Isotopic (δ18O, δD and deuterium excess) records from the TALDICE ice core (East Antarctica) (Invited)

NASA Astrophysics Data System (ADS)

Stenni, B.; Buiron, D.; Masson-Delmotte, V.; Bonazza, M.; Braida, M.; Chappellaz, J.; Frezzotti, M.; Falourd, S.; Minster, B.; Selmo, E.

2010-12-01

Paleotemperature reconstructions from Antarctic ice cores rely mainly on δD and δ18O records and the main key factors controlling the observed distribution of δD and δ18O in Antarctic surface snow are mainly related to the condensation temperature of the precipitation and the origin of moisture. The deuterium excess, d = δD - 8*δ18O, contains information about climate conditions prevailing in the source regions of precipitation and can be used as an integrated tracer of past hydrological cycle changes. In the framework of the TALos Dome Ice CorE (TALDICE) project, a deep ice core (1620 m) has been drilled at Talos Dome, a peripheral dome of East Antarctica facing the Ross Sea, about 550 km north of Taylor Dome and 1100 km East from the EPICA Dome C drilling site. The TALDICE coring site (159°11'E 72°49'S; 2315 m; T -41°C; www.taldice.org) is located near the dome summit and is characterised by an annual snow accumulation rate of 80 mm water equivalent. Backtrajectory analyses suggest that Talos Dome is mainly influenced by air masses arriving both from the Pacific (Ross Sea) and Indian Ocean sectors. A preliminary dating based on an ice flow model and an inverse method suggests for the upper 1580 m an age of about 300,000 years BP. The full TALDICE δ18O record obtained from the bag samples as well as δD and deuterium excess data are presented here. The δ18O and δD measurements were carried out in Italy and France on a continuous basis of 1 m. These new records will be compared to the ones obtained from the EDC ice core as well as with other East Antarctic ice core records. In particular, we will focus on the whole isotopic profiles, in good agreement with other inland deep ice cores, and on the last deglaciation, showing climatic changes at Talos Dome in phase with the Antarctic plateau and suggesting that the bipolar see saw with Greenland temperature is also valid for this new coastal site facing the Ross Sea sector.

Quanitfying atmospheric nitrogen loading to watersheds using nitrate isotopes (15N, 17O, 18O)

NASA Astrophysics Data System (ADS)

Wankel, S. D.; Kendall, C.

2002-12-01

Over the past century, human activity has greatly increased the amount of reactive nitrogen (N) in the atmosphere and the N inputs to terrestrial and aquatic ecosystems. Recent studies in the northeastern US have indicated that atmospheric N deposition is a significant source to land and water in the region, with contributions ranging from 15 to 60%. Estimates of the importance of atmospheric N have been plagued with uncertainty, however, due to incomplete data from atmospheric monitoring networks, to the varied spatial and temporal scales of databases dealing with agricultural, population, and land use, and to simplifications that are necessary to describe the complex rates of N accumulation and transformation. The principal objective of this study is the evaluation of new stable isotope techniques for quantifying the relative contributions atmospheric sources of anthropogenic nitrogen to the landscape and to the total N exported from watersheds in the northeastern US. In the last decade, several studies have used d18O and d15N of nitrate to evaluate the relative contributions of riverine nitrate derived from atmospheric sources. Very recent advances in analytical techniques (by Michalski, Thiemens, and colleagues) that allow the analysis of nitrate for d17O have shown that atmospheric nitrate is labeled with an anomalous, non-terrestrial, d17O signature. Hence, we now have three isotopes of nitrate that can be used to quantify sources of riverine nitrate. To test whether the analysis of nitrate for d17O enhances our ability to quantify atmospheric contributions to the total nitrate exported by major river basins, we have initiated a pilot study of many of the major rivers in the Ohio Basin and the northeastern USA. Published studies in these basins suggest that nitrate from basins dominated by urban, forested, and undeveloped landuses frequently has d18O values consistent with significant input from atmospheric sources. Preliminary d18O and d15N of nitrate data

Long-Term Precipitation Isotope Ratios (δ18O, δ2H, d-excess) in the Northeast US Reflect Atlantic Ocean Warming and Shifts in Moisture Sources

NASA Astrophysics Data System (ADS)

Puntsag, T.; Welker, J. M.; Mitchell, M. J.; Klein, E. S.; Campbell, J. L.; Likens, G.

2014-12-01

The global water cycle is exhibiting dramatic changes as global temperatures increase resulting in increases in: drought extremes, flooding, alterations in storm track patterns with protracted winter storms, and greater precipitation variability. The mechanisms driving these changes can be difficult to assess, but the spatial and temporal patterns of precipitation water isotopes (δ18O, δ2H, d-excess) provide a means to help understand these water cycle changes. However, extended temporal records of isotope ratios in precipitation are infrequent, especially in the US. In our study we analyzed precipitation isotope ratio data from the Hubbard Brook Experimental Forest in New Hampshire that has the longest US precipitation isotope record, to determine: 1) the monthly composited averages and trends from 1967 to 2012 (45 years); ; 2) the relationships between abiotic properties such as local temperatures, precipitation type, storm tracks and isotope ratio changes; and 3) the influence of regional shifts in moisture sources and/or changes in N Atlantic Ocean water conditions on isotope values. The seasonal variability of Hubbard Brook precipitation isotope ratios is consistent with other studies, as average δ18O values are ~ -15‰ in January and ~ -5 ‰ in July. However, over the 45 year record there is a depletion trend in the δ 18O values (becoming isotopically lighter with a greater proportion of 16O), which coupled with less change in δ 2H leads to increases in d-excess values from ~ -10‰ around 1970 to greater than 10‰ in 2009. These changes occurred during a period of warming as opposed to cooling local temperatures indicating other processes besides temperature are controlling long-term water isotope traits in this region. We have evidence that these changes in precipitation isotope traits are controlled in large part by an increases in moisture being sourced from a warming N Atlantic Ocean that is providing evaporated, isotopically

Isotopic Changes During Digestion: Protein

NASA Astrophysics Data System (ADS)

Tuross, N.

2013-12-01

Nutrient and hydrological inputs traverse a complicated route of pH, enzymatic and cellular processes in digestion in higher animals. The end products of digestion are the starting products for biosynthesis that are often used to interpret past life-ways. Using an artificial gut system, the isotopic changes (dD, d18O, d13C and d15N) of protein are documented. Three separate protein sources are subjected to the conditions, chemical and enzymatic, found in the stomach and upper small intestine with only a small shift in the oxygen isotopic composition of the proteins observed. Middle to lower small intestine parameters produced both greater isotopic effects and significantly lower molecular weight products. The role of the gastric enterocyte and the likely involvement of the internal milieu of this cell in the isotopic composition of amino acids that are transported to the liver are reported.

Localization of groundwater infiltration in the combined sewers of Brussels by stable isotopes measurements (δ18O, δD) by Cavity Ring Down Spectroscopy.

NASA Astrophysics Data System (ADS)

De Bondt, Kevin; Claeys, Philippe

2014-05-01

In the last 20 years research has been conducted to quantify the infiltration of groundwater into the sewers. This groundwater, called parasitic water, increases the volume of waste-water to be treated and consequently the cost of this treatment. Moreover, in the case of combined sewer systems, the parasitic water also limits the sewer capacity and indirectly increases the risks of combined sewer overflows and floods. The infiltration of groundwater occurs trough cracks, sewer collapses and from direct connections with old springs. Different methods quantify the intrusion of parasitic water. Among these, the use of the stable isotopes of water (δ18O & δD) shows good result in catchments or cities close to Mountainous regions (example from Lyon, Zurich), where isotopic signals vary significantly because of continental and altitude effects. However many cities, such as Brussels, are located in more oceanic settings and theoretically offer less potential for the application of the stable isotopes method. In the case of Brussels, river-water from the Meuse is used to produce domestic-water. The catchment of this river extends into the Ardennes, which are affected by slightly different climatic conditions. δ18O & δD analyzes of groundwater from the main aquifer (Ledo-Paniselian-Brusselian) and domestic-water from the Callois reservoir fed by the Meuse River show sufficient isotopic differences in the south of Brussels, but only during the summer. The discrimination potential is better with δD than with δ18O. The improvement of δD measurements (precision, costs,...) brought by Cavity Ring Down Spectroscopy largely contributes to the potential of using stable isotopes method to trace water in Brussels. The first campaigns in the sewers also show a little enrichment (in heavy isotopes) of the waste-water in comparison with the reservoir waters and tap waters. This increases the potential of the method but constrains the sampling to pure waste-water in sewer segments

99 Tc NMR determination of the oxygen isotope content in 18 O-enriched water.

PubMed

Tarasov, Valerii P; Kirakosyan, Gayana А; German, Konstantin E

2018-03-01

99 Tc NMR has been suggested as an original method of evaluating the content of oxygen isotopes in oxygen-18-enriched water, a precursor for the production of radioisotope fluorine-18 used in positron emission tomography. To this end, solutions of NH 4 TcO 4 or NaTcO 4 (up to 0.28 mol/L) with natural abundance of oxygen isotopes in virgin or recycled 18 O-enriched water have been studied by 99 Tc NMR. The method is based on 16 O/ 17 O/ 18 O intrinsic isotope effects in the 99 Tc NMR chemical shifts, and the statistical distribution of oxygen isotopes in the coordination sphere of TcO 4 - and makes it possible to quantify the composition of enriched water by measuring the relative intensities of the 99 Tc NMR signals of the Tc 16 O 4-n 18 O n - isotopologues. Because the oxygen exchange between TcO 4 - and enriched water in neutral and alkaline solutions is characterized by slow kinetics, gaseous HCl was bubbled through a solution for a few seconds to achieve the equilibrium distribution of oxygen isotopes in the Tc coordination sphere without distortion of the oxygen composition of the water. Pertechnetate ion was selected as a probe due to its high stability in solutions and the significant 99 Tc NMR shift induced by a single 16 O→ 18 O substitution (-0.43 ± 0.01 ppm) in TcO 4 - and spin coupling constant 1 J( 99 Tc- 17 O) (131.46 Hz) favourable for the observation of individual signals of Tc 16 O 4-n 18 O n - isotopologues. Copyright © 2017 John Wiley & Sons, Ltd.

Estimation of groundwater discharge and associated chemical fluxes into Poyang Lake, China: approaches using stable isotopes (δD and δ18O) and radon

NASA Astrophysics Data System (ADS)

Liao, Fu; Wang, Guangcai; Shi, Zheming; Cheng, Guoqiang; Kong, Qingmin; Mu, Wenqing; Guo, Liang

2018-05-01

Poyang Lake is the largest freshwater lake in China and is well known for its ecological and economic importance. Understanding the contribution of groundwater to Poyang Lake is important for the lake's protection and management. In this study, stable isotopes (δD and δ18O), 222Rn measurements, and corresponding models (222Rn and 18O mass balance models) were employed to evaluate the groundwater discharge and associated chemical inputs to Poyang Lake. The results showed that the distribution of δ18O in the lake water reflects the groundwater discharge into the lake. The groundwater discharge estimated using the 222Rn mass balance model was in reasonable agreement with the groundwater discharge derived from the 18O mass balance model. The 222Rn mass balance model showed that the groundwater discharge rate was 24.18 ± 6.85 mm/d with a groundwater discharge flux of (2.24 ± 0.63) × 107 m3/d, which accounts for 6.52-11.14% of river-water input in the Poyang Lake area. The groundwater discharge flux estimated using the 18O mass balance model was 3.17 × 107 m3/d, and the average groundwater discharge rate was 26.62 mm/d. The estimated groundwater discharge was used to estimate the associated chemical fluxes. It was found that groundwater-derived heavy metals such as iron and manganese are potential threats to the lake ecological system because of their large inputs from groundwater discharge.

Oxygen isotopes in nitrate: New reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration

USGS Publications Warehouse

Böhlke, J.K.; Mroczkowski, S.J.; Coplen, T.B.

2003-01-01

Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO3− in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying δ18O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope-ratio measurements: USGS34 (KNO3) with low δ18O and USGS35 (NaNO3) with high δ18O and ‘mass-independent’ δ17O. The procedure used to produce USGS34 involved equilibration of HNO3 with 18O-depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO3− reference materials with a range of δ18O values and normal (mass-dependent) 18O:17O:16O variation. Preliminary data indicate that the equilibrium O isotope-fractionation factor (α) between [NO3−] and H2O decreases with increasing temperature from 1.0215 at 22°C to 1.0131 at 100°C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high 17O:18O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO3− isotopic reference materials IAEA-N3 (=IAEA-NO-3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass-independent effects on N and O isotope-ratio measurements in a wide variety of environmental NO3− samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of ±0.2–0.3‰, 1σ): IAEA-N3 has δ18O = +25.6‰ and δ17O = +13.2‰; USGS32 has δ18O = +25.7‰; USGS34 has δ18O = −27.9‰ and δ17O = −14.8‰; and USGS35 has δ18O = +57.5‰ and δ17O = +51.5‰.

A precise method for the analysis of d18O of dissolved inorganic phosphate in seawater

USGS Publications Warehouse

McLaughlin, K.; Silva, S.; Kendall, C.; Stuart-Williams, Hilary; Paytan, A.

2004-01-01

A method for preparation and analysis of the oxygen isotope composition (d18O) of dissolved inorganic phosphate (DIP) has been developed and preliminary results for water samples from various locations are reported. Phosphate is extracted from seawater samples by coprecipitation with magnesium hydroxide. Phosphate is further purified through a series of precipitations and resin separation and is ultimately converted to silver phosphate. Silver phosphate samples are pyrolitically decomposed to carbon monoxide and analyzed for d18O. Silver phosphate samples weighing 0.7 mg (3.5 mol oxygen) can be analyzed routinely with an average standard deviation of about 0.3. There is no isotope fractionation during extraction and blanks are negligible within analytical error. Reproducibility was determined for both laboratory standards and natural samples by multiple analyses. A comparison between filtered and unfiltered natural seawater samples was also conducted and no appreciable difference was observed for the samples tested. The d18O values of DIP in seawater determined using this method range from 18.6 to 22.3, suggesting small but detectable natural variability in seawater. For the San Francisco Bay estuary DIP d18O is more variable, ranging from 11.4 near the San Joaquin River to 20.1 near the Golden Gate Bridge, and was well correlated with salinity, phosphate concentration, and d18O of water.

D and 18O enrichment measurements in biological fluids in a continuous-flow elemental analyser with an isotope-ratio mass spectrometer using two configurations.

PubMed

Ripoche, N; Ferchaud-Roucher, V; Krempf, M; Ritz, P

2006-09-01

In doubly labelled water studies, biological sample enrichments are mainly measured using off-line techniques (equilibration followed by dual-inlet introduction) or high-temperature elemental analysis (HT-EA), coupled with an isotope-ratio mass spectrometer (IRMS). Here another continuous-flow method, (CF-EA/IRMS), initially dedicated to water, is tested for plasma and urine analyses. The elemental analyser configuration is adapted for each stable isotope: chromium tube for deuterium reduction and glassy carbon reactor for 18O pyrolysis. Before on-line conversion of water into gas, each matrix is submitted to a short and easy treatment, which is the same for the analysis of the two isotopes. Plasma is passed through centrifugal filters. Urine is cleaned with black carbon and filtered (0.45 microm diameter). Tested between 150 and 300 ppm in these fluids, the D/H ratio response is linear with good repeatability (SD<0.2 ppm) and reproducibility (SD<0.5 ppm). For 18O/16O ratios (from 2000 to 2200 ppm), the same repeatability is obtained with a between-day precision lower than 1.4 ppm. The accuracy on biological samples is validated by comparison to classical dual-inlet methods: 18O analyses give more accurate results. The data show that enriched physiological fluids can be successfully analysed in CF-EA/IRMS. Copyright (c) 2006 John Wiley & Sons, Ltd.

Impact of convective activity on precipitation δ18O in isotope-enabled models

NASA Astrophysics Data System (ADS)

Hu, J.; Emile-Geay, J.; Dee, S.

2017-12-01

The ^18O signal preserved in paleo-archives (e.g. speleothem, tree ring cellulose, ice cores) is widely used to reconstruct precipitation or temperature. In the tropics, the inverse relationship between precipitation ^18O and rainfall amount, namely "amount effect" [Dansgaard, Tellus, 1964], is often used to interpret precipitation ^18O. However, recent studies have shown that precipitation ^18O is also influenced by precipitation type [Kurita et al, JGR, 2009; Moerman et al, EPSL, 2013], and recent observations indicate that it is negatively correlated with the fraction of precipitation associated with stratiform clouds [Aggarwal et al, Nature Geosci, 2016]. It is thus important to determine to what extent isotope-enabled climate models can reproduce these relationships. Here we do so using output from LMDZ, CAM2, and isoGSM from the Stable Water Isotope Intercomparison Group, Phase 2 (SWING2) project and results of SPEEDY-IER [Dee et al, JGR, 2015] from an AMIP-style experiment. The results show that these models simulate the "amount effect" well in the tropics, and the relationship between precipitation ^18O and precipitation is reversed in many places in mid-latitudes, in accordance with observations [Bowen, JGR, 2008]. Also, these models can all reproduce the negative correlation between monthly precipitation ^18O and stratiform precipitation proportion in mid-latitude (30°N-50°N; 50°S-30°S), but in the tropics (30°S-30°N), models show a positive correlation instead. The reason for this bias will be investigated within idealized experiments with SPEEDY-IER. The correct simulations of the impact of convective activity on precipitation ^18O in isotope-enabled models will improve our interpretation of paleoclimate proxies with respect to hydroclimate variability. P. K. Aggarwal et al. (2016), Nature Geosci., 9, 624-629, doi:10.1038/ngeo2739. G. J. Bowen. (2008), J. Geophys. Res., 113, D05113, doi:10.1029/2007JD009295. W. Dansgaard (1964), Tellus, 16(4), 436

Helium Catalyzed D-D Fusion in a Levitated Dipole

NASA Astrophysics Data System (ADS)

Kesner, J.; Bromberg, L.; Garnier, D. T.; Hansen, A.; Mauel, M. E.

2003-10-01

Fusion research has focused on the goal of deuterium and tritium (D-T) fusion power because the reaction rate is large compared with the other fusion fuels: D-D or D-He3. Furthermore, the D-D cycle is difficult in traditional confinement devices, such as tokamaks, because good energy confinement is accompanied by good particle confinement which leads to an accumulation of ash. Fusion reactors based on the D-D reaction would be advantageous to D-T based reactors since they do not require the breeding of tritium and can reduce the flux of energetic neutrons that cause material damage. We propose a fusion power source based on the levitated dipole fusion concept that uses a "helium catalyzed D-D" fuel cycle, where rapid circulation of plasma allows the removal of tritium and the re-injection of the He3 decay product, eliminating the need for a massive blanket and shield. Stable dipole confinement derives from plasma compressibility instead of the magnetic shear and average good curvature. As a result, a dipole magnetic field can stabilize plasma at high beta while allowing large-scale adiabatic particle circulation. These properties may make the levitated dipole uniquely capable of achieving good energy confinement with low particle confinement. We find that a dipole based D-D power source can provide better utilization of magnetic field energy with a comparable mass power density to a D-T based tokamak power source.

Mechanisms linking metabolism of Helicobacter pylori to 18O and 13C-isotopes of human breath CO2

PubMed Central

Som, Suman; De, Anulekha; Banik, Gourab Dutta; Maity, Abhijit; Ghosh, Chiranjit; Pal, Mithun; Daschakraborty, Sunil B.; Chaudhuri, Sujit; Jana, Subhra; Pradhan, Manik

2015-01-01

The gastric pathogen Helicobacter pylori utilize glucose during metabolism, but the underlying mechanisms linking to oxygen-18 (18O) and carbon-13 (13C)-isotopic fractionations of breath CO2 during glucose metabolism are poorly understood. Using the excretion dynamics of 18O/16O and 13C/12C-isotope ratios of breath CO2, we found that individuals with Helicobacter pylori infections exhibited significantly higher isotopic enrichments of 18O in breath CO2 during the 2h-glucose metabolism regardless of the isotopic nature of the substrate, while no significant enrichments of 18O in breath CO2 were manifested in individuals without the infections. In contrast, the 13C-isotopic enrichments of breath CO2 were significantly higher in individuals with Helicobacter pylori compared to individuals without infections in response to 13C-enriched glucose uptake, whereas a distinguishable change of breath 13C/12C-isotope ratios was also evident when Helicobacter pylori utilize natural glucose. Moreover, monitoring the 18O and 13C-isotopic exchange in breath CO2 successfully diagnosed the eradications of Helicobacter pylori infections following a standard therapy. Our findings suggest that breath 12C18O16O and 13C16O16O can be used as potential molecular biomarkers to distinctively track the pathogenesis of Helicobacter pylori and also for eradication purposes and thus may open new perspectives into the pathogen’s physiology along with isotope-specific non-invasive diagnosis of the infection. PMID:26039789

Isotopically (δ13C and δ18O) heavy volcanic plumes from Central Andean volcanoes: a field study

NASA Astrophysics Data System (ADS)

Schipper, C. Ian; Moussallam, Yves; Curtis, Aaron; Peters, Nial; Barnie, Talfan; Bani, Philipson; Jost, H. J.; Hamilton, Doug; Aiuppa, Alessandro; Tamburello, Giancarlo; Giudice, Gaetano

2017-08-01

Stable isotopes of carbon and oxygen in volcanic gases are key tracers of volatile transfer between Earth's interior and atmosphere. Although important, these data are available for few volcanoes because they have traditionally been difficult to obtain and are usually measured on gas samples collected from fumaroles. We present new field measurements of bulk plume composition and stable isotopes (δ13CCO2 and δ18OH2O+CO2) carried out at three northern Chilean volcanoes using MultiGAS and isotope ratio infrared spectroscopy. Carbon and oxygen in magmatic gas plumes of Lastarria and Isluga volcanoes have δ13C in CO2 of +0.76‰ to +0.77‰ (VPDB), similar to slab carbonate; and δ18O in the H2O + CO2 system ranging from +12.2‰ to +20.7‰ (VSMOW), suggesting significant contributions from altered slab pore water and carbonate. The hydrothermal plume at Tacora has lower δ13CCO2 of -3.2‰ and δ18OH2O+CO2 of +7.0‰, reflecting various scrubbing, kinetic fractionation, and contamination processes. We show the isotopic characterization of volcanic gases in the field to be a practical complement to traditional sampling methods, with the potential to remove sampling bias that is a risk when only a few samples from accessible fumaroles are used to characterize a given volcano's volatile output. Our results indicate that there is a previously unrecognized, relatively heavy isotopic signature to bulk volcanic gas plumes in the Central Andes, which can be attributed to a strong influence from components of the subducting slab, but may also reflect some local crustal contamination. The techniques we describe open new avenues for quantifying the roles that subduction zones and arc volcanoes play in the global carbon cycle.

Environmental isotopes (18O, 2H, and 87Sr/86Sr) as a tool in groundwater investigations in the Keta Basin, Ghana

NASA Astrophysics Data System (ADS)

Jørgensen, Niels; Banoeng-Yakubo, Bruce

2001-03-01

Analyses of environmental isotopes (18O, 2H, and 87Sr/86Sr) are applied to groundwater studies with emphasis on saline groundwater in aquifers in the Keta Basin, Ghana. The 87Sr/86Sr ratios of groundwater and surface water of the Keta Basin primarily reflect the geology and the mineralogical composition of the formations in the catchments and recharge areas. The isotopic compositions of 18O and 2H of deep groundwater have small variations and plot close to the global meteoric water line. Shallow groundwater and surface water have considerably larger variations in isotopic compositions, which reflect evaporation and preservation of seasonal fluctuations. A significant excess of chloride in shallow groundwater in comparison to the calculated evaporation loss is the result of a combination of evaporation and marine sources. Groundwaters from deep wells and dug wells in near-coastal aquifers are characterized by relatively high chloride contents, and the significance of marine influence is evidenced by well-defined mixing lines for strontium isotopes, and hydrogen and oxygen stable isotopes, with isotopic compositions of seawater as one end member. The results derived from environmental isotopes in this study demonstrate that a multi-isotope approach is a useful tool to identify the origin and sources of saline groundwater. Résumé. L'analyse des isotopes du milieu (18O, 2H, et 87Sr/86Sr) a été mise en œuvre pour des études hydrogéologiques portant sur des eaux souterraines salées des aquifères du bassin de Keta (Ghana). Les rapports isotopiques 87Sr/86Sr de l'eau souterraine et de l'eau de surface du bassin de Keta reflètent principalement la géologie et la composition minéralogique des formations des bassins d'alimentation et des zones de recharge. Les compositions isotopiques en 18O et en 2H des eaux souterraines profondes présentent de faibles variations et se placent près de la droite des eaux météoriques mondiales. Les eaux des nappes peu profondes

Patterns of d18O in fish tissues in two Oregon Coast range streams

EPA Science Inventory

We are using stable isotopes of C, N, O and S (H planned) to study the ecology of coho salmon in streams of the Oregon Coast Range. As part of this work we have examined changes in d18O in coho salmon juveniles (from eggs to smolting) and sculpin (from 0.5 to 20 gm.). For fish...

A Method to Determine 18O Kinetic Isotope Effects in the Hydrolysis of Nucleotide Triphosphates

PubMed Central

Du, Xinlin; Ferguson, Kurt; Sprang, Stephen R.

2007-01-01

A method to determine 18O kinetic isotope effects (KIE) in the hydrolysis of GTP is described that is generally applicable to reactions involving other nucleotide triphosphates. Internal competition, wherein the substrate of the reaction is a mixture of 18O-labeled and unlabeled nucleotides, is employed and the change in relative abundance of the two species in the course of the reaction is used to calculate KIE. The nucleotide labeled with 18O at sites of mechanistic interest also contains 13C at all carbon positions, while the 16O-nucleotide is depleted of 13C. The relative abundance of the labeled and unlabeled substrates or products is reflected in the carbon isotope ratio (13C/12C) in GTP or GDP, which is determined by use of a liquid chromatography-coupled isotope ratio mass spectrometer (LC-coupled IRMS). The LC is coupled to the IRMS by an Isolink™ interface (ThermoFinnigan). Carbon isotope ratios can be determined with accuracy and precision greater than 0.04%, and are consistent over an order of magnitude in sample amount. KIE values for Ras/NF1333-catalyzed hydrolysis of [β18O3,13C]GTP were determined by change in the isotope ratio of GTP or GDP or the ratio of the isotope ratio of GDP to that of GTP. KIE values computed in the three ways agree within 0.1%, although the method using the ratio of isotope ratios of GDP and GTP gives superior precision (< 0.1%). A single KIE measurement can be conducted in 25 minutes with less than 5 μg nucleotide reaction product. PMID:17963711

Relation between D/H ratios and 18O /16O ratios in cellulose from linen and maize - Implications for paleoclimatology and for sindonology

NASA Astrophysics Data System (ADS)

DeNiro, Michael J.; Sternberg, Leonel D.; Marino, Bruno D.; Druzik, James R.

1988-09-01

The 18O /16O ratios of cellulose and the D/H ratios of cellulose nitrate were determined for linen, a textile produced from the fibers of the flax plant Linum usitatissimum, and for maize ( Zea mays) from a variety of geographic locations in Europe, the Middle East, and North and South America. The regression lines of δD values on δ 18O values had slopes of 5.4 and 5.8 for the two species. Statistical analysis of results reported in the only other study in which samples of a single species (the silver fir Abies pindrow) that grew under a variety of climatic conditions were analyzed yielded slopes of ~6 when δD values of cellulose nitrate were regressed on δ 18O values of cellulose. The occurrence of this previously unrecognized relationship in three species suggests it may obtain in other plants as well. Determining the basis for this relationship, which is not possible given current understanding of fractionation of the isotopes of oxygen and hydrogen by plants, should lead to increased understanding of how D/H and 18O /16O ratios in cellulose isolated from fossil plants are related to paleoclimates. The separation of most linen samples from Europe from those originating in the Middle East when δD values are plotted against δ 18O values suggests it may be possible to use the isotope ratios of cellulose prepared from the Shroud of Turin to resolve the controversy concerning its geographic origin.

Laser based water equilibration method for d18O determination of water samples

NASA Astrophysics Data System (ADS)

Mandic, Magda; Smajgl, Danijela; Stoebener, Nils

2017-04-01

Determination of d18O with water equilibration method using mass spectrometers equipped with equilibration unit or Gas Bench is known already for many years. Now, with development of laser spectrometers this extends methods and possibilities to apply different technologies in laboratory but also in the field. The Thermo Scientific™ Delta Ray™ Isotope Ratio Infrared Spectrometer (IRIS) analyzer with the Universal Reference Interface (URI) Connect and Teledyne Cetac ASX-7100 offers high precision and throughput of samples. It employs optical spectroscopy for continuous measurement of isotope ratio values and concentration of carbon dioxide in ambient air, and also for analysis of discrete samples from vials, syringes, bags, or other user-provided sample containers. Test measurements and conformation of precision and accuracy of method determination d18O in water samples were done in Thermo Fisher application laboratory with three lab standards, namely ANST, Ocean II and HBW. All laboratory standards were previously calibrated with international reference material VSMOW2 and SLAP2 to assure accuracy of the isotopic values of the water. With method that we present in this work achieved repeatability and accuracy are 0.16‰ and 0.71‰, respectively, which fulfill requirements of regulatory method for wine and must after equilibration with CO2.

Geology, Petrology and O and H isotope geochemistry of remarkably 18O depleted Paleoproterozoic rocks of the Belomorian Belt, Karelia, Russia, attributed to global glaciation 2.4 Ga

NASA Astrophysics Data System (ADS)

Bindeman, I. N.; Serebryakov, N. S.

2011-06-01

This paper deals with strongly 18O-depleted (down to - 27.3‰ VSMOW) 1.9Ga Paleoproterozoic mid-grade metamorphic rocks found in the Belomorian Belt of Karelia (E. Baltic Shield). The protolith of these rocks is attributed to have been altered by glacial meltwaters during the world's first 2.4-2.3 Ga Paleoproterozoic "Slushball" glaciation, when Karelia was located near equatorial latitudes. We describe in detail three and report seven new localities with unusually depleted 18O signatures that now span 220 km across the Belomorian Belt. Hydrogen isotope ratios measured in amphibole, biotite and staurolite also display remarkably low values of - 212 to - 235‰. Isotope mapping in the three best exposed localities has allowed us to identify the world's most 18O depleted rock, located at Khitostrov with a δ 18O value - 27‰. In Khitostrov samples, zircons have normal δ 18O detrital cores and low-δ 18O metamorphic rims. Mapping demonstrates that zones of δ 18O depletion occur in a concentric pattern 100-400 m in dimension, and each locality displays significant δ 18O and δD heterogeneity on a meter to centimeter scale, characteristic of meteoric-hydrothermal systems worldwide. The zone of maximum δ 18O depletions usually has the highest concentration of metamorphic corundum, rutile, and zircon and also display doubled concentrations of insoluble trace elements (Zr, Ti, Cr, HREE). These results are explained by elemental enrichment upon mass loss during hydrothermal dissolution in pH-neutral meteoric fluid. Remarkably low-δ 18O and δD values suggest that alteration could have only happened by glacial meltwaters in a subglacial rift zone. Many localities with δ 18O depletions occur inside metamorphozed 2.4 Ga gabbro-noritic intrusions, or near their contact with Belomorian gneisses, implying that the intrusions were driving meteoric hydrothermal systems during the known 2.4 Ga episode of Belomorian rifting. Given that the isotopically-depleted localities now

Oxygen-18 isotope of breath CO2 linking to erythrocytes carbonic anhydrase activity: a biomarker for pre-diabetes and type 2 diabetes

PubMed Central

Ghosh, Chiranjit; Banik, Gourab D.; Maity, Abhijit; Som, Suman; Chakraborty, Arpita; Selvan, Chitra; Ghosh, Shibendu; Chowdhury, Subhankar; Pradhan, Manik

2015-01-01

Carbonic anhydrase (CA), a well-characterized metalloenzyme, is associated with oxygen-18 ( 18O)-isotopic fractionations of CO2. To investigate how CA activity links the 18O of breath CO2 to pre-diabetes (PD) and type 2 diabetes (T2D) during metabolism, we studied pre- and post-dose CA activities in erythrocytes with simultaneous monitoring of 18O/ 16O-isotope ratios of breath CO2 and thereafter elucidated potential metabolic pathways underlying CA alteration in the pathogenesis of T2D. Here we show that the post-dose CA activity in both T2D and PD was markedly enhanced, whereas the non-diabetic controls (NDC) exhibited a considerable reduction in post-dose CA activity when compared with their basal CA activities. However, T2D and PD exhibited isotopic enrichments of 18O in breath CO2, while a marked depletion of 18O in CO2 was manifested in NDC. Thus, the isotopic enrichments and depletions of 18O in breath CO2 were well correlated with the changes in CA activities for controls, PD and T2D. Our findings suggest the changes in CA activities in erythrocytes may contribute to the pathogenesis of T2D and the breath C 18O 16O regulated by the CA activity as a potential biomarker for non-invasive assessment of T2D, and thus may open a new method for treating T2D. PMID:25633556

Reconstructing relative humidity from plant δ18O and δD as deuterium deviations from the global meteoric water line.

EPA Science Inventory

Cellulose δ18O and δD in preserved plant material can provide insights on climates and hydrological cycling in the distant past. However, most studies of plant cellulose have used only one isotope, most commonly δ18O, resulting in difficulties partitioning variation between chang...

Oxygen isotope effects of enzyme-catalyzed organophosphorus hydrolysis reactions: implications for interpretation of dissolved PO4 δ18O values in natural waters

NASA Astrophysics Data System (ADS)

Liang, Y.; Blake, R. E.

2002-12-01

The geochemical cycling of P in Earth surface environments is controlled largely by biota. It has been recently demonstrated that intracellular cycling of P in microbial cultures and biological turnover of P in natural waters leads to temperature-dependent O isotope equilibrium between dissolved inorganic PO4 (Pi) and ambient water, and that the δ18O of Pi can be a useful tracer of biological reactions and P cycling in aquatic systems/sediments. Oxygen isotope exchange between Pi and water during biological turnover of P is catalyzed by enzymes at low-temperature. Phosphoenzymes play a crucial role in the intracellular functions of all living organisms and also have important extracellular functions in aquatic ecosystems such as regeneration of Pi from organophosphorus compounds (e.g., phosphoesters). Laboratory experiments indicate that extracellular enzyme reactions may result in incomplete Pi turnover and non-equilibrium Pi-water O isotope exchange. Determination of the O isotope effects of phosphoenzyme-catalyzed reactions is fundamental to the understanding of mechanisms of PO4-water O isotope exchange, pathways of biogeochemical P cycling, and interpretation of PO4 δ18O values from natural systems. Here we report on the O isotope fractionation between enzymatically-released Pi and water, in cell-free abiotic systems. Alkaline phosphatase (Apase) is a non-specific phosphohydrolase commonly found in fresh and marine coastal waters that catalyzes the hydrolysis of Pi from phosphomonoesters. We examined the O isotope effects of Apase derived from both microbial and eukaryotic sources and acting on different phosphomonoester substrates (e.g., α-D-Glucose 1-Phosphate, β-Glycerophosphate, AMP) in 18O-labeled waters. Oxygen isotope ratios of Pi released by Apase indicate that only 1 of the 4 O atoms in PO4 is incorporated from water with little or no apparent O isotopic fractionation at the site of incorporation. This observation is consistent with

The {sup 18}O(d,p){sup 19}O reaction and the ANC method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burjan, V.; Hons, Z.; Kroha, V.

2014-05-09

The neutron capture rate {sup 18}O(n,γ){sup 19}O is important for analysis of nucleosynthesis in inhomogeneous Big Bang models and also for models of processes in massive red giant stars and AGB stars. Angular distributions of the {sup 18}O(d,p){sup 19}O reaction were measured at a deuteron energy of 16.3 MeV in NPI in Řež, Czech Republic, with the aim to determine Asymptotic Normalization Coefficients which can then be used for indirect determination of the direct contribution to the {sup 18}O(n,γ){sup 19}O process. In the experiment, the gas target with {sup 18}O isotope of high purity 99.9 % was used thus eliminatingmore » any contaminating reactions. Reaction products were measured by the set of 8 ΔE-E telescopes consisting of thin and thick silicon surface-barrier detectors. Angular distributions of proton transfers corresponding to 6 levels of {sup 19}O up to the 4.1093 MeV excitation energy were determined. The analysis of angular distributions in the angular range from 6 to 64 degree including also the angular distribution of elastically scattered deuterons was carried out by means of ECIS and DWUCK codes. From the determined ANCs the direct contribution to the radiative capture {sup 18}O(n,γ){sup 19}O was deduced and compared with existing direct measurements.« less

Combined 34S, 33S and 18O isotope fractionations record different intracellular steps of microbial sulfate reduction

NASA Astrophysics Data System (ADS)

Antler, Gilad; Turchyn, Alexandra V.; Ono, Shuhei; Sivan, Orit; Bosak, Tanja

2017-04-01

Several enzymatic steps in microbial sulfate reduction (MSR) fractionate the isotope ratios of 33S/32S, 34S/32S and 18O/16O in extracellular sulfate, but the effects of different intracellular processes on the isotopic composition of residual sulfate are still not well quantified. We measured combined multiple sulfur (33S/32S, 34S/32S) and oxygen (18O/16O) isotope ratios of sulfate in pure cultures of a marine sulfate reducing bacterium Desulfovibrio sp. DMSS-1 grown on different organic substrates. These measurements are consistent with the previously reported correlations of oxygen and sulfur isotope fractionations with the cell-specific rate of MSR: faster reduction rates produced smaller isotopic fractionations for all isotopes. Combined isotope fractionation of oxygen and multiple sulfur isotopes are also consistent with the relationship between the rate limiting step during microbial sulfate reduction and the availability of the DsrC subunit. These experiments help reconstruct and interpret processes that operate in natural pore waters characterized by high 18O/16O and moderate 34S/32S ratios and suggest that some multiple isotope signals in the environment cannot be explained by microbial sulfate reduction alone. Instead, these signals support the presence of active, but slow sulfate reduction as well as the reoxidation of sulfide.

Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico.

PubMed

Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

2013-12-01

[1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings ( δ 18 O tr ). Interannual variation in δ 18 O tr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ 13 C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ 18 O tr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18 O-depleted rain in the region and seem to have affected the δ 18 O tr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ 18 O tr of M . acantholoba can be used as a proxy for source water δ 18 O and that interannual variation in δ 18 O prec is caused by a regional amount effect. This contrasts with δ 18 O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in

MnO2 nanosheet mediated "DD-A" FRET binary probes for sensitive detection of intracellular mRNA.

PubMed

Ou, Min; Huang, Jin; Yang, Xiaohai; Quan, Ke; Yang, Yanjing; Xie, Nuli; Wang, Kemin

2017-01-01

The donor donor-acceptor (DD-A) FRET model has proven to have a higher FRET efficiency than donor-acceptor acceptor (D-AA), donor-acceptor (D-A), and donor donor-acceptor acceptor (DD-AA) FRET models. The in-tube and in-cell experiments clearly demonstrate that the "DD-A" FRET binary probes can indeed increase the FRET efficiency and provide higher imaging contrast, which is about one order of magnitude higher than the ordinary "D-A" model. Furthermore, MnO 2 nanosheets were employed to deliver these probes into living cells for intracellular TK1 mRNA detection because they can adsorb ssDNA probes, penetrate across the cell membrane and be reduced to Mn 2+ ions by intracellular GSH. The results indicated that the MnO 2 nanosheet mediated "DD-A" FRET binary probes are capable of sensitive and selective sensing gene expression and chemical-stimuli changes in gene expression levels in cancer cells. We believe that the MnO 2 nanosheet mediated "DD-A" FRET binary probes have the potential as a simple but powerful tool for basic research and clinical diagnosis.

The evolution of Phanerozoic seawater - Isotope paleothermometry finds consensus on Early Paleozoic warmth and constant seawater δ18O

NASA Astrophysics Data System (ADS)

Grossman, E. L.; Henkes, G. A.; Passey, B. H.; Shenton, B.; Yancey, T. E.; Perez-Huerta, A.

2015-12-01

Evolution of metazoan life is closely linked to the Phanerozoic evolution of ocean temperatures and chemistry. Oxygen isotopic evidence for early Phanerozoic paleotemperatures has been equivocal, with decreasing δ18O values with age being interpreted as warmer early oceans, decreasing seawater δ18O with age, or increasing diagenetic alteration in older samples. Here we compare an updated compilation of oxygen isotope data for carbonate and phosphate fossils and microfossils (Grossman, 2012, Geol. Time Scale, Elsevier, 195-220) with a compilation of new and existing clumped isotope data. Importantly, these data are curated based on sample preservation with special consideration given to screening techniques, and tectonic and burial history. Burial history is critical in the preservation of carbonate clumped isotope temperatures in particular, which can undergo reordering in the solid state. We use a model derived for reordering kinetics (Henkes et al., 2014, Geochim. Cosmochim. Acta 139:362-382) to screen clumped isotope data for the effects of solid-state burial alteration. With minor but significant exceptions (Late Cretaceous, Early Triassic), average δ18O values (4 m.y. window, 2 m.y. steps) for post-Devonian brachiopods, belemnites, and foraminifera, representing tropical-subtropical surface ocean conditions, yield average isotopic temperatures below 30°C (assuming a seawater δ18O value [ -1‰ VSMOW] of an "ice-free" world). In contrast, Ordovician to Devonian data show sustained temperatures of 35-40°C. Likewise, isotopic paleotemperatures from conodont apatite, known to be resistant to isotopic exchange, follow the same pattern. Clumped isotope data derived from Paleozoic brachiopod shells that experienced minimal burial (< 100 °C) and <1% reordering according to the taxon-specific clumped isotope reordering model yield typical temperatures of 25-30°C for the Carboniferous, and 35-40°C for the Ordovician-Silurian. Inserting clumped temperatures and

Future stable water isotope projection with an isotope-AGCM driven by CMIP5 SSTs

NASA Astrophysics Data System (ADS)

Yoshimura, K.

2016-12-01

Stable water isotope ratios (dD and d18O) are widely used as proxy of past climate changes, and it is extremely important to understand and predict the mechanism of current isotopic spatio-temporal behavior with regard to the on-going climate change. However, as compared many studies on reproduction of isotopes for the past, there are few studies on future projection of isotopes. Therefore, in this study, a set of experiments using an isotope-incorporate AGCM (IsoGSM) with SST and sea ice field simulated from multiple CMIP5 models, namely MIROC5, CCSM4, and MRI-CGCM3, were conducted for the end of 20th century (1980-1990) and the end of 21st century (2080-2090) under RCP2.6 and RCP8.5 scenarios. Thus the responses in stable water isotope ratio in precipitation and water vapor in accordance to the global warming were investigated. As results, the changes in global surface air temperature were about +1K and +3K with RCP2.6 and RCP8.5, respectively. Similarly, the global precipitation changes were about +0.07mm/day (about +2%) and +0.18mm/day (about +5%), and the global precipitable water changes were about +2mm (+7%) and +6mm (+24%), respectively. The moisture was increased in accordance to the Clausius-Clapayron theory (7%/K), but the increase in precipitation is not that large. This indicates that the global hydrological cycle was slowed down in the globally warmed experiments. On the other hand, for the isotopic signals, the changes in globally averaged d18O in precipitation were about 0.2‰ and 0.4‰, and those in precipitable water were 0.2‰ and 0.5‰, in RCP2.6 and RCP8.5, respectively. It is well-known that there are temperature effect (positive correlation in air temperature and precipitation isotopes) and amount effect (negative correlation in precipitation amount and isotopes), but in the globally warmed world, these effects were offset, and only weaker temperature effect was appeared in the global mean isotope signals. Regional details will be shown

Should Variations of d2H, d18O and d17O in Precipitation be Considered 'Settled Science' or a 'New Frontier' For Understanding Cloud Dynamics and Microphysics?

NASA Astrophysics Data System (ADS)

Aggarwal, P. K.; araguas Araguas, L.; Belachew, D.; Terzer, S.; Wassenaar, L. I.; Longstaffe, F. J.; Schumacher, C.; Funk, A. B.; Steinacker, R.; Kaltenboeck, R.

2017-12-01

After more than 60 years of isotope measurements in precipitation, there are relatively well established patterns of variation, but their origin and controlling parameters remain a matter of debate, preventing a fuller integration of isotope-based information in meteorology. The prevailing hypothesis based on temperature and Rayleigh distillation has been successful in explaining many of the patterns, particularly at a seasonal or annual scale, and attempts to explain variances by 'tweaking' the prevailing hypothesis suggest that the underlying science may be considered to be 'settled'. A rigorous evaluation at the storm event scale, where precipitation acquires its isotope composition, however, does not provide a satisfactory explanation in most cases. We have conducted an year-long study with high-frequency sampling (5-15 min) of mid-latitude precipitation at Vienna and more than 1000 samples have been analyzed for d2H, d18O and d17O. We have also collected profiles of reflectivity and doppler velocity using a vertically pointed micro-rain radar, particle size distribution in precipitation using a disdrometer, and conducted aerological analysis of air and moisture circulation using sounding data. A combined evaluation of isotope and meteorological data provides a detailed understanding of isotope variability. We will discuss these results and the light they shed on boundary layer and tropospheric moisture circulation in frontal or convective precipitation, the relative roles of vapor deposition and riming growth of precipitation, and the origin of d-excess. The agreement between meteorological observations and isotopic variability is extremely promising and may help open a new frontier in the use of isotopes for weather and climate studies.

The oxygen isotope composition of Karoo and Etendeka picrites: High δ18O mantle or crustal contamination?

NASA Astrophysics Data System (ADS)

Harris, Chris; le Roux, Petrus; Cochrane, Ryan; Martin, Laure; Duncan, Andrew R.; Marsh, Julian S.; le Roex, Anton P.; Class, Cornelia

2015-07-01

Oxygen isotope compositions of Karoo and Etendeka large igneous province (LIP) picrites and picrite basalts are presented to constrain the effects of crustal contamination versus mantle source variation. Olivine and orthopyroxene phenocrysts from lavas and dykes (Mg# 64-80) from the Tuli and Mwenezi (Nuanetsi) regions of the ca 180 Ma Karoo LIP have δ18O values that range from 6.0 to 6.7 ‰. They appear to have crystallized from magmas having δ18O values about 1-1.5 ‰ higher than expected in an entirely mantle-derived magma. Olivines from picrite and picrite basalt dykes from the ca 135 Ma Etendeka LIP of Namibia and Karoo-age picrite dykes from Dronning Maud Land, Antarctica, do not have such elevated δ18O values. A range of δ18O values from 4.9 to 6.0 ‰, and good correlations between δ18O value and Sr, Nd and Pb isotope ratios for the Etendeka picrites are consistent with previously proposed models of crustal contamination. Explanations for the high δ18O values in Tuli/Mwenezi picrites are limited to (1) alteration, (2) crustal contamination, and (3) derivation from mantle with an abnormally high δ18O. Previously, a variety of models that range from crustal contamination to derivation from the `enriched' mantle lithosphere have been suggested to explain high concentrations of incompatible elements such as K, and average ɛNd and ɛSr values of -8 and +16 in Mwenezi (Nuanetsi) picrites. However, the primitive character of the magmas (Mg# 73), combined with the lack of correlation between δ18O values and radiogenic isotopic compositions, MgO content, or Mg# is inconsistent with crustal contamination. Thus, an 18O-enriched mantle source having high incompatible trace element concentration and enriched radiogenic isotope composition is indicated. High δ18O values are accompanied by negative Nb and Ta anomalies, consistent with the involvement of the mantle lithosphere, whereas the high δ18O themselves are consistent with an eclogitic source. Magma δ18

δ 18O(PO 43-) and δ 18O(CO 32-) from belemnite guards from Eastern Europe: implications for palaeoceanographic reconstructions and for the preservation of pristine isotopic values

NASA Astrophysics Data System (ADS)

Longinelli, Antonio; Wierzbowski, Hubert; Di Matteo, Antonella

2003-04-01

. Two different hypotheses are suggested to explain these results, other hypotheses being rejected as unreliable. (1) Phosphate derived from the decaying organic matter of belemnites might have been introduced into belemnite rostra by early diagenetic fluids. If the phosphate of belemnite organic matter was isotopically heavy as happens nowadays in the flesh of molluscs, the inflow of this phosphate into the rostra could be responsible for the very positive δ 18O values shown by many belemnite rostra (this hypothesis is suggested by H.W.); (2) previous oxygen isotope measurements on Upper Cretaceous belemnites yielded δ 18O values very close to the most positive values obtained from Lower Tertiary pelecypods and fish teeth which are known to precipitate their phosphate under isotopic equilibrium conditions with seawater. These data suggest the possibility that the phosphate in belemnite rostra is primary phosphate so that the very positive data reported here can be considered the result of good preservation of the pristine isotopic composition of primary phosphate. Consequently, the only way to explain the very positive δ 18O values is to consider the oxygen isotopic composition of Jurassic ocean water to be more positive than nowadays by at least 3‰. This hypothesis is suggested by A.L. and A.D.M.

D-dimers (DD) in CVST.

PubMed

Wang, Hui Fang; Pu, Chuan Qiang; Yin, Xi; Tian, Cheng Lin; Chen, Ting; Guo, Jun Hong; Shi, Qiang

2017-06-01

We were interested in further confirming whether D-dimers (DD) are indeed elevated in cerebral venous sinus thrombosis (CVST) as reported in those studies. CVST patients who had a plasma D-dimer test (139 cases) were included and divided into two groups: elevated D-dimer group (EDG) (>0.5 μg/mL; 65 cases) and normal D-dimer group (NDG) (≤0.5 μg/mL; 74 cases). The two groups were compared in terms of demographic data, clinical manifestation, laboratory and imaging data, using inferential statistical methods. The chi-squared and Fisher exact test showed that, compared to the NDG (74 cases), patients with elevated D-dimer levels were more likely to have a shorter symptom duration (SD) (30 ± 83.9 versus 90 ± 58.9 d, p = 0.003), more risk factors (75.4% versus 52.7%, p = 0.006), higher multiple venous sinus involvement (75.4% versus 59.5%, p = 0.037), increased fibrinogen (43.1% versus 18.9%, p = 0.037) and higher levels of blood glucose (18.3% versus 11%, p = 0.037). According to correlation analyses, D-dimer levels were positively correlated with number of venous sinuses involvement (NVS) (r = 0.321, p = 0.009) in the EDG. Multivariate logistic regression analysis showed that SD (OR, 0.025; 95% CI, 1.324-6.043; p = 0.000), NVS (OR, 1.573; 95% CI, 1.15-2.151; p = 0.005) and risk factors (OR, 3.321; 95% CI, 1.451-7.564; p = 0.004) were significantly different between the two groups. D-dimer is elevated in patients with acute/subacute CVST.

A Novel Method for Relative Quantitation of N-Glycans by Isotopic Labeling Using 18O-Water

PubMed Central

Tao, Shujuan; Orlando, Ron

2014-01-01

Quantitation is an essential aspect of comprehensive glycomics study. Here, a novel isotopic-labeling method is described for N-glycan quantitation using 18O-water. The incorporation of the 18O-labeling into the reducing end of N-glycans is simply and efficiently achieved during peptide-N4-(N-acetyl-β-glucosaminyl) asparagine amidase F release. This process provides a 2-Da mass difference compared with the N-glycans released in 16O-water. A mathematical calculation method was also developed to determine the 18O/16O ratios from isotopic peaks. Application of this method to several standard glycoprotein mixtures and human serum demonstrated that this method can facilitate the relative quantitation of N-glycans over a linear dynamic range of two orders, with high accuracy and reproducibility. PMID:25365792

Evaluation of Canisterized Foams and Evaluation of Radiation Hardened Foams for D&D Activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicholson, J. C.

The introduction of polyurethane foams has previously been examined elsewhere within the DOE complex with regards to decontamination and decommissioning (D&D) activities, though its use has been prohibited as a result of excessive heat generation and flammability concerns per the safety basis. Should these foams be found compatible with respect to the facility safety basis requirements, D&D work involving large void containing structures such as gloveboxes could be eased through the fixation of residual contamination after decontamination efforts have concluded. To this end, SRNL embarked on a characterization of commercial epoxy foams to identify the characteristics that would be mostmore » important to safety basis requirements. Through SRNL’s efforts, the performance of commercial two-part epoxy foams was evaluated for their foaming characteristics, temperature profiles, loading capability with high-Z (high density) additives, and applicability for shielding gamma emission from isotopes including; Am-241, Cs-137, and Co-60. It was found that these foams are capable of encapsulation of a desired volume, though the ideal and experimental expansion coefficients were found to differ. While heat is generated during the reaction, no samples generated heat above 70 °C. Of the down–selected materials, heating was on the order of 40 °C for the flexible foam and 60 °C for the rigid foam. Both were found to return to room temperature after 20 minutes regardless of the volume of foam cast. It was also found that the direct introduction of high-Z additives were capable of attenuating 98% of Am-241 gamma signal, 16% of Cs-137 signal, and 9.5% of Co-60 signal at 1:1 loading capacities of total liquid constituent weight to additive weight. These efforts are currently being reviewed for the ASTM January 2017 subcommittee discussions to address the lack of test methods and standards regarding these materials with respect to D&D environments.« less

A stratigraphic network across the Subtropical Front in the central South Atlantic: Multi-parameter correlation of magnetic susceptibility, density, X-ray fluorescence and @d^1^8O records [rapid communication

NASA Astrophysics Data System (ADS)

Hofmann, Daniela I.; Fabian, Karl; Schmieder, Frank; Donner, Barbara; Bleil, Ulrich

2005-12-01

Computer aided multi-parameter signal correlation is used to develop a common high-precision age model for eight gravity cores from the subtropical and subantarctic South Atlantic. Since correlations between all pairs of multi-parameter sequences are used, and correlation errors between core pairs ( A, B) and ( B, C) are controlled by comparison with ( A, C), the resulting age model is called a stratigraphic network. Precise inter-core correlation is achieved using high-resolution records of magnetic susceptibility κ, wet bulk density ρ and X-ray fluorescence scans of elemental composition. Additional δ18O records are available for two cores. The data indicate nearly undisturbed sediment series and the absence of significant hiatuses or turbidites. After establishing a high-precision common depth scale by synchronously correlating four densely measured parameters (Fe, Ca, κ, ρ), the final age model is obtained by simultaneously fitting the aligned δ18O and κ records of the stratigraphic network to orbitally tuned oxygen isotope [J. Imbrie, J. D. Hays, D. G. Martinson, A. McIntyre, A. C. Mix, J. J. Morley, N. G. Pisias, W. L. Prell, N. J. Shackleton, The orbital theory of Pleistocene climate: support from a revised chronology of the marine δ18O record, in: A. Berger, J. Imbrie, J. Hays, G. Kukla, B. Saltzman (Eds.), Milankovitch and Climate: Understanding the Response to Orbital Forcing, Reidel Publishing, Dordrecht, 1984, pp. 269-305; D. Martinson, N. Pisias, J. Hays, J. Imbrie, T. C. Moore Jr., N. Shackleton, Age dating and the orbital theory of the Ice Ages: development of a high-resolution 0 to 300.000-Year chronostratigraphy, Quat. Res. 27 (1987) 1-29.] or susceptibility stacks [T. von Dobeneck, F.Schmieder, Using rock magnetic proxy records for orbital tuning and extended time series analyses into the super-and sub-Milankovitch Bands, in: G. Fischer, G. Wefer (Eds.), Use of proxies in paleoceanography: Examples from the South Atlantic, Springer

[Clinical Values of Combined Detection of CRP and D-D for AL Patients Complicated with DIC].

PubMed

Ji, Xue-Hong

2015-12-01

To explore the clinical values of the combined detection of C-reactive protein (CRP) and D-dimer (D-D) for acute leukemia (AL) patients complicated with disseminated intravascular coagulation (DIC). Among 52 cases of AL, 20 cases of AL complicated with DIC were selected as AL+DIC group, 32 cases of AL were selected as AL group, 30 healthy volunteers were used as control group; the detected values of CRP and D-D in 3 groups were compared. The CRP and D-D levels in AL+DIC group were significantly higher than those in AL and control groups (P < 0.05); the CRP and D-D levels in AL group were significatly higher than those in control group (P < 0.05). The D-D level and complicated DIC rate in patients with CRP < 10 mg/L were significantly lower than those in patients with CRP 10-100 and >100 mg/L (P <0.05), while the D-D level and complicated DIC rate in patients with 10-100 mg/L were significantly lower than those in patients with CRP > 100 mg/L (P <0.05). After treatment of patients, the CRP and D-D levels in AL and AL+DIC groups were obviously reduced as compared with levels of these 2 groups before treatment (P <0.05); the CRP and D-D levels in AL+DIC after treatment were significantly higher than those in AL group (P <0.05). The combined detection of CRP and D-D possesses a higher reference value for diagnosis and differentiation of AL and AL complicated with DIC, thus also has an important role in evaluation of therapeutic efficacy of AL.

Identification of the geographical place of origin of an unidentified individual by multi-isotope analysis.

PubMed

Font, Laura; van der Peijl, Gerard; van Leuwen, Carina; van Wetten, Isis; Davies, Gareth R

2015-01-01

A multi-isotope investigation (Sr and Pb isotopes and δ18O, δ13C and δ15N) was applied to bone and teeth from an unidentified male found drowned in the"IJ" Ruyterkade in Amsterdam, The Netherlands in March of 1999. The individual remained unidentified until mid 2013, after the isotope study was completed. Coupled δ13C and δ15N values in bone collagen recovered from rib and femur are consistent with an omnivore living in a region where C3-type diet dominates (i.e. Europe). Integrated Sr and Pb isotopes and δ18O values in canine and third molar teeth and femur and rib bone data exclude extended residence in north-west Europe and particularly The Netherlands. Characteristic Pb isotope ratios coupled with inferred δ18O values of drinking water argue for a most probable place of origin for the unidentified individual in west and south Poland, south-east Slovakia and the region of Ukraine-Romania-Bulgaria, specifically the region associated with the Carpathian Mountains. Independent of the isotope study, the Cold Case Team made a positive identification with an individual from south-west Poland, validating the results of the multiple-isotopic approach. Copyright © 2014 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

Rapid Shifts in Oxygen and Hydrogen Isotopes, and Chemical Components in Pore Waters During mid-Oligocene in Sediments from IODP 351drilling

NASA Astrophysics Data System (ADS)

Zhang, Z.

2017-12-01

A total of 65 pore water samples were obtained from a sediment sequence in the Amami-Sankaku Basin during the IODP 351 Expedition, which consists of a 160 m thick section of terrestrial origin and underlying 1.3 km thick volcaniclastic section sampled at site U1438. Downcore variations of chemical compositions are characterized by increasing salinity/pH, increasing concentrations of Cl and Ca, and decreasing concentrations of Mg, K and Na, as well as decreasing d18O and dD. The rapid changes in those chemical components and isotopic composition occurred deeper than the lithology boundary between Unit III and Unit II, most likely as a result of substantial difference in extent of alteration above and below this boundary. The strong alterations of volcanicalstic minerals below the boundary not only result in diminishment of K, Mg, Si, and Mn, and an increase of Ca and Cl, but also depleted d18O in pore water. However, hydrogen fractionation factors between pore water and secondary minerals are less 1, and depleted dD values in pore water most likely reflect the signal of paleo-seawater. As a result, samples below the boundary are all plotted on the left side of the meteorite water line (MWL) on the dD vs. d18O plot. Above the boundary, they are placed to the right side of MWL due to substantially weakened alteration, reflecting an evolving trend in sediment setting from the predominance of alterated volcaniclasts to terrestrial pelagic sediments.

Isotopic (d18O/d2H) integrity of water samples collected and stored by automatic samplers

USDA-ARS?s Scientific Manuscript database

Stable water isotopes are increasingly becoming part of routine monitoring programs that utilize automatic samplers. The objectives of this study were to quantify the uncertainty in isotope signatures due to the length of sample storage (1-24 d) inside autosamplers over a range of air temperatures (...

Analysis of δ18O and δD values of environmental waters at high temporal and spatial resolution by continuous diffusion sampling cavity ring-down spectrometry

NASA Astrophysics Data System (ADS)

Munksgaard, Niels; Bass, Adrian; Wurster, Chris; Bird, Michael

2013-04-01

A novel sampling device utilises diffusion through porous PTFE tubing to deliver water vapour continuously from a liquid water source for analysis of δ18O and δD values by Cavity Ring-Down Spectrometry (CRDS). Comparison of isotopic data for a range of water samples analysed by Diffusion Sampling-CRDS (DS-CRDS) and Isotope Ratio Mass Spectrometry (IRMS) shows significant linear correlations between the two methods allowing for accurate standardisation of DS-CRDS data. The internal precision for an integration period of 3 min (standard deviation = 0.1 ‰ and 0.3 ‰ for δ18O and δD values, respectively) is similar to analysis of water by injection/evaporation CRDS of discrete water samples. The isotopic effects of variable air and water temperature, water vapour concentration and water pumping rate were found to be either negligible or correctable by analysis of water standards. Separation of the analysed water vapour from non-volatile dissolved and particulate contaminants in the liquid sample minimises interferences associated with CRDS analyses of many aqueous samples. Coupling of the DS-CRDS instrument to an auto sampler enables rapid analysis (10 min) of discrete water samples. The DS-CRDS system was used in the first continuous shipboard measurement of δ18O and δD of water. Combined with continuous salinity recordings, a data set of nearly 6,000 isotope measurements was made at 30-s intervals during a 3-day voyage through the Great Barrier Reef Lagoon. Precise identification of river plumes within the Great Barrier Reef Lagoon was possible because unique δ18O/δD-salinity relationships of individual plumes were measured at high spatial and temporal resolution. Continuous shipboard measurement of δ18O/δD values by DS-CRDS provides additional discriminatory power for assessing water mass formation processes and histories at a small fraction of the cost of traditional isotope analysis of discrete samples. In a second application of DS-CRDS, continuous

Identifying source and formation altitudes of nitrates in drinking water from Réunion Island, France, using a multi-isotopic approach.

PubMed

Rogers, Karyne M; Nicolini, Eric; Gauthier, Virginie

2012-09-01

Nitrate concentrations, water isotopes (δ(2)H and δ(18)O(water)) and associated nitrate isotopes (δ(15)N(nitrate) and δ(18)O(nitrate)) from 10 drinking water wells, 5 fresh water springs and the discharge from 3 wastewater treatment stations in Réunion Island, located in the Indian Ocean, were analysed. We used a multi isotopic approach to investigate the extent of nitrate contamination, nitrate formation altitude and source of nitrates in Réunion Island's principal aquifer. Water from these study sites contained between 0.1 and 85.3 mg/L nitrate. δ(15)N(nitrate) values between +6 and +14‰ suggested the main sources of contamination were animal and/or human waste, rather than inorganic (synthetic) fertilisers, infiltrating through the subsurface into the saturated zone, due to rainfall leaching of the unsaturated zone at various altitudes of precipitation. Based on δ(15)N(nitrate) values alone, it was not possible to distinguish between animal and human activities responsible for the contamination of each specific catchment. However, using a multi isotope approach (δ(18)O(water) and δ(15)N(nitrate)), it was possible to relate the average altitude of rainfall infiltration (δ(18)O(water)) associated with the nitrate contamination (δ(18)O(nitrate)). This relationship between land use, rainfall recharge altitude and isotopic composition (δ(15)N(nitrate) and δ(18)O(water)) discriminated between the influences of human waste at lower (below 600 m elevation) or animal derived contamination (at elevations between 600 and 1300 m). By further comparing the theoretical altitude of nitrate formation calculated by the δ(18)O(nitrate), it was possible to determine that only 5 out of 15 fresh water wells and springs followed the conservative nitrate formation mechanism of 2/3δ(18)O(water)+1/3δ(18)O(air), to give nitrate formation altitudes which corresponded to land use activities. Copyright © 2012 Elsevier B.V. All rights reserved.

Deuterium and oxygen-18 isotope effects on nucleophilic displacement by water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J.

1981-01-01

Kinetic deuterium isotope effects (k/sub H/sub 2/O//k/sub D/sub 2/O/) have been measured for nucleophilic attack by water at primary alkyl carbon (S-methylthiophenium ion (MeTh+), methyl trifluoromethane-sulfonate (MeOTf), methyl and ethyl perchlorate (MeOClO/sub 3/, EtOClO/sub 3/)) in aprotic solvents (acetonitrile (MeCN) and tetrahydrothiophene-1, 1-dioxide (TMSO/sub 2/; solfolane)) and L/sub 2/O. In L/sub 2/O solvent k/sub H/sub 2/O//k/sub D/sub 2/O/ is significantly greater than unity while it is reduced to near unity in aprotic solvents. The oxygen-18 isotope effect has also been observed to be 1.002 +- 0.004 for the reaction of MeTh/sup +/ with dilute H/sub 2/O in TMSO/sub 2/ atmore » 35/sup 0/C. For the reaction of MeTh/sup +/ and MeOClO/sub 3/ in aprotic solvents the chemical reaction kinetics are discussed.« less

The evolution of a calc-alkaline basic to silicic magma system: Geochemical and Rb-Sr, Sm-Nd, and 18O /16O isotopic evidence from the Late Hercynian Atesina-Cima d'Asta volcano-plutonic complex, northern Italy

NASA Astrophysics Data System (ADS)

Barth, Susanne; Oberli, Felix; Meier, Martin; Blattner, Peter; Bargossi, Giuseppe M.; Di Battistini, Gianfranco

1993-09-01

Geochemical and Sr-Nd-O isotopic data presented for basaltic andesitic to rhyolitic and for quartz noritic to monzogranitic rock suites from the Late Hercynian calc-alkaline Atesina volcanic complex (AVC) and the Cima d'Asta pluton (CAP), Southern Alps (northern Italy), provide information on both the primary magmatic processes and the effects of (mainly Triassic) hydrothermal overprint. Fluid infiltration led to mobilization of major and trace elements (K 2O, Na 2O, CaO, Rb, Sr, and Ba), opensystem behavior in total-rock Rb-Sr, and shift in δ18O to elevated values (total rock up to 16.6%. and volcanic matrix up to 17.8%.). Oxygen isotopic disequilibrium between quartz-feldspar pairs suggests water-rock interaction at medium/low temperatures. The δ18O values of quartz, the REE characterized by regular LREE enrichment/HREE depletion, and the Sm-Nd isotopic signatures, however, remained virtually unaffected by secondary processes. The initial ɛNd values (at 270 Ma) of the AVC and CAP magmatites are restricted to overlapping ranges of -3.6 to -6.5 and of -2.7 to -6.5, respectively, indicating significant crustal contribution; these values and associated T DM model ages of 1.1-1.6 Ga agree well with those of typical South Alpine lower crustal magmatites. The AVC and CAP rocks do not follow the "normal" trend of increasingly crustal Nd isotopic signatures with progressive degree of magma evolution expected for a single-stage AFC-type process, but instead display an inversion of this relationship. Geochemical and isotopic constraints favor a model of a large-scale MASH-type melting and mixing zone at or near the base of the continental crust. Distinct elemental enrichment/depletion and REE crossover patterns displayed by high-silica as compared to less silicic AVC rhyolites suggest subsequent magma evolution within a shallow-level compositionally zoned chamber.

Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico

NASA Astrophysics Data System (ADS)

Brienen, Roel J. W.; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

2013-12-01

Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes

Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico

PubMed Central

Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

2013-01-01

[1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes

Measurement of δ18O, δ17O, and 17O-excess in Water by Off-Axis Integrated Cavity Output Spectroscopy and Isotope Ratio Mass Spectrometry

PubMed Central

Berman, Elena S.F.; Levin, Naomi E.; Landais, Amaelle; Li, Shuning; Owano, Thomas

2013-01-01

Stable isotopes of water have long been used to improve understanding of the hydrological cycle, catchment hydrology, and polar climate. Recently, there has been increasing interest in measurement and use of the less-abundant 17O isotope in addition to 2H and 18O. Off-axis integrated cavity output spectroscopy (OA-ICOS) is demonstrated for accurate and precise measurements δ18O, δ17O, and 17O-excess in liquid water. OA-ICOS involves no sample conversion and has a small footprint, allowing measurements to be made by researchers collecting the samples. Repeated (514) high-throughput measurements of the international isotopic reference water standard GISP demonstrate the precision and accuracy of OA-ICOS: δ18OVSMOW-SLAP =−24.74 ± 0.07 ‰ (1σ) and δ17OVSMOW-SLAP = −13.12 ± 0.05 ‰ (1σ). For comparison, the IAEA value for δ18OVSMOW-SLAP is −24.76 ± 0.09 ‰ (1σ) and an average of previously reported values for δ17OVSMOW-SLAP is −13.12 ± 0.06 ‰ (1σ). Multiple (26) high-precision measurements of GISP provide a 17O-excessVSMOW-SLAP of 23 ± 10 per meg (1σ); an average of previously reported values for 17O-excessVSMOW-SLAP is 22 ± 11 per meg (1σ). For all these OA-ICOS measurements, precision can be further enhanced by additional averaging. OA-ICOS measurements were compared with two independent isotope ratio mass spectrometry (IRMS) laboratories and shown to have comparable accuracy and precision as the current fluorination-IRMS techniques in δ18O, δ17O, and 17O-excess. The ability to measure accurately δ18O, δ17O, and 17O-excess in liquid water inexpensively and without sample conversion is expected to increase vastly the application of δ17O and 17O-excess measurements for scientific understanding of the water cycle, atmospheric convection, and climate modeling among others. PMID:24032448

Application of stable isotope (δ13C and δ18O) composition of mollusc shells in palaeolimnological studies - possibilities and limitations

NASA Astrophysics Data System (ADS)

Apolinarska, Karina; Pełechaty, Mariusz; Kossler, Annette; Pronin, Eugeniusz; Noskowiak, Daria

2017-04-01

monospecific and composed of at least several shells. The number of shells being dependent on the difference between the minimum and maximum values within the sediment layer. The research was funded by the Polish Ministry of Science and Higher Education, Iuventus Plus Program, grant No. IP2010 000670. Apolinarska, K., 2013. Stable isotope compositions of recent Dreissena polymorpha (Pallas) shells: paleoenvironmental implications. Journal of Paleolimnology 50, 353-364. Apolinarska, K., Pełechaty, M. & Kossler, A., 2015a. Within-sample variability of δ13C and δ18O values of freshwater gastropod shells and the optimum number of shells to measure per sediment layer in the Paddenluch palaeolacustrine sequence, Germany. Journal of Paleolimnology 54, 305-323. Apolinarska, K., Pełechaty, M. & Noskowiak, D., 2015b. Differences in stable isotope compositions of freshwater snails from surface sediments of two Polish shallow lakes. Limnologica 53, 95-105. Apolinarska, K., Pełechaty, M. & Pronin, E., 2016. Discrepancies between the stable isotope compositions of water, macrophyte carbonates and organics, and mollusc shells in the littoral zone of a charophyte-dominated lake (Lake Lednica, Poland). Hydrobiologia 768, 1-17. Apolinarska, K. & Pełechaty, M., Inter- and intra-specific variability in δ13C and δ18O values of freshwater gastropod shells from Lake Lednica, western Poland. DOI: 10.1515/agp-2016-0028

13C-18O isotope signatures and ‘clumped isotope’ thermometry in foraminifera and coccoliths

NASA Astrophysics Data System (ADS)

Tripati, Aradhna K.; Eagle, Robert A.; Thiagarajan, Nivedita; Gagnon, Alexander C.; Bauch, Henning; Halloran, Paul R.; Eiler, John M.

2010-10-01

Accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes. Most proxies for temperature are not thermodynamically based, appear to be subject to biological processes, require regional calibrations, and/or are influenced by fluid composition. As a result, their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated. Independent proxies for past temperature could provide an important means of testing and/or expanding on existing reconstructions. Here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths, relate those abundances to independently estimated growth temperatures, and discuss the possible scope of equilibrium and kinetic isotope effects. The proportions of 13C- 18O bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonate-containing minerals (apatite from fish, reptile, and mammal teeth; calcitic brachiopods and molluscs; aragonitic coral and mollusks). Most species that exhibit non-equilibrium 18O/ 16O (δ 18O) and 13C/ 12C (δ 13C) ratios are characterized by 13C- 18O bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium, with possible exceptions among benthic foraminiferal samples from the Arctic Ocean where temperatures are near-freezing. Observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species.

Accurate experimental determination of the isotope effects on the triple point temperature of water. II. Combined dependence on the 18O and 17O abundances

NASA Astrophysics Data System (ADS)

Faghihi, V.; Kozicki, M.; Aerts-Bijma, A. T.; Jansen, H. G.; Spriensma, J. J.; Peruzzi, A.; Meijer, H. A. J.

2015-12-01

This paper is the second of two articles on the quantification of isotope effects on the triple point temperature of water. In this second article, we address the combined effects of 18O and 17O isotopes. We manufactured five triple point cells with waters with 18O and 17O abundances exceeding widely the natural abundance range while maintaining their natural 18O/17O relationship. The 2H isotopic abundance was kept close to that of VSMOW (Vienna Standard Mean Ocean Water). These cells realized triple point temperatures ranging between  -220 μK to 1420 μK with respect to the temperature realized by a triple point cell filled with VSMOW. Our experiment allowed us to determine an accurate and reliable value for the newly defined combined 18, 17O correction parameter of AO  =  630 μK with a combined uncertainty of 10 μK. To apply this correction, only the 18O abundance of the TPW needs to be known (and the water needs to be of natural origin). Using the results of our two articles, we recommend a correction equation along with the coefficient values for isotopic compositions differing from that of VSMOW and compare the effect of this new equation on a number of triple point cells from the literature and from our own institute. Using our correction equation, the uncertainty in the isotope correction for triple point cell waters used around the world will be  <1 μK.

Groundwater discharge and hydrologic partition of the lakes in desert environment: Insights from stable 18O/2H and radium isotopes

NASA Astrophysics Data System (ADS)

Luo, Xin; Jiao, Jiu Jimmy; Wang, Xu-sheng; Liu, Kun; Lian, Ergang; Yang, Shouye

2017-03-01

Studies of isotope characteristics of lake water in a desert can provide important information on groundwater discharge and hydrologic partition of the lakes in the desert. This paper presents the investigation of 18O and 2H stable isotopes and radiogenic radium of different water endmembers in three representative lakes of Badain-E, Badain-W and Sumujilin-S in the Badain Jaran Desert (BJD), the fourth largest desert in the world. A stable 18O and 2H isotopic buildup model is constructed to classify the hydrologic conditions of the desert lakes by estimating the ratio between groundwater discharge rate (Fin) and lake surface evaporation (E). Then the radium mass balance models are developed to quantify Fin. Based on the obtained Fin/E and Fin, Badain-E, Badain-W and Sumujilin-S are classified as flowing through, terminal and desiccating lakes, respectively, and their hydrologic partition is obtained. The groundwater discharge rate of Badain-E, Badain-W and Sumujilin-S, is estimated to be 8-10 mm d-1, 4-5 mm d-1, and 7-8 mm d-1, respectively. The total groundwater discharge to the lake areas in the BJD is about 1.68 × 105 m3 d-1. The flow-through condition explains the existence of the fresh lakes, while the terminal and desiccating conditions lead to the lake salinization over time. This study represents the first attempt to couple both stable and radium isotopic approaches to investigate the groundwater discharge and hydrologic partition of desert lakes in the BJD and is instructional to lake studies in other deserts in the world.

Disentangling the complexity of nitrous oxide cycling in coastal sediments: Results from a novel multi-isotope approach

NASA Astrophysics Data System (ADS)

Wankel, S. D.; Buchwald, C.; Charoenpong, C.; Ziebis, W.

2014-12-01

Although marine environments contribute approximately 30% of the global atmospheric nitrous oxide (N2O) flux, coastal systems appear to comprise a disproportionately large majority of the ocean-atmosphere flux. However, there exists a wide range of estimates and future projections of N2O production and emission are confounded by spatial and temporal variability of biological sources and sinks. As N2O is produced as an intermediate in both oxidative and reductive microbial processes and can also be consumed as an electron acceptor, a mechanistic understanding of the regulation of these pathways remains poorly understood. To improve our understanding of N2O dynamics in coastal sediments, we conducted a series of intact flow-through sediment core incubations (Sylt, Germany), while manipulating both the O2 and NO3- concentrations in the overlying water. Steady-state natural abundance isotope fluxes (δ15N and δ18O) of nitrate, nitrite, ammonium and nitrous oxide were monitored throughout the experiments. We also measured both the isotopomer composition (site preference (SP) of the 15N in N2O) as well as the Δ17O composition in experiments conducted with the addition of NO3- with an elevated Δ17O composition (19.5‰), which provide complementary information about the processes producing and consuming N2O. Results indicate positive N2O fluxes (to the water column) across all conditions and sediment types. Decreasing dissolved O2 to 30% saturation resulted in reduced N2O fluxes (5.9 ± 6.5 μmol m2 d-1) compared to controls (17.8 ± 6.5 μmol m-2 d-1), while the addition of 100 μM NO3- yielded higher N2O fluxes (49.0 ± 18.5 μmol m-2 d-1). In all NO3- addition experiments, the Δ17O signal from the NO3- was clearly observed in the N2O efflux implicating denitrification as a large source of N2O. However, Δ17O values were always lower (1.9 to 8.6‰) than the starting NO3- indicating an important role for nitrification-based N2O production and/or O isotope exchange

Ab initio study of nitrogen and position-specific oxygen kinetic isotope effects in the NO + O3 reaction

NASA Astrophysics Data System (ADS)

Walters, Wendell W.; Michalski, Greg

2016-12-01

Ab initio calculations have been carried out to investigate nitrogen (k15/k14) and position-specific oxygen (k17/k16O & k18/k16) kinetic isotope effects (KIEs) for the reaction between NO and O3 using CCSD(T)/6-31G(d) and CCSD(T)/6-311G(d) derived frequencies in the complete Bigeleisen equations. Isotopic enrichment factors are calculated to be -6.7‰, -1.3‰, -44.7‰, -14.1‰, and -0.3‰ at 298 K for the reactions involving the 15N16O, 14N18O, 18O16O16O, 16O18O16O, and 16O16O18O isotopologues relative to the 14N16O and 16O3 isotopologues, respectively (CCSD(T)/6-311G(d)). Using our oxygen position-specific KIEs, a kinetic model was constructed using Kintecus, which estimates the overall isotopic enrichment factors associated with unreacted O3 and the oxygen transferred to NO2 to be -19.6‰ and -22.8‰, respectively, (CCSD(T)/6-311G(d)) which tends to be in agreement with previously reported experimental data. While this result may be fortuitous, this agreement suggests that our model is capturing the most important features of the underlying physics of the KIE associated with this reaction (i.e., shifts in zero-point energies). The calculated KIEs will useful in future NOx isotopic modeling studies aimed at understanding the processes responsible for the observed tropospheric isotopic variations of NOx as well as for tropospheric nitrate.

Oxygen isotope effect in YBa2Cu3O7 prepared by burning YBa2Cu3 in 16O and 18O

NASA Astrophysics Data System (ADS)

Yvon, Pascal J.; Schwarz, R. B.; Pierce, C. B.; Bernardez, L.; Conners, A.; Meisenheimer, R.

1989-04-01

We prepared YBa2Cu3 powder by ball milling a 2:1 molar mixture of the intermetallics BaCu and CuY. We synthesized YBa2Cu3(16O)7-x and YBa2Cu3(18O)7-x by oxidizing the YBa2Cu3 powder in 16O and 18O. The 16O/18O ratios were determined by laser-ionization and sputtering-ionization mass spectroscopy. The YBa2Cu3(160)7-x sample had 99.8 at. %16O, and the YBa2Cu3(18O)7-x sample had 96.5 at. %18O. Susceptibility measurements of the superconducting transition temperature (Tc=91.7 K for 16O; half-point transition at 84 K show an isotope effect of 0.4+/-0.1 K.

Characterizing sources and natural attenuation of nitrate contamination in the Baix Ter aquifer system (NE Spain) using a multi-isotope approach.

PubMed

Puig, Roger; Soler, Albert; Widory, David; Mas-Pla, Josep; Domènech, Cristina; Otero, Neus

2017-02-15

Nitrate pollution is a widespread issue affecting global water resources with significant economic and health effects. Knowledge of both the corresponding pollution sources and of processes naturally attenuating them is thus of crucial importance in assessing water management policies and the impact of anthropogenic activities. In this study, an approach combining hydrodynamic, hydrochemical and multi-isotope systematics (8 isotopes) is used to characterize the sources of nitrate pollution and potential natural attenuation processes in a polluted basin of NE Spain. δ 2 H and δ 18 O isotopes were used to further characterize the sources of recharge of the aquifers. Results show that NO 3 - is not homogeneously distributed and presents a large range of concentrations, from no NO 3 - to up to 480mgL -1 . δ 15 N and δ 18 O of dissolved NO 3 - identified manure as the main source of nitrate, although sewage and mineral fertilizers can also be isotopically detected using boron isotopes (δ 11 B) and δ 34 S and δ 18 O of dissolved sulphate, respectively. The multi-isotope approach proved that natural denitrification is occurring, especially in near-river environments or in areas hydrologically related to fault zones. δ 34 S and δ 18 O indicated that denitrification is not driven by pyrite oxidation but rather by the oxidation of organic matter. This could not be confirmed by the study of δ 13 C HCO3 that was buffered by the entanglement of other processes and sources. Copyright © 2016 Elsevier B.V. All rights reserved.

Stable isotope time-series in mammalian teeth: In situ δ18O from the innermost enamel layer

NASA Astrophysics Data System (ADS)

Blumenthal, Scott A.; Cerling, Thure E.; Chritz, Kendra L.; Bromage, Timothy G.; Kozdon, Reinhard; Valley, John W.

2014-01-01

Stable carbon and oxygen isotope ratios in mammalian tooth enamel are commonly used to understand the diets and environments of modern and fossil animals. Isotope variation during the period of enamel formation can be recovered by intra-tooth microsampling along the direction of growth. However, conventional sampling of the enamel surface provides highly time-averaged records in part due to amelogenesis. We use backscattered electron imaging in the scanning electron microscope (BSE-SEM) to evaluate enamel mineralization in developing teeth from one rodent and two ungulates. Gray levels from BSE-SEM images suggest that the innermost enamel layer, <20 μm from the enamel-dentine junction, is highly mineralized early in enamel maturation and therefore may record a less attenuated isotopic signal than other layers. We sampled the right maxillary incisor from a woodrat subjected to an experimentally induced water-switch during the period of tooth development, and demonstrate that secondary ion mass spectrometry (SIMS) can be used to obtain δ18O values with 4-5-μm spots from mammalian tooth enamel. We also demonstrate that SIMS can be used to discretely sample the innermost enamel layer, which is too narrow for conventional microdrilling or laser ablation. An abrupt δ18O switch of 16.0‰ was captured in breath CO2, a proxy for body water, while a laser ablation enamel surface intra-tooth profile of the left incisor captured a δ18O range of 12.1‰. The innermost enamel profile captured a δ18O range of 15.7‰, which approaches the full magnitude of δ18O variation in the input signal. This approach will likely be most beneficial in taxa such as large mammalian herbivores, whose teeth are characterized by less rapid mineralization and therefore greater attenuation of the enamel isotope signal.

Medical Isotope Program: O-18, C-13, and Xe-129 Final Report CRADA No. TC-2043-02

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheibner, K. F.; Fought, J.

This was a collaborative effort between the University of California, Lawrence Livermore National Laboratory (LLNL) and Spectra Gases, Inc., to develop new and cheaper sources of Oxgyen-18 (O-18), Carbon-13 (C-13), and Xenon-129 (Xe-129), and to develop new applications of these stable medical isotopes in medicine resulting in a substantial increase in stable isotopes that are important to human health sciences.

Tracing ground-water movement by using the stable isotopes of oxygen and hydrogen, upper Penitencia Creek alluvial fan, Santa Clara Valley, California

USGS Publications Warehouse

Muir, K.S.; Coplen, Tyler B.

1981-01-01

Starting in 1965 the Santa Clara Valley Water District began importing about i00,000 acre-feet per year of northern California water. About one-half of this water was used to artificially recharge the Upper Penitencia Creek alluvial fan in Santa Clara Valley. In order to determine the relative amounts of local ground water and recharged imported water being pumped from the wells, stable isotopes of oxygen and hydrogen were used to trace the movement of the imported water in the alluvial fan. To trace the movement of imported water in the Upper Penitencia Creek alluvial fan, well samples were selected to give areal and depth coverage for the whole fan. The stable isotopes of oxygen-16, oxygen-18, and deuterium were measured in the water samples of imported water and from the wells and streams in the Santa Clara Valley. The d18oand dD compositions of the local runoff were about -6.00 o/oo (parts per thousand) and -40 o/oo, respectively; the average compositions for the local native ground-water samples were about -6.1 o/oo and -41 o/oo, respectively; and the average compositions of the imported water samples were -10.2 o/oo and -74 o/oo, respectively. (The oxygen isotopic composition of water samples is reported relative to Standard Mean Ocean Water, in parts per thousand.) The difference between local ground water and recharged imported water was about 4.1 o/oo in d18o and 33 o/oo in dL. The isotopic data indicate dilution of northern California water with local ground water in a downgradient direction. Two wells contain approximately 74 percent northern California water, six wells more than 50 percent. Data indicate that there may be a correlation between the percentage of northern California water and the depth or length of perforated intervals in wells.

Periodicity analysis of δ18O in precipitation over Central Europe: Time-frequency considerations of the isotopic 'temperature' effect

NASA Astrophysics Data System (ADS)

Salamalikis, V.; Argiriou, A. A.; Dotsika, E.

2016-03-01

In this paper the periodic patterns of the isotopic composition of precipitation (δ18O) for 22 stations located around Central Europe are investigated through sinusoidal models and wavelet analysis over a 23 years period (1980/01-2002/12). The seasonal distribution of δ18O follows the temporal variability of air temperature providing seasonal amplitudes ranging from 0.94‰ to 4.47‰; the monthly isotopic maximum is observed in July. The isotopic amplitude reflects the geographical dependencies of the isotopic composition of precipitation providing higher values when moving inland. In order to describe the dominant oscillation modes included in δ18O time series, the Morlet Continuous Wavelet Transform is evaluated. The main periodicity is represented at 12-months (annual periodicity) where the wavelet power is mainly concentrated. Stations (i.e. Cuxhaven, Trier, etc.) with limited seasonal isotopic effect provide sparse wavelet power areas at the annual periodicity mode explaining the fact that precipitation has a complex isotopic fingerprint that cannot be examined solely by the seasonality effect. Since temperature is the main contributor of the isotopic variability in mid-latitudes, the isotope-temperature effect is also investigated. The isotope-temperature slope ranges from 0.11‰/°C to 0.47‰/°C with steeper values observed at the southernmost stations of the study area. Bivariate wavelet analysis is applied in order to determine the correlation and the slope of the δ18O - temperature relationship over the time-frequency plane. High coherencies are detected at the annual periodicity mode. The time-frequency slope is calculated at the annual periodicity mode ranging from 0.45‰/°C to 0.83‰/°C with higher values at stations that show a more distinguishable seasonal isotopic behavior. Generally the slope fluctuates around a mean value but in certain cases (sites with low seasonal effect) abrupt slope changes are derived and the slope becomes

Evaluating the source of streamwater nitrate using d15N and d18O in nitrate in two watersheds in New Hampshire, USA

Treesearch

Linda H. Pardo; Carol Kendall; Jennifer Pett-Ridge; Cecily C.Y. Chang; Cecily C.Y. Chang

2004-01-01

The natural abundance of nitrogen and oxygen isotopes in nitrate can be a powerful tool for identifying the source of nitrate in streamwater in forested watersheds, because the two main sources of nitrate, atmospheric deposition and microbial nitrification, have distinct d18O values. Using a simple mixing model, we estimated the relative fractions in streamwater...

Decadal time scale variability recorded in the Quelccaya summit ice core δ18O isotopic ratio series and its relation with the sea surface temperature

NASA Astrophysics Data System (ADS)

Mélice, J. L.; Roucou, P.

The spectral characteristics of the δ18O isotopic ratio time series of the Quelccaya ice cap summit core are investigated with the multi taper method (MTM), the singular spectrum analysis (SSA) and the wavelet transform (WT) techniques for the 500 y long 1485-1984 period. The most significant (at the 99.8% level) cycle according to the MTM F-test has a period centered at 14.4 y while the largest variance explaining oscillation according to the SSA technique has a period centered at 12.9 y. The stability over time of these periods is investigated by performing evolutive MTM and SSA on the 500 y long δ18O series with a 100 y wide moving window. It is shown that the cycles with largest amplitude and that the oscillations with largest extracting variance have corresponding periods aggregated around 13.5 y that are very stable over the period between 1485 and 1984. The WT of the same isotopic time series reveals the existence of a main oscillation around 12 y which are also very stable in time. The relation between the isotopic data at Quelccaya and the annual sea surface temperature (SST) field anomalies is then evaluated for the overlapping 1919-1984 period. Significant global correlation and significant coherency at 12.1 y are found between the isotopic series and the annual global sea surface temperature (GSST) series. Moreover, the correlation between the low (over 8 y) frequency component of the isotopic time series and the annual SST field point out significant values in the tropical North Atlantic. This region is characterized by a main SST variability at 12.8 y. The Quelccaya δ18O isotopic ratio series may therefore be considered as a good recorder of the tropical North Atlantic SSTs. This may be explained by the following mechanism: the water vapor amount evaporated by the tropical North Atlantic is function of the SST. So is the water vapor δ18O isotopic ratio. This water vapor is advected during the rainy season by northeast winds and precipitates at the

A Two-year Record of Daily Rainfall Isotopes from Fiji: Implications for Reconstructing Precipitation from Speleothem δ18O

NASA Astrophysics Data System (ADS)

Brett, M.; Mattey, D.; Stephens, M.

2015-12-01

Oxygen isotopes in speleothem provide opportunities to construct precisely dated records of palaeoclimate variability, underpinned by an understanding of both the regional climate and local controls on isotopes in rainfall and groundwater. For tropical islands, a potential means to reconstruct past rainfall variability is to exploit the generally high correlation between rainfall amount and δ18O: the 'amount effect'. The GNIP program provides δ18O data at monthly resolution for several tropical Pacific islands but there are few data for precipitation isotopes at daily resolution, for investigating the amount effect over different timescales in a tropical maritime setting. Timescales are important since meteoric water feeding a speleothem has undergone storage and mixing in the aquifer system and understanding how the isotope amount effect is preserved in aquifer recharge has fundamental implications on the interpretation of speleothem δ18O in terms of palaeo-precipitation. The islands of Fiji host speleothem caves. Seasonal precipitation is related to the movement of the South Pacific Convergence Zone, and interannual variations in rainfall are coupled to ENSO behaviour. Individual rainfall events are stratiform or convective, with proximal moisture sources. We have daily resolution isotope data for rainfall collected at the University of the South Pacific in Suva, covering every rain event in 2012 and 2013. δ18O varies between -18‰ and +3‰ with the annual weighted averages at -7.6‰ and -6.8‰ respectively, while total recorded rainfall amount is similar in both years. We shall present analysis of our data compared with GNIP, meteorological data and back trajectory analyses to demonstrate the nature of the relationship between rainfall amount and isotopic signatures over this short timescale. Comparison with GNIP data for 2012-13 will shed light on the origin of the amount effect at monthly and seasonal timescales in convective, maritime, tropical

A multi-model-proxy comparison study to refine the climatic interpretations of a speleothem δ18O record

NASA Astrophysics Data System (ADS)

Jex, C.; Phipps, S. J.; Baker, A.; Bradley, C.; Scholz, D.

2012-12-01

Speleothem δ18O (δ18Ospel) is arguably one of the best proxies for understanding seasonal groundwater recharge dynamics on all timescales, and therefore for inferring past changes in regional hydroclimate. Statistical relationships between δ18Ospel and the amount of seasonally effective precipitation or its isotopic composition may be demonstrated at cave sites where there is a reliable seasonally distinct composition of δ18O of precipitation (δ18Opptn). This is often the case where recharge is driven by spring snow-melt, seasonal soil moisture excess, or in monsoonal regimes with distinct changes in moisture source. We suggest that there are also three main areas of uncertainty that need to be addressed with any individual record of δ18Ospel. Here we present the results of a multi-model-proxy comparison using a published record of δ18Ospel from Turkey that has grown over the last 500 years in order to quantify these three main areas of uncertainty. First, we assess the stability of previously observed relationships between local climate parameters and regional circulation dynamics over the last 1ka using the CSIRO Mk3L climate system model [Phipps et al., 2011] in order to estimate the variability of δ18Opptn that could be explained by internal climate variability alone. Second, we estimate the variability in δ18Odw that could be explained by storage and routing of water in the karst aquifer over the last 1 ka using the temperature and precipitation output of a three-member ensemble of transient simulations and synthetic δ18Opptn for this location, to drive the KarstFor karst systems model [Baker et al., 2012]. Finally, we estimate the variability in δ18Ospel that may be attributed to kinetic fractionation processes associated with non-equilibrium CaCO3 formation for this cave system [Scholz et al., 2009]. Baker, A., C. Bradley, S. J. Phipps, M. Fischer, I. J. Fairchild, L. Fuller, C. Spötl, and C. Azcurra (2012), Millennial-length forward models and

Temperature derivatives for fusion reactivity of D-D and D-T

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langenbrunner, James R.; Makaruk, Hanna Ewa

Deuterium-tritium (D-T) and deuterium-deuterium (D-D) fusion reaction rates are observable using leakage gamma flux. A direct measurement of γ-rays with equipment that exhibits fast temporal response could be used to infer temperature, if the detector signal is amenable for taking the logarithmic time-derivative, alpha. We consider the temperature dependence for fusion cross section reactivity.

Fluctuations in Tree Ring Cellulose d18O during the Little Ice Age Correlate with Solar Activity

NASA Astrophysics Data System (ADS)

Yamaguchi, Y. T.; Yokoyama, Y.; Miyahara, H.; Nakatsuka, T.

2008-12-01

The Maunder Minimum (AD1645-1715), when sunspots became exceedingly rare, is known to coincide with the coldest period during the Little Ice Age. This is a useful period to investigate possible linkage between solar activity and climate because variation in solar activity was different from that of today. The solar cycle length was longer (14 and 28 years) than that of today (11 and 22 years) hence any climate archives that have similar periodic changes could be separated from other internal climate forcing. We have reported that Greenland temperature variations coincided with decadal-scale variability in solar activity during the Maunder Minimum (Miyahara et al. 2008). Here we report interannual and intra-annual relative humidity (RH) variations in central Japan during that period, using tree ring cellulose d18O in a 382-year-old Japanese cedar tree (Cryptomeria japonica). The isotopic composition of tree rings can be a powerful tool to study the relationship between solar activity and climate, because we can directly compare solar activity (D14C) and climate (d18O) with little dating error. The climate proxy obtained using tree ring cellulose d18O is correlated both negatively and positively with RH and d18O in precipitation, respectively. Since d18O in precipitation is negatively correlated with the amount of precipitation in the monsoon area, tree ring cellulose d18O can be a reliable proxy for past RH and/or amount of precipitation in the area of the interest. Tree ring cellulose d18O of the cedar tree during AD1938-1998 in fact correlates significantly with the mean RH in June in central Japan. Tree ring d18O inferred RH variability during the Maunder Minimum shows distinct high RH spikes with an approximate 14-year quasiperiodicity. All nine solar minima during AD1640-1756 deduced from tree ring D14C coincided with high RH spikes, and seven of which coincided within 1-year. Interannual RH variations also coincided with Greenland temperature during this

Stable isotope analyses of oxygen (18O:17O:16O) and chlorine (37Cl:35Cl) in perchlorate: reference materials, calibrations, methods, and interferences

USGS Publications Warehouse

Böhlke, John Karl; Mroczkowski, Stanley J.; Sturchio, Neil C.; Heraty, Linnea J.; Richman, Kent W.; Sullivan, Donald B.; Griffith, Kris N.; Gu, Baohua; Hatzinger, Paul B.

2017-01-01

RationalePerchlorate (ClO4−) is a common trace constituent of water, soils, and plants; it has both natural and synthetic sources and is subject to biodegradation. The stable isotope ratios of Cl and O provide three independent quantities for ClO4− source attribution and natural attenuation studies: δ37Cl, δ18O, and δ17O (or Δ17O or 17Δ) values. Documented reference materials, calibration schemes, methods, and interferences will improve the reliability of such studies.MethodsThree large batches of KClO4 with contrasting isotopic compositions were synthesized and analyzed against VSMOW-SLAP, atmospheric O2, and international nitrate and chloride reference materials. Three analytical methods were tested for O isotopes: conversion of ClO4− to CO for continuous-flow IRMS (CO-CFIRMS), decomposition to O2 for dual-inlet IRMS (O2-DIIRMS), and decomposition to O2 with molecular-sieve trap (O2-DIIRMS+T). For Cl isotopes, KCl produced by thermal decomposition of KClO4 was reprecipitated as AgCl and converted into CH3Cl for DIIRMS.ResultsKClO4 isotopic reference materials (USGS37, USGS38, USGS39) represent a wide range of Cl and O isotopic compositions, including non-mass-dependent O isotopic variation. Isotopic fractionation and exchange can affect O isotope analyses of ClO4− depending on the decomposition method. Routine analyses can be adjusted for such effects by normalization, using reference materials prepared and analyzed as samples. Analytical errors caused by SO42−, NO3−, ReO42−, and C-bearing contaminants include isotope mixing and fractionation effects on CO and O2, plus direct interference from CO2 in the mass spectrometer. The results highlight the importance of effective purification of ClO4− from environmental samples.ConclusionsKClO4 reference materials are available for testing methods and calibrating isotopic data for ClO4− and other substances with widely varying Cl or O isotopic compositions. Current ClO4−extraction, purification

Radiation effect of neutrons produced by D-D side reactions on a D-3He fusion reactor

NASA Astrophysics Data System (ADS)

Bahmani, J.

2017-04-01

One of the most important characteristics in D-3He fusion reactors is neutron production via D-D side reactions. The neutrons can activate structural material, degrading them and ultimately converting them into high-level radioactive waste, while it is really costly and difficult to remove them. The neutrons from a fusion reactor could also be used to make weapons-grade nuclear material, rendering such types of fusion reactors a serious proliferation hazard. A related problem is the presence of radioactive elements such as tritium in D-3He plasma, either as fuel for or as products of the nuclear reactions; substantial quantities of radioactive elements would not only pose a general health risk, but tritium in particular would also be another proliferation hazard. The problems of neutron radiation and radioactive element production are especially interconnected because both would result from the D-D side reaction. Therefore, the presentation approach for reducing neutrons via D-D nuclear side reactions in a D-3He fusion reactor is very important. For doing this research, energy losses and neutron power fraction in D-3He fusion reactors are investigated. Calculations show neutrons produced by the D-D nuclear side reaction could be reduced by changing to a more 3He-rich fuel mixture, but then the bremsstrahlung power loss fraction would increase in the D-3He fusion reactor.

Late-Holocene hydroclimate and atmospheric circulation variability in southern Patagonia: insights from triple stable isotopes (δ18O, δ13C, δD) of peat bog Sphagnum moss

NASA Astrophysics Data System (ADS)

Xia, Z.; Yu, Z.; Zheng, Y.; Loisel, J.; Huang, Y.

2017-12-01

The Southern Hemisphere Westerly Winds (SHWWs) exert important influences on regional and global climates, but their long-term behaviors and dynamics are still poorly understood but critical for projecting future changes. Here we present a 5,500-year record from a Sphagnum-dominated peat bog located on the lee side of the Andes at 54.2 °S in southern Patagonia—based on plant macrofossils, Sphagnum cellulose δ18O and δ13C, and lipid δD data—to document and understand the variability in hydroclimate and atmospheric circulation. There is a striking negative correlation between cellulose δ18O and the Southern Annular Mode (SAM) index over the last millennium; particularly the 2.5‰ negative shift of δ18O is concurrent with the observed positive trend in the SAM over the recent decades. The interval of Medieval Climate Anomaly (MCA, 850-600 yr BP) is characterized by a 2.5‰ negative shift of δ18O and low δ13C values, while the Little Ice Age (LIA, 500-300 yr BP) is characterized by a 2.5‰ positive shift of δ18O and high δ13C values. Furthermore, we find the largest negative shift of δ18O ( 3‰) at 2,300 yr BP, suggesting a significantly positive shift in the SAM. We interpret high Sphagnum abundance and high cellulose δ13C values to reflect great moss moisture conditions, while cellulose δ18O variations primarily reflect moisture sources and atmospheric circulation. During the positive phase of SAM (e.g., the MCA and recent decades), strengthened SHWWs enhance the rain-shadow effect, resulting in dry climate and 18O-depleted precipitation (low δ18O values) in the study region. During the negative phase of SAM (e.g., the LIA), weakened SHWWs reduce rain-shadow effect, resulting in wet climate and high δ18O values caused by increases in moisture contributions from the southerly and easterly flows that do not experience strong Rayleigh distillation process during air mass transports. Furthermore, coupling cellulose δ18O and lipid δD enables

Active Neutron-Based Interrogation System with D-D Neutron Source for Detection of Special Nuclear Materials

NASA Astrophysics Data System (ADS)

Takahashi, Y.; Misawa, T.; Yagi, T.; Pyeon, C. H.; Kimura, M.; Masuda, K.; Ohgaki, H.

2015-10-01

The detection of special nuclear materials (SNM) is an important issue for nuclear security. The interrogation systems used in a sea port and an airport are developed in the world. The active neutron-based interrogation system is the one of the candidates. We are developing the active neutron-based interrogation system with a D-D fusion neutron source for the nuclear security application. The D-D neutron source is a compact discharge-type fusion neutron source called IEC (Inertial-Electrostatic Confinement fusion) device which provides 2.45 MeV neutrons. The nuclear materials emit the highenergy neutrons by fission reaction. High-energy neutrons with energies over 2.45 MeV amount to 30% of all the fission neutrons. By using the D-D neutron source, the detection of SNMs is considered to be possible with the attention of fast neutrons if there is over 2.45 MeV. Ideally, neutrons at En>2.45 MeV do not exist if there is no nuclear materials. The detection of fission neutrons over 2.45 MeV are hopeful prospect for the detection of SNM with a high S/N ratio. In the future, the experiments combined with nuclear materials and a D-D neutron source will be conducted. Furthermore, the interrogation system will be numerically investigated by using nuclear materials, a D-D neutron source, and a steel container.

The co-evolution of seawater δ18O and δD

NASA Astrophysics Data System (ADS)

Pope, E. C.

2017-12-01

The δ18O of marine carbonate and silica precipitates has increased by 15‰ over the last ca. 3.5 billion years. Whether this shift reflects a parallel increase in oxygen isotope compositions of seawater with time, Precambrian atmospheric temperatures >55°C, or complete alteration of ancient samples during diagenesis, remains controversial despite nearly a half-century of debate. Early mass balance models of the modern ocean system suggested near constant δ18OSEAWATER over time due to the buffering capacity of fresh oceanic crust. However, fluxes controlling 18O sources and sinks to the ocean (high-temperature alteration of the seafloor, and low-temperature weathering of continental and ocean crust, respectively) have not remained fixed throughout Earth history. I adapted published mass balance models for δ18OSEAWATER to evaluate how continental growth, the subaerial emergence of continents, and decreasing mantle temperature affect the magnitude of 18O sources and sinks, and thus the evolution of seawater δ18O since the early Archean. These factors also affect the δD of seawater, which is controlled by the flux of water between mantle, crustal and glacial reservoirs, such that its evolution can be used as an independent constraint on the magnitude that these variables have had on δ18O evolution. The models indicate that a key parameter controlling δ18OSEAWATER is the flux of water between the mantle and free water of the exosphere. Recent geophysical models suggest that the capacity for subducting slabs to sequester water into the deep ocean has increased as the mantle has cooled. Hydrous minerals in subducted oceanic crust have a net δ18O lower than seawater. Incomplete recycling of water from these phases in subduction zones results in progressive removal of 16O from the ocean and thus can explain a significant portion of the increase in δ18O recorded in the marine sediment record. However, mass balance constraints on the global hydrogen budget limits

Combinatorial effects on clumped isotopes and their significance in biogeochemistry

NASA Astrophysics Data System (ADS)

Yeung, Laurence Y.

2016-01-01

The arrangement of isotopes within a collection of molecules records their physical and chemical histories. Clumped-isotope analysis interrogates these arrangements, i.e., how often rare isotopes are bound together, which in many cases can be explained by equilibrium and/or kinetic isotope fractionation. However, purely combinatorial effects, rooted in the statistics of pairing atoms in a closed system, are also relevant, and not well understood. Here, I show that combinatorial isotope effects are most important when two identical atoms are neighbors on the same molecule (e.g., O2, N2, and D-D clumping in CH4). When the two halves of an atom pair are either assembled with different isotopic preferences or drawn from different reservoirs, combinatorial effects cause depletions in clumped-isotope abundance that are most likely between zero and -1‰, although they could potentially be -10‰ or larger for D-D pairs. These depletions are of similar magnitude, but of opposite sign, to low-temperature equilibrium clumped-isotope effects for many small molecules. Enzymatic isotope-pairing reactions, which can have site-specific isotopic fractionation factors and atom reservoirs, should express this class of combinatorial isotope effect, although it is not limited to biological reactions. Chemical-kinetic isotope effects, which are related to a bond-forming transition state, arise independently and express second-order combinatorial effects related to the abundance of the rare isotope. Heteronuclear moeties (e.g., Csbnd O and Csbnd H), are insensitive to direct combinatorial influences, but secondary combinatorial influences are evident. In general, both combinatorial and chemical-kinetic factors are important for calculating and interpreting clumped-isotope signatures of kinetically controlled reactions. I apply this analytical framework to isotope-pairing reactions relevant to geochemical oxygen, carbon, and nitrogen cycling that may be influenced by combinatorial

Microanalyses of O isotopes and elemental ratios of reef building coral (Montastrea annularis) by ion microprobe

NASA Astrophysics Data System (ADS)

Gabitov, R. I.; Carricart Ganivet, J. P.; Prieto, R. I.

2012-12-01

Our understanding of climate change and oceanographic variability through time is largely derived from knowledge of oxygen isotopes (δ18O) and elemental ratios (X/Ca) signatures in coral reefs. However, the existence of inconsistencies in isotopic composition between different coral specimens suggests that factors other than temperature and seawater composition affect isotopic and chemical records. We conducted in situ Secondary Ion Mass Spectrometry (SIMS) analyses on the reef building coral (Montastraea annularis) from Veracuz Reef in the southern Gulf of Mexico. Coral specimen was sliced in perpendicular and parallel directions of its growth. Therefore, one of the sections exposed simultaneously grown skeletal material; another section represents a time series of continuously extended skeleton. The complex microstructure of the coral yields a few morphologically different zones (architectural elements). There are theca-wall (Th), septa (S), costa (C), exothecal (ExD) and endothecal dissepiments (EnD). Dissepiments formation in Montastraea annularis is linked to moon cycles and there are 12 or 13 ExD formed per year; meanwhile, there are 24 or 26 EnD per year (Dávalos-Dehullu et al. 2008). SIMS analyses were performed on Th, S, C, ExD, and EnD at lateral spatial resolution of ~20 μm. SIMS spot profiles with 100 and 500 μm steps were conducted on Th wall in the direction of coral growth. SIMS analyses demontrate that δ18O in Th, S, C, and ExD that grown at the same time are similar to each other within 1 sigma error. However, δ18O in EnD is isotopically heavier by 1 ‰ than those of simultaneously grown T,S, and ExD. The reverse dependence of δ18O on growth rate of corals and inorganically precipitated aragonite was reported by previous works and potentially could explain the δ18O enrichment in EnD, which grow by 35% slower than ExD (McConnaughey 1989; Dávalos-Dehullu et al. 2008; Gabitov 2012). SIMS spot profiles in the coral growth direction yielded

Improving plant water isotope models with precise estimates of source water δ2H and δ18O values for trees from precipitation δ2H and δ18O values

NASA Astrophysics Data System (ADS)

Kahmen, A.; Brinkmann, N.; Seeger, S.; Buchmann, N. C.; Eugster, W.; Weiler, M.

2016-12-01

δ2H and δ18O values in plant water and plant organic compounds have established as powerful tools in ecology, biogeochemistry and paleoclimatology. In general, the δ2H and δ18O values in plants are driven by (i) the isotope composition of the plants' source water, (ii) the evaporative 2H or 18O enrichment of foliar water, and (iii) fractionations during the biosynthesis of organic compounds. While we have a robust understanding of what determines the evaporative 2H or 18O enrichment in plant water and biosynthetic fractionation factors have also been reasonably well constrained, our understanding how a plant's source water δ2H and δ18O values are linked to seasonal variation in precipitation δ2H and δ18O values is surprisingly poor. Precise estimates of a plant's source water δ2H and δ18O values, e.g. from the GNIP database are thus not possible and limit the application of plant water isotope models for the interpretation of δ2H and δ18O in plants. Here we present a four-year dataset of precipitation, soil water (0 - 80 cm) and plant source water δ2H and δ18O values from a mixed temperate forest. We employed this dataset to (i) estimate the link between precipitation and soil water δ2H and δ18O values at different soil depths, (ii) apply a hydrological model to estimate the mean residence time of precipitation water in different soil depths and (iii) estimate the integration time of seasonal precipitation for the source water δ2H and δ18O values of four tree species. Our data show a seasonal amplitude in δ2H and δ18O of precipitation of xx and xx, respectively. This seasonal variability in precipitation is transferred into the soil, where it declines with soil depth. Mean residence time of precipitation is xx days in the upper soil layers (5 cm) and increases to xx days in the lower soil layers (80 cm). The trees' source water originated from soil depths between 20 and 70 cm. The δ2H and δ18O values of the trees source water resemble mean

Coordinated Isotopic and Mineral Characterization of Highly Fractionated 18O-Rich Silicates in the Queen Alexandra Range 99177 CR3 Chondrite

NASA Technical Reports Server (NTRS)

Nguyen, A. N.; Keller, L. P.; Messenger, S.; Rahman, Z.

2016-01-01

Carbonaceous chondrites contain a mixture of solar system condensates, pre-solar grains, and primitive organic matter. Each of these materials record conditions and processes in different regions of the solar nebula, on the meteorite parent body, and beyond the solar system. Oxygen isotopic studies of meteorite components can trace interactions of distinct oxygen isotopic reservoirs in the early solar system and secondary alteration processes. The O isotopic compositions of the earliest solar system condensates fall along a carbonaceous chondrite anhydrous mineral (CCAM) line of slope approximately 1 in a plot of delta 17O against delta 18O. This trend is attributed to mixing of material from 16O-poor and 16O-rich reservoirs. Secondary processing can induce mass-dependent fractionation of the O isotopes, shifting these compositions along a line of slope approximately 0.52. Substantial mass-dependent fractionation of O isotopes has been observed in secondary minerals in CAIs, calcite, and FUN inclusions. These fractionations were caused by significant thermal or aqueous alteration. We recently reported the identification of four silicate grains with extremely fractionated O isotopic ratios (delta 18O equals 37 - 55 per mille) in the minimally altered CR3 chondrite QUE 99177. TEM analysis of one grain indicates it is a nebular condensate that did not experience substantial alteration. The history of these grains is thus distinct from those of the aforementioned fractionated materials. To constrain the origin of the silicate grains, we conducted further Mg and Fe isotopic studies and TEM analyses of two grains.

Aircraft profile measurements of 18O/16O and D/H isotope ratios of cloud condensate and water vapor constrain precipitation efficiency and entrainment rates in tropical clouds

NASA Astrophysics Data System (ADS)

Noone, D. C.; Raudzens Bailey, A.; Toohey, D. W.; Twohy, C. H.; Heymsfield, A.; Rella, C.; Van Pelt, A. D.

2011-12-01

Convective clouds play a significant role in the moisture and heat balance of the tropics. The dynamics of organized and isolated convection are a function of the background thermodynamic profile and wind shear, buoyancy sources near the surface and the latent heating inside convective updrafts. The stable oxygen and hydrogen isotope ratios in water vapor and condensate can be used to identify dominant moisture exchanges and aspects of the cloud microphysics that are otherwise difficult to observe. Both the precipitation efficiency and the dilution of cloud updrafts by entrainment can be estimated since the isotopic composition outside the plume is distinct from inside. Measurements of the 18O/16O and D/H isotope ratios were made in July 2011 on 13 research flights of the NCAR C130 aircraft during the ICE-T (Ice in Clouds Experiment - Tropical) field campaign near St Croix. Measurements were made using an instrument based on the Picarro Wave-Length Scanning Cavity Ring Down platform that includes a number of optical, hardware and software modifications to allow measurements to be made at 5 Hz for deployment on aircraft. The measurement system was optimized to make precise measurements of the isotope ratio of liquid and ice cloud condensate by coupling the gas analyzer to the NCAR Counter flow Virtual Impactor inlet. The inlet system provides a particle enhancement while rejecting vapor. Sample air is vigorously heated before flowing into the gas phase analyzer. We present statistics that demonstrate the performance and calibration of the instrument. Measured profiles show that environmental air exhibits significant layering showing controls from boundary layer processes, large scale horizontal advection and regional subsidence. Condensate in clouds is consistent with generally low precipitation efficiency, although there is significant variability in the isotope ratios suggesting heterogeneity within plumes and the stochastic nature of detrainment processes

USGS48 Puerto Rico precipitation - A new isotopic reference material for δ2H and δ18O measurements of water

USGS Publications Warehouse

Qi, Haiping; Coplen, Tyler B.; Tarbox, Lauren V.; Lorenz, Jennifer M.; Scholl, Martha A.

2014-01-01

A new secondary isotopic reference material has been prepared from Puerto Rico precipitation, which was filtered, homogenised, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and calibrated by dual-inlet isotope-ratio mass spectrometry. This isotopic reference material, designated as USGS48, is intended to be one of two isotopic reference waters for daily normalisation of stable hydrogen (δ2H) and stable oxygen (δ18O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The δ2H and δ18O values of this reference water are−2.0±0.4 and−2.224±0.012 ‰, respectively, relative to Vienna Standard Mean Ocean Water on scales normalised such that the δ2H and δ18O values of Standard Light Antarctic Precipitation reference water are−428 and−55.5 ‰, respectively. Each uncertainty is an estimated expanded uncertainty (U=2uc) about the reference value that provides an interval that has about a 95 % probability of encompassing the true value. This isotopic reference water is available by the case of 144 glass ampoules containing 5 mL of water in each ampoule.

δ18O water isotope in the iLOVECLIM model (version 1.0) - Part 3: A paleoperspective based on present-day data-model comparison for oxygen stable isotopes in carbonates

NASA Astrophysics Data System (ADS)

Caley, T.; Roche, D. M.

2013-03-01

Oxygen stable isotopes (18O) are among the most usual tools in paleoclimatology/paleoceanography. Simulation of oxygen stable isotopes allows testing how the past variability of these isotopes in water can be interpreted. By modelling the proxy directly in the model, the results can also be directly compared with the data. Water isotopes have been implemented in the global three-dimensional model of intermediate complexity iLOVECLIM allowing fully coupled atmosphere-ocean simulations. In this study, we present the validation of the model results for present day climate against global database for oxygen stable isotopes in carbonates. The limitation of the model together with the processes operating in the natural environment reveal the complexity of use the continental calcite 18O signal of speleothems for a data-model comparison exercise. On the contrary, the reconstructed surface ocean calcite δ18O signal in iLOVECLIM does show a very good agreement with late Holocene database (foraminifers) at the global and regional scales. Our results indicate that temperature and the isotopic composition of the seawater are the main control on the fossil δ18O signal recorded in foraminifer shells and that depth habitat and seasonality play a role but have secondary importance. We argue that a data-model comparison for surface ocean calcite δ18O in past climate, such as the last glacial maximum (≈21 000 yr), could constitute an interesting tool for mapping the potential shifts of the frontal systems and circulation changes throughout time. Similarly, the potential changes in intermediate oceanic circulation systems in the past could be documented by a data (benthic foraminifers)-model comparison exercise whereas future investigations are necessary in order to quantitatively compare the results with data for the deep ocean.

Stable isotope (2H, 17O, 18O) and hydro chemical patterns of precipitation collected in weekly resolution at Hannover, Germany

NASA Astrophysics Data System (ADS)

Koeniger, Paul; Himmelsbach, Thomas

2016-04-01

Long-term observations of stable isotopes (δ18O and δ2H) in precipitation were initiated in May 2008 at the Federal Institute of Geosciences and Natural Resources (BGR) in Hannover, Germany. In 2014 all precipitation samples were re-analyzed because a purchase of a new laser spectrometer (Picarro L2140-i) now allowed measurements of δ17O and a calculation of the 17O-excess parameter. Starting in October 2015 a routine analysis of hydro chemical parameters was added whenever enough sample aliquot was available (major ions, trace elements). A discussion of the stable isotope data of the seven year series of weekly precipitation samples (n = 370) will be presented. Beneath general patterns (seasonality and trends) we also focus on importance of amount weighing procedures, corrections for minor rain amounts, aspects of sample storage and re-analyzes, as well as impacts through changes in analytical equipment (IRMS, CRD spectroscopy) which is visible from the data. For stable isotopes a Thermo Fisher delta plus IRMS (Gasbench and H-Device) was used until 2011 and from 2012 on a Picarro L2120-i water vapor analyzer with long-term accuracies for quality check samples better than 0.2‰ and 0.8‰ for δ18O and δ2H, respectively.

Isotope ratios of H, C, and O in CO2 and H2O of the martian atmosphere.

PubMed

Webster, Chris R; Mahaffy, Paul R; Flesch, Gregory J; Niles, Paul B; Jones, John H; Leshin, Laurie A; Atreya, Sushil K; Stern, Jennifer C; Christensen, Lance E; Owen, Tobias; Franz, Heather; Pepin, Robert O; Steele, Andrew; Achilles, Cherie; Agard, Christophe; Alves Verdasca, José Alexandre; Anderson, Robert; Anderson, Ryan; Archer, Doug; Armiens-Aparicio, Carlos; Arvidson, Ray; Atlaskin, Evgeny; Aubrey, Andrew; Baker, Burt; Baker, Michael; Balic-Zunic, Tonci; Baratoux, David; Baroukh, Julien; Barraclough, Bruce; Bean, Keri; Beegle, Luther; Behar, Alberto; Bell, James; Bender, Steve; Benna, Mehdi; Bentz, Jennifer; Berger, Gilles; Berger, Jeff; Berman, Daniel; Bish, David; Blake, David F; Blanco Avalos, Juan J; Blaney, Diana; Blank, Jen; Blau, Hannah; Bleacher, Lora; Boehm, Eckart; Botta, Oliver; Böttcher, Stephan; Boucher, Thomas; Bower, Hannah; Boyd, Nick; Boynton, Bill; Breves, Elly; Bridges, John; Bridges, Nathan; Brinckerhoff, William; Brinza, David; Bristow, Thomas; Brunet, Claude; Brunner, Anna; Brunner, Will; Buch, Arnaud; Bullock, Mark; Burmeister, Sönke; Cabane, Michel; Calef, Fred; Cameron, James; Campbell, John; Cantor, Bruce; Caplinger, Michael; Caride Rodríguez, Javier; Carmosino, Marco; Carrasco Blázquez, Isaías; Charpentier, Antoine; Chipera, Steve; Choi, David; Clark, Benton; Clegg, Sam; Cleghorn, Timothy; Cloutis, Ed; Cody, George; Coll, Patrice; Conrad, Pamela; Coscia, David; Cousin, Agnès; Cremers, David; Crisp, Joy; Cros, Alain; Cucinotta, Frank; d'Uston, Claude; Davis, Scott; Day, Mackenzie; de la Torre Juarez, Manuel; DeFlores, Lauren; DeLapp, Dorothea; DeMarines, Julia; DesMarais, David; Dietrich, William; Dingler, Robert; Donny, Christophe; Downs, Bob; Drake, Darrell; Dromart, Gilles; Dupont, Audrey; Duston, Brian; Dworkin, Jason; Dyar, M Darby; Edgar, Lauren; Edgett, Kenneth; Edwards, Christopher; Edwards, Laurence; Ehlmann, Bethany; Ehresmann, Bent; Eigenbrode, Jen; Elliott, Beverley; Elliott, Harvey; Ewing, Ryan; Fabre, Cécile; Fairén, Alberto; Farley, Ken; Farmer, Jack; Fassett, Caleb; Favot, Laurent; Fay, Donald; Fedosov, Fedor; Feldman, Jason; Feldman, Sabrina; Fisk, Marty; Fitzgibbon, Mike; Floyd, Melissa; Flückiger, Lorenzo; Forni, Olivier; Fraeman, Abby; Francis, Raymond; François, Pascaline; Freissinet, Caroline; French, Katherine Louise; Frydenvang, Jens; Gaboriaud, Alain; Gailhanou, Marc; Garvin, James; Gasnault, Olivier; Geffroy, Claude; Gellert, Ralf; Genzer, Maria; Glavin, Daniel; Godber, Austin; Goesmann, Fred; Goetz, Walter; Golovin, Dmitry; Gómez Gómez, Felipe; Gómez-Elvira, Javier; Gondet, Brigitte; Gordon, Suzanne; Gorevan, Stephen; Grant, John; Griffes, Jennifer; Grinspoon, David; Grotzinger, John; Guillemot, Philippe; Guo, Jingnan; Gupta, Sanjeev; Guzewich, Scott; Haberle, Robert; Halleaux, Douglas; Hallet, Bernard; Hamilton, Vicky; Hardgrove, Craig; Harker, David; Harpold, Daniel; Harri, Ari-Matti; Harshman, Karl; Hassler, Donald; Haukka, Harri; Hayes, Alex; Herkenhoff, Ken; Herrera, Paul; Hettrich, Sebastian; Heydari, Ezat; Hipkin, Victoria; Hoehler, Tori; Hollingsworth, Jeff; Hudgins, Judy; Huntress, Wesley; Hurowitz, Joel; Hviid, Stubbe; Iagnemma, Karl; Indyk, Steve; Israël, Guy; Jackson, Ryan; Jacob, Samantha; Jakosky, Bruce; Jensen, Elsa; Jensen, Jaqueline Kløvgaard; Johnson, Jeffrey; Johnson, Micah; Johnstone, Steve; Jones, Andrea; Joseph, Jonathan; Jun, Insoo; Kah, Linda; Kahanpää, Henrik; Kahre, Melinda; Karpushkina, Natalya; Kasprzak, Wayne; Kauhanen, Janne; Keely, Leslie; Kemppinen, Osku; Keymeulen, Didier; Kim, Myung-Hee; Kinch, Kjartan; King, Penny; Kirkland, Laurel; Kocurek, Gary; Koefoed, Asmus; Köhler, Jan; Kortmann, Onno; Kozyrev, Alexander; Krezoski, Jill; Krysak, Daniel; Kuzmin, Ruslan; Lacour, Jean Luc; Lafaille, Vivian; Langevin, Yves; Lanza, Nina; Lasue, Jeremie; Le Mouélic, Stéphane; Lee, Ella Mae; Lee, Qiu-Mei; Lees, David; Lefavor, Matthew; Lemmon, Mark; Lepinette Malvitte, Alain; Léveillé, Richard; Lewin-Carpintier, Éric; Lewis, Kevin; Li, Shuai; Lipkaman, Leslie; Little, Cynthia; Litvak, Maxim; Lorigny, Eric; Lugmair, Guenter; Lundberg, Angela; Lyness, Eric; Madsen, Morten; Maki, Justin; Malakhov, Alexey; Malespin, Charles; Malin, Michael; Mangold, Nicolas; Manhes, Gérard; Manning, Heidi; Marchand, Geneviève; Marín Jiménez, Mercedes; Martín García, César; Martin, Dave; Martin, Mildred; Martínez-Frías, Jesús; Martín-Soler, Javier; Martín-Torres, F Javier; Mauchien, Patrick; Maurice, Sylvestre; McAdam, Amy; McCartney, Elaina; McConnochie, Timothy; McCullough, Emily; McEwan, Ian; McKay, Christopher; McLennan, Scott; McNair, Sean; Melikechi, Noureddine; Meslin, Pierre-Yves; Meyer, Michael; Mezzacappa, Alissa; Miller, Hayden; Miller, Kristen; Milliken, Ralph; Ming, Douglas; Minitti, Michelle; Mischna, Michael; Mitrofanov, Igor; Moersch, Jeff; Mokrousov, Maxim; Molina Jurado, Antonio; Moores, John; Mora-Sotomayor, Luis; Morookian, John Michael; Morris, Richard; Morrison, Shaunna; Mueller-Mellin, Reinhold; Muller, Jan-Peter; Muñoz Caro, Guillermo; Nachon, Marion; Navarro López, Sara; Navarro-González, Rafael; Nealson, Kenneth; Nefian, Ara; Nelson, Tony; Newcombe, Megan; Newman, Claire; Newsom, Horton; Nikiforov, Sergey; Nixon, Brian; Noe Dobrea, Eldar; Nolan, Thomas; Oehler, Dorothy; Ollila, Ann; Olson, Timothy; de Pablo Hernández, Miguel Ángel; Paillet, Alexis; Pallier, Etienne; Palucis, Marisa; Parker, Timothy; Parot, Yann; Patel, Kiran; Paton, Mark; Paulsen, Gale; Pavlov, Alex; Pavri, Betina; Peinado-González, Verónica; Peret, Laurent; Perez, Rene; Perrett, Glynis; Peterson, Joe; Pilorget, Cedric; Pinet, Patrick; Pla-García, Jorge; Plante, Ianik; Poitrasson, Franck; Polkko, Jouni; Popa, Radu; Posiolova, Liliya; Posner, Arik; Pradler, Irina; Prats, Benito; Prokhorov, Vasily; Purdy, Sharon Wilson; Raaen, Eric; Radziemski, Leon; Rafkin, Scot; Ramos, Miguel; Rampe, Elizabeth; Raulin, François; Ravine, Michael; Reitz, Günther; Rennó, Nilton; Rice, Melissa; Richardson, Mark; Robert, François; Robertson, Kevin; Rodriguez Manfredi, José Antonio; Romeral-Planelló, Julio J; Rowland, Scott; Rubin, David; Saccoccio, Muriel; Salamon, Andrew; Sandoval, Jennifer; Sanin, Anton; Sans Fuentes, Sara Alejandra; Saper, Lee; Sarrazin, Philippe; Sautter, Violaine; Savijärvi, Hannu; Schieber, Juergen; Schmidt, Mariek; Schmidt, Walter; Scholes, Daniel; Schoppers, Marcel; Schröder, Susanne; Schwenzer, Susanne; Sebastian Martinez, Eduardo; Sengstacken, Aaron; Shterts, Ruslan; Siebach, Kirsten; Siili, Tero; Simmonds, Jeff; Sirven, Jean-Baptiste; Slavney, Susie; Sletten, Ronald; Smith, Michael; Sobrón Sánchez, Pablo; Spanovich, Nicole; Spray, John; Squyres, Steven; Stack, Katie; Stalport, Fabien; Stein, Thomas; Stewart, Noel; Stipp, Susan Louise Svane; Stoiber, Kevin; Stolper, Ed; Sucharski, Bob; Sullivan, Rob; Summons, Roger; Sumner, Dawn; Sun, Vivian; Supulver, Kimberley; Sutter, Brad; Szopa, Cyril; Tan, Florence; Tate, Christopher; Teinturier, Samuel; ten Kate, Inge; Thomas, Peter; Thompson, Lucy; Tokar, Robert; Toplis, Mike; Torres Redondo, Josefina; Trainer, Melissa; Treiman, Allan; Tretyakov, Vladislav; Urqui-O'Callaghan, Roser; Van Beek, Jason; Van Beek, Tessa; VanBommel, Scott; Vaniman, David; Varenikov, Alexey; Vasavada, Ashwin; Vasconcelos, Paulo; Vicenzi, Edward; Vostrukhin, Andrey; Voytek, Mary; Wadhwa, Meenakshi; Ward, Jennifer; Weigle, Eddie; Wellington, Danika; Westall, Frances; Wiens, Roger Craig; Wilhelm, Mary Beth; Williams, Amy; Williams, Joshua; Williams, Rebecca; Williams, Richard B; Wilson, Mike; Wimmer-Schweingruber, Robert; Wolff, Mike; Wong, Mike; Wray, James; Wu, Megan; Yana, Charles; Yen, Albert; Yingst, Aileen; Zeitlin, Cary; Zimdar, Robert; Zorzano Mier, María-Paz

2013-07-19

Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and (18)O/(16)O in water and (13)C/(12)C, (18)O/(16)O, (17)O/(16)O, and (13)C(18)O/(12)C(16)O in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established ~4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing.

A 220 ka terrestrial δ18O and deuterium excess biomarker record from an eolian permafrost paleosol sequence, NE-Siberia

NASA Astrophysics Data System (ADS)

Tuthorn, Mario; Zech, Michael; Detsch, Florian; Rozanski, Kazimierz; Zech, Roland; Zöller, Ludwig; Zech, Wolfgang; Glaser, Bruno

2013-04-01

The natural abundances of stable oxygen (18O/16O) and hydrogen isotopes (D/H) are valuable proxies of climate changes in the past. Yet, to date no continuous δ18O and only few δD records are available from loess-paleosol sequences. Taking advantage of a recently developed method based on compound-specific δ18O analyzes of hemicellulose sugar biomarkers in soils (Zech and Glaser, 2009), we here present a first terrestrial δ18O biomarker record from an eolian permafrost paleosol sequence in NE-Siberia that covers the last ~220 ka. The δ18O values of the hemicellulose biomarkers arabinose and xylose range from 22.5 to 32.8‰ and from 21.3 to 31.9‰, respectively, and reveal systematic glacial - interglacial shifts. The modern topsoil and the interglacial paleosols exhibit more positive δ18O values, whereas the glacial paleosols are characterized by more negative δ18O values. This is in agreement with the δD record obtained for sedimentary n-alkane leaf wax biomarkers. We present a conceptual model for interpreting the combined δ18O and δD biomarker record. Based on this model, we suggest that both our δ18O and the δD record primarily reflect the temperature-controlled isotopic composition of paleoprecipitation modified by evaporative isotope enrichment of leaf water during transpiration. Considering fractionation factors during sugar and n-alkane biomarker biosynthesis allows reconstructing the leaf water isotopic composition and the deuterium excess of the leaf water. The deuterium excess may serve as proxy for evaporative enrichment and allows calculating relative humidity using a Craig-Gordon model. Accordingly, relative humidity in NE-Siberia was higher during marine isotope stage (MIS) 6 compared to MIS 2, 4 and 5d and thus could help explaining the much larger extent of the Late Saalian glaciation compared to the Weichselian glaciations. Using the Craig-Gordon model, we also calculated δ18O of the plant source water (δ18Osource water), which can

The effect of saline groundwater exchange, evaporation and variable river flows and on stable isotopes (18O and 2H) and major ion concentrations along the Darling River, NSW, Australia

NASA Astrophysics Data System (ADS)

Meredith, K. T.; Hughes, C. E.; Hollins, S. E.; Cendón, D. I.; Hankin, S.

2009-04-01

Australia's longest river, the Darling River, faces extreme pressure from drought and over extraction of water from its catchment. The lack of detailed baseline hydrochemical and isotopic data for the Darling River has prompted research aimed at using hydrological tracers to assess water gains and losses within the Darling River Drainage Basin. This study uses temporal hydrochemical and stable isotope data (18O and 2H) that has been monitored from gauging stations along the Barwon-Darling catchment over a five-year period from 2002 to 2007 as part of the Global Network for Isotopes in Rivers (GNIR) monitoring programme. Stream flow data, monthly δ18O and δ2H values and major ion chemistry is presented. Individual flow events were found to be isotopically distinct but the LELs that develop after these events have a very similar slope indicating similar climatic conditions across this region. During low flow conditions, salt concentrations increase systematically, δ18O and δ2H become enriched and d-excess becomes more negative indicating significant evaporation. Flow events input isotopically depleted fresh waters to the system and the d-excess returns towards the local meteoric water line. The major ions increase in concentration at a greater rate at Louth than they do at upstream at Bourke or downstream at Wilcannia, despite similar decreases in flow rates for all three sites. The hydrological response of the river to drought has had detrimental affects on the surface water system because it provides a pathway for saline groundwater to discharge into the river system.

Fractionation of Oxygen Isotopes by Thermal Ionization Mass Spectrometry Inferred from Simultaneous Measurement of (17)O/(16)O and (18)O/(16)O Ratios and Implications for the (182)Hf-(182)W Systematics.

PubMed

Trinquier, Anne

2016-06-07

Accurate (182)Hf-(182)W chronology of early planetary differentiation relies on highly precise and accurate tungsten isotope measurements. WO3(-) analysis by negative thermal ionization mass spectrometry requires W(17)O(16)O2(-), W(17)O2(16)O(-), W(18)O(16)O2(-), W(17)O3(-), W(17)O(18)O(16)O(-), and W(18)O2(16)O(-) isotopologue interference corrections on W(16)O3(-) species ( Harper et al. Geochim. Cosmochim. Acta 1996 , 60 , 1131 ; Quitté et al. Geostandard. Newslett. 2002 , 26 , 149 ; Trinquier et al. Anal. Chem. 2016 , 88 , 1542 ; Touboul et al. Nature 2015 , 520 , 530 ; Touboul et al. Int. J. Mass Spectrom. 2012 , 309 , 109 ). In addition, low ion beam intensity counting statistics combined with Faraday cup detection noise limit the precision on the determination of (18)O/(16)O and (17)O/(16)O relative abundances. Mass dependent variability of (18)O/(16)O over the course of an analysis and between different analyses calls for oxide interference correction on a per integration basis, based on the in-run monitoring of the (18)O/(16)O ratio ( Harper et al. Geochim. Cosmochim. Acta 1996 , 60 , 1131 ; Quitté et al. Geostandard. Newslett. 2002 , 26 , 149 ; Trinquier et al. Anal. Chem. 2016 , 88 , 1542 ). Yet, the (17)O/(16)O variation is normally not being monitored and, instead, inferred from the measured (18)O/(16)O variation, assuming a δ(17)O-δ(18)O Terrestrial Fractionation Line ( Trinquier et al. Anal. Chem. 2016 , 88 , 1542 ). The purpose of the present study is to verify the validity of this assumption. Using high resistivity amplifiers, (238)U(17)O2 and (238)U(18)O2 ion beams down to 1.6 fA have been monitored simultaneously with (235,238)U(16)O2 species in a uranium certified reference material. This leads to a characterization of O isotope fractionation by thermal ionization mass spectrometry in variable loading and running conditions (additive-to-sample ratio, PO2 pressure, presence of ionized metal and oxide species). Proper determination of O

The Oxygen Isotopic Composition (18O/16O) in the Dust of Comet 67P/Churyumov-Gerasimenko Measured by COSIMA On-board Rosetta

NASA Astrophysics Data System (ADS)

Paquette, J. A.; Engrand, C.; Hilchenbach, M.; Fray, N.; Stenzel, O. J.; Silen, J.; Rynö, J.; Kissel, J.

2018-03-01

The oxygen isotopic ratio 18O/16O has been measured in cometary gas for a wide variety of comets, but the only measurements in cometary dust were performed by the Stardust cometary sample return mission. Most such measurements find a value of the ratio that is consistent with Vienna Standard Mean Ocean Water (VSMOW) within errors. In this work we present the result of a measurement, using the COSIMA instrument on the Rosetta orbiter, of the oxygen isotopic ratio in dust from Comet 67P/Churyumov-Gerasimenko. Measuring the 18O/16O ratio with COSIMA is challenging for a number of reasons, but it is possible with a reasonable degree of precision. We find a result of 2.00 × 10-3 ± 1.2 × 10-4 which is consistent within errors with VSMOW.

The oxygen isotopic composition (18O/16O) in the dust of comet 67P/Churyumov-Gerasimenko measured by COSIMA on-board Rosetta

NASA Astrophysics Data System (ADS)

Paquette, J. A.; Engrand, C.; Hilchenbach, M.; Fray, N.; Stenzel, O. J.; Silen, J.; Rynö, J.; Kissel, J.

2018-07-01

The oxygen isotopic ratio 18O/16O has been measured in cometary gas for a wide variety of comets, but the only measurements in cometary dust were performed by the Stardust cometary sample return mission. Most such measurements find a value of the ratio that is consistent with Vienna Standard Mean Ocean Water (VSMOW) within errors. In this work we present the result of a measurement, using the COSIMA (the COmetary Secondary Ion Mass Analyser) instrument on the Rosetta orbiter, of the oxygen isotopic ratio in dust from Comet 67P/Churyumov-Gerasimenko. Measuring the 18O/16O ratio with COSIMA is challenging for a number of reasons, but it is possible with a reasonable degree of precision. We find a result of 2.00 × 10-3 ± 1.2 × 10-4, which is consistent within errors with VSMOW.

Dolomite clumped isotope constraints on the oxygen isotope composition of the Phanerozoic Sea

NASA Astrophysics Data System (ADS)

Ryb, U.; Eiler, J. M.

2017-12-01

The δ18O value of the Phanerozoic Sea has been debated several decades, largely motivated by an 8‰ increase in δ18O of sedimentary carbonates between the Cambrian and the present. Some previous studies have interpreted this increase to be a primary depositional signal, resulting from an increase in the 18O content of ocean water over time, or from a decrease in ocean temperature increasing the oxygen isotope fractionation between seawater and carbonates. In contrast, other studies have interpreted lower δ18O compositions as the products of diagenetic alteration at elevated burial temperatures. Here, we show that the Phanerozoic dolomite δ18O record overlaps with that of well-preserved calcite fossils, and use carbonate clumped isotope measurements of Cambrian to Pleistocene dolomites to calculate their formation temperatures and the isotopic compositions of their parent-waters. The observed variation in dolomite δ18O is largely explained by dolomite formation at burial temperatures of up to 158°C. The δ18O values of dolomite parent-waters range -2 to +12‰ and are correlated with formation temperatures. Such correlation is consistent with the modification of seawater (0±2‰, VSMOW) toward isotopically heavier compositions through water-rock reactions at elevated burial temperatures. The similarity between the dolomite and calcite δ18O records, and published clumped isotope-based calculations of water compositions, suggests that like dolomite, temporal variations of the calcite δ18O record may also be largely driven by diagenetic alteration. Finally, the relationship we observe between temperature of dolomitization and d18O of dolomite suggests platform carbonates generally undergo dolomitization through reaction with modified marine waters, and that there is no evidence those waters were ever significantly lower in d18O than the modern ocean.

High Precision Isotope Analyses Using Multi-Collector SIMS: Applications to Earth and Planetary Science.

NASA Astrophysics Data System (ADS)

Kita, N. T.; Ushikubo, T.; Valley, J. W.

2008-05-01

The CAMECA IMS-1280 large radius, multicollector ion microprobe at the Wisc-SIMS National Facility is capable of high accuracy and precision for in situ analysis of isotope ratios. With improved hardware stability and software capability, high precision isotope analyses are routinely performed, typically 5 min per spot. We have developed analytical protocols for stable isotope analyses of oxygen, carbon, Mg, Si and Sulfur using multi-collector Faraday Cups (MCFC) and achieved precision of 0.1-0.2 ‰ (1SD) from a typically 10μm spot analyses. A number of isotopically homogeneous mineral standards have been prepared and calibrated in order to certify the accuracy of analyses in the same level. When spatial resolution is critical, spot size is reduced down to sub- μm for δ 18O to obtain better than 0.5‰ (1SD) precision by using electron multiplier (EM) on multi-collection system. Multi-collection EM analysis is also applied at 10 ppm level to Li isotope ratios in zircon with precision better than 2‰ (1SD). A few applications will be presented. (1) Oxygen three isotope analyses of chondrules in ordinary chondrites revealed both mass dependent and mass independent oxygen isotope fractionations among chondrules as well as within individual chondrules. The results give constraints on the process of chondrule formation and origin of isotope reservoirs in the early solar system. (2) High precision 26Al-26Mg (half life of 0.73 Ma) chronology is applied to zoned melilite and anorthite from Ca, Al-rich inclusions (CAI) in Leoville meteorite, and a well-defined internal isochron is obtained. The results indicate the Al- Mg system was remained closed within 40ky of the crystallization of melilite and anorthite in this CAI. (3) Sub- μm spot analyses of δ18O in isotopically zoned zircon from high-grade metamorphism reveals a diffusion profile of ~6‰ over 2μm, indicating slow diffusion of oxygen in zircon. This result also implies that old Archean detrital zircons (> 4

Kinetic isotopic fractionation during diffusion of ionic species in water

NASA Astrophysics Data System (ADS)

Richter, Frank M.; Mendybaev, Ruslan A.; Christensen, John N.; Hutcheon, Ian D.; Williams, Ross W.; Sturchio, Neil C.; Beloso, Abelardo D.

2006-01-01

Experiments specifically designed to measure the ratio of the diffusivities of ions dissolved in water were used to determine DLi/DK,D/D,D/D,D/D,andD/D. The measured ratio of the diffusion coefficients for Li and K in water (D Li/D K = 0.6) is in good agreement with published data, providing evidence that the experimental design being used resolves the relative mobility of ions with adequate precision to also be used for determining the fractionation of isotopes by diffusion in water. In the case of Li, we found measurable isotopic fractionation associated with the diffusion of dissolved LiCl (D/D=0.99772±0.00026). This difference in the diffusion coefficient of 7Li compared to 6Li is significantly less than that reported in an earlier study, a difference we attribute to the fact that in the earlier study Li diffused through a membrane separating the water reservoirs. Our experiments involving Mg diffusing in water found no measurable isotopic fractionation (D/D=1.00003±0.00006). Cl isotopes were fractionated during diffusion in water (D/D=0.99857±0.00080) whether or not the co-diffuser (Li or Mg) was isotopically fractionated. The isotopic fractionation associated with the diffusion of ions in water is much smaller than values we found previously for the isotopic fractionation of Li and Ca isotopes by diffusion in molten silicate liquids. A major distinction between water and silicate liquids is that water surrounds dissolved ions with hydration shells, which very likely play an important but still poorly understood role in limiting the isotopic fractionation associated with diffusion.

Assessment of water sources to plant growth in rice based cropping systems by stable water isotopes

NASA Astrophysics Data System (ADS)

Mahindawansha, Amani; Kraft, Philipp; Racela, Heathcliff; Breuer, Lutz

2016-04-01

Rice is one of the most water-consuming crops in the world. Understanding water source utilization of rice will help us to improve water use efficiency (WUE) in paddy management. The objectives of our study are to evaluate the isotopic compositions of surface ponded water, soil water, irrigation water, groundwater, rain water and plant water and based on stable water isotope signatures to evaluate the contributions of various water sources to plant growth (wet rice, aerobic rice and maize) together with investigating the contribution of water from different soil horizons for plant growth in different maturity periods during wet and dry seasons. Finally we will compare the water balances and crop yields in both crops during both seasons and calculate the water use efficiencies. This will help to identify the most efficient water management systems in rice based cropping ecosystems using stable water isotopes. Soil samples are collected from 9 different depths at up to 60 cm in vegetative, reproductive and matured periods of plant growth together with stem samples. Soil and plant samples are extracted by cryogenic vacuum extraction. Root samples are collected up to 60 cm depth from 10 cm intercepts leading calculation of root length density and dry weight. Groundwater, surface water, rain water and irrigation water are sampled weekly. All water samples are analyzed for hydrogen and oxygen isotope ratios (d18O and dD) using Los Gatos Research DLT100. Rainfall records, ground water level, surface water level fluctuations and the amount of water irrigated in each field will be measured during the sampling period. The direct inference approach which is based on comparing isotopic compositions (dD and d18O) between plant stem water and soil water will be used to determine water sources taken up by plant. Multiple-source mass balance assessment can provide the estimated range of potential contributions of water from each soil depth to root water uptake of a crop. These

Real time, ambient air laser monitor for rare CO2 isotopic tracers: Δ13 C18 O16 O and Δ17 O

NASA Astrophysics Data System (ADS)

Nelson, David; Shorter, Joanne; McManus, Barry; Jervis, Dylan; Zahniser, Mark; Ono, Shuhei

2017-04-01

Greenhouse gas (GHG) emissions are the primary drivers of global climate change and hence there is a crucial need to quantify their sources and sinks. A powerful technique to help constrain source and sink strengths in GHG exchange processes is the analysis of the relative proportions of isotopic variants of GHGs. We present a new laser isotope monitor based on Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) to measure the primary clumped isotopologue of CO2 (Δ13 C18 O16 O) and to simultaneously measure the mass independent 17 O-CO2 content (Δ17 O). The instrument directly measures dried atmospheric samples without cryogenic preconcentration of CO2 . The instrument has several novel features. The instrument's sensitivity is enhanced by employing a 400 meter optical absorption cell. Measurement drift is suppressed by using a rapid sample switching method with frequent comparison to a working reference. A new dual-pressure measurement scheme is demonstrated. This scheme solves the dynamic range challenge that arises in simultaneously measuring the main isotopologues of CO2 together with much less abundant clumped isotopologue species. Our initial results address measurement precision, measurement drift and calibration. We show the potential to reach 0.03 per mil repeatability with time resolution of 3 minutes and with minimal drift over an 18 hour measurement period. The instrument is sufficiently compact to be field deployed thus providing the possibility of continuous measurements of Δ13 C18 O16 O and Δ17 O rather than occasional flask samples.

Arctic Marine Water Isotope Characteristics: In-situ, Continuous Surface and Water Column Isoscapes (δ18O and δ2H) and Linkages into the Marine Food Web

NASA Astrophysics Data System (ADS)

Welker, J. M.; Klein, E. S.; Collins, E.; Iken, K.; Hopcroft, R. R.; Norcross, B.

2016-12-01

The Arctic is under going rapid and profound sea ice, temperature, food web, ocean current, precipitation and synoptic weather changes. Delineating these changes requires a suite of tools, especially those that have the ability to depict the interactive nature of the marine system. Understanding the marine water isotope cycle is paramount to recognizing the unique isotopic properties of this region and to characterize possibly the reorganization of the Arctic. The Arctic marine water isotope system has been primarily examined with shore-based stations and or episodic station sampling; without continuous surface water sampling in combination with station-specific water column and organismic measurements. New technologies that allow in situ and continuous water isotope measurements (vapor and liquid) and the integration of inorganic and organic water isotope geochemistry provide a means to reveal in more detail the fundamental traits of the Arctic marine water isotope system. In July and August of 2016, we are measuring seawater surface (8 m depth) isotopes (δ18O and δ2H) in-situ and continuously (Picarro CWS system) along a research transect (60oN to 77oN) from the Gulf of Alaska to the Arctic Ocean Basin. These continuous surface water isotope measurements are being combined with periodic water column isotope profiling and corresponding organic δ18O and δ2H measurements of pelagic and benthic organisms (microbes to fish) to depths of up to 2600m. We measured surface seawater δ18O that from -1‰ to -6‰; while seawater profiles followed vertical separation in the water column; possibly reflecting divergent currents of the Arctic. Station based δ18O and δ2H values of surface water did not vary by more than 1‰ δ18O over the course of our 24-36 hour sampling periods. The δ18O and δ2H values of marine organism throughout the water column and by trophic level will be analyzed and a seawater-food web model will be developed in addition to surface and water

N and O isotope (δ15 Nα , δ15 Nβ , δ18 O, δ17 O) analyses of dissolved NO3- and NO2- by the Cd-azide reduction method and N2 O laser spectrometry.

PubMed

Wassenaar, Leonard I; Douence, Cedric; Altabet, Mark A; Aggarwal, Pradeep K

2018-02-15

The nitrogen and oxygen (δ 15 N, δ 18 O, δ 17 O) isotopic compositions of NO 3 - and NO 2 - are important tracers of nutrient dynamics in soil, rain, groundwater and oceans. The Cd-azide method was used to convert NO 3 - or NO 2 - to N 2 O for N and triple-O isotopic analyses by N 2 O laser spectrometry. A protocol for laser-based headspace isotope analyses was compared with isotope ratio mass spectrometry. Lasers provide the ability to directly measure 17 O anomalies which can help discern atmospheric N sources. δ 15 N, δ 18 O and δ 17 O values were measured on N/O stable isotopic reference materials (IAEA, USGS) by conversion to N 2 O using the Cd-azide method and headspace N 2 O laser spectrometry. A 15 N tracer test assessed the position-specific routing of N to the α or β positions in the N 2 O molecule. A data processing algorithm was used to correct for isotopic dependencies on N 2 O concentration, cavity pressure and water content. NO 3 - /NO 2 - nitrogen is routed to the 15 N α position of N 2 O in the azide reaction; hence the δ 15 N α value should be used for N 2 O laser spectrometry results. With corrections for cavity pressure, N 2 O concentration and water content, the δ 15 N α AIR , δ 18 O VSMOW and δ 17 O VSMOW values (‰) of international reference materials were +4.8 ± 0.1, +25.9 ± 0.3, +12.7 ± 0.2 (IAEA NO 3 ), -1.7 ± 0.1, -26.8 ± 0.8, -14.4 ± 1.1 (USGS34) and +2.6 ± 0.1, +57.6 ± 1.2, +51.2 ± 2.0 (USGS35), in agreement with their values and with the isotope ratio mass spectrometry results. The 17 O excess for USGS35 was +21.2 ± 9‰, in good agreement with previous results. The Cd-azide method yielded excellent results for routine determination of δ 15 N, δ 18 O and δ 17 O values (and the 17 O excess) of nitrate or nitrite by laser spectrometry. Disadvantages are the toxicity of Cd-azide chemicals and the lack of automated sampling devices for N 2 O laser spectrometers. The 15 N-enriched tracer test revealed potential

Observation of Isotope Ratios (δ2H, δ18O, 87Sr/86Sr) of Tap Water in Urban Environments

NASA Astrophysics Data System (ADS)

Mancuso, C. J.; Tipple, B. J.; Ehleringer, J. R.

2014-12-01

Urban environments are centers for rapidly growing populations. In order to meet the culinary water needs of these areas, municipal water departments use water from multiple locations and/or sources, often piped differentially to different locations within a municipality. This practice creates isotopically distinct locations within an urban area and therefore provides insight to urban water management practices. In our study we selected urban locations in the Salt Lake Valley, UT (SLV) and San Francisco Bay Area, CA (SFB) where we hypothesized geographically distinct water isotopic ratio differences existed. Within the SLV, municipal waters come from the same mountainous region, but are derived from different geologically distinct watersheds. In contrast, SFB waters are derived from regionally distinct water sources. We hypothesized that the isotope ratios of tap waters would differ based upon known municipal sources. To test this, tap water samples were collected throughout the urban regions in SLV and SFB and analyzed for δ2H, δ18O and 87Sr/86Sr isotope ratios. Seasonal collections were also made to assess if isotope ratios differed throughout the year. Within SLV and SFB, different regions were characterized by distinct paired δ18O and 87Sr/86Sr values. These different realms also agreed with known differences in municipal water supplies within the general geographic region. Waters from different cities within Marin County showed isotopic differences, consistent with water derived from different local reservoirs. Seasonal variation was observed in paired δ18O and 87Sr/86Sr values of tap water for some locations within SLV and SFB, indicating management decisions to shift from one water source to another depending on demand and available resources. Our study revealed that the δ18O and 87Sr/86Sr values of tap waters in an urban region can exhibit significant differences despite close spatial proximity if districts differ in their use of local versus

Constraining N2O emissions since 1940 using firn air isotope measurements in both hemispheres

NASA Astrophysics Data System (ADS)

Prokopiou, Markella; Martinerie, Patricia; Sapart, Célia J.; Witrant, Emmanuel; Monteil, Guillaume; Ishijima, Kentaro; Bernard, Sophie; Kaiser, Jan; Levin, Ingeborg; Blunier, Thomas; Etheridge, David; Dlugokencky, Ed; van de Wal, Roderik S. W.; Röckmann, Thomas

2017-04-01

N2O is currently the third most important anthropogenic greenhouse gas in terms of radiative forcing and its atmospheric mole fraction is rising steadily. To quantify the growth rate and its causes over the past decades, we performed a multi-site reconstruction of the atmospheric N2O mole fraction and isotopic composition using new and previously published firn air data collected from Greenland and Antarctica in combination with a firn diffusion and densification model. The multi-site reconstruction showed that while the global mean N2O mole fraction increased from (290 ± 1) nmol mol-1 in 1940 to (322 ± 1) nmol mol-1 in 2008, the isotopic composition of atmospheric N2O decreased by (-2.2 ± 0.2) ‰ for δ15Nav, (-1.0 ± 0.3) ‰ for δ18O, (-1.3 ± 0.6) ‰ for δ15Nα, and (-2.8 ± 0.6) ‰ for δ15Nβ over the same period. The detailed temporal evolution of the mole fraction and isotopic composition derived from the firn air model was then used in a two-box atmospheric model (comprising a stratospheric box and a tropospheric box) to infer changes in the isotopic source signature over time. The precise value of the source strength depends on the choice of the N2O lifetime, which we choose to fix at 123 years. The average isotopic composition over the investigated period is δ15Nav = (-7.6 ± 0.8) ‰ (vs. air-N2), δ18O = (32.2 ± 0.2) ‰ (vs. Vienna Standard Mean Ocean Water - VSMOW) for δ18O, δ15Nα = (-3.0 ± 1.9) ‰ and δ15Nβ = (-11.7 ± 2.3) ‰. δ15Nav, and δ15Nβ show some temporal variability, while for the other signatures the error bars of the reconstruction are too large to retrieve reliable temporal changes. Possible processes that may explain trends in 15N are discussed. The 15N site preference ( = δ15Nα - δ15Nβ) provides evidence of a shift in emissions from denitrification to nitrification, although the uncertainty envelopes are large.

Spectroscopic studies on [(DD18C6H 2)(HPA) 2](PA) 2 and [(DD18C6H 2)(DDQ) 2](DDQH) 2 formed in the reaction of N, N'-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane with HPA and DDQ

NASA Astrophysics Data System (ADS)

Teleb, Said M.; Gaballa, Akmal S.; Elmosallamy, M. A. F.; Nour, El-Metwally

2005-09-01

The interaction of the mixed oxygen-nitrogen cyclic base, N, N'-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DD18C6) with π-acceptors such as picric acid (HPA) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been studied spectrophotometrically in chloroform at 25 °C. The results obtained indicate the formation of 1:4 charge-transfer complexes with the general formula (DD18C6)(acceptor) 4. The electronic and infrared spectra of charge-transfer complexes along with the 1H NMR spectra were recorded and discussed. Based on the data obtained, the complexes were formulated as [(DD18C6H 2)(HPA) 2](PA) 2 and [(DD18C6H 2)(DDQ) 2](DDQH) 2. A general mechanism explaining the formation of the DDQ complex has been suggested.

An innovative application of stable isotopes (δ2H and δ18O) for tracing pollutant plumes in groundwater.

PubMed

Negrel, Philippe; Ollivier, Patrick; Flehoc, Christine; Hube, Daniel

2017-02-01

The identification of the sources of contaminants present in groundwater at industrial sites is primordial to address environmental and industrial issues. However, available tools are often inadequate or expensive. Here, we present the data of stable isotopes (δ 18 O and δ 2 H) of the water molecule at an industrial site where electrochemistry plant occurs impacting the groundwater quality. High ClO 3 and ClO 4 contents and 2 H enrichment have been measured in groundwater. Recharge of aquifer relates to infiltration of rainwater and by subsurface inflow. On-site, industrial products are generated by electrolysis. We show that the electrolysis process leads to a large 2 H enrichment (+425‰) in solutions. In the absence of hydrothermal water input containing H 2 S, we demonstrate that the relationship between δ 18 O and δ 2 H can be easily used in a way to trace the origin of the ClO 3 and ClO 4 in groundwater. Isotopes evidenced first a leakage from end-product storage tanks or during the production process itself. Then, an accumulation and release of ClO 3 and ClO 4 from soil is demonstrated. Our study successfully shows that stable isotopes are a powerful and low cost tool for tracing pollutant plumes in an industrial context using electrolysis process. Copyright © 2016 Elsevier B.V. All rights reserved.

The δ18O of Atmospheric Water Vapour is Recorded in the Oxygen Isotope Ratios of Leaf water and Organic Molecules at High Relative Humidity

NASA Astrophysics Data System (ADS)

Lehmann, M. M.; Goldsmith, G. R.; Schmid, L.; Siegwolf, R. T.; Gessler, A.; Saurer, M.

2016-12-01

The oxygen stable isotope ratios (δ18O) of water and organic molecules in plants hold information about plant physiology, ecohydrology, and environmental conditions. For instance, the δ18O ratio of leaf water reflects both the δ18O ratios of water in the soil and in the atmosphere. This water, which is incorporated into organic molecules at the time of synthesis, thus serves to record the environment in which the plant was growing. However, how δ18O of atmospheric water vapour affects the δ18O ratio of organic molecules remains poorly understood. In order to investigate the effects of fog and rain (e.g. high atmospheric water availability) on δ18O ratios of leaf water and organic molecules, we exposed oak tree saplings (Quercus robur) in wet and dry soil treatments to 18O-depleted water vapour at ca. 90% relative humidity for 5 h. We harvested plant material over 24 h to trace the movement of the isotopic label in water and organics throughout the plant from the leaves to the stem. The atmospheric water vapour caused a strong 18O-depletion in leaf and xylem water, as well as in leaf carbohydrates, with the most negative ratios observed at the end of the fogging. Moreover, the label was clearly observed in twig and stem phloem carbohydrates following a short delay. A detailed compound-specific isotope analysis of the leaf carbohydrates revealed that the label caused an 18O-depletion in fructose, glucose, and sucrose. Quercitol, an oak-specific alditol, did not show 18O-depletion. Clear soil moisture treatment effects were only observed for twig phloem carbohydrates, with a stronger 18O-depletion in wet plants than in dry plants, suggesting retarded leaf-to-phloem sugar export in trees under drought. We demonstrate that labelling with 18O-depleted water is a potential tool to trace the movement and incorporation of oxygen stable isotopes in plants. We clearly show that changes in δ18O of atmospheric water vapour are quickly imprinted on leaf water and

Sources of nitrate in the Arno River waters: Constraints from d15N and d18O

USGS Publications Warehouse

Nisi, Barbara; Vaselli, Orlando; Buccianti, Antonella; Silva, Steven R.

2005-01-01

Running waters in anthropogenically affected areas are susceptible to nitrate contamination. Source identification is a fundamental step for the development of effective remediation. Previous studies pointed to pollution by nitrogen-bearing contaminants in the Arno Basin. In this paper, eleven surface water samples have been analysed for main and trace components and 15N/14N and 18O/16O ratios, with the aim of identifying for the first time the origin of nitrate in the Arno River Basin so that further investigations can appropriately be designed. d18O(NO3)and d15N(NO3) values have allowed to hypothesise the main sources of nitrate, as follows: i) mineralized fertilizer, ii) soil-organic nitrogen, iii) manure and septic waste. The anomalously high d15N and d18O values in the Chiana (d15N=24.9‰ and d18O=15.5‰) and Usciana tributaries (d15N=30.1‰ and d18O=7.2‰) show a low probability of belonging to the same population as that of the other samples and can be related to denitrification process of nitrate from animal waste/sewage and/or an industrial process (e.g. tanneries).

Stable isotopic compositions in Australian precipitation

NASA Astrophysics Data System (ADS)

Liu, Jianrong; Fu, Guobin; Song, Xianfang; Charles, Stephen P.; Zhang, Yinghua; Han, Dongmei; Wang, Shiqin

2010-12-01

Stable deuterium (δD) and oxygen-18 (δ18O) isotopes in 1962 to 2002 precipitation from the seven Australian stations of the Global Network of Isotopes in Precipitation (GNIP) were used to investigate isotope characteristics including temporal and spatial distributions across different regions of Australia. On the basis of 1534 samples, the local meteoric water line (LMWL) was established as δD = 7.10δ18O + 8.21. δ18O showed a depletion trend from north and south to central Australia (a continental effect) and from west to east. Precipitation amount effects were generally greater than temperature effects, with quadratic or logarithmic correlations describing δ/T and δ/P better than linear relationships. Nonlinear stepwise regression was used to determine the significant meteorological control factors for each station, explaining about 50% or more of the δ18O variations. Geographical control factors for δ18O were given by the relationship δ18O (‰) = -0.005 longitude (°) - 0.034 latitude (°)-0.003 altitude (m) - 4.753. Four different types of d-excess patterns demonstrated particular precipitation formation conditions for four major seasonal rainfall zones. Finally, wavelet coherence (WTC) between δ18O and SOI confirmed that the influence of ENSO decreased from east and north to west Australia.

Constraining the origin of the Messinian gypsum deposits using coupled measurement of δ^{18}O$/δD in gypsum hydration water and salinity of fluid inclusions

NASA Astrophysics Data System (ADS)

Evans, Nicholas P.; Gázquez, Fernando; McKenzie, Judith A.; Chapman, Hazel J.; Hodell, David A.

2016-04-01

We used oxygen and hydrogen isotopes of gypsum hydration water (GHW) coupled with salinity deduced from ice melting temperatures of primary fluid inclusions in the same samples (in tandem with 87Sr/86Sr, δ34S and other isotopic measurements) to determine the composition of the mother fluids that formed the gypsum deposits of the Messinian Salinity Crisis from shallow and intermediate-depth basins. Using this method, we constrain the origin of the Messinian Primary Lower Gypsum (PLG) of the Sorbas basin (Betic foreland) and both the Upper Gypsum (UG) and the Lower Gypsum of the Sicilian basin. We then compare these results to measurements made on UG recovered from the deep Ionian and Balearic basins drilled during DSDP Leg 42A. The evolution of GHW δ18O/δD vs. salinity is controlled by mixing processes between fresh and seawater, coupled with the degree of evaporation. Evaporation and subsequent precipitation of gypsum from fluids dominated by freshwater will result in a depressed 87Sr/86Sr values and different trajectory in δ18O/δD vs. salinity space compared to fluids dominated by seawater. The slopes of these regression equations help to define the end-members from which the fluid originated. For example, salinity estimates from PLG cycle 6 in the Sorbas basin range from 18 to 51ppt, and after correction for fractionation factors, estimated δ18O and δD values of the mother water are low (-2.6 < δ18O < 2.7‰ ; -16.2 < δD < 15.8‰). The intercepts of the regression equations (i.e. at zero salinity) are within error of the average isotope composition of the modern precipitation and groundwater in this region of SE Spain. This indicates there was a significant contribution of meteoric water during gypsum deposition, while 87Sr/86Sr (0.708942 < 87Sr/86Sr < 0.708971) indicate the ions originated from the dissolution of previously marine evaporites. Gypsum from cycle 2 displays similar mother water values (-2.4 < δ18O < 2.4‰ ; -13.2 < δD < 17.0‰) to

Continuous-flow water sampler for real-time isotopic water measurements

NASA Astrophysics Data System (ADS)

Carter, J.; Dennis, K.

2013-12-01

continuous-flow water sample employs active control for all pertinent parameters, significantly increasing its stability and usability. We will present data from controlled laboratory experiments demonstrating sample-to-sample precision and long-term stability. We will also show experimental data that highlights the instrumental sample-to-sample memory, which we have decreased significantly from previous implementations of this technology. Additionally, we will present field results from the Sacramento River, CA. Dansgaard, W. (1964) 'Stable isotopes in precipitation', Tellus, 16(4), p. 436-468. Munksgaard, N.C., Wurster, C.M., Bass, A., Zagorskis, I., and Bird, M.I. (2012) 'First continuous shipboard d18O and dD measurements in seawater by diffusion sampling--cavity ring-down spectrometry', Environmental Chemistry Letters, 10, p.301-307. Munksgaard, N.C., Wurster, C.M., and Bird, M.I., (2011), 'Continuous analysis of δ18O and δD values of water by diffusion sampling cavity ring-down spectrometry: a novel sampling device for unattended field monitoring of precipitation, ground and surface waters', Rapid Communications in Mass Spectrometry, 25, p. 3706-3712.

Evaluating the skills of isotope-enabled general circulation models against in situ atmospheric water vapor isotope observations

NASA Astrophysics Data System (ADS)

Steen-Larsen, H. C.; Risi, C.; Werner, M.; Yoshimura, K.; Masson-Delmotte, V.

2017-01-01

The skills of isotope-enabled general circulation models are evaluated against atmospheric water vapor isotopes. We have combined in situ observations of surface water vapor isotopes spanning multiple field seasons (2010, 2011, and 2012) from the top of the Greenland Ice Sheet (NEEM site: 77.45°N, 51.05°W, 2484 m above sea level) with observations from the marine boundary layer of the North Atlantic and Arctic Ocean (Bermuda Islands 32.26°N, 64.88°W, year: 2012; south coast of Iceland 63.83°N, 21.47°W, year: 2012; South Greenland 61.21°N, 47.17°W, year: 2012; Svalbard 78.92°N, 11.92°E, year: 2014). This allows us to benchmark the ability to simulate the daily water vapor isotope variations from five different simulations using isotope-enabled general circulation models. Our model-data comparison documents clear isotope biases both on top of the Greenland Ice Sheet (1-11‰ for δ18O and 4-19‰ for d-excess depending on model and season) and in the marine boundary layer (maximum differences for the following: Bermuda δ18O = 1‰, d-excess = 3‰; South coast of Iceland δ18O = 2‰, d-excess = 5‰; South Greenland δ18O = 4‰, d-excess = 7‰; Svalbard δ18O = 2‰, d-excess = 7‰). We find that the simulated isotope biases are not just explained by simulated biases in temperature and humidity. Instead, we argue that these isotope biases are related to a poor simulation of the spatial structure of the marine boundary layer water vapor isotopic composition. Furthermore, we specifically show that the marine boundary layer water vapor isotopes of the Baffin Bay region show strong influence on the water vapor isotopes at the NEEM deep ice core-drilling site in northwest Greenland. Our evaluation of the simulations using isotope-enabled general circulation models also documents wide intermodel spatial variability in the Arctic. This stresses the importance of a coordinated water vapor isotope-monitoring network in order to discriminate amongst these model

Tracing groundwater recharge sources in the northwestern Indian alluvial aquifer using water isotopes (δ18O, δ2H and 3H)

NASA Astrophysics Data System (ADS)

Joshi, Suneel Kumar; Rai, Shive Prakash; Sinha, Rajiv; Gupta, Sanjeev; Densmore, Alexander Logan; Rawat, Yadhvir Singh; Shekhar, Shashank

2018-04-01

Rapid groundwater depletion from the northwestern Indian aquifer system in the western Indo-Gangetic basin has raised serious concerns over the sustainability of groundwater and the livelihoods that depend on it. Sustainable management of this aquifer system requires that we understand the sources and rates of groundwater recharge, however, both these parameters are poorly constrained in this region. Here we analyse the isotopic (δ18O, δ2H and tritium) compositions of groundwater, precipitation, river and canal water to identify the recharge sources, zones of recharge, and groundwater flow in the Ghaggar River basin, which lies between the Himalayan-fed Yamuna and Sutlej River systems in northwestern India. Our results reveal that local precipitation is the main source of groundwater recharge. However, depleted δ18O and δ2H signatures at some sites indicate recharge from canal seepage and irrigation return flow. The spatial variability of δ18O, δ2H, d-excess, and tritium reflects limited lateral connectivity due to the heterogeneous and anisotropic nature of the aquifer system in the study area. The variation of tritium concentration with depth suggests that groundwater above c. 80 mbgl is generally modern water. In contrast, water from below c. 80 mbgl is a mixture of modern and old waters, and indicates longer residence time in comparison to groundwater above c. 80 mbgl. Isotopic signatures of δ18O, δ2H and tritium suggest significant vertical recharge down to a depth of 320 mbgl. The spatial and vertical variations of isotopic signature of groundwater reveal two distinct flow patterns in the aquifer system: (i) local flow (above c. 80 mbgl) throughout the study area, and (ii) intermediate and regional flow (below c. 80 mbgl), where water recharges aquifers through large-scale lateral flow as well as vertical infiltration. The understanding of spatial and vertical recharge processes of groundwater in the study area provides important base-line knowledge

δ18O and δD variations in Holocene massive ice in the Sabettayakha river mouth, northern Yamal Peninsula

NASA Astrophysics Data System (ADS)

Vasil'chuk, Yu. K.; Podborny, Ye. Ye.; Budantseva, N. A.; Vasil'chuk, A. C.; Sullina, A. N.; Chizhova, Ju. N.

2016-10-01

The conditions of formation of massive ice near the South Tambey gas-condensate field in northern Yamal Peninsula are studied. It is shown that massive ice bodies up to 4.5 m thick occur in the Holocene deposits of the high laida and the first terrace. Therefore, they cannot be the remains of glaciers; they are ground ice formations. All three types of massive ice have quite various isotopic compositions: the values of δD range from-107 to-199.7, and δ18O from-15.7 to-26.48‰. Such a significant differentiation in isotopic composition is a result of cryogenic fractionation in a freezing water-saturated sediment. The most negative isotope values are even lower in this Holocene massive ice than in the Late Pleistocene ice-wedge ice of Yamal Peninsula.

Isotopic Studies of O-O Bond Formation During Water Oxidation (SISGR)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roth, Justine P.

Isotopic Studies of O-O Bond Formation During Water Oxidation (SISGR) Research during the project period focused primarily on mechanisms of water oxidation by structurally defined transition metal complexes. Competitive oxygen isotope fractionation of water, mediated by oxidized precursors or reduced catalysts together with ceric, Ce(IV), ammonium nitrate in aqueous media, afforded oxygen-18 kinetic isotope effects (O-18 KIEs). Measurement, calculation, and interpretation of O-18 KIEs, described in the accompanying report has important ramifications for the production of electricity and solar hydrogen (as fuel). The catalysis division of BES has acknowledged that understanding mechanisms of transition metal catalyzed water oxidation has majormore » ramifications, potentially leading to transformation of the global economy and natural environment in years to come. Yet, because of program restructuring and decreased availability of funds, it was recommended that the Solar Photochemistry sub-division of BES would be a more appropriate parent program for support of continued research.« less

Predictions and Verification of an Isotope Marine Boundary Layer Model

NASA Astrophysics Data System (ADS)

Feng, X.; Posmentier, E. S.; Sonder, L. J.; Fan, N.

2017-12-01

A one-dimensional (1D), steady state isotope marine boundary layer (IMBL) model is constructed. The model includes meteorologically important features absent in Craig and Gordon type models, namely height-dependent diffusion/mixing and convergence of subsiding external air. Kinetic isotopic fractionation results from this height-dependent diffusion which starts as pure molecular diffusion at the air-water interface and increases linearly with height due to turbulent mixing. The convergence permits dry, isotopically depleted air subsiding adjacent to the model column to mix into ambient air. In δD-δ18O space, the model results fill a quadrilateral, of which three sides represent 1) vapor in equilibrium with various sea surface temperatures (SSTs) (high d18O boundary of quadrilateral); 2) mixture of vapor in equilibrium with seawater and vapor in the subsiding air (lower boundary depleted in both D and 18O); and 3) vapor that has experienced the maximum possible kinetic fractionation (high δD upper boundary). The results can be plotted in d-excess vs. δ18O space, indicating that these processes all cause variations in d-excess of MBL vapor. In particular, due to relatively high d-excess in the descending air, mixing of this air into the MBL causes an increase in d-excess, even without kinetic isotope fractionation. The model is tested by comparison with seven datasets of marine vapor isotopic ratios, with excellent correspondence; >95% of observational data fall within the quadrilateral area predicted by the model. The distribution of observations also highlights the significant influence of vapor from the nearby converging descending air on isotopic variations in the MBL. At least three factors may explain the <5% of observations that fall slightly outside of the predicted region in both δD-δ18O and d-excess - δ18O space: 1) variations in seawater isotopic ratios, 2) variations in isotopic composition of subsiding air, and 3) influence of sea spray. The model

Temporal variation in stable isotopes ( 18O and 2H) and major ion concentrations within the Darling River between Bourke and Wilcannia due to variable flows, saline groundwater influx and evaporation

NASA Astrophysics Data System (ADS)

Meredith, K. T.; Hollins, S. E.; Hughes, C. E.; Cendón, D. I.; Hankin, S.; Stone, D. J. M.

2009-11-01

SummaryThe Darling River faces environmental pressures from both climate change and anthropogenic influences leading to a reduction in fresh water availability for the river system. This study uses temporal hydrochemical and stable isotope data ( 18O and 2H) that has been collected over a five-year period (2002 to 2007), as part of the Global Network for Isotopes in Rivers (GNIR) programme, which is aimed at monitoring hydrological processes in large river systems throughout the world. Daily stream flow, monthly stable isotope and major ion chemistry data is presented for sampling locations along the Darling River at Bourke, Louth and Wilcannia, as well as additional more detailed data from locations near Glen Villa. The hydrochemical data is used to partition groundwater influx that is not readily separable by using only the available isotopic data. Individual flow events in the river were found to be isotopically distinct but the Local Evaporation Lines (LELs) that develop after these events have a similar slope indicating similar climatic conditions across this region. After a storm event, fresh waters that are isotopically depleted are introduced to the system and d-excess ( d) values return towards meteoric values. During low flow, the Cl -, Na +, Mg 2+, SO 42-, δ 18O and δ 2H values all increase systematically, and d values become more negative. Hydrochemical and isotopic tracers in conjunction with high resolution sampling strategies have been used to quantify the contribution of evaporation, bank storage release and saline groundwater influx to the evolution of the river waters. Fractional contributions (% of volume) of groundwater to the river water were calculated for different reaches using Cl - concentrations, δ 18O and d values and it was found that river waters comprised of approximately 60-99% saline groundwater during zero flow. The reduced water levels in the river during the drought conditions experienced in the period of this study had

Assessing modern climatic controls on southern Sierra Nevada precipitation and speleothem δ18O

NASA Astrophysics Data System (ADS)

McCabe-Glynn, S. E.; Johnson, K. R.; Berkelhammer, M. B.

2012-12-01

Precipitation in the southwestern United States (SW US) is highly seasonal and exhibits inter-annual to inter-decadal variability. A 1154-year δ18O time series obtained from a southwestern Sierra Nevada Mountain stalagmite from Crystal Cave, CRC-3, (36.58°N; 118.56°W; 1540 m) reveals substantial decadal to multi-decadal variability closely linked to the Pacific Decadal Oscillation (PDO), and more specifically, to sea surface temperatures (SSTs) in the Kuroshio Extension region, which impact the atmospheric trajectory and isotopic composition of moisture reaching the study site. The instrumental portion of the CRC-3 δ18O time series suggests that more negative precipitation δ18O values are delivered from higher latitudes during positive phases of the PDO and/or when SSTs in the Kuroshio Extension region are anomalously cool, such as during La Niña events. In order to improve our understanding of the controls on speleothem δ18O in this region, we have conducted a detailed modern study of the climate, hydrology, and stable isotopic composition of meteoric waters (precipitation and drip water) at the cave. Here we present Crystal Cave drip logger results from 2010 to 2012, the isotopic composition of North American Deposition Program precipitation samples collected from 2001 to 2012 from several locations near our site including Ash Mountain (ASM), Sequoia National Park-Giant Forest (Ca75), and Yosemite National Park (Ca99), and isotopic composition of cave drip water and glass plate calcite. We also compare the δ18O values in the precipitation to satellite imagery, NCAR/NCEP data, and NOAA Hysplit Model backward trajectories between the sites. Results indicate that this site is particularly sensitive to "Pineapple Express" type storms, a persistent flow of atmospheric moisture and heavy rainfall extending from near the Hawaiian Islands to the coast of North America, which average about twice as much precipitation as other storms in the Sierra Nevada during

EVALUATION OF PROMPT DOSE ENVIRONMENT IN THE NATIONAL IGNITION FACILITY DURING D-D AND THD SHOTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khater, H; Dauffy, L; Sitaraman, S

2009-04-28

Evaluation of the prompt dose environment expected in the National Ignition Facility (NIF) during Deuterium-Deuterium (D-D) and Tritium-Hydrogen-Deuterium (THD) shots have been completed. D-D shots resulting in the production of an annual fusion yield of up to 2.4 kJ (200 shots with 10{sup 13} neutrons per shot) are considered. During the THD shot campaign, shots generating a total of 2 x 10{sup 14} neutrons per shot are also planned. Monte Carlo simulations have been performed to estimate prompt dose values inside the facility as well as at different locations outside the facility shield walls. The Target Chamber shielding, along withmore » Target Bay and Switchyard walls, roofs, and shield doors (when needed) will reduce dose levels in occupied areas to acceptable values during these shot campaigns. The calculated dose values inside occupied areas are small, estimated at 25 and 85 {micro}rem per shot during the D-D and THD shots, respectively. Dose values outside the facility are insignificant. The nearest building to the NIF facility where co-located workers may reside is at a distance of about 100 m from the Target Chamber Center (TCC). The dose in such a building is estimated at a fraction of a ?rem during a D-D or a THD shot. Dose at the nearest site boundary location (350 m from TCC), is caused by skyshine and to a lesser extent by direct radiation. The maximum off-site dose during any of the shots considered is less than 10 nano rem.« less

Water - Isotope - Map (δ 18O, δ 2H, 3H) of Austria: Applications, Extremes and Trends

NASA Astrophysics Data System (ADS)

Wyhlidal, Stefan; Kralik, Martin; Benischke, Ralf; Leis, Albrecht; Philippitsch, Rudolf

2016-04-01

The isotopic ratios of oxygen and hydrogen in water (2H/1H and 18O/16O) are important tools to characterise waters and their cycles. This starts in the atmosphere as rain or snow and continues in surface water and ends in shallow groundwater as well as in deep groundwater. Tritium formed by natural cosmic radiation in the upper atmosphere and in the last century by tests of thermonuclear bombs in the atmosphere, is characterised by its radioactive decay with a half-life of 12.32 years and is an ideal age-marker during the last 60 years. To determine the origin and mean age of waters in many projects concerning water supply, engineering and scientific projects in the last 45 years on more than 1,350 sites, more than 40,000 isotope measurements were performed in Austria. The median value of all sites of oxygen-18 is δ 18O -10.7 ‰ and for hydrogen-2 δ 2H -75 ‰. As the fractionation is mainly temperature dependent the lowest negative values are observed in winter precipitation (oxygen-18 as low as δ 18O -23 ‰) and in springs in the mountain regions (δ 18O -15.1 ‰). In contrast the highest values were observed in summer precipitation (up to δ 18O - 0.5 ‰) and in shallow lakes in the Seewinkel (up to δ 18O + 5 ‰). The isotopic ratios of the Austrian waters are also influenced by the origin of the evaporated water masses. Therefore the precipitation in the region south of the main Alpine crest (East-Tyrol, Carinthia and South-East Styria) is approximately 1 ‰ higher in δ 18O-values than sites at the same altitude in the northern part. This is most probably caused by the stronger influence of precipitation from the mediterranean area. The median value of all 1,120 sampling sites of decay corrected (2015) tritium measurements is 6.2 tritium units (TU). This is somewhat smaller than the median value of all precipitation stations with 7.2 TU. This can be explained by the fact that in most cases in groundwater the median value has been reduced by decay

Vibrational spectra and structure of benzil and its 18O- and d 10-labelled derivatives: a quantum chemical and experimental study

NASA Astrophysics Data System (ADS)

Kolev, Tsonko M.; Stamboliyska, Bistra A.

2002-12-01

Geometry and vibrational spectroscopic data of benzil-d 0 benzil-d 10 and benzil- 18O calculated at various levels of theory (RHF/6-31G*, B3LYP/6-31G*, BLYP/6-31G*) are reported. The theoretical results are discussed mainly in terms of the comparisons with infrared (4000-100 cm -1) and Raman (4000-50 cm -1) spectral data. The calculated isotopic frequency shifts, induced by the 18O- and d 10-labeling, are in a good agreement with the measured values. A complete vibrational assignment was made with the help of ab initio force field calculations. The data thus obtained were used for reassigning some vibrational frequencies. The results of the optimized molecular structure obtained on the basis of RHF and the DFT calculations are presented and compared with the experimental X-ray diffraction for the benzil-d 0 single crystal. It turns out that the best structural parameters are predicted by the B3LYP/6-31G* method.

Vibrational spectra and structure of benzil and its 18O- and d10-labelled derivatives: a quantum chemical and experimental study.

PubMed

Kolev, Tsonko M; Stamboliyska, Bistra A

2002-12-01

Geometry and vibrational spectroscopic data of benzil-d0 benzil-d10 and benzil-18O calculated at various levels of theory (RHF/6-31G*, B3LYP/6-31G*, BLYP/6-31G*) are reported. The theoretical results are discussed mainly in terms of the comparisons with infrared (4000-100 cm(-1)) and Raman (4000-50 cm(-1)) spectral data. The calculated isotopic frequency shifts, induced by the 18O- and d10-labeling, are in a good agreement with the measured values. A complete vibrational assignment was made with the help of ab initio force field calculations. The data thus obtained were used for reassigning some vibrational frequencies. The results of the optimized molecular structure obtained on the basis of RHF and the DFT calculations are presented and compared with the experimental X-ray diffraction for the benzil-d0 single crystal. It turns out that the best structural parameters are predicted by the B3LYP/6-31G* method.

Multi-isotope (C - O - S - H - B - Mg - Ca - Ba) and trace element variations along a vertical pore water profile across a brackish-fresh water transition, Baltic Sea

NASA Astrophysics Data System (ADS)

Böttcher, Michael E.; Lapham, Laura; Gussone, Nikolaus; Struck, Ulrich; Buhl, Dieter; Immenhauser, Adrian; Moeller, Kirsten; Pretet, Chloé; Nägler, Thomas F.; Dellwig, Olaf; Schnetger, Bernhard; Huckriede, Hermann; Halas, Stan; Samankassou, Elias

2013-04-01

The Holocene Baltic Sea has been switched several times between fresh water and brackish water modes. Modern linear sedimentation rates, based on 210-Pb, 137-Cs, and Hg dating of surface sediments, are between 0.1 and 0.2 mm per year. The change in paleo-environmental conditions caused downcore gradients in the concentrations of dissolved species from modern brackish waters towards fresh paleo-pore waters, interrupted by the brief brackish Yoldia stage. These strong physico-chemical changes had consequences for e.g., microbial activity and further physical and chemical water-solid interactions associated with multiple stable isotope fractionation processes, and, in turn, have strong implications for isotope and trace element partitioning upon early diagenetic mineral (trans)formations. In this communication, we present the results from the first integrated multi-isotope and trace element investigation conducted in this type of salinity-gradient system. It is found that concentrations of conservative elements (e.g., Na, Cl) decrease with depth due to diffusion of ions from brackish waters into underlying fresh waters. This is associated with pronounced depletions in H-2 and O-18 of pore water with depth. Covariations of both isotope systems are close to the meteoric water line as defined by modern Baltic Sea surface waters. A downward increase and decrease of Ca and Mg concentrations, respectively, is associated with decreasing Ca-44 and Mg-26 isotope values. B-11 isotope values decrease in the limnic part of the sediments, too. On the other hand, an increase in Ba concentrations with depth is associated with an increase in Ba-137/134 isotope values. Microbial sulfate reduction and organic matter oxidation lead to an increase in DIC, but a decrease in sulfate concentrations and in C-13 contents of DIC with depth. Suess (1981) was probably the first to propose, that desorption of Ca and Ba from glacial sediments due to downward diffusing ions may be responsible for a

Stable Isotope Systematics in Grasshopper Assemblages Along an Elevation Gradient, Colorado

NASA Astrophysics Data System (ADS)

Kohn, M. J.; Evans, S.; Dean, J.; Nufio, C.

2012-12-01

Insects comprise over three quarters of all animal species, yet studies of body water isotopic composition are limited to only the cockroach, the hoverfly, and chironomid flies. These studies suggest that oxygen and hydrogen isotopic compositions in body water are primarily controlled by dietary water sources, with modification from respiratory and metabolic processes. In particular, outward diffusion of isotopically depleted water vapor through insect spiracles at low humidity enriches residual body water in 18O and 2H (D). Stable isotope compositions (δ18O and δD) also respond to gradients in elevation and humidity, but these influences remain poorly understood. In this study, we measured grasshopper body water and local vegetation isotopic compositions along an elevation gradient in Colorado to evaluate three hypotheses: 1) Insect body water isotopic composition is directly related to food source water composition 2) Water vapor transport alters body water isotopic compositions relative to original diet sources, and 3) Elevation gradients influence isotopic compositions in insect body water. Thirty-five species of grasshopper were collected from 14 locations in Colorado grasslands, ranging in elevation from 450 to 800 meters (n=131). Body water was distilled from previously frozen grasshopper specimens using a vacuum extraction line, furnaces (90 °C), and liquid nitrogen traps. Water samples were then analyzed for δ18O and δD on an LGR Liquid Water Isotope Analyzer, housed in the Department of Geosciences, Boise State University. Grasshopper body water isotopic compositions show wide variation, with values ranging between -76.64‰ to +42.82‰ in δD and -3.06‰ to +26.78‰ in δ18O. Precipitation δ18O values over the entire Earth excluding the poles vary by approximately 30‰, comparable to the total range measured in our single study area. Most grasshopper values deviate from the global meteoric water line relating δ18O and δD in precipitation

Plan of study to determine if the isotopic ratios [delta]15 N and [delta]18 O can reveal the sources of nitrate discharged by the Mississippi River into the Gulf of Mexico

USGS Publications Warehouse

Battaglin, William A.; Kendall, Carol; Goolsby, Donald A.; Boyer, Laurie L.

1997-01-01

Nitrate and other nutrients discharged from the Mississippi River basin are suspected of causing a zone of depleted dissolved oxygen (hypoxic zone) in the Gulf of Mexico each summer. The hypoxic zone may have an adverse effect on aquatic life and commercial fisheries. Commercial fertilizers are the dominant source of nitrogen input to the Mississippi basin. Other nitrogen sources include animal waste, fixation of atmospheric nitrogen by legumes, precipitation, domestic and industrial effluent, and the soil. The inputs of nitrogen from most of these sources to the Mississippi basin can be estimated and the outputs in surface water can be measured. However, nitrogen from each source is affected differently by physical, chemical, and biological processes that control nitrogen cycling in terrestrial and aquatic systems. Hence, the relative contributions from the various sources of nitrogen to nitrate load in the Mississippi River are unknown because the different sources may not contribute proportionally to their inputs in the basin. It may be possible to determine the relative contributions of the major sources of nitrate in river water using the stable isotopic ratios d15N and d18O of the nitrate ion. A few researchers have used the d15N and/or d18O isotope ratios to determine sources of nitrate in ground water, headwater catchments, and small rivers, but little is known about the isotopic composition of nitrate in larger rivers. The objective of this study is to measure the isotopic composition of nitrate and suspended organic matter in the Mississippi River and its major tributaries, in discharge to the Gulf of Mexico, and in streamflow from smaller watersheds that have distinct sources of nitrogen (row crops, animal wastes, and urban effluents) or are minimally impacted by man (undeveloped). Samples from seven sites on the Mississippi River and its tributaries and from 17 sites in smaller watersheds within the Mississippi River basin will be analyzed for d15N and

Leaf cellulose δD and δ18O trends with elevation differ in direction among co-occurring, semiarid plant species

USGS Publications Warehouse

Terwilliger, Vallery J.; Betancourt, Julio L.; Leavitt, Steven W.; Van De Water, Peter K.

2002-01-01

The potential to reconstruct paleoclimate from analyses of stable isotopes in fossil leaf cellulose could be enhanced by adequate calibration. This potential is likely to be particularly great in mid-latitude deserts, where a rich store of fossil leaves is available from rodent middens. Trends in ??D and ??18O of leaf cellulose were examined for three species growing across climatic gradients caused by elevation and slope aspect in southeastern Utah, USA. The species differed in morphology (Pinus edulis vs. Yucca glauca), photosynthetic pathway (C3 Y. glauca vs. CAM Yucca baccata) or both (P. edulis vs. Y. baccata). The ??DLCN (leaf cellulose nitrate) and ??18OLC (leaf cellulose) values of P. edulis decreased with elevation. Stem water ??D values either increased (in spring) or did not change with elevation (in summer). Needle water ??D values usually decreased with elevation and differed greatly with leaf age. These results suggest that ?? cellulose values of P. edulis record the effects of climate on the isotopic composition of leaf water but not climate effects on meteoric water. In contrast to P. edulis, ??DLCN values of Y. glauca increased with elevation. The ??18O LC values ofc Y. glauca also increased with elevation but less significantly and only on south-facing slopes. The ?? cellulose values in both P. edulis and Y. glauca were most significantly related to changes in temperature, although temperature and precipitation were negatively correlated in the study area. Where all three species co-occurred, their ??DLCN values differed but their ??18O LC values were the same. The disparity in ??DLCN between Y. baccata and the other species corresponds to differences in biochemical fractionations associated with photosynthetic pathway. Biochemical fractionations may also contribute to differences between the two C3 species. Knowledge of factors affecting responses of individual plant species to environment may be required to infer climate from ??DLCN and ??18OLC

Growth Rates, Stable Oxygen Isotopes (18O), and Strontium (Sr/Ca) Composition in Two Species of Pacific Sclerosponges (Acanthocheatetes wellsi and Astrosclera willeyana) with 18O Calibration and Application to Paleoceanography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grottoli, A.; Adkins, J; Panero, W

2010-01-01

The isotopic and elemental composition of sclerosponge skeletons is used to reconstruct paleoceanographic records. Yet few studies have systematically examined the natural variability in sclerosponge skeletal {delta}{sup 18}O, growth, and Sr/Ca, and how that may influence the interpretation of sclerosponge proxy records. Here, we analyzed short records in seven specimens of Acanthocheatetes wellsi (high-Mg calcite, 21 mol% Mg) from Palau, four A. wellsi (high-Mg calcite, 21 mol% Mg) from Saipan, and three Astrosclera willeyana (aragonite) sclerosponges from Saipan, as well as one long record in an A. wellsi specimen from Palau spanning 1945-2001.5. In Saipan, species-specific and mineralogical effects appearmore » to have a negligible effect on sclerosponge {delta}{sup 18}O, facilitating the direct comparison of {delta}{sup 18}O records between species at a given location. At both sites, A. wellsi {delta}{sup 18}O and growth rates were sensitive to environmental conditions, but Sr/Ca was not sensitive to the same conditions. High-resolution {delta}{sup 18}O analyses confirmed this finding as both A. wellsi and A. willeyana deposited their skeleton in accordance with the trends in isotopic equilibrium with seawater, though with a 0.27{per_thousand} offset in the case of A. willeyana. In the high-Mg-calcite species A. wellsi, Mg may be interfering with Sr incorporation into the skeleton. On multidecadal timescales, A. wellsi sclerosponge {delta}{sup 18}O in Palau tracked the Southern Oscillation Index variability post-1977, but not pre-1977, coincident with the switch in the Pacific Decadal Oscillation (PDO) at {approx}1976. This suggests that water mass circulation in the region is influenced by El Nino-Southern Oscillation variability during positive PDO phases, but not during negative ones.« less

Neural circuit rewiring: insights from DD synapse remodeling.

PubMed

Kurup, Naina; Jin, Yishi

2016-01-01

Nervous systems exhibit many forms of neuronal plasticity during growth, learning and memory consolidation, as well as in response to injury. Such plasticity can occur across entire nervous systems as with the case of insect metamorphosis, in individual classes of neurons, or even at the level of a single neuron. A striking example of neuronal plasticity in C. elegans is the synaptic rewiring of the GABAergic Dorsal D-type motor neurons during larval development, termed DD remodeling. DD remodeling entails multi-step coordination to concurrently eliminate pre-existing synapses and form new synapses on different neurites, without changing the overall morphology of the neuron. This mini-review focuses on recent advances in understanding the cellular and molecular mechanisms driving DD remodeling.

Sources and fractionation processes influencing the isotopic distribution of H, O and C in the Long Valley hydrothermal system, California, U.S.A.

USGS Publications Warehouse

White, A.F.; Peterson, M.L.; Wollenberg, H.; Flexser, S.

1990-01-01

The isotopic ratios of H, O and C in water within the Long Valley caldera, California reflect input from sources external to the hydrothermal reservoir. A decrease in ??D in precipitation of 0.5??? km-1, from west to east across Long Valley, is caused by the introduction of less fractionated marine moisture through a low elevation embayment in the Sierra Nevada Mountain Range. Relative to seasonal fluctuations in precipitation (-158 to -35??.), ??D ranges in hot and cold surface and groundwaters are much less variable (-135 to -105??.). Only winter and spring moisture, reflecting higher precipitation rates with lighter isotopic signatures, recharge the hydrological system. The hydrothermal fluids are mixtures of isotopically heavy recharge (??D = - 115???, ??18O = - 15???) derived from the Mammoth embayment, and isotopically lighter cold water (??D = -135???, ??18O = -18???). This cold water is not representative of current local recharge. The ??13C values for dissolved carbon in hot water are significantly heavier (- 7 to - 3???) than in cold water (-18 to -10???) denoting a separate hydrothermal origin. These ??13C values overlie the range generally attributed to magmatic degassing of CO2. However, ??13C values of metamorphosed Paleozoic basement carbonates surrounding Long Valley fall in a similar range, indicating that hydrothermal decarbonization reactions are a probable source of CO2. The ??13C and ??18O values of secondary travertime and vein calcite indicate respective fractionation with CO2 and H2O at temperatures approximating current hydrothermal conditions. ?? 1990.

Deacylation transition states of a bacterial DD-peptidase.

PubMed

Adediran, S A; Kumar, I; Pratt, R F

2006-10-31

Beta-lactam antibiotics restrict bacterial growth by inhibiting DD-peptidases. These enzymes catalyze the final transpeptidation step in bacterial cell wall biosynthesis. Although much structural information is now available for these enzymes, the mechanism of the actual transpeptidation reaction has not been studied in detail. The reaction is known to involve a double-displacement mechanism with an acyl-enzyme intermediate, which can be attacked by water, specific amino acids, peptides, and other acyl acceptors. We describe in this paper an investigation of acyl acceptor specificity and assess the need for general base catalysis in the deacylation transition state of the Streptomyces R61 DD-peptidase. We show, by the criterion of solvent deuterium kinetic isotope effect measurements and proton inventories, that the transition states of specific and nonspecific substrates are very similar, at least with respect to proton motion. The transition states for attack (tetrahedral intermediate formation) by d-amino acids and Gly-l-Xaa dipeptides do not include a general base catalyst, while such catalysis is essential for reaction with water and d-alpha-hydroxy acids. D-Alpha-hydroxy acids act as acyl acceptors for glycyl substrates but not for more specific d-alanyl substrates; hydroxy acids actually behave, more generally, as mixed inhibitors of the DD-peptidase. The structural and mechanistic bases of these observations are discussed; they should inform transition state analogue design.

Multi-scale study of the isotope effect in ISTTOK

NASA Astrophysics Data System (ADS)

Liu, B.; Silva, C.; Figueiredo, H.; Pedrosa, M. A.; van Milligen, B. Ph.; Pereira, T.; Losada, U.; Hidalgo, C.

2016-05-01

The isotope effect, namely the isotope dependence of plasma confinement, is still one of the principal scientific conundrums facing the magnetic fusion community. We have investigated the impact of isotope mass on multi-scale mechanisms, including the characterization of radial correlation lengths (\\boldsymbol{L}{r} ) and long-range correlations (LRC) of plasma fluctuations using multi-array Langmuir probe system, in hydrogen (H) and deuterium (D) plasmas in the ISTTOK tokamak. We found that when changing plasma composition from the H dominated to D dominated, the LRC amplitude increased markedly (10-30%) and the \\boldsymbol{L}{r} increased slightly (~10%). The particle confinement also improved by about 50%. The changes of LRC and \\boldsymbol{L}{r} are congruent with previous findings in the TEXTOR tokamak (Xu et al 2013 Phys. Rev. Lett. 110 265005). In addition, using biorthogonal decomposition, both geodesic acoustic modes and very low frequency (<5 kHz) coherent modes were found to be contributing to LRC.

Analysis of stable isotope ratios (δ18O and δ2H) in precipitation of the Verde River watershed, Arizona 2003 through 2014

USGS Publications Warehouse

Beisner, Kimberly R.; Paretti, Nicholas V.; Tucci, Rachel S.

2016-04-25

Stable isotope delta values (δ18O and δ2H) of precipitation can vary with elevation, and quantification of the precipitation elevation gradient can be used to predict recharge elevation within a watershed. Precipitation samples were analyzed for stable isotope delta values between 2003 and 2014 from the Verde River watershed of north-central Arizona. Results indicate a significant decrease in summer isotopic values overtime at 3,100-, 4,100-, 6,100-, 7,100-, and 8,100-feet elevation. The updated local meteoric water line for the area is δ2H = 7.11 δ18O + 3.40. Equations to predict stable isotopic values based on elevation were updated from previous publications in Blasch and others (2006), Blasch and Bryson (2007), and Bryson and others (2007). New equations were separated for samples from the Camp Verde to Flagstaff transect and the Prescott to Chino Valley transect. For the Camp Verde to Flagstaff transect, the new equations for winter precipitation are δ18O = -0.0004z − 8.87 and δ2H = -0.0029z − 59.8 (where z represents elevation in feet) and the summer precipitation equations were not statistically significant. For the Prescott to Chino Valley transect, the new equations for summer precipitation are δ18O = -0.0005z − 3.22 and δ2H = -0.0022z − 27.9; the winter precipitation equations were not statistically significant and, notably, stable isotope values were similar across all elevations. Interpretation of elevation of recharge contributing to surface and groundwaters in the Verde River watershed using the updated equations for the Camp Verde to Flagstaff transect will give lower elevation values compared with interpretations presented in the previous studies. For waters in the Prescott and Chino Valley area, more information is needed to understand local controls on stable isotope values related to elevation.

Complete Measurement of Stable Isotopes in N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O) Using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS)

NASA Astrophysics Data System (ADS)

Leen, J. B.; Gupta, M.

2014-12-01

Nitrate contamination in water is a worldwide environmental problem and source apportionment is critical to managing nitrate pollution. Fractionation caused by physical, chemical and biological processes alters the isotope ratios of nitrates (15N/14N, 18O/16O and 17O/16O) and biochemical nitrification and denitrification impart different intramolecular site preference (15N14NO vs. 14N15NO). Additionally, atmospheric nitrate is anomalously enriched in 17O compared to other nitrate sources. The anomaly (Δ17O) is conserved during fractionation processes, providing a tracer of atmospheric nitrate. All of these effects can be used to apportion nitrate in soil. Current technology for measuring nitrate isotopes is complicated and costly - it involves conversion of nitrate to nitrous oxide (N2O), purification, preconcentration and measurement by isotope ratio mass spectrometer (IRMS). Site specific measurements require a custom IRMS. There is a pressing need to make this measurement simpler and more accessible. Los Gatos Research has developed a next generation mid-infrared Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) analyzer to quantify all stable isotope ratios of N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O). We present the latest performance data demonstrating the precision and accuracy of the OA-ICOS based measurement. At an N2O concentration of 322 ppb, the analyzer quantifies [N2O], δ15N, δ15Na, δ15Nb, and δ18O with a precision of ±0.05 ppb, ±0.4 ‰, ±0.45 ‰, and ±0.6 ‰, and ±0.8 ‰ respectively (1σ, 100s; 1σ, 1000s for δ18O). Measurements of gas standards demonstrate accuracy better than ±1 ‰ for isotope ratios over a wide dynamic range (200 - 100,000 ppb). The measurement of δ17O requires a higher concentration (1 - 50 ppm), easily obtainable through conversion of nitrates in water. For 10 ppm of N2O, the instrument achieves a δ17O precision of ±0.05 ‰ (1σ, 1000s). This performance is sufficient to quantify atmospheric

USGS46 Greenland ice core water – A new isotopic reference material for δ2H and δ18O measurements of water

USGS Publications Warehouse

Coplen, Tyler B.; Qi, Haiping; Tarbox, Lauren V.; Lorenz, Jennifer M.; Buck, Bryan

2015-01-01

Ice core from Greenland was melted, filtered, homogenised, loaded into glass ampoules, sealed, autoclaved to eliminate biological activity, and calibrated by dual-inlet isotope-ratio mass spectrometry. This isotopic reference material (RM), USGS46, is intended as one of two secondary isotopic reference waters for daily normalisation of stable hydrogen (δ2H) and stable oxygen (δ18O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The measured δ2H and δ18O values of this reference water were −235.8 ± 0.7‰ and −29.80 ± 0.03‰, respectively, relative to VSMOW on scales normalised such that the δ2H and δ18O values of SLAP reference water are, respectively, −428 and −55.5‰. Each uncertainty is an estimated expanded uncertainty (U = 2uc) about the reference value that provides an interval that has about a 95-percent probability of encompassing the true value. This reference water is available in cases containing 144 glass ampoules that are filled with either 4 ml or 5 ml of water per ampoule.

Shutdown Dose Rate Analysis for the long-pulse D-D Operation Phase in KSTAR

NASA Astrophysics Data System (ADS)

Park, Jin Hun; Han, Jung-Hoon; Kim, D. H.; Joo, K. S.; Hwang, Y. S.

2017-09-01

KSTAR is a medium size fully superconducting tokamak. The deuterium-deuterium (D-D) reaction in the KSTAR tokamak generates neutrons with a peak yield of 3.5x1016 per second through a pulse operation of 100 seconds. The effect of neutron generation from full D-D high power KSTAR operation mode to the machine, such as activation, shutdown dose rate, and nuclear heating, are estimated for an assurance of safety during operation, maintenance, and machine upgrade. The nuclear heating of the in-vessel components, and neutron activation of the surrounding materials have been investigated. The dose rates during operation and after shutdown of KSTAR have been calculated by a 3D CAD model of KSTAR with the Monte Carlo code MCNP5 (neutron flux and decay photon), the inventory code FISPACT (activation and decay photon) and the FENDL 2.1 nuclear data library.

Constraining N2O emissions since 1940 by firn air isotope measurements in both hemispheres

NASA Astrophysics Data System (ADS)

Prokopiou, Markella; Martinerie, Patricia; Sapart, Celia; Witrant, Emmanuel; Monteil, Guillaume; Ishijima, Kentaro; Kaiser, Jan; Levin, Ingeborg; Sowers, Todd; Blunier, Thomas; Etheridge, David; Dlugokencky, Ed; van de Wal, Roderik; Röckmann, Thomas

2017-04-01

N2O is currently the 3rd most important anthropogenic greenhouse gas in terms of radiative forcing and its atmospheric mole fraction is rising steadily. To quantify the growth rate and its causes, we performed a multi-site reconstruction of the atmospheric N2O mole fraction and isotopic composition using firn air data collected from Greenland and Antarctica in combination with a firn diffusion and densification model. The multi-site reconstruction showed that while the global mean N2O mole fraction increased from (290±1) nmol mol-1 in 1940 to (322±1) nmol mol-1 in 2008 the isotopic δ values of atmospheric N2O decreased by (- 2.2±0.2) ‰ for δ15Nav, (- 1.0±0.3) ‰ for δ18O, (- 1.3±0.6) ‰ for δ15Nα, and (- 2.8±0.6) ‰ for δ15Nβover the same period. The detailed temporal evolution of the mole fraction and isotopic composition derived from the firn air model was then used in a two-box atmospheric model (comprising a stratospheric and a tropospheric box) to infer changes in the isotopic source signature over time. The precise value of the source strength depends on the choice of the N2O lifetime, which we choose to be 123 a. Adopting this lifetime results in total average source isotopic signatures of (- 7.6±0.8) ‰ (vs. Air-N2) for δ15Nav, (32.2±0.2) ‰ (vs. VSMOW) for δ18O, (- 3.0±1.9) ‰ (vs. Air-N2) for δ15Nα, and (- 11.7±2.3) ‰ (vs. Air-N2) for δ15Nβ over the investigated period. δ15Navand δ15Nβ show some temporal variability while the other source isotopic signatures remain unchanged. The 15N site-preference (= δ15Nα - δ15Nβ) can be used to reveal further information on the source emission origins. Based on the changes in the isotopes we conclude that the main contribution to N2O changes in the atmosphere since 1940 is from soils, with agricultural soils being the principal anthropogenic component, which is in line with previous studies.

Note: Coincidence measurements of 3He and neutrons from a compact D-D neutron generator.

PubMed

Ji, Q; Lin, C-J; Tindall, C; Garcia-Sciveres, M; Schenkel, T; Ludewigt, B A

2017-05-01

Tagging of neutrons (2.45 MeV) with their associated 3 He particles from deuterium-deuterium (D-D) fusion reactions has been demonstrated in a compact neutron generator setup enabled by a high brightness, microwave-driven ion source with a high fraction of deuterons. Energy spectra with well separated peaks of the D-D fusion reaction products, 3 He, tritons, and protons, were measured with a silicon PIN diode. The neutrons were detected using a liquid scintillator detector with pulse shape discrimination. By correlating the 3 He detection events with the neutron detection in time, we demonstrated the tagging of emitted neutrons with 3 He particles detected with a Si PIN diode detector mounted inside the neutron generator vacuum vessel.

Towards a Better Understanding of the Oxygen Isotope Signature of Atmospheric CO2: Determining the 18O-Exchange Between CO2 and H2O in Leaves and Soil On-line with Laser-Based Spectroscopy

NASA Astrophysics Data System (ADS)

Gangi, L.; Rothfuss, Y.; Vereecken, H.; Brueggemann, N.

2013-12-01

The oxygen isotope signature of carbon dioxide (δ18O-CO2) is a powerful tool to disentangle CO2 fluxes in terrestrial ecosystems, as CO2 attains a contrasting 18O signature by the interaction with isotopically different soil and leaf water pools during soil respiration and photosynthesis, respectively. However, using the δ18O-CO2 signal to quantify plant-soil-atmosphere CO2 fluxes is still challenging due to a lack of knowledge concerning the magnitude and effect of individual fractionation processes during CO2 and H2O diffusion and during CO2-H2O isotopic exchange in soils and leaves, especially related to short-term changes in environmental conditions (non-steady state). This study addresses this research gap by combined on-line monitoring of the oxygen isotopic signature of CO2 and water vapor during gas exchange in soil and plant leaves with laser-based spectroscopy, using soil columns and plant chambers. In both experimental setups, the measured δ18O of water vapor was used to infer the δ18O of liquid water, and, together with the δ18O-CO2, the degree of oxygen isotopic equilibrium between the two species (θ). Gas exchange experiments with different functional plant types (C3 coniferous, C3 monocotyledonous, C3 dicotyledonous, C4) revealed that θ and the influence of the plant on the ambient δ18O-CO2 (CO18O-isoforcing) not only varied on a diurnal timescale but also when plants were exposed to limited water availability, elevated air temperature, and abrupt changes in light intensity (sunflecks). Maximum θ before treatments ranged between 0.7 and 0.8 for the C3 dicotyledonous (poplar) and C3 monocotyledonous (wheat) plants, and between 0.5 and 0.6 for the conifer (spruce) and C4 plant (maize) while maximum CO18O-isoforcing was highest in wheat (0.03 m s-1 ‰), similar in poplar and maize (0.02 m s-1 ‰), and lowest in spruce (0.01 m s-1 ‰). Multiple regression analysis showed that up to 97 % of temporal dynamics in CO18O-isoforcing could be

Use of Isotope Ratio Mass Spectrometry (IRMS) Determination ((18)O/(16)O) to Assess the Local Origin of Fish and Asparagus in Western Switzerland.

PubMed

Rossier, Joël S; Maury, Valérie; de Voogd, Blaise; Pfammatter, Elmar

2014-10-01

Here we present the use of isotope ratio mass spectrometry (IRMS) for the detection of mislabelling of food produced in Switzerland. The system is based on the analysis of the oxygen isotope distribution in water (δ(18)O). Depending on the location on the earth, lake or groundwater has a specific isotopic distribution, which can serve as a fingerprint in order to verify whether a product has grown by means of the corresponding water. This report presents specifically the IRMS technique and the results obtained in the origin detection of fish grown in selected Swiss lakes as well as asparagus grown in Valais ground. Strengths and limitations of the method are presented for both cited products; on one hand, the technique is relatively universal for any product which contains significant water but on the other hand, it necessitates a rather heavy workload to build up a database of water δ(18)O values of products of different origins. This analytical tool is part of the concept of combating fraud currently in use in Switzerland.

An assessment of the isotopic (2H/18O) integrity of water samples collected and stored by unattended precipitation totalizers

NASA Astrophysics Data System (ADS)

Terzer, Stefan; Wassenaar, Leonard I.; Douence, Cedric; Araguas-Araguas, Luis

2016-04-01

The IAEA-WMO Global Network of Isotopes in Precipitation (GNIP) provides worldwide δ18O and δ2H data for numerous hydrological and climatological studies. The traditional GNIP sample collection method relies on weather station operators to accumulate precipitation obtained from manual rain gauges. Over the past decades, widespread weather station automatization resulted in the increased use of unattended precipitation totalizers that accumulate and store the rainwater in the field for up to one month. Several low-tech measures were adopted to prevent in situ secondary evaporative isotopic enrichment (SEE) of totalized water samples (i.e. disequilibrium isotopic fractionation after precipitation is stored in the collection device). These include: (a) adding a 0.5-1 cm floating layer of paraffin oil to the totalizer bottle, (b) using an intake tube leading from the collection funnel and submerged to the bottom of the totalizer bottle, or (c) placing a table tennis ball in the funnel aiming to reduce evaporation of the collected water from the receiving bottle to the atmosphere. We assessed the isotopic integrity of stored rainwater samples for three totalizers under controlled settings: each aforementioned totalizer was filled with a 100 or 500 mL of isotopically known water and installed in the field with the intake funnels sheltered to prevent rainwater collection. Potential evapotranspiration (PET) was obtained from on-site meteorological recordings. Stored evaporative loss from each totalizer was evaluated on a monthly basis; gravimetrically and by analysing δ18O and δ2H of the stored water, for a period of 6 months and a cumulative PET of ˜500 mm. The gravimetric and isotope results revealed that for smaller water volumes (100 ml, corresponding to ca. 5 mm of monthly precipitation), negligible isotope enrichment (δ18O) was observed in the paraffin-oil based totalizer, whereas unacceptable evaporative isotope effects were observed for the ball

Hydrogeochemistry and stable isotopes of ground and surface waters from two adjacent closed basins, Atacama Desert, northern Chile

USGS Publications Warehouse

Alpers, Charles N.; Whittemore, Donald O.

1990-01-01

The geochemistry and stable isotopes of groundwaters, surface waters, and precipitation indicate different sources of some dissolved constituents, but a common source of recharge and other constituents in two adjacent closed basins in the Atacama Desert region of northern Chile (24??15???-24??45???S). Waters from artesian wells, trenches, and ephemeral streams in the Punta Negra Basin are characterized by concentrations of Na>Ca>Mg and Cl ???SO4, with TDS Mg ??? Ca and SO4 > Cl, with TDS also Mg ??? Ca and SO4 > Cl, but with TDS up to 40 g/l. The deep mine waters have pH between 3.2 and 3.9, and are high in dissolved CO2 (??13 C = -4.8%PDB), indicating probable interaction with oxidizing sulfides. The deep mine waters have ??18O values of ???-1.8%.compared with values < -3.5??? for other Hamburgo Basin waters; thus the mine waters may represent a mixture of meteoric waters with deeper "metamorphic" waters, which had interacted with rocks and exchanged oxygen isotopes at elevated temperatures. Alternatively, the deep mine waters may represent fossil meteoric waters which evolved isotopically along an evaporative trend starting from values quite depleted in ??18O and ??Dd relative to either precipitation or shallow groundwaters. High I/Br ratios in the Hamburgo Basin waters and La Escondida mine waters are consistent with regionally high I in surficial deposits in the Atacama Desert region and may represent dissolution of a wind-blown evaporite component. Rain and snow collected during June 1984, indicate systematic ??18O and ??D fractionation with increasing elevation between 3150 and 4180 m a.s.l. (-0.21??.??18O and -1.7??.??D per 100 m). Excluding the deep mine waters from La Escondida, the waters from the Hamburgo and Punta Negra Basins have similar ??D and ??18O values and together show a distinct evaporative trend (??D = 5.0 ??18O - 20.2). Snowmelt from the central Andes Cordillera to the east is the most likely source of recharge to both basins. Some of the

A novel methylation derivatization method for δ(18)O analysis of individual carbohydrates by gas chromatography/pyrolysis-isotope ratio mass spectrometry.

PubMed

Lehmann, Marco M; Fischer, Maria; Blees, Jan; Zech, Michael; Siegwolf, Rolf T W; Saurer, Matthias

2016-01-15

The oxygen isotope ratio (δ(18)O) of carbohydrates derived from animals, plants, sediments, and soils provides important information about biochemical and physiological processes, past environmental conditions, and geographical origins, which are otherwise not available. Nowadays, δ(18)O analyses are often performed on carbohydrate bulk material, while compound-specific δ(18)O analyses remain challenging and methods for a wide range of individual carbohydrates are rare. To improve the δ(18)O analysis of individual carbohydrates by gas chromatography/pyrolysis-isotope ratio mass spectrometry (GC/Pyr-IRMS) we developed a new methylation derivatization method. Carbohydrates were fully methylated within 24 h in an easy-to-handle one-pot reaction in acetonitrile, using silver oxide as proton acceptor, methyl iodide as methyl group carrier, and dimethyl sulfide as catalyst. The precision of the method ranged between 0.12 and 1.09‰ for the δ(18)O values of various individual carbohydrates of different classes (mono-, di-, and trisaccharides, alditols), with an accuracy of a similar order of magnitude, despite high variation in peak areas. Based on the δ(18)O values of the main isomers, important monosaccharides such as glucose and fructose could also be precisely analyzed for the first time. We tested the method on standard mixtures, honey samples, and leaf carbohydrates extracted from Pinus sylvestris, showing that the method is also applicable to different carbohydrate mixtures. The new methylation method shows unrivalled accuracy and precision for δ(18)O analysis of various individual carbohydrates; it is fast and easy-to-handle, and may therefore find wide-spread application. Copyright © 2015 John Wiley & Sons, Ltd.

Correction algorithm for online continuous flow δ13C and δ18O carbonate and cellulose stable isotope analyses

NASA Astrophysics Data System (ADS)

Evans, M. N.; Selmer, K. J.; Breeden, B. T.; Lopatka, A. S.; Plummer, R. E.

2016-09-01

We describe an algorithm to correct for scale compression, runtime drift, and amplitude effects in carbonate and cellulose oxygen and carbon isotopic analyses made on two online continuous flow isotope ratio mass spectrometry (CF-IRMS) systems using gas chromatographic (GC) separation. We validate the algorithm by correcting measurements of samples of known isotopic composition which are not used to estimate the corrections. For carbonate δ13C (δ18O) data, median precision of validation estimates for two reference materials and two calibrated working standards is 0.05‰ (0.07‰); median bias is 0.04‰ (0.02‰) over a range of 49.2‰ (24.3‰). For α-cellulose δ13C (δ18O) data, median precision of validation estimates for one reference material and five working standards is 0.11‰ (0.27‰); median bias is 0.13‰ (-0.10‰) over a range of 16.1‰ (19.1‰). These results are within the 5th-95th percentile range of subsequent routine runtime validation exercises in which one working standard is used to calibrate the other. Analysis of the relative importance of correction steps suggests that drift and scale-compression corrections are most reliable and valuable. If validation precisions are not already small, routine cross-validated precision estimates are improved by up to 50% (80%). The results suggest that correction for systematic error may enable these particular CF-IRMS systems to produce δ13C and δ18O carbonate and cellulose isotopic analyses with higher validated precision, accuracy, and throughput than is typically reported for these systems. The correction scheme may be used in support of replication-intensive research projects in paleoclimatology and other data-intensive applications within the geosciences.

Growth rates, stable oxygen isotopes (δ18O), and strontium (Sr/Ca) composition in two species of Pacific sclerosponges (Acanthocheatetes wellsi and Astrosclera willeyana) with δ18O calibration and application to paleoceanography

NASA Astrophysics Data System (ADS)

Grottoli, AndréA. G.; Adkins, Jess F.; Panero, Wendy R.; Reaman, Daniel M.; Moots, Kate

2010-06-01

The isotopic and elemental composition of sclerosponge skeletons is used to reconstruct paleoceanographic records. Yet few studies have systematically examined the natural variability in sclerosponge skeletal δ18O, growth, and Sr/Ca, and how that may influence the interpretation of sclerosponge proxy records. Here, we analyzed short records in seven specimens of Acanthocheatetes wellsi (high-Mg calcite, 21 mol% Mg) from Palau, four A. wellsi (high-Mg calcite, 21 mol% Mg) from Saipan, and three Astrosclera willeyana (aragonite) sclerosponges from Saipan, as well as one long record in an A. wellsi specimen from Palau spanning 1945-2001.5. In Saipan, species-specific and mineralogical effects appear to have a negligible effect on sclerosponge δ18O, facilitating the direct comparison of δ18O records between species at a given location. At both sites, A. wellsi δ18O and growth rates were sensitive to environmental conditions, but Sr/Ca was not sensitive to the same conditions. High-resolution δ18O analyses confirmed this finding as both A. wellsi and A. willeyana deposited their skeleton in accordance with the trends in isotopic equilibrium with seawater, though with a 0.27‰ offset in the case of A. willeyana. In the high-Mg-calcite species A. wellsi, Mg may be interfering with Sr incorporation into the skeleton. On multidecadal timescales, A. wellsi sclerosponge δ18O in Palau tracked the Southern Oscillation Index variability post-1977, but not pre-1977, coincident with the switch in the Pacific Decadal Oscillation (PDO) at ˜1976. This suggests that water mass circulation in the region is influenced by El Niño— Southern Oscillation variability during positive PDO phases, but not during negative ones.

Oxygen isotope ratios (18O/16O) of hemicellulose-derived sugar biomarkers in plants, soils and sediments as paleoclimate proxy I: Insight from a climate chamber experiment

NASA Astrophysics Data System (ADS)

Zech, Michael; Mayr, Christoph; Tuthorn, Mario; Leiber-Sauheitl, Katharina; Glaser, Bruno

2014-02-01

The oxygen isotopic composition of cellulose is a valuable proxy in paleoclimate research. However, its application to sedimentary archives is challenging due to extraction and purification of cellulose. Here we present compound-specific δ18O results of hemicellulose-derived sugar biomarkers determined using gas chromatography-pyrolysis-isotope ratio mass spectrometry, which is a method that overcomes the above-mentioned analytical challenges. The biomarkers were extracted from stem material of different plants (Eucalyptus globulus, Vicia faba and Brassica oleracea) grown in climate chamber experiments under different climatic conditions. The δ18O values of arabinose and xylose range from 31.4‰ to 45.9‰ and from 28.7‰ to 40.8‰, respectively, and correlate highly significantly with each other (R = 0.91, p < 0.001). Furthermore, δ18Ohemicellulose (mean of arabinose and xylose) correlate highly significantly with δ18Oleaf water (R = 0.66, p < 0.001) and significantly with modeled δ18Ocellulose (R = 0.42, p < 0.038), as well as with relative air humidity (R = -0.79, p < 0.001) and temperature (R = -0.66, p < 0.001). These findings confirm that the hemicellulose-derived sugar biomarkers, like cellulose, reflect the oxygen isotopic composition of plant source water altered by climatically controlled evapotranspirative 18O enrichment of leaf water. While relative air humidity controls most rigorously the evapotranspirative 18O enrichment, the direct temperature effect is less important. However, temperature can indirectly exert influence via plant physiological reactions, namely by influencing the transpiration rate which affects δ18Oleaf water due to the Péclet effect. In a companion paper (Tuthorn et al., this issue) we demonstrate the applicability of the hemicellulose-derived sugar biomarker δ18O method to soils and provide evidence from a climate transect study confirming that relative air humidity exerts the dominant control on evapotranspirative 18O

48 CFR 245.606-70 - Instructions for completing DD Form 1342, DoD Property Record.

Code of Federal Regulations, 2010 CFR

2010-10-01

... PROPERTY Reporting, Redistribution, and Disposal of Contractor Inventory 245.606-70 Instructions for completing DD Form 1342, DoD Property Record. (a) The contractor shall list excess industrial plant equipment... completing DD Form 1342, DoD Property Record. 245.606-70 Section 245.606-70 Federal Acquisition Regulations...

Evaporation induced 18O and 13C enrichment in lake systems: A global perspective on hydrologic balance effects

NASA Astrophysics Data System (ADS)

Horton, Travis W.; Defliese, William F.; Tripati, Aradhna K.; Oze, Christopher

2016-01-01

Growing pressure on sustainable water resource allocation in the context of global development and rapid environmental change demands rigorous knowledge of how regional water cycles change through time. One of the most attractive and widely utilized approaches for gaining this knowledge is the analysis of lake carbonate stable isotopic compositions. However, endogenic carbonate archives are sensitive to a variety of natural processes and conditions leaving isotopic datasets largely underdetermined. As a consequence, isotopic researchers are often required to assume values for multiple parameters, including temperature of carbonate formation or lake water δ18O, in order to interpret changes in hydrologic conditions. Here, we review and analyze a global compilation of 57 lacustrine dual carbon and oxygen stable isotope records with a topical focus on the effects of shifting hydrologic balance on endogenic carbonate isotopic compositions. Through integration of multiple large datasets we show that lake carbonate δ18O values and the lake waters from which they are derived are often shifted by >+10‰ relative to source waters discharging into the lake. The global pattern of δ18O and δ13C covariation observed in >70% of the records studied and in several evaporation experiments demonstrates that isotopic fractionations associated with lake water evaporation cause the heavy carbon and oxygen isotope enrichments observed in most lakes and lake carbonate records. Modeled endogenic calcite compositions in isotopic equilibrium with lake source waters further demonstrate that evaporation effects can be extreme even in lake records where δ18O and δ13C covariation is absent. Aridisol pedogenic carbonates show similar isotopic responses to evaporation, and the relevance of evaporative modification to paleoclimatic and paleotopographic research using endogenic carbonate proxies are discussed. Recent advances in stable isotope research techniques present unprecedented

Late-Glacial to Late-holocene Shifts in Global Precipitation Delta(sup 18)O

NASA Technical Reports Server (NTRS)

Jasechko, S.; Lechler, A.; Pausata, F.S.R.; Fawcett, P.J.; Gleeson, T.; Cendon, D.I.; Galewsky, J.; LeGrande, A. N.; Risi, C.; Sharp, Z. D.;

Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butorin, S.M.; Guo, J.; Magnuson, M.

1997-04-01

Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of themore » exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state.« less

D/H diffusion in serpentine

NASA Astrophysics Data System (ADS)

Pilorgé, Hélène; Reynard, Bruno; Remusat, Laurent; Le Floch, Sylvie; Montagnac, Gilles; Cardon, Hervé

2017-08-01

Interactions between aqueous fluids and ultrabasic rocks are essential processes in a broad range of contexts including hydrothermal alteration on the parent body of carbonaceous chondrites, at mid-oceanic ridge, and in subduction zones. Tracking these processes and understanding reaction kinetics require knowledge of the diffusion of water in rocks, and of isotope fractionation in major minerals forming under hydrous conditions, such as serpentines. We present a study of D/H inter-diffusion in antigorite, a common variety of serpentine. Experiments were performed in a belt apparatus at 315 °C, 450 °C and 540 °C and at 3.0 GPa on natural antigorite powders saturated with interstitial D2O. An experiment was performed in a diamond anvil cell at 350 °C and 2.5 GPa on an antigorite single-crystal loaded with pure D2O. D/(D + H) ratios were mapped using Raman spectroscopy for the experiments at 315 °C, 450 °C and 540 °C and by NanoSIMS for the experiment at 350 °C. As antigorite is a phyllosilicate, diffusion coefficients were obtained for crystallographic directions parallel and perpendicular to the silicate layers (perpendicular and parallel to the c∗-axis, respectively). Arrhenius relations for D/H inter-diffusion coefficients were determined to be DD/H (m2/s) = 4.71 × 10-2 × exp(-207(-33/+58) (kJ/mol)/RT) and DD/H (m2/s) = 1.61 × 10-4 × exp(-192(-34/+93) (kJ/mol)/RT) perpendicular and parallel to the c∗-axis, respectively, and DD/H (m2/s) = 7.09 × 10-3 × exp(-202(-33/+70) (kJ/mol)/RT) for the bulk diffusivity. Assuming D/H inter-diffusion coefficients for antigorite are the same for all serpentine species, closure temperature and diffusion durations are applied to hydrothermal alteration in the oceanic lithosphere, and in CI, CM and CR chondrites. Closure temperatures lie below 300 °C for terrestrial hydrothermal alteration and depend on serpentine variety because they have different typical grain sizes. Closure temperatures lie below 160 °C for

Simulations of the HDO and H2O-18 atmospheric cycles using the NASA GISS general circulation model - Sensitivity experiments for present-day conditions

NASA Technical Reports Server (NTRS)

Jouzel, Jean; Koster, R. D.; Suozzo, R. J.; Russell, G. L.; White, J. W. C.

1991-01-01

Incorporating the full geochemical cycles of stable water isotopes (HDO and H2O-18) into an atmospheric general circulation model (GCM) allows an improved understanding of global delta-D and delta-O-18 distributions and might even allow an analysis of the GCM's hydrological cycle. A detailed sensitivity analysis using the NASA/Goddard Institute for Space Studies (GISS) model II GCM is presented that examines the nature of isotope modeling. The tests indicate that delta-D and delta-O-18 values in nonpolar regions are not strongly sensitive to details in the model precipitation parameterizations. This result, while implying that isotope modeling has limited potential use in the calibration of GCM convection schemes, also suggests that certain necessarily arbitrary aspects of these schemes are adequate for many isotope studies. Deuterium excess, a second-order variable, does show some sensitivity to precipitation parameterization and thus may be more useful for GCM calibration.

Comparison of δ18O measurements in nitrate by different combustion techniques

USGS Publications Warehouse

Revesz, Kinga; Böhlke, John Karl

2002-01-01

Three different KNO3 salts with δ18O values ranging from about −31 to +54‰ relative to VSMOW were used to compare three off-line, sealed glass tube combustion methods (widely used for isotope studies) with a more recently developed on-line carbon combustion technique. All methods yielded roughly similar isotope ratios for KNO3 samples with δ18O values in the midpoint of the δ18O scale near that of the nitrate reference material IAEA-NO-3 (around +21 to +25‰). This reference material has been used previously for one-point interlaboratory and intertechnique calibrations. However, the isotope ratio scale factors by all of the off-line combustion techniques are compressed such that they are between 0.3 and 0.7 times that of the on-line combustion technique. The contraction of the δ18O scale in the off-line preparations apparently is caused by O isotope exchange between the sample and the glass combustion tubes. These results reinforce the need for nitrate reference materials with δ18O values far from that of atmospheric O2, to improve interlaboratory comparability.

Prompt-gamma neutron activation analysis system design: Effects of D-T versus D-D neutron generator source selection

USDA-ARS?s Scientific Manuscript database

Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV and D-T with...

A new instrument for stable isotope measurements of 13C and 18O in CO2 - instrument performance and ecological application of the Delta Ray IRIS analyzer

NASA Astrophysics Data System (ADS)

Braden-Behrens, Jelka; Yan, Yuan; Knohl, Alexander

2017-11-01

We used the recently developed commercially available Delta Ray isotope ratio infrared spectrometer (IRIS) to continuously measure the CO2 concentration c and its isotopic composition δ13C and δ18O in a managed beech forest in central Germany. Our objectives are (a) to characterize the Delta Ray IRIS and evaluate its internal calibration procedure and (b) to quantify the seasonal variability of c, δ13C, δ18O and the isotopic composition of nighttime net ecosystem CO2 exchange (respiration) Reco13C and Reco18O derived from Keeling plot intercepts. The analyzer's minimal Allan deviation (as a measure of precision) was below 0.01 ppm for the CO2 concentration and below 0.03 ‰ for both δ values. The potential accuracy (defined as the 1σ deviation from the respective linear regression that was used for calibration) was approximately 0.45 ppm for c, 0.24 ‰ for 13C and 0.3 ‰ for 18O. For repeated measurements of a target gas in the field, the long-term standard deviation from the mean was 0.3 ppm for c and below 0.3 ‰ for both δ values. We used measurements of nine different inlet heights to evaluate the isotopic compositions of nighttime net ecosystem CO2 exchange Reco13C and Reco18O in a 3-month measurement campaign in a beech forest in autumn 2015. During this period, an early snow and frost event occurred, coinciding with a change in the observed characteristics of both Reco13C and Reco18O. Before the first snow, Reco13C correlated significantly (p < 10-4) with time-lagged net radiation Rn, a driver of photosynthesis and photosynthetic discrimination against 13C. This correlation became insignificant (p > 0.1) for the period after the first snow, indicating a decoupling of δ13C of respiration from recent assimilates. For 18O, we measured a decrease of 30 ‰ within 10 days in Reco18O after the snow event, potentially reflecting the influence of 18O depleted snow on soil moisture. This decrease was 10 times larger than the corresponding decrease in δ18

An Experimental Study on What Controls the Ratios of 18O/16O and 17O/16O of O2 During Microbial Respiration

NASA Astrophysics Data System (ADS)

Stolper, D. A.; Ward, B. B.; Fischer, W. W.; Bender, M. L.

2015-12-01

18O/16O and 17O/16O ratios of atmospheric and dissolved oceanic O2 are key biogeochemical tracers of total photosynthesis and respiration on global to local length scales and glacial/interglacial time scales (Luz et al., 1999). Critical to the use of these ratios as biogeochemical tracers is knowledge of how they are affected by production, consumption, and transport of O2. We present new measurements of O2 respiration by E. coli and N. oceanus, an ammonia oxidizing bacterium, to test three assumptions of isotopically enabled models of the O2 cycle: (i) laboratory-measured respiratory 18O/16O isotope effects (18α) of microorganisms are constant under all experimental and natural conditions (e.g., temperature and growth rate); (ii) the respiratory 'mass law' relationship between 18O/16O and 17O/16O [17α = (18α)β] is universal; and (iii) 18α and β for aerobic ammonia and organic carbon oxidation are identical. For E. coli, we find that both 18α and β are variable. From 37°C to 15°C, 18α varies linearly with temperature from 17 to 14‰, and β varies linearly from 0.513 to 0.508. 18α and β do not appear to vary with growth rate (as tested using different carbon sources). Both 18α and β are lower than previous observations for bacteria: 18α = 17-20‰ (Kiddon et al., 1993) and β = 0.515 (Luz and Barkan, 2005). We were able to simulate the observed temperature dependence of 18α and β using a model of respiration with two isotopically discriminating steps: O2 binding to cytochrome bo oxidase (the respiratory enzyme) and reduction of O2 to H2O. Finally, initial results on N. oceanus suggest it has similar values for 18α and β as previously studied aerobic bacteria that consume organic carbon, providing the first support for assumption (iii). Based on these results, isotopically constrained biogeochemical models of O2 cycling may need to consider a temperature dependence for 18α and β for microbial respiration. For example, these results may

Biscayne aquifer drinking water (USGS45): a new isotopic reference material for δ2H and δ18O measurements of water

USGS Publications Warehouse

Lorenz, Jennifer M.; Tarbox, Lauren V.; Buck, Bryan; Qi, Haiping; Coplen, Tyler B.

2014-01-01

RATIONALE As a result of the scarcity of isotopic reference waters for daily use, a new secondary isotopic reference material for international distribution has been prepared from drinking water collected from the Biscayne aquifer in Ft. Lauderdale, Florida. METHODS This isotopic reference water was filtered, homogenized, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and measured by dual-inlet isotope-ratio mass spectrometry. This reference material is available by the case of 144 glass ampoules containing either 4 mL or 5 mL of water in each ampoule. RESULTS The δ2H and δ18O values of this reference material are –10.3 ± 0.4 ‰ and –2.238 ± 0.011 ‰, respectively, relative to VSMOW, on scales normalized such that the δ2H and δ18O values of SLAP reference water are, respectively, –428 and –55.5 ‰. Each uncertainty is an estimated expanded uncertainty (U = 2uc) about the reference value that provides an interval that has about a 95 % probability of encompassing the true value. CONCLUSIONS This isotopic reference material, designated as USGS45, is intended as one of two isotopic reference waters for daily normalization of stable hydrogen and oxygen isotopic analysis of water with an isotope-ratio mass spectrometer or a laser absorption spectrometer. 

Multi-substrate biodegradation interaction of 1, 4-dioxane and BTEX mixtures by Acinetobacter baumannii DD1.

PubMed

Zhou, YuYang; Huang, Huanlin; Shen, Dongsheng

2016-02-01

This study evaluated substrate interactions during the aerobic biodegradation of 1, 4-dioxane and BTEX mixtures by a pure culture, Acinetobacter baumannii DD1, which is capable of utilizing 1, 4-dioxane for growth. A. baumannii DD1 could utilize BTEX as a sole carbon source, but could not utilize m-xylene and p-xylene. In binary mixtures, there was a lag of about 14 h before the degradation of BTE, and 1, 4-dioxane only started to be utilized when BTE was completely degraded by 1, 4-dioxane-grown DD1. Furthermore, the biodegradation rate of 1, 4-dioxane decreased from 73.33 to 40.74 mg/(h g dry weight) after the biodegradation of benzene. 1, 4-dioxane could not be degraded after the biodegradation of o-xylene in 80 h. DD1 could also not degrade m-xylene and p-xylene coexisting with 1, 4-dioxane. The ability of DD1 to degrade BTEX occurred in the following order: benzene > ethylbenzene > toluene > o-xylene > m-xylene = p-xylene. The biodegradation of 1, 4-dioxane was not activated in the mixture with o-xylene, primarily because of the accumulation of the specific toxic intermediate, 2, 3-dimethylphenol. The lag in BTE degradation was presumably because of the induction of enzymes necessary for BTE degradation. Additionally, SDS-PAGE analysis demonstrated that there were different proteins during the degradation of benzene and 1, 4-dioxane.

McCall Glacier record of Arctic climate change: Interpreting a northern Alaska ice core with regional water isotopes

NASA Astrophysics Data System (ADS)

Klein, E. S.; Nolan, M.; McConnell, J.; Sigl, M.; Cherry, J.; Young, J.; Welker, J. M.

2016-01-01

We explored modern precipitation and ice core isotope ratios to better understand both modern and paleo climate in the Arctic. Paleoclimate reconstructions require an understanding of how modern synoptic climate influences proxies used in those reconstructions, such as water isotopes. Therefore we measured periodic precipitation samples at Toolik Lake Field Station (Toolik) in the northern foothills of the Brooks Range in the Alaskan Arctic to determine δ18O and δ2H. We applied this multi-decadal local precipitation δ18O/temperature regression to ∼65 years of McCall Glacier (also in the Brooks Range) ice core isotope measurements and found an increase in reconstructed temperatures over the late-20th and early-21st centuries. We also show that the McCall Glacier δ18O isotope record is negatively correlated with the winter bidecadal North Pacific Index (NPI) climate oscillation. McCall Glacier deuterium excess (d-excess, δ2H - 8*δ18O) values display a bidecadal periodicity coherent with the NPI and suggest shifts from more southwestern Bering Sea moisture sources with less sea ice (lower d-excess values) to more northern Arctic Ocean moisture sources with more sea ice (higher d-excess values). Northern ice covered Arctic Ocean McCall Glacier moisture sources are associated with weak Aleutian Low (AL) circulation patterns and the southern moisture sources with strong AL patterns. Ice core d-excess values significantly decrease over the record, coincident with warmer temperatures and a significant reduction in Alaska sea ice concentration, which suggests that ice free northern ocean waters are increasingly serving as terrestrial precipitation moisture sources; a concept recently proposed by modeling studies and also present in Greenland ice core d-excess values during previous transitions to warm periods. This study also shows the efficacy and importance of using ice cores from Arctic valley glaciers in paleoclimate reconstructions.

The oxygen-18 isotope approach for measuring aquatic metabolism in high-productivity waters

USGS Publications Warehouse

Tobias, C.R.; Böhlke, J.K.; Harvey, J.W.

2007-01-01

We examined the utility of ??18O2 measurements in estimating gross primary production (P), community respiration (R), and net metabolism (P:R) through diel cycles in a productive agricultural stream located in the midwestern U.S.A. Large diel swings in O2 (??200 ??mol L-1) were accompanied by large diel variation in ??18O2 (??10???). Simultaneous gas transfer measurements and laboratory-derived isotopic fractionation factors for O2 during respiration (??r) were used in conjunction with the diel monitoring of O2 and ??18O2 to calculate P, R, and P:R using three independent isotope-based methods. These estimates were compared to each other and against the traditional "open-channel diel O2-change" technique that lacked ??18O2. A principal advantage of the ??18O2 measurements was quantification of diel variation in R, which increased by up to 30% during the day, and the diel pattern in R was variable and not necessarily predictable from assumed temperature effects on R. The P, R, and P:R estimates calculated using the isotope-based approaches showed high sensitivity to the assumed system fractionation factor (??r). The optimum modeled ??r values (0.986-0.989) were roughly consistent with the laboratory-derived values, but larger (i.e., less fractionation) than ??r values typically reported for enzyme-limited respiration in open water environments. Because of large diel variation in O2, P:R could not be estimated by directly applying the typical steady-state solution to the O2 and 18O-O2 mass balance equations in the absence of gas transfer data. Instead, our results indicate that a modified steady-state solution (the daily mean value approach) could be used with time-averaged O2 and ??18O2 measurements to calculate P:R independent of gas transfer. This approach was applicable under specifically defined, net heterotrophic conditions. The diel cycle of increasing daytime R and decreasing nighttime R was only partially explained by temperature variation, but could be

Following 18O uptake in scCO2–H2O mixtures with Raman spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Windisch, Charles F.; Schaef, Herbert T.; Martin, Paul F.

2012-03-01

The kinetics of 18O/16O isotopic exchange in scCO2 containing liquid water was followed with Raman spectroscopy using a specially designed high-pressure optical cell. Characteristic bands from the C16O18O and C18O2 molecules were identified in the supercritical phase and measured in the spectra as a function of time after introducing liquid H218O into scC16O2. Temporal dependence indicated the isotopic exchange was diffusion-limited in our cell for both molecules, and that the chemical reactions within the liquid phase were comparatively rapid. However, the ratio of concentrations of the 18O-labeled CO2 molecules, C18O2/C16O18O, was much higher than expected in the supercritical phase, suggestingmore » the role of an intermediate step, possibly desorption, in moderating the concentrations of these species in the liquid water phase.« less

32 CFR Appendix D to Part 113 - Sample DD Form 2654, “Involuntary Allotment Notice and Processing”

Code of Federal Regulations, 2010 CFR

2010-07-01

... 32 National Defense 1 2010-07-01 2010-07-01 false Sample DD Form 2654, âInvoluntary Allotment Notice and Processingâ D Appendix D to Part 113 National Defense Department of Defense OFFICE OF THE..., App. D Appendix D to Part 113—Sample DD Form 2654, “Involuntary Allotment Notice and Processing...

Insights into the origin of low- δ18O basaltic magmas in Hawaii revealed from in situ measurements of oxygen isotope compositions of olivines

NASA Astrophysics Data System (ADS)

Wang, Zhengrong; Eiler, John M.

2008-05-01

In situ measurements of oxygen isotope and elemental compositions of olivines from subaerial Mauna Kea lavas reveal that their δ18O values correlate positively with their forsterite contents, consistent with addition of one or more low- δ18O components into magmas from which they grew over the course of their crystallization-differentiation histories. This result supports previous suggestions that low- δ18O components to Mauna Kea lavas are contaminants derived from hydrothermally-altered rocks in the volcanic edifice or lithosphere, rather than components of the underlying mantle sources of these lavas. The slope of the correlation between δ18O values and forsterite contents of olivines is steeper for subaerial Mauna Kea lavas than for submarine Mauna Kea lavas, and olivines from Mauna Loa lavas exhibit negligible changes in δ18O values over a similar range of forsterite contents. Models of assimilation-fractional crystallization (AFC) processes can explain our observations if the δ18O values of crustal contaminants decrease sharply at the submarine-subaerial transition in Mauna Kea volcano, and if Mauna Loa lavas are either uncontaminated or contaminated only by rocks that have δ18O values similar to that of primary Mauna Loa magmas. We suggest that the differences in oxygen isotope systematics among Mauna Loa, submarine Mauna Kea and subaerial Mauna Kea lavas principally reflect the sources and amounts of water available to hydrothermal systems in the volcanic edifice.

Kinetics of reactions of the Actinomadura R39 DD-peptidase with specific substrates.

PubMed

Adediran, S A; Kumar, Ish; Nagarajan, Rajesh; Sauvage, Eric; Pratt, R F

2011-01-25

The Actinomadura R39 DD-peptidase catalyzes the hydrolysis and aminolysis of a number of small peptides and depsipeptides. Details of its substrate specificity and the nature of its in vivo substrate are not, however, well understood. This paper describes the interactions of the R39 enzyme with two peptidoglycan-mimetic substrates 3-(D-cysteinyl)propanoyl-D-alanyl-D-alanine and 3-(D-cysteinyl)propanoyl-D-alanyl-D-thiolactate. A detailed study of the reactions of the former substrate, catalyzed by the enzyme, showed DD-carboxypeptidase, DD-transpeptidase, and DD-endopeptidase activities. These results confirm the specificity of the enzyme for a free D-amino acid at the N-terminus of good substrates and indicated a preference for extended D-amino acid leaving groups. The latter was supported by determination of the structural specificity of amine nucleophiles for the acyl-enzyme generated by reaction of the enzyme with the thiolactate substrate. It was concluded that a specific substrate for this enzyme, and possibly the in vivo substrate, may consist of a partly cross-linked peptidoglycan polymer where a free side chain N-terminal un-cross-linked amino acid serves as the specific acyl group in an endopeptidase reaction. The enzyme is most likely a DD-endopeptidase in vivo. pH-rate profiles for reactions of the enzyme with peptides, the thiolactate named above, and β-lactams indicated the presence of complex proton dissociation pathways with sticky substrates and/or protons. The local structure of the active site may differ significantly for reactions of peptides and β-lactams. Solvent kinetic deuterium isotope effects indicate the presence of classical general acid/base catalysis in both acylation and deacylation; there is no evidence of the low fractionation factor active site hydrogen found previously in class A and C β-lactamases.

Estimation and Validation of \\delta18O Global Distribution with Rayleigh-type two Dimensional Isotope Circulation Model

NASA Astrophysics Data System (ADS)

Yoshimura, K.; Oki, T.; Ohte, N.; Kanae, S.; Ichiyanagi, K.

2004-12-01

A simple water isotope circulation model on a global scale that includes a Rayleigh equation and the use of _grealistic_h external meteorological forcings estimates short-term variability of precipitation 18O. The results are validated by Global Network of Isotopes in Precipitation (GNIP) monthly observations and by daily observations at three sites in Thailand. This good agreement highlights the importance of large scale transport and mixing of vapor masses as a control factor for spatial and temporal variability of precipitation isotopes, rather than in-cloud micro processes. It also indicates the usefulness of the model and the isotopes observation databases for evaluation of two-dimensional atmospheric water circulation fields in forcing datasets. In this regard, two offline simulations for 1978-1993 with major reanalyses, i.e. NCEP and ERA15, were implemented, and the results show that, over Europe ERA15 better matched observations at both monthly and interannual time scales, mainly owing to better precipitation fields in ERA15, while in the tropics both produced similarly accurate isotopic fields. The isotope analyses diagnose accuracy of two-dimensional water circulation fields in datasets with a particular focus on precipitation processes.

Nitrogen isotopes as indicators of streamflow generation processes in a headwater forested catchment: Focusing on atmospheric NO3- contribution using δ 18O signature

NASA Astrophysics Data System (ADS)

Ohte, N.; Sebestyen, S. D.; Doctor, D. H.; Wankel, S. D.; Shanley, J. B.; Kendall, C.; Boyer, E. W.

2003-12-01

To quantify the contributions of atmospheric nitrogen deposition and mechanisms of nitrate discharge to stream, nitrogen chemistry and isotopes (δ 15N and δ 18O of NO3-) of streamwater were studied as part of an ongoing study of nutrient dynamics at the Sleepers River Research Watershed in Vermont, USA. We employed novel analytical procedures for high throughput of NO3- isotopic measurements. The denitrifier method for measurement of δ 15N and δ 18O of NO3- requires a smaller volume of water samples than previously applied methods, thus it enables fine resolution analysis of isotopes for stream, well, and soil water samples. Samples were collected throughout the spring 2003 snowmelt. Snowmelt runoff was initiated in the middle of March and peaked at the end of the month. Then, the runoff rate decreased gradually through April and May, and responded to several storm events. The highest concentration of NO3- in the stream was observed at the beginning of snowmelt (the end of March), and thereafter it declined continuously. The temporal course of NO3- discharge process during snowmelt period was divided into four phases based on changes in the relationship between runoff rate and NO3- concentration. During the earliest phase (very low runoff rate and highest NO3- concentration) isotope signatures, especially δ 18O of NO3-, indicated higher contribution of the atmospherically derived NO3-, meaning that the direct discharge from snow pack was the dominant source of NO3- to the stream. This also suggested that streamwater consisted only of a small volume of groundwater discharge and melt water of the in-stream snow pack and/or stream-covering snow pack. The δ 15N and δ 18O isotope compositions of NO3- during the middle phase of snowmelt indicated that the contribution of the NO3- generated by nitrifiers in soil increased gradually accompanied with increase of groundwater level. These detailed descriptions in the changes of NO3- discharge during snowmelt events

Compact D-D Neutron Source-Driven Subcritical Multiplier and Beam-Shaping Assembly for Boron Neutron Capture Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Francesco Ganda; Jasmina Vujic; Ehud Greenspan

2010-12-01

This work assesses the feasibility of using a small, safe, and inexpensive keff 0.98 subcritical fission assembly [subcritical neutron multiplier (SCM)] to amplify the treatment neutron beam intensity attainable from a compact deuterium-deuterium (D-D) fusion neutron source delivering [approximately]1012 n/s. The objective is to reduce the treatment time for deep-seated brain tumors to [approximately]1 h. The paper describes the optimal SCM design and two optimal beam-shaping assemblies (BSAs) - one designed to maximize the dose rate and the other designed to maximize the total dose that can be delivered to a deep-seated tumor. The neutron beam intensity amplification achieved withmore » the optimized SCM and BSA results in an increase in the treatment dose rate by a factor of 18: from 0.56 Gy/h without the SCM to 10.1 Gy/h. The entire SCM is encased in an aluminum structure. The total amount of 20% enriched uranium required for the SCM is 8.5 kg, and the cost (not including fabrication) is estimated to be less than $60,000. The SCM power level is estimated at 400 W when driven by a 1012 n/s D-D neutron source. This translates into consumption of only [approximately]0.6% of the initially loaded 235U atoms during 50 years of continuous operation and implies that the SCM could operate continuously for the entire lifetime of the facility without refueling. Cooling the SCM does not pose a challenge; it may be accomplished by natural circulation as the maximum heat flux is only 0.034 W/cm2.« less

Oscillator strength of symmetry-forbidden d-d absorption of octahedral transition metal complex: theoretical evaluation.

PubMed

Saito, Ken; Eishiro, Yoshinori; Nakao, Yoshihide; Sato, Hirofumi; Sakaki, Shigeyoshi

2012-03-05

The theoretical evaluation of the oscillator strength of a symmetry-forbidden d-d transition is not easy even nowadays. A new approximate method is proposed here and applied to octahedral complexes [Co(NH(3))(6)](3+) and [Rh(NH(3))(6)](3+) as an example. Our method incorporates the effects of geometry distortion induced by molecular vibration and the thermal distribution of such distorted geometries but does not need the Herzberg-Teller approximation. The calculated oscillator strengths of [Co(NH(3))(6)](3+) agree well with the experimental values in both (1)A(1g) → (1)T(1g) and (1)A(1g) → (1)T(2g) transitions. In the Rh analogue, though the calculated oscillator strengths are somewhat smaller than the experimental values, computational results reproduce well the experimental trends that the oscillator strengths of [Rh(NH(3))(6)](3+) are much larger than those of the Co analogue and the oscillator strength of the (1)A(1g) → (1)T(1g) transition is larger than that of the (1)A(1g) → (1)T(2g) transition. It is clearly shown that the oscillator strength is not negligibly small even at 0 K because the distorted geometry (or the uncertainty in geometry) by zero-point vibration contributes to the oscillator strength at 0 K. These results are discussed in terms of frequency of molecular vibration, extent of distortion induced by molecular vibration, and charge-transfer character involved in the d-d transition. The computational results clearly show that our method is useful in evaluating and discussing the oscillator strength of symmetry-forbidden d-d absorption of transition metal complex.

von Willebrand factor (VWF) propeptide binding to VWF D'D3 domain attenuates platelet activation and adhesion.

PubMed

Madabhushi, Sri R; Shang, Chengwei; Dayananda, Kannayakanahalli M; Rittenhouse-Olson, Kate; Murphy, Mary; Ryan, Thomas E; Montgomery, Robert R; Neelamegham, Sriram

2012-05-17

Noncovalent association between the von Willebrand factor (VWF) propeptide (VWFpp) and mature VWF aids N-terminal multimerization and protein compartmentalization in storage granules. This association is currently thought to dissipate after secretion into blood. In the present study, we examined this proposition by quantifying the affinity and kinetics of VWFpp binding to mature VWF using surface plasmon resonance and by developing novel anti-VWF D'D3 mAbs. Our results show that the only binding site for VWFpp in mature VWF is in its D'D3 domain. At pH 6.2 and 10mM Ca(2+), conditions mimicking intracellular compartments, VWFpp-VWF binding occurs with high affinity (K(D) = 0.2nM, k(off) = 8 × 10(-5) s(-1)). Significant, albeit weaker, binding (K(D) = 25nM, k(off) = 4 × 10(-3) s(-1)) occurs under physiologic conditions of pH 7.4 and 2.5mM Ca(2+). This interaction was also observed in human plasma (K(D) = 50nM). The addition of recombinant VWFpp in both flow-chamber-based platelet adhesion assays and viscometer-based shear-induced platelet aggregation and activation studies reduced platelet adhesion and activation partially. Anti-D'D3 mAb DD3.1, which blocks VWFpp binding to VWF-D'D3, also abrogated platelet adhesion, as shown by shear-induced platelet aggregation and activation studies. Our data demonstrate that VWFpp binding to mature VWF occurs in the circulation, which can regulate the hemostatic potential of VWF by reducing VWF binding to platelet GpIbα.

Biscayne aquifer drinking water (USGS45): a new isotopic reference material for δ2H and δ18O measurements of water.

PubMed

Lorenz, Jennifer M; Tarbox, Lauren; Buck, Bryan; Qi, Haiping; Coplen, Tyler B

2014-10-15

As a result of the scarcity of isotopic reference waters for daily use, a new secondary isotopic reference material for international distribution has been prepared from drinking water collected from the Biscayne aquifer in Ft. Lauderdale, Florida. This isotopic reference water was filtered, homogenized, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and measured by dual-inlet isotope-ratio mass spectrometry. This reference material is available by the case of 144 glass ampoules containing either 4 mL or 5 mL of water in each ampoule. The δ(2)H and δ(18)O values of this reference material are -10.3 ± 0.4‰ and -2.238 ± 0.011‰, respectively, relative to VSMOW, on scales normalized such that the δ(2)H and δ(18)O values of SLAP reference water are, respectively, -428 and -55.5‰. Each uncertainty is an estimated expanded uncertainty (U = 2uc ) about the reference value that provides an interval that has about a 95% probability of encompassing the true value. This isotopic reference material, designated as USGS45, is intended as one of two isotopic reference waters for daily normalization of stable hydrogen and oxygen isotopic analysis of water with an isotope-ratio mass spectrometer or a laser absorption spectrometer. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA.

On the electron-induced isotope fractionation in low temperature (32)O(2)/(36)O(2) ices--ozone as a case study.

PubMed

Sivaraman, B; Mebel, A M; Mason, N J; Babikov, D; Kaiser, R I

2011-01-14

The formation of six ozone isotopomers and isotopologues, (16)O(16)O(16)O, (18)O(18)O(18)O, (16)O(16)O(18)O, (18)O(18)O(16)O, (16)O(18)O(16)O, and (18)O(16)O(18)O, has been studied in electron-irradiated solid oxygen (16)O(2) and (18)O(2) (1 ∶ 1) ices at 11 K. Significant isotope effects were found to exist which involved enrichment of (18)O-bearing ozone molecules. The heavy (18)O(18)O(18)O species is formed with a factor of about six higher than the corresponding (16)O(16)O(16)O isotopologue. Likewise, the heavy (18)O(18)O(16)O species is formed with abundances of a factor of three higher than the lighter (16)O(16)O(18)O counterpart. No isotope effect was observed in the production of (16)O(18)O(16)O versus(18)O(16)O(18)O. Such studies on the formation of distinct ozone isotopomers and isotopologues involving non-thermal, non-equilibrium chemistry by irradiation of oxygen ices with high energy electrons, as present in the magnetosphere of the giant planets Jupiter and Saturn, may suggest that similar mechanisms may contribute to the (18)O enrichment on the icy satellites of Jupiter and Saturn such as Ganymede, Rhea, and Dione. In such a Solar System environment, energetic particles from the magnetospheres of the giant planets may induce non-equilibrium reactions of suprathermal and/or electronically excited atoms under conditions, which are quite distinct from isotopic enrichments found in classical, thermal gas phase reactions.

Antarctic ice-core water (USGS49) – A new isotopic reference material for δ2H and δ18O measurements of water

USGS Publications Warehouse

Lorenz, Jennifer M.; Qi, Haiping; Coplen, Tyler B.

2017-01-01

As a result of the scarcity of isotopic reference waters for daily use, a new secondary isotopic reference material for international distribution has been prepared from ice-core water from the Amundsen–Scott South Pole Station. This isotopic reference material, designated as USGS49, was filtered, homogenised, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity and measured by dual-inlet isotope-ratio mass spectrometry. The δ2H and δ18O values of USGS49 are −394.7 ± 0.4 and −50.55 ± 0.04 mUr (where mUr = 0.001 = ‰), respectively, relative to VSMOW, on scales normalised such that the δ2H and δ18O values of SLAP reference water are, respectively, −428 and −55.5 mUr. Each uncertainty is an estimated expanded uncertainty (U = 2uc) about the reference value that provides an interval that has about a 95% probability of encompassing the true value. This isotopic reference material is intended as one of two isotopic reference waters for daily normalisation of stable hydrogen and oxygen isotopic analysis of water with an isotope-ratio mass spectrometer or a laser absorption spectrometer. It is available by the case of 144 glass ampoules or as a set of sixteen glass ampoules containing 5 ml of water in each ampoule.

AmpH, a bifunctional DD-endopeptidase and DD-carboxypeptidase of Escherichia coli.

PubMed

González-Leiza, Silvia M; de Pedro, Miguel A; Ayala, Juan A

2011-12-01

In Escherichia coli, low-molecular-mass penicillin-binding proteins (LMM PBPs) are important for correct cell morphogenesis. These enzymes display DD-carboxypeptidase and/or dd-endopeptidase activities associated with maturation and remodeling of peptidoglycan (PG). AmpH has been classified as an AmpH-type class C LMM PBP, a group closely related to AmpC β-lactamases. AmpH has been associated with PG recycling, although its enzymatic activity remained uncharacterized until now. Construction and purification of His-tagged AmpH from E. coli permitted a detailed study of its enzymatic properties. The N-terminal export signal of AmpH is processed, but the protein remains membrane associated. The PBP nature of AmpH was demonstrated by its ability to bind the β-lactams Bocillin FL (a fluorescent penicillin) and cefmetazole. In vitro assays with AmpH and specific muropeptides demonstrated that AmpH is a bifunctional DD-endopeptidase and DD-carboxypeptidase. Indeed, the enzyme cleaved the cross-linked dimers tetrapentapeptide (D45) and tetratetrapeptide (D44) with efficiencies (k(cat)/K(m)) of 1,200 M(-1) s(-1) and 670 M(-1) s(-1), respectively, and removed the terminal D-alanine from muropeptides with a C-terminal D-Ala-D-Ala dipeptide. Both DD-peptidase activities were inhibited by 40 μM cefmetazole. AmpH also displayed a weak β-lactamase activity for nitrocefin of 1.4 × 10(-3) nmol/μg protein/min, 1/1,000 the rate obtained for AmpC under the same conditions. AmpH was also active on purified sacculi, exhibiting the bifunctional character that was seen with pure muropeptides. The wide substrate spectrum of the DD-peptidase activities associated with AmpH supports a role for this protein in PG remodeling or recycling.

Spatial and temporal variation of H and O isotopic compositions of the Xijiang River system, Southwest China.

PubMed

Han, Guilin; Lv, Pin; Tang, Yang; Song, Zhaoliang

2018-05-01

Ratios of stable isotopes of hydrogen and oxygen ( 2 H/ 1 H and 18 O/ 16 O) in river waters were measured to investigate the hydrological pathway of the Xijiang River, Southwest China. The δ 2 H and δ 18 O values of river waters exhibit significant spatial and temporal variations and the isotopic compositions vary with elevation, temperature and precipitation of the recharge area. Spatially, δ 18 O values of river waters from high mountain areas are lower than those from the lower reaches of the Xijiang River due to lower temperature and higher elevation for the recharge area. However, both 2 H and 18 O are enriched differently in river waters from the middle reaches during the high flow season, depending on the season and degree of anthropogenic disturbances (e.g. water impoundments). In contrast, deuterium excess (d-excess) values of waters from the middle reaches are substantially lower than those from the upper and lower reaches, suggesting that river waters may be resided in the reservoir and evaporation increases in the middle reaches of the Xijiang River.

C, N, and O Isotopic Heterogeneities in Low-density Supernova Graphite Grains from Orgueil

NASA Astrophysics Data System (ADS)

Groopman, Evan; Bernatowicz, Thomas; Zinner, Ernst

2012-07-01

We report on the results of NanoSIMS isotope imaging of low-density supernova graphite grains from the Orgueil meteorite. 70 nm thick microtomed sections of three supernova graphite grains were deposited on Si wafers and isotopically imaged in the NanoSIMS. These sections contain hotspots of excesses in 18O and 15N, which are spatially well correlated, and are likely carried by internal TiC subgrains. These hotspots are considerably more enriched in 18O and 15N than the host graphite grain. Correlations between 18O and 15N excesses indicate that the grains incorporated material from the He/C supernova zone. Isotope images of the surfaces of some grains show heterogeneities in their N and O isotope compositions, with extreme excesses in 15N and 18O. In the microtome sections, we also observe two types of heterogeneities in the grains' C isotopic compositions: smooth, radial gradients in 12C/13C, with this ratio trending toward solar with increasing radius; and highly anomalous pockets up to 2 μm in size with 12C/13C Gt solar that are located near the centers of the grain sections. Partial isotopic equilibration does not likely explain the C isotopic heterogeneities. These grains and their constituent parts probably formed in a stellar environment with changing isotopic composition.

DD 13 - A very young and heavily reddened early O star in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Conti, Peter S.; Fitzpatrick, Edward L.

1991-01-01

This paper investigates the Large Magellanic Cloud star DD 13, which is likely the major ionizing source of the nebula N159A. New optical spectroscopy and new estimates of the broadband photometric properties of DD 13 are obtained. A spectral type of O3-O6 V, E(B-V) = 0.64, and M(V) = -6.93 is found. The spectral type cannot be more precisely defined due to contamination of the spectral data by nebular emission, obliterating the important He I classification lines. These results, plus a published estimate of the Lyman continuum photon injection rate into N159A, suggest that DD 13 actually consists of about 2-4 young, early O stars still enshrouded by their natal dust cloud. The star DD 13 may be a younger example of the type of tight cluster represented by the LMC 'star' Sk-66 deg 41, recently revealed to be composed of six or more components.

One Year of Monthly N and O Isotope Measurements in Nitrate from 18 Streamwater Monitoring Stations Within the Predominantly Pastoral Upper Manawatu Catchment, New Zealand

NASA Astrophysics Data System (ADS)

Baisden, W. T.; Douence, C.

2010-12-01

New Zealand's intensive pastoral agricultural systems have a significant impact on water quality due to nitrogen loading in rivers. A research programme has been designed to develop indicators of the sources and denitrification losses of nitrate in streamwater. This work describes the results of one year of monthly measurements at ~18 monitoring locations in the 1260 square km upper Manawatu River catchment. The catchment was chosen for study because it is among the most pastoral catchments in New Zealand, with little non-pastoral agriculture and limited forest area outside of the Tararua mountain range on the west side of the catchment. The use of N and O isotope ratios in nitrate has considerable potential to elucidate the sources and fate of nitrate with greater precision than in most other nations due to the lack of nitrate in atmospheric deposition and the lack of nitrates used as fertilizer. We measured N and O isotope ratios in nitrate plus nitrite using cadmium and azide chemical denitrification method, and refer to the results as nitrate for brevity due to low nitrite concentrations. When examined as annual averages at each monitoring site, we found the lowest N and O isotope ratios in our only site draining native forest. All agricultural monitoring sites sit approximately on a 1:1 line, enriched in N-15 and O-18 by 2-6 per mil relative to the native forest subcatchment. The three main effluent point sources in the catchment demonstrated unexpected variability in isotope ratios. Two modern sewage treatment ponds had N and O isotope ratios close to those found in agricultural catchments, while a closed meat freezing factory effluent pond had isotope ratios strongly enriched in N-15 and O-18. The lack of summer low flows during monitoring period, combined with the variability in isotope ratios from point source, appeared to be responsible for our inability to clearly detect the effect of point sources in the isotope data from stations upstream and

Spatial and temporal variation in the stable isotope composition (δ18O and δ2H) of rain across the tropical island of Sri Lanka.

PubMed

Edirisinghe, E A N V; Pitawala, H M T G A; Dharmagunawardhane, H A; Wijayawardane, R L

2017-12-01

Seasonal and spatial variation in δ 18 O and δ 2 H in rainwater was determined in three selected transects across Sri Lanka, the tropical island in the Indian Ocean. Local meteoric water lines (LMWLs) for three distinguished climatic zones; wet, dry and intermediate were constructed. LMWLs show slight variations in their gradients and respective d-excess values, depending on the air moisture origin, circulation and environmental conditions of each climatic zone. The elevation effect and amount effect could be identified but the continental effect is not significantly seen in the isotope composition of rain in the concerned areas. The results reasonably revealed that the distinct rainfall regimes; two monsoonal rains and two convectional (inter-monsoon) rains have characteristic isotopic signatures. Also the impact of (i) terrestrial and oceanic moisture sources, (ii) depression and cyclonic conditions of the Bay of Bengal, and (iii) topography of the country on the variation of the isotopic composition of rain in Sri Lanka could be satisfactorily identified.

Latitudinal change in precipitation and water vapor isotopes over Southern ocean

NASA Astrophysics Data System (ADS)

Rahul, P.

2015-12-01

The evaporation process over ocean is primary source of water vapor in the hydrological cycle. The Global Network of Isotopes in Precipitation (GNIP) dataset of rainwater and water vapor isotopes are predominantly based on continental observations, with very limited observation available from the oceanic area. Stable isotope ratios in precipitation provide valuable means to understand the process of evaporation and transport of water vapor. This is further extended in the study of past changes in climate from the isotopic composition of ice core. In this study we present latitudinal variability of water vapor and rainwater isotopic composition and compared it with factors like physical condition of sea surface water from near equator (1°S) to the polar front (56°S) during the summer time expedition of the year 2013. The water vapor and rainwater isotopes showed a sharp depletion in isotopes while progressively move southward from the tropical regions (i.e. >30°S), which follows the pattern recorded in the surface ocean water isotopic composition. From the tropics to the southern latitudes, the water vapor d18O varied between -11.8‰ to -14.7‰ while dD variation ranges between -77.7‰ to -122.2‰. Using the data we estimated the expected water vapor isotopic composition under kinetic as well as equilibrium process. Our observation suggests that the water vapor isotopic compositions are in equilibrium with the sea water in majority of cases. At one point of observation, where trajectory of air parcel originated from the continental region, we observed a large deviation from the existing trend of latitudinal variability. The deduced rainwater composition adopting equilibrium model showed a consistent pattern with observed values at the tropical region, while role of kinetic process become dominant on progressive shift towards the southern latitudes. We will draw comparison of our observation with other data available in the literature together with isotope

Investigating human geographic origins using dual-isotope (87Sr/86Sr, δ18O) assignment approaches.

PubMed

Laffoon, Jason E; Sonnemann, Till F; Shafie, Termeh; Hofman, Corinne L; Brandes, Ulrik; Davies, Gareth R

2017-01-01

Substantial progress in the application of multiple isotope analyses has greatly improved the ability to identify nonlocal individuals amongst archaeological populations over the past decades. More recently the development of large scale models of spatial isotopic variation (isoscapes) has contributed to improved geographic assignments of human and animal origins. Persistent challenges remain, however, in the accurate identification of individual geographic origins from skeletal isotope data in studies of human (and animal) migration and provenance. In an attempt to develop and test more standardized and quantitative approaches to geographic assignment of individual origins using isotopic data two methods, combining 87Sr/86Sr and δ18O isoscapes, are examined for the Circum-Caribbean region: 1) an Interval approach using a defined range of fixed isotopic variation per location; and 2) a Likelihood assignment approach using univariate and bivariate probability density functions. These two methods are tested with enamel isotope data from a modern sample of known origin from Caracas, Venezuela and further explored with two archaeological samples of unknown origin recovered from Cuba and Trinidad. The results emphasize both the potential and limitation of the different approaches. Validation tests on the known origin sample exclude most areas of the Circum-Caribbean region and correctly highlight Caracas as a possible place of origin with both approaches. The positive validation results clearly demonstrate the overall efficacy of a dual-isotope approach to geoprovenance. The accuracy and precision of geographic assignments may be further improved by better understanding of the relationships between environmental and biological isotope variation; continued development and refinement of relevant isoscapes; and the eventual incorporation of a broader array of isotope proxy data.

Combined Use of GIS, Hydrostratigraphic, Geochemical, and Multi-Isotope Analysis for Groundwater Preservation and Development in a Complex Karst Setting

NASA Astrophysics Data System (ADS)

Murgulet, D.; Cook, M. R.

2011-12-01

The complex stratigraphy and geologic structure characteristic to fractured karst aquifers underlying an urban part of the north-central Alabama Valley and Ridge Setting make the development and protection of groundwater sources difficult. In this area, population growth accompanied by increased impervious surfaces, storm water runoff, contaminants, subsidence, and pumping rates have rendered the groundwater resource. The potential for aquifer recharge and flow conditions were evaluated in order to determine the current and future alternative water sources available in this area. Geochemical and multi-isotope techniques were coupled with hydrostratigraphic and geomorphic spatial (GIS) analyses to determine the primary mechanisms controlling recharge and flow and evaluate seasonal impacts on groundwater resources and recharge environments. Groundwater samples, collected in summer and fall (2010) from wells developed in the Bangor Limestone and Tuscumbia Fort Payne aquifers (north-central Alabama), were analyzed for major ions, stable isotopes of oxygen (δ^18O), hydrogen (δD), and carbon (δ^13C), and anthropogenic isotopes such as chlorofluorocarbon (CFCs) and sulphur hexafluoride (SF_6). Stable isotope investigations suggest that recharge occurs under relatively closed conditions, with fast percolation rates in short periods (characteristic to karst aquifers) and low evaporation rates during the colder seasons. The average δ^13C value (-11.4±2% PDB, n=9) lies near the combined average δ^13C values of soil CO_2 and the carbonate. Therefore, groundwater δ^13C signature is mainly controlled by two factors: soil CO_2 and carbonate dissolution. Static water levels decrease over the summer causing drawdowns (2 to 5.2 meters) in all the production wells and a slight shift of the δ^18O and δD values towards a more positive member (summer range--δ^18O: -5.1±0.1 to -5.7±0.1% VSMOW, n=11; δD: -25.0±1 to -30.6±1% VSMOW, n=11 and fall range--δ^18O: -4.8±0.1 to

D/H isotopic fractionation effects in the H2-H2O system: An in-situ experimental study at supercritical water conditions

NASA Astrophysics Data System (ADS)

Foustoukos, D.; Mysen, B. O.

2011-12-01

Understanding the effect of temperature on the relative distribution of volatiles in supercritical aqueous solutions is important to constrain elemental and isotopic partitioning/fractionation effects in systems applicable to planetary interiors where the temperature-pressure conditions are often beyond existing experimental or theoretical datasets. For example, very little exists for the fundamental equilibria between H2, D2 and HD (H2 + D2 = 2HD), which, in turn, constrains the internal D/H isotope exchange and the evolution of HD in H2-containing systems such as H2-CH4 and H2-H2O. Theoretical calculations considering the partition functions of the molecules predict that with temperature increase, the equilibrium constant of this reaction approximates values that correspond to the stochastic distribution of species. These calculations consider pure harmonic vibrational frequencies, which, however, do not apply to the diatomic molecule of hydrogen, especially because anharmonic oscillations are anticipated to become stronger at high temperatures. Published experimental data have been limited to conditions lower than 468°C with large uncertainties at elevated temperatures. To address the lack of experimental data, a series of hydrothermal diamond anvil experiments has been conducted utilizing vibrational spectroscopy as a novel quantitative method to explore the relative distribution of H- and D-bearing volatiles in the H2-D2-D2O-H2O-Ti-TiO2 system. The fundamentals of this methodology are based on the distinct Raman frequency shift resulting from deuterium substitution in the H-H and O-H bonds. In detail, H2O-D2O solutions (1:1) were reacted with Ti metal (for 3-9hrs) at 600-800°C and pressures of 0.5-1 GPa, leading to formation of H2, D2, HD and HDO species through Ti oxidation and H-D isotope exchange reactions. Experimental results obtained in-situ and in the quenched gas phase, indicate a significant deviation from the theoretical estimate of the equilibrium

Glacial to Holocene dynamics of Indonesian precipitation - New insights from plant-wax dD off Northwest Sumatra

NASA Astrophysics Data System (ADS)

Niedermeyer, E. M.; Mohtadi, M.; Sessions, A. L.; Feakins, S. J.

2012-12-01

We used the stable hydrogen and stable carbon isotopic composition (dD and d13C, respectively) of terrestrial plant leaf waxes as a proxy for past rainfall variations over northwestern Indonesia. Our study site lies within the western boundary of the Indo-Pacific Warm Pool (IPWP), a key evaporative site for the global hydrologic cycle. At present, rainfall intensity in tropical Indonesia is influenced by the Pacific Ocean El Nino Southern Oscillation (ENSO) (see Kirono et al., 1999), the Indian Ocean Dipole (IOD) mode (Saji et al., 1999), and to some extend by the position of the Intertropical Convergence Zone (ITCZ) (e.g. Koutavas and Lynch-Stieglitz, 2005). Paleoclimate studies show that these systems have varied in the past, however, the impact of these changes on regional paelo-hydrology of Indonesia is yet unknown. We worked on marine sediment core SO189-144KL (1°09,300 N; 98°03,960 E) retrieved at 480 m water depth off Northwest Sumatra from the eastern Indian Ocean. Sediments consist of material from marine and terrestrial sources, and radiocarbon dating indicates an age of ~300 years at the core top and of ~24,000 years at the base. We used d13C and dD values of the n-C30 alkanoic acid as proxies for changes in vegetation composition (C3 vs. C4 plants) and rainfall variability on land, respectively. Values of d13C show only little variation and suggest persistent dominance of tropical trees throughout the past 24,000 years. Values of dD display distinct variability throughout the record, however, mean rainfall intensities during the late Last Glacial compare to those during the Holocene. This is in agreement with rather consistent vegetation at the study site but in sharp contrast with reconstructions of contemporaneous rainfall patterns at the nearby islands Borneo (Partin et al., 2007) and Flores (Griffiths et al., 2009), indicating multiple controls on regional hydrology of Indonesia. In combination with previous studies of late Pleistocene to Holocene

Determination of the delta(18O/16O)of Water: RSIL Lab Code 489

USGS Publications Warehouse

Revesz, Kinga; Coplen, Tyler

2008-01-01

The purpose of the technique described by the Reston Stable Isotope Laboratory (RSIL) lab code 489 is to present a method to determine the delta(180/160), abbreviated as delta-180, of water. This delta-18O measurement of water also is a component of National Water Quality Laboratory (NWQL in USGS) schedules 1142 and 1172. Water samples are loaded into glass sample containers on a vacuum manifold to equilibrate gaseous CO2 at constant temperature (25 deg C) with water samples. After loading water samples on the vacuum manifold, air is evacuated through capillary to avoid evaporation, and CO2 is added. The samples are shaken to increase the equilibration rate of water and CO2. When isotopic equilibrium has been attained, an aliquot of CO2 is extracted sequentially from each sample container, separated from water vapor by means of a dry ice trap, and introduced into a dual-inlet isotope-ratio mass spectrometer (DI-IRMS) for determination of the delta-18O value. There is oxygen isotopic fractionation between water and CO2, but it is constant at constant temperature. The DI-IRMS is a DuPont double-focusing mass spectrometer. It has a double collector. One ion beam passes through a slit in a forward collector and is collected in the rear collector. The other ion beams are collected in the front collector. The instrument is capable of measuring mass/charge (m/z) 44 and 45 or 44 and 46 by changing the ion-accelerating voltage under computer control. The ion beams from these m/z values are as follows: m/z 44=CO2=12C16O16O, m/z 45=CO2=13C16O16O primarily, and m/z 46 = CO2=12C16O18O primarily. The data acquisition and control software calculates delta-18O values.

48 CFR 245.7206 - Transmitting DD Form 1342, DoD Property Record.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Instructions 245.7206 Transmitting DD Form 1342, DoD Property Record. As a minimum, the plant clearance officer... contractor acquired the equipment; (g) Location of the industrial plant equipment; (h) Total acquisition cost..., DoD Property Record. 245.7206 Section 245.7206 Federal Acquisition Regulations System DEFENSE...

Co-occurring species differ in tree-ring δ18O trends.

Treesearch

John D. Marshall; Robert A. Monserud

2006-01-01

The stable oxygen isotope ratio (δ18O) of tree-ring cellulose is jointly determined by the δ18O of xylem water, the δ18O of atmospheric water vapor, the humidity of the atmosphere and perhaps by species-specific differences in leaf structure and function. Atmospheric...

Calculation of individual isotope equilibrium constants for geochemical reactions

USGS Publications Warehouse

Thorstenson, D.C.; Parkhurst, D.L.

2004-01-01

Theory is derived from the work of Urey (Urey H. C. [1947] The thermodynamic properties of isotopic substances. J. Chem. Soc. 562-581) to calculate equilibrium constants commonly used in geochemical equilibrium and reaction-transport models for reactions of individual isotopic species. Urey showed that equilibrium constants of isotope exchange reactions for molecules that contain two or more atoms of the same element in equivalent positions are related to isotope fractionation factors by ?? = (Kex)1/n, where n is the number of atoms exchanged. This relation is extended to include species containing multiple isotopes, for example 13C16O18O and 1H2H18O. The equilibrium constants of the isotope exchange reactions can be expressed as ratios of individual isotope equilibrium constants for geochemical reactions. Knowledge of the equilibrium constant for the dominant isotopic species can then be used to calculate the individual isotope equilibrium constants. Individual isotope equilibrium constants are calculated for the reaction CO2g = CO2aq for all species that can be formed from 12C, 13C, 16O, and 18O; for the reaction between 12C18 O2aq and 1H218Ol; and among the various 1H, 2H, 16O, and 18O species of H2O. This is a subset of a larger number of equilibrium constants calculated elsewhere (Thorstenson D. C. and Parkhurst D. L. [2002] Calculation of individual isotope equilibrium constants for implementation in geochemical models. Water-Resources Investigation Report 02-4172. U.S. Geological Survey). Activity coefficients, activity-concentration conventions for the isotopic variants of H2O in the solvent 1H216Ol, and salt effects on isotope fractionation have been included in the derivations. The effects of nonideality are small because of the chemical similarity of different isotopic species of the same molecule or ion. The temperature dependence of the individual isotope equilibrium constants can be calculated from the temperature dependence of the fractionation

Isotope effect on superconductivity and Raman phonons of Pyrochlore Cd2Re2O7

NASA Astrophysics Data System (ADS)

Razavi, F. S.; Hajialamdari, M.; Reedyk, M.; Kremer, R. K.

2018-06-01

Cd2Re2O7 is the only α-Pyrochlore exhibiting superconductivity with a transition temperature (Tc) of ∼ 1 K. In this study, we present the effect of oxygen isotope (18O) as well as combined 18O and cadmium isotope (116Cd) substitution on the superconductivity and Raman scattering spectrum of Cd2Re2O7. The change of Tc and the energy gap Δ(T) are reported using various techniques including point contact spectroscopy. The shift in Raman phonon frequencies upon isotope substitution will be compared with measurement of the isotope effect on the superconducting transition temperature.

Extraction of CO2 from air samples for isotopic analysis and limits to ultra high precision delta18O determination in CO2 gas.

PubMed

Werner, R A; Rothe, M; Brand, W A

2001-01-01

The determination of delta18O values in CO2 at a precision level of +/-0.02 per thousand (delta-notation) has always been a challenging, if not impossible, analytical task. Here, we demonstrate that beyond the usually assumed major cause of uncertainty - water contamination - there are other, hitherto underestimated sources of contamination and processes which can alter the oxygen isotope composition of CO2. Active surfaces in the preparation line with which CO2 comes into contact, as well as traces of air in the sample, can alter the apparent delta18O value both temporarily and permanently. We investigated the effects of different surface materials including electropolished stainless steel, Duran glass, gold and quartz, the latter both untreated and silanized. CO2 frozen with liquid nitrogen showed a transient alteration of the 18O/16O ratio on all surfaces tested. The time to recover from the alteration as well as the size of the alteration varied with surface type. Quartz that had been ultrasonically cleaned for several hours with high purity water (0.05 microS) exhibited the smallest effect on the measured oxygen isotopic composition of CO2 before and after freezing. However, quartz proved to be mechanically unstable with time when subjected to repeated large temperature changes during operation. After several days of operation the gas released from the freezing step contained progressively increasing trace amounts of O2 probably originating from inclusions within the quartz, which precludes the use of quartz for cryogenically trapping CO2. Stainless steel or gold proved to be suitable materials after proper pre-treatment. To ensure a high trapping efficiency of CO2 from a flow of gas, a cold trap design was chosen comprising a thin wall 1/4" outer tube and a 1/8" inner tube, made respectively from electropolished stainless steel and gold. Due to a considerable 18O specific isotope effect during the release of CO2 from the cold surface, the thawing time had to

Using Isotope Ratio Infrared Spectrometer to determine δ13C and δ18O of carbonate samples

NASA Astrophysics Data System (ADS)

Smajgl, Danijela; Stöbener, Nils; Mandic, Magda

2017-04-01

The isotopic composition of calcifying organisms is a key tool for reconstruction past seawater temperature and water chemistry. Therefore stable carbon and oxygen isotopes (δ13C and δ18O) in carbonates have been widely used for reconstruction of paleoenvironments. Precise and accurate determination of isotopic composition of carbon (13C) and oxygen (18O) from carbonate sample with proper referencing and data evaluation algorithm presents a challenge for scientists. Mass spectrometry was the only widely used technique for this kind of analysis, but recent advances make laser based spectroscopy a viable alternative. The Thermo Scientific Delta Ray Isotope Ratio Infrared Spectrometer (IRIS) analyzer with the Universal Reference Interface (URI) Connect is one of those alternatives and with TELEDYNE Cetac ASX-7100 autosampler extends the traditional offerings with a system of high precision and throughput of samples. To establish precision and accuracy of measurements and also to develop optimal sample preparation method for measurements with Delta Ray IRIS and URI Connect, IAEA reference materials were used. Preparation is similar to a Gas Bench II method. Carbonate material is added into the vials, flushed with CO2 free synthetic air and acidified with few droplets of 104% H3PO4. Sample amount used for analysis can be as low as 200 μg. Samples are measured after acidification and equilibration time of one hour at 70°C. The CO2 gas generated by reaction is flushed into the variable volume inside the URI Connect through the Nafion based built-in water trap. For this step, carrier gas (CO2 free air) is used to flush the gas from the vial into the variable volume with a maximum volume of 100 ml. A small amount of the sample is then used for automatic concentration determination present in the variable volume. The Thermo Scientific Qtegra Software automatically adjusts any additional dilution of the sample to achieve the desired concentration (usually 400 ppm) in the

17DD and 17D-213/77 yellow fever substrains trigger a balanced cytokine profile in primary vaccinated children.

PubMed

Campi-Azevedo, Ana Carolina; de Araújo-Porto, Luiza Pacheco; Luiza-Silva, Maria; Batista, Maurício Azevedo; Martins, Marina Angela; Sathler-Avelar, Renato; da Silveira-Lemos, Denise; Camacho, Luiz Antonio Bastos; de Menezes Martins, Reinaldo; de Lourdes de Sousa Maia, Maria; Farias, Roberto Henrique Guedes; da Silva Freire, Marcos; Galler, Ricardo; Homma, Akira; Ribeiro, José Geraldo Leite; Lemos, Jandira Aparecida Campos; Auxiliadora-Martins, Maria; Caldas, Iramaya Rodrigues; Elói-Santos, Silvana Maria; Teixeira-Carvalho, Andréa; Martins-Filho, Olindo Assis

2012-01-01

This study aimed to compare the cytokine-mediated immune response in children submitted to primary vaccination with the YF-17D-213/77 or YF-17DD yellow fever (YF) substrains. A non-probabilistic sample of eighty healthy primary vaccinated (PV) children was selected on the basis of their previously known humoral immune response to the YF vaccines. The selected children were categorized according to their YF-neutralizing antibody titers (PRNT) and referred to as seroconverters (PV-PRNT(+)) or nonseroconverters (PV-PRNT(-)). Following revaccination with the YF-17DD, the PV-PRNT(-) children (YF-17D-213/77 and YF-17DD groups) seroconverted and were referred as RV-PRNT(+). The cytokine-mediated immune response was investigated after short-term in vitro cultures of whole blood samples. The results are expressed as frequency of high cytokine producers, taking the global median of the cytokine index (YF-Ag/control) as the cut-off. The YF-17D-213/77 and the YF-17DD substrains triggered a balanced overall inflammatory/regulatory cytokine pattern in PV-PRNT(+), with a slight predominance of IL-12 in YF-17DD vaccinees and a modest prevalence of IL-10 in YF-17D-213/77. Prominent frequency of neutrophil-derived TNF-α and neutrophils and monocyte-producing IL-12 were the major features of PV-PRNT(+) in the YF-17DD, whereas relevant inflammatory response, mediated by IL-12(+)CD8(+) T cells, was the hallmark of the YF-17D-213/77 vaccinees. Both substrains were able to elicit particular but relevant inflammatory events, regardless of the anti-YF PRNT antibody levels. PV-PRNT(-) children belonging to the YF-17DD arm presented gaps in the inflammatory cytokine signature, especially in terms of the innate immunity, whereas in the YF-17D-213/77 arm the most relevant gap was the deficiency of IL-12-producing CD8(+)T cells. Revaccination with YF-17DD prompted a balanced cytokine profile in YF-17DD nonresponders and a robust inflammatory profile in YF-17D-213/77 nonresponders. Our findings

High Resolution deglacial monsoon δ18O record from a new stalagmite from the Kailash Cave, Central India

NASA Astrophysics Data System (ADS)

Allu C, Narayana; Pawan K, Gautam; Shraddha, Band; Madhusudan G, Yadava; Rengaswamy, Ramesh; Shen, Chuan-Chou

2016-04-01

High resolution δ18O and δ13C data from absolutely dated stalagmites have been useful for reconstructing the Asian monsoon variability (e.g., Yadava et al., 2004; Laskar et al., 2013; Allu et al., 2014; Lone et al., 2014; Sinha et al., 2015). However, many studies lack high resolution spatial and temporal records leaving significant gaps which need to be filled for a vivid understanding of monsoonal variability. We report here the first high resolution stalagmite δ18O isotope results during the last deglacial obtained from the Kailash cave located from the core monsoon region. The length of stalagmite was 480 mm, with an average diameter of 120 mm. The sample was cut for continuous micro milling at 400μm intervals along the growth axis (using new wave research micro-mill-101288) for the analyses of stable oxygen and carbon isotopes using a Delta V plus IRMS at the Physical Research Laboratory, Ahmedabad. The physical appearance of the sample section reveals very fine, straight and clear laminations from the top to 310 mm from below, which have thick laminae. U-Th dates obtained from a Thermo Fisher NEPTUNE multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) at High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), National Taiwan University, Taiwan (Shen et al., 2012) showed the record spanned ~2400 years from ~14.6 ka to ~12.2 ka. Linear Age-Depth model constructed from dates suggests that the sample grew for ~2.400 years from ~14.6 ka to ~12.2 ka with varying resolutions from ~6 months to ~8 years. Hendy's test from 8 distinct layers shows poor correlation between δ18O and δ13C suggesting the isotopic equilibrium conditions at the time of crystallization. δ18O and δ13C results appear to be cyclic in nature varying in the range from +0.37‰ to -6.07‰ and -1.59‰ to -10.59‰ respectively. Enriched δ18O in top portion represents poor monsoon during the onset of Younger Drayas. Later, the δ18O signals

Isotopic inhomogeneity of leaf water: Evidence and implications for the use of isotopic signals transduced by plants

NASA Astrophysics Data System (ADS)

Yakir, Dan; DeNiro, Michael J.; Rundel, Philip W.

1989-10-01

Variations as large as 11%. in δ18O values and 50%. in δD values were observed among different fractions of water in leaves of ivy (Hedera helix) and sunflower (Helianthus annuus). This observation contradicts previous experimental approaches to leaf water as an isotopically uniform pool. Using ion analysis of the water fractions to identify sources within the leaf, we conclude that the isotopic composition of the water within cells, which is involved in biosynthesis and therefore recorded in the plant organic matter, differs substantially from that of total leaf water. This conclusion must be taken into account in studies in which isotope ratios of fossil plant cellulose are interpreted in paleoclimatic terms. In addition, our results have implications for attempts to explain the Dole effect and to account for the variations of 18O/16O ratios in atmospheric carbon dioxide, since the isotopic composition of cell water, not of total leaf water, influences theδ18O values of O2 and CO2 released from plants into the atmosphere.

Eocene high-latitude temperature gradients over time and space based on d18O values of fossil shark teeth

NASA Astrophysics Data System (ADS)

Zeichner, S. S.; Kim, S.; Colman, A. S.

2015-12-01

Early-Mid Eocene (56.0-33.9Mya) is characterized by a temperate Antarctic climate and shallower latitudinal temperature gradients than those in present day. The warmer waters off the coast of the Antarctic Peninsula provided suitable habitats for taxa (i.e., sharks) that live today at lower latitudes. Stable isotope analysis of Eocene shark teeth provides a proxy to understand high latitude temperature gradients. However, shark ecology, in particular migration and occupation of tidal versus pelagic habitats, must be considered in the interpretation of stable isotope data. In this study, we analyze d18OPO4 values from the enameloid of Striatolamia (synonymized with Carcharias) shark teeth from the La Meseta formation (Seymour Island, Antarctica) to estimate paleotemperature in Early-Mid Eocene Antarctica, and assess the impact of ecology versus environmental signals on d18OPO4 values. We compare the ranges and offsets between our measured shark tooth d18OPO4 and published bivalve d18OCO3 values to test whether shark teeth record signals of migration across latitudinal temperature gradients, or instead reflect seasonal and long-term temporal variation across La Meseta stratigraphic units.

Can tree-ring isotopes (δ18O and δ13C) improve our understanding of hydroclimate variability in the Columbia River Basin?

NASA Astrophysics Data System (ADS)

Csank, A. Z.; Wise, E.; McAfee, S. A.

2015-12-01

The trajectory of incoming storms from the Pacific Ocean has a strong impact on hydroclimate in the Pacific Northwest. Shifts between zonal and meridional flow are a key influence on drought and pluvial regimes in both the PNW and the western United States as a whole. Circulation-dependent variability in the isotopic composition of precipitation can be recorded and potentially reconstructed using δ18O records derived from tree-rings. Here we present isotopic records of δ18O and δ13C from ponderosa pine (Pinus ponderosa) for the period 1950-2013 from six sites located in the lee of the Cascades in eastern Washington. Because of the orientation of the Cascades, zonal flow will result in an intensified rain shadow whereas meridional flow allows moisture to penetrate at a lower elevation leading to a lower rainout effect. This means zonal flow results in drier conditions in eastern Washington and the converse for meridional flow. We hypothesized that more depleted precipitation δ18O values will occur with periods of more zonal flow across the PNW and will be recorded by trees at our sites. Results show a strong relationship between our δ18O chronologies and winter precipitation (R = -0.50; p<0.001). δ13C chronologies from the same trees showed a relationship to prior fall/winter (pOct-pDec) precipitation (R = -0.46; p<0.005) suggesting a possible link to antecedent moisture conditions. With a focus on years with clear zonal and meridional flow regimes, we regressed the tree-ring δ18O anomaly against the instrumental record of total precipitation and compared the residual series to records of storm track for the period 1978-2008, and we found a detectable signal where the most depleted δ18O was generally associated with zonal flow and the most enriched δ18O with meridional flow. However, there are still some years where the relationship is unclear. Further work is aimed at understanding these anomalous years and extending our record beyond the instrumental

Controls of precipitation δ18O on the northwestern Tibetan Plateau: A case study at Ngari station

NASA Astrophysics Data System (ADS)

Guo, Xiaoyu; Tian, Lide; Wen, Rong; Yu, Wusheng; Qu, Dongmei

2017-06-01

The shifting atmospheric circulation between the Indian monsoon and the westerlies on the northwestern Tibetan Plateau (TP) influences precipitation as well as precipitation isotopes. Isotopic records will therefore show historical fluctuations. To understand better the factors controlling present day precipitation δ18O values on the northwestern TP, we made continuous observations of precipitation isotopes at Ngari station from 2010 to 2013. The drivers of precipitation δ18O were investigated using analyses of their statistical relations with temperature, precipitation amount, relative humidity, and convective activities based on outgoing longwave radiation (OLR) data from NOAA satellites, and downward shortwave radiation (DSR) data collected at the Ngari automatic weather station. Atmospheric circulation patterns from NCAR reanalysis, and moisture transport paths of individual events derived from the HYSPLIT model using NCEP data, were also used to trace moisture sources. The results of our study include: (1) The slope and intercept of the Local Meteoric Water Line (LMWL) at Ngari (δD = 8.51 δ18O + 11.57 (R2 = 0.97, p < 0.01)) were higher than for the Global Meteoric Water Line (GMWL), indicating drier local climatic conditions; (2) Precipitation δ18O values showed a weak ;temperature effect; and a weak ;precipitation amount effect; at Ngari; and (3) Convection (or temperature patterns) integrated over several days (0-20) preceding each event were determined to be the main driver of precipitation isotopic values in monsoon (or non-monsoon) season. The longer (shorter) periods of τm days when correlation coefficients between precipitation δ18O and OLR were at their maxima (minima) indicate deep convective activities (shorter moisture transportation pathways) in August (June, July, and September).

Sea Surface Temperature and Seawater Oxygen Isotope Variability Recorded in a Madagascar Coral Record

NASA Astrophysics Data System (ADS)

Zinke, J.; Dullo, W. Chr; Eisenhauer, A.

2003-04-01

We analysed a 336 year coral oxygen isotope record off southwest Madagascar in the Mozambique Channel. Based on temporal variability of skeletal oxygen isotopes annual mean sea surface temperatures are reconstructed for the period from 1659 to 1995. Sr/Ca ratios were measured for selected windows with monthly resolution (1973 to 1995, 1863 to 1910, 1784 to 1809, 1688 to 1710) to validate the SST reconstructions derived from oxygen isotopes. The coral proxy data were validated against gridded SST data sets. The coral oxygen isotope record is coherent with Kaplan-SST and GISST2.3b on an interdecadal frequency of 17 years, which is the most prominent frequency band observed in this region. The Sr/Ca-SST agree well with SST observations in the validation period (1863 to 1910), whereas the d18O derived SST show largest discrepencies during this time interval. By taking into account the SST values derived from coral Sr/Ca, we were able to reconstruct d18O seawater variability. This indicates that d18O seawater variations contributed significantly to interannual and interdecadal variations in coral d18O. We propose that the local surface-ocean evaporation-precipitation balance and remote forcing by ENSO via South Equatorial Current and/or Indonesian throughflow variability may contribute to observed d18O variability. Our results indicate that coral d18O may be used to reconstruct temporal variations in the fresh water balance within the Indian Ocean on interannual to interdecadal time scales.

Salinity information in coral δ18O records

NASA Astrophysics Data System (ADS)

Conroy, J. L.; Thompson, D. M.; Dassié, E. P.; Stevenson, S.; Konecky, B. L.; DeLong, K. L.; Sayani, H. R.; Emile-Geay, J.; Partin, J. W.; Abram, N. J.; Martrat, B.

2017-12-01

Coral oxygen isotopic ratios (δ18O) are typically utilized to reconstruct sea surface temperature (SST), or SST-based El Niño-Southern Oscillation metrics (e.g., NIÑO3.4), despite the influence of both SST and the oxygen isotopic composition of seawater (δ18Osw) on coral δ18O. The ideal way to isolate past δ18Osw variations is to develop independent and univariate SST and δ18Osw responders, for instance, via paired coral δ18O and Sr/Ca analyses. Nonetheless, many coral δ18O records without paired Sr/Ca records already exist in the paleoclimatic literature, and these may be able to provide some insight into past δ18Osw and salinity changes due to the nature of the significant positive relationship between instrumental salinity and δ18Osw. Here we use coral δ18O records from the new PAGES Iso2k database to assess the regions in which coral δ18O has the greatest potential to provide salinity information based on the strength of the relationship between instrumental salinity and coral δ18O values. We find from annual pseudocoral similations that corals in the western tropical Pacific share a substantial fraction of their variance with δ18Osw rather than SST. In contrast, in the Indian Ocean and eastern tropical Pacific it is SST that predominantly explains coral δ18O variance. In agreement with this variance decomposition, we find that coral δ18O time series from the western tropical Pacific are significantly correlated with mid to late 20th century salinity. However, variations in the strength of the δ18Osw-salinity relationship across the western tropical Pacific will likely have a significant influence on coral δ18O-based salinity reconstructions. Additionally, in some cases a strong, negative correlation between SST and δ18Osw might not allow their influences to be adequately separated in coral δ18O records without the use of coupled Sr/Ca estimates of the temperature contribution. Overall, we find a range of modern salinity and SST

DD genotype of ACE gene I/D polymorphism is associated with Behcet disease in a Turkish population.

PubMed

Yigit, Serbülent; Tural, Sengül; Rüstemoglu, Aydin; Inanir, Ahmet; Gul, Ulker; Kalkan, Goknur; Akkanet, Songul; Karakuş, Nevin; Ateş, Omer

2013-01-01

Behcet's disease (BD) is a chronic, multi-systemic and inflammatory disorder. The local renin-angiotensin system (RAS) in the vessel wall plays a role in the endothelial control and contributes to inflammatory processes. Angiotensin-converting enzyme (ACE) is the regulatory component of the RAS. This study was conducted in Turkish patients with BD to determine the frequency of I/D polymorphism genotypes of ACE gene. Genomic DNA obtained from 566 persons (266 patients with BD and 300 healthy controls). ACE gene I/D polymorphism genotypes were determined using polymerase chain reaction using I and D allele-specific primers. There was statistically significant difference between the groups with respect to genotype distribution (p < 0.001). This study is the largest study in Turkish population that ACE gene I/D polymorphism investigated in BD. As a result of this study, ACE gene I/D polymorphism DD genotype could be a genetic marker in BD in Turkish study population.

Analysis of Hydrogen Isotopic Exchange: Lava Creek Tuff Ash and Isotopically Labeled Water

NASA Astrophysics Data System (ADS)

Ross, A. M.; Seligman, A. N.; Bindeman, I. N.; Nolan, G. S.

2015-12-01

Nolan and Bindeman (2013) placed secondarily hydrated ash from the 7.7 ka eruption of Mt. Mazama (δD=-149‰, 2.3wt% H2Ot) in isotopically labeled water (+650 ‰ δD, +56 ‰ δ18O) and observed that the H2Ot and δ18O values remained constant, but the δD values of ash increased with the surrounding water at 20, 40 and 70 °C. We expand on this work by conducting a similar experiment with ash from the 640 ka Lava Creek Tuff (LCT, δD of -128 ‰; 2.1 wt.% H2Ot) eruption of Yellowstone to see if significantly older glass (with a hypothesized gel layer on the surface shielding the interior from alteration) produces the same results. We have experiments running at 70, 24, and 5 °C, and periodically remove ~1.5 mg of glass to measure the δD (‰) and H2Ot (wt.%) of water extracted from the glass on a TC/EA MAT 253 continuous flow system. After 600 hours, the δD of the samples left at 5 and 24 °C remains at -128 ‰, but increased 8‰ for the 70 °C run series. However, there is no measurable change in wt.% of H2Ot, indicating that hydrogen exchange is not dictated by the addition of water. We are measuring and will report further progress of isotope exchange. We also plan to analyze the water in the LCT glass for δ18O (‰) to see if, as is the case for the Mt. Mazama glass, the δ18O (‰) remains constant. We also analyzed Mt. Mazama glass from the Nolan and Bindeman (2013) experiments that have now been sitting in isotopically labeled water at room temperature for ~5 years. The water concentration is still unchanged (2.3 wt.% H2Ot), and the δD of the water in the glass is now -111 ‰, causing an increase of 38 ‰. Our preliminary results show that exchange of hydrogen isotopes of hydrated glass is not limited by the age of the glass, and that the testing of hydrogen isotopes of secondarily hydrated glass, regardless of age, may not be a reliable paleoclimate indicator.

AmpH, a Bifunctional dd-Endopeptidase and dd-Carboxypeptidase of Escherichia coli▿

PubMed Central

González-Leiza, Silvia M.; de Pedro, Miguel A.; Ayala, Juan A.

2011-01-01

In Escherichia coli, low-molecular-mass penicillin-binding proteins (LMM PBPs) are important for correct cell morphogenesis. These enzymes display dd-carboxypeptidase and/or dd-endopeptidase activities associated with maturation and remodeling of peptidoglycan (PG). AmpH has been classified as an AmpH-type class C LMM PBP, a group closely related to AmpC β-lactamases. AmpH has been associated with PG recycling, although its enzymatic activity remained uncharacterized until now. Construction and purification of His-tagged AmpH from E. coli permitted a detailed study of its enzymatic properties. The N-terminal export signal of AmpH is processed, but the protein remains membrane associated. The PBP nature of AmpH was demonstrated by its ability to bind the β-lactams Bocillin FL (a fluorescent penicillin) and cefmetazole. In vitro assays with AmpH and specific muropeptides demonstrated that AmpH is a bifunctional dd–endopeptidase and dd-carboxypeptidase. Indeed, the enzyme cleaved the cross-linked dimers tetrapentapeptide (D45) and tetratetrapeptide (D44) with efficiencies (kcat/Km) of 1,200 M−1 s−1 and 670 M−1 s−1, respectively, and removed the terminal d-alanine from muropeptides with a C-terminal d-Ala-d-Ala dipeptide. Both dd-peptidase activities were inhibited by 40 μM cefmetazole. AmpH also displayed a weak β-lactamase activity for nitrocefin of 1.4 × 10−3 nmol/μg protein/min, 1/1,000 the rate obtained for AmpC under the same conditions. AmpH was also active on purified sacculi, exhibiting the bifunctional character that was seen with pure muropeptides. The wide substrate spectrum of the dd-peptidase activities associated with AmpH supports a role for this protein in PG remodeling or recycling. PMID:22001512

13C 18O clumping in speleothems: Observations from natural caves and precipitation experiments

NASA Astrophysics Data System (ADS)

Daëron, M.; Guo, W.; Eiler, J.; Genty, D.; Blamart, D.; Boch, R.; Drysdale, R.; Maire, R.; Wainer, K.; Zanchetta, G.

2011-06-01

The oxygen isotope composition of speleothems is an important proxy of continental paleoenvironments, because of its sensitivity to variations in cave temperature and drip water δ 18O. Interpreting speleothem δ 18O records in terms of absolute paleotemperatures and δ 18O values of paleo-precipitation requires quantitative separation of the effects of these two parameters, and correcting for possible kinetic isotope fractionation associated with precipitation of calcite out of thermodynamic equilibrium. Carbonate clumped-isotope thermometry, based on measurements of Δ47 (a geochemical variable reflecting the statistical overabundance of 13C 18O bonds in CO 2 evolved from phosphoric acid digestion of carbonate minerals), potentially provides a method for absolute speleothem paleotemperature reconstructions independent of drip water composition. Application of this new technique to karst records is currently limited by the scarcity of published clumped-isotope studies of modern speleothems. The only modern stalagmite reported so far in the literature yielded a lower Δ47 value than expected for equilibrium precipitation, possibly due to kinetic isotope fractionation. Here we report Δ47 values measured in natural speleothems from various cave settings, in carbonate produced by cave precipitation experiments, and in synthetic stalagmite analogs precipitated in controlled laboratory conditions designed to mimic natural cave processes. All samples yield lower Δ47 and heavier δ 18O values than predicted by experimental calibrations of thermodynamic equilibrium in inorganic calcite. The amplitudes of these isotopic disequilibria vary between samples, but there is clear correlation between the amount of Δ47 disequilibrium and that of δ 18O. Even pool carbonates believed to offer excellent conditions for equilibrium precipitation of calcite display out-of-equilibrium δ 18O and Δ47 values, probably inherited from prior degassing within the cave system. In addition

Hydrogen isotope fractionation between C-H-O species in magmatic fluids

NASA Astrophysics Data System (ADS)

Foustoukos, D. I.; Mysen, B. O.

2012-12-01

Constraining the hydrogen isotope fractionation between H-bearing volatiles (e.g. H2, CH4, hydrocarbons, H2O) as function of temperature and pressure helps to promote our understanding of the isotopic composition of evolved magmatic fluids and the overall mantle-cycling of water and reduced C-O-H volatiles. To describe the thermodynamics of the exchange reactions between the different H/D isotopologues of H2 and CH4 under supercritical water conditions, a novel experimental technique has been developed by combining vibrational Raman spectroscopy with hydrothermal diamond anvil cell designs (HDAC), which offers a method to monitor the in-situ evolution of H/D containing species. To this end, the equilibrium relationship between H2-D2-HD in supercritical fluid was investigated at temperatures ranging from 300 - 800 oC and pressures ~ 0.3 - 1.3 GPa [1]. Experimental results obtained in-situ and ex-situ show a significant deviation from the theoretical values of the equilibrium constant predicted for ideal-gas reference state, and with an apparent negative temperature effect triggered by the enthalpy contributions due to mixing in supercritical water. Here, we present a series of HDAC experiments conducted to evaluate the role of supercritical water on the isotopic equilibrium between H/D methane isotopologues at 600 - 800 oC and 409 - 1622 MPa. In detail, tetrakis-silane (Si5C12H36) was reacted with H2O-D2O aqueous solution in the presence of either Ni or Pt metal catalyst, resulting to the formation of deuterated methane species such as CH3D, CHD3, CH2D2 and CD4. Two distinctly different set of experiments ("gas phase"; "liquid phase") were performed by adjusting the silane/water proportions. By measuring the relative intensities of Raman vibrational modes of species, experimental results demonstrate distinctly different thermodynamic properties for the CH4-CH3D-CHD3-CH2D2 equilibrium in gas and liquid-water-bearing systems. In addition, the D/H molar ratio of

Ice Core Depth-Age Relation for Vostok delta-D and Dome Fuji delta-18O Records Based on the Devils Hole Paleotemperature Chronology

USGS Publications Warehouse

Landwehr, Jurate Maciunas

2002-01-01

This report presents the data for the Vostok - Devils Hole chronology, termed V-DH chronology, for the Antarctic Vostok ice core record. This depth - age relation is based on a join between the Vostok deuterium profile (D) and the stable oxygen isotope ratio (18O) record of paleotemperature from a calcitic core at Devils Hole, Nevada, using the algorithm developed by Landwehr and Winograd (2001). Both the control points defining the V-DH chronology and the numeric values for the chronology are given. In addition, a plausible chronology for a deformed bottom portion of the Vostok core developed with this algorithm is presented. Landwehr and Winograd (2001) demonstrated the broader utility of their algorithm by applying it to another appropriate Antarctic paleotemperature record, the Antarctic Dome Fuji ice core 18O record. Control points for this chronology are also presented in this report but deemed preliminary because, to date, investigators have published only the visual trace and not the numeric values for the Dome Fuji 18O record. The total uncertainty that can be associated with the assigned ages is also given.

[Temporal and spatial variations of hydrogen and oxygen isotopes in Tuojia River and its influencing factors.

PubMed

Wu, Hong Bao; Zhao, Qiang; Qin, Xiao Bo; Gao, Qing Zhu; Lyu, Cheng Wen

2018-05-01

The characteristics of hydrogen and oxygen stable isotopes in river is important for regional hydrologic cycle research. To uncover water supply sources in subtropical agricultural basin from a perspective of stable isotopes, field measurements were conducted in four reaches (S 1 , S 2 , S 3 and S 4 ) of Tuojia River from April to August 2017. We analyzed the spatial and temporal variations in hydrogen and oxygen isotopes and deuterium excess parameters and their relationship with precipitation, altitude and water quality. Results showed that hydrogen and oxygen isotopes and deuterium excess values ranged from -43.17‰ to -26.43‰ (-35.50‰±5.44‰), -7.94‰ to -5.70‰ (-6.86‰±0.74‰), and 16.77‰ to 23.49‰ (19.39‰±1.95‰), respectively. Under the influence of monsoon circulation, hydrogen and oxygen isotopes showed substantial seasonal variation, with spring (δD: -29.88‰±3.31‰; δ 18 O: -6.18‰±0.57‰) > summer (δD: -39.25‰±2.65‰; δ 18 O: -7.32‰±0.42‰). The spatial distribution of hydrogen and oxygen isotopes values increased fluctuantly with the position from the sampling site to the river's source, with δD: S 1 ＜S 4 ＜S 3 ＜S 2 , and δ 18 O: S 1 ＜S 3 ＜S 4 ＜S 2 . The deuterium excess values had no significant temporal variation, while it spatially increased gradually with the river levels. The slope and intercept of water line in this river were smaller than that of the local meteoric water line, suggesting that precipitation was the primary water source for this river. At the seasonal scale, both δD and δ 18 O were significantly negatively correlated with water temperature (δD: r=-0.92; δ 18 O: r=-0.88) and δ 18 O was negatively correlated with altitude (r=-0.96). At spatial scale, δ 18 O had a significantly positive correlation with water temperature. The δD and δ 18 O had negative correlation with precipitation, but being not statistically significant.

Oxygen isotope evolution of the Lake Owyhee volcanic field, Oregon, and implications for low-δ18O magmas of the Snake River Plain - Yellowstone hotspot

NASA Astrophysics Data System (ADS)

Blum, T.; Kitajima, K.; Nakashima, D.; Valley, J. W.

2013-12-01

The Snake River Plain - Yellowstone (SRP-Y) hotspot trend is one of the largest known low-δ18O magmatic provinces, yet the timing and distribution of hydrothermal alteration relative to hotspot magmatism remains incompletely understood. Existing models for SRP-Y low-δ18O magma genesis differ regarding the timing of protolith alteration (e.g. Eocene vs. present), depth at which alteration occurs (e.g. 15 km vs. <5 km), and physical controls on the extent of alteration (e.g. caldera collapse, crustal scale fluid flow, etc.). We expand the existing oxygen isotope data set for zircon in the Lake Owyhee volcanic field (LOVF) of east central Oregon to further identify magmatic oxygen isotope trends within the field. These data offer insight into the timing of alteration and the extent of the greater SRP-Y low-δ18O province, as well as the conditions that generate large low-δ18O provinces. 16-14 Ma silicic volcanism in the LOVF is linked to the pre-14 Ma SRP-Y hotspot, with volcanism partially overlapping extension in the north-south trending Oregon-Idaho Graben (OIG). Ion microprobe analyses of zircons from 16 LOVF silicic lavas and tuffs reveal homogeneous zircons on both the single grain and hand sample scales: individual samples have 2 S.D. for δ18O ranging from 0.27 to 0.96‰ (SMOW), and sample averages ranging from 1.8 to 6.0‰, excluding texturally chaotic and/or porous zircons which have δ18O values as low as 0.0‰. All low-δ18O LOVF magmas, including the caldera-forming Tuff of Leslie Gulch and Tuff of Spring Creek, are confined to the OIG, although not all zircons from within the OIG have low δ18O values. The presence and sequence of low-δ18O magmas in the LOVF and adjacent central Snake River Plain (CSRP) cannot be explained by existing caldera subsidence or pre-hotspot source models. These data, however, combined with volumetrically limited low-δ18O material in the adjacent Idaho Batholith and Basin and Range, are consistent with low-δ18O magmas

Theoretical estimates of equilibrium 13C-18O clumping in carbonates and organic acids

NASA Astrophysics Data System (ADS)

Schauble, E. A.; Eiler, J. M.

2004-12-01

The development of techniques for measuring small gas-phase molecules containing more than one rare stable isotope (e.g., 13C18O16O) at natural, ppm-level abundances1,2 has made it possible to track sources and sinks of atmospheric gases from a new perspective. Similar measurements of 13C-18O clumping in ancient samples could improve our understanding of ancient climates, if the abundances of `clumped' rare stable isotopes in materials that retain isotopic signatures over geologic time can be measured with sufficient precision. This theoretical study estimates the abundances of such 13C-18O `clumps' in carbonates and organic acids and discusses their potential applications. Accompanying abstracts by Eiler et al. and Ghosh et al. will present the analytical methods and some initial data for carbonate minerals to examine the applicability of our theoretical models. Equilibrium isotopic speciations in carbonate minerals and organic acids are calculated from the reduced partition function ratios of isotopically substituted crystals and molecules. Vibrational frequencies used as input for these calculations come from ab initio force fields, determined using density functional theory. Our calculations indicate that carbonate minerals, including calcite, dolomite, and aragonite, when equilibrated at earth-surface temperatures, will have a slight overabundance of CO32- groups containing both 13C and 18O (i.e., 13C18O16O22-) relative to what would be expected if carbon and oxygen isotopes were distributed randomly in the crystal lattice. Calcite and dolomite crystals are predicted to have 0.4‰ excesses of 13C18O16O22- at 298 K; in aragonite the excess will be about 0.05‰ larger. The excesses are smaller for crystals formed or equilibrated at higher temperatures, decreasing by 0.003\\permil/oC at room temperature and essentially disappearing at temperatures of 1000 K or higher. Similarly, there is an excess of both 13C18O16OH and 13C16O18OH groups in organic acids like

Coupling δ18O values of rodent tooth and mollusc shell carbonates: a new approach to reconstructing Pleistocene palaeotemperatures?

NASA Astrophysics Data System (ADS)

Peneycad, Elizabeth; Candy, Ian; Schreve, Danielle

2017-04-01

The ratio of stable oxygen isotopes in fossil rodent teeth (δ18Ort) can potentially provide valuable quantitative information about terrestrial palaeoclimate conditions. Grimes et al. (2004) suggested that δ18Ort could be usefully combined with the δ18O values of coeval biominerals, e.g. mollusc shells (δ18Oms), to estimate past summer temperatures during the Quaternary period. Nevertheless, until now, the application of this approach to Quaternary palaeoclimate reconstruction has remained unexplored. In addition, the success of this approach is dependent upon the establishment of a statistically robust relationship between δ18Ort and the δ18O of meteoric water (δ18Omw) in the modern environment. However, such a relationship is yet to be quantified in relation to rodent tooth carbonate. Here, we present the preliminary results of 2 studies investigating the validity of δ18Ort as a climate proxy. Firstly, isotope analyses were undertaken on modern vole (Microtus agrestis) teeth from 3 locations across the UK. The results of these analyses reveal a significant linear correlation between the mean δ18Ort and the mean δ18Omw. These findings therefore demonstrate that a quantifiable relationship exists between δ18Ort and δ18Omw, highlighting the potential of δ18Ort as an accurate recorder of local climatic conditions. This modern relationship was subsequently applied to the reconstruction of past δ18Omw values for two Pleistocene interglacial sites in the UK. The δ18Omw values were calculated using δ18Ort, and then combined with δ18Oms values derived from coeval fossil gastropod assemblages in order to estimate mean summer palaeotemperatures. The results of these calculations are in close agreement with multi-proxy temperature reconstructions derived from the same deposits. This suggests that coupling the δ18O values of rodent tooth and mollusc shell carbonates offers great potential as an approach to quantifying summer palaeotemperatures in Europe

D/H diffusion in serpentine

NASA Astrophysics Data System (ADS)

Pilorgé, Hélène; Reynard, Bruno; Remusat, Laurent; Le Floch, Sylvie; Montagnac, Gilles; Cardon, Hervé

2017-04-01

Interactions between aqueous fluids and ultrabasic rocks are essential processes in a broad range of contexts including hydrothermal alteration on the parent body of carbonaceous chondrites, at mid-oceanic ridge, and in subduction zones. Tracking these processes and understanding reaction kinetics require knowledge of the diffusion of water in rocks, and of isotope fractionation in major minerals forming under hydrous conditions, such as serpentines. We present a study of D/H inter-diffusion in antigorite, a common variety of serpentine. High-temperature (HT) experiments were performed in a belt apparatus at 540˚ C and 3.0 GPa on natural antigorite powders saturated with interstitial D2O. A low-temperature (LT) experiment was performed in diamond anvil cell at 350˚ C and 2.5 GPa on an antigorite single-crystal loaded with pure D2O. D/(D+H) ratios were mapped using Raman spectroscopy for the HT experiment and NanoSIMS for the LT experiment. As antigorite is a phyllosilicate, diffusion coefficients were obtained for crystallographic directions parallel and perpendicular to the antigorite layers (perpendicular and parallel to the c∗-axis, respectively). The equations of D/H inter-diffusion coefficients were determined to be DD/H (m2/s) = 5.04 x 10-5 x exp(-170(±53) (kJ/mol) / RT) and DD/H (m2/s) = 1.52 x 10-7 x exp(-157(±32) (kJ/mol) / RT) perpendicular and along the c∗-axis, respectively, and DD/H (m2/s) = 7.29 x 10-6 x exp(-166(±14) (kJ/mol) / RT) for the bulk diffusivity. These results are similar to those obtained on chlorite, in agreement with the similar crystallographic structures and atomic bonds in the two minerals. Assuming D/H inter-diffusion coefficients for antigorite are the same for all serpentine species, closure temperature and diffusion durations are applied to hydrothermal fields and in CI, CM and CR chondrites. Closure temperatures lie below 300˚ C for terrestrial hydrothermal alteration and depend on serpentine variety because they have

Down-conversion IM-DD RF photonic link utilizing MQW MZ modulator.

PubMed

Xu, Longtao; Jin, Shilei; Li, Yifei

2016-04-18

We present the first down-conversion intensity modulated-direct detection (IM-DD) RF photonic link that achieves frequency down-conversion using the nonlinear optical phase modulation inside a Mach-Zehnder (MZ) modulator. The nonlinear phase modulation is very sensitive and it can enable high RF-to-IF conversion efficiency. Furthermore, the link linearity is enhanced by canceling the nonlinear distortions from the nonlinear phase modulation and the MZ interferometer. Proof-of-concept measurement was performed. The down-conversion IM-DD link demonstrated 28dB improvement in distortion levels over that of a conventional IM-DD link using a LiNbO₃ MZ modulator.

Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO{sub 2} levels: The added value of the isotope ({delta}{sup 13}C and {delta}{sup 18}O CO{sub 2}; {delta}{sup 13}C and {delta}D CH{sub 4}) approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Widory, D., E-mail: d.widory@brgm.fr; Proust, E.; Bellenfant, G.

2012-09-15

Highlights: Black-Right-Pointing-Pointer Comparison of the isotope and mass balance approaches to evaluate the level of methane oxidation within a landfill. Black-Right-Pointing-Pointer The level of methane oxidation is not homogenous under the landfill cover and is strongly correlated to the methane flux. Black-Right-Pointing-Pointer Isotope tracking of the contribution of the methane oxidation to the CO{sub 2} concentrations in the ambient air. - Abstract: We are presenting here a multi-isotope approach ({delta}{sup 13}C and {delta}{sup 18}O of CO{sub 2}; {delta}{sup 13}C and {delta}D of CH{sub 4}) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through amore » landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO{sub 2} levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH{sub 4} oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH{sub 4} is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH{sub 4} oxidation by the methanotrophic bacteria. {delta}{sup 13}C of CO{sub 2} samples taken at different heights (from below the cover up to 8 m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.« less

Effects of the finite size of the ion (dd{mu}){sup +} on the energy levels of the molecules (dd{mu})e and (dd{mu})dee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harston, M.R.; Hara, S.; Kino, Y.

1997-10-01

The energy shift due to the finite size of the pseudonucleus (dd{mu}){sub 11}{sup +} in the molecules (dd{mu}){sub 11}e and (dd{mu}){sub 11}dee, the subscripts indicating the first excited state with total angular momentum of one unit, is of importance in the theoretical estimation of the rate of d-d fusion catalyzed by negative muons. The energy shift in the molecule (dd{mu}){sub 11}e is calculated using perturbation theory up to second order. The finite-size shift is found to be 1.46 meV. This is significantly larger than the value of 0.7 meV for this energy shift calculated by Bakalov [Muon Catalyzed Fusion {boldmore » 3}, 321 (1988)] by a method similar to the present method; recently found excellent agreement of theory with experimental results for the formation rate of the molecule (dd{mu}){sub 11}dee was based on Bakalov{close_quote}s value with some modifications. The results of a direct calculation of the finite-size energy shifts in (dd{mu}){sub 11}dee using first-order perturbation theory are presented. The contribution from the quadrupole component of the (dd{mu}){sub 11} charge distribution, which is not taken into account in the conventional scaling procedure based on the finite-size energy shifts of (dd{mu}){sub 11}e, is found to be of the order of 1 meV and to depend on the angular-momentum states of (dd{mu}){sub 11}dee. Sources of uncertainty in the current theoretical estimates are also discussed. {copyright} {ital 1997} {ital The American Physical Society}« less

The non-statistical dynamics of the 18O + 32O2 isotope exchange reaction at two energies

NASA Astrophysics Data System (ADS)

Van Wyngarden, Annalise L.; Mar, Kathleen A.; Quach, Jim; Nguyen, Anh P. Q.; Wiegel, Aaron A.; Lin, Shi-Ying; Lendvay, Gyorgy; Guo, Hua; Lin, Jim J.; Lee, Yuan T.; Boering, Kristie A.

2014-08-01

The dynamics of the 18O(3P) + 32O2 isotope exchange reaction were studied using crossed atomic and molecular beams at collision energies (Ecoll) of 5.7 and 7.3 kcal/mol, and experimental results were compared with quantum statistical (QS) and quasi-classical trajectory (QCT) calculations on the O3(X1A') potential energy surface (PES) of Babikov et al. [D. Babikov, B. K. Kendrick, R. B. Walker, R. T. Pack, P. Fleurat-Lesard, and R. Schinke, J. Chem. Phys. 118, 6298 (2003)]. In both QS and QCT calculations, agreement with experiment was markedly improved by performing calculations with the experimental distribution of collision energies instead of fixed at the average collision energy. At both collision energies, the scattering displayed a forward bias, with a smaller bias at the lower Ecoll. Comparisons with the QS calculations suggest that 34O2 is produced with a non-statistical rovibrational distribution that is hotter than predicted, and the discrepancy is larger at the lower Ecoll. If this underprediction of rovibrational excitation by the QS method is not due to PES errors and/or to non-adiabatic effects not included in the calculations, then this collision energy dependence is opposite to what might be expected based on collision complex lifetime arguments and opposite to that measured for the forward bias. While the QCT calculations captured the experimental product vibrational energy distribution better than the QS method, the QCT results underpredicted rotationally excited products, overpredicted forward-bias and predicted a trend in the strength of forward-bias with collision energy opposite to that measured, indicating that it does not completely capture the dynamic behavior measured in the experiment. Thus, these results further underscore the need for improvement in theoretical treatments of dynamics on the O3(X1A') PES and perhaps of the PES itself in order to better understand and predict non-statistical effects in this reaction and in the formation

Oxygen isotope fractionation in the CaCO3-DIC-H2O system

NASA Astrophysics Data System (ADS)

Devriendt, Laurent S.; Watkins, James M.; McGregor, Helen V.

2017-10-01

The oxygen isotope ratio (δ18O) of inorganic and biogenic carbonates is widely used to reconstruct past environments. However, the oxygen isotope exchange between CaCO3 and H2O rarely reaches equilibrium and kinetic isotope effects (KIE) commonly complicate paleoclimate reconstructions. We present a comprehensive model of kinetic and equilibrium oxygen isotope fractionation between CaCO3 and water (αc/w) that accounts for fractionation between both (a) CaCO3 and the CO32- pool (α c / CO32-) , and (b) CO32- and water (α CO32- / w) , as a function of temperature, pH, salinity, calcite saturation state (Ω), the residence time of the dissolved inorganic carbon (DIC) in solution, and the activity of the enzyme carbonic anhydrase. The model results suggest that: (1) The equilibrium αc/w is only approached in solutions with low Ω (i.e. close to 1) and low ionic strength such as in the cave system of Devils Hole, Nevada. (2) The sensitivity of αc/w to the solution pH and/or the mineral growth rate depends on the level of isotopic equilibration between the CO32- pool and water. When the CO32- pool approaches isotopic equilibrium with water, small negative pH and/or growth rate effects on αc/w of about 1-2‰ occur where these parameters covary with Ω. In contrast, isotopic disequilibrium between CO32- and water leads to strong (>2‰) positive or negative pH and growth rate effects on α CO32-/ w (and αc/w) due to the isotopic imprint of oxygen atoms derived from HCO3-, CO2, H2O and/or OH-. (3) The temperature sensitivity of αc/w originates from the negative effect of temperature on α CO32-/ w and is expected to deviate from the commonly accepted value (-0.22 ± 0.02‰/°C between 0 and 30 °C; Kim and O'Neil, 1997) when the CO32- pool is not in isotopic equilibrium with water. (4) The model suggests that the δ18O of planktic and benthic foraminifers reflects a quantitative precipitation of DIC in isotopic equilibrium with a high-pH calcifying fluid, leading

THz and Ft-Ir Study of 18-O Isotopologues of Sulfur Dioxide: 32S16O18O and 32S18O_2

NASA Astrophysics Data System (ADS)

Margulès, L.; Motiyenko, R. A.; Demaison, J.; Perrin, Agnes; Kwabia Tchana, F.; Manceron, Laurent

2016-06-01

Sulfur dioxide is a molecule that have a great interest in different domains: for atmospheric and planetology chemistry, it is also ubiquitous and abundant in interstellar medium. If the 16O species were extensively studied, this is not the case of the 18O isotopologues. The aim of this study is first to complete the rotational spectra of the ground state with these new measurements up to 1.5 THz, previous measurements are up to 1050 GHz for the 32S16O18O species, and 145 GHz concerning the 32S18O_2 species. The second part is making a global fit of the rotational and vibrational transitions for the excited vibrational states. For the v_2 band, we will complete the recent I.R. analysis. About the triad (v_1, 2v_2, v_3): 32S18O_2 species was studied, but not the 32S16O18O one. and 145 GHz concerning the 32S18O_2 species. The second part is making a global fit of the rotational and vibrational transitions for the excited vibrational states. For the v_2 band, we will complete the recent I.R. analysis. About the triad (v_1, 2v_2, v_3): 32S18O_2 species was studied, but not the 32S16O18O one. The FT-IR spectra were recorded on the AILES Beamline at Synchrotron SOLEIL using the Synchrotron light source, coupled to the Bruker IFS125HR Fourier transform spectrometer. The THz spectra were obtained from 150 to 1500 GHz using the Lille's solid state spectrometer. The analysis is in progress, the latest results will be presented. Support from the French Laboratoire d'Excellence CaPPA (Chemical and Physical Properties of the Atmosphere) through contract ANR-10-LABX-0005 of the Programme d'Investissements d'Avenir is acknowledged Belov, S. P.; et al., 1998, J. Mol. Spectrosc. 191, 17 Lindermayer, J.; et al., 1985, J. Mol. Spectrosc. 110, 357 Gueye, F.; et al. Mol. Phys. in press Ulenikov, O. N.; et al., 2015, JQSRT 166, 13 Brubach, J.; et al., 2010, AIP Conf. Proc. 1214, 81 Zakharenko, O.; et al., 2015, J. Mol. Spectrosc. 317, 41

Evaluating Snowmelt Runoff Processes Using Stable Isotopes in a Permafrost Hillslope

NASA Astrophysics Data System (ADS)

Carey, S. K.

2004-05-01

Conceptual understanding of runoff generation in permafrost regions have been derived primarily from hydrometric information, with isotope and hydrochemical data having only limited application in delineating sources and pathways of water. Furthermore, when stable isotope data are used to infer runoff processes, it often provides conflicting results from hydrometric measurements. In a small subarctic alpine catchment within the Wolf Creek Research Basin, Yukon, Canada, experiments were conducted during the melt period of 2002 and 2003 to trace the stable isotopic signature (d18O) of meltwater from a melting snowpack into permafrost soils and laterally to the stream to identify runoff processes and evaluate sources of error for traditional hydrograph separation studies in snowmelt-dominated permafrost basins. Isotopic variability in the snowpack was recorded at 0.1 m depth intervals during the melt period and compared with the meltwater isotopic signature at the snowpack base collected in lysimeters. Throughout the melt period in both years, there was an isotopic enrichment of meltwater as the season progressed. A downslope transect of wells and piezometers were used to evaluate the influence of infiltrating meltwater and thawing ground on the subsurface d18O signature. As melt began, meltwater infiltrated the frozen porous organic layer, leading to liquid water saturation in the unsaturated pore spaces. Water sampled during this initial melt stage show soil water d18O mirroring that of the meltwater signal. As the melt season progressed, frozen soil began to melt, mixing enriched pre-melt soil water with meltwater. This mixing increased the overall value of d18O obtained from the soil, which gradually increased as thaw progressed. At the end of snowmelt, soil water had a d18O value similar to values from the previous fall, suggesting that much of the initial snowmelt water had been flushed from the hillslope. Results from the hillslope scale are compared with two

Hydrogen and oxygen isotope exchange reactions between clay minerals and water

USGS Publications Warehouse

O'Neil, J.R.; Kharaka, Y.K.

1976-01-01

The extent of hydrogen and oxygen isotope exchange between clay minerals and water has been measured in the temperature range 100-350?? for bomb runs of up to almost 2 years. Hydrogen isotope exchange between water and the clays was demonstrable at 100??. Exchange rates were 3-5 times greater for montmorillonite than for kaolinite or illite and this is attributed to the presence of interlayer water in the montmorillonite structure. Negligible oxygen isotope exchange occurred at these low temperatures. The great disparity in D and O18 exchange rates observed in every experiment demonstrates that hydrogen isotope exchange occurred by a mechanism of proton exchange independent of the slower process of O18 exchange. At 350?? kaolinite reacted to form pyrophyllite and diaspore. This was accompanied by essentially complete D exchange but minor O18 exchange and implies that intact structural units in the pyrophyllite were inherited from the kaolinite precursor. ?? 1976.

Stable isotope systematics in mesozoic granites of Central and Northern California and Southwestern Oregon

USGS Publications Warehouse

Masi, U.; O'Neil, J.R.; Kistler, R.W.

1981-01-01

18O, D, and H2O+ contents were measured for whole-rock specimens of granitoid rocks from 131 localitics in California and southwestern Oregon. With 41 new determinations in the Klamath Mountains and Sierra Nevada, initial strontium isotope ratios are known for 104 of these samples. Large variations in ??18O (5.5 to 12.4), ??D (-130 to -31), water contents (0.14 to 2.23 weight percent) and initial strontium isotope ratios (0.7028 to 0.7095) suggest a variety of source materials and identify rocks modified by secondary processes. Regular patterns of variation in each isotopic ratio exist over large geographical regions, but correlations between the ratios are generally absent except in restricted areas. For example, the regular decrease in ??D values from west to east in the Sierra Nevada batholith is not correlative with a quite complex pattern of ??18O values, implying that different processes were responsible for the isotopic variations in these two elements. In marked contrast to a good correlation between (87Sr/86Sr)o and ??18O observed in the Peninsular Ranges batholith to the south, such correlations are lacking except in a few areas. ??D values, on the other hand, correlate well with rock types, chemistry, and (87Sr/86Sr)o except in the Coast Ranges where few of the isotopic signatures are primary. The uniformly low ??D values of samples from the Mojave Desert indicate that meteoric water contributed much of the hydrogen to the rocks in that area. Even so, the ??18O values and 18O fractionations between quartz and feldspar are normal in these same rocks. This reconnaissance study has identified regularities in geochemical parameters over enormous geographical regions. These patterns are not well understood but merit more detailed examination because they contain information critical to our understanding of the development of granitoid batholiths. ?? 1981 Springer-Verlag.

Stable isotope composition of cocoa beans of different geographical origin.

PubMed

Perini, Matteo; Bontempo, Luana; Ziller, Luca; Barbero, Alice; Caligiani, Augusta; Camin, Federica

2016-09-01

The isotopic profile (δ(13) C, δ(15) N, δ(18) O, δ(2) H, δ(34) S) was used to characterise a wide selection of cocoa beans from different renowned production areas (Africa, Asia, Central and South America). The factors most influencing the isotopic signatures of cocoa beans were climate and altitude for δ(13) C and the isotopic composition of precipitation water for δ(18) O and δ(2) H, whereas δ(15) N and δ(34) S were primarily affected by geology and fertilisation practises. Multi-isotopic analysis was shown to be sufficiently effective in determining the geographical origin of cocoa beans, and combining it with Canonical Discriminant Analysis led to more than 80% of samples being correctly reclassified. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Monte Carlo simulation of explosive detection system based on a Deuterium-Deuterium (D-D) neutron generator.

PubMed

Bergaoui, K; Reguigui, N; Gary, C K; Brown, C; Cremer, J T; Vainionpaa, J H; Piestrup, M A

2014-12-01

An explosive detection system based on a Deuterium-Deuterium (D-D) neutron generator has been simulated using the Monte Carlo N-Particle Transport Code (MCNP5). Nuclear-based explosive detection methods can detect explosives by identifying their elemental components, especially nitrogen. Thermal neutron capture reactions have been used for detecting prompt gamma emission (10.82MeV) following radiative neutron capture by (14)N nuclei. The explosive detection system was built based on a fully high-voltage-shielded, axial D-D neutron generator with a radio frequency (RF) driven ion source and nominal yield of about 10(10) fast neutrons per second (E=2.5MeV). Polyethylene and paraffin were used as moderators with borated polyethylene and lead as neutron and gamma ray shielding, respectively. The shape and the thickness of the moderators and shields are optimized to produce the highest thermal neutron flux at the position of the explosive and the minimum total dose at the outer surfaces of the explosive detection system walls. In addition, simulation of the response functions of NaI, BGO, and LaBr3-based γ-ray detectors to different explosives is described. Copyright © 2014 Elsevier Ltd. All rights reserved.

The fusion of advanced fuels to produce medical isotopes using inertial electrostatic confinement

NASA Astrophysics Data System (ADS)

Cipiti, Benjamin B.

Experiments are described that used an Inertial Electrostatic Confinement (IEC) fusion device to create radioisotopes for medical diagnostics. The IEC concept utilizes spherically concentric electrodes to accelerate fusion ions to high energies, allowing the use of the D-D and advanced D-3He fusion reactions. The D-3He reaction produces a high-energy 14.7 MeV proton, and this proton is energetic enough to be used to create radioisotopes. This dissertation focuses first on where specifically the fusion reactions are occurring in the IEC device. It was found that at 2 mtorr operating pressures, 70% of the D-D reactions occur throughout the entire volume of the vacuum chamber. About 22% of the reactions occur in a small core in the center of the device, and the other 8% are due to embedded D-D reactions in the cathode of the device. On the other hand, for D-3He, 95% of the reactions are due to embedded reactions, and the other 5% come from a small core in the center of the device. Beam-target D-3He fusion was used to create medical isotopes in two different systems. The designs focused on creating short-lived species capable of use in Positron Emission Tomography. The first isotope created was 94mTc, a positron emitter with a 52-minute half-life. Approximately 1.5 nCi of 94mTc were created using the 94Mo(p,n) 94mTc reaction. The second isotope created was 13N, a positron emitter with a ten-minute half-life. Approximately 1.0 nCi of 13N was created using the 16O(p,alpha)13N reaction. The final part of the research investigated the effects of deuterium and helium implantation in the tungsten-rhenium cathode of the IEC device. The effect of the implantation on the surface morphology of pure tungsten was also determined using scanning electron microscopy. Deuterium did not appear to affect the surface of tungsten after high temperature (>800 C) implantation. Helium created a porous surface structure at the same temperatures starting at about 4 x 1016 ions/cm2. The pores

Stable isotope paleoaltimetry and the evolution of landscapes and life

NASA Astrophysics Data System (ADS)

Mulch, Andreas

2016-01-01

Reconstructing topography of our planet not only advances our knowledge of the geodynamic processes that shape the Earth's surface; equally important it adds a key element towards understanding long-term continental moisture transport, atmospheric circulation and the distribution of biomes and biodiversity. Stable isotope paleoaltimetry exploits systematic decreases in the oxygen (δ18O) or hydrogen (δD) isotopic composition of precipitation along a mountain front when the interaction of topography and advected moist air masses induces orographic precipitation. These changes in δ18O or δD can be recovered from the geologic record and recent geochemical and modeling advances allow a broad range of proxy materials to be evaluated. Over the last 10 yr stable isotope paleoaltimetry has witnessed rapidly expanding research activities and has produced a broad array of fascinating tectonic and geomorphologic studies many of which have concentrated on determining the elevation history of continental plateau regions. These single-site studies have greatly expanded what used to be very sparse global paleoaltimetric data. The challenge now lies in disentangling the surface uplift component from the impact of climate change on δ18O and δD in precipitation. The robustness of stable isotope paleoaltimetry can be enhanced when high-elevation δ18O or δD data are referenced against low-elevation sites that track climate-modulated sea level δ18O or δD of precipitation through time (' δ- δ approach'). Analysis of central Andean paleosols documents that differences in δ18O of soil carbonate between the Subandean foreland and the Bolivian Altiplano are small between 11 and 7 Ma but rise rapidly to ca. 2.9‰ after 7 Ma, corroborating the magnitude of late Miocene change in δ18O on the Altiplano. Future advances in stable isotope paleoaltimetry will greatly benefit from addressing four key challenges: (1) Identifying topographically-induced changes in atmospheric

[Hydrogen and oxygen isotopes of lake water and geothermal spring water in arid area of south Tibet].

PubMed

Xiao, Ke; Shen, Li-Cheng; Wang, Peng

2014-08-01

The condition of water cycles in Tibet Plateau is a complex process, and the hydrogen and oxygen isotopes contain important information of this process. Based on the analysis of isotopic composition of freshwater lake, saltwater lake and geothermal water in the southern Tibetan Plateau, this study investigated water cycling, composition and variation of hydrogen and oxygen isotopes and the influencing factors in the study area. The study found that the mean values of delta18O and deltaD in Daggyaima lake water (-17.0 per thousand for delta18O and -138. 6 per thousand for deltaD), Langcuo lake water (-6.4 per thousand for delta18O and -87.4 per thousand for deltaD) and Dagejia geothermal water (-19.2 per thousand for delta18 and -158.2 per thousand for deltaD) all showed negative delta18O and deltaD values in Tibetan Plateau by the influence of altitude effects. Lake water and geothermal water were influenced by evaporation effects in inland arid area, and the slope of evaporation line was less than 8. Deuterium excess parameters of lake water and geothermal water were all negative. The temperature of geothermal reservoirs in Dagejia geothermal field was high,and oxygen shift existed in the relationship of hydrogen and oxygen isotopes.

The evolution of 13C and 18O isotope composition of DIC in a calcite depositing film of water with isotope exchange between the DIC and a CO2 containing atmosphere, and simultaneous evaporation of the water. Implication to climate proxies from stalagmites: A theoretical model

NASA Astrophysics Data System (ADS)

Dreybrodt, Wolfgang; Romanov, Douchko

2016-12-01

The most widely applied climate proxies in speleothems are the isotope compositions of carbon and oxygen expressed by δ13C and δ18O values. However, mechanisms, which are not related to climate changes, overlay the climate signal. One is the temporal increase of both, δ13C and δ18O values by kinetic processes during precipitation of calcite. Isotope exchange between DIC in the water and the CO2 in the surrounding cave atmosphere can also change isotope composition. Here we present a theoretical model of the temporal isotope evolution of DIC in a thin water layer during precipitation of calcite and simultaneous isotope exchange with the cave atmosphere, and simultaneous evaporation of water. The exchange of oxygen isotopes in the DIC with those in the water is also considered.

Isotopic Ordering in Atmospheric O2 as a Tracer of Ozone Photochemistry and the Tropical Atmosphere

NASA Technical Reports Server (NTRS)

Yeung, Laurence Y.; Murray, Lee T.; Ash, Jeanine L.; Young, Edward D.; Boering, Kristie A.; Atlas, Elliot L.; Schauffler, Sue M.; Lueb, Richard A.; Langenfelds, Ray L.; Krummel, Paul B.;

High-precision determination of 18O/16O ratios of silver phosphate by EA-pyrolysis-IRMS continuous flow technique.

PubMed

Lécuyer, Christophe; Fourel, François; Martineau, François; Amiot, Romain; Bernard, Aurélien; Daux, Valérie; Escarguel, Gilles; Morrison, John

2007-01-01

A high-precision, and rapid on-line method for oxygen isotope analysis of silver phosphate is presented. The technique uses high-temperature elemental analyzer (EA)-pyrolysis interfaced in continuous flow (CF) mode to an isotopic ratio mass spectrometer (IRMS). Calibration curves were generated by synthesizing silver phosphate with a 13 per thousand spread in delta(18)O values. Calibration materials were obtained by reacting dissolved potassium dihydrogen phosphate (KH(2)PO(4)) with water samples of various oxygen isotope compositions at 373 K. Validity of the method was tested by comparing the on-line results with those obtained by classical off-line sample preparation and dual inlet isotope measurement. In addition, silver phosphate precipitates were prepared from a collection of biogenic apatites with known delta(18)O values ranging from 12.8 to 29.9 per thousand (V-SMOW). Reproducibility of +/- 0.2 per thousand was obtained by the EA-Py-CF-IRMS method for sample sizes in the range 400-500 microg. Both natural and synthetic samples are remarkably well correlated with conventional (18)O/(16)O determinations. Silver phosphate is a very stable material and easy to degas and, thus, could be considered as a good candidate to become a reference material for the determination of (18)O/(16)O ratios of phosphate by high-temperature pyrolysis. Copyright 2006 John Wiley & Sons, Ltd.

Intra-event isotope and raindrop size data of tropical rain reveal effects concealed by event averaged data

NASA Astrophysics Data System (ADS)

Managave, S. R.; Jani, R. A.; Narayana Rao, T.; Sunilkumar, K.; Satheeshkumar, S.; Ramesh, R.

2016-08-01

Evaporation of rain is known to contribute water vapor, a potent greenhouse gas, to the atmosphere. Stable oxygen and hydrogen isotopic compositions (δ18O and, δD, respectively) of precipitation, usually measured/presented as values integrated over rain events or monthly mean values, are important tools for detecting evaporation effects. The slope ~8 of the linear relationship between such time-averaged values of δD and δ18O (called the meteoric water line) is widely accepted as a proof of condensation under isotopic equilibrium and absence of evaporation of rain during atmospheric fall. Here, through a simultaneous investigation of the isotopic and drop size distributions of seventeen rain events sampled on an intra-event scale at Gadanki (13.5°N, 79.2°E), southern India, we demonstrate that the evaporation effects, not evident in the time-averaged data, are significantly manifested in the sub-samples of individual rain events. We detect this through (1) slopes significantly less than 8 for the δD-δ18O relation on intra-event scale and (2) significant positive correlations between deuterium excess ( d-excess = δD - 8*δ18O; lower values in rain indicate evaporation) and the mass-weighted mean diameter of the raindrops ( D m ). An estimated ~44 % of rain is influenced by evaporation. This study also reveals a signature of isotopic equilibration of rain with the cloud base vapor, the processes important for modeling isotopic composition of precipitation. d-excess values of rain are modified by the post-condensation processes and the present approach offers a way to identify the d-excess values least affected by such processes. Isotope-enabled global circulation models could be improved by incorporating intra-event isotopic data and raindrop size dependent isotopic effects.

Continental water recycling and H2(18)-O concentrations

NASA Technical Reports Server (NTRS)

Koster, Randal D.; De Valpine, D. Perry; Jouzel, Jean

1993-01-01

Using a General Circulation Model (GCM) fitted with tracer diagnostics, we examine how continental moisture recycling affects the stable water isotope content of precipitation, focusing on its contribution to the 'noise' in the well-established relationship between temperature and delta O-18. On a global basis, for temperatures between -30 and 15 C, continental recycling explains more than a third of the variability in annual delta O-18 that is not explained by temperature. Recycling appears almost as important as temperature in defining delta O-18 distributions during northern hemisphere summer.

A Zonal Mode in the Indian Ocean over the Past Millennium? Isotopic Evidence from Continental Climate Archives and Model Simulations

NASA Astrophysics Data System (ADS)

Konecky, B.; Russell, J. M.; Vuille, M.; Rodysill, J. R.; Cohen, L. R.; Chuman, A. F.; Huang, Y.

2011-12-01

We present new evidence for multi-decadal to millennial scale hydro-climatic change in the continental Indian Ocean region over the past two millennia. We assess regional hydrological variability using new records of the δD of terrestrial plant waxes from the sediments of several lakes in tropical East Africa and Indonesia. We compare these new data to previous δ18O and δD records from the region and interpret these results in light of an isotope-enabled climate model simulation of the past 130 years. Long-term trends in our data support a southward migration of the Intertropical Convergence Zone (ITCZ)'s mean position over the past millennium, bringing progressively wetter conditions and D-depleted waxes to our southernmost site (~8°S) starting around 950 C.E. while maintaining overall wet conditions at our northernmost site (~0°N) until the end of the 19th century. Superimposed on this long-term trend are a series of pronounced, multi-decadal to centennial scale isotopic excursions that are of the same timing but in opposite directions on the two sides of the Indian Ocean. These zonally asymmetric isotopic fluctuations become progressively more pronounced beginning around 1400 C.E., with the onset of Little Ice Age cool conditions recorded in sea surface temperature reconstructions from the Northern Hemisphere and the Indo-Pacific Warm Pool (IPWP). Previous work in the IPWP region suggests cooler SST, reduced boreal summer Asian monsoon intensity, and less ENSO-like activity during the Little Ice Age [Oppo et al., 2009, Nature 460:1113, and references therein], although recent paleolimnological reconstructions from Java indicate punctuated droughts during this time [Rodysill et al., 2010, Eos Trans. AGU, 91(52), Fall Meet. Suppl., Abstract PP51B-04]. Our records suggest that multi-decadal to centennial precipitation variability was in fact enhanced during this time period in parts of equatorial East Africa and western Indonesia. The direction of isotopic

The 17D-204 and 17DD yellow fever vaccines: an overview of major similarities and subtle differences.

PubMed

Ferreira, Clarissa de Castro; Campi-Azevedo, Ana Carolina; Peruhype-Magalhāes, Vanessa; Costa-Pereira, Christiane; Albuquerque, Cleandro Pires de; Muniz, Luciana Feitosa; Yokoy de Souza, Talita; Oliveira, Ana Cristina Vanderley; Martins-Filho, Olindo Assis; da Mota, Licia Maria Henrique

2018-01-01

The yellow fever vaccine is a live attenuated virus vaccine that is considered one of the most efficient vaccines produced to date. The original 17D strain generated the substrains 17D-204 and 17DD, which are used for the current production of vaccines against yellow fever. The 17D-204 and 17DD substrains present subtle differences in their nucleotide compositions, which can potentially lead to variations in immunogenicity and reactogenicity. We will address the main changes in the immune responses induced by the 17D-204 and 17DD yellow fever vaccines and report similarities and differences between these vaccines in cellular and humoral immunity . This is a relevant issue in view of the re-emergence of yellow fever in Uganda in 2016 and in Brazil in the beginning of 2017. Areas covered: This article will be divided into 8 sections that will analyze the innate immune response, adaptive immune response, humoral response, production of cytokines, immunity in children, immunity in the elderly, gene expression and adverse reactions. Expert commentary: The 17D-204 and 17DD yellow fever vaccines present similar immunogenicity, with strong activation of the cellular and humoral immune responses. Additionally, both vaccines have similar adverse effects, which are mostly mild and thus are considered safe.

First results from a novel methodological approach for δ18O analyses of sugars using GC-Py-IRMS

NASA Astrophysics Data System (ADS)

Zech, Michael; Saurer, Matthias; Tuthorn, Mario; Rinne, Katja; Werner, Roland; Juchelka, Dieter; Siegwolf, Rolf; Glaser, Bruno

2013-04-01

statistically not significant) for δ18O of sucrose (n = 7) and bulk δ18O (R = 0.62), δ13C of sucrose (R = 0.55) and maximum day temperature (R = 0.58) and negative correlation for δ18O of sucrose and cloudiness (R = -0.80). This highlights the great potential of compound-specific δ18O analyses of sucrose for (paleo-) plimate studies. Zech, M., Glaser, B., 2009. Compound-specific d18O analyses of neutral sugars in soils using GC-Py-IRMS: problems, possible solutions and a first application. RCM 23, 3522-3532. Zech, M., Tuthorn, M., Glaser, B., Amelung, W., Huwe, B., Zech, W., Zöller, L., Löffler, J., 2013. Natural abundance of 18O of sugar biomarkers in topsoils along a climate transect over the Central Scandinavian Mountains, Norway. JPNSS, in press. Zech, M., Werner, R., Juchelka, D., Kalbitz, K., Buggle, B., Glaser, B., 2012. Absence of oxygen isotope fractionation/exchange of (hemi-) cellulose derived sugars during litter decomposition. Org Geochem 42, 1470-1475.

Understanding N2O sources and sinks with laser based isotopic analysis

NASA Astrophysics Data System (ADS)

Mohn, Joachim; Harris, Eliza; Tuzson, Béla; Emmenegger, Lukas

2015-04-01

Nitrous oxide (N2O) is a potent greenhouse gas and the strongest ozone-destroying substance. The main emissions of N2O are linked to different microbial processes, therefore the sources are disperse and highly variable, complicating the development of effective mitigation strategies. Isotopic measurements have great potential to unravel spatial and temporal variations in sources, sinks and chemistry of N2O. Recent developments in quantum cascade laser spectroscopy (QCLAS) [1] allow both the intermolecular distribution of 15N substitutions ('site preference'; 15N14N16O versus 14N15N16O) and the oxygen isotopic composition (d18O) of N2O to be measured in real-time and at high precision of <0.2 ‰ [2]. Additionally, N2O isotopic analysis by QCLAS has demonstrated excellent compatibility to the standard technique isotope-ratio mass-spectrometry [3]. In a number of laboratory and pilot plant studies we investigated the isotopic signature of distinct microbial and abiotic N2O production and consumption pathways in soil and aqueous solution [e.g. 4]. Specific pathways were favoured by selection of the nitrogen substrates and process conditions and their isotopic signatures identified by real-time laser spectroscopic analysis. Results from our laboratory studies are in accordance with pure culture experiments and can therefore be applied to other ecosystems. Recently, high precision isotopic analysis at ambient N2O is also feasible by combining laser spectroscopy with automated preconcentration [5]. The field deployment was demonstrated by real-time monitoring isotopic composition of N2O emissions from an intensively managed grassland in central Switzerland for three months. The responses of the N2O isotopic signatures were analysed with respect to management events and weather influences [2]. In a follow-up project we intend to combine real-time N2O isotopic analysis at a tall tower in central Switzerland with atmospheric transport simulations and a biogeochemical model

Evidence for a functional link between Dd-STATa and Dd-PIAS, a Dictyostelium PIAS homologue.

PubMed

Kawata, Takefumi; Hirano, Tatsunori; Ogasawara, Shun; Aoshima, Ryota; Yachi, Ayako

2011-09-01

Several mammalian protein families inhibit the activity of signal transducer and activator of transcription (STAT) proteins. The protein inhibitor of activated STAT (PIAS) was initially identified through its ability to interact with human STAT proteins. We isolated a gene (pisA) encoding a Dictyostelium orthologue of PIAS, Dd-PIAS, which possesses almost all the representative motifs and domains of mammalian PIAS proteins. A Dd-PIAS null mutant strain displays a normal terminal morphology but with accelerated development once cells are aggregated. In contrast, Dd-PIAS overexpressor strains demonstrate delayed aggregation, almost no slug phototaxis, impaired slug motility, and a prolonged slug migration period. This strain is a near phenocopy of the Dd-STATa null mutant, although it eventually forms a fruiting body, albeit inefficiently. The expression of several Dd-STATa-activated genes is upregulated in the Dd-PIAS null mutant and there is ectopic expression of pstAB makers. The concentration of a PIAS-green fluorescent protein (GFP) fusion protein, expressed under the PIAS promoter, is greatest in the pstO cells and gradually decreases with proximity to the tip of the slug and culminant: a pattern diametrically opposite to that of Dd-STATa. Our results suggest a functional interrelationship between Dd-PIAS and Dd-STATa that influences gene expression and development. © 2011 The Authors. Development, Growth & Differentiation © 2011 Japanese Society of Developmental Biologists.

Transformational dynamics of BZO and BHO nanorods imposed by Y2O3 nanoparticles for improved isotropic pinning in YBa2Cu3O7 -δ thin films

NASA Astrophysics Data System (ADS)

Gautam, Bibek; Sebastian, Mary Ann; Chen, Shihong; Shi, Jack; Haugan, Timothy; Xing, Zhongwen; Zhang, Wenrui; Huang, Jijie; Wang, Haiyan; Osofsky, Mike; Prestigiacomo, Joseph; Wu, Judy Z.

2017-07-01

An elastic strain model was applied to evaluate the rigidity of the c-axis aligned one-dimensional artificial pinning centers (1D-APCs) in YBa2Cu3O7-δ matrix films. Higher rigidity was predicted for BaZrO3 1D-APCs than that of the BaHfO3 1D-APCs. This suggests a secondary APC doping of Y2O3 in the 1D-APC/YBa2Cu3O7-δ nanocomposite films would generate a stronger perturbation to the c-axis alignment of the BaHfO3 1D-APCs and therefore a more isotropic magnetic vortex pinning landscape. In order to experimentally confirm this, we have made a comparative study of the critical current density Jc (H, θ, T) of 2 vol.% BaZrO3 + 3 vol.%Y2O3 and 2 vol.%BaHfO3 + 3 vol.%Y2O3 double-doped (DD) YBa2Cu3O7-δ films deposited at their optimal growth conditions. A much enhanced isotropic pinning was observed in the BaHfO3 DD samples. For example, at 65 K and 9.0 T, the variation of the Jc across the entire θ range from θ=0 (H//c) to θ=90 degree (H//ab) is less than 18% for BaHfO3 DD films, in contrast to about 100% for the BaZrO3 DD counterpart. In addition, lower α values from the Jc(H) ˜ H-α fitting were observed in the BaHfO3 DD films in a large θ range away from the H//c-axis. Since the two samples have comparable Jc values at H//c-axis, the improved isotropic pinning in BaHfO3 DD films confirms the theoretically predicted higher tunability of the BaHfO3 1D-APCs in APC/YBa2Cu3O7-δ nanocomposite films.

The impact of storage time and temperature in polyethylen bottles on the multi isotope composition of water

NASA Astrophysics Data System (ADS)

Schmiedinger, Iris; Böttcher, Michael E.

2017-04-01

Storage of water samples in polyethylen bottles for later hydrogeochemical analysis is a common practice in laboratories world-wide. It is, however, known for a long time to geochemists that aqueous solutions lose water as a function of time due to the diffusion of water molecules (similar to CO2 or H2S) through the polymer membrane, a process that is suspected to increase with rising temperature. First observations on the impact of storage on O-18 and H-2 contents in water were reported by Spangenberg & Vennemann (RCIM 2008) and Spangenberg (RCIM 2012), but no study considered systematically the effect of temperature, sofar. In the present study we carried out long-term experiments to investigate the impact of storage of fresh water in LDPE bottles for up to 18 months at 4 different temperatures (4°, 10°, 23°, and 60°C). The loss of water was followed gravimetrically, and the stable isotope composition of the water sample was analyzed with a Picarro CRDS 2140-i system. Whereas, at the low temperatures of 4° and 10°C, no measurable loss of water was observed during a storage time up to 1.5 years, a substantial loss of water was observed at 23°C and 60°C. This change was associated with, for instance at 60°C: an increase in d18O (up to 10 ‰), d2H (up to 28 ‰), d17O (up to 5 ‰). The deuterium excess was shifted towards lower values by up to 55 ‰. The magnitude of the isotope effect mostly depends on the extend of evaporation from the bottles, allowing for an estimate of the fractionation factor by considering a closed Rayleigh-type system.

Soft Fusion Energy Path: Isotope Production in Energy Subcritical/Economy Hypercritical D +D Colliding-Beam Mini Fusion Reactor `Exyder'

NASA Astrophysics Data System (ADS)

Hester, Tim; Maglich, Bogdan; Calsec Collaboration

2015-03-01

Bethe1 and Sakharov2 argued for soft fusion energy path via isotope production, substantiated by Manheimer3. - Copious T and 3He production4 , 5 from D(d, p) T and D(d, n) 3He reactions in 725 KeV D +D colliding beams was measured in weak-focusing Self-Collider6 , 7 radius 0.15 m, in B = 3.12 T, non-linearly stabilized by electron cloud oscillations8 to confinement time = 24 s. Simulations6 predict that by switching to strong focusing9, 10 deuterons 0.75 MeV each, generate 1 3He +1T +1p + 1n at total input energy cost 10.72 MeV. Economic value of T and 3He is 65 and 120 MeV/atom, respectively. We obtain economic gain 205MeV/10.72 MeV ~ 2,000% i.e. 3He production funds cost of T. If first wall is made of Thorium n's will breed 233U releasing 200 MeV/fission, at neutron cost 5.36 MeV versus 160 MeV in beam on target, resulting in no cost 3He production, valued 75K/g. 1. Physics Today, May 1979, p.44; 2. Memoirs, Vintage Books, (1992); 3. Phys. Today, May 2012 p. 12; 4. Phys. Rev. Lett. 54, 796 (1985); 5. Bull. APS, 57, No. 3 (2012); 6. Part. Acc.1, (1970); 7. ANEUTRONIC FUSION NIM A 271 1-167 (1988); 8. Phys. Rev. Lett. 70, 1818 (1993); 9. Part. Acc. 34, 13 (1990).

Covariance of oxygen and hydrogen isotopic composition in plant water: Species effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, L.W.; DeNiro, M.J.

1989-12-01

Leaf water becomes enriched in the heavy isotopes of oxygen and hydrogen during evapotranspiration. The magnitude of the enrichment has been shown to be influenced by temperature and humidity, but the effects of species-specific factors on leaf water enrichment of D and {sup 18}O have not been studied for different plants growing together. To learn whether leaf water enrichment patterns and processes for D and {sup 18}O are different for individual species growing under the same environmental conditions the authors tested the proposal that leaf waters in plants with crassulacean acid metabolism (CAM) show high sloped (m in the leafmore » water equation {delta}D = m {delta}{sup 18}O + b) than in C{sub 3} plants. They determined the relationships between the stable hydrogen ({delta}D) and oxygen ({delta}{sup 18}O) isotope ratios of leaf waters collected during the diurnal cycle of evapotranspiration for Yucca schidigera, Ephedra aspera, Agave deserti, Prunus ilicifolia, Yucca whipplei, Heteromeles arbutifolia, Dyckia fosteriana, Simmondsia chinensis, and Encelia farinosa growing at two sites in southern California. The findings indicate that m in the aforementioned equation is related to the overall residence time for water in the leaf and proportions of water subjected to repeated evapotranspiration enrichments of heavy isotopes.« less

Detecting influences on California drought intervals using isotopes in tree-ring cellulose

NASA Astrophysics Data System (ADS)

Kanner, L. C.; Buenning, N. H.; Stott, L. D.; Stahle, D. W.

2012-12-01

Multi-decadal drought events have characterized climate variability in California over the last century. However, the causes of interannual precipitation variability and the origins of multi-decadal drought in California remain unclear. We utilize the oxygen isotopic composition (δ18O) of tree-ring cellulose in combination with previously developed ring-width measurements to trace the delivery of moisture to the region and investigate ocean-atmosphere patterns that might generate prolonged drought. Of the 36 Quercus douglasii (blue oak) sites in the California central valley, we have focused our work at two locations - one north of Los Angeles (34.74°N, 120°W, 1036 masl) and the other east of San Francisco (37.88°N 121.97°W, 182 masl). Using cores from at least five different trees at each location, tree-ring cellulose δ18O was measured for each year of growth from 1954 to 2004. The δ18O values of tree-ring cellulose range from 29‰ to 34‰ (VSMOW) at both sites and exhibit shared interannual variance (r = 0.43, p < 0.01). To trace changes in moisture delivery, we apply a biophysical model of cellulose δ18O and derive a proxy for rainfall δ18O. A reasonable approximation of rainfall δ18O is soil water δ18O, which, based on the biophysical model, can be estimated using cellulose δ18O, relative humidity, and temperature. High-resolution climate data from PRISM are combined with our cellulose measurements to compute soil water δ18O (and thus rainfall δ18O). Calculated rainfall δ18O is well correlated between the two locations (r = 0.55, p < 0.001) and the variance in δ18O at each site is 6‰. In terms of regional climate changes, our rainfall δ18O proxy exhibits a positive correlation with local precipitation amount, inferred from tree-ring width (r = 0.66, p < 0.001). This positive correlation suggests rainfall amount cannot be the main influence on the isotopic composition because changes in δ18O solely due to amount typically occur in the

Thermal neutron capture cross sections for 16,171,18O and 2H

NASA Astrophysics Data System (ADS)

Firestone, R. B.; Revay, Zs.

2016-04-01

Thermal neutron capture γ -ray spectra for 16,17,18O and 2H have been measured with guided cold neutron beams from the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) reactor and the Budapest Research Reactor (BRR) on natural and O,1817 enriched D2O targets. Complete neutron capture γ -ray decay schemes for the 16,17,18O(n ,γ ) reactions were measured. Absolute transition probabilities were determined for each reaction by a least-squares fit of the γ -ray intensities to the decay schemes after accounting for the contribution from internal conversion. The transition probability for the 870.76-keV γ ray from 16O(n ,γ ) was measured as Pγ(871 )=96.6 ±0.5 % and the thermal neutron cross section for this γ ray was determined as 0.164 ±0.003 mb by internal standardization with multiple targets containing oxygen and stoichiometric quantities of hydrogen, nitrogen, and carbon whose γ -ray cross sections were previously standardized. The γ -ray cross sections for the O,1817(n ,γ ) and 2H(n ,γ ) reactions were then determined relative to the 870.76-keV γ -ray cross section after accounting for the isotopic abundances in the targets. We determined the following total radiative thermal neutron cross sections for each isotope from the γ -ray cross sections and transition probabilities; σ0(16O )=0.170 ±0.003 mb; σ0(17O )=0.67 ±0.07 mb; σ0(18O )=0.141 ±0.006 mb; and σ0(2H )=0.489 ±0.006 mb.

Simultaneous analysis of 17O/16O, 18O/16O and 2H/1H of gypsum hydration water by cavity ring‐down laser spectroscopy

PubMed Central

Mather, Ian; Rolfe, James; Evans, Nicholas P.; Herwartz, Daniel; Staubwasser, Michael; Hodell, David A.

2015-01-01

Rationale The recent development of cavity ring‐down laser spectroscopy (CRDS) instruments capable of measuring 17O‐excess in water has created new opportunities for studying the hydrologic cycle. Here we apply this new method to studying the triple oxygen (17O/16O, 18O/16O) and hydrogen (2H/1H) isotope ratios of gypsum hydration water (GHW), which can provide information about the conditions under which the mineral formed and subsequent post‐depositional interaction with other fluids. Methods We developed a semi‐automated procedure for extracting GHW by slowly heating the sample to 400°C in vacuo and cryogenically trapping the evolved water. The isotopic composition (δ17O, δ18O and δ2H values) of the GHW is subsequently measured by CRDS. The extraction apparatus allows the dehydration of five samples and one standard simultaneously, thereby increasing the long‐term precision and sample throughput compared with previous methods. The apparatus is also useful for distilling brines prior to isotopic analysis. A direct comparison is made between results of 17O‐excess in GHW obtained by CRDS and fluorination followed by isotope ratio mass spectrometry (IRMS) of O2. Results The long‐term analytical precision of our method of extraction and isotopic analysis of GHW by CRDS is ±0.07‰ for δ17O values, ±0.13‰ for δ18O values and ±0.49‰ for δ2H values (all ±1SD), and ±1.1‰ and ±8 per meg for the deuterium‐excess and 17O‐excess, respectively. Accurate measurement of the 17O‐excess values of GHW, of both synthetic and natural samples, requires the use of a micro‐combustion module (MCM). This accessory removes contaminants (VOCs, H2S, etc.) from the water vapour stream that interfere with the wavelengths used for spectroscopic measurement of water isotopologues. CRDS/MCM and IRMS methods yield similar isotopic results for the analysis of both synthetic and natural gypsum samples within analytical error of the two methods. Conclusions We

New tool for getting data on the field for paleoclimate and paleoceanography data based on isotope 13C and 18O measurements

NASA Astrophysics Data System (ADS)

Mandic, M.; Stöbener, N.; Smajgl, D.

2017-12-01

For many decades different instrumental methods involving generations of the isotope ratio mass spectrometers with different periphery units for sample preparation, have provided scientifically required high precision, and high throughput of samples for varies application - from geological and hydrological to food and forensic. With this work we introduce automated measurement of δ13C and δ18O from solid carbonate samples, DIC and δ18O of water. We have demonstrated usage of a Thermo Scientific™ Delta Ray™ IRIS with URI Connect on certified reference materials and confirmed the high achievable accuracy and a precision better then <0.1‰ for both δ13C and δ18O, in the laboratory or the field with same precision and throughput of samples. With equilibration method for determination of δ18O in water samples, which we present in this work, achieved repeatability and accuracy are 0.12‰ and 0.68‰ respectively, which fulfill requirements of regulatory methods. The preparation of the samples for carbonate and DIC analysis on the Delta Ray IRIS with URI Connect is similar to the previously mentioned Gas Bench II methods. Samples are put into vials and phosphoric acid is added. The resulting sample-acid chemical reaction releases CO2 gas, which is then introduced into the Delta Ray IRIS via the Variable Volume. Three international standards of carbonate materials (NBS-18, NBS-19 and IAEA-CO-1) were analyzed. NBS-18 and NBS-19 were used as standards for calibration, and IAEA-CO-1 was treated as unknown. For water sample analysis equilibration method with 1% of CO2 in dry air was used. Test measurements and conformation of precision and accuracy of method determination δ18O in water samples were done with three lab standards, namely ANST, OCEAN 2 and HBW. All laboratory standards were previously calibrated with international reference material VSMOW2 and SLAP2 to assure accuracy of the isotopic values. The Principle of Identical Treatment was applied in sample

Calibration of δ13C and δ18O measurements in CO2 using Off-axis Integrated Cavity Output Spectrometer (ICOS)

NASA Astrophysics Data System (ADS)

Joseph, Jobin; Külls, Christoph

2014-05-01

The δ13C and δ18O of CO2 has enormous potential as tracers to study and quantify the interaction between the water and carbon cycles. Isotope ratio mass spectrometry (IRMS) being the conventional method for stable isotopic measurements, has many limitations making it impossible for deploying them in remote areas for online or in-situ sampling. New laser based absorption spectroscopy approaches like Cavity Ring Down Spectroscopy (CRDS) and Integrated Cavity Output Spectroscopy (ICOS) have been developed for online measurements of stable isotopes at an expense of considerably less power requirement but with precision comparable to IRMS. In this research project, we introduce a new calibration system for an Off- Axis ICOS (Los Gatos Research CCIA-36d) for a wide range of varying concentrations of CO2 (800ppm - 25,000ppm), a typical CO2 flux range at the plant-soil continuum. The calibration compensates for the concentration dependency of δ13C and δ18O measurements, and was performed using various CO2 standards with known CO2 concentration and δC13 and δO18 values. A mathematical model was developed after the calibration procedure as a correction factor for the concentration dependency of δ13C and δ18O measurements. Temperature dependency of δ13C and δ18O measurements were investigated and no significant influence was found. Simultaneous calibration of δ13C and δ18O is achieved using this calibration system with an overall accuracy of (~ 0.75±0.24 ‰ for δ13C, ~ 0.81 ±0.26‰ for δ18O). This calibration procedure is found to be appropriate for making Off-Axis ICOS suitable for measuring CO2 concentration and δ13C and δ18O measurements at atmosphere-plant-soil continuum.

A reconnaissance study of oxygen, hydrogen and strontium isotopes in geochemically diverse lakes, Western Nebraska, USA

USGS Publications Warehouse

Gosselin, D.C.; Nabelek, P.E.; Peterman, Z.E.; Sibray, S.

1997-01-01

Reconnaissance ??18O,, ??D, and ??87Sr data for fifteen lakes in the Western Lakes Region of the Sand Hills of Nebraska indicate dynamic hydrologic systems. The rather narrow range of ??87Sr from lake water (1.1 to 2.1) and groundwater (0.9 to 1.7) indicates that the groundwater is generally unradiogenic. Groundwater residence times and relatively unradiogenic volcanic ash within the dune sediments control the ??87Sr values. Based on the mutual variations of ??18O and ??D, the lakes can be divided into three groups. In Group 1, both ??18O and ??D values increase from spring to fall. The ??18O and ??D values in Group 2 decreased from spring to fall. Group 3 are ephemeral lakes that went dry some time during 1992. The data and isotopic modeling show that variations in the ratio of evaporation relative to groundwater inflow, local humidity conditions, and the ??(a) has substantial influence on the isotopic composition. In addition, isotopic behavior in ephemeral hakes can be rather unusual because of the changing activities of water and mineral precipitation and redissolution. The annual and interannual isotopic variability of these lakes which is reflected in the paleonvironmental indicators may be the rule rather than the exception in these types of systems.

δ18O and δD of lake waters across the Coast Range and Cascades, central Oregon: Modern insights from hydrologically open lakes into the control of landscape on lake water composition in deep time

NASA Astrophysics Data System (ADS)

Finkelstein, D. B.; Curtin, T.

2016-12-01

Reconstructing the stable isotopic composition of paleolake water normally requires an assumption of paleotemperature. However, hydrologically open paleolakes with short water residence times may have recorded paleoprecipitation along topographic gradients that are independent of lake water temperature. To identify the environmental and geographic controls on the isotopic composition of lake water, we sampled 22 natural lakes and reservoirs along a longitudinal and elevation gradient from the Pacific Ocean up and over the Coast and Cascade Ranges of central Oregon to the High Lava Plains in 2013 and 2015. The transect spans lakes of different origins, 6 geomorphic regions and an elevation range of 2-1942 m absl. The Coast Range lakes are sand hosted whereas the remaining are bedrock (volcanic and sedimentary) hosted. The lakes are hydrologically open and dominated by meteoric recharge. The water residence time ranges from months to decades. Samples were analyzed for temperature, pH, and total dissolved solids (TDS) in the field, and alkalinity and major cations and anions and stable isotopes of D and O in the lab. The pH ranges from 7 to 9.8 and shows no systematic variation based on substrate type or elevation. The lakes are dilute (avg. TDS = 35.8 ppm) and have low alkalinties (18.9 mg/L CaCO3) except for those in the High Lava Plains (avg. TDS = 337 ppm, alk: 291.2 mg/L CaCO3). In the Coast Range, Na is the major cation on an equivalent basis, reflecting proximity to the ocean. The easternmost lakes within the Coast Range are dominated by Ca, reflecting different drainage basins and substrate type. Lakes in the Western and High Cascades are dominated by Ca. The dominant cation and stable isotopic analyses clearly differentiate waters from different geomorphic regions. The δ18O ranges from -5.7 to -9.3 ‰ (VSMOW), and δD ranges from -37.8 to -63.6 ‰ (VSMOW) in the Coast Range whereas the δ18O ranges from -9.7 to -12.1 ‰ (VSMOW) and δD ranges from -71

Stable Isotopes (O, H, and S) in the Muteh Gold Deposit, Golpaygan Area, Iran

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdollahi, M. J.; Karimpour, M. H.; Kheradmand, A.

2009-06-15

The Muteh gold district with nine gold deposits is located in the Sanandaj-Sirjan metamorphic zone. Gold mineralization occurs in a pre-Permian complex which mainly consists of green schists, meta-volcanics, and gneiss rocks. Shear zones are the host of gold mineralization. Gold paragenesis minerals include pyrite, chalcopyrite, pyrrhotite, and secondary minerals. Pyrites occur as pre-, syn-, and post-metamorphism minerals. To determine the source of the ore-bearing fluids, fifty samples were selected for petrographical and stable isotope studies. The mean values of 12.4 per mille , and -42 per mille for {delta}{sup 18}O and {delta}D isotopes, respectively, and a mean value ofmore » 7.75 per mille of calculated fractionation factors for {delta}{sup 18}O H{sub 2}O, from quartz veins indicate that metamorphic host rocks are the most important source for the fluids and gold mineralization. Three generations of pyrite can be distinguished showing a wide range of {delta}{sup 34}S. Gold mineralization is closely associated with intense hydrothermal alteration along the ductile shear zones. The characteristics of the gold mineralization in the study area are similar to those of orogenic gold deposits elsewhere.« less

State of the art of D&D Instrumentation Technology: Alpha counting in the presence of high background

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickerman, C.E.

1995-08-01

Discrimination of alpha activity in the presence of a high radiation background has been identified as an area of concern to be studied for D&D applications. Upon evaluating the range of alpha detection needs for D&D operations, we have expanded this study to address the operational concern of greatly expediting alpha counting of rough surfaces and rubble. Note that the term, ``rough surfaces`` includes a wide range of practical cases, including contaminated equipment and work surfaces. We have developed provisional applications requirements for instrumentation of this type; and we also have generated the scope of a program of instrument evaluationmore » and testing, with emphasis on practical implementation. In order to obtain the full operational benefit of alpha discrimination in the presence of strong beta-gamma radiation background, the detection system must be capable of some form of remote or semi-remote operation in order to reduce operator exposure. We have identified a highly promising technique, the long-range alpha detector (LRAD), for alpha discrimination in the presence of high radiation background. This technique operates upon the principle of transporting alphaionized air to an ionization detector. A transport time within a few seconds is adequate. Neither the provisional requirements nor the evaluation and testing scope were expressly tailored to force the selection of a LRAD technology, and they could be used as a basis for studies of other promising technologies. However, a technology that remotely detects alpha-ionized air (e. g., LRAD) is a natural fit to the key requirements of rejection of high background at the survey location and operator protection. Also, LRAD appears to be valuable for D&D applications as a means of greatly expediting surface alpha-activity surveys that otherwise would require performing time-consuming scans over surfaces of interest with alpha detector probes, and even more labor-intensive surface wipe surveys.« less

Reducing uncertainty in the climatic interpretations of speleothem δ18O

NASA Astrophysics Data System (ADS)

Jex, C. N.; Phipps, S. J.; Baker, A.; Bradley, C.

2013-05-01

We explore two principal areas of uncertainty associated with paleoclimate reconstructions from speleothem δ18O (δ18Ospel): potential non-stationarity in relationships between local climate and larger-scale atmospheric circulation, and routing of water through the karst aquifer. Using a δ18Ospel record from Turkey, the CSIRO Mk3L climate system model and the KarstFOR karst hydrology model, we confirm the stationarity of relationships between cool season precipitation and regional circulation dynamics associated with the North Sea-Caspian pattern since 1 ka. Stalagmite δ18O is predicted for the last 500 years, using precipitation and temperature output from the CSIRO Mk3L model and synthetic δ18O of precipitation as inputs for the KarstFOR model. Interannual variability in the δ18Ospel record is captured by KarstFOR, but we cannot reproduce the isotopically lighter conditions of the sixteenth to seventeenth centuries. We argue that forward models of paleoclimate proxies (such as KarstFOR) embedded within isotope-enabled general circulation models are now required.

Oxygen isotope ratios (18O/16O) of hemicellulose-derived sugar biomarkers in plants, soils and sediments as paleoclimate proxy II: Insight from a climate transect study

NASA Astrophysics Data System (ADS)

Tuthorn, Mario; Zech, Michael; Ruppenthal, Marc; Oelmann, Yvonne; Kahmen, Ansgar; Valle, Héctor Francisco del; Wilcke, Wolfgang; Glaser, Bruno

2014-02-01

The oxygen isotopic composition of precipitation (δ18Oprec) is well known to be a valuable (paleo-)climate proxy. Paleosols and sediments and hemicelluloses therein have the potential to serve as archives recording the isotopic composition of paleoprecipitation. In a companion paper (Zech et al., 2014) we investigated δ18Ohemicellulose values of plants grown under different climatic conditions in a climate chamber experiment. Here we present results of compound-specific δ18O analyses of arabinose, fucose and xylose extracted from modern topsoils (n = 56) along a large humid-arid climate transect in Argentina in order to answer the question whether hemicellulose biomarkers in soils reflect δ18Oprec. The results from the field replications indicate that the homogeneity of topsoils with regard to δ18Ohemicellulose is very high for most of the 20 sampling sites. Standard deviations for the field replications are 1.5‰, 2.2‰ and 1.7‰, for arabinose, fucose and xylose, respectively. Furthermore, all three hemicellulose biomarkers reveal systematic and similar trends along the climate gradient. However, the δ18Ohemicellulose values (mean of the three sugars) do not correlate positively with δ18Oprec (r = -0.54, p < 0.014, n = 20). By using a Péclet-modified Craig-Gordon (PMCG) model it can be shown that the δ18Ohemicellulose values correlate highly significantly with modeled δ18Oleaf water values (r = 0.81, p < 0.001, n = 20). This finding suggests that hemicellulose biomarkers in (paleo-)soils do not simply reflect δ18Oprec but rather δ18Oprec altered by evaporative 18O enrichment of leaf water due to evapotranspiration. According to the modeling results, evaporative 18O enrichment of leaf water is relatively low (˜10‰) in the humid northern part of the Argentinian transect and much higher (up to 19‰) in the arid middle and southern part of the transect. Model sensitivity tests corroborate that changes in relative air humidity exert a dominant

First on-line isotopic characterization of N2O emitted from intensively managed grassland

NASA Astrophysics Data System (ADS)

Wolf, B.; Merbold, L.; Decock, C.; Tuzson, B.; Harris, E.; Six, J.; Emmenegger, L.; Mohn, J.

2015-01-01

The analysis of the four main isotopic N2O species (14N14N16O, 14N15N16O, 15N14N16O, 14N14N18O) and especially the intramolecular distribution of 15N (site preference, SP) has been suggested as a tool to distinguish source processes and to help constrain the global N2O budget. However, current studies suffer from limited spatial and temporal resolution capabilities due to the combination of discrete flask sampling with subsequent laboratory-based mass spectrometric analysis. Quantum cascade laser absorption spectroscopy (QCLAS) allows selective high-precision analysis of N2O isotopic species at trace levels and is suitable for in situ measurements. Here, we present results from the first field campaign, conducted on an intensively managed grassland in central Switzerland. N2O mole fractions and isotopic composition were determined in the atmospheric surface layer (2 m height) at high temporal resolution with a modified state-of-the-art laser spectrometer connected to an automated N2O preconcentration unit. The analytical performance was determined from repeated measurements of a compressed air tank and resulted in measurement repeatability of 0.20, 0.12 and 0.11‰ for δ15Nα, δ15Nβ and δ18O, respectively. Simultaneous eddy-covariance N2O flux measurements were used to determine the flux-averaged isotopic signature of soil-emitted N2O. Our measurements indicate that in general, nitrifier-denitrification and denitrification were the prevalent sources of N2O during the campaign, and that variations in isotopic composition were rather due to alterations in the extent to which N2O was reduced to N2, than other pathways such as hydroxylamine oxidation. Management and rewetting events were characterized by low values of the intra-molecular 15N site preference (SP), δ15Nbulk and δ18O, suggesting nitrifier denitrification and incomplete heterotrophic bacterial denitrification responded most strongly to the induced disturbances. Flux-averaged isotopic composition of N

First on-line isotopic characterization of N2O above intensively managed grassland

NASA Astrophysics Data System (ADS)

Wolf, B.; Merbold, L.; Decock, C.; Tuzson, B.; Harris, E.; Six, J.; Emmenegger, L.; Mohn, J.

2015-04-01

The analysis of the four main isotopic N2O species (14N14N16O, 14N15N16O, 15N14N16O, 14N14N18O) and especially the intramolecular distribution of 15N ("site preference", SP) has been suggested as a tool to distinguish source processes and to help constrain the global N2O budget. However, current studies suffer from limited spatial and temporal resolution capabilities due to the combination of discrete flask sampling with subsequent laboratory-based mass-spectrometric analysis. Quantum cascade laser absorption spectroscopy (QCLAS) allows the selective high-precision analysis of N2O isotopic species at trace levels and is suitable for in situ measurements. Here, we present results from the first field campaign, conducted on an intensively managed grassland site in central Switzerland. N2O mole fractions and isotopic composition were determined in the atmospheric surface layer (at 2.2 m height) at a high temporal resolution with a modified state-of-the-art laser spectrometer connected to an automated N2O preconcentration unit. The analytical performance was determined from repeated measurements of a compressed air tank and resulted in measurement repeatability of 0.20, 0.12 and 0.11‰ for δ15Nα, δ15Nβ and δ18O, respectively. Simultaneous eddy-covariance N2O flux measurements were used to determine the flux-averaged isotopic signature of soil-emitted N2O. Our measurements indicate that, in general, nitrifier-denitrification and denitrification were the prevalent sources of N2O during the campaign and that variations in isotopic composition were due to alterations in the extent to which N2O was reduced to N2 rather than to other pathways, such as hydroxylamine oxidation. Management and rewetting events were characterized by low values of the intramolecular 15N site preference (SP), δ15Nbulk and δ18O, suggesting that nitrifier-denitrification and incomplete heterotrophic bacterial denitrification responded most strongly to the induced disturbances. The flux

Geochemical and isotopic (Nd-Pb-Sr-O) variations bearing on the genesis of volcanic rocks from Vesuvius, Italy

USGS Publications Warehouse

Ayuso, R.A.; de Vivo, B.; Rolandi, G.; Seal, R.R.; Paone, A.

1998-01-01

commonly seen in rocks generated at orogenic margins are absent in our samples. Sr isotopic compositions are known to be variable within some of the units, in agreement with our data (87Sr/86Sr ~ 0.70699 to 0.70803) and with contributions from several isotopic components. Isotopic compositions for ??18O (7.3 to 10.2%), Pb for mineral separates and whole rocks (206Pb/204Pb ~ 18.947 to 19.178, 207Pb/204/Pb ~ 15.617 to 15.769, 208Pb/204Pb ~38.915 to 39.345), and Nd (143Nd ~ 0.51228 to 0.51251) also show variability. Oxygen isotope data show that pumices have higher ??18O values than cogenetic lavas, and that ??18O values and SiO2 are correlated. Radiogenic and stable isotope data plot within range of isotopic compositions for the Roman comagmatic province. Fractional crystallization cannot account for the radiogenic isotopic compositions of the Vesuvius magmas. We favor instead the combined effects of heterogeneous magma sources, together with isotopic exchange near the roof of the magma chamber. We suggest that metasomatized continental mantle lithosphere is the principal source of the magmas. This kind of enriched mantle was melted and reactivated in an area of continental extension (incipient rift setting) without direct reliance on contemporaneous subduction processes but possibly with input from mantle sources that resemble those that produce ocean island basalts.

Development of Measurement Methods for Detection of Special Nuclear Materials using D-D Pulsed Neutron Source

NASA Astrophysics Data System (ADS)

Misawa, Tsuyoshi; Takahashi, Yoshiyuki; Yagi, Takahiro; Pyeon, Cheol Ho; Kimura, Masaharu; Masuda, Kai; Ohgaki, Hideaki

2015-10-01

For detection of hidden special nuclear materials (SNMs), we have developed an active neutron-based interrogation system combined with a D-D fusion pulsed neutron source and a neutron detection system. In the detection scheme, we have adopted new measurement techniques simultaneously; neutron noise analysis and neutron energy spectrum analysis. The validity of neutron noise analysis method has been experimentally studied in the Kyoto University Critical Assembly (KUCA), and was applied to a cargo container inspection system by simulation.

δ18O water isotope in the iLOVECLIM model (version 1.0) - Part 2: Evaluation of model results against observed δ18O in water samples

NASA Astrophysics Data System (ADS)

Roche, D. M.; Caley, T.

2013-09-01

The H218O stable isotope was previously introduced in the three coupled components of the earth system model iLOVECLIM: atmosphere, ocean and vegetation. The results of a long (5000 yr) pre-industrial equilibrium simulation are presented and evaluated against measurement of H218O abundance in present-day water for the atmospheric and oceanic components. For the atmosphere, it is found that the model reproduces the observed spatial distribution and relationships to climate variables with some merit, though limitations following our approach are highlighted. Indeed, we obtain the main gradients with a robust representation of the Rayleigh distillation but caveats appear in Antarctica and around the Mediterranean region due to model limitation. For the oceanic component, the agreement between the modelled and observed distribution of water δ18O is found to be very good. Mean ocean surface latitudinal gradients are faithfully reproduced as well as the mark of the main intermediate and deep water masses. This opens large prospects for the applications in palaeoclimatic context.

δ18O water isotope in the iLOVECLIM model (version 1.0) - Part 2: Evaluation of model results against observed δ18O in water samples

NASA Astrophysics Data System (ADS)

Roche, D. M.; Caley, T.

2013-03-01

The H218O stable isotope was previously introduced in the three coupled components of the Earth System Model iLOVECLIM: atmosphere, ocean and vegetation. The results of a long (5000 yr) pre-industrial equilibrium simulation are presented and evaluated against measurement of H218O abundance in present-day water for the atmospheric and oceanic components. For the atmosphere, it is found that the model reproduces the observed spatial distribution and relationships to climate variables with some merit, though limitations following our approach are highlighted. Indeed, we obtain the main gradients with a robust representation of the Rayleigh distillation but caveats appear in Antarctica and around the Mediterranean region due to model limitation. For the oceanic component, the agreement between the modelled and observed distribution of water δ18O is found to be very good. Mean ocean surface latitudinal gradients are faithfully reproduced as well as the mark of the main intermediate and deep water masses. This opens large prospects for the applications in paleoclimatic context.

Observation of a Neutral Structure near the DD[over ¯]^{*} Mass Threshold in e^{+}e^{-}→(DD[over ¯]^{*})^{0}π^{0} at sqrt[s]=4.226 and 4.257 GeV.

PubMed

Ablikim, M; Achasov, M N; Ai, X C; Albayrak, O; Albrecht, M; Ambrose, D J; Amoroso, A; An, F F; An, Q; Bai, J Z; Ferroli, R Baldini; Ban, Y; Bennett, D W; Bennett, J V; Bertani, M; Bettoni, D; Bian, J M; Bianchi, F; Boger, E; Boyko, I; Briere, R A; Cai, H; Cai, X; Cakir, O; Calcaterra, A; Cao, G F; Cetin, S A; Chang, J F; Chelkov, G; Chen, G; Chen, H S; Chen, H Y; Chen, J C; Chen, M L; Chen, S Chen; Chen, S J; Chen, X; Chen, X R; Chen, Y B; Cheng, H P; Chu, X K; Cibinetto, G; Dai, H L; Dai, J P; Dbeyssi, A; Dedovich, D; Deng, Z Y; Denig, A; Denysenko, I; Destefanis, M; De Mori, F; Ding, Y; Dong, C; Dong, J; Dong, L Y; Dong, M Y; Du, S X; Duan, P F; Fan, J Z; Fang, J; Fang, S S; Fang, X; Fang, Y; Fava, L; Feldbauer, F; Felici, G; Feng, C Q; Fioravanti, E; Fritsch, M; Fu, C D; Gao, Q; Gao, X L; Gao, X Y; Gao, Y; Gao, Z; Garzia, I; Goetzen, K; Gong, W X; Gradl, W; Greco, M; Gu, M H; Gu, Y T; Guan, Y H; Guo, A Q; Guo, L B; Guo, R P; Guo, Y; Guo, Y P; Haddadi, Z; Hafner, A; Han, S; Hao, X Q; Harris, F A; He, K L; He, X Q; Held, T; Heng, Y K; Hou, Z L; Hu, C; Hu, H M; Hu, J F; Hu, T; Hu, Y; Huang, G M; Huang, G S; Huang, J S; Huang, X T; Huang, Y; Hussain, T; Ji, Q; Ji, Q P; Ji, X B; Ji, X L; Jiang, L W; Jiang, X S; Jiang, X Y; Jiao, J B; Jiao, Z; Jin, D P; Jin, S; Johansson, T; Julin, A; Kalantar-Nayestanaki, N; Kang, X L; Kang, X S; Kavatsyuk, M; Ke, B C; Kiese, P; Kliemt, R; Kloss, B; Kolcu, O B; Kopf, B; Kornicer, M; Kühn, W; Kupsc, A; Lange, J S; Lara, M; Larin, P; Leng, C; Li, C; Li, Cheng; Li, D M; Li, F; Li, F Y; Li, G; Li, H B; Li, H J; Li, J C; Li, Jin; Li, K; Li, K; Li, Lei; Li, P R; Li, T; Li, W D; Li, W G; Li, X L; Li, X M; Li, X N; Li, X Q; Li, Z B; Liang, H; Liang, J J; Liang, Y F; Liang, Y T; Liao, G R; Lin, D X; Liu, B J; Liu, C X; Liu, D; Liu, F H; Liu, Fang; Liu, Feng; Liu, H B; Liu, H H; Liu, H H; Liu, H M; Liu, J; Liu, J B; Liu, J P; Liu, J Y; Liu, K; Liu, K Y; Liu, L D; Liu, P L; Liu, Q; Liu, S B; Liu, X; Liu, Y B; Liu, Z A; Liu, Zhiqing; Loehner, H; Lou, X C; Lu, H J; Lu, J G; Lu, Y; Lu, Y P; Luo, C L; Luo, M X; Luo, T; Luo, X L; Lyu, X R; Ma, F C; Ma, H L; Ma, L L; Ma, M M; Ma, Q M; Ma, T; Ma, X N; Ma, X Y; Maas, F E; Maggiora, M; Mao, Y J; Mao, Z P; Marcello, S; Messchendorp, J G; Min, J; Mitchell, R E; Mo, X H; Mo, Y J; Morales, C Morales; Moriya, K; Muchnoi, N Yu; Muramatsu, H; Nefedov, Y; Nerling, F; Nikolaev, I B; Ning, Z; Nisar, S; Niu, S L; Niu, X Y; Olsen, S L; Ouyang, Q; Pacetti, S; Pan, Y; Patteri, P; Pelizaeus, M; Peng, H P; Peters, K; Pettersson, J; Ping, J L; Ping, R G; Poling, R; Prasad, V; Qi, M; Qian, S; Qiao, C F; Qin, L Q; Qin, N; Qin, X S; Qin, Z H; Qiu, J F; Rashid, K H; Redmer, C F; Ripka, M; Rong, G; Rosner, Ch; Ruan, X D; Sarantsev, A; Savrié, M; Schoenning, K; Schumann, S; Shan, W; Shao, M; Shen, C P; Shen, P X; Shen, X Y; Sheng, H Y; Shi, M; Song, W M; Song, X Y; Sosio, S; Spataro, S; Sun, G X; Sun, J F; Sun, S S; Sun, X H; Sun, Y J; Sun, Y Z; Sun, Z J; Sun, Z T; Tang, C J; Tang, X; Tapan, I; Thorndike, E H; Tiemens, M; Ullrich, M; Uman, I; Varner, G S; Wang, B; Wang, D; Wang, D Y; Wang, K; Wang, L L; Wang, L S; Wang, M; Wang, P; Wang, P L; Wang, S G; Wang, W; Wang, W P; Wang, X F; Wang, Y D; Wang, Y F; Wang, Y Q; Wang, Z; Wang, Z G; Wang, Z H; Wang, Z Y; Wang, Z Y; Weber, T; Wei, D H; Wei, J B; Weidenkaff, P; Wen, S P; Wiedner, U; Wolke, M; Wu, L H; Wu, L J; Wu, Z; Xia, L; Xia, L G; Xia, Y; Xiao, D; Xiao, H; Xiao, Z J; Xie, Y G; Xiu, Q L; Xu, G F; Xu, J J; Xu, L; Xu, Q J; Xu, X P; Yan, L; Yan, W B; Yan, W C; Yan, Y H; Yang, H J; Yang, H X; Yang, L; Yang, Y; Yang, Y X; Ye, M; Ye, M H; Yin, J H; Yu, B X; Yu, C X; Yu, J S; Yuan, C Z; Yuan, W L; Yuan, Y; Yuncu, A; Zafar, A A; Zallo, A; Zeng, Y; Zeng, Z; Zhang, B X; Zhang, B Y; Zhang, C; Zhang, C C; Zhang, D H; Zhang, H H; Zhang, H Y; Zhang, J; Zhang, J J; Zhang, J L; Zhang, J Q; Zhang, J W; Zhang, J Y; Zhang, J Z; Zhang, K; Zhang, L; Zhang, X Y; Zhang, Y; Zhang, Y N; Zhang, Y H; Zhang, Y T; Zhang, Yu; Zhang, Z H; Zhang, Z P; Zhang, Z Y; Zhao, G; Zhao, J W; Zhao, J Y; Zhao, J Z; Zhao, Lei; Zhao, Ling; Zhao, M G; Zhao, Q; Zhao, Q W; Zhao, S J; Zhao, T C; Zhao, Y B; Zhao, Z G; Zhemchugov, A; Zheng, B; Zheng, J P; Zheng, W J; Zheng, Y H; Zhong, B; Zhou, L; Zhou, X; Zhou, X K; Zhou, X R; Zhou, X Y; Zhu, K; Zhu, K J; Zhu, S; Zhu, S H; Zhu, X L; Zhu, Y C; Zhu, Y S; Zhu, Z A; Zhuang, J; Zotti, L; Zou, B S; Zou, J H

2015-11-27

A neutral structure in the DD[over ¯]^{*} system around the DD[over ¯]^{*} mass threshold is observed with a statistical significance greater than 10σ in the processes e^{+}e^{-}→D^{+}D^{*-}π^{0}+c.c. and e^{+}e^{-}→D^{0}D[over ¯]^{*0}π^{0}+c.c. at sqrt[s]=4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as Z_{c}(3885)^{0}. Assuming the presence of a resonance, its pole mass and width are determined to be [3885.7_{-5.7}^{+4.3}(stat)±8.4(syst)]  MeV/c^{2} and [35_{-12}^{+11}(stat)±15(syst)]  MeV, respectively. The Born cross sections are measured to be σ[e^{+}e^{-}→Z_{c}(3885)^{0}π^{0},Z_{c}(3885)^{0}→DD[over ¯]^{*}]=[77±13(stat)±17(syst)]  pb at 4.226 GeV and [47±9(stat)±10(syst)]  pb at 4.257 GeV. The ratio of decay rates B[Z_{c}(3885)^{0}→D^{+}D^{*-}+c.c.]/B[Z_{c}(3885)^{0}→D^{0}D[over ¯]^{*0}+c.c.] is determined to be 0.96±0.18(stat)±0.12(syst), consistent with no isospin violation in the process, Z_{c}(3885)^{0}→DD[over ¯]^{*}.

Stable oxygen and hydrogen isotope analyses of bowhead whale baleen as biochemical recorders of migration and arctic environmental change

NASA Astrophysics Data System (ADS)

deHart, Pieter A. P.; Picco, Candace M.

2015-06-01

An analysis of the stable isotopes of oxygen (δ18O) and hydrogen (δD) was used to examine the linkage between sea ice concentration and the migration of western arctic bowhead whales (Balaena mysticetus; WABW). We compared δ18O and δD variability along the length of WABW baleen with isotopic values of zooplankton prey from different WABW habitat, with published δ13C and δ15N data, and with historical sea ice records. Zooplankton signatures varied widely (δ18O = -13‰-56‰; δD = -220‰ to -75‰), with regional separation between winter (Bering Sea) and summer (eastern Beaufort Sea) habitats of WABW observable in δD. The δ18O and δD of WABW varied significantly along the length of baleen (δ18O = 8-18‰; δD = -180 to -80‰), confirming seasonal migration and reflecting distinct regional dietary variation in isotopes. WABW migration appears to have varied concomitant with temporal sea ice concentration (SIC) changes; in years with high SIC, the difference in δD of WABW baleen between seasonal habitats was significantly greater than low SIC periods. This work shows that SIC is not only a determinant of habitat accessibility for WABW, but baleen may also be a record of historical SIC and Arctic climate.

Rainfall and cave water isotopic relationships in two South-France sites

NASA Astrophysics Data System (ADS)

Genty, D.; Labuhn, I.; Hoffmann, G.; Danis, P. A.; Mestre, O.; Bourges, F.; Wainer, K.; Massault, M.; Van Exter, S.; Régnier, E.; Orengo, Ph.; Falourd, S.; Minster, B.

2014-04-01

This article presents isotopic measurements (δ18O and δD) of precipitation and cave drip water from two sites in southern France in order to investigate the link between rainfall and seepage water, and to characterize regional rainfall isotopic variability. These data, which are among the longest series in France, come from two rainfall stations in south-west France (Le Mas 1996-2012, and Villars 1998-2012; typically under Atlantic influence), and from one station in the south-east (Orgnac 2000-2012; under both Mediterranean and Atlantic influence). Rainfall isotopic composition is compared to drip water collected under stalactites from the same sites: Villars Cave (four drip stations 1999-2012) in the south-west, and Chauvet Cave (two drip stations 2000-2012) in the south-east, near Orgnac. The study of these isotopic data sets allows the following conclusions to be drawn about the rainfall/drip water relationships and about rainfall variability: (1) the cave drip water isotopic composition does not show any significant changes since the beginning of measurements; in order to explain its isotopic signature it is necessary to integrate weighted rainfall δ18O of all months during several years, which demonstrates that, even at shallow depths (10-50 m), cave drip water is a mixture of rain water integrated over relatively long periods, which give an apparent time residence from several months to up to several years. These results have important consequences on the interpretation of proxies like speleothem fluid inclusions and tree-ring cellulose isotopic composition, which are used for paleoclimatic studies; (2) in the Villars Cave, where drip stations at two different depths were studied, lower δ18O values were observed in the lower galleries, which might be due to winter season overflows during infiltration and/or to older rain water with a different isotopic composition that reaches the lower galleries after years; (3) local precipitation is characterized by

18O/16O in CO2 evolved from goethite during some unusually rapid solid state α-FeOOH to α-Fe2O3 phase transitions: Test of an exchange model for possible use in oxygen isotope analyses of goethite

NASA Astrophysics Data System (ADS)

Yapp, Crayton J.

2015-12-01

The initial ∼60% of an isothermal vacuum dehydration of goethite can commonly be approximated by first order kinetics. Also, natural goethites contain small amounts of an Fe(CO3)OH component in apparent solid solution. The 18O/16O of CO2 evolved from the Fe(CO3)OH during isothermal vacuum dehydrations is related to the 18O/16O of the goethite by an apparent fractionation factor (αapp) that is, in turn, correlated with a first order rate constant, |m|. A kinetic exchange model predicts that αapp should decrease as |m| increases for a range of |m| that corresponds to relatively slow rates of dehydration. This pattern has been observed in published results. In contrast, for rapid rates of dehydration, αapp is predicted to increase with increasing |m|. Isothermal vacuum dehydrations of two natural goethites had unusually large values of |m| and provided serendipitous tests of this rapid-rate prediction. For these experiments, the measured values of αapp were consistent with patterns of variation predicted by the model. This allowed an estimate of the activation energy (E2) of a model parameter, K2, which is the rate constant for oxygen isotope exchange between CO2 and H2O during the solid-state goethite to hematite phase transition. The estimated value of E2 is only ∼9 kJ/mol. Heterogeneous catalysis tends to decrease the activation energies of gas reactions. Consequently, the inferred value of E2 suggests that goethite and/or hematite catalyze oxygen isotope exchange between CO2 and H2O during the solid-state phase change. Yield, δ13C, and δ18O values are routinely measured for increments of CO2 evolved from the Fe(CO3)OH component during isothermal vacuum dehydration of goethite. Model-predicted values of αapp can be combined with plateau δ18O values of the evolved CO2 to estimate the δ18O of the goethite with a less than optimal, but potentially useful, precision of about ±0.8‰. Therefore, a single analytical procedure (incremental dehydration

Triple oxygen isotope analysis of tropospheric CO2 on the two sides of the Pacific Ocean

NASA Astrophysics Data System (ADS)

Liang, M. C.; Newman, S.; Laskar, A. H.

2017-12-01

The abundance variations of near surface atmospheric CO2 isotopologues (primarily 16O12C16O, 16O13C16O, 17O12C16O, and 18O12C16O) represent an integrated signal from anthropogenic/biogeochemical processes, including fossil fuel burning, biospheric photosynthesis and respiration, hydrospheric isotope exchange with water, stratospheric photochemistry, cross-tropopause exchange, and subsequent vertical mixing between the free troposphere and planetary boundary. Oxygen isotopes, in particular, are affected by both the carbon and water cycles. Being a useful tracer that directly probes governing processes in CO2 biogeochemical cycles, D17O (= ln(1+d17O) - 0.516 ln(1+d18O)) provides a powerful constraint on the strengths of the associated cycles involving CO2. Here, we report and compare summer to winter seasons CO2 isotopic composition from Taiwan (Taipei) and USA (Palos Verdes, CA). On average, the D17O values from Taiwan are significantly higher than those in USA. Analysis shows that the impact of 2014-2016 El Nino event on the observed D17O values is not visible, in contrast to what was reported for the 1997-1998 El Nino from the CO2 data collected from La Jolla, CA. Attempts are made to understand the elevated D17O values in the eastern Pacific compared to those in the western Pacific. Implications for utilizing the new tracer D17O along with the conventional d18O for carbon cycling studies are also discussed.

The NO+O3 reaction: a triple oxygen isotope perspective on the reaction dynamics and atmospheric implications for the transfer of the ozone isotope anomaly.

PubMed

Savarino, J; Bhattacharya, S K; Morin, S; Baroni, M; Doussin, J-F

2008-05-21

Atmospheric nitrate shows a large oxygen isotope anomaly (Delta 17 O), characterized by an excess enrichment of 17 O over 18 O, similar to the ozone molecule. Modeling and observations assign this specific isotopic composition mainly to the photochemical steady state that exists in the atmosphere between ozone and nitrate precursors, namely, the nitrogen oxides (NOx=NO+NO2). However, this transfer is poorly quantified and is built on unverified assumptions about which oxygen atoms of ozone are transferred to NO(x), greatly weakening any interpretation of the nitrate oxygen isotopic composition in terms of chemical reaction pathways and the oxidation state of the atmosphere. With the aim to improve our understanding and quantify how nitrate inherits this unusual isotopic composition, we have carried out a triple isotope study of the reaction NO+O3. Using ozone intramolecular isotope distributions available in the literature, we have found that the central atom of the ozone is abstracted by NO with a probability of (8+/-5)%(+/-2 sigma) at room temperature. This result is at least qualitatively supported by dynamical reaction experiments, the non-Arrhenius behavior of the kinetic rate of this reaction, and the kinetic isotope fractionation factor. Finally, we have established the transfer function of the isotope anomaly of O3 to NO2, which is described by the linear relationship Delta 17 O(NO2)=A x Delta 17 O(O3)+B, with A=1.18+/-0.07(+/-1 sigma) and B=(6.6+/-1.5)[per thousand](+/-1 sigma). Such a relationship can be easily incorporated into models dealing with the propagation of the ozone isotope anomaly among oxygen-bearing species in the atmosphere and should help to better interpret the oxygen isotope anomaly of atmospheric nitrate in terms of its formation reaction pathways.

Hydrochemical and isotopic characterization of groundwater in the Ghis-Nekor plain (northern Morocco)

NASA Astrophysics Data System (ADS)

Chafouq, D.; El Mandour, A.; Elgettafi, M.; Himi, M.; Chouikri, I.; Casas, A.

2018-03-01

The coastal aquifer of Ghis-Nekor (Morocco) was studied to identify the major processes causing salinization of groundwater. In fact, a geochemical approach multi tracer (general chemistry and isotopes - δ2H, δ18O-H2O, δ34S, δ18O-SO4) was utilized, with the hydrodynamics to explain the processes responsible for the salinization of groundwater, and for identttifying areas most vulnerable to seawater intrusion. The recharge of the aquifer is mainly by the Al-Khattabi dam, the Nekor River and the Ghis River, on the eastern border of the plain. The water that feeds the aquifer shows a relatively high level of salinity and for this reason, the majority of sampled wells indicate high values of electric conductivity and total salinity which arrives at 7.5 g L-1. The plot of the geochemical results analyzes of groundwater in the Piper diagram shows two distinct chemical facies; sodium chloride-facies and chlorinated calcium and magnesium sulfated facies. The concentrations of 18O range between -4.15‰ and -5.73‰, while the values of 2H range between -28.4‰ and -41.7‰. The Nekor river water is depleted in heavy isotopes, and the isotopic compositions are in the order on -6‰ for 18O and -40.5‰ for deuterium. Most of the wells have a slope <8 indicating a slight evaporation before infiltration. The data show low and variable d-excess values (range from -0.02‰ to 11.6‰), reflect recharge during different climatic conditions. The isotopic concentrations of 18O-SO4 vary between 4.35‰ and 8.60‰, while the 34S isotope values range from -4.3‰ to 9.9‰. For Ghis River, these values are between -4.4‰ and 4.95‰, respectively, for sulfur and oxygen. The interpretation of the chemical and isotopic results suggesting the intrusion of seawater to increase salinity of groundwater in the region is low. However, only the NE area shows probable contamination of seawater. In contrast, wells are saline independent of seawater intrusion, the origin of the high

The Austrian Network of Isotopes in Precipitation and Surface water: more than 50 years applications and interpretations of basic isotope-hydrological data for Central Europe

NASA Astrophysics Data System (ADS)

Wyhlidal, S.; Rank, D.; Kralik, M.

2017-12-01

Austria runs one of the longest-standing and most dense isotope precipitation collection networks worldwide, resulting in a unique isotope time series. Stable isotope variations in precipitation are a consequence of isotope effects accompanying each step of the water cycle. Therefore, stable isotope ratios of oxygen (18O/16O) and hydrogen (2H/1H) in precipitation provide important information about the origin and atmospheric transport of water vapour. The separation of a remote moisture source signals from local influences is thereby challenging. The amount of precipitation in Austria is highly influenced by the Alpine mountain range (400-3.000 mm/a). The amount of annual precipitation increases towards the mountain ranges. However, strong regional differences exist between the north and south of the Austrian Alps because the Alpine range functions as weather divide. The isotope time series of the stations of the Austrian precipitation network show significant but not uniform long-term trends. While the 10-year running mean of some mountain stations exhibit a highly significant increase in δ18O of about 1 ‰ since 1975, the change of δ18O at the valley stations is less pronounced. The increasing δ18O values can be correlated to an increase mean air temperature in the Alpine area and can be used as an additional indicator of climate change in this region. The differences in δ18O-values of sampling stations at similar altitudes can be explained by the origin of the air moisture. An Atlantic influence causes lower δ18O-values than sources from the Mediterranean. This can be explained by the different distances to the sea. Deuterium excess is a second-order isotopic parameter which is often interpreted as a tracer of the evaporation conditions of water vapor at the moisture source in terms of relative humidity, wind speed, and sea surface temperature, but can also be modified by local influences, such as below-cloud evaporation and equilibrium fractionation under

Preservation of carbonate clumped isotopes in sedimentary paleoclimate archives

NASA Astrophysics Data System (ADS)

Henkes, G. A.; Passey, B. H.; Grossman, E. L.; Shenton, B.; Perez-Huerta, A.

2014-12-01

Carbonate clumped isotope thermometry is increasingly used to reconstruct paleotemperatures of ancient terrestrial environments. One promising application is elucidating paleoelevation from carbonate archives such as paleosols, lacustrine marls, and fossil freshwater shells. Unlike conventional stable isotope approaches (e.g., mineral δ18O or δD), clumped isotope thermometry is independent of the isotopic composition of the precipitating waters and can therefore be used to reconstruct elevation by both the temperature-altitude relationship and the rainfall δ18O-altitude relationship. However, interpretation of clumped isotope data is not without its own complications. Like conventional stable isotopes, clumped isotope paleotemperatures can be effectively reset to warmer values by dissolution/reprecipitation-type diagenesis during sedimentary burial. It is also known that carbonate clumped isotope bonds (i.e., 13C-18O) are susceptible to 'reordering' in the solid mineral lattice at warmer burial temperatures, with laboratory studies of natural carbonates indicating activation of this phenomenon at temperatures as low as 100 °C over geologic timescales. A challenge in applying carbonate clumped isotope thermometry to natural samples is now evaluating terrestrial archives with respect to both types of alteration: 'open-system' alteration and 'closed-system' bond reordering. In this talk we will review our experimental efforts to constrain the kinetics of clumped isotope reordering, with relevance to low-temperature carbonates like fossil shells and early diagenetic minerals, and present new laboratory data that further inform our theoretical framework for the mechanism(s) of 13C-18O bond reordering. Together with traditional analytical and petrographic screening for recrystallization, empirical and laboratory studies of carbonate clumped isotope reordering represent the next steps in evaluating isotopic records of paleoclimate, paleobiology, and paleoelevation

Optical Lattice Bose-Einstein Condensates and the dd Fusion - Iwamura Connection

NASA Astrophysics Data System (ADS)

Chubb, Talbot

2003-03-01

My conjecture: LENR dd fusion occurs in PdDx when a subset of the interstitial deuterons occupy tetrahedral sites in a PdDx crystallite. The tetrahedral deuterons(d's), which occupy shallow potential wells, behave as a superfluid, similar to ultracold Na atoms in shallow-well optical traps, as modeled by Jaksch et al.(D. Jaksch, et al, Phys. Rev. Lett., 81, 3108 (1998).) The tetrahedral d's form a deuteron (d) subsystem, which is neutralized by an electron subsystem containing an equal number of electrons. In the superfluid all the properties of each quasiparticle d are partitioned among N_s_i_te equivalent sites. The partitioning of the d point charge reduces the Coulomb self-repulsion within each quasiparticle pair, which causes wave function overlap at large N_s_i_t_e, allowing d-d fusion. Similarly, partitioning of the point charge of each single quasiparticle d reduces the Coulomb repulsion between it and an obstructing impurity atom, which causes wave function overlap between quasiparticle and atom at large N_s_i_t_e, allowing transmutation of the impurity atom. The Iwamura reaction(Y. Iwamura, et al, Japan J. of Appl. Physics, 41A, 4642 (2002).) is 4 ^2D^+_B_l_o_ch + 4 e^-_B_l_o_ch + ^1^3^3Cs arrow ^1^4^1Pr, with the reaction energy incoherently transferred to the lattice.

Water isotope tracers of tropical hydroclimate in a warming world

NASA Astrophysics Data System (ADS)

Konecky, B. L.; Noone, D.; Nusbaumer, J. M.; Cobb, K. M.; Di Nezio, P. N.; Otto-Bliesner, B. L.

2016-12-01

The tropical water cycle is projected to undergo substantial changes under a warming climate, but direct meteorological observations to contextualize these changes are rare prior to the 20th century. Stable oxygen and hydrogen isotope ratios (δ18O, δD) of environmental waters preserved in geologic archives are increasingly being used to reconstruct terrestrial rainfall over many decades to millions of years. However, a rising number of new, modern-day observations and model simulations have challenged previous interpretations of these isotopic signatures. This presentation systematically evaluates the three main influences on the δ18O and δD of modern precipitation - rainfall amount, cloud type, and moisture transport - from terrestrial stations throughout the tropics, and uses this interpretive framework to understand past changes in terrestrial tropical rainfall. Results indicate that cloud type and moisture transport have a larger influence on modern δ18O and δD of tropical precipitation than previously believed, indicating that isotope records track changes in cloud characteristics and circulation that accompany warmer and cooler climate states. We use our framework to investigate isotopic records of the land-based tropical rain belt during the Last Glacial Maximum, the period of warming following the Little Ice Age, and the 21st century. Proxy and observational data are compared with water isotope-enabled simulations with the Community Earth System Model in order to discuss how global warming and cooling may influence tropical terrestrial hydroclimate.

Qualitative Distinction of Autotrophic and Heterotrophic Processes at the Leaf Level by Means of Triple Stable Isotope (C-O-H) Patterns.

PubMed

Kimak, Adam; Kern, Zoltan; Leuenberger, Markus

2015-01-01

Foliar samples were harvested from two oaks, a beech, and a yew at the same site in order to trace the development of the leaves over an entire vegetation season. Cellulose yield and stable isotopic compositions (δ(13)C, δ(18)O, and δD) were analyzed on leaf cellulose. All parameters unequivocally define a juvenile and a mature period in the foliar expansion of each species. The accompanying shifts of the δ(13)C-values are in agreement with the transition from remobilized carbohydrates (juvenile period), to current photosynthates (mature phase). While the opponent seasonal trends of δ(18)O of blade and vein cellulose are in perfect agreement with the state-of-art mechanistic understanding, the lack of this discrepancy for δD, documented for the first time, is unexpected. For example, the offset range of 18 permil (oak veins) to 57 permil (oak blades) in δD may represent a process driven shift from autotrophic to heterotrophic processes. The shared pattern between blade and vein found for both oak and beech suggests an overwhelming metabolic isotope effect on δD that might be accompanied by proton transfer linked to the Calvin-cycle. These results provide strong evidence that hydrogen and oxygen are under different biochemical controls even at the leaf level.

A Stable Isotope Study of Fluid-Rock Interactions in the Saddlebag Lake Roof Pendant, Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Lojasiewicz, I.; Hartman, S. M.; Holk, G. J.; Paterson, S. R.

2015-12-01

The Saddlebag Lake Pendant (SLP) is a ~ 100 km2 zone of Ordovician-Cretaceous metasedimentary and metavolcanic rocks just east of the 95-85 Ma Tuolumne Intrusive Complex (TIC) in the Sierra Nevada of central California. Western SLP and adjacent parts of TIC are affected by the Steelhead Lake Shear Zone (SLSZ), with leucogranitic dikes, abundant qz-tm veins, ductile epidote-chlorite alteration, and massive qz veins. While TIC shows uniform stable isotope values, isotope studies of other Sierra Nevada pendants evidence diversity of fluid sources: Jurassic seawater, Cretaceous magmatic fluids, metamorphic fluids, and meteoric-hydrothermal fluids. We conducted a stable isotope study of 49 samples from units across the SLSZ, focusing on the shear zone. Unlike other pendants, both δ18 O and δD values from SLSZ showed great variability, and most samples were not in isotopic equilibrium. Overall, δ18 O mineral values ranged from -1.5‰(plag) to +15.8‰(bt); mineral δD values ranged from -140‰(tm) to -67‰(bt). TIC δ18 O was +7.8 to +10.0 (plag) and +4.8 to +9.2 (tm), normal magmatic values, and δD were -105 to -75. Paleozoic and Triassic metasedimentary units had most qz δ18 O from +11.3 to +15.8, so within metamorphic range, and δD from -100 to -72 (ep and tm). Jurassic metasedimentary units (Sawmill) and Triassic metavolcanics (Koip) had largest isotopic variability: δ18 O qz from +8.1 to +14.8, plag from -1.1 to +11.8, but ep and tm between +1.3 and +9.3 and δD between -108 and -81. All lower (submagmatic) isotopic values were from a wider, possibly transtensional, part of the SLSZ, transected by Sawmill Canyon. Although TIC and many of the Paleozoic units do not show isotopic evidence for alteration, the Koip and Sawmill units were likely infiltrated by later magmatic waters, and then subjected to very localized meteoric water infiltration in the area surrounding Sawmill Canyon.