vegetation was not collected, concentration in soil the relative difference at an island will in radionuclide ~ reflect the relative difference expected in the radionuclide concentrations in vegetation from that island. Concentrations of radionuclides in vegetation may depend on radionuclides’ distribution with depth in the soil column. trying to evaluate this dependence. the ~ We are currently The low uptake of 90sr, the very low uptake of trgnsuranic radionuclides by plants, and the general binding of these radionuclides, especially 99Sr, by the soil matrix, makes them less mobile than !37cs. Thus, once Sr, Pu, and Am are mixed to a depth of 40 cm, as has happened at both Bikini and Eneu Islands to varying degrees, the redistribution to the surface and also down the soi? column is a much slower process than is the case for '3/cs. The 13/Cs is distributed in a more exponential] manner on Eneu Island because of the biological availability of '37Cs in coral soil and, thus, its uptake by plants. Because of its mobility in the Atoll ecosystem, '37cs is brought to the surface by the process of uptake into redistributed plants down and subsequent the soil litter fall column by rainfall and is subsequently and other environmental processes. CONCENTRATION RATIO Almost all plants at the Atoll take up !37cs from the soil. The Atoll soils are, in general, low in available K; thus, !37Cs is readily accumulated in the plants as an analog for needed K. Most of the plants concentrate !3/Cs at a level proportional to the concentration of !3’Cs in the soil. This accumulation of !37Cs has been represented in terms of a concentration ratio, C.R. This ratio is almost always greater than 1 for !3’cCs, as is shown in Table 32. Most of the edible foods have C.R.s greater than 2 for !37Cs. However, the C.R. for 90Sr is almost always less than 0.01, and for 239+240py and 24lam less than 0.0001, indicating a discrimiration against these radionuclides in the edible portion of food crops. The source of 90s¢, 239+240py, and 241am in food crops is definitely root absorption. All of the edible portion of the food crops that we evaluate at the Atoll are covered by at least one, if mot several, layers of thick, protective skin or husks; when these layers are peeled away, there is very little chance that resuspended material is included in the sample. a In addition, our resuspension studiesat 66