SAMPLE HETEROGENEITY
715
creased below the plowed zone. Figure 4isa similar diagram for pico-
curies of “’cs per kilogram of soil in the same soil specimens that
were analyzed for the Sr of Fig. 3, and the variability, though greater
than that of “Sr, was distributed similarly. The variation in fission-
product concentrations shown in the figures includes that introduced
(1) during sampling of the soil profile in the field, (2) in the selecting
of representative subsamples for chemical analyses, (3) from chemical
treatment to extract radionuclides, (4) from the uncertainties in count-
ing the isotopes extracted, and (5) by the actual variation in radioactiv-
ity among the specimens in the field (evaluation of this factor was the
reason for collecting the specimens).
The Sr and '8"Cs computed from the data illustrated in the pre-
ceding figures are given in nanocuries per square meter for different
depths in the soil profile in Figs. 5 and 6. These figures illustrate the
uncertainty that is associated with mean values that purport to describe
the fission products of a relatively small field. The components of the
variances in these computed values were discussed earlier. In the first
0
Poly
oOo
Tg, co
00
lo
mo
Oo
°!
|
6
_
2
Om
0
4
oo
Oo
6
o
pe- ©
00
o
COD
Oo
z er
<r
beamo
a
o
oo
390
ax
o
o
o
60 0
4
4
4
o
4
ud
O 10 r-
a
-OCED
—
2-F
=
pam 8
4@e
°
7
_|
=
_
16 foaco
18
0
_
3°
60
Pt
4
tt
500
75, PC/KG PER INCH OF INCREMENT
1000
Fig. 4—Deviations in the
concentration of ’Cs among
specimens fromsoil samples
collected at different positions in the profile of field 4,
November 1962,