j place after the first 1 or 2 years after deposition®’”. Since in 1967 the soil samples indicate most of the activity is still in the first inch of soil we can probably discount weathering aS an important factor in lowering the exposure rates on Bikini Island. The levels on Nam and on some of the other larger complexes, where Sco and other relatively short-lived isotopes are the major contributors, although at present in general higher on the average than Bikini Island, will decrease more rapidly and in a few €°Go half- | lives will probably exhibit levels generally much lower than Bikini Island. Since the scil on some of these islands contain very little organic material, weathering may result in an even more rapid decrease in exposure rates. Thus, the! levels on Bikini Island itself are likely to be the limiting! factor in assessing the long term hazards to any future population living cn the atoll and centered on Bikini Island.: i The consistency of the various pcertable detector, | | | \ ionization chamber, TLD, ard spectrometer results indicate we have obtained a reliable and comprehensive picture of the external gamma radiaticn environment or the atoll. The soil Sample results, although nct as ccnsistent with the other data as could be desired due to the problems of obtaining representative samples in a very irhonogenecus distribution, do nevertheless substantiate the fieid spectrometric predictions as tc the relative impcrtance of various emitters in the soil. The importance of the f_eid spectrometric measurements in expanding and increasing the information of the survey meter readings again illustrates the utility of such a system in undertaking an environmental radiation survey. Comparabie data on the compcsition of the radiation field could only have been cbhtained by analyzing hundreds of carefully obtained soil samples. if at all. The data in this report shculd form a solid basis for estimating external dose to a ret arning popyvlation as a function of time after return. assuming with the aid of the survey team's anthropologist various realistic models for their living conditions, abits. areas of habitation, and daily Department of Energy yistorian’s Office ARCHIVES ~ 42 -