In Situ Enhancement of Anaerobic Microbial Dechlorination of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Marine and Estuarine Sediments

摘要

The management of marine and estuarine sediments contaminated with toxic organic compounds, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), is a major problem with far-reaching economic and ecological consequences. Enhancement of microbial degradation of PCDD/Fs in situ is an attractive remediation alternative that could potentially detoxify sediments, avoid the problematic redistribution of contaminants that is associated with dredging, and decrease the cost of sediment management. Reductive dehalogenation is a promising mechanism for the removal of toxic organohalides from estuarine and marine sediments. Anaerobic dechlorination of PCDD/Fs has been reported in marine and estuarine sediments, however, rates are slow and the activity may be the result of a combination of both respiratory and cometabolic processes. For in situ bioremediation, it would be most desirable to stimulate respiratory dechlorination, which is typically associated with higher dechlorination rates. Anaerobic reductive dechlorination is the first step required for the ultimate complete degradation of highly chlorinated PCDD/F congeners. Therefore, identification of the organisms involved, determination of their dechlorinating potential, characterization of how they compete for reducing equivalents with other members of the community, and development of strategies for enhancing their dehalogenating activities, are all needed. The overarching goal of this project, therefore, was to identify environmental conditions and amendments that enhance and accelerate dechlorination of PCDD/Fs by indigenous microbial populations and to identify the organisms responsible for the dechlorination using biomolecular methods. Results from this project show that anaerobic dehalogenation of PCDD/Fs was readily promoted in estuarine, marine and freshwater, sediments from several sites. This project has expanded our understanding of the microorganisms that carry out dehalogenation of PCDD/Fs.