~ 8. In addition to these investigations, land and marine biological surveys will be conducted on Eniwetok and Bikini Atolls and in their lagoons. Samples of water, lagoon life, and animal iifeon the atolls will be collected and analyzed for radioactivity. Fallout Monitoring in United States The heavier particles fall out of the radioactive cloud at early times after a detonation, while their radioactivity is still high. Therefore, the highest levels of radioactivity occur over a local area downwind from the point of detonation. The area of significant fallout is expected to ceccur entirely within the uninhabited danger area surrounding the Eniwetok Provine Grounds. As the radioactive cloud is transported away from the point of detonation, it is widely dispersed by air currents and diluted by normal air. Its radioactiv- ity also decreases rapidly because of the normal process of radioactive decay. 2 By the time the cloud from an ZRadioactive fallout consists of a mixture of radioisotopes, with varying half-lives. The mixture as a whole decreases in radioactivity in such a way that for every seven fold increase in age, the total radioactivity is decreased 10-rold. Thus, the radioactivity at seven hours after the explosion is only one-tenth that at one hour, and in 49 hours is one-hundredth, etc. (more)