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Sulfur Biogeochemistry

Principal redox states

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Sulfur Biogeochemistry

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    1. Sulfur Biogeochemistry Outline Redox chemistry of sulfur Global balance of sulfur Key processes in the sulfur cycle Examples Sulfate reduction and arsenic remediation

    2. Principal redox states & common forms S2-: sulfide (H2S, HS-, S2-; sulfhydryl (R-SH) S0: (elemental sulfur) S6+: sulfate (SO42-) mineral forms: gypsum (CaSO4·2H2O), pyrite (FeS2), native sulfur (S)

    3. THE FORMS OF SULFUR

    5. Sulfur in the Atmosphere

    6. Sources of Sulfur in the Atmosphere

    7. Sulfur in Rivers

    8. Marine sulfur cycle

    9. Global Sulfur Cycle

    14. CHANGES OF FORMS

    15. Thiobacillus

    16. S is oxidized by autotrophs for energy

    17. S oxidation and acid mine drainage

    18. Beggiatoa

    19. Sulfolobus

    20. SULFUR OXIDIZING FUNGI

    21. S oxidation under anaerobic condition Photosynthetic process

    22. GREEN SULFUR BACTERIA Photolithotrophic and Anaerobic Straight or curved rods to star-like extrusions, some spiral forms Gram negative Non motile Colonies are green, and brown (if carotenoids are present) Nitrogen fixation Non spore forming

    23. PURPLE SULFUR BACTERIA Anoxygenic Phototrophic Anaerobic or Microaerophilic Gram negative May be motile (polar flagella). Rods, cocci, and pleomorphic. Red, brown, purple, and orange pigments expressed. Yellow and red carotenoids. Bacteriochlorophylls a and b. Non spore-forming.

    24. Importance of S oxidation Produce available SO4= So application lowers soil pH Mineral weathering Acid mine drainage

    25. REDUCTION OF OXIDIZED S Environmental conditions: Anaerobic conditions (All O2 and NO3- gone) Available organic C exist Desulfuring microorganisms exist (Desulfovibrio)

    26. SR is important in anoxic habitats, limited by availability of sulfate in FW systems.

    28. Desulfovibrio desulfuricans Obligate anaerobes Curved rod-shaped cells Non-spore forming Gram negative Polarly flagellated

    29. Iron corrosion and S reduction

    30. Desulfotomaculum reduces arsenate (AsO43-) to arsenite (AsO32-), also reducing sulfate to bisulfide, precipitating arsenic sulfide (As2S3) in the process. This biomineralization process can detoxify mobile arsenic in the environment.

    31. Importance of S reduction Reduces available S Corrodes metal pipes Formation of S deposits

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