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Abstract Details

The Role of Uranium Speciation in its Isotopic Fractionation

Bernier-Latmani R, Brown A, Pan Z, Faisova R, Sato A, Roebbert Y, Vitova T, Mazzanti M, Abe M & Weyer S

Bernier-Latmani R, Brown A, Pan Z, Faisova R, Sato A, Roebbert Y, Vitova T, Mazzanti M, Abe M & Weyer S (2020) Goldschmidt Abstracts, 2020 177

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08b: Room 3, View in program

Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.

Submitted by Pieter Bots on
Thank you for your presentations, this was really interesting! I was wondering if it is known if and/or how DPAEA impacts on the mechanisms of microbial redox reactions and the respective fractionation; does the DPAEA impact on the U(VI) -> U(V) -> U(IV) reaction mechanisms and fractionation, and could DPAEA impact on the isotopic exchange between U(V) and U(IV)? I am also curious if the fractionation and the variations in the fractions could help distinguishing between e.g. direct enzymatic reduction, reduction coupled to oxidation of enzymatically reduced Fe/S, and/or disproportionation? Thanks again (P. Bots)
Thank you, Pieter. yes, we think that the U(IV) product may include DPAEA, which would mean that it may sequester the U in such a way as to preclude isotopic exchange. But, we don't know this for a fact. I think the second part of your question refers to the use of DPAEA in other systems. This could be an interesting idea for abiotic systems. We haven't done that at all as of yet. Thank you.

Submitted by Ruth Tinnacher on
Submitted by Pieter Bots on Monday, June 15 08:02 (America/Los_Angeles) Thank you for your presentations, this was really interesting! I was wondering if it is known if and/or how DPAEA impacts on the mechanisms of microbial redox reactions and the respective fractionation; does the DPAEA impact on the U(VI) -> U(V) -> U(IV) reaction mechanisms and fractionation, and could DPAEA impact on the isotopic exchange between U(V) and U(IV)? I am also curious if the fractionation and the variations in the fractions could help distinguishing between e.g. direct enzymatic reduction, reduction coupled to oxidation of enzymatically reduced Fe/S, and/or disproportionation? Thanks again (P. Bots) From Ruth Tinnacher: Very interesting presentation. Thank you! Not being an isotope geochemist, I was wondering about the following. *) Would you expect that the kinetically limited U isotope exchange between U(V)-DPAEA and U(IV)-DPAEA is affected by the fact that U(V)-DPAEA stays in solution while U(IV)-DPAEA forms a solid? *) Can you make any guesses if we should see similar behavior for other U solution complexes, e.g. with carbonate ligands?


Submitted by Ruth Tinnacher on
Very interesting talk. Thank you. Two questions from someone who is not an isotope geochemist: *) Would you expect that the kinetically limited U isotope exchange between U(V)-DPAEA and U(IV)-DPAEA is affected by the fact that U(V)-DPAEA stays in solution while U(IV)-DPAEA forms a solid? *) Can you make any guesses if we should see similar behavior for other U solution complexes, e.g. with carbonate ligands?
Thanks for your question. No, I don't think so because we have tested this with other U-ligand species that can adsorb and the same result is observed. For U-carbonate systems, the U(IV) species are likely to undergo isotope exchange much more readily. Hence, the enzymatic fractionation may be overprinted by the isotopic exchange.

Submitted by Stephen Romaniello on
Hi Rizlan, great talk and a very nice experimental system! Extrapolating from this work, do you think the reason we typically see larger isotopic fractionation during biotic reduction is that something in that process is facilitating isotopic exchange between U(6) and U(4)?
Thanks Steve. Well, the product of biotic reduction is typically non-crystalline U(IV). The hypothesis is that this type of U(IV) species is readily available for isotopic exchange. But, this remains a hypothesis since it has not been probed yet. We are working on this and hope to be able to answer the question in the near future.

Submitted by Rizlan Bernier-Latmani on
Thanks Steve. Well, the product of biotic reduction is typically non-crystalline U(IV). The hypothesis is that this type of U(IV) species is readily available for isotopic exchange. But, this remains a hypothesis since it has not been probed yet. We are working on this and hope to be able to answer the question in the near future.


Submitted by Rizlan Bernier-Latmani on
Thanks Steve. Well, the product of biotic reduction is typically non-crystalline U(IV). The hypothesis is that this type of U(IV) species is readily available for isotopic exchange. But, this remains a hypothesis since it has not been probed yet. We are working on this and hope to be able to answer the question in the near future.


Submitted by Rizlan Bernier-Latmani on



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