CHAPTER 4 . Redox Processes in Anoxic Waters
Fig. 4.17. Plots of the changes
20 ,..--.----.---,-----r--y--..,.--- ,
of TeOz and TA vs. the concentration of HzS in the anoxic
waters of the Framvaren Fjord
(Yao and Millero 1995b)
16
~ 12
g
~
4
2
3
4
5
6
7
H 2 S(mM)
109
24
20
16
~
12 !
8' "
I"
4
0
tions in the ratios TAIHzS and TCOzIHzS, the removal process ofHzS should not change
the TA. In other words, sulfide should be removed from the water column as FeSz and
elemental sulfur or polysulfides
again, without altering both TA and TCO z . If the product is SO~- instead of So, the alkalinity will be lowered. Millero et al. (1987a) found that the main reaction product
between H2S and O2 was SO~- when O2 was in excess. The calculated Peo z in the surface water in June 1993 is 250 flatm.
Ammonium increased below the interface due to the anaerobic decomposition of
organic matter. Based on the model, a plot of NHt vs. H2S should give a slope of 0.30.
Our experimental result gives the same value 0.30 ( ±0.01) for all data from 20-175 m
(Fig. 4.18). A lower value of NHt I HzS = 0.25 (±0.02) is found for data from 30-80 m.
The ratio ofNHt to H2S in Cariaco Trench (0.31, Zhang and Millero 1993b) agreed with
the model value while it is lower (0.23) in the Black Sea (Table 4.2). Due to the possible removal of HzS as discussed earlier, the real ratio of NHt to HzS must be lower
than the model value. One explanation for this is that the C/N ratio in organic matter
is higher than lO6116.
The phosphorus transformations unlike nitrogen are simple because of its single
oxidation state. Phosphate, however, can absorb onto particles such as FeOOH and
MnOz. The rapid increase of phosphate below the interface also results from the anaerobic respiration of organic matter. The ratio of PO~- to HzS should be 0.019. Our experimental result gives exactly the same value 0.0191 (±0.0004) for all data from 20-175 m
(Fig. 4.18). A similar value of 0.0188 (±0.0021) is found for 30-80 m. The ratio of PO~-
Fig. 4.17. Plots of the changes
20 ,..--.----.---,-----r--y--..,.--- ,
of TeOz and TA vs. the concentration of HzS in the anoxic
waters of the Framvaren Fjord
(Yao and Millero 1995b)
16
~ 12
g
~
4
2
3
4
5
6
7
H 2 S(mM)
109
24
20
16
~
12 !
8' "
I"
4
0
tions in the ratios TAIHzS and TCOzIHzS, the removal process ofHzS should not change
the TA. In other words, sulfide should be removed from the water column as FeSz and
elemental sulfur or polysulfides
again, without altering both TA and TCO z . If the product is SO~- instead of So, the alkalinity will be lowered. Millero et al. (1987a) found that the main reaction product
between H2S and O2 was SO~- when O2 was in excess. The calculated Peo z in the surface water in June 1993 is 250 flatm.
Ammonium increased below the interface due to the anaerobic decomposition of
organic matter. Based on the model, a plot of NHt vs. H2S should give a slope of 0.30.
Our experimental result gives the same value 0.30 ( ±0.01) for all data from 20-175 m
(Fig. 4.18). A lower value of NHt I HzS = 0.25 (±0.02) is found for data from 30-80 m.
The ratio ofNHt to H2S in Cariaco Trench (0.31, Zhang and Millero 1993b) agreed with
the model value while it is lower (0.23) in the Black Sea (Table 4.2). Due to the possible removal of HzS as discussed earlier, the real ratio of NHt to HzS must be lower
than the model value. One explanation for this is that the C/N ratio in organic matter
is higher than lO6116.
The phosphorus transformations unlike nitrogen are simple because of its single
oxidation state. Phosphate, however, can absorb onto particles such as FeOOH and
MnOz. The rapid increase of phosphate below the interface also results from the anaerobic respiration of organic matter. The ratio of PO~- to HzS should be 0.019. Our experimental result gives exactly the same value 0.0191 (±0.0004) for all data from 20-175 m
(Fig. 4.18). A similar value of 0.0188 (±0.0021) is found for 30-80 m. The ratio of PO~-