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Acid Mine Drainage

Acid Mine Drainage . Acid Mine Drainage. Air , bacteria and moisture during mining. P yrite. Yellow boy in a stream receiving acid drainage from surface coal mining . An Enviromental problem in coal-Mining region

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Acid Mine Drainage

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  1. Acid Mine Drainage

  2. Acid Mine Drainage Air, bacteriaand moisture during mining Pyrite • Yellow boy in a stream receiving acid drainage from surface coal mining. An Enviromental problem in coal-Mining region Degrades water quality > Mixing of acid mine water into natural in river Polluted water for human consumption and industrial use Pyrite Oxidation Propagation cycle Initiator reaction Formation of AMD

  3. The breakdown of pyrite • Leads to the formation of sulfuric acid and ferrous iron • pH values ranging from 2 to 4.5 • Sulfateion concentrations ranging from 1,000 to 20,000 mg L−1 but a nondetectable ferrous iron concentration • The acid formed attack other minerals associated with the coal and pyrite, causing breakdown of rock fabric • Alumunium : Highly toxic

  4. In AMD will be detectable some of acidophilic iron oxidizing thiobacilli. Acidithiobacillus ferrooxidans is involved, pyrite biooxidation proceeds • Pyrit Oxidation : • Ferric ion oxidation • Acidithiobacillusthiooxidans : Oxidized elemental sulfur (S0) and other partially reduced sulfur species : Intermediates in pyrite oxidation to sulfuric acid • Metallogenium-like organism that they isolated from AMD (Walsh and Mitchell (1972) ) - pH drops below 3.5.

  5. An early study by Harrison (1978) Inoculated : 20 L of an emulsion of acid soil, drainage water, and mud from a spoil from an old coal strip mine Microbialsuccession in coal spoil under laboratory conditions

  6. Result... • After 8 weeks : heterotrophs were still dominant • pH had dropped from 7 to 5. • pH to just below 5 >> caused by a burst of growth by sulfur-oxidizing bacteria, >> then died off progressively. • The heterotrophic population increased again to just below 107 g−1. • The sulfur-oxidizing bacteria were assumed to be making use of elemental sulfur resulting fromthe oxidation of pyrite by ferric sulfate: FeS2 + Fe2(SO4)3 → 3FeSO4 + 2S0 • Between 12 and 20 weeks : The population decreased

  7. NEW DISCOVERIES RELATING TO ACID MINE DRAINAGE • A fairly recent study of abandoned mines at Iron Mountain, California. • The ore body at Iron Mountain • various metal sulfides and was a source of Fe, Cu, Ag, and Au. • A signifi cant part of the iron was in the form of pyrite. The drainage currently coming • The distribution ofAcidithiobacillusferrooxidansandLeptospirillumferrooxidansfrom a pyrite deposit • in the Richmond Mine, seepage from a tailings pileand AMD storage tanks outside this mine

  8. The Richmond Mine revealed the presence of Archaea • in summer and fall months: Archaearepresented ∼50% of the total population • correlated these population fluctuations with rainfall and conductivity, (dissolved solids), pH, and temperature of the mine water • Ferroplasmaacidarmanus, grew in slime streamers on the pyrite surfaces. • extremely acid-tolerant : pH optimum at 1.2 • Its cells lack a wall • Archaeanorder Thermoplasmales

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