Application and Comparison of Two Biotic Ligand Models Predicting Copper Toxicity and Accumulation in Heavy Metal Tolerant Moss

Abstract

Two biotic ligand models (BLMs) predicting copper accumulation and toxicity to heavy metal tolerant moss (Funaria hygrometrica Hedw.) were developed in the present study. Although BLMs developed in this study could predict the effects of pH and calcium on copper accumulation and toxicity, stability constants representing the binding strength between cations and the biotic ligand for the toxicity model were different than those for the accumulation model. Stability constants of copper, calcium and proton for the toxicity model were logKCu = 2.98, logKCa = 3.38, and logKH = 4.17, respectively, and for the accumulation model were logKCu = 4.46, logKCa = 3.28, and no effect, respectively. Proton competition with copper accumulation was not observed. Difference in logKCu between the two models indicated that tolerance with copper results in the decrease in KCu. In addition, it was indicated that decreases in copper toxicity due to increases in proton concentration was not caused by the competitive effects of proton but by the changes in internalization flux.