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A Risk-Management Strategy for PCB-Contaminated Sediments (2001) / Chapter Skim
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Appendix E: PCB Biodegradation
Pages 329-333

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From page 329...
... In general, those with fewer chlorine atoms tend to be more readily biotransformed under aerobic conditions, and the higher chlorinated congeners are more readily biotransformed under anaerobic conditions. The potential for biodegradation is a function not only of the number of chlorine atoms on a given PCB molecule but also of their placement.
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From page 330...
... Dehalorespiration tends to be a more efficient dehalogenating process because the organisms can grow catalytically by the process; reaction rates tend to be higher, and the use of available electron donors is more efficient. Whether cometabolic or through dehalorespiration, reductive dehalogenation generally requires the presence of other organic matter, such as decaying vegetable matter, to provide the electron donor required for the process to occur.
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From page 331...
... This partitioning process also means that the more highly chlorinated species have less tendency to move from sediments to overlying waters. Transformation rates are generally directly proportional to solution concentrations rather than total sediment concentrations.
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From page 332...
... In any event, complete anaerobic dehalogenation of PCBs in sediments has not yet been reported in the peer-reviewed literature. Combined Anaerobic and Aerobic Biodegradation Because anaerobic conditions are best for decomposition of more-chiorinated PCBs and aerobic conditions for less-chlorinated PCBs, it would appear that sequential anaerobic and aerobic treatment could result in complete PCB degradation.
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From page 333...
... 1993. A highly purified enrichment culture couples the reductive dechlorination oftetrachloroethene to growth.
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Key Terms

  • chlorine atoms
  • reductive dechlorination
  • aerobic biodegradation
  • electron donor
  • biphenyl molecule

  • anaerobic conditions
  • highly chlorinated
  • solution concentrations
  • ortho chlorines
  • aerobic conditions

  • chlorinated congeners
  • pcb congeners
  • readily biotransformed
  • pcb dehalogenating
  • microbial reductive

  • chlorine atom
  • chlorinated species
  • transformation rates
  • anaerobic biodegradation
  • plateau appeared

  • organic matter
  • suggested various
  • ring effectively
  • polychlorinated biphenyl
  • molecular hydrogen

  • effectively block
  • dehalorespiration tends
  • anaerobic microbial
  • removal rates
  • organic materials


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