(Reprinted from Nature, Vol, 230, No. 5294, pp. 450-451, April 16, 1971) Silver-108m in Biota and Sediments at Bikini and Eniwetok Atolls THE occurrence! of the long lived silver radionuclide 1°°™Ag (T,;2> 100 yr) in biota from the Pacific Ocean has been held to suggest that the silver radionuclide ratio 11°™Ag/?°%™Ag may be useful as a tracer of environmental processes. It also appears! that large amounts of 1'°™Ag and !°8™Ag were not produced during the 1958 test series or earlier, and that the production activity ratio !!°™Ag/?°5™Ag was 162, a ratio derived solely from the thermal neutron activation of stable silver. We consider that their observations require reconsideration, We have found /°8™Ag in biota and sediments collected at previous nuclear testing sites in the Pacific. Wefirst detected the radionuclide in a composite sample of the hepatopancreases of spiny lobsters collected at Bikimi Atoll in 1969, and have since measured its concentration in several samples from Bikini and Eniwetok Atolls. Gamma-ray spectra were made using both Nal(Tl) and a solid state Ge(Li) detector system. The resolution of the Ge(Li) detection system permitted precise ce me i nt identification of the radionuclide photopeaks and the Nai(T]) crystal systems were used to quantitatively measure the }°8™Ag, Morespecific information was obtained by chemically isolating the '°8™Ag using a solvent extraction technique? by means of which the silver radionuclides are effectively separated from a number of other radio elements, especially 17°Sb, 2°’Bi, °°Co, “4+Mn, 192Ry and 230,232Th Comparison (Table 1) of the the hepatopancreas of spiny with biota reported in ref. specimens contain 2 to 3 times apn EEREH Sateee AR ~~. the concentration of '°8™Ag concentrations of '°8™Ag in lobsters taken from Bikini 1 shows that the Bikini more '°8™Ag, By contrast, in the composite sample from Eniwetok is less than that in the Guadalupe lobster specimen. The last test series at Bikini and Eniwetok Atolls occurred in 1958, so that the time between the cessation of tests and the colfection of the specimens ranges from 6 to 12 yr. It is reasonable to conclude that higher concentrations of both 108mAg and '!9™Ag were present at earlier times. Indeed, Seymour* has reported a '!°™Ae concentration of approximately 100 d.p.m./g of wet tissue for the hepatopancreas of a spiny lobster collected at Guam in November 1959, and although 108™Ag was not determined in the sample, it is significant that this activity was observed in biota collected 1,200 miles downstream of the test site as early as 1959.