(Vou. $1 fallout tends (Alexander ies of fallout ints, but the et al, 1962) » plants such d0ssibility is of cultivated s for uptake ve array of L959, Menzel 2mieal propost of these he soil solumetabolism iseuss all of vailability is 1964} Ss @ percent to 0.06%.’’ percentage as reported may be reare 0.025% and Ce-144 ants. Sub- of develop- bsorbed by lows: Sr-89 shita et al. 3 days, 28 311 The distribution of mixed fission product activity in the above ground parts of plants grown on fallout contaminated soils is also relatively eonsistent. The concentration of activity is generally greater in leaves than in stems and much greater in stems in either fruits or seeds (Nishita et al. 1960). The uptake of fission products from cultivated soils can be modified by the addition of fertilizers, organic matter, ete.; but aecording to Menzel (1959), ‘‘The effects of amendments on availability of Sr-90 in the soil are rather small, Additions of lime, gypsum, fertilizers, or organic matter in practical doses usually reduces uptake by less than half. ... The optimum use of soil amendments for maximum crop production mayoften coineide with their optimum use for the reduction of Sr-90 uptake. Amendments mayhave larger effects on the availability of other fission products such as Ru-106, Cs-137, and Ce-144, but these fission produets are normallyless of a hazard than Sr-90.’’ Table 9. Sr-90 in the bones of jack rabbits living in an area contaminated* by fallout (ca. 100 mi. from Ground Zero). Date of Collections Sept. ive material ibly in relathe physical d species of studies conm a@ variety (1960) re- WARTIN : RADIOECOLOGY AND STUDY OF ENVIRONMENTAL RADIATION Sept. 3, 1957 5, 1957 Sept. 9, 1957 Sept. 13, 1957 Sr Units** in Bone Date of Colleetion 20.7*** July 1958 26.8 25.0 May 1960 May 1961 22,7 Aug. 1959 Sr Units in Bone 19.4 20.0 19.3 < 10.0 * Fallout oecurred on Aug. 31, 1957. **=2.2 d/m Sr90/g Ca. *** Precontamination level was ca. 20 Sr units. After: Neel & Larson (1961). 3. Animals. Studies made during the Upshot/Knothole, Teapot, and Plumbbob Test Series (Lindberg et al. 1954, 1959, Larson et al. 196?) have provided a considerable amount of data concerning the biological availability and accumulation of Sr-90 by small mammals living in areas contaminated by fallout from the Nevada Test Site. The significant results of these studies have been summarized by Neel and Larson (1961) and by Larson et al. (1960, 1962). Table 9 provides data which illustrate the accumulation and persistence of Sr-90 in the bones of jack rabbits (Lepus caltfornicus) living in a fallout contaminated environment. The bones of animals collected in this area prior to its contamination by fallout on August 31, 1957 contained Sr-90 equiva- lent to an average of 20.6 Sr Units (Sr Unit = 2.2 d/m Sr-90/.g Ca}, and the Sr-90 level in soil was about 65 me/mi’. The maximum level of Sr-90 in the bones of jack rabbits (26.8 Sr Units) occurred about 10 days after fallout, and a comparable level (19.3 Sr Units) was maintained for about 3 years. Soil samples collected in 1958 and 1959