Homoky, WB orcid.org/0000-0002-9562-8591, Conway, TM, John, SG et al. (4 more authors) (2021) Iron colloids dominate sedimentary supply to the ocean interior. Proceedings of the National Academy of Sciences of USA, 118 (13). e2016078118. ISSN 0027-8424
Abstract
Dissolution of marine sediment is a key source of dissolved iron (Fe) that regulates the ocean carbon cycle. Currently, our prevailing understanding, encapsulated in ocean models, focuses on low-oxygen reductive supply mechanisms and neglects the emerging evidence from iron isotopes in seawater and sediment porewaters for additional nonreductive dissolution processes. Here, we combine measurements of Fe colloids and dissolved δ56Fe in shallow porewaters spanning the full depth of the South Atlantic Ocean to demonstrate that it is lithogenic colloid production that fuels sedimentary iron supply away from low-oxygen systems. Iron colloids are ubiquitous in these oxic ocean sediment porewaters and account for the lithogenic isotope signature of dissolved Fe (δ56Fe = +0.07 ± 0.07‰) within and between ocean basins. Isotope model experiments demonstrate that only lithogenic weathering in both oxic and nitrogenous zones, rather than precipitation or ligand complexation of reduced Fe species, can account for the production of these porewater Fe colloids. The broader covariance between colloidal Fe and organic carbon (OC) abundance suggests that sorption of OC may control the nanoscale stability of Fe minerals by inhibiting the loss of Fe(oxyhydr)oxides to more crystalline minerals in the sediment. Oxic ocean sediments can therefore generate a large exchangeable reservoir of organo-mineral Fe colloids at the sediment water interface (a “rusty source”) that dominates the benthic supply of dissolved Fe to the ocean interior, alongside reductive supply pathways from shallower continental margins.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Editors: |
|
Copyright, Publisher and Additional Information: | © 2021 National Academy of Sciences. This is an author produced version of an article published in Proceedings of the National Academy of Sciences. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | ocean sediment, porewater, iron colloid, organo-mineral, iron isotopes |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 17 Feb 2021 14:21 |
Last Modified: | 30 Sep 2021 00:38 |
Status: | Published |
Publisher: | National Academy of Sciences |
Identification Number: | 10.1073/pnas.2016078118 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:170459 |
Downloads
Filename: Homoky etal_PNAS_Author Accepted MS.pdf
Licence: CC-BY 4.0
Filename: Homoky etal PNAS SI Appendix.pdf
Licence: CC-BY 4.0