-21- C During unusual surface conditions, plutonium aerosol activity (normalized well. The corresponding agree 3.10 on Bikini Island. such as immediately after tilling, by enhancement means of the enhancement factor) also factors were 4.41 on Engebi Island and Plutonium resuspension fluxes due to continuous wind erosion and resuspension were estimated for Bikini by a meteorological flux-gradient equation to be a minimum of 0.49 pCi m-z year ‘1 in the coconut grove and 6.3 pCi m-2 year-l over a bare field stabilized by light rain. Since fields do not remain unvegetated for more than a few months, the coconut grove resuspension flux is probably representative of the Island as a whole, even though the wind speeds are one-fourth as high in the coconut grove canopy as in the open. ,, Particle size distributions measured by both optical and cascade impactor methods show that over the rain-stabilized bare field, the total aerosol size distribution is log-normal with median aerodynamic diameter of 2.44 urnand geometric standard deviation of 3.0, but there is no significant size difference between aerosol plutonium activity and aerosol mass concentration, During the unusual condition of tilling, the size distribution significantly shifts from a median aerodynamic diameter of 2.44 urnto about 2.0 wm with a concurrent increase in plutonium enhancement factor from less than one to 3.1 on Bikini (4.4 on Engebi) and an increase in the pulmonary respirable-fraction from O.19 to 0.24. In the case of a soil disturbed by tilling on Bikini, the plutonium concentration increased by a factor of 19.1 due to a 3.23 x increase in enhancement factor and a 5.91 x increase in dust aerosol concentrations. “.,. . ..,:.: .. <. ● ‘. ,, ,. ● /. Vehicular traffic produced dust pulses of nominal 10 s duration in a 4.5 m S-l wind, which were log-normally distributed having time-averaged concentrations above background of 28 vg m-3 less than 50% of the time and 211 ~g m-3 less than 5% of the time. (Peak concentrations were a factor of 3.6 higher. ) The plutonium enhancement factors for vehicular traffic was 2.5. Foot and bicycle traffic produced dust pulses about one-fourth as large as vehicular traffic. Personal dosimetry showed that under various exposure conditions, workers inhaled different fractions of inorganic dust and salt, while the organic fraction remained constant at about 10%. Consequently, a personal dosimeter enhancement factor was defined to express the effect a worker has by stirring up dust in his own immediate environment. As a result, pulmonary deposition of plutonium could be calculated for various exposure conditions as determined by inhalation rate, aerosol dust concentration, plutonium activity in soil, plutonium enhancement factor, personal dosimeter enhancement factor, and the pulmonary respirablefraction. Under the worst case (during tilling), pulmonary deposition was 1476 aCi h-l, and in the best case (light work in a coconut grove), it was 12 aCi h-l. Intermediate cases were for heavy outdoor work (139 aCi h-l) and for light work in and around houses (78 aCi h-]). Walking along a road produced an exposure of 1.58 aCi h-l above background for one vehicular pass per hour. But even with a worst case exposure scenario for 30 years, the lung dose and bone dose Federal Radiation Guidelines. due to inhalation on Bikini are well below present ,. In conclusion, this study has been the most comprehensive to date, in providing the key parameters for inhalation dose assessment of exposure to plutonium . ., ,. c .