239
Dissolved Gases Other than CO 2
By studying several gases, it is possible to determine the magnitudes of these processes.
Xe and Kr are not sensitive to air injection, so they can be used to examine temperature
effects. He is sensitive to air injection but is not affected by temperature effects. Since Ar
and O 2 are affected by nearly the same amounts, Ar is the best nonreactive gas for separating the biological and physical processes for O 2 .
The saturation anomalies for N 2 have been studied by a number of workers. The results
(Kester, 1975) are shown in Table 6.7. All the waters are within ±1.4% of the saturated values
(which is within the standard error 3%). The high standard errors could be related to real
variations caused by oceanic processes (air injection, etc.). Since biochemical processes
are known that convert N 2 to organically bound nitrogen and N 2 can be produced from
Temperature (°C)
0
5
10
15
20
25
30
Solubility (cm
3
dm
–1
atm
–1
)
0
20
40
60
80
100
Kr
Ar
O 2
N 2
Ne
He
Figure 6.5
The effect of temperature on the solubility of gases in seawater.
Table 6.6
Comparison of the Mole Fraction (X i ) of Gases Dissolved in Saturated Seawater
and in Dry Air and the Saturation Anomaly of Air Resulting from the Injection
of 1 cm 3 of Air at STP per Kilogram of Seawater a
N 2
O 2
Ar
CO 2
Ne
He
Kr
Xe
X air
0.780 0.209 0.009 0.0003 18.2 × 10 –6
5.2 × 10 –6
1.1 × 10 –6
0.09 × 10 –6
X SW
0.626 0.343 0.016 0.014
9.7 × 10 –6
2.3 × 10 –6
3.8 × 10 –6
0.54 × 10 –6
Air (%)
7.7
3.8
3.5
0.1
11.6
13.8
1.8
1.0
a All seawater values are based on 15°C and S = 35.