The extraction of bitumen from the cretaceous oil sands ore within the Athabasca Oil Sands Region (AOSR) in Northern Alberta has generated over 1.18 trillion liters of by product in the form of Fluid Fine Tailings (FFT) and Oil Sands Process Water (OSPW)3. A reclamation strategy being investigated is water capped tailings technology (WCTT), that involves the development of Pit Lakes (PLs) by sequestering FFT below a water cap composed of both OSPW and fresh water to steadily densify these tailings over time4. A challenge that may impede this reclamation strategy is that as FFT densifies porewater containing oxygen consuming constituents (OCC) derived from anaerobic microbial degradation of labile petroleum hydrocarbons, such as gases (e.g. H2S, CH4), dissolved organic carbon (DOC) and dissolved ions (e.g. NH4+, HS-, and Fe2+), have the potential to be mobilized into to the overlying water cap. This dissertation is focused on developing an optimized comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC/TOFMS) methodology for analyzing the spatial distribution for a subset of identifiable solvent extractable PHCs species from FFT within Base Mine Lake (BML) the first full-scale demonstration of PL technology. The chemical “fingerprint” constructed from the concentration of each identified PHC isomer at a given depth and cosine theta (cos-Ɵ) similarity metric suggested the contribution of a singular source of PHCs within BML. Although a similar source fingerprint persisted throughout the study site, the spatial distribution for the isomers identified suggested differences in PHC input contributions across the FFT sampling platforms with the largest variation in concentration being attributed to the labile low molecular weight n-alkanes (C11 – C13) and postulated biomarker, drimane. These low molecular weight compounds, with the exception of drimane, are suspected components of residual naphtha, and the large variabilities in concentration are suggestive that these species may be linked with fluctuating inputs and/or sorption of naphtha to the organic phase of the FFT. Equally possible, the pronounced variability in the low molecular weight n-alkanes concentrations / Thesis / Master of Science (MSc)

The microbial origin of methane produced from sedimentary basins is a subject of great interest, with implications for the global cycling of carbon as well as natural gas exploration. Despite the growing body of research in sedimentary basin methanogenesis, few studies have sought to understand the subsurface microbial communities that produce methane, the metabolic pathways involved in the decomposition of ancient organic matter, or the components of ancient organic matter that are consumed. This research examined shale-derived dissolved organic matter (DOM) as a potential substrate to support a subsurface methanogenic community in a known microbial shale gas reserve, the Antrim Shale in the Michigan Basin, USA. Experiments were conducted that enriched fermentative and sulfate-reducing microbial communities from Antrim Shale formation waters. Additionally, 1H NMR spectroscopy was used to characterize shale-derived DOM solutions before and after they were used as growth media for fermentative and sulfate-reducing microbial communities, and to characterize the DOM of the Antrim Shale formation waters. The results of the enrichment studies demonstrate that both fermentative and sulfate-reducing microbial communities from the Antrim Shale are capable of growth using shale-derived DOM as their only source of organic carbon; further, the production of methane in a fermentative enrichment demonstrates that methanogenesis can be supported by shale-derived DOM alone. The 1H NMR characterization studies of the shale-derived DOM solutions before and after growth revealed subtle but detectable differences in DOM compositions, indicating the production and consumption of DOM components by the fermentative and sulfate-reducing microbial communities. Characterization analyses of Antrim Shale formation waters suggest that salinity and microbiological activity may influence the liberation of aliphatic and aromatic compounds from shale. The DOM characterization studies also suggest that carboxylic acids may be consumed by methanogenic communities in the Antrim Shale, and aromatic compounds may be produced by the enriched microbial communities and the communities present in the Antrim Shale.

Seven distinctly different museum-quality concretionary morphotypes of elongate, spheroidal, banded, botryoidal, columnar, rosette, and speleothem in regolith at two small sites at the base of the Meski Plateau near Erfoud, Morocco are described. Although most are isolated hand samples, the largest concretions are meter-sized blocks. Not one sample resembles any surrounding outcrop or bedrock. The barite rosettes formed first via periodic mixing of Ba2+/SO42- saturated solutions. They provided nuclei for cyclical precipitation-based concentric concretion development. The speleothem formed via precipitation from a carbonate-saturated solution in a large void within porous sandstone. The sand concretions formed when calcite precipitated around grains in unconsolidated quartz sands with cyclic fluctuation of Ca2+/CO32- saturated ground water. Petrographic analyses, stable isotope data, sample morphology, coupled with light and scanning electron microscopy indicate that microbial processes induced the periodic cement precipitation that produced the unique concretions.

Seasonal sea ice is an important component of the global climate system. Sea ice influences exchange rates of heat, moisture, and gas between the ocean and atmosphere. Sea ice also plays critical roles in high latitude ecosystems and marine carbon cycling. Records of sea-ice extent and duration in the Arctic Ocean and its marginal seas through geologic time are valuable resources for better understanding the intricate relationships between sea ice and climate. IP25, a compound biosynthesized exclusively by diatoms associated with sea ice, has been used to construct qualitative records of sea ice from sediment cores in some areas of the Arctic. However, IP25 has not previously been applied to sediments from the Bering and Chukchi Seas. This area exhibits a wide range of interannual seasonal ice duration, which makes the region a promising natural laboratory for developing a quantitative core-top calibration between sea ice and the IP25 biomarker. A sample suite of surface sediments from the Bering and Chukchi Seas representing a range of latitudes (60-72o N) and durations of sea ice per year (0.5-11 months/year) are analyzed for this study. Gas chromatography/mass spectrometry analysis of sediment solvent extracts reveals the presence of IP25 in all samples and higher IP25 concentrations in the Chukchi Sea compared to in the Bering Sea. IP25 concentrations are compared with data for several sea surface conditions: mean annual sea-ice duration, sea surface temperature and salinity, and insolation data. An exponential relationship between TOC-normalized IP25 concentration and average annual duration of sea ice is identified. Negative exponential relationships are identified between IP25 and the other sea surface conditions: average annual and August sea surface temperature and average annual and August sea surface salinity. Exponential relationships are also identified between TOC-normalized IP25 concentrations and insolation, and insolation coupled with sea-ice concentration. IP25 in surface sediments is a viable quantitative proxy for sea-ice duration in the Bering and Chukchi Seas. However, sea surface conditions, such as temperature, salinity, sea-ice duration/concentration, and insolation are not independent variables. Therefore it is difficult to determine which of these environmental factors has/have the most influence on IP25 production. Further research and statistical analysis may serve to refine these relationships.

No description available.

Coastal ecosystems are faced with increasing pressures from human activities. Perhaps one of the most profound impacts is that of excess nitrogen loading which drives a series of negative consequences. Excess nitrogen fuels primary productivity and the subsequent enhanced microbial decomposition of organic matter, consumes oxygen and releases carbon dioxide, which causes large fluctuations in pH. Changes in organic matter availability, oxygen concentrations, and pH can have significant yet unconstrained implications for sediment recycling and removal of biologically important nutrients such as nitrogen and phosphorus. Such changes can also impact the production and consumption of two powerful greenhouse gases – nitrous oxide and methane. Here I use two temperate estuaries, Long Island Sound (New York, USA) and Waquoit Bay (Massachusetts, USA) to assess the role of human impacts on coastal sediment biogeochemical fluxes. In Chapter 1, I investigate the influence of organic matter loading on sediment nutrient cycling, excess nitrogen filtering, and greenhouse gas emissions in Long Island Sound, a heavily nutrient polluted estuary. To provide a comprehensive analysis of these benthic fluxes and their environmental drivers, I incubated sediment cores from five stations along a west to east transect representing a gradient of high to low nutrient inputs and organic matter deposition. I found sediments across the estuary removed only 9% of land-based nitrogen entering the system and had a nitrogen removal efficiency of 30%. Additionally, sediments were often a source of inorganic nitrogen and phosphorus as well as nitrous oxide and methane. This study provides the first directly measured rates of sediment nitrogen removal and production in Long Island Sound. In Chapters 2 and 3, I investigate the effect of coastal acidification on benthic fluxes of greenhouse gases and nutrients across the sediment-water interface in Waquoit Bay. I collected sediment cores from two sites experiencing different rates of nutrient loading and experimentally altered the overlying water pH through a series of incubations representing moderate (pH 7.3) and extreme (pH 6.3) pH conditions. My results show low pH conditions have a strong effect on greenhouse gas and nutrient fluxes and responses vary by site. Specifically, in the high nutrient impacted site, nitrous oxide flux increased and methane flux decreased under acidification. In the low nutrient impacted site acidification drove reduced nitrous oxide flux, while methane flux decreased in the moderate treatment and increased in the extreme treatment. Acidification also affected benthic nutrient fluxes and drove the high nutrient impacted site to become phosphorus limited. Furthermore, the relationships and drivers between nutrient availability and nutrient fluxes shifted under acidification. This dissertation provides additional insight into how coastal ecosystems respond to human impacts. In Chapter 1, I present a critical missing piece of the nitrogen budget of a heavily impacted estuary. In Chapters 2 and 3, I begin to elucidate how low pH conditions can impact sediment biogeochemistry in estuarine ecosystems. Efforts to improve our understanding of human impacts on sediment biogeochemical fluxes will create better informed coastal management practices for these dynamic systems under a changing climate. / 2025-10-23T00:00:00Z

Soils contain the largest terrestrial pool of carbon (C), but the magnitude and distribution of the soil C sink may be sensitive to climate change. My dissertation aims to identify key processes that mediate patterns of belowground carbon storage across the globe and quantify the effect of environmental perturbations associated with global change on existing soil carbon stocks in peatland ecosystems. Using meta-analysis, I show that the relationship between plant growth, C allocation, and soil nutrient availability varies on a global scale and high-latitude ecosystems allocate >60% of fixed C to belowground structures. As high latitude ecosystems are warming faster than the global mean, the future of this belowground C store is potentially sensitive to climate change. In high latitude ecosystems in particular, I further show that belowground warming increases the rate of peatland carbon dioxide (CO2) and methane (CH4) losses, although CH4 emissions are more sensitive to warming than CO2 emissions, which is likely to shift the nature of greenhouse gas emissions and increase the importance of CH4 as a radiative forcing agent in the near-term. I also use a natural peatland water table gradient to identify the effect of water table reduction on peatland C and N cycling and find that microbial community shifts in C and N demand may attenuate production of C-degrading enzymes and C mineralization in the presence of plant roots and in areas with low water tables. Together, my dissertation work highlights the important role of belowground plant and microbial processes in high latitude ecosystems, and identifies the potential influence of factors associated with global change on belowground C and nutrient cycling.

No description available.

No description available.

No description available.