Production of standard gases for routine calibration of stable isotope ratios of N2 and N2O
2 Institute of Meteorology and Climate Research Atmospheric Environmental Research
3 Laboratory of Isotope Geology and Geoecology, Institute of Geological Sciences, University of Wrocław
4 Empa Swiss Federal Laboratories for Materials Science and Technology
P 5.8 in Methods, Models, Standards
There is need to calibrate raw data of N2 and N2O isotopocules due to effects of non-linearity, instability, matrix effects and interference with trace gases. Our objective was thus to supply a variety of suitable standard gases for members of the DASIM research unit (www.DASIM.de) and their partners in sufficient amount for routine use to enable calibration for extended time. In total 23 different mixtures were produced to cover all isotopic approaches to study N2 and N2O production and cycling in soils with stable isotopes and suitable for IRMS and laser spectroscopy.
Standards for the 15N gas flux method should mimic mixtures of N2 and N2O emitted from highly 15N enriched nitrate in soil and atmospheric background. These must thus contain unlabelled, single-labelled as well as double-labelled N2 and N2O.
N2O standards for natural abundance must cover a range of N2O concentrations and isotopocule values typically found in field flux and laboratory incubation studies to correct for non-linearity and bias.
Premixtures were prepared by mixing isotopically enriched or depleted gases which were either commercially available or produced in the lab. Moreover, pure N2O of natural abundance was supplied from a previous project (Mohn et al., 2022, https://doi.org/10.1002/rcm.9296). Premixtures were diluted in artificial atmospheres and compressed in commercial tanks.
We will explain the production of mixtures, give an overview of the manufactured mixtures and show first results of analysis in comparison with ideal values.