Water Deuterium Research Articles

Local Structure around the Amino Group of Glycine Carbamate in Concentrated Aqueous Solutions

Abstract Neutron diffraction measurements were carried out on aqueous alkaline 2 mol % glycine heavy water solutions absorbing CO2. 14N/15N isotopic substitution was applied to obtain information on the molecular structure of glycine carbamate formed in the solution and the hydration structure around the nitrogen atom of the carbamate molecule. The least-squares fitting analysis of the higher-Q region of the observed first-order difference function Δ′N(Q) between 14N- and 15N-enriched sample solutions revealed that the intramolecular distances within the carbamate molecule, r(N–CC) = 1.58(1) Å and r(CC–OC) = 1.25(1) Å, where CC and OC denote the carbamate carbon and oxygen atoms, respectively. It was shown that on the average 2.1(2) D2O molecules were hydrogen-bonded to the amino-hydrogen atoms of the carbamate molecule with the intermolecular distances of r(N···OW) = 2.86(3) Å and r(N···DW) = 3.18(5) Å (OW: water oxygen, DW: water deuterium atoms), respectively.

Metabolic precursors of surfactant disaturated-phosphatidylcholine in preterms with respiratory distress

Our objective was to study the metabolic precursors of surfactant disaturated-phosphatidylcholine (DSPC) in preterm infants with respiratory distress syndrome (RDS) on mechanical ventilation. We performed 46 DSPC kinetic studies in 23 preterms on fat-free parenteral nutrition and mechanical ventilation (birth weight = 1167 +/- 451 g, gestational age = 28.5 +/- 2.0 weeks). Eight infants received a simultaneous intravenous infusion of U(13)C-glucose and [16,16,16](2)H-palmitate, eight infants received U(13)C-glucose and (2)H(2)O, and seven received U(13)C-palmitate and (2)H(2)O. Surfactant DSPC kinetics were calculated from the isotopic enrichments of DSPC-palmitate from sequential tracheal aspirates and its metabolic precursors in plasma or urine. DSPC fractional synthesis rate (FSR) was 17 +/- 11, 21 +/- 16, and 15 +/- 6%/day from glucose, palmitate, and body water, respectively (P = 0.36). DSPC-FSR from U(13)C-glucose and (2)H(2)O were significantly correlated and yielded similar estimates (difference of -0.1 +/- 3%) (P = 0.91). The difference in the 15 infants receiving palmitate versus (2)H(2)O or palmitate versus glucose was +6.0 +/- 12%/day (P = 0.21). There was a significant correlation between DSPC-FSRs from plasma glucose and plasma FFA. The contribution of glucose versus palmitate to DSPC-FSR was 49 +/- 20% versus 51 +/- 20%, respectively. Plasma glucose and FFA showed similar contributions to DSPC-FSR in infants with RDS and fat-free parenteral nutrition. FSRs from (2)H(2)O or glucose were highly correlated.

A compound-specific n-alkane δ13C and δD approach for assessing source and delivery processes of terrestrial organic matter within a forested watershed in northern Japan

Abstract We measured molecular distributions and compound-specific hydrogen (δD) and stable carbon isotopic ratios (δ13C) of mid- and long-chain n-alkanes in forest soils, wetland peats and lake sediments within the Dorokawa watershed, Hokkaido, Japan, to better understand sources and processes associate with delivery of terrestrial organic matter into the lake sediments. δ13C values of odd carbon numbered C23–C33 n-alkanes ranged from −37.2‰ to −31.5‰, while δD values of these alkanes showed a large degree of variability that ranged from −244‰ to −180‰. Molecular distributions in combination with stable carbon isotopic compositions indicate a large contribution of C3 trees as the main source of n-alkanes in forested soils whereas n-alkanes in wetland soil are exclusively derived from marsh grass and/or moss. We found that the n-alkane δD values are much higher in forest soils than wetland peat. The higher δD values in forest samples could be explained by the enrichment of deuterium in leaf and soil waters due to increased evapotranspiration in the forest or differences in physiology of source plants between wetland and forest. A δ13C vs. δD diagram of n-alkanes among forest, wetland and lake samples showed that C25–C31 n-alkanes deposited in lake sediments are mainly derived from tree leaves due to the preferential transport of the forest soil organic matter over the wetland or an increased contribution of atmospheric input of tree leaf wax in the offshore sites. This study demonstrates that compound-specific δD analysis provides a useful approach for better understanding source and transport of terrestrial biomarkers in a C3 plant-dominated catchment.

Stable isotopes applied as water tracers in column and field studies

The stable isotopes deuterium (2H, D) and oxygen 18 (18O) were applied in water for use as tracers in column experiments and in two field studies. Their performance was compared against uranine and was used to characterize saturated and unsaturated water movement and depths of plant water uptake. Deuterium and 18O are completely soluble and chemically and biologically stable. They are not subject to radioactive decay like tritium, nor photodegradation and sorption processes, like uranine. The column studies were conducted under saturated conditions; they explored variations of (i) flow rates (1.4–3.5mlmin−1), (ii) column lengths (0.5, 1.0, 1.5m), and (iii) tracer concentrations (0.07, 0.14, 0.28ml of a 99.8% D2O solution). A one dimensional dispersion model was used to generate parameters that allowed us to compare the tracers. The column experiments showed higher mean transport velocities and smaller dispersion coefficients for deuterium in comparison to uranine. The first field study, on a rain dominated floodplain, found unsaturated flow rates of 0.03–0.04mday−1. The second field study examined snowmelt infiltration on a loess soil and found unsaturated flow velocities of 0.002–0.004mday−1 over a sixmonth period. Plant samples taken from the soil plots during late spring and summer reflect decreasing soil water deuterium concentrations and indicate depths of plant water uptake. Stable isotopes of water proved to be useful as a tracer in all studies and offer a suite of new possibilities in the field of biogeosciences because of the ability to directly label water molecules and to analyze small sample aliquots.

DEUTERIUM DEPLETED WATER EFFECTS ON WALKER TUMOURS

The usual concentration of deuterium in water is a bout 144 ppm D/(D+H). It is known that the increase of deuterium in the body of living animals is a naturally bioaccumulation process and could b e enhanced by adding in their diet heavy water - with obviously dramatically changes in health state. Th e aim of this study was to investigate the effect of DDW over experimental Walker tumours inducted at Wistar rats and how far can influence the decrease of deuterium 's value at treated animals. The result shows that DDW has a significant effect over the sub epidermal tum ours and it has no side effects. The deuterium's an alyses results show that DDW's rate of depletion is in cor relation with a couple of factors (the concentratio n of deuterium depleting agent; the period of administra tion of deuterium depleting agent).

VARIATION OF THE DEUTERIUM CONCENTRATION IN RATS` BLOOD AFTER DEUTERIUM DEPLETED WATER ADMINISTRATION AND INTOXICATION WITH CADMIUM

The effects of cadmium pollution are highlighted in many studies, [7,14]. Cadmium, absorbed within the organism, inhibits the action of some antioxidant enzymes, especially those which contain SH and affect especially the liver and kidneys. The level of deuterium in tap water is 150 ppm and in deuterium depleted water are under 80 ppm. Deuterium depleted water with a deuterium level of 30 ppm has an antioxidant effect on the organism [9, 10]. The present study has asses the effects of deuterium depleted water (30 ppm) on the deuterium blood level in the rats exposed to cadmium (20 ppm Cd/kg administered as CdCl2 solution in a single dose). The intoxication with cadmium modified the blood level of deuterium in the animals and the kidney, liver and spleen weight. The blood level of deuterium was determined through weight spectroscopy with the spectrofotometer SMAD 1. We observed a protective effect of deuterium depleted water on the rat organism, for preventive administration, as well as treatment and the important role in eliminating cadmium

ESEEM Measurements of Local Water Concentration in D2O-Containing Spin-Labeled Systems

To calibrate electron spin echo envelope modulation (ESEEM) amplitudes with respect to the deuterium water content in spin-labeled biological systems, ESEEM of nitroxide TEMPO has been studied in frozen glassy D2O-dimethylsulfoxide mixtures of different composition. The interaction between the unpaired electron of nitroxide and the deuterium nuclei manifests itself in a cosine Fourier transform spectrum as the sum of a narrow line with the doublet quadrupole splitting and of a broad one. The narrow line arises from interaction with distant deuterium nuclei, the broad one arises from interaction with nearby nuclei belonging to nitroxide-water molecule complexes. The dependence on water concentration was found to be nonlinear for the intensity of the narrow line and close to linear for the intensity of the quadrupole doublet. Therefore, the intensity of the quadrupole doublet is suggested as a measure of concentration of free water around a spin label in biological objects. Fourier transform line shape was theoretically simulated for different model distributions of water molecules around the spin label. Simulations confirm the linear dependence of the quadrupole doublet intensity on water concentration seen in the experiment. The suggested approach was applied to analyze data for spin-labeled dipalmitoylphosphatidylcholine (DPPC) and DPPC-cholesterol D2O-hydrated model membranes. The concentration of free water near the spin-labeled fourth carbon atom along the lipid chain was estimated as 5.2 and 7.2 M for DPPC and DPPC-cholesterol membranes, respectively.

Simplified method for microlitre deuterium measurements in water and urine by gas chromatography–high‐temperature conversion–isotope ratio mass spectrometry

Deuterium (2H) in water and urine can be measured by off-line and, more recently, on-line techniques using isotope ratio mass spectrometry (IRMS). We describe a new simple on-line pyrolysis method for the analysis of 2H/1H in water and urine samples by continuous flow IRMS, normally used for 2H/1H measurements in organic compounds. A deactivated column connected the split injector to a high-temperature conversion reactor (TC HD), and 0.5 microL of sample was injected. Accuracy and precision were determined with Vienna Standard Mean Ocean Water (VSMOW), Standard Light Antarctic Precipitation (SLAP), and Greenland Ice Sheet Precipitation (GISP). The range of linearity was measured with a calibration curve of enriched water from 0 up to 0.1 atom percent excess (APE) (i.e. -72 up to 6323 delta per mil (deltaD per thousand)) with a precision of <5 per thousand and accuracy ranging between 1 and 55 per thousand. Blinded reanalysis of urine samples by an equilibration device (Gas Bench) and by a dedicated pyrolysis system (TC/EA) was performed and results compared by the Bland-Altman test. Enrichments ranged between 600 and 2400 per thousand deltaD(VSMOW) with a precision of +/-5 per thousand. Urine enrichments described by our method were strongly correlated with values obtained by Gas Bench and TC/EA (p < 0.0001). There was a significant memory effect that was reduced by injecting the sample 15 times and discarding the first 10 injections, together with accurate furnace conditioning and appropriate cleaning of the syringe. Data indicate that the method is accurate, and that it can be used for water and urine deuterium determination when a Gas Bench or TC/EA instrument is not available and the amount of sample is limited.

Evaporative isotope enrichment as a constraint on reach water balance along a dryland river

Deuterium and oxygen-18 enrichment in river water during its transit across dryland region is found to occur systematically along evaporation lines with slopes of close to 4 in 2H–18O space, largely consistent with trends predicted by the Craig–Gordon model for an open-water dominated evaporating system. This, in combination with reach balance assessments and derived runoff ratios, strongly suggests that the enrichment signal and its variability in the Barwon–Darling river, Southeastern Australia is acquired during the process of evaporation from the river channel itself, as enhanced by the presence of abundant weirs, dams and other storages, rather than reflecting inherited enrichment signals from soil water evaporation in the watershed. Using a steady-state isotope mass balance analysis based on monthly 18O and 2H, we use the isotopic evolution of river water to re-construct a perspective of net exchange between the river and its contributing area along eight reaches of the river during a drought period from July 2002 to December 2003, including the duration of a minor flow event. The resulting scenario, which uses a combination of climatological averages and available real-time meteorological data, should be viewed as a preliminary test of the application rather than as a definitive inventory of reach water balance. As expected for a flood-driven dryland system, considerable temporal variability in exchange is predicted. While requiring additional real-time isotopic data for operational use, the method demonstrates potential as a non-invasive tool for detecting and quantifying water diversions, one that can be easily incorporated within existing water quality monitoring activities.

Neutron Studies of Impurity Gels of Heavy Water and Deuterium in Superfluid He-II

The main goal of this work is to explore feasibility of a new method for producing high density of ultra cold neutrons. The method proposed consists in the cooling of very cold neutrons owing to their many collisions with ultracold nanoparticles made of low adsorbing materials (heavy water, deuterium) down to the temperature of this particles during the diffusion motion of neutrons through a macroscopically large ensemble of nanoparticles—a sample of high porous impurity gel in superfluid He-II. At the first stage of this experimental program we have studied propagation and small angle scattering of cold neutrons in the gel samples cooled down to 1.6 K. The results obtained look very encouraging: estimated characteristic dimensions of impurity clusters are 3≤d≤150 nm for as-prepared deuterium gel sample and d≤15 nm for heavy-water gel samples. In the next series of experiments we plan to study the inelastic scattering of cold neutrons in the bulk of deuterium and heavy water gel samples.

Capillary electrophoretic studies on the photogenotoxic potential of pharmaceutical substances

Drug-induced phototoxic skin responses, including photoirritation, photoallergy and photogenotoxicity, are identified as adverse reactions. In this study, we attempted to develop effective analytical tools to predict the photogenotoxic potential of pharmaceutical substances with the use of pBR322 DNA, a plasmid DNA. pBR322 DNA was irradiated with simulated solar light in the presence of photosensitizers, and its structural conversion was assessed by agarose gel electrophoresis (AGE), transmission electron microscopy (TEM) and capillary gel electrophoresis (CGE). The generation of reactive oxygen species (ROS) from photoirradiated photosensitizers was also assessed by spectrophotometrical determination. Concomitant ultraviolet (UV) exposure of pBR322 DNA and photosensitizers resulted in significant oxidative damage to the DNA, as evidenced by AGE, TEM and CGE data, indicating a structural transition from supercoiled form to open circular form. Photosensitizer-induced DNA damage was attenuated by the addition of radical scavengers, especially sodium azide, a typical scavenger of singlet oxygen ( 1O 2), and enhanced by the addition of deuterium water, an enhancer of the life time of 1O 2. These data, taken together with the results of the ROS assay, suggest that singlet oxygen might act as a major toxic species in quinine-induced photogenotoxicity. The structural analysis of plasmid DNA by CGE after exposure to UVA/B in the presence of photosensitizers could be automated, allowing easy, fast and highly reliable prediction for the photogenotoxic potential of a large number of drug candidates.

Scattering of Cold Neutrons on Gel Samples Formed by Impurity Clusters in Superfluid He-II

The approach we have proposed earlier for a large increase in ultracold neutron density was based on equilibrium thermalization of cold neutrons during their diffusive motion in a large sample of an impurity-helium gel which consists of weakly bounded deuterium or heavy water nanoclusters in He-II cooled below a few mK. It is clear that the nanoparticles should provide a sufficiently large cross-section of coherent scattering of cold neutrons, but the scattering of neutrons on impurity gel samples in He-II has been never investigated earlier. In this paper we present results of the first observations of the scattering of a beam of cold neutrons with mean velocities from 30 to 160 m/s on heavy water and deuterium gel samples in He-II at temperatures T∼1.6 K. It has been observed that the beam transmission through the heavy water gel sample has been changed from ∼0% to ∼50% upon increasing the neutron velocity from 30 to 160 m/s, and that the neutron transmission trough the deuterium gel sample is less than 5% at all velocities. The angular distribution of the neutron scattering changes with variations in the neutron velocity: for both the gels at large neutron energies the scattering is directed in a front hemisphere mainly, and at low energies the angular distribution of scattered neutrons is close to uniform.

Tracing infiltration and recharge using stable isotope in Taihang Mt., North China

The groundwater in headwater region is an important recharge source for the adjacent mountain-front plain. In order to reveal the relationship among precipitation, soil water and groundwater, from June to September in 2004, stable isotopes (deuterium and oxygen-18) in precipitation and soil waters at the depths of 10, 20, 30, 50, 70, 90, and 110 cm were analyzed at two sites covered by black locust (Robinia Pseudoacia L.) (Site A) and grass predominated by Themeda triandra (T. japonica (Willd.) Tanaka) and Bothriochloa ischaemum (B. ischaemum (L.) Keng) (Site B) in an experimental catchment at Taihang Mt., North China, respectively. The δ18O of precipitation in daily rain events shows large variations (−13.3 to −4.3‰) with a mean of 8.1‰. The δ18O and δ D of soil waters along profiles in two sites suggest that the influence of canopy cover was just up to 10 cm in top soil water. The soil water moved over the zero flux plane at 70 cm in-depth is expected to escape the evaporative effect at the end of September in both sites. The results show that the stable isotope, instead of tritium as tradition, can be used to trace the soil water behaviors based on the movement of isotopic peak along the vertical profiles in this semi-arid and semi-humid mountainous region. The infiltration depths of soil water in Taihang Mt. are 12 and 10 mm/day from June to September in 2004 in Site A and Site B, respectively. Tracing by stable isotope, recharge fluxes of soil water to local groundwater are of 3.8 and 3.2 mm/day in Site A and Site B, respectively. The results provide desirable information for assessment of local groundwater resources.

Effects of derivatization on solar-induced decomposition of polycyclic aromatic hydrocarbons in aqueous media

The solar-induced decomposition of 10 polycyclic aromatic hydrocarbons (PAHs) was observed in aqueous media. All 10 PAHs observed were half-decomposed within 120 min. Among anthracene derivatives, the decomposition rates were: anthracene = 1-methylanthracene < 2-methylanthracene < 9-methylanthracene < 9,10-dimethylanthracene ∼ 2-aminoanthracene. The addition of commercial humic acid had no effect on the decomposition rates of these PAHs. Deuterium water also hastened the decomposition of PAH. The products obtained by the solar radiation of PAH after extraction to DCM were mainly ketone and hydroxyl derivatives. To explaine these results, reactivities and electron charges at the constituent carbon atoms in each anthracene derivative were examined by an ab initio molecular orbital calculation method.

Spectroscopic investigation of laser–water interaction beyond the breakdown threshold energy

The interaction between ns-laser pulse at 532 nm and water, or heavy water (deuterium dioxide), has been studied by Stimulated Raman Scattering (SRS) and optical emission spectroscopy. Both the photolysis and breakdown processes have been considered. When the photolysis is the main process, structural change in water occurs as a consequence of electron and proton hydration. The rearrangement of the water structure and the subsequent photon absorption by free electrons raising the breakdown threshold occur. Moreover, charge separation in bulk water, under laser induced electromagnetic field, leads to a notable enhancement of the SRS signal. On the other hand, for a high laser pulse energy density, electrons gain energy enough to escape from the hydrating water structure, generating electron impact dominated plasma.

Hydration Structure around the Carbonyl Group of an Urea Molecule in Concentrated Aqueous Solutions Studied by Neutron Diffraction with 12C/13C Isotopic Substitution

Abstract Neutron diffraction measurements were carried out at 25 °C on aqueous 15 mol % urea heavy water solutions, [(ND2)2*C=O]0.15(D2O)0.85, in which the 12C/13C isotopic composition of the carbonyl-carbon atom was changed. The hydration structure around the carbonyl-carbon atom was derived from the least-squares fitting analysis of the observed first-order difference function, ΔC(Q). From the analysis, 4.3(3) water molecules are hydrogen-bonded to the carbonyl-oxygen atom with the intermolecular C···DW1 (DW1: water deuterium atom) distance of 2.46(3) Å. The average angle, ∠C···DW1–OW (OW: water oxygen atom), was determined to be 124(5)°.

Secondary isotope effects in liquid chromatography behaviour of 2H and 3H labelled solutes and solvents

The separation of solutes that differ only in the extent of isotopic substitution of their hydrogen atoms, using either mixtures of isotopically non-modified or perdeuterated solvents as mobile phases, is described. The occurrence of a secondary isotope effect is demonstrated in reversed-phase liquid chromatography, which is independent of the nature of the stationary phase (different octadecyl-bonded silicas, an embedded alkylamide-bonded silica, as well as one polymeric stationary phase were tested), and the water content and the nature of organic modifier of the mobile phase. The separation of 24 structurally different isotopologue pairs (apolar compounds and polar compounds with exchangeable or non-exchangeable hydrogen atoms) is examined using reversed-phase liquid chromatography. It is found that the greater the number of isotopically substituted hydrogen atoms in a given organic solute, the better is the separation of a particular isotopologue pair. The single secondary isotope effect is shown to be dependent on the number of isotopic substitutions. The greater the number of these substitutions, the smaller is the single isotope effect. The single secondary isotope effect is higher for aromatic hydrocarbons than for aliphatic hydrocarbons. A secondary isotope effect is also observed in chiral chromatography and normal-phase liquid chromatography, as well as on changing the nature of the substituting isotope, i.e.: tritium instead of deuterium. Thus, we have demonstrated that the total secondary isotopic effect for hydrogen/tritium is higher than for hydrogen/deuterium. This isotope effect involves only the consequences of changes in interactions due to nuclear motions. Overall this study confirms the predominance of hydrophobic effects in retention processes in reversed-phase liquid chromatography. In reversed-phase liquid chromatography, a secondary isotope effect related to mobile phase composition is also observed. The behaviour of deuterium oxide and water in mobile phases of the same composition (%, w/w) is compared. Independent of the nature of the organic modifier (methanol, acetonitrile or ethanol), the effect of replacing H 2O with 2H 2O in the mobile phase, is an increase in the retention factors and an improvement in the chromatographic resolution of isotopologue pairs. This increase in the resolution is not accompanied by a change in the chromatographic selectivity. The measurement of liquid–liquid extraction coefficients proves that the effect is mainly due to the modification of the phase ratio. In general the effect of 2H-labelled solvents ( 2H 2O and C 2H 3CN) as mobile phase components, compared to their isotopically non-modified isomers, can be rationalized on the basis of their lower polarisabilities. Overall the use of perdeuterated rather than isotopically non-modified solvents as mobile phase components leads to the most efficient separation systems.

The hydrogen and oxygen isotopic composition of precipitation, evaporated mine water, and river water in Montana, USA

Summary The isotopic composition of 42 samples of rain and snow collected in 2004 were used to construct a local meteoric water line (LMWL) for Butte, Montana. The derived equation (δD = 7.31δ 18 O − 7.5, r 2 = 0.987), represents one of the first published LMWLs based on direct precipitation for any location in the northern Rocky Mountains. Samples of underground and surface mine waters in Butte, including the Berkeley pit-lake and a nearby tailings pond, define a linear trend with a much lower slope and intercept than the LMWL (δD = 5.00δ 18 O − 49.5, r 2 = 0.991), consistent with non-equilibrium evaporation at an average relative humidity of roughly 65%. Detailed evaporation calculations are presented which indicate that the shallow Berkeley pit-lake was approximately 25% evaporated in October, 2003, whereas the surface of the tailings pond was at least 50% evaporated. The intersection of the LMWL and mine water evaporation trend was used to calculate the average composition of recharge water to the flooded mine complex (δD = −139‰, δ 18 O = −18.0‰). These values are considerably lighter than the weighted total of precipitation for the 2004 calendar year (δD = −118‰, δ 18 O = −15.3‰), which is partly explained by the unusually low snowfall that Montana experienced in 2004. Based on this study, the LMWL recently proposed by Kendall and Coplen (2001) [Kendall, C., Coplen, T.B., 2001. Distribution of oxygen-18 and deuterium in river waters across the United States, Hydrological Processes 15, 1363–1393] from regression of isotopic data from a number of Montana rivers is more accurately interpreted as an evaporation line. Isotopic trends based on river data should be treated with caution, particularly in a semi-arid region such as Montana where rivers are often influenced by dams and irrigation withdrawals.

High‐Pressure Neutron Diffraction Study of Superhydrated Natrolite.

AbstractFor Abstract see ChemInform Abstract in Full Text.

LOCATING TRITIUM SOURCES IN A RESEARCH REACTOR BUILDING

Despite renovation of the D2O facility, tritium concentrations in the condensates of reactor room air showed tens of Bq mL before venting resumption on July 1997. This suggested the presence of tritium sources in the research reactor-containment building. An investigation was therefore initiated to locate the source and determine the distribution of tritium in the containment building. Air monitoring in the working area using a dish of water placed in the building suggested that the source of tritium was near the reactor core. Monitoring exhaust air from the two facilities (a cold neutron source and a D(2)O tank) showed high specific activity on the order of 10 Bq mL(-1), suggesting the presence of tritium in condensates near the reactor core. The major concern was whether the leakage of liquid deuterium (4 L) and heavy water (2 x 10(3) L) used as a moderator had occurred. The concentration of tritium in condensates has not increased over the past few years in either the exhaust line or working area, and the deuterium itself has not been found in the surrounding environment. The concentration of tritium measured using an ionization chamber after Ar decay was dependent on the thermal output of the research reactor, indicating that the tritium was produced by the irradiation process within shielding/moderator materials or cover gas with neutrons.