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Previous studies have come to contrasting conclusions regarding nutrient limitation of hydrocarbon biodegradation in the Gulf of Mexico, and rate measurements are needed to support oil plume modeling. Thus, this study investigates the rates and controls of biodegradation in seawater and sediments, largely in the deepsea. Sediment and seawater samples were collected on research cruises in the northern Gulf from 2012 to 2014, where the seafloor was impacted by the Deepwater Horizon (DWH) oil spill. Biodegradation was clearly limited by both nitrogen and phosphorus availability in surface waters with significant rates of CO₂ production (100 μmol CO₂ l⁻¹ d⁻¹) only observed in treatments amended with ammonium and phosphate. In deepsea sediments, nutrient amendments resulted in an average of 6 fold higher degradation rates (0.49 μmol CO₂ g sed⁻¹ d⁻¹) compared to unamended controls. Microbial communities responded to oil contamination rapidly in a series of enrichment cultures, and selection was observed for populations of native hydrocarbon-degrading bacteria. Temperature was shown to be a major factor in controlling microbial community composition in the enrichments. At room temperature, community diversity in the enrichments was significantly reduced in the presence of oil, while under 4 °C, the community diversity and evenness remained relatively high upon oil amendment. From the same deepsea sediments, 30 strains of known oil-degrading bacteria (Rhodococcus and Halomonas) were enriched and isolated with hexadecane, phenanthrene, and Macondo oil as the sole carbon and energy source. Detection of these strains in sequence libraries indicates that they may have contributed to the degradation of oil deposited onto the sediments. Rhodococccus strain PC20 degraded approximately one-third of total petroleum hydrocarbons amended into cultures within 7 days. This work elucidates the controls of biodegradation and we provide model pure cultures to further elucidate the ecophysiology of hydrocarbon degradation, focusing on deepsea sediments of the northern Gulf of Mexico.

C3H6 oxidation over a Pt/Al2O3 catalyst with or without NOx present was investigated. In particular, its reaction mechanism was studied using diffuse reflectance infrared spectroscopy (DRIFTS), a reactor system designed for monolith-supported catalysts and a micro-reactor system designed for powder catalysts referred to as CATLAB. These experiments reveal that C3H6 oxidation is inhibited by the presence of NO, NO oxidation is inhibited by the presence of CeH6, and that adsorbed NOx can react with gas phase C3H6. DRIFTS and CATLAB results confirm the reaction between C3H6 and nitrates, which are formed during NOx adsorption, with linear nitrites observed as reaction products. Therefore, a reaction route is proposed for C3H6 oxidation in the presence of NOx, namely, nitrates acting as oxidants. Using NO2 instead of NO, or using a high NOx/C3H6 ratio, which is beneficial for nitrate formation, favors this reaction pathway. Data also showed that Pt is required for this reaction, which suggests the nitrates in proximity to the Pt particles are affected/relevant. Reaction kinetics studies of C3H6 oxidation over Pt/Al2O3 and Pt/SiO2 catalysts were performed in CATLAB using a temperature-programmed oxidation method with different oxidants: O2, NO2 and nitrates. The reaction kinetics of these possible reactions were compared in order to determine which reaction is more important. NOx adsorption does not occur on the SiO2 surface so the reaction between C3H6 and NO2 could be isolated and the effect of nitrates could be observed as well when compared to the results from Pt/Al2O3. The Pt dispersions were determined using H2 chemisorption and were 1.3 and 1.6% for Pt/Al2O3 and Pt/SiO2, respectively. C3H6 oxidation starts at a lower temperature with O2 than with NO2 but the activation energy was lower with NO2. This gives indication that hydrocarbons must be activated first for NO2 to be favored in hydrocarbon oxidation. When the experiment was done with C3H6 and nitrates, the reaction did not occur until NOx started to desorb from the catalyst at higher temperatures, when nitrates become unstable and decompose. Therefore, O2 was added to the system and the reaction began at even lower temperature than with just C3H6 and O2. This proved that hydrocarbons need to be activated in order for surface nitrates to affect C3H6 oxidation and this reaction also resulted in a lower activation energy than with just C3H6 and O2. Nitrate consumption was also observed as less NOx desorbed from the catalyst at the later stage of the temperature ramp compared to the amount desorbed when the catalyst was not exposed to C3H6.

Research was conducted into using supercritical fluid extraction (SFE) for removing hydrocarbons from drill cuttings slurries, which will be used in a pilot-scale continuous SFE system currently under development. A laboratory-scale batch SFE system employing supercritical carbon dioxide (CO2) was used in this research. Based on the measured hydrocarbon solubility and apparent hydrocarbon solubility in supercritical CO2, conditions of 14.5 MPa and 40oC were selected for SFE treatment. The slurries require a minimum water to drill cuttings ratio of 1:1 (mass basis) to be free-flowing and therefore suitable for treatment in a continuous system. Water in the slurries leads to lower hydrocarbon extraction efficiencies during SFE treatment compared to the treatment of drill cuttings without slurrying. However, effective mixing and introduction of the supercritical CO2 at the bottom of the extraction vessel resulted in treated slurries containing less than 1% hydrocarbons (dry mass basis). / Environmental Engineering

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The occurrence of palaeo-oil columns in Late Jurassic and Cretaceous reservoirs in the Vulcan sub-basin indicates that hydrocarbon accumulations have leaked. It is unclear whether accumulations have leaked through breach of top seal or fault seal. This study evaluates the top seal potential for hydrocarbon accumulations in the Vulcan Sub-basin. For this purpose a top seal potential assessment methodology was developed. Seal potential (SP) combines seal capacity (the hydrocarbon column height that can physically be held back by seal), seal geometry (the areal extent and thickness of the seal) and seal integrity (rock mechanical properties of the seal). Seal capacities are measured using mercury injection capillary pressure calculations. Areal extent is evaluated using sedimentological and sequence stratigraphic principles. Thickness is determined empirically from well logs and seismic data. Seal integrity is derived from a brittleness index. In addition, a component relating to data quality and quantity is included in seal potential evaluation. The main sample set for this study is composed of drill cuttings. For this reason a comparison of seal capacity results measured from cuttings and cores has verified that cuttings samples provide accurate seal capacity measurements. Lower Vulcan Formation SP ranges from low to high due to variations in seal capacity and thickness risks as well as data quality and quantity. High SP occurs in the main depocentres and low SP occurs on the palaeo-highs and basin margins. Upper Vulcan Formations SP ranges from low to moderate due to variations in seal capacity. Moderate SP occurs in the depocentres and low SP on the basin margins. In the Echuca Shoals Formations seal capacity. Formation seal extent and integrity as well as data quality and quantity are good. However seal thickness is inconsistent, resulting in SP variations from good to poor as a function of thickness. Jamieson Formation has high seal capacities, is thick and areally extensive, however the seal potential is locally moderate (for example on the Ashmore Platform) due to seal integrity risk. SP for the Jamieson is controlled by the thickness and the amount of calcite present in the rock, which affects the brittleness of the formation and hence the seal integrity. The Woolaston, Gibson and Fenelon (WGF) Formations are grouped together as a regional seal and in this group SP varies from low to high. The WGF rocks generally have high seal capacities, are areally extensive and thick with good data quality and quantity sample set wise. Where the WGF is predominantly marl and calcilutite some of the highest brittleness index values were recorded and hence the WGF has a low SP in these areas. Based on the overall seal potential analysis, almost all seals in the area are capable of holding back hydrocarbon columns greater then present or palaeocolums recorded. This suggests that hydrocarbon leakage in the Vulcan Sub-Basin did not occur as a result of top seal capillary failure. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1313021 / Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 2008

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on April 16, 2008). Includes bibliographical references (p. 157-174).