Physical Sciences and Mathematics Commons^™

Topographic Influences On Trends And Cycles In Nutrient Export From Forested Catchments On The Precambrian Shield, Samson G. Mengistu

Electronic Thesis and Dissertation Repository

This dissertation explored topographic controls on spatial and temporal patterns in water yield and nutrient (carbon, nitrogen and phosphorus) export from forested headwater catchments in the Turkey Lakes Watershed in central Ontario, where other factors contributing to differences in water yield and nutrient export, including climate, geology, forest, and soils, are relatively constant. Topographic characteristics, including (a) hydrological flushing potential (expansion of water table into nitrate-N producing areas); (b) hydrological storage potential (area of wetlands, which can alternatively allow water and nutrients to bypass wetlands when storage capacity is filled with water or to trap them when not filled); and …

Characterization Of Novel Ichnofossils In Meteorite Impact Glass From The Ries Impact Structure, Germany, Haley M. Sapers

Electronic Thesis and Dissertation Repository

The initial catastrophic biological effects of hypervelocity impacts are well established. However, a growing body of evidence suggests that meteorite impact events have beneficial effects for microbial life. This, in turn, has led many to suggest that impact craters may have been important habitats for life on early Earth. Any large meteorite impact into a water-rich target on a solid planetary body has the potential to generate hydrothermal systems. Impact-generated hydrothermal systems expand the potential environments for microbial colonization to environments without endogenous volcanic heat sources to drive hydrothermal activity. Examination of impact glass from the Ries impact structure, Germany, …

Biogeochemical Processes In Hydrosoil Of A Pilot-Scale Constructed Wetland Treatment System Designed For Treatment Of Metals, Kristen Jurinko

All Theses

Environmental conditions, metal (Cd, Cu, Ni, and Zn) distribution, and metal fractionation in hydrosoil (sediment and overlying organic detritus) of a free water surface pilot-scale constructed wetland treatment system (CWTS) were investigated to determine treatment processes. Chemical and mineralogical analyses were performed on organic detritus samples and sediment cores collected from two cells planted with Schoenoplectus californicus and two cells planted with Typha angustifolia. T-tests indicate that cells planted with S. californicus and those planted with T. angustifolia were equally effective in promoting conditions in the detritus favorable for sorption of metals and complexation with acid-volatile sulfide (AVS). For the …

A Geochemical Analysis Of Fulgurites: From The Inner Glass To The Outer Crust, Michael L. Joseph

USF Tampa Graduate Theses and Dissertations

Cloud-to-ground lightning strikes produce natural glasses on the surface of the Earth, called fulgurites. These natural glasses are tubular in shape with a central void surrounded by an inner glass, and the inner glass is surrounded by an outer crust or toasted region. Previous studies report different kinds of melts existing in several different types of fulgurites; however, little to no chemical data has been collected that tracks chemical variations from the inner glass to the outer crust of a fulgurite. This study uses microprobe and laser ablation inductively coupled plasma mass spectrometer analytical techniques to collect transects of chemical …

Production Of Bioactive Secondary Metabolites By Florida Harmful Bloom Dinoflagellates Karenia Brevis And Pyrodinium Bahamense, Cheska Burleson

USF Tampa Graduate Theses and Dissertations

Despite the critical role algae serve as primary producers, increases or accumulation of certain algae may result in Harmful Algal Blooms (HABs). Algal toxins from these blooms contribute significantly to incidences of food borne illness, and evidence suggests HABs are expanding in frequency and distribution. Mitigation of these HABs without knowledge of the ecological purpose and biochemical regulation of their toxins is highly unlikely. The production, function, and potential of secondary metabolites produced by the dinoflagellates Karenia brevis and Pyrodinium bahamense, were investigated.

Brevetoxins were demonstrated by two different methods to localize within the cytosol of Karenia brevis. …

Spectroscopic Characterization Of Dissolved Organic Matter: Insights Into Composition, Photochemical Transformation And Carbon Cycling, John Robert Helms

Chemistry & Biochemistry Theses & Dissertations

This dissertation explores processes affecting the composition of dissolved organic matter (DOM) and how DOM composition changes in sunlit surface waters and in the dark interior ocean. Simulated solar irradiations were used to investigate the impact of photochemistry on terrestrial waters and deep ocean DOM. The photochemically mediated processes observed in Dismal Swamp samples included (i) light induced flocculation of up to 12% of the organic matter and 84% of the dissolved iron originally present; (ii) 74-88% mineralization of dissolved organic carbon (DOC) and 95-99% bleaching of chromophoric DOM (CDOM) during 110 days of irradiation; and (iii) nearly complete loss …

The Relation Among Essential Habitat, Ocean Acidification, And Calcification On The Nantucket Bay Scallop (Argopecten Irradians), Bryanna Joy Broadaway

Graduate Doctoral Dissertations

The relation among essential habitat, ocean acidification, and calcification in Argopecten irradians (Lamarck 1819) was examined through field and laboratory research. Three major questions were addressed: 1) What habitat conditions are associated with abundant populations of bay scallops in Nantucket Harbor? 2) How might future predictions of ocean pH decline affect the biomineralization of shell by bay scallop across juvenile and adult life stages? 3) Are there biochemical indicators that can inform our understanding on how the bay scallop may cope with ocean acidifying events? Elemental fingerprinting of adult and juvenile Nantucket bay scallop shells, A. irradians, revealed distinct element/Ca …

Bacterial Communities And Their Influence On The Formation And Development Of Potholes In Sandstone Surfaces Of The Semi-Arid Colorado Plateau, Kebbi A. Hughes

Electronic Thesis and Dissertation Repository

Potholes are weathering features, of various sizes and shapes, which are found in exposed rock surfaces that lack vegetative and soil cover. Biofilms associated with the ephemeral aquatic pothole environments of the Colorado Plateau were examined as initial and intermediate stages of colonisation of arid, oligotrophic rock surfaces.

Imaging of the interface between pothole biofilms and their host rock revealed features of biological weathering; chiefly, the breakdown of silicate minerals and precipitation of clay and carbonate minerals. High pH measured in pothole water reflected deposition of secondary carbonate minerals at some locations and indicated the development of high pH microenvironments …

The Weathering Of Platinum From Nuggets And Platinum Immobilisation By Cupriavidus Metallidurans, Sean Gordon Campbell

Electronic Thesis and Dissertation Repository

Two studies were conducted to investigate the biogeochemistry of platinum. In the first project, platinum nuggets were examined to evaluate mineral dissolution-precipitation processes occurring at the nugget-‘soil solution’ interface. The presence of dissolution ‘pits’, cavities, and striations as well as acicular, iron oxides coating the grain surface evidence that this interface is an important site of mechanical and chemical weathering. Element mapping revealed that structural and chemical signatures can be linked to morphological features on the grain surface. In the second study, the soil bacterium Cupriavidus metallidurans was reacted with aqueous platinum chloride and rapidly immobilised platinum. XANES/EXAFS analysis of …

The Carbon Budget Impact Of Sagebrush Degradation, Andrew Connor Austreng

Boise State University Theses and Dissertations

More than 20,000 km2 of sagebrush (Artemesia spp.) ecosystems within the Great Basin have been replaced, often following wildfire, by the nonnative winter annual cheatgrass (Bromus tectorum). At a field site in the central Snake River Plain of southern Idaho, the impact of this invasion on the soil carbon (C) reservoir has been evaluated and the potential soil C benefits of bunchgrass (Agropyron cristatum) seeding was assessed. Using a large soil C dataset (n = 850), differences in total organic carbon and root biomass were quantified in immediately-adjacent sagebrush, cheatgrass, and bunchgrass communities. Statistical …

Using Emerging Methods To Investigate Stream And Groundwater Interaction At Multiple Spatial Scales, Martin Ashley Briggs

Earth & Environmental Sciences - Dissertations

Fundamentally, streams represent physical conduits of water across gradients, yet a more holistic definition reveals stream corridors support a mosaic of living communities in a blend of surface and ground waters. The physical and biogeochemical patterns these dynamic systems support affect natural habitat and water quality, directly impacting the human experience. Our understanding of stream and groundwater interactions is at a time of rapid expansion due to an increase in environmental awareness, accountability, and emerging techniques which can be used to decipher underlying controls and develop predictive relationships. Water temperature has been used as a qualitative environmental tracer during the …

Natural And Constructed Wetlands For Ecosystem And Engineering Services In The Arid And Semi-Arid Regions, Achyut Raj Adhikari

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Las Vegas Wash (LVW) has undergone significant wetlands degradation and soil erosion over the past thirty years due to increasing flow resulting from urbanization and large rainfall events in the Las Vegas Valley Watershed. The increased flow and associated pollution load in the LVW and its adverse impact in Lake Mead have alerted stakeholders to pay a greater attention to explore alternative measures for rehabilitation of wetland ecosystems. This dissertation, using the case of changes in LVW, analyzes and describes ecological and engineering services provided by wetlands in arid and semi-arid regions and provides a knowledge base that can …

Reconstructing Fire Severity From The Oxygen-Isotope Compositions Of Plant Char, Michael W. Hamilton

Electronic Thesis and Dissertation Repository

This study assessed whether variations in the oxygen-isotope compositions of char formed from biomass burning could be related to burning severity. Ground samples of oak (Quercus alba), pine (Pinus resinosa), and grass (Andropogon gerardii) were charred for 5 and 30 minutes at constant temperatures between 200 and 900°C under oxygenated versus anaerobic conditions. Char oxygen-isotope values became progressively depleted of ¹⁸O by up to 25.8‰ for wood and 16.5‰ for grass as temperature, duration of burning, and amount of oxygen increased. The primary reason for the decrease in oxygen-isotope values is the loss …

Phosphate Availability During Sediment Resuspension Events In The Great Bay Estuary, Taylor Langkau

Honors Theses and Capstones

Phosphate is an important nutrient to marine ecosystems such as the Great Bay Estuary. However, its bioavailability is limited due to its tendency to adsorb to marine sediments, especially iron oxides. This paper investigates phosphate dynamics during a simulated storm compared to calm conditions and aims to quantify the mechanisms of phosphate adsorption.

A Geobiological Investigation Of The Mazon Creek Concretions Of Northeastern Illinois, Mechanisms Of Formation And Diagenesis, Andrea S. Fernandes

Electronic Thesis and Dissertation Repository

Siderite concretions from the mid-Pennsylvanian Francis Creek Shale of the Mazon Creek area, in northeastern Illinois, contain exceptionally preserved soft-tissue fossils. Scanning electron microscopy, energy dispersive spectroscopy, time of flight-secondary ion mass spectrometry and micro-x-ray diffraction on polychaete worm, jellyfish and holothurian samples highlighted detrital clay and quartz grains in siderite cement. The worm and jellyfish are pyritised and surrounded by pyrite halos, whereas the holothurian is preserved as a weathered impression. Specimens possessed either microbial textures or framboidal pyrite, in carbon-enriched zones. The carbon-enriched zones contained organic compounds, indicating that extensive degradation associated with high temperature diagenesis did not …

The Impact Of Decadal Land Cover Change On The Global Warming Potential Of Beringian Arctic Tundra, David Hwei-Len Lin

Open Access Theses & Dissertations

Arctic terrestrial ecosystems play an important role in the global carbon cycle. If arctic warming continues to rise as projected, large amounts of soil carbon stored in these ecosystems could be released to the atmosphere as carbon dioxide or methane and positively enhance greenhouse warming. Thus, improving understanding of the likely future state and fate of arctic soil carbon, and the carbon uptake potential of arctic terrestrial ecosystems are well recognized research priorities.

At the pan-arctic scale, decadal increases in NDVI (Normalized Difference Vegetation Index), an index of vegetation productivity, have been observed from satellite imagery, indicating a general greening …

Implications Of Decade Time Scale Arctic Plant Community Change On Ecosystem Function, Mark Jason Lara

Open Access Theses & Dissertations

Almost half the global soil organic carbon pool is found in northern high latitudes. The majority of this soil carbon is stored in a greenhouse inert state within permafrost. As pronounced warming of high northern latitudes ensues, there is a strong likelihood that this substantial soil organic carbon pool will be mobilized to the atmosphere where it is likely to positively enhance greenhouse warming. Modeling studies suggest this positive feedback could alter future climate states of the Arctic and the globe, and affect how humans may need to adapt to climate change. Accordingly, understanding the patterns and controls and the …

Variability In Hydrology And Ecosystem Properties And Their Role In Regulating Soil Organic Matter Stability In Wetlands Of West-Central Florida, Sharon Jean Feit

USF Tampa Graduate Theses and Dissertations

Soil organic matter (SOM) provides many ecosystem services that are necessary for continued ecosystem function. The accumulation of SOM in an ecosystem is a function of its persistence time which can range from days to thousands of years. Ecosystem properties including dominant vegetation type, soil texture, and soil moisture in various habitats can regulate the persistence time of SOM.

Wetlands, because of their associated ecosystem properties, promote SOM accumulation, but little has been done to determine the ecosystem properties that regulate its persistence over time. In west-central Florida, urbanization and increased water demands have suppressed water tables in isolated wetland …