It appears that the physical redistribution of *°7Bi in the lagoon is similar to that of ® Co, but since the levels of 207Ri are lower than those of ©0Co by a factor of about 20, we are at the limits of detection, with the method used, for samples distant from the crater. The use of larger samples, chemical separation and more sensitive counting methods would make it possible to determine 60¢9:207Ri ratios in sediments, lagoon water and organisms in different parts of the lagoon. These ratios would indicate whether transported radionuclides were primarily in solution or on particles. If the ratios remained constant, that would be a strong indication of transport on particles. The results of analyses of selected samples for 207B4 by gamma-ray spectrometry and by chemical separation are compared in Table 19. Bismuth-207 will be a useful tracer in the future because it has a long half-life, 30 years compared to 5.2 years for ®°Co. Plutonium-239, with a half-life in excess of 24,000 years, is another potentially useful tracer at Bikini. The presence of 239 240py and 297p4 (Table 12) in goatfish viscera is consistent and probably results from direct ingestion of fine particles of sediment during feeding. Two samples of goatfish viscera collected at Nam I. in 1969 contained 239pu in concen- trations of 13 pCi/g dry and 29 pCi/g dry. The absence of 238pu in goatfish viscera as compared with the sediment merely reflects a low concentration of this radionuclide, below the limits of detection. Although none of the 1969 or 1970 samples were analyzed for the x-ray emitter ©3Ni, this radionuclide was found in concentrations of 80 d/m/g dry weight in Bravo Crater sediment collected in 1967 (Beasley and Held, 1969). Nickel-63 is of particular interest as a tracer since it has a half-life of 92 years. In addition, the clam kidney accumulated 63Ni, as it does ®%Co, and is therefore an indicator organism for the presence of 6 3Ni. Another long-lived radionuclide, !°8™ag, with a half-life of approximately 125 years, has been identified for the first time among the radionuclides at Bikini (Beasley and Held, 1971). This radionuclide was first detected from the gamma-ray spectrum of the hepatopancreas of spiny lobsters collected in 1969 (Fig. 4), and quantitative analysis of pooled samples from Eneu I. in June, 1969, and Bikini 1. in June, 1970, gave results of 0.50 + 0.13 pCi/g dry, respectively. The spiny lobster hepatopancreas is a known concentrator of silver isotopes (Seymour, 1963). Thus, 1!9®8™jg is another potentially useful long-lived tracer, with its indicator organism. 4.5 WATER Tritium in well water is present at low concentrations; the maximum value found in 1969 was 14 pCi/ml, or 4300 tritium units, at Nam I., whereas at Bikini and Eneu Islands the concentration was 2 pCi/ml, or approximately 600 fT. U. Samples taken in 1970 from well-points 4 and 5 and from the cistern at Bikini and from the well and cistern at Eneu all contained less than 400 T. U. These values fall within the range of tritium concentrations PyCeP ve Gece gt 13 72 O