- 54- * phan 1.651 mm, 0,589 - 1.651 mm, 0. 147 - 0.589 mm, 0.074 - 0.147 mm, “and less than 0,074 mm. In the Enibuk low tide-line samples the two amall- er particle size fractions did not account for more than 0.3 percent of any of the increments. Although there was a tendency for a smaller average particle size with tncreased depth of water in the lagoon there was no detectable change of pattern regarding particle size in the increments of individual profiles, The smaller particles tend to have higher specific radioactivities than do the larger particles (Fig. 14B), and the percentof total activity contributed by the smaller particle size groups tends to increase with increase in depth within the soil profile (Fig. 14C) down to 6 or 8 inches. Radiostrontium analyses were made onthe top inch and the seventh inch of the lagoon bottom profile taken under 6 feet of water off Kabelle. In both samples Sr?° accounted for 0.7 percent of the activity (maximum and mini- mum in 4 samples: 0,64 % and 0.78 %). | The sand profile in 49 feet of water off Rongelap Island had the lowest _levelof radioactivity of the lagoon bottom profiles taken in October 1955. i ‘The average radioactivity level for the top 8 inches of sand in this sample Was 0.19 wc/kg. Using this value as the average of the radioactive contamination on the bottom of Rongelap lagoon and a Sr®9 content of 0.7 percent, a total of 380 curies of sr?? for the top 8 inches of lagoon bottom is obtained. This is probably a minimum value. INTV. Ob