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REDOX: IRON, SULFUR, & SILICA

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

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  1. REDOX: IRON, SULFUR, & SILICA

  2. 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

  3. Redox vs. pH

  4. Redox (mv) of common liquids

  5. Example of Redox data

  6. pH and ORP in Lake Skiennungen

  7. Fe & Mn in oligotrophic and eutrophic lakes

  8. Iron and Manganese in a Productive Lake

  9. Redox: Sulfur and Iron

  10. Particulate Fe and Fe (II) through the year

  11. Sulfur and Iron in Mud

  12. Fe & Mn in Crooked lake(mesotrophic)

  13. Fe & Mn in Little Crooked lake(eutrophic)

  14. Transport of Fe in a lake

  15. Iron Oxidizing Bacteria • Gallionella (an iron-oxidizing bacterium) • 4Fe (HCO3)2 + O2 + 6H2O 4Fe (OH)3 + 4H2CO3 + 4CO2 + 58 kcal

  16. Ferrobacillus iron bacteria • 4FeCO3 + O2+ 6H2O Fe(OH)3 + 4CO2

  17. Mn cycling relative to O2

  18. REDOX and Sulfur

  19. S in oligotrophic and eutrophic lakes

  20. SO4 in a mesotrophichardwater lake

  21. SO4 budget for Linsley Pond

  22. ORP, pH, and Sulfur bacteria

  23. 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

  24. Bacterial Transformations of Sulfur • Sulfate-Reducing Bacteria (heterotrophic and anaerobic) • Sulfur-Oxidizing Bacteria • Chemosynthetic • Pigmented Autotrophic

  25. Sulfate-Reducing Bacteria • Ex: Desulfovibrio • Heterotrophic and anaerobic • H2SO4 + 2(CH2O) 2CO2 2H2O + H2S • H2SO4 + 4H2 H2S + 4H2O

  26. Chemosynthetic Sulfur-Oxidizing Bacteria • 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

  27. Green Sulfur Bacteria • Ex: Chlorobium • Uses a pigment similar to chlorophyll • CO2 + 2H2SLIGHT Food + H2O + 2S • 2CO2 + 2 H2O + H2S LIGHT Food + H2SO4

  28. Purple Sulfur Bacteria • Ex: Chromatium • They deposit sulfur intracellularly • Same reactions as Chlorobium

  29. Purple Non-Sulfur Bacteria • Ex: Rhodobacter • Na2S2O3+2CO2 +3H2O LIGHT Food + Na2SO4 +H2SO4

  30. Microbial-mediated Sulfur cycle in a lake

  31. Sulfate reduction in Lake Gek Gel and the Black Sea

  32. Distribution of sulfur in meromictic Lake Belovod

  33. Abandoned Mine Drainage

  34. Microbial Oxidation of Pyrite

  35. AMD Discharges

  36. Acid Precipitation

  37. Si in lakes

  38. Some Common Diatoms

  39. Si in oligotrophic Lawrence Lake

  40. Si and diatom population dynamics in Lake Windermere

  41. Dynamics of diatom periphyton and plankton

  42. Green Algae and Diatoms

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