some depth (Fig. 3, trace D); these profiles generally correlated with areas which had been subjected to testing, construction, or earthmoving activities. Several of the profiles indicated that 239 py may have migrated beyond the depth sampled, Penetration of (1976) Pu remained unknown. of radionuclide concentrations thus the total depth of A 1974 study by Noshkin et al, in the ground water reservoir of one of the islands revealed that 739?" %py had migrated to a depth of 80 m below the island surface (Fig. 4). Plutonium-239,240 was detected environments. As was shown in the soil profiles presented by Lynch and Gudiksen (1973), Noshkin (1976) also observed that the vertical distributions of 779-?"°pu at any one test weil were unrelated to the distributions found on other islands or at different test wells on the same island. Nevissi et al, (1976) discussed the distribution of 739'?"°pu in soils of Bikini Atoll. Plutonium-239,240 was detected as deep as 100 cm in soil profile samples with the distribution shown in Fig. 5. Trace A ts a profile characteristic of a disturbed soil, possibly due to earth movement, construction, or clean up efforts, Traces B and C are two additional plutonium profiles from Bikini Atoll. It was noted that all the profiles exhibited 7°*'?**pu distributions similar to those of 3%r measured on the same samples. . According to Nevissi (1976) there are three possible transport mechanisms for plutonium in Bikini soils: solution transport, biological transport, and suspension transport. Based on the soil and biological conditions at Bikini, it was concluded that solution transport and bioclogical transport were not the major methods by which plutonium migrated downward. The suspension and resuspension of plutonium and plutoniumbearing particles was the principal mode of plutonium transport in these soils. Nevissi (1976) noted the cbservation of Held et al. {1965} that the algal crust of the atoll soils tend to retain a greater portion of @11 radionuclides. Although it was not possible to predict the mechanism Depth Below Ground Surface (m) at all intermediate depths sampled, suggesting that a portion of the 233,2495) was very mobile throughout the water-saturated coral-sand Fig. 4. 239,240 by (FCI /1) 0 , : 20h 4 40F ; 60 be a 0 Vertical a 2 2 (Adapted 239¢240R, and their dis- tribution at Bikini, are not likely to change significantly in the immediate future unless mechanical disruption of the soil occurs. Safety Shot Sites A program is in progress under the auspices of NAEG to determine the inventory, distribution, and biological fate of transuranics and other Prevalent radionuclides at the Safety Shot Sites of NTS. To date, this program has generated data on soil plutonium, americium, and uranium distributions for areas where safety tests of nuclear weapons have occurred. 52 A 4 Distribution of Enewetak Atoll Of plutonium retention by the organic crust, the properties of the algal layers and the large adsorptive surface area may be one explanation. It was concluded that the present Isvels of . 53 2 6 239,240. 8 Pu in a Test Well, from Noshkin et al., 1976).