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Published January 2016 | Published
Journal Article Open

Neodymium isotope analyses after combined extraction of actinide and lanthanide elements from seawater and deep-sea coral aragonite

Abstract

Isotopes of the actinide elements protactinium (Pa), thorium (Th), and uranium (U), and the lanthanide element neodymium (Nd) are often used as complementary tracers of modern and past oceanic processes. The extraction of such elements from low abundance matrices, such as seawater and carbonate, is however labor-intensive and requires significant amounts of sample material. We here present a combined method for the extraction of Pa, Th, and Nd from 5 to 10 L seawater samples, and of U, Th, and Nd from <1 g carbonate samples. Neodymium is collected in the respective wash fractions of Pa-Th and U-Th anion exchange chromatographies. Regardless of the original sample matrix, Nd is extracted during a two-stage ion chromatography, followed by thermal ionization mass spectrometry (TIMS) analysis as NdO+. Using this combined procedure, we obtained results for Nd isotopic compositions on two GEOTRACES consensus samples from Bermuda Atlantic Time Series (BATS), which are within error identical to results for separately sampled and processed dedicated Nd samples (ε_(Nd) = −9.20 ± 0.21 and −13.11 ± 0.21 for 15 and 2000 m water depths, respectively; intercalibration results from 14 laboratories: ε_(Nd) = −9.19 ± 0.57 and −13.14 ± 0.57). Furthermore, Nd isotope results for an in-house coral reference material are identical within analytical uncertainty for dedicated Nd chemistry and after collection of Nd from U-Th anion exchange chromatography. Our procedure does not require major adaptations to independently used ion exchange chromatographies for U-Pa-Th and Nd, and can hence be readily implemented for a wide range of applications.

Additional Information

© 2015 American Geophysical Union. Received 5 OCT 2015; Accepted 5 DEC 2015; Accepted article online 14 DEC 2015; Published online 9 JAN 2016. We thank the team on the second leg of the first GEOTRACES intercalibration cruise for sample collection, Joanne Goudreau, Kuo Fang Huang, Jurek Bluztajn for help at the WHOI Plasma facility, Martin Fleisher and Sven Kretschmer for discussion, and Derek Vance for sharing his 150Nd spike. Torben Stichel is acknowledged for help during column calibration. All data presented in this manuscript can be found in the table included in the main body of the text. Funding that supported this work was received from the National Science Foundation (NSF 0752402), the Leverhulme Trust (RPG-398), the Natural Environmental Research Council (NE/J021636/1 and NE/N003861/1), the European Research Council (278705), and the Grantham Institute for Climate Change. We thank Marcus Gutjahr and an anonymous reviewer for constructive comments on the manuscript and acknowledge the editorial handling by Yusuke Yokoyama.

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Created:
August 22, 2023
Modified:
October 18, 2023