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Title: Redox Controls over the Stability of U(IV) in Floodplains of the Upper Colorado River Basin

Abstract

Here, aquifers in the Upper Colorado River Basin (UCRB) exhibit persistent uranium (U) groundwater contamination plumes originating from former ore processing operations. Previous observations at Rifle, Colorado, have shown that fine grained, sulfidic, organic-enriched sediments accumulate U in its reduced form, U(IV), which is less mobile than oxidized U(VI). These reduced sediment bodies can subsequently act as secondary sources, releasing U back to the aquifer. There is a need to understand if U(IV) accumulation in reduced sediments is a common process at contaminated sites basin-wide, to constrain accumulated U(IV) speciation, and to define the biogeochemical factors controlling its reactivity. We have investigated U(IV) accumulation in organic-enriched reduced sediments at three UCRB floodplains. Noncrystalline U(IV) is the dominant form of accumulated U, but crystalline U(IV) comprises up to ca. 30% of total U at some locations. Differing susceptibilities of these species to oxidative remobilization can explain this variability. Particle size, organic carbon content, and pore saturation, control the exposure of U(IV) to oxidants, moderating its oxidative release. Further, our data suggest that U(IV) can be mobilized under deeply reducing conditions, which may contribute to maintenance and seasonal variability of U in groundwater plumes in the UCRB.

Authors:
ORCiD logo [1];  [2];  [2];  [1];  [1];  [3];  [4]; ORCiD logo [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
  3. Stanford Univ., Stanford, CA (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1457054
Grant/Contract Number:
AC02-05CH11231; AC02-76SF00515
Resource Type:
Journal Article: 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

Citation Formats

Noel, Vincent, Boye, Kristin, Lezama Pacheco, Juan S., Bone, Sharon E., Janot, Noemie, Cardarelli, Emily, Williams, Kenneth H., and Bargar, John R. Redox Controls over the Stability of U(IV) in Floodplains of the Upper Colorado River Basin. United States: N. p., 2017. Web. doi:10.1021/acs.est.7b02203.
Noel, Vincent, Boye, Kristin, Lezama Pacheco, Juan S., Bone, Sharon E., Janot, Noemie, Cardarelli, Emily, Williams, Kenneth H., & Bargar, John R. Redox Controls over the Stability of U(IV) in Floodplains of the Upper Colorado River Basin. United States. doi:10.1021/acs.est.7b02203.
Noel, Vincent, Boye, Kristin, Lezama Pacheco, Juan S., Bone, Sharon E., Janot, Noemie, Cardarelli, Emily, Williams, Kenneth H., and Bargar, John R. Tue . "Redox Controls over the Stability of U(IV) in Floodplains of the Upper Colorado River Basin". United States. doi:10.1021/acs.est.7b02203.
@article{osti_1457054,
title = {Redox Controls over the Stability of U(IV) in Floodplains of the Upper Colorado River Basin},
author = {Noel, Vincent and Boye, Kristin and Lezama Pacheco, Juan S. and Bone, Sharon E. and Janot, Noemie and Cardarelli, Emily and Williams, Kenneth H. and Bargar, John R.},
abstractNote = {Here, aquifers in the Upper Colorado River Basin (UCRB) exhibit persistent uranium (U) groundwater contamination plumes originating from former ore processing operations. Previous observations at Rifle, Colorado, have shown that fine grained, sulfidic, organic-enriched sediments accumulate U in its reduced form, U(IV), which is less mobile than oxidized U(VI). These reduced sediment bodies can subsequently act as secondary sources, releasing U back to the aquifer. There is a need to understand if U(IV) accumulation in reduced sediments is a common process at contaminated sites basin-wide, to constrain accumulated U(IV) speciation, and to define the biogeochemical factors controlling its reactivity. We have investigated U(IV) accumulation in organic-enriched reduced sediments at three UCRB floodplains. Noncrystalline U(IV) is the dominant form of accumulated U, but crystalline U(IV) comprises up to ca. 30% of total U at some locations. Differing susceptibilities of these species to oxidative remobilization can explain this variability. Particle size, organic carbon content, and pore saturation, control the exposure of U(IV) to oxidants, moderating its oxidative release. Further, our data suggest that U(IV) can be mobilized under deeply reducing conditions, which may contribute to maintenance and seasonal variability of U in groundwater plumes in the UCRB.},
doi = {10.1021/acs.est.7b02203},
journal = {Environmental Science and Technology},
number = 19,
volume = 51,
place = {United States},
year = {Tue Sep 05 00:00:00 EDT 2017},
month = {Tue Sep 05 00:00:00 EDT 2017}
}

Journal Article:
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