Extrapolation studies on adsorption of thorium and uranium at different solution compositions on soil sediments

Syed, H. S.

doi:10.1007/bf02386674

Cited by 8 publications

(2 citation statements)

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“…This hypothesis was consistent with published research on the sorptive partitioning of Th. For example, a direct measurement of distribution coefficients ( K D = [μg g −1 solid/μg mL −1 liquid]) for uranium and thorium on natural soils (Syed, 1998) resulted in a differential of two orders of magnitude (i.e., log K D Th = 5.8 vs. log K D U = 3.38 in dilute electrolytes). A study of disequilibrium decay series in a basaltic aquifer in Idaho (Luo et al, 2000) showed a potentially greater disparity in nature, with rapid sorption and “retardation factors,” R E , including the effects of sorption, precipitation, and α recoil, yielding R Th > 10 7 ; R U ∼10 3 The differential retardation during subsurface migration, allowing also for the complicating possibility of differential removal and partial regeneration of 234 Th could thus explain the apparent disparity in 235 U: 238 U between the boreholes represented in Fig.…”

Section: Resultsmentioning

confidence: 99%

Geochemical Controls on Contaminant Uranium in Vadose Hanford Formation Sediments at the 200 Area and 300 Area, Hanford Site, Washington

McKinley

Zachara

Wan

et al. 2007

Vadose Zone Journal

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Long‐term historic spills of uranium at the 300 Area fuel fabrication site (58,000 kg of disposed uranium over 32 yr) and at the 200 East Area BX tank farm (7000 kg of spilled uranium in one event), both within the Hanford formation in the Hanford Site, Washington State, were investigated by subsurface sampling and subsequent microscale investigations of excavated samples. The 200 Area sediments contained uranyl silicate mineralization (sodium boltwoodite) in restrictive microfractures in granitic clasts, in the vadose zone over a narrow range in depth. Well logging and column experiments indicated that tank wastes migrated deeper than observed in core samples. The 300 Area sediments included metatorbernite and uranium at low concentrations associated with detrital aluminosilicates, along with other mineral phases that could accommodate uranyl, such as uranophane and calcium carbonate. The association of contaminant uranyl with Hanford formation sediments provided a persistent source of uranium to groundwater. The results of both studies suggest that the formation of secondary solid uranyl‐bearing phases influences the subsequent release of uranium to the environment and that our understanding of these processes and individual waste sites is incomplete.

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Section: Resultsmentioning

confidence: 99%

Geochemical Controls on Contaminant Uranium in Vadose Hanford Formation Sediments at the 200 Area and 300 Area, Hanford Site, Washington

McKinley

Zachara

Wan

et al. 2007

Vadose Zone Journal

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show abstract

“…This hypothesis was consistent with published research on the sorptive partitioning of Th. For example, a direct measurement of distribution coefficients (K d = [µg g -1 solid / µg ml -1 liquid] ) for uranium and thorium on natural soils (Syed, 1998) resulted in a differential of two orders of magnitude (i.e., Log K d Th = 5.8 versus Log K d U = 3.38 in dilute electrolytes). A study of disequilibrium decay series in a basaltic aquifer in Idaho (Luo et al 2000) showed a potentially greater disparity in nature, with rapid sorption and "retardation factors, R f ," including the effects of sorption, precipitation, and α recoil, yielding R Th > 10 7 ; R U ~ 10 3 .…”

Section: 8mentioning

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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Can we predict uranium bioavailability based on soil parameters? Part 1: Effect of soil parameters on soil solution uranium concentration

Vandenhove

Hees

Wouters

et al. 2007

Environmental Pollution

111

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Extrapolation studies on adsorption of thorium and uranium at different solution compositions on soil sediments

Cited by 8 publications

References 1 publication

Geochemical Controls on Contaminant Uranium in Vadose Hanford Formation Sediments at the 200 Area and 300 Area, Hanford Site, Washington

Geochemical Controls on Contaminant Uranium in Vadose Hanford Formation Sediments at the 200 Area and 300 Area, Hanford Site, Washington

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Can we predict uranium bioavailability based on soil parameters? Part 1: Effect of soil parameters on soil solution uranium concentration

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