The effects of database parameter uncertainty on uranium(VI) equilibrium calculations

Denison, Frank H.; Garnier‐Laplace, Jacqueline

doi:10.1016/j.gca.2004.09.033

Cited by 44 publications

(15 citation statements)

References 25 publications

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“…Uranium speciation in the exposure solutions was calculated with the chemical speciation model JCHESS (Java Chemical Equilibrium Speciation with Surfaces; École des Mines de Paris, Fontainebleau, France) with an updated thermodynamic database prepared from a recent review of available thermodynamic data [20].…”

Section: Methodsmentioning

confidence: 99%

Metal‐phytoplankton interactions: Modeling the effect of competing ions (H⁺, Ca²⁺, and Mg²⁺) on uranium uptake

Fortin

Denison

Garnier‐Laplace

2007

Enviro Toxic and Chemistry

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The influence of pH and hardness cation concentrations on uranium uptake by a green alga, Chlamydomonas reinhardtii, was investigated through short-term exposure experiments. Uranium uptake at pH 5 and at pH 7 was measured over a large concentration range (0.020-2.0 microM 233U), and the effects of hardness cations were studied over environmentally pertinent concentration ranges (approximately 0.05-2 mM) at a constant uranium concentration (0.25 microM). Calcium and magnesium inhibited uranyl uptake, but the influence of pH was more complex than anticipated. The equilibrium biotic ligand paradigm of metal bioavailability predicts that two distinct phenomena of antipathetic effect will influence uranium availability as pH is varied. Increasing pH reduces the concentration of protons, thus reducing competition for the physiologically active sites, whereas the concomitant complexation by carbonates and hydroxides reduces the free uranyl activity. Maximum uranium uptake rates observed at pH 7, however, were far greater than those observed at pH 5, suggesting a noncompetitive inhibition of metal transport by protons. Modeling on the basis of our results strongly suggests that cells grown and exposed at pH 7 have either a greater internalization rate of uranyl or a higher number of transport sites compared with cells grown and exposed at pH 5. We thus conclude that the simple proton-metal competition described by the biotic ligand model cannot successfully depict uranium-algae interactions. The development of an appropriate model incorporating the influence of protons to predict metal uptake and toxicity will be more challenging than anticipated.

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Section: Methodsmentioning

confidence: 99%

Metal‐phytoplankton interactions: Modeling the effect of competing ions (H⁺, Ca²⁺, and Mg²⁺) on uranium uptake

Fortin

Denison

Garnier‐Laplace

2007

Enviro Toxic and Chemistry

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“…Uranium speciation in the exposure solutions was calculated with the chemical speciation model MINEQL+ (Ver. 4.6; ) with updated equilibrium constants , using total metal concentrations as input data. All calculations were constrained to a fixed input pH (7 or 5) at equilibrium with the atmosphere (pCO 2 = 10 −3.5 atm).…”

Section: Methodsmentioning

confidence: 99%

Uranium accumulation and toxicity in the green alga Chlamydomonas reinhardtii is modulated by pH

Lavoie

Sabatier

Garnier‐Laplace

et al. 2014

Enviro Toxic and Chemistry

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The effects of pH on metal uptake and toxicity in aquatic organisms are currently poorly understood and remain an evolving topic in studies about the biotic ligand model (BLM). In the present study, the authors investigated how pH may influence long‐term (4 d) uranium (U) accumulation and chronic toxicity in batch cultures of the freshwater green alga Chlamydomonas reinhardtii. The toxicity expressed as a function of the free uranyl ion was much greater at pH 7 (effective concentration, 50% [EC50] = 1.8 × 10−9 M UO22+) than at pH 5 (EC50 = 1.2 × 10−7 M UO22+). The net accumulation rate of U in algal cells was much higher at pH 7 than at pH 5 for the same free [UO22+], but the cells exposed at pH 5 were also more sensitive to intracellular U than the cells at pH 7 with EC50s of 4.0 × 10−15 and 7.1 × 10−13 mol of internalized U cell−1, respectively. The higher cellular sensitivity to U at pH 5 than at pH 7 could be explained partly by the increase in cytosolic U binding to algal soluble proteins or enzymes at pH 5 as observed by subcellular fractionation. To predict U accumulation and toxicity in algae accurately, the important modulating effects of pH on U accumulation and U cellular sensitivity should be considered in the BLM. Environ Toxicol Chem 2014;33:1372–1379. © 2014 SETAC

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“…The quality of calculations is mainly related to the quality and completeness of the entry data. Moreover, the uncertainty on thermodynamic formation constants can result in considerable output uncertainty, particularly for species like uranium that undergoes a complex aqueous speciation [4]. Within the working group "Speciation" of the CETAMA (Analytical methods establishment committee of the French Atomic Energy commission, CEA) a modelling exercise was conducted about the U(VI) speciation in waters of known compositions as previously carried out for other chemical systems [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…No uncertainty evaluation was asked in the present exercise. Such an evaluation requires a complete assessment of all the sources of uncertainties [4,[27][28][29], and might be the aim of other dedicated exercises. This practical and theoretical exercise was established from water conditions as those found in Finnish well-waters, containing significant amounts of dissolved uranium [17].…”

Section: Introductionmentioning

confidence: 99%

A modelling exercise on the importance of ternary alkaline earth carbonate species of uranium(VI) in the inorganic speciation of natural waters

Vercouter

Reiller

Ansoborlo

et al. 2015

Applied Geochemistry

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International audiencePredictive modelling of uranium speciation in natural waters can be achieved using equilibrium thermodynamic data and adequate speciation software. The reliability of such calculations is highly dependent on the equilibrium reactions that are considered as entry data, and the values chosen for the equilibrium constants. The working group “Speciation” of the CETAMA (Analytical methods establishment committee of the French Atomic Energy commission, CEA) has organized a modelling exercise, including four participants, in order to compare modellers’ selections of data and test thermodynamic data bases regarding the calculation of U(VI) inorganic speciation. Six different compositions of model waters were chosen so that to check the importance of ternary alkaline earth carbonate species of U(VI) on the aqueous speciation, and the possible uranium solid phases as solubility-limiting phases. The comparison of the results from the participants suggests (i) that it would be highly valuable for end-users to review thermodynamic constants of ternary carbonate species of U(VI) in a consistent way and implement them in available speciation data bases, and (ii) stresses the necessary care when using data bases to avoid biases and possible erroneous calculation

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The effects of database parameter uncertainty on uranium(VI) equilibrium calculations

Cited by 44 publications

References 25 publications

Metal‐phytoplankton interactions: Modeling the effect of competing ions (H⁺, Ca²⁺, and Mg²⁺) on uranium uptake

Metal‐phytoplankton interactions: Modeling the effect of competing ions (H⁺, Ca²⁺, and Mg²⁺) on uranium uptake

Uranium accumulation and toxicity in the green alga Chlamydomonas reinhardtii is modulated by pH

A modelling exercise on the importance of ternary alkaline earth carbonate species of uranium(VI) in the inorganic speciation of natural waters

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The effects of database parameter uncertainty on uranium(VI) equilibrium calculations

Cited by 44 publications

References 25 publications

Metal‐phytoplankton interactions: Modeling the effect of competing ions (H+, Ca2+, and Mg2+) on uranium uptake

Metal‐phytoplankton interactions: Modeling the effect of competing ions (H+, Ca2+, and Mg2+) on uranium uptake

Uranium accumulation and toxicity in the green alga Chlamydomonas reinhardtii is modulated by pH

A modelling exercise on the importance of ternary alkaline earth carbonate species of uranium(VI) in the inorganic speciation of natural waters

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Metal‐phytoplankton interactions: Modeling the effect of competing ions (H⁺, Ca²⁺, and Mg²⁺) on uranium uptake

Metal‐phytoplankton interactions: Modeling the effect of competing ions (H⁺, Ca²⁺, and Mg²⁺) on uranium uptake