28 27 concentrations in the lagoon. given in Table 5. A summary of the mean concentrations is In 1972 the average 23942405, concentration in the lagoon was determined for 34 unfiltered surface and bottom samples. more detailed water sampling program was conducted in 1974, (No78c). A In 1976, a smaller number of water samples were collected around the perimeter of the lagoon 2 km off the shore of the reef. low activity sea water contained in dialysis bags is achieved in 3 da to the environmental waters has very solute-like characteristics. In the It ts tempting to suggest, considering the environment, that the remohilijzed chemical species is some form of carbonate complex, Water samples collected during 1974 and 1976 were filtered through l-um filters. These characteristics suggest that the plutonium remobilized The average concentration cf total 2394240, uoin the water was essentially the same in 1972 and 1974 but a marked dectcase was noted discussion to follow, the estimated average soluble 2394240), during 1976. concentrations shown in Table 5 refers to material passing through a filterable material in the lagoon doubled over the mean 1974 level and l-um filter. the mean soluble concentration was reduced to half. During July 1974, the soluble 229249 Pu in concentration from 2 to 75 fCi/l. in the lagoon water ranged The percentage of the total activity associated with the filterable material in the water samples during 1974 and 1976 ranged from 2 to 54% and from 12 to 94%, vespectively, The concentrations of plutonium radionuclides in solution above fallout background concentrations in the lagoon water is direct evidence of the remobilization of transuranics from the solid phases of the environment. Dissolved plutonium released from the sediments of Cactus Crater was traced for considerable distances along the reef by a plutonium radionuclide balance, involving the change in the samples were collected tn 1976 than in 1974, During the 1974 program, samples were taken at stations throughout the lagoon, whereas the 15976 samplings were restricted to locations only 2 km from the reef. 23942405, concentrations were found in water samples frov The dissolved plutonium passes readily through dialysis membranes (No78c), Equilitration between dissolved plutonium in the crater sea water and Sisilar the few 1974 locations resampled in 1976, which suggests that any corputed rean concentration in the lagoon is contingent on the number and locetier of samples. The rean 2 238, 2594240, u ratio in the lagoon water samples 1972, 1974, and 1976 were virtually the same. Difference: in in sarple ratios between soluble and particulate phases were noted sometimes, but stations were not significantly different. The dissolved plutonium moves in solution apparently without interacting with the sediments deposits during transport. Forty percent fewer the average ratios associated with the two phases from all 2385, 2394240, ratio in the water, and dyes to trace the crater water (No78c). In 1976, the average concentration associatcd with the During 1974 and 1976, 1.5 and 0.7 Ci of 239+240,, u, respectively, were found in solution and 0.?/7 and 0.53 Ci were assuctoted with particulate material. ef These latter quantities represent the plutonium inventory fn the surface sediment and less than o. Tess Vw than O.04%