The distribution coefficient (Kd) of material between soil and soil solution is one of the most important factors in evaluating the transport of pollutant from soil to plant root. However, Kd value varies largely depending on the environmental conditions. Therefore, careful examination for conditions is necessary when reported Kd value is to be used for assessment of material transport in the ground.
In this study, effect of three environmental factors (temperature, soil-pH, and co-existing ions) on Kd of zinc was investigated by batch and column experiments. The results obtained are as follows:
1) Linear relationship was derived in the batch experiment between logarithm of Kd of zinc and that of cation equivalent in the equilibrium solution.
2) Effect of soil-pH on Kd of zinc became larger at lower ion concentration.
3) Effect of temperature on Kd of zinc was relatively small compared with the effect by the other two factors.
4) Physicochemically, equilibrium soil must be used for Kd determination by the column method. Ten pore volumes of influent solution were required to get the stationary ion composition in the column effluent.
5) Kd value determined by the column method was almost equal to that determined by the batch method.
