DISTRIBUTION COEFFICIENT IN THE SORPTION OF RADIONUCLIDES ONTO ANDO SOIL IN THE PRESENCE OF HUMIC ACID - INFLUENCE OF THE MOLECULAR SIZE OF HUMIC ACID

摘要

Influence of humic acid (HA) on the sorption of Co-60, Sr-85 and Am-241 onto Ando soil was examined with respect to HA of various molecular sizes. Distribution coefficient (K-d) in the sorption of Co-60 On this type of soil was only slightly affected by the presence of KA. The K-d Of Sr-85 as th, HA concentration increased. The K-d of Am-241 decreased as the HA concentration increased and the K-d Of HA showed a similar trend. In the solution, Am-241 selectively formed stable compounds with an HA ranging from 30,000 to 100,000 in molecular weight (MW), whereas Co-60 and Sr-85 preferentially but weakly interacted with HA fractions smaller than 100,000 MW. These results suggest that the K-d in the case of Co-60 and Sr-85 is mainly controlled by sorption of both cationic species and humic compounds, while the K-d Of Am-241 is controlled by the sorption of HA. [References: 13]