Actinide Speciation in the Presence of Humic Substances in Natural Water Conditions

Moulin, Valérie; Tits, J.; Ouzounian, G.

doi:10.1524/ract.1992.5859.1.179

Cited by 82 publications

(67 citation statements)

References 17 publications

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“…The formation of U complexes with HS generally decreases, with increasing U concentration, once the binding saturation of the HS by U is reached [75]. Uranyl-carbonate and uranyl-hydroxide-carbonate species become more important than uranyl complexes with HS as the hardness, alkalinity, and pH of the water increase (usually > pH 7) [73]. This is exemplified for pH in Fig.…”

Section: Speciation Freshwatermentioning

confidence: 88%

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Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

191

142

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The speciation of uranium (U) in relation to its bioavailability is reviewed for surface waters (fresh-and seawater) and their sediments. A summary of available analytical and modeling techniques for determining U speciation is also presented. U(VI) is the major form of U in oxic surface waters, while U(IV) is the major form in anoxic waters. The bioavailability of U (i.e., its ability to bind to or traverse the cell surface of an organism) is dependent on its speciation, or physicochemical form. U occurs in surface waters in a variety of physicochemical forms, including the free metal ion (U 4+ or UO 2 2+ ) and complexes with inorganic ligands (e.g., uranyl carbonate or uranyl phosphate), and humic substances (HS) (e.g., uranyl fulvate) in dissolved, colloidal, and/or particulate forms. Although the relationship between U speciation and bioavailability is complex, there is reasonable evidence to indicate that UO 2 2+ and UO 2 OH + are the major forms of U(VI) available to organisms, rather than U in strong complexes (e.g., uranyl fulvate) or adsorbed to colloidal and/or particulate matter. U(VI) complexes with inorganic ligands (e.g., carbonate or phosphate) and HS apparently reduce the bioavailability of U by reducing the activity of UO 2 2+ and UO 2 OH + . The majority of studies have used the results from thermodynamic speciation modeling to support these conclusions. Time-resolved laser-induced fluorescence spectroscopy is the only analytical technique able to directly determine specific U species, but is limited in use to freshwaters of low pH and ionic strength. Nearly all of the available information relating the speciation of U to its bioavailability has been derived using simple, chemically defined experimental freshwaters, rather than natural waters. No data are available for estuarine or seawater. Furthermore, there are no available data on the relationship between U speciation and bioavailability in sediments. An understanding of this relationship has been hindered due to the lack of direct quantitative U speciation techniques for particulate phases. More robust analytical techniques for determining the speciation of U in natural surface waters are needed before the relationship between U speciation and bioavailability can be clarified.

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Section: Speciation Freshwatermentioning

confidence: 88%

“…In addition to carbonate, natural DOM, in the form of HS (fulvic and humic acids), is a very effective complexing agent of U in fresh surface waters [14,73]. HS may be soluble or insoluble, depending on molecular weight, state of aggregation, degree of protonation, the extent of U binding, and the ionic strength of the water.…”

Section: Speciation Freshwatermentioning

confidence: 99%

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

191

142

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“…Colloidal materials that occur naturally in the groundwater or are generated during corrosion of engineered barrier materials will be available to sorb radionuclides [193,269]. This material may remain suspended in solution, or may eventually be sorbed by immobile phases, may be filtered from the solution by microprobes, or may flocculate and settle out of solution.…”

Section: Effects Of Other Materials On Actinide Dispositionmentioning

confidence: 99%

“…Sorption may result in a change in the oxidation state of the radionuclide. Competition between actinides and other metal ions in complexation and sorption reactions results in complex chemistries in real systems, and will, in general, decrease the amounts of radionuclides removed from solution.Colloidal materials that occur naturally in the groundwater or are generated during corrosion of engineered barrier materials will be available to sorb radionuclides [193,269]. This material may remain suspended in solution, or may eventually be sorbed by immobile phases, may be filtered from the solution by microprobes, or may flocculate and settle out of solution.…”

mentioning

confidence: 99%

The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

Ebert

1995

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Argonne National Lahoratory. wi1th facilitie, in the states of liiinois and Idaho. is owned by the united States govern lent, and operated by The Un diversity of Chicago under the provisions of a contract with thie department of Enery. DISCLAIM ER THE FFFECTS OF THE GLASS SURFACE AREA/SOLUTION VOLUME RATIO ON GLASS CORROSION: A CRITICAL REVIEW William L. Ebert ABSTRACTThis report reviews and summarizes the present state of knowledge regarding the effects of the glass surface area/solution volume (SA/V) ratio on the corrosion behavior of borosilicate waste glasses. The SA/V ratio affects the rate of glass corrosion through the extent of dilution ok corrosion products released from the glass into the leachate solution: glass corrosion products are diluted more in tests conducted at low SA/V ratios than they are in tests conducted at high SAN ratios. Differences in the solution chemistries generated in tests conducted at different SA/V ratios then affect the observed glass corrosion behavior. Corrosion of borosilicate waste glasses results in the dissolution of soluble components and the accumulation of sparingly soluble components in a layer on the surface of the corroding glass. Laboratory tests performed to distinguish the effects of the solution chemistry and the surface layer on the glass corrosion rate have shown the rate to be controlled primarily by the solution chemistry. Therefore, any testing parameter that affects the solution chemistry will also affect the glass corrosion rate. The results of static leach tests conducted to assess the effects of the SAN are discussed with regard to the effects of SAN on the solution chemistry. The effects of the SA/V ratio observed in static tests can be understood based on the effects of the solution chemistry on glass corrosion behavior. Test results show several remaining issues with regard to the long-term glass corrosion behavior: Can the SAN ratio be used as an accelerating parameter to characterize the advanced stages of glass corrosion relevant to long disposal times? Is the alteration of the glass surface the same in tests conducted at different SAN, and in tests conducted with monolithic and crushed glass samples? What are the effects of the SAN and the extent of glass corrosion on the disposition of released radionuclides? These issues will bear on the prediction of the long-term performance of waste glasses during storage. The results of an experimental program conducted at ANL to address these and other remaining issues regarding the effects of SA/V on glass corrosion are described. I 2 SUMMARYThis report reviews and summarizes the present state of knowledge regarding the effects of the glass surface area/solution volume ratio (SA/V) on the corrosion behavior of borosilicate waste glasses. The effects of the SA/ occur through dilution of corrosion products and through the effects of the corrosion products on the glass corrosion mechanism and rate. Therefore, the effects of the SA/V on glass corrosion are discussed in terms of the various effects of t...

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“…present in wastes [63,70,219] or with natural organic matter (i.e., fulvic and humic acids) eluted from soils ( [151,154,220], see also Chapter 5). A review on complex formation of humic substances with actinides (Th, U, Np, Pu, Am, Cu) and with important cations in natural waters was recently published by Moulin et al [16], These authors presented calculated speciation diagrams for natural system conditions (pH 4-9, and 0.1 to 10 ppm humic substances). Humic substances dominated actinide (Th, U, Am) speciation up to pH 7 or 8.…”

Section: Groundwatersmentioning

confidence: 99%

Speciation of Radionuclides in the Environment

Gunten

Beneš

1995

Radiochimica Acta

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Methods for the determination of the speciation of radionuclides in aerosols, in aquatic solutions, in sediments, soils and rocks are reviewed. At present, most of the results about speciation are deduced from model calculations, model experiments, and separation of species (forms) of radionuclides, e.g., by sequential extraction procedures. Methods of direct determination of speciation of radionuclides (e.g., by laser induced spectroscopy) are in general not yet sensitive enough for a measurement of the very low concentrations of radionuclides in the environment. The methodological part of this paper is followed by a review of the very abundant literature about speciation of important radionuclides in the environment, i.e., in the atmosphere, hydrosphere and lithosphère. The review does not include the biosphere. Literature up to spring 1993 is included (with a few more recent additions).

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Actinide Speciation in the Presence of Humic Substances in Natural Water Conditions

Cited by 82 publications

References 17 publications

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

Speciation of Radionuclides in the Environment

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