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Inter-laboratory comparison of oxygen isotope compositions from biogenic silica |
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| Authors: | Bernhard Chapligin Melanie J. Leng Anne Alexandre Akira Ijiri Aldo Shemesh Ulrike Herzschuh Hanno Meyer Yusuke Okazaki Zachary D. Sharp Corinne Sonzogni Florence Sylvestre Ruth Yam |
| Affiliation: | a Alfred Wegener Institute (AWI) for Polar and Marine Research, Research Unit Potsdam and Bremerhaven, Telegrafenberg A43, D-14473 Potsdam, Germany b NERC Isotope Geosciences Laboratory (NIGL), British Geological Survey, Keyworth, Nottingham NG12 5GG, UK c Laboratory for Stable Isotope Science, Department of Earth Sciences, The University of Western Ontario (UWO), London, Ontario, Canada N6A 5B7 d CEREGE, CNRS, IRD, Université Aix-Marseille, Europôle de l’Arbois, BP 80, 13545 Aix-en-Provence Cedex 4, France e Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico (UNM), Albuquerque, NM 87131, USA f Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan g Institute of Bio- and Geosciences, IBG-3: Agrosphere, Research Centre Jülich, D-52425 Jülich, Germany h Weizmann Institute of Science (WIS), Rehovot 76100, Israel i Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK j School of Geography, University of Nottingham, University Park, Nottingham NG7 2RD, UK k Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK |
| Abstract: | Several techniques have been introduced in the last decades for the dehydration and release of O2 from biogenic silica (opal-A) for oxygen-isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of oxygen-isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ18O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ18O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ18O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ18O analyses, available on request through the relevant laboratories. |
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