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ABSTRACT
Contaminated sediments dredged from navigable waterways often are placed in confined disposal facilities to prevent further spread of the pollutants. Reducing contaminants to acceptable levels would allow for disposal of the sediments and further dredging activity. A greenhouse study was conducted to evaluate plant treatments and the addition of an organic amendment to decrease the concentration of PCB congeners found in Arochlor 1260. Sediment treated with the amendment and either low transpiring plants or no plants had the greatest removal of the PCB congeners. High-transpiring plants apparently prevented the highly reducing conditions required for reductive dechlorination of highly chlorinated PCBs. Most likely, the amendment provided labile carbon that initiated the reducing conditions needed for dechlorination. The sediment moisture content and moisture-related plant parameters were significant predictors of the PCB loss. Carex aquatalis and Spartina pectinata are predicted to be the most effective plant treatments for phytoremediation of PCBs.
POLYCHLORINATED BIPHENYLS (PCBs) were first manufactured in 1881 and became widely used in the United States in 1929. These chemicals have been utilized in a wide variety of applications including transformer oils to facilitate cooling, hydraulic fluids, surface coatings for carbonless copy paper, plasticizers, sealants, caulking, synthetic resins, paints, waxes, and as flameretardants in lubricating oils (Agency for Toxic Substances and Disease Registry, 2000). The known health effects and recalcitrance of PCBs in the environment resulted in Congress enacting section 6(e) of the Toxic Substances Control Act (TSCA) in 1976. This included prohibitions on the manufacture, processing, and distribution of PCBs. More than 680000 metric tons of PCBs were manufactured in the United States before cessation of production in 1977 (USEPA, 2006). Polychlorinated biphenyls were manufactured under the trade name Arochlor in the United States, and the most common were Arochlor 1232, 1242, 1254, and 1260. Each Arochlor is composed of 60 to 90 different PCB congeners (Frame et al., 1996). Arochlor 1260 is the most recalcitrant of these compounds (Quensen et al., 1990).
The wide use of PCBs and their resistance to degradation has caused these contaminants to have a broad geographic distribution (MacDonald et al., 2000). Polychlorinated biphenyls have a high affinity for soil, sediments, colloids, and hydrophobia organic solids (Wijayaratnet and Means, 1984; Amellal et al., 2001). Biological remediation is difficult because...