Fig. 6. The effect of organic ligands on the E value of Cd in the calcareous soil. Values represent the ratio of the E value measured in the presence of the ligand against that measured in the absence of the ligand at pH 7.5. Symbols and error bars represent the mean and standard deviation of triplicate measurements. The symbols represent: (0.25–5 mM) sodium citrate (), (0.25–1 mM) histidine (), (0.5–1 mM) tartrate (), and (0.25–0.5 mM) DMA (+).