Environmental Engineering Reference
In-Depth Information
TABLE A.1
(Continued
)
Process
Chemical Reaction
Location or Conditions
HCOO
2
1
H
1
Fermentation
2CH
2
O
1
H
2
O
!
CH
3
OH
1
Where O
2
is absent and
OM is abundant
(wetlands, aquatic
sediments, wet soils)
SO
2
2
H
1
!
HS
2
Sulfate
reduction
2CH
2
O
1
1
2CO
2
1
2H
2
O
1
Where O
2
is absent and
OM and sulfate are
abundant (salt marshes,
marine sediments, wet
soils, freshwater wetlands
and sediments)
Methano-
genesis
2CH
2
O
!
CO
2
1
CH
4
Where O
2
and other
electron acceptors are
absent and OM is
abundant (freshwater
sediments)
Methane
oxidation
CH
4
1
2O
2
!
CO
2
1
2H
2
O
Interfaces of organic-rich
anaerobic sites and
oxygenated waters or soils
(wetlands, wet soils)
B. Oxidation of reduced inorganic species (may provide energy for chemosynthesis; materials other than
organic carbon are the electron donor)
Sulfide
oxidation
H
2
S
2O
2
!
H
2
SO
4
These reactions typically
take place near interfaces
of organic-rich anaerobic
sites and oxygenated
waters or soils (wetlands,
wet soils, thermoclines of
eutrophic lakes)
1
Ferrous
oxidation
4Fe(HCO
3
)
2
1
O
2
1
6H
2
O
!
4Fe(OH)
3
1
4H
2
CO
3
1
4CO
2
NH
4
1
1
NO
3
2
1
2H
1
1
Nitrification
2O
2
!
H
2
O
Manganous
oxidation
4MnCO
3
1
O
2
!
2Mn
2
O
3
1
4CO
2
C. Photosynthesis
!
Oxygenic
photosynthesis
CO
2
1
H
2
O
1
light
CH
2
O
1
O
2
Where there is light
Photosynthesis
by sulfur
bacteria
2CO
2
1
2H
2
O
H
2
S
light
!
2(CH
2
O)
H
2
SO
4
Sites that are lighted and
anoxic or nearly so
1
1
1
D. Nitrogen fixation
N
2
1
8H
1
1
8e
2
1
energy
!
2NH
3
1
H
2
Intracellular
Note:
OM
organic matter.
Modified from
Stumm and Morgan (1995)
and
Wetzel (2001)
.
5
