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SUMMARY
AND CONCLUSIONS
(
Mass loading (all aerosols) on a HV filter was 55 ~g m-3 on Bikini Island
over stabilized and vegetated surfaces (e.g., in a bare field following rain and
in a coconut grove). This compares to 56 pg m ‘3 measured at a vegetated site
on Engebi Island of Enewetak Atoll in February 1977, and a 42 vg m-3 weekly
average for 10 weeks in a coconut grove on Eneu Island of Bikini Atoll May-August,
1978. (Wind speeds were comparable, 4-5 m s-], in all cases.) The more detailed
studies at Bikini revealed that 34 ug m-3 of the mass loading was salt from sea
spray, and that this sea spray contribution remained constant across Bikini
Island beyond 20-50 m from the windward beach.
,,
,.
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The “background” concentrations of aerosol plutonium on Bikini are
~omparable to those on Engebi Island, Enewetak, when one considers the surface
soil plutonium activity (Table 8). And, by assuming that Engebi Island had
the same aerosol sea spray background (34 ug m-3) as Bikini (which has not been
verified by actual measurement) we found that the enhancement factors agree
,, reasonably well.
The normal enhancement factor is 0.56, if one assumes that
values less than one (Table 8) represent normal variations about the mean of
0.56. Apparently, the process of resuspension is preferentially selective to
non-contaminated particles on these atolls to the extent that an aerosol
plutonium dilution of 1.8:1 normally occurs.
TABLE 8.
Location
Plutonium Aerosol Concentrations
(Winds 4-5 m s-l).
Surface
Description
Bikini
Coconut Grove
Bikini
Stabilized Bare Soil
Engebi
on Bikini and Enewetak Atolls Ccmpared
Plutonium
Aerosol
Concentration
(aCi m-3)
‘Vegetated Field
60
(
Surface Soil
Plutonium
Activity
.(pCi q-l)
Estimated
Enhancement
Factor*
8.01
0.41
264
15.3
0.82
240
24.2
0.45
15.3
3.10
Unusual Conditions
Bikini
Field, freshly tilled
6466
Engebi
Garc!en, freshly tilled
7420
24.2
4.41
Engebi
Garden, 1 wk after tilled 3060
24.2
2.55
Bikini
Road with traffic
421
Engebi
Downwind of road
1090
4.10
,’
35.2
;
2.50
0.56
*Calculated by assuming 34 pg m-s sea spray which has been verified by
measurement on Bikini.
.
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