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The boron isotopic ratio of 11B/10B (δ11BSRM951) and trace element composition of marine carbonates are key proxies for understanding carbon cycling (pH) and palaeoceanographic change. However, method validation and comparability of results between laboratories requires carbonate reference materials. Here, we report results of an inter-laboratory comparison study to both assign δ11BSRM951 and trace element compositions to new synthetic marine carbonate reference materials (RMs), NIST RM 8301 (Coral) and NIST RM 8301 (Foram) and to assess the variance of data among laboratories. Non-certified reference values and expanded 95% uncertainties for δ11BSRM951 in NIST RM 8301 (Coral) (+24.17‰ ± 0.18‰) and NIST RM 8301 (Foram) (+14.51‰ ± 0.17‰) solutions were assigned by consensus approach using inter-laboratory data. Differences reported among laboratories were considerably smaller than some previous inter-laboratory comparisons, yet discrepancies could still lead to large differences in calculated seawater pH. Similarly, variability in reported trace element information among laboratories (e.g., Mg/Ca ± 5% RSD) was often greater than within a single laboratory (e.g., Mg/Ca < 2%). Such differences potentially alter proxy-reconstructed seawater temperature by more than 2 °C. These now well-characterised solutions are useful reference materials to help the palaeoceanographic community build a comprehensive view of past ocean changes.
Bibliographical noteFunding Information:
We thank all staff at NIST involved with RM production and the participants (and support staff) at each research institution that contributed data from the inter‐laboratory exercise, without whom generation of these results would not be have been possible. We thank B. Hönisch and J. Farmer for their helpful discussion and advice when preparing these standards and co‐ordinating the inter‐laboratory exercise. We are grateful to J. Waters and R.M. Verkouteren for helpful suggestions when writing the manuscript. Boron isotopes and trace element content measurements were funded by the French National Research Agency projects ANR CARBORIC (Grant No. ANR‐13‐BS06‐0013‐04) and ANR HAMOC (Grant No. ANR‐13‐BS06‐0003‐02) at LSCE; NERC NE/N003861/1 & NE/S001743/1 at Bristol; NERC NE/N011716/1 and ERC Grant agreement No. 805246 at the University of St Andrews. We thank the editor Thomas Meisel and two anonymous reviewers whose helpful comments improved this manuscript.
© 2020 The Authors. Geostandards and Geoanalytical Research published by John Wiley & Sons Ltd on behalf of the International Association of Geoanalysts
- boron isotopes
- trace elements
- reference materials
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1/02/19 → 31/03/23
1/02/19 → 31/01/22
1/12/15 → 11/06/19