Publication Date:
2022-05-26
Description:
Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Radiocarbon 59 (2017): 179-193, doi:10.1017/RDC.2017.3.
Description:
We estimate the blank carbon mass over the course of a typical Ramped PyrOx (RPO)
analysis (150 to 1000 °C; 5 °C×min-1) to be (3.7 ± 0.6) μg C with an Fm value of 0.555 ± 0.042
and a δ13C value of (-29.0 ± 0.1) ‰ VPDB. Additionally, we provide equations for RPO Fm and
δ13C blank corrections, including associated error propagation. By comparing RPO mass-weighted mean and independently measured bulk δ13C values for a compilation of environmental
samples and standard reference materials (SRMs), we observe a small yet consistent 13C
depletion within the RPO instrument (mean – bulk: μ = -0.8 ‰; ±1σ = 0.9 ‰; n = 66). In
contrast, because they are fractionation-corrected by definition, mass-weighted mean Fm values
accurately match bulk measurements (mean – bulk: μ = 0.005; ±1σ = 0.014; n = 36). Lastly, we
show there exists no significant intra-sample δ13C variability across carbonate SRM peaks,
indicating minimal mass-dependent kinetic isotope fractionation during RPO analysis. These
data are best explained by a difference in activation energy between 13C- and 12C-containing
compounds (13–12ΔE) of 0.3 to 1.8 J×mol-1, indicating that blank and mass-balance corrected
RPO δ13C values accurately retain carbon source isotope signals to within 1 to 2‰.
Description:
J.D.H.
was partly supported by the NSF Graduate Research Fellowship Program under grant number
2012126152; V.V.G. was partly supported by the US National Science Foundation (grants OCE-
0851015 and OCE-0928582), the WHOI Coastal Ocean Institute (grant 27040213) and an
Independent Study Award (grant 27005306) from WHOI; G.S. and P.K.Z. were supported by the
WHOI Postdoctoral Scholar Program with funding provided by NOSAMS (OCE-1239667).
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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