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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
391

Scarlet Macaws, Long-Distance Exchange, and Placemaking in the U.S. Southwest and Mexican Northwest, ca 900-1450 CE

January 2020 (has links)
abstract: Exchange is fundamental to the establishment and maintenance of social institutions and political economies in all scales of societies. While today people rapidly exchange goods and information over great distances, in the past, long-distance exchange necessitated the mobilization of vast networks of interaction with substantial transport costs. Objects traded over long distances were often valuable and challenging to obtain, granting them multifaceted significance that is difficult to understand using traditional archaeological approaches. This research examines human interactions with scarlet macaws (Ara macao) in the United States (U.S.) Southwest and Mexican Northwest (SW/NW) between 900 and 1450 CE. This period saw large-scale cultural change in the form of migrations, rapid population aggregation, and an expansion of long-distance exchange relations in regional centers at Pueblo Bonito (900-1150 CE) in northwestern New Mexico, Wupatki (1085-1220 CE) in north-central Arizona, and Paquimé (1200-1450 CE) in northern Chihuahua. Despite the distant natural habitat of scarlet macaws, their importation, exchange, and sacrifice appear to have played integral roles in the process of placemaking at these three regional centers. Here, I use an Archaeology of the Human Experience approach and combine radiogenic strontium isotope analysis with detailed contextual analyses using a Material Histories theoretical framework to (1) discern whether macaws discovered in the SW/NW were imported or raised locally, (2) characterize the acquisition, treatment and deposition of macaws at Pueblo Bonito, Wupatki, and Paquimé, and (3) identify patterns of continuity or change in acquisition and deposition of macaws over time and across space in the SW/NW. Findings from radiogenic strontium isotope analysis indicate that scarlet macaws from all case studies were primarily raised locally in the SW/NW, though at Paquimé, macaws were procured from sites in the Casas Grandes region and extra-regionally. Variation in the treatment and deposition of scarlet macaws suggests that despite their prevalence, macaws were interpreted and interacted with in distinctly local ways. Examination of the human experience of transporting and raising macaws reveals previously unconsidered challenges for keeping macaws. Overall, variation in the acquisition and deposition of scarlet macaws indicates changing strategies for placemaking in the SW/NW between 900 and 1450 CE. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2020
392

Mid-Pliocene to Early Pleistocene Sea Surface and Land Temperature History of NW Australia Based on Organic Geochemical Proxies from Site U1463

Smith, Rebecca 25 October 2018 (has links)
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 remain poorly constrained. In this study organic geochemical biomarkers preserved in marine sediments are used to reconstruct both sea surface and continental air temperatures in Northwest (NW) Australia from sediments spanning the mid-Pliocene Warm Period (mPWP), a critical carbon dioxide (CO2) and temperature analogue period for modern climate change spanning 3.3-3.0 Ma. These sediments were collected during IODP Expedition 356 from Site U1463, located near the outlet of the ITF, and are therefore sensitive to changes in ITF behavior over time. Here, NW Australian air temperatures were reconstructed from 1.5-3.5 Ma using the MBT’5ME proxy (Weijers et al., 2007a; De Jonge et al., 2014a), and offshore sea surface temperatures (SSTs) were reconstructed using both the TEX86 proxy (Schouten et al., 2002; Tierney & Tingley, 2014) and the Long Chain Diol Index (LDI; Rampen et al., 2012). Global climate events, including Marine Isotope Stages (MIS) 55, 63, 64, 82, 84, 88, 92, G10, G18, G20, G22, and M2 (Lisiecki & Raymo, 2005) are apparent in all of our records. TEX86 SSTs suggest a stronger cooling signal during MIS Stages G18, G20 and G22 relative to cooling during MIS M2, however LDI SSTs do not yield the same result. Overall, all three proxies indicate higher temperatures across the Pliocene and a cooling trend from ~1.7-1.5 Ma. Cooling occurs during an arid interval identified by Christensen et al. (2017), from 2.4-1.0 Ma, which suggests that offshore cooling contributed to shifts in NW Australian continental hydrology. Cooling from 3.5-1.5 Ma at Site U1463 was likely a reflection of 1) constriction of the ITF from 5-2 Ma and a switch from warm South Pacific to cool North Pacific source waters, and 2) an increase in meridional SST gradients at 1.8 Ma; the particularly strong cooling signal identified in all three records at 1.7 Ma is likely a direct response to the latter. This study helps elucidate ITF variability and shifts in thermohaline circulation across the Plio-Pleistocene and the mPWP, which will help modelers better predict the effects of future climate change.
393

Hydrologic Controls on Phosphorus Speciation and Mobilization in a Subalpine Watershed (East River, Colorado)

Arthen-Long, Lucia Isobel 20 October 2021 (has links)
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 transect with a high resolution analysis of P response to saturation, providing insight into both P cycling and flood-induced mobilization in the East River watershed in Gothic, Colorado. P-XANES, 31P NMR, and sequential extractions revealed that P concentrations were greatest in the floodplain and dominated by inorganic P (Pi) bound to primary minerals, while hillslope P was lower and characterized by more bioavailable and organic (Po) pools. Time series analysis of P response to extended water saturation confirmed our hypothesis that P mobilization would occur in two phases, first driven by lysis of microbial cells upon initial rewetting, and later driven by the reductive dissolution of Fe oxides with extended saturation. These findings indicated that (i) the interaction of weathering and hydrology dictate P speciation across the transect; (ii) hillslope P may be concentrated in microbial pools while floodplain P is primarily bound by minerals; (iii) bioavailable P pools may be dominated by Po; and (iv) Po is more vulnerable to mobilization during initial rewetting of dried soils while Pi responds more to changes in redox potential during extended saturation. Results from this study underscore the significance of hydrology in determining P speciation and mobilization, indicating that long-term changes in precipitation may influence P bioavailability and export from alpine watersheds. Understanding the mechanisms by which P is mobilized is therefore of critical importance to better predict soil P response to saturation in a changing climate.
394

The hydrology and dissolved organic carbon (DOC) biogeochemistry in a boreal peatland /

Fraser, Colin J. D. January 1999 (has links)
No description available.
395

Évaluation à l'aide d'indicateurs biogéochimiques du succès de création des mares de tourbières situées au Québec et au Nouveau-Brunswick dans un contexte de restauration

Jolin, Émilie 04 1900 (has links)
L'extraction de la tourbe pour en produire des substrats horticoles entraine la perte de leur capacité à séquestrer le carbone (C) dans les sols. Cependant, depuis plus d’une trentaine d’années, de nombreuses tourbières se sont vues restaurées et dans certains cas des mares sont intégrées. Les mares de tourbières sont présentes surtout dans les régions côtières et maritimes et sont généralement émettrices de C, à l’inverse des tourbières. Or, les mares sont des micro-habitats ayant un grand potentiel lié à la biodiversité et jouent ainsi un rôle très important pour de nombreuses espèces. De manière générale, la mesure du succès de la restauration des mares se concentre surtout sur le retour des espèces végétales typiques des mares naturelles et la présence d’un niveau d’eau constant à l’année. Très peu d’études se concentrent sur la biogéochimie des mares pour évaluer le succès de la restauration. Mon projet de recherche vise à évaluer le succès de la création des mares dans les projets de restauration de tourbière en utilisant des variables biogéochimiques. La recherche vise donc à identifier les différences biogéochimiques entre les mares créées et naturelles en plus de déterminer la trajectoire biogéochimique des mares créées dans le temps. Pour ce faire, nous avons mesuré différentes variables biogéochimiques telles le pH, les concentrations d’azote (N), de phosphore (P), de carbone organique dissout (DOC), de cations basiques – calcium (Ca), sodium (Na), magnésium (Mg) et potassium (K) et des gaz dissouts - méthane (CH4), dioxyde de carbone (CO2) et protoxyde d’azote (N2O) -. L’échantillonnage s’est fait dans 62 mares réparties au sein de 7 tourbières situé au Québec et au Nouveau-Brunswick : des mares naturelles et des mares créées il y a entre 3 et 22 ans. Les mares naturelles et créées ont des caractéristiques biogéochimiques différentes, et ce sans prendre en compte l’année de création. De ce fait, l’eau des mares créées est moins acide (pH >5) et plus concentrée en nutriments - N et P - que les mares naturelles. Cependant, les mares créées les plus anciennes ont tendance à se rapprocher des caractéristiques biogéochimiques des mares naturelles où la variation de la nappe phréatique et par le fait même la profondeur des mares viendraient jouer un rôle important sur les variables biogéochimiques. Des mares créées plus profondes et plus grandes pourraient ainsi permettre une présence d’eau permanente sans qu’elles s’assèchent durant l’été et ainsi favoriser le retour des conditions biogéochimiques similaires aux mares naturelles. / The extraction of peat to produce horticultural substrates leads to the loss of their ability to sequester carbon (C) in soils. However, over the past 30 years, many peatlands have been restored and open-water pools have been incorporated in some cases. Pools are naturally present in some bogs, especially in coastal and maritime regions, and are generally net C emitters, unlike peatlands. Pools are known to be micro-habitats with great potential for biodiversity and play a very important role for many species. In general, the measurement of the success of pool creation focuses on the return of bog plant species and a constant presence of water throughout the year. Currently, very few studies focus on the biogeochemistry of created pools to assess success. My research project uses biogeochemical variables to evaluate the success of created pools in peatland restoration projects. The research aims to identify biogeochemical differences between created and natural pools and to determine the biogeochemical trajectory of created pools over time. We measured different biogeochemical variables such as pH, nitrogen (N), phosphorus (P), dissolved organic carbon (DOC), base cations - calcium (Ca), sodium (Na), magnesium (Mg) and potassium (K) and dissolved gases - methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) -. Sampling was done in 62 pools located in 7 peatlands in Quebec and New Brunswick. We sampled both natural pools and pools created between 3 and 22 years ago. Natural and created pools have different biogeochemical characteristics, without considering the year of creation. Water in created pools is less acidic (pH >5) and more concentrated in nutrients - N and P - than in natural pools. However, the oldest created pools tend to be closer to the biogeochemical characteristics of natural pools. The variation of the water table and the depth of the pools play an important role for the return towards natural biogeochemical characteristics. Deeper and larger created pools could allow a permanent water presence during dry periods in summer and thus promote the return of biogeochemical conditions similar to natural pools.
396

Identifying biogeochemical factors responsible for the cyclical precipitation of sphalerite and galena in low temperature Mississippi Valley Type ore deposits

Makowsky, Daniel John 10 December 2021 (has links)
Mississippi Valley Type (MVT) lead and zinc deposits provide a significant source of sedimentary galena and sphalerite. However, geochemical characteristics and genesis including the source and production of hydrogen sulfide required for galena and sphalerite ore formation and the reasoning for quick, episodic mineralization is not fully understood. By simulating regional MVT brines, the input and effect of biological by-products during the development of these ores as well as the cause of cyclicity within MVT deposits have been observed. Experiments using compositions from MVT fluid inclusions were conducted over two-week periods. Variables during the experiments included temperature, CO2, hydrogen sulfide (H2S), lead and zinc. Removal of H2S at 70 oC caused no sulfide precipitation. Conclusions of this study are that fluid mixing or in-situ sulfur reduction by thermochemical or biogenic means are the primary mechanisms of MVT deposition, while at low temperatures biogenic sulfur reduction is the main driver.
397

Linking watershed-scale features and processes to carbon, nitrogen, and phosphorus fluxes

Knoll, Lesley Beth 16 November 2011 (has links)
No description available.
398

Biogeochemistry of Sulfur Isotopes in Crystal Lake, Clark County, West-Central Ohio.

Meyer, Amanda Lynn January 2014 (has links)
No description available.
399

BIOGEOCHEMISTRY OF LAKE ERIE SEDIMENT AND PORE WATER

Rebecca , Steely L. 03 June 2015 (has links)
No description available.
400

Methylmercury Bioaccumulation in Spotted Salamanders (Ambystoma maculatum) in Southern Ohio

Walker, Rachel Alex 06 June 2017 (has links)
No description available.

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