Dissertations / Theses on the topic 'Oxyen isotopes'
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Vaiglova, Petra. "Neolithic agricultural management in the Eastern Mediterranean : new insight from a multi-isotope approach." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:c8824136-da35-43b2-a700-f458d0cc2fdf.
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The work presented in this dissertation explores the nature of agro-pastoral strategies developed by Neolithic farmers as a way to understand how early food production was inter-twined with environmental and socio-economic opportunities and constraints. Towards this end, a multi-isotope approach is used to address questions of scale and intensity of crop cultivation and animal management at the archaeological sites of Kouphovouno, southern Greece, Makriyalos, northern Greece, and Çatalhöyük, south-central Turkey. Measurements of stable carbon, nitrogen, oxygen and strontium isotope values of carbonized plant remains, human and animal bone collagen and animal tooth enamel are used to examine the similarities and differences in the types of treatments that individual species of plants and animals received during the agricultural cycle at the distinct locations. The results show that farmers at the three sites developed variable methods for exploiting the arable and pastoral landscape and catering to their economic and culinary needs. The discussion considers the implications of these findings to our understanding of the complexity and adaptability of early farming systems.
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Grefe, Imke. "Concentration and isotopic composition of marine nitrous oxide, in particular the oxygen-17 isotope excess." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/48791/.
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The oxygen isotope excess Δ(17O) is a potential tracer of biological nitrous oxide (N2O) cycling. This study presents the first measurements of Δ(17O) in marine N2O together with details about the design and development of a custom-built Gas Chromatography-Isotope Ratio Mass Spectrometry (GC-IRMS) analytical system for δ(15N), δ(18O) and Δ(17O) of N2O. Δ(17O) values between 0.1 and 4.6 ‰ (relative to VSMOW) were observed during three field campaigns in the temperate, subtropical and tropical Atlantic Ocean, the Scotia Sea and the Weddell Sea. This indicates a biological source for oxygen isotope excess in N2O, as oceanic N2O was not in equilibrium with the atmosphere (0.9 ‰). δ(15N) values ranged from 2.3 to 25.1 ‰ (relative to Air-N2). δ(18O) measured in the Weddell Sea ranged from 44.9 to 48.8 ‰ (relative to VSMOW). The dataset from the Atlantic Ocean and the Atlantic sector of the Southern Ocean suggest nitrification and nitrifier-denitrification as the main N2O production pathway in the oxic, deep ocean. High δ(15N) values in the south Atlantic Gyre are presumably associated with a denitrification source. A novel off-the-shelf N2O analyser was tested in combination with an equilibrator for semiautonomous concentration measurements in the surface ocean. The subtropical gyres in the Atlantic Ocean were confirmed to be weak sinks ((-0.14±0.31) μmol m-2 d-1 N2O flux to the ocean in the northern, and (-0.16±0.33) μmol m-2 d-1 in the southern gyre) and the equatorial region was a source of N2O to the atmosphere (flux of 0.53 μmol m-2 d-1). New data from the Scotia Sea identified a strong source region ((2.9±2.7) μmol m-2 d-1), while the Weddell Sea was closer to equilibrium with the atmosphere ((0.9±1.0) μmol m-2 d-1).
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Buchwald, Carolyn. "Oxygen isotope systematics of nitrification." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/114328.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2007.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 39-41).
During nitrification there is an exchange of oxygen atoms between water and nitrite, causing the [delta]¹⁸O of nitrate produced by nitrification to be closer to the [delta]¹⁸O of water than expected. A series of lab and field experiments were set up in order to quantify the exchange, and then calculate the [delta]¹⁸O of nitrate with these values. The lab experiments tested the exchange in ammonia oxidation, using ammonia oxidizing bacteria, Nitrosomonas sp. C113a and Nitrococcus oceani, and nitrite oxidation using cultures of the nitrite oxidizing bacterium, Nitrosococcus mobilis. The exchange value in the ammonia oxidation experiments could not be calculated because of unexpected complications in the analysis in the [delta]¹⁸O of nitrite. Although we weren't able to obtain a confident value for the exchange we were able to find a way to correct the [delta]¹⁸O of nitrite, for blank and exchange that affects the sample [delta]¹⁸O value for nitrite measured by the mass spectrometer. The exchange in the nitrite oxidation experiment could not be measured because there was full abiotic exchange in the bottle preventing us from calculating biotic exchange. A control experiment was successful in eliminating this exchange by adjusting the pH to a value higher than 8 prior to inoculation of the media during the experiment. In a future nitrite oxidation experiment this change in experimental design would make it possible to measure the exchange during nitrite oxidation. The experiments were a good step toward developing the best way to measure microbially-catalyzed exchange, and hopefully this value can be quantified in future analysis.
by Carolyn Buchwald.
S.B.
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趙雪蓮 and Suet-lin Shirley Chiu. "Predissociation line width of the Schumann-Runge bands of oxygen and its isotopes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31209658.
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Ritz, P. "An appraisal of the doubly labelled water method for energy expenditure measurements." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319821.
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Missell, Christine Ann. "Thermoregulatory adaptations of Acrocanthosaurus atokensis - evidence from oxygen isotopes." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-12312003-115912/.
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Isotopic analyses of bone phosphate oxygen from a modern alligator, ostrich, and elephant have provided a means for examining diagenesis and thermoregulatory strategy within the dinosaur Acrocanthosaurus atokensis. The Acrocanthosaurus specimen is assumed to retain an original isotopic signature, based on a lack of linear correlation between δ18Ophosphate and structural δ18Ocarbonate, equal standard deviations between δ18Ophosphate values for spongy and compact bone, and a significant difference between δ18Ophosphate and cement δ18Ocarbonate. Interbone and intrabone temperature variation patterns suggest that Acrocanthosaurus followed a homeothermic pattern of heat distribution (i.e. maintenance of a 4°C temperature range). Comparison with the modern animals yields a closer resemblance to the ostrich and elephant versus the alligator, thereby suggesting Acrocanthosaurus was endothermic. The Acrocanthosaurus sacral spines and palatal bones show evidence of use as heat shedding structures and the braincase yields a significantly higher calculated temperature than the body.
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Al-Qattan, Nasser M. E. N. A. A. "Interpretation of Oxygen Isotopic Values (d18O) of North American Land Snails." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1404460805.
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Chiu, Suet-lin Shirley. "Predissociation line width of the Schumann-Runge bands of oxygen and its isotopes /." [Hong Kong] : University of Hong Kong, 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12920575.
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Rebenack, Carrie E. "A Carbon and Oxygen Stable Isotope-Dendrochronology Study of Trees from South Florida: Implications for the Development of a High-Resolution Subtropical Paleoclimate Record." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3009.
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The global paleoclimate archive is lacking in tropical dendrochronology studies as a result of limitations from inconsistent tree-ring production imposed by precipitation-driven seasonality. The slash pine, Pinus elliottii Engelm. var. densa, is the dominant canopy species of Big Pine Key (BPK) rocklands and has been shown to produce complicated, but distinct, ring structures; however, traditional dendrochronology studies have not established correlations between ring width measurements and major climate drivers controlling South Florida precipitation. My study utilized the carbon (δ13C) and oxygen (δ18O) isotope records in the α-cellulose component of tree-rings to extract information about the physiological responses of trees to climate and tropical cyclone activity. The δ13C measurements in the earlywood and latewood of four P. elliottii var. densa trees were used to build a chronology (1922-2005) and to distinguish annual growth from intra-annual density fluctuations (IADFs). Empirical orthogonal functions were used to determine individual response to precipitation, El Niño-Southern Oscillation (ENSO), and the Atlantic Multidecadal Oscillation (AMO). There is a distinct relationship between the δ13C values of cellulose and ENSO; however the nature (direct vs. inversely correlated) is temporally controlled by the prevailing phase of the AMO. The appearance of some IADFs coincide with the timing of El Niño winters occurring during the cool AMO phase, resulting in enriched δ13C values. The additional precipitation may encourage tree growth, but subsequent dry periods may slow growth and cause the tree to employ water-conservation strategies. Tree growth is influenced by the major climate drivers and the control they exert over the timing of precipitation; however, growth is ultimately controlled by the microenvironment surrounding individual trees. The δ18O and δ13C values of the latewood cellulose were compared to tropical cyclone activity occurring within a 100km radius of BPK. Tropical storms and depressions appeared as anomalously depleted values in the δ18O residual record, reflecting large amounts of tropical rain. The effects of hurricanes varied by storm; however, many of the major hurricanes (category 3-5) were preserved as an enrichments in the δ13C value of the following earlywood season. The application of stable isotope analyses greatly increases the breadth of paleoclimate information available from the trees.
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Baraut, Lambert. "Etudes expérimentales des fractionnements isotopiques indépendants de la masse dans la réaction de formation de l'ozone en phase plasma." Thesis, Paris, Muséum national d'histoire naturelle, 2019. http://www.theses.fr/2019MNHN0002.
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L'atmosphère terrestre a subi, au cours de son histoire précoce, de très violents changements dans sa composition chimique. L'émergence des premiers êtres vivants photosynthétique a provoqué la mise en place et la modification des grands cycles biogéochimiques. L'usage des isotopes comme traceurs des processus physico-chimiques actifs pendant ces périodes s'est développé depuis les années 80. L'observation de compositions isotopiques anormales dans certaines molécules atmosphériques (ozone notamment), similaires à celles observées dans les météorites par Clayton (1973), pose question. De nombreuses hypothèses ont été proposées pour expliquer ce phénomène "anormal". L'objectif principal de cette thèse de doctorat est de développer, par l'expérimentation, l'étude d'un certain nombre de réactions en phase plasma du point de vue isotopique. Seront particulièrement étudiées des réactions appelées réactions à trois corps de formation de l'ozone, où la formation d'un complexe intermédiaire excité entre en jeu dans les mécanismes de génération de ces fractionnements isotopiques anormauxThe Earth's atmosphere has undergone, during its early history, very violent changes in its chemical composition. The emergence of the first photosynthetic living beings has led to the establishment and modification of major biogeochemical cycles. The use of isotopes as tracers of active physico-chemical processes during these periods has been developed since the 1980s. The observation of abnormal isotopic compositions in certain atmospheric molecules (ozone in particular), similar to those observed in meteorites by Clayton (1973), raises questions. Many hypotheses have been proposed to explain this "abnormal" phenomenon. The main objective of this doctoral work is to develop, through experimentation, the study of plasma reactions from an isotopic point of view. In particular, ozone formation third-body reactions, where the formation of an excited intermediate complex is involved in the mechanisms of generating these abnormal isotopic fractionations, will be studied
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Seligman, Angela. "Oxygen and hydrogen investigation of volcanic rocks: Petrogenesis to paleoclimate." Thesis, University of Oregon, 2016. http://hdl.handle.net/1794/20547.
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Knowledge of the isotopic evolution of volcanic eruptions is essential to volcanologists, geochemists, and paleoclimatologists. I isotopically evaluate the evolution of magmas from their initial formation, to eruption, and then to their alteration during the diffusion of environmental waters into volcanic glass. I focus first on the formation and evolution of large, caldera-forming eruptions from both Gorely volcano in Kamchatka, Russia and 30–40 Ma caldera forming eruptions through Oregon in the United States of America. I utilize oxygen (δ18O), hafnium (εHf), strontium (87Sr/86Sr), and neodymium (143Nd/144Nd) isotopes to document the creation of caldera-forming eruptions at these eruptive centers through the melting of surrounding crust. I also use U-Pb and 40Ar/39Ar to document the timescales of the formation of these large-volume silicic eruptions.
Following eruption, the volcanic glass in tephra and ash can slowly take in environmental water. It is thought that the hydrogen isotopic ratio (δD) of these waters can be used to determine paleoenvironments from the time that the volcanic glass was deposited. The latter portion of my dissertation focuses on the use of hydrogen isotopes of environmentally hydrated volcanic glass to determine paleoenvironments, and the calibration of the TCEA to analyze oxygen isotopes of hydrated volcanic glass. I first focus on the rate of diffusion of water at ambient temperature to better understand the time frame necessary to hydrate volcanic glass for use as a paleoenvironmental indicator. I also document the hydrogen isotopic ratios that result from the diffusion of water into volcanic glass, which is documented as a decrease in δD with an increase in secondary hydration in all regions worldwide except equatorial. Finally, I focus on the earliest stages of diffusion of water into volcanic glass by analyzing tephra deposits that were collected within days of the 1980 eruptions of Mount St. Helens as well as tephra deposits recently collected in 2015 to identify changes in water concentration and hydrogen isotopic ratios over an ~35 year period.
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Lee, Vanessa Eileen. "Characterising dissolved nitrate in precipitation using stable nitrogen and oxygen isotopes /." Internet access available to MUN users only, 2005. http://collections.mun.ca/u?/theses,18576.
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Motz, John Edward. "Oxygen and hydrogen isotopes in fossil insect chitin as paleoenvironmental indicators." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ51214.pdf.
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Wellman, Toby. "Carbon and oxygen stable isotopes from recent and fossil Australian crustaceans /." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09SB/09sbw4528.pdf.
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White, Rowan May Patricia. "Isotope systematics of the freshwater mollusca Lymnaea peregra." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266733.
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Leavitt, William Davie. "On the mechanisms of sulfur isotope fractionation during microbial sulfate reduction." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11511.
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Underlying all applications of sulfur isotope analyses is our understanding of isotope systematics. This dissertation tests some fundamental assumptions and assertions, drawn from equilibrium theory and a diverse body of empirical work on biochemical kinetics, as applied to the multiple sulfur isotope systematics of microbial sulfate reduction. I take a reductionist approach, both in the questions addressed and experimental approaches employed. This allows for a mechanistic, physically consistent interpretation of geological and biological sulfur isotope records. The goal of my work here is to allow interpreters a more biologically, chemically and physically parsimonious framework to decipher the signals coded in modern and ancient sulfur isotope records.Earth and Planetary Sciences
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Mellor, Ian. "Isotopic oxygen exchange reactions on magnesium oxide." Thesis, Nottingham Trent University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298901.
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Cliff, Steven Scott. "Oxygen isotopic studies of atmospheric nitrous oxide /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9906467.
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Bates, Steven Matthew. "Conodont oxygen isotope records of late carboniferous paleoenvironmental variability /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1426047.
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Winters, Tim. "Oxygen isotope ratios in seawater of the North Atlantic." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323347.
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Gloel, Johanna. "Triple oxygen isotopes and oxygen/argon ratio measurements to enhance coastal and open ocean production/respiration comparisons." Thesis, University of East Anglia, 2012. https://ueaeprints.uea.ac.uk/42341/.
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The accurate measurement of marine plankton production is required to constrain the global carbon balance. Traditional methods rely on bottle incubations, which are thought to underestimate plankton production. This study presents in situ measurements of gross oxygen production (G) derived from triple oxygen isotope analysis and of net community oxygen production (N) derived from O2/Ar ratios at station L4, which is part of the Western English Channel Observatory (WECO) and a latitudinal transect through the subtropical gyres in the Atlantic Ocean in October/November 2010. G and N were determined at weekly intervals between September 2009 and September 2010 at station L4. Annual N was positive (net autotrophic) at (0.88±0.24) mol m-2 a-1 O2. The triple oxygen isotope method overestimated G during winter months due to entrainment of waters from below the mixed layer. N of (3.8 ± 3.1) mmol m-2 a-1 O2 in the North Atlantic Gyre (NAG) and (2.9 ± 2.4) mmol m-2 a-1 O2 in the South Atlantic Gyre (SAG) show both gyres to be net autotrophic at the time of sampling. G values of (169±106) mmol m-2 a-1 O2 in the NAG and (250±130) mmol m-2 a-1 O2 in the SAG were higher than published results. Diapycnal mixing was found to contribute about 20% to apparent mixed layer N in both gyres and to G in the NAG. In order to achieve these results, a gas extraction line was built and tested. A method to halt biological activity in triple oxygen isotope and discrete O2/Ar samples was assessed. Benzalkonium chloride was found to be a less toxic alternative to mercuric chloride on short time scales of three days. Our results of N agree with previous in situ productivity measurements in these regions and highlight the importance of including physical effects in the estimates of G.
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Morin, Samuel. "Analyse de la composition isotopique de l'ion nitrate dans la basse atmosphère polaire et marine." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00326229.
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Les oxydes d'azote atmosphériques (NOx=NO+NO2) sont des composés clefs en chimie de l'environnement, jouant un rôle central pour la capacité oxydante de l'atmosphère et le cycle de l'azote. La composition isotopique du nitrate atmosphérique (NO?3 particulaire et HNO3 gazeux), constituant leur puits ultime, renseigne sur leur bilan chimique. Le rapport 15N/14N donne une indication de leurs sources, alors que l'anomalie isotopique en oxygène (?17O=d17O-0.52×d18O) révèle la nature de leurs mécanismes d'oxydation. Des études couplées de d15N et ?17O d'échantillons de nitrate atmosphérique collectés dans l'Arctique, en Antarctique et dans l'atmosphère marine au dessus de l'Océan Atlantique, où le bilan des NOx est souvent mal connu ont été effectuées. À ces fins, le défi que constitue la mesure simultanée des trois rapports isotopiques du nitrate (17O/16O, 18O/16O et 15N/14N) dans le même échantillon représentant moins d'une micromole a été relevé. La solution adoptée tire avantage des propriétés d'une bactérie dénitrifiante, utilisée pour convertir le nitrate en N2O, dont la composition isotopique totale a été mesurée en utilisant un système automatisé de chromatographie en phase gazeuse et spectrométrie de masse de rapport isotopique. Les principaux résultats obtenus via les isotopes de l'oxygène permettent l'identification claire de transitions saisonnières entre voies d'oxydation des NOx, y compris le rôle majeur des composés halogénés réactifs au printemps polaire en régions côtières. Les isotopes de l'azote ont quant à eux permis d'apporter de nouvelles contraintes sur le cycle de l'azote dans les régions polaires, grâce au fractionnement significatif induit par les phénomènes de remobilisation post-dépôt affectant le nitrate dans le manteau neigeux, et l'émission de NOx qui en découle
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McCabe, Justin R. "Investigations of the oxidation capacities of polar atmospheres with multiple oxygen isotopes /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3244178.
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Ryabenko, Evgenia [Verfasser]. "Nitrogen Isotopes in the Atlantic and Pacific Oxygen Minimum Zones / Evgenia Ryabenko." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1138992550/34.
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Warrington, Anita Glasgow. "Stable isotopes of carbon and oxygen in the shells of terrestrial molluscs." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316976.
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Harwood, Kirsty. "Variation in the stable isotopes of oxygen and carbon within forest canopies." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360330.
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Halenyane, Keolebogile. "Investigating recharge rates in Table Mountain springs using oxygen and hydrogen isotopes." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/27834.
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This thesis investigates the monthly variation in hydrogen and oxygen isotope composition of four springs at the foot of Table Mountain, and by comparing this variation with that of local rainfall, estimates are made of their recharge rate. The oxygen, hydrogen, and EC data for Main spring, De Waal spring, Albion spring, and Newlands springs for the years 2013 to 2016 are presented. The oxygen and hydrogen isotope composition of monthly rainfall collected nearby at the University of Cape Town (UCT) over the same period are also presented. The rainfall data ranges in δD and δ¹⁸O values from -57 to +18 ‰ and -8.1 to +3.19 ‰, respectively, with most δD and δ¹⁸O values between -60 and -20‰, and -10 and +4‰. The data shows seasonal pattern, with lower δD and δ¹⁸O values in winter and higher in summer. The UCT monthly rainfall samples define a meteoric water line whose equation is δD = 6.03*δ¹⁸O + 7.07, which is similar to previous versions of the equation from the 1995 to 2008 data. The range of recorded EC values for the springs are distinct, the average EC values for each of the spring is; Albion spring 207 μS/cm, Newlands spring 128 μS/cm, Main spring 171 μS/cm and De Waal 166 μS/cm. The isotope compositions of the springs are also well grouped, with each spring plotting in a distinct field on a δD and δ¹⁸O plot. Main spring has the lowest δD and δ¹⁸O values and De Waal spring has the highest δD and δ¹⁸O values. The springs' average δD and δ¹⁸O values for the three years sampled are -7.7 and -2.74‰ (Albion), -6.48 and -2.46‰ (De Waal), -11.52 and -3.48‰ (Main) and -8.49 and -3.14‰ (Newlands). The d-excess of the rainfall range between -11.56 and +33.12 and for the springs is between 0.17 and 27.97. The summer months (low rainfall) have lower d-excess values than the winter months (higher rainfall). There is a positive relationship between the rainfall d-excess, springs d-excess and the rainfall amount, as the amount of rainfall increases the d-excess values of both the rainfall and springs increase. The change in the springs d-excess values clearly mimics that of the rainfall. The similar pattern changes of the d-excess values and δD and δ¹⁸O of the rainfall is reflected in the spring water, suggesting that recharge is occurring rather rapidly and from the d-excess values, the recovery seem to occur for some springs from month to month. De Waal spring mimics the rainfall d-excess very closely, the changes are almost at the same time, and therefore the De Waal spring is recharged the fastest, recovery occurs from month to month. Newlands d-excess does not change at the same time at the rainfall's d-excess, Newlands is the slowest spring to recover, with recharge occurring at least within three months. Main spring and Albion spring fall in between the fastest and slowest recovering spring. The springs are recharged at different rates but with the general average of recharge rate of one to three months of recovery. The difference in δD and δ¹⁸O values between the springs is best explained in terms of difference in average altitude of the potential recharge areas. Average altitude of potential recharge estimated from the topographic map is as follows: Albion spring 286 m, Newlands spring 359 m, Main Spring 518 m and for the De Waal spring 335 m. There is a strong negative correlation between δD and average altitude (r = -0.90) and for δ¹⁸O and average altitude (r = -0.82). In 2012 the annual weighted mean δ¹⁸O value of rainfall on top of Table Mountain was -4.0 ‰, therefore De Waal spring (δ¹⁸O -2.46 ‰) has a small component of mountain rainfall compared to Main spring (δ¹⁸O -3.48 ‰), with Albion spring and Newlands spring in between.
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Winhusen, Eric. "PRECAMBRIAN SEAWATER TEMPERATURE ANALYSIS USING OXYGEN ISOTOPES FROM HAMERSLEY CARBONATES, WESTERN AUSTRALIA." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin992268720.
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Kim, Sang-Tae 1970. "Oxygen isotope systematics in carbonate-water systems : influence of temperature, solution chemistry, and kinetic isotope fractionation." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111838.
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The oxygen isotope fractionation between HCO3-/CO 32- and H2O was determined experimentally in order to elucidate the precipitation mechanisms of orthorhombic carbonate minerals in solutions. The oxygen isotope composition of BaCO3 (witherite), precipitated quantitatively from solutions of various pH and the relative contribution of carbonic acid species to DIC (total dissolved inorganic carbon) at each pH in these solutions were used to generate the following fractionations at 25°C: 1000lnaHCO -3-H2O =30.53+/-0.08 1000lna&parl0;CO 2-3-H2 O&parr0;=23.17+/-0.08Based upon the above oxygen isotope fractionation and the oxygen isotope systematics of aragonite and witherite obtained from various precipitation experiments, it was discovered that CO32- rather than the more abundant HCO3- ions are preferentially incorporated into the growing carbonate crystal. Furthermore, it was proposed that the faster deprotonation kinetics of isotopically light HCO 3- ions and the preferential incorporation of light CO3 2- isotopologues could account for the kinetic isotope effects observed in these carbonate minerals.
Aragonite was inorganically precipitated from Na-Ca-Mg-Cl-HCO3 solutions at 0, 5, 10, 25, and 40°C to determine the temperature dependence of the equilibrium oxygen isotope fractionation between this mineral and the parental solution. To establish a reliable relationship between temperature and oxygen isotope fractionation as well as discount potential experimental artifacts, three different precipitation protocols were employed but statistically identical results were obtained under the conditions investigated. In addition, the extent of kinetic isotope effects induced by variations of the precipitation rate, pH, and Mg2+ concentration of the parent solutions, were thoroughly tested to establish that equilibrium oxygen isotope fractionation occurs.
In order to obtain accurate oxygen isotope compositions of the aragonite precipitates by the conventional phosphoric acid dissolution method, a statistically reliable acid fractionation factor for aragonite (and calcite) was also determined from pure natural aragonite (and calcite) specimens. From a large number (i.e., 29 and 60 individual analyses for aragonite and calcite, respectively) of replicate total oxygen isotope analyses and the isotopic composition of the acid-liberated CO2 between 25 to 75°C, the following two new equations are proposed: 1000lnaCO2&parl0;ACID &parr0;-Calcite=3.59&parl0; 103/T&parr0;-1.79 1000lnaCO2&parl0;ACID &parr0;-Aragonite=3.39&parl0; 103/T&parr0;-0.83
By combining the new acid fractionation factor of 1.01063 for aragonite at 25°C with the oxygen isotope data from the synthesis experiments determined in this study, a new relationship is reported for the temperature dependence of the aragonite-water oxygen isotope fractionation over the temperate range of 0-40°C: 1000lnaaragonite-water=17. 88+/-0.13&parl0;103/T&parr0; -31.14+/-0.46
This new experimental calibration of the aragonite-water fractionation yields a positive aragonite-calcite oxygen isotope fractionation over the temperature range investigated, in agreement with theoretical calculations. This result also provides a baseline to quantify vital or kinetic effects that are frequently observed in natural abiogenic or biogenic aragonite minerals.
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Gentry, David Keith. "Seasonal isotope and trace-metal profiles of serially-sampled Conus gastropods: proxies for paleoenvironmental change." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/3871.
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We test the fidelity of shallow-water gastropod skeletons as multi-proxy archives of seasonal paleo-environmental change by performing isotopic and trace-metal analyses on specimens of Conus ermineus from the Gulf of Mexico. Four adult specimens were collected from Stetson Bank in the Flower Garden Banks National Marine Sanctuary during the summer of 2002. Shell samples were milled along axes of growth to produce time-series profiles spanning up to eight years. We corrected the profiles for growth rate effects and compared the tuned results with in situ temperature and salinity records at the reef surface and temperature profiles from nearby surface buoys. Examination of sample densities in δ18O cycles shows that shell growth is faster during summers and slower during winters. Tuning the profiles versus time yields δ18O values that co-vary closely with seasonal temperatures to a high degree of coherency (R2 = 0.84). The δ13C profiles show cyclic variation modified by ontogenetic decreases in δ13C. These ontogenetic trends are attributable to decreasing metabolic efficiency, while seasonal cycles reflect hydrographic changes in the gastropods habitat. Salinity and δ13C of dissolved inorganic carbon show a strong correlation at Stetson Bank (R2 = 0.80), and early summer shell δ13C minima coincide with local salinity minima during times of peak river discharge. The terminations of these δ13C minima occur during annual upcoast reversals of shelf currents in this area. These effects are augmented by summer stratification and productivity minima that further decrease seawater δ13C. Sr/Ca ratios increase through ontogeny, most likely due to decreasing metabolic efficiency. However, seasonal variations in Sr/Ca profiles show strong similarity with δ18O profiles, confirming the temperature dependence of Sr/Ca and minimal influence of salinity on shell δ18O at Stetson Bank. The results of this study show that tuned δ18O and Sr/Ca profiles can be used to reconstruct seasonal paleotemperatures. Carbon isotope profiles and environmental data also demonstrate the utility of Conus δ13C as a proxy for freshwater flux and shelf circulation.
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Moerman, Jessica. "Regional hydrology captured in northern Borneo rainwater and dripwater isotope variability." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53523.
Full textAbstract:
Oxygen and hydrogen isotopes (δ18O, δD) are increasingly powerful tools for reconstructing past hydroclimate variability. The utility of δ18O- and δD-based paleoclimate records, however, depends on our understanding of how well these tracers reflect past climate conditions. The dynamics controlling the relationship between climate and water isotope variability are highly complex and often poorly constrained, especially in the tropics, where many key high-resolution paleoclimate records rely on past rainfall isotopes as proxies for hydroclimate. In this dissertation, I use multi-year timeseries of daily rainfall and biweekly dripwater δ18O from northern Borneo – a site for stalagmite δ18O-based paleoclimate reconstruction in the heart of the West Pacific Warm Pool – to track the cloud-to-calcite transformation of δ18O and its relationship to large-scale climate variability. Chapter 2 investigates the variability of rainfall δ18O variability from northern Borneo on diurnal to interannual timescales and its relationship with local and regional climate. Chapter 3 investigates the rainfall-to-dripwater transformation of climate-related isotopic signals following water transit through the Borneo cave system. Overall, this dissertation provides empirical support for the interpretation of northern Borneo stalagmite δ18O as a robust indicator of regional-scale hydroclimate variability, where higher δ18O reflects regional drying. More generally, this research provides a roadmap for obtaining more nuanced interpretations of speleothem δ18O records from multi-year, high-resolution, paired timeseries of rainfall and dripwater δ18O.
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Nasdala, Lutz, Fernando Corfu, John W. Valley, Michael J. Spicuzza, Fu-Yuan Wu, Qiu-Li Li, Yue-Heng Yang, et al. "Zircon M127 - A Homogeneous Reference Material for SIMS U-Pb Geochronology Combined with Hafnium, Oxygen and, Potentially, Lithium Isotope Analysis." WILEY-BLACKWELL, 2016. http://hdl.handle.net/10150/621937.
Full textAbstract:
In this article, we document a detailed analytical characterisation of zircon M127, a homogeneous 12.7 carat gemstone from Ratnapura, Sri Lanka. Zircon M127 has TIMS-determined mean U-Pb radiogenic isotopic ratios of 0.084743 +/- 0.000027 for Pb-206/U-238 and 0.67676 +/- 0.00023 for Pb-207/U-235 (weighted means, 2s uncertainties). Its Pb-206/U-238 age of 524.36 +/- 0.16 Ma (95% confidence uncertainty) is concordant within the uncertainties of decay constants. The delta O-18 value (determined by laser fluorination) is 8.26 +/- 0.06 parts per thousand VSMOW (2s), and the mean Hf-176/Hf-177 ratio (determined by solution ICP-MS) is 0.282396 +/- 0.000004 (2s). The SIMS-determined delta Li-7 value is -0.6 +/- 0.9 parts per thousand (2s), with a mean mass fraction of 1.0 +/- 0.1 mu g g(-1) Li (2s). Zircon M127 contains similar to 923 mu g g(-1) U. The moderate degree of radiation damage corresponds well with the time-integrated self-irradiation dose of 1.82 x 10(18) alpha events per gram. This observation, and the (U-Th)/He age of 426 +/- 7 Ma (2s), which is typical of unheated Sri Lankan zircon, enable us to exclude any thermal treatment. Zircon M127 is proposed as a reference material for the determination of zircon U-Pb ages by means of SIMS in combination with hafnium and stable isotope (oxygen and potentially also lithium) determination.
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Feng, Xiahong. "Oxygen isotope studies of zeolites: Stilbite, analcime, heulandite and clinoptilolite." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1059573322.
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Baker, Evan. "Carbon and Oxygen Isotope Fractionation in Laboratory-Precipitated, Inorganic Calcite." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19311.
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Carbon and oxygen isotopes in calcite crystals provide a record of the environmental conditions under which the crystals formed. To investigate the influence of temperature, pH, and growth rate on isotope discrimination by calcite, we measured carbon and oxygen isotope fractionation through a series of calcite precipitation experiments at T = 25C and pH = 7.5 - 9.3. We observe that neither the carbon nor oxygen isotope compositions correspond to the theoretical equilibrium isotope fractionation between calcite and solution. We also demonstrate that the fractionation of oxygen isotopes between calcite and water decreases with increasing pH, consistent with available data from experiments in which the enzyme carbonic anhydrase was used. Finally, we compare the carbon and oxygen isotopes of our calcite crystals to those of biogenic carbonates.
This thesis includes previously unpublished co-authored material.
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Motimele, Kanting Evidence. "A relativistic analysis of proton-induced knockout reactions from oxygen isotopes with direct and inverse kinematics." University of the Western Cape, 2020. http://hdl.handle.net/11394/8187.
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>Magister Scientiae - MScIn this study a complete set of exclusive (~p; 2p) polarization transfer observables of closed-shell oxygen isotopes are calculated using both direct and inverse kinematics using the relativistic plane wave impulse approximation. The interaction matrix is written in terms of the SPVAT (scalar, pseudoscalar, vector axial vector, tensor) covariants where each amplitude is obtained directly from experimental phase shifts. A relativistic mean eld theory approximation is used to compute boundstate wave functions of the nucleons. We study the evolution of polarization transfer observables within oxygen isotopes and identify observables which may discriminate between these isotopes. The same kinematical conditions are considered for both direct and inverse kinematics: the incident energy is set at 504 MeV and coplanar angles are xed at (22:12 ;40:30 ). The results indicate that only three spin observables, namely, Ay, P and Dnn distinguish di erent oxygen isotopes at these kinematical conditions in the inverse kinematics.
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Galeazzo, Tommaso. "Tracking volcanic sulphate : modelling tropospheric volcanic sulphate formation and its oxygen isotopic signatures." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS300.
Full textAbstract:
Les émissions volcaniques sont une source importante de soufre. Le soufre volcanique est oxydé et forme des aérosols sulfatés qui influencent le climat en absorbant et en dispersant le rayonnement solaire incident. Les émissions de soufre dans la troposphère influencent le climat local et régional, mais de grandes incertitudes subsistent en ce qui concerne l’oxydation et sa conversion en aérosols de sulfate volcanique. L’oxydation du soufre dans une vaste gamme de panaches volcaniques et l’influence des halogènes volcaniques sur la chimie du panache sont étudiées à l’aide d’un modèle de boîte chimique. Parallèlement, la composition isotopique en oxygène du sulfate volcanique, à savoir l’excès de 17-O (∆17O), est à l’étude, ce qui peut limiter les voies d’oxydation du soufre. Les résultats suggèrent qu’en présence de gouttelettes d’eau et de cendres, l’oxydation du soufre dans les panaches est principalement due à l’oxydation en phase aqueuse avec de l’O2 catalysé par des ions de métaux de transition (TMI). Les émissions d’halogènes favorisent la dominance de l’O2 /TMI en induisant des phénomènes d’appauvrissement de la couche d’ozone (ODE). En l’absence de gouttelettes d’eau, la chimie du panache est largement déterminée par la chimie hétérogène des aérosols primaires sulfatés. Les oxydants dominants dans ces panaches sont OH et H2O2. Le taux d’oxydation du soufre est considérablement réduit par rapport aux panaches contenant des gouttelettes d’eau. Les résultats montrent que les isotopes de l’oxygène dans les sulfates exercent de fortes contraintes sur l’équilibre chimique du soufre dans les panaches volcaniques et sur le rôle des halogènes volcaniquesVolcanic emissions are a major source of sulphur. Volcanic sulphur is oxidized and forms sulphate aerosols that influence the climate by absorbing and dispersing incident solar radiation. Sulphur emissions in the troposphere influence local and regional climate, but large uncertainties remain regarding oxidation and its conversion into volcanic sulphate aerosols. The oxidation of sulphur in a wide range of volcanic plumes and the influence of volcanic halogens on plume chemistry are studied using a chemical box model. At the same time, the isotopic oxygen composition of volcanic sulphate, namely the excess of 17-O (∆17O), is being explored, which can provide constraints on sulphur oxidation pathways. The results suggest that in the presence of water droplets and ash, the oxidation of sulphur in plumes is mainly due to aqueous phase oxidation with O2 catalyzed by transition metal ions (TMI). Halogen emissions promote the domi- nance of O2 /TMI by inducing ozone depletion events (ODEs). In the absence of water droplets, plume chemistry is largely determined by heterogeneous chemistry on primary sulphate aerosols. The dominant oxidants in these plumes are OH and H2O2. The oxidation rate of sulphur is significantly reduced compared to plumes containing water droplets. The results show that oxygen isotopes in sulphates provide strong constraints on the chemical balance of sulphur in volcanic plumes and on the role of volcanic halogens
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Remmelzwaal, Serginio. "Assessing past oxygen in the ocean using Cr isotopes as a palaeo-proxy." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/d38b75bf-f8bb-4671-bcbb-f3d71629b900.
Full textAbstract:
As greenhouse gas emissions into the atmosphere persist, both oceanic and atmospheric temperatures are projected to continue rising with major consequences for the marine environment. One of the major environmental hazards of this century is the spread of low-oxygen environments or ocean deoxygenation. While modern hypoxic environments are closely monitored, the mechanisms leading to these conditions are not fully understood in the context of an Earth system. Past ocean deoxygenation can be used as an analogue to shed light on oceanic dissolved oxygen responses to global warming. The aim of this study is to ground truth the palaeo-redox proxy of the Cr isotopic composition of foraminifera and bulk carbonates to elucidate the processes that led to and the eventual extent of hypoxic and anoxic environments during past climatic events. The potential of foraminiferal Cr isotopes as a new redox proxy was assessed by determining element partitioning and isotopic fractionation of Cr by foraminifera using a variety of geochemical techniques (LA-MC-ICP-MS, (MC-)ICP-MS, nanoSIMS). To date, Cr isotopes in biogenic carbonates have been interpreted to record the seawater δ53Cr composition at the site of test mineralisation in the surface ocean. While Cr is distributed throughout the foraminiferal test in both fossil and modern samples, sediment (fossil) core-top samples have up to two orders of magnitude more Cr than non-sedimentary and culture samples. This study concludes that Cr in foraminifera is mostly post-depositional and records bottom/pore water signals. Chromium isotopes in carbonates were applied to study how climate change influenced ocean deoxygenation during the Pleistocene, Palaeocene-Eocene Thermal Maximum, Eocene Thermal Maximum 2, Ocean Anoxic Event 2 and Ocean Anoxic Event 1a. Chromium isotopes in carbonates record local seawater deoxygenation during these events. Open ocean deoxygenation can mainly be pinned to rising temperatures in intermediate ocean waters.
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Juranek, Lauren Wray. "Assessment of Pacific Ocean carbon production and export using measurements of dissolved oxygen isotopes and oxygen/argon gas ratios /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/11055.
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Towers, Jacqueline R. "An isotopic investigation into calving seasonality, diet and dairying in British Prehistoric cattle. Reconstructing animal husbandry at a sub-annual resolution using multi-isotope analysis and intra-tooth sampling." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/7352.
Full textAbstract:
The detection of dairying is essential to understand prehistoric economies, particularly in northwest Europe, where a high degree of lactose tolerance implies that fresh milk has long been a significant dietary component. Domestic cattle (Bos taurus) are biologically able to breed year-round, potentially enabling farmers to select a calving strategy to suit their economic focus. Published literature and interviews with farmers suggests that spring calving would have been favoured by economies focussed on meat or storable dairy products, whereas the year-round provision of fresh milk would have required two calving seasons, in spring and autumn, or an extended period through spring, summer and autumn.
This thesis uses intra-tooth isotope ratio analysis of cattle tooth enamel to predict birth seasonality as an indicator of dairying. Analysis was performed on first, second and third cattle molars from the archaeological sites of Mine Howe, Pool and Earl’s Bu (Iron Age and Viking period Orkney), Old Scatness (Iron Age Shetland) and Grimes Graves (Bronze Age Norfolk). Modern molars from Chillingham Wild White cattle were also analysed.
A new method to determine cattle birth seasonality has been proposed utilising the isotopic patterning (δ13C, δ18O) recorded within first and second molar enamel. Results suggest that birth seasonality estimates are of sufficient accuracy to discriminate between single-and multiple-season calving. Although Pool and Grimes Graves have been interpreted as dairying sites from their age-at-death slaughter patterns, birth seasonality predictions imply an economy focussed on year-round fresh milk at Pool but an emphasis on storable dairy products at Grimes Graves.
In addition, it has been demonstrated that intra-tooth enamel data can provide information regarding sub-annual variation in diet and environment. A new method to investigate weaning strategy has also been proposed.
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Rowell, Kirsten. "Isotopic Logs of The Sea of Cortez: Oxygen and Carbon Stable Isotopes in Otoliths of Marine Fish Record the Impact of Diverting the Colorado River from the Sea." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194512.
Full textAbstract:
I use microchemistry in fish otoliths to test the hypothesis that diverting Colorado River flow from reaching the Gulf of California has impacted two endemic fish: the threatened gulf Corvina, (Cynoscion othonopterus) and the endangered totoaba (Totoaba macdonaldi). The oxygen and carbon stable isotope ratios in otoliths help to reconstruct conditions of the environment during key life history stages before and after the damming and diverting the Colorado River. The δ¹⁸O in otoliths illustrate that both C. othonopterus and T. macdonaldi seek out brackish habitat provided by the Colorado River during their early life history. The δ¹⁸O of C. othonopterus otolith have a strong negative correlation with Colorado River flow. I found that previously published relationships between otolith δ¹⁸O and ambient temperature along with δ¹⁸O of the water are sufficient to predict ranges of expected δ¹⁸O values for T. macdonaldi in the field. The δ¹⁸O in pre-dam T. macdonaldi otoliths show significant divergence from modern T. macdonaldi otoliths’ values, indicating that these fish used the brackish waters of the Colorado River estuary. The δ¹³C in T. macdonaldi otoliths has a significant proportion of its δ¹³C derived from diet. Pre-dam T. macdonaldi juveniles have a significantly different diet, which reflects that the Colorado River estuary had higher productivity before diversion of the river. Lastly, T. macdonaldi grew faster before the dams and in association with Colorado River flow measured by the δ¹⁸O.
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Laukert, Georgi [Verfasser]. "Ocean circulation and shelf processes in the Arctic Mediterranean traced by radiogenic neodymium isotopes, rare earth elements and stable oxygen isotopes / Georgi Laukert." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1128149257/34.
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Towers, Jacqueline Ruth. "An isotopic investigation into calving seasonality, diet and dairying in British prehistoric cattle : reconstructing animal husbandry at a sub-annual resolution using multi-isotope analysis and intra-tooth sampling." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/7352.
Full textAbstract:
The detection of dairying is essential to understand prehistoric economies, particularly in northwest Europe, where a high degree of lactose tolerance implies that fresh milk has long been a significant dietary component. Domestic cattle (Bos taurus) are biologically able to breed year-round, potentially enabling farmers to select a calving strategy to suit their economic focus. Published literature and interviews with farmers suggests that spring calving would have been favoured by economies focussed on meat or storable dairy products, whereas the year-round provision of fresh milk would have required two calving seasons, in spring and autumn, or an extended period through spring, summer and autumn. This thesis uses intra-tooth isotope ratio analysis of cattle tooth enamel to predict birth seasonality as an indicator of dairying. Analysis was performed on first, second and third cattle molars from the archaeological sites of Mine Howe, Pool and Earl’s Bu (Iron Age and Viking period Orkney), Old Scatness (Iron Age Shetland) and Grimes Graves (Bronze Age Norfolk). Modern molars from Chillingham Wild White cattle were also analysed. A new method to determine cattle birth seasonality has been proposed utilising the isotopic patterning (δ13C, δ18O) recorded within first and second molar enamel. Results suggest that birth seasonality estimates are of sufficient accuracy to discriminate between single-and multiple-season calving. Although Pool and Grimes Graves have been interpreted as dairying sites from their age-at-death slaughter patterns, birth seasonality predictions imply an economy focussed on year-round fresh milk at Pool but an emphasis on storable dairy products at Grimes Graves. In addition, it has been demonstrated that intra-tooth enamel data can provide information regarding sub-annual variation in diet and environment. A new method to investigate weaning strategy has also been proposed.
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Fiebig, Jens. "Oxygen isotope microanalysis of silicates with application to fluid rock interfaces." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=963754106.
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Weis, Franz. "Oxygen Isotope Signatures of the Apatite-Iron Oxide Ore at Grängesberg." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173031.
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The origin of apatite iron oxide ores, like the deposit at Grängesberg in the Bergslagen mining district, has been a subject of much discussion through the years. Some support a formation by hydrothermal fluids while others suggest that the ore is orthomagmatic, i.e. formed directly from a magma as suggested for the iron ore deposits of El Laco in Chile or the deposits in Kiruna, although also these two are still subjected to controversies. In 2009 sampling was done on drillcores through the Grängesberg ore. On these samples an oxygen isotope study on magnetite, quartz and whole rock samples from both the ore and its host rocks was conducted in order to obtain new knowledge about the ore forming processes. The data allowed modeling to simulate a possible origin by different magmas or hydrothermal fluids as well as a possible temperature of formation. In addition, the data set was compared to published oxygen isotope analyses of the possible magmatic iron ores of Kiruna and El Laco. The results of the Grängesberg analysis revealed that the ore in the area seems to have an origin from both magmatic and hydrothermal sources.
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Oliveira, Carlos. "Exploring the physiological variables of oxygen isotope composition in chondrychthyan teeth." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-395647.
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Since the discoveries of vertebrate bioapatite’s ability to record oxygen isotopecomposition of ambient seawater were made (Kolodny, 1983), oxygen isotopes have beenwidely used as a climatic and oceanographic proxy. The δ18OP aquatic vertebrate apatite isa function of the δ18Ow value of the ambient water, yet “vital effects” on the δ18OP compositionhave been reported previously (Venneman et al., 2013). I have analysed δ18O compositionin the teeth of six extant shark and ray (chondrichthyan) species from the tropical ocean tankof the Blackpool Sea Life Center, UK. The teeth were naturally shed and collected from thetank substrate.Preparation of samples was performed in the Laboratory of Isotope Geology at the NaturalHistory Museum of Stockholm (Sweden), and the δ18O was measured at the NordSIM facility,using secondary ionization mass spectrometry (SIMS) by a high precision and high spatialresolutionCAMECA IMS 1280 ion microprobe.Data treatment was followed by statistical analysis. Results show significant δ18O differencesat inter-tissue level. I could also illustrate the impact of organics-pretreatment on the finalδ18O values, with the outcome of one more favourable pretreatment for SIMS analysis. Intertaxonvariability was observed, without much statistical confidence, but I hypothesize that itmay be due to the difference in tissue crystallization and organic quantity between species.
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Seguro, Requejo Maria Isabel. "Shelf-sea gross and net production estimates from triple oxygen isotopes and oxygen-argon ratios in relation with phytoplankton physiology." Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/69374/.
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Shelf seas represent only 10 % of the ocean area, but support 30 % of oceanic primary production. There are few measurements of biological production at high spatial and temporal resolution in such physically dynamic systems. Here, I use dissolved oxygento- argon (O2/Ar) ratios and triple oxygen isotopes (δ(17O), δ(18O)) to estimate net and gross biological production seasonally in the Celtic Sea between summer 2014 and summer 2015, as part of the NERC Shelf-Sea Biogeochemistry programme. O2/Ar was measured continuously using a shipboard membrane inlet mass spectrometer. Discrete water samples from hydrocasts were used to measure O2/Ar, δ(17O) and δ(18O) depth profiles. The data were combined with wind-speed based gas exchange parameterisations to calculate biological air-sea oxygen fluxes. These fluxes were corrected for non-steady state and diapycnal diffusion to give net community production (N(O2/Ar)) and gross O2 production (G(17O)). N(O2/Ar) was highest in spring at (33±41) mmol m-2 d-1, and G(17O) was highest in summer at (494±370) mmol m-2 d-1, while autumn was net heterotrophic with N(O2/Ar) = (–14±28) mmol m-2 d-1. During spring, biological production was spatially heterogeneous, highlighting the importance of high resolution biological production measurements. The ratio of N(O2/Ar) to G(17O), ƒ(O2), was highest in spring at 0.18±0.03 corresponding to 0.34±0.06 in carbon equivalents; about 0.05 in summer and < 0 in autumn/winter. Statistical measurement uncertainties increase when terms other than air-sea exchange fluxes are included in the calculations. Additionally, electron transfer rate derived from fast repetition rate fluorometry measurements was compared with G(17O), but no simple relationship was found. This study characterised the seasonal biological patterns in production rates and shows that the Celtic Sea is a net carbon sink in spring and summer. Such measurements can help reconcile the differences between satellite and in situ productivity estimates, and improve our understanding of the biological carbon pump.
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Woodley, Ewan James. "Reconstructing the climate of Scotland using stable carbon and oxygen isotopes in tree-rings." Thesis, Swansea University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678326.
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Stephenson, Richard Javier. "Tropical land snails as precipitation proxies: Oxygen stable isotopes of shells from Trinidad Island." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563273765452653.
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Duffy, Margaret R. "Determining the biological turnover rate of phosphate in agricultural soils using stable oxygen isotopes." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1593864445251739.
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Brooks-English, Nathanael Talman. "Stable Isotopes in the Spines of Columnar Cactus: a New Proxy for Climate and Ecophysiological Research." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195268.
Full textAbstract:
There are relatively few annually resolved climate proxies in arid and semi-arid regions. Columnar cactuses are common in these regions and the stable isotopes of carbon and oxygen in durable spines record variations in rainfall, humidity and ecophysiology as they grow in series along the sides of cactuses. Despite their spines, columnar cactuses provide important ecosystem resources and services in drought prone areas, however, the impact that long-term climate variability and infrequent storms (El Niño or tropical storms) have on the ecology and ecophysiology of columnar cactus is less clear. Stable isotopes in trees and corals serve as useful proxies of climate and ecophysiological information, but for cactus we lack the most rudimentary information about the isotopic systems and their links to the environment. Here, we present an isotopic framework that begins with developing semi-empirical mechanistic models of δ¹³C, δ¹⁸O and δ²H variation in saguaro cactuses that link physical and physiological fractionation factors in stem water and spines to rainfall and humidity. We also review a novel method for determining the age of spines, an important step in developing useful chronologies of isotopic variation in spines. The mechanistic models combined with local climate records enhance our understanding of isotopic variation in daily and annually dated spine δ¹³C and δ¹⁸O records and explain the statistical association of δ¹³C and δ¹⁸O in spines with rainfall, vapor pressure deficit, and El Niño enhanced winter rains. While there are still some challenges to overcome, we expect that isotopic spine series will be used as climate proxies to answer questions regarding regional climate variability or to enhance current models of past and future climates. Likewise, ecophysiologists can use the isotopic spine series in conjunction with gas exchange or carbohydrate studies to look at reproductive or biological responses to changing environments.