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Title: Field Application of 238U/ 235U Measurements To Detect Reoxidation and Mobilization of U(IV)

Abstract

We present that biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective strategy for decreasing aqueous U(VI) concentrations in contaminated groundwater systems. If oxidation of U(IV) occurs following the biostimulation phase, U(VI) concentrations increase, challenging the long-term effectiveness of this technique. However, detecting U(IV) oxidation through dissolved U concentrations alone can prove difficult in locations with few groundwater wells to track the addition of U to a mass of groundwater. We propose the 238U/ 235U ratio of aqueous U as an independent, reliable tracer of U(IV) remobilization via oxidation or mobilization of colloids. Reduction of U(VI) produces 238U-enriched U(IV), whereas remobilization of solid U(IV) should not induce isotopic fractionation. The incorporation of remobilized U(IV) with a high 238U/ 235U ratio into the aqueous U(VI) pool produces an increase in 238U/ 235U of aqueous U(VI). Lastly, during several injections of nitrate to induce U(IV) oxidation, 238U/ 235U consistently increased, suggesting 238U/ 235U is broadly applicable for detecting mobilization of U(IV).

Authors:
ORCiD logo [1];  [2];  [1];  [1];  [3];  [3]
  1. University of Illinois at Urbana−Champaign, Urbana, IL (United States). Department of Geology
  2. Oregon State Univ., Corvallis, OR (United States). College of Earth, Ocean, and Atmospheric Sciences
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1477271
Grant/Contract Number:  
AC02-05CH11231; SC0006755
Resource Type:
Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 52; Journal Issue: 6; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES

Citation Formats

Jemison, Noah E., Shiel, Alyssa E., Johnson, Thomas M., Lundstrom, Craig C., Long, Philip E., and Williams, Kenneth H. Field Application of 238U/235U Measurements To Detect Reoxidation and Mobilization of U(IV). United States: N. p., 2018. Web. doi:10.1021/acs.est.7b05162.
Jemison, Noah E., Shiel, Alyssa E., Johnson, Thomas M., Lundstrom, Craig C., Long, Philip E., & Williams, Kenneth H. Field Application of 238U/235U Measurements To Detect Reoxidation and Mobilization of U(IV). United States. doi:10.1021/acs.est.7b05162.
Jemison, Noah E., Shiel, Alyssa E., Johnson, Thomas M., Lundstrom, Craig C., Long, Philip E., and Williams, Kenneth H. Wed . "Field Application of 238U/235U Measurements To Detect Reoxidation and Mobilization of U(IV)". United States. doi:10.1021/acs.est.7b05162. https://www.osti.gov/servlets/purl/1477271.
@article{osti_1477271,
title = {Field Application of 238U/235U Measurements To Detect Reoxidation and Mobilization of U(IV)},
author = {Jemison, Noah E. and Shiel, Alyssa E. and Johnson, Thomas M. and Lundstrom, Craig C. and Long, Philip E. and Williams, Kenneth H.},
abstractNote = {We present that biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective strategy for decreasing aqueous U(VI) concentrations in contaminated groundwater systems. If oxidation of U(IV) occurs following the biostimulation phase, U(VI) concentrations increase, challenging the long-term effectiveness of this technique. However, detecting U(IV) oxidation through dissolved U concentrations alone can prove difficult in locations with few groundwater wells to track the addition of U to a mass of groundwater. We propose the 238U/235U ratio of aqueous U as an independent, reliable tracer of U(IV) remobilization via oxidation or mobilization of colloids. Reduction of U(VI) produces 238U-enriched U(IV), whereas remobilization of solid U(IV) should not induce isotopic fractionation. The incorporation of remobilized U(IV) with a high 238U/235U ratio into the aqueous U(VI) pool produces an increase in 238U/235U of aqueous U(VI). Lastly, during several injections of nitrate to induce U(IV) oxidation, 238U/235U consistently increased, suggesting 238U/235U is broadly applicable for detecting mobilization of U(IV).},
doi = {10.1021/acs.est.7b05162},
journal = {Environmental Science and Technology},
number = 6,
volume = 52,
place = {United States},
year = {2018},
month = {2}
}

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