Thesis (M.S.) University of Alaska Fairbanks, 2010"Polychlorinated Biphenyls (PCBs) are priority pollutants targeted for remediation efforts in many areas of the world. Rhizoremediation, the use of plants and their associated root microorganisms for the degradation of a pollutant, may be an inexpensive and effective approach to biodegrading PCBs and detoxifying contaminated soils in situ. Two Alaskan native tree species, Salix alaxensis (willow) or Picea glauca (white spruce), were assessed for the ability to stimulate microbial PCB degradation by measuring PCB loss, toxicity and microbial community shifts in soil microcosms following the addition of crushed roots. Incubation of polluted soils with root crushates of S. alaxensis led to significant losses (up to 30% in 180 days) of several PCB congeners, including many of the most toxic congeners, PCB 77, 105 and 169. Soil toxicity, measured using the Microtox assay, also decreased as a result of treatment with willow-roots. Treatment of soils with salicylate, a willow secondary compound hypothesized to promote aromatic pollutant biodegradation, inhibited PCB degradation, suggesting that other willow biodegradation are responsible for biostimulation. The disappearance of PCB congeners, detoxification of soil, and detection of microbes with PCB degrading abilities suggests that S. alaxensis is a promising plant candidate for rhizoremediation of PCBs"--Leaf iiiIntroduction -- 1. Rhizoremediation of PCB contaminated soils : a review -- 2. Assessment of an Alaskan willow, Salix alaxensis, with potential for PCB rhizoremediation -- 3. Supplemental studies -- Conclusion
