In the four oceanic surveys made at the Eniwetok Test Site during 1956 and 1958, the ratios of particulate activity to soluble activity in water samples exhibited similar patterns (Fig. 4), with ratios relatively high at the surface, dropping to a minimum value at 25—50 m,and rising again near the thermocline. Only in the 1956 (Walton) surface samples, taken 4—23 days after observed during the Walton survey resulted from a surface land detonation which, at the time of sampling (23 days after detonation), included an area approximately 100 miles in diameter. Another fallout area with much lower activity, observed during the Walton survey, resulted from two devicesfired over water 4 and 6 days before sampling. The contaminated area was approximately 30 miles in diameter. Thefallout material from the surface shot contained large amounts of calcium compounds, whereas the material from the over-water shots was mixed, for the most part, with evaporated salts from sea water and the material surrounding the nuclear device. The radioactivity was not distributed evenly throughout the mixed layer in either contaminated area, and in the areas of high activity from both the surface shot and the over-water detonation the activity in the water tended to be concentrated near the thermocline (Fig. 7a). 500 i. 3 200 | < + oe Pree ae g secre COLLECTED 23 ITA wn SURFACE SHOT eo lh i the relative radioactivity of the water epth sampled. Maximum value at each as 100 o ss5 RANGE OF UPPER EOGE oF THERMOCLINE aad a Pr au Pereee PP Oe D/M ao qn on on an Oo CE ad a an ve) ww in An an wn os nn = o yr “a » r wo oa an wi _ ALINCWICN NYONONCNTy ae contamination, did the particulate fraction contain a greater amount of radioactivity than the soluble fraction. The major part of the radioactivity Le, pee ; fawn AFTER Es 4 aA DEPTH IN OVER -WATER SHOT METERS Fig. 7a Total activity in water from two contaminated areas: one from a surface shot and one from an over-water detonation ae Marshall Islands and as far\west ain 6-—8 weeks after contamination aken during four different surveys vas not uniformly distributed in the ; after contamination and 6 weeks particulate matter to those in the The radioactivity in the water was about six times as high in the area contaminated by the surface detonation as in that contaminated by the over-water shot. The water samples from these two areas were combined into two samples to determine if any differences in distribution of activity with depth was apparent between the two types of fallout. In the area of fallout containing relatively large amounts of calcium compounds, the radioactivity in the water | throughout the depths ‘above the in these two figures are averagesof | trends. The lack of homogeneity ked at individual collection stations Within the upper thermocline the radioactivity was about the same as that at 25 m. The ratio of radioactivity associated with particulate matter to that associated with matter in solution was high at the surface (ratio=1.17), low at 25 m (ratio —0.03), and rose with increasing depth into the thermocline to 1e upper mixed layer (Fig. 4). Also washigh at the surface, low at 25 m, and again high just above the thermocline. a value of 0.39 at 100m (Fig. 7b). 8° 115 ~ AEG + we