Table 3 Source functions of cosmogenic nuclides in the oceans, for nuclides of half-lives 410 days, arranged in order of increasing
half-lives
Nuclide
Half-life
Principal target element (s)
Global average surface
injection rate
a
Integrated in situ oceanic
production rate
Atmosphere
In ocean water
(atoms cm
À 2
min
À 1
)
(atoms cm
À 2
min
À 1 )
32
P
14.3 d
Ar
Cl, S, K
5.82 Â 10
À3
7.6 Â 10
À4
33
P
25.3 d
Ar
Cl, S, K
6.93 Â 10
À3
2.9 Â 10
À4
37
Ar
35.0 d
Ar
K, Ca
9.10 Â 10
À6
8.1 Â 10
À6
7
Be
53.3 d
N,O
O
1.27
6.0 Â 10
À3
35
S
87.4 d
Ar
Cl, Ca, K
2.84 Â 10
À2
5.1 Â 10
À4
22
Na
2.6 y
Ar
Na
3.75 Â 10
À3
3.9 Â 10
À4
3
H
12.3 y
N,O
O,
2 H
1.39 Â 10
1
1.2 Â 10
À2
32
Si
B150 y
Ar
S, Ca
9.60 Â 10
À3
2.5 Â 10
À5
39
Ar
269 y
Ar
K, Ca
2.00 Â 10
À1
1.2 Â 10
À5
14
C
5,730 y
N,O
O
1.20 Â 10
2
9.0 Â 10
À3
41
Ca
a
1.0 Â 10
5 y
—
Ca
—
2.4 Â 10
À5 (n)
a
81
Kr
2.1 Â 10
5 y
Kr
Sr
2.30 Â 10
À5
1.9 Â 10
À8 (n)
c
36
Cl
b
3.0 Â 10
5 y
Ar
Cl
6.60 Â 10
À2
1.06 Â 10
À1 (n)
c
26
Al
7.2 Â 10
5 y
Ar
S, K, Ca
8.40 Â 10
À3
6.8 Â 10
À6
10
Be
1.6 Â 10
6 y
N,O
O
2.70
1.8 Â 10
À3
a Flux to oceans from rivers should be included to take into account production in rocks and soil by
40 Ca(n, g)
41
Ca reaction; this
estimate is not given here because of large uncertainties in these calculations.
b As above, due to
35
Cl(n,g)
36
Cl reaction.
c (n), The in situ production of
41 Ca,
81
Kr and
36 Cl in the oceans is primarily due to the relevant thermal neutron capture reaction. Note
the 50% greater in situ production of
36 Cl in the oceans compared to its atmospheric source.
Table 2 Production rates of several isotopes in the Earth’s atmosphere; arranged in order of decreasing half-lives
a
Isotope
Half-life
Production rate (atoms cm
À 2
s
À 1 )
Global inventory
Troposphere
Total atmosphere
3
He
Stable
6.7 Â 10
À2
0.2
3.2 Â 10
3 tons
b
10
Be
1.5 Â 10
6 y
1.5 Â 10
À2
4.5 Â 10
À2
260 tons
26
Al
7.1 Â 10
5 y
3.8 Â 10
À5
1.4 Â 10
À4
1.1 tons
81
Kr
c
2.3 Â 10
5 y
5.2 Â 10
À7
1.2 Â 10
À6
8.5 kg
36
Cl
3.0 Â 10
5 y
4 Â 10
À4
1.1 Â 10
À3
15 tons
e
14
C
5730 y
1.1
2.5
75 tons
39
Ar
d
268 y
4.5 Â 10
À3
1.3 Â 10
À2
52 kg
32
Si
B150 y
5.4 Â 10
À5
1.6 Â 10
À4
0.3 kg
3
H
12.3 y
8.4 Â 10
À2
0.25
3.5 kg
22
Na
2.6 y
2.4 Â 10
À5
8.6 Â 10
À5
1.9 g
35
S
87 d
4.9 Â 10
À4
1.4 Â 10
À3
4.5 g
7
Be
53 d
2.7 Â 10
À2
8.1 Â 10
À2
3.2 g
37
Ar
35 d
2.8 Â 10
À4
8.3 Â 10
À4
1.1 g
33
P
25.3 d
2.2 Â 10
À4
6.8 Â 10
À4
0.6 g
32
P
14.3 d
2.7 Â 10
À4
8.1 Â 10
À4
0.4 g
a Based on Lal and Peters (1967).
b The inventory of this stable nuclide is based on its atmospheric inventory, which includes an appreciable contribution from crustal
degassing of
3 He.
c Based on atmospheric
81 Kr/Kr ratio of (5.2 7 0.4) Â 10
À13
.
d Based on atmospheric
39 Ar/Ar ratio of (0.107 7 0.004) d.p.m. l
À1 Ar (STP).
e Includes a rough estimate of
36
Cl produced by the capture of neutrons at the earth’s surface.
COSMOGENIC ISOTOPES 227