土壌中における放射性よう素の挙動 Ｉ よう化物イオンの砂質土壌への収着・脱離現象に関する研究

Abstract

Iodine-129 will be accumulated in the environment owing to its long half-life. In order to estimate its impact on man, it is necessary to obtain the information about its accumulation and movement in the environment over the long period. In this paper, the sorption and desorption of iodide (I-) on sandy soils were examined by using column and batch experiments. The results obtained were as follows:1) Every breakthrough curves of I- showed plateau, before the ratio of concentration (C/C0) were reached 1.0. The ratio C/C0 on plateau in the effluent was affected by the kind of soil and NaI concentration in the inflow solution.2) Iodine once sorbed on soil would be scarcely removed with 5.0×10-4mol/l CaCl2 solution.3) Chemical form of iodine in the effluent was identified, showing that, more than 90% was recovered as I-.4) In batch experiment, the equilibrium period on the sorption of I- by anion exchange resin and soil was examined. The equilibrum period on the sorption by anion exchange resin was within 3hr, but the period by soil was more than 15 days. This means that the sorption phenomenon of I- to soil is not always based on an ion exchange reaction on the surface of soil particle.5) A new theory should be examined for evaluating the movement of I- in a soil.