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Title: Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions

Abstract

Here, uranium (U) contamination occurs as a result of mining and ore processing; often in alluvial aquifers that contain organic-rich, reduced sediments that accumulate tetravalent U, U(IV). Uranium(IV) is sparingly soluble, but may be mobilized upon exposure to nitrate (NO 3 ) and oxygen (O 2), which become elevated in groundwater due to seasonal fluctuations in the water table. The extent to which oxidative U mobilization can occur depends upon the transport properties of the sediments, the rate of U(IV) oxidation, and the availability of inorganic reductants and organic electron donors that consume oxidants. We investigated the processes governing U release upon exposure of reduced sediments to artificial groundwater containing O 2 or NO 3 under diffusion-limited conditions. Little U was mobilized during the 85-day reaction, despite rapid diffusion of groundwater within the sediments and the presence of nonuraninite U(IV) species. The production of ferrous iron and sulfide in conjunction with rapid oxidant consumption suggested that the sediments harbored large concentrations of bioavailable organic carbon that fueled anaerobic microbial respiration and stabilized U(IV). Our results suggest that seasonal influxes of O 2 and NO 3 may cause only localized mobilization of U without leading to export of Umore » from the reducing sediments when ample organic carbon is present.« less

Authors:
ORCiD logo [1];  [2];  [3]; ORCiD logo [2];  [4];  [5]; ORCiD logo [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Stanford Univ., Stanford, CA (United States)
  3. Stanford Univ., Stanford, CA (United States); Univ. of Massachusetts, Amherst, MA (United States)
  4. U.S. Geological Survey, Menlo Park, CA (United States)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); 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:
1463304
Alternate Identifier(s):
OSTI ID: 1476550
Grant/Contract Number:  
[AC02-76SF00515; AC02-05CH11231]
Resource Type:
Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
[ Journal Volume: 51; Journal Issue: 19]; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Bone, Sharon E., Cahill, Melanie R., Jones, Morris E., Fendorf, Scott, Davis, James, Williams, Kenneth H., and Bargar, John R. Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions. United States: N. p., 2017. Web. doi:10.1021/acs.est.7b02241.
Bone, Sharon E., Cahill, Melanie R., Jones, Morris E., Fendorf, Scott, Davis, James, Williams, Kenneth H., & Bargar, John R. Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions. United States. doi:10.1021/acs.est.7b02241.
Bone, Sharon E., Cahill, Melanie R., Jones, Morris E., Fendorf, Scott, Davis, James, Williams, Kenneth H., and Bargar, John R. Wed . "Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions". United States. doi:10.1021/acs.est.7b02241. https://www.osti.gov/servlets/purl/1463304.
@article{osti_1463304,
title = {Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions},
author = {Bone, Sharon E. and Cahill, Melanie R. and Jones, Morris E. and Fendorf, Scott and Davis, James and Williams, Kenneth H. and Bargar, John R.},
abstractNote = {Here, uranium (U) contamination occurs as a result of mining and ore processing; often in alluvial aquifers that contain organic-rich, reduced sediments that accumulate tetravalent U, U(IV). Uranium(IV) is sparingly soluble, but may be mobilized upon exposure to nitrate (NO3–) and oxygen (O2), which become elevated in groundwater due to seasonal fluctuations in the water table. The extent to which oxidative U mobilization can occur depends upon the transport properties of the sediments, the rate of U(IV) oxidation, and the availability of inorganic reductants and organic electron donors that consume oxidants. We investigated the processes governing U release upon exposure of reduced sediments to artificial groundwater containing O2 or NO3– under diffusion-limited conditions. Little U was mobilized during the 85-day reaction, despite rapid diffusion of groundwater within the sediments and the presence of nonuraninite U(IV) species. The production of ferrous iron and sulfide in conjunction with rapid oxidant consumption suggested that the sediments harbored large concentrations of bioavailable organic carbon that fueled anaerobic microbial respiration and stabilized U(IV). Our results suggest that seasonal influxes of O2 and NO3– may cause only localized mobilization of U without leading to export of U from the reducing sediments when ample organic carbon is present.},
doi = {10.1021/acs.est.7b02241},
journal = {Environmental Science and Technology},
number = [19],
volume = [51],
place = {United States},
year = {2017},
month = {9}
}

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