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(W/MF158) Integration of chemical, biological and toxicological methods for monitoring biorestoration of PCB-contaminated soil microcosms. Gravelat, Fabrice1, Pandard, pascal2, Giaccomazzi, Sophie3, Thybaud, Eric2, Truffaut, Nicole1, 1 2 3 ABSTRACT- Despite stopping production of polychlorinated biphenyls (PCBs) in the eighties, these molecules remain in the environment as widespread contaminants. They raise problems due to their long-term environmental persistence, toxicity, and potential role as human endocrine-antagonists. Bioremediation strategies were encouraged against incineration, as a cheaper and less polluting alternative. Under anaerobic conditions, bacterial cultures perform dehalogenation of highly chlorinated congeners (above 6 chlorines). Nevertheless the involved bacterial pathways remain unclear, and despite successes in enrichment of dehalogenating bacteria in cultures, attemps to isolate those bacteria have failed until now. Moreover the dehalogenation does not alterate the biphenyl cycle. On the other hand, aerobic bacterial pathways are well known and efficient in PCBs degradation, nevertheless they are only able to degrade low chlorinated congeners. In order to assess bioremediation of a highly chlorinated PCBs contaminated soil, an alternation of anaerobic and aerobic treatments was undertaken as a convenient way for biorestoration. The protocol was the following: a sandy soil containing highly chlorinated PCB (mainly PCB 101, 118, 138, 153, 180) was used to perform microcosms. This sand was mixed with natural soil, or with river sediments. N2 gas and water saturation allowed to maintain anaerobic conditions, and dehalogenating bacterial populations were stimulated by addition of various dihalobiphenyls (dHB) as primers. Chemical analyses assessed the dehalogenation of highly chlorinated congeners. The microcosms were then drained and bacteria were added. The bacteria were selected on the basis of their ability to degrade biphenyls and low chlorinated congeners. Molecular tools were designed to monitor bacterial evolution by quantitative PCR. Analytical and ecotoxicological tests were performed to evaluate the efficiency of remediation process. Key words: bioremediation, polychlorinated biphenyls, quantitative PCR, ecotoxicology |
