Petroleum contamination is ubiquitous worldwide, and poses significant health risks to humans, organisms, and the environment. Understanding the fate and behaviour of these chemicals is extremely important in order to predict and mitigate the effects of spills and accidental releases, and limit the exposure of these contaminants to humans and ecosystems. The physical and biological interactions with various petroleum hydrocarbons released into the environment were examined throughout this thesis in two different environmental settings; offshore bay sediments near Deepwater Horizon oil spill impacted sites, and an experimental aquifer injected with compounds representative of ethanol blended fuels. Stable carbon isotopes were used to identify carbon sources in a given environment as well as utilized by microbial communities during biodegradation of petroleum hydrocarbons. Patterns of n-alkanes, low levels of UCM and the lack of PAHs suggest hydrocarbons in Barataria Bay sediments were of dominantly terrestrial origin. Stable carbon isotope analysis of microbial lipids and n-alkanes indicate the presence of some petroleum residues, however there is no strong evidence of Deepwater Horizon oil. Dissolved ethanol, toluene, and MTBE were continuously injected into a pilot-scale laboratory tank simulating an unconfined sand aquifer contaminated with ethanol blended fuel. Ethanol, toluene and MTBE all experienced significant mass loss within the aquifer, which was attributed to biological degradation using stable carbon isotope analysis of residual hydrocarbons. Isotopic analysis of PLFA indicated a strong ethanol sourced signature used in microbial metabolism with some indications of an additional carbon sources such as toluene or MTBE. / Thesis / Master of Science (MSc)

In the wake of concerns about the long-term integrity and containment of sub-surface CO₂ sequestration reservoirs, many efforts have been made to improve the monitoring, verification, and accounting methods for geo-sequestered CO₂. This Ph.D. project has been part of a larger U.S. Department of Energy (DOE) sponsored research project to demonstrate the feasibility of a system designed to tag CO₂ with radiocarbon at a concentration of one part per trillion, which is the ambient concentration of ¹⁴C in the modern atmosphere. Because carbon found at depth is naturally free of ¹⁴C, this tag would easily differentiate pre-existing carbon in the underground from anthropogenic, injected carbon and provide an excellent handle for monitoring its whereabouts in the subsurface. It also creates an excellent handle for adding up anthropogenic carbon inventories. Future inventories in effect count ¹⁴C atoms. Accordingly, we developed a ¹⁴C tagging system suitable for use at the part-per-trillion level. This tagging system uses small containers of tracer fluid of ¹⁴C enriched CO₂. The content of these containers is transferred into a CO₂ stream readied for underground injection in a controlled manner so as to tag it at the part-per-trillion level. These containers because of their shape are referred to in this document as tracer loops. The demonstration of the tracer injection involved three steps. First, a tracer loop filling station was designed and constructed featuring a novel membrane based gas exchanger, which degassed the fluid in the first step and then equilibrated the fluid with CO₂ at fixed pressure and fixed temperature. It was demonstrated that this approach could achieve uniform solutions and prevent the formation of bubbles and degassing downstream. The difference between measured and expected results of the CO₂ content in the tracer loop was below 1%. Second, a high-pressure flow loop was built for injecting, mixing, and sampling of the fast flowing stream of pressurized CO₂ tagged with our tracer. The laboratory scale evaluation demonstrated the accuracy and effectiveness of our tracer loops and injection system. The ¹⁴C/¹²C ratio we achieved in the high pressure flow loop was at the part per trillion level, and deviation between the experimental result and theoretical expectation was 6.1%. Third, a field test in Iceland successfully demonstrated a similar performance whereby ¹⁴CO₂ tracer could be injected in a controlled manner into a CO₂ stream at the part per trillion level over extended periods of time. The deviation between the experimental result and theoretical expectation was 7.1%. In addition the project considered a laser-based ¹⁴C detection system. However, the laser-based ¹⁴C detection system was shown to possess inadequate sensitivity for detecting ambient levels of ¹⁴CO₂. Alternative methods for detecting ¹⁴C, such as saturated cavity absorption ring down spectroscopy and scintillation counting may still be suitable. In summary, the project has defined the foundation of carbon-14 tagging for the monitoring, verification, and accounting of geological carbon sequestration.

A model system to calculate single-path coupling constant was devised to see if the couplings are additive in a system which has a dual-pathway. The system chosen was o-methyl-13C-benzoic acid. Because of anomalies in the data, the series was extended. Hybridization of the label appeared to have relatively little effect, and the conformation of the substituents very important.

The upper Homerian Mulde Event was a mass extinction that devastated graptolite diversity and occurred before and during the onset of a major perturbation to the global carbon cycle recorded as a double-peaked positive carbon isotope excursion (CIE). Whereas the Mulde Event and associated CIE are well-documented globally, changes in global sea level associated with the Mulde Event have only been investigated in detail in the West Midlands, England and Gotland, Sweden. A critical step toward understanding both the drivers and results of global climatic change during the Mulde Event is to constrain changes in eustasy. This study integrates carbon isotope chemostratigraphy and conodont biostratigraphy of Homerian strata in Tennessee, Indiana, and Ohio in an effort to determine if a global type-1 sequence boundary is recorded within the ascending limb of the Mulde CIE, and to produce a high-resolution chronostratigraphic framework for Homerian strata in the midcontinent USA. Six sections, two from each state, were measured and described. Five were sampled for carbon isotope chemostratigraphy, and one for conodont biostratigraphy. All sections from Tennessee and Indiana evidently contain the Mulde CIE, whereas the sections from Ohio are less clear due to the truncation of upper Homerian strata. These data demonstrate that a sequence boundary identified herein in Indiana and Tennessee is the same sequence boundary that occurred during the ascending limb of the Mulde Excursion in the West Midlands and Gotland.

Recent episodes of extreme weather and the drastic consequences they can have for ecosystems, societies, and economies, emphasize the need for a better understanding of Earths climate. In order to gain a better understanding of modern and future climate, a more thorough knowledge of past climates at the highest resolution possible from different regions is necessary. To this end, a study of seasonal temperature variability in the waters off the northern coast of Iceland was undertaken. Twenty-six bivalves were selected from marine sediment cores recovered from the northern and northwestern coasts of Iceland. Bivalves were selected from intervals of climatic interest as determined from sedimentological characteristics. Shells were micromilled and the carbonate analysed for stable oxygen and carbon isotope values. Oxygen isotope values are driven principally by the temperature of the water from which the shell was precipitated. These data provide a time-series of discrete climate profiles of seasonal temperature variations from c. 360 cal yr BC to cal yr AD 1660, each recording 2 to 9 consecutive years of temperature variability. Several notable warm and cold periods were identified and characterized in terms of maximum and minimum temperatures. As this period overlaps the Viking Age (c. 790 to 1070) and the establishment of Norse colonies in Iceland and Greenland, the temperature record was compared with historical records and demonstrates the significant impact of variation in temperature seasonality on the establishment, development, and in some cases, collapse of societies in the North Atlantic.

Recent episodes of extreme weather and the drastic consequences they can have for ecosystems, societies, and economies, emphasize the need for a better understanding of Earths climate. In order to gain a better understanding of modern and future climate, a more thorough knowledge of past climates at the highest resolution possible from different regions is necessary. To this end, a study of seasonal temperature variability in the waters off the northern coast of Iceland was undertaken. Twenty-six bivalves were selected from marine sediment cores recovered from the northern and northwestern coasts of Iceland. Bivalves were selected from intervals of climatic interest as determined from sedimentological characteristics. Shells were micromilled and the carbonate analysed for stable oxygen and carbon isotope values. Oxygen isotope values are driven principally by the temperature of the water from which the shell was precipitated. These data provide a time-series of discrete climate profiles of seasonal temperature variations from c. 360 cal yr BC to cal yr AD 1660, each recording 2 to 9 consecutive years of temperature variability. Several notable warm and cold periods were identified and characterized in terms of maximum and minimum temperatures. As this period overlaps the Viking Age (c. 790 to 1070) and the establishment of Norse colonies in Iceland and Greenland, the temperature record was compared with historical records and demonstrates the significant impact of variation in temperature seasonality on the establishment, development, and in some cases, collapse of societies in the North Atlantic.

No description available.

Afforestation and reforestation programs utilizing available fields for biofuel production, carbon sequestration, and other uses linked to climate change are looking to tree physiologists to identify species and genotypes best-suited to their purposes. The ideal poplar genotype for use in Canadian programs would be drought-resistant, cold-climate adapted, and fast-growing, thus requiring an understanding of links between a variety of physiological traits linked to growth and productivity. This study examined the basis for variations in water-use efficiency within four selected populations of Populus trichocarpa and Populus balsamifera (2 provenances each). Each species included both a northern and a southern provenance. Correlations between water-use efficiency, nitrogen-use efficiency, ¹³C/¹²C isotope ratio, stomatal conductance, and overall productivity were evaluated. Gas exchange variables measured included net photosynthesis, transpiration rate, stomatal conductance, and intercellular CO₂ content. Water-use efficiency and ¹³C content across all genotypes were highly correlated. Results suggested that variation in water-use efficiency was primarily related to variation in stomatal conductance across all genotypes. Whereas differences in net photosynthesis in this study were not significant between species, P. balsamifera did reveal a higher average stem volume overall. Although variation in stomatal conductance was the major determinant of differences in water-use efficiency, positive correlations were found between ¹³C isotope abundance and net photosynthesis in both P. balsamifera provenances. In this regard, results for the northern P. balsamifera provenance are the most consistent across all gas-exchange and growth trait correlations, in terms of meeting expectations for sink-driven water-use efficiency. The findings in this study suggest the possibility of identifying poplar genotypes with an absence of trade-off between water-use efficiency and nitrogen-use efficiency, notably among genotypes from the northern P. balsamifera provenance, near Gillam.

<p>Methane is an important greenhouse gas, and an ideal target for greenhouse gas emissions reductions. Unlike carbon dioxide, methane has a relatively short atmospheric lifetime, so reductions in methane emissions could have large and immediate impacts on anthropogenic radiative forcing. A more detailed understanding of the global methane budget could help guide effective emissions reductions efforts.</p><p>Humans have greatly altered the methane budget. Anthropogenic methane sources are approximately equal in flux to natural sources, and the current atmospheric methane concentration is ~2.5 times pre-industrial levels. The advent of hydraulic fracturing and resulting increase in unconventional natural gas extraction have introduced new uncertainties in the methane budget. At the same time, the next few decades could be a crucial period for controlling greenhouse gas emissions to avoid irreversible and catastrophic changes in global climate. Natural gas could provide lower-carbon fossil energy, but the climate benefits of this fuel source are highly dependent on the associated methane emissions. In this context of increasing uncertainty and growing necessity, quantifying the impact of natural gas extraction and use on the methane budget is an essential step in making informed decisions about energy.</p><p>In the work presented here, I track methane in the environment to address several areas of uncertainty in our present understanding of the methane budget. I apply the tools of methane analysis in a variety of environments, from rural groundwater supplies to an urban atmosphere, and at a range of scales, from individual point sources to regional flux. I first show that carbon isotopes of methane and co-occurrence of ethane are useful techniques for differentiating a range of methane sources. In so doing, I also show that leaks from natural gas infrastructure are a major source of methane in my study area, Boston, MA. I then build on this work by applying the same methane carbon isotope and ethane signatures to partition methane flux for the Boston metro region. I find that 88% of the methane enhancement in the atmosphere above Boston is due to pipeline natural gas. </p><p>In the final portion of this thesis and the two appendices, I move from the distribution side of the natural gas production chain to extraction, specifically addressing the potential impacts from hydraulic fracturing in my home state of North Carolina. I combine the methane source identification techniques of the previous sections with additional geochemical analyses to document the pre-drilling water quality in the Deep River Triassic Basin, an area which could be drilled for natural gas in the future. This data set is unique in that North Carolina has no pre-existing commercial oil and gas extraction, unlike other states where unconventional gas extraction is currently taking place. This research is, to my knowledge, the first to examine the hydrogeology of the Deep River Basin, in addition to providing an important background data set that could be used to track changes in water quality accompanying hydraulic fracturing in the region in the future.</p> / Dissertation

No description available.