The Use of Geochemical Speciation Modelling to Predict the Impact of Uranium to Freshwater Biota

Markich, Scott J.; Brown, Paul L.; Jeffree, Ross A.

doi:10.1524/ract.1996.74.special-issue.321

Cited by 36 publications

(32 citation statements)

References 11 publications

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“…2). 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].…”

Section: Speciation Freshwatermentioning

confidence: 99%

“…Markich et al [75] found that a fivefold increase in the bicarbonate concentration of synthetic Magela Creek water, at a fixed pH (5) and water hardness (3.5 mg CaCO 3 l -1 ), resulted in a 20% reduction in the toxicity (DVO) of U to V. angasi. The decrease in U toxicity corresponded to a similar factor of decrease in the calculated percentages of UO 2 2+ and UO 2 OH + , or an increase in UO 2 CO 3 due to UO 2 2+ complexation with carbonate.…”

Section: Effects Of Carbonate and Phosphatementioning

confidence: 99%

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Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

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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%

Section: Effects Of Carbonate and Phosphatementioning

confidence: 99%

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

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203

142

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“…Several studies (e.g., Manley and Davenport, 1979;Kramer et al, 1989;Huebner and Pynnönen, 1992;Markich et al, 1996;Fdil et al, 2006;Schwartzmann et al, 2011) have confirmed that valve movement behavior can be used to sensitively quantify biological reactions in real-time (Figure 10) for assessing the toxicological effects of metal exposures. The observations found that upon exposure to toxic concentrations of metals, bivalves have the ability to reduce the exposure of their soft tissues for extended periods by closing their valve (Manley and Davenport, 1979;Kramer et al, 1989;Salánki and Balogh, 1989;Huebner and Pynnönen, 1992).…”

Section: Future Application Approachesmentioning

confidence: 97%

The Application of Long-Lived Bivalve Sclerochronology in Environmental Baseline Monitoring

Steinhardt¹,

Butler

Carroll

et al. 2016

Front. Mar. Sci.

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Assessments of the impact of construction, operation, and removal of large infrastructures and other human activities on the marine environment are limited because they do not fully quantify the background baseline conditions and relevant scales of natural variability. Baselines as defined in Environmental Impact Assessments typically reflect the status of the environment and its variability drawn from published literature and augmented with some short term site specific characterization. Consequently, it can be difficult to determine whether a change in the environment subsequent to industrial activity is within or outside the range of natural background variability representative of an area over decades or centuries. An innovative approach that shows some promise in overcoming the limitations of traditional baseline monitoring methodology involves the analysis of shell material (sclerochronology) from molluscs living upon or within the seabed in potentially affected areas. Bivalves especially can be effective biomonitors of their environment over a wide range of spatial and temporal scales. A rapidly expanding body of research has established that numerous characteristics of the environment can be reflected in morphological and geochemical properties of the carbonate material in bivalve shells, as well as in functional responses such as growth rates. In addition, the annual banding pattern in shells can provide an absolute chronometer of environmental variability and/or industrial effects. Further, some species of very long-lived bivalves can be crossdated back in time, like trees, by comparing these annual banding patterns in their shells. It is therefore feasible to develop extended timeseries of certain marine environmental variables that can provide important insights into long temporal scales of baseline variability. We review recent innovative work on the shell structure, morphology, and geochemistry of bivalves and conclude that they have substantial potential for use as monitors of environmental variability and the effects of pollutants and disturbance.

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“…This is highly unlikely and leads us to believe that uranium uptake does not comply to the FIM of metal bioavailability. More than one transport mechanism (facilitated diffusion of the free uranyl ion) might contribute to uranium intake: i) The facilitated diffusion of hydroxo-complexes [15]; or ii) The passive diffusion of neutral lipophilic complexes such as U02(OH)2° (.e.g. analogue to HgCl 2° movement across membranes [16]).…”

Section: Concentration Dependence Of Uranium Uptake and Adsorptionmentioning

confidence: 99%

“…However, a number of intriguing experiments have been reported in the literature where the metal's "residual" bioavailability in the presence of hydrophilic MIv complexes has been found to exceed that which would have been predicted on the basis of the free-metal ion concentration at equilibrium [2]. Such intriguing results have been reported for U toxicity (valve movement response) toward the bivalve, Velesunio angasi, in laboratory exposure experiments [3]. Increasing pH from 5.0 to 6.0 decreased uranium toxicity, however, this amelioration could not be solely related to the decrease in {U0 2 2+ } within this range.…”

Section: Introductionmentioning

confidence: 99%

Establishing links between uranium aqueous speciation and uptake by a unicellular alga

2002

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Abstract. The bioavailability and toxicity of dissolved metals are closely linked to the metals' chemical speciation in solution. Normally the complexation of a metal by a ligand would be expected to decrease its bioavailability. The aqueous speciation of uranium undergoes tremendous changes within a pH range of 4 to 8 and in the presence of ligands commonly found in natural waters (carbonate, phosphate, hydroxide and natural organic matter). In the present project, we intend to establish links between speciation, medium composition and bioavailability of uranium. To study these links, we have chosen a unicellular green alga. Short-term metal uptake rates are determined in simple inorganic media with particular emphasis on the differentiation between adsorbed and intracellular metal. The Free-Ion Model (FIM) is tested to determine if U uptake is governed by the free uranyl species (U02 2 *) or if other species can be assimilated (i.e. passive diffusion of neutral, presumably lipophilic, species such as U0 2 (OH) 2 ; facilitated diffusion of metal bound to an assimilable ligand such as uranium-phosphate complexes). Results of our preliminary experiments indicate that complexation by phosphate decreases uranium bioavailability, as predicted by the FIM. However, uptake was stimulated when pH was increased from 5 to 7 in spite of the substantial decrease (55 -> 0.02 %) in free uranyl ion concentration in solution.

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The Use of Geochemical Speciation Modelling to Predict the Impact of Uranium to Freshwater Biota

Cited by 36 publications

References 11 publications

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

The Application of Long-Lived Bivalve Sclerochronology in Environmental Baseline Monitoring

Establishing links between uranium aqueous speciation and uptake by a unicellular alga

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