RADIOISOTOPES

It is important to understand potassium (K) behavior in soils since K fertilization is one of the most effective countermeasures to reduce the radiocaesium (RCs) uptake by crops. The K behavior in soils is highly influenced by the clay mineral composition. In this study, we investigated the K behavior for non-vermiculitic and vermiculitic nature of soils at Fukushima Prefecture in Japan. In the adsorption experiments, vermiculitic nature of soils exhibited more adsorption of K onto the soils as compared to non-vermiculitic nature of soil. One dimensional column transport experiments using ⁴²K as a radioisotope tracer showed that almost similar K mobility for all soils as supported by adsorption isotherms of K. However, percentage of exchangeable K in the total K retained in the soil was higher in non-vermiculitic nature of soil, while the percentage of fixed K was higher in vermiculitic nature of soils. Thus, the existence of vermiculite with high K fixation capacity was suggested to reduce K retention as an exchangeable form in vermiculitic nature of soils.