Dispersion of plutonium from contaminated pond sediments

Abstract

Sediment--water distributions of plutonium as a function of pH and contact time were investigated in a holding pond. Although plutonium has been shown to sorb from natural waters onto sediments, the results of this study indicate that under the proper conditions it can be redispersed at pH 9 and above. Concentrations greater than 900 pCi Pu/L result after 34 h contract at pH 11 or 12 and the distribution coefficient, defined as the ratio of concentration in the sediment to that in the liquid, decreases from 1.1 x 10/sup 5/ at pH 7 to 1.2 x 10/sup 3/ at pH 11. The plutonium is probably dispersed as discrete colloids or as hydrolytic species adsorbed onto colloidal sediment particles whose average size decreases with increasing pH above pH 9. About 5% of the total plutonium is dispersed at pH 12, and the dispersion seems to readsorb on the sediment with time. Consequently, migration of plutonium from the pond should be slow, and it would be difficult to remove this element completely from pond sediment by leaching with high pH solutions.