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Title

Application of the biotic ligand model to explain potassium interaction with thallium uptake and toxicity to plankton

Authors
Chafin, Ryan D.
Klinger, Mary Beth
Twiss, Michael R.
Published in Environmental Toxicology & Chemistry. 2007, vol. 26, no. 6, p. 1139
Abstract Competitive interaction between Tl(I) and K was successfully predicted by the biotic ligand model (BLM) for the microalga Chlorella sp. (Chlorophyta; University of Toronto Culture Collection strain 522) during 96-h toxicity tests. Because of a greater affinity of Tl(I) (log K = 7.3–7.4) as compared to K (log K = 5.3–6.3) for biologically sensitive sites, an excess of 40-to 160-fold of K is required to suppress Tl(I) toxic effects on Chlorella sp., regardless of [Tl(I)] in solution. Similar excess of K is required to suppress Tl(I) toxicity to Synechococcus leopoliensis (Cyanobacteria; University of Texas Culture Collection strain 625) and Brachionus calyciflorus (Rotifera; strain AB-R1F). The mechanism for the mitigating effect of K on Tl(I) toxicity was investigated by measuring 204Tl(I) cellular uptake flux and efflux in Chlorella sp. Potassium shows a competitive effect on Tl(I) uptake fluxes that could be modeled using the BLM-derived stability constants and a Michaelis—Menten relationship. A strong Tl efflux dependent only on the cellular Tl concentration was measured. Although Tl efflux does not explain the effect of K on Tl(I) toxicity and uptake, it is responsible for a high turnover of the cellular Tl pool (intracellular half-life = 12–13.5 min). No effect of Na+, Mg2+, or Ca2+ was observed on Tl+ uptake, whereas the absence of trace metals (Cu, Co, Mo, Mn, Fe, and Zn) significantly increased Tl uptake and decreased the mitigating effect of K+. The importance of K+ in determining the aquatic toxicity of Tl+ underscores the use of ambient K+ concentration in the establishment of Tl water-quality guidelines and the need to consider K in predicting biogeochemical fates of Tl in the aquatic environment.
Keywords AlgaeBiotic ligand modelCyanobacteriaGrowth rateWater-quality guidelines
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Other version: http://doi.wiley.com/10.1897/06-315R.1
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HASSLER, Christel et al. Application of the biotic ligand model to explain potassium interaction with thallium uptake and toxicity to plankton. In: Environmental Toxicology & Chemistry, 2007, vol. 26, n° 6, p. 1139. https://archive-ouverte.unige.ch/unige:26428

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Deposited on : 2013-02-20

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