Yan, X, Zhu, M, Li, W et al. (7 more authors) (2021) Cadmium Isotope Fractionation during Adsorption and Substitution with Iron (Oxyhydr)oxides. Environmental science & technology. ISSN 0013-936X
Abstract
Cadmium (Cd) isotopes have great potential for understanding Cd geochemical cycling in soil and aquatic systems. Iron (oxyhydr)oxides can sequester Cd via adsorption and isomorphous substitution, but how these interactions affect Cd isotope fractionation remains unknown. Here, we show that adsorption preferentially enriches lighter Cd isotopes on iron (oxyhydr)oxide surfaces through equilibrium fractionation, with a similar fractionation magnitude (Δ114/110Cdsolid-solution) for goethite (Goe) (−0.51 ± 0.04‰), hematite (Hem) (−0.54 ± 0.10‰), and ferrihydrite (Fh) (−0.55 ± 0.03‰). Neither the initial Cd2+ concentration or ionic strength nor the pH influence the fractionation magnitude. The enrichment of the light isotope is attributed to the adsorption of highly distorted [CdO6] on solids, as indicated by Cd K-edge extended X-ray absorption fine-structure analysis. In contrast, Cd incorporation into Goe by substitution for lattice Fe at a Cd/Fe molar ratio of 0.05 preferentially sequesters heavy Cd isotopes, with a Δ114/110Cdsolid-solution of 0.22 ± 0.01‰. The fractionation probably occurs during the transformation of Fh into Goe via dissolution and reprecipitation. These results improve the understanding of the Cd isotope fractionation behavior being affected by iron (oxyhydr)oxides in Earth’s critical zone and demonstrate that interactions with minerals can obscure anthropogenic and natural Cd isotope characteristics, which should be carefully considered when applying Cd isotopes as environmental tracers.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2021 American Chemical Society. This is an author produced version of an article published in Environmental Science & Technology. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | metal (oxyhydr)oxides, heavy-metal isotopes, adsorption, coprecipitation, mineral transformation, extended X-ray absorption fine structure spectroscopy |
Dates: |
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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) |
Funding Information: | Funder Grant number Royal Society IEC\NSFC\191423 |
Depositing User: | Symplectic Publications |
Date Deposited: | 17 Aug 2021 14:04 |
Last Modified: | 09 Aug 2022 00:15 |
Status: | Published online |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acs.est.0c06927 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:177162 |