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Limits to Petroleum Degradation

Limits to Petroleum Degradation. Name the 3 most common things that most often limit in situ petroleum hydrocarbon degradation. Nitrogen Phosphorus Oxygen. Oxidation/Reduction Reactions. Hydrocarbon biodegradation is essentially an oxidation/reduction reaction

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Limits to Petroleum Degradation

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  1. Limits to Petroleum Degradation Name the 3 most common things that most often limit in situ petroleum hydrocarbon degradation • Nitrogen • Phosphorus • Oxygen

  2. Oxidation/Reduction Reactions • Hydrocarbon biodegradation is essentially an oxidation/reduction reaction • Hydrocarbon is oxidized and Electron acceptor is reduced hydrocarbon + electron acceptor + microorganisms + nutrients  carbon dioxide + microorganisms + waste products Electron acceptors include: O2, NO3-, iron oxides (Fe(OH)3), SO42-, H2O

  3. Aerobic Degradation • Aerobic bacteria use O2 as their terminal electron acceptor • Water saturated with air contains 6 – 12 mg/L dissolved O2 • Complete conversion of hydrocarbons to CO2 and H2O requires ~3 mg/L of O2 for each 1 mg/L hydrocarbon • Maximum of 12 mg/L dissolved O2 = maximum 4 mg/L hydrocarbon degradation • Unlikely to have saturated dissolved O2

  4. Organic Chemistry polycyclic aromatic hydrocarbon monocyclic aromatic hydrocarbons primary alkane biphenyl type benzenoid ring organohalide nitro compound

  5. BTEX Benzene, Toluene, Ethylbenzene, Xylene • Volatile monoaromatic hydrocarbons • Commonly found together in crude petroleum and petroleum products such as gasoline • Major cause of environmental pollution • LUSTs: leaking underground storage tanks • ~35% of 1.4 million gas storage tanks in the US are leaking

  6. Biocatalysis/Biodegradation Database http://umbbd.ahc.umn.edu Microbial biocatalytic reactions and biodegradation pathways primarily for xenobiotic, chemical compounds.

  7. Aerobic BTEX Degradation • Pseudomonads: chemoorganotrophs, aerobic, rod-shaped bacteria • Important genera are: Pseudomonas, Burkhoderia, and sometimes Xanthomonas • Isolated from the environment • Some are pathogenic • 1968: strain of Pseudomonas putida isolated • grew on ethylbenzene, benzene, and toluene • toluene dioxygenase!

  8. Toluene Dioxygenase -Catalyzes over 108 reactions 1. Monocyclic aromatics 2. Fused Aromatics 3. Linked aromatics 4. Miscellaneous

  9. Anaerobic BTEX Degradation • Wide variety of microorganisms • Denitrifiers, example is Thauera aromatica • Iron Reducers • Sulfate reducers, examples are Desulfovibrio, Desulfobacter • Methanogens • Usually requires a consortium

  10. Field Studies • Crude oil study in MN in 2000 • Buried oil pipeline ruptured in 1979 = 3200 barrels of oil spilled into subsurface • Growth of aquifer microbial populations (dominated by aerobes, iron reducers, methanogens) • Biodegradation caused a number of FOOTPRINTS near the plume = geochemical changes What might FOOTPRINTS be???

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