To date no information has been found on *“)am distribution in soils from global fallout. However, should be forthcoming, interest in the distribution of 24lam in soils since the importance of Am related to plant uptake and biological hazards has been recognized (Fowler and Essington, 1974). local Fallout 1,6, 16, and 44 km northeast of GZ within the fallout pathway. Plutonium-239,240 at the control site, which represented global fallout, was too low to be detected below the 2.5- to 5.0-cm increment. On the other hand, 239,240n, was found to adepthof about 30 cm at the 44-km station. Figure 2 reproduces four of the profiles reported by Nyhan (1976) and is representative of the high degree of variability in ' Pu distributions with depth. There was no consistent distribution pattern that could be related to obvious physical, chemical, or biological factors. The maximum depth of penetration, however, appeared to be related to the average maximum rain water penetration into the soil. The Trinity event was the first atmospheric nuclear explosion. Plutonium distributions in soils near the Trinity Site, Alamogordo, NM, were reported for samples collected more than 20 years ago by Olafson et al, (1957). A 1972 study on this site was made by Hakonson and Johnson (1974) and Plutonium distributions have been studied in more detail by Nyhan et al. (1976). Olafson (1957) reported measurable downward plutonium movement occurring only where previous surface contamination was high and that the plutonium distribution followed the same trend as that found for fission products. Samples collected in 1948, three years after the event, showed the plutonium localized in the top 2 in. of soil. Hakonson and Johnson (1974) reported 2738/2355 distribution in soil profiles collected near Ground Zero (GZ) and at various distances along the fallout pathway to 56.4 km. Soil profile samples were obtained using a coring method resulting in O- to 2.5-, 2.5- to 7.5-, and 7.5- to 30-cm increments. Positive total plutonium (234 pu plus 239,2405,) levels were found in the 7.5- to 30-cm increments in nearly all the profiles investigated out to 56.4 km? This suggests that some of the plutonium initially deposited 27 years ago had migrated to a depth of 7.5-30 cm in the soil. Except for the GZ profile, the plutonium concentrations in the Q- to 2.5-cm increments generally increased toward the outer end of the sampling transect. This observation is consistent with the fallout zone mapped by Olafson (1957), where the highest plutonium concentrations in soils, vegetation, and small mammals outside the GZ area occurred about 45 km from Gz. The vertical distribution of plutonium was relatively uniform in most of the More distant procore samples between GZ and the 24.1-km station. files reflected a preponderance of plutonium in the surface 2.5 cm simiand Olafson and lar to the original observations of Olafson (1957) Larson (1961). Hakonson and Johnson (1974) suggested that many factors could have accounted for Olafson's observations including differences with distance from GZ in the chemical and physical form of the plutonium and differences in the chemical, physical, and biological make- ire up of the environment. Nyhan (1976) observed that samples collected at greater distances from GZ reflected increased amounts of ?77,?*"pu associated with <100 um- diam. particles. Various factors were noted as possible reasons for the increased 239: ?*%py migration at the 44-km site. This site receives 20% more rainfall than the other sites. Soils in this area con- tain gypsum, which could enhance the displacement of 773'?"%py from soil binding sites due to the high concentration of soluble calcium ions and the enhanced water percolation due to flocculation of soil clays by the calcium ions. Another consideration was soil disturbance by the digging activities of badgers and other ground dwelling small mammals. Atmospheric nuclear explosions also took place at NTS. Unfortunately, there is no record of measured transuranic nuclide distribution in soil profiles for any of those atmospheric nuclear explosions. Two areas where atmospheric nuclear weapons testing has been conducted, and for which the vertical distribution of plutonium and americium has been measured, are the Enewetak and Bikini Atolls. Lynch and Gudiksen (1973) measured 239py (7399.2"%5G) and ?*!'am in the coral soils and sands of Enewetak Atoll. Soil profile samples were collected to total depths of 35 to 195 cm. Concentrations of *°%Pu were reported in all profiles; 24) am analyses were performed on many of the samples, but 7*!am data were not interpreted by the authors. Profile samPles showed a wide range of activity distributions as a function of depth on different parts of the atoll, as shown in Fig. 3. Although meaningful generalizations regarding the 7**pu distribution could not be made, Nervik (1973) commented on several of the groups of profiles observed. On the southern islands of the atoll, construction or other GZ earth moving activities, Nyhan (1976) carried out a soil profile sampling program at Trinity in 1974 and 1975 to determine the maximum depth of 235,240p, penetration and the variability of 779°2*°pu penetration with location. Four sites were chosen: a control site 4.8 km south of GZ and three sites 48 activity levels were usually low throughout the full range of depths sampled; some sampling locations showed *?*pu concentrations decreasing somewhat from the surface through the first 10 or 20 cm of soil (Fig. 3, note trace A). Soil profiles inland on the islands subjected to fallout but not to showed a rapid and fairly steady decrease of 239py levels from the surface to total depth, as shown in Fig. 3, trace B. In contrast, *??Pu profiles from beaches and other. exposed areas showed uniform or slowly decreasing 239bu activity levels from the surface to total depth (Fig. 3, trace C}. Occasionally, distribution patterns showed accumulation of 239puy at 49