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TitleEffect of pH and environmental ligands on accumulation and toxicity of Ni2+ to Lemna minor
AuthorGopalapillai, Y; Vigneault, B; Hale, B
SourceEnvironmental Chemistry vol. 9, no. 6, 2012 p. 547-557,
Alt SeriesEarth Sciences Sector, Contribution Series 20120326
Mediapaper; digital; on-line
File formatpdf
Subjectsenvironmental geology; vegetation; environmental analysis; environmental studies; environmental impacts; acidity; pH patterns; heavy metals contamination; pollutants; pollution; groundwater pollution; nickel; Lemna minor
Illustrationsgraphs; tables; plots
ProgramManagement, Environmental Geoscience
AbstractEffects of water chemistry and metal speciation on metal uptake and toxicity to aquatic plants such as Lemna minor are not fully understood. The present study examined the effect of pH and environmental ligands (dissolved organic carbon (DOC) and mining related flotation ligands diethylenetriamine (DETA), triethylenetetramine (TETA), sodium isopropyl xanthate), on Ni toxicity to L. minor. Exposure and tissue residue toxicity thresholds were assessed to validate the use of a Biotic Ligand Model (BLM) or a Tissue Residue Approach (TRA) as a framework for predicting Ni toxicity. An increase in the activity of H+ non-linearly decreased the toxicity of free Ni ion activity, whereas Ni accumulation kinetics indicated that the mechanism of Ni2+ and H+ interaction was not competitive inhibition as expected by the BLM framework. The effect of DOC on the toxicity of total Ni concentration was relatively small (toxicity decreased by less than a factor of 2) and was explained solely by the complexation of Ni2+ by DOC. Alternatively, the protective effect of flotation ligands (DETA and TETA) was much less than expected based on estimated Ni complexation. Overall, a TRA model was directly applicable in the presence of organic ligands but not to varying pH, whereas a BLM-type model was applicable with changes in pH and DOC but not in the presence of the lesser studied flotation ligands. Such mechanistic information is essential for the development of reliable Ni toxicity models that would aid in risk assessment and regulation of Ni in the environment, particularly in mining-affected regions.