Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record
Past changes in seawater lead (Pb) isotopes record the temporal evolution of anthropogenic pollution, continental weathering inp uts, and ocean current transport. To advance our ability to reconstruct this signature, we present methodological developments that allow us to make precise and accurate P...
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ftimperialcol:oai:spiral.imperial.ac.uk:10044/1/44293 2023-05-15T13:51:15+02:00 Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record Wilson, DJ Van de Flierdt, T Adkins, JF The Leverhulme Trust Natural Environment Research Council (NERC) 2017-01-31 http://hdl.handle.net/10044/1/44293 https://doi.org/10.1016/j.gca.2017.01.052 unknown Elsevier Geochimica et Cosmochimica Acta © 2017 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). CC-BY 374 350 Geochemistry & Geophysics 0402 Geochemistry 0403 Geology Journal Article 2017 ftimperialcol https://doi.org/10.1016/j.gca.2017.01.052 2018-09-16T05:58:06Z Past changes in seawater lead (Pb) isotopes record the temporal evolution of anthropogenic pollution, continental weathering inp uts, and ocean current transport. To advance our ability to reconstruct this signature, we present methodological developments that allow us to make precise and accurate Pb isoto pe measurements on deep-sea coral aragonite, and apply our approach to generate the f irst Pb isotope record for the glacial to deglacial mid-depth Southern Ocean. Our refined methodology includes a two-step anion e xchange chemistry procedure and measurement using a 207 Pb- 204 Pb double spike on a ThermoFinnigan Triton TIMS instrument. By employing a 10 12 Ω resistor (in place of a 10 Ω resistor) to measure the low- abundance 204 Pb ion beam, we improve the internal precision on 206,207,208 Pb/ 204 Pb for a 2 ng load of NIST-SRM-981 Pb from typically ~420 ppm to ~260 ppm (2 s.e.), and the long term external reproducibility from ~960 ppm to ~580 ppm (2 s.d.). Furthermore, for a typical 500 mg coral sample with low Pb concentrations (~6-10 p pb yielding ~3-5 ng Pb for analysis), we obtain a comparable internal precision of ~150-250 ppm for 206,207,208 Pb/ 204 Pb, indicating a good sensitivity for tracing natural Pb sources to the oceans. Successful extraction of a seawater signal from deep-sea coral aragonite furth er relies on careful physical and chemical cleaning steps, which are necessary to remove anthr opogenic Pb contaminants and obtain results that are consistent with ferromanganese cru sts. Applying our approach to a collection of late glaci al and deglacial corals (~12-40 ka BP) from south of Tasmania at ~1.4-1.7 km water dep th, we generated the first intermediate water Pb isotope record from the Southern Ocean. Th at record reveals millennial timescale variability, controlled by binary mixing between tw o Pb sources, but no distinct glacial- interglacial Pb isotope shift. Mixing between natur al endmembers is fully consistent with our data and points to a persistence of the same Pb sou rces through time, although we cannot rule out a minor influence from recent anthropogenic Pb. Whereas neodymium (Nd) isotopes in the Southern Ocean respond to global ocean circulat ion changes between glacial and interglacial periods, Pb isotopes record more local ised mixing within the Antarctic Circumpolar Current, potentially further modulated by climate through changing terrestrial inputs from southern Africa or Australia. Such deco upling between Pb and Nd isotopes in the Southern Ocean highlights their potential to provid e complementary insights into past oceanographic variability. Article in Journal/Newspaper Antarc* Antarctic Southern Ocean Imperial College London: Spiral Antarctic Southern Ocean The Antarctic Triton ENVELOPE(-55.615,-55.615,49.517,49.517) Geochimica et Cosmochimica Acta 204 350 374 |
institution |
Open Polar |
collection |
Imperial College London: Spiral |
op_collection_id |
ftimperialcol |
language |
unknown |
topic |
Geochemistry & Geophysics 0402 Geochemistry 0403 Geology |
spellingShingle |
Geochemistry & Geophysics 0402 Geochemistry 0403 Geology Wilson, DJ Van de Flierdt, T Adkins, JF Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record |
topic_facet |
Geochemistry & Geophysics 0402 Geochemistry 0403 Geology |
description |
Past changes in seawater lead (Pb) isotopes record the temporal evolution of anthropogenic pollution, continental weathering inp uts, and ocean current transport. To advance our ability to reconstruct this signature, we present methodological developments that allow us to make precise and accurate Pb isoto pe measurements on deep-sea coral aragonite, and apply our approach to generate the f irst Pb isotope record for the glacial to deglacial mid-depth Southern Ocean. Our refined methodology includes a two-step anion e xchange chemistry procedure and measurement using a 207 Pb- 204 Pb double spike on a ThermoFinnigan Triton TIMS instrument. By employing a 10 12 Ω resistor (in place of a 10 Ω resistor) to measure the low- abundance 204 Pb ion beam, we improve the internal precision on 206,207,208 Pb/ 204 Pb for a 2 ng load of NIST-SRM-981 Pb from typically ~420 ppm to ~260 ppm (2 s.e.), and the long term external reproducibility from ~960 ppm to ~580 ppm (2 s.d.). Furthermore, for a typical 500 mg coral sample with low Pb concentrations (~6-10 p pb yielding ~3-5 ng Pb for analysis), we obtain a comparable internal precision of ~150-250 ppm for 206,207,208 Pb/ 204 Pb, indicating a good sensitivity for tracing natural Pb sources to the oceans. Successful extraction of a seawater signal from deep-sea coral aragonite furth er relies on careful physical and chemical cleaning steps, which are necessary to remove anthr opogenic Pb contaminants and obtain results that are consistent with ferromanganese cru sts. Applying our approach to a collection of late glaci al and deglacial corals (~12-40 ka BP) from south of Tasmania at ~1.4-1.7 km water dep th, we generated the first intermediate water Pb isotope record from the Southern Ocean. Th at record reveals millennial timescale variability, controlled by binary mixing between tw o Pb sources, but no distinct glacial- interglacial Pb isotope shift. Mixing between natur al endmembers is fully consistent with our data and points to a persistence of the same Pb sou rces through time, although we cannot rule out a minor influence from recent anthropogenic Pb. Whereas neodymium (Nd) isotopes in the Southern Ocean respond to global ocean circulat ion changes between glacial and interglacial periods, Pb isotopes record more local ised mixing within the Antarctic Circumpolar Current, potentially further modulated by climate through changing terrestrial inputs from southern Africa or Australia. Such deco upling between Pb and Nd isotopes in the Southern Ocean highlights their potential to provid e complementary insights into past oceanographic variability. |
author2 |
The Leverhulme Trust Natural Environment Research Council (NERC) |
format |
Article in Journal/Newspaper |
author |
Wilson, DJ Van de Flierdt, T Adkins, JF |
author_facet |
Wilson, DJ Van de Flierdt, T Adkins, JF |
author_sort |
Wilson, DJ |
title |
Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record |
title_short |
Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record |
title_full |
Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record |
title_fullStr |
Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record |
title_full_unstemmed |
Lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial Southern Ocean record |
title_sort |
lead isotopes in deep-sea coral skeletons: ground-truthing and a first deglacial southern ocean record |
publisher |
Elsevier |
publishDate |
2017 |
url |
http://hdl.handle.net/10044/1/44293 https://doi.org/10.1016/j.gca.2017.01.052 |
long_lat |
ENVELOPE(-55.615,-55.615,49.517,49.517) |
geographic |
Antarctic Southern Ocean The Antarctic Triton |
geographic_facet |
Antarctic Southern Ocean The Antarctic Triton |
genre |
Antarc* Antarctic Southern Ocean |
genre_facet |
Antarc* Antarctic Southern Ocean |
op_source |
374 350 |
op_relation |
Geochimica et Cosmochimica Acta |
op_rights |
© 2017 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1016/j.gca.2017.01.052 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
204 |
container_start_page |
350 |
op_container_end_page |
374 |
_version_ |
1766255015915159552 |