Sources And Controls Of Carbon Dioxide In Inland Waters At Watershed, Regional, And Continental Scales, Brian Saccardi

Doctoral Dissertations

Inland waters are significant sources of carbon dioxide to the atmosphere, and estimates of emissions are similar in magnitude to those of the carbon dioxide sequestered by the net terrestrial sink. Currently, methods of estimating carbon dioxide emissions are based on statistical approaches and often do not consider landscape attributes such as human development, agriculture, or the hydrologic connectivity of the stream network. The following research addresses these issues in chapter 1 by developing and validating a reactive transport model at the watershed scale, then in chapter 2 by applying the reactive transport model at the continental scale across US …

Thames River Subwatershed Soil, Sediment, Water Data, Justin B. Richardson, Mark J. Butler

Data and Datasets

Trace element and nutrient data are for riparian soils, suspended sediments, eddy bottom sediments, and river water collected between 2019 and 2020 in the Thames River watershed of Connecticut, USA. Trace elements and nutrients were measured using EPA 3050B digestion method and analyzed by ICP-OES or ICP-MS.

Manganese Bioavailability Drives Organic Matter Transformations Across Oxic-Anoxic Interfaces Via Biotic And Abiotic Pathways, Nathan A. Chin

Masters Theses

Soil organic matter decomposition is a critical process that affects nutrient cycling, CO₂ emissions, and carbon storage in terrestrial environments. Recent evidence suggests reactive manganese (Mn) phases, potent oxidants that depolymerize compounds like lignocellulose in soil organic matter, act as critical drivers of organic matter decomposition in soil and sediment environments. Furthermore, oxic-anoxic interfaces (OAIs) have been shown to be crucial hotspots for the formation of reactive Mn(III) species and associated organic matter degradation. However, the extent to which microbially mediated Mn(III) formation and subsequently Mn(III)-driven organic matter oxidation depends on Mn availability remains largely unknown. Additionally, the relative …

Hydrologic Controls On Phosphorus Speciation And Mobilization In A Subalpine Watershed (East River, Colorado), Lucia Isobel Arthen-Long

Masters Theses

The cycling of phosphorus (P) through floodplain environments is critical to ecosystem productivity and has significant implications on both water quality and soil fertility. P export from soils in response to saturation has been well documented, but the relative vulnerability of specific P pools to mobilization remains poorly constrained, as do the mechanisms mediating its release. The prediction of P availability in and export from mountainous floodplain soils is of great importance as global climate change is projected to significantly alter precipitation regimes in alpine systems. This study combined a thorough characterization of P distribution across a hillslope to floodplain …

Physiological Constraints, Mechanisms, And Mineral Transformations Of Iron Reduction In Hyperthermophilic Crenarchaea, Srishti Kashyap

Doctoral Dissertations

Dissimilatory iron reduction by hyperthermophilic archaea occurs in many geothermal environments and typically relies on microbe-mineral interactions that transform various iron oxide minerals. However, the kinds of iron oxides that can be used, growth rates, extent of iron reduction, and the mineral transformations that occur due to this metabolism are poorly understood. This dissertation improves our fundamental understanding of the physiological mechanisms and mineral transformations of hyperthermophilic iron reduction using two model crenarchaea, Pyrodictium delaneyi and Pyrobaculum islandicum. Using growth yields and metabolite production rates, we demonstrated that a broad range of Fe(III) (oxyhydr)oxides of variable thermodynamic stability was …

Investigating Gallium Inclusion In Aluminum And Iron Oxyhydroxides, Corey A. Palmer

Masters Theses

Because Ga shares many physicochemical properties with Al and Fe, Ga may be able to incorporate into Al and Fe oxy-hydroxides. Understanding how Ga incorporates into these oxy-hydroxides may be crucial for finding Ga-rich bauxite deposits. In order to find the difference in Ga inclusion rates into oxy-hydroxides, as well as understand the mechanisms for this Ga inclusion, Al and Fe oxy-hydroxides were synthesized in the lab with Ga additions of 2 mol % Ga and 20 mol % Ga for a low-Ga and high-Ga treatment, respectively, along with a no added Ga control. X-Ray diffraction analyses confirmed the formation …

Middle To Late Pleistocene Paleoenvironmental Reconstructions From Lake El'gygytgyn, Arctic Russia, Mary Helen Habicht

Doctoral Dissertations

Climate change is a major issue challenging the world today. Our global society faces rising temperatures, variable weather patterns, and rising sea level among other associated issues. Our action (or inaction) to address current changes will have serious ramifications for life on our planet in the coming centuries and millennia. In order to provide context for these present and future changes, we can utilize the paleo record to understand the natural variability of Earth’s climate system. One region of the world is changing more rapidly than the global average. Over recent decades, the Arctic has experienced warmer temperatures, reduced sea …

Sorption Temperature And And The Stability Of Iron-Bound Soil Organic Matter, Michael L. Nguyen

Doctoral Dissertations

The preservation of soil organic matter (SOM) is an important control on the global cycling of carbon. Long-term preservation of SOM has important implications on soil fertility and climate regulation. Minerals, such as iron oxides, can react with SOM and serve as a preservation mechanism for SOM. Globally, iron oxide-SOM interactions form a “rusty carbon sink” which protects up to 22% of organic carbon in marine sediments. Climate changes, such as warming, may alter the size or efficacy of the “rusty carbon sink.” The effects of temperature, SOM composition, and mineral particle size on the formation and stability of iron …

Wildfires In The Northeastern United States: Evaluating Fire Occurrence And Risk In The Past, Present, And Future, Daniel R. Miller

Doctoral Dissertations

Climate change is one of the most complex and challenging issues facing the world today. A changing climate will affect humankind in many ways and alter our physical environment, presenting ethical challenges in how we respond. The impact of climate change will likely be exacerbated in heavily populated regions of the planet, such as the Northeastern United States (NEUS). The NEUS is comprised of complex, sprawling urban centers and rural regions, both of which are vital to the economic and cultural character of the region. Furthermore, both urban and rural areas in the NEUS contain communities that have been historically …

Root-Driven Weathering Impacts On Mineral-Organic Associations Over Pedogenic Time Scales, Mariela Garcia Arredondo

Masters Theses

Plant roots are critical weathering agents in deep soils, yet the impact of resulting mineral transformations on the vast deep soil carbon (C) reservoir are largely unknown. Root-driven weathering of primary minerals may cause the formation of reactive secondary minerals, which protect mineral-organic associations (MOAs) for centuries or millennia. Conversely, root-driven weathering may also transform secondary minerals, potentially enhancing the bioavailability of C previously protected in MOAs. Here we examined the impact of root-driven weathering on MOAs and their capacity to store C over pedogenic time scales. I compared soil that experienced root-driven weathering, resulting in the formation of discrete …

Mineral And Redox Controls On Soil Carbon Cycling In Seasonally Flooded Soils, Rachelle Lacroix

Masters Theses

Soils contain nearly three times the amount of carbon (C) than the atmosphere, with C turnover times ranging from centuries to millennia. Although wetland soils represent a relatively small portion of the terrestrial landscape, they account for an estimated 20-30% of the global C reservoir. Seasonally flooded soils are likely the most vulnerable wetlands to climate change, as changing temperature and precipitation patterns are expected to alter the timing and duration of flooding. Seasonal variations in soil moisture are recognized as a critical control on soil C stocks and CO₂emissions. However, the relative influence of associated changes in …

Mid-Pliocene To Early Pleistocene Sea Surface And Land Temperature History Of Nw Australia Based On Organic Geochemical Proxies From Site U1463, Rebecca Smith

Masters Theses

Ocean gateways facilitate water circulation between ocean basins, and therefore directly impact thermohaline circulation and global climate. In order to better predict the effects of future climate change, it is critical to constrain past changes in ocean gateway behavior, and corresponding changes in thermohaline circulation, particularly during analogue periods for modern climate change. The Indonesian Throughflow (ITF) is a primary ocean gateway and vital component of the global conveyor that transports water from the Pacific Ocean into the Indian Ocean, however due to a lack of long and continuous sedimentary records from locations under its influence, changes in ITF behavior …

Estimation Of Cdom In Inland Waters Via Water Bio-Optical Properties Using A Remote Sensing Approach, Jiwei Li

Doctoral Dissertations

Monitoring of Colored dissolved organic matter (CDOM) in inland waters provides important information for tracing carbon cycle at the land-water interface and studying aquatic ecosystem. Remote sensing estimation of CDOM in the inland waters offers an alternative approach to field samplings in examining CDOM spatial-temporal dynamics. However, CDOM retrieval is a challenge due to the lack of algorithm for resolving bottom effect in shallow inland waters. Moreover, an effective approach based on multi-spectral, high spatial resolution and global coverage satellite images is in urgent need. To resolve these challenges, shallow water bio-optical properties (SBOP) algorithm was developed to overcome bottom …

Arctic And North Atlantic Paleo-Environmental Reconstructions From Lake Sediments, Gregory A. De Wet

Doctoral Dissertations

ABSTRACT

Facilitate Visualization And Distribution Of Nasa's Environmental Science Data Through Open Standards And Open Source Software For Geospatial, Yaxing Wei, Zhaoying (Angie) Wei, Suresh Santhanavannan

Free and Open Source Software for Geospatial (FOSS4G) Conference Proceedings

This paper introduces the utilization of open standards and open source software for visualization and distribution of geospatial environmental science data at the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC). The ORNL DAAC is one of the NASA Earth Observing System Data and Information System (EOSDIS) data centers. A big challenge for the ORNL DAAC (https://daac.ornl.gov) is to efficiently manage over a thousand heterogeneous environmental data, collected through field campaigns, aircraft/satellite observations, and model simulations. ORNL DAAC also has to provide tools to easily find, visualize, and access the heterogeneous data. To address this challenge, the ORNL …

Micropaleontology And Isotope Stratigraphy Of The Upper Aptian To Lower Cenomanian (~114-98 Ma) In Odp Site 763, Exmouth Plateau, Nw Australia, Ali Alibrahim

Masters Theses

The biostratigraphy and isotope stratigraphy of the upper Aptian to lower Cenomanian interval including oceanic anoxic events OAE1b, 1c and 1d are investigated in ODP Site 763, drilled on the Exmouth Plateau offshore northwest Australia. Benthic foraminifera suggest that Site 763 was situated in outer neritic to upper bathyal water depths (~150-600 m). OAEs of the Atlantic basin and Tethys are typically associated with organic carbon-rich black shales and δ¹³C excursions. However, OAEs at this high latitude site correlate with ocean acidification and/or pyrite formation under anoxic conditions rather than black shales. Ocean acidification maybe responsible for sporadic …

A High-Resolution Paleoenvironmental And Paleoclimatic History Of Extreme Events On The Laminated Sediment Record From Basin Pond, Fayette, Maine, U.S.A., Daniel R. Miller

Masters Theses

Future impacts from climate change can be better understood by placing modern climate trends into perspective through extension of the short instrumental records of climate variability. This is especially true for extreme climatic events, such as extreme precipitation and wildfires, as the period of instrumental records provides only a few examples and these have likely have been influenced by anthropogenic warming. Multi-parameter records showing the past range of climate variability can be obtained from lakes. Lakes are particularly good recorders of climate variability because sediment from the surrounding environment accumulates in lakes, making them sensitive recorders of climate variability and …

Examining The Mid- Brunhes Event In The Terrestrial Arctic: An Organic Geochemical Record From Lake El’Gygytgyn, Russia, Mary Helen Habicht

Masters Theses

The characteristic glacial and interglacial cycles of the Pleistocene underwent a climatic transition at ~430 ka known as the Mid- Brunhes Event (MBE). Many studies, particularly from the Southern Hemisphere have noted that after this transition, the amplitude of the climatic cycles increased. Despite the indication of an MBE signal in many globally distributed paleoclimate records, the geographic extent of the climatic transition remains unknown and its presence in northern hemisphere and terrestrial records is debated. Lake El’gygytgyn is located in the far- east Russian Arctic and provides the longest, most continuous record of Arctic climate (3.6 Ma). This study …

Arctic Environmental Change Across The Pliocene-Pleistocene Transition, Benjamin Andrew Keisling

Masters Theses

Environmental change in the Arctic proceeds at an unprecedented rate. The Pliocene epoch (5-2.65 million years ago) represents an analog for future climate conditions, with pCO₂ and continental configurations similar to present. Yet conditions in the Pliocene Arctic are poorly characterized because of sparse sampling. The records that do exist indicate periods of extreme warmth, as well as the first expansion of large ice-sheets in the Northern Hemisphere, took place from the end of the Pliocene into the early Pleistocene. Understanding these deposits and their implications for our future requires developing a sense of climatic evolution across the …

Sedimentological, Geochemical And Isotopic Evidence For The Establishment Of Modern Circulation Through The Bering Strait And Depositional Environment History Of The Bering And Chukchi Seas During The Last Deglaciation, Ben M. Pelto

Masters Theses

Sea level regression during the Last Glacial Maximum exposed the Bering Land Bridge, and cut off the connection between the North Pacific and Arctic Ocean, ending the exchange of North Pacific Water through the Bering Strait. Exchange of North Pacific Water comprises a major portion of fresh water input to the Arctic Ocean, and is of vital importance to North Atlantic Deep Water formation, a vital component of Atlantic Meridional Overturning Circulation. Bering Strait throughflow thus plays an integral role in global climate stability. A suite of four cores was selected, three in the Bering Sea and one in the …

Microbe-Mineral Relationships And Biogenic Mineral Transformations In Actively Venting Deep-Sea Hydrothermal Sulfide Chimneys, Tzihsuan J. Lin

Doctoral Dissertations

This dissertation uses a combination of microbiology, mineralogy, and geochemistry to understand dissimilatory iron reduction in hyperthermophilic archaea and the role and potential impact of these and other vent microorganisms within active deep-sea hydrothermal vent chimneys. The central objective of the dissertation is to determine if mineral composition and chimney type are among the primary determinants of microbial community composition and hyperthermophilic, dissimilatory iron reducer growth, in addition to other environmental factors such as nutrient availability, temperature, pH, and chlorinity. This is done using samples and organisms collected from the Endeavour Segment of the Juan de Fuca Ridge in the …

Holocene Paleo-Environmental Variability Reconstructed From A Lake Sediment Record From Southeast Greenland, Gregory A. De Wet

Masters Theses 1911 - February 2014

Arctic climate variability over the Holocene has been both extensive and, at times, abrupt. Current understanding of these changes is still quite limited with few high-resolution paleoclimate records available for this period. In order to place observed and predicted 21^st century climate change in perspective, reliable and highly resolved paleo-reconstructions of Arctic climate are essential. Using an 8.5 m sediment core from Nanerersarpik Lake, this project will characterize climate changes during the Holocene, including the deglacial transition, the rapid changes that are known to have occurred around 8,200 years ago, the transition from Holocene thermal maximum (HTM) to the …

7700 Years Of Holocene Climatic Variability In Sermilik Valley, Southeast Greenland Inferred From Lake Sediments, Samuel H. Davin

Masters Theses 1911 - February 2014

During the latter half of the 20^th century until present day there has been an unprecedented rise in global annual mean temperatures accompanied by rising sea levels and a decrease in Northern Hemisphere snow cover, which if it continues will lead to widespread disruption of climate patterns, ecosystems, and present-day landscapes. It is therefore of critical importance to establish an expanded network of paleoclimate records across the globe in order to better assesses how the global climate system has changed in the past, that we may create a metric by which to address modern change. Herein is presented a7,700 …

Biomarker And Sedimentological Investigations Of Mis 8 Through Mis 12 From Lake El'gygytgyn, Ne Arctic Russia, Jeremy H. Wei

Masters Theses 1911 - February 2014

Abstract

Multiple proxy analysis of lake sediment records are crucial for understanding changes in environmental and climate conditions over historical and geological time. Most recently, the use of biomarker proxies coupled with sedimentological investigations provides a new approach for gaining insight into the lake processes that capture information about past climate change. This approach is applied here to better understand the paleoclimate record from Lake El’gygytgyn in Western Beringia. Multiple organic geochemical compound concentrations were measure as proxies for both aquatic and terrestrial biological productivity. Measurements of n-alkane (plant leaf waxes) as well as concentrations of the compounds arborinol …

Biogeochemical Evidence For Hydrologic Change During The Holocene In A Lake Sediment Record From Southeast Greenland, Nicholas L. Balascio, William J. D'Andrea, Raymond S. Bradley, Bianca B. Perren

Raymond S Bradley

Holocene paleoclimate records from Greenland help us understand the response of the Greenland Ice Sheet and regional oceanic and atmospheric circulation systems to natural climate variability in order to place recent changes in a longer-term perspective. Here biogeochemical analysis of a lake sediment core from southeast Greenland is used to define changes in moisture balance and runoff during the Holocene in a catchment near the margin of the Greenland Ice Sheet. A 1.6 m sediment core that spans the last 8.8 ka was recovered from Flower Valley Lake on Ammassalik Island. Magnetic susceptibility, diatoms, bulk biogeochemical properties (TOC, C/N, δ13Corg), …

A Paleoclimate Modeling Experiment To Calculate The Soil Carbon Respiration Flux For The Paleocene-Eocene Thermal Maximum, David M. Tracy

Masters Theses 1911 - February 2014

The Paleocene-Eocene Thermal Maximum (PETM) (55 million years ago) stands as the largest in a series of extreme warming (hyperthermal) climatic events, which are analogous to the modern day increase in greenhouse gas concentrations. Orbitally triggered (Lourens et al., 2005, Galeotti et al., 2010), the PETM is marked by a large (-3‰) carbon isotope excursion (CIE). Hypothesized to be methane driven, Zeebe et al., (2009) noted that a methane based release would only account for 3.5°C of warming. An isotopically heavier carbon, such as that of soil and C3 plants, has the potential to account for the …

Holocene Climate And Environmental Changes: Disentangling Natural And Anthropogenic Signals In The Sedimentary Record Of Lake Lilandsvatnet (Nw Norway), Robert M. D'Anjou

Masters Theses 1911 - February 2014

This thesis presents a multi-proxy paleoenvironmental reconstruction from the sedimentary archives of Lilandsvatnet, a small arctic lake on Vestvågøy, in the Lofoten Islands, Norway. Lofoten has a rich history of human settlements existing throughout the Holocene. The catchment of Lilandsvatnet was the location of a prominent Viking chieftain farm that existed throughout the Iron Age, and the sedimentary archive contains a strong signal of prehistoric and historic human settlements and land-use practices. Paleoenvironmental reconstructions in this thesis show evidence for Holocene environmental variability in response to both natural and anthropogenic forcing. Cryptotephra deposits from Icelandic eruptions further contrain sediment chronology …

Evaluating Holocene Climate Change In Northern Norway Using Sediment Records From Two Contrasting Lake Systems., Nicholas L. Balascio, Raymond S. Bradley

Raymond S Bradley

We analyzed Holocene sedimentary records from two lakes in the Lofoten Islands, northern Norway to evaluate environmental changes during the Holocene related to northern North Atlantic climate dynamics. The lakes are located in different geomorphological settings, and thus provide a contrast in their response to regional climate change. Environmental changes at both lakes were interpreted based on magnetic susceptibility, organic-matter flux, C/N, d13 Corg , Ti concentrations, and mass accumulation rates. Chronologies were established using 16 AMS radiocarbon dates, and average deposition rates in both environments are higher than 0.2 mm/year throughout the Holocene. At Vikjordvatnet, sedimentary geochemical properties define …

Biogeochemical Evidence For Prehistoric Human Impacts On The Environment In Northwestern Norway, Raymond S. Bradley, Robert D'Anjou, Nicholas L. Balascio, David B. Finkelstein

Raymond S Bradley

Disentangling the effects of climate change and anthropogenic activities on the environment is a major challenge in paleoenvironmental research. Here, we used fecal sterols and other biogeochemical compounds in lake sediments from northern Norway to identify both natural and anthropogenic signals of environmental change during the late Holocene. The area was first occupied by humans and their grazing animals at ∼2,250 ± 75 calendar years before 1950 AD (calendar years before present). The arrival of humans is indicated by an abrupt increase in coprostanol (and its epimer epicoprostanol) in the sediments and an associated increase in 5β-stigmastanol (and 5β-epistigmastanol), which …

A Mild Little Ice Age And Unprecedented Warmth In An 1800 Year Record From Svalbard, William J. D'Andrea, Raymond S. Bradley, David Vaillencourt, Nicholas L. Balascio, Al Werner, Steve Roof, Michael J. Retelle

Raymond S Bradley

The Arctic region is subject to a great amplitude of climate variability and is currently undergoing large-scale changes due in part to anthropogenic global warming. Accurate projections of future change depend on anticipating the response of the Arctic climate system to forcing, and understanding how the response to human forcing will interact with natural climate variations. The Svalbard Archipelago occupies an important location for studying patterns and causes of Arctic climate variability; however, available paleoclimate records from Svalbard are of restricted use due to limitations of existing climate proxies. Here we present a sub-decadal- to multidecadal-scale record of summer temperature …