Uranium Geochemistry in Vadose Zone and Aquifer Sediments from the 300 Area Uranium Plume

Zachara, John M.; Davis, Jim; Liu, Chongxuan; McKinley, James P.; Qafoku, N. P.; Wellman, Dawn M.; Yabusaki, Steven B.

doi:10.2172/15020114

Cited by 66 publications

(140 citation statements)

References 62 publications

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“…The results of these more detailed studies (Task 3) of U(VI) adsorption and desorption suggest that the fate of uranium in the existing 200-UP-1 groundwater plume is quite complicated. These studies and numerous other studies (both laboratory and field) show that the K d for U(VI) is quite sensitive to groundwater alkalinity (total bicarbonate/carbonate), pH, dissolved U(VI) concentration, and time of reaction (kinetics) (see discussions both germane to Hanford and other sites in Serne et al (2002), Zachara et al (2005), Davis et al (2004)). …”

Section: Column Experiments For U(vi)mentioning

confidence: 67%

“…These studies and numerous other studies (both laboratory and field) show that the K d values for U(VI) are quite sensitive to groundwater alkalinity (total bicarbonate/carbonate) and pH, and in some cases although not manifested for the 200-UP-1 existing plume, to dissolved U(VI) concentration. See discussions both germane to Hanford and other sites in Serne et al (2002), Zachara et al (2005), Davis et al (2004), and Bargar et al (2000). If remediation of the existing groundwater U(VI) plume at 200-UP-1/200-ZP-1 operable units is required and some form of pump and treat is chosen, it is recommended that the aquifer be treated with chemicals to increase pH and alkalinity and to decrease dissolved calcium and magnesium (to prevent the precipitation of additional calcite).…”

Section: Discussionmentioning

confidence: 99%

“…However, if the dissolved calcium and magnesium are not reduced, it is quite possible that increasing the alkalinity and pH will cause the co-precipitation of U(VI) with calcite or other alkaline-earth carbonates, thus making it more difficult to remove uranium from the aquifer. Such a uranium sequestration process has been suggested as being a likely cause for strong binding of U(VI) in the sediments below the TX tank farm (see Appendix D in Myers 2005) and in the 300 Area (see Zachara et al 2005).…”

Section: Column Experiments For U(vi)mentioning

confidence: 99%

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Characterization of 200-UP-1 Aquifer Sediments and Results of Sorption-Desorption Tests Using Spiked Uncontaminated Groundwater

Um¹,

Serne²,

Bjornstad³

et al. 2005

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Se-79, and Np-237 during FY 2005. The study completed and summarized in this report will help determine the current risk of the groundwater plume and aid in choosing remediation alternatives for the COC in 200-UP-1 subsurface environments should remediation be necessary.Sediment characterization showed only 4 out of 13 core liner samples were intact, and the others were slough material that dropped to the bottom of the borehole before the split-spoon sampling. The intact samples showed typical Ringold Unit E characteristics such as being dominated by gravel and sand. Moderately reducing conditions are inferred in some core from borehole C4299. This reducing condition was likely caused by the hard tool process used to drill the wells. One core liner from C4299 (B19140) showed significant presence of ferric iron oxide/clay coatings on the gravel surfaces. The 200-UP-1 sediments do contain some clay minerals that exhibit significant cation exchange capacity and thus should be good adsorbents of cationic contaminants. This is especially true of the Ringold Lower mud sample, B19377, from borehole C4300. No highly contaminated sediments-including uranium-were found in the cores from the three new boreholes in the 200-UP-1 operable unit. The presence of slough and "flour" caused by hard tooling is a serious challenge to obtaining field-representative sediments for use in geochemical experiments to determine the adsorption-desorption tendencies of redox sensitive elements such as uranium.The adsorption of COC on intact Ringold Formation sediments and Fe/clay coatings showed that most of the anionic contaminants [Tc(VII), Se(VI), U(VI), Cr(VI), and I(-I)] did not adsorb well compared to cationic [Np(V), Sr(II), and Cs(I)] radionuclides. The high hydrous iron oxide content in Fe oxide/clay coatings caused the highest K d values for U and Np, suggesting that these hydrous iron oxides are the key solid adsorbent in the sediments that control the fate of U and Np. Enhanced adsorption behavior for Tc and Cr, and perhaps Se, on the composite B19136 and B19137 sediment was considered an "artifact" caused by the induced reducing conditions from the hard tool drilling.Additional U(VI) adsorption K d studies were performed on Ringold Formation sediments subjected to varying solution geochemical conditions such as varying the dissolved U and total bicarbonate/carbonate concentration in the groundwater to develop a more robust data base of U(VI) K d s. The <2 mm size fraction of three 200-UP-1 sediments showed a linear U (VI) adsorption isotherm up to 1 ppm of total U (VI) concentration in solution. This fact validates the use of a linear adsorption isotherm (K d ) to predict U (VI) adsorption for sediments in the 200-UP-1 groundwater plume. However, this is not the same as stating that the U (VI) K d value will be constant if the groundwater chemical composition at 200-UP-1 changes with space or time.iv The additional U (VI) K d s obtained from varying carbonate concentrations in solution indicated that U (VI) adsorption was stro...

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Section: Column Experiments For U(vi)mentioning

confidence: 67%

Section: Discussionmentioning

confidence: 99%

Section: Column Experiments For U(vi)mentioning

confidence: 99%

See 1 more Smart Citation

Characterization of 200-UP-1 Aquifer Sediments and Results of Sorption-Desorption Tests Using Spiked Uncontaminated Groundwater

Um¹,

Serne²,

Bjornstad³

et al. 2005

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“…Consequently, the reversibility of U sorption may change as a function of the time that it has been associated with sediment. This phenomenon is frequently observed and has been reported as an increase of the dissociation constant, or Kd, and has been attributed to diffusion into cracks or pores on the particle surface or interaggregate sequestration (2,3).…”

Section: Introductionmentioning

confidence: 93%

Uranium Extraction From Laboratory-Synthesized, Uranium-Doped Hydrous Ferric Oxides

Smith

Douglas

Moore

et al. 2009

Environ. Sci. Technol.

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The extractability of uranium (U) from synthetic uranium-hydrous ferric oxide (HFO) coprecipitates has been shown to decrease as a function of mineral ripening, consistent with the hypothesis that the ripening process will decrease uranium lability. To evaluate this process, three HFO suspensions were coprecipitated with uranyl (UO 2 2+) and maintained at pH 7.0 ( 0.1. Uranyl was added to the HFO postprecipitation in a fourth suspension. Two suspensions also contained either coprecipitated silicate (Si-U-HFO) or phosphate (P-U-HFO). After precipitation of the HFOs, at time intervals of 1 week, 1 month, 6 months, 1 year, and 2 years, aliquots of each suspension were contacted with five extractant solutions for a range of time. Uranium was preferentially extracted over Fe in varying degrees from all coprecipitates, by all extractants. The preference was dependent on the duration of mineral ripening and adjunct anion. Micro-X-ray diffraction analysis provides evidence for the transformation from amorphous material to phases containing substantial proportions of crystalline goethite and hematite, except the P-U-HFO, which remained primarily amorphous. Analysis of the U-HFO coprecipitate by the Mössbauer technique and scanning electron microscopy provides confirmation of an increase in particle size and evidence of mineral ripening to crystalline phases.

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“…The Solinst loggers also recorded specific conductance (millis per centimeter, mS/cm) and temperature (degrees centigrade, °C) on an hourly basis, which were used evaluate the presence/absence of groundwater. Specific conductance was used as a measure of groundwater presence because Hanford groundwater has a higher ion composition than the Columbia River (Zachara et al 2005). The specific conductance of shallow groundwater on the Hanford Site usually ranges between 0.350 and 0.450 mS/cm, whereas near-shore river water typically ranges from 0.130 to 0.150 mS/cm (Peterson and Connelly 2001).…”

Section: Collection Of Hydrologic and Water Quality Datamentioning

confidence: 99%

Evaluation of Using Caged Clams to Monitor Contaminated Groundwater Exposure in the Near-Shore Environment of the Hanford Site 300 Area

Larson¹,

Poston²,

Tiller³

2008

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Uranium Geochemistry in Vadose Zone and Aquifer Sediments from the 300 Area Uranium Plume

Cited by 66 publications

References 62 publications

Characterization of 200-UP-1 Aquifer Sediments and Results of Sorption-Desorption Tests Using Spiked Uncontaminated Groundwater

Characterization of 200-UP-1 Aquifer Sediments and Results of Sorption-Desorption Tests Using Spiked Uncontaminated Groundwater

Uranium Extraction From Laboratory-Synthesized, Uranium-Doped Hydrous Ferric Oxides

Evaluation of Using Caged Clams to Monitor Contaminated Groundwater Exposure in the Near-Shore Environment of the Hanford Site 300 Area

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