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Zn isotopic fractionation caused by sorption on goethite and 2-Lines ferrihydrite
- Source :
- Geochimica et Cosmochimica Acta, Geochimica et Cosmochimica Acta, Elsevier, 2008, 72, pp.4886-4900, HAL
- Publication Year :
- 2008
- Publisher :
- Elsevier BV, 2008.
-
Abstract
- Zn isotopic fractionation caused by sorption on 2-Lines ferrihydrite (Fh2L) and goethite was investigated to assess the role of reactions at the Fe-oxyhydroxide/water interface in changes of the isotopic distribution of Zn. Since sorption reactions are ubiquitous in Earth’s surface environments, it is important to evaluate their influence on the isotopic distribution of Zn before it can be used to track and quantify contributions of various sources and/or biogeochemical processes involving this element. Our results show that Zn isotopes are fractionated upon sorption on Fe-oxyhydroxides with an enrichment of the heavy isotopes present on the solid’s surface. This fractionation appears to proceed through an equilibrium mechanism and yields different (Δ 66/64 Zn) sorbed–aqueous values for Zn sorption on goethite [(Δ 66/64 Zn) sorbed–aqueous around +0.29‰] and Fh2L [(Δ 66/64 Zn) sorbed–aqueous around +0.53‰]. These different magnitudes of Zn fractionation are related to structural differences between Zn complexes existing on the surface of goethite (octahedrally coordinated Zn by oxygen atoms) and Fh2L (tetrahedrally coordinated Zn by oxygen atoms), as evidenced by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and CD-MUSIC modeling. These results show the importance of accounting for reactions at the Fe-oxyhydroxide/water interface when dealing with the isotopic distribution of Zn at the Earth’s surface. Considering the large range of other possible sorbents (Mn or Al oxides, phyllosilicates, carbonates, biologic surfaces, etc.) and the importance of reactions at sorbent/water interfaces for other non-traditional stable isotopes (i.e. Cr, Fe, Ni and Cu) that are increasingly used in environmental studies, these results emphasize the need for further experimental studies that are needed to quantify the isotopic fractionation of these elements possibly accompanying their sorption.
- Subjects :
- Goethite
Extended X-ray absorption fine structure
Chemistry
Stable isotope ratio
Inorganic chemistry
Sorption
Fractionation
010501 environmental sciences
010502 geochemistry & geophysics
01 natural sciences
Equilibrium fractionation
Ferrihydrite
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry
13. Climate action
Geochemistry and Petrology
visual_art
visual_art.visual_art_medium
ComputingMilieux_MISCELLANEOUS
Earth (classical element)
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 00167037
- Volume :
- 72
- Database :
- OpenAIRE
- Journal :
- Geochimica et Cosmochimica Acta
- Accession number :
- edsair.doi.dedup.....6ca11506f7bcc771a8cee45caf89f825