EXCHANGE ISOTHERM OF TOXIC METAL CATIONS ON SOILS IN CONSIDERATION OF COEXISTENCE IN WIDE CONCENTRATION RANGE FOR METAL CONTAMINATION SURVEY

The cation-exchange equilibrium of toxic metal cations were investigated in wide concentration range to predict their behavior in contaminated soils. When the concentration of toxic metal cation in water was high enough, the exchange amount became saturation at the cation exchange capacity of each soil. The exchange isotherms in low concentration range showed the linear relation ship in logC1 vs. logQ1 diagram with slope n1. The value of n1 was not based on the kind of soil, but was determined for each cation. The influence of coexisting cation was expressed quantitatively by the multiple isotherm equation proposed in this study. The concentrations of H+ and Al3+ gave the strong effects to the exchange of toxic cations.