No description available.

Abstract Amorphous Calcium Carbonate (ACC) is a naturally occurring amorphous form of the widely distributed mineral calcium carbonate (CaCO3). ACC has been found increasingly as a precursor phase, calcium storage site, or strengthening structural phase in a wide array of different biomineralizing organisms. An accurate understanding of the widely used classic carbonate-water paleothermometry relies on formation of CaCO3 minerals and associated oxygen isotope effects. Moreover, ACC has oft been pointed to as a possible reason for non-equilibrium isotope effects, also called vital effects, in biogenic carbonates. It is, therefore, vital to understand whether ACC can reach equilibrium with its surrounding solution, as well as the role of ACC precursors in the isotopic composition and evolution of the final crystalline phase they transform into. This study is designed to answer these questions through the precipitation of stable ACC by two methods, the alkaline method (AM) which utilizes high pH to precipitate ACC, and the silica method (SM) which envelopes precipitating ACC particles in silica vesicles to prevent crystallization. These differently precipitated ACCs are then subjected to several different experimental treatments. This is achieved by monitoring the crystallization by X-ray Diffraction (XRD), and isotopic evolution of the ACC precipitates by Isotope Ratio Mass Spectrometry (IRMS) as they age and concurrently crystallize in parent solution, or in 18O enriched re-equilibration solution. This research indicated a marked difference in the crystallization behaviour, isotopic composition, and isotopic evolution of ACC produced by these two precipitation methods. With the AM method, ACC precipitates (AM-ACC) crystallized more predictably to calcite and maintained δ18O signatures that were slightly lower than the equilibrium CO32- and resisted further isotopic exchange with surrounding solution. We propose that the former is mostly due to an incomplete DIC-water oxygen isotope equilibrium prior to the AM-ACC precipitation and the latter is a result of the high pH of the precipitating solution decreasing the solubility of the precipitated ACC phase, disallowing isotope exchange, and favouring crystallization by solid-state transformation. Conversely, while ACC precipitated using the SM (SM-ACC) yielded much more variable results, both in terms of mineralogical identity upon crystallization, and δ18O values. Isotopic results were much closer to the expected equilibrium δ18O value for calcite, hinting at an expedited oxygen isotope exchange between SM-ACC and parent solution. Furthermore, SM-ACC was capable of isotopic exchange with the 18O enriched re-equilibration solution, a feat corresponding AM-ACC was incapable of. Overall, our experimental results gleaned here that precipitation method or precipitation environment play a critical role in the isotopic evolution of precursor ACC to crystalline CaCO3, suggesting ACC as an important source of the vital effect. / Thesis / Master of Science (MSc)

No description available.

Global warming and extreme weather events have impacted the ability of Earth’s forest ecosystems to sequester atmospheric carbon dioxide. The full effects of these events on forest productivity, vulnerability, and the carbon cycle have not yet been fully assessed. One potentially fruitful approach is to explore past climate and forest growth patterns through tree ring records. These records may be used to explore how past environmental events may have impacted tree growth and provide insight into the functioning of forest ecosystems in the future. The stable isotope ratios (e.g. 13C to 12C) of tree ring material also provide additional information about tree growth trajectories and environmental stressors that may not be recognized in radial growth. In this study, tree ring and stable isotope records were measured and constructed to explore the dynamics of growth over the lifespan of plantation pine stands in southern Ontario. Tree ring growth records were used to determine the effects of climate and other environmental changes on radial growth. These records were constructed from two white pine (Pinus strobus L.) plantations established in 1939 (TP39) and 1974 (TP74) and one red pine plantation established in 1931 (TP31). Air temperature, precipitation, and drought indices were analyzed at monthly combinations to determine controls on growth. Temperature was consistently negatively correlated to growth, while precipitation and Palmer Drought Severity Index (PDSI) were consistently positively correlated to growth. The effectiveness of each climate variable to control ring growth differed between sites which may be related to stand age, stand density, and management factors. In both white pine plantations, inter-annual eddy-flux quantifications of gross ecosystem productivity (GEP) was found to be significantly related to tree ring growth over the overlapping period from 2003 to 2017. These relationships enabled an inter-annual estimate of GEP to be constructed for both growth chronologies over the period 1942 to 2017 for TP39 and 1981 to 2017 for TP74). Additionally, growth rings from three specimens in two different-age (14- and 77-year old) white pine plantation forests were analyzed for stable carbon isotope ratios to identify both short- and long-term variations in the physiological response to changing environmental conditions. Variations in δ13C time series from whole wood samples provided a potential record of intrinsic water use efficiency (iWUE) for these three trees. These iWUE records were compared to climate records and inter-annual eddy-flux quantifications of GEP and evapotranspiration (ET). Long-term iWUE was found to increase by 50 μmol mol–1 yr–1, with nearly all of the increase occurring as the tree shifted into active homeostasis of stomatal control in the late 1960s. Changes in time series of internal and external concentration of CO2 (ratio) also displayed a significant shift from first increasing and then decreasing trend. In the three wood samples, air temperature, ET, and GEP were found to be significantly, but inconsistently related to iWUE. The work of this thesis shows that tree ring properties are strongly related to key environmental variables such as temperature and drought stress in pine plantation forests in southern Ontario, Canada. Results also suggest that dendrochronology and isotope tracers are useful tools to be used to evaluate historical environmental impacts on growth in these different-age plantation stands. The background knowledge of climate drivers acting on tree ring growth and ring isotopic compositions over the forests’ history may be used to make informed management decisions to promote tree productivity in a changing climate in Eastern North America. / Thesis / Doctor of Philosophy (PhD) / The full effect of water availability and environmental factors on forest productivity, vulnerability, and the carbon cycle has not been fully assessed. Tree ring chronologies offer one approach to explore past climate and forest growth patterns. These records may be used to identify past environmental events may have impacted tree growth and provide insight into the functioning of forest ecosystems in the future. Additionally, stable carbon isotope ratios (δ13C, or 13C to 12C) of tree ring material provide information about tree intrinsic water use efficiency (iWUE) which is not captured in radial width measurements. Lastly, inter-annual eddy-flux quantifications record stand-level dynamics of ecosystem productivity. In this study, tree ring, stable isotopes, and eddy-flux records were measured and constructed to explore the dynamics of growth over the lifespan of plantation pine stands in southern Ontario. In all three techniques, records were constructed from three white pine (Pinus strobus L.) plantations established in 1939 (TP39), 1974 (TP74) and 2002 (TP02). Air temperature, precipitation, and drought indices were analyzed at monthly resolution to determine controls on water use and productivity. Temperature was consistently negatively correlated to growth, while precipitation and PDSI were consistently positively correlated to growth. Variations in the δ13C time series from whole wood samples also provided a record of iWUE. Long-term iWUE was found to increase by 50 μmol mol–1 yr–1, with nearly all of the increase occurring as the tree shifted into active homeostasis of stomatal control in the late 1960s. In all three white pine plantations, inter-annual eddy-flux quantifications ecosystem productivity were found to be significantly related to tree ring growth over the overlapping period from 2003 to 2017. These relationships enabled an inter-annual estimate of tree ring-inferred fluxes to be constructed for all three growth chronologies. These results suggest that dendrochronology and isotope tracers are useful tools to be used to evaluate historical environmental impacts on growth in these different-age plantation stands. The interrelationships of tree ring growth, ring isotopic compositions, and eddy-flux quantifications found here serve as useful background knowledge on which to base additional studies of forest climate change impacts.

The technique of high resolution solid state carbon-13 NMR, achieved with magic angle spinning (MAS) and high power 13c-1H dipolar decoupling and cross polarization, was applied to a number of multicomponent polymer systems. Specific problems which were addressed are: (1) the nature of domain structure and molecular motion of two thermoplastic elastomer systems, including a series of styrene isoprene-styrene linear triblock copolymers (SIS’s) of various compositions, molecular weights and sample histories, and a poly(ester)- urethane based on poly(1,4-butylene adipate) and 4,4¹ -diphenylmethane diisocyanate, (2) the compatibility at the molecular level of polymer blends containing poly{vinylidene fluoride) (PVF2), including solution and mechanical blends with poly{methyl methacrylate) {PMMA}, poly(vinyl acetate} (PVAc) and poly(vinyl methyl ether) (PVME). For the thermoplastic copolymers, higher degree of phase separation between the hard and soft domains was indicated by two facts: First, ¹³C resonances of either domain could be selectively observed with different experimental conditions. Second, there was a one-component, first-order, spin-lattice relaxation behavior of the ¹³C nuclei in the soft domains. For the SIS copolymers, results of T₁ and T₂* determinations (beth with MAS) suggest that molecular motion, in terms of frequency, was independent of composition, molecular weight and selective casting solvents. However, from static spectra, molecular motion of the isoprene blocks was found to be more anisotropic for the samples cast from a poor solvent for polyisoprene {MEK) in contrast to samples cast from a good solvent of polyisoprene (hexane). For the polymer blends of poly(vinylidene fluoride), the level of molecular intermixing was reflected through the degree of ¹³C NMR signal attenuations of the non-PVF₂ polymers. These attenuations are mainly due to undecoupled intermolecular ¹³C-¹⁹F dipolar interactions. With a MAS rate of 2KHz, resolution of the intimacy of mixing between the two constituent polymers in the blends was estimated to be in the range of 3 to 4 angstroms. Varying degrees of NMR signal attenuations among the individual chemically different carbons of a polymer support a postulation of weak intermolecular 'acid-base' association between the acidic protons of PVF₂ and basic carbonyl groups in the case of both the PMMA and PVAc. / Ph. D.

Die Verhältnisse der stabilen Isotope des Sauerstoffs (16O, 17O, 18O) und des Kohlenstoffs (12C, 13C) im biogenen Apatit des Zahn- und Knochenmaterials von Säugetieren lassen Rückschlüsse auf die Isotopie der entsprechenden Sauerstoff- und Kohlenstoffquellen zu. Die Isotopenverhältnisse dieser Quellen (z.B. Trinkwasser, Luftsauerstoff, Nahrung) sind an bestimmte Umwelt- und Klimabedingungen wie Temperatur, Luftfeuchtigkeit, CO2-Konzentration, Bioproduktivität, Art der Vegetation, Grad der Vegetationsdichte etc. geknüpft. Bestimmt man die Sauerstoff- und Kohlensoffisotopenverhältnisse in diagenetisch unalteriertem fossilem Säugetiermaterial können Aussagen über solche Klima- und Umweltparameter weit in die Erdgeschichte zurück getroffen werden. Darüber hinaus ist es möglich Informationen über Lebensweise und Verhalten der untersuchten Taxa, wie z.B. Wanderverhalten, Geburtensaisonalität, Trinkverhalten, Nahrungspräferenzen, Ressourcenteilung und Habitatnutzung zu erlangen. Seit dem Beginn der Forschungen auf diesem Gebiet in der 70er und 80er Jahren des 20. Jahrhunderts ist eine große Zahl von Studien erschienen, welche sich der Untersuchung der Sauerstoff- und Kohlenstoffisotopie (18O/16O, 13C/12C) des Zahn- und Knochenmaterials rezenter und fossiler (vorwiegend großer) Säugetiere zu diesen Zwecken widmen. Noch keine zwei Jahrzehnte ist es her, dass erkannt wurde, das troposphärischer Sauerstoff eine anomale 3-O-Isotopenzusammensetzung (17O/16O, 18O/16O) besitzt, die signifikant von fast allen anderen terrestrischen Materialien abweicht. Diese wird in Folge von nicht massenabhängiger Fraktionierung durch photochemische Prozesse in der Stratosphäre hervorgerufen und durch Gasaustausch in die Troposphäre übertragen. Die Magnitude dieser Sauerstoffisotopenanomalie ist eine Funktion der atmosphärischen CO2-Konzentration, sowie der globalen Bioproduktivität. Kann die 3-O-Isotopie des Luftsauerstoffs zu vergangenen Zeitpunkten in der Erdgeschichte rekonstruiert werden, lässt dies somit auch Rückschlüsse auf die entsprechende CO2-Konzentration bzw. die globale Bioproduktivität zu. Geologische Archive die dies ermöglichen sind jedoch kaum vorhanden. Da für Säugetiere der eingeatmete Luftsauerstoff neben Trinkwasser und freiem Wasser in der Nahrung zu den wichtigsten Sauerstoffquellen zählt, ist biogener Apatit rezenter und fossiler Säugetiere eines der wenigen möglichen Materialien die das Potential haben, ein solches Archiv darzustellen. Die vorliegende Arbeit untersucht die Variation der 3-O-Isotopenzusammensetzung im Bioapatit rezenter Säugetiere, sowie deren Bedeutung als neuen Proxy zur paläo-CO2-Rekonstruktion und als Indikator für diagenetisch alteriertes Skelettmaterial. Desweiteren werden zwischenartliche, innerartliche und intraindividuelle Variationen der Sauerstoff- und Kohlenstoffisotopie im Bioapatit rezenter Nagetiere untersucht um eine bessere Interpretationsgrundlage für entsprechende Analysedaten fossiler Vertreter dieser größten Ordnung der Säugetiere herzustellen. Kapitel 2 beschäftigt sich mit der Frage, ob die anomale Isotopensignatur troposphärischen Sauerstoffs als Indikator für diagenetische Alteration des Zahn- und Knochenmaterial von fossilen Säugern genutzt werden kann. Hierzu wurde die 3-O-Isotopie von Zahnschmelz, Dentin und in geringem Umfang auch Knochenmaterial von einzelnen Individuen känozoischer Nagetiere separat analysiert. Während alle Zahnschmelzproben eine deutliche Sauerstoffisotopenanomalie aufweisen, welche in einer Größenordnung liegt die für diagenetisch unalterierten Bioapatit kleiner Säugetiere zu erwarten wäre, zeigen alle Dentinproben eine deutlich niedrigere bis gar keine Anomalie, was auf Isotopenaustausch mit diagenetischen Fluiden hindeutet. In Kapitel 3 werden die Variationen der anomalen Isotopensignatur troposphärischen Sauerstoffs im Skelettmaterial von rezenten Säugetieren evaluiert. Dies geschieht anhand zweier voneinander unabhängiger Ansätze: 1. durch 3-O-Isotopenanalyse von rezentem Bioapatit und 2. durch ein detailliertes Massenbilanzmodell. Da der Anteil des veratmeten Luftsauerstoffs im Verhältnis zu den weiteren Sauerstoffquellen in erster Linie von der spezifischen metabolischen Rate abhängt, die weitgehend mit dem Körpergewicht skalierbar ist, wurden Arten aus einem möglichst großen Körpergewichtsbereich von wenigen g bis zu einigen tausend kg untersucht. Es zeigte sich, dass das anomale Isotopensignal mit sinkender Körpermasse zunimmt. Auf Basis der daraus gewonnenen Erkenntnisse wurde versucht die Magnitude der anomalen Sauerstoffisotopensignatur in der Troposphäre zu verschiedenen Zeitpunkten im Känozoikum durch 3-O-Isotopenanalyse von eozänem, oligozänem und miozänem Zahnschmelzmaterial von Nagetieren zu bestimmen um daraus Erkenntnisse über die entsprechenden CO2-Konzentrationen zu erhalten. Das theoretische Massenbilanzmodell stimmt gut mit den analytisch gewonnenen Daten überein, beide zeigen eine Vergrößerung der 3-O-Isotopenanomalie im Bioapatit mit sinkender Körpermasse. Die rekonstruierten CO2-Konzentrationen stimmen generell mit vorhandenen Daten diverser Proxies überein, jedoch erlaubt der assoziierte Fehler es nicht, CO2-Schwankungen im Bereich von wenigen 100 ppm aufzulösen. An der Grenze von Paläozän zu Eozän fand eine der einschneidendsten Umwelt- und Klimaveränderungen des Känozoikums statt, welche ihren Höhepunkt im sogenannten “Palaeocene Eocene Thermal Maximum” (PETM) hatte. Dieses war verbunden mit einer globalen negativen Kohlenstoffisotopenexkursion (CIE), deren Quelle bis heute kontrovers diskutiert wird. Kapitel 4 beschäftigt sich mit den Temperaturschwankungen und Veränderungen der CO2-Konzentration im Übergangsbereich dieser beiden Zeitalter. Dies geschieht anhand einer diesen Zeitabschnitt umspannenden Probenserie von Zahnschmelz der Säugetiergattung Ectocion aus dem Clarks Fork Basin (Wyoming, USA). Die rekonstruierten Temperaturschwankungen stimmen gut mit bereits vorhandenen Studien des 18O/16O Verhältnisses an biogenem Apatit aus diesem Zeitintervall überein. Die aus der 3-O-Isotopenzusammensetzung rekonstruierten CO2-Konzentration deuten darauf hin, dass auch während des Temperaturmaximums an der Paläozän-Eozän Grenze ein Wert von 1550 ppm nicht überschritten wurde, was auf die Dissoziierung von marinem Methanhydrat als Hauptquelle der CIE hinweist. Kapitel 5 untersucht die zwischenartlichen, innerartlichen und intraindividuellen Variationen der Karbonatsauerstoff-, Phosphatsauerstoff- und Kohlenstoffisotopie sieben verschiedener Nagetierarten anhand von Proben aus Eulengewöllen eines einzelnen Fundortes. Die Ergebnisse werden mit ähnlichen Studien an Großsäugern verglichen, und es werden Schlüsse zum Umgang mit Probenmaterial kleiner Säugetiere bei der Verwendung zur Paläoklimarekonstruktion mittels stabiler Isotope gezogen. Die Variabilität der Sauerstoff- und Kohlenstoffisotopie der untersuchten Zähne und Knochen ist nicht höher als die vieler Großsäuger, was die Relevanz der im Fossilbericht viel häufigeren Nagetiere für derartige Studien unterstützt. Jedoch sollte strikt darauf geachtet werden, dass auf Rezentmaterial basierende Bioapatit-Temperatur-Kalibrationen exakt auf dem gleichen Skelettelement beruhen welches auch als Fossilmaterial untersucht wird, da durch die unterschiedliche Mineralisierungsintervalle verschiedener Zähne und Knochen deutliche Unterschiede in den entsprechenden Isotopenzusammensetzungen, insbesondere in der des Sauerstoffs beobachtet werden konnten.

This thesis investigates the potential of the bivalve Arctica islandica (Linnaeus, 1767) from fjordic sites in NW Scotland for reconstructing past marine environmental /climatic variability. Using dendrochronological and sclerochronological techniques, six master chronologies were created which when compared show little common variability between the sites, indicating no common response to regional scale forcing. The chronologies were compared to local and regional scale SST and land based datasets, with no significant, time stable responses to climate found. It is clear the growth/climate response of A. islandica from these sites is complex, potentially due to the shallow nature of the sample sites, direct local drivers such as food availability and, potentially, anthropogenic activity in the region. Geochemical analyses of the shell material were undertaken to examine the timing and magnitude of the radiocarbon bomb-peak and the stable carbon isotope signature of the oceanic Suess Effect. The timing of the radiocarbon bomb-peak in Loch Etive does not appear to match previously published results from other marine locations and are a potentially serious challenge to the assumption that A. islandica GI are always annual features. Results comparing δ¹³C values and the age of the specimen when these values are incorporated into the shell material strongly indicate an ontogenetic control over δ¹³C, meaning the Suess Effect could not be effectively investigated. To take these ontogenetic influences into account it is suggested that any data from the juvenile period of shell life is not used. Analysis of shell biometrics and morphology indicate significant relationships between shell age and height and age and weight, however the errors for these are large (±78 years and ±80 years respectively). These results indicate that despite large errors shell height, as a predictor of age, has the potential to be used for in situ population studies.

<p>The objective of this thesis is to improve the understanding of what processes and mechanism affects the distribution of polychlorinated biphenyls (PCBs) and organic carbon in coastal sediments. Because of the strong association of hydrophobic organic contaminants (HOCs) such as PCBs with organic matter in the aquatic environment, these two entities are naturally linked. The coastal environment is the most complex and dynamic part of the ocean when it comes to both cycling of organic matter and HOCs. This environment is characterised by the largest fluxes and most diverse sources of both entities. A wide array of methods was used to study these processes throughout this thesis. In the field sites in the Stockholm archipelago of the Baltic proper, bottom sediments and settling particulate matter were retrieved using sediment coring devices and sediment traps from morphometrically and seismically well-characterized locations. In the laboratory, the samples have been analysed for PCBs, stable carbon isotope ratios, carbon-nitrogen atom ratios as well as standard sediment properties. From the fieldwork in the Stockholm Archipelago and the following laboratory work it was concluded that the inner Stockholm archipelago has a low (≈ 4%) trapping efficiency for freshwater-derived organic carbon. The corollary is a large potential for long-range waterborne transport of OC and OC-associated nutrients and hydrophobic organic pollutants from urban Stockholm to more pristine offshore Baltic Sea ecosystems.</p><p>Theoretical work has been carried out using Geographical Information Systems (GIS) and statistical methods on a database of 4214 individual sediment samples, each with reported individual PCB congener concentrations. From this work it was concluded that the continental shelf sediments are key global inventories and ultimate sinks of PCBs. Depending on congener, 10-80% of the cumulative historical emissions to the environment are accounted for in continental shelf sediments. Further it was concluded that the many infamous and highly contaminated surface sediments of urban harbours and estuaries of contaminated rivers cannot be of importance as a secondary source to sustain the concentrations observed in remote sediments. Of the global shelf PCB inventory < 1% are in sediments near population centres while ≥ 90% is in remote areas (> 10 km from any dwellings). The remote sub-basin of the North Atlantic Ocean contains approximately half of the global shelf sediment inventory for most of the PCBs studied.</p>

The focus of my research is to apply stable isotopes as a new tool to understand free radical chemistry in the troposphere. Stable carbon isotope ratios are used as indirect tracers of the reaction of nonmethane hydrocarbons (NMHC) with OH radicals in ambient air from Toronto and Vancouver air-sheds, Canada. Compound-specific stable carbon isotope ratios of NMHC were determined in ambient air from urban, suburban, rural and source sites in the air-sheds using Gas Chromotograph-Isotope Ratio Mass Spectrometry (GC-IRMS). In the Greater Toronto Area, the average isotope ratio of all ambient measurements of NMHC, including halogenate NMHC was found to be -25.7 + 3.4 %o. Traffics related source sites in the Greater Toronto Area have an average isotope ratio of -25.7 + 3.5 %o, whereas the ratio for traffic related emissions in the Lower Fraser Valley are -25.9 + 4.2 %o. The extent of chemical processing due to OH radical reactions that the individual NMHC has experienced since emission is quantitatively determined. It is shown that in combination with concentration measurements, isotope ratio measurements are an extremely valuable new approach to study the spatial and temporal differences in chemical removal mechanisms, mixing and dilution processes.

Although studies on stable-carbon isotopes in trees from temperate zones provide abundant paleoclimatic data, tropical trees are still understudied in this context. Therefore this study examined the variability of intra- and inter-annual stable-carbon isotopic pattern in several tree species from various tropical climates. The 𝛿¹³C values of samples of 12 broadleaved trees (seven species) from various paleotropical and neotropical sites along a climatic moisture gradient were investigated. The inter-annual variability between species and sites was studied. Further the relationship between 𝛿¹³C and precipitation time series was analyzed. Results show that tropical tree species show a similar variability in carbon isotopic composition as temperate tree species. Significant correlations between annual precipitation and tree-ring 𝛿¹³C time series were negative. Successful crossdating of a tree-ring 𝛿¹³C time series highlights the potential of carbon isotope measurements for tropical tree-ring analytical studies. Tropical broadleaved trees are able to capture a carbon isotopic signal in their annual rings even under everwet conditions and show good potential for paleoclimatic research.