months from tide and wave action and in summer months from ‘tides and the North Equatorial Current. The surface movement of waterborne radioactivity from Bikini and Eniwetok atolls would therefore be westward toward the Philippine Islands, with the possibility UNCLASSIFIED of the most radioactive clam kidney from Eniwetok Atoll in an anticoincidence shielded x-ray counter gave a positive indication of ®°Ni (at a counting error of 1 S.D.), with an upper limit of some 0.1 disintegration per of some movement back toward the minute per gram of dry weight. No 59Ni was detected in 1000-minute in the Cromwell Current (73). Both counts of soil samples obtained from either atoll. It is probable, therefore, that no large amounts of 5°Ni were east in the Equatorial Countercurrent and possibly eastward at shallow depth Christmas Island and Penrhyn Atoll lie in the path of the westward-moving South Equatorial Current and consequently would be unlikely recipients of waterborne radioactivity emanating from Bikini and Eniwetok lagoons. Nickel-58 comprises some 68 percent of stable nickel, and we have consid- ered the possibility of the production of 5°Ni (half-life, 80,000 years) both by (n,y) interactions with stable nickel, (pn) reactions with stable cobalt, and (p,a@) reactions with “*Fe (92 percent abundance). Based on abundances, cross sections, and decay constants, we calculated an activity ratio of “Ni to 59Ni of approximately 600 for the (n,y) production of **Ni. Nickel-59 decays by electron capture and is determined by measuring the 6.9-kev x-ray which results from the de-excitation of its daughter, ®°Co. A 3000-minute count produced, and that the presence of small amounts of 5°Ni precludes its usefulness as a tracer in oceanic processes. A realistic assessment of the total ®Ni present at Bikini and Eniwetok atolls is not possible from the data presented here, although knowledge of such an inventory and of the rate at which it is injected into the North Equatorial Current would help one to determine its usefulness as a downstream tracer for these waters. However, the giant clam Tridacna sp. ap- pears to be an excellent indicator organism, which could be used to deline- ate the downstream penetration of ®Ni. THOMAS M. BEASLEY Epwarpb E, HELp Laboratory ef Radiation Ecology, University of Washington, Seattle UNCLASSIFIED References and Notes 1. F. G. Lowman, in Disposal of Radioactive Wastes, K. Saddington and W. L. Templeton, Eds. (Macmillan, New York, 1959), pp. 105-138. 2. G. M. Lederer, J. M. Hollander, I. Perlman, Table of Isotopes (Wiley, New York, ed. 6, 1967). 3. W. S. Broecker, in The Sea, M. N. Hill, Ed. (Interscience, New York, 1963), vol. 2, pp. 88-108. 4. E. D. Goldberg, in The Sea, M. N. Hill, Ed. (Interscience, New York, 1962), vol. 1, pp. 3-25. 5. R. C. Voter and C, V. Banks, Anal, Chem. 21, 1320 (1949). 6. J. M. Nielsen and T. M. Beasley, in Assess- ment of Radioactivity in Man (International Atomic Energy Agency, Vienna, 1964), pp. 245-260. 7. G. D. Nicholls, H. Curl, Jr., V. T. Bowen, Limnol. Oceanogr. 4, 472 (1959). 8. L. J. Kirby, The Radiochemistry of Nickel (National Academy of Sciences—National Research Council Report No. NAS-NS 3051, Washington, D.C., 1961). 9. T. R. Folson and D. R. Young, Nature 206, 803 (1965). 10. W. C. Hanson, D. G. Watson, R. W. Perkins, in Radioecological Concentration Processes, B. Aberg and F. B. Hungate, Eds. (Pergamon Press, Oxford, 1967), pp. 233-245. 11. The concentrations of 5’Co were measured at the time of collection and are tabulated in this laboratory. 12, W. S. von Arx, Trans. Amer. Geophys. Union 29, 861 (1948). 13, J. A. Knaus, in The Sea, M. N. Hill, Ed. (Interscience, New York, 1963), vol. 2, pp. 235-252. 14, We thank Dr. W. Pearcy of Oregon State University for supplying samples of chaetognaths; Dr. T. R. Folsom of Scripps Institute of Oceanography and C. H. Fiscus of the Marine Biological Laboratory, Bureau of Commercial Fisheries, for supplying squid specimens. Supported by AEC under contract No. AT(26-1) -269. 3 March 1969