26 an the filling of Cactus Crater, the concentration of 779+ **pu in the fresh water within the crater was 0.116 + 0.062 pCi/L; the cr ter sediments had a concentration of 82 + 2 pCi/g (dry weight) (Noshk n 1980, Table 4). These values are higher than the concentrations measured from within the containment structure (see section 4.3). 5.3 Transuranics in the Surrounding Environment Radionuclides in the groundwater at Runit were measured in 19% prior to the cleanup, by Noshkin and co-workers (1976). These me ments showed that plutonium had penetrated the groundwater to the deepest depths measured (73 m). Dissolved *3**?**py ranged in va from 0.01 to 0.66 pCi/£ and in many of the wells was found to increase with depth. Two of the wells measured in 1975 are betwe Cactus Crater and the lagoon and are very near the two wells disc in section 4.3. in the two cases Measured values of dissolved 73°*?*! py are similb (between 0.08 and 0.17 pCi/L) and both show a hik concentration in the well closer to the lagoon. The largest quantities of transuranics at Enewetak are in the lagoon sediments. The entire distribution of the transuranics in the benthic environment at Enewetak has recently been reviewed by No (1960, Table 1). He estimates that the top 16 cm of the sediments an inventory of 1185 Ci of 73**#**py, 167 Ci of *** pu, 2190 of 2 and 475 Ci of *"'Am. These are distributed nonuniformly with the highest surface concentrations near the location of test sites. highest concentrations are in the northwest area of the lagoon wilere surface activities of 73% *?**pu are some four times higher than Runit were surface activities range from 2 to 170 pCi/g dff (dry weight). The vertical distribution of the transuranics within the sedimen column is highly variable from place to place with depth) and cannot be generalized easily. (sometimes increasing Transuranics within the water column of the lagoon show a comgplex distribution, the spatial patterns being differe™:: f5r surface agd bottom concentrations of 73°***py as well as f.. dissolved and guspended components. In 1974 the soluble ?73°*#**pu ranged in conckn- tration from 0.002 to 0.075 pci/t. The total inventory in the whter column of the lagoon in 1974 was 1.5 Ci in solution and 0.7 Ci absoci- ated with particulate material. Thus, the average quantity of plutonium in the water column is a small fraction of the sedimen inventory. The investigations of Noshkin and co-workers have shown that at both Enewetak and Bikini from 75 to 94 percent of the soluble 239426853 in the lagoon water is in the oxidized state (+5 or +64 with the remainder being in the reduced state (+3 or +4). All the plutonium associated with the particulate material is in the redhbced state. WNoshkin (1980) believes that most of the plutonium assodiated with the lagoon particulates is from resuspended sediments and transported out of the lagoon. On the other hand, the dissolved iB not plutonium passes readily through dialysis membranes and seems tc move without interaction with the sediment (Noshkin 1980). The water in the lagoon is exchanged with the ocean approxim tely twice a year. Thus, about 3 Ci of dissolved *3°*?**pu are remove from the atoll each year and an equivalent quantity remobilized [from the sediments and other sources on the atoll. Noshkin has sho that