Contract Number (DOE): W-7405-ENG-48 Document Type: Report Language: English Journal Announcement: EDB7809 Availability: Dep. NTIS, PC A02/MF A0Ql. Subfile: NTS (NTIS); ERA (Energy Research Abstracts); INS (US Atomindex input); TIC (Technical Information Center). ‘ Country of Origin: United States Country of Publication: United States _ Abstract: As part of the Lawrence Livermore Laboratory Enewetak Radioecology Research Program, we studied radionuclide cycling from soil to plant to soil on Engebi Island at the Enewetak Atoll. Mature and dying leaves, young and old litter, humus, and soil beneath these organic strata were collected from 1975-76 at three Engebi sites. To study radionuclide depth distributions, five trenches of > 1m were dug é and sampled. From three representative sites, we found that /sup 137/Cs rapidly cycles from the plant biomass through the litter and humus into the vegetation. Continuously deposited litter decomposes within 6 to 12 months, but the constituent radionuclides are released early during physical decomposition. Soil radionuclides generally occur in the upper 40 cm of the soil profile, strongly associated with the organic horizon. Radionuclides such as /sup 60/Co, /sup 152 -155/Eu, /sup 207/Bi, and /sup 241/Am are complexed in the finely divided organic matter or humus where /sup 137/Cs and /sup 40/K predominate. Our data suggest that there is a circulating pool of rapidly cycling /sup 137/Cs in the Engebi ecosystem that may be entirely associated with the plant biomass and organic strata of the soil. Soilbound radionuclides below the humus are low in concentration and may not enter into this pool because they are below the vegetation root zone, where they may be leached by rainwater. This information is needed in making realistic long-term radionuclide dose assessments for the Enewetak peoples.; Major Descriptors: *AMERICIUM 241 -- DIFFUSION; *AMERICIUM 241 -- RADIOECOLOGICAL CONCENTRATION; *ANTIMONY 125 -- DIFFUSION; *ANTIMONY 125 -- RADIOECOLOGICAL CONCENTRATION; *BISMUTH 207 -- DIFFUSION; *BISMUTH 207 -- RADIOECOLOGICAL CONCENTRATION; *CESIUM 137 -- DIFFUSION *CESIUM 137 -- RADIOECOLOGICAL CONCENTRATION; *COBALT 60 -- DIFFUSION *COBALT 60 -- RADIOECOLOGICAL CONCENTRATION; *ENIWETOK -RADIOECOLOGY; *ENIWETOK -- RADIONUCLIDE KINETICS; *ENIWETOK -RADIONUCLIDE MIGRATION; *EUROPIUM 152 -- DIFFUSION; *EUROPIUM 152 -RADIOCECOLOGICAL CONCENTRATION; *EUROPIUM 155 -- DIFFUSION; *EUROPIUM 155 -- RADIOECOLOGICAL CONCENTRATION; *HUMUS -- RADIONUCLIDE MIGRATION; *PLANTS -- RADIONUCLIDE KINETICS; *POTASSIUM 40 -- DIFFUSION; *POTASSIUM 40 -- RADIOECOLOGICAL CONCENTRATION; *SOILS -- RADIONUCLIDE MIGRATION Descriptors: FOREST LITTER Broader Terms: ACTINIDE ISOTOPES; ACTINIDE NUCLEI; ALKALI METAL ISOTOPES; ALPHA DECAY RADIOISOTOPES; AMERICIUM ISOTOPES; ANTIMONY ISOTOPES; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BETA-PLUS DECAY RADIOISOTOPES; BIOLOGICAL MATERIALS; BIOMASS; BISMUTH ISOTOPES; CESIUM ISOTOPES; COBALT ISOTOPES; ECOLOGICAL CONCENTRATION; ECOLOGY; ELECTRON CAPTURE RADIOISOTOPES; ENERGY SOURCES; ENVIRONMENTAL TRANSPORT; EUROPIUM ISOTOPES; HEAVY NUCLEI; HOURS LIVING RADIOISOTOPES; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; ISLANDS; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; LIGHT NUCLEI; MARSHALL ISLANDS; MASS TRANSFER; MINUTES LIVING RADIOISOTOPES; NUCLEI; ODD-EVEN NUCLEI; Js ODD-ODD NUCLEI; POTASSIUM ISOTOPES; RADIOISOTOPES; RARE EARTH ISOTOPES; tr5 RARE EARTH NUCLEI; RENEWABLE ENERGY SOURCES; YEARS LIVING RADIOISOTOPES<> Subject Categories: 510300* -- Environment, Materials Monitoring & Transport 560173 -- -- Terrestrial -- Radioactive (-1989) cc -- Radiation Effects -- Nuclide Kinetics & Toxicology -- Plantsc (-1987) INIS Subject Categories: B31* -- Land C21 -- Tissue Distribution, Metabolism, Radionuclides 10/5/950 ot (Item 650 from file: 103) i> Toxicology & Removal of