Table 3. Adsorption of Plutonium From Enewetak Reef Seawater by Different Ion Exchange Resins (a) Resin (b) Type 2399240py, fCi/liter (to %) on resin column % Adsorbed AG-50-4x, 100-200 mesh Cation 23(14) 28 AG-21K, 100-200 mesh Anion 18(11) 23 AG-1-4x, 100-200 mesh Anion 23(9) 28 Chelex~100, 50-100 mesh Chelating 81(7) 103 (a) Reef seawater filtered through 1 um cartridge. (b) Column dimension was 5.0 cm dia x 25 cm length. Average 239°240py in filtered sample was 79 + 7 £Ci/liter. In conclusion, we have demonstrated with simple equipment that plutonium radionuclides can be preconcentrated in the field using MnO» impregnated cartridges from large-volume water samples. Using both the MnO» cartridges and radiochemical techniques, we have shown that various inert and complexed chemical forms of plutonium exist in Enewetak reef and groundwater compared to the highly exchangeable species in the lagoon water and open-ocean water. Plutonium remobilized to solution by active processes at Enewetak appears initially to be relatively inert and highly complexed, and in a relatively short period of time, natural interactions convert this plutonium to a more exchangeable form when it enters the lagoon. The adsorption characteristics of lagoon Pu appear to be similar to fallout Pu in the open-ocean water. ACKNOWLEDGMENTS Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under Contract Number W-7405-ENG-48. References to a company or product name does not imply approval or recommendation of the product by the University of California or the U.S. Department of Energy to the exclusion of others that may be suitable. 590