Talk:Δ13C

isotope discrimination, atmospheric values, canopy effect, up or lc delta?
Just a few of the points missing. I suggest you delete this article. 69.9.28.55 (talk) 20:24, 25 January 2011 (UTC)
 * Deletion is a bit drastic, if you know about it, how about you help to improve it? I'm willing to help. SmartSE (talk) 20:42, 25 January 2011 (UTC)
 * because there is no assured convergence of the edits. If you insist, you can research and write an entry for each term I listed, then correct all the other articles that use the concept for consistency. 69.9.27.73 (talk) 01:59, 8 January 2013 (UTC)

Pronunciation?
Is it pronounced "delta"? Worth adding to the intro. --Chriswaterguy talk 06:30, 4 April 2014 (UTC)

Yes "delta 13 C". A link to the delta article would also work. GraemeLeggett (talk) 11:09, 4 April 2014 (UTC)

Excursions
I am still confused! What is the normal level of delta 13 C for carbonate rocks, and what is it for natural gas, oil, and coal? When we talk about a positive excursion is that when the d13C of limestone (and not gas oil and coal) becomes less negative e.g. changing from -30 to -20? And does this signify more organic burial or less? By asking these questions I have now got a better idea of the answers, but it would be nice if readers unfamiliar with c13C could have these points made clear in the first place. A B McDonald (talk) 21:46, 4 November 2015 (UTC)

Foraminifera
What is the relevance of the image of foraminifera? Very nice, but d13C is relevant to all organisms not just tiny ones? — Preceding unsigned comment added by 194.66.246.8 (talk) 21:59, 26 June 2017 (UTC)

Calculation error
In the Reference Standard section the following solution of the main equation is just an approximation. "Therefore the correct 13C:12C ratio of PDB derived from NBS-19 should be 0.011202×(1-1.95/1000)=0.01118." The algebraically correct and very simple solution is the following.

Let the 13C:12C ratio of NBS-19 is R(NBS19)= 0.011202 and Δ13C of NBS19 = 1,95‰

The 13C:12C ratio of PDB standard R(PDB) what you are looking for.

The definition: Δ13C=((NBS19) / R(PDB) - 1)*1000

R(NBS19)/ R(PDB) = (Δ13C/1000 + 1)

R(PDB)= R(NBS19) / (Δ13C/1000 + 1) = 0,011202 / (1,95/1000 +1)= 0,011202/1,00195=0,0111802

The basic idea of the approximativ solution is that 1/(1+x)≈1-x if x is very small. 193.225.105.50 (talk) 06:52, 26 April 2019 (UTC)


 * Honestly, I find the whole section very confusing and contradictory (see also my earlier comment below). Also, Reference materials for stable isotope analysis says that NBS-19 supply is also exhausted (also states your value of 0.0111802). And the reference given in the last line actually defined NBS-19 as d13C of 1.95 per mil - I suppose the reason for your starting point in the calculations above. Perhaps the easiest would simply be to rewrite this to say (1) PDB was exhausted, so (2) a new standard NBS-19 was chosen and defined to have a d13C of 1.95 per mil, (3) all d13C measurements are now back-calculated to express them with respect to VPDB, a theoretical standard at d13C of zero. I don't think the in-line calculations are helping the section at all, nor are they necessary for an encyclopedic coverage of the topic. Kyle MoJo (talk) 21:11, 7 May 2020 (UTC)

Reference standard section contradictory
The section of reference standards seems to contradict itself, possibly related to the edit by. First it says that there is a widely used, incorrect PDB ratio of 0.0112372 that was caused by a calculation error, but the last line of the paragraph says this is the correct value for the VPDB standard. The numbers are too similar to be a coincidence, so one of these must be mistaken. Kyle MoJo (talk) 06:28, 5 February 2020 (UTC)

About Causes of δ13C variations
"Therefore, an increase in δ13C in marine fossils is indicative of an increase in the abundance of vegetation."

This should be advised since it is not always true. Inorganic carbon could have an increase in δ13C as time goes on. In this article https://www.nature.com/articles/nature24019 it states that "a δ13C value of marine inorganic carbon in the Eoarchean is estimated to be higher than the maximum value". — Preceding unsigned comment added by 74.101.197.83 (talk) 15:42, 23 February 2020 (UTC)