493
Processes in the Oceans
similar value of 0.0188 (±0.0021) was found for 30 to 80 m. The ratio of PO 4
3– to H 2 S in the
Cariaco Trench (0.018; Zhang and Millero, 1993a,b) agreed fairly well with the predicted
value, while it was only half of the model value (0.009) in the Black Sea. This low recycling efficiency of PO 4
3– in the Black Sea might partially be due to the removal of PO 4
3– by
adsorption onto particles. Again, the good agreement between the measured ratio of PO 4
3–
to H 2 S in the Framvaren and the model value might be incidental when we consider the
possible removal of H 2 S produced by sulfate reduction.
The linear correlation between sulfide and silicate in the anoxic waters of the Framvaren
gave a slope of 0.11 (±0.01) (Figure 10.82), indicating that silicate was also released proportionately to the production of hydrogen sulfide. There is no theoretical ratio of Si to H 2 S
from the oxidation of biogenic organic matter because it depends on the relative abundance of siliceous phytoplankton (e.g., diatoms). The ratios were 0.61 and 0.91 for the Black
Sea and Cariaco Trench, respectively. The concentration of silicate in the Framvaren was
relatively low compared to the sulfide level. Little is known about the effect of anoxic environments on the dissolution of silicate.
Table 10.11
Stoichiometric Ratios in Anoxic Waters of Different Basins
Basin
TCO 2 :H 2 S
TA:H 2 S
PO 4 :H 2 S
NH 4 :H 2 S
Si:H 2 S
C:N:P
Framvaren
3.00
3.42
0.019
0.30
0.11
155:16:1
Black Sea
2.30
3.05
0.009
0.23
0.61
255:25:1
Cariaco Trench
2.01
2.43
0.018
0.31
0.91
112:17:1
Model value
2.00
2.30
0.019
0.30
—
106:16:1
0.0
0.4
0.8
1.2
1.6
NH
4 , SiO
2 (mM)
SiO 2
NH 4
0
1
2
3
4
5
6
0.00
0.04
0.08
0.12
0.16
0.20
PO 4
H 2 S (mM)
PO
4 (mM)
Figure 10.82
Plots of the changes in ammonia, phosphate, and silicate versus the concentration of H 2 S in the anoxic waters
of the Framvaren Fjord.
Processes in the Oceans
similar value of 0.0188 (±0.0021) was found for 30 to 80 m. The ratio of PO 4
3– to H 2 S in the
Cariaco Trench (0.018; Zhang and Millero, 1993a,b) agreed fairly well with the predicted
value, while it was only half of the model value (0.009) in the Black Sea. This low recycling efficiency of PO 4
3– in the Black Sea might partially be due to the removal of PO 4
3– by
adsorption onto particles. Again, the good agreement between the measured ratio of PO 4
3–
to H 2 S in the Framvaren and the model value might be incidental when we consider the
possible removal of H 2 S produced by sulfate reduction.
The linear correlation between sulfide and silicate in the anoxic waters of the Framvaren
gave a slope of 0.11 (±0.01) (Figure 10.82), indicating that silicate was also released proportionately to the production of hydrogen sulfide. There is no theoretical ratio of Si to H 2 S
from the oxidation of biogenic organic matter because it depends on the relative abundance of siliceous phytoplankton (e.g., diatoms). The ratios were 0.61 and 0.91 for the Black
Sea and Cariaco Trench, respectively. The concentration of silicate in the Framvaren was
relatively low compared to the sulfide level. Little is known about the effect of anoxic environments on the dissolution of silicate.
Table 10.11
Stoichiometric Ratios in Anoxic Waters of Different Basins
Basin
TCO 2 :H 2 S
TA:H 2 S
PO 4 :H 2 S
NH 4 :H 2 S
Si:H 2 S
C:N:P
Framvaren
3.00
3.42
0.019
0.30
0.11
155:16:1
Black Sea
2.30
3.05
0.009
0.23
0.61
255:25:1
Cariaco Trench
2.01
2.43
0.018
0.31
0.91
112:17:1
Model value
2.00
2.30
0.019
0.30
—
106:16:1
0.0
0.4
0.8
1.2
1.6
NH
4 , SiO
2 (mM)
SiO 2
NH 4
0
1
2
3
4
5
6
0.00
0.04
0.08
0.12
0.16
0.20
PO 4
H 2 S (mM)
PO
4 (mM)
Figure 10.82
Plots of the changes in ammonia, phosphate, and silicate versus the concentration of H 2 S in the anoxic waters
of the Framvaren Fjord.