Abstract
The association properties of Am and Pu with aquatic fulvic acid in a 0.01 M NaClO4 solution at pH 6-7 were studied on the basis of molecular size distribution. Seven fulvic acids (FA) were isolated from river, lake, and groundwater samples using XAD extraction technique. They were used for comparison of their effects on the association of Am and Pu. In the absence of FA, about 80% of Am and 75% of Pu were found to have molecular size greater than 450 nm (particulate forms). On the other hand, in the presence of FA, particulate forms of Am and Pu decreased with increasing FA concentration, and were negligible at the FA concentration of 10 mg/L. Both Am and Pu were associated mainly with aquatic FA having two size fractions of 30-10 kDa or less than 5 kDa. The differences between Am and Pu were rather small and the association patterns were divisible into two groups: size-selective and non-size-selective. Complexation of FA with Am and Pu was controlled by the amount of FA, the percentage, and characteristics of each size fraction of FA.
