Details
| Original language | English |
|---|---|
| Pages (from-to) | 7959-7969 |
| Number of pages | 11 |
| Journal | Environmental Science and Technology |
| Volume | 55 |
| Issue number | 12 |
| Early online date | 26 May 2021 |
| Publication status | Published - 15 Jun 2021 |
Abstract
Uranium (U) isotopes are suggested as a tool to trace U reduction. However, noncrystalline U(IV), formed predominantly in near-surface environments, may be complexed and remobilized using ligands under anoxic conditions. This may cause additional U isotope fractionation and alter the signatures generated by U reduction. Here, we investigate the efficacy of noncrystalline U(IV) mobilization by ligand complexation and the associated U isotope fractionation. Noncrystalline U(IV) was produced via the reduction of U(VI) (400 μM) by Shewanella oneidensis MR-1 and was subsequently mobilized with EDTA (1 mM), citrate (1 mM), or bicarbonate (500 mM) in batch experiments. Complexation with all investigated ligands resulted in significant mobilization of U(IV) and led to an enrichment of 238U in the mobilized fraction (δ238U = 0.4−0.7 % for EDTA; 0.3 % for citrate; 0.2−0.3 % for bicarbonate). For mobilization with bicarbonate, a Rayleigh approach was the most suitable isotope fractionation model, yielding a fractionation factor α of 1.00026− 1.00036. Mobilization with EDTA could be modeled with equilibrium isotope fractionation (α: 1.00039−1.00049). The results show that U isotope fractionation associated with U(IV) mobilization under anoxic conditions is significant and needs to be considered when applying U isotopes in remediation monitoring or as a paleo-redox proxy.
Keywords
- Complexation, Fractionation, Laboratory batch experiments, Ligands, Uranium
ASJC Scopus subject areas
- Chemistry(all)
- General Chemistry
- Environmental Science(all)
- Environmental Chemistry
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In: Environmental Science and Technology, Vol. 55, No. 12, 15.06.2021, p. 7959-7969.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Uranium Isotope Fractionation during the Anoxic Mobilization of Noncrystalline U(IV) by Ligand Complexation
AU - Roebbert, Yvonne
AU - Rosendahl, Chris Daniel
AU - Brown, Ashley
AU - Schippers, Axel
AU - Bernier-Latmani, Rizlan
AU - Weyer, Stefan
N1 - Funding Information: We thank Walter Schenkeveld, Stephan Krämer, Luca Loreggian, Zezhen Pan, Stephan Schuth, Maria Kirchenbaur, Ingo Horn, Minori Abe, Sabrina Hedrich, and Isabell Kruckemeyer for their support during the generation and discussion of the data. Associate Editor Daniel Giammar, Xiangli Wang, and two anonymous reviewers are thanked for their helpful comments. Funding for this work was provided by the DFG/SNSF grants (WE 2850-16/1 and 200021E-164209: Fate of tetravalent uranium under reducing conditions) and an ERC consolidator grant of R. Bernier-Latmani (725675: UNEARTH: “Uranium isotope fractionation: a novel biosignature to identify microbial metabolism on early Earth”).
PY - 2021/6/15
Y1 - 2021/6/15
N2 - Uranium (U) isotopes are suggested as a tool to trace U reduction. However, noncrystalline U(IV), formed predominantly in near-surface environments, may be complexed and remobilized using ligands under anoxic conditions. This may cause additional U isotope fractionation and alter the signatures generated by U reduction. Here, we investigate the efficacy of noncrystalline U(IV) mobilization by ligand complexation and the associated U isotope fractionation. Noncrystalline U(IV) was produced via the reduction of U(VI) (400 μM) by Shewanella oneidensis MR-1 and was subsequently mobilized with EDTA (1 mM), citrate (1 mM), or bicarbonate (500 mM) in batch experiments. Complexation with all investigated ligands resulted in significant mobilization of U(IV) and led to an enrichment of 238U in the mobilized fraction (δ238U = 0.4−0.7 % for EDTA; 0.3 % for citrate; 0.2−0.3 % for bicarbonate). For mobilization with bicarbonate, a Rayleigh approach was the most suitable isotope fractionation model, yielding a fractionation factor α of 1.00026− 1.00036. Mobilization with EDTA could be modeled with equilibrium isotope fractionation (α: 1.00039−1.00049). The results show that U isotope fractionation associated with U(IV) mobilization under anoxic conditions is significant and needs to be considered when applying U isotopes in remediation monitoring or as a paleo-redox proxy.
AB - Uranium (U) isotopes are suggested as a tool to trace U reduction. However, noncrystalline U(IV), formed predominantly in near-surface environments, may be complexed and remobilized using ligands under anoxic conditions. This may cause additional U isotope fractionation and alter the signatures generated by U reduction. Here, we investigate the efficacy of noncrystalline U(IV) mobilization by ligand complexation and the associated U isotope fractionation. Noncrystalline U(IV) was produced via the reduction of U(VI) (400 μM) by Shewanella oneidensis MR-1 and was subsequently mobilized with EDTA (1 mM), citrate (1 mM), or bicarbonate (500 mM) in batch experiments. Complexation with all investigated ligands resulted in significant mobilization of U(IV) and led to an enrichment of 238U in the mobilized fraction (δ238U = 0.4−0.7 % for EDTA; 0.3 % for citrate; 0.2−0.3 % for bicarbonate). For mobilization with bicarbonate, a Rayleigh approach was the most suitable isotope fractionation model, yielding a fractionation factor α of 1.00026− 1.00036. Mobilization with EDTA could be modeled with equilibrium isotope fractionation (α: 1.00039−1.00049). The results show that U isotope fractionation associated with U(IV) mobilization under anoxic conditions is significant and needs to be considered when applying U isotopes in remediation monitoring or as a paleo-redox proxy.
KW - Complexation
KW - Fractionation
KW - Laboratory batch experiments
KW - Ligands
KW - Uranium
UR - http://www.scopus.com/inward/record.url?scp=85108303747&partnerID=8YFLogxK
U2 - 10.1021/acs.est.0c08623
DO - 10.1021/acs.est.0c08623
M3 - Article
C2 - 34038128
AN - SCOPUS:85108303747
VL - 55
SP - 7959
EP - 7969
JO - Environmental Science and Technology
JF - Environmental Science and Technology
SN - 0013-936X
IS - 12
ER -