Individual and combined phytotoxic effects of cadmium, lead and arsenic on soybean in Phaeozem

Acute laboratory toxicity tests were carried out to assess the individual and combined toxic effects of metals including cadmium (Cd), lead (Pb) and the metalloid arsenic (As) in Phaeozem on the seed germination and seedling growth of soybean, Glycine max. Seeds were exposed to varied concentrations of Cd, Pb and As individually and in mixtures including Cd + Pb, Cd + As, Pb + As and Cd + Pb + As. The sum of toxic units (TU) for medium effective concentration of the mixture (EC 50mix ) was calculated based on the dose (TU-based)-response relationship using the Trimmed Spearman-Karber method. Binary metal combinations of Cd + Pb, Cd + As and Pb + As produced additive, synergistic and antagonistic effects, respectively, on shoot growth and synergistic, synergistic and antagonistic effects on root growth. Ternary combination of Cd + Pb + As had a synergistic effect on shoot growth and an additive effect on root growth. Bioaccumulation of metals was observed in soybean and inhibited or enhanced bioaccumulations of individual metals were found in mixtures due to different combinations of metals.