Doctor of Philosophy (PhD)


Civil and Environmental Engineering

Document Type



Sediment capping remains an effective remediation technique for contaminated sediments due to its capability to contain contaminants and provide a sound habitat for indigenous biota. This research investigated the effect of capping on biodegradation of organic contaminants in Anacostia River sediments using both experimental and modeling techniques. 14C–Phenanthrene mineralization was monitored under various redox conditions in Anacostia River sediments. Mineralization of 14C–phenanthrene was strongly linked to sulfate reduction, which was the more energetic process than any other anaerobic condition in Anacostia sediments. Sulfate is a more promising terminal electron acceptor for intrinsic degradation in Anacostia River and other PAH contaminated sites. A sediment flux model was developed as a framework for simulations pertinent to this work and for future use in the field of environmental remediation. The model can be used to predict the response of the primary nutrients and overall sediment redox state after step changes in boundary conditions in sediment. Further, this study investigated the effects of reactive capping on long-term attenuation of organic contaminants, polycyclic aromatic hydrocarbons (PAHs) and hexachlorobenzene (HCB). Microcosm studies were conducted to investigate the attenuation potential of PAHs and HCB in Anacostia River sediment mixed with BionSoil as a capping material. BionSoil was used because it is rich in organic and carbon sources for driving anaerobic biodegradation and reductive dechlorination reactions. Faster removal kinetics and high sorption potential of HCB were observed in higher ratios of BionSoil than lower ones while for PAHs there were no differences among the treatments. Generally, degradation kinetics of PAHs and HCB were observed to be the fastest under sulfate-reducing conditions followed by ferric iron-reducing, methanogenesis, and manganic manganese-reducing conditions. Hydrogen concentration trends also suggested that hydrogen was used as an electron donor during both sulfate reduction and methanogenesis. BionSoil was found to be a promising material for ex-situ bioremediation in chlorinated solvents contaminated sites. Detection of the 16S rDNA of Pelobacter sp. and Desulfuromonas sp. by DNA extraction, PCR amplification, cloning and sequencing observed in Anacostia sediment under sulfate reducing conditions. Microbial community analysis results suggested that Pelobacter sp. and Desulfuromonas sp., which are members of Geobacteraceae family, possibly played important roles in the anaerobic degradation of PAHs.



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Committee Chair

John H. Pardue