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Final Progress Reports: Duke University: Microbial and Photolytic Transformations of Superfund Chemicals

Superfund Research Program

Microbial and Photolytic Transformations of Superfund Chemicals

Project Leader: Andrew J. Schuler
Co-Investigator: Karl G. Linden (University of Colorado, Boulder)
Grant Number: P42ES010356
Funding Period: 2000-2011

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Final Progress Reports

Year:   2004 

This project has focused on microbiological and photolytic processes for degradation of Superfund chemicals and their intermediate products. Very little work has been done on the interaction between microbiological and photodegradation processes, yet this combination may be particularly important in estuary systems, where chemicals suspended in the water column are exposed to microbes and to sunlight, and it may hold promise for the development of new engineered systems for remediation.

Microbial studies focused in part on the degradation of mixtures of PAHs by mixed bacterial populations. Sediment and water samples were collected from a salt-marsh tidal inlet along the Elizabeth River adjacent to the Atlantic Woods Industries Superfund site in Virginia as inoculum for the microbial studies. Enrichment cultures were established from the sediment samples and grown on fluorene, dibenzofuran, or dibenzothiophene as sole carbon sources, and the resulting mixed bacterial populations have been genetically identified. Growth studies on the enrichment cultures have been conducted to assess degradation rates and carbon source requirements. Studies are underway to monitor microbial community dynamics during PAH degradation.  Several bacterial isolates obtained with Elizabeth River sediments as inoculum and dibenzothiophene as sole carbon source have been genetically identified.  These were able to grow on a wide range of PAHs.  The discovery of an isolate able to grow on benzo[a]pyrene as sole carbon source is unique and may suggest a novel biodegradation pathway of this recalcitrant PAH.

The ultraviolet degradation portion of this work has focused on 3,5,6-trichloro-2-pyridinol (TCP), a degradation product of the organophosphorus pesticide chlorpyrifos. TCP degradation kinetics by UV and UV/H2O2 treatments at various aqueous solution pH values were investigated. The photodegradation rate of TCP increased with pH and with addition of H2O2. The kinetics and mechanism of photodegradation of fluorene, dibenzofuran and dibenzothiophene are currently being investigated. Biodegradation of non-oxidized and photo-oxidized forms of these compounds and photodegradation of biological intermediates will be studied next.

It was also determined that several PAH degradation intermediates are toxic with respect to embryonic and early life history stages in fish. Several hydroxynapthoic acids, bacterial metabolites of phenanthrene, anthracene, and 2-methylnaphthalene, lead to specific morbidity such as tube heart formation in Orange Red strain medaka embryos. Future work will focus on screening naphthoic acid isomer UV degradation byproduct toxicity.

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