Location located nbsp km to the
The distribution of Pu, 241Am, and 137Cs contamination as a function of distance from the SDA was investigated by analyzing soil samples collected between the northeastern corner of the SDA and location 10-1 (Fig. 1). As shown in Table 1, 238Pu, 239+240Pu and 241Pu concentrations are observed to decrease by roughly an order of magnitude as the distance from the SDA increases from the first set of locations (1-4 and 1-5) to the last pair of locations (3-3 and 3-4, located 400–600 m from the SDA), with concentrations approaching those of global + regional nuclear weapons fallout at location 10-1 (2.5 km from SDA). Additionally, as shown in Table 2, the 240Pu/239Pu BYL-719 ratios are observed to be very low within ∼250 m of the SDA (0.0587–0.0696 at locations 1-4, 1-5, 2-3, and 2-4), slightly higher at 400–600 m (0.073–0.082, locations 3-3 and 3-4), and finally converge to fallout values by location 10-1. In the case of 137Cs/239+240Pu activity ratios, values are observed to be very low at the northeastern SDA corner and gradually increase with increasing distance to approach fallout values by location 10-1. These data indicate an enrichment of relatively low isotopic Pu in soils in the near field of the SDA, with contamination patterns suggesting Pu of an SDA origin as previously suggested by Markham et al. (Markham et al., 1978). It is important to point out monocots while locations 1-4 and 1-5 represent highly disturbed soils collected in a drainage basin between the perimeter of the SDA and the flood dike, Markham reported that other samples were taken from undisturbed locations (Markham et al., 1978).