Polycyclic aromatic hydrocarbons (PAHs) and metals are co-contaminants of aquatic environments near industrial and urbanized areas. Mixtures could result in synergistic toxicity impairing macrophyte growth and potentially causing bioaccumulation and biomagnification throughout the ecosystem. In this study, combinations of 1,2-dihydroxyanthraquinone (1,2-dhATQ) and copper (Cu) at low concentrations synergistically inhibited Lemna gibba (duckweed) growth. Further analysis using fluorescence techniques showed an increase in reactive oxygen species (ROS) levels upon Cu exposures possibly through redox cycling in the chloroplasts. Pulse amplitude modulated (PAM) and fast repetition rate fluorometry (FRRF) indicated that plants exposed to 1,2-dhATQ had impaired photosynthetic electron transport that manifested as a decrease in the yield of photosynthesis and change in the redox status of the plastoquinone (PQ) pool. At the gene expression level acetyl coA carboxylase (ACC), a key enzyme in membrane repair, and serine decarboxylase (SDC), another enzyme needed for membrane repair were up-regulated in response to copper and 1,2-dhATQ, respectively. The mechanism for mixtures toxicity is thought to involve the reduced PQ pool which could serve as a source of electrons for copper redox cycling thereby increasing ROS production and causing synergistic growth inhibition. When the antioxidant glutathione (GSH) was added, copper toxicity was ameliorated but 1,2-dhATQ toxicity increased possibly through formation of reactive conjugates or suppression of the native antioxidant system. This study emphasizes that mixtures of toxicants at low concentrations can cause more biological damage than individual toxicants via alterations of the redox status and increases in ROS production.

Polycyclic aromatic hydrocarbons (PAH) have been identified as a serious environmental problem. In past research it has been proven that naphthalene, the simplest PAH, could be biodegraded using roller bioreactors and Pseudomonas putida. In this previous work it became apparent that the mass transfer rate of the hydrophobic naphthalene was the rate limiting factor in biodegradation, as the bacteria could degrade the naphthalene as fast as it entered solution. The challenge for the present research was to find a simple, inexpensive method for increasing the mass transfer rates within the framework of the previously successful reactor. <p>After some deliberation, the addition of inert particles (glass beads) was determined to be the preferred option to increase mass transfer. The inert particles visibly increased the turbulence in the reactor and significant increases in both mass transfer and bioremediation rates were achieved. The augmentation of mass transfer rates was found to be dependent on the type, size and relative loading of the particles. Two types of inert particles were investigated to increase mass transfer rates, spherical glass beads and Raschig rings. Glass beads were found to be far superior to Raschig rings for the intended purpose. Three sizes of spherical glass beads were then compared experimentally (1, 3, and 5mm). It was discovered that the 3mm beads were vastly superior to 1mm beads and 5 mm beads were slightly superior to 3mm beads. Different bead loadings (volume of particles / total working volume) were then explored with 10%, 25% and 50% bead loading investigated. Although slight increases in mass transfer were observed at higher bead loadings, the reduction in working volume for biodegradation meant that 50% was accepted as the optimum loading parameter. <p>The optimum conditions for maximum mass transfer occurred using 5 mm spherical glass beads at 50% loading. The increase in mass transfer and biodegradation rates compared to a traditional roller bioreactor were found to be 10 fold and 11 fold, respectively. The optimum mass transfer conditions were then applied to 2-methylnaphthalene with increases in mass transfer and biodegradation equal to 6 fold and 8 fold, respectively. The candidate bacteria used in this study was found incapable of degrading 1,5 dimethylnaphthalene although the mass transfer results demonstrate promise for the developed technology. To determine the effects of scale on the process, two larger reactors were finally studied. They were eight times and twenty-one times the size of the initial bioreactor. The process was shown to speed up at larger scale which shows great promise for future applications. The maximum degradation rate achieved in the larger reactor was 148 mgL-1h-1. This compares very well with the best result found in literature, 119 mgL-1h-1, which was achieved in a much more complex system. Clearly, the bead mill bioreactor designed during the present work is a simple concept that shows superior performance for the bioremediation of PAHs.

<p>Dibenzothiophene (DBT) is a constituent of creosote and petroleum waste contamination, it is a model compound for more complex thiophenes, and its degradation by mixed microbial communities has received little attention. The chemical characteristics, environmental fate and ecotoxicology of DBT degradation products are not well understood. This research investigated DBT degradation in an enrichment culture derived from creosote-contaminated estuarian sediment using a suite of assays to monitor bacterial populations, bacterial growth, degradation products, DBT loss, and toxicity. Ultraviolet (UV) irradiation was evaluated as a sequential treatment following biodegradation. Additionally, to advance SYBR-Green qPCR methodology for characterizing mixed microbial communities, an alternative approach for evaluating qPCR data using a sigmoidal model to fit the amplification curve was compared to the conventional approach in artificial mixed communities. The overall objective of this research was to gain a comprehensive understanding of the degradation of a model heterocyclic PAH, DBT, by a mixed microbial community, particularly within the context of remediation goals.</p><p>DBT biodegradation was evaluated in laboratory scale cultures with and without pH control. The microbial community was monitored with 10 primer sets using SYBR-Green quantitative polymerase chain reaction (qPCR). Twenty-seven degradation products were identified by gas chromatography and mass spectrometry (GC/MS). The diversity of these products indicated that multiple pathways functioned in the community. DBT degradation appeared inhibited under acidic conditions. Toxicity to bioluminescent bacteria <italic>Vibrio fischeri</italic> more than doubled in the first few days of degradation, was never reduced below initial levels, and was attributed in part to one or more degradation products. UV treatment following biodegradation was explored using a monochromatic (254 nm) low-pressure UV lamp. While DBT was not extensively photooxidized, several biodegradation products were susceptible to UV treatment. At higher doses, UV treatment following DBT biodegradation exacerbated cardiac defects in <italic>Fundulus heteroclitus</italic> embryos, but slightly reduced toxicity to <italic>V. fischeri</italic>.</p><p>This research provides a uniquely comprehensive view of the DBT degradation process, identifying bacterial populations previously unassociated with PAH biodegradation, as well as potentially hazardous products that may form during biodegradation. Additionally, this research contributes to development of unconventional remediation strategies combining microbial degradation with subsequent UV treatment.</p> / Dissertation

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 119-136).

Thesis (M.Sc.)(Microbiology))--University of Pretoria, 2009. / Summary in English. Includes bibliographical references.

Thesis (M.S. in environmental engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 14, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 41-42).

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xvi, 377 p. : ill. Includes abstract. Includes bibliographical references (p. 120-128).

Thesis (Ph. D.) in Microbiology--University of Maine, 2001. / Includes vita. Advisory Committee: Gary King, Clare S. Darling Prof. of Oceanography and Prof. of Microbiology and Marine Studies, Advisor; Katherine Boettcher, Asst. Prof. of Microbiology; Daniel Distel, Assoc. Prof. of Biochemistry, Microbiology & Molecular Biology; Jean MacRae, Asst. Prof. of Civil & Environmental Engineering; John Singer, Prof. of Microbiology and Chair of Dept. of Biochemistry, Microbiology & Molecular Biology. Includes bibliographical references (leaves 77-91).

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiv, 235 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 201-235).

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy