levels present (compare with soil data in Table 2). Additional work is under way to determine the extent to which this finding is related to physical and chemical differences in source material and to edaphic characteristics. The activity levels for these radionuclides in fruit pods were from one-tenth to one-hundredth of the levels found in the forage tissue. The CR values for Pu in soybean leaf and stem tissues ranged from 10-" to 10-3, and the fruit pod values ranged from 107© to 10°*. Fox Am, the CR values ranged from 1073 to 107! for leaf and stem tissue and 10° to 107% for fruit pods. It should be understood that the CR vaiue is a ratio of the vegetation to soil activity level which expresses the relative uptake of a radionuclide through the plant root system. It should not be misconstrued to be an index representing contamination hazards even though it may give an indication, for a given contamination condition, of the relative proportion of that contaminant which might be expected to be incorporated in vegetation through the plant root system. We believe that »rerhaps the most important finding from these experiments pertains to the greater uptake of 24 1am through plant roots in proportion to the uptake of 2385 240p, demonstrated by these experiments. The magnitude of this differential uptake can be ascertained by comparing the Pu/Am ratios for vegetation (Tables 3, 4, and 5) with the Pu/Am ratios for the soils on which the plants were grown (Tables 1 and 2). In spite of the erratic data for barley (Table 3), the Pu/Am ratios for plant tissues were, in many cases, much less than the average Pu/Am ratio of 6.74 for Area 13 soil. Data for alfalfa (Table 4) conclusively showed greater uptake of 24lam over 239°240py uptake by a factor of at least ten for the unamended soil. In those cases where the acidulation amendment had markedly enhanced 239°240py uptake, this effect was still around a factor of 5. Even higher factors indicating preferential uptake of 24!am through roots are evident from the soybean data in Table 5. We believe that this differential uptake characteristic for Am probably contributes to the slightly lower Pu/Am ratios often encountered for vegetation samples collected in the aged fallout areas (Romney et al., 1974, 1975) compared to Pu/Am ratios for the soils. The impact of this finding for 24lam uptake assumes greater importance when coupled with the fact that this radionuclide is an ingrowth product of the source material in the aged fallout areas (Fowler and Essington, 1974). About 50 years of time still must elapse before the ingrowth of this radionuclide will peak out. It appears, therefore, that potential problems from Am are equally as important, if not of greater concern, as the aged plutonium source material in these fallout areas. FUTURE PLANS As the result of experimental findings, work on the soil amendments has been discontinued, except for chelating agents. The acidulation effects of sulfur have no practical value other than to raise the question of whether or not these transuranic radionuclides might be more available to plants in the event of future contamination problems at sites involving acidic soils. 62