Stable Hydrogen Isotope Ratios Research Articles

Chlorine isotopes as tracers of solute origin and age of groundwaters from the Eastern Desert of Egypt

Chlorine-36 abundances and stable chlorine isotope ratios (37Cl/35Cl) were analyzed to decipher sources of chloride and to estimate subsurface residence times of groundwaters from the Nubian Sandstone Aquifer System (NSAS), alluvial aquifers, and fractured basement aquifers in the Eastern Desert of Egypt. Chlorine-36 isotopic abundances (36Cl/Cl) ranged from 5 × 10−15 to 343 × 10−15. The range in δ37Cl values was −0.61 to +0.90‰. Groundwater solute compositions were dominated by Na, Ca, Cl, and SO4 with total dissolved solids ranging from 445 to 13,700 mg/L. Chemical and isotopic data indicate that dry fallout of marine aerosols and evaporated vadose-zone residues from precipitation that recharged the aquifers may have been the main sources of groundwater solutes. Apparent groundwater 36Cl model ages range from 0 (+/−40) to 1300 (+300/−180) kyr. Groundwater from the fractured basement aquifers in the southwestern part of the study area had the youngest apparent ages, while that from deep wells tapping the Nubian aquifer had the oldest apparent ages. Shallow alluvial aquifers having anomalously old apparent 36Cl model ages indicate mixing of old Nubian aquifer water with modern recharge in alluvial aquifers. Stable isotope ratios of hydrogen and oxygen support this inferred mixing relationship and allowed quantitative estimation of old/young water mixing fractions.

Quantitative analysis and detection of chaptalization and watering down of wine using isotope ratio mass spectrometry

In early 1990's European Union has established new isotopic approach for detection of wine authenticity. In this article we setup the possibility of using new approach using new EIM – Module – IRMS (Ethanol Isotope Measurement – Module – Isotope Ratio Mass Spectrometry) instrumental technique and new analytical parameter δDn(δ2Hn) wine ethanol value, which represents δ2H value of non-exchangeable hydrogen stable isotope ratio in ethanol, with other isotopic species (δ18O values in wine water) to improve detection of illegal wine production practices such as addition of sugar and/or dilution with water. Total of 42 wine samples were analyzed. 10 wine samples (out of 42) were prepared from grapes by alcoholic fermentation and analyzed for δDn values of ethanol. 19 wine samples (out of 42) were collected from wine producers in Serbia plus 1 wine samples designated from United States was taken from Serbian market and analyzed for δDn values of ethanol, δ18O values in wine water and also δ13C values in wine ethanol. Furthermore 9 wine samples (out of 42) were taken from Hungarian market and analyzed for δDn values of ethanol, and also 3 wine samples (out of 42) were taken from Austrian market and analyzed for δDn values of ethanol. All experiments were done in 4 isotope laboratories located in US, Austria, Hungary and People's Republic of China. δDn values of ethanol were measured by using EIM Module connected to FlashHT 2000 pyrolizer (one laboratory – Imprint Analytics GmbH, Austria), while in other 3 laboratories (US – COIL – Cornell University, Stable Isotope Laboratory, Hungary – Isotoptech Ltd, Debrecen, Hungary and China – C.N.R.I.F.F.I. – China National Institute of Food and Fermentation Industries Limited) EIM Module was connected to TC/EA (High Temperature Conversion Elemental Analyzer). Peripherals in all laboratories were further interfaced with isotope ratio mass spectrometer. Furthermore δ18O values in wine water were measured by using Gas Bench II interfaced also with isotope ratio mass spectrometer (one laboratory – US). Obtained results from all 4 laboratories have shown that this new approach which uses δDn in wine ethanol is more effective in improving detection of illegal wine production practices (sugar enrichment and water dilution) and origin of ethanol, and also detecting the addition of corn or beet sugar, sugar syrup to wine, or dilution of grape must with water prior to alcoholic fermentation. Keywords: Wine authenticity; EIM – Module – IRMS; Stable Isotope; Isotope Ratio Mass Spectrometry; Wine; Watering; Chaptalization.

Influence of water hydrogen on the hydrogen stable isotope ratio of methane at low versus high temperatures of methanogenesis

Our laboratory experiments simulated hydrocarbon gas generation from source rocks by using low-temperature (≤200 °C) and long-term (1 month and 5 years) heating of pre-evacuated and sterilized immature shales and coals (vitrinite reflectance (VR) values of 0.21–0.47 %Ro). Source rock powders and chips were sealed in gold and Pyrex® glass tubes in the presence of waters with variable hydrogen isotopic compositions (i.e., δ2Hwater values of −137‰ and +1246‰) to assess the influence of water-derived hydrogen on generated gaseous hydrocarbons. In addition, hydrous pyrolysis (HP) experiments using pre-extracted shales at 330 °C and H-isotopically distinct waters were performed for comparison. The isotopic transfer of water-hydrogen to hydrocarbons generated at both low and high temperatures was quantified. Isotopic mass-balances indicate that the methane to butane (CCH4–CC4H10) hydrocarbon gases from high-temperature HP experiments received an average of 53% of their hydrogen from water, whereas at low-temperatures the hydrogen transfer from water to methane ranged only from ∼1% to ∼13% of organic hydrogen.A possible explanation for differences in the extent of hydrogen transfer is that during lower-temperature hydrocarbon gas generation carbon-carbon bond breaking occurs close to the interface between minerals and organic matter, where hydrophobic organic microdomains limit the access of water. This would explain why methane generated at low temperatures mostly inherits its hydrogen from pre-existing organic hydrogen and not from water, in contrast to methane generated at higher temperatures. At higher temperatures, the physico-chemical properties of water are altered compared to those at lower temperatures. Experiments at 330 °C enhance water solubility in organic phases and facilitate stronger isotopic interactions between water and organic hydrogen. Therefore, by comparing the results obtained at low-temperature and high-temperature conditions, our laboratory experiments offer insights into the mechanisms controlling the contribution of water hydrogen to hydrocarbon gas generation in sedimentary basins.

Regional groundwater flow system in a stratovolcano adjacent to a coastal area: a case study of Mt. Fuji and Suruga Bay, Japan

Groundwater movement through the slope area of Mt. Fuji to the coastal area of Suruga Bay (central Japan) was investigated using spatially dense geochemical data, as a case study for elucidating the groundwater flow system in a stratovolcano adjacent to the coast. Spatial distributions of the hydrogen stable isotope ratio, vanadium concentration, and water temperature in the groundwater showed anomalies at the coastal area of Suruga Bay. The anomalies were characterized as depleted isotope ratio, high vanadium concentration, and low water temperature relative to surroundings. This can be explained as a regional deep groundwater flow from the slope of Mr. Fuji to the coastal area of Suruga Bay because groundwater recharged at higher elevation has a depleted isotope ratio caused by the altitude effect and high vanadium concentration as a result of dissolution from the basaltic aquifer. These characteristics also imply a hierarchical flow system, which is incorporated into a hydrogeological model of the coastal aquifer.

Effect of heat and singeing on stable hydrogen isotope ratios of bird feathers and implications for their use in determining geographic origin.

Stable hydrogen isotope (δ2 H) ratios of animal tissues are useful for assessing movement and geographic origin of mobile organisms. However, it is uncertain whether heat and singeing affects feather δ2 H values and thus subsequent geographic assignments. This is relevant for birds of conservation interest that are burned and killed at concentrating solar-energy facilities that reflect sunlight to a receiving tower and generate a solar flux field. We used a controlled experiment to test the effect of known heat loads (exposure to 200, 250 or 300°C for 1 min) on the morphology and δ2 H values of feathers from two songbird species. Subsequently, we examined the effects of singeing on δ2 H values of feathers from three other songbird species that were found dead in the field at a concentrating solar-energy facility. Relative to control samples, heating caused visual morphological changes to feathers, including shriveling at 250°C and charring at 300°C. The δ2 H values significantly declined by a mean of 27.8‰ in experimental samples exposed to 300°C. There was no statistically detectable difference between δ2 H values of the singed and unsinged portions of field-collected feathers from the same bird. Limited singeing that did not dramatically alter the feather morphology did not substantially affect δ2 H values of feathers from these songbirds. However, higher temperatures induced charring and reduced δ2 H values. Therefore, severely charred feathers should be avoided when selecting feathers for δ2 H-based assessment of geographic origin.

Net fractionation of hydrogen isotopes in n-alkanoic acids from soils in the northern boreal forest

Plant-derivedn-alkyl lipids are well-preserved in sedimentary archives, and their stable hydrogen isotope ratio (δDwax) is a proxy for precipitation δD and climate. Net fractionation of H isotopes between plant source water andn-alkyl lipids (εwax/water) is the largest uncertainty for interpreting this proxy and depends on plant type and environment. Although popular proxies,n-alkanoic acids (n-acids) are less frequently calibrated in modern environments thann-alkanes. We constrain the net fractionation (εwax/MAP – Mean Annual Precipitation) for the northern boreal forest based onn-C24,26,28acids in topsoils from a 13-site network in Yukon, Alaska and Northwest Territories (60–68°N).n-Acid homologue distributions for common boreal plants (gymnosperm trees, shrubs, forbs, C3 grasses and mosses) show that soiln-acids are dominated by mosses, but with a reduced carbon preference index compared to fresh mosses, possibly owing to post-depositional degradation. Regionally averaged εwax/MAP values are −93 ± 10‰, −101 ± 11‰ and −95 ± 11‰ for n-C24,26,28 acids, respectively, which are similar to values reported from low and high latitude regions. We find that εwax/MAP for n-C26,28 acids (but not n-C24) is significantly (p ≤ 0.05) smaller with increasing latitude and decreasing mean annual temperature, factors that covary across our network. Since latitude is typically known for ancient deposits, we parsed the dataset to obtainlatitude-specific εwax/MAPvalues for 60–64°N (−107 ± 8‰ for n-C26; and −101 ± 8‰ for n-C28) and 65–68°N (−94 ± 11‰ for n-C26; and −89 ± 10‰ for n-C28).These soil-derived values are relevant for hydroclimate reconstructions using fossiln-acids in paleosols from a comparable paleoflora and latitude.

Tracking the Strength of the Walker Circulation with Stable Isotopes in Water Vapor.

General circulation models (GCMs) predict that the global hydrological cycle will change in response to anthropogenic warming. However, these predictions remain uncertain, in particular for precipitation [IPCC, 2013]. Held and Soden [2006] suggest that as lower-tropospheric water vapor concentration increases in a warming climate, the atmospheric circulation and convective mass fluxes will weaken. Unfortunately, this process is difficult to constrain, as convective mass fluxes are poorly observed and incompletely simulated in GCMs. Here, we demonstrate that stable hydrogen isotope ratios in tropical atmospheric water vapor can trace changes in temperature, atmospheric circulation and convective mass flux in a warming world. We evaluate changes in temperature, the distribution of water vapor, vertical velocity (ω) and advection, and water isotopes in vapor (δD V ) in water isotopeenabled GCM experiments for modern vs. high CO 2 atmospheres to identify spatial patterns of circulation change over the tropical Pacific. We find that slowing circulation in the tropical Pacific moistens the lower troposphere and weakens convective mass flux, both of which impact the δD of water vapor in the mid-troposphere. Our findings constitute a critical demonstration of how water isotope ratios in the tropical Pacific respond to changes in radiative forcing and atmospheric warming. Moreover, as changes in δD V can be observed by satellites, our results develop new metrics for the detection of global warming impacts to the hydrological cycle and, specifically, the strength of the Walker Circulation.

Enantiomeric resolution of methylamphetamine and ephedrine: Does this affect the δ13C, δ15N, and δ2H stable isotope ratios of the product?

The use of stable isotope ratio mass spectrometry (IRMS) as a profiling tool for methylamphetamine has evolved over the last decade. Stable isotope ratios of carbon (δ13 C), nitrogen (δ15 N), and hydrogen (δ2 H) of methylamphetamine are useful in determining the precursor used to manufacture methylamphetamine, and in many cases the synthetic origin of the methylamphetamine precursor. More recently, samples of seized methylamphetamine show that a resolution step is being employed in the manufacturing process. We sought to determine whether the δ13 C, δ15 N, and δ2 H values were affected by either a resolution performed on racemic methylamphetamine or a resolution on racemic ephedrine, a commonly used precursor to methylamphetamine. We found that for the types of resolution studied, IRMS is still able to provide useful information on the provenance of a methylamphetamine sample.

Earliest Eocene cold period and polar amplification - Insights from δ2H values of lignin methoxyl groups of mummified wood

Three well-preserved mummified wood specimens have been excavated from three earliest Eocene (~55.5, 55.2 and 53.3 Ma) kimberlite pipes in the subarctic Northwest Territories, Canada (~64°N). Each specimen contained multi-decadal length tree-ring series and allowed measurements of stable hydrogen isotope ratios (δ2H values) of the lignin methoxyl groups (commonly used cellulose was largely degraded). We used these δ2H signatures for the reconstruction of three representative δ2H values of the local precipitation by applying calibrated isotope fractionations to investigate deep-time paleoclimatology. Our reconstructions indicate unprecedented low values for the subarctic early Eocene which, however, show within ~2.2 Myr an increasing trend from −206 ± 17, −202 ± 17 to −168 ± 17‰. These values were interpreted along with other Arctic, subarctic and mid-latitudinal proxy records of that time period indicating in total a period of low stable hydrogen and oxygen isotope ratios in precipitation (onset between ~55.7 and 54.9 Ma and a recovery at 53.3 ± 0.6 Ma) which is assumed to have been primarily caused by a continental cold period. An increased magnitude of this cold period was noted for our subarctic reconstructions pointing to a polar amplification where surface air temperature changes in the Arctic exceed the global trend (in response to climate forcing). In an attempt to quantify the polar amplification magnitude we estimated Arctic temperature changes using our δ2H results in combination with existing relationships between early Eocene temperatures and stable water isotopes. Comparing the Arctic temperature change with a global estimation proposes a polar amplification of magnitude <4. Our estimate for the earliest Eocene shows either agreement or indicates a lower magnitude when compared to previously described Cenozoic polar amplifications commonly ranging between 2 and 4.

Isotopic composition and elemental concentrations in groundwater in the Kuiseb Basin and the Cuvelai-Etosha Basin, Namibia

Abstract. We assessed environmental tracers in groundwater in two contrasting basins in Namibia; the Kuiseb Basin, which is a predominantly dry area and the Cuvelai-Etosha Basin, which is prone to alternating floods and droughts. We aimed to determine why the quality of groundwater was different in these two basins which occur in an arid environment. We analysed groundwater and surface water for the stable isotope ratios of hydrogen (δ2H) and oxygen (δ18O) by cavity ring-down spectroscopy and metals by inductively coupled plasma mass spectrometry. The δ2H and δ18O of surface water in the Cuvelai-Etosha Basin plot on an evaporation trend below the global meteoric water line (GMWL) and the local meteoric water line (LMWL). The δ2H and δ18O of some groundwater samples in the Cuvelai-Etosha Basin also plot on the evaporation trend, indicating recharge by evaporated rain or evaporated surface water. In contrast, the δ2H and δ18O of groundwater samples in the Kuiseb Basin plot mostly along the GMWL and the LMWL, indicating direct recharge from unevaporated rain or unevaporated surface water. Fifty percent of groundwater samples in the Cuvelai-Etosha Basin was potable (salinity &lt; 1 ppt) compared to 79 % in the Kuiseb Basin. The high salinity in the groundwater of the Cuvelai-Etosha Basin does not appear to be caused by evaporation of water (evapo-concentration) on surface prior to groundwater recharge, but rather by the weathering of the Kalahari sediments. The low salinity in the Kuiseb Basin derives from rapid recharge of groundwater by unevaporated rain and limited weathering of the crystalline rocks. The order of abundance of cations in the Kuiseb Basin is Na &gt; K &gt; Ca &gt; Mg vs. Na &gt; Mg &gt; Ca &gt; K for the Cuvelai-Etosha Basin. For metals in the Kuiseb Basin the order of abundance is Fe &gt; Al &gt; V &gt; As &gt; Zn vs. Al &gt; Fe &gt; V&gt; As &gt; Zn for the Cuvelai-Etosha Basin. The relative abundance of cations and metals are attributed to the differences in geology of the basins and the extent of water-rock interaction. Our results show that the quality of groundwater in Cuvelai-Etosha Basin and Kuiseb Basin which vary in the extent of aridity, is controlled by the extent of water-rock interaction at the surface and in the groundwater aquifer.

Heat budget contribute rate in the Three Gorges Reservoir tributary bay between mainstream and tributary using stable isotope analysis

Abstract Understanding the interaction processes between the mainstream and its tributaries and detailing the rates of contribution of water and heat from two different water bodies in the tributary bay are essential for water management in the Three Gorges Reservoir (TGR). The stable isotope ratios of hydrogen (δD) and oxygen (δ18O) were applied to explore the interactions between the TGR mainstream and the tributary, Zhuyi River. A heat budget of the TGR tributary bay was constructed for the year 2014 using data for water temperature, meteorological data and water mixing ratio. The results showed that approximately 91% of the water in the tributary bay was from the TGR mainstream. And the heat budget reveals that the tributary bay net heat flux is dominated by the mainstream advective heat, and the average contribution rate is 87% during the whole year, while the tributary advective heat and atmosphere make a minor contribution to the tributary bay heat budget.

Interlaboratory comparison of &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C and &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;D measurements of atmospheric CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; for combined use of data sets from different laboratories

Abstract. We report results from a worldwide interlaboratory comparison of samples among laboratories that measure (or measured) stable carbon and hydrogen isotope ratios of atmospheric CH4 (δ13C-CH4 and δD-CH4). The offsets among the laboratories are larger than the measurement reproducibility of individual laboratories. To disentangle plausible measurement offsets, we evaluated and critically assessed a large number of intercomparison results, some of which have been documented previously in the literature. The results indicate significant offsets of δ13C-CH4 and δD-CH4 measurements among data sets reported from different laboratories; the differences among laboratories at modern atmospheric CH4 level spread over ranges of 0.5 ‰ for δ13C-CH4 and 13 ‰ for δD-CH4. The intercomparison results summarized in this study may be of help in future attempts to harmonize δ13C-CH4 and δD-CH4 data sets from different laboratories in order to jointly incorporate them into modelling studies. However, establishing a merged data set, which includes δ13C-CH4 and δD-CH4 data from multiple laboratories with desirable compatibility, is still challenging due to differences among laboratories in instrument settings, correction methods, traceability to reference materials and long-term data management. Further efforts are needed to identify causes of the interlaboratory measurement offsets and to decrease those to move towards the best use of available δ13C-CH4 and δD-CH4 data sets.

On-line in situ determination of deuterium content in water via FTIR spectroscopy.

Hydrogen stable isotope ratios are critical indicators in environmental geochemical studies for characterizing runoff, determination of groundwater groups and water uptake by plants etc. (generally used in combination with 18O analysis). While the common technique for this hydrogen isotope measurement is Mass Spectrometry, FTIR (Fourier transform infra-red) spectroscopy may be an alternative method, with the advantage of direct and simple operating measurements. The FTIR spectrometer has the advantage of performing in situ measurements, which can delineate continuous geochemical processes. In situ measurements decrease errors that may be a consequence of sample delivery to the laboratory and off-site analysis procedures. In this study, we have developed a new simple procedure for in situ hydrogen stable isotope ratio measurements. We discovered that the HDO (hydrogen, deuterium, and oxygen) absorbance peak at 2504 cm−1 is the most suitable for water sample direct analysis, with the FTIR device, using a circular sample cell for liquid samples. A case study analyzing water samples from a karstic cave (Sif cave, Israel) verified the following: (a) on-line determination of water D/H ratio can be carried out with the portable FTIR spectrometer (and thus can be used for field measurements such as in the Sif cave) and (b) the D concentration sensitivity achieved was at a 0.01‰ level, with a standard deviation of 0.006‰.

Comparisons of stable isotope (C, H, N) signatures for revealing organic matter sources and trophic relationships in headwater streams

We compared the efficacy of stable carbon, hydrogen, and nitrogen isotope ratios in identifying the resources used by insect consumers in headwater streams of southern California. We also compared gut contents with consumer stable isotope ratios and mixing model estimates of resource contributions to predator diet. Stable hydrogen isotope ratios (as δ2H) of algivores were well separated from ratios for detritivores, whereas relationships between stable carbon (as δ13C) and nitrogen (as δ15N) ratios of consumers and their expected diets were weaker and more ambiguous. δ2H values of primary consumers more strongly reflected the proportions of their gut contents consisting of algae than δ13C values. Τhe proportions of algivorous prey in predator gut contents increased with mixing model estimates of algivore contributions to predator diet using δ2H but not δ13C values. Our findings support the use of hydrogen isotope ratios in food web studies of streams in southern California and their potential use in assessing the effects of anthropogenic and natural disturbance on basal resource contributions to food webs that might not otherwise be identified using carbon isotope ratios.

Insight into the source of grapevine water acquisition during key phenological stages using stable isotope analysis

Background and Aims Stable isotope analysis of grapevine water provides insight into seasonal water use trends, soil depth of active water/nutrient uptake, and the role of water in the physiological processes of grapevines. This technique identifies the sources of water utilised and the functional rooting depth for vine water uptake over the growing season to support development of efficient irrigation strategies while managing grape and wine composition. Methods and Results The hydrogen stable isotope ratio (δD) values of vine water identify rain as the principal water source during budburst and flowering/fruitset, and various combinations of rain and groundwater in summer and autumn, with an increasing proportion of groundwater in the mixture, as veraison/ripening continues and fruit maturity is achieved at harvest. The seasonal water use trend demonstrates a variable functional rooting depth for grapevine water acquisition over time, with the shallow roots utilising rain water as a main source in spring and a root system that can reach progressively deeper into the soil profile as the growing season advances. Conclusions Water acquired by grapevines during the 2015 growing season originated from various depths and was derived from a combination of meteorological sources prior to recharging the soil water reservoir. The isotopic composition of grapevine water demonstrates that the functional rooting depth for water uptake is highly variable during the different phenological stages of the grapevines. Significance of the Study The preferential vine water use allows irrigation recommendations to be made/forecasted to maximise water uptake efficiency and water conservation. This study site has an udic moisture regime, potentially providing insensitive isotopic variations due to the evenness of rainfall; thus, the success of this approach suggests that these methods will be highly effective in identifying seasonal patterns in ustic and xeric moisture regimes.

Contributions of terrestrial organic carbon to northern lake sediments

AbstractSediments of northern lakes sequester large amounts of organic carbon (OC), but direct evidence of the relative importance of their sources is lacking. We used stable isotope ratios of nonexchangeable hydrogen (δ2Hn) in topsoil, algae, and surface sediments in order to measure the relative contribution of terrestrial OC in surface sediments of 14 mountainous arctic and lowland boreal lakes in Sweden. The terrestrial contribution to the sediment OC pool was on average 66% (range 46–80) and similar between arctic and boreal lakes. Proxies for the supply of terrestrial and algal OC explained trends in the relative contribution of terrestrial OC across lakes. However, the data suggest divergent predominant sources for terrestrial OC of sediments in Swedish lakes, with dissolved matter dominating in lowland boreal lakes and particulate OC in mountainous arctic lakes.

Origin of water in the Badain Jaran Desert, China: new insight from isotopes

Abstract. To better understand the origin of water in the Badain Jaran Desert, China, water samples were collected from lakes, a spring and local unconfined aquifer for analyses of radiocarbon (14C), tritium (3H), stable hydrogen and oxygen isotope ratios (δ2H – δ18O), and d-excess values ( = δ2H – 8δ18O). A series of evaporation experiments were also conducted in the desert to examine how the isotopic signature of water may change during evaporation and infiltration under local environmental conditions. The results show that the lakes in the southeastern sand dune area are fed by groundwater discharging into the lakes and that local groundwater, on the other hand, is derived primarily from modern meteoric precipitation in the region. Although dissolved inorganic carbon (DIC) in groundwater yielded very old radiocarbon ages, the presence of detectable amounts of tritium in groundwater samples, together with their δ2H, δ18O and d-excess characteristics, strongly suggests that the old radiocarbon ages of DIC do not represent the residence time of water in the aquifer but are the result of addition of old DIC derived from dissolution of ancient carbonates in the aquifer. The data do not support the hypothesis that the water in the Badain Jaran Desert was sourced in remote mountains on the northern Tibetan Plateau. This study also finds no support for the hypothesis that present-day water resources in the desert were recharged by the precipitation that fell in the past during the early Holocene when the climate was much wetter than today. Instead, this study shows that both groundwater and lake water originated from meteoric precipitation in the region including mountainous areas adjacent to the desert under the modern climatic condition.

Warm season precipitation signal in δ2 H values of wood lignin methoxyl groups from high elevation larch trees in Switzerland.

In this study, we tested stable hydrogen isotope ratios of wood lignin methoxyl groups (δ2 Hmethoxyl values) as a palaeoclimate proxy in dendrochronology. This is a quite new method in the field of dendrochronology and the sample preparation is much simpler than the methods used before to measure δ2 H values from wood. We measured δ2 Hmethoxyl values in high elevation larch trees (Larix decidua Mill.) from Simplon Valley (southern Switzerland). Thirty-seven larch trees were sampled and five individuals analysed for their δ2 Hmethoxyl values at annual (1971-2009) and pentadal resolution (1746-2009). The δ2 Hmethoxyl values were measured as CH3 I released upon treatment of the dried wood samples with hydroiodic acid. 10-90 μL from the head-space were injected into the gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/HTC-IRMS) system. Testing the climate response of the δ2 Hmethoxyl values, the annually resolved series show a positive correlation of r = 0.60 with June/July precipitation. The pentadally resolved δ2 Hmethoxyl series do not show any significant correlation to climate parameters. Increased precipitation during June and July, which are on average warm and relatively dry months, results in higher δ2 H values of the xylem water and, therefore, higher δ2 H values in the lignin methoxyl groups. Therefore, we suggest that δ2 Hmethoxyl values of high elevation larch trees might serve as a summer precipitation proxy.

Testing the usefulness of hydrogen and compound-specific stable isotope analyses in seabird feathers: a case study in two sympatric Antarctic storm-petrels

Nitrogen and carbon stable isotopes provide tools to investigate ecological segregation, prey choice and spatial distribution in seabirds. However, the interpretation of stable isotopes is frequently hampered by a lack of isotopic baseline data. In this study, two techniques proposed to overcome such shortages were tested: compound-specific isotope analyses of amino acids (AA-CSIA) and the analysis of hydrogen stable isotope ratios (HSIA). Feathers of two sympatric storm-petrels were compared. The two species, Black-bellied storm-petrels Fregetta tropica and Wilson’s storm-petrels Oceanites oceanicus, moult in oceanic waters and differ in diet composition. For HSIA, a range of species with broad diet and non-breeding distribution was also investigated. Differences in carbon isotope values suggested differences in the spatial distribution and thus, in isotopic baseline values, during moult. Bulk nitrogen analyses of adult feathers did not detect species differences in trophic level. However, AA-CSIA detected clear differences in trophic levels in line with expectations: Black-bellied storm-petrels fed at a higher trophic level than Wilson‘s storm-petrels. Hydrogen values also differed between the species, but contrary to expectations were highly enriched in Black-bellied storm-petrels, but much less enriched in Wilson’s storm-petrels. Hydrogen data of seven petrel species challenge the suggestion that depleted δD values indicate a higher percentage of isosmotic fish. The present results suggest that the difference in hydrogen ratios may be explained by these petrels moulting in different ocean zones. Amino acid-specific stable isotope analyses were useful for estimating isotopic baselines and thus true trophic levels, whereas hydrogen isotopes were not.

Global Inventory of Gas Geochemistry Data from Fossil Fuel, Microbial and Burning Sources, version 2017

Abstract. The concentration of atmospheric methane (CH4) has more than doubled over the industrial era. To help constrain global and regional CH4 budgets, inverse (top-down) models incorporate data on the concentration and stable carbon (δ13C) and hydrogen (δ2H) isotopic ratios of atmospheric CH4. These models depend on accurate δ13C and δ2H end-member source signatures for each of the main emissions categories. Compared with meticulous measurement and calibration of isotopic CH4 in the atmosphere, there has been relatively less effort to characterize globally representative isotopic source signatures, particularly for fossil fuel sources. Most global CH4 budget models have so far relied on outdated source signature values derived from globally nonrepresentative data. To correct this deficiency, we present a comprehensive, globally representative end-member database of the δ13C and δ2H of CH4 from fossil fuel (conventional natural gas, shale gas, and coal), modern microbial (wetlands, rice paddies, ruminants, termites, and landfills and/or waste) and biomass burning sources. Gas molecular compositional data for fossil fuel categories are also included with the database. The database comprises 10 706 samples (8734 fossil fuel, 1972 non-fossil) from 190 published references. Mean (unweighted) δ13C signatures for fossil fuel CH4 are significantly lighter than values commonly used in CH4 budget models, thus highlighting potential underestimation of fossil fuel CH4 emissions in previous CH4 budget models. This living database will be updated every 2–3 years to provide the atmospheric modeling community with the most complete CH4 source signature data possible. Database digital object identifier (DOI): https://doi.org/10.15138/G3201T.