The University of Southampton
University of Southampton Institutional Repository

Constraints on the source of reactive phases in sediment from a major Arctic river using neodymium isotopes

Constraints on the source of reactive phases in sediment from a major Arctic river using neodymium isotopes
Constraints on the source of reactive phases in sediment from a major Arctic river using neodymium isotopes
Riverine suspended particulate matter (SPM) is essential for the delivery of micronutrients such as iron (Fe) to the oceans. SPM is known to consist of multiple phases with differing reactivity, but their role in the delivery of elements to the oceans is poorly constrained. Here we provide new constraints on the source and composition of reactive phases in SPM from the Mackenzie River, the largest sediment source to the Arctic Ocean. Sequential leaching of SPM shows that river sediments contain labile Fe phases. We estimate the labile Fe flux is substantial (0.21(+0.06,−0.05) Tg/yr) by quantifying Fe concentrations in weak leaches of the SPM. The labile Fe phase hosts a considerable amount of rare earth elements (REE), including neodymium (Nd). We demonstrate that the labile Fe phase and dissolved load have radiogenic Nd isotope ratios that are identical within uncertainty, but up to 8 epsilon units distinct from the silicate phase. We interpret this as evidence for dynamic cycling between Fe-oxide phases in SPM and the river water, demonstrating the high reactivity of the labile Fe phase. Nd isotope and elemental molar ratios suggest that a significant amount of labile Fe- and Nd-bearing phases are derived from Fe-oxides within the sedimentary source rock rather than silicate mineral dissolution. Thus, sedimentary rock erosion and weathering provides an important source of labile Fe, manganese (Mn) and by extension potentially other trace metals. Our results imply that both past and future environmental change in the Arctic, such as permafrost thaw, may trigger changes to the supply of reactive trace metals. These results demonstrate that a re-evaluation of sediment reactivity within rivers is required where uplifted sedimentary rocks are present.
0012-821X
Larkin, Christina S.
7e5477b9-0a3d-4580-ba78-2e6282f010cc
Piotrowski, Alexander M.
9b0f2ed4-4133-4809-a58a-02639f0bba8a
Hindshaw, Ruth S.
9812db4a-00ac-4859-b178-5c0b927bfcf1
Bayon, Germain
eb490cce-e67d-4789-98e9-66e789bf6c20
Hilton, Robert G.
63b6109b-020f-4cdd-8c16-7a8137f9343a
Baronas, J. Jotautas
9c9473d9-6376-4dc7-b940-ee6d0427ef01
Dellinger, Mathieu
490bf91e-800f-4f71-ae20-4608d9353146
Wang, Ruixue
0baf61f1-82c7-45d9-b8d6-c4483d7733ba
Tipper, Edward T.
b966fdef-6e38-40dd-b22e-c529f4b974d0
Larkin, Christina S.
7e5477b9-0a3d-4580-ba78-2e6282f010cc
Piotrowski, Alexander M.
9b0f2ed4-4133-4809-a58a-02639f0bba8a
Hindshaw, Ruth S.
9812db4a-00ac-4859-b178-5c0b927bfcf1
Bayon, Germain
eb490cce-e67d-4789-98e9-66e789bf6c20
Hilton, Robert G.
63b6109b-020f-4cdd-8c16-7a8137f9343a
Baronas, J. Jotautas
9c9473d9-6376-4dc7-b940-ee6d0427ef01
Dellinger, Mathieu
490bf91e-800f-4f71-ae20-4608d9353146
Wang, Ruixue
0baf61f1-82c7-45d9-b8d6-c4483d7733ba
Tipper, Edward T.
b966fdef-6e38-40dd-b22e-c529f4b974d0

Larkin, Christina S., Piotrowski, Alexander M., Hindshaw, Ruth S., Bayon, Germain, Hilton, Robert G., Baronas, J. Jotautas, Dellinger, Mathieu, Wang, Ruixue and Tipper, Edward T. (2021) Constraints on the source of reactive phases in sediment from a major Arctic river using neodymium isotopes. Earth and Planetary Science Letters, 565. (doi:10.1016/j.epsl.2021.116933).

Record type: Article

Abstract

Riverine suspended particulate matter (SPM) is essential for the delivery of micronutrients such as iron (Fe) to the oceans. SPM is known to consist of multiple phases with differing reactivity, but their role in the delivery of elements to the oceans is poorly constrained. Here we provide new constraints on the source and composition of reactive phases in SPM from the Mackenzie River, the largest sediment source to the Arctic Ocean. Sequential leaching of SPM shows that river sediments contain labile Fe phases. We estimate the labile Fe flux is substantial (0.21(+0.06,−0.05) Tg/yr) by quantifying Fe concentrations in weak leaches of the SPM. The labile Fe phase hosts a considerable amount of rare earth elements (REE), including neodymium (Nd). We demonstrate that the labile Fe phase and dissolved load have radiogenic Nd isotope ratios that are identical within uncertainty, but up to 8 epsilon units distinct from the silicate phase. We interpret this as evidence for dynamic cycling between Fe-oxide phases in SPM and the river water, demonstrating the high reactivity of the labile Fe phase. Nd isotope and elemental molar ratios suggest that a significant amount of labile Fe- and Nd-bearing phases are derived from Fe-oxides within the sedimentary source rock rather than silicate mineral dissolution. Thus, sedimentary rock erosion and weathering provides an important source of labile Fe, manganese (Mn) and by extension potentially other trace metals. Our results imply that both past and future environmental change in the Arctic, such as permafrost thaw, may trigger changes to the supply of reactive trace metals. These results demonstrate that a re-evaluation of sediment reactivity within rivers is required where uplifted sedimentary rocks are present.

Text
Larkin_Mackenzie_accepted - Accepted Manuscript
Download (10MB)

More information

Accepted/In Press date: 2 April 2021
e-pub ahead of print date: 16 April 2021
Published date: July 2021

Identifiers

Local EPrints ID: 455845
URI: http://eprints.soton.ac.uk/id/eprint/455845
ISSN: 0012-821X
PURE UUID: dfa510ea-9b27-4e4d-86cc-0a8e252ba024
ORCID for Christina S. Larkin: ORCID iD orcid.org/0000-0002-6420-0461

Catalogue record

Date deposited: 06 Apr 2022 16:49
Last modified: 17 Mar 2024 07:11

Export record

Altmetrics

Contributors

Author: Christina S. Larkin ORCID iD
Author: Alexander M. Piotrowski
Author: Ruth S. Hindshaw
Author: Germain Bayon
Author: Robert G. Hilton
Author: J. Jotautas Baronas
Author: Mathieu Dellinger
Author: Ruixue Wang
Author: Edward T. Tipper

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×