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Institute of Food and Agricultural Sciences (IFAS)
Biogeochemistry of Wetlands
Science and Applications
SULFUR
Wetland Biogeochemistry Laboratory
Soil and Water Science Department
University of Florida
Instructor :
Patrick Inglett
[email protected]
5/23/2017
5/23/2017
5/23/2017
WBL
P.W. Inglett
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1
Sulfur
 Introduction


S Forms, Distribution, Importance
Basic processes of S Cycles
 Examples
of current research
 Examples of applications

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Key points learned
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2
Sulfur
Learning Objectives
 Identify the forms of S in wetlands
 Understand the importance of S in
wetlands/global processes
 Define the major S processes/transformations
 Understand the importance of microbial activity
in S transformations
 Understand the potential regulators of S
processes
 See the application of S cycle principles to
understanding natural and man-made
ecosystems
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Sources of Sulfur
• Sulfur is a ubiquitous element.
• Various sulfur compounds are present in:
–
–
–
–
–
–
–
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The atmosphere
Minerals
Soils
Plant tissue
Animal tissue
Microbial biomass
Sediment
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Reservoirs of Sulfur
•Atmosphere
•Lithosphere
•Hydrosphere
– Sea
– Freshwater
•Pedosphere
– Soil
– Soil Organic matter
•Biosphere
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4.8 x 109 kg
24.3 x 1018 kg
1.3 x 1018 kg
3.0 x 1012 kg
2.6 x 1014 kg
0.1 x 1014 kg
8.0 x 1012 kg
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General Forms of Sulfur in the
Environment
• Organic S in plant, animal, and microbial tissue (as
essential components of amino acids and proteins)
Methionine
Cysteine
H3C-S-CH2-CH2-
HS-CH2Thioester
O
R1-C~S-R2
– Organic sulfur primarily in soil and sediments as humic
material (naturally occurring soil and sediment organic
matter)
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General Forms of Sulfur in the
Environment
• Gaseous S compounds (SO2, H2S, DMSO, DMS)
• Oxidized Inorganic S (sulfate, SO42-, is the primary
compound).
Seawater contains about 2,700 mg/L (ppm) of sulfate
• Reduced Inorganic S (elemental sulfur, So, and
sulfide, S2-)
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General Forms of Sulfur in the
Environment
• Minerals
Galena (PbS2)
Gypsum (CaSO4)
Jarosite(Fe2S)
Barite (BaSO4)
Pyrite (FeS2)
• Fossil Fuels
– Petroleum (0.1-10%)
– Coal (1-20%)
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Oxidation states of selected
sulfur compounds
•
•
•
•
•
•
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Organic S (R-SH)
Sulfide (S2-)
Elemental S (S0)
Sulfur dioxide (SO2)
Sulfite (SO3-2)
Sulfate (SO42-)
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-2
-2
0
+4
+4
+6
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Global Sulfur Cycle
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Sulfur Cycling Processes
1. Dissimilatory sulfate reduction
2. Assimilatory sulfate reduction
3. Desulfurylation
4. Sulfide oxidation
5. Sulfur oxidation
6. Dissimilatory So reduction
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Sulfur Cycle
So
4
5
SH groups
2
Aerobic
of protein
SO42-
3
Anaerobic
1
S2-
2
Anaerobic
Aerobic
3
SH groups
5
of protein
4
6
So
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Distribution of sulfur in soils
Organic sulfur [93%]
– Carbon-bonded sulfur (cysteine and methionine) 41%
– Non-carbon-bonded sulfur (ester sulfates) 52%
Inorganic sulfur [7%]
– Adsorbed + soluble sulfates 6%
– Inorganic compounds less oxidized than sulfates and
reduced sulfur compounds (e.g. sulfides) 1%
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Organic Sulfur Forms
20
Freshwater
Sulfur, g/kg
15
10
Brackish
Salt
5
0
Ester
C-S
Total
Organic Geochemistry vol. 18, no. 4, pp. 489-500, 1992
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Inorganic Sulfur Forms
4
400
Freshwater
3
Brackish
2
200
Salt
100
1
0
0
FeS
So
FeS2
Sulfur, g/kg
Sulfur, mg/kg
300
HCl
Krairapanond et al. 1992. Organic Geochemistry 18: 489-500.
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Organic S Hydrolysis
R - S-H2 + H2O
Thiol
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R-OH + H2S
Sulfohydrolase
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Sulfur – Organism Groups
Assimilatory Sulfate Reduction
• Bacteria, fungi, algae, and plants
Dissimilatory Sulfate Reduction
• Hetrerotrophs
Desulfovibrio, Desulfotomaculum, Desulfobacter,
Desulfuromonas
Sulfide Oxidation
• Phototrophs: Chlorobium, Chromatium
• Chemolithoautotrophs: Thiobacillus, Beggiatoa
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Sulfate Reducing Bacteria: SRB
(habitats)
Desulfovibrio - found in water-logged soils.
Desulfotomaculum - spoilage of canned foods.
Desulfomonas - found in intestines.
Archaeglobus - a thermophilic Archea whose optimal
growth temperature is 83oC.
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Sulfate Reduction
Deposition
SO42Tidal Exchange
SO42AEROBIC
SO42-
Reduction
S2-
Reduction
SO42-
So
Microbial
Biomass-S
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Adsorbed
SO42-
ANAEROBIC
20
Glucose Oxidation
Oxidation – Reduction Reaction
C6H12O6 + 6O2 = 6CO2 + 6H2O
kJ/mol
Glucose
2,880
5C6H12O6 + 24NO3- + 24H+ = 30CO2 + 12N2 +42H2O
2, 712
C6H12O6 + 12MnO2 + 24H+ = 6CO2 + 12Mn2+ + 18H2O
1,920
C6H12O6 + 24Fe(OH)3 + 48H+ = 6CO2 + 24 Fe2+ +66H2O
C6H12O6 + 3SO42- = 6CO2 + 3S2- + 6H2O
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381
21
Oxygen EquivalentsEnergy Yield from Glucose
% of Aerobic Energy Yield
120
100
80
60
40
20
0
O2
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NO3MnO2
Fe(OH)3
Electron Acceptors
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SO4222
Oxidation-Reduction
SO42CO2
Mn4+
S2-
CH4
-200
Fe3+
-100
0
Mn2+
NO3-
Fe2+
+100
+200
O2
H2O
N2
+300 +400
Redox Potential, mV (at pH 7)
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Sequential Reduction of
Electron Acceptors
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Redox Zones With Depth
WATER
Depth
SOIL
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I
Oxygen Reduction Zone
Eh = > 300 mV
II
Nitrate Reduction Zone
Mn4+ Reduction Zone
Eh = 100 to 300 mV
III
Fe3+ Reduction Zone
Eh = -100 to 100 mV
IV
Sulfate Reduction Zone
Eh = -200 to -100 mV
V
Methanogenesis
Eh = < -200 mV
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Aerobic
Facultative
Anaerobic
25
Redox Potential and pH
1000
800
Eh [mV]
600
400
200
0
-200
-400
-600
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0
2
4
pH
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6
8
10 12
Baas Becking et al. 26
Microbial Activity
[Site: Water Conservation 2A]
y = 0.33x + 1.3
r2 = 0.88; n = 24
50
[mg kg-1 hour-1]
Sulfate reducing conditions
60
40
30
20
10
0
0
10
20
30
40
50
60
Aerobic [mg kg-1 hour-1]
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Sulfate Respiration
Detrital Matter
Complex Polymers
Enzyme
Hydrolysis
Monomers
Sugars, Amino Acids
Fatty Acids
Cellulose, Hemicellulose,
Proteins, Lipids, Waxes, Lignin
Uptake
Glucose
Glycolysis
Oxidative phosphorylation
Pyruvate
TCA Cycle
Products:
CO2, H2O, S2-,
Nutrients
CO2
Substrate level
phosphorylation
Acetate
SO42- + e-
Uptake
Lactate
Substrate level phosphorylation
Organic Acids
[acetate, propionate, butyrate,
lactate, alcohols, H2, and CO2]
ATP
[Sulfate Reducing Bacterial Cell]
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[Fermenting Bacterial Cell]
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Electron donors used during
sulfate reduction
• SRB lack enzymes necessary for
complex carbon assimilation
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Electron donors used during
sulfate reduction
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Decreasing
energy
yield
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Electron Donors
Capone and Kiene. 1988. Limnol Oceanogr, 33: 725-749.
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Sulfate Reduction Rates
Activity
[nmol/g per day]
Low carbon wetland
23
Peaty wetland
130
Oligotrophic lake
707
Eutrophic lake
1,224
Marine and salt-marsh
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744-24,000
33
Salt Marshes
Respiration [g C/m2 year]
Sapelo Island Sippewissett
Sapelo Island
[GA]
[MA]
(1997)
Aerobic respiration
Denitrification
Mn and Fe reduction
Sulfate reduction
Methanogenesis
S Respiration
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390
10
ND
850
40
~65%
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390
3
ND
1,800
1-8
~82%
2,000
~69-87%
34
Sulfate Respiration
Capone and Kiene. 1988. Limnol Oceanogr, 33: 725-749.
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Capone and Kiene. 1988. Limnol Oceanogr, 33: 725-749.
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Seasonal Effects
Jorgensen, 1977. Marine Biology 41:7-17.
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Seasonal Effects
Spartina alterniflora marsh
Great Sippewissett
Marsh
Moles SO42- m-2 d-1
0.5
0.4
0.3
0.2
0.1
0.0
J
F
M
A
M
J
J
A
S
O
N
D
Months
Howarth and Giblin, 1983. Limnol and Oceanogr, 28:70-82.
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Seasonal Effects
Spartina alterniflora marsh
0.5
0.4
Moles O2 m-2 d-1
Moles SO42- m-2 d-1
0.03
0.3
0.2
0.1
0.02
0.01
0.0
-5
0
5
10
15
20
25
30
Temp (C)
-5
0
5
10
15
20
25 30
Temp (C)
Howarth and Teal. 1979. Limnol and Oceanogr, 24: 999-1013.
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Regulators of Sulfate Reduction
• Presence of electron acceptor with higher
reduction potentials
• Oxygen is toxic to sulfate reducers
• Sulfate concentration
– Freshwater (< 0.1 mM)
– Marine (20-30 mM)
• Substrate/Electron Donor
• Temperature
• Microbial populations
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Decreasing
energy
yield
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Anaerobic Sludge Reactor
(FISH)
Sulfidogenic aggregate
Sulfidogenic/Methanogenic aggregate
Archeal Probe
SRB Probe
Appl Environ Microbiol. 1999 October; 65(10): 4618–4629.
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Competition With Methanogens
X
X
X
X
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Sulfate Reducers vs Methanogens
Sulfate reducers
Vmax
Vmax
Methanogens
V = [Vmax S]/Km + S
Km
Km
[Substrate]
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Sulfate Reduction
Typical Lake Sediments
mM SO42-
CH4
20
SO42-
0.4
10
mM CH4
0.6
0.2
0
20
40
60
80
100
Days
from Jorgensen: in Microbial Geochemistry. Krumbein, ed: 1983 Blackwell.
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Sulfate Reduction
Typical Lake Sediments
mM SO42-
mM SO420.1
0.2
20
10
0
12
8
SO42-
SO42-
0.5
1.0
0
m
cm
4
4
CH4
8
12
CH4
2.0
1
2
mM CH4
Freshwater
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1.5
0.5
1.0
mM CH4
Marine
from Jorgensen: in Microbial Geochemistry. Krumbein, ed: 1983 Blackwell.
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Sulfate Reduction
Cattail Marsh – Sunnyhill Farm Wetland
CH4 (mg L-1)
0
5
10
15
10
Water
0
Depth (cm)
Soil
CH4
-10
SO42-20
-30
0
20
40
60
80
100
SO42- (mg L-1)
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Sulfate Reduction
Iversen and Jorgensen. 1985. Limnol Oceanogr, 30: 944-955.
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Sulfur Emissions
H2S
DMS
Mineralization
Org-S
H2S
DMS
Mineralization
Org-S
AEROBIC
Reduction
S2-
Reduction
So
SO42-
ANAEROBIC
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Gaseous S Emissions
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Gaseous Speciation
DeLaune et al. 2001
SALT
H3C-S-CH3
BRACKISH
H 2S
FRESH
CO-S
ug S m-2 hr-1
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Sulfide Formation
H2S
DMS
Mineralization
Org-S
H2S
DMS
Mineralization
Org-S
AEROBIC
Reduction
S2-
Reduction
So
SO42-
ANAEROBIC
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Sulfide Speciation
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Problems With Hydrogen Sulfide
• Malodorous (rotten egg smell)
• Acidic (corrosion/fouling)
• Toxic (reactive with
metalloenzyme systems)
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Sulfide Toxicity
Tall vs. Short Spartina alterniflora
Short Form
Tall Form
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Tall vs. Short Spartina alterniflora
Sapelo Island Marsh
Creek
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Tall
Short
Kostka et al., 2002. Biogeochemistry 60:49-76.
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Sulfide Toxicity
Tall vs. Short Spartina alterniflora
NH4+ Uptake
Lower Vmax
Higher Vmax
Higher Km
Lower Km
MHT
MLT
Inc. NH4+, S2-, and Salt Concentrations
Inc. Flood Frequency, Pore Water Turnover
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Sulfide Precipitation
AEROBIC
Reduction
S2-
Me+-S
Reduction
So
SO42-
ANAEROBIC
FeS2
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Iron and Sulfide Interactions
2FeOOH + H2S = So + 2Fe2+ + 4OHFe2+ + H2S = FeS + 2H+
FeS + So = FeS2
Acid Volatile S
(AVS)
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Chromium Reducible S
(CRS)
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Pyrite Framboids
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Pyrite Formation
Fe
Oxides
Monosulfides
(AVS)
FeS
ΣH2S
S0
Intermediate
Redox S
FeS2
Sulfate
Reduction
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Pyrite (CRS)
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Pyrite Formation
Sapelo Island Marsh
Solid-Fe
AVS
CRS
Creek
Tall
Short
Kostka et al., 2002. Biogeochemistry 60:49-76.
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ZnS
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Metal Sulfide Solubility% Uptake of added 35S
Uptake by Rice Plant
5
Na2S
4
3
2
MnS
FeS ZnS
1
0 0
10
10-10
10-20
CuS
10-30
10-40
HgS
10-50
Solubility Product (Ksp)
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Engler and Patrick, 1981
65
Metal Sulfide Solubility
Yu et al. 2001. Wat Res. 35:4086-4094.
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Sulfur Oxidation
Tidal Exchange
SO42H2S
DMS
Oxidation
Oxidation
So
SO42-
AEROBIC
Reduction
S2-
So
ANAEROBIC
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Sulfide Oxidation
2H2S + O2 = 2So + 2H2O
-204 kJ/reaction
2So + 3O2 + 2H2O = 2SO42- + 4H+
-583 kJ/reaction
H2S + 2O2 = SO42- + 2H+
-786 kJ/reaction
H2S
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SO32P.W. Inglett
SO4268
Sulfur Cycling
Cyanobacterial Mat Sediments
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Sulfur Cycling
Cyanobacterial Mat Sediments
Surface
Aphanothece
Diatoms
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Green Layer
Phormidium,
Lyngbya
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Red Layer
Chromatium salexigens
Thiocapsa halophila.
70
Oxidation-Reduction
Soil-floodwater Interface
O2
Floodwater
Aerobic soil
SO42-
H2S + O2
SO42-
H2S
Anaerobic soil
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Sulfur Cycling
Salt Marsh Surface Sediments
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Oxidation-Reduction
Root- Soil Interface
AEROBIC
ANAEROBIC
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Oxidation-Reduction
Infaunal Burrows
Uca spp.
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Oxidation-Reduction
Infaunal Burrows
ca. 12” Deep
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Sulfur Cycle
Rates = mmol/m2 day
from Jorgensen: in Microbial Geochemistry. Krumbein, ed: 1983 Blackwell.
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Pyrite Oxidation
FeS2 + 3.5O2 + H2O = Fe2+ + 2SO42- + 2H+
Fe2+ + 0.25O2 + H+ = Fe3+ + 0.5H2O
(1) FeS2 + 3.75O2 + 0.5H2O = Fe3+ + 2SO42- + H+
(2) FeS2 + 14Fe3++ 8H2O = 15Fe2+ + 2SO42- + 16H+
O2
Fe2+
Fast
Chemical/
Biological
Slow (at low pH)
Biological
[Thiobacillus ferrooxidans]
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SO42- + H+
Fe3+
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FeS2
78
Drainage Effects on Acid Sulfate Soils
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Acid Sulfate Soils
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Acid Mine
Drainage
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Sulfur Cycling in Wetlands
Plant Biomass-S
Deposition
SO42Litterfall
H2S
DMS
Tidal Exchange
SO42Mineralization
Org-S
H2S
DMS
Mineralization
S2-
SO42-
Org-S
Oxidation
Oxidation
So
Reduction
S2-
Me+-S
.
SO42-
Reduction
SO42-
So
Microbial
Biomass-S
AEROBIC
Adsorbed
SO42-
ANAEROBIC
FeS2
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Hg Methylation
Gilmore et al., 1992. Env Sci Tech. 26:2281-2287.
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Hg Methylation
Gilmore et al., 1992
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Hg Methylation
Desulfobacteriaceae
Acetate
Lactate
Control
King et al., 2000. Applied and Environmental Microbiology, June 2000, p. 2430-2437.
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Hg Methylation
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Periphyton Delta 32S
September 1996
Methylmercury in Floating
Periphyton
All Cycles 1995-1996
ug/k
g
>
6
4
2
0
Kendall et al., http://sofia.usgs.gov/publications/posters/
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Hg Methylation
S2S0
Hg
HgS0
HgS2
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?
H3C-Hg
SRB
SO42P.W. Inglett
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Importance of Sulfur in Wetlands
•
•
•
•
•
•
•
Source of nutrient
Source of energy
Role in decomposition of organic matter
Adverse effects of sulfide on plant growth
Immobilization of toxic metals
Contribution to acid development (oxidation)
Role in methylation of Hg
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