Biotransformation of PuEDTA: Implications to Pu Immobilization Page: 1 of 3
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2006 ERSD Annual Report
DOE-BER Environmental Remediation Sciences Project # 1010283
Biotransformation of PuEDTA: Implications to Pu Immobilization
PI: Harvey Bolton Jr.'
Co-PIs: Dhanpat Rail and Luying Xun2
Pacific Northwest National Laboratory, Richland, WA'
Washington State University, Pullman, WA2
This project integrates three distinct goals to develop a fundamental understanding of the
potential fate and disposition of plutonium in sediments that are co-contaminated with
EDTA. The three objectives are:
1. Develop thermodynamic data for Pu-EDTA species and determine the dominant
mobile form of Pu under anaerobic conditions.
2. Elucidate the mechanism and rates of Pu(IV) and Pu(IV)-EDTA reduction by
metal-reducing bacteria and determine where the Pu is located (in solution,
3. Enrich and isolate anaerobic EDTA-degrading microorganisms to investigate the
anaerobic biodegradation of Pu-EDTA
The research related to objectives 1 and 2 above is being carried out at PNNL, while that
related to objective 3 is at WSU.
Research Progress and Implications:
This report presents research conducted during the first 2 years of a 3 year project.
Extensive studies are being carried out to obtain values for thermodynamic equilibrium
constants for the formation of Pu(III)-EDTA complexes. Our approach consists of
developing extensive data 1) to determine the solubility product for PuPO4(s), currently
unavailable, through studies of PuPO4(s) as a function of pH at fixed phosphate
concentrations, and as a function of phosphate concentrations at a fixed pH value and to
use this information to accurately define Pu3 activities required for determining Pu(III)-
EDTA complexes. The data on Pu(III)-EDTA complexes will be obtained through
extensive PuPO4(s) solubility studies 1) as a function of pH (1.5 - 14), and at fixed
phosphate concentration of 10-3s M and EDTA concentrations of 1034 and 1027, and 2)
as a function of EDTA concentrations ranging from 0.0001 M to 0.1 M, and at fixed pH
values (4, 11, 13) and at fixed phosphate concentrations of 10-3 M. Reducing agents are
used in all of the studies to maintain Pu in the trivalent state. The Pitzer model will be
used to interpret the data and will yield thermodynamic equilibrium constants necessary
to determine Pu behavior in anaerobic geologic environments. Experimental work on
these various aspects under this task is nearly complete, and emphasis will now shift to
interpretation of data and drafting manuscripts for publication in the open literature. This
work [specifically the extraction techniques developed as a side line to quantify the Pu
oxidation states, especially the Pu(III)] has already led to techniques to quantitatively
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Bolton, Harvey, Jr. Biotransformation of PuEDTA: Implications to Pu Immobilization, report, June 1, 2006; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc883642/m1/1/: accessed December 10, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.