal. Chem., 2007), thus providing an unprecedented latitudinal profile of nitrate isotopes in the MBL. Variations of nitrate isotopic compositions are studied as a function of particle size and changing MBL background chemistry, ranging from the remote and unpolluted Southern Atlantic Ocean (O₃ 20 nmol~mol^-1) to the polluted English Channel area (O₃ 45 nmol~mol^-1), through air masses influenced by North-African desert dust in the subtropical North Atlantic. Known main chemical mechanisms responsible for the formation of atmospheric nitrate are used to test our understanding of the causes for the variations of Δ¹⁷O(NO₃^-) in different atmospheric environments.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0365 Troposphere: composition and chemistry
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0469 Nitrogen cycling
DE: 9325 Atlantic Ocean
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting