Understanding the processes controlling Pu mobility in the subsurface environment is important for estimating the amount of Pu waste that can be safely disposed in vadose zone burial sites. To study long-term Pu mobility, four 52-L lysimeters filled with sediment collected from the Savannah River Site near Aiken, South Carolina were amended with well-characterized solid Pu sources (PuIIICl3, PuIV(NO3)4, PuIV(C2O4)2, and PuVIO2(NO3)2) and left exposed to natural precipitation for 2-11 years. Pu oxidation state distribution in the Pu(III) and Pu(IV) lysimeters sediments (a red clayey sediment, pH = 6.3) were similar, consisting of 0% Pu(III), >92% Pu(IV), 1% Pu(V), 1% Pu(VI), and the remainder was a Pu polymer. These three lysimeters also had near identical sediment Pu concentration profiles, where >95% of the Pu remained within 1.25 cm of the source after 11 years; the other 5% of Pu moved at an overall rate of 0.9 cm yr(-1). As expected, Pu moved more rapidly through the Pu(VI) lysimeter, at an overall rate of 12.5 cm yr(-1). Solute transport modeling of the sediment Pu concentration profile data in the Pu(VI) lysimeter indicated that some transformation of Pu into a much less mobile form, presumably Pu(IV), had occurred during the course of the two-year study. This modeling also supported previous laboratory measurements showing that Pu(V) or Pu(VI) reduction was 5 orders of magnitude faster than corresponding Pu(III) or Pu(IV) oxidation. The slow oxidation rate (1 x 10(-8) hr(-1); t1/2 = 8000 yr) was not discernible from the Pu(VI) lysimeter data that reflected only two years of transport butwas readily discernible from the Pu(III) and Pu(IV) lysimeter data that reflected 11 years of transport.
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1021/es050073o | DOI Listing |
Environ Sci Technol
January 2025
Xi'an AMS Center, State Key Laboratory of Loess Science, Shaanxi Key Laboratory of Accelerator Mass Spectrometry Technology and Application, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, P. R. China.
There has been a sharp rise in the extent and scale of human activities since the mid-20th century, termed the "Great Acceleration", and nuclear activities are one of the defining technological processes for this period. Pu released by atmospheric nuclear weapons tests provides an ideal chronostratigraphic marker for labeling this change due to its global fallout feature, temporal mutation, and long half-lives. However, the accumulation dynamics of plutonium from atmospheric deposition to preservation in the sediment is still controversial.
View Article and Find Full Text PDFEnviron Sci Technol
September 2024
Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, 301 Stinson-Remick, Notre Dame, Indiana 46556, United States.
We explored the speciation and kinetics of the Pu(VI)-citrate and Pu(III)-citrate systems (pH = 2.5-11.0, = 0.
View Article and Find Full Text PDFInorg Chem
May 2024
Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Freemont Avenue, Idaho Falls, Idaho 83415, United States.
Careful manipulation of the plutonium oxidation states is essential in the study and utilization of its rich redox chemistry. To achieve this level of control, a comprehensive mechanistic understanding of radiation-induced plutonium redox chemistry is critical due to the unavoidable exposure of plutonium to ionizing radiation fields, both inherent and from in-process applications. To this end, we have developed an experimentally evaluated multiscale computer model for the prediction of gamma radiation-induced Pu(IV) redox chemistry in concentrated nitric acid solutions (1.
View Article and Find Full Text PDFInorg Chem
February 2024
Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
Inorg Chem
November 2023
Department of Chemistry, University of California-Irvine, Irvine, California 92697, United States.
The pursuit of a trivalent plutonium halide phosphine oxide compound, e.g., "PuBr(OPR)," instead led to the isolation of the tetravalent -PuBr(OPCy), , compound by spontaneous oxidation of Pu.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!