Application of the N2/Ar technique to measuring soil-atmosphere N2 fluxes

Wendy H. Yang, Whendee L. Silver

Research output: Contribution to journalArticlepeer-review


RATIONALE The emission of dinitrogen (N2) gas from soil is the most poorly constrained flux in terrestrial nitrogen (N) budgets because the high background atmospheric N2 concentration makes soil N2 emissions difficult to measure. In this study, we tested the theoretical and analytical feasibility of using the N2/Ar technique to measure soil-atmosphere N2 fluxes. METHODS Dual inlet isotope ratio mass spectrometry was used to measure δAr/N2 values of gas sampled from surface flux chambers. In laboratory experiments using dry sand in a diffusion box, we induced a known steady-state flux of N2, and then measured the change in the N2/Ar ratio of chamber headspace air samples to test our ability to reconstruct this flux. We m\odeled solubility, thermal, and water vapor flux fractionation effects on the N2/Ar ratio to constrain physical effects on the measured N2 flux. RESULTS In dry sand, an actual N2 flux of 108 mg N m-2 day -1 was measured as 111 ± 19 mg N m-2 day -1 (± standard error (SE)). In wet sand, an actual N 2 flux of 160 mg N m-2 day-1 was measured as 146 ± 20 mg N m-2 day-1 when solubility and water vapor flux fractionation were taken into account. Corrections for thermal fractionation did not improve estimates of N2 fluxes. CONCLUSIONS We conclude that our application of the N2/Ar technique to soil surface fluxes is valid only above a detection limit of approximately 108 mg N m -2 day-1. The N2/Ar method is currently best used as a validation tool for other methods in ecosystems with high soil N 2 fluxes, but, with future improvements, it holds promise to provide high-resolution measurements in systems with low soil N2 fluxes.

Original languageEnglish (US)
Pages (from-to)449-459
Number of pages11
JournalRapid Communications in Mass Spectrometry
Issue number4
StatePublished - Feb 29 2012
Externally publishedYes

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry


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