A Comparison of Natural Humic Acids with Synthetic Humic Acid Model Substances : Characterization and Interaction with Uranium(VI)

Pompe, S.; Bubner, M.; Denecke, Melissa A.; Reich, Tobias; Brachmann, A.; Geipel, Gerhard; Nicolai, R.; Heise, Katja; Nitsche, H.

doi:10.1524/ract.1996.74.special-issue.135

Cited by 66 publications

(43 citation statements)

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“…Sorption to clay minerals (e.g., smectite or montmorillonite) below pH 5, and to Fe and Al (oxy)hydroxides, silica, and biotic surfaces, at higher pH, reduces the mobility of U in oxic freshwaters [76,77,78]. Sorption of U to insoluble organic matter, or organic matter attached to particles (e.g., hydrous iron oxides), also reduces the mobility of U [79]. It is generally established that sorption of U to particles increases with increasing pH until a threshold point is reached [80], which varies as a function of the concentration of U, adsorbent, competing ions (e.g., carbonate), chelating agents, and ionic strength [81].…”

Section: Speciation Freshwatermentioning

confidence: 99%

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

203

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: 99%

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

203

142

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“…The amount of uranyl ions to prepare D l at pH [8][9][10] For samples Cl-C3, which were prepared at pH S I, fewer .functional groups wizl deprotonate and can complex with uranyl ions. Additionally, the uranyl concentration in solution relative to the HA% PEC at pH 4 exceeded the lS-18% level for.sahple3 Cl-C3 and D2-DS.…”

Section: A2mentioning

confidence: 99%

Characterization of the Interaction of Uranyl Ions with Humic Acids by X-Ray Absorption Spectroscopy

Reich¹,

Denecke²,

Pompe³

et al. 1996

Synchrotron Radiation Techniques in Industrial, Chemical, and Materials Science

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“…There are various methods for determination of HA oxygencontaining functional groups, [4][5][6] but they exhibit some difficulties and uncertainties due to HS complexity. Beside those methods, some authors studied the differentiation between various hydroxyl groups of HA by derivatization [7][8][9][10][11] providing HA with selectively blocked functional groups.…”

Section: Introductionmentioning

confidence: 99%