Adsorption and desorption of radioiodine in a calcareous soil

The adsorption and desorption of radioiodine in a calcareous soil from Jiuquan County of Gansu Province (China) was studied using batch and column experiments. The adsorption and desorption isotherms and the breakthrough curves for the untreated soil and for soil treated to remove organic matter were determined at pH 8.1 and in the presence of CaCl₂, respectively. It was found that radioiodine is a very mobile nuclide in calcereous soil, that the organic matter of the soil is the main component for the retention of radioiodine at very low concentration and that intra-organic diffusion of matter is the predominant rate-limiting step in the adsorption of the I^- ion. It may be concluded that organic matter is a significant sink for radioiodine in calcareous soil.