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REDOX: IRON, SULFUR, & SILICA. Redox Potential. pE = -log free electrons When corrected to pH 7 (H + = OH - ), called E h When E h positive – oxidizing environment When E h negative – reducing environment. Redox vs. pH. Redox ( mv ) of common liquids. Example of Redox data.

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Redox iron sulfur silica

REDOX: IRON, SULFUR, & SILICA


Redox potential
Redox Potential

  • pE = -log free electrons

  • When corrected to pH 7 (H+ = OH-), called Eh

  • When Eh positive – oxidizing environment

  • When Eh negative – reducing environment


Redox vs ph
Redox vs. pH


Redox mv of common liquids
Redox (mv) of common liquids


Example of redox data
Example of Redox data


Ph and orp in lake skiennungen
pH and ORP in Lake Skiennungen


Fe mn in oligotrophic and eutrophic lakes
Fe & Mn in oligotrophic and eutrophic lakes



Redox sulfur and iron
Redox: Sulfur and Iron




Fe mn in crooked lake mesotrophic
Fe & Mn in Crooked lake(mesotrophic)


Fe mn in little crooked lake eutrophic
Fe & Mn in Little Crooked lake(eutrophic)



Iron oxidizing bacteria
Iron Oxidizing Bacteria

  • Gallionella (an iron-oxidizing bacterium)

  • 4Fe (HCO3)2 + O2 + 6H2O 4Fe (OH)3 + 4H2CO3 + 4CO2 + 58 kcal


Ferrobacillus iron bacteria
Ferrobacillus iron bacteria

  • 4FeCO3 + O2+ 6H2O Fe(OH)3 + 4CO2


Mn cycling relative to o 2
Mn cycling relative to O2


Redox and sulfur
REDOX and Sulfur


S in oligotrophic and eutrophic lakes
S in oligotrophic and eutrophic lakes


So 4 in a mesotrophic hardwater lake
SO4 in a mesotrophichardwater lake


So 4 budget for linsley pond
SO4 budget for Linsley Pond


Orp ph and sulfur bacteria
ORP, pH, and Sulfur bacteria


Autotrophic sulfur oxidizing bacteria and iron transformations
Autotrophic Sulfur-Oxidizing Bacteria and Iron Transformations

  • Thiobacillus

  • Some of the reactions that it can mediate

  • FeS2 + 3½O2+H2O FeSO4 + H2SO4

  • 2FeSO4 + ½O2+ H2SO4 Fe2(SO4)3 + H2O


Bacterial transformations of sulfur
Bacterial Transformations of Sulfur Transformations

  • Sulfate-Reducing Bacteria (heterotrophic and anaerobic)

  • Sulfur-Oxidizing Bacteria

    • Chemosynthetic

    • Pigmented Autotrophic


Sulfate reducing bacteria
Sulfate-Reducing Bacteria Transformations

  • Ex: Desulfovibrio

  • Heterotrophic and anaerobic

  • H2SO4 + 2(CH2O) 2CO2 2H2O + H2S

  • H2SO4 + 4H2 H2S + 4H2O


Chemosynthetic sulfur oxidizing bacteria
Chemosynthetic Sulfur-Oxidizing Bacteria Transformations

  • Ex: Beggiatoa

  • Deposit elemental S inside cell

  • H2S + ½O2 S + H2O

  • S + 1½O2 + H2O H2SO4

  • Ex: Thiobacillus

  • Deposit elemental S outside

  • 2Na2S2O3 + O2 2S + 2Na2SO4


Green sulfur bacteria
Green Sulfur Bacteria Transformations

  • Ex: Chlorobium

  • Uses a pigment similar to chlorophyll

  • CO2 + 2H2SLIGHT Food + H2O + 2S

  • 2CO2 + 2 H2O + H2S LIGHT Food + H2SO4


Purple sulfur bacteria
Purple Sulfur Bacteria Transformations

  • Ex: Chromatium

  • They deposit sulfur intracellularly

  • Same reactions as Chlorobium


Purple non sulfur bacteria
Purple Non-Sulfur Bacteria Transformations

  • Ex: Rhodobacter

  • Na2S2O3+2CO2 +3H2O LIGHT Food + Na2SO4 +H2SO4



Sulfate reduction in lake gek gel and the black sea
Sulfate reduction in Lake TransformationsGek Gel and the Black Sea


Distribution of sulfur in meromictic lake belovod
Distribution of sulfur in Transformationsmeromictic Lake Belovod


Abandoned mine drainage
Abandoned Mine Drainage Transformations



Amd discharges
AMD Discharges Transformations


Acid precipitation
Acid Precipitation Transformations


Si in lakes
Si in lakes Transformations


Some common diatoms
Some Common Diatoms Transformations


Si in oligotrophic lawrence lake
Si in Transformationsoligotrophic Lawrence Lake



Dynamics of diatom periphyton and plankton
Dynamics of diatom Transformationsperiphyton and plankton


Green algae and diatoms
Green Algae and Diatoms Transformations


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