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. plume: a continuous emission from a point source of contamination that has a starting point and a noticeable pathway

6. Typical hydrocarbon plume undergoing natural attenuation

7. 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

8. Biocatalysis/Biodegradation Database
Microbial biocatalytic reactions and biodegradation pathways primarily for xenobiotic, chemical compounds.

10. 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!

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

12. 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

14. What might FOOTPRINTS be???
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???

16. Chlorinated Solvents