and the fallout was directed northward, intercepting the anchored lagoon stations and ihe northern islands. The close-in fallout pattern is illustrated by the data pvints and estimated contours in Figure 3.7. Since the yield of the detonation was valy 130 kt, this pattern represents a large fraction of the total fallout. One gamma-rate record was obtained from Site bog, indicating a decay exponent of residual radiation between 1.1 and 1.25. The fallout arrived at about H + 2) miautes, and a maximum exposurerate of 23 r/hr was observed at H + 40 minutes. The integrated exposure till H + 15 hours was 51 r. 3.3.5 Shot 4. Most of the Bikini Atoll stations did not receive appreciable fallout during Shot4. The shot location and the winds localized the radiation levels of military significance to the northeastern portion of the atoll. Wand readings and ¢ .ntours derived from sample counting and Rad-Safe surveys are illustrated in Figure 3.3 for the atoll area only. A gamma-rate record from Site George, about three mile; from ground zero, indicated] a time of arrival of 20 minutes, a peak exposure rate of $70 r/hr at i + 40 minutes, and a decay exponent of 1.4. 3.3.6 Shot 5. The only close-in data available for Shot 5 are from Rad-Safe surveys. The extensive downwind fallout pattern was documentedfor ine first time by a combined water-surface survey, aerial survey, and water-sampiing operation. The results of these surveys are represented in the contours of Figure 3.9, in which the dashed contours near the atoll have been drawn by interpolating between the survey results and the RadSafe data. 3.3.7 Shot 6. The pattern on the northern end cf Eniwetck Atoll was documented by counting fallout samples frm land and raft stations, and by Rad-Saie surveys on land. The aerial survey operated north of the atoll to determine contours, and two tugs gathered water samples throughout the fallout area. Analysis of the water samples, combined with an estimate of the depth of mixing, served to determine the !and-equivalent exposure rate at a numberof points; the aerial survey served to fill in the contours. The results are illustrated in Figure 3.10. 3.4 PHYSICAL AND CHEMICAL CHARACTERISTICS CF FALLOUT Samples from the land-surface Shots 1 and 3 generally contained both solid and liquid components, although the liquid could have been due in part to rain and ncean spray. The solid component consisted mostly of white, opaque, irregularly shaped particles. The water-surface Shots 2, 4, and 6 produced predominantly liquid fallout, with some solid particulate observed after Shot 6. An appreciable part of the activity from water-surface bursts was probably in the form of an aerosol, which produced high activity levels on identification flags of the floating stations after Shot 2. The particle-size distribution of solid fallout during Shot 1 at Bikini Atoll and at the distant atolls is summarized in the form of integral distribut(ons on a log-probit plot in Figure 3.11. The data appear to fit long-normal] distributions with different mean sizes and standard deviations for the different downwind distances. Between 92 and 98 percent of the activity from land-surface—burst fallout was associated with solid material, but only 25 to 40 percent of the activity from the barge shots was not in solution. The pH of the land-surface—burst fallout was between 9.0 and 12.3, 48