Reassessment of the NH NO thermal decomposition technique for calibration of the N O isotopic composition.

Rationale: In the last few years, the study of N O site-specific nitrogen isotope composition has been established as a powerful technique to disentangle N O emission pathways. This trend has been accelerated by significant analytical progress in the field of isotope ratio mass spectrometry (IRMS) and more recently quantum cascade laser absorption spectroscopy (QCLAS).

Methods: The ammonium nitrate (NH NO ) decomposition technique provides a strategy to scale the N site-specific (SP ≡ δ N - δ N ) and bulk (δ N  = (δ N  + δ N )/2) isotopic composition of N O against the international standard for the N/ N isotope ratio (AIR-N ).