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An analysis of the hydrolytic polymerization of Pu(IV) and its reaction paths in nitric acid solution. J Radioanal Nucl Chem 2020. [DOI: 10.1007/s10967-020-07494-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Zhou X, Dang H, Han X, Li W, Wang Y, Wang W, Chai N. The speciation, transformation kinetics and fate of spiked Pu (IV) in highly saline groundwater. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 225:103505. [PMID: 31174143 DOI: 10.1016/j.jconhyd.2019.103505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Revised: 05/07/2019] [Accepted: 05/24/2019] [Indexed: 06/09/2023]
Abstract
The mobility of plutonium (Pu) in groundwater is dependent of its speciation distribution and transformation. The speciation and transformation kinetics of Pu(IV) and its colloids in highly saline groundwater have, however, been rarely studied. In the present study, groundwater (Ionic strength 1 M) from Dunhuang region, NW China, was collected for investigating the speciation, transformation kinetics and fate of spiked Pu (IV) with aging time. The results showed that ~99% of the spiked Pu (IV) (over initial concentration c0 range 2.5 × 10-10-7.8 × 10-7 mol·L-1) was easily associated with the natural colloids and transformed into relatively unstable Pu pseudo-colloids in 1 day, which then gradually deposited and/or adsorbed on the container walls with aging. The suspended Pu pseudo-colloids decreased in similar exponential models, with rate equations r(t) = -3.1 × 10-10e- t/4 and -1.3 × 10-8e-/3 for c0 = 1.25 × 10-9 mol·L-1and 4.17 × 10-8 mol·L-1, respectively. The chemical speciation of the suspended colloidal Pu was dominated by "Fe/Mn Oxides" at the early time, while "Carbonates" with slower depositing rate (r(t) = -6.9 × 10-12e- 0.149t) dominated it (~82%) at equilibrium state. Whatever the c0 was, the concentration of dissolved Pu (i.e., the apparent solubility of Pu) kept at 0.7 × 10-11 mol·L-1 over aging. The valence of dissolved Pu was dominated by Pu(IV) at early time, while Pu(V + VI) would become dominant (~95%) at equilibrium state with transformation rate of r(t) = -92.9e- t/16.6 + 96.9. The equilibrium times of Pu deposition (and/or adsorption), speciation transformation of the suspended colloidal Pu, and valence change of the dissolved Pu were 30 d, 80 d and 120 d, respectively. The kinetic process for each Pu species could be well fitted with exponential model. These results suggest that the majority of released Pu(IV) into highly saline groundwater will be easily associated with natural aquatic colloids and then become immobile in short time due to deposition (and/or adsorption) onto the environmental medium, but potential migration risk caused by stable suspended Pu colloids cannot be ignored.
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Affiliation(s)
- Xu Zhou
- Northwest Institute of Nuclear Technology, Xi'an 710024, China.
| | - Haijun Dang
- Northwest Institute of Nuclear Technology, Xi'an 710024, China
| | - Xiaoyuan Han
- Northwest Institute of Nuclear Technology, Xi'an 710024, China
| | - Weiping Li
- Northwest Institute of Nuclear Technology, Xi'an 710024, China
| | - Yu Wang
- Northwest Institute of Nuclear Technology, Xi'an 710024, China
| | - Weixian Wang
- Northwest Institute of Nuclear Technology, Xi'an 710024, China
| | - Nana Chai
- Northwest Institute of Nuclear Technology, Xi'an 710024, China
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Lin P, Xu C, Zhang S, Fujitake N, Kaplan DI, Yeager CM, Sugiyama Y, Schwehr KA, Santschi PH. Plutonium Partitioning Behavior to Humic Acids from Widely Varying Soils Is Related to Carboxyl-Containing Organic Compounds. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:11742-11751. [PMID: 28933160 DOI: 10.1021/acs.est.7b03409] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In order to examine the influence of the HA molecular composition on the partitioning of Pu, ten different kinds of humic acids (HAs) of contrasting chemical composition, collected and extracted from different soil types around the world were equilibrated with groundwater at low Pu concentrations (10-14 M). Under mildly acidic conditions (pH ∼ 5.5), 29 ± 24% of the HAs were released as colloidal organic matter (>3 kDa to <0.45 μm), yet this HA fraction accounted for a vast majority of the bound Pu, 76 ± 13% on average. In comparison, the particulate HA fraction bound only 8 ± 4% on average of the added Pu. The truly dissolved Pu fraction was typically <1%. Pu binding was strongly and positively correlated with the concentrations of organic nitrogen in both particulate (>0.45 μm) and colloidal phases in terms of activity percentage and partitioning coefficient values (logKd). Based on molecular characterization of the HAs by solid state 13C nuclear magnetic resonance (NMR) and elemental analysis, Pu binding was correlated to the concentration of carboxylate functionalities and nitrogen groups in the particulate and colloidal phases. The much greater tendency of Pu to bind to colloidal HAs than to particulate HA has implications on whether NOM acts as a Pu source or sink during natural or man-induced episodic flooding.
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Affiliation(s)
- Peng Lin
- Department of Marine Science, Texas A & M University at Galveston , Galveston, Texas 77553, United States
| | - Chen Xu
- Department of Marine Science, Texas A & M University at Galveston , Galveston, Texas 77553, United States
| | - Saijin Zhang
- Department of Marine Science, Texas A & M University at Galveston , Galveston, Texas 77553, United States
| | - Nobuhide Fujitake
- Division of Agroenvironmental Biology, Graduate School of Agriculture Science, Kobe University , Kyoto, 606-8501, Japan
| | - Daniel I Kaplan
- Savannah River National Laboratory , Aiken, South Carolina 29808, United States
| | - Chris M Yeager
- Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Yuko Sugiyama
- School of Human Science and Environment, University of Hyogo , 1-1-12 Shinzaike-Honcho, Himeji, Hyogo 670-0092, Japan
| | - Kathleen A Schwehr
- Department of Marine Science, Texas A & M University at Galveston , Galveston, Texas 77553, United States
| | - Peter H Santschi
- Department of Marine Science, Texas A & M University at Galveston , Galveston, Texas 77553, United States
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Zhao P, Begg JD, Zavarin M, Tumey SJ, Williams R, Dai ZR, Kips R, Kersting AB. Plutonium(IV) and (V) Sorption to Goethite at Sub-Femtomolar to Micromolar Concentrations: Redox Transformations and Surface Precipitation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:6948-56. [PMID: 27268262 DOI: 10.1021/acs.est.6b00605] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Pu(IV) and Pu(V) sorption to goethite was investigated over a concentration range of 10(-15)-10(-5) M at pH 8. Experiments with initial Pu concentrations of 10(-15) - 10(-8) M produced linear Pu sorption isotherms, demonstrating that Pu sorption to goethite is not concentration-dependent across this concentration range. Equivalent Pu(IV) and Pu(V) sorption Kd values obtained at 1 and 2-week sampling time points indicated that Pu(V) is rapidly reduced to Pu(IV) on the goethite surface. Further, it suggested that Pu surface redox transformations are sufficiently rapid to achieve an equilibrium state within 1 week, regardless of the initial Pu oxidation state. At initial concentrations >10(-8) M, both Pu oxidation states exhibited deviations from linear sorption behavior and less Pu was adsorbed than at lower concentrations. NanoSIMS and HRTEM analysis of samples with initial Pu concentrations of 10(-8) - 10(-6) M indicated that Pu surface and/or bulk precipitation was likely responsible for this deviation. In 10(-6) M Pu(IV) and Pu(V) samples, HRTEM analysis showed the formation of a body centered cubic (bcc) Pu4O7 structure on the goethite surface, confirming that reduction of Pu(V) had occurred on the mineral surface and that epitaxial distortion previously observed for Pu(IV) sorption occurs with Pu(V) as well.
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Affiliation(s)
- Pihong Zhao
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - James D Begg
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Mavrik Zavarin
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Scott J Tumey
- Center for Accelerator Mass Spectrometry, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Ross Williams
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Zurong R Dai
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Ruth Kips
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - Annie B Kersting
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
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Francis AJ, Dodge CJ. Microbial mobilization of plutonium and other actinides from contaminated soil. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2015; 150:277-285. [PMID: 26406590 DOI: 10.1016/j.jenvrad.2015.08.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 08/17/2015] [Accepted: 08/24/2015] [Indexed: 06/05/2023]
Abstract
We examined the dissolution of Pu, U, and Am in contaminated soil from the Nevada Test Site (NTS) due to indigenous microbial activity. Scanning transmission x-ray microscopy (STXM) analysis of the soil showed that Pu was present in its polymeric form and associated with Fe- and Mn- oxides and aluminosilicates. Uranium analysis by x-ray diffraction (μ-XRD) revealed discrete U-containing mineral phases, viz., schoepite, sharpite, and liebigite; synchrotron x-ray fluorescence (μ-XRF) mapping showed its association with Fe- and Ca-phases; and μ-x-ray absorption near edge structure (μ-XANES) confirmed U(IV) and U(VI) oxidation states. Addition of citric acid or glucose to the soil and incubated under aerobic or anaerobic conditions enhanced indigenous microbial activity and the dissolution of Pu. Detectable amount of Am and no U was observed in solution. In the citric acid-amended sample, Pu concentration increased with time and decreased to below detection levels when the citric acid was completely consumed. In contrast, with glucose amendment, Pu remained in solution. Pu speciation studies suggest that it exists in mixed oxidation states (III/IV) in a polymeric form as colloids. Although Pu(IV) is the most prevalent and generally considered to be more stable chemical form in the environment, our findings suggest that under the appropriate conditions, microbial activity could affect its solubility and long-term stability in contaminated environments.
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Affiliation(s)
- A J Francis
- Biological, Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
| | - C J Dodge
- Biological, Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
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6
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Xu C, Zhang S, Kaplan DI, Ho YF, Schwehr KA, Roberts KA, Chen H, DiDonato N, Athon M, Hatcher PG, Santschi PH. Evidence for Hydroxamate Siderophores and Other N-Containing Organic Compounds Controlling (239,240)Pu Immobilization and Remobilization in a Wetland Sediment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:11458-67. [PMID: 26313339 DOI: 10.1021/acs.est.5b02310] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Pu concentrations in wetland surface sediments collected downstream of a former nuclear processing facility in F-Area of the Savannah River Site (SRS), USA, were ∼2.5 times greater than those measured in the associated upland aquifer sediments; similarly, the Pu concentration solid/water ratios were orders of magnitude greater in the wetland than in the low-organic matter content aquifer soils. Sediment Pu concentrations were correlated to total organic carbon and total nitrogen contents and even more strongly to hydroxamate siderophore (HS) concentrations. The HS were detected in the particulate or colloidal phases of the sediments but not in the low molecular weight fractions (<1000 Da). Macromolecules which scavenged the majority of the potentially mobile Pu were further separated from the bulk mobile organic matter fraction ("water extract") via an isoelectric focusing experiment (IEF). An electrospray ionization Fourier-transform ion cyclotron resonance ultrahigh resolution mass spectrometry (ESI FTICR-MS) spectral comparison of the IEF extract and a siderophore standard (desferrioxamine; DFO) suggested the presence of HS functionalities in the IEF extract. This study suggests that while HS are a very minor component in the sediment particulate/colloidal fractions, their concentrations greatly exceed those of ambient Pu, and HS may play an especially important role in Pu immobilization/remobilization in wetland sediments.
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Affiliation(s)
- Chen Xu
- Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77554, United States
| | - Saijin Zhang
- Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77554, United States
| | - Daniel I Kaplan
- Savannah River National Laboratory , Aiken, South Carolina 29808, United States
| | - Yi-Fang Ho
- Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77554, United States
| | - Kathleen A Schwehr
- Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77554, United States
| | - Kimberly A Roberts
- Savannah River National Laboratory , Aiken, South Carolina 29808, United States
| | - Hongmei Chen
- Department of Chemistry and Biochemistry, College of Sciences, Old Dominion University , Norfolk, Virginia 23529, United States
| | - Nicole DiDonato
- Department of Chemistry and Biochemistry, College of Sciences, Old Dominion University , Norfolk, Virginia 23529, United States
| | - Matthew Athon
- Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77554, United States
| | - Patrick G Hatcher
- Department of Chemistry and Biochemistry, College of Sciences, Old Dominion University , Norfolk, Virginia 23529, United States
| | - Peter H Santschi
- Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77554, United States
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Tinnacher RM, Begg JD, Mason H, Ranville J, Powell BA, Wong JC, Kersting AB, Zavarin M. Effect of fulvic acid surface coatings on plutonium sorption and desorption kinetics on goethite. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:2776-2785. [PMID: 25607800 DOI: 10.1021/es505120s] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The rates and extent of plutonium (Pu) sorption and desorption onto mineral surfaces are important parameters for predicting Pu mobility in subsurface environments. The presence of natural organic matter, such as fulvic acid (FA), may influence these parameters. We investigated the effects of FA on Pu(IV) sorption/desorption onto goethite in two scenarios: when FA was (1) initially present in solution or (2) found as organic coatings on the mineral surface. A low pH was used to maximize FA coatings on goethite. Experiments were combined with kinetic modeling and speciation calculations to interpret variations in Pu sorption rates in the presence of FA. Our results indicate that FA can change the rates and extent of Pu sorption onto goethite at pH 4. Differences in the kinetics of Pu sorption were observed as a function of the concentration and initial form of FA. The fraction of desorbed Pu decreased in the presence of FA, indicating that organic matter can stabilize sorbed Pu on goethite. These results suggest that ternary Pu-FA-mineral complexes could enhance colloid-facilitated Pu transport. However, more representative natural conditions need to be investigated to quantify the relevance of these findings.
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Affiliation(s)
- Ruth M Tinnacher
- Glenn T. Seaborg Institute, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , P.O. Box 808, Livermore, California 94550, United States
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Kurosaki H, Kaplan DI, Clark SB. Impact of environmental curium on plutonium migration and isotopic signatures. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:13985-13991. [PMID: 25350948 DOI: 10.1021/es500968n] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Plutonium (Pu), americium (Am), and curium (Cm) activities were measured in sediments from a former radioactive waste disposal basin located on the Savannah River Site, South Carolina, and in subsurface aquifer sediments collected downgradient from the basin. In situ Kd values (Pu concentration ratio of sediment/groundwater) derived from this field data and previously reported groundwater concentration data compared well to laboratory Kd values reported in the literature. Pu isotopic signatures confirmed multiple sources of Pu contamination. The ratio of (240)Pu/(239)Pu was appreciably lower for sediment samples compared to the associated groundwater. This isotopic ratio difference may be explained by the following: (1) (240)Pu produced by decay of (244)Cm may exist predominantly in high oxidation states (Pu(V)O2(+) and Pu(VI)O2(2+)) compared to Pu derived from the disposed waste effluents, and (2) oxidized forms of Pu sorb less to sediments than reduced forms of Pu. Isotope-specific Kd values calculated from measured Pu activities in the sediments and groundwater indicated that (240)Pu, which is derived primarily from the decay of (244)Cm, had a value of 10 ± 2 mL g(-1), whereas (239)Pu originating from the waste effluents discharged at the site had a value of 101 ± 8 mL g(-1). One possible explanation for the isotope-specific sorption behavior is that (240)Pu likely existed in the weaker sorbing oxidation states, +5 or +6, than (239)Pu, which likely existed in the +3 or +4 oxidation states. Consequently, remediation strategies for radioactively contaminated systems must consider not only the discharged contaminants but also their decay products. In this case, mitigation of Cm as well as Pu will be required to completely address Pu migration from the source term.
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Affiliation(s)
- Hiromu Kurosaki
- Department of Chemistry, Washington State University , Post Office Box 644630, Pullman, Washington 99164, United States
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Powell BA, Kaplan DI, Serkiz SM, Coates JT, Fjeld RA. Pu(V) transport through Savannah River Site soils - an evaluation of a conceptual model of surface- mediated reduction to Pu (IV). JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2014; 131:47-56. [PMID: 24238838 DOI: 10.1016/j.jenvrad.2013.10.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 10/07/2013] [Accepted: 10/08/2013] [Indexed: 06/02/2023]
Abstract
Over the last fifteen years the Savannah River Site (SRS) in South Carolina, USA, was selected as the site of three new plutonium facilities: the Mixed Oxide Fuel Fabrication Facility, Pit Disassembly and Conversion Facility, and the Pu Immobilization Plant. In order to assess the potential human and environmental risk associated with these recent initiatives, improved understanding of the fate and transport of Pu in the SRS subsurface environment is necessary. The hypothesis of this study was that the more mobile forms of Pu, Pu(V) and Pu(VI), would be reduced to the less mobile Pu(III/IV) oxidation states under ambient SRS subsurface conditions. Laboratory-scale dynamic flow experiments (i.e., column studies) indicated that Pu(V) was very mobile in SRS sediments. At higher pH values the mobility of Pu decreased and the fraction of Pu that became irreversibly sorbed to the sediment increased, albeit, only slightly. Conversely, these column experiments showed that Pu(IV) was essentially immobile and was largely irreversibly sorbed to the sediment. More than 100 batch sorption experiments were also conducted with four end-member sediments, i.e., sediments that include the chemical, textural, and mineralogical properties likely to exist in the SRS. These tests were conducted as a function of initial Pu oxidation state, pH, and contact time and consistently demonstrated that although Pu(V) sorbed initially quite weakly to sediments, it slowly, over the course of <33 days, sorbed very strongly to sediments, to approximately the same degree as Pu(IV). This is consistent with our hypothesis that Pu(V) is reduced to the more strongly sorbing form of Pu, Pu(IV). These studies provide important experimental support for a conceptual geochemical model for dissolved Pu in a highly weathered subsurface environment. That is that, irrespective of the initial oxidation state of the dissolved Pu introduced into a SRS sediment system, Pu(IV) controls the environmental transport within a couple weeks and Pu strongly binds to the sediment, limiting its mobility.
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Affiliation(s)
- Brian A Powell
- Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC 29625, USA.
| | | | - Steven M Serkiz
- Savannah River National Laboratory, Aiken, SC 29808, USA; Department of Physics and Astronomy, Clemson University, Clemson, SC 29631, USA
| | - John T Coates
- Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC 29625, USA
| | - Robert A Fjeld
- Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC 29625, USA.
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Xu C, Athon M, Ho YF, Chang HS, Zhang S, Kaplan DI, Schwehr KA, DiDonato N, Hatcher PG, Santschi PH. Plutonium immobilization and remobilization by soil mineral and organic matter in the far-field of the Savannah River Site, U.S. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:3186-3195. [PMID: 24555528 DOI: 10.1021/es404951y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
To study the effects of natural organic matter (NOM) on Pu sorption, Pu(IV) and (V) were amended at environmentally relevant concentrations (10(-14) M) to two soils of contrasting particulate NOM concentrations collected from the F-Area of the Savannah River Site. More Pu(IV) than (V) was bound to soil colloidal organic matter (COM). A de-ashed humic acid (i.e., metals being removed) scavenged more Pu(IV,V) into its colloidal fraction than the original HA incorporated into its colloidal fraction, and an inverse trend was thus observed for the particulate-fraction-bound Pu for these two types of HAs. However, the overall Pu binding capacity of HA (particulate + colloidal-Pu) decreased after de-ashing. The presence of NOM in the F-Area soil did not enhance Pu fixation to the organic-rich soil when compared to the organic-poor soil or the mineral phase from the same soil source, due to the formation of COM-bound Pu. Most importantly, Pu uptake by organic-rich soil decreased with increasing pH because more NOM in the colloidal size desorbed from the particulate fraction in the elevated pH systems, resulting in greater amounts of Pu associated with the COM fraction. This is in contrast to previous observations with low-NOM sediments or minerals, which showed increased Pu uptake with increasing pH levels. This demonstrates that despite Pu immobilization by NOM, COM can convert Pu into a more mobile form.
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Affiliation(s)
- Chen Xu
- Department of Marine Sciences, Texas A&M University , Building 3029, Galveston, Texas 77553, United States
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Li D, Kaplan DI, Roberts KA, Seaman JC. Mobile colloid generation induced by a cementitious plume: mineral surface-charge controls on mobilization. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:2755-2763. [PMID: 22316126 DOI: 10.1021/es2040834] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Cementitious materials are increasingly used as engineered barriers and waste forms for radiological waste disposal. Yet their potential effect on mobile colloid generation is not well-known, especially as it may influence colloid-facilitated contaminant transport. Whereas previous papers have studied the introduction of cement colloids into sediments, this study examined the influence of cement leachate chemistry on the mobilization of colloids from a subsurface sediment collected from the Savannah River Site, USA. A sharp mobile colloid plume formed with the introduction of a cement leachate simulant. Colloid concentrations decreased to background concentrations even though the aqueous chemical conditions (pH and ionic strength) remained unchanged. Mobile colloids were mainly goethite and to a lesser extent kaolinite. The released colloids had negative surface charges and the mean particle sizes ranged primarily from 200 to 470 nm. Inherent mineralogical electrostatic forces appeared to be the controlling colloid removal mechanism in this system. In the background pH of ~6.0, goethite had a positive surface charge, whereas quartz (the dominant mineral in the immobile sediment) and kaolinite had negative surface charges. Goethite acted as a cementing agent, holding kaolinite and itself onto the quartz surfaces due to the electrostatic attraction. Once the pH of the system was elevated, as in the cementitious high pH plume front, the goethite reversed to a negative charge, along with quartz and kaolinite, then goethite and kaolinite colloids were mobilized and a sharp spike in turbidity was observed. Simulating conditions away from the cementitious source, essentially no colloids were mobilized at 1:1000 dilution of the cement leachate or when the leachate pH was ≤ 8. Extreme alkaline pH environments of cementitious leachate may change mineral surface charges, temporarily promoting the formation of mobile colloids.
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Affiliation(s)
- Dien Li
- Savannah River National Laboratory, Aiken, South Carolina 29808, United States.
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Liu J, Liang X, Yang J, Ye Y, Su M, Nie Z, Chen Y. Size distribution and composition of phosphorus in the East Tiao River, China: the significant role of colloids. ACTA ACUST UNITED AC 2011; 13:2844-50. [PMID: 21915398 DOI: 10.1039/c1em10482a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The environmental risk of aquatic phosphorus (P) critically depends on its mobility and bioavailability, both of which are greatly affected by the size distribution and composition of P. The size distribution (particulate, colloidal and truly dissolved phase) of P, composed of molybdate reactive P (MRP) and molybdate unreactive P (MUP), was determined at twenty-three typical sections of the East Tiao River, China in the plum rain season. Results indicated particulate P was dominant followed by the truly dissolved P, while colloidal P was quantitatively the lowest in the whole river. From upstream to downstream, particulate P sharply increased, along with a slight decrease of truly dissolved P. However, colloidal P remained at a relatively stable level in the whole river, ranging from below detection limit to 0.025 mg L(-1), 0 to 13.4% of total P (TP). Furthermore, colloidal MRP exhibited a rising trend downriver as compared to upriver, with the notable transfer of MRP from the truly dissolved phase to particulate and colloidal phases. Particle concentration effect for colloids, observed in the study of MRP distribution, further corroborated the role of colloids in MRP solid/liquid partitioning. These observations, in this large-scale field investigation, fitted the "colloidal pumping" hypothesis. It may be concluded that colloids act as the intermediate and buffer in the dynamically balanced transfer of P from truly dissolved phase to large particulate phase, having a significant role in size distribution of P.
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Affiliation(s)
- Jin Liu
- Key Laboratory for Water Pollution Control and Environmental Safety, Zhejiang Province, Hangzhou, 310029, China
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Otosaka S, Schwehr KA, Kaplan DI, Roberts KA, Zhang S, Xu C, Li HP, Ho YF, Brinkmeyer R, Yeager CM, Santschi PH. Factors controlling mobility of 127I and 129I species in an acidic groundwater plume at the Savannah River Site. THE SCIENCE OF THE TOTAL ENVIRONMENT 2011; 409:3857-3865. [PMID: 21641630 DOI: 10.1016/j.scitotenv.2011.05.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 05/10/2011] [Accepted: 05/10/2011] [Indexed: 05/30/2023]
Abstract
In order to quantify changes in iodine speciation and to assess factors controlling the distribution and mobility of iodine at an iodine-129 ((129)I) contaminated site located at the U.S. Department of Energy's Savannah River Site (SRS), spatial distributions and transformation of (129)I and stable iodine ((127)I) species in groundwater were investigated along a gradient in redox potential (654 to 360 mV), organic carbon concentration (5 to 60 μmol L(-1)), and pH (pH 3.2 to 6.8). Total (129)I concentration in groundwater was 8.6±2.8 Bq L(-1) immediately downstream of a former waste seepage basin (well FSB-95DR), and decreased with distance from the seepage basin. (127)I concentration decreased similarly to that of (129)I. Elevated concentrations of (127)I or (129)I were not detected in groundwater collected from wells located outside of the mixed waste plume of this area. At FSB-95DR, the majority (55-86%) of iodine existed as iodide for both (127)I and (129)I. Then, as the iodide move down gradient, some of it transformed into iodate and organo-iodine. Considering that iodate has a higher K(d) value than iodide, we hypothesize that the production of iodate in groundwater resulted in the removal of iodine from the groundwater and consequently decreased concentrations of (127)I and (129)I in downstream areas. Significant amounts of organo-iodine species (30-82% of the total iodine) were also observed at upstream wells, including those outside the mixed waste plume. Concentrations of groundwater iodide decreased at a faster rate than organo-iodine along the transect from the seepage basin. We concluded that removal of iodine from the groundwater through the formation of high molecular weight organo-iodine species is complicated by the release of other more mobile organo-iodine species in the groundwater.
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Affiliation(s)
- Shigeyoshi Otosaka
- Laboratory for Oceanographic and Environmental Research, Department of Marine Sciences, Texas A&M University, Building 3029, 200 Seawolf Parkway, Galveston, TX 77553, USA.
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Abstract
Abstract
This paper describes the development of a radioanalytical procedure to separate Am3+ and Cm3+ that relies on chromatography with the TRU® resin available from Eichrom Technologies, Inc. Although the TRU chromatographic materials are not currently recommended for the separation of the trivalent actinides from each other, our work demonstrates their suitability. We explored parameters such as nitric acid concentration, column length, and flow rate; standard chromatographic parameters such as resolution, theoretical plates, and total separation time are reported for each variable. The advantages of the method described herein include use of a commercially available product and no application of an organic solvent during elution. Optimal resolution between the Am3+ and Cm3+ was achieved with the slowest flow rate.
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