Browsing by Subject "Crude oil"
Now showing 1 - 5 of 5
- Results Per Page
- Sort Options
Item Effects of crude oil, chemical dispersant, and UV radiation on copepod nauplii from the Gulf of Mexico(2015-05) Harvey, Tracy E.; Buskey, Edward Joseph, 1952-; Erdner, Deana; Liu, ZhanfeiAnthropogenic oil spills continue to have devastating effects on the ecosystems in which they occur. Understanding how marine ecosystems are affected by these events is important for future mitigation and the improvement of preventative and restoration methods. The goal of this study was to investigate how copepods, the predominant group of zooplankton and base of the marine food web, respond under oil spill conditions. Two important and novel aspects were included: (1) exposing copepods at an early life stage when individuals tend to be more vulnerable to contaminant exposure and (2) including UV radiation as a factor in toxicity analysis. Three species of copepod nauplii, native to the Gulf of Mexico, were exposed to concentrations of crude oil (0.5-2 µL/L) and chemical dispersant (0.5 µL/L) for 48 hours. Survival, growth, and swimming behavior of the copepod nauplii were examined. At relatively low concentrations of oil (≥1 µL/L) sublethal effects were observed, including changes in growth and swimming behavior. Most notably, oil (1 µL/L) + dispersant, in the presence of UV caused a significant increase in mortality by 8X and oil (2 µL/L) in the presence of UV caused a significant increase in mortality by 13X, compared to the controls. A LC50 of 2.0 µL/L of crude oil was observed without UV exposure and a LC50 of 1.3 µL/L of crude oil was observed in the presence of UV. These results demonstrate the importance of considering factors such as UV exposure, chemical dispersant, and life stage when evaluating the potential toxicity of an oil spill to marine organisms.Item Experimental Evaluation of Co-Solvents in Development of High Performance Alkali/Surfactant/Polymer Formulations for Enhanced Oil Recovery(2009-12) Sahni, Vinay Manmohan; Pope, Gary A.The ability to select low-cost, high-performance surfactants for a wide range of crude oils under a wide range of reservoir conditions has improved dramatically. There are thousands of possible combinations of the chemicals (including salinities, hardness, oil concentrations) that could be tested for each oil, and each chemical combination requires many observations at reservoir temperature for proper evaluation, so it would take too long, cost too much and in many cases not even be feasible to test all combinations. The research presented in this work uses and describes a scientific understanding of how to match up the surfactant/co-surfactant/co-solvent characteristics with the oil characteristics, temperature, salinity and hardness. The work describes the role of co-solvents including some novel co-solvents in the formulation design and testing procedure. It is essential that the surfactant solution be a clear, stable aqueous phase. Surfactants that show ultra-low interfacial tension and excellent microemulsion phase behavior are often not sufficiently soluble at optimum salinity to give clear, stable aqueous solutions. Even slightly cloudy solutions often show phase separation or precipitation after a few days at reservoir temperature, which is very short compared to reservoir flooding times. The addition of polymer often makes the problem worse although the low solubility of the surfactant at high salinity is the fundamental problem. Surfactants with large hydrophobes produce the lowest IFT, but are often not sufficiently water soluble at optimum salinity. Hydrophilic co-surfactants and/or co-solvents are needed to make the solutions pass the stringent aqueous stability test. This research shows why this is so important, how to select and test the best co-solvents, and illustrates the results with core floods where the oil recovery was doubled by simply adding a small concentration of co-solvent to make the ASP slug clear. In such cases, the co-solvent more than pays for itself in terms of higher oil recovery because of the lower surfactant retention and improved effectiveness of the polymer for mobility control.Item Remediation of soiled masonry in historic structures contaminated by the Gulf Coast oil spill of 2010(2011-08) Vora, Payal Rashmikant; Holleran, Michael; Gale, Frances R.The objective of this thesis was to understand the factors that affect the selection of remedial treatments for the complex staining of masonry materials on cultural resources located in environmentally sensitive sites such as Fort Livingston, Louisiana, on the Gulf Coast of the United States and other locations impacted by pollutants including crude oil. After the Deepwater Horizon oil spill in April 2010, the brick-and-tabby Fort was stained by crude oil. The EPA recommends SWA for removal of oil from solid surfaces such as masonry; however, limited research has been conducted into SWA effective for removal of crude oil from masonry, particularly in remote and environmentally sensitive locations. Research was conducted collaboratively at NCPTT and UT-Austin to identify a series of suitable SWA and to develop methods for evaluating SWA effectiveness in the laboratory. Products were selected for laboratory evaluation that do not require long dwell times, are easy to transport to the site, can be applied with portable equipment, produce effluent that can be collected for off-site disposal, and are listed on the EPA-published NCP Product Schedule. Two sets of 36 brick samples each were soiled with crude oil from the Fort. One set of samples was artificially weathered and one set was unweathered prior to being cleaned with selected six SWA. Laboratory evaluation shows that the primary factor affecting cleaner selection for remediation of brick masonry stained by light crude oil is the extent of weathering of oil on the masonry. For light crude oil, such as that spilled in the Gulf, organic solvent-based cleaners may be most effective if cleaning is possible soon after the staining occurs. Aqueous surfactant cleaners are most effective for removing weathered light crude oil from masonry. The following SWA listed in order of performance are recommended for field trials at Fort Livingston: 1. Cytosol; 2. SC-1000; 3. De-Solv-It APC; 4. De-Solv-It Industrial followed by De-Solv-It APC; 5. De-Solv-It Industrial followed by SC-1000.Item The environmental influences on the growth and grazing of marine protists(2020-12-03) Tang, Chi Hung; Buskey, Edward Joseph, 1952-; Erdner, Deana L; Liu, Zhanfei; Stoecker, Diane KMarine protists are important components at the base of the marine food web. The growth and grazing of protistan organisms in response to the toxicity of petroleum hydrocarbons and elevated seawater temperature at the community and species levels were investigated. In exposure to 10 μL L⁻¹ of chemically dispersed crude oil in the mesocosms, the grazing impacts of microzooplankton (20-200 μm) on phytoplankton were reduced. While the microzooplankton grazing accounted for ~50% of the phytoplankton’ population growth in the control treatment, there was a de-coupling between these two parameters in the oil-loaded treatment. The de-coupling could potentially lead to algal blooms in the natural environment under certain conditions. In contrast, in exposure to chemically dispersed crude oil in the microcosms, the grazing impacts of nanoplankton (2-20 μm) on bacteria did not differ among the treatments of control and low (2 μL L⁻¹) and high (8 μL L⁻¹) concentrations. The tight couplings between the nanoplankton grazing and bacterial population growth in the control and oil-loaded treatments could have kept the abundance of bacterial cells steady. The community compositions of bacteria in the low and high dose crude oil treatments became increasing similar and different from those in the control treatment. It is believed to be related to the availability of carbon and inorganic nutrients. The relatively high abundance of hydrocarbon-degrading bacteria Cycloclasticus and Alcanivorax in the oil-loaded treatments indicated the presence of biodegradation. Exposure experiments were conducted to investigate the responses of marine protistan species to the toxicity of soluble petroleum hydrocarbon and elevated seawater temperature. In exposure to increasing concentrations of the water accommodated fraction (WAF) of crude oil, the heterotrophic dinoflagellates Oxyrrhis marina and Protoperidinium sp. and ciliates Euplotes sp. and Metacylis sp. showed species- specific vulnerabilities to oil toxicity, as reflected by their specific growth rates. When compared to the control treatment, their population grazing impacts and per capita ingestion rates were reduced with exposure to the WAF of crude oil alone and the mixture of crude oil and dispersant at the same concentration. In exposure to elevated seawater temperature, the Florida strain of mixotrophic dinoflagellate Fragilidium subglobosum obtained a specific growth rate of ~0.3 d⁻¹ at both 19°C and 23°C in mono-specific culture but zero or negative growth rates in cultures with added prey dinoflagellate Tripos tripos. F. subglobosum grown at 19°C showed higher maximum photosynthetic efficiency than at 23°C but did not differ in cellular chlorophyll-a content or cell size. This strain of F. subglobosum is believed to be non-mixotrophic and therefore the hypothesis that this dinoflagellate species becomes more heterotrophic at elevated temperature was not proved or disapprovedItem The value of commodity price forecasts in the presence of futures under uncertainty(2007-08) MacAskie, Robert Marcus; Jablonowski, Christopher J.This thesis examines the value obtained from the implementation of energy commodity forecasts in the context of a hedging decision. A decision-analytic model to value commodity price forecasts in the presence of futures is developed and subsequently applied to a data set of crude oil and natural gas prices. The findings include a method for evaluating the added value of such forecasts as well as appropriate improvements in forecast attributes to increase forecast value. Furthermore, it is found that for forecasts to be valuable, they must be accurate at predicting both gains and losses, and that there are positive and diminishing marginal returns to forecast value from improvement in key measure of accuracy in most cases. Forecast value is specific to user class, and that value is unique to specific users within each class. Lastly, the inclusion of an exponential utility function into the decision-analytic model enhances the reality of the decision characteristics of actual producers and consumers of crude oil. It is found that a producer or consumer of the commodity must be highly risk averse for price forecasts to have value when considering profit maximization alone among price forecast benefits.