Global sulfur cycle

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Lecture 4

• Global sulfur cycle
• Acid rain Origins and Formation
• Introduction to aqueous chemical equilibrium

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Homogeneous Gas-phase Mechanism
SO3(g) H2O ? H2SO4(g)
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Aqueous-phase Mechanism
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Alkalinity

• Alkalinity
• OH- HCO3- CO32- NH3 other
  proton acceptors H
• Alkalinity is a conserved property adding or
  removing a weak acid to or from water does not
  change the alkalinity.
• If either two of the three variables CT, pH and
  Alk are known, the remaining one can be known as
  well.

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Procedures to solve equilibrium problems

• Make a list of unknowns and assemble all relevant
  equations of equilibria.
• Use charge balance, mass balance and/or
  alkalinity to solve, using some reasonable
  assumptions. Note that for chemical species that
  are in equilibrium with the atmosphere or solid,
  mass balance does not work.
• Check whether the assumptions you have made are
  consistent with your answers.