ion of ve clam as shown in Figures 1.2 and 1.3. The raw data show Co" (off scale) and Co®in of trace of cobalt in the tuna liver. s particularly the epidermis and skeleton, was found to contain essentially radiopure Zn*°. Co*, ‘ganation. actied the tridacna liver, a mixture of Co®’, Co®, and Zn** in a bass liver, and Zn® with a The liver of the tuna contained traces of Co*’ and Co®’, but the remainder ofthe fish, The distribution of radioactivity in various organs of different species of fish is shown in Tables 1.10 and 1.12. In general, the gal] bladder, liver, and spleen exhibited the greatest concentration of activity with lesser amounts of activity in the epidermis, fins, and vertebra] column. On a gram basis the least activity was found in the edible muscle. On the otber hand, because of quantity, the total activity of the muscle may be 30 to 50 percent of the total activity of the whole fish. At Ailinginae Atoll only a slight difference in the gross activity of corals and clams was noted between specimens from the lagoon side and those from the ocean side of the reef. Two fish of different feeding habits taken from the same reef near Bikini Island showed different qualities of contamination. Aljthough the organs of both fish showed the same level of gamma contamination (Table 1.12), the radiochemical] analysis of the combined organs of each fish (Table 1.11) indicated the presence of Zn®* in the detritus- feeding goat fish and Mn™, Co®’, Co®?, zn®, Ruand Cein the plankton-feeding mullet. . Tridacna clam livers were found to be the most radioactive item throughout the EPG lagoons with a range of activity from 1,000 to 45,000 (y/min)/gm and as high as 107 y/min per whole liver. Co®® was identified as the principal isotope with Co*’, Ru’, zn**, and Mn™ present in the liver and muscle; traces of Ce, Co®*, and Mn™ present in the shell, and Ce’, Ru! Co, Co®, and Zn® in the stomach. The ratio of Co® to Co*’ appeared as a constant 4.2 as of 1 May 1956. Phytoplankton and inorganic particulate matter filtered from the lagoon water, con- tained chiefly Ce! and Ru’ with no detectable amounts of Co" or Zn®. The fact that water-filtering organisms, such as mullets and tridacna clams, contain large amounts of Co™ and Zn** which are undetectable in the water, indicates that these radioisotopes . Ru nevertheless were probably present in the water either as dissolved or particulate inorganic matter, or as dissolved or particulate organic matter. Possibly the cobalt and zinc isotopes were picked up at an earlier date when the water was first contaminated. The coral, mollusk shelis, and calcareous algae exhibited Ce! and Ru! in varying amounts with cerium predominating in the coral and shells and ruthenium predominating in the algae. Bottom organisms such as the beche-de-mer (sea cucumber), finger snail, spiny lobster, sea urchin, and foraminifera exhibited varying amounts of Ce™ and Ru!with a trace of Zn* present in the forams. 1.6.5 Deep Sea Sediments. Coring and dredging results clearly indicated the presence of a considerable amount of radioactive contamination on the sea floor in an arc extending northwest to northeast of Bikini. This coincided to a large extent with the and ual Operation Castle fallout pattern; in addition, the Bikini eddy may have permitted the water to remain in approximately the same areauntil the additional settling of particulate matter occurred. Figure 1.5 gives the gammaactivity per gram of sediment at seventeen stations throughout the EPG. The most active sample, C-10A, obtained from 1,460 meters depth at Station 29 northwest of Bikini Atoll emitted 2,450 (y/min)/gm of dry weight. An analysis of C-10A gave 1,910 uuce Ce’, 1,180 upc Ru, 60 pyc Zn®, and 70 pyc sp'?5 per gram of fine coral sand and foraminifera as shown in Table 1.13. 27