[CF-metadata] New standard name for 14CO2

From: Wesloh, Daniel <dfw5129>
Date: Thu, 21 Feb 2019 22:37:07 +0000

Hello everyone,

Roy kindly pointed out that the paper I referenced used uppercase D14C,
not lowercase d14C.
The reference trail from that paper leads to the Stuiver and Polach
(1977) paper referenced here.
I also just confirmed with the person doing the analysis that they use
the 13CO2 correction for their reported values,
so a definition including that update would be:

enrichment_of_14C_in_air_expressed_as_uppercase_delta_14C (Canonical unit: 1e-3)
'Isotopic enrichment of 14C, often called d14C or delta14C (lower case delta), is a parameterisation of the 14C/12C isotopic ratio in the sample with respect to the isotopic ratio in a reference standard. It is computed using the formula (((14C/12C)sample / (14C/12C)standard) - 1) * 1000. The quantity called D14C, or Delta14C (upper case delta) is d14C corrected for isotopic fractionation using the 13C/12C ratio as follows: D14C = d14C - 2(dC13 + 25)(1+d14C/1000). If the sample is enriched in 14C relative to the standard, then the data value is positive. Reference: Stuiver, M. and H.A. Polach, 1977, Discussion reporting of 14C data, Radiocarbon, Volume 19, No. 3, 355-363, doi: 10.1017/S0033822200003672. The reference standard used in the calculation of delta14C should be specified by attaching a long_name attribute to the data variable. "C" means the element carbon and "14C" is the radioactive isotope "carbon-14", having six protons and eight neutrons and used in radiocarbon dating.'


My first email was based on an incorrect understanding of the issues
involved.
I was too eager to join the discussion I neglected my due diligence in
understanding.

Sorry for the confusion. I will be more careful in the future.

Daniel

On 02/21/2019 07:52 AM, Alison Pamment - UKRI STFC wrote:
> Dear Roy,
>
> On reflection, I think you're right that it is better not to put the reference standard into the definition. One could argue that, even if everyone is currently using the same reference material, it is still an experimental detail and therefore doesn't belong in either the standard name or its definition. Using a different reference would change the value of (14C/12C)standard) in the first formula, but not the formula itself, so the standard name would apply to all Delta14C measurements. As you say, experimental details should be specified using long_name and/or comment attributes. That would be consistent with our usual approach to standard names while providing a means of recording the precise details of how the data values were calculated.
>
> Here's the revised version (including the addition of our standard sentence about 14C that was accidentally omitted last time):
> enrichment_of_14C_in_air_expressed_as_uppercase_delta_14C (Canonical unit: 1e-3)
> 'Isotopic enrichment of 14C, often called d14C or delta14C (lower case delta), is used to calculate the fossil fuel contribution to atmospheric carbon dioxide using isotopic ratios of carbon. It is a parameterisation of the 14C/12C isotopic ratio in the sample with respect to the isotopic ratio in a reference standard. It is computed using the formula (((14C/12C)sample / (14C/12C)standard) - 1) * 1000. The quantity called D14C, or Delta14C (upper case delta) is d14C corrected for isotopic fractionation using the 13C/12C ratio as follows: D14C = d14C - 2(dC13 + 25)(1+d14C/1000). If the sample is enriched in 14C relative to the standard, then the data value is positive. Reference: Stuiver, M. and H.A. Polach, 1977, Discussion reporting of 14C data, Radiocarbon, Volume 19, No. 3, 355-363, doi: 10.1017/S0033822200003672. The reference standard used in the calculation of delta14C should be specified by attaching a long_name attribute to the data variable. "C" means the element carbon and "14C" is the radioactiv
e isotope "carbon-14", having six protons and eight neutrons and used in radiocarbon dating.'
>
> Best wishes,
> Alison
>
> -----------------------------------------------------------------------------------------------------------
> Alison Pamment Tel: +44 1235 778065
> NCAS/Centre for Environmental Data Analysis Email: alison.pamment at stfc.ac.uk
> STFC Rutherford Appleton Laboratory
> R25, 2.22
> Harwell Oxford, Didcot, OX11 0QX, U.K.
>
> From: Lowry, Roy K. <rkl at bodc.ac.uk>
> Sent: 20 February 2019 19:30
> To: Pamment, Alison (STFC,RAL,RALSP) <alison.pamment at stfc.ac.uk>; cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New standard name for 14CO2
>
> Dear Alison,
>
> I would suggest that if the reference standard isn't included in the Standard Name then I wouldn't put it into the definition. I don't like the idea of having narrower semantics in the definition compared to the name. How about putting a recommendation that the standard be specified in the long name into the definition?
>
> Cheers, Roy.
>
> I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address.
>
> ________________________________________
> From: CF-metadata <mailto:cf-metadata-bounces at cgd.ucar.edu> on behalf of Alison Pamment - UKRI STFC <mailto:alison.pamment at stfc.ac.uk>
> Sent: 20 February 2019 16:40
> To: mailto:cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New standard name for 14CO2
>
> Dear Katherine, Roy, Jonathan, Daniel,
>
> Thank you all for the very clear and interesting discussion - I have learned a lot from reading all your comments and the various references. It seems that we are inching towards agreement on:
> enrichment_of_14C_in_air_expressed_as_uppercase_delta_14C (Canonical unit: 1e-3).
>
> Certainly it is shorter and more readable if we don't include the reference standard in the name itself. I suggest that we include it in the definition for completeness, but leave it out of the name. In future, if someone were to propose a similar quantity based on a different standard we could add more detail into the names and turn the original one into an alias. However, the references I have looked at seem to indicate that the same international standard has been in use since the 1950s, so it isn't something that changes on a regular basis.
>
> Based on Roy's suggested definition, other comments in the discussion, and text used in the definitions of existing standard names, we would have something like the following:
> 'Isotopic enrichment of 14C, often called d14C or delta14C (lower case delta), is used to calculate the fossil fuel contribution to atmospheric carbon dioxide using isotopic ratios of carbon. It is a parameterisation of the 14C/12C isotopic ratio in the sample with respect to the isotopic ratio in a reference standard, in this case the radiocarbon absolute reference standard, Oxalic Acid I. It is computed using the formula (((14C/12C)sample / (14C/12C)standard) - 1) * 1000. The quantity called D14C, or Delta14C (upper case delta) is d14C corrected for isotopic fractionation using the 13C/12C ratio as follows: D14C = d14C - 2(dC13 + 25)(1+d14C/1000). If the sample is enriched in 14C relative to the standard, then the data value is positive. Reference: Stuiver, M. and H.A. Polach, 1977, Discussion reporting of 14C data, Radiocarbon, Volume 19, No. 3, 355-363, doi: 10.1017/S0033822200003672.'
>
> Does that sound okay?
>
> Best wishes,
> Alison
>
> -----------------------------------------------------------------------------------------------------------
> Alison Pamment Tel: +44 1235 778065
> NCAS/Centre for Environmental Data Analysis Email: mailto:alison.pamment at stfc.ac.uk
> STFC Rutherford Appleton Laboratory
> R25, 2.22
> Harwell Oxford, Didcot, OX11 0QX, U.K.
>
>
> Hi Jonathan and Roy,
>
>
> I do not feel there is need to mention the reference material. Oxalic Acid has been agreed upon as the primary reference material and any other reference materials are all traceable to the primary standards for radiocarbon analysis.
>
> Thanks,
>
> Katherine
>
> On 16/02/2019, 16:04, "CF-metadata on behalf of Jonathan Gregory" <mailto:cf-metadata-bounces at cgd.ucar.edu on behalf of j.m.gregory at reading.ac.uk> wrote:
>
> Dear Roy
>
> I went for "big" because it's shorter and a bit more amusing. If we have
> "uppercase" it would also be OK - no need for _ in the middle of it, I think.
>
> Yes, it would be good to hear an authoritative view on whether there is more
> than one standard in use.
>
> Best wishes
>
> Jonathan
>
> ----- Forwarded message from "Lowry, Roy K." <mailto:rkl at bodc.ac.uk> -----
>
> > Date: Fri, 15 Feb 2019 15:24:06 +0000
> > From: "Lowry, Roy K." <mailto:rkl at bodc.ac.uk>
> > To: Jonathan Gregory <mailto:j.m.gregory at reading.ac.uk>, "mailto:cf-metadata at cgd.ucar.edu"
> > <mailto:cf-metadata at cgd.ucar.edu>
> > Subject: Re: [CF-metadata] New standard name for 14CO2
> >
> > Dear Jonathan,
> >
> > I am almost happy with 'big_delta14C', but would prefer 'upper_case_delta14C'.
> >
> > I still feel that unless explicitly told otherwise by a domain expert the reference standard needs to be there. As I mentioned in a previous posting there have been multiple 14C standards used over the past 40 years, although I cannot say for certain whether more than one is in current use.
> >
> > Cheers, Roy.
> >
> >
> > I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address.
> >
> > ________________________________
> > From: CF-metadata <mailto:cf-metadata-bounces at cgd.ucar.edu> on behalf of Jonathan Gregory <mailto:j.m.gregory at reading.ac.uk>
> > Sent: 15 February 2019 15:00
> > To: mailto:cf-metadata at cgd.ucar.edu
> > Subject: Re: [CF-metadata] New standard name for 14CO2
> >
> > Dear all
> >
> > Thank you for the clarifications. Actually I still do not understand what the
> > normalisation does, but evidently it's a well-defined procedure.
> >
> > I'm in favour of precision, of course, when there is a danger of ambiguity.
> > Roy proposes
> >
> > enrichment_with_respect_to_radiocarbon_absolute_reference_standard_of_14C_in_carbon_dioxide_in_air_expressed_as_D14C
> >
> > I would like to ask if we could make it
> >
> > enrichment_of_14C_in_carbon_dioxide_in_air_expressed_as_big_delta14C
> >
> > That is: (a) Do we have to mention the reference standard? Katherine does not
> > specify this. Is there more than one standard in use? If so, we do need to
> > include it, I agree. (b) It seems clearer to me to spell out delta than to
> > put just D. (c) I appreciate that the small-delta version is obsolete but we
> > can't rule out it being needed sometime (or perhaps a similar distinction is
> > in actual use with other isotopes?), and I think it would be unreliable to
> > distinguish two standard names just because one had a small d where the other
> > had a big D. If we ever need the small-delta version we can put small_delta.
> >
> > Best wishes
> >
> > Jonathan
> >
>
Received on Thu Feb 21 2019 - 15:37:07 GMT