Simulation of reactive transport of uranium(VI) in groundwater with variable chemical conditions

Curtis, Gary P.; Davis, James A.; Naftz, David L.

doi:10.1029/2005wr003979

Cited by 104 publications

(118 citation statements)

References 44 publications

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“…Consideration of adsorbed contaminant U(VI) yielded larger surface area normalized K d values (6.35 and 1.29 mL m À2 ). These larger values were comparable to those on some of the phyllosilicates (Table 3), and to those reported for sediments with similar mineralogical and solution conditions (Curtis et al, 2006;Um et al, 2007;Zachara et al, 2007;Bond et al, 2008).…”

Section: U(vi) Adsorptionsupporting

confidence: 70%

Determining individual mineral contributions to U(VI) adsorption in a contaminated aquifer sediment: A fluorescence spectroscopy study

Wang

Zachara

Boily

et al. 2011

Geochimica et Cosmochimica Acta

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The adsorption and speciation of U(VI) was investigated on contaminated, fine grained sediment materials from the Hanford 300 area (SPP1 GWF) in simulated groundwater using cryogenic laser-induced U(VI) fluorescence spectroscopy combined with chemometric analysis. A series of reference minerals (montmorillonite, illite, Michigan chlorite, North Carolina chlorite, California clinochlore, quartz and synthetic 6-line ferrihydrite) was used for comparison that represents the mineralogical constituents of SPP1 GWF. Surface area-normalized K d values were measured at U(VI) concentrations of 5 Â 10 À7 and 5 Â 10 À6 mol L À1 that displayed the following affinity series: 6-line-ferrihydrite > North Carolina chlorite % California clinochlore > quartz % Michigan chlorite > illite > montmorillonite. Both time-resolved spectra and asynchronous twodimensional (2D) correlation analysis of SPP1 GWF at different delay times indicated that two major adsorbed U(VI) species were present in the sediment that resembled U(VI) adsorbed on quartz and phyllosilicates. Simulations of the normalized fluorescence spectra confirmed that the speciation of SPP1 GWF was best represented by a linear combination of U(VI) adsorbed on quartz (90%) and phyllosilicates (10%). However, the fluorescence quantum yield for U(VI) adsorbed on phyllosilicates was lower than quartz and, consequently, its fractional contribution to speciation may be underestimated. Spectral comparison with literature data suggested that U(VI) exist primarily as inner-sphere complexes with surface silanol groups on quartz and as surface U(VI) tricarbonate complexes on phyllosilicates. Published by Elsevier Ltd.

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Section: U(vi) Adsorptionsupporting

confidence: 70%

Determining individual mineral contributions to U(VI) adsorption in a contaminated aquifer sediment: A fluorescence spectroscopy study

Wang

Zachara

Boily

et al. 2011

Geochimica et Cosmochimica Acta

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“…Moreover, such codes have been applied to describe U(VI) groundwater-contaminant-plume dynamics associated with uranium-mill tailings (Curtis et al 2006), and are, therefore, applicable to field-scale migration processes. In addition, mechanistic models and sorption data collected in an appropriate fashion provide the necessary paradigms upon which technically defensible "empirical" K d values can be defended.…”

Section: Variable K D Versus Constant Value K Dmentioning

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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“…Postulating multiple site-types is also important for simulating peak tailing observed in experimental studies of U(VI) transport in columns (Kohler et al, 1996). Reactive transport simulations that use multisite adsorption models can also simulate significant peak tailing in field-scale simulations (Curtis et al, 2006;Kent et al, 2000Kent et al, , 2008Kent et al, , 2007.…”

Section: Experimental and Modeling Issues Associated With Scms For Somentioning

confidence: 99%

Mathematical Formulation Requirements and Specifications for the Process Models

Steefel¹,

Moulton²,

Pau³

et al. 2010

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Simulation of reactive transport of uranium(VI) in groundwater with variable chemical conditions

Cited by 104 publications

References 44 publications

Determining individual mineral contributions to U(VI) adsorption in a contaminated aquifer sediment: A fluorescence spectroscopy study

Determining individual mineral contributions to U(VI) adsorption in a contaminated aquifer sediment: A fluorescence spectroscopy study

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Mathematical Formulation Requirements and Specifications for the Process Models

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