ee The plankton, fish, and clams are reported as gammas emitted per minute per gram of wet weight compared to either a Co” or a Zn"* standard. The bottom sediments, sbells, coral, and algae are reported as gammas per minute per gram compared to Ru'™ and Cesources. In all cases the gammasinclude all photons between 0.075 and 1.5 Mev. +t lia wee Ne ek A Tm 6 wn 8 oe teem background has been subtracted from all values. The reported values include the naturally occurring isotopes as well as the artificial contamination. The results of the gamma spectrographic analyses and radiochemical analyses are reported as yuc of the individual isotopes contained per gram of living organ er organism. The sediments are reported as gamma photons emitted per gram of dry matter or as pyc of a specific isotope per gram of dry sediment. All reported values have been extrapolated to 1 May 1956. 1.6 RESULTS AND DISCUSSION 1.6.1 Radioactivity of the Open Ocean Waters. Throughout the EPG area the radioactivity of the sea water was found to be fairly uniform. The surface water varied from 300 y/min from 2 liters; the activity of the suspended particulate and colloidal matter in the 2 liters was 45 y/min or 15 percent. For subsurface water at Station 27, the total activity in 6 liters of water taken as a vertical column from depths between 50 and 1,500 meters was 1,030 y/min from 6 liters, while that of the particulate matter waa only 20 y/min from 6 liters, or 2 percent. Vertical profiles of radioactivity for ten stations are shown in Table 1.3. The radio- activity of the sea water in this table is expressed as total gamma photons (0.075 to 1.5 Mev) emitted per liter of water, standardized against Co® and Zn** calibrated sources. The values reported include the natural K® gamma activity. No positive identification of the radioisotopes present in the sea water was completed. The activity of the water was constant with the exception of one layer of water between 800 and 1,200 meters found northwest of Bikini Atoll at Stations 6, 7, 8, and 29. This mass of water, situ- ated on the edge of a large eddy current found around Bikini, appeared to be two to four times as active as the surface water. The salinity values for Station 29 are listed in Table 1.3. There appeared to be no relationship between the variation in radioactivity with the slight variation that exists in salinity. Radiochemical analysis of gross zooplankton (Table 1.4) showed a hundredfold con- centration of artificial radioactivity over the total radioactivity of the water from which the plankton was taken. The radionuclides detected in the zooplankton were Mn*, zn'5, Co*’, Co®, and a trace of the rare earths.. The probable error of the measurements of surface water activity, excluding the alkali metals, by Fe(OH); precipitation was kept below 20 percent. The radioassay of 150 to 750 mi subsurface samples by evaporation and direct gamma counting of the reSulting salt entailed a probable counting error of 30 to 50 percent and occasionally over 100 percent. 20 ee por eae determine if the activity was present in the upper layers as disscived substances or as particulate matter greater than 0.5 micron diameter. Most of the activity was found to be in the dissolved phase. For example, at Station 14 at the surface, the water emitted te ter. Surface water at severa) stations was filtered through a miilipore filter in order to ee tre 6 tein. ~mnpeninantitilly qytindnmo aly mi a on Te AN OE Ever oo vile | OR te eele 100 (y/min)/liter in the eastern area to 400 (y/min)/liter west of Bikini Atoll, or from one to five times the natura] potassium gammabackground of 74 (y/min)/liter of sea wa-