Isotopic data for P18 2016 is being merged in, there is some new stuff in there that needs documenting:
Existing Param Updates
N2O
Add NMOL/L (molar vs molal) as acceptable for this parameter, nc_name of nitrous_oxide_l following the existing de facto conventions.
Expand the definition a bit to be a little more descriptive that this is a gas dissolved in sea water.
D15N_N2O
Since the 15N substitution can occur in one of two positions[^1], and which position can be measured, clarify that this refers to what is sometimes "bulk" D15N which is a substitution in any position.
New Param
D15N_ALPHA_N20
whp_units: /MILLE
nc_units: 1e-3 (i.e. dimensionless ratio)
nc_name: `d15n_alpha_n2o
Definition
Enrichment of 15N vs 14N in N2O (nitrous oxide) where the substitution has occurred at the center position of the N2O molecule as compared to a standard. N2O where the substitution has occurred in the end nitrogen atom is called D15N_BETA and is not usually measured. D15N_BETA can be calculated from bulk D15N and D15N_ALPHA using equation 25 from Toyoda and Yoshida 1999[^2]:
$$\delta^{15}\text{N}^\beta = \delta^{15}\text{N}^\text{bulk} + A( \delta^{15}\text{N}^\text{bulk} - \delta^{15}\text{N}^\alpha)/(2-A)$$
Toyoda and Yoshida give the value of A=0.998, though this needs to be determined experimentally for the standard in use. We have seen data using a value of A=1 in data submitted to CCHDO.
[^1]: Substitution can occur in both positions simultaneously, but this is rare enough to be ignored, see the introduction of Toyoda and Yoshida 1999[^2]
[^2]: Determination of Nitrogen Isotopomers of Nitrous Oxide on a Modified Isotope Ratio Mass Spectrometer; Sakae Toyoda and Naohiro Yoshida; Analytical Chemistry 1999 71 (20), 4711-4718; DOI: 10.1021/ac9904563
Isotopic data for P18 2016 is being merged in, there is some new stuff in there that needs documenting:
Existing Param Updates
N2ONMOL/L(molar vs molal) as acceptable for this parameter, nc_name ofnitrous_oxide_lfollowing the existing de facto conventions.D15N_N2ONew Param
D15N_ALPHA_N20/MILLE1e-3(i.e. dimensionless ratio)Definition
Enrichment of 15N vs 14N in N2O (nitrous oxide) where the substitution has occurred at the center position of the N2O molecule as compared to a standard. N2O where the substitution has occurred in the end nitrogen atom is called D15N_BETA and is not usually measured. D15N_BETA can be calculated from bulk D15N and D15N_ALPHA using equation 25 from Toyoda and Yoshida 1999[^2]: $$\delta^{15}\text{N}^\beta = \delta^{15}\text{N}^\text{bulk} + A( \delta^{15}\text{N}^\text{bulk} - \delta^{15}\text{N}^\alpha)/(2-A)$$
Toyoda and Yoshida give the value of A=0.998, though this needs to be determined experimentally for the standard in use. We have seen data using a value of A=1 in data submitted to CCHDO.
[^1]: Substitution can occur in both positions simultaneously, but this is rare enough to be ignored, see the introduction of Toyoda and Yoshida 1999[^2]
[^2]: Determination of Nitrogen Isotopomers of Nitrous Oxide on a Modified Isotope Ratio Mass Spectrometer; Sakae Toyoda and Naohiro Yoshida; Analytical Chemistry 1999 71 (20), 4711-4718; DOI: 10.1021/ac9904563