transuranics introduced from these source terms is associated with components of the marine environment, components of the benthic environment, more extensive investigations, concentrating on measurement of Because of the high level of deposition the Atoll is now its own transuranic source term, Plutonium, for example, is not permanently The survey was followed by other transuranice to better assess the impact of these radionuclides on the environment and inhabitants of the Atoll and to increase our fixed with the carbonates and other material with which it was understanding of the mobilization, reconcentration, and redistribution originally deposited in the lagoon and reef during nuclear testing. processes from sources within the environment. Small amounts of plutonium are now remobilized, resuspended, This paper contains a summary of data related to the concentrations assimilated, and transferred continuously within the Atoll environment of the transuranium elements in components of by physical, chemical, and biological processes. environment of the Atoll More than half of the United States nuclear tests in the Pacifie were conducted at Fnewetak Atoll. Surface and tower shots left craters lapoon. the benthic and pelagic Data from the survey re part (Ne/4), more recent publications, and unpublished results from this laboratory will be discussed. Some published and unpublished data from our studies and contaminated scrap on land and generated radiouctive debris that was at Bikini Atoll] will be presented when necessary for comparison with redistributed to the adjacent reef and lagoon. Enewe tak data and in the ahsence of Enewetak data, Megaton tests that left for the clarificatior underwater craters and barge shots in the lagoon contributed of characteristics of transuranic radlonuclide concentration. at the significantly to the present transuranic inventory. Atolls. The impact of nuclear testing and the fate of the residual Whenever possible, the Atoll] data will be compared with that from other marine ecosystems, tadioactive materials introduced to the aquatic environment at both Enewetak and Bikini Atolls are the subjects of reports too numerous to list herein. However, not until late 1972 when a radiological resurvey GEOGRAPHY AND ATOLL TEST HISTORY Enewetak Atoll, with U.S.-assigned and native names and several of Enewetak Atoll was conducted to gather data for the development of landmarks including the locations of craters formed by nuclear tests, cleanup and rehabilitation procedures for the resettlement of the shown in Fig. 1, Enewetak people to their homeland did extensive measurements of this report. transuranics in the Atoll environment begin. The information was is U.S.-assigned island names will be used throughout The Atoll consisted of a ring of 42 low islands arranged on a published in the survey report (Ne73), which contains data on most roughly elliptical reef, 40.2 x 32.2 km long-lived residual radionuclides, including plutonium and americium, in in the northwesterly direction, (fm54), with the elonpeted axis Nuclear testing completely destroyed por acer _ wre