This proposal investigates the working hypothesis that phytoremediation can be used to degradeairborne PCB congeners from soil and groundwater sources. Plants stimulate the microbial communityin the root zone and contribute to microbial degradation of RGBs (rhizodegradation). Higher-chlorinatedPCBs are dechlorinated under reducing (anaerobic) conditions; resulting lesser-chlorinated congenerscan undergo oxidative mineralization under aerobic conditions. Alternating reducing and oxidizingconditions in the rhizosphere makes the plant-soil system a natural two-stage bioreactor for initial PCBtransformation. Lesser-chlorinated PCBs can also be taken-up and transformed inside plan tissues.
The specific aims of the project are (1) to test the hypothesis that poplar plants can take up and detoxifylesser-chlorinated PCB congeners by identifying metabolic pathways of PCBs and genes that encodefor catabolic enzymes, (2) to test the hypothesis that bacteria in the rhizosphere can reductivelydechlorinate higher-chlorinated PCBs and can mineralize resulting lesser-chlorinated congeners underoxidizing conditions; this will be tested using anaerobic and aerobic batch bioreactors with rhizospheresoils contaminated with PCBs, (3) to test the hypothesis that phytoremediation will allow for significantreductions in the airborne transfer of PCBs from waste disposal sites and mitigate exposure to humansand ecosystems; this innovative cleaning up strategy (based on hypotheses 1 and 2) will be tested atthe bench scale and by pot-studies in the greenhouse, (4) to test the hypothesis that residues of PCBsin plant tissues are non-toxic or of greatly reduced toxicity to biota by conducting an eco-toxicologicalevaluation of the phytoremediation process using a battery of toxicity tests, and (5) to test thehypothesis that higher plants play a significant role in the environmental cycling of airborne PCBs byfield analyses of PCB accumulation on vegetation. The significance of this project is that it provides anintervention and remedy for contaminated waste sites that will help to break the continuous cycling ofPCBs in the atmosphere and the subsequent exposure to humans.
Showing the most recent 10 out of 298 publications
