New Views of an Old Planet scales

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Outline Aqueous Geochemistry
Everything is everywhere, the environment
selects. L.M.G. Baas-Becking (Dutch
microbiologist)

• New Views of an Old Planet (scales)
• Microbial Environments focus on aqueous aspects
  (buffering Gibbs free energy)
• Geochemical Processesinorganic composition
  (elemental speciation)chemical reactions and the
  law of mass actionacid/base and redox buffering
  (EH-pH diagrams)

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Anatomy of a Black Smoker
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Aqueous Depositional Environments
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Unit conversions for water chemistry Converting
mg/L (ppm) to mol/L and meq/L
45 mg/L Na x 1 mmol Na /22.98 mg Na 1.96
mmol/L 1.96 mmol/L x 1 meq Na /mmol Na
1.96 meq/L
70 mg/L SO42- x 1 mmol SO42- /96 mg SO42- 0.73
mmol/L 0.73 mmol/L x 2 meq SO42- /mmol SO42-
1.46 meq/L
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Log K -?Gº/5.708 for kJ/mol
EH Eº (0.059/n) log (aox/ared)
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Acid/base Systems Carbonic Acid
pK1
pHpK16.35
pHpK26.35
pK2
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Carbonic Acid Dissociation Reactions 1 H2CO3
? H HCO3- K1 H HCO3-/H2CO3 HCO3-/
H2CO31 when pK1 pH 2 HCO3- ? H CO3 K2
H CO3/HCO3- CO3/HCO3-1 when pK2
pH remember pK -logK just like pH-logH
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H2S
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EH-pH diagrams
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Considersminerals
EH-pH diagrams for Sulfur
Aqueous only
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Silicate Classification
Isolated (olivine) Single Ch. (pyroxene) Double
Ch. (amphibole/hornblende) Sheet (mica biotite
or muscovite) 3D-framework feldspar
(orthoclase, plagioclase), quartz
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Calcite