The Sulfur Cycle

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The Sulfur Cycle
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• The symbol for sulfur is S and its Lewis
  structure is
• The sulfur cycle is primarily gaseous
•  Most sulfur found in underground rocks FeS2,
  iron pyrite and CaSO4, gypsum

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•      Natural release of sulfur into the
  atmosphere comes from
• o   weathering,
• o   gases from sea floor vents
• o   volcanic eruptions

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•      Most S enters the atmosphere through human
  activity
• Burning high sulfur fossil fuels, coal and oil,
  
• Smelting metal ores containing sulfur
•  Utilizing sulfuric acid in industrial processes
  and manufacture
•   Refining of petroleum

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•   Plants assimilate sulfur in the form of sulfate
  salts. Plants take in the sulfur (through several
  steps) and converts it into cell material in the
  form of macromolecules proteins
• Biotin, thiamin,(vitamins)
• insulin and some amino acids

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• When sulfur is used as an electron acceptor for
  energy metabolism it is referred to as
  dissimilative metabolism Sulfur is reduced and
  excreted to the environment
• H2S and SO2 is released to the atmosphere and
  the sulfur cycle through volcanoes and geysers
• H2s is also released in the breakdown of organic
  material in swamps, bogs and tidal flats.

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•  Some marine phytoplankton also produce CH3SCH3
  (DMS) dimethyl sulfide
• SO2 reacts with O2 to produce SO3 gas. SO3
  reacts with water to form, sulfuric acid (major
  contributor to acid rain. Creates human health
  problems, damage crops, buildings, reduce
  visibility.
• This is an example of a synergistic effect.

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• Sulfur containing clouds are brighter and
  increase Earths albedo provides a cooling
  effect which may offset a minor portion of
  earths heating caused by CO2 and other
  greenhouse gases.

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