Hydrogen Isotope Analysis Research Articles

The Significance of Hydrogen and Oxygen Stable Isotopes in the Water Vapor Source in Dingxi Area

Deuterium excess and stable oxygen isotopes in precipitation have been widely applied to trace the source of water vapor. In this study, hydrogen and oxygen isotope analyses of samples were collected on seven sampling stations in Dingxi area from April 2019 to April 2020. The seasonal variation of hydrogen and oxygen stable isotopes as well as the d-excess indicate that the source of water vapor in Dingxi area is mostly from a single source. However, there are different sources of water vapor in the summer. Meanwhile, water vapor sources were analyzed using the Lagrange algorithm, indicating two different principal water vapor sources for precipitation in the area: some locally recycled water vapor in summer and autumn, and most water vapor from the westerly belt. Further studies using the PSCF and CWT analysis methods show that the locally recycled water vapor contributes more to its precipitation in the northwest of Dingxi area.

Oxygen and hydrogen isotope analysis of experimentally generated magmatic and metamorphic aqueous fluids using laser spectroscopy (WS-CRDS)

We report a new procedure for the analysis of oxygen and hydrogen isotopes in water that is experimentally produced in high-temperature high-pressure experiments via wavelength-scanned cavity ring down spectroscopy (WS-CRDS). This work builds on a recently developed method by Affolter et al. (2014) for the analysis of fluid inclusions in cave carbonate deposits. We show that a simple modification of the setup allows extraction and analysis of experimentally produced fluids from their noble metal capsules in an online water extraction line, and analyse them without further treatment of the water molecule prior to isotope determination. We tested this method on standard water reference samples and water experimentally generated during thermal decomposition of hydrous minerals in hydrothermally altered rocks. Preliminary results indicate that fluids released from hydrothermally altered rocks at conditions of 640 °C and 100 MPa maintain isotopic compositions close to those of the meteoric water involved in their alteration. Further development and application of this method will offer great insights into the origin and evolution of water in magmatic and metamorphic systems, and be a valuable tool in the determination of experimentally derived fluid-melt and fluid-mineral isotope fractionation.

Compound-specific stable hydrogen isotope (δ2 H) analyses of fatty acids: A new method and perspectives for trophic and movement ecology.

Compound-specific stable isotope analysis (CSIA) is a powerful tool for a better understanding of trophic transfer of dietary molecules in and across ecosystems. Hydrogen isotope values (δ2 H) in consumer tissues have potential to more clearly distinguish dietary sources than 13 C or 15 N values within and among habitats, but have not been used at the fatty acid level for ecological purposes. Here we demonstrate a new online high-capacity gas chromatography-isotope ratio mass spectrometry technique (2 H-CSIA) that offers accurate and reproducible determination of δ2 H values for a range of fatty acids from organisms of aquatic food webs. We show that lipid extracts obtained from aquatic sources, such as biofilms, leaves, invertebrates, or fish muscle tissue, have distinctive δ2 H values that can be used to assess sources and trophic interactions, as well as dietary allocation and origin of fatty acids within consumer tissue. The new 2 H-CSIA method can be applied to evaluate sources and trophic dynamics of fatty acids in organisms ranging from food web ecology to migratory connectivity.

Leaf Wax and Sr‐Nd Isotope Evidence for High‐Latitude Dust Input to the Central South China Sea and Its Implication for Fertilization

AbstractRecent time‐series from sediment traps show abnormally high chlorophyll‐a concentrations and primary productivity in the oligotrophic central South China Sea (SCS), especially during wintertime. Here we present new insights from compound‐specific hydrogen isotopic analysis of leaf wax n‐alkanes and Sr‐Nd isotope compositions extracted from four basin‐wide surface sediment transects. We find that the deepest surface sediments in the central basin contain the most depleted n‐alkane hydrogen isotopes, suggesting inputs from higher latitude soils in northern China. This is supported by the Sr‐Nd isotope compositions of the same surface sediments. We propose that aeolian dust is transported by the winter monsoon and might fertilize the phytoplankton bloom in the central SCS. This process may have been enhanced in ancient times when the winter monsoon was stronger, driving both vertical mixing and dust transport to the central basin.

Controls Over Oxygen Isotope Fractionation in the Waters and Bivalves (Arthritica helmsi) of an Estuarine Lagoon System

AbstractOxygen isotope ratios in bivalve shells have long been used as a proxy for environmental change, reflecting both temperature and the oxygen isotope composition of host water. In estuarine systems, the oxygen isotope composition of water is complicated by variable mixing between river and seawater, as well as evaporative enrichment. In addition, due to species‐specific variation in temperature‐dependent fractionation into bivalve carbonate, modern calibrations are necessary prior to applications in paleoenvironmental studies. In this study, live specimens of the micromollusc Arthritica helmsi were collected from five sites in the Coorong Lagoon, an estuarine system at the mouth of the River Murray, Australia, on six occasions from November 2016 to May 2018. Whole shell oxygen and carbon isotope compositions (n = 131) were measured alongside monthly temperature and oxygen and hydrogen isotope analyses of waters from the Coorong and neighboring Lake Alexandrina (n = 137). Oxygen and hydrogen isotope ratios in water were mostly controlled by evaporation of source waters, though a period of high river water discharge was reflected in the isotopic values of the Coorong North Lagoon. A species‐specific temperature‐dependent oxygen isotope fractionation equation was calibrated for A. helmsi: T (°C) = (21.39 ± 0.45) − (4.43 ± 0.38) × (δ18Oshell − δ18Owater). This equation is similar to other published paleotemperature equations for biogenic carbonates. These contemporary observations of the isotope hydrology of the Coorong, coupled with our contemporary calibration of oxygen isotope fractionation, lay the foundation for paleoenvironmental studies using bivalves collected from the sediments of the Coorong.

Provenancing wood used in the Norse Greenlandic settlements: A biogeochemical study using hydrogen, oxygen, and strontium isotopes

A growing number of studies strive to examine wooden archaeological remains recovered from Norse sites in the North Atlantic, contributing to a better understanding of patterns in both wood exploitation and woodland management. Despite the limited diversity and abundance of trees in the North Atlantic islands, the Medieval Norse kept using wood in most everyday activities including the construction and repair of buildings and boats, the production of artifacts and tools, and as a source of fuel. The proximity of the Greenland settlements with the northeastern American coast, puts them at the forefront in the exploration and exploitation of remote resource regions. While some species may have arrived both as driftwood or imported material, there is currently no method to conclusively identify archaeological wood remains as driftwood. Here, we use biogeochemical analysis of stable hydrogen ( δ 2 H), stable oxygen ( δ 18 O), and radiogenic strontium ( 87 Sr/ 86 Sr) isotopes in soil, water, and modern plant samples from various sites in Greenland and Canada to characterize expected local isotopic baselines. While 87 Sr/ 86 Sr isotope ratios do not provide a clear distinction between the regions of interest, δ 2 H and δ 18 O ratios appear to help discriminate not only between regions but also specific sites. In addition, we completed a pilot study of archaeological wood samples obtained in Greenland to test the effectiveness of the 87 Sr/ 86 Sr biogeochemical baseline. Results demonstrate that at least in some cases, diagenetic processes were not sufficient to mask a non-local 87 Sr/ 86 Sr signature. ● Hydrogen and oxygen isotope ratios discriminate between regions and specific sites ● Strontium isotope ratios do not provide a clear distinction between studied regions ● Diagenetic processes do not always mask the original biogenic isotope value ● Wood identification and isotopes help examine the origins of Greenland wood artifacts

A new automated method for high-throughput carbon and hydrogen isotope analysis of gaseous and dissolved methane at atmospheric concentrations.

The dual isotope ratio analysis, carbon (δ13 C value) and hydrogen (δ2 H value), of methane (CH4 ) is a valuable tracer tool within a range of areas of scientific investigation, not least wetland ecology, microbiology, CH4 source identification and the tracing of geological leakages of thermogenic CH4 in groundwater. Traditional methods of collecting, purification, separating and analysing CH4 for δ13 C and δ2 H determination are, however, very time consuming, involving offline manual extractions. Here we describe a new gas chromatography, pyrolysis/combustion, isotope ratio mass spectrometry (IRMS) system for the automated analysis of either dissolved or gaseous CH4 down to ambient atmospheric concentrations (2.0 ppm). Sample introduction is via a traditional XYZ autosampler, allowing either helium (He) purging of gas or sparging of water from a range of suitable, airtight bottles. The system routinely achieves precision of <0.3‰ for δ13 C values and <3.0‰ for δ2 H values, based on long-term replicate analysis of an in-house CH4 /He mix standard (BGS-1), corrected to two externally calibrated reference gases at near atmospheric concentrations of methane. Depending upon CH4 concentration and therefore bottle size, the system runs between 21 (140-mL bottle) and 200 samples (12-mL exetainer) in an unattended run overnight. This represents the first commercially available IRMS system for dual δ13 C and δ2 H analysis of methane at atmospheric concentrations and a step forward for the routine (and high-volume) analysis of CH4 in environmental studies.

Migratory connectivity then and now: a northward shift in breeding origins of a long-distance migratory bird wintering in the tropics.

Temporal variation in the connectivity of populations of migratory animals has not been widely documented, despite having important repercussions for population ecology and conservation. Because the long-distance movements of migratory animals link ecologically distinct and geographically distant areas of the world, changes in the abundance and migratory patterns of species may reflect differential drivers of demographic trends acting over various spatial scales. Using stable hydrogen isotope analyses (δ2H) of feathers from historical museum specimens and contemporary samples obtained in the field, we provide evidence for an approximately 600 km northward shift over 45 years in the breeding origin of a species of songbird of major conservation concern (blackpoll warbler, Setophaga striata) wintering in the foothills of the eastern Andes of Colombia. Our finding mirrors predictions of range shifts for boreal-breeding species under warming climate scenarios and habitat loss in the temperate zone, and underscores likely drivers of widespread declines in populations of migratory birds. Our work also highlights the value of natural history collections to document the effects of global change on biodiversity.

Detection of exogenous sugars in pineapple juice using compound-specific stable hydrogen isotope analysis

An improved procedure for determining 2H/1H isotope ratios, using gas chromatography-isotope ratio mass spectrometry, has been used to detect the addition of exogenous C4-plant-derived sugars to pineapple juice. Isotopic techniques are commonly used to identify the addition of low-cost sugars to fruit juices and are difficult to subvert as it is not economically viable to change the isotopic ratios of the sugars. However, the addition of cane sugar to pineapple juice has presented a significant challenge that is only detected by site-specific 13C analysis of the methyl and methylene positions of ethanol derived from pineapple sugars, measured by nuclear magnetic resonance. This new GC-IRMS-based procedure utilises the trifluoroacetate derivative of sucrose to allow direct measurement of the carbon-bound non-exchangeable hydrogen. This provides advantages over alternative isotopic methods in terms of analysis time and sensitivity. This feasibility study has demonstrated the potential to reliably differentiate between authentic pineapple juices and those adulterated with commercial beet and cane sucrose.

Origin and Source Characterization of Methane in the Shallow-Water Environment of Southern Lake Tanganyika Rift Basin, Tanzania

Lake Tanganyika, located in the western part of Tanzania between 3°S and 9°S lat, harbours hydrocarbon and non-hydrocarbon gases in its northern and southern shallow-water environment. In this study, a geochemical analysis of stable carbon and hydrogen isotopes and an interpretation of individual gas molecular composition were done in order to determine the origin and composition of the naturally occurring hydrocarbon gases in Tanganyika Basin. Nitrogen, a non-hydrocarbon gas is a major component (76.69%–78.31%) by volume percentage followed by methane (11.68%–12.94%) and other higher hydrocarbons (0.16%–1.63%). The isotopic composition of carbon δ 13 C 1 and hydrogen δ DC 1 ranges from –65.32‰ to –65.81‰ and –272.5‰ to –275.9‰ respectively. The isotopic compositions of ethane (δ DC 2 = –36.7‰ to –35.2‰) and propane (δ DC 3 = –31.3‰ to –27.5‰) reflect the thermogenic origin of these higher hydrocarbons. According to molecular characterization of carbon and hydrogen isotope ratios and δ D-values, methane gas falls in the biogenic origin category and is formed by carbon dioxide reduction. The isotopic composition of CO 2 varies between –8.6‰ and –3.4‰. CO 2 reduction is also regarded as a mechanism of biogenic methane formation based on carbon isotope fractionation factors (greater than 0.16).

Hydrogen isotopic fractionations during syntheses of lipid biomarkers in the seeds of broomcorn millet (Panicum miliaceum L.) under controlled environmental conditions

• Broomcorn millet was grown under controlled condition. • H/D fractionation during seeds n -alkanes and miliacin synthesis was examined. • Leaf water δ 2 H value is the primary driver of lipid δ 2 H values. • Relative humidity could explain subtle differences in ε bio between n -alkanes. Compound specific hydrogen isotopic analyses have the potential to reveal the biosynthetic pathways of biomarkers and to reconstruct the effects of water stress in a plant, or in an ecosystem. Although C4 graminoids are of great geological interest and are some of the world's leading crops, there are few experimental studies of their biomarker responses to hydrological conditions. Here, we study a C4 graminoid, broomcorn millet, and compare the effects of controlled changes in environmental conditions on the distributions of n -alkane homologues and on the pentacyclic triterpene, miliacin, which is a biomarker for broomcorn millet; both were measured in the seeds of the graminoid. Broomcorn millet plants were propagated in hydroponic solutions with four different δ 2 H values for each of two growth chambers, differing in relative humidity (58 and 74%). Analyses of δ 2 H values of the lipid compounds (miliacin and n -alkanes) in seeds and water extracted from transpiring and non-transpiring organs allowed us to quantify the apparent (lipids vs. source water to plant) and biosynthetic (lipids vs. leaf water) fractionations during miliacin and n -alkane syntheses. Miliacin and n -alkane δ 2 H values were linearly related to leaf water δ 2 H values, permitting credible biosynthetic fractionations to be calculated for n -alkanes (average −149.5‰ ± 11) and miliacin (−118‰ ± 5). These biosynthetic fractionations were within the range of published values for compounds with their respective biosynthetic pathways, although a 2 H-enrichment of miliacin compared to n -alkanes remains unexplained. Whereas a 16% decrease in relative humidity had no significant impact on the biosynthetic fractionation of miliacin, n -C 25 and n -C 27 alkanes, it led to a ~25‰ decrease in biosynthetic fractionation for n -C 31 and n -C 33 alkanes. This could be the consequence of a contribution of more depleted pools of hydrogen atoms in cytoplasmic water (compared to chloroplastic hydrogen pools) during the n -alkyl lipid elongation process. This finding suggests that the respective influences of source water δ 2 H values and relative humidity on the δ 2 H values of organic compounds may be discretely inferred by examining the δ 2 H values of compounds synthesized from distinct sources of hydrogen in cells. This provides clues to the biosynthetic fractionations in a C4 plant for compounds derived from distinct pathways, but also highlights specific issues related to seed lipids which require further research.

Evaluation of a quick one-step sample preparation method for the determination of the isotopic fingerprint of rapeseed (Brassica napus): Investigation of the influence of the use of 2,2-dimethoxypropane on compound-specific stable carbon and hydrogen isotope analyses by gas chromatography combustion/pyrolysis isotope ratio mass spectrometry.

Gas chromatographic analyses for vegetable oils require transesterification, which generally involves multiple steps, mainly to generate fatty acid methyl esters (FAMEs). A quick method based on acid-catalyzed transesterification using 2,2-dimethoxypropane (DMP) enables the conversion in one step, in a single reactor. For compound-specific stable carbon and hydrogen isotope analyses (C- and H-CSIA) of individual fatty acids (FAs) in oil, the verification of this one-step method has not yet been reported. In this study, we evaluated the feasibility of the one-step method for C- and H-CSIA of individual FAMEs in rapeseed samples. The focus was on the investigation of the influence of methanol, which was produced from the reactions of DMP with glycerol and water during transesterification, on the accuracy of isotope composition of FAMEs, consequently of the FAs. The reproducibility of the one-step method was assessed by the measurement of the FAMEs from rapeseed and rapeseed oil. For the C- and H-CSIA of individual FAMEs, a gas chromatography combustion/pyrolysis isotope ratio mass spectrometry system was used. Our results showed that no significant differences arise in the carbon and hydrogen isotope compositions of the selected main FAMEs produced with and without DMP except for the H-CSIA value of C18:3. The reproducibility of the one-step method for rapeseed was in the range of ±0.1 mUr to ± 0.3 mUr for C-CSIA and ±1 mUr to ±3 mUr for H-CSIA of the main FAMEs. DMP improves the transesterification efficiency without influencing the accuracy of the C- and H-CSIA of FAMEs. The performance of the one-step method for rapeseed samples for the determination of C- and H-CSIA values of FAMEs is satisfactory. Thus, the applicability of the one-step method for isotopic fingerprint analyses of FAs in oilseeds is reported for the first time.

Surface geochemical survey in the vicinity of decommissioned coal mine shafts.

Methane observed in soil atmosphere above active and abandoned bituminous coal mines has a thermogenic (coalbed) and/or microbial (produced by anaerobic bacteria or resulted from in situ coal biodegradation) origin or it may be a mixture of gases generated from various sources. Identification of the origin of methane may support or refute the thesis on the uncontrolled migration of mine gases in rock formations followed by their emission to the atmosphere at coal extraction sites. Surface geochemical surveys were carried out in the vicinity of the decommissioned mine shafts at the Murcki-Staszic Coal Mine, located in the Upper Silesian Coal Basin (southern Poland). Over a 3-month period, measurements were carried out cyclically at 2 locations. Totally, 43 fixed geochemical probes were installed in the area of the Murcki II "Stanisław" Shaft, in which measurements were carried out in six sessions. Next 29 probes were installed in the area of the Staszic III Shaft, where measurements were taken twice. Each measurement included concentrations of 5 components (methane, non-methane volatile organic compounds, total hydrocarbons, carbon dioxide and oxygen), which provided a total number of 1405 individual analytical determinations. For measurements, portable EcoProbe 5 instrument was used. The stable carbon isotope composition of methane and carbon dioxide was analyzed in selected 10 samples. The isotopic composition of hydrogen in methane was also measured in one sample. The comparative material consisted of eight samples of soil gases and two samples of mine gases, which were used as reference 'soil' gases. The isotopic analyses were conducted using a mass spectrometry method. Based on the results of our analyses, it is stated that both the Murcki II "Stanisław" and the Staszic III shafts were properly decommissioned. The successful sealing of mine shafts prevented mine gases from migration through the shaft into the atmosphere. However, at a single geochemical probe located more than 100m from the former shaft center, methane concentration in soil gases reached over 1vol%. This confirms the general observation that mine gas migrates from coal seams and/or gobs through crushed rocks into the atmosphere. The stable carbon isotope analysis of methane and carbon dioxide as well as stable hydrogen isotope analysis of methane suggest that methane in the soil atmosphere is of thermogenic origin with minor contribution of microbial component.

Isotope ratio infrared spectroscopy analysis of water samples without memory effects.

Since their introduction more than a decade ago, isotope ratio infrared spectroscopy (IRIS) systems have rapidly become the standard for oxygen (δ18 O) and hydrogen (δ2 H) isotope analysis of water samples. An important disadvantage of IRIS systems is the well-documented sample-to-sample memory effect, which requires each sample to be analyzed multiple times before the desired accuracy is reached, lengthening analysis times and driving up the costs of analyses. We present an adapted set-up and calculation protocol for fully automated analysis of water samples using a Picarro L2140-i cavity ring-down spectroscopy instrument. The adaptation removes memory effects by use of a continuously moisturized nitrogen carrier gas. Water samples of 0.5 μL are measured on top of the water vapor background, after which isotope ratios are calculated by subtraction of the background from the sample peaks. With this new technique, single injections of water samples have internal precisions (1σ) below 0.05‰ for δ18 O values and 0.1‰ for δ2 H values, regardless of the isotope ratio of the previous sample. Precision is worse, however, when the isotope difference between the sample and background water is too large (i.e., exceeding approximately 9‰ for δ18 O values and 70‰ for δ2 H values). Isotope ratios show negligible drift across the four weeks within which the experiments were performed. The single-injection 1σ precision for 17 O excess (Δ'17 O) determined with this method is 60 per meg. Our experiments demonstrate that by removing sample-to-sample memory effects with a moisturized carrier gas, the time for measurement of δ18 O and δ2 H values using an IRIS system can be reduced markedly without compromising the analytical precision and accuracy. Thorough replication is needed to achieve sufficiently low uncertainties for Δ'17 O.

New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes

Oval caves have recently been discovered in the Bashuihe granite pluton of Laoshan Mountain, China. Oval caves typically occur in alkaline granites. This study conducted microthermometry and stable isotope analysis of quartz inclusions from oval caves and host rocks from the Bashuihe pluton to reconstruct the diagenetic evolutionary history of the Laoshan area. The temperature measurement results indicated a homogenisation temperature range from 162.5 to 261.6°C (mean 203.9°C), a salinity range of 2.1–8.3 wt% (mean 5.07 wt%), and a density range of 0.8–0.98 g/cm3 (mean 0.90 g/cm3), indicating a low-temperature, low-salinity, and low-density fluid. The emplacement depth ranged from 2.73 km to 4.43 km, indicating medium-shallow granite. A hydrogen and oxygen isotope analysis ( δ D = − 83.58 – − 67.17 , δ 18 O H 2 O = 0.83 – 0.39 ) revealed that the diagenetic fluids of the Bashuihe pluton represented a mixed hydrothermal solution composed of meteoric water and magmatic water. The results of a whole rock, H–O isotopes, rare earth element, and high field strength element analysis on the Laoshan alkali granites suggest significant hydrothermal activity in the late stage of magmatism. Primary oval caves in the Bashuihe pluton most likely evolved in the following sequence: fluid was enriched in the late diagenetic stage, diagenetic minerals crystallised under low temperature and pressure conditions, the crystallisation rate accelerated, and the magma condensed rapidly. Moreover, the increase in magma fluid enabled the movement and convergence of fluid. The accumulated fluid and volatiles occupied more space, and rapid magma condensation trapped the accumulated fluid and volatiles in the pluton, forming the oval granite cave. This research provides a crucial theoretical reference for the development and utilisation of underground space and engineering buildings in granite regions.

New method for calibration of a quadrupole mass spectrometer for hydrogen isotopes measurements

Abstract Quantitative analysis of hydrogen isotopes is an essential problem when it comes to accurately determine the performance of ITER hydrogen isotope separation system, or in case of the purity of tritium gas for injection into the Tokamak, to know the level of impurities, in terms of protium and deuterium (H, D). Mass spectrometry is a reliable method to accurately measure low or high concentrations of hydrogen isotopes (H and D) in various gas mixtures. Due to the interferences caused by the triatomic ions formed in the ion source as a result of the interactions between ions and neutral molecules, corrections must be applied in order to get accurate results. In this paper, a new method for calibration of a quadrupole mass spectrometer for hydrogen isotopes (protium and deuterium) is presented, taking into account the contributions and corrections due to the interferences caused by the triatomic ions at the interest m/z ratios. Also, the uncertainty of the measurement and the detection limit of the method are determined. In order to verify the validity of the method, an intercomparison between the results obtained using Fourier-Transform Infrared Spectroscopy method (a FTIR spectrometer) and the quadrupole mass spectrometer (QMS) was performed for the quantitative analysis of hydrogen isotopes.

Hydrogen isotopic analysis of nuclear reactor materials using ultrafast laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy is a promising method for rapidly measuring hydrogen and its isotopes, critical to a wide range of disciplines (e.g. nuclear energy, hydrogen storage). However, line broadening can hinder the ability to detect finely spaced isotopic shifts. Here, the effects of varying plasma generation conditions (nanosecond versus femtosecond laser ablation) and ambient environments (argon versus helium gas) on spectral features generated from Zircaloy-4 targets with varying hydrogen isotopic compositions were studied. Time-resolved 2D spectral imaging was employed to detail the spatial distribution of species throughout plasma evolution. Results highlight that hydrogen and deuterium isotopic shifts can be measured with minimal spectral broadening in a ∼ 10 Torr helium gas environment using ultrafast laser-produced plasmas.

Groundwater Quality of Aquifers Overlying the Oxnard Oil Field, Ventura County, California

Groundwater samples collected from irrigation, monitoring, and municipal supply wells near the Oxnard Oil Field were analyzed for chemical and isotopic tracers to evaluate if thermogenic gas or water from hydrocarbon-bearing formations have mixed with surrounding groundwater. New and historical data show no evidence of water from hydrocarbon-bearing formations in groundwater overlying the field. However, thermogenic gas mixed with microbial methane was detected in 5 wells at concentrations ranging from 0.011-9.1mg/L. The presence of these gases at concentrations <10mg/L do not indicate degraded water quality posing a known health risk. Analysis of carbon isotopes (δ13C-CH4) and hydrogen isotopes (δ2H-CH4) of methane and ratios of methane to heavier hydrocarbon gases were used to differentiate sources of methane between a) microbial, b) thermogenic or c) mixed sources. Results indicate that microbial-sourced methane is widespread in the study area, and concentrations overlap with those from thermogenic sources. The highest concentrations of thermogenic gas were observed in proximity to relatively high density of oil wells, large injection volumes of water disposal and cyclic steam, shallow oil development, and hydrocarbon shows in sediments overlying the producing oil reservoirs. Depths of water wells containing thermogenic gas were within approximately 200m of the top of the Vaca Tar Sand production zone (approximately 600m below land surface). Due to the limited sampling density, the source and pathways of thermogenic gas detected in groundwater could not be conclusively determined. Thermogenic gas detected in the absence of co-occurring water from hydrocarbon-bearing formations may result from natural gas migration over geologic time from the Vaca Tar Sand or deeper formations, hydrocarbon shows in sediments overlying producing zones, and/or gas leaking from oil-field infrastructure. Denser sampling of groundwater, potential end-members, and pressure monitoring could help better distinguish pathways of thermogenic gases.

Paleotemperature reconstructions using speleothem fluid inclusion analyses from Hungary

Abstract The combined use of the stable isotope compositions of speleothem carbonate and inclusion-hosted water presents great potential in paleotemperature reconstructions, due to the various temperature-dependent isotope fractionations detected in cave systems and their environment. This paper evaluates the applicational possibilities of hydrogen and oxygen isotope measurements of inclusion-hosted water and its host calcite, in three different approaches: i) direct determination of calcite-water oxygen isotope fractionation by measuring inclusion water and carbonate compositions, ii) calculation of water oxygen isotope composition from hydrogen isotope data and of temperature from the inferred calcite-water fractionation, and iii) calculation of formation temperature from measured hydrogen isotope data and its temperature dependence in the modern precipitation water. Fluid inclusion oxygen and hydrogen isotope compositions as well as calcite oxygen isotope compositions were determined for five speleothem occurrences in Hungary. Although the background processes are not resolved, calculations involving measured calcite and water oxygen isotope compositions yielded unrealistic paleotemperatures, likely because of syn-formation isotope fractionation processes and diagenetic alterations. The hydrogen isotope data may yield realistic temperatures, provided that long-term isotopic composition - temperature relationships are known and the stable hydrogen isotope composition of the precipitation waters in the study area is temperature-controlled. Winter half-year and annual isotope-temperature relationships (δ2H/T gradients) were calculated using multidecadal isotope composition records from the Global Network of Isotopes in Precipitation (GNIP), gridded surface temperatures, and precipitation amounts from the E-OBS 21.0e database. The calculations yielded a paleotemperature record for the last ~250 ka, with average precisions ranging from ±0.6 °C for interglacial to ±2.4 °C for glacial periods. Clumped isotope analyses of cave-hosted flowstones support the inferred formation temperatures based on gradients, while detection of kinetic fractionations by combined hydrogen and oxygen isotope analyses of calcite and inclusion water lead to filtering clumped isotope (Δ47) data and more coherent Δ47-temperature relationships.

Analysis of hydrogen isotopes in construction materials by means of electron spectroscopy

The possibility of measuring hydrogen depth profiles by means of electron spectroscopy is demonstrated. In the near-surface layer with a thickness corresponding to the inelastic mean free path (IMFP) the elastic peak electron spectroscopy (EPES) is employed for this purpose. For measuring hydrogen isotope depth profiles deeper in the solid at depths corresponding to the transport mean free path (which is by several orders of magnitude larger than the IMFP) the so-called spectroscopy of reflected electrons (SRE) is used. In this work, the SRE technique is employed for the investigation of a pure beryllium sample and a beryllium sample implanted with deuterium atoms.