-16- TABLE 5. Radioactive isotope ratios in soil and aerosols at a stabilized bare field on Bikini Island 238PU Soil FSD* Aerosols (HV) . FSD* *Fractional 241AM 137CS 90cjp 239+240pu 239+24Cpu 239+240pu 0.0013 0.556 9.80 9.15 0.56 0.55 0.48 0.52 0.050 0.439 0.64 0.34 Standard Deviations 61.4 23g+240Pu 12.8 0.51 0.32 [ 239+240pu (pCi g-l) 15.3 0.57 * > 12.6 0.35 (s/~) view volume about 5 cm depth and the exponential decrease of isotope concentration with depth gives lower mean values. After correction by a factor 1.44, the ISG method was the primary method for mapping 2u1Am as a tracer for the source of suspended plutonium isotopes. The horizontal variations in soil isotope concentrations (ISG data) were small enough so that one could justify mean values as local regional values for soil. For example, on the one-hectare, bare field, it was determined that plutonium in surface soil had the mean value 15.3 pCi g-l with an observed range of 2.3 to 28, and a fractional standard deviation (s/X) of 0.57. There was no apparent pattern to the soil concentrations and they exhibit approximately normal, random variation perhaps due to previous tilling and (The data did not fit a log-normal distribution any better. ) blading locally. ,-., .( ... In the context of this surface soil contamination, personal dosimeters (PD) provided information about inhalation exposure of individuals relative to the It was found that the fraction of dust in the total reference HV monitors. aerosol collected by the PD was greatest for workers exposed during heavy tilling but was also high for workers exposed in and around houses (Table 6) partly because of-a lowered fraction of sea spray in both cases. In this and prior studies, we found that the ratio of PD Dust/HV Dust has a value of approximately 0.5 where both PD and HV are sampling the same aerosol cloud of this size particles (2.5 urn MAD) because of the cyclone particle-discriminator on the PD. Therefore, the enhancement of inhalation exposure by a worker’s own actions where the PD and HV are ~ sampling the same cloud can be estimated by a personal —-----,cIo~jrne~&ra-e-nha ncement. (PDE): PDE = 2x (PD Dust/HV Dust) . [4] Values so computed show significant enhancement (PDE) of inhalation exposure (2.64) during heavy work outdoors by persons) sitting or kneeling while digging or using tools on the ground (Table 6). The second highest enhancement (1.86) came from persons with duties in and arou,nd the houses. Other work, including . .. :., c. ., ..