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Adsorption of Curium-244: Effects of Dissolved Organics and Sediment Extractions¹

ABSTRACT

Adsorption of ²⁴⁴Cm, a transuranic isotope that absorbs strongly to suspended sediments, was measured on untreated and extracted sediments in filtered and ultrafiltered water. Partition coefficients (K^d) ranged from 7 x 10³ to 5 x 10⁵. The most important observations concern the role of dissolved and particulate organic matter. Ultrafiltration of water to remove dissolved organic compounds significantly reduced the concentration of soluble Cm and increased K_d for all types of sediments. Extraction of sediments with NaOH to remove humic and fulvic acids also increased K_d values. This may result because previously blocked adsorption sites are available for Cm adsorption or because particulate organics in unextracted sediments are solubilized during the experiments. Removal of hydrous oxides from sediments by extraction with sodium citrate/sodium dithionate or hydroxylamine-hydrochloride did not produce consistent effects. It is suggested that hydrous oxides may be important for long-term sediment-water partitioning of Cm, but the initial adsorption is determined by interactions with dissolved and particulate organic matter.

Key Words: partition coefficients • fresh water • dissolved organics • transuranic elements

¹ Contribution from the Savannah River Ecology Laboratory, Inst. of Ecology, Univ. of Georgia, Aiken, SC 29801. This research was in part supported by contract EY-76-C-09-0819 between the Univ. of Georgia and the U.S. Dep. of Energy.

² Research assistant professor, Laboratory of Radiation Ecology (WH-10), Univ. of Washington, Seattle, WA 98195; and director, Sapelo Island Marine Inst., Sapelo Island, GA 31327, respectively.

Received for publication August 27, 1983.