762
MARTIN
post to facilitate its relocation and positive identification. Plant samples were collected by clipping twigs and foliage from the crowns of
desert shrubs growing within a radius of 150 ft from each station
marker. Artemisia tridentata (sagebrush) was the species collected at
all stations in Groom Valley and the Currant Area, and Atriplex confertifolia (shadscale) was collected at all but three of the stations in
Penoyer and Railroad valleys. Most of the rabbits representing a given
location were shot within a few hundred yards of a station marker, but
rabbits taken within a 1-mile radius were accepted as representatives
of the general location. Most of the rabbits collected were blacktailed
jackrabbits (Lepus californicus), but a fewcottontail rabbits (Sy/vilagus
auduboni) were taken in mountainous areas where jackrabbits were not
always available.
Radiochemical analyses were made to determine the ™Sr and 1
contents of plant samples, the *Sr content of rabbit bone ash, and the
1317 content of rabbit thyroids. The stomach contents of rabbits were
analyzed for ‘I, but the samples remaining after aliquots were re-
moved for this purpose were too small to be used in making analyses
for ®sr. Following each determination, a decay correction was made to
indicate the Sr or '4] concentration at the time the sample was col-
lected. The procedures followed in making these analyses are described elsewhere !!’!%-” in considerable detail.
For simplicity, the only samples considered inthis paper are those
collected at the 20 representative locations indicated in Fig. 2. Addi-
tional data are given in other publications.'?:'® Estimates of the initial
gamma dose rates (Ry) = mr/hr at 3 ft aboveground at H + 24) were obtained from a tracing of Guillou’s”’ original large-scale map prepared
from aerial surveys made before and after the detonation.
Correlation and regression analyses were made to examine the
relation between initial gamma dose rates, Ry, and initial concentra-
ations of ®Sr or '5!I on plants, Py; between P, and maximum concentrations of ™Sr in rabbit bone ash, Bg; and between P, and maximum
concentrations of '"I in rabbit thyroids, A;. Similar analyses were also
made to determine the relations between S,) and Ry, As, and Sy, where Sp
represents the initial concentration of '°'I in rabbit-stomach contents.
Estimates of ®sr and ‘I retention by plants in relation to theo-
f,=
P |»
retical deposition rates, different parts of the fallout field, and different plant species were based on Eq. 1:
(1)
where f, = retention index of N, deposited on plants, sq ft/g [N.B. This
index multiplied by G = (dry weight) of plants per square
foot would give the fraction of N, deposited on plants |
a, = pe Ni/g (dry)/Ry deposited on plants