HR: 1330h
AN: A52A-0764    [PDF]
TI: Absolute calibration of the intramolecular nitrogen isotope distribution in N$_{2}$O
AU: * Kaiser, J
EM: kaiser@princeton.edu
AF: Princeton University, Dept. of Geosciences, Guyot Hall, Princeton, NJ 08544 United States
AU: * Kaiser, J
EM: kaiser@princeton.edu
AF: Max Planck Institute for Chemistry, Dept. of Atmospheric Chemistry, Becherweg 29, Mainz, NJ 55128 Germany
AU: * Kaiser, J
EM: kaiser@princeton.edu
AF: Max Planck Institute for Nuclear Physics, Atmospheric Physics Division, Saupfercheckweg 1, Heidelberg, NJ 69117 Germany
AU: Park, S
EM: sunyoung@uclink4.berkeley.edu
AF: University of California, Dept. of Earth and Planetary Sciences, Giauque Hall, Berkeley, CA 94720 United States
AU: Boering, K A
EM: boering@cchem.berkeley.edu
AF: University of California, Dept. of Earth and Planetary Sciences, Giauque Hall, Berkeley, CA 94720 United States
AU: Boering, K A
EM: boering@cchem.berkeley.edu
AF: University of California, Dept. of Chemistry, Giauque Hall, Berkeley, CA 94720 United States
AU: Brenninkmeijer, C A
EM: carlb@mpch-mainz.mpg.de
AF: Max Planck Institute for Chemistry, Dept. of Atmospheric Chemistry, Becherweg 29, Mainz, NJ 55128 Germany
AU: Hilkert, A
EM: andreas.hilkert@thermo.com
AF: Thermo Finnigan MAT, Barkhausenweg, Bremen, NJ 28 Germany
AU: R\"{o}ckmann, T
EM: T.Roeckmann@mpi-hd.mpg.de
AF: Max Planck Institute for Nuclear Physics, Atmospheric Physics Division, Saupfercheckweg 1, Heidelberg, NJ 69117 Germany
AB: A mass spectrometric method to determine the absolute intramolecular (position-dependent) nitrogen isotope ratios of nitrous oxide (N$_{2}$O) has been developed. It is based on the addition of different amounts of doubly-labeled $^{15}$N$_{2}$O to an N$_{2}$O sample of the isotope ratio mass spectrometer reference gas, and subsequent measurement of the relative ion current ratios of species with mass 30, 31, 44, 45 and 46. All relevant quantities are measured by isotope ratio mass spectrometers, which means that the latters inherent high precision of the order of 10$^{-5}$ can be fully exploited. External determination of dilution factors with generally lower precision is avoided. The method itself can be implemented within a day, but a calibration of the oxygen and average nitrogen isotope ratios relative to a primary isotopic reference material of known absolute isotopic composition has to be performed separately. Considering all known statistical uncertainties of measured quantities and absolute isotope ratios of primary isotopic reference materials, we achieve an overall uncertainty of 0.9$\permil$ (1$\sigma$). Using tropospheric N$_{2}$O as common reference point for intercomparison purposes, we find a substantially higher relative enrichment of $^{15}$N at the central nitrogen atom over $^{15}$N at the terminal nitrogen atom than measured previously for tropospheric N$_{2}$O, based on a chemical conversion method: (46.3$\pm$1.4)$\permil$ as opposed to (18.7$\pm$2.2)$\permil$. However, our method depends critically on the absolute isotope ratios of the primary isotopic reference materials air-N$_{2}$ and VSMOW. If they are systematically wrong, our estimates will also necessarily be incorrect.
UR: http://www.princeton.edu/~kaiser
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
DE: 1040 Isotopic composition/chemistry
DE: 1094 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting