title: Measurement of rare isotopologues of nitrous oxide by high-resolution multi-collector mass spectrometry.
abstract: Bulk and position-specific stable isotope characterization of nitrous oxide represents one of the most powerful tools for identifying its environmental sources and sinks. Constraining (14) N(15) N(18) O and (15) N(14) N(18) O will add two new dimensions to our ability to uniquely fingerprint N2 O sources.
  
  
  
  We describe a technique to measure six singly and doubly substituted isotopic variants of N2 O, constraining the values of δ(15) N, δ(18) O, ∆(17) O, (15) N site preference, and the clumped isotopomers (14) N(15) N(18) O and (15) N(14) N(18) O. The technique uses a Thermo MAT 253 Ultra, a high-resolution multi-collector gas source isotope ratio mass spectrometer. It requires 8-10 hours per sample and ~10 micromoles or more of pure N2 O.
  
  
  
  We demonstrate the precision and accuracy of these measurements by analyzing N2 O brought to equilibrium in its position-specific and clumped isotopic composition by heating in the presence of a catalyst. Finally, an illustrative analysis of biogenic N2 O from a denitrifying bacterium suggests that its clumped isotopic composition is controlled by kinetic isotope effects in N2 O production.
  
  
  
  We developed a method for measuring six isotopic variants of N2 O and tested it with analyses of biogenic N2 O. The added isotopic constraints provided by these measurements will enhance our ability to apportion N2 O sources.
authors: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA.
authors: Paul M
authors: 0000-0003-0234-247X
authors: PM
authors: Magyar
authors: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA.
authors: Victoria J
authors: VJ
authors: Orphan
authors: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA.
authors: John M
authors: JM
authors: Eiler