Thesis Abstracts 2003
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Potential for Phytoremediation of Polychlorinated Biphenyl (PCB) Contaminated Soil
By: Jane Amphlett (MASc. - Environmental Engineering)
Supervisors: Dr. Kenneth Reimer and Dr. Barbara A. Zeeb
Abstract
Polychlorinated biphenyls are persistent organic pollutants that present many remediation challenges. This study assessed the feasibility of using plants to remove PCBs from soil. This approach to contaminant removal is a low-cost and publicly acceptable alternative to current PCB remediation options, and is one aspect of an emerging area of study known as phytoremediation.
Three weathered soils contaminated with commercial grade Aroclor 1260 were used in greenhouse experiments. Aroclor 1260 contains a large amount of persistent PCB congeners and is traditionally the most difficult Aroclor formulation to remediate. The three soils contained a range of PCB concentrations (70-4750 ug/g) and a range of total organic content (0.06-2.02%) and permitted the evaluation of plant uptake in different soil environments. Nine plant species (Festuca arundinacea, Glycine max, Medicago sativa, Phalaris arundinacea, Lolium multiflorum, Carex normalis, and three varieties of Cucurbita pepo) were screened for their potential to extract PCBs from these soils. Experiments were performed in a greenhouse designed to control for PCB volatilization, temperature, and light. PCB concentrations ranging from < 1 ug/g to 470 ug/g were observed in shoot tissues. Although higher PCB concentrations were observed in root tissues, the absolute amounts (ug) of PCBs observed in shoot tissue were significant (1.7-288 ug). Congener signatures indicated that lower-chlorinated congeners (tetra, penta, and hexa chlorobiphenyls) contributed the largest proportions to shoots, either because of preferential uptake or degradation of higher-chlorinated congeners.
Overall, results indicate that varieties of C. pepo are more effective at removing PCBs from soil than other plants screened. Plant varieties and concentrations of PCBs in soil had a direct influence on the PCB burden observed in plants. Total organic content in soil did not influence plant uptake in this study. Furthermore, PCB volatilization did not appear to be a significant contributor to PCBs observed in plant shoots.
This study demonstrated conclusively, for the first time, the ability of plants to take up and translocate highly-chlorinated and persistent congeners found in Aroclor 1260. No detectable decreases in soil PCB concentrations were observed in these short-term greenhouse experiments but the results suggest that this could be achieved through multiple plantings. The knowledge gained in greenhouse experiments allowed for the design of an outdoor phytoremediation project, which is the next step in the development of this new technology.
