-6- TABLE 1. Variation of Na and Mg aerosols and sea spray with distance from the waterline (impingers, effectively at a 2 m height). Distance (m) Mg (U9 m-3) (pgN;-3) c Calculated Sea Spray (P9 m-3) . ~c 3 56.2’ ~ “ - 6.17 175 26 13.3 1.45 41 52 10.5 1.21 35 - 102 10.4 1.30 34 10.5 1.26 34 Background (HV) .. -. as well, but it occurred in a surprisingly short range compared to sea spray aerosols measured by other investigators (2,5,6). The rapid drop-off of sea spray from the shoreline is thought to be due to the presence of a massive vegetative barrier along the shore and we expect that the horizontal flux is already reduced at the shore because the sea spray is mostly generated at the surf line on the coral reef nearly a kilometer upwind from the beach. The HV measurements show that the background sea spray aerosol calculated from Na and Mg concentrations was remarkably uniform throughout the remainder of the island (X= 34ug m-3, S= 8.7, n= 27). The HV results are summarized in Table 2. Background is here defined as the aerosol concentrations at the 1.1 m height over surfaces which are relatively stabilized and under normal wind conditions. After a week, even the bare soil tended to reach the same average level of dust aerosol concentrations (21 ug m-3) as the coconut grove (Table 2). An analysis of the personal dosimeter data (discussed later) showed that about 10% of the 239+240PU concentration (aCi/m3) was a background dust aerosol was organic. factor of 258/60 = 4.3 greater over bare soil than in the coconut grove. (Soil activity was 15.3 and 8.01 pCi/g respectively, which is not significantly different within the normal variation encountered. ) If we examine the vertical fluxes of plutonium (aCi m-2 s-l), the ratio of fluxes from the two sites will be proportional to the ratio of their wind friction velocities, u*, where: u* = CD u~ $ . - .* [1] and CD is a drag coefficient equal to 0.106 in the coconut grove and 0.077 in the bare field as determined by our wind profile measurements and U1 is the wind speed at the 1 m height, which was 4.1 x greater for the bare field than the coconut grove. By Equation..l,.the.-rati,oof frjction velocities .is 3 x greater -in-~he .bare..field-.thanin the coconut grove. ~he..rat.i.o--of_”ther.r plutonium fluxes .is..alsoproportional to.the..ratio of. theib concentrations; _lIeo,cfLs_.t!3e plutoniu-~. flux is._tif-acto.r’_ol.-!$~.3_x_.3_=...12.9 greater in the stabilized bare field tlian”-fn —-—,------ . . . L