Cadmium Isotope Fractionation during Adsorption and Substitution with Iron (Oxyhydr)oxides
نویسندگان
چکیده
Cadmium (Cd) isotopes have great potential for understanding Cd geochemical cycling in soil and aquatic systems. Iron (oxyhydr)oxides can sequester via adsorption isomorphous substitution, but how these interactions affect isotope fractionation remains unknown. Here, we show that preferentially enriches lighter on iron (oxyhydr)oxide surfaces through equilibrium fractionation, with a similar magnitude (Δ114/110Cdsolid-solution) goethite (Goe) (-0.51 ± 0.04‰), hematite (Hem) (-0.54 0.10‰), ferrihydrite (Fh) (-0.55 0.03‰). Neither the initial Cd2+ concentration or ionic strength nor pH influence magnitude. The enrichment of light is attributed to highly distorted [CdO6] solids, as indicated by K-edge extended X-ray absorption fine-structure analysis. In contrast, incorporation into Goe substitution lattice Fe at Cd/Fe molar ratio 0.05 sequesters heavy isotopes, Δ114/110Cdsolid-solution 0.22 0.01‰. probably occurs during transformation Fh dissolution reprecipitation. These results improve behavior being affected Earth's critical zone demonstrate minerals obscure anthropogenic natural characteristics, which should be carefully considered when applying environmental tracers.
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ژورنال
عنوان ژورنال: Environmental Science & Technology
سال: 2021
ISSN: ['1520-5851', '0013-936X']
DOI: https://doi.org/10.1021/acs.est.0c06927