Дисертації з теми "Hydrogen isotopic composition"

This study examines variability in the isotopic composition of precipitation in southern Illinois, USA using a 5-year, event-based record, novel in its duration and in potential to extract important isotopic information of precipitation in a dynamic region, and the seasonality of major moisture sources. The isotopic composition of precipitation exhibited seasonal variations in δ18O and δ2H, where values are distinctively higher (lower) during summer (winter). Average values for d-excess were the highest (lowest) during autumn (summer). Seasonality is also present in events originating from the Gulf of Mexico (GOM), isolated by Langrangian methods. GOM JJA events showed more isotopically depleted precipitation than of non-GOM events due to a stronger “amount effect” signal (R2 = -0.40). To date, the amount effect has never been reported this far inland in the US. Precipitation analysis as it related to the ENSO phases exhibited statically significant differences in d-excess values. Precipitation events that occurred during a La Niña phase exhibited positive d¬-excess values, with an average value of 25.18‰. δ18O and δ2H values during El Niño phase were on average more depleted. Overall results highlight that the GOM, as a dominating moisture source, and ENSO phases can modulate the seasonal and intra-seasonal variability in the isotopic composition of precipitation in this region. The data collected, from a single location, can highlight moisture dynamics occurring on a regional scale and highlight the importance of the GOM as prevailing source of moisture for the Midwestern US. The second part of this study involved determining what were the best predictors for 18O and d-excess values. The study revealed that sea surface temperature and oxygen isotope values in the ambient vapor were the best predictors for 18O values but were the poorest predictors of d-excess values. The best predictors of d-excess were land surface characteristics such as the volumetric soil moisture, evaporation from bare soil variable, as well as SST, temperature of the air and specific humidity of the air. However, these predictors worked best with positive d-excess values that equaled or above 20‰.

Stable hydrogen and carbon isotopic compositions of biogenic methanes collected from the sediments of several deep-sea, nearshore marine-estuarine, and freshwater environments were determined. The isotopic compositions of methane samples from eight different DSDP Sites (mean σD-CH4 = -1850>/∞, std. dev. = 70>/∞, n = 75; mean σ13C-CH4 = -71.30/∞, std. dev. = 6.30/∞, n = 44) are generally typical of methane formed via C02 reduction in deep-sea sediments. Methane collected from several freshwater environments was D-depleted (mean σD-CH4 = -3000>/∞ , std. dev. = 260/∞, n = 20) and 13C-enriched (mean σ13C-CH4 = -60.10/∞, std. dev. = 6.10/∞, n = 20) compared to the deep-sea methane. Normally, acetate dissimilation is thought to account for about 60 to 70% of the total methane production in freshwater sediments. Nearshore marine-estuarine methanes appear to be isotopically intermediate (mean σD-CH4 = -2580>/∞ , std. dev. = 230/∞, n = 46; σ13C-CH4 = -61.80/∞, std. dev. = 3.10/∞, n = 46) between deep-sea and freshwater methanes. Variation in the relative importance of the two main methanogenic pathways, acetate dissimilation and C02 reduction, is probably the single most important factor responsible for the differences in methane isotopic compositions among these three different types of environments. Other factors that probably contribute to the methane isotopic differences are temperature, sedimentation rate, organic matter type and amount, concentration of alternate electron acceptors, rate of methane formation and possibly postgenerative isotopic equilibration. Shallow aquatic sediments are thought to be an important source of methane to the atmosphere; the methane produced in these systems, including the ones sampled in this study, is generally substantially more 13C-depleted than expected based on the σ13C of atmospheric methane and the isotopic fractionation associated with the atmospheric sink process. Too few oD data are available to allow evaluation of the role of shallow aquatic sediments in determining atmospheric σD-CH4.

Contraindre la concentration et la composition isotopique de l'hydrogène dans le manteau terrestre apporte des informations cruciales sur le cycle global de l'eau et la nature des hétérogénéités mantelliques. Dans ce but, les bordures vitreuses des basaltes sont les échantillons les plus adaptés Lors de cette étude, 170 échantillons provenant de 4 rides océaniques et 2 points chauds ont été analysés pour leurs concentrations en eau et leur δ D. Au cours de ce travail, un biais analytique lié à l'utilisation de creusets en platine pour extraire le éléments volatils a été mis en évidence. L'utilisation de tubes en silice a donc été préférée. Les δD re-mesurés sur des échantillons précédemment analysés avec des creusets en platine sont en moyenne 15%o plus élevés. Le δ D et le rapport H2O/Ce présentent des hétérogénéités régionales et locales et constituent de traceurs de source. La source des basaltes de ride contient 175+/-70 ppm d'eau, et pour un S8\deltaSD de -61+/-6%o. Les MORB de l'océan Atlantique sont plus riches en eau (~250ppm in thé source) et en D ( δ D—57%o) que ceux de la dorsale Sud-Est Indienne (140 ppm et -63%o en moyenne), illustrant des processus de mélange différents également vus à travers les rapports Pb/Ce. L'étude de la dorsale Sud-Ouest Indienne a montré que δ D et H2O/Ce sont des traceurs du métasomatisme. Les concentrations en eau dans les sources des E-MORB et des OIB sont plu élevées et plus variables (entre 250 et 700 ppm). Les sources enrichies en eau et en élément incompatibles ont des δ D qui couvrent une gamme aussi large que celle des N-MORB (allant d -70 à -40%o). La confrontation avec les compositions isotopiques du néon et de Pb, Sr et Nd montre que le réservoir contenant des gaz rares primitifs est vraisemblablement pauvre en eau, et donc distinct du FOZO. Par conséquent, il est possible de recycler efficacement de l'eau sans en changer la composition isotopique en hydrogène dans certaines zones de subduction
Constraining the concentration and isotopic composition of hydrogen in Earth's mantle brings crucial insights on the global water cycle and the nature of mantle heterogeneities. For this purpose, glassy rims of basalts are the best samples. In this study, 170 samples from 4 oceanic ridges and 2 hotspots were analysed for water content and ô D. During this work, we showed that using platinum crucibles to extract the volatiles was the cause of an analytical bias in earlier data. The use of silicate tubes was thus prefered. δ D re-measured on samples previously analyzed using platinum crucibles are, on average, 15%o higher. The δ D and the H2O/Ce ratio are hétérogeneous, both between areas and locally, and caracterize the sources. The source of N-MORB contains 175+/-70 ppm of water and has a δ D of -61+/-6%o. MORB from the Altantic ocean are richer in water (-250 ppm in the source) and D ( δ D—57%o), than those from thé South-East Indian (H2O~140 ppm and δ DS\simS-63%o), illustrating different mixing processes, also seen through the Pb/Ce ratios. The study of the MORB from the South-West Indian ridge showed that δ D and H2O/Ce are sensitive to metasomatism. The concentrations of water in E-MORB and OIB sources are higher and more variable (from 250 to 700 ppm). The ô D of water- and incompatible elements-enriched sources range from -70 to -40%o, showing as much variations as depleted sources. Confrontation with the isotopic compositions of Ne, Pb, Sr and Nd shows that the resevoir containing the primitive rare gases cannot be water-rich, and is thus different from the FOZO. Therefore, efficient recycling of water with no modification of its isotopic composition in hydrogen at subdcution zone can occur at some subduction zones

Early research into the stable hydrogen isotopic compositions (δD) of petroleum involved bulk deuterium/hydrogen (D/H) measurements which, while providing some useful information, had to contend with the analysis of complex mixtures of hydrocarbons, and alteration resulting from the rapid exchange of nitrogen-, oxygen- and sulphur-bound hydrogen. The use of gas chromatography-isotope ratio mass spectrometry (GC-irMS) overcomes these problems by allowing the analysis of individual compounds containing only the most isotopically conservative aliphatic carbon-bound (C-bound) hydrogen. This project investigates the geochemical utility and reliability of compound-specific δD values, with the aim to better understand and exploit this analytical capability. To demonstrate the source diagnostic potential of compound-specific δD values, normal and branched alkanes extracted from series of immature bog-head coals (torbanites) were analysed. The torbanites contain immature organic matter predominantly from a single, freshwater algal source, i.e. Botryococcus braunii (B. braunii). The δD values of n-alkanes reflect the climate regime at the time of deposition of the torbanites, and vary mainly in response to the δD values of the source meteoric waters in their depositional environments. n-Alkanes from torbanites deposited at high latitude in a glacial climate are depleted in D by up to 70% relative to those from a torbanite deposited at low latitude under a tropical climate regime. Torbanites deposited in a mid-latitude region under cool-temperate conditions contain n-alkanes with δD values falling in between those of n-alkanes from tropical and glacial torbanites.The δD values of the n-alkanes also reflect their multiple source inputs. For example, a saw-toothed profile of n-alkane δD values in Australian torbanites is attributed to a dual-source system: a predominant B. braunii input, with a minor terrestrial plant input to odd-carbon-numbered n-alkanes in the range n-C20 [subscript] to n-C29 [subscript]. The δD values of n-alkanes and isoprenoids (pristane and phytane) differ significantly in two Permian torbanites from Australia, thought to be reflective of the offset between the δD values of their precursors in extant organisms. The torbanite data indicate that a biological δD signal has been preserved for at least 260–280 million years, extending the utility of δD values for palaeoclimate studies. To elucidate the effect of sedimentary processes on the δD values of petroleum hydrocarbons, three sedimentary sequences have been studied. These comprise one from the Perth Basin (Western Australia) and two from the Vulcan Sub-basin (northern Australia) covering a wide range of maturities, i.e. 0.53–1.6% vitrinite reflectance (Ro). The δD values of n-alkanes extracted from immature-early mature sediments (marine shales/siltstones and mudstones) are consistent with that expected of marine-derived n-alkyl lipids. The hydrocarbons become enriched in D with increasing maturity. The large (ca. 115%) biologically-derived offset between the δD values of n-alkanes and acyclic isoprenoids from immature sediments gradually decreases with increasing maturity, as the isoprenoids become enriched in D more rapidly than the n-alkanes. The D-enrichment in isoprenoids correlates strongly with Ro and traditional molecular maturity parameters.This suggests that H/D exchange during maturation occurs via a mechanism involving carbocation-like intermediates, which proceeds more rapidly with compounds containing tertiary carbon centres. Significant epimerisation of pristane and phytane coincides with their D-enrichment, suggesting that hydrogen exchange occurs at their tertiary carbons. A mechanism is proposed which can account for both H/D exchange and the epimerisation of pristane and phytane in the sedimentary environment. Pristane and phytane extracted from a post-mature sediment from the Paqualin-1 sequence are significantly enriched in D (ca. 40%) relative to the n-alkanes, indicating that D-enrichment persists at very high maturity, and is more pronounced for the regular isoprenoids than the n-alkanes. This supports the notion that H/D exchange causes the observed shift in δD values, rather than free-radical hydrogen transfer. The differences between the δD values of pristane and phytane show opposite trends in the Perth Basin and Vulcan Sub-basin sediments. In the Perth Basin, phytane is enriched in D relative to pristane, likely due to a dominant algal source. In the Vulcan Sub-basin, pristane is enriched in D relative to phytane, and thus is attributed to a lower relative input of algal organic matter. The variance of the δD values of pristane and phytane is generally consistent throughout the maturity range and provides evidence that pristane and phytane exchange hydrogen at similar rates. δD analysis of crude oils and condensates reservoired in the Perth Basin and Vulcan Sub-basin has been carried out to evaluate potential applications in oil-source correlation.The n-alkanes from crude oils and condensates are often more enriched in D than n-alkanes extracted from their supposed source rocks, and the oils also show relatively small differences between the δD values of n-alkanes and isoprenoids. These results suggest significant H/D exchange has occurred, implying that the liquids were generated from mature source rocks. A Perth Basin crude oil (Gage Roads-1) thought to be derived from a lacustrine/terrestrial source contains hydrocarbons that are significantly depleted in D relative to Perth Basin oils derived from a marine source, attributed to variability in the isotopic composition of marine and terrestrial source waters. δD values of n-alkanes from Vulcan Sub-basin crude oils and condensates are largely consistent with their prior classification into two groups: Group A, having a marine source affinity; and Group B, having a terrigenous source affinity. Some oils and condensates are suggested to be mixtures of Group A and Group B hydrocarbons, or Group A hydrocarbons and other as yet unknown sources. An exception is a former Group A oil (Tenacious-1) containing n-alkanes that are enriched in D relative to those from other Group A oils and condensates, attributed to mixing with another source of more mature hydrocarbons. The n-alkane δD profile appears to be indicative of source and sedimentary processes. One Perth Basin crude oil (Dongara-14) contains lower-molecular-weight n-alkanes that are depleted in D relative to higher-molecular-weight n-alkanes, attributed to a mixed marine/terrestrial source.Group A crude oils and condensates from the Vulcan Sub-basin display a ‘bowl-shaped’ profile of n-alkane δD values. An upward inflection in the n-alkane δD profile from n-C11 [subscript] to n-C15 [subscript] is suggested to represent the addition of D-enriched lower-molecular-weight n-alkanes from a more mature wet gas/condensate to an initial charge of lower maturity oil. Ultimately, this project has demonstrated that the δD values of individual petroleum hydrocarbons can be used to elucidate the nature of source organic matter and depositional environments. The preservation potential of lipid δD values is greater than previously thought, although it is clear that H/D exchange accompanying maturation can have a significant effect on the δD values of certain hydrocarbons. Thus, great care must be taken when interpreting δD values of individual hydrocarbons, particularly those derived from sediments of high thermal maturity.

Early research into the stable hydrogen isotopic compositions (δD) of petroleum involved bulk deuterium/hydrogen (D/H) measurements which, while providing some useful information, had to contend with the analysis of complex mixtures of hydrocarbons, and alteration resulting from the rapid exchange of nitrogen-, oxygen- and sulphur-bound hydrogen. The use of gas chromatography-isotope ratio mass spectrometry (GC-irMS) overcomes these problems by allowing the analysis of individual compounds containing only the most isotopically conservative aliphatic carbon-bound (C-bound) hydrogen. This project investigates the geochemical utility and reliability of compound-specific δD values, with the aim to better understand and exploit this analytical capability. To demonstrate the source diagnostic potential of compound-specific δD values, normal and branched alkanes extracted from series of immature bog-head coals (torbanites) were analysed. The torbanites contain immature organic matter predominantly from a single, freshwater algal source, i.e. Botryococcus braunii (B. braunii). The δD values of n-alkanes reflect the climate regime at the time of deposition of the torbanites, and vary mainly in response to the δD values of the source meteoric waters in their depositional environments. n-Alkanes from torbanites deposited at high latitude in a glacial climate are depleted in D by up to 70% relative to those from a torbanite deposited at low latitude under a tropical climate regime. Torbanites deposited in a mid-latitude region under cool-temperate conditions contain n-alkanes with δD values falling in between those of n-alkanes from tropical and glacial torbanites.
The δD values of the n-alkanes also reflect their multiple source inputs. For example, a saw-toothed profile of n-alkane δD values in Australian torbanites is attributed to a dual-source system: a predominant B. braunii input, with a minor terrestrial plant input to odd-carbon-numbered n-alkanes in the range n-C20 [subscript] to n-C29 [subscript]. The δD values of n-alkanes and isoprenoids (pristane and phytane) differ significantly in two Permian torbanites from Australia, thought to be reflective of the offset between the δD values of their precursors in extant organisms. The torbanite data indicate that a biological δD signal has been preserved for at least 260–280 million years, extending the utility of δD values for palaeoclimate studies. To elucidate the effect of sedimentary processes on the δD values of petroleum hydrocarbons, three sedimentary sequences have been studied. These comprise one from the Perth Basin (Western Australia) and two from the Vulcan Sub-basin (northern Australia) covering a wide range of maturities, i.e. 0.53–1.6% vitrinite reflectance (Ro). The δD values of n-alkanes extracted from immature-early mature sediments (marine shales/siltstones and mudstones) are consistent with that expected of marine-derived n-alkyl lipids. The hydrocarbons become enriched in D with increasing maturity. The large (ca. 115%) biologically-derived offset between the δD values of n-alkanes and acyclic isoprenoids from immature sediments gradually decreases with increasing maturity, as the isoprenoids become enriched in D more rapidly than the n-alkanes. The D-enrichment in isoprenoids correlates strongly with Ro and traditional molecular maturity parameters.
This suggests that H/D exchange during maturation occurs via a mechanism involving carbocation-like intermediates, which proceeds more rapidly with compounds containing tertiary carbon centres. Significant epimerisation of pristane and phytane coincides with their D-enrichment, suggesting that hydrogen exchange occurs at their tertiary carbons. A mechanism is proposed which can account for both H/D exchange and the epimerisation of pristane and phytane in the sedimentary environment. Pristane and phytane extracted from a post-mature sediment from the Paqualin-1 sequence are significantly enriched in D (ca. 40%) relative to the n-alkanes, indicating that D-enrichment persists at very high maturity, and is more pronounced for the regular isoprenoids than the n-alkanes. This supports the notion that H/D exchange causes the observed shift in δD values, rather than free-radical hydrogen transfer. The differences between the δD values of pristane and phytane show opposite trends in the Perth Basin and Vulcan Sub-basin sediments. In the Perth Basin, phytane is enriched in D relative to pristane, likely due to a dominant algal source. In the Vulcan Sub-basin, pristane is enriched in D relative to phytane, and thus is attributed to a lower relative input of algal organic matter. The variance of the δD values of pristane and phytane is generally consistent throughout the maturity range and provides evidence that pristane and phytane exchange hydrogen at similar rates. δD analysis of crude oils and condensates reservoired in the Perth Basin and Vulcan Sub-basin has been carried out to evaluate potential applications in oil-source correlation.
The n-alkanes from crude oils and condensates are often more enriched in D than n-alkanes extracted from their supposed source rocks, and the oils also show relatively small differences between the δD values of n-alkanes and isoprenoids. These results suggest significant H/D exchange has occurred, implying that the liquids were generated from mature source rocks. A Perth Basin crude oil (Gage Roads-1) thought to be derived from a lacustrine/terrestrial source contains hydrocarbons that are significantly depleted in D relative to Perth Basin oils derived from a marine source, attributed to variability in the isotopic composition of marine and terrestrial source waters. δD values of n-alkanes from Vulcan Sub-basin crude oils and condensates are largely consistent with their prior classification into two groups: Group A, having a marine source affinity; and Group B, having a terrigenous source affinity. Some oils and condensates are suggested to be mixtures of Group A and Group B hydrocarbons, or Group A hydrocarbons and other as yet unknown sources. An exception is a former Group A oil (Tenacious-1) containing n-alkanes that are enriched in D relative to those from other Group A oils and condensates, attributed to mixing with another source of more mature hydrocarbons. The n-alkane δD profile appears to be indicative of source and sedimentary processes. One Perth Basin crude oil (Dongara-14) contains lower-molecular-weight n-alkanes that are depleted in D relative to higher-molecular-weight n-alkanes, attributed to a mixed marine/terrestrial source.
Group A crude oils and condensates from the Vulcan Sub-basin display a ‘bowl-shaped’ profile of n-alkane δD values. An upward inflection in the n-alkane δD profile from n-C11 [subscript] to n-C15 [subscript] is suggested to represent the addition of D-enriched lower-molecular-weight n-alkanes from a more mature wet gas/condensate to an initial charge of lower maturity oil. Ultimately, this project has demonstrated that the δD values of individual petroleum hydrocarbons can be used to elucidate the nature of source organic matter and depositional environments. The preservation potential of lipid δD values is greater than previously thought, although it is clear that H/D exchange accompanying maturation can have a significant effect on the δD values of certain hydrocarbons. Thus, great care must be taken when interpreting δD values of individual hydrocarbons, particularly those derived from sediments of high thermal maturity.

The compound-specific δD values and molecular distributions of n-alkanes preserved in sediment archives are used as paleoclimate proxies. This use is based on two assumptions, 1) n-alkane δD values are highly correlated with source water δD values (Sachse 2012), and 2) the δD values of n-alkanes within a single site show little variation (Hou 2007). n-alkane molecular distributions are also used to infer the dominant source of n-alkanes input into sediment archives (Seki 2010). Despite this, paleoclimate reconstructions are being made without full understanding of how the δD values of nalkanes relate to the D isotopic compositions of meteoric waters in the region of synthesis, or how variable n-alkanes δD values could be within a single species. Using an in-depth investigation of Scots pine (Pinus sylvestris), significant variations in n-alkane molecular distributions and δD values were detected. These results suggest height of sample collection within a natural forest exerts a strong control on both n-alkane compositions, and δD values. Furthermore, this investigation indicates evergreen coniferous species synthesize both odd and even-chain-length n-alkanes, with high abundances of mid-chain n-alkanes, previously a diagnostic of aquatic plants. Both of these conclusions could significantly influence paleoclimate interpretations. Moreover, n-alkane δD values from Scots pine and Salix indicate little control of xylem water δD values on n-alkane δD values, suggesting that n-alkanes synthesized during spring are more representative of D-enriched stored assimilates. In addition, this study suggests too favourable conditions for photosynthesis could lead to reduced D-enrichment of leaf water, which is subsequently imprinted on the δD values of n-alkanes. These data suggest that under-estimations of climatic conditions present during the synthesis of n-alkane in sediments could occur if n-alkanes from existing plants are synthesized during periods of climatic stress.

To support population growth in Las Vegas, Nevada, large scale increases in groundwater pumping are planned across the state. This pumping could affect riparian areas in Great Basin National Park by lowering groundwater levels, reducing stream flows, and xerifying riparian vegetation. Great Basin National Park (GBNP) is mandated to manage its resources unimpaired for future generations. Loss of biodiversity is unacceptable under this mandate. If groundwater levels are reduced beyond a threshold, aquatic and riparian diversity would be lost, but the effects on small mammal communities are less clear. To provide baseline information and to consider the effects of groundwater withdrawal a priori, we sampled and compared small mammal communities in two watersheds susceptible to groundwater withdrawal and one non-susceptible watershed. We also used to stable isotopes of nitrogen, carbon, deuterium and oxygen to characterize small mammal communities. Evenness was higher in susceptible watersheds, which were distinct in species composition. Riparian and upland habitats in susceptible watersheds supported complementary small mammal communities, while communities in the non-susceptible watershed were more homogenous. Susceptible watersheds are located at the lowest elevations of GBNP where habitat heterogeneity due to the contrast between mesic riparian and xeric upland habitats is important in maintaining small mammal diversity. Partitioning was primarily seen in nitrogen and carbon isotopes which reflect feeding ecology (trophic level and primary production source), but was also seen in oxygen isotopes. Major differences in nitrogen and carbon isotopes were between taxonomic groups, while similarity was highest within these groups. Shrews and ermine were highest in nitrogen reflecting their high trophic positions. Harvest and piñon mice were intermediate in nitrogen suggesting omnivory, while chipmunks, voles, woodrats and pocket mice were apparently herbivorous. Carbon ratios were consistent with C3 based diets but were relatively enriched in Sigmodontinae species. Small mammal deuterium was similar to stream water suggesting that stream water is an important water source of water to small mammals. Oxygen enrichment relative to stream water and precipitation suggested that small mammals are sensitive to body water evaporation. Contrary to a previous study, oxygen isotopes were inversely related to water use efficiency. Increases in the rate of groundwater pumping adjacent to Great Basin National Park could lower water tables, reduce stream flows, and xerify riparian vegetation. We suggest that groundwater levels, streams flow and riparian vegetation, in addition to small mammal species composition will be important response variables in monitoring the effects of groundwater withdrawal. If predictions of groundwater withdrawal are realized, groundwater levels, stream flows, vegetation, microclimate, and invertebrates riparian dependent as well as small mammals will be negatively affected resulting in a decrease in diversity and loss of riparian species from affected areas.

Les météorites de Fer sont généralement considérées comme étant des débris des noyaux de planétésimaux différenciés. Il existe pourtant des incertitudes concernant la formation de ces météorites de Fer. Un des outils que l’on peut utiliser afin de confirmer ou d’infirmer différentes hypothèses est le rapport isotopique de l’Hydrogène. En effet, le rapport isotopique de l’Hydrogène est très différent selon l’espèce porteuse de cet Hydrogène et selon les processus subis par le corps parent. Le rapport isotopique et les concentrations en Hydrogène ont été mesurés dans plusieurs météorites de Fer avec une sonde ionique IMS 3f. Les rapports isotopiques de l’Hydrogène varient de 93 ± 9 à 126 ± 11 x10-6 pour des concentrations variant de 0,5 ± 0,1 ppb à 120 ± 130 ppb. Deux groupes se distinguent lorsque l’on considère les concentrations : les météorites de Fer magmatiques contiennent très peu d’Hydrogène alors que les météorites de Fer non-magmatiques sont les plus riches en Hydrogène
Irons meteorites are generally considered as remains of differentiated planetesimal cores. Yet, there are still some uncertainties regarding their formation. One proxy that could be used to confirm or not the different hypothesis regarding the formation of Iron meteorites is the Hydrogen isotopic ratio. Indeed, the Hydrogen isotopic ratio varies according to the bearing species and the process that had happened on the parent bodies. The Hydrogen isotopic ratio, as well as its concentration, have been measured in several Iron meteorites using an ion microprobe IMS 3f. Hydrogen isotopic ratios vary from 93 ± 9 to 126 ± 11 x10-6, while the concentrations vary from 0,5 ± 0,1 ppb to 120 ± 130 ppb. Two groups can be distinguished in regard of the concentrations. The magmatic irons have a very low H content while the non-magmatic irons are systematically richer in H

The Sirte Basin is a major oil producing area in Libya, but the understanding of the processes that have led to the petroleum accumulation is still limited. Exploration studies of this area have shown that the oils are mixtures of several charges and may be from different source rocks. The main aims of this thesis are to improve our understanding of the petroleum accumulation history in the East Sirte Basin.Biomarker ratios, together with stable carbon (δ[superscript]1[superscript]3C) and hydrogen (δD) isotopic compositions of individual hydrocarbons have been applied to 24 crude oils from the East Sirte Basin to delineate their sources and respective thermal maturities. The crude oil samples are divided into two main families (A and B) based on differences in source inputs and thermal maturity. Using source-specific biomarker parameters based on pristane/phytane (Pr/Ph), hopane/sterane ratios, dibenzothiophene (DBT) / phenanthrene (P), Pr/n-C[subscript]1[subscript]7, Ph/n-C[subscript]l[subscript]8 and the distribution of tricyclic and tetracyclic terpanes, family B oils are ascribed a marine source rock deposited under sub-oxic conditions, whereas family A oils have a more terrestrial source affinity. This source classification is supported by the stable carbon isotopic compositions (δ[superscript]1[superscript]3C) of the n-alkanes. Family A oils were found to be more mature based on differences between the stable hydrogen isotopic compositions (δD) of Pr and Ph and the n-alkanes, as well as the δ[superscript]1[superscript]3C values of n-alkanes.Within a complex geological setting several potential source rocks have been recognised, ranging in age from Precambrian to Eocene. Biomarker ratios, together with δ[superscript]1[superscript]3C and δD of individual hydrocarbons have been applied to 21 source rock extracts from the East Sirte Basin to establish their respective thermal maturity and palaeoenvironmental conditions of deposition. Rock Eval pyrolysis data obtained from the source rocks of the Sirte, Tagrifet, Rakb, Rachmat, Bahi and Nubian Formations show that the organic matter (OM) is mainly dominated by a Type II/III kerogen. Vitrinite reflectance (% R[subscript]o range: 0.46 – 1.38) data support variations in thermal maturity and indicate mature to post mature rocks of Sirte and Rachmat Formations and early to mid stage maturities for the rest of the formations. The Sirte Formation in the studied area was found to be relatively more thermally mature than the Tagrifet, Rakb, Rachmat, Bahi, and Nubian Formations, reflected by δD of Pr and Ph (less depleted in D).Various unusual steroid biomarkers in the oils and East Sirte source-rocks were identified by gas chromatography- mass spectrometry (GC-MS) and GC- metastable reaction monitoring (MRM) mass spectrometry. These included 24-norcholestanes, dinosteranes, 4α-methyl-24-ethylcholestanes and triaromatic steroids. Diatoms, dinoflagellates and/or their direct ancestors are the proposed sources of these components. These biomarker parameters have been used to establish a Mesozoic oil-source correlation of the East Sirte Basin. This is consistent with the presence of dinoflagellate cysts in the Nubian Formation of Lower Cretaceous age.

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The water in the current martian atmosphere contains [...] 5 times more deuterium (D) than water on Earth (corresponding to a [...] value of [...] +4000) resulting from preferential loss of hydrogen relative to deuterium from the martian atmosphere. This thesis places constraints on the D/H of other martian water reservoirs by measuring the D/H of water in hydrous phases within the SNC meteorites, thought to be samples of martian igneous rocks. Results from vacuum extractions of volatiles from bulk SNC samples by stepwise heating show the water yields to decrease and [...] values to increase to well above terrestrial values with increasing temperature, indicative of mixing between terrestrial water (contamination) released at low temperatures and martian water released at high temperatures. The high temperature [...] values reach [...] +2000 for Shergotty, the most Denriched sample. However, even the highest [...] values measured may represent lower limits on the true values due to partial exchange with lighter terrestrial water. D/H and water contents of individual amphibole, biotite and apatite grains in several SNC meteorites were measured using an ion microprobe. The amphiboles contain an order of magnitude less water than previously assumed, suggesting that SNC parent magmas may have been less hydrous than previously proposed. The [...] values of the phases range from [...]. The variability and D-enriched nature of these values imply that the primary igneous phases have not retained a martian magmatic water signature. Rather, the high and variable D/H of the water in these phases, like that released at high temperatures from bulk SNC samples, is concluded to result from the interaction of the samples with D-enriched martian crustal fluids after crystallization, probably in an environment similar to terrestrial magmatic hydrothermal systems. The data presented in this thesis represent the first direct evidence for ubiquitous crustal water-igneous rock interaction on another planet. Moreover, the results imply that a large amount of water must have been lost from the martian system since water in the martian crust, in addition to the atmosphere, appears to reflect D-enrichment processes.

Rice grows in saturated soil water condition and its requirement for water is highest amongst other cereal crops. In India, the southwest monsoon wind regime brings rainfall that provides a favourable environment for rice cultivation. Thus, there is significant dependency ofrice production on the southwest monsoon rainfall. Being a crop that grows across diverse climatic regions in India ranging from the humid to semi-arid, it offers possibility to explore therelationship between stable isotopic compositions in the grain organic matter with the climaticfactors relevant for its growth. In this thesis, we measured the isotopic compositions of oxygen, hydrogen and carbon of several rice genotypes that were cultivated during the southwest monsoon in diverse climatic regions across the Indian landmass. These isotopic values were then compared with the seasonalaverage values of climate factors such as relative humidity and temperature. Together with thiswe also studied the dependency of the oxygen isotope composition of the grain OM (δ18OOM) onthat of the source water (δ18OSW). Upon removal of δ18OSW effect from δ18OOM, we obtained astrong and significant relationship between the 18O enrichment in grain organic matter (definedas 18OOM) with relative humidity. The gradient recorded was 0.45‰ shift in 18OOM with 1%change in the relative humidity level. This relationship can potentially be used to estimate thepast variations in relative humidity (and by extension, can provide a measure of monsoon rainfallvariations). We further validated this relationship based on experiments carried out in aglasshouse where all the physical factors were well-monitored. Together with this, carbonisotopic composition measured in the rice grain organic matter were used to infer the water useefficiency of rice grown in different climatic settings. The stable isotope approach was furtherimplemented for studying the archaeological rice grains recovered from archaeological sites. Analysis of carbon isotopic composition of archaeological rice grains from seven archaeologicalsites (Balu, Kanmer, Ojiyana, Lahuradewa, JognaKhera, Hulas and Kunal), belonging to theHarappan civilization and other contemporary cultures provided a new suit of data on quantitativeestimate of the hydroclimatic condition (specifically relative humidity) and water availabilityduring the existence of this civilization.

Rice grows in saturated soil water condition and its requirement for water is highest amongst other cereal crops. In India, the southwest monsoon wind regime brings rainfall that provides a favourable environment for rice cultivation. Thus, there is significant dependency ofrice production on the southwest monsoon rainfall. Being a crop that grows across diverse climatic regions in India ranging from the humid to semi-arid, it offers possibility to explore therelationship between stable isotopic compositions in the grain organic matter with the climaticfactors relevant for its growth. In this thesis, we measured the isotopic compositions of oxygen, hydrogen and carbon of several rice genotypes that were cultivated during the southwest monsoon in diverse climatic regions across the Indian landmass. These isotopic values were then compared with the seasonalaverage values of climate factors such as relative humidity and temperature. Together with thiswe also studied the dependency of the oxygen isotope composition of the grain OM (δ18OOM) onthat of the source water (δ18OSW). Upon removal of δ18OSW effect from δ18OOM, we obtained astrong and significant relationship between the 18O enrichment in grain organic matter (definedas 18OOM) with relative humidity. The gradient recorded was 0.45‰ shift in 18OOM with 1%change in the relative humidity level. This relationship can potentially be used to estimate thepast variations in relative humidity (and by extension, can provide a measure of monsoon rainfallvariations). We further validated this relationship based on experiments carried out in aglasshouse where all the physical factors were well-monitored. Together with this, carbonisotopic composition measured in the rice grain organic matter were used to infer the water useefficiency of rice grown in different climatic settings. The stable isotope approach was furtherimplemented for studying the archaeological rice grains recovered from archaeological sites. Analysis of carbon isotopic composition of archaeological rice grains from seven archaeologicalsites (Balu, Kanmer, Ojiyana, Lahuradewa, JognaKhera, Hulas and Kunal), belonging to theHarappan civilization and other contemporary cultures provided a new suit of data on quantitativeestimate of the hydroclimatic condition (specifically relative humidity) and water availabilityduring the existence of this civilization

Rice grows in saturated soil water condition and its requirement for water is highest amongst other cereal crops. In India, the southwest monsoon wind regime brings rainfall that provides a favourable environment for rice cultivation. Thus, there is significant dependency ofrice production on the southwest monsoon rainfall. Being a crop that grows across diverse climatic regions in India ranging from the humid to semi-arid, it offers possibility to explore therelationship between stable isotopic compositions in the grain organic matter with the climaticfactors relevant for its growth. In this thesis, we measured the isotopic compositions of oxygen, hydrogen and carbon of several rice genotypes that were cultivated during the southwest monsoon in diverse climatic regions across the Indian landmass. These isotopic values were then compared with the seasonalaverage values of climate factors such as relative humidity and temperature. Together with thiswe also studied the dependency of the oxygen isotope composition of the grain OM (δ18OOM) onthat of the source water (δ18OSW). Upon removal of δ18OSW effect from δ18OOM, we obtained astrong and significant relationship between the 18O enrichment in grain organic matter (definedas 18OOM) with relative humidity. The gradient recorded was 0.45‰ shift in 18OOM with 1%change in the relative humidity level. This relationship can potentially be used to estimate thepast variations in relative humidity (and by extension, can provide a measure of monsoon rainfallvariations). We further validated this relationship based on experiments carried out in aglasshouse where all the physical factors were well-monitored. Together with this, carbonisotopic composition measured in the rice grain organic matter were used to infer the water useefficiency of rice grown in different climatic settings. The stable isotope approach was furtherimplemented for studying the archaeological rice grains recovered from archaeological sites. Analysis of carbon isotopic composition of archaeological rice grains from seven archaeologicalsites (Balu, Kanmer, Ojiyana, Lahuradewa, JognaKhera, Hulas and Kunal), belonging to theHarappan civilization and other contemporary cultures provided a new suit of data on quantitativeestimate of the hydroclimatic condition (specifically relative humidity) and water availabilityduring the existence of this civilization

The isotopic composition of water vapor and precipitation at continental and oceanic sites depends on factors such as: the geographical location of the sampling site, meteorological conditions at the moisture source areas, local meteorological conditions, rainout history of air-masses along their trajectory, large-scale moisture recycling below cloud evaporation, etc. The present study aims at identification and quantification of such processes over the Indian subcontinent and the Southern Ocean based on observed stable isotopic composition in precipitation and atmospheric moisture. The oxygen and hydrogen isotopic composition of precipitation at Srinagar, Kashmir, allowed delineating the respective role of large-scale moisture transport processes vs that of other meteorological factors such as temperature and precipitation amount. The time integrated, large-scale convective activity over several days, constitutes a major factor governing the isotopic composition of precipitation at Srinagar, whereas local meteorological factors play a minor role. Over the Southern Ocean, as opposed to local factors, atmospheric pressure and air temperature majorly govern the precipitation isotopic composition. The isotopic data was further used to estimate the moisture sources contributing to the summer precipitation at Kolkata and summer/winter precipitation at Srinagar. A simple box model was developed to simulate the moisture transport and mixing to estimate the contribution of sources to precipitation at Srinagar and Kolkata. Precipitation at Srinagar, during the active period of the Western Disturbances, carries 80% of moisture from the Mediterranean region while the balance originates from the Arabian area. Adopting moisture source isotope signatures observed over a long-time span at the New viii Abstract ix Delhi station, the Rayleigh’s distillation model explains the observed variability in the isotopic data at Kashmir Valley during the Indian Summer Monsoon. At Kolkata, the Bay of Bengal is a major moisture contributor to precipitation supplying overall 65-75% of the total precipitation during the south west and the continental contribution varies from 25-35%. Over the Himalayan region, a discrepancy was noted between the measured isotopic composition of precipitation and that simulated by an isotope enabled general circulation model. The model underestimates the number of precipitation days as well as the magnitude of isotopic values. This may be attributed to deficiencies in the meteorological inputs or inadequate estimates of other parameters used in the model, as distinct hydrological parameterizations do lead to large differences in isotopic responses. The Craig and Gordon models are used to calculate the isotopic composition of evaporation flux in many isotope enabled general circulation models. The parameters governing the isotopic composition of evaporation flux can be considered separately or simultaneously in the Traditional and the Unified Craig-Gordon (CG) models. These models were tested for different molecular diffusivity ratios and ocean surface conditions to identify the parameterizations that best match the observed relationships between the meteorological parameters and the isotopic composition of water vapor. The model that matches best is used to calculate the isotopic composition of the local evaporation along the Southern Ocean sampling transect. The advected end member isotopic composition is assumed from the previous observations along the path followed by the air trajectories. Solving in a two-component mixing framework, the relative contribution of advected and evaporated vapor along the sampling transect is established. The advected moisture is a prominent component of the ambient vapor and its contribution becomes greater with increasing latitudes. South of 65 S the amount of moisture present in the atmosphere is less and is majorly local in origin with a small mixing of light Antarctic moisture. Results from this study should be useful to tune the models, and further help in the interpretation of regional paleo-climate data based on isotope proxies.

碩士
國立中央大學
水文所
94
Feitsui Reservoir provides water supply in Taipei City as well as parts of Taipei County in northern Taiwan. The variations of hydrogen, oxygen, and carbon isotope compositions of waters record the sources and mixtures of waters; they are ideal and important tools to study hydrology. This study discussed the relationships among the waters in Feitsui Reservoir, rain waters and river in its watershed in order to provide basic isotope information in hydrology for the appropriate water resource management. From April 2003 to April 2004, rain waters of respective rainy days were collected at Feitsui Reservoir; waters of the reservoir and major branches of its watershed were also sampled monthly. These water samples were analyzed for hydrogen, oxygen, and carbon isotope compositions. In addition, information of meteorology and hydrology was also compiled and integrated with isotope data to study the hydrology cycle of Feitsui Reservoir. Analytical results showed that the hydrogen and oxygen isotope compositions of rain waters in Feitsui Reservoir exhibit a negative correlation with air temperature; an opposite feature with those observed in the continent. Apparently, the variations of hydrogen and oxygen isotope compositions of the rain waters in Feitsui Reservoir’s watershed have been primarily affected by the air masses of different seasons rather than the air temperature; because the sources and the paths of air masses change with seasons and cause distinct isotope fractionations accordingly. Two intervals (southwest and northeast monsoons) were differentiated to discuss the meteoric water lines in this study. Southwest monsoon prevails from May to September, and the ranges of δ18O and δD were -0.7‰ ~ -11.7‰ and1.1‰ ~ -87.4‰, respectively; the least-squares regression line was: �n�n �n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�n�nNortheast monsoon prevails from October to March, and the ranges of δ18O and δD were 0.6‰ ~ -6.2‰ and 20.5‰ ~ -38.4‰, respectively; the least-squares regression line was: .Over this study period, the least-squares regression line of all precipitation data was: . The hydrogen and oxygen isotope compositions of the river waters in Feitsui Reservoir’s watershed showed significant and systematic discrepancy with those of rain waters. The isotope data of rain samples were processed as five-month moving average and weighted according to the precipitation amount. The resulting trends of processed rain waters showed similar seasonal pattern with those of river waters probably due to the hysteresis effect of rain infiltration. The isotopic ranges of the river waters were relatively smaller and depleted than those of the precipitation. The possible causes are: (1) Rain waters had a larger precipitation amount effect in summer with relatively depleted isotope signatures and higher amount of infiltration; (2) The isotope compositions of the rain waters have an altitude effect that provides relatively depleted isotope values at higher locations; (3) The isotope compositions of the rain waters for previous years might carry relatively depleted isotope values. The main source of the Reservoir derives from upstream branch waters, and base flows of those branches are groundwaters after rain infiltration. The observed seasonal isotope fluctuations of base flows were small, δ18O ranging from -4.7‰ to -8.3‰ with a mean value of -5.8‰. On the other hand, the overland flow displayed a large impact on the isotope compositions of the Reservoir during the typhoon periods. For example, the lowest δ18O (-8.3‰) value was detected in the middle water layer of the Feitsui Reservoir after the typhoon of September 2003. The dissolved δ13C values of water samples ranged from -11.7‰ to -16.0 ‰, with relative enriched compositions in June and depleted values in March. The main cause of this season discrepancy is due to the higher growth of algae in June, which absorbed the lighter carbon, leaving the water carbon isotope relatively enriched. The chlorophyll reduced significantly after July with carbon dioxide continually introduced from respiration, resulting lighterδ13C values in the reservoir. In short, results of this work demonstrated that hydrogen, oxygen, and carbon isotope compositions are good tracers in studying hydrology. These isotope tracers not only can effectively explain the sources and mixtures from various sources in Feitsui Reservoir but also enhance our understanding of the hydrology cycle in its watershed and the close relationship between the biology and geochemistry. The isotope data collected in this study are also valuable in the management of the Feitsui Reservoir waters in terms of quality and quantity.