ESTIMATED INVENTORY OF PLUTONIUM AND URANIUM RADIONUCLIDES FOR VEGETATION IN AGED FALLOUT AREAS E. M. Romney, A. Wallace, and Jean Kinnear UCLA, Laboratory of Nuclear Medicine and Radiation Biology and R. O. Gilbert Battelle Pacific Northwest Laboratories ABSTRACT This interim report is third in a series reporting data pertinent to the contamination of vegetation by plutonium and other radionuclides in aged fallout areas on the Nevada Test Site (NTS) and the Tonopah Test Range (TTR). The standing biomass of vegetation estimated by nondestructive dimensional methods varied from about 200 to 600 g/m? for the different fallout areas. Estimated 239°240py inventories (in millicuries) for vegetation of sites located at NTS were 0.47 for Area 5 (GMX); 0.098, 2.2, 3.8, and 6.7 for Area ll, Sites A, B, C, and D, respectively; and 28.2 for Area 13 (Project 57). The inventory estimates for sites at TTR were 0.39, 0.54, 2.6, and 5.7 for DT, CS1, CS2, and CS3, respectively. Estimated standard errors for these inventory estimates are given in this report. Comparisons of soil and vegetation inven- tory estimates indicate that the standing vegetation contributes an insignifi- cant portion of the total amount of 239°240py present in these aged fallout areas. The amounts of plutonium available for vegetation-transport to animals grazing on-site would appear to be relatively small in comparison to the total amounts deposited upon soil. Findings indicate that most of the contaminant found on vegetation probably is attributable to resuspendable materials. For those sites presently under investigation, the contamination level on vegetation amounts, in almost all cases, to less than one-thousandth of that which is present on soil. It is important to recognize that the standing vegetation of these aged fallout areas acts as a windbreak and probably reduces the amount of contaminant that otherwise would move by resuspension should these fallout areas ever become denuded. ‘ Inventory estimates of total uranium for vegetation varied among the different fallout areas from about three grams for Site A in Area 11 to more than 200 grams for the large (4.7 x 10© m2) ABCD region in Area 11. Too few samples have been analyzed to ascertain the significance of the uranium results and their relationship to original fallout depositions and natural background levels at this point in time. 35