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Title: Influence of Sources on Plutonium Mobility and Oxidation State Transformations in Vadose Zone Sediments

Abstract

Well-defined solid sources of Pu(III) (PuCl3), Pu(IV) (Pu (NO3)4 and Pu (C2O4)2), and Pu(VI) (PuO2(NO3)2) were placed in lysimeters containing vadose zone sediments and exposed to natural weather conditions for 2 or 11 years. The objective of this study was to measure the release rate of Pu and the changes in the Pu oxidation states from these Pu sources with the intent to develop a reactive transport model source-term. Pu(III) and Pu(IV) sources had identical Pu concentration depth profiles and similar Pu release rates. Source release data indicate that PuIV(C2O4)2 was the least mobile, whereas PuVIO2(NO3)2 was the most mobile. Synchrotron X-ray fluorescence (SXRF) revealed that Pu was very unevenly distributed on the sediment and Mn concentrations were too low (630 mg kg-1) and perhaps of the wrong mineralogy to influence Pu distribution. The high stability of sorbed Pu(IV) is proposed to be due to the formation of a stable hydrolyzed Pu(IV) surface species. Plutonium X-ray absorption near-edge spectroscopy (XANES) analysis conducted on sediment recovered at the end of the study from the PuIV(NO3)4- and PuIIICl3-amended lysimeters contained essentially identical Pu distributions: approximately 37% Pu(III), 67% Pu(IV), 0% Pu(V), and 0% Pu(VI). These results were similar to those using amore » wet chemistry Pu oxidation state assay, except the latter method did not detect any Pu(III) present on the sediment but instead indicated that 93-98% of the Pu existed as Pu(IV). This discrepancy was likely attributable to incomplete extraction of sediment Pu(III) by the wet chemistry method. Although Pu has been known to exist in the +3 oxidation state under microbially induced reducing conditions for decades, to our knowledge, this is the first observation of steady-state Pu(III) in association with natural sediments. On the basis of thermodynamic considerations, Pu(III) has a wide potential distribution, especially in acidic environments, and as such may warrant further investigation.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
959798
Report Number(s):
BNL-82784-2009-JA
Journal ID: ISSN 0013-936X; ESTHAG; TRN: US1005810
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 41; Journal Issue: 21
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ABSORPTION; CHEMISTRY; DISTRIBUTION; FLUORESCENCE; LYSIMETERS; MINERALOGY; PLUTONIUM; SEDIMENTS; SPECTROSCOPY; STABILITY; SYNCHROTRONS; THERMODYNAMICS; TRANSFORMATIONS; TRANSPORT; VALENCE; WEATHER; national synchrotron light source

Citation Formats

Kaplan,D., Powell, B., Duff, M., Demirkanli, D., Denham, M., Fjeld, R., and Molz, F.. Influence of Sources on Plutonium Mobility and Oxidation State Transformations in Vadose Zone Sediments. United States: N. p., 2007. Web. doi:10.1021/es0706302.
Kaplan,D., Powell, B., Duff, M., Demirkanli, D., Denham, M., Fjeld, R., & Molz, F.. Influence of Sources on Plutonium Mobility and Oxidation State Transformations in Vadose Zone Sediments. United States. doi:10.1021/es0706302.
Kaplan,D., Powell, B., Duff, M., Demirkanli, D., Denham, M., Fjeld, R., and Molz, F.. Mon . "Influence of Sources on Plutonium Mobility and Oxidation State Transformations in Vadose Zone Sediments". United States. doi:10.1021/es0706302.
@article{osti_959798,
title = {Influence of Sources on Plutonium Mobility and Oxidation State Transformations in Vadose Zone Sediments},
author = {Kaplan,D. and Powell, B. and Duff, M. and Demirkanli, D. and Denham, M. and Fjeld, R. and Molz, F.},
abstractNote = {Well-defined solid sources of Pu(III) (PuCl3), Pu(IV) (Pu (NO3)4 and Pu (C2O4)2), and Pu(VI) (PuO2(NO3)2) were placed in lysimeters containing vadose zone sediments and exposed to natural weather conditions for 2 or 11 years. The objective of this study was to measure the release rate of Pu and the changes in the Pu oxidation states from these Pu sources with the intent to develop a reactive transport model source-term. Pu(III) and Pu(IV) sources had identical Pu concentration depth profiles and similar Pu release rates. Source release data indicate that PuIV(C2O4)2 was the least mobile, whereas PuVIO2(NO3)2 was the most mobile. Synchrotron X-ray fluorescence (SXRF) revealed that Pu was very unevenly distributed on the sediment and Mn concentrations were too low (630 mg kg-1) and perhaps of the wrong mineralogy to influence Pu distribution. The high stability of sorbed Pu(IV) is proposed to be due to the formation of a stable hydrolyzed Pu(IV) surface species. Plutonium X-ray absorption near-edge spectroscopy (XANES) analysis conducted on sediment recovered at the end of the study from the PuIV(NO3)4- and PuIIICl3-amended lysimeters contained essentially identical Pu distributions: approximately 37% Pu(III), 67% Pu(IV), 0% Pu(V), and 0% Pu(VI). These results were similar to those using a wet chemistry Pu oxidation state assay, except the latter method did not detect any Pu(III) present on the sediment but instead indicated that 93-98% of the Pu existed as Pu(IV). This discrepancy was likely attributable to incomplete extraction of sediment Pu(III) by the wet chemistry method. Although Pu has been known to exist in the +3 oxidation state under microbially induced reducing conditions for decades, to our knowledge, this is the first observation of steady-state Pu(III) in association with natural sediments. On the basis of thermodynamic considerations, Pu(III) has a wide potential distribution, especially in acidic environments, and as such may warrant further investigation.},
doi = {10.1021/es0706302},
journal = {Environmental Science and Technology},
number = 21,
volume = 41,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}