-8- grove. the coconut with the equation, In our previous work, we calculated plutonium aerosol flux F=-pku*X C... [2] 1 where p is the exponent of a presumed power-law distribution of Pu with height (negative sign indicating decreasing concentration with height), k is Karman’s constant equal to 0.4, and X1 is the plutonium concentration in the height range fromO.5 to 2.Om (7). The exponent p is the slope of the Pu concentration versus height on a log-log scale. The impinger measurements at the 1 m and 4 m heights along a 60 m wide clearing parallel to the mean wind direction showed a p-value of 0.55 for calcium on Bikini Island which we presume is the major host . of terrestrial Pu contamination. Previous work indicates p values between 0.25 ‘“.. and 0.35 for dust aerosols in !’lesternU.S. (7). Using the local p-value of 0.55 and measured values of u* and the background plutonium concentration, Xl, (60 . aCi m-3) as typical for._the coconut grove we obtain a pl.utoni’umresuspension flux of 1..5.4..aCi m-2 s- ~ ‘“–” (a49 pCi-m-2 year ‘~) which compares to_19.9 aCi m-z””s-l” ‘--”.., ‘—-”–:1) . from .the stabilized bare field.. This discussion of flux (6~cpci.m:~-.war._. “ia-nnotexplain why the dust aerosol concentration is the same at both sites, ,.,. ., I but presumably the mixture of calcareous aerosols, organic matter, and other components of dust are quite different for each site. . Resuspension of Radioactive Particles from a Bare Field on Bikini Island On May 6, 1978, a field was chosen for convenience (adjacent to House No. 36) and bulldozed bare of vegetation without stripping the soil. At the windward end of the 100 m x 200 m field, the array of instruments (10 HV, 2 CIP, and 2 UHV) were set up in a regular grid covering about one hectare. The upwind fetch to During Flay the nearest instrument was 60 m and lateral borders were 30 m wide. 6-8, three HV and two cascade impactors (CIP) were run during the highest resuspension (disturbed) phase immediately after bulldozing, followed by extensive runs with all instruments during the stable phase, May 9-16. Wind speeds and direction remained relatively constant (Table 2). Plutonium aerosol concentration (aCi m-3) vias increased in the period May 6-8 over the period May 9-16, by a factor of 25 to 30 as shown by the HV and CIP data of Table 2. Because the disturbed surface was stabilized by light rain at the end of the run on May 8, the cascade impactor data showed significant differences in the plutonium~activity size distribution asshown on Figure 2 (ordinate dy/d in D in units pCi g‘1 of dust aerosol). The plutonium activity curves of Figure 1 ;4J are calculated log-normal distributions with the median aerodynamic diameters (MAD) and geometric standard deviations (GSD) obtained by fitting cascade impactor data (Table 3). The aerosol size distributions for plutonium activity determined by CIP and the total mass loading (sea spray plus dust) determined by optical particle analyzer were satisfactorily approximated by a log normal distribution with the given GSD values in Table 3. All other MAD values of Table 3 were determined by cascade impactor, but more data would be required to determine if a log normal distribution exists for the other aerosol definitions. Two typical cases of number density (dN/d in D) and volume ’density distributions (dV/d In D) determined by the optical particle analyzer over the stabilized bare soil surface on May 9 and May 11 are shown in Figure 3. It should be not:d that the optical particle analyzer sees 511 liquid and solid aerosols including . L