Carbonate Leaching of Uranium from Contaminated Soils

Mason, C.F.V.; Turney, W.R.J.R.; Thomson, Bruce M.; Lu, Norman; Longmire, Patrick; Chisholm-Brause, Catherine J.

doi:10.1021/es960843j

Cited by 144 publications

(92 citation statements)

References 12 publications

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“…The enhanced formation of uranyl-carbonate-aqueous complexes as pH and alkalinity increase (Section 4) cause marked and systematic decreases in U(VI) K d (Mason et al 1997;Wazne et al 2003;Zhou and Gu 2005). River waters of low-ionic strength and low dissolved bicarbonate/carbonate seasonally invade the 300 Area U plume during periods of high-river stage, and these mix with and dilute groundwaters of higher bicarbonate concentration.…”

Section: Case Studies Of Different Hanford Disposal Sitesmentioning

confidence: 99%

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Zachara¹,

Brown²,

Christensen³

et al. 2007

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Executive SummaryUranium (U) is an important risk-driving contaminant at the Hanford Site. Over 200,000 kg have been released to the vadose zone over the course of site operations, and a number of vadose zone and groundwater plumes containing the uranyl cation [UO 2 2+ , U(VI)] have been identified. U is recognized to be of moderate-to-high mobility, conditions dependent. The site is currently making decisions on several of these plumes with long-lasting implications, and others are soon to come.Uranium is one of nature's most intriguing and chemically complex elements. The fate and transport of U(VI) has been studied over the long lifetime of the Hanford Site by various contractors, along with the Pacific Northwest National Laboratory (PNNL) and its collaborators. Significant research has more recently been contributed by the national scientific community with support from the U.S. Department of Energy's (DOE) Office of Science through its Environmental Remediation Sciences Division (ERSD). This report represents a first attempt to integrate these findings into a cohesive view of the subsurface geochemistry of U at the Hanford Site. The objective is to inform all interested Hanford parties about the in-ground inventory of U and its geochemical behavior. This report also comments on the prospects for the development of a robust generic model to more accurately forecast future U(VI) migration at different Hanford waste sites, along with further research necessary to reach this goal.To accomplish the report objectives, the environmental geochemistry of U at the Hanford Site is discussed in terms of both the vadose and saturated zone, to the extent that it is known. Hexavalent uranium [U(VI)] is the dominant valence form of U under the predominantly oxidizing subsurface conditions at the Hanford Site, and the researchers' analyses consequently emphasize this species. The nature and concentration of background U in Hanford subsurface sediments is identified to place contaminant U(VI) concentrations and behavior in perspective to the natural system. In-ground U-waste inventories are quantified and characterized with regard to source term, to the extent possible, and the most important sites from an inventory perspective are identified. The U-isotopic content of various waste streams are discussed from the perspective of waste-source tracking. The geochemical attenuation processes responsible for slowing the rate of subsurface U migration, relative to the transporting water front, are illustrated through careful consideration of both field characterization studies of existing U vadose-zone and groundwater plumes, and laboratory studies of derived contaminated and uncontaminated sediments. Both empirical and more mechanistic models of these attenuation processes are considered as well as the parameters that define attenuation magnitude. Attention is given to the behavior of contaminant U(VI) that has been in contact with Hanford sediments for extended periods (circa 10-50 years), as long contact imparts unique characte...

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Section: Case Studies Of Different Hanford Disposal Sitesmentioning

confidence: 99%

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Zachara¹,

Brown²,

Christensen³

et al. 2007

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“…It has been established that the use of phosphate fertilisers may enrich the soil with uranium (Schnug and Haneklaus, 2008). The soil of the study region is rich in CaCO 3 (Gill et al, 2005) and the leaching of uranium in the carbonate medium has already been confirmed by some authors (Mason et al, 1997).…”

Section: Resultsmentioning

confidence: 76%

Health risk assessments due to uranium contamination of drinking water in Bathinda region, Punjab state, India

Singh

Kumar

et al. 2012

Radioprotection

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The mass concentration of uranium in water samples collected from the Bathinda district of Punjab state, India, was estimated using the laser fluorimetric technique. The study region has shown a pronounced number of cancer cases in the recent period. The study aims to calculate the human radiological risk and chemical toxicity associated with uranium consumption through drinking water. The mass concentration of uranium was found to vary from 0.48 to 571.7 µg/l with a mean value of 84.70 µg/l. The radiological risk due to consumption of uranium through contaminated drinking water was observed to be in the range of 1.34 × 10 -6 to 1.60 × 10 -3 with a mean value of 2.37 × 10 -4 . The chemical toxicity was found to vary from 0.04-43.11 µg.kg -1 .day -1 with a mean value of 6.38 µg.kg -1 .day -1 .

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“…It is estimated that 60% to 80% of uranium can be recovered from a uranium deposit by the alkaline-carbonate ISR process (Taylor et al 2004;Pelizza 2008). Mason et al (1997) observed 75%-95% recovery when using carbonate solutions to remove uranium from contaminated soil, which they mentioned is approximately the amount of oxidized uranium in the soil. Mason et al (1997) suggested that the carbonate removed both adsorbed and either uranium released from mineral structures or by diffusive mass transfer from dead-end pores; they further confirm that carbonate is specific to uranium without significant amounts of dissolved minerals or metals being released.…”

Section: 5mentioning

confidence: 99%

“…Mason et al (1997) observed 75%-95% recovery when using carbonate solutions to remove uranium from contaminated soil, which they mentioned is approximately the amount of oxidized uranium in the soil. Mason et al (1997) suggested that the carbonate removed both adsorbed and either uranium released from mineral structures or by diffusive mass transfer from dead-end pores; they further confirm that carbonate is specific to uranium without significant amounts of dissolved minerals or metals being released. Phillips et al (1995) combined bicarbonate extraction with microbially induced reductive precipitation for isolating concentrated uranium.…”

Section: 5mentioning

confidence: 99%

Evaluation of Soil Flushing for Application to the Deep Vadose Zone in the Hanford Central Plateau

Truex¹,

Oostrom²,

Zhang³

et al. 2010

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Soil flushing was included in the Deep Vadose Zone Treatability Test Plan for the Hanford CentralPlateau (DOE-RL 2008 1 ) as a technology with the potential to remove contaminants from the vadose zone. Soil flushing operates through the addition of water, and if necessary an appropriate mobilizing agent, to mobilize contaminants and flush them from the vadose zone and into the groundwater where they are subsequently captured by a pump-and-treat system. There are uncertainties associated with applying soil flushing technology to contaminants in the deep vadose zone at the Hanford Central Plateau. The modeling and laboratory efforts reported herein are intended to provide a quantitative assessment of factors that impact water infiltration and contaminant flushing through the vadose zone and into the underlying groundwater. Once in the groundwater, capture of the contaminants would be necessary, but this aspect of implementing soil flushing was not evaluated in this effort. Soil flushing was evaluated primarily with respect to applications for technetium and uranium contaminants in the deep vadose zone of the Hanford Central Plateau. SummarySoil flushing operates through addition of water, and if necessary an appropriate mobilizing agent, to mobilize contaminants and flush them from the vadose zone and into the groundwater where they are subsequently captured by a pump-and-treat system. As described in the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau (DOE-RL 2008), investigation of these vadose zone processes through modeling and laboratory evaluation is needed as a first step in providing information for considering soil flushing in subsequent feasibility studies for the Hanford Site deep vadose zone.Numerical modeling and laboratory flow-cell experiments were conducted to investigate the characteristics of water flow and solute transport through the vadose zone as a function of the imposed infiltration condition, subsurface properties, and properties of the leaching solution. Information on previous uranium leaching studies, infiltration studies at the Hanford Site data, and relevant uranium mining operations were compiled and evaluated with respect to how these approaches potentially apply to soil flushing in the Hanford Central Plateau.There are uncertainties associated with applying soil flushing technology to contaminants in the deep vadose zone at the Hanford Central Plateau. Modeling and laboratory efforts reported herein are intended to provide a quantitative assessment of factors that impact water infiltration and contaminant flushing through the vadose zone and into the underlying groundwater. Once in the groundwater, capture of the contaminants would be necessary, but this aspect of implementing soil flushing was not evaluated in this effort. Soil flushing was evaluated primarily with respect to applications for technetium and uranium contaminants in the deep vadose zone of the Hanford Central Plateau.Contaminants such as technetium do not interact significantly...

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Carbonate Leaching of Uranium from Contaminated Soils

Cited by 144 publications

References 12 publications

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Health risk assessments due to uranium contamination of drinking water in Bathinda region, Punjab state, India

Evaluation of Soil Flushing for Application to the Deep Vadose Zone in the Hanford Central Plateau

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