Hydrogen Isotope Analysis Research Articles

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

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 δ2H values for each of two growth chambers, differing in relative humidity (58 and 74%). Analyses of δ2H 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 δ2H values were linearly related to leaf water δ2H 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 2H-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-C25 and n-C27 alkanes, it led to a ~25‰ decrease in biosynthetic fractionation for n-C31 and n-C33 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 δ2H values and relative humidity on the δ2H values of organic compounds may be discretely inferred by examining the δ2H 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

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 0.011–9.1 mg/L. The presence of these gases at concentrations <10 mg/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 200 m of the top of the Vaca Tar Sand production zone (approximately 600 m 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

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.

An Ion-Optical Circuit of a Small-Sized Mass-Spectrometer for the Isotope Analysis of Hydrogen–Helium Mixtures

We discuss an ion-optical system (IOS) of a mass spectrometer designed for isotopic measurements of light gases, containing a magnetic prism with plane-parallel pole tips and two sector-wise, cylindrical-capacitor identical in geometry, symmetrically located relative to the prism. The relationships between the geometric parameters of the capacitors and the prism are given, which are necessary to ensure achromatic focusing of the ion beam in the plane of the detector receiving slit. We assessed numerically the effect of IOS aberrations on the mass resolution of the IOS and determined the optimal emittance of the ion beam at the source output, which enables achieving a resolution at the level of 3000–3500 with an output slit of the ion source of approximately 50 μm, high transmittance of the mass analyzer, small dimensions of the magnetic prism, and a moderate total length of the central ion trajectory (less than 1 m). The IOS is characterized by a high dispersion in masses, which is much larger than the dispersion of conventional sector magnetic mass spectrometers of the same dimensions. The IOS consists of simple geometry elements, which reduces the costs of its implementation and makes the mass spectrometer technologically advanced and convenient to set up and operate.

A conceptual framework of groundwater flowpath and recharge in Ziban aquifer: south of Algeria

The Zyban aquifers (southern Algeria) are an important source of groundwater and are mainly found in limestone and dolomite from the Senono-Eocene. To be able to assess the effects of overuse of the Zeban groundwater, it is necessary to understand the origin of the recharge and determine its path out of the recharge zones. This study aims to better understand the flow path and replenishment areas using hydrology. For this purpose, 145 water samples were collected and analyzed for the determination of major ions and isotopes (18O, 2H and 3H). The isotope analysis of hydrogen, oxygen and tritium allowed a certain distinction between the origin and the mixture of water. The study area is located in the fault corridor of the South Atlas, a network of migration and folding defects that leads to a complex structure characterized by the subdivision of the formations and the variety of facies. The regional flow pattern is mainly influenced by the topography, and this is through the distribution of supply and flow, which is produced by transport at many depths and levels of distribution (local or regional). The rocky nature and the severe fractures are responsible for the division of the hydrogeological units and play an important role in the dynamics and transport of the groundwater. The hydrodynamic analysis shows the dominance of regional hydrogeology in terms of geological nature and structure. This is supported by a hydrochemical signal showing the distribution and evolution of the elements according to the structural and geological scheme (evolution from calcium bicarbonate facies to calcium sulphate medium facies).

Using oxygen and hydrogen stable isotopes to track the migratory movement of Sharp-shinned Hawks (Accipiter striatus) along Western Flyways of North America.

The large-scale patterns of movement for the Sharp-shinned Hawk (Accipiter striatus), a small forest hawk found throughout western North America, are largely unknown. However, based on field observations we set out to test the hypothesis that juvenile migratory A. striatus caught along two distinct migration routes on opposite sides of the Sierra Nevada Mountains of North America (Pacific Coast and Intermountain Migratory Flyways) come from geographically different natal populations. We applied stable isotope analysis of hydrogen (H) and oxygen (O) of feathers, and large scale models of spatial isotopic variation (isoscapes) to formulate spatially explicit predictions of the origin of the migrant birds. Novel relationships were assessed between the measured hydrogen and oxygen isotope values of feathers from A. striatus museum specimens of known origin and the isoscape modeled hydrogen and oxygen isotope values of precipitation at those known locations. We used these relationships to predict the origin regions for birds migrating along the two flyways from the measured isotope values of migrant’s feathers and the associated hydrogen and oxygen isotopic composition of precipitation where these feathers were formed. The birds from the two migration routes had overlap in their natal/breeding origins and did not differentiate into fully separate migratory populations, with birds from the Pacific Coast Migratory Flyway showing broader natal geographic origins than those from the Intermountain Flyway. The methodology based on oxygen isotopes had, in general, less predictive power than the one based on hydrogen. There was broad agreement between the two isotope approaches in the geographic assignment of the origins of birds migrating along the Pacific Coast Flyway, but not for those migrating along the Intermountain Migratory Flyway. These results are discussed in terms of their implications for conservation efforts of A. striatus in western North America, and the use of combined hydrogen and oxygen stable isotope analysis to track the movement of birds of prey on continental scales.

Partial migration of White-winged snowfinches is correlated with winter weather conditions

Seasonal movements are a response to variability in resource availability and result from a complex interaction between the behavioral and physiological traits of a species and its prevailing environment. A widespread bird migration strategy is partial latitudinal migration, where some proportion of the population moves from breeding to winter grounds, while the remaining individuals stay year-round on the breeding grounds. Deciphering how and why some individuals migrate while others stay is essential to understanding population and community structure and dynamics. Little is known about the drivers of partial migration strategies of high-mountain birds that are subjected to strong seasonal environmental fluctuations and count among the species most threatened by climate change. In this study, we investigated the migratory pattern of an alpine songbird, the White-winged Snowfinch (Montifringilla nivalis nivalis), through the analysis of stable hydrogen isotopes of feathers (δ2Hf), and how it relates to weather factors. First, values of δ2Hf were used to assess the probability that snowfinches wintering in the Spanish Pyrenees and Cantabrian Mountains have a breeding origin in the Alps. Second, we analysed whether winter weather conditions (ambient temperature and precipitation) in the Alps may play a role in migratory movements towards the southern wintering grounds. Overall, ca 98% and 86% of the individuals sampled in winter in the Spanish Pyrenees and Cantabrian Mountains, respectively, were likely to originate from breeding populations in the Alps. Snowfinches also had a higher propensity for large-scale movements to the South in winters where the average monthly temperature was particularly low in the Alps, typically < −2 °C (i.e., in the 42% coldest winters). Our results suggest that snowfinches adopt a partial migratory strategy, with different patterns among and within populations that have important implications in terms of population connectivity, spatio-temporal dynamics and structuring. Considering the role of cold winter conditions in migration propensity of snowfinches, there is a risk of increased isolation of the southern populations under a scenario of global warming, insofar as the hypothetical settling of winter immigrants could no longer contribute to a demo-genetic rescue. Future research should decipher how these risks affect alpine species that are particularly exposed to climatic shifts, and how they adapt and evolve.

Stopover refuelling, movement and departure decisions in the white-throated sparrow: The influence of intrinsic and extrinsic factors during spring migration.

Differential migration timing between sex or age classes is an example of how migratory movement strategies can differ among subgroups within a population. However, in songbirds, evidence for intrinsic differences in en route migratory behaviour is often mixed, suggesting that the local environmental context may play a role in accentuating or diminishing patterns. We evaluated how multiple intrinsic and extrinsic variables influenced refuelling rates, local movement behaviour and departure decisions in the white-throated sparrow Zonotrichia albicollis during spring migration. This species exhibits a unique genetically based plumage dimorphism, providing a unique class of individual in which to evaluate patterns and processes of differential migration, in addition to sex, age and migration distance. At a migratory stopover site, plasma metabolite analysis was used to quantify individual variation in stopover refuelling rate. In after second year adults, automated and manual radio telemetry was used to quantify daily activity timing, daily movement distances, stopover duration and departure time. Arrival timing to the stopover site was determined using capture data. Non-breeding and previous breeding/natal latitude were determined using analysis of hydrogen isotopes in claws and feathers. Males arrived at the stopover site 11days on average before females, but no difference in migration timing was observed between plumage morph or age classes. After second year, adults with more southern previous breeding latitudes arrived at stopover earlier, whereas second year birds making their first return migration arrived at stopover in an inverse relationship to non-breeding latitude. Stopover refuelling rate did not differ between ages, sexes or plumage morphs, and daily departure probability of adults was higher under warmer temperatures and favourable tailwinds. White-striped morphs moved greater distances during stopover, initiated daily activity earlier in the morning and departed for migration earlier in the evening than tan-striped morphs. Our results show that while individual phenotype can influence some aspects of local stopover-scale movement behaviour, evidence for differential stopover behaviour was weak. Differential migration timing is unlikely to result from intrinsic differences in en route refuelling rate and departure decisions, especially because the latter is strongly influenced by meteorological conditions.

An isotope ratio mass spectrometry-based method for hydrogen isotopic analysis in sub-microliter volumes of water: Application for multi-isotope investigations of gases extracted from fluid inclusions.

The study of multi-isotope systematics of fluid inclusions is of great importance for understanding of the sources and evolution of fluid phases in mantle rocks and ore deposits. The most appropriate technique for such investigations is a (stepwise) crushing method that is widely used for noble gases and nitrogen. However, because of the possible influence of mechanochemical reactions and back sorption, analyses of the isotope composition of water extracted by crushing from fluid inclusions are challenging. An isotope ratio mass spectrometry (IRMS)-based method for hydrogen (and oxygen) isotopic analysis in sub-microliter volumes of water extracted from fluid inclusions by crushing is presented. The verification of the possible influence of adsorption processes and mechanochemical reactions on the results of isotope analysis was performed for the first time. For that a series of parallel analyses of hydrogen isotopic ratios from water inclusions in quartz applying physically different extraction methods (crushing and thermodecrepitation) was conducted. Four series of quartz aliquots were analyzed: three series extracting water by crushing (two series for δ2 H values and one for δ18 O values) and one by thermodecrepitation. The mean value for the crushing results is δ2 H = -85.3 ± 3.6 ‰ (1σ, n = 11), which coincides well with the thermodecrepitation data (-86.3 ± 2.0 ‰, 1σ, n = 5), suggesting that our methodological approach allows the influence of back sorption or mechanochemical reactions during the crushing experiment to be minimized. The reproducibility of the oxygen isotopic ratios is ±0.9 ‰ (1σ, n = 5). The conducted experiments have shown that the influence of back sorption or mechanochemical reactions during crushing on isotopic results is not crucial for our method. The developed IRMS-based method for hydrogen (and oxygen) isotopic analysis in sub-microliter volumes of water is well applicable for multi-isotope investigations of gases extracted from fluid inclusions. As an application a well-defined 40 Ar/36 Ar-δ2 H correlation in mantle rocks is presented for the first time.