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Manganese Bioavailability Drives Organic Matter Transformations Across Oxic-Anoxic Interfaces Via Biotic And Abiotic Pathways, Nathan A. Chin
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
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 …
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 …
Examining The Mid- Brunhes Event In The Terrestrial Arctic: An Organic Geochemical Record From Lake El’Gygytgyn, Russia, Mary Helen Habicht
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 …
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
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), …
Evaluating Holocene Climate Change In Northern Norway Using Sediment Records From Two Contrasting Lake Systems., Nicholas L. Balascio, Raymond S. Bradley
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
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 …