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Development of the terrestrial biotic ligand model for predicting nickel toxicity to barley ( Hordeum Vulgare ): Ion effects at low pH
Author(s) -
Antunes Paula M.C.,
Kreager Nancy J.
Publication year - 2009
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 - 10.1897/08-387.1
Subject(s) - hordeum vulgare , biotic ligand model , nickel , environmental chemistry , toxicity , chemistry , botany , poaceae , biology , ecotoxicology , organic chemistry
The focus of the present study was to investigate the potential for Al 3 +,Mg 2 +, and H+ to influence Ni 2 + toxicity for barley seedlings grown in acidic aqueous solutions and to assess the capacity of a two‐site terrestrial biotic ligand model (tBLM) to accurately predict 50% effect activities (EA50s). To accomplish these objectives, 48‐h EA50 Ni 2+ values were obtained for three sets of exposures in which the pH and activity of Al 3+ and Mg 2+ were varied. Exposures contained both Al alone and in combination with Mg so that compound ion effects could be investigated. A tBLM was then constructed to predict EA50 Ni 2+ values from the exposure solution chemistry. The results show a slight protective effect of H + against Ni 2+ toxicity and a strong protective effect of Mg 2 +, as indicated by a 4.6‐and 8.0‐fold increase in the measured EA50 Ni 2+ values corresponding to changes in pH from 6.0 to 4.5 and {Mg 2 +} from 0 to 1.40 mM, respectively. Increasing solution {Al 3 +} from 0 to 0.5 μM had no effect on Ni 2 + toxicity, although Al itself negatively affected root elongation. Comparison of EA50 values calculated as both Ni 2 + and measured concentration of total Ni in the root ([Root‐Ni] T ) showed [Root‐Ni] T to be a more normalized measure of Ni bioavailability. The strong correlation between root growth inhibition and tBLM‐predicted root‐Ni accumulation suggests that toxicity was influenced by Ni 2 + binding to low‐affinity ligands within the cell wall, in addition to Ni 2 + uptake through Mg 2 + transporters. Predicted EA50 Ni 2+ values generated with the model were all within a factor of ± 1.5 from measured values‐a result that emphasizes the advantage of using the tBLM for risk assessment.