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

Hassler, CS; Chafin, RD; Klinger, MB; Twiss, MR

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

Hassler, CS Chafin, RD Klinger, MB Twiss, MR

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Publication Type:: Journal Article
Citation:: Environmental Toxicology and Chemistry, 2007, 26 (6), pp. 1139 - 1145
Issue Date:: 2007-06-01

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Field	Value	Language
dc.contributor.author	Hassler, CS	en_US
dc.contributor.author	Chafin, RD	en_US
dc.contributor.author	Klinger, MB	en_US
dc.contributor.author	Twiss, MR	en_US
dc.date.issued	2007-06-01	en_US
dc.identifier.citation	Environmental Toxicology and Chemistry, 2007, 26 (6), pp. 1139 - 1145	en_US
dc.identifier.issn	0730-7268	en_US
dc.identifier.uri	http://hdl.handle.net/10453/8447
dc.description.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. © 2007 SETAC.	en_US
dc.relation.ispartof	Environmental Toxicology and Chemistry	en_US
dc.relation.isbasedon	10.1897/06-315R.1	en_US
dc.subject.classification	Environmental Sciences	en_US
dc.subject.mesh	Plankton	en_US
dc.subject.mesh	Potassium	en_US
dc.subject.mesh	Thallium	en_US
dc.subject.mesh	Ligands	en_US
dc.subject.mesh	Environmental Restoration and Remediation	en_US
dc.title	Application of the biotic ligand model to explain potassium interaction with thallium uptake and toxicity to plankton	en_US
dc.type	Journal Article
utslib.citation.volume	6	en_US
utslib.citation.volume	26	en_US
utslib.for	0602 Ecology	en_US
utslib.for	03 Chemical Sciences	en_US
utslib.for	05 Environmental Sciences	en_US
utslib.for	06 Biological Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
utslib.copyright.status	closed_access
pubs.issue	6	en_US
pubs.publication-status	Published	en_US
pubs.volume	26	en_US

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. © 2007 SETAC.

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