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Modeling toxicity of binary metal mixtures (Cu 2+ –Ag + , Cu 2+ –Zn 2+ ) to lettuce, Lactuca sativa , with the biotic ligand model
Author(s) -
Yen Le T.T.,
Vijver Martina G.,
Jan Hendriks A.,
Peijnenburg Willie J.G.M.
Publication year - 2013
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.2039
Subject(s) - metal , biotic ligand model , chemistry , ligand (biochemistry) , metal ions in aqueous solution , zinc , copper , lactuca , nuclear chemistry , stability constants of complexes , toxicity , copper toxicity , ion , analytical chemistry (journal) , environmental chemistry , botany , receptor , biology , organic chemistry , biochemistry
The biotic ligand model (BLM) was applied to predict metal toxicity to lettuce, Lactuca sativa . Cu 2+ had the lowest median effective activity (EA50 M ), compared with Ag + and Zn 2+ (EA50 Cu = 2.60 × 10 −8 M, EA50 Ag = 1.34 × 10 −7 M, EA50 Zn = 1.06 × 10 −4 M). At the 50% response level, the fraction of the total number of biotic ligands occupied by ions ( f 50 M ) was lowest for Ag + among the metals ( f 50 Ag = 0.22, f 50 Cu = 0.36, f 50 Zn = 0.42). Cu 2+ had the highest affinity for biotic ligands compared with Ag + and Zn 2+ , as shown by stability constants of the cation–biotic ligand binding, expressed as log K MBL (log K CuBL = 7.40, log K AgBL = 6.39, log K ZnBL = 4.00). Furthermore, the BLM was combined with the toxic equivalency factor approach in predicting toxicity of mixtures of Cu 2+ –Zn 2+ and Cu 2+ –Ag + . The fraction of biotic ligands occupied by ions was used to determine the relative toxic potency of metals and the toxic equivalency quotient (TEQ) of mixtures. This approach allowed for including interactions in estimating mixture toxicity and showed good predictive power ( r 2 = 0.64–0.84). The TEQ at the 50% response level (TEQ50, Cu 2+ equivalents) for Cu 2+ –Zn 2+ mixtures was significantly lower than the value for Cu 2+ –Ag + mixtures. Joint toxicity depended on both TEQ and specific composition of the mixture. The present study supports the use of the accumulation of metal ions at the biotic ligands as a predictor of toxicity of single metals and mixtures. Environ. Toxicol. Chem. 2013;32:137–143. © 2012 SETAC