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\WARTIN : RADIOECOLOGY AND STUDY OF ENVIRONMENTAL RADIATION
285
their daughter products, Lowder and Solon (1956) have listed 17 other
radionuclides which are known to occur in air, soil, or water.
Carbon-14 and tritium (H-3) are produced in the upper atmosphere by
nuclear reactions between cosmic rays and molecules of nitrogen and water.
The air near the ground may also contain small quantities of gaseous
deeay products which are derived from soil. According to one estimate
Table 1.
Estimated activity of naturally occurring radionuclides in an acre-foot of
soil derived from igneous rock*
Radio-
Activity in
nuclides
K-40
Rb-87
C-14 & H-3
Radio-
Activity in
euries/acre-foot
nuelides
curies/acre-foot
33 x 10-3
6 x 1073
Ra-226
Th-232
1.5 x 10-3
1.9 « 10-3
**
U-238
3.0 x 10-3
*The formula for these calculations and those in Table 2 is:
C=SAx AI x AE x grams/aere-foot
C = Activity of radionuclide in euries per acre-foot
SA = Specifie activity of radionuclides in curies per gram
AI= Abundance of radionuclides (% x 10-2) in natural element
ble infor-
the fors and of
terials in
ee
AE = Abundanee of element (% x 10-2) in environmental media
Grams peracre foot =
Soil: 15 x 108
Water: 1234 x 10°
Sources of basie data:
“SA”: Kinsman (1957)
“AT”: Handbook of Physies and chemistry, 39th ed.
“AE”: Lowder & Solon (1956)
** 0-14 in organic matter amounts to about lx 10-12 e/g carbon
H-3 in soil water amounts to about 5x 10-16 e/g water
Table 2.
Hstimated activity of naturally occurring radionuclides in an acre-foot
of sea water*
Radio-
Activity in
nuclides
K-40
Rb-87
C-14 & H-3
*
**
Radio-
Activity in
curies/aere-foot
nuclides
curies/acre-foot
39 x 1078
32 x 10-10
*%
Ra-226
Th-232
U-238
62 x 10-4
eR
H4*
See footnote following Table 1.
C-14: ca. 1x 10-12 e/g of Carbon
H-3 ca. 1x 10-16 e/g =ea, 1.2 10-3 e/aere-foot of Sea Water
*** Not calculated.
(Koval 1945) the gas which emanates from soils containing radium and
other long-lived radio-elements has an average activity of ea. 2x 10° e/m?
(e/m' = curies per cubic meter). Most of this is due to the presence of radioisotopes of radon (Rd-219,220,222) produced by the deeay of Ra-226.
Hess (1943) has reported that the radon content of air near the ground
is usually less than 1x10? ¢/m*, but one sample, collected during calm
winter weather from a low area having no snow cover, contained 3 x 10°
c/mof radon.