Integrated Chemical-biological Processes to Enhance Remediation of Estuarine Sediments Contaminated with Polybrominated Diphenylethers (PBDEs)
DescriptionPolybrominated diphenylethers (PBDEs), widely used flame-retardant additives, are persistent and toxic contaminants. Due to their widely uses globally, PBDEs are found in various environmental compartments, and pose adverse effects on human and environmental health. The estuary, a special coastal zone, is an area strongly influenced by human impacts, and estuarine sediment serves as a pollutant sink. Extremely high concentrations of PBDEs have been recorded in estuarine sediments around the world. Although penta- and octa-BDEs have been banned since 2000s and deca-BDEs production has also been ceased in 2013, PBDEs have been exponentially concentrated in the environment as a consequence of long-term usage. It is urgently needed to develop effective remediation technologies to eliminate PBDEs in contaminated environments. Physical and chemical processes have been employed to remove PBDEs from sewage and aqueous solution but they are often expensive and contain toxic chemicals. Their effectiveness and applicability in contaminated sediments are also uncertain. Biological process relies on aerobic and anaerobic biodegradation is far cheaper but its effectiveness is limited by the low bioavailability and the steric effects of substituted halogen moieties of PBDEs. It has been proposed that abiotic reactions can help reducing the limitations of biodegradation, and integrated chemical-biological processes may enhance the success of remediation.However, previous research on integrated remediation processes in contaminated sediment is rare. The possible impacts of the added chemicals on indigenous microbial communities in sediments and the effects of microorganisms on the abiotic process are basically unknown. The relative contribution of abiotic reactions and biodegradation processes in different estuarine sediments has seldom been reported. The proposed study attempts to investigate the effects of different abiotic reactions (zero-valent irons and small organic stimulants) on the changes of the structure and function of microbial communities, particularly those involved in PBDE degradation, and the microbial degradation of PBDEs, aiming to elucidate how integrated chemical-biological processes enhance the remediation of PBDE-contaminated estuarine sediments. The kinetics, pathways and mechanisms of the remediation processes will be determined using microcosm studies and the results will be verified by a field trial. The study will also evaluate the fate of chemicals (zero-valent irons and small organic stimulants) used in abiotic reactions during the remediation processes and how the presence of microorganisms affect their fates. The results from the proposed study will fill the knowledge gap on PBDE removal and provide scientific information for developing cost-effective remediation technologies to clean-up contaminated environments.
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