Environmental Engineering Reference
In-Depth Information
50
Japan
40
Romania
30
Czechoslovakia
West Germany
20
Yugoslavia
Netherlands
UK
Swede
Norway
Switzerland
10
USA
0
0
1
2
3
4
5
Nitrate intake (mmoles person
-1
day
-1
)
FIGURE 13.7
A correlation between nitrate intake and rates of gastrointestinal cancer
(after P. E. Hartman. © 1983, reprinted by permission of Wiley-Liss, Inc., a subsidiary of
John Wiley & Sons, Inc.).
Sulfide can combine with metals to form
pyrites,
the most common be-
ing iron pyrite (fool's gold). These precipitates have very low solubility un-
der anoxic conditions and can represent an important loss of iron to
aquatic ecosystems. The precipitate is black and gives anoxic sediments
their characteristic black color.
Some Sulfur Transformations
a
TABLE 13.1
Equation
Condition
Name
Classification
S
o
H
2
S
1
⁄
2
O
2
→
H
2
O
Oxic
Sulfide oxidation
Abiotic and dissimilatory
biotic
S
o
H
2
O
1
1
⁄
2
O
2
→
H
2
SO
4
Oxic
Elemental sulfur oxidation
Abiotic and dissimilatory
biotic
4NO
3
3S
o
3SO
4
2
→
2N
2
Anoxic
Inorganic sulfur oxidation
Dissimilatory biotic
2CO
2
2H
2
S
2H2O
Anoxic
Photosynthetic sulfur oxidation
Biotic
light
→
2(CH
2
O)
H
2
SO
4
(anoxygenic photosynthesis)
4S
o
CH
3
COOH
2H
2
O
→
Anoxic
Acetate oxidation
Dissimilatory, reduction
2CO
2
4H
2
S
2(CH
2
O)
H
2
SO
4
→
2CO
2
Anoxic
Anaerobic respiration, sulfate as
Dissimilatory, reduction
2H
2
O
H
2
S
the electron acceptor
4 H
2
H
2
SO
4
→
4H
2
O
H
2
S
Anoxic
Anaerobic hydrogen respiration
Dissimilatory, reduction
SO
4
2
S
2
H
S
2
O
3
→
Anoxic
Disproportionation
Dissimilatory
SO
4
2
S
2
→
→
cysteine
Oxic/anoxic
Assimilation
Biotic
Fe
2
H
2
S
→
FeS + H
2
Anoxic
Iron pyrite formation
Abiotic, spontaneous
a
Note that others occur, but this table partially illustrates the complexity of the sulfur cycle.
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