For comparison, during the Pact year and a halt, air samples obtained from
Johnston Atoll and analyzed hy USAT/MCL with techniques the same as used for
the Enewetak samples, save uv yoni eiwe result on only one cecasion. The posi-~
tive sample measured 0.057 ici fi wiile all ether samples were typically less
than about .005 fCi/m’. the upvind inewetak samples indicate some Pu is pre~
sent in the atr, but tha coscentretions are not much greater than fallout Pu
background iu wcound-level, aiv at come locations in the CONUS. It will be interesting to learn whether the hi¢her down-wind levels correlate with vehtcular
operations or are the result of “natural" wind resuspension.
3. The concentration of resuspended Pa at sanpling locations is below permissible Limits. According to 10 CPn 20, individuals in a restricted area may
not bg exposed to airborne Tu at aa wWwerage concentration greater than 2000
{Ci/m? while the limits set for unrestricted areas are 60 fCi/m’. If, how-
ever, the Pu is resuspended by velteles, then higher levels may exist near
the vehicles than near the efr sample locations. As stated itn NUREG-0041,
Manual.ofRespiratoryProteerton, "Potential errors of 2- to 30-fold have
been measured between parsmmal aad @ixed atv swaplers; the fixed samplers
tend to read lower." Additionally, a study performed at the Savannah River
Fiant of resuspension caused by a tractor operating in an agricultural experiment, found Pu concentrations were a factor of 5 lower at 30m downwind
of the tractor, but a factor of 4 higher at 8m downwind of the tractor.
4&. Downwind locations on both Enjebi. and Lojwa indicate Pu concentrations in 3
air much preater than found by the AEC Survey tn 1972 for Enjebt (0.006 fCi/m
and less) and comparablg to whet was tound on Yvonne near the Fig/Quince ground
zero (1.8 and 2.6 €Ci/m3 ). The differences could be caused by sampler location,
mechanical activities associated wlth the aggregate operation, or because of
differing weather conditions which prevailed during the two measurement periods,
5. The air sample data can be used to determine resuspension factors. Assuming the average Pu concentration for Enjebi is 15.4 pCi/g (based on AEC Survey date) for the top 15 em of scil, with a proportionate amount in the top
1 em, and a soil density of 1.5 ¢ em? , then the “surface” concentration is
0. 23 uci /m* » (One ca depth is recommended by EPA in their draft guidelines for
use as a resuspension depth.) For ap assumed average concentration of 2.2 pCifg
for Lojwa, the surface concentration is 023 uCi/m+. With these surface concen~
trations and the down-wind Fu concentrations, resuspension factors are as
follows:
Mnfebi 22 Apr
26 Apr
« 1.3 x 10~oart
G.7 x 10° “m
28 Any
1.9 x L978qo
29 Apr
6.6 x log,7+
30 Apr
20 Apt
21
0.7 x i078aT}
g.6 x 108,
ApY
“0.8
Priobt Rearh 31
Any
3 May
x
107 rm
Ao 978,71
bx oem