Jena Reference Air Set (JRAS): a multi-point scale anchor for isotope measurements of CO<sub>2</sub> in air

Abstract

The need for a unifying scale anchor for isotopes of CO₂ in air was brought to light at the WMO CO₂ Experts Meeting in Tokyo 2001. During discussions about persistent discrepancies in isotope measurements between the worlds leading laboratories it was concluded that a unifying scale anchor for VPDB of CO₂ in air was desperately needed. Now, 10 yr later, the 2011 CO₂-Experts-Meeting in Wellington has decided that the Jena Reference Air Set or JRAS is recommended as official scale anchor for isotope measurements of CO₂ in air. <br><br> The JRAS gases consist of reference CO₂ mixed into CO₂ free air. To safeguard both stability and longevity of the CO₂, it is directly generated from two solid reference calcites. That the reference CO₂ is supplied in air is unique to JRAS. This is made to ensure that any measurement bias arising from the extraction procedure is eliminated. As every lab has its own procedure for extracting the CO₂ this is of paramount importance if the local scales are to be unified. <br><br> For a period of four years, JRAS has been evaluated through the IMECC program, which made it possible to distribute sets of JRAS gases to 11 laboratories worldwide. A summary of the results is reported here along with a description of the production and maintenance of the JRAS scale anchors

Automated simultaneous measurement of the δ13C and δ2H values of methane and the δ13C and δ18O values of carbon dioxide in flask air samples using a new multi cryo‐trap/gas chromatography/isotope ratio mass spectrometry system

“…These data can be compared with the > 15 years BGC stable isotope record on air-CO 2 generated by cryogenic extraction and dual-inlet measurement, which exhibits about 3 times better precision, albeit from a much larger sample size (600 mL instead of 200 mL). [57][58][59] We believe that the data presented in Fig. 21 are close to the optimum that one can achieve using direct measurement of the CO 2 stable isotopes from air samples following GC separation without cryogenic isolation of CO 2 from air.…”

“…Here, the δ 13 C and δ 18 O precision values are 0.04 ‰ and 0.07 ‰, respectively. These data can be compared with the > 15 years BGC stable isotope record on air‐CO 2 generated by cryogenic extraction and dual‐inlet measurement, which exhibits about 3 times better precision, albeit from a much larger sample size (600 mL instead of 200 mL) . We believe that the data presented in Fig.…”

Acid digestion of carbonates using break seal method for clumped isotope analysis

“…These various CaCO 3 minerals are well characterized and widely reported in the literature . The Carrara‐1 and OMC used in this study are similar in composition to what was used earlier in the work of Ghosh et al and Wendeberg et al The sample grain size was 250 μm for NBS 19 and NBS 18 while <50 μm size fractions were used for OMC and other carbonates. Based on the recommendation of Wacker et al the sample size was maintained at a minimum of 10 mg for all acid digestions in this study.…”

Living on borrowed time – Amazonian trees use decade‐old storage carbon to survive for months after complete stem girdling

“…Samples were analyzed against a laboratory air standard thus satisfying the principle of identical treatment (Werner et al, 2001). d 13 C values are reported on the VPDB scale realized by the Jena Reference Air Set-06 (JRAS-06) scale for isotopes of CO 2 in air (Wendeberg et al, 2013).…”