WorldWideScience

Sample records for chemical isotope exchange

  1. Isotope separation by chemical exchange

    International Nuclear Information System (INIS)

    Nitrogen-15 and oxygen-18 enrichment by chemical exchange in the (NO/NO2) - (H2O/HNO3) system, using a laboratory-scale experimental plant and a cascade for production of two isotopes, is presented. The results obtained from the laboratory-scale plant indicate that optimal flow rate for 15N separation is 1.55 - 1.86 ml/cm2 · min at 8 - 10 M/l nitric acid and 63.4 mg at. oxygen/cm2 · min for 18O separation at 5.8 M/l nitric acid. The height equivalent to a theoretical plate (HETP) of 4.11 - 4.56 cm is in good agreement with other published data for 15N separation using exchange column with Helipak packing. The HETP of 7.74 - 10.58 cm for 18O separation is greater by 20 - 30 % than those presented by Saxena and Taylor for 'Helipak' column packing, but in good agreement with the HRTP published by Borisov et al. on 'Levina' column packing. The HETP obtained for 15N separation by the production plant is in the range 11.5 - 13.8 cm at a flow rate of 2.2 ml HNO3(10M/l)/cm2 · min for the first column and 4.4 - 4.7 cm at a flow rate of 1.66 ml HNO3(10M/l)/cm2 · min for the second column. The optimal flow rate for 18O separation by the production plant is about 63 mg at. oxygen/cm2 · min (1.01 ml HNO3/cm2 · min). Enrichment of 13C and 18O by chemical exchange of carbon dioxide with its monoethanolamine carbamate in methanol and di-n-butylamine carbamate in triethylamine has also been studied, and optimum operating conditions for the separation of 13C in a packed column was determined. The HETP obtained for the 13C in a packed column was determined. The HETP obtained for the 13C separation column is 3.62 - 8.26 cm at a flow rate of 1.1 - 4.0 mmol carbamate/cm2 · min using the same column packing as for 15N and 18O separation, that is, stainless steel triangular wire springs (2.3 x 2.3 x 0.2 mm). (author)

  2. Stable Isotope Enrichment by Thermal Diffusion, Chemical Exchange, and Distillation

    Energy Technology Data Exchange (ETDEWEB)

    Schwind, Dr. Roger A.; Rutherford, Dr. William M.

    1973-03-01

    Applications of stable isotopes in medicine are becoming more widespread. This has resulted from the increased availability and reduced cost of these isotopes and the improved reliability and sensitivity of detection techniques such as carbon-13 nuclear magnetic resonance. Isotopes are used in compounds labeled with either the stable isotope itself, such as carbon-13 and oxygen-18, or with the radioactive isotope that can be produced by irradiating the stable isotope, such as the irradiation of xenon-124 to produce iodine-125. As the demand for stable isotopes increases, larger scale production facilities will be justifiable. The increased size of production facilities should result in yet lower unit selling prices. A large number of methods has been suggested for the separation of stable isotopes. This paper concerns itself with four methods which have proven extremely useful for the separation of the isotopes of low and medium atomic weight elements. The four processes discussed are gas phase thermal diffusion, liquid phase thermal diffusion, chemical exchange, and distillation.

  3. Modeling and analysis of uranium isotope enrichment by chemical exchange

    International Nuclear Information System (INIS)

    A theoretical study of uranium isotopes separation by chemical exchange, starting with an accurate mathematical model, is presented. The experimental data used in this study were obtained by reverse break-through operation and the numerical algorithm, developed for simulation in a previous study, was adapted to be suitable for this kind of processes. The model parameters were identified from experimental data and simulations were carried out for different experimental conditions. (author)

  4. Design of Uranium Isotope Separation Plant by Chemical Exchange

    International Nuclear Information System (INIS)

    The methodology to design a solvent extraction plant for uranium isotope separation by chemical exchange is outlined. This process involves the calculator of the number of stages,the capacity of the plant,the flow rates,and reflux ration in banks of mixer settlers or pulse column used in such a plant. The feed is introduced at the middle of the plant,and the product is withdrawn at one end and the tailings at another. The redox reaction system selected is U(IV)-U(VI) and the equilibrium data of the 40% tri-n-octylamine (TOA) in benzene as the organic phase and 4 M HCI as the aqueous phase are used for the design of the real plant. The resulting analysis for the uranium isotope separation shows that more than 4000 number of stages are required and the reflux ratio is around 700 to produce only 1m3 of product containing 3% of U235 and 0,3% of U235 in the tailings. It is also known that the larger the isotope separation constant the smaller the number of stages needed. The method of design can be used for other systems where the isotope separation constants are more favorable

  5. Isotope separation by chemical exchange process: Final technical report

    International Nuclear Information System (INIS)

    The feasibility of a chemical exchange method for the separation of the isotopes of europium was demonstrated in the system EuCl2-EuCl3. The single stage separation factor, α, in this system is 1.001 or 1.0005 per mass unit. This value of α is comparable to the separation factors reported for the U4+ - U6 and U3+ - Y4+ systems. The separation of the ionic species was done by precipitation of the Eu2+ ions or by extraction of the Eu3+ ions with HDEHP. Conceptual schemes were developed for a countercurrent reflux cascades consisting of solvent extraction contractors. A regenerative electrocel, combining simultaneous europium reduction, europium oxidation with energy generation, and europium stripping from the organic phase is described. 32 refs., 22 figs., 6 tabs

  6. Chemical exchange equilibria in isotope separation. Part I : Evaluation of separation factors

    International Nuclear Information System (INIS)

    The theory of chemical exchange equilibria as applied to the isotope separation processes and the isotope effects on equilibrium constants of different exchange reactions has come a long way since its inception by Urey and Rittenberg. An attempt has been made to bring relevant information together and present a unified approach to isotopic chemical exchange equilibrium constant evaluation and its implications to separation processes. (auth.)

  7. Early history of chemical exchange isotope enrichment and lessons we learn

    International Nuclear Information System (INIS)

    The chemical exchange isotope enrichment process has an advantage over other isotope separation methods in that it involves two chemicals rather than one and, consequently, relatively large separation factors can be obtained. However, the chemical exchange method requires a chemical conversion of the substance enriched in the target isotope into the second substance. The idiosyncrasies of the isotope separation process by this method are pointed out using McCabe-Thiele diagram and, from them, the difficulties involved in the chemical exchange methods are itemized. Examples of the points being made are taken from the pioneering works of this field carried out by Harold C. Urey, his contemporaries, the students and the students' students. Lessons we learn from these works are discussed. (author)

  8. Separation of selected stable isotopes by liquid-phase thermal diffusion and by chemical exchange

    International Nuclear Information System (INIS)

    Useful applications of enriched stable nuclides are unduly restricted by high cost and limited availability. Recent research on liquid phase thermal diffusion (LTD) has resulted in practical processes for separating 34S, 35Cl, and 37Cl in significant quantities (100 to 500 g/yr) at costs much lower than those associated with the electromagnetic (Calutron) process. The separation of the isotopes of bromine by LTD is now in progress and 79Br is being produced in relatively simple equivalent at a rate on the order of 0.5 g/day. The results of recent measurements show that the isotopes of Zn can be separated by LTD of zinc alkyls. The isotopes of calcium can be separated by LTD and by chemical exchange. The LTD process is based on the use of aqueous Ca(NO3)2 as a working fluid. The chemical exchange method involves isotopically selective exchange between an aqueous phase containing a calcium salt and an organic phase containing calcium in the form of a complex with a macrocyclic ligand. The LTD method is suitable for high enrichments at low through-puts; whereas, the chemical exchange techniques is appropriate for lower enrichments at much higher production rates. Current research is directed toward reducing these concepts to practical processes

  9. Separation of boron isotopes at chemical isotopic exchange between, boron trifluoride and its complex with anisole in multitube mass-exchange column

    International Nuclear Information System (INIS)

    The results are given on continuous counterflow two-phase process of boron isotopes 10B and 11B separation at chemical isotopic exchange between gaseous BF3 and its liquid complex with anisole, the process is realized in the module of three packed columns with parallel operation; each of the columns in its bottom part is connected with the others by the common unit of flow reversal (desorber), has the diameter of 78 mm, height of 46.5 m, and is filled with wire spiral-prismatic pack with 3.5·3.5·0.2 mm element

  10. Separation and sampling technique of light element isotopes by chemical exchange process

    International Nuclear Information System (INIS)

    Lithium and boron isotope separation technique were studied. Granulation of lithium isotope separation agent was carried out by cure covering in solution. Separation of lithium isotope was stepped up by ammonium carbonate used as elusion agent. Styrene and ester resin derived three kinds of agents such as 2-amino-1, 3-propanediol (1, 3-PD), 2-amino-2-methyl-1, 3-propanediol (Me-1,3-PD) and tris(2-hydroxyethyl)amine (Tris) were used as absorbent.The ester resin with Tris showed larger amount of adsorption (1.4 mmol/g) than other resins. However, all resins with agent indicated more large adsorption volume of boron than the objective value (0.5 mmol/g). Large isotope shift was shown by the unsymmetrical vibration mode of lithium ion on the basis of quantum chemical calculation of isotope effect on dehydration of hydrated lithium ion. (S.Y.)

  11. 2,4-Difluoro anisole. A promising complexing agent for boron isotopes separation by chemical exchange reaction and distillation

    International Nuclear Information System (INIS)

    Although methods of boron isotopes separation were intensively pursued about 60 years, the chemical exchange distillation is the only method that has been applied in industrial scale production of 10B. The present anisole BF3 system suffers from the drawbacks like high melting point, relatively low separation coefficient and instability under reaction conditions, which demand a continuous search for more effective and efficient donors for boron isotope separation. A series of fluoro-substituted anisole derivatives were screened in this paper, among which 2,4-difluoro anisole exhibited good properties compared with anisole. Studies on the boron trifluoride and 2,4-difluoro anisole adduct, its thermodynamic and physical properties related to large-scale isotopic separation is reported. The results showed that 2,4-difluoro anisole is better than anisole in separation coefficient, freezing point and stability under pyrolysis conditions, which suggest a further detailed investigations on boron trifluoride and 2,4-difluoro anisole adduct. (author)

  12. Separation of stable isotopes of alkali and alkaline earth metals in chemical exchange systems with crown ethers

    International Nuclear Information System (INIS)

    Chemical isotope exchange in two-phase water - organic systems Men+ (water) - MeLn+ (org), where Me = Li, Ca, K, Mg; L = crown ethers with 5 to 6 oxygen atoms in macrocyclic ring; org = CHCl3, CH2Cl2 has been studied. The process of isotope separation has been realized by extraction chromatography. The chromatographic column contained a fixed aqueous phase. The organic solution of metal complex with crown ether was eluted through the column. On contact with the fixed aqueous phase in the course of chromatography, metal salt reextraction occurred and interphase isotope exchange between aqueous and organic phases resulted. Isotope separation factors in these systems were in the range of: 1.0032 - 1.020 (6Li/7Li), 1.0016 - 1.0038 (40Ca/44Ca), 1.0007 - 1.0011 (39K/41K), 1.0014 - 1.0044 (24Mg/26Mg). The theoretical model has been proposed to interpret the high separation factors in crown ether extraction systems. According to this model, the potential in such systems has a very flat bottom. This type of potential results in weakening the force field and decreasing of β-factor (i.e., (s/s')f) in spite of comparatively high energy of complexation. This model can interpret both high separation factors and their strong dependence on the type of crown ether. (author)

  13. Physico-Chemical Study of the Separation of Calcium Isotopes by Chemical Exchange Between Amalgam and Salt Solutions

    International Nuclear Information System (INIS)

    In a preliminary study of the isotopic exchange between Ca amalgam and aqueous or organic solutions of Ca salts, the main parameters governing the feasibility of a separation process based on these systems such as separation factor, exchange kinetics, rate of decomposition of the amalgam were investigated. The separation factor between 40Ca and 46Ca was found to be of the order of 1.02. The rate of the exchange reaction is rather low for aqueous solutions, extremely low for organic solutions. The amalgam seems not to be attacked by dimethyl-formamide solutions; but it is rapidly decomposed by aqueous solutions of Ca halides. This decomposition is slow in the case of aqueous solutions of calcium formate and still slower for Ca(OH)2; however, except in particular conditions, the observed rate is often much higher, owing to interfering reactions between amalgam and water vapor contained in H2 bubbles. (authors)

  14. Hydrogen isotope exchange reactions

    International Nuclear Information System (INIS)

    The two most widely used methods for following hydrogen isotope exchange reactions, namely dedeuteriation and detritiation, involve in the first place the synthesis of an appropriately labelled compound. Rates of dedeuteriation are usually followed by measuring changes in the 1H n.m.r. spectrum of the substrate (examples are given); the method not only gives the rate but also the site(s) of exchange. It is limited to rather slow reactions and is not as accurate as some of the other methods. The development of deuterium n.m.r. spectroscopy means that changes in the 2H n.m.r. spectrum can also be used to measure rates of dedeuteriation. The development of liquid scintillation counting greatly eased the problem of how to detect weak β emitters; the attractions of tritium as a tracer were thereby much enhanced. Nowadays the study of rates of detritiation constitutes one of the most versatile and accurate methods of following hydrogen isotope exchange. Examples of the technique are given. (U.K.)

  15. No oxygen isotope exchange between water and APS-sulfate at surface temperature: Evidence from quantum chemical modeling and triple-oxygen isotope experiments

    Science.gov (United States)

    Kohl, Issaku E.; Asatryan, Rubik; Bao, Huiming

    2012-10-01

    In both laboratory experiments and natural environments where microbial dissimilatory sulfate reduction (MDSR) occurs in a closed system, the δ34S ((34S/32S)sample/(34S/32S)standard - 1) for dissolved SO42- has been found to follow a typical Rayleigh-Distillation path. In contrast, the corresponding δ18O ((18O/16O)sample/(18O/16O)standard) - 1) is seen to plateau with an apparent enrichment of between 23‰ and 29‰ relative to that of ambient water under surface conditions. This apparent steady-state in the observed difference between δ18O and δ18OO can be attributed to any of these three steps: (1) the formation of adenosine-5'-phosphosulfate (APS) from ATP and SO42-, (2) oxygen exchange between sulfite (or other downstream sulfoxy-anions) and water later in the MDSR reaction chain and its back reaction to APS and sulfate, and (3) the re-oxidation of produced H2S or precursor sulfoxy-anions to sulfate in environments containing Fe(III) or O2. This study examines the first step as a potential pathway for water oxygen incorporation into sulfate. We examined the structures and process of APS formation using B3LYP/6-31G(d,p) hybrid density functional theory, implemented in the Gaussian-03 program suite, to predict the potential for oxygen exchange. We conducted a set of in vitro, enzyme-catalyzed, APS formation experiments (with no further reduction to sulfite) to determine the degree of oxygen isotope exchange between the APS-sulfate and water. Triple-oxygen-isotope labeled water was used in the reactor solutions to monitor oxygen isotope exchange between water and APS sulfate. The formation and hydrolysis of APS were identified as potential steps for oxygen exchange with water to occur. Quantum chemical modeling indicates that the combination of sulfate with ATP has effects on bond strength and symmetry of the sulfate. However, these small effects impart little influence on the integrity of the SO42- tetrahedron due to the high activation energy required for

  16. Research on separation and extraction technology of the light element isotopes by the chemical exchange process

    International Nuclear Information System (INIS)

    It was clarified that the separation coefficient became 1.036, and succeeded in the development of the new, efficient lithium separator (Sodium Super-Ionic Conductor: NASICON) which is the elution liquid in the acid processed phosphate system for the lithium isotope separation technology. NASICON can be used in the column for the isotope separation, repeatedly if the nitric acid is used for the elution liquid and the hydroxide lithium or the acetic acid lithium solution as an adsorption solution of the lithium. Furthermore, the separation coefficient of 1.029 was obtained using the glucamine resin of the ester system for the boron isotope separation technology. (H. Katsuta)

  17. Chemical exchange program analysis.

    Energy Technology Data Exchange (ETDEWEB)

    Waffelaert, Pascale

    2007-09-01

    As part of its EMS, Sandia performs an annual environmental aspects/impacts analysis. The purpose of this analysis is to identify the environmental aspects associated with Sandia's activities, products, and services and the potential environmental impacts associated with those aspects. Division and environmental programs established objectives and targets based on the environmental aspects associated with their operations. In 2007 the most significant aspect identified was Hazardous Materials (Use and Storage). The objective for Hazardous Materials (Use and Storage) was to improve chemical handling, storage, and on-site movement of hazardous materials. One of the targets supporting this objective was to develop an effective chemical exchange program, making a business case for it in FY07, and fully implementing a comprehensive chemical exchange program in FY08. A Chemical Exchange Program (CEP) team was formed to implement this target. The team consists of representatives from the Chemical Information System (CIS), Pollution Prevention (P2), the HWMF, Procurement and the Environmental Management System (EMS). The CEP Team performed benchmarking and conducted a life-cycle analysis of the current management of chemicals at SNL/NM and compared it to Chemical Exchange alternatives. Those alternatives are as follows: (1) Revive the 'Virtual' Chemical Exchange Program; (2) Re-implement a 'Physical' Chemical Exchange Program using a Chemical Information System; and (3) Transition to a Chemical Management Services System. The analysis and benchmarking study shows that the present management of chemicals at SNL/NM is significantly disjointed and a life-cycle or 'Cradle-to-Grave' approach to chemical management is needed. This approach must consider the purchasing and maintenance costs as well as the cost of ultimate disposal of the chemicals and materials. A chemical exchange is needed as a mechanism to re-apply chemicals on site. This

  18. Isotope exchange reactions in hydrogen mixtures

    International Nuclear Information System (INIS)

    The rates of isotopic exchange for the excited states of muonic hydrogen are calculated as functions of collision energy. Ground state population q1s for different collision energies, target densities and isotope concentrations is obtained. It is shown that for principal quantum numbers n > 5 the isotopic exchange still considerably influences the value of q1s. (author)

  19. Contrasting styles of oxygen isotope exchange

    OpenAIRE

    Valley, J. W.; Eiler, J. M.; Kohn, M.J.; Spicuzza, M.J; Baumgartner, L. P.; Elsenheimer, D.; Graham, C. M.

    1994-01-01

    Exchange of oxygen isotopes encrypts a sensitive record of the thermal evolution and fluid-exchange history of igneous and metamorphic rocks. Deciphering this record requires measurement of isotope ratios at an appropriate scale together with understanding of the processes involved: diffusion, recrystallization, new mineral growth, and fluid flow.

  20. Chlorine isotope effects in ion exchange reactions with a strongly basic anion exchanger

    International Nuclear Information System (INIS)

    As can be shown by the results of this study, the chemical preenrichment of the stable chlorine isotopes in inorganic ion-exchange equilibria is feasible in principle. This process should be performed in chromotographic separation columns at temperatures as low as possible. Because of the dependence of the isotopic effect on the elution medium concentration a very low concentration is desirable for the chemical enrichment process. Smaller elution concentrations however result in increasingly longer elution times. (HK)

  1. Study of isotopic exchange reactors (1961)

    International Nuclear Information System (INIS)

    A study is made of the general case of the theory of first-order isotopic chemical exchange between a gaseous and a liquid phase in a reactor, starting from fundamental reaction kinetics data, and without making any limiting hypothesis concerning the value of the separation factor. The cases of counter-current reactors and of co-current reactors are considered successively. The general deuterium conservation equation requires the definition of the quotient of the reactor; the performances of this reactor are characterised by its overall efficiency. The idea of the ratio is introduced because it represents a convenient intermediary in the calculations. The search for an additive value for reactors in series leads logically to the defining of an exchange capacity, and a total efficiency, or number of theoretical reactors. This method of expressing the performances of a reactor is more general than the efficiency due to Murphee which only has a physical significance in the particular case of homogeneous liquid reactors. The relationships between these various quantities are established, and the representation due to Mc Cabe and Thiele is generalized. The reactor performances are linked to the first - order reaction kinetics by the transfer number. The relationships are given for a certain number of concrete cases. Finally the application of these calculations is given, together with the approximations necessary in the case where, because of the presence of several components in each phase, the exchange reaction no longer obeys a single kinetic law. (authors)

  2. Tritium isotopic exchange in air detritiation dryers

    International Nuclear Information System (INIS)

    Isotopic exchange between tritiated and non-tritiated water species in a molecular sieve bed has been demonstrated. At high humidities (+6 degrees Celsius dew point) the rate of tritium isotopic exchange in a 2.4 L molecular sieve bed has been demonstrated to be at least 50% of published exchange rates. In an industrial-sized air detritiation dryer, utilizing the pretreatment technique of H2O steam washing to elute the residual tritium, a DF of 12 600 has been demonstrated when operating at an inlet vapor tritium concentration of 14 Ci/kg and at inlet and outlet dew points of 4.8 and -54 degrees Celsius, respectively. In the NPD dryer bed studied, which was not optimally designed for full benefit from isotopic exchange, at least one order of magnitude in additional detritiation is attributed to isotopic exchange in the unsaturated zone. The technique of eluting the residual tritium from an industrial sized bed by H2O washing at high temperature, high humidity and low bed loading has been demonstrated to be a fast and effective way of removing tritium from a molecular sieve bed during regeneration. The isotopic exchange model accurately predicted the exchange between tritiated and non-tritiated water species in a molecular sieve bed where there is no net adsorption or desorption. The model's prediction of the tritium breakthrough trend observed in the NPD tests was poor; however, a forced fit can be achieved if the exchange rates in the MTZ and the unsaturated zone are manipulated. More experiments are needed to determine the relative rates of tritium exchange in the saturated, mass transfer, and unsaturated zones of a dryer bed

  3. Unbiased isotope equilibrium factors from partial isotope exchange experiments in 3-exchange site systems

    Science.gov (United States)

    Agrinier, Pierre; Javoy, Marc

    2016-09-01

    Two methods are available in order to evaluate the equilibrium isotope fractionation factors between exchange sites or phases from partial isotope exchange experiments. The first one developed by Northrop and Clayton (1966) is designed for isotope exchanges between two exchange sites (hereafter, the N&C method), the second one from Zheng et al. (1994) is a refinement of the first one to account for a third isotope exchanging site (hereafter, the Z method). In this paper, we use a simple model of isotope kinetic exchange for a 3-exchange site system (such as hydroxysilicates where oxygen occurs as OH and non-OH groups like in muscovite, chlorite, serpentine, or water or calcite) to explore the behavior of the N&C and Z methods. We show that these two methods lead to significant biases that cannot be detected with the usual graphical tests proposed by the authors. Our model shows that biases originate because isotopes are fractionated between all these exchanging sites. Actually, we point out that the variable mobility (or exchangeability) of isotopes in and between the exchange sites only controls the amplitude of the bias, but is not essential to the production of this bias as previously suggested. Setting a priori two of the three exchange sites at isotopic equilibrium remove the bias and thus is required for future partial exchange experiments to produce accurate and unbiased extrapolated equilibrium fractionation factors. Our modeling applied to published partial oxygen isotope exchange experiments for 3-exchange site systems (the muscovite-calcite (Chacko et al., 1996), the chlorite-water (Cole and Ripley, 1998) and the serpentine-water (Saccocia et al., 2009)) shows that the extrapolated equilibrium fractionation factors (reported as 1000 ln(α)) using either the N&C or the Z methods lead to bias that may reach several δ per mil in a few cases. These problematic cases, may be because experiments were conducted at low temperature and did not reach high

  4. Physico-Chemical Study of the Separation of Calcium Isotopes by Chemical Exchange Between Amalgam and Salt Solutions; Etude physico-chimique de la separation des isotopes du calcium par echange chimique entre amalgame et solution saline

    Energy Technology Data Exchange (ETDEWEB)

    Duie, P.; Dirian, G. [Commissariat a l' Energie Atomique. Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

    1962-07-01

    In a preliminary study of the isotopic exchange between Ca amalgam and aqueous or organic solutions of Ca salts, the main parameters governing the feasibility of a separation process based on these systems such as separation factor, exchange kinetics, rate of decomposition of the amalgam were investigated. The separation factor between {sup 40}Ca and {sup 46}Ca was found to be of the order of 1.02. The rate of the exchange reaction is rather low for aqueous solutions, extremely low for organic solutions. The amalgam seems not to be attacked by dimethyl-formamide solutions; but it is rapidly decomposed by aqueous solutions of Ca halides. This decomposition is slow in the case of aqueous solutions of calcium formate and still slower for Ca(OH){sub 2}; however, except in particular conditions, the observed rate is often much higher, owing to interfering reactions between amalgam and water vapor contained in H{sub 2} bubbles. (authors) [French] On a fait une etude preliminaire, pour des systemes amalgame de calcium - solution aqueuse ou organique de sels de calcium, des principaux parametres pouvant intervenir dans l'application d'un procede d'echange a l'enrichissement isotopique du calcium: facteur de separation, cinetique de l'echange, cinetique de la decomposition de l'amalgame. Les facteurs de separation {sup 40}Ca-{sup 46}Ca sont de l'ordre de 1,02. L'echange est assez lent pour les solutions aqueuses, extremement lent pour les solutions organiques. La decomposition de l'amalgame est pratiquement inexistante avec les solutions dans le dimethyl- formamide, appreciable pour les solutions alcooliques, rapide pour les solutions aqueuses d'halogenures; elle est normalement lente pour les solutions aqueuses de formiate et surtout de chaux, mais la decomposition est en general acceleree par une reaction parasite entre l'amalgame et l'eau a l'etat vapeur, reaction que l'on n'evite dans des

  5. Intermediates in Isotopic Exchange Reactions Involving Diborane

    International Nuclear Information System (INIS)

    By conventional mass spectrometric analysis, the self-exchange reaction of diborane was studied by using boron and hydrogen isotopes as tracers. The ratio of deuterium to boron exchange was found to be 2.8. This suggests that the reaction is not completely proceeding by exchange of BH3's as an entity, and that the mechanism is more complicated than simply a stripping reaction between diborane and a borane. It was therefore decided to attempt to get some knowledge of the intermediates that are present in diborane dissociation since they may shed light on the mechanism of the exchange. Using a specially constructed mass spectrometer of high sensitivity coupled with a flow reactor, it was possible to make a direct detection of the intermediate involved in the diborane equilibria. The intermediates BH3 and BH2 were found to be present and their ionization potentials were measured. In addition, a small amount of B3Hn was observed but the value of n could not be determined because of the weak peaks obtained. An attempt is made to interpret the self-exchange reaction of diborane in terms of these intermediates. The results suggest that diborane is in rapid equilibrium with borane (BH3). In addition, apparently diborane can also dissociate in BH2 which was about twice as abundant as BH3. The B3Hn intermediate that was observed is believed to arise from the reaction. BH3 + B2H6 -> B3H9. In applying this information to the isotopic self-exchange in diborane, it appears that the exchange cannot be going by a stripping mechanism such as BD3 + BH3 - BH3 - BD3 - BH3 + BH3, since the deuterium-to-boron isotopic ratio then should be 3. Another possible mechanism of exchange is BD3 + B2H6 ⇌ B3D3H6; the B3 complex can be pictured as a symmetrical one. If the bonds were all exactly equivalent the D/ 10B ratio would statistically become 3; however, some isotope effect may be present in the fragmentation of the complex and the ratio could deviate from 3. Another possible way in which

  6. Experimental catalytic isotopic exchange column control

    International Nuclear Information System (INIS)

    Full text: In this paper we present a method for monitoring and control of the experimental catalytic isotopic exchange column which is part of ETRF (experimental tritium removal facility) of the ICIT Rm. Valcea. The initial data acquisition system based on analogue instruments is now upgraded to a fully digital system. Therefore we chose to use Compact Field Point which is a programmable automation controller (PAC) and LabVIEW software. To operate the catalytic isotopic exchange column there are some control loops that need to be operated simultaneously, namely: the heavy water column feed temperature and flow rate; the hydrogen gas column feed temperature; the flow rate and pressure at the top of the column; the water vapor flow rate; the hydrogen gas temperature at the condenser output. The human machine interface (HMI) realized with LabVIEW software is very friendly. The use of the PAC graphics interface makes isotopic exchange process operation easier for operators and researchers. The HMI has the functions to provide visualization of process parameters, to enable interaction with the process and also to provide alarms and event notification to operators about any abnormal situation in the plant. To interact with the process, detailed displays which contain specific control functions to operate the column, can be used. Usually, the faceplate display shows the controlled process variable and the output of the control loop. Furthermore, the set point and the operating mode of the control loop can be changed. Additionally, detailed information is available related to the parameters of PID controller and the different alarms that can be authorized in this control loop with its corresponding values of activation. (authors)

  7. Isotope effect on exchange in antiferromagnetic insulators

    International Nuclear Information System (INIS)

    Motivated by the recent proposal of a nonvanishing isotope effect α on the Heisenberg exchange integral J in La2CuO4, we have constructed a spin-phonon Hamiltonian as an effective model for strongly interacting electrons at half filling, coupling to local anharmonic phonons. We have studied the model in the limit when the typical phonon energy is much larger than J. Applying our results to La2CuO4 and using realistic parameters, we can explain the order of magnitude of α. (author). 18 refs

  8. Isotopic anomalies - Chemical memory of Galactic evolution

    Science.gov (United States)

    Clayton, Donald D.

    1988-01-01

    New mechanisms for the chemical memory of isotopic anomalies are proposed which are based on the temporal change during the chemical evolution of the Galaxy of the isotopic composition of the mean ejecta from stars. Because of the differing temporal evolution of primary and secondary products of nucleosynthesis, the isotopic composition of the bulk interstellar medium changes approximately linearly with time, and thus any dust component having an age different from that of average dust will be isotopically anomalous. Special attention is given to C, O, Mg, Si, and isotopically heavy average-stellar condensates of SiC.

  9. Progressive extraction method applied to isotopic exchange of carbon-14

    International Nuclear Information System (INIS)

    Isotopic exchange in natural settings is essentially an irreversible process, so that it progresses continuously until there is complete isotopic equilibrium. In soils, this process involves interaction between isotopes in the liquid and solid phases, and complete isotopic equilibrium may take a very long time. Measurements after partial isotopic exchange have been used to characterize the labile fraction of elements in soils. We describe a method to characterize the extent of isotopic exchange, with application here to incorporation of inorganic carbon-14 (14C) into mineral carbonates and organic matter in soils. The procedure uses a continuous addition of extractant, acid, or H2O2in the examples presented here, coupled with sequential sampling. The method has been applied to demonstrate the degree of isotopic exchange in soil. The same strategy could be applied to many other elements, including plant nutrients. (author)

  10. Isotopes in chemical analysis for water management

    International Nuclear Information System (INIS)

    Surface or underground water circulations and interactions are more and more often studied with the help of geochemistry and more particularly by using isotopic tracers. These isotopic tracer techniques allow, in particular, to define for each system under study, the natural or anthropic origin of the chemical elements, their behaviour, their transport in the different compartments, the circulation schemes of deep fluids and their interaction with the surrounding rocks. This article presents: 1 - the isotopes: definition, measurements and uses (stable and instable isotopes, measurement means, some examples: stable isotopes of the water molecule, boron isotopes, sulfur and oxygen isotopes of sulfates, strontium isotopes, nitrogen isotopes of nitrates); 2 - isotopes and water cycle: atmospheric tracing (rainfall signal at the drainage basin scale and at the country scale, aerosols characterization in urban areas), management of alluvial aquifers, underground waters and origin of nitrogenous contaminations, underground and surface waters in the context of aquifer floods: the case of the Somme basin, underground waters at the basin scale: heterogeneities, interactions and management processes (stable isotopes of the water molecule, S and O isotopes of dissolved sulfates, strontium isotopes); 3 - conclusion. (J.S.)

  11. An NMR investigation of isotope exchange involving multiply labelled intermediates

    International Nuclear Information System (INIS)

    Information about enzyme systems can be obtained from studies of isotope exchange reactions. NMR can monitor these reactions continuously, even in intact biological samples. In this paper 1H NMR is used to study a 1H/2H exchange process which involves multiple labelling of NADH. The NADH is an intermediate in an exchange process involving the glycolytic enzymes glyceraldehyde phosphate dehydrogenase, lactate dehydrogenase, triose phosphate isomerase and aldolase. The form of the observed exchange is predicted by an extended theory of isotope exchange. (author)

  12. Heat Exchanger Lab for Chemical Engineering Undergraduates

    Science.gov (United States)

    Rajala, Jonathan W.; Evans, Edward A.; Chase, George G.

    2015-01-01

    Third year chemical engineering undergraduate students at The University of Akron designed and fabricated a heat exchanger for a stirred tank as part of a Chemical Engineering Laboratory course. The heat exchanger portion of this course was three weeks of the fifteen week long semester. Students applied concepts of scale-up and dimensional…

  13. Introduction of tritium into organic compounds by isotope exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    Myasoedov, N.F. (AN SSSR, Moscow (Russian Federation). Inst. Molekulyarnoj Genetiki)

    1993-05-01

    Various isotope exchange reactions for the introduction of tritium into a range of organic compounds have been investigated. The influence of the catalyst, solvent and reaction conditions on the yield and specific activities of a number of steroids, phytohormones and sugars are reported. Heterogeneous hydrogen isotope exchange with gaseous tritium has also been used to label a number of nonpolar compounds. Similarly the potential of solid state hydrogen isotope exchange has been explored. The reaction mechanism is discussed as well as the influence of the reaction conditions on the specific activity and the label distribution. (author).

  14. Introduction of tritium into organic compounds by isotope exchange reactions

    International Nuclear Information System (INIS)

    Various isotope exchange reactions for the introduction of tritium into a range of organic compounds have been investigated. The influence of the catalyst, solvent and reaction conditions on the yield and specific activities of a number of steroids, phytohormones and sugars are reported. Heterogeneous hydrogen isotope exchange with gaseous tritium has also been used to label a number of nonpolar compounds. Similarly the potential of solid state hydrogen isotope exchange has been explored. The reaction mechanism is discussed as well as the influence of the reaction conditions on the specific activity and the label distribution. (author)

  15. Separation of boron isotopes using NMG type anion exchange resin

    International Nuclear Information System (INIS)

    Ion exchange separation of boron isotopes (B-10 and B-11) has been studied by using a special boron selective ion exchange resin; NMG (n-methyl glucamine)-type anion exchange resin. The resin has shown a large isotope separation coefficient of 1.02 at the experimental conditions of temperature, 80degC, and boric acid concentration, 0.2 M (mole/dm3). Enriched B-10 (92%) was obtained after the migration of 1149 m by a recyclic operation of ion exchange columns in a merry-go-round method. (author)

  16. Measurement of exchangeable aluminium in soils and clay minerals by isotopic exchange

    International Nuclear Information System (INIS)

    Isotopically exchangeable Al was determined in soils and clay minerals by equilibration with 28Al. Best results were obtained with a weak extractant and an equilibration time of eight min. The calculated amount of isotopically exchangeable Al was independent of the amount of carrier-Al added with the 28Al. In some soils isotopically exchangeable Al did not appear to be related to the amount of Al which could be extracted by various electrolyte solutions. This technique provides an improved means of studying the exchange reactions of Al in acid soils and clay minerals

  17. Rhodium catalysts for isotopic exchange between hydrogen and water vapor

    International Nuclear Information System (INIS)

    Catalysts were prepared by depositing rhodium on porous polystyrene copolymer. The activity of the catalysts for the isotopic exchange reaction in the hydrogen-water vapor system was determined by the nearness of approach to isotopic equilibrium between the two reactants after passing through the column. A known quantity of catalyst was packed in a 1 cm diameter glass column to depth varying 2 to 5 cm. The degree of approach to isotopic equilibrium was as high as 60 to 100 %

  18. Energetics and control of ultracold isotope-exchange reactions between heteronuclear dimers in external fields

    CERN Document Server

    Tomza, Michał

    2015-01-01

    We show that isotope-exchange reactions between ground-state alkali-metal, alkaline-earth-metal, and lanthanide heteronuclear dimers consisting of two isotopes of the same atom are exothermic with an energy change in the range of 1-8000$\\,$MHz thus resulting in cold or ultracold products. For these chemical reactions there are only one rovibrational and at most several hyperfine possible product states. The number and energetics of open and closed reactive channels can be controlled by the laser and magnetic fields. The exothermic isotope-exchange reactions can be tuned to become endothermic by employing a laser-induced state-selective Stark shift control thus providing a ground for testing models of the chemical reactivity. The present proposal opens the way for studying the state-to-state dynamics of ultracold chemical reactions beyond the universal limit with a meaningful control over quantum states of both reactants and products.

  19. The isotope separation by ion exchange chromatography. Application to the lithium isotopes separation

    International Nuclear Information System (INIS)

    In this work is described the used study step to demonstrate the industrial feasibility of a lithium isotopes separation process by ion exchange chromatography. After having recalled how is carried out the exchange reaction between the lithium isotopes bound on the cations exchanger resin and those which are in solution and gave the ion exchange chromatography principle, the authors establish a model which takes into account the cascade theory already used for enriched uranium production. The size parameters of this model are: the isotopic separation factor (which depends for lithium of the ligands nature and of the coordination factor), the isotopic exchange kinetics and the mass flow (which depends of the temperature, the lithium concentration, the resins diameter and the front advance). The way they have to be optimized and the implementation of the industrial process are given. (O.M.)

  20. Studies on separation of boron isotopes by ion exchange

    International Nuclear Information System (INIS)

    Studies have been carried out for the enrichment of boron isotopes by the ion exchange method using various anion exchange resins available. The elementary separation factors and heights equivalent of theoretical plate were measured at different concentrations and flow rates. A number of experiments were performed to study the displacement of borate band on ion exchange columns. The problem of CO2 evolution during displacement was also studied and a solution was found. (author). 9 refs

  1. Specific surface of thin-layer inorganic sorbents and possibilities of radionuclides concentration and elements determination by isotope exchange

    International Nuclear Information System (INIS)

    Methodological features of application of heterogeneous isotope exchange on an example of thin-layer sulfide sorbents depending on conditions (solubility and chemical purity of sulfide layer) is considered in this work. The rate of reaction of isotope exchange at different temperatures ranges and metal concentrations is defined. The activation energy is defined as well. Dependencies of sorption ratio on element concentration in solution are obtained. Data on dynamics of isotop exchange on granular sorbents samples is presented. As radionuclides were used zinc-65, cadmium-115, and lead-212. As carrier were used triacetate cellulose layer, cellulose granules and titanium hydroxide, obtained by sol gel method.

  2. Isotope exchange between gaseous hydrogen and uranium hydride powder

    International Nuclear Information System (INIS)

    Highlights: • Isotope exchange between hydrogen gas and uranium hydride powder can be rapid and reversible. • Gas–solid exchange rate is controlled by transport within ∼0.7 μm hydride particles. • Gas chromatographic separation of hydrogen isotopes using uranium hydride is feasible. - Abstract: Isotope exchange between gaseous hydrogen and solid uranium hydride has been studied by flowing hydrogen (deuterium) gas through packed powder beds of uranium deuteride (hydride). We used a residual gas analyzer system to perform real-time analysis of the effluent gas composition. We also developed an exchange and transport model and, by fitting it to the experimental data, extracted kinetic parameters for the isotope exchange reaction. Our results suggest that, from approximately 70 to 700 kPa and 25 to 400 °C, the gas-to-solid exchange rate is controlled by hydrogen and deuterium transport within the ∼0.7 μm diameter uranium hydride particles. We use our kinetic parameters to show that gas chromatographic separation of hydrogen and deuterium using uranium hydride could be feasible

  3. Isotopic exchange in ion-molecule reactions: interstellar implications

    International Nuclear Information System (INIS)

    The results of a study of the rates of isotopic exchange in several positive ion/molecule reactions are outlined. The data were obtained over the temperature range 90 - 550 K using a SIFT apparatus. Reversible reactions of the kind: 13C+ + 12CO reversible 12C+ + 13CO were studied and the rate coefficients were determined. Other similar reactions studied were those between HCO+ and CO in which the carbon and oxygen were variously isotopically labelled. Differences between the rate coefficients were apparent at the lower temperatures which, it is suggested, contribute to the observed enhanced concentrations of the rarer isotopes in interstellar CO and HCO+. Isotopic exchange in the reactions of CH+, CH2+ and CH3+ with HD and D2 and in the reactions of CD+, CD2+ and CD3+ with HD and H2 has also been studied and these data are briefly discussed. (Auth.)

  4. Isotopic enrichment of 15N by ionic exchange cromatography

    International Nuclear Information System (INIS)

    The ionic exchange chromatographic method in columns of resin which is employed in the study of isotopic enrichment of 15N is presented. Determinations are made of the isotopic separation constant for the exchange of isotopes 15N and 14N in the equilibrium involving ammonium hidroxide in the solution phase and ions NH4+ adsorbed in cationic resins: Dowex 50W-X8 and X12, 100-200 mesh. Experiments are also conducted for determination of height of theoretical plates for situations of equilibrium of the NH4+ band in two systems of resin's columns aimed at estimating the experimental conditions used. The isotopic analyses of nitrogen are carried out by mass spectrometry

  5. Dynamics of helix-coil transition and isotope exchange reaction

    International Nuclear Information System (INIS)

    A dynamical theory is presented for the helix-coil transition and the isotope exchange reaction in a short polypeptide chain. In this theory it is assumed that there is always one and only one helical sequence. The boundaries of the helix are assumed to move randomly along the chain. If we assume slow movement of the boundaries, our model theory explains the experimental results, i.e., the very low rate of the isotope exchange in the central portion of the chain and the site dependence of the rate. (author)

  6. Isotope effects of sulfur in chemical reactions

    International Nuclear Information System (INIS)

    Sulfur is an important component of organic matter because it forms compounds with many elements. Due to high chemical activity of sulfur, it takes part in biological and geological processes in which isotope effects are occurring. It has been shown during last years research of isotope effects that we have take into account not only mass difference but also many other physical properties of nuclides e.g. even or odd number of neutrons in nuclei, shape and distribution of charge, turn of nuclear spin etc. The factor remains that new theoretical ideas have been formed on the base of data, being obtained in fractionation processes of heavy element isotope, particularly uranium. Now it is being well known that effects unconnected with vibration energy have also caused an effect on fractionation of considerably lighter elements like iron and magnesium. The important question is, if these effects would come to light during the separation of sulfur isotopes. Sulfur have three even isotopes M = (32, 34, 36) and one odd M 33). This problem is still open. (author)

  7. Technical evaluation on some chemical exchange process for uranium enrichment

    International Nuclear Information System (INIS)

    In CEA in France, Asahi Chemical Industry Co., Ltd., in Japan and others, the industrialization of the uranium enrichment by chemical processes has been studied independently for ten years, using large amount of research expenses. In this study, technological examination was carried out on such processes and their separation characteristics, based on the published literatures. As the results, it was recognized that they have sufficient separation capability to aim at the industrialization, and the power required can be limited relatively low. However, very precise plant design and operation control system are required for them, and it is necessary to watch the future course to carry out the objective evaluation of the economic efficiency. The electric power has become a dominant factor in the production cost of enriched uranium. The separation of uranium isotopes with anion exchange resin being developed by Asahi Chemical Industry Co., Ltd., and the isotope separation by electron exchange using solvent extraction method being developed by CEA in France are introduced. Though the equilibrium separation factor is very small, they utilize reversible processes, and have the possibility of large power reduction and the cost reduction due to scaling-up. (Kako, I.)

  8. Concentrating Low-Level Tritiated Water Through Isotope Exchange

    International Nuclear Information System (INIS)

    Trapping of tritium on polymers with specific functional groups was investigated as a means of treating waste streams containing low levels of tritium. Chemical exchange of tritium with hydrogen on the functional group was used as the mechanism for trapping. The polymers tested include Aurorez polybenzimidazole resin beads, Chelex 100 resin beads, Duolite GT-73, microcrystalline cellulose, and polyethylenimine. The tests were performed under simulated operating conditions on water obtained from the Radioactive Liquid Waste Treatment Facility at Los Alamos National Laboratory. Tritiated water from the Tritium Systems Test Assembly is discharged to this plant. Polyethylenimine is a water-soluble polymer that was tested using a stirred membrane cell with an ultrafiltration membrane. All of the polymers except polyethylenimine took up tritium from the water. Polybenzimidazole demonstrated the highest tritium uptake. The results are explained on the basis of the type of functional group, hydrogen bonding, and rigidity of the molecular structure of the polymer. The theoretical calculations indicate that significant isotope discrimination requires high-frequency modes with hydrogen bonding contribution and support the experimental findings. Modeling suggested trends that may lead to structures that are more efficient in trapping tritium

  9. Concentrating low-level tritiated water through isotope exchange

    International Nuclear Information System (INIS)

    Trapping of tritium on polymers with specific functional groups was investigated as a means of treating waste streams containing low levels of tritium. Chemical exchange of tritium with hydrogen on the functional group was used as the mechanism for trapping. The polymers tested include Aurorez polybenzimidazole resin beads, Chelex 100 resin beads, Duolite GT-73, microcrystalline cellulose, and polyethylenimine. The tests were performed under simulated operating conditions on water obtained from the Radioactive Liquid Waste Treatment Facility at Los Alamos National Laboratory, Tritiated water from the Tritium Systems Test Assembly is discharged to this plant. Polyethylenimine is a water-soluble polymer that was tested using a stirred membrane cell with an ultrafiltration membrane. All of the polymers except polyethylenimine took up tritium from the water. Polybenzimidazole demonstrated the highest tritium uptake. The results are explained on the basis of the type of functional group, hydrogen bonding, and rigidity of the molecular structure of the polymer. The theoretical calculations indicate that significant isotope discrimination requires high-frequency modes with hydrogen bonding contribution and support the experimental findings. Modeling suggested trends that may lead to structures that are more efficient in trapping tritium

  10. Nitrogen isotope exchange in between nitric oxide and nitric acid

    International Nuclear Information System (INIS)

    The exchange rate law experimentally observed for 15 N/14 N exchange in NO - HNO3 system at low nitric acid concentration, both at atmospheric pressure and at low pressure of NO: R k[H+][NO3-][HNO2], is identical with the rate law for the reaction between NO and HNO3, when HNO2 is formed.The rate of nitrogen isotope exchange between NO and HNO3 has been measured as a function of nitric acid concentration of 1.5 4 M.l-1. The exchange rate law is shown to be R k[HNO3]2[N2O3] and the measured activation energy is E = 67.78 kJ.M-1. It is concluded that N2O3 participates in 15 N/14 N exchange between NO and HNO3 at nitric acid concentration higher than 1.5 M.l-1. The rate of the same isotope exchange in NO - HNO3 system has been also measured as a function of nitric oxide pressure 0.1 0.4 M.Pa for 1 and 2 M.l-1 HNO3. It is demonstrated that 15 N/14 N exchange in this system has a linear dependence on NO pressure as indicated by rate measurements at different NO partial pressures and constant overall pressure, by adding helium in reactor. Using the rate law presented above the nitrogen isotope exchange rate for nitric acid concentration 1.5 10 M.l-1 were calculated. Nitrogen isotope exchange between nitric oxide and concentrated nitric acid with a single stage separation factor = 1.055, for 10 M.l-1 nitric acid, at 25 deg. C, provides the bases for 15 N separation process that is most widely used at the present time, i.e. the method of Spindel and Taylor. In order to know what happens in 15N separation at higher pressure, when the isotopic transport is improved, a stainless steel laboratory experimental plant with a 1000 mm long and 18 mm i.d. column, packed with triangular wire springs of 1.8 x 1.8 x 0.2 mm, was utilised. At 1.5 atm (absolute) and 2.36 ml.cm-2.min-1 flow rate, HETP was 7% smaller than at atmospheric pressure and 1.5 times smaller flow rate. The operation of 15 N separation plant at 1.8 atm (absolute), instead atmospheric pressure, will permit doubling

  11. Isotopic exchange reactions. Kinetics and efficiency of the reactors using them in isotopic separation

    International Nuclear Information System (INIS)

    In the first part, some definitions and the thermodynamic and kinetic isotopic effect concepts are recalled. In the second part the kinetic laws are established, in homogeneous and heterogeneous medium (one component being on occasions present in both phases), without and with isotopic effects. Emphasis is put on application to separation of isotopes, the separation factor α being close to 1, one isotope being in large excess with respect to the other one. Isotopic transfer is then given by: J = Ka (x - y/α) where x and y are the (isotopic) mole fractions in both phases, Ka may be either the rate of exchange or a transfer coefficient which can be considered as the 'same in both ways' if α-1 is small compared to the relative error on the measure of Ka. The third part is devoted to isotopic exchange reactors. Relationships between their efficiency and kinetics are established in some simple cases: plug cocurrent flow reactors, perfectly mixed reactors, countercurrent reactors without axial mixing. We treat only cases where α and the up flow to down flow ratio is close to 1 so that Murphee efficiency approximately overall efficiency (discrete stage contactors). HTU (phase 1) approximately HTU (phase 2) approximately HETP (columns). In a fourth part, an expression of the isotopic separative power of reactors is proposed and discussed

  12. Isotope exchange by Ion Cyclotron Wall Conditioning on JET

    Energy Technology Data Exchange (ETDEWEB)

    Wauters, T., E-mail: t.wauters@fz-juelich.de [Laboratory for Plasma Physics, ERM/KMS, TEC Partner, 1000 Brussels (Belgium); Douai, D.; Kogut, D. [CEA, IRFM, F-13108 St-Paul-Lez-Durance (France); Lyssoivan, A. [Laboratory for Plasma Physics, ERM/KMS, TEC Partner, 1000 Brussels (Belgium); Brezinsek, S. [Forschungszentrum Jülich, Institut für Energie- und Klimaforschung Plasmaphysik, 52425 Jülich (Germany); Belonohy, E. [Max-Planck Institut für Plasmaphysik, 85748 Garching (Germany); Blackman, T. [JET-EFDA, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Bobkov, V. [Max-Planck Institut für Plasmaphysik, 85748 Garching (Germany); Crombé, K. [Laboratory for Plasma Physics, ERM/KMS, TEC Partner, 1000 Brussels (Belgium); Drenik, A. [Jožef Stefan Institute, 1000 Ljubljana (Slovenia); Graham, M. [JET-EFDA, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Joffrin, E. [CEA, IRFM, F-13108 St-Paul-Lez-Durance (France); Lerche, E. [Laboratory for Plasma Physics, ERM/KMS, TEC Partner, 1000 Brussels (Belgium); Loarer, T. [CEA, IRFM, F-13108 St-Paul-Lez-Durance (France); Lomas, P.L.; Mayoral, M.-L.; Monakhov, I. [JET-EFDA, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Oberkofler, M. [Max-Planck Institut für Plasmaphysik, 85748 Garching (Germany); Philipps, V. [Forschungszentrum Jülich, Institut für Energie- und Klimaforschung Plasmaphysik, 52425 Jülich (Germany); Plyusnin, V. [IST, Instituto de Plasmas e Fusão Nuclear, 1049-001 Lisboa (Portugal); and others

    2015-08-15

    The isotopic exchange efficiencies of JET Ion Cyclotron Wall Conditioning (ICWC) discharges produced at ITER half and full field conditions are compared for JET carbon (C) and ITER like wall (ILW). Besides an improved isotope exchange rate on the ILW providing cleaner plasma faster, the main advantage compared to C-wall is a reduction of the ratio of retained discharge gas to removed fuel. Complementing experimental data with discharge modeling shows that long pulses with high (∼240 kW coupled) ICRF power maximizes the wall isotope removal per ICWC pulse. In the pressure range 1–7.5 × 10{sup −3} Pa, this removal reduces with increasing discharge pressure. As most of the wall-released isotopes are evacuated by vacuum pumps in the post discharge phase, duty cycle optimization studies for ICWC on JET-ILW need further consideration. The accessible reservoir by H{sub 2}-ICWC at ITER half field conditions on the JET-ILW preloaded by D{sub 2} tokamak operation is estimated to be 7.3 × 10{sup 22} hydrogenic atoms, and may be exchanged within 400 s of cumulated ICWC discharge time.

  13. Isotope exchange kinetics in metal hydrides I : TPLUG model.

    Energy Technology Data Exchange (ETDEWEB)

    Larson, Rich; James, Scott Carlton; Nilson, Robert H.

    2011-05-01

    A one-dimensional isobaric reactor model is used to simulate hydrogen isotope exchange processes taking place during flow through a powdered palladium bed. This simple model is designed to serve primarily as a platform for the initial development of detailed chemical mechanisms that can then be refined with the aid of more complex reactor descriptions. The one-dimensional model is based on the Sandia in-house code TPLUG, which solves a transient set of governing equations including an overall mass balance for the gas phase, material balances for all of the gas-phase and surface species, and an ideal gas equation of state. An energy equation can also be solved if thermodynamic properties for all of the species involved are known. The code is coupled with the Chemkin package to facilitate the incorporation of arbitrary multistep reaction mechanisms into the simulations. This capability is used here to test and optimize a basic mechanism describing the surface chemistry at or near the interface between the gas phase and a palladium particle. The mechanism includes reversible dissociative adsorptions of the three gas-phase species on the particle surface as well as atomic migrations between the surface and the bulk. The migration steps are more general than those used previously in that they do not require simultaneous movement of two atoms in opposite directions; this makes possible the creation and destruction of bulk vacancies and thus allows the model to account for variations in the bulk stoichiometry with isotopic composition. The optimization code APPSPACK is used to adjust the mass-action rate constants so as to achieve the best possible fit to a given set of experimental data, subject to a set of rigorous thermodynamic constraints. When data for nearly isothermal and isobaric deuterium-to-hydrogen (D {yields} H) and hydrogen-to-deuterium (H {yields} D) exchanges are fitted simultaneously, results for the former are excellent, while those for the latter show

  14. Isotope Fractionation of chlorine in Aqueous System: One Study on Anion-Exchange Chromatography.

    Science.gov (United States)

    Musashi, M.; Oi, T.; Eggenkamp, H.; Van Cappellen, P.

    2001-05-01

    Stable chlorine isotopes such as 37Cl and 35Cl have been paid attention as useful tool identifying the source, and monitoring the transport process and natural fate of chlorinated organic pollutants in air and groundwater. However, it is not established yet whether any isotope effects accompany biodegradation or reductive dehalogenation of the pollutants (Clark and Fritz, 1997). Here we first present an experimental determination of isotope fractionation factor of chlorine in aqueous system by using anion-exchange chromatographic technique. Into the Cl-free anion exchange resin (Muromac, OH- form) packed in a 30 cm long pyrex glass column and controlled temperature at 25 oC, hydrochloric solution was fed with controlling the flow rate constant. Effluent from the column was recovered by an automatic fraction collector and prepared for Cl isotope analysis. The Cl isotope ratio (δ 37Cl vs. SMOC) was measured by IR-MS at the Utrecht University with precision of 0.06 per-mil. Magnitude of the factor obtained was 1.00035 at 25 oC. The result indicates that the lighter isotope (35Cl) was preferably fractionated into the resin phase, while the heavier one (37Cl) was enriched into the aqueous phase. This trend suggests that molecular structure of hydrolysis with Cl in aqueous phase may be more stable than that of Cl ionically bonding with the resin. This result may offer physico-chemical insights into behavior and fate of the pollutants.

  15. Isotopic exchange in mixed valence compounds in the solid state

    International Nuclear Information System (INIS)

    This work aims at the determination of isotopic exchange kinetics and mechanism in two mixed valence compounds: Cs10(Sbsup(V)Cl6) (Sbsup(III)Cl6)3 and Tl3sup(I)(Tlsup(III)Cl6). The synthesis of the first compound is very difficult because in most of the cases mixtures of chloroantimoniates are obtained. Exchange in Tl4Cl6 labelled on Tlsup(III) is studied in detail by radiochemical analysis and physical techniques: ionic conductivity and positon annihilation. Cation vacancies are easily created in the lattice with formation enthalpy of 0.35 eV and migration enthalpy of 0.52 eV. Isochronic and isothermal exchange curves are described by a kinetic based on species diffusion. Models are given. Exchange is increased by grinding probably because extrinseque defects are introduced

  16. Iron isotope fractionation between aqueous Fe(II) and goethite revisited: New insights based on a multi-direction approach to equilibrium and isotopic exchange rate modification

    Science.gov (United States)

    Frierdich, Andrew J.; Beard, Brian L.; Reddy, Thiruchelvi R.; Scherer, Michelle M.; Johnson, Clark M.

    2014-08-01

    over long reaction times. Experiments at higher temperature result in a smaller fractionation between Fe(II)aq and goethite, consistent with a 1/T2 temperature dependence. Coarsened and trace-element substituted goethites that had low surface areas produced much slower rates of isotopic exchange than the chemically pure forms or goethite of smaller crystal size, resulting in only partial isotopic mixing (10-40%). Fractionation-exchange trajectories produced during slow isotopic exchange are linear, however, and extrapolate to the same (within error) Fe(II)aq-goethite fractionations at 100% isotopic mixing as that for reactions of pure goethite. We conclude that the equilibrium 56Fe/54Fe fractionation for Fe(II)aq-goethite at 22 °C ranges between -1.04 ± 0.08‰ and -1.22 ± 0.11‰ (2σ), depending on particle size, where the more negative fractionation is influenced by surface Fe that has distinct isotopic properties; these results are consistent with earlier measurements by Beard et al. (2010). This work highlights the utility of using multiple exchange-fractionation trajectories to verify the attainment of equilibrium and resolving kinetic isotope effects, and the importance of isotopic exchange rate on disequilibrium mixing between components. We recommend that these techniques are essential for unambiguously demonstrating that measured fractionations during isotopic exchange experiments are, in fact, equilibrium fractionations.

  17. Characterization of the available soil Ni by the isotopic exchange kinetics

    International Nuclear Information System (INIS)

    The aim of this study was to demonstrate that soil Ni available for plants can be characterized by the isotopic exchange kinetics method. Therefore, isotopic exchange kinetics were performed in soil-solution systems to quantify the pool of soil isotopically exchangeable Ni (E value). Another isotopic exchange method in soil-plant was designed to measure the pool of soil available Ni (L value). Results clearly demonstrated that the pool of isotopically exchangeable soil Ni for a given time is the pool of available soil Ni. (author)

  18. Uranium isotope separation by continuous anion exchange chromatography

    International Nuclear Information System (INIS)

    This paper reports a process for producing nuclear quality Uranium 235 (U235) from a substantially impure feed stock containing a mixture of uranium isotopes, including U235, forming a stationary phase from an anion exchange resin in the annulus of a rotating annular chromatograph; feeding the feed stock to the stationary phase to load less than 10% of the stationary phase; injecting a mobile phase comprising an eluant selected from the group consisting of aqueous solutions of sulfates, chlorides, nitrates and carbonates into the stationary phase; continuously rotating the annular chromatograph; collecting the U235 isotope in substantially pure, enriched form from the stationary phase; precipitating the U235 isotope as ammonium diurante with ammonium hydroxide; and calcining the ammonium diuranate to produce uranium oxide rich in U235 suitable for nuclear applications requiring substantially pure U235

  19. Boron isotope separation by ion exchange chromatography using weakly basic anion exchange resin

    International Nuclear Information System (INIS)

    Isotopic plateau displacement chromatography, a useful method for isotope separation is presented. The boric acid band formed in a column of weakly basic anion exchange resin Diaion WA21 can be eluted with pure water. In order to obtain good accumulation of the isotope effect, a series of experiments with different migration length were carried out. The boron-10 enriched part of the boric acid absorbed band was always preceded by the isotopic plateau part, in which the atomic fraction of boron-10 was maintained at its original value. The atomic fraction of boron-10 at the end of the chromatogram increased with migration length, and in the case of 256-m migration, boron-10 was enriched from its original atomic fraction of 19.84 to 91.00%, the separation factor S being constant irrespective of migration length: S = 1.0100 +- 0.0005. (author)

  20. Calcium hydroxide isotope effect in calcium isotope enrichment by ion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Jepson, B.E.; Shockey, G.C.

    1984-01-01

    The enrichment of calcium isotopes has been observed in ion-exchange chromatography with an aqueous phase of calcium hydroxide and a solid phase of sulfonic acid resin. The band front was exceedingly sharp as a result of the acid-base reaction occuring at the front of the band. Single-stage separation coefficients were found to be epsilon(/sup 44/Ca//sup 40/Ca) = 11 x 10 /sup -4/ and epsilon(/sup 48/Ca//sup 40/Ca) = 18 x 10/sup -4/. The maximum column separation factors achieved were 1.05 for calcium-44 and 1.09 for calcium-48 with the heavy isotopes enriching in the fluid phase. The calcium isotope effect between fully hydrated aqueous calcium ions and undissociated aqueous calcium hydroxide was estimated. For the calcium-44/40 isotope pair the separation coefficient was 13 x 10/sup -4/. 20 references, 2 figures.

  1. Isotope exchange in some solid complexes of rhodium (III)

    International Nuclear Information System (INIS)

    Studies of thermal isotopic exchange in the complexes of trans-(Rh(en)2xCl2)Cl, trans-(Rh(NH3)4xCl2)Cl.H2O and (Rh(NH3)5xCl)Cl2 were carried out at 1750C, 2000C and 2250C. In each case initially faster exchange followed by slower exchange was observed. At 2250C the half-times for the slower isotopic exchange in trans-(Rh(en)2xCl2)Cl and (Rh(NH3)5xCl)Cl2 were 1980 and 89 hours respectively, and for trans-(Rh(NH3)4xCl)Cl2xH2O at 2000C was 642 hours. For (Rh(NH3)5xCl)C12 an activation energy of 88 kj moel-1 was found. Neutron irradiation of trans-(Rh(en)2xCl2)Cl for various times between 24 hours and one week in the J1 position of the Herald reactor induced only a small exchange of the C1-36, (approx. 5%). The annealing at 2250C of pre-neutron irradiated samples showed a small increase in the rate of exchange compared with non-irradiated samples. Co-60 gamma irradiation for various times from 24 hours to 500 hours at a dose rate of 3 Marad h-1 induced isotopic exchange in these complexes. The plot of 1n (1-F) against dose showed a linear dependence in each case. The half-dose for trans-(Rh(en)2xCl2)Cl, trans-(Rh(NH3)4xCl2)Cl.H2O and (Rh(NH3)5xCl) Cl2 were 2505, 3000 and 3375 Mrad, respectively. After pre-irradiation with Co-60 gamma radiation, trans-(Rh(en)2xCl2)Cl and trans-(Rh(NH3)4xCl2)Cl.H2O showed a limited amount of rapid exchange on annealing at 2250C and 2000C respectively. This occurred to a greater extent with the trans-(Rh(NH3)4xCl2)Cl.H2O. A slower exchange followed with similar rates to those found for thermal isotopic exchange. For (Rh(NH3)5xCl)Cl2, annealing at 2250C of pre Co-60 gamma irradiated samples showed the same rate of exchange, and after a pre Co-60 gamma dose of 120 Mrad the same activation energy in the temperature range 1750C to 2250C as for non-irradiated samples

  2. Contamination weeping: A chemical ion exchange model

    International Nuclear Information System (INIS)

    Experiments have been conducted to determine the applicability of a chemical ion-exchange model to characterize the problem of nuclear fuel transportation cask contamination and release (''weeping''). Surface charge characteristics of Cr2O3 and stainless steel (304) powders have been measured to determine the potential for ion exchange at metal oxide -- aqueous interfaces. The solubility of pool contaminant Co and Cs electrolytes at varying pH and the adsorption characteristics of these ions on Cr2O3 and stainless steel powders in aqueous slurries have been studied. Experiments show that Co ions do reversibly adsorb on these powder surfaces and, more specifically, that adsorption occurs in the nominal pH range (pH = 4--6) of a boric acid-moderated spent fuel pool. Desorption has been demonstrated to occur at pH ≤ 3. Cs ions also have been shown to have an affinity for these surfaces although the reversibility of Cs+ bonding by H+ ion exchange has not been fully demonstrated. These results have significant implications for effective decontamination and coating processes used on nuclear fuel transportation casks. 9 refs., 5 figs., 1 tab

  3. Sulfur Isotope Exchange between S-35 Labeled Inorganic Sulfur-Compounds in Anoxic Marine-Sediments

    DEFF Research Database (Denmark)

    FOSSING, H.; THODEANDERSEN, S.; JØRGENSEN, BB

    1992-01-01

    of isotope exchange, specific radioactivities of the reduced sulfur pools were poorly defined and could not be used to calculate their rates of formation. Such isotope exchange reactions between the reduced inorganic sulfur compounds will affect the stable isotope distribution and are expected to decrease...

  4. Tritium separation factors in distillation and chemical exchange processes

    International Nuclear Information System (INIS)

    The vapour pressures of different isotopic hydrogen, water and ammonia molecules have been calculated. These vapour pressures can be used to evaluate relative volatilities of different species for separation of tritium isotopes by distillation. The equilibrium constants for various exchange reactions involving different deuterated and tritiated species of hydrogen, water and ammonia molecules have also been calculated for different temperatures. (author)

  5. Kinetics, equilibrium and isotope exchange in ion exchange systems Pt. 3

    International Nuclear Information System (INIS)

    The kinetics of isotope exchange in the sup(23)Na-sup(22)Na strongly acidic cation exchanger system was studied in a batch stirred reactor. Samples of exchangers OSTION KS (containing divinylbenzene (DVB) in the range of 1.5-12%) and AMBERLITE IR 120 were used for experimental work. In all cases the concentration of the aqueous solution was 02.M NaNOsub(3). Fick's equation was used for the description of diffusion of ions in the particle. By evaluating the experimental data, values were obtained for the self-diffusion coefficients of sodium ions in the exchangers and their dependences on the content of DVB and on the concentration of functional groups in the resin particle. (author)

  6. Isotopic exchange between gaseous hydrogen and scandium dideuteride thin films

    International Nuclear Information System (INIS)

    As part of a study to understand the long-term storage effects on scandium hydride thin films, an experiment has been conducted in which scandium dideuteride thin films were exposed to a hydrogen environment for various periods of time at ambient temperature. The resulting films were analysed using neutron reflectivity using the surface profile analysis reflectometer (SPEAR) at the Los Alamos Neutron Science Center. Using neutron reflectivity and taking advantage of the large difference in the neutron scattering lengths of hydrogen and deuterium, the resulting changes in the film composition due to isotopic exchange and diffusion were observed as a function of the film depth. (orig.)

  7. Study on influencing factors for hydrogen isotopic exchange

    International Nuclear Information System (INIS)

    Background: Hydrogen-water catalytic exchange reaction offers an approach to hydrogen isotope separation, which can be applied in heavy water detritiation. Purpose: To optimize the operating condition for hydrogen-water catalytic exchange reaction, we analysed the influence of different factors on the transfer coefficient. Methods: In detail, the isotope exchange experiments of H-D system were carried out in a self-designed catalytic bed loaded with hydrophobic catalyst and hydrophilic packing with certain volume ratio. The experiments showed the changes of both the transfer coefficient and the pressure drop of column with the changing of the operational temperatures (29℃, 45℃, 60℃ and 75℃), the ratios of gas to liquid (0.58, 1.17, 2.65, 3.54) and the deuterium concentrations (5.05×10-3, 1.0144×10-2, 2.01×10-2). Results: Results showed that 45℃ is the optimal temperature for operating. The transfer coefficient increases with the increasing of the ratio of gas to liquid in the ranges of 0.58 to 1.17 and 2.65 to 3.56, while decreases with the deuterium concentration increases from 5.05×10-3 to 2.01×10-2. The pressure drop of column increases with increasing of gas flow rate. Conclusions: The experiment proves that the ratio of gas to liquid, the reaction temperature and the deuterium concentration are all important factors, which influence the transfer coefficient of deuterium obviously. The optimal operating condition for hydrogen-water catalytic exchange reaction are as follows: the temperature is 45℃, the ratio of gas to liquid is 3.56, and the deuterium concentration is 2.01×10-2. (authors)

  8. Regeneration of the iodine isotope-exchange efficiency for nuclear-grade activated carbons

    International Nuclear Information System (INIS)

    The removal of radioactive iodine from air flows passing through impregnated activated carbons depends on a minimum of three distinguishable reactions: (1) adsorption on the carbon networks of the activated carbons, (2) iodine isotope exchange with impregnated iodine-127, and (3) chemical combination with impregnated tertiary amines when present. When a carbon is new, all three mechanisms are at peak performance and it is not possible to distinguish among the three reactions by a single measurement; the retention of methyl iodide-127 is usually equal to the retention of methyl iodide-131. After the carbon is placed in service, the three mechanisms of iodine removal are degraded by the contaminants of the air at different rates; the adsorption process degrades faster than the other two. This behavior will be shown by comparisons of methyl iodide-127 and methyl iodide-131 penetration tests. It was found possible to regenerate the iodine isotope-exchange efficiency by reaction with airborne chemical reducing agents with little or no improvement in methyl iodine-127 retention. Examples will be given of the chemical regeneration of carbons after exhaustion with known contaminants as well as for many carbons removed from nuclear power operations. The depth profile of methyl iodide-131 penetration was determined in 2-inch deep layers before and after chemical treatments

  9. Proton NMR investigation of heme pocket mobility in hemoglobin via hydrogen isotope exchange kinetics

    International Nuclear Information System (INIS)

    Dynamic mobility of heme cavity, the active site of Hb, was investigated by analyzing the hydrogen isotope exchange kinetics of the proximal histidyl ring NH of various kinds of Hbs with the aid of the high field Fourier Transform 1 H NMR spectroscopy. The exchange reaction occurs faster in oxy or R-state Hb than in deoxy or T-state Hb and there exists a good correlation between the oxygen affinity of Hb and the heme pocket mobility reflected in the hydrogen exchange rate. The effect of pH on the exchange is dramatically different for the two subunits of Hb A. Studying the exchange characteristics of mutant Hbs and chemically modified Hbs not only showed the existence of three well-defined localized paths for transmission of conformational changes between different heme pockets through a1b2 subunit interface, but also indicated that the heme pocket mobility is regulated by the quaternary state of Hb as well as by the ligation state of Hb. Finally, the effect of the quaternary state on the heme pocket mobility is separated from that of the ligation by following the exchange reactions in Hbs where only their quaternary structure transition can be achieved without changing their ligation states by adjusting experimental conditions such as adding inositol hexaphosphate

  10. An integrated chemical and stable-isotope model of the origin of Midocean Ridge Hot Spring Systems

    OpenAIRE

    Bowers, Teresa Suter; Taylor, Hugh P., Jr.

    1985-01-01

    Chemical and isotopic changes accompanying seawater-basalt interaction in axial midocean ridge hydrothermal systems are modeled with the aid of chemical equilibria and mass transfer computer programs, incorporating provision for addition and subtraction of a wide-range of reactant and product minerals, as well as cation and oxygen and hydrogen isotopic exchange equilibria. The models involve stepwise introduction of fresh basalt into progressively modified seawater at discrete temperature int...

  11. Use of type-II strong base anion exchange resins for ion exchange chromatographic separation of isotopes of boron

    International Nuclear Information System (INIS)

    The optimum conditions for the regeneration of strong base anion exchange resins of type-I and type-II were determined for cost - effective separation of isotopes of boron by ion exchange chromatography. The possibility of using unspent alkali content of the effluent was also exploited. Removal of carbonate impurity from rayon grade caustic lye (used as regenerant after dilution) and recycling of Ba(OH)2 was studied to avoid waste disposal problems. The determination of (i) ion exchange capacity of Duolite-162 resin for hydroxyl - chloride and hydroxyl - borate exchanges, (ii) isotopic exchange separation factor by batch method and (iii) effect of concentration of boric acid (in presence and absence of mannitol) on isotopic exchange separation factor to test the suitability of the type-II resin for this process are discussed. (author)

  12. Separation of boron isotopes in anion exchange resin column. Isotopic enrichment of 10 B

    International Nuclear Information System (INIS)

    The separation of boron isotopes (10 B and 11 B) was carried out by isotopic exchange reaction between boric acid in solution and borate/poly borate anions adsorbed on an ammonium quaternary (Dowex 1 X 8 and 2 X 8) anion exchange resin packed in columns. Each resin column had 100 cm length and 1.4 cm in diameter. The columns were connected in series during displacement of boric bands. The enrichment line used pressure ranging from 2.5 to 3.0 Kg f.cm-2. N2 gas was used as in inert atmosphere in order to prevent C O2 formation. Enrichments in 10 B of 43% were obtained using Dowex 1 X 8 resin, 0.1 eq.L-1 H3 B O3 solution and band displacement of 1,876 cm. With Dowex 2 X 8 the enrichment was 40% with 1,330 cm of band displacement and 0.1 eq. L-1 H3 B O3. The boron isotopes were analysed, as methyl borate, by mass spectrometry. (author). 13 refs, 5 figs, 2 tabs

  13. Measurement of the acidities of several cation-exchange resins using hydrogen-isotope exchange reaction

    International Nuclear Information System (INIS)

    The hydrogen-isotope exchange reaction between ethanol (unlabeled) and one of three cation-exchange resins labeled with tritium has been observed at 40-80degC. The acidity (acidity based on kinetic logic) at each temperature has been obtained from a A'-McKay plot based on the respective data obtained. The following results have been obtained on the basis of both the acidities obtained in this work and the acidities (of several materials) obtained previously. (1) The order of the reactivity is (Amberlite IRC-76)>(Dowex A-1)>(PVA2000>(Amberlite IRC-50) at 60degC. (2) The higher the temperature, the larger is the reactivity of each material. (3) The temperature dependence of the reactivity of Dowex A-1 is the largest in the four. (4) The reactivity of the functional group (i.e., COOH group or OH group) bonded to the polymer chain can be clarified using the A'-McKay plot method. (5) It seems that method can be applied to analyze other reactions, e.g., other isotope-exchange reactions, surface reactions, catalytic reactions, etc. (author)

  14. Carbon Monoxide Isotopes: On the Trail of Galactic Chemical Evolution

    Science.gov (United States)

    Langer, W.

    1995-01-01

    From the early days of the discovery of radio emission from carbon monoxide it was realized that it offered unusual potential for under- standing the chemical evolution of the Galaxy and external galaxies through measurements of molecular isotopes. These results bear on stellar nucleosynthesis, star formation, and gases in the interstellar medium. Progress in isotopic radio measurements will be reviewed.

  15. Separation of boron isotopes by ion exchange chromatography: studies with Duolite-162, a type-II resin

    International Nuclear Information System (INIS)

    The selection of resin plays an important role in the process of separation of boron isotopes by ion exchange chromatography. The determination of (i) ion exchange capacity of Duolite-162 resin for hydroxyl - chloride exchange, (ii) hydroxyl - borate exchange, (iii) isotopic exchange separation factor by batch method and (iv) effect of concentration of boric acid on isotopic exchange separation factor to test the suitability of the above resin for this process are discussed in this report. (author)

  16. Determination of the hydrodynamical characteristics of the sieve plates in H2 O - H2 S isotopic exchange columns

    International Nuclear Information System (INIS)

    Hydrodynamical characteristics of the sieve plates in isotopic exchange were experimentally determined. Operational diagrams are obtained for three different sieve plate types which were utilized in determination of the optimal fluid flow in the isotopic exchange columns. 2 Figs

  17. A determination of elementary separation factors of isotopes 235U and 238U in the ionic exchange process and of eluents in the water-glycerine system

    International Nuclear Information System (INIS)

    In the experiments focused on uranium isotope separation by ion and chemical exchange, the water-glycerine system was employed. The principle of the method consists in shifting a uranium band along an ion-exchange resin column by means of an eluent. The isotope effect of reactions determining the band heading into the column where complex bands between the metal ion and the ligand form and break up under the resin influence, is determined by the difference in affinity between the two isotopes as against the eluent. The isotope effect in question determines a unit deviation of the equilibrium constant for the classical isotope exchange reaction. Starting from the experimental results obtained, it was concluded that the ion and chemical exchange between the IV and VI valence forms of uranium can be applied to isotope separation in terms of the separation unit. As against the methods that have been applied at present (gaseous scattering, hydro-extracting and the nozzle method), for which every new stage corresponds to a separation elementary factor, several separation elementary factors can be cumulated into a single stage in a chemical and ion exchange unit, by the optimization of the shifting band and length. (author)

  18. Theoretical investigation of isotope exchange reaction in tritium-contaminated mineral oil in vacuum pump

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Liang; Xie, Yun [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Du, Liang [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); School of Radiation Medicine and Protection (SRMP), School for Radiological and Interdisciplinary Sciences (RAD-X), Suzhou 215000 (China); Li, Weiyi [School of Physics and Chemistry, Xihua University, Chengdu 610065 (China); Tan, Zhaoyi, E-mail: zhyitan@126.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2015-04-28

    Highlights: • This is the first theoretical investigation about T–H exchange in vacuum oil. • T–H isotope exchange is accomplished through two different change mechanisms. • Isotope exchange is selective, molecules with −OH and −COOH exchange more easily. • The methyl and methylene radicals in waste oil were observed by {sup 1}HNMR. - Abstract: The mechanism of the isotope exchange reaction between molecular tritium and several typical organic molecules in vacuum pump mineral oil has been investigated by density functional theory (DFT), and the reaction rates are determined by conventional transition state theory (TST). The tritium–hydrogen isotope exchange reaction can proceed with two different mechanisms, the direct T–H exchange mechanism and the hyrogenation–dehydrogenation exchange mechanism. In the direct exchange mechanism, the titrated product is obtained through one-step via a four-membered ring hydrogen migration transition state. In the hyrogenation–dehydrogenation exchange mechanism, the T–H exchange could be accomplished by the hydrogenation of the unsaturated bond with tritium followed by the dehydrogenation of HT. Isotope exchange between hydrogen and tritium is selective, and oil containing molecules with −OH and −COOH groups can more easily exchange hydrogen for tritium. For aldehydes and ketones, the ability of T–H isotope exchange can be determined by the hydrogenation of T{sub 2} or the dehydrogenation of HT. The molecules containing one type of hydrogen provide a single product, while the molecules containing different types of hydrogens provide competitive products. The rate constants are presented to quantitatively estimate the selectivity of the products.

  19. Theoretical investigation of isotope exchange reaction in tritium-contaminated mineral oil in vacuum pump

    International Nuclear Information System (INIS)

    Highlights: • This is the first theoretical investigation about T–H exchange in vacuum oil. • T–H isotope exchange is accomplished through two different change mechanisms. • Isotope exchange is selective, molecules with −OH and −COOH exchange more easily. • The methyl and methylene radicals in waste oil were observed by 1HNMR. - Abstract: The mechanism of the isotope exchange reaction between molecular tritium and several typical organic molecules in vacuum pump mineral oil has been investigated by density functional theory (DFT), and the reaction rates are determined by conventional transition state theory (TST). The tritium–hydrogen isotope exchange reaction can proceed with two different mechanisms, the direct T–H exchange mechanism and the hyrogenation–dehydrogenation exchange mechanism. In the direct exchange mechanism, the titrated product is obtained through one-step via a four-membered ring hydrogen migration transition state. In the hyrogenation–dehydrogenation exchange mechanism, the T–H exchange could be accomplished by the hydrogenation of the unsaturated bond with tritium followed by the dehydrogenation of HT. Isotope exchange between hydrogen and tritium is selective, and oil containing molecules with −OH and −COOH groups can more easily exchange hydrogen for tritium. For aldehydes and ketones, the ability of T–H isotope exchange can be determined by the hydrogenation of T2 or the dehydrogenation of HT. The molecules containing one type of hydrogen provide a single product, while the molecules containing different types of hydrogens provide competitive products. The rate constants are presented to quantitatively estimate the selectivity of the products

  20. Concurrent reduction and distillation: an improved technique for the recovery and chemical refinement of the isotopes of cadmium and zinc

    International Nuclear Information System (INIS)

    The Electromagnetic Isotope Separations Program of the Oak Ridge National Laboratory has been involved in the separation, chemical recovery, and refinement of the stable isotopes of cadmium and zinc since 1946. Traditionally, the chemical refinement procedures for these elements consisted of ion exchange separations using anion exchange resins followed by pH-controlled hydrogen sulfide precipitations. The procedures were quite time-consuming and made it difficult to remove trace quantities of sulfur which interferes in subsequent attempts to prepare rolled metal foils. As demands for 113Cd and 68Zn (a precursor for the production of the radiopharmaceutical 67Ga) increased, it became evident that a quicker, more efficient refinement procedure was needed. Details of an improved method, which employs concurrent hydrogen reduction and distillation in the recovery and refinement of isotopically enriched zinc, are described. Modifications of the procedure suitable for the refinement of cadmium isotopes are also described. 3 figures, 1 table

  1. Hydrogen isotope exchange between boranes and deuterated aromatic hydrocarbons: evidence for reversible hydroboration of benzene

    International Nuclear Information System (INIS)

    Pentaborane, B5H9, and diborane, B2H6, undergo hydrogen isotope exchange with deuterated aromatic hydrocarbons. Lewis acid catalyzed hydrogen isotope exchange occurs between benzene-d6 and the apical hydrogen atom of B5H9 to form 1-DB5H8 at ambient temperature. In uncatalyzed exchanges, B5H9 reacts with deuterated aromatic hydrocarbons to produce 1,2,3,4,5-D5B5H4 at +450C and B5D9 at +1200C. This thermally induced hydrogen isotope exchange apparently occurs via a reversible hydroboration of the aromatic ring. Diborane undergoes a similar isotope exchange with benzene-d6 under mild thermal conditions. 18 references, 6 figures, 3 tables

  2. Biological, chemical, electrochemical, and photochemical fractionation of Fe isotopes

    Science.gov (United States)

    John, S.; King, A.; Hutchins, D.; Adkins, J. F.; Fu, F.; Wasson, A.; Hodierne, C.

    2012-12-01

    Iron is an important nutrient for life in the ocean, where low Fe concentrations often limit the growth of marine phytoplankton. Fe stable isotope ratios (δ56Fe) are a potentially valuable new tool for studying the marine biological cycling of Fe. In order to effectively use Fe isotopes as a biological tracer, however, it is important to parameterize the isotope effect for biological uptake. We have therefore measured the biological fractionation of Fe isotopes by the marine diatoms Thalassiosira pseudonana, T. oceanica, and Phaeodactylum tricornutum in culture. During biological Fe acquisition, Fe(III) is often first reduced from Fe(III) to Fe(II), either in seawater or at the cell surface. Therefore, we have also measured the isotope effect for Fe(III) reduction by chemical, electrochemical, and photochemical processes. Diatoms were cultured in EDTA or NTA buffered media under varying Fe concentrations from Fe-sufficiency to Fe-limitation. Biological fractionation of Fe isotopes was determined by comparing δ56Fe of phytoplankton to the media. The use of a cell wash allows us to distinguish between isotopic fractionation during extracellular adsorption and intracellular uptake. The biological fractionation of Fe isotopes is highly dependent on culture conditions with Δδ56Fe ranging from +0.6 ‰ to -0.5 ‰ depending on ligand composition, species, and Fe-limitation status. Isotope effects for chemical, electrochemical, and photochemical reduction of Fe(III) to Fe(II) span an even larger range. For example, chemical reduction of Fe(III)-EDTA with hydroxylamine hydrochloride has an isotope effect of Δδ56Fe = -2.8 ‰. By contrast, photochemical reduction of Fe(III)-EDTA has an isotope effect of Δδ56Fe = +0.9 ‰. Isotope effects for electrochemical reduction of Fe(III) using a rotating disc electrode allow for greater control of experimental conditions, such as differentiating between the effects of electric potential (voltage) and mass transport (diffusion

  3. Ion-Isotopic Exchange Reaction Kinetics using Anion Exchange Resins Dowex 550A LC and Indion-930A

    Directory of Open Access Journals (Sweden)

    P.U. Singare

    2014-06-01

    Full Text Available The present paper deals with the characterization of ion exchange resins Dowex 550A LC and Indion-930A based on kinetics of ion-isotopic exchange reactions for which the short lived radioactive isotopes 131I and 82Br were used as a tracers. The study was performed for different concentration of ionic solution varying from 0.001 mol/L to 0.004 mol/L and temperature in the range of 30.0 °C to 45.0 °C. The results indicate that as compared to bromide ion-isotopic exchange reaction, iodide exchange reaction take place at the faster rate. For both the ion-isotopic exchange reactions, under identical experimental conditions, the values of specific reaction rate increases with increase in the ionic concentration and decreases with rise in temperature. It was observed that at 35.00C, 1.000 g of ion exchange resins and 0.002 mol/L labeled iodide ion solution for iodide ion-isotopic exchange reaction, the values of specific reaction rate (min-1, amount of ion exchanged (mmol, initial rate of ion exchange (mmol/min and log Kd were 0.270, 0.342, 0.092 and 11.8 respectively for Dowex 550A LC resin, which was higher than the respective values of 0.156, 0.241, 0.038 and 7.4 as that obtained for Indion-930A resins. From the results, it appears that Dowex 550A LC resins show superior performance over Indion-930A resins under identical experimental conditions.

  4. Data acquisition system for optimization and control of the processes in isotopic exchange columns

    International Nuclear Information System (INIS)

    The increase of tritium level concentration in heavy water raises problems in operation of nuclear reactors as well as for the environment. Therefore, most owners of Candu reactors are making researches and develop technologies for heavy water detritiation. As it is well known after several years of functioning the level radioactivity in the moderator attains a value that imposes heavy water detritiation. The technology developed at the Institute of Cryogenics and Isotope Separations is based on catalytic isotope exchange between water and hydrogen gas both carrying various isotopes of hydrogen: normal hydrogen, deuterium, and tritium. This isotope exchange is followed by cryogenic distillation separating the various isotopes of hydrogen gas. The detritiation process was simulated using as working fluids water with a small content of deuterium and a gaseous mixture of hydrogen and deuterium. The experimental data obtained on catalyst isotopic exchange column on tritium or deuterium transfer from water to gas and the mathematical model to simulate the column behavior allowed to determine the performance of isotopic exchange column. After interpreting the experimental data, we determined the reaction rate constants, which characterize the isotopic exchange for distillation, and catalytic process, respectively, as a function of the experimental conditions: tritium or deuterium concentration in the feed water of the system, distillation and catalyst isotope exchange. The reactions governing the isotopic exchange between tritiated heavy water and deuterium (DTO-D2), and deuterated -water and hydrogen, respectively are given. The experimental dates obtained in the tritium isotopic exchange process proved that the reaction rate constants are half of the deuterium reaction rate constants. These experimental data and the computed values of the reaction rate constants represent the features of catalyst performances of deuterium and tritium isotopic exchange. The mathematical

  5. Characterization of hydrophobic catalysts for hydrogen isotope exchange

    International Nuclear Information System (INIS)

    Domestic hydrophobic catalysts, KC-1 and KC-2, which were developed for the liquid phase catalytic exchange process separating hydrogen isotopes, were tested against Japanese catalyst, Kogel, which is being used in the Fugen's heavy water upgrader in Japan. KC-1 and KC-2 have different characteristics due to the differences of the solvent and solvent composition used. The test results of domestic hydrophobic catalysts characteristics such as pore distribution, specific surface area, platinum loading, and platinum dispersion from AECL agreed well with the results obtained by KEPRI/KAERI. The shape of KC-1 and KC-2 were 4x4 mm cylindrial pellet and that of Kogel catalyst was 4∼5.5mm sphere. The platinum loading of all catalysts were 0.8 wt%. The BET surface areas were 442, 247, 514m2 ·g-1 for KC-1, KC-2, and Kogel respectively, among which the BET surface area of KC-2 was the smallest. The platinum dispersion area was 2.47, 2.07, 1.90 m2g-1 and the platinum dispersion was 100, 100, 92% for KC-1, KC-2, and Kogel respectively, which showed domestic catalysts had higher values than Kogel catalyst. The average pore size was the largest in KC-2

  6. Laser isotope separation - a new class of chemical process

    International Nuclear Information System (INIS)

    Lasers may soon find several applications in chemical processing. The applications that have attracted the most research funding to date involve isotope separation for the nuclear industry. These isotopes have an unusually high value (≥$1000/kg) compared to bulk chemicals (∼$1/kg) and are generally required in very large quantities. In a laser isotope separation process, light is used to convert a separation that is very difficult or even impossible by conventional chemical engineering techniques to one that is readily handled by conventional separation technology. For some isotopes this can result in substantial capital and energy savings. A uranium enrichment process developed at the Lawrence Livermore National Laboratory is the closest to commercialization of the large scale laser isotope separation processes. Of particular interest to the Canadian nuclear industry are the laser separation of deuterium, tritium, zirconium-90 and carbon-14. In this paper, the basic principles behind laser isotope separation are reviewed and brief dscriptions of the more developed processes are given

  7. Lead exchange in teeth and bone--a pilot study using stable lead isotopes.

    OpenAIRE

    Gulson, B L; Gillings, B R

    1997-01-01

    Stable lead isotopes and lead concentrations were measured in the enamel and dentine of permanent (n = 37) and deciduous teeth (n = 14) from 47 European immigrants to Australia to determine whether lead exchange occurs in teeth and how it relates to lead exchange in bone. Enamel exhibits no exchange of its European-origin lead with lead from the Australian environment. In contrast, dentine lead exchanges with Australian lead to the extent of approximately 1% per year. In one subject, trabecul...

  8. Development of an analytical diffusion model for modeling hydrogen isotope exchange

    International Nuclear Information System (INIS)

    We create a model for H retention depth profiles in W and subsequently model how this profile changes after isotope exchange. This is accomplished by calculating how trapping defects in W accumulate D (or H) inventory as W is being exposed to plasma. Each trapping site is characterized by a trapping rate and a release rate, where the only free parameters are the distribution of these trapping sites in the material. The filled trap concentrations for each trap type are modeled as a diffusion process because post-mortem deuterium depth profiles indicate that traps are filled well beyond the ion implantation zone (2–5 nm). Using this retention model, an isotope exchange rate is formulated. The retention model and isotope exchange rate are compared to low temperature isotope exchange experiments in tungsten with good agreement. The limitations of the current model highlight important physics and motivate future work

  9. Film diffusion-controlled kinetics of isotopic exchange in a finite bath

    International Nuclear Information System (INIS)

    This paper examines an isotopic exchange process in which the spherical ion-exchange resins are immersed in an agitated solution of finite volume. It assumes an unstirred liquid film of thickness b-a, a nonlinear concentration profile described by Fick's second law, a concentration of radioactive isotopes in a bulk solution that varies with time, and a constant diffusion coefficient in the liquid film. A rate equation, a diffusion equation, and Laplace transforms along with plots of logs are presented

  10. Low-temperature, non-stoichiometric oxygen isotope exchange coupled to Fe(II)-goethite interactions

    Energy Technology Data Exchange (ETDEWEB)

    Frierdich, Andrew J. [Univ. of Wisconsin, Madison, WI (United States); Univ. of Iowa, Iowa City, IA (United States); Beard, Brian L. [Univ. of Wisconsin, Madison, WI (United States); Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Scherer, Michelle M. [Univ. of Iowa, Iowa City, IA (United States); Spicuzza, Michael J. [Univ. of Wisconsin, Madison, WI (United States); Valley, John W. [Univ. of Wisconsin, Madison, WI (United States); Johnson, Clark M. [Univ. of Wisconsin, Madison, WI (United States)

    2015-07-01

    The oxygen isotope composition of natural iron oxide minerals has been widely used as a paleoclimate proxy. Interpretation of their stable isotope compositions, however, requires accurate knowledge of isotopic fractionation factors and an understanding of their isotopic exchange kinetics, the latter of which informs us how diagenetic processes may alter their isotopic compositions. Prior work has demonstrated that crystalline iron oxides do not significantly exchange oxygen isotopes with pure water at low temperature, which has restricted studies of isotopic fractionation factors to precipitation experiments or theoretical calculations. Using a double three-isotope method (¹⁸O-¹⁷O-¹⁶O and ⁵⁷Fe-⁵⁶Fe-⁵⁴Fe) we compare O and Fe isotope exchange kinetics, and demonstrate, for the first time, that O isotope exchange between structural O in crystalline goethite and water occurs in the presence of aqueous Fe(II) (Fe(II)aq) at ambient temperature (i.e., 22–50 °C). The three-isotope method was used to extrapolate partial exchange results to infer the equilibrium, mass-dependent isotope fractionations between goethite and water. In addition, this was combined with a reversal approach to equilibrium by reacting goethite in two unique waters that vary in composition by about 16‰ in ¹⁸O/¹⁶O ratios. Our results show that interactions between Fe(II)aq and goethite catalyzes O isotope exchange between the mineral and bulk fluid; no exchange (within error) is observed when goethite is suspended in ¹⁷O-enriched water in the absence of Fe(II)aq. In contrast, Fe(II)-catalyzed O isotope exchange is accompanied by significant changes in ¹⁸O/¹⁶O ratios. Despite significant O exchange, however, we observed disproportionate amounts of Fe versus O exchange, where Fe isotope exchange in goethite was roughly three times that of O. This disparity provides novel insight into the reactivity of oxide minerals in aqueous

  11. Infrared study of isotopic exchange during methanation over supported rhodium catalysts: an inverse spillover effect

    International Nuclear Information System (INIS)

    Infrared spectroscopy has been employed to study the reduction of carbon dioxide on supported catalyst films. The investigation included isotopic labeling using D2 as the reduction gas. Isotopic exchange was observed for both CO2/D2 and CH4/D2 mixtures. The mechanism of this isotopic exchange involves migration of hydrogen from the support to the Rh sites, an ''inverse spillover effect''. A key intermediate in the dissociation of CO2 on the supported Rh films was a carbonyl hydride species. 21 refs., 2 figs

  12. Observation of Large Enhancement of Charge Exchange Cross Sections with Neutron-Rich Carbon Isotopes

    CERN Document Server

    Tanihata, I; Kanungo, R; Ameil, F; Atkinson, J; Ayyad, Y; Cortina-Gil, D; Dillmann, I; Estradé, A; Evdokimov, A; Farinon, F; Geissel, H; Guastalla, G; Janik, R; Knoebel, R; Kurcewicz, J; Litvinov, Yu A; Marta, M; Mostazo, M; Mukha, I; Nociforo, C; Ong, H J; Pietri, S; Prochazka, A; Scheidenberger, C; Sitar, B; Strmen, P; Takechi, M; Tanaka, J; Toki, H; Vargas, J; Winfield, J S; Weick, H

    2015-01-01

    Production cross sections of nitrogen isotopes from high-energy carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes. The fragment separator FRS at GSI was used to deliver C isotope beams. The cross sections of the production of N isotopes were determined by charge measurements of forward going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge exchange reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and Fermi transition strength at low excitation energies for neutron-rich isotopes. It was also observed that the cross sections were enhanced much more strongly for neutron rich isotopes in the C-target data.

  13. Some considerations on the treatment of the kinetic data of heterogeneous isotope exchange

    International Nuclear Information System (INIS)

    A direct curve simulation treatment was worked out for the evaluation of the kinetic curves of heterogeneous isotope exchange. Based on the data obtained by a personal computer, some considerations were made on the transport processes in the fully and half exchanged sodium forms of crystalline zirconium phosphate. (author)

  14. Separation of boron isotopes by ion exchange chromatography: studies on regeneration of strong base anion exchange resins

    International Nuclear Information System (INIS)

    The optimum conditions for the regeneration of strong base anion exchange resins of type-I and type-II were determined for cost-effective separation of isotopes of boron by ion exchange chromatography where the hydroxyl form of an anion exchange resin is equilibrated with boric acid solution containing mannitol as a complexing reagent. The possibility of using unspent alkali content of the effluent was also exploited. Removal of carbonate impurity from Rayon grade caustic lye (used as regenerant after dilution) and recycling of Ba(OH)2 was studied to avoid waste disposal problems. (author)

  15. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    13 meteoric stations were selected in syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the syrian or local meteoric line (SMWL) was estimated with a slope of 6.63 and that of both syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude was determined by 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14% and - 0.84%/100 m elevation respectively). The spatial variability of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content of precipitation, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern mediterranean climate type over this region. (author)

  16. Study of solid-state isotopic exchange of hydrogen in L-alanine

    International Nuclear Information System (INIS)

    The solid-state isotopic exchange of L-Ala with the spillover tritium activated on Rh(Pd) supported catalysts and the reactivity of hydrogen at C(2) and C(3) carbon atoms of L-Ala were studied using tritium NMR. The activation energy of the catalyzed isotopic exchange was measured. Ab initio calculations of the reaction of hydrogen exchange in the alanine molecule with H3O+ ion were carried out. The mechanism and transition states of this reaction were proposed. 22 refs.; 4 figs.; 4 tabs

  17. Homogeneous isotope exchange between thiourea and bis (thiourea) mercury (II) complex

    International Nuclear Information System (INIS)

    The isotope exchange behavior of thiourea with bis (thiourea) mercury (II) complex has been studied. The concentrations of both the metal ion and the complex were varied. The results show that the complex is labile in the kinetic sense. An increase in concentration increases the rate of exchange. Increase in temperature also results in an increase of the late of exchange. (author). 7 refs., 3 tabs

  18. Ion exchange nonwoven fabric chemical filter. 2

    International Nuclear Information System (INIS)

    This report outlined the characteristics of EPIX filter and its complex with activated carbon to eliminate organic compounds from solvent. Elimination performance of this filter was determined using an ion chromatographic analyzer. EPIX filter showed high performance to eliminate trace amount of ionic compounds. The rate of elimination was both 99% or more for NH3 and SO2 in an early phase of filtration. Release of dust as well as impurities was significantly reduced by the use of EPIX filter. Gases once adsorbed on the filter were not released even at an elevated temperature of atmosphere. Combined use of non-woven fabrics was possible. For EPIX filter, there are three kinds; strong acid cation exchange filter and strong/weak basic anion filters. The weak basic anion filter has been applied to the conventional apparatus in wafer makers because the filter was very effective for selective boron trapping. When polyethyleneterephthalate was used as the base polymer, radical groups produced on the polymer were co-polymerized with monomer substances. The lifetime of filter was estimated on a base of gas concentration and wind velocity to determine the time to replace with a new one. Furthermore, the loss of pressure became less than a half when EPIX filter was used. (M.N.)

  19. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    The objective of this study is to determine isotopic characteristics of precipitation, the climatic and geographical conditions affecting isotopic composition in order to obtain the input function of groundwater to evaluate the water resources.13 meteoric stations were selected in Syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the Syrian meteoric line (SMWL) was estimated with a slope of 6.62 and that of both Syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude of 18O was about 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14 % and -0.84% /100m respectively). The spatial distribution of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern Mediterranean climate type over this region.(author)

  20. Isotope exchange kinetic of phosphorus in soils from Pernambuco State -Brazil

    International Nuclear Information System (INIS)

    The applicability of isotopic exchange kinetics of 32 p to characterize phosphorus available to plants and to diagnose the reactivity of soil-fertilizer-P in six soils from Pernambuco is described. This methodology was compared with anion exchange resin, isotopic exchange equilibrium methods (E-value and L-value) and P absorption by plants. The first greenhouse experiment had the following treatments: 1) with P and, 2) with addition of 43.7 mg P/Kg of soil, incubated for O, 42 and 84 days before seeding. The kinetic of isotopic exchange (KIE), resin-P and E-value were determined before seeding and after harvesting pearl millet grown for 42 days. Results indicated that the KIE parameters rated the soils more efficiently, in terms of available P and soil-fertilizer-P reactivity, than resin-P, E-value and L-value. (author). 38 refs, 2 figs, 18 tabs

  1. Fundamental studies on the ion-exchange separation of boron isotopes

    International Nuclear Information System (INIS)

    The single-stage separation factors for boron isotopes between an ion-exchange resin and an external solution were determined, using an ion-exchange breakthrough operation. The lighter isotope boron-10 was considerably enriched in the anion-exchange resin phase. The separation factor was very much influenced by the boric acid concentration in the external solution, but not as much influenced by the kind of the anion exchange resin used and operation temperature. The separation factor increased with a decrease in the boric acid concentration of external solution from 1.008 (0.501 mol/l) to 1.016 (0.010 mol/l). The value of the separation factors obtained experimentally were compared with those estimated on the basis of the theory of the two-phase distribution of isotopes. (auth.)

  2. CPMG sequences with enhanced sensitivity to chemical exchange

    International Nuclear Information System (INIS)

    Improved relaxation-compensated Carr-Purcell-Meiboom-Gill pulse sequences are reported for studying chemical exchange of backbone 15N nuclei. In contrast to the original methods [J. P. Loria, M. Rance, and A. G. Palmer, J. Am. Chem. Soc.121, 2331-2332 (1999)], phenomenological relaxation rate constants obtained using the new sequences do not contain contributions from 1H-1H dipole-dipole interactions. Consequently, detection and quantification of chemical exchange processes are facilitated because the relaxation rate constant in the limit of fast pulsing can be obtained independently from conventional 15N spin relaxation measurements. The advantages of the experiments are demonstrated using basic pancreatic trypsin inhibitor

  3. Isotopic Constraints on the Chemical Evolution of Geothermal Fluids, Long Valley, CA

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Shaun; Kennedy, Burton; DePaolo, Donald; Evans, William

    2008-08-01

    A spatial survey of the chemical and isotopic composition of fluids from the Long Valley hydrothermal system was conducted. Starting at the presumed hydrothermal upwelling zone in the west moat of the caldera, samples were collected from the Casa Diablo geothermal field and a series of monitoring wells defining a nearly linear, ~;;14 km long, west-to-east trend along the proposed fluid flow path (Sorey et al., 1991). Samples were analyzed for the isotopes of water, Sr, Ca, and noble gases, the concentrations of major cations and anions and total CO2. Our data confirm earlier models in which the variations in water isotopes along the flow path reflect mixing of a single hydrothermal fluid with local groundwater. Variations in Sr data are poorly constrained and reflect fluid mixing, multiple fluid-pathways or water-rock exchange along the flow path as suggested by Goff et al. (1991). Correlated variations among total CO2, noble gases and the concentration and isotopic composition of Ca suggest progressive fluid degassing (loss of CO2, noble gases) driving calcite precipitation as the fluid flows west-to-east across the caldera. This is the first evidence that Ca isotopes may trace and provide definitive evidence of calcite precipitation along fluid flow paths in geothermal systems.

  4. On-line stable isotope measurements during plant and soil gas exchange

    International Nuclear Information System (INIS)

    Recent techniques for on-line stable isotope measurements during plant and soil exchange of CO2 and/or water vapor are briefly reviewed. For CO2, these techniques provide means for on-line measurements of isotopic discrimination during CO2 exchange by leaves in the laboratory and in the field, of isotopic discrimination during soil respiration and during soil-atmosphere CO2 exchange, and of isotopic discrimination in O2 during plant respiration. For water vapor, these techniques provide means to measure oxygen isotopic composition of water vapor during leaf transpiration and for the analysis of sub microliter condensed water vapor samples. Most of these techniques involve on-line sampling of CO2 and water vapor from a dynamic, intact soil or plant system. In the laboratory, these systems also allow on-line isotopic analysis by continuous-flow isotope ratio mass spectrometry. The information obtained with these on-line techniques is becoming increasingly valuable, and often critical, for ecophysiologial research and in the study of biosphere-atmosphere interactions. (author)

  5. Rhodium trichloride as a homogeneous catalyst for isotopic hydrogen exchange

    International Nuclear Information System (INIS)

    The use of rhodium trichloride as a homogeneous catalyst for the exchange of aromatic compounds and alkanes is described; comparison of the results with corresponding data from heterogeneous rhodium metal and other homogeneous systems, e.g., platinum and iridium, supports the proposal that specific type of π-complex mechanisms are common to all such exchange systems. (author)

  6. Understanding the remobilization of copper, zinc, cadmium and lead due to ageing through sequential extraction and isotopic exchangeability.

    Science.gov (United States)

    Kumar, Manish

    2016-06-01

    Artificial infiltration facilities (AIFs) are useful to control urban runoff and regulate combined sewer overflows. Over the years, AIFs accumulate significant amounts of soakaway sediments and organic matter. The prolonged retention of soakaway sediments in AIFs is likely to cause metal remobilization due to ageing processes. The measurement of the individual consequence of ageing demands homogeneity in physical and chemical profiles of samples. This leads to assessment of metal remobilization in a single soil core through solid-phase extractions and isotopic exchangeability (E value). Depth-wise variation in the physicochemical properties and metal content of the underlying soil (below 1 m of AIFs) was created through 2 weeks of continuous leaching with artificial road runoff (ARR). Ten samples obtained from a 50-cm core by sectioning it at 5-cm intervals were subsequently incubated for 18 months. The results suggest that degradation of organic matter and changes in functional groups due to ageing govern metal remobilization. In general, the top segment showed significant alteration due to ageing. Post incubation, Zn increased dramatically in contrast to subdued Cu and Pb levels in exchangeable fractions with concomitant rise in organic-bound fractions. Isotopic exchangeability of Cd and Zn showed pronounced effect of ageing, although the effect of ageing was distinct in chemical partitioning and isotopic exchangeability of metals; a comparative study of short-term versus long-term incubation will benefit assessment of initial dynamics and final equilibrium. Consequently, the outcome from this work is a viable tool in risk prediction related to soakaway sediment accumulation in AIF. PMID:27236447

  7. Stochastic Simulation of Chemical Exchange in Two Dimensional Infrared Spectroscopy

    CERN Document Server

    Sanda, F; Sanda, Frantisek; Mukamel, Shaul

    2006-01-01

    The stochastic Liouville equations are employed to investigate the combined signatures of chemical exchange (two-state-jump) and spectral diffusion (coupling to an overdamped Brownian oscillator) in the coherent response of an anharmonic vibration to three femtosecond infrared pulses. Simulations reproduce the main features recently observed in the OD stretch of phenol in benzene.

  8. Use of micrometeorological techniques to study the isotopic exchange in ecosystems

    Science.gov (United States)

    Santos, E.; Wagner-Riddle, C.; Brown, S. E.; Stropes, K.

    2015-12-01

    The combination of micrometeorological techniques with high frequency concentration measurements of stable isotopes are a powerful tool to study the temporal dynamics of isotope signatures at the ecosystem level. The objective of this study was to study the isotopic composition of the net CO2 exchange (NEE) above and with corn and tall grass canopies. Profiles of stable isotopes of CO2 (12C-CO2, 13C-CO2 and 18O-CO2) were measured using tunable diode laser trace gas analyzers and multiport sampling systems in corn (12C-CO2 and 13C-CO2, only) and tall grass canopies. These measurements were combined with the flux gradient method and Lagrangian dispersion analysis to estimate the isotopic signatures of the net CO2 flux. The use of a gradient of a concentration threshold to screen half hourly period improved the estimates of flux signatures by the isotope flux ratio approach. The Langrangian dispersion analysis and the isotope flux ratio method estimates showed good agreement above the corn canopy, indicating that the former method can be a viable alternative to study the isotopic exchange within plant canopies. The 13CO2 composition of NEE showed a downward trend near the end of the growing season, which may be related to a reduction of autotrophic respiration in the soil.

  9. Isotope exchange investigation of nitrogen redistribution in expanded austenite

    International Nuclear Information System (INIS)

    Sequential plasma and gaseous nitriding of Fe–18Cr–10Ni–3Mo stainless steel at 390 °C with 14N and 15N isotopes followed by denitriding in flowing hydrogen was investigated. Redistribution of plasma-inserted nitrogen atoms (15N) by subsequent gaseous nitriding (14N) was observed. Denitriding after plasma- and gaseous nitriding resulted in predominant retraction of 14N, and only a minor amount of 15N. The nitrogen isotope diffusion behaviour is explained by two different states of nitrogen bonding and short-range ordering between nitrogen and chromium

  10. Determination of labile pool of iron in citrus soils of Antalya region by isotopic exchange

    International Nuclear Information System (INIS)

    This investigation was made to determine the equilibration time and the labile pool (LP) of iron by isotopic exchange and the effect of pH of the extracting mixture on the LP in representative Citrus Soils of Antalya Region. The results obtained can be summarized as follows: 1. Isotopic exchange of 59Fe reached a steady state concentration after 48 hours of equilibration. 2. The proportions in soil solution of the isotopically exchangeable Fe with pH 5, 7 and 8 were 82.76, 77.18 and 76.34 percent, respectively. 3. DTPA-CaCl2-NaAc mixture at pH 5 resulted higher labile pool of Fe than at pH 7 and 8. LP of Fe was decreased with increasing of pH. (author)

  11. Investigation of Catalytic NOx, reduction with transient techniques, isotopic exchange and FT-IR spectroscopy

    International Nuclear Information System (INIS)

    Emissions from vehicles are suppressed by catalytic conversion, i.e. total oxidation of carbon monoxide and hydrocarbons and reduction of nitrogen oxides. The on-going demand for lower emissions requires more detailed knowledge about the catalytic reaction mechanisms and kinetics on the level of elementary steps, especially because of the mutual interactions in the complex reaction mixture. The reaction mechanisms for the abatement of nitrogen oxides (NOx) are of particular interest, since they are environmentally very unfriendly compounds. Transient experimental techniques can be used as a tool to understand the reaction mechanisms and to develop mathematical models allowing simulation and optimisation of the behaviour of three-way catalyst converters. In chemical kinetics, isotope-labelled reactants are frequently employed to follow reaction pathways and to determine reaction mechanisms. The kinetics and mechanisms of the catalytic reduction of nitrogen oxide (NO) by hydrogen as well as self-decomposition of NO and N2O were studied over alumina based palladium and rhodium-alumina monoliths. In addition, NO reduction with H2 and D2, isotope exchange of hydrogen atoms in water, ammonia and hydrogen with deuterium, as well as adsorption of ammonia and water on the Pd-monolith were studied with transient experiments. Transient step-response experiments, isotopic jumping techniques, steady- state isotopic-transient analysis, temperature programmed desorption (TPD) and Fourier-transformed infrared spectroscopy (FT-IR) were used as experimental techniques. The catalysts were characterised by carbon monoxide chemisorption, nitrogen physisorption and X-ray photoelectron spectroscopy (XPS). Nitrogen, nitrous oxide, ammonia, and water were detected as reaction products in NO reduction by hydrogen. The transient and FT-IR experiments yielded information about the surface reaction mechanisms. The dissociation of NO on the catalyst surface is the crucial step, dominating the

  12. Study of oxygen mobility in some synthetic faujasites by isotopic exchange with CO2

    International Nuclear Information System (INIS)

    Oxygen isotopic exchange between CO2 and Na-Y, Na-X, and the germanic homologue of Na-X was studied at 25 to 5000C by mass-spectrometric analysis of the change in the 18O/16O ratio in the gas circulated across the zeolite. Infrared spectra of CO2 adsorption and reaction with the X zeolites were obtained under similar experimental conditions. Isotopic exchange is measurable in all of the zeolites at room temperature. However, exchange in Na-X and NaGe-X was much more rapid under comparable conditions than exchange in Na-Y. This difference in behavior must be attributed to the effects associated with the substitution of Al3+ and Ge4+ for Si4+ in the tetrahedral sites of X zeolites. In particular, the infrared results demonstrate that various chemisorbed carbonate species can form on the X varieties. Isotopic exchange is promoted by some of these species, whereas others can evidently block active exchange sites on the zeolite surface. The absence of chemisorbed CO2 species on Na-Y accounts for the relatively low rate of exchange in this molecular sieve

  13. Isotope exchange investigation of nitrogen redistribution in expanded austenite

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Drouet, M.; Martinavičius, A.;

    2013-01-01

    Sequential plasma and gaseous nitriding of Fe–18Cr–10Ni–3Mo stainless steel at 390°C with 14N and 15N isotopes followed by denitriding in flowing hydrogen was investigated. Redistribution of plasma-inserted nitrogen atoms (15N) by subsequent gaseous nitriding (14N) was observed. Denitriding after...

  14. Experimental studies of the transfer phenomena of tritium in an isotope exchange column for tritium recovery

    International Nuclear Information System (INIS)

    In order to extract the tritium generated in the heavy water moderated power reactors we chosen the catalytic isotope exchange process in liquid phase combined with cryogenic distillation LPCE-CD. This paper presents the experimental studies of the catalytic isotope transfer of tritium. The catalytic isotope exchange process is realized in a column filled with successive layers of catalyst Pt/C/PTFE and B7 type ordered package of phosphorous bronze. The catalyst and the package are manufactured in our institute. The catalyst consists of 95.5 wt.% of PTFE, 4.1 wt. % of carbon and 0.40 wt. % of platinum and was in the form of Raschig rings with dimensions of 10 x 10 x 2 mm. The B7 type ordered package consists of a phosphorous bronze 4x1 wire mesh and the mesh dimension is 0.18 mm x 0.48 mm. The paper also presents the mathematical model which is used to evaluate the performance of this process. The mathematical model and the experimental data allowed the determination of two rate constants for isotope exchange process and for distillation process. By considering the values of these rate constants it is possible to improve the hydrophobic Pt catalyst and to design the H2/H2O isotopic exchange column package with this catalyst. (author)

  15. Chemical and isotopic fingerprinting of ancient Chinese porcelains

    International Nuclear Information System (INIS)

    We have obtained unequivocal fingerprinting for many Chinese porcelains of utmost significance, based on high-precision multi-element and isotopic analysis by inductively-coupled mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS) in our laboratory. As most ancient Chinese kilns used raw materials mined from local areas, differences in the geochemistry and mineralogy of these raw materials are expected to be preserved as distinctive geochemical and isotopic signatures in finished products and this may be useful for identifying their sources. Production techniques, such as purifying and mixing of different raw materials, may also vary from kiln to kiln, or may even change over time. All of that could also potentially leave a characteristic chemical and isotopic signature in a kiln's finished products. Using a tiny amount (often a few tens milligrams) of porcelain material, more than 40 element concentrations and Sr-Nd isotopic compositions can be rapidly and precisely determined on the ICP-MS and TIMS, respectively. The analytical results show that visibly similar Chinese porcelains made in different places and/or dynasties are strikingly distinctive. The data also allow modern fakes to be readily distinguished from antique porcelains. (author). 4 refs., 7 figs

  16. Molecular imaging of tumors and metastases using chemical exchange saturation transfer (CEST) MRI

    Science.gov (United States)

    Rivlin, Michal; Horev, Judith; Tsarfaty, Ilan; Navon, Gil

    2013-10-01

    The two glucose analogs 2-deoxy-D-glucose (2-DG) and 2-fluoro-2-deoxy-D-glucose (FDG) are preferentially taken up by cancer cells, undergo phosphorylation and accumulate in the cells. Owing to their exchangeable protons on their hydroxyl residues they exhibit significant chemical exchange saturation transfer (CEST) effect in MRI. Here we report CEST-MRI on mice bearing orthotopic mammary tumors injected with 2-DG or FDG. The tumor exhibited an enhanced CEST effect of up to 30% that persisted for over one hour. Thus 2-DG/FDG CEST MRI can replace PET/CT or PET/MRI for cancer research in laboratory animals, but also has the potential to be used in the clinic for the detection of tumors and metastases, distinguishing between malignant and benign tumors and monitoring tumor response to therapy as well as tumors metabolism noninvasively by using MRI, without the need for radio-labeled isotopes.

  17. Application of personal computers to study the kinetics of heterogeneous isotopic exchange

    International Nuclear Information System (INIS)

    The kinetics of some heterogeneous isotopic exchange reactions of alkaline metal ions between solid (crystalline zirconium phosphate) and liquid phases were investigated. Ion diffusion in solid phase was considered as rate controlling step. The Laplace transformation solution of Fick's II law was used with a Sinclair ZX Spectrum personal computer. In some cases the exchange reaction should be regarded as a superposition of diffusion and a first order process. (author)

  18. Some notes on hydrogen-related point defects and their role in the isotope exchange and electrical conductivity in olivine

    Science.gov (United States)

    Karato, Shun-ichiro

    2015-11-01

    Nominally anhydrous minerals such as olivine dissolve hydrogen in a variety of forms including free (or interstitial) proton (Hrad) and two protons trapped at the M-site ((2 H)M×). The strength of chemical bonding between protons and the surrounding atoms are different among different species, and consequently protons belonging to different species likely have different mobility (diffusion coefficients). I discuss the role of diffusion of protons in different species in the isotope exchange and hydrogen-assisted electrical conductivity adding a few notes to the previous work by Karato (2013) including a new way to test the model. I conclude that in the case of isotope exchange, the interaction among these species is strong because diffusion is heterogeneous, whereas there is no strong interaction among different species in electrical conduction where diffusion is homogeneous (in an infinite crystal). Consequently, the slowest diffusing species controls the rate of isotope exchange, whereas the fastest diffusing species controls electrical conductivity leading to a different temperature dependence of activation energy and anisotropy. This model explains the differences in the activation energy and anisotropy between isotope diffusion and electrical conductivity, and predicts that the mechanism of electrical conductivity changes with temperature providing an explanation for most of the discrepancies among different experimental observations at different temperatures except for those by Poe et al. (2010) who reported anomalously high water content dependence and highly anisotropic activation energy. When the results obtained at high temperatures are used, most of the geophysically observed high and highly anisotropic electrical conductivity in the asthenosphere can be explained without invoking partial melting.

  19. Comparison between water distillation process and hydrogen isotope exchange process for depletion and enrichment of tritium in light water

    International Nuclear Information System (INIS)

    Numerical comparison between the water distillation column process and multiunit separated-bed hydrogen isotopic exchange column process with hydrophobic Pt-catalyst shows that the column inner diameter and the column height in the hydrogen isotope exchange process are shorter than in the water distillation process for the case of the depletion and the enrichment of the tritium in light water. (author)

  20. Isotopic exchange in mineral-fluid systems. II. Oxygen and hydrogen isotopic investigation of the experimental basalt-seawater system

    Science.gov (United States)

    Cole, David R.; Mottl, Michael J.; Ohmoto, Hiroshi

    1987-06-01

    Oxygen and hydrogen isotopic exchange reactions between basalt and seawater at T = 300° to 500°C were investigated, using oceanic tholeiitic basalt ( δ 18O = ˜5.7%.; δD = ˜-70%. ), natural seawater ( δ 18O = 1.2%.; δD = + 5%. ) and artificial seawater ( δ 18O = -5.3%. ) as starting materials. The starting basalts varied in the crystallinity (from holocrystalline to glass) but were ground to approximately the same grain size (-100 mesh). The water/rock mass ratios ranged from 1 to 3 and the duration of the experiments ranged from 167 to 576 days. In general, depletion of 18O and enrichment of D in basalts occur at all temperatures, with the magnitudes of change being greater as temperature, time and to a lesser degree, glass content increases. The trends in isotopic shifts are directly related to changes in the style and intensity of mineralogic alterations in the basalt ( e.g., smectite at 300°C, talc-actinoiite at 400°-500°C). The changes in the δ 18O values of basalts and seawater in the experimental systems were observed to follow closely with those expected from a first-order rate law. Rate constants for the oxygen isotopic exchange between rock and water range from 10 -9.5 to 10 -8.0 moles oxygen/m 2 of solid surface/sec for temperatures of 300° to 500°C. The activation energy for the isotopic exchange reaction was calculated to be 11.5 Kcal/ mol. An application of our experimental rate data to natural systems suggests that the oxygen isotope equilibrium between basalt and seawater in the mid-oceanic ridge may take place within approximately 1000 years at 350°C. Our experimental data also suggest the equilibrium oxygen isotopic fractionation factors between the altered basalt and seawater to be 3.5 ± 0.5%. at 300°C, 2.0 ± 0.4%. at 400°C and 0.5 ± 0.25%. at 500°C. The observed hydrogen isotopic fractionation factors between the altered basalts and seawater in our experimental systems were about -74%. at 300°C. about -62%. at 400°C and

  1. Os, Sr, Nd, and Pb isotope systematics of southern African peridotite xenoliths - Implications for the chemical evolution of subcontinental mantle

    Science.gov (United States)

    Walker, R. J.; Carlson, R. W.; Shirey, S. B.; Boyd, F. R.

    1989-01-01

    Isotope analyses of Os, Sr, Nd, and Pb elements were caried out on twelve peridotite xenoliths from the Jagersfontein, Letseng-la-terae, Thaba Patsoa, Mothae, and Premier kimberlites of southern Africa, to investigate the timing and the nature of melt extraction from the continental lithosphere and its relation to the continent formation and stabilization. The distinct Os and Pb isotopic characteristics found in these samples suggested that both the low- and the high-temperature peridotites reside in an ancient stable lithospheric 'keel' to the craton that has been isolated from chemical exchange with the sublithospheric mantle for time periods in excess of 2 Ga.

  2. Ion-exchange membranes in chemical synthesis – a review

    Directory of Open Access Journals (Sweden)

    Jaroszek Hanna

    2016-12-01

    Full Text Available The applicability of ion-exchange membranes (IEMs in chemical synthesis was discussed based on the existing literature. At first, a brief description of properties and structures of commercially available ion-exchange membranes was provided. Then, the IEM-based synthesis methods reported in the literature were summarized, and areas of their application were discussed. The methods in question, namely: membrane electrolysis, electro-electrodialysis, electrodialysis metathesis, ion-substitution electrodialysis and electrodialysis with bipolar membrane, were found to be applicable for a number of organic and inorganic syntheses and acid/base production or recovery processes, which can be conducted in aqueous and non-aqueous solvents. The number and the quality of the scientific reports found indicate a great potential for IEMs in chemical synthesis.

  3. Glucans monomer-exchange dynamics as an open chemical network

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Riccardo, E-mail: riccardo.rao@uni.lu; Esposito, Massimiliano, E-mail: massimiliano.esposito@uni.lu [Complex Systems and Statistical Mechanics, Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg (Luxembourg); Lacoste, David [Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI - 10 rue Vauquelin, F-75231 Paris (France)

    2015-12-28

    We describe the oligosaccharides-exchange dynamics performed by the so-called D-enzymes on polysaccharides. To mimic physiological conditions, we treat this process as an open chemical network by assuming some of the polymer concentrations fixed (chemostatting). We show that three different long-time behaviors may ensue: equilibrium states, nonequilibrium steady states, and continuous growth states. We dynamically and thermodynamically characterize these states and emphasize the crucial role of conservation laws in identifying the chemostatting conditions inducing them.

  4. Glucans monomer-exchange dynamics as an open chemical network

    CERN Document Server

    Rao, Riccardo; Esposito, Massimiliano

    2015-01-01

    We describe the oligosaccharides-exchange dynamics performed by so-called D-enzymes on polysaccharides. To mimic physiological conditions, we treat this process as an open chemical network by assuming some of the polymer concentrations fixed (chemostatting). We show that three different long-time behaviors may ensue: equilibrium states, nonequilibrium steady states, and continuous growth states. We dynamically and thermodynamically characterize these states and emphasize the crucial role of conservation laws in identifying the chemostatting conditions inducing them.

  5. Aspartate beta-decarboxylase from Alcaligenes faecalis: carbon-13 kinetic isotope effect and deuterium exchange experiments

    International Nuclear Information System (INIS)

    The authors have measured the 13C kinetic isotope effect at pH 4.0, 5.0, 6.0, and 6.5 and in D2O at pH 5.0 and the rate of D-H exchange of the alpha and beta protons of aspartic acid in D2O at pH 5.0 for the reaction catalyzed by the enzyme aspartate beta-decarboxylase from Alcaligenes faecalis. The 13C kinetic isotope effect, with a value of 1.0099 +/- 0.0002 at pH 5.0, is less than the intrinsic isotope effect for the decarboxylation step, indicating that the decarboxylation step is not entirely rate limiting. The authors have been able to estimate probable values of the relative free energies of the transition states of the enzymatic reaction up to and including the decarboxylation step from the 13C kinetic isotope effect and the rate of D-H exchange of alpha-H. The pH dependence of the kinetic isotope effect reflects the pKa of the pyridine nitrogen of the coenzyme pyridoxal 5'-phosphate but not that of the imine nitrogen. A mechanism is proposed for the exchange of aspartate beta-H that is consistent with the stereochemistry suggested earlier

  6. Aspartate beta-decarboxylase from Alcaligenes faecalis: carbon-13 kinetic isotope effect and deuterium exchange experiments

    Energy Technology Data Exchange (ETDEWEB)

    Rosenberg, R.M.; O' Leary, M.H.

    1985-03-26

    The authors have measured the /sup 13/C kinetic isotope effect at pH 4.0, 5.0, 6.0, and 6.5 and in D/sub 2/O at pH 5.0 and the rate of D-H exchange of the alpha and beta protons of aspartic acid in D/sub 2/O at pH 5.0 for the reaction catalyzed by the enzyme aspartate beta-decarboxylase from Alcaligenes faecalis. The /sup 13/C kinetic isotope effect, with a value of 1.0099 +/- 0.0002 at pH 5.0, is less than the intrinsic isotope effect for the decarboxylation step, indicating that the decarboxylation step is not entirely rate limiting. The authors have been able to estimate probable values of the relative free energies of the transition states of the enzymatic reaction up to and including the decarboxylation step from the /sup 13/C kinetic isotope effect and the rate of D-H exchange of alpha-H. The pH dependence of the kinetic isotope effect reflects the pKa of the pyridine nitrogen of the coenzyme pyridoxal 5'-phosphate but not that of the imine nitrogen. A mechanism is proposed for the exchange of aspartate beta-H that is consistent with the stereochemistry suggested earlier.

  7. Chemical and Isotopic Thresholds in Charring: Implications for the Interpretation of Charcoal Mass and Isotopic Data.

    Science.gov (United States)

    Pyle, Lacey A; Hockaday, William C; Boutton, Thomas; Zygourakis, Kyriacos; Kinney, Timothy J; Masiello, Caroline A

    2015-12-15

    Charcoal plays a significant role in the long-term carbon cycle, and its use as a soil amendment is promoted as a C sequestration strategy (biochar). One challenge in this research area is understanding the heterogeneity of charcoal properties. Although the maximum reaction temperature is often used as a gauge of pyrolysis conditions, pyrolysis duration also changes charcoal physicochemical qualities. Here, we introduce a formal definition of charring intensity (CI) to more accurately characterize pyrolysis, and we document variation in charcoal chemical properties with variation in CI. We find two types of responses to CI: either linear or threshold relationships. Mass yield decreases linearly with CI, while a threshold exists across which % C, % N, and δ(15)N exhibit large changes. This CI threshold co-occurs with an increase in charcoal aromaticity. C isotopes do not change from original biomass values, supporting the use of charcoal δ(13)C signatures to infer paleoecological conditions. Fractionation of N isotopes indicates that fire may be enriching soils in (15)N through pyrolytic N isotope fractionation. This influx of "black N" could have a significant impact on soil N isotopes, which we show theoretically using a simple mass-balance model. PMID:26523420

  8. Process for the production of heavy water by H2-methylamine isotopic exchange

    International Nuclear Information System (INIS)

    An isotopic exchange process for separating D2 from H2 is presented. The H2-monomethylamine system is studied on the laboratory scale (kinetics, H2 solubility, thermal stability and solubility of the catalyst) and on the pilot plant scale (operating conditions and economics)

  9. The introduction of tritium in lactose and saccharose by isotope exchange with gaseous tritium

    International Nuclear Information System (INIS)

    Methods for conducting reactions of catalytic protium-tritium isotopic exchange with gaseous tritium were developed in order to synthesize tritium labelled lactose and saccharose. These methods enabled to prepare these labelled disaccharides with high molar activity. The yield was equal to 50-60%, radiochemical purity ∼ 95%

  10. Isotope exchange study of the dissociation of metal - humic substance complexes

    Czech Academy of Sciences Publication Activity Database

    Mizera, J.; Jansová, A.; Hvoždová, I.; Beneš, P.; Novák, František

    2003-01-01

    Roč. 53, A (2003), s. A97-A101. ISSN 0011-4626 Institutional research plan: CEZ:AV0Z6066911; CEZ:MSM 210000019 Keywords : isotope exchange * dissociation of metal * humic substance complexes Subject RIV: EH - Ecology, Behaviour Impact factor: 0.263, year: 2003

  11. Study of kinetics, equilibrium and isotope exchange in ion exchange systems Pt. 5

    International Nuclear Information System (INIS)

    The kinetics of Na+ - UO22+ and Mg2+ - UO22+ ion exchange on strongly acidic cation exchangers in a batch stirred reactor was studied. The exchangers Ostion KS (containing DVB in the range of 1.5-12%) and Amberlite IR 120 for experimental work were used; the concentration of the aqueous nitrate solution was always 0.2 molx1-1. The Nernst-Planck equation was applied for description of ion diffusion in the particle. The diffusion coefficients of UO22+ ions in the exchangers and their dependence on the content of DVB were obtained by evaluating the experimental data. (author)

  12. Study of kinetics, equilibrium and isotope exchange in ion exchange systems Pt. 4

    International Nuclear Information System (INIS)

    The kinetics of ion exchange in the Nasup(+)-Mgsup(2+)-strongly acidic cation exchanger system in a batch stirred reactor was studied. The samples of exchangers OSTION KS (containing DVB in the range of 1.5 - 12%) and AMBERLITE IR 120 for experimental work were used; the concentration of the aqueous nitrate solution was always 0.2M. The Nernst-Planck equation for description of diffusion of ions in a particle was used. The values of diffusion coefficients of magnesium ions in the exchangers and their dependence on the content of DVB were obtained by evaluating the experimental data and using the self-diffusion coefficients of sodium. (author)

  13. Study of the isotope effect in hydrogen exchange reactions in liquid hydrogen bromide and liquid ammonia

    International Nuclear Information System (INIS)

    The subject of the investigation was the thermodynamic isotope effects in naphthalene-hydrogen bromide and benzene-ammonia systems in the presence of potassium amide acting as a catalyst. Protium, deuterium and tritium atoms were present in the system during the experiments. In the experiments on direct and ''reverse'' exchange, the kinetic isotope effects of hydrogen were measured in the liquid-phase systems hydrogen bromide-diphenvl and benzene-ammonia. The mechanisms of exchange reactions of aromatic hydrocarbons with HBr and NH3 are considered with regard to the findings of kinetic experiments. There is a brief description of the methods of preparation in which deuterized and tritiated compounds are used. For tritium counting a scintillation coincidence system was used; and spectroscopic and mass spectrometric methods were used for the isotopic analysis of deuterized substances. (author)

  14. Separation of boron isotopes by exchange distillation process

    International Nuclear Information System (INIS)

    Boron has two stable isotopes namely 10B and 11B with natural abundance of 19.9 % and 80.1 % respectively. Both the isotopes find extensive use in the nuclear industry and can be used for the production of two radioisotopes: 11C and 13N as well as tracers to study reaction mechanisms in biological systems. 10B has a large neutron capture cross-section and, therefore, used to assist control of nuclear reactors, a shield against radiation and in neutron detection. 10B is also used in boron neutron capture therapy (BNCT) of brain cancer patients. 11B is useful as a neutron reflector and largely immune to radiation damage so can be very useful in radiation hardened semiconductor designs to be used in spacecrafts. 11B is also an attractive candidate as a fuel for aneutronic fusion. The full potential of 11B is yet to be realized in the last two applications and its demand likely to pick up in future

  15. Separation of hydrogen isotopes by exchange reaction between water and hydrogen using hydrophobic platinum catalyst

    International Nuclear Information System (INIS)

    The case of utilizing exchange reaction and distillation has been found very frequently in practical scale in the separation process of hydrogen isotopes such as heavy water and deuterium. Distillation consumes a large quantity of energy, but it is a promising method in future because of the stability and simplicity of the process utilizing phase equilibrium. In the exchange reaction method, there are four excellent reactions involving the exchange reaction between gas and liquid, and in the practical process, counter flow gas-liquid contact towers are used. In this case, single temperature exchange method and double temperature exchange method are conceivable. In order to prevent the condensation of water molecules on active platinum surface, the catalyst has been made hydrophobic. The evaluation of catalyst activity and its basic theory, the lowering of catalyst activity and the effect of regeneration, the rate of exchange reaction and activation energy, and overall mass transfer coefficient are discussed. The performance of hydrogen isotope separation in a counter flow type exchange tower is represented by two factors in gas and liquid phase reactions, and to improve the performance, the transfer at gas-liquid interface must be accelerated, (Kako, I.)

  16. Assessment of the bioavailability of heavy metals in soils using isotopic exchange kinetics method

    Energy Technology Data Exchange (ETDEWEB)

    Echevarria, G.; Gerard, E.; Shallari, S.; Massoura, S.; Schwartz, C.; Morel, J.L. [Ecole Nationale Superieur d' Agronomie et des Industries Alimentaires (ENSAIA-INRA), Lab. Sols et Environnement, 54 - Vandoeuvre les Nancy (France)

    2001-07-01

    The aim of this paper was to investigate the potential risk of food chain contamination of soils from urban and industrial sites by nickel and cadmium. Therefore, the isotopic exchange kinetics (IEK) method, which allows to understand the potential transfer from soil to plant of these two metals, was carried out on soil samples from agricultural, urban and industrial areas contaminated by mining, smelting and other metal industry activities. The IEK method have been successfully used to assess metal bioavailability in natural and anthropogenic metal rich soils and have succeeded in predicting metal transfer to plants, especially to hyper-accumulators. This method allows indeed to characterize the three main characteristics of bioavailability of metals in soils (intensity, quantity and capacity). The latter being the most difficult to assess with traditional chemical extraction procedures. A further step in improving the method would be to characterize for each soil sample the part of the metal in solution which is actually under the form M{sup 2+} rather than assuming that the total metal in solution is M{sup 2+}. It is therefore possible to assess the risk associated with the presence of metals in urban and industrial soils and also to evaluate the management practices on these areas. Their use has also allowed to assess the effect of management practices on contaminated agricultural, urban and industrial soils (liming, sewage sludge applications, phyto-extraction). The effect of such practices is often a combined effect directly on the solubility of the metals (intensity), on the increase or decrease of the exchangeable pool (quantity) and on the decrease or increase of the capacity.

  17. Multiphysics Model of Palladium Hydride Isotope Exchange Accounting for Higher Dimensionality

    Energy Technology Data Exchange (ETDEWEB)

    Gharagozloo, Patricia E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Eliassi, Mehdi [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bon, Bradley Luis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    This report summarizes computational model developm ent and simulations results for a series of isotope exchange dynamics experiments i ncluding long and thin isothermal beds similar to the Foltz and Melius beds and a lar ger non-isothermal experiment on the NENG7 test bed. The multiphysics 2D axi-symmetr ic model simulates the temperature and pressure dependent exchange reactio n kinetics, pressure and isotope dependent stoichiometry, heat generation from the r eaction, reacting gas flow through porous media, and non-uniformities in the bed perme ability. The new model is now able to replicate the curved reaction front and asy mmetry of the exit gas mass fractions over time. The improved understanding of the exchange process and its dependence on the non-uniform bed properties and te mperatures in these larger systems is critical to the future design of such sy stems.

  18. Hydrogen isotope exchanges between water and methanol in interstellar ices

    CERN Document Server

    Faure, A; Theulé, P; Quirico, E; Schmitt, B

    2015-01-01

    The deuterium fractionation of gas-phase molecules in hot cores is believed to reflect the composition of interstellar ices. The deuteration of methanol is a major puzzle, however, because the isotopologue ratio [CH2DOH]/[CH3OD], which is predicted to be equal to 3 by standard grain chemistry models, is much larger (~20) in low-mass hot corinos and significantly lower (~1) in high-mass hot cores. This dichotomy in methanol deuteration between low-mass and massive protostars is currently not understood. In this study, we report a simplified rate equation model of the deuterium chemistry occurring in the icy mantles of interstellar grains. We apply this model to the chemistry of hot corinos and hot cores, with IRAS 16293-2422 and the Orion~KL Compact Ridge as prototypes, respectively. The chemistry is based on a statistical initial deuteration at low temperature followed by a warm-up phase during which thermal hydrogen/deuterium (H/D) exchanges occur between water and methanol. The exchange kinetics is incorpor...

  19. Submarine and superimposed contact metamorphic oxygen isotopic exchange in an oceanic area, Sawyers Bar area, central Klamath Mountains, California, USA

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, W.G. [Stanford Univ., CA (United States); Kolodny, Y. [Hebrew Univ., Jerusalem (Israel)

    1997-02-01

    New bulk-rock oxygen isotope data indicate a complicated history of fluid-rock interactions in the upper few kilometers of a basaltic arc. attending its Mesozoic accretion to the western margin of North America. Folded, multiply recrystallized, weakly metasomatized mafic volcanics and interstratified sediments of the Sawyers Bar terrane, an eastern segment of the western Triassic and Paleozoic belt, were investigated. The following scenario can now be reconstructed: (1) island-arc tholeiites (IATs), ocean-island basalts (OIBs), and distal turbidites were deposited in a subsea environment during Permian and Early Mesozoic time (170-245 Ma). Basaltic rocks underwent low-temperature alteration by seawater; recrystallization occurred at 100-200{degrees}C and < 1 kbar. Alkali exchange and variable Mg-enrichment were accompanied by increases in bulk-rock {delta}{sup 18}O values of the greenstones from 6 to approximately 10{per_thousand}, preceeding initial stages of island-arc formation. (2) Middle Jurassic (165-170 Ma) suturing of the seaward oceanic arc structurally beneath a landward, 227 Ma blueschist terrane resulted in regional deformation and greenschist-facies metamorphism. Pervasive overprinting took place without important chemical or isotopic exchange under conditions of 300-425{degrees}C, 3 {+-} 1 kbar. (3) Granitoid plutons, emplaced during late-Middle Jurassic time (160-165 Ma), heated adjacent wallrocks to {approximately}500-600{degrees}C at pressures of approximately 2-3 kbar; thermal upgrading resulted in devolatilization of isotopically heavy metasediments and in the exchange of high {delta}{sup 18}O fluids with intercalated greenstones. {delta}{sup 18}O values in IAT and OIB metavolcanics increased from 9 to 10{per_thousand} alone axial portions of NS-trending folds to more than 15{per_thousand} where metabasalts are intimately interlayered with the metasediments. 72 refs., 5 figs., 1 tab.

  20. Tritium removal by hydrogen isotopic exchange between hydrogen gas and water on hydrophobic catalyst

    International Nuclear Information System (INIS)

    Many kinds of the hydrophobic catalysts for hydrogen isotopic exchange between hydrogen gas and water have been prepared. The carriers are the hydrophobic organic materials such as polytetrafluoroethylene(PTFE), monofluorocarbon-PTFE mixture(PTFE-FC), and styrene-divinylbenzene copolymer(SDB). 0.1 to 2 wt % Pt is deposited on the carriers. The Pt/SDB catalyst has much higher activity than the Pt/PTFE catalyst and the Pt/PTFE-FC catalyst shows the intermediate value of catalytic activity. The observation of electron microscope shows that the degrees of dispersion of Pt particles on the hydrophobic carriers result in the difference of catalytic activities. A gas-liquid separated type column containing ten stages is constructed. Each stage is composed of both the hydrophobic catalyst bed for the hydrogen gas/water vapor isotopic exchange and the packed column type bed for the water vapor/liquid water isotopic exchange. In the column hydrogen gas and water flow countercurrently and hydrogen isotopes are separated

  1. Charge exchange and chemical reactions with trapped Th3+

    International Nuclear Information System (INIS)

    We have measured the reaction rates of trapped, buffer gas cooled Th3+ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th3+ make them more prone to loss. Our results show that reactions of Th3+ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th3+ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th3+ and carbon dioxide. Loss rates of Th3+ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th3+ with nitrogen and argon depend on the internal electronic configuration of the Th3+.

  2. Charge Exchange and Chemical Reactions with Trapped Th$^{3+}$

    CERN Document Server

    Churchill, L R; Chapman, M S

    2010-01-01

    We have measured the reaction rates of trapped, buffer gas cooled Th$^{3+}$ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th$^{3+}$ make them more prone to loss. Our results show that reactions of Th$^{3+}$ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th$^{3+}$ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th$^{3+}$ and carbon dioxide. Loss rates of Th$^{3+}$ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th$^{3+}$ with nitrogen and argon depend on the internal electronic configuration of the Th$^{3+}$.

  3. Measurements of tritium recycling and isotope exchange in TFTR

    International Nuclear Information System (INIS)

    Tritium Balmer-alpha (Tα) emission, along with Hα and Dα is observed in the current D-T experimental campaign in TFTR. The data are a measure of the fueling of the plasma by tritium accumulated in the TFTR limiter and the spectral profile maps neutral hydrogenic velocities. Tα is relatively slow to appear in tritium neutral beam heated discharges, (Tα/(Hα + Dα + Tα) = 11% after 8 tritium-only neutral beam discharges). In contrast, the Tα fraction in a sequence of six discharges fueled with tritium puff,s increased to 44%. Larger transient increases (up to 75% Tα) were observed during subsequent tritium gas puffs. Analysis of the Doppler broadened spectral profiles revealed overall agreement with the dissociation, charge exchange, sputtering and reflection velocities predicted by the neutral Monte-Carlo code DEGAS with some deficiency in the treatment of dissociation products in the 10--100 eV range

  4. Isotope exchange reactions on ceramic breeder materials and their effect on tritium inventory

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, M.; Baba, A. [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering; Kawamura, Y.; Nishi, M.

    1998-03-01

    Though lithium ceramic materials such as Li{sub 2}O, LiAlO{sub 2}, Li{sub 2}ZrO{sub 3}, Li{sub 2}TiO{sub 3} and Li{sub 4}SiO{sub 4} are considered as breeding materials in the blanket of a D-T fusion reactor, the release behavior of the bred tritium in these solid breeder materials has not been fully understood. The isotope exchange reaction rate between hydrogen isotopes in the purge gas and tritium on the surface of breeding materials have not been quantified yet, although helium gas with hydrogen or deuterium is planned to be used as the blanket purge gas in the recent blanket designs. The mass transfer coefficient representing the isotope exchange reaction between H{sub 2} and D{sub 2}O or that between D{sub 2} and H{sub 2}O in the ceramic breeding materials bed is experimentally obtained in this study. Effects of isotope exchange reactions on the tritium inventory in the bleeding blanket is discussed based on data obtained in this study where effects of diffusion of tritium in the grain, absorption of water in the bulk of grain, and adsorption of water on the surface of grain, together with two types of isotope exchange reactions are considered. The way to estimate the tritium inventory in a Li{sub 2}ZrO{sub 3} blanket used in this study shows a good agreement with data obtained in such in-situ experiments as MOZART, EXOTIC-5, 6 and TRINE experiments. (author)

  5. Determination of phosphorus in urban sewage sludge using the isotopic exchange kinetics method

    International Nuclear Information System (INIS)

    The aim of this work was to assess the differences among soil available P, the use by the plants of sludge P, and of a water soluble fertilizer (Ca(H2PO4)2 ) P, using isotopic exchange kinetics methods. The sludge was provided by the Sewage Sludge Treatment Plant of Tucuman City, Argentina. The isotopic exchange kinetics experiment, in which the fate of carrier free 32PO4 added to the soil solution at a steady state was studied, gives information on soil P exchangeability. The experiment was carried out in the laboratory, where sewage sludge and water soluble fertilizer were added to soil samples taken at a depth of 0-25 and 25-40 cm. Changes in the soil P isotopically exchangeable within 1 minute measurements in the soil with sludge and in the soil with water soluble fertilizer showed that the 0-25 cm deep soil samples had a low P sorption capacity (r1 /R values were low). The sludge had high total and organic P, but the P in the soil solution was lower than the P provided by the water soluble fertilizer. Therefore, despite its higher total P content, this sludge contained slow available forms of P

  6. Determination of uranium isotopes in environmental samples by anion exchange in sulfuric and hydrochloric acid media.

    Science.gov (United States)

    Popov, L

    2016-09-01

    Method for determination of uranium isotopes in various environmental samples is presented. The major advantages of the method are the low cost of the analysis, high radiochemical yields and good decontamination factors from the matrix elements, natural and man-made radionuclides. The separation and purification of uranium is attained by adsorption with strong base anion exchange resin in sulfuric and hydrochloric acid media. Uranium is electrodeposited on a stainless steel disk and measured by alpha spectrometry. The analytical method has been applied for the determination of concentrations of uranium isotopes in mineral, spring and tap waters from Bulgaria. The analytical quality was checked by analyzing reference materials. PMID:27451111

  7. Study of carbon-isotope exchange reactions between potassium cyanide and some carbonates, and their use for obtaining C14-labelled potassium cyanide

    International Nuclear Information System (INIS)

    The authors examine the results of a study on the isotope exchange of potassium cyanide with compounds differing greatly from it both in composition and structure, such as carbonates of alkaline and alkali-earth metals. The carbon-isotope exchange reaction in the KC12N-BaC14O3 system was studied at 600-800oC. The ratio between the components of this system and those given below agreed with the equimolecular ratio. The authors show that at high temperatures complete exchange between these compounds can be secured. The exchange reaction begins when the cyanide melt is formed; later it occurs between the liquid and the solid phases, and its speed increases with temperature; at 800oC it is completed in 2 h. With carbonates of alkali metals the exchange reaction occurs in the melt and is completed at lower temperatures. The authors obtained cyanide-labelled potassium by the following method : (1) The isotope exchange reaction KC12N-BaC14O3 is produced at 800oC in 2 h. (2) The mixture KCN+BaCO3 is separated by extracting the KCN with liquid ammonia in a circulating extractor. By exchanging the equimolecular quantities KCN and BaCO3, potassium cyanide is obtained with a chemical yield of more than 90% and a basic-substance content of 96-97%. By using BaCO3 with a high specific activity (60-70 mc/g), a KCN specific activity of over 80 mc/g may be obtained. The barium carbonate depleted of isotope C14 regenerates after the ammonia extraction without appreciable loss. (author)

  8. Chemical separation of Mo and W from terrestrial and extraterrestrial samples via anion exchange chromatography.

    Science.gov (United States)

    Nagai, Yuichiro; Yokoyama, Tetsuya

    2014-05-20

    A new two-stage chemical separation method was established using an anion exchange resin, Eichrom 1 × 8, to separate Mo and W from four natural rock samples. First, the distribution coefficients of nine elements (Ti, Fe, Zn, Zr, Nb, Mo, Hf, Ta, and W) under various chemical conditions were determined using HCl, HNO3, and HF. On the basis of the obtained distribution coefficients, a new technique for the two-stage chemical separation of Mo and W, along with the group separation of Ti-Zr-Hf, was developed as follows: 0.4 M HCl-0.5 M HF (major elements), 9 M HCl-0.05 M HF (Ti-Zr-Hf), 9 M HCl-1 M HF (W), and 6 M HNO3-3 M HF (Mo). After the chemical procedure, Nb remaining in the W fraction was separated using 9 M HCl-3 M HF. On the other hand, Nb and Zn remaining in the Mo fraction were removed using 2 M HF and 6 M HCl-0.1 M HF. The performance of this technique was evaluated by separating these elements from two terrestrial and two extraterrestrial samples. The recovery yields for Mo, W, Zr, and Hf were nearly 100% for all of the examined samples. The total contents of the Zr, Hf, W, and Mo in the blanks used for the chemical separation procedure were 582, 9, 29, and 396 pg, respectively. Therefore, our new separation technique can be widely used in various fields of geochemistry, cosmochemistry, and environmental sciences and particularly for multi-isotope analysis of these elements from a single sample with significant internal isotope heterogeneities. PMID:24801276

  9. Chemical and environmental isotopes study of precipitation in Syria

    International Nuclear Information System (INIS)

    Chemical and isotopic compositions of monthly precipitation were monitored at 12 stations distributed over the entire region in Syria for a period of 4 years from December 1999 to April 2003. Amount of precipitation and mean air temperature of rain monthly were also recorded. The conductivity of rain waters varies between 35 μ/cm in the mountainous stations and 336 μ/cm at Deir Az-Zor station. Excepted Tartous station, the mean value of Cl in the rainfall in all station is 3.8 mg/l. The seasonal variations in δ18O are smaller at west stations than to the east stations due to low seasonal temperature variations. All stations are characterized by water lines with slopes significantly lower than GMWL, except Bloudan, suggesting the influence of local factors on the isotopic composition of the precipitation. d-excess values decrease from 19% in the western part to 13% in the eastern part of Syria, indicating the influence of the precipitation generated by the air masses coming from the Mediterranean Sea over Syria. A reliable altitude effect represent by depletion of heavy stable isotopes of about -0.21, and -1.47, per 100 m elevation of 18O and δ2H, respectively. Monthly tritium activity and seasonal variations pattern are low in the west stations than at the east stations. The weighted mean tritium values are between 3 to 9 TU during 2000-2003, and it is increasing with distance from the Syrian coast by 1 TU /100 Km. (author)

  10. Dual Studies on a Hydrogen–Deuterium Exchange of Resorcinol and the Subsequent Kinetic Isotope Effect

    OpenAIRE

    Giles, Richard; Kim, Iris; Chao, Weyjuin Eric; Moore, Jennifer; Jung, Kyung Woon

    2014-01-01

    An efficient laboratory experiment has been developed for undergraduate students to conduct hydrogen–deuterium (H–D) exchange of resorcinol by electrophilic aromatic substitution using D2O and a catalytic amount of H2SO4. The resulting labeled product is characterized by 1H NMR. Students also visualize a significant kinetic isotope effect (k H/k D ≈ 3 to 4) by adding iodine tincture to solutions of unlabeled resorcinol and the H–D exchange product. This method is highly adaptable to fit a tar...

  11. Short-lived isotopes in central chemical control of ventilation

    International Nuclear Information System (INIS)

    Central chemical ventilatory drive is dependent on elecrolyte and acid-base status of brain ECF, as well as the interaction between H+ metabolism and CO2 fixation and metabolism of amino acid neutrotransmitters - GABA and glutamate. In the anesthetized dogs, using the short-lived positron emitting isotope of carbon (11C) either in the form of molecular CO2 or as HCO3- injected intraarterially it was demonstrated that there is first pass uptake of 16% of HCO3- from blood into brain and 86% uptake of molecular CO2, thus indicating that the brain-blood barrier is permeable to HCO3-, but that HCO3- content in the CNS is regulated as a function of dissociation of strong ions such as Cl- and Na+. Relationship between CO2 fixations and brain glutamine was studied with intraarterial injection of 13N-ammonia and its turnover into glutamine when PCO2 was increased. Ammonia turnover into glutamine was increased by a factor of 2 when PaCO2 was increased by 35 torr, and this rise in glutamine was linearly related to the rise in CSF [HCO3-]. Glutamine is then converted into the active neurotransmitters GABA and glutamate. Thus, the short-lived isotopes allow for assessment of the interaction of biochemical events in the CNS in the central respiratory drive. (orig.)

  12. Chemical and environmental isotope study of precipitation in Syria

    International Nuclear Information System (INIS)

    The rain waters from a network covering 9 meteorological stations distributed mainly in the western part of Syria have been investigated using chemical and environmental isotope techniques during a period of 5 months from December 1989 to April 1990. The chemistry of rain waters falling over the mountainous stations shows a low solute concentration (16-55 mg/L) comparing with those falling over the coastal and anterior stations (36-150 mg/L). The study shows also that the rain water are generally characterized by a high deuterium excess (d = 19 per mille) comparing with that of the global meteoric waters (d = 10 per mille). Mean while, the estimated deuterium excess is found to be lower than that given for the eastern Mediterranean meteoric water (d = 22 per mille). The altitude effect is shown up by a depletion of heavy stable isotopes of about -0.23 per mille and -1.65 per mille per 100 meters for δoxygen-18 and δdeuterium, respectively. The spatial distribution pattern of tritium contents shows a gradual build up with the increasing distance from the Syrian coast. The weighted mean tritium content in rain waters falling over the country is estimated to be around 9.5 TU during the period of observation. (author). 22 refs, 9 figs, 2 tabs

  13. Chemical and environmental isotope study of precipitation in Syria

    International Nuclear Information System (INIS)

    Waters from a network of rainfall collection covering mine meteorological stations distributed mainly in the western part of Syria have been assayed using chemical and environmental isotope techniques for a period of 5 months from Dec. 1989 to Apr. 1990. The chemistry of rain waters falling over the mountainous stations shows a low solute concentration (20-105 mg 1-1) compared with those falling over the coastal and anterior stations (50-210 mg 1-1). The rain waters was generally characterized by a high deuterium excess (d=19%) compared with that of typical global meteoric waters (d=10%). The estimated deuterium excess is lower than that for the eastern Mediterranean meteoric waters (d=22%). The altitude effect is shown up by a depletion of heavy stable isotopes of about - 0.23% and -1.65% per 100 m elevation of δ 18O and δD, respectively. The spatial distribution pattern of tritium contents shows a gradual build up with increasing distance from the Syrian coast. The weighted mean tritium content in rain waters falling over the country is estimated to amount to 9.5 tritium units (TU) during the period of observation. (author)

  14. The kinetics of the 15N/14N isotopic exchange between nitric oxide and nitric acid

    International Nuclear Information System (INIS)

    The rate of the 15N isotopic exchange between NO-NHO3 at high nitric acid concentration (2-10M) have been measured. The experimental data were obtained by contacting nitric oxide at atmospheric pressure with nitric acid solution labelled with 15N, in a glass contactor. The measurements were carried out in a glass vessel with magnetic stirrer maintaining always the same stirring rate (17 rot.s-1). The temperature was kept constant at 25 +-0.5 deg C. The reaction vessel was connected to a vacuum line and a purified nitric oxide source. The rate of the isotopic exchange and of the nitric oxide absorption in nitric acid were determined with a gas-burette in the simple apparatus described earlier. (T.G.)

  15. Oxygen isotope exchange between metabolites and water during biochemical reactions leading to cellulose synthesis

    International Nuclear Information System (INIS)

    Cellulose was produced heterotrophically from different carbon substrates by carrot tissue cultures and Acetobacter xylinum (a cellulose-producing bacterium) and by castor bean seeds germinated in the dark, in each case in the presence of water having known concentration of oxygen-18 (18O). We used the relationship between the amount of 18O in the water and in the cellulose that was synthesized to determine the number and 18O content of the substrate oxygens that exchanged with water during the reactions leading to cellulose synthesis. Our observations support the hypothesis that oxygen isotope ratios of plant cellulose are determined by isotopic exchange occurring during hydration of carbonyl groups of the intermediates of cellulose synthesis. (author)

  16. Preparation of Pt-PTFE hydrophobic catalyst for hydrogen-water isotope exchange

    International Nuclear Information System (INIS)

    The hydrophobic catalyst used in the hydrogen-water isotope exchange is prepared with Pt as the active metal, PTFE as the hydrophobic material, active carbon or silicon dioxide as the support. The isotope catalytic exchange reaction between hydrogen and water is carried out in the trickle bed and the effects of different carriers, mass fraction of Pt and PTFE on the catalytic activity are discussed. The experimental results show that the activity of Pt-C-PTFE hydrophobic catalyst with the ratio between PTFE and Pt-C from 1 to 2 is higher than other kinds of catalysts and the overall volume transfer coefficient is increased with the increasing of the hydrogen flow rate and reaction temperature

  17. Examination of the isotopic exchange columns used in heavy water fabrication by nondestructive metallography

    International Nuclear Information System (INIS)

    In this paper the results are presented of an investigation using nondestructive metallography of the isotopic exchange columns used for heavy water fabrication in ROMAG PROD plant at Drobeta Turnu Severin. The nondestructive metallography is based on the examination of the surface moulds. Thus the corroded areas on the inner walls of the isotopic exchange columns are investigated with metallographic replicas to observe microstructures in steel G 52/28 and reveal possible microcracks. Finally, metallographic structures of the investigated areas were determined but structural modifications with respect to the control ones were not observed. Only, in the tray 30 in the C 1106 column microcracks were evidenced in the characteristic areas at the welded joins were the tray attached to the column. So a new intervention was needed

  18. Calculation of isotopic profile during band displacement on ion exchange resins

    International Nuclear Information System (INIS)

    A method has been developed to calculate the isotopic profile during band displacement on ion exchange resins using computer simulation. Persoz had utilized this technique earlier for calculating the isotopic profile during band displacement as well as frontal analysis. The present report deals with a simplification of the method used by Persoz by reducing the number of variables and making certain approximations where the separation factor is not far from unity. Calculations were made for the typical case of boron isotope separation. The results obtained by the modified method were found to be in very good agreement with those obtained by using an exact equation, at the same time requiring conside--rably less computer time. (author)

  19. Corrosion and iron transport in H2 O - H2 S isotopic exchange installations

    International Nuclear Information System (INIS)

    The paper describes the corrosion effects in the H2 O - H2 S isotopic exchange installation and presents the non-destructive methods of continuous testing of the exposed surfaces of the equipment and piping system. Two solutions worked out to prevent corrosion processes are provided. They were implemented at large scale on the GS Ramnicu Valcea pilot and the heavy water plant ROMAG Drobeta Tr.Severin

  20. Oxygen Isotope Exchange between Carbon Dioxide and Solid Ti(18)O(2)

    Czech Academy of Sciences Publication Activity Database

    Civiš, Svatopluk; Ferus, Martin

    New York : IEEE, 2011, s. 1-3. ISBN 978-1-4577-0880-0. [International Conference on Transparent Optical Networks (ICTON) /13./. Stockholm (SE), 26.06.2011-30.06.2011] R&D Projects: GA AV ČR IAA400400705; GA AV ČR IAAX00100903 Institutional research plan: CEZ:AV0Z40400503 Keywords : TiO2 * oxygen isotope exchange * Raman spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry

  1. Isotope exchange study of the dissociation of metal-humic complexes

    International Nuclear Information System (INIS)

    Prediction of the migration of toxic metals and radionuclides in the environment requires knowledge of equilibrium and kinetic parameters characterising their interaction with humic substance (HS). In this work, isotope exchange of Eu and Co in the systems containing HS has been used to study dissociation of the cations from their complexes with HS under quasi-stationary conditions. In the experimental arrangement of the so-called diaphragm method, a dialysis membrane divides two compartments containing solutions of metal and HS, identical in both half-cells but for radiolabeling (152Eu and 60Co) applied only in one cell. The membrane is permeable for free metal cation but not for the metal-HS complex. The slow dissociation of metal cation from HS is reflected by retardation (compared to a reference system in the absence of HS) of the rate of the isotope exchange between the two compartments. However, only an apparent dissociation rate can be observed, as detection of fast dissociation is limited by the rate of diffusion of dissociated cations through membrane and by their recombination with available binding sites of HS. The rate of isotope exchange of Eu and Co in the systems with HS (Aldrich sodium humate, soil humic and fulvic acid) was monitored as function of pH (4 and 6), ionic strength (0.01 and 0.1 M), and the degree of HS loading with metal ([M]0 = 10-7 - 2x10-5 M at 10 mg/L HS). For Co, the rate of 60Co2+ diffusion through the membrane showed up to control the rate of the isotope exchange indicating that the Co-HS dissociation is too fast to be followed by the diaphragm method, and that the abundance of non-complexed Co is not negligible. The apparent rate of Eu-HS dissociation was found to be enhanced by decreasing pH value, increasing ionic strength, and increasing metal loading (i.e., metal/HS ratio). For interpretation of the experimental kinetic data, a discrete 2-component model (bi-exponential decay function) was applied. Based on comparison of

  2. Isotope effects and O-exchange with water during N2O production by denitrifying fungi

    Science.gov (United States)

    Rohe, Lena; Braker, Gesche; Well, Reinhard; Giesemann, Anette; Anderson, Traute-Heidi; Wrage-Mönnig, Nicole; Flessa, Heinz

    2013-04-01

    N2O from soil denitrification originates from bacteria and - to an unknown extent - also from fungi. In pure culture studies, bacterial and fungal denitrification showed differences in isotopomer ratios of N2O. Isotopomer ratios of N2O can be expressed as 15N site preference (SP), i.e. the difference between δ15N of the central and terminal N-position of the asymmetric N2O molecule and might be suitable to distinguish between bacterial and fungal N2O under denitrifying soil conditions. Oxygen exchange takes place between H2O and intermediates during the denitrification process. Several studies showed that O-exchange of bacterial denitrifiers varies, but information about fungal O-exchanges is lacking. The objectives of the study presented are i) to verify SP of fungal N2O reported for two strains from pure culture studies and ii) to analyze the oxygen exchange between intermediates and H2O during denitrification in fungal pure cultures. Six different fungal pure cultures known to be capable of denitrification were incubated under anaerobic conditions, either with nitrite or nitrate. Gas samples were analysed for concentration and isotopic signatures (SP, average δ15N, δ18O) of N2O. To investigate the oxygen exchange, both treatments were also established in a tracer experiment where 18O-labelled water was used in the medium. The fungal strains evaluated so far indicate similar SP as reported previously. Concerning the amount of N2O produced, the nitrite led to a higher yield than nitrate. O-exchange with 18O-labelled water during fungal denitrification was visible. Using nitrite, the exchange ranged amounted from 39% to full exchange while nitrate led to exchange rates between 13% and full exchange. Detailed results will be presented.

  3. Submarine and superimposed contact metamorphic oxygen isotopic exchange in an oceanic area, Sawyers Bar area, central Klamath Mountains, California, USA

    International Nuclear Information System (INIS)

    New bulk-rock oxygen isotope data indicate a complicated history of fluid-rock interactions in the upper few kilometers of a basaltic arc. attending its Mesozoic accretion to the western margin of North America. Folded, multiply recrystallized, weakly metasomatized mafic volcanics and interstratified sediments of the Sawyers Bar terrane, an eastern segment of the western Triassic and Paleozoic belt, were investigated. The following scenario can now be reconstructed: (1) island-arc tholeiites (IATs), ocean-island basalts (OIBs), and distal turbidites were deposited in a subsea environment during Permian and Early Mesozoic time (170-245 Ma). Basaltic rocks underwent low-temperature alteration by seawater; recrystallization occurred at 100-200 degrees C and 18O values of the greenstones from 6 to approximately 10 per-thousand, preceeding initial stages of island-arc formation. (2) Middle Jurassic (165-170 Ma) suturing of the seaward oceanic arc structurally beneath a landward, 227 Ma blueschist terrane resulted in regional deformation and greenschist-facies metamorphism. Pervasive overprinting took place without important chemical or isotopic exchange under conditions of 300-425 degrees C, 3 ± 1 kbar. (3) Granitoid plutons, emplaced during late-Middle Jurassic time (160-165 Ma), heated adjacent wallrocks to ∼500-600 degrees C at pressures of approximately 2-3 kbar; thermal upgrading resulted in devolatilization of isotopically heavy metasediments and in the exchange of high δ18O fluids with intercalated greenstones. δ18O values in IAT and OIB metavolcanics increased from 9 to 10 per-thousand alone axial portions of NS-trending folds to more than 15 per-thousand where metabasalts are intimately interlayered with the metasediments. 72 refs., 5 figs., 1 tab

  4. OXYGEN ISOTOPIC COMPOSITIONS OF THE ALLENDE TYPE C CAIs: EVIDENCE FOR ISOTOPIC EXCHANGE DURING NEBULAR MELTING AND ASTEROIDAL THERMAL METAMORPHISM

    Energy Technology Data Exchange (ETDEWEB)

    Krot, A N; Chaussidon, M; Yurimoto, H; Sakamoto, N; Nagashima, K; Hutcheon, I D; MacPherson, G J

    2008-02-21

    that CAIs 100, 160 and CG5 experienced melting in an {sup 16}O-rich ({Delta}{sup 17}O < -20{per_thousand}) nebular gas in the CAI-forming region. The Type C and Type-B-like portions of CAI 6-1-72 experienced melting in an {sup 16}O-depleted ({Delta}{sup 17}O {ge} -13{per_thousand}) nebular gas. CAIs ABC, TS26 and 93 experienced isotopic exchange during re-melting in the presence of an {sup 16}O-poor ({Delta}{sup 17}O {ge} -10{per_thousand}) nebular gas in the chondrule-forming region(s). Subsequently, Allende Type C CAIs experienced post-crystallization isotopic exchange with an {sup 16}O-poor reservoir that affected largely melilite and anorthite. Because pseudomorphic replacement of lacy melilite by grossular, monticellite and forsterite occurred during thermal metamorphism, some oxygen isotopic exchange of melilite and anorthite must have continued after formation of these secondary minerals. We suggest that some or all oxygen isotopic exchange in melilite and anorthite occurred during fluid-assisted thermal metamorphism on the CV parent asteroid. Similar processes may have also affected melilite and anorthite of CAIs in metamorphosed CO chondrites.

  5. Direct measurement of biosphere-atmosphere isotopic CO2 exchange using the eddy covariance technique

    Science.gov (United States)

    Griffis, T. J.; Sargent, S. D.; Baker, J. M.; Lee, X.; Tanner, B. D.; Greene, J.; Swiatek, E.; Billmark, K.

    2008-04-01

    Quantifying isotopic CO2 exchange between the biosphere and atmosphere presents a significant measurement challenge, but has the potential to provide important constraints on local, regional, and global carbon cycling. Past approaches have indirectly estimated isotopic CO2 exchange using relaxed eddy accumulation, the flask-based isoflux method, and flux-gradient techniques. Eddy covariance (EC) is an attractive method because it has the fewest theoretical assumptions and the potential to give a direct measure of isotopic CO2 flux, but it requires a highly sensitive and relatively fast response instrument. To date, no such field measurements have been reported. Here we describe the use of a closed-path tunable diode laser absorption spectroscopy and eddy covariance (EC-TDL) system for isotopic (C16O2, 13CO2, C18O16O) flux measurements. Results are presented from an intensive field experiment conducted over a soybean canopy from 18 July to 20 September 2006. This experiment represents a rigorous field test of the EC-TDL technique because the transport was dominated by relatively high frequency eddies. Net ecosystem CO2 exchange (FN) measured with the EC-TDL system showed strong correlation (r2 = 0.99) in the half-hourly fluxes with an EC open-path infrared gas analyzer (EC-IRGA) over the 60-d period. Net CO2 flux measured with the EC-IRGA and EC-TDL systems agreed to within 9%. Flux loss associated with diminished frequency response beyond 1 Hz for the EC-TDL system was approximately 8% during daytime windy (>4 m s-1) conditions. There was no significant evidence of a kinetic-type fractionation effect related to a phase shift among isotopologues due to tube attenuation. Investigation of isotopic spectral similarity in the flux ratio (δNx) for both 13CO2 and C18O16O transport showed that δNx was relatively independent of eddy scale for this ecosystem type. Flux loss, therefore, did not significantly bias δNx. There was excellent agreement between isofluxes (F

  6. Isotopic study of water exchange between atmosphere and biosphere at Changa Manga site in Pakistan

    International Nuclear Information System (INIS)

    Study of water exchange between atmosphere and biosphere was initiated to understand the ties between these two spheres. Samples of leaves and stems of 23 woody plants along with soil from the surface and from the depth of 7 cm were collected from Changa Manga forest. Moisture content from these samples was extracted using the vacuum distillation method and analyzed for stable isotopes (/sup 18/O and /sup 2/H). Air moisture was also collected in the field. Isotopic data plotted long with the Local Meteoric Water Line (LMWL) indicates that /sup 18/O and /sup 2/H contents of moisture in the leaves of woody plants are higher than their respective stems. This behavior is due to the evaporative enrichment trend originating from the soil moisture in active root zone and also from the leaf surface. The stem samples did not show any significant variation in gamma /sup 18/O suggesting no significant evaporation from stems of big trees. Degree of enrichment of leave samples of woody plants indicated the species-specific effects in isotopes during transpiration. Pine and Eucalyptus leaves showed more variation in the isotopic contents as compared to other species. Temporal variations of /sup 18/O and /sup 2/H in the leaves indicated enriched isotopic values during hot and dry periods as compared to those during wet period (monsoon and winter rains) mainly due to higher transpiration rates at high temperature and low humidity. (orig./A.B.)

  7. Evaluation of Hydrogen Isotope Exchange Methodology on Adsorbents for Tritium Removal

    International Nuclear Information System (INIS)

    The Savannah River National Laboratory has demonstrated a potential process that can be used to remove tritium from tritiated water using Pt-catalyzed molecular sieves. The process is an elemental isotope exchange process in which H2 (when flowed through the molecular sieves) will exchange with the adsorbed water, D2O, leaving H2O adsorbed on the molecular sieves. Various formulations of catalyzed molecular sieve material were prepared using two different techniques, Pt-implantation and Pt-ion exchange. This technology has been demonstrated for a protium (H) and deuterium (D) system, but can also be used for the removal of tritium from contaminated water (T2O, HTO, and DTO) using D2 (or H2)

  8. Evaluation of hydrogen isotope exchange methodology on adsorbents for tritium removal

    International Nuclear Information System (INIS)

    The Savannah River National Laboratory has demonstrated a potential process that can be used to remove tritium from tritiated water using Pt-catalyzed molecular sieves. The process is an elemental isotope exchange process in which H2 (when flowed through the molecular sieves) will exchange with the adsorbed water, D2O, leaving H2O adsorbed on the molecular sieves. Various formulations of catalyzed molecular sieve material were prepared using two different techniques, Pt-implantation and Pt-ion exchange. This technology has been demonstrated for a protium (H) and deuterium (D) system, but can also be used for the removal of tritium from contaminated water (T2O, HTO, and DTO) using D2 (or H2). (authors)

  9. Exchange of hydrogen isotopes in oxide ceramics and water-vapor using ERD technique

    International Nuclear Information System (INIS)

    This paper describes the exchange of deuterium in a tritium breeding ceramics, Li2ZrO3, for protium by exposure to air-vapor which has been studied by means of the elastic recoil detection technique with 1.7 MeV He+ ion beam. The ceramic specimen implanted up to saturation concentration at room temperature with 5 keV D2+ ions is exposed to normal air introduced into the vacuum chamber at room temperature. It is found that the retained number of D implanted decreases, while the retain number of H increases as the exposure time to normal air increases. The exchange behavior of D for H in Li2ZrO3 is compared with that in SrCe0.95Yb0.05O3-δ studied previously and the processes for hydrogen isotope exchange observed are discussed

  10. Experimental investigation of rates and mechanisms of isotope exchange (O, H) between volcanic ash and isotopically-labeled water

    Science.gov (United States)

    Nolan, Gary S.; Bindeman, Ilya N.

    2013-06-01

    The hydrogen and oxygen isotope ratios in hydrous minerals and volcanic glass are routinely used as paleo-proxies to infer the isotopic values of meteoric waters and thus paleo-climatic conditions. We report a series of long-term exposure experiments of distal 7700 BP Mt. Mazama ash (-149‰ δ2H, +7‰ δ18O, 3.8 wt.% H2O) with isotopically-labeled water (+650‰ δ2H, +56‰ δ18O). Experiments were done at 70, 40 and 20 °C, and ranged in duration from 1 to 14454 h (˜20 months), to evaluate the rates of deuterium and 18O exchange, and investigate the relative role of exchange and diffusion. We also investigate the effect of drying on H2Otot and δ2H in native and reacted ash that can be used in defining the protocols for natural sample preparation. We employ Thermal Conversion Elemental Analyzer (TCEA) mass spectrometry, thermogravimetric analysis and a KBr pellet technique with infrared spectroscopy to measure the evolution of δ2H, total water, and OH water peaks in the course of exposure experiments, and in varying lengths of vacuum drying. Time series experiments aided by infrared measurements demonstrate the following new results: (i) It wasobserved that from 5 to >100‰ δ2H increases with time, with faster deuterium exchange at higher temperatures. Times at 15% of theoretical "full δ2H exchange" are: 15.8 years at 20 °C, 5.2 years at 40 °C, and 0.4 years at 70 °C. (ii) Even at extended exposure durations experiments show no net increase in water weight percent nor in δ18O in ash; water released from ash rapidly by thermal decomposition is not enriched in δ18O. This observation clearly suggests that it is hydrogen exchange, and not water addition or oxygen exchange that characterizes the process. (iii) Our time series drying, Fourier transform infrared (FTIR)-KBr and Thermogravimetric Analyzer (TGA) analyses collectively suggest a simple mechanistic view that there are three kinds of "water" in ash: water (mostly H2O) that is less strongly bonded

  11. IPILPS: Modelling Stable Water Isotopes Exchanges Between the Land and the Atmosphere

    Science.gov (United States)

    Sellers, A.; Yoshimura, K.; Fischer, M.; Aleinov, I.; Irannejad, P.; McGuffie, K.; Riley, W. J.; Schmidt, G. A.; Sturm, K.

    2005-12-01

    iPILPS, 'Isotopes in the Project for Intercomparison of Land-Surface Parameterization Schemes', is a World Climate Research Programme project operating under the auspices of the Global Energy and Water Cycle Experiment. iPILPS adds stable water isotopes to PILPS' overarching goal of improving understanding of the parameterization of interactions between the atmosphere and land surface in climate and weather forecast models. Land and atmosphere exchanges are complex functions of many physical and biochemical processes that have a range of temporal and spatial scales. Many of these processes also result in fractionation of stable water isotopologues (SWIs), allowing isotopes (a) to be used to investigate latent and sensible heat fluxes and (b) to investigate the differences between, and how well, different parameterisations of the complex processes simulate energy and moisture exchanges. In Phase 1 of iPILPS, several isotope-enabled land surface schemes (ILSS) were run off-line with forcing derived by nesting the regional model REMOiso into an isotope-enabled GCM (ECHAM 4). Phase 1 intercomparisons initially focussed on comparing (i) the conservation and equilibrium state of SWIs achieved by each ILSS and (ii) the energy and SWI balance over several years at 3 different locations: mid-latitude (deciduous) grass/woods, Munich 48°N 11°E; tropical (evergreen) rainforest, Manaus 3°S 60°W; mid-latitude eucalypt (evergreen) forest, Tumbarumba 35°S 148°E. This paper presents results of these experiments from selected participant ILSSs (REMOiso, iso-MATSIRO, ICHASM, ISOLSM and GISS Model E). These preliminary results demonstrate the merit in SWI evaluation of continental parameterization, although the large variation in the energy and SWI budgets points to the continuing need for improvement in land surface schemes.

  12. Global changes and the air-sea exchange of chemicals

    International Nuclear Information System (INIS)

    Present and potential future changes to the global environment have important implications for marine pollution and for the air-sea exchange of both anthropogenic and natural substances. This report addresses three issues related to the potential impact of global change on the air-sea exchange of chemicals: Global change and the air-sea transfer of the nutrients nitrogen and iron. Global change and the air-sea exchange of gases. Oceanic responses to radiative and oxidative changes in the atmosphere. The deposition of atmospheric anthropogenic nitrogen has probably increased biological productivity in coastal regions along many continental margins. Atmospheric deposition of new nitrogen may also have increased productivity somewhat in mid-ocean regions. The projected future increases of nitrogen oxide emissions from Asia, Africa and South America will provide significant increases in the rate of deposition of oxidized nitrogen to the central North Pacific, the equatorial Atlantic, and the equatorial and central South Indian Oceans. Atmospheric iron may be an important nutrient in certain open regions. Future changes will likely occur if there are changing patterns of aridity and wind speed as a result of climate change. The most important future effects on surface ocean pCO2 will likely be caused by changes in ocean circulation. The pH of the ocean would decrease by ∼0.3 units for a doubling of pCO2, reducing the capacity of the ocean to take up CO2. There is increasing evidence that dimethyl sulfide from the ocean is a source of cloud condensation nuclei and thus a factor controlling cloud albedo. By 2060 in the southern hemisphere reduction in total column stratospheric ozone from recent levels could reach 2 to 5% in the tropics, 10% at mid latitudes, and over 20% at 60 deg C. S. In this same time frame increases in ground-level effective UV-B radiation could reach 5%, 26% and 66%, at low, mid, and high latitudes in the southern hemisphere. Changes in

  13. Isotopic exchange between CO2 and H2O and labelling kinetics of photosynthetic oxygen

    International Nuclear Information System (INIS)

    The reaction of carbon dioxide with water has been studied by measuring the rate of oxygen exchange between C18O2 and H216O. The mathematical treatment of the kinetics allows to determine with accuracy the diffusion flow between the gas and the liquid phase, in the same way as the CO2 hydration rate. The velocity constant of this last process, whose value gives the in situ enzymatic activity of carbonic anhydrase, has been established in the case of chloroplast and Euglena suspensions and of aerial leaves. The study of the isotopic exchange between C18O2 and a vegetable submitted to alternations of dark and light has allowed to calculate the isotopic abundance of the metabolized CO2 whose value has been compared to that of the intracellular water and that of photosynthetic oxygen. In addition, a new method using 13C18O2 gives the means to measure with accuracy eventual isotopic effects. The labelling kinetics of the oxygen evolved by Euglena suspensions whose water has been enriched with 18O have been established at different temperatures. (author)

  14. Boron isotope separation by ion exchange chromatography using weakly basic anion exchange resin

    International Nuclear Information System (INIS)

    Influences of operating temperatures and concentrations of feed boric acid solutions were examined on the above titled process over the ranges of 25 - 70 0C and 0.1 - 1.6 mol/dm3 (M), respectively. The ideal displacement chromatography with a very sharp-cut boundary of the boric acid adsorption band was realized at higher temperatures and lower boric acid concentrations within the experimental conditions. The isotope separation coefficient epsilon was found to decrease with increases in either temperature or the boric acid concentration. The observed values of epsilon at 25 0C were 0.013, 0.012 and 0.011 corresponding to feed boric acid concentrations of 0.1 M, 0.4 M and 0.8 M, respectively. The epsilon's at 70 0C were 0.0097 (0.1 M), 0.0086 (0.4 M), 0.0083 (0.8 M) and 0.0073 (1.6 M). A temperature of 40 0C and 0.4 M of boric acid concentration was considered the optimum operating condition for the production of enriched 10B. (author)

  15. Solubility, diffusivity, and isotopic exchange rate of hydrogen isotopes in Li-Pb

    International Nuclear Information System (INIS)

    The diffusion, solution and permeation coefficients of hydrogen isotopes in liquid Li-Pb which is a candidate liquid blanket material for fusion reactors were determined in the temperature range 573-973 K using an unsteady permeation method. Each coefficients was correlated to temperature as follows: DLi-Pb = 1.8 x 10-8 exp(-11590/RT) [m2/s] (1) KLi-Pb = 2.1x10-6 exp(-18700/RT) [1/Pa0.5] (2) PLi-Pb = 1.8x10-9 exp(-30290/RT) [mol/msPa0.5] (3) The hydrogen permeation flux depends on the square root of pressure at 773-973 K. Although the power of pressure declined below 0.4 when temperature was below 673 K, the effects of surface resistance were neglected above 673 K. The hydrogen solubility in liquid Li-Pb was found to correlate with a Sievert's constant. We calculated a height-equivalent to theoretical-plate of a gas-liquid countercurrent extraction tower for tritium recovery rates in liquid Li-Pb to be HL= 7.0x10-2 [m] (4). (authors)

  16. Solubility, diffusivity, and isotopic exchange rate of hydrogen isotopes in Li-Pb

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, Y.; Edao, Y.; Yamaguchi, S.; Fukada, S. [Dept. of Advanced Energy Engineering Science Interdisciplinary, Graduate School of Engineering Sciences, Kyushu Univ., Hakozaki, Higashi-ku, Fukuoka 812-8581 (Japan)

    2008-07-15

    The diffusion, solution and permeation coefficients of hydrogen isotopes in liquid Li-Pb which is a candidate liquid blanket material for fusion reactors were determined in the temperature range 573-973 K using an unsteady permeation method. Each coefficients was correlated to temperature as follows: D{sub Li-Pb} = 1.8 x 10{sup -8} exp(-11590/RT) [m{sup 2}/s] (1) K{sub Li-Pb} = 2.1x10{sup -6} exp(-18700/RT) [1/Pa{sup 0.5}] (2) P{sub Li-Pb} = 1.8x10{sup -9} exp(-30290/RT) [mol/msPa{sup 0.5}] (3) The hydrogen permeation flux depends on the square root of pressure at 773-973 K. Although the power of pressure declined below 0.4 when temperature was below 673 K, the effects of surface resistance were neglected above 673 K. The hydrogen solubility in liquid Li-Pb was found to correlate with a Sievert's constant. We calculated a height-equivalent to theoretical-plate of a gas-liquid countercurrent extraction tower for tritium recovery rates in liquid Li-Pb to be H{sub L}= 7.0x10{sup -2} [m] (4). (authors)

  17. A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean

    Science.gov (United States)

    Wilson, David J.; Piotrowski, Alexander M.; Galy, Albert; McCave, I. Nicholas

    2012-08-01

    The use of neodymium (Nd) isotopes to reconstruct past water mass mixing relies upon the quasi-conservative behaviour of this tracer, whereas recent studies in the modern oceans have suggested that boundary exchange, involving the addition of Nd from ocean margin sediments, may be an important process in the Nd cycle. Here we suggest that the relative importance of water mass advection versus boundary exchange can be assessed where the deep western boundary current in the Indian Ocean flows past the Madagascan continental margin; a potential source of highly unradiogenic Nd. Foraminiferal coatings and bulk sediment reductive leachates are used to reconstruct bottom water Nd isotopic composition (εNd) in 8 Holocene age coretops, with excellent agreement between the two methods. These data record spatial variability of ∼4 εNd units along the flow path of Circumpolar Deep Water; εNd≈-8.8 in the deep southern inflow upstream of Madagascar, which evolves towards εNd≈-11.5 offshore northern Madagascar, whereas εNd≈-7.3 where deep water re-circulates in the eastern Mascarene Basin. This variability is attributed to boundary exchange and, together with measurements of detrital sediment εNd, an isotope mass balance suggests a deep water residence time for Nd of ≤400 yr along the Madagascan margin. Considering deglacial changes, a core in the deep inflow upstream of Madagascar records εNd changes that agree with previous reconstructions of the Circumpolar Deep Water composition in the Southern Ocean, consistent with a control by water mass advection and perhaps indicating a longer residence time for Nd in the open ocean away from local sediment inputs. In contrast, sites along the Madagascan margin record offset εNd values and reduced glacial-interglacial variability, underlining the importance of detecting boundary exchange before inferring water mass source changes from Nd isotope records. The extent of Madagascan boundary exchange appears to be unchanged

  18. Chemical and isotopic characteristics of hot springs along the along the Neogene Malawi rift.

    Science.gov (United States)

    Atekwana, E. A.; Tsokonombwe, G. W.; Elsenbeck, J.; Wanless, V. D.; Atekwana, E. A.

    2015-12-01

    We measured the concentrations of major ions and dissolved inorganic carbon (DIC) and the stable isotopes of carbon (δ13CDIC), hydrogen (δD) and oxygen (δ18O) of hot springs along the Neogene Malawi rift. We compared the results with those of streams and a cold spring. We aimed to assess the hot springs for evidence of addition of mantle mass, specifically water and carbon and (2) determine the processes that control the chemical and isotopic evolution of the hot springs. Understanding the source(s) of heat for the springs and if the chemical and isotopic characteristics show evidence of mantle processes is an important goal of the Project for Rift Initiation, Development and Evolution (PRIDE). The temperature of the hot springs ranged from 35 to 80 ºC. High temperature anomalies are observed between latitudes 10 to 11, 12 to 13 and 15 to 16 degrees south along the rift axis. The δD and δ18O for the cold spring, hot springs and streams had a similar range, were positively correlated and lie on the trend of the local meteoric water line. We suggest negligible contribution of water from a connate or magmatic source and limited oxygen exchange from water-rock interaction or CO2 exchange from deep sedimentary carbonates. The DIC concentrations of the hot springs are higher (5 to 61 mg C/L) than those of streams (2 to 28 mg C/L) indicating addition of carbon to the DIC pool during the circulation of some springs. The range in the δ13CDIC of the hot springs (-17 to -8‰) is broader and lower compared to streams (-12 to -5‰) due to addition of carbon with a δ13CDIC of -15‰ to the spring water during circulation. Our results indicate that (1) the source of water for the hot springs is meteoric, (2) the hot springs have not experienced extensive water-rock interaction due to fast circulation suggesting highly permeable fault zones, (3) the source of carbon in the DIC of the hot springs is mostly CO2(g) from the soil zone and (4) the springs are heated by normal

  19. Oxygen and hydrogen isotope exchange of geopressured thermal water in the central Guanzhong basin

    Institute of Scientific and Technical Information of China (English)

    YU Juan; MA Zhi-yuan; WANG Zhao-wei; LI Wei-liang; SU Yan

    2009-01-01

    Geothermal water of Xi'an and Xianyang in the central Guanzhong basin is typically geopressured thermal water in China. δ18O and δD data of geopressured thermal water in Xi'an and Xianyang, combined with data from the perimeter of the basin, are analyzed to study features of hydrogen and oxygen shifts. The results show that 18O exchange of geothermal water at the pc-rimeter of the basin and in the non-geopressured thermal water in the center of the basin is not evident, while in most of the geo-pressured thermal water in the central basin, in cities such as Xi'an and Xianyang, significant oxygen exchange had taken place as well as hydrogen exchange, suggesting that isotope exchanges would slowly move the geothermal water system towards equilib-rium. Thermal water reservoirs in the central basin have passed through significant water-rock reactions. Moreover, the geothermal reservoir of Xianyang city is relatively much more enclosed than that of Xi'an city. It has been observed that the more enclosed the geological environment of geothermal water is, the more obvious the oxygen shifts are. With the increasing of the depth, residence time, total amounts of thssolute solids and temperatures of geothermal waters, the oxygen exchange accelerates.

  20. Assessment of diel chemical and isotopic techniques to investigate biogeochemical cycles in the upper Klamath River, Oregon, USA

    Science.gov (United States)

    Poulson, S.R.; Sullivan, A.B.

    2009-01-01

    The upper Klamath River experiences a cyanobacterial algal bloom and poor water quality during the summer. Diel chemical and isotopic techniques have been employed in order to investigate the rates of biogeochemical processes. Four diel measurements of field parameters (temperature, pH, dissolved oxygen concentrations, and alkalinity) and stable isotope compositions (dissolved oxygen-??18O and dissolved inorganic carbon-??13C) have been performed between June 2007 and August 2008. Significant diel variations of pH, dissolved oxygen (DO) concentration, and DO-??18O were observed, due to varying rates of primary productivity vs. respiration vs. gas exchange with air. Diel cycles are generally similar to those previously observed in river systems, although there are also differences compared to previous studies. In large part, these different diel signatures are the result of the low turbulence of the upper Klamath River. Observed changes in the diel signatures vs. sampling date reflect the evolution of the status of the algal bloom over the course of the summer. Results indicate the potential utility of applying diel chemical and stable isotope techniques to investigate the rates of biogeochemical cycles in slow-moving rivers, lakes, and reservoirs, but also illustrate the increased complexity of stable isotope dynamics in these low-turbulence systems compared to well-mixed aquatic systems. ?? 2009 Elsevier B.V.

  1. Upper limit on the rate constant for isotope exchange between molecular oxygen and ozone at 298 K

    Science.gov (United States)

    Anderson, S. M.; Morton, J.; Mauersberger, K.

    1987-01-01

    The gas phase bimolecular isotope exchange reaction between molecular oxygen and ozone has been investigated directly for the first time. Its rate coefficient is found to be less than 2 x 10 to the -25th cu cm/sec at 298 K, over six orders of magnitude below recent estimates. Much faster exchange was observed over condensed ozone at 77 K, suggesting isotopic scrambling is catalyzed under these conditions. The low rate coefficient implies that homogeneous exchange between ground state oxygen and ozone molecules cannot play a significant role in heavy ozone chemistry.

  2. Experimental studies of alunite: II. Rates of alunite-water alkali and isotope exchange

    Science.gov (United States)

    Stoffregen, R.E.; Rye, R.O.; Wasserman, M.D.

    1994-01-01

    Rates of alkali exchange between alunite and water have been measured in hydrothermal experiments of 1 hour to 259 days duration at 150 to 400??C. Examination of run products by scanning electron microscope indicates that the reaction takes place by dissolution-reprecipitation. This exchange is modeled with an empirical rate equation which assumes a linear decrease in mineral surface area with percent exchange (f) and a linear dependence of the rate on the square root of the affinity for the alkali exchange reaction. This equation provides a good fit of the experimental data for f = 17% to 90% and yields log rate constants which range from -6.25 moles alkali m-2s-1 at 400??C to - 11.7 moles alkali m-2s-1 at 200??C. The variation in these rates with temperature is given by the equation log k* = -8.17(1000/T(K)) + 5.54 (r2 = 0.987) which yields an activation energy of 37.4 ?? 1.5 kcal/mol. For comparison, data from O'Neil and Taylor (1967) and Merigoux (1968) modeled with a pseudo-second-order rate expression give an activation energy of 36.1 ?? 2.9 kcal/mol for alkali-feldspar water Na-K exchange. In the absence of coupled alkali exchange, oxygen isotope exchange between alunite and water also occurs by dissolution-reprecipitation but rates are one to three orders of magnitude lower than those for alkali exchange. In fine-grained alunites, significant D-H exchange occurs by hydrogen diffusion at temperatures as low as 100??C. Computed hydrogen diffusion coefficients range from -15.7 to -17.3 cm2s-1 and suggest that the activation energy for hydrogen diffusion may be as low as 6 kcal/mol. These experiments indicate that rates of alkali exchange in the relatively coarse-grained alunites typical of hydrothermal ore deposits are insignificant, and support the reliability of K-Ar age data from such samples. However, the fine-grained alunites typical of low temperature settings may be susceptible to limited alkali exchange at surficial conditions which could cause

  3. Predicting the bioavailability of phosphorus in soil amended with phosphate rocks using isotopic exchange kinetics

    International Nuclear Information System (INIS)

    Investigations on plant responses to applications of various forms and rates of P fertilizers usually involve glasshouse and/or field experiments. This traditional procedure assumes that whatever the soil-fertilizer-plant system, increase in total P uptake by plant between no P treatment (control) and fertilizer treatment equals the plant P uptake from fertilizer. This study uses the isotopic exchange techniques in the laboratory to predict bioavailability of P fertilizers without the need to conduct glasshouse or field experiments. Serdang series soil (Typic Paleudult) was incubated with 7 sources of P fertilizers comprising of triple superhosphate (TSP) and phosphate rocks from North Carolina (NCPR), Algeria (APR), Tunisia (TPR), Jordan (JPR), Christmas Island (CIPR) and China (CPR) at the rates of 0, 2, 4, 6 and 8g Kg-' soil with 20% moisture content at room temperature in three replications. The soils were sampled at 1, 3, 6 and 9 months after incubation and isotopically exchangeable p determined by the method of Fardeau and Jappe (1976). Intensity, quantity and capacity factors of soil P were calculated and the residual availability of these fertilizers were predicted. Phosphorus in solution was highest in TSP treated soil for all treatments. Among the phosphate rocks, NCPR at rate 8g kg-' soil gave the highest value while, CPR at rate 2 gave the lowest value. Thus showing that these PRs have different reactivities in this soil, where NCPR, APR, TPR and JPR were the reactive PR, while CIPR and CPR were the unreactive ones. The isotopically exchangeable P at one minute (1) in the soil sampled 9 months after incubation was found to correlate very well with plant P uptake by oil palm seedlings grown under the same conditions. Calculations made on the percentage of P derived from these fertilizers up to a period of more than one year after application showed that the reactive PRs to have more residual P made available to plants than the unreactive PR

  4. Isotopic air sampling in a tallgrass prairie to partition net ecosystem CO2 exchange

    Science.gov (United States)

    Lai, Chun-Ta; Schauer, Andrew J.; Owensby, Clenton; Ham, Jay M.; Ehleringer, James R.

    2003-09-01

    Stable isotope ratios of various ecosystem components and net ecosystem exchange (NEE) CO2 fluxes were measured in a C3-C4 mixture tallgrass prairie near Manhattan, Kansas. The July 2002 study period was chosen because of contrasting soil moisture contents, which allowed us to address the effects of drought on photosynthetic CO2 uptake and isotopic discrimination. Significantly higher NEE fluxes were observed for both daytime uptake and nighttime respiration during well-watered conditions when compared to a drought period. Given these differences, we investigated two carbon-flux partitioning questions: (1) What proportions of NEE were contributed by C3 versus C4 species? (2) What proportions of NEE fluxes resulted from canopy assimilation versus ecosystem respiration? To evaluate these questions, air samples were collected every 2 hours during daytime for 3 consecutive days at the same height as the eddy covariance system. These air samples were analyzed for both carbon isotope ratios and CO2 concentrations to establish an empirical relationship for isoflux calculations. An automated air sampling system was used to collect nighttime air samples to estimate the carbon isotope ratios of ecosystem respiration (δR) at weekly intervals for the entire growing season. Models of C3 and C4 photosynthesis were employed to estimate bulk canopy intercellular CO2 concentration in order to calculate photosynthetic discrimination against 13C. Our isotope/NEE results showed that for this grassland, C4 vegetation contributed ˜80% of the NEE fluxes during the drought period and later ˜100% of the NEE fluxes in response to an impulse of intense precipitation. For the entire growing season, the C4 contribution ranged from ˜68% early in the spring to nearly 100% in the late summer. Using an isotopic approach, the calculated partitioned respiratory fluxes were slightly greater than chamber-measured estimates during midday under well-watered conditions. In addition, time series

  5. Site selective syntheses of [(3)H]omeprazole using hydrogen isotope exchange chemistry.

    Science.gov (United States)

    Pollack, Scott R; Schenk, David J

    2015-01-01

    Omeprazole (Prilosec®) is a selective and irreversible proton pump inhibitor used to treat various medical conditions related to the production of excess stomach acids. It functions by suppressing secretion of those acids. Radiolabeled compounds are commonly employed in the drug discovery and development process to support efforts including library screening, target identification, receptor binding, assay development and validation and safety assessment. Herein, we describe synthetic approaches to the controlled and selective labeling of omeprazole with tritium via hydrogen isotope exchange chemistry. The chemistry may also be used to prepare tritium labeled esomeprazole (Nexium®), the active pure (S)-enantiomer of omeprazole. PMID:26380956

  6. Development of a high temperature isotopic exchange process for recovering tritium from fusion fuel impurities

    International Nuclear Information System (INIS)

    A High Temperature Isotopic Exchange (HITEX) process has been developed for processing of fusion fuel streams. The design has advantages over previous systems which have been based on catalytic oxidation or decomposition of impurities, since it eliminates the need for impurity oxidation and electrolysis of DTO, and does not rely on complicated catalytic decomposition reactions. A conceptual flowsheet of complete HITEX-based fuel processing system is described. Testing of the HITEX reactor is underway with deuterated impurities. Details of the experimental HITEX test loop are reported in this paper, and the test loop is compared to a HITEX design recently proposed for ITER (International Thermonuclear Experimental Reactor)

  7. Selection of the process for the heavy water production using isotopic exchange amonia-hydrogen

    International Nuclear Information System (INIS)

    The utilization of the Petroleos Mexicanos ammonia plants for heavy water production by the isotopic exchange NH3-H2 process is presented, in addition a description of the other heavy water production processes was presented. In the ammonia hydrogen process exist two possible alternatives for the operation of the system, one of them is to carry out the enrichment to the same temperature, the second consists in making the enrichment at two different temperatures (dual temperature process), an analysis was made to select the best alternative. The conclusion was that the best operation is the dual temperature process, which presents higher advantages according to the thermodynamics and engineering of the process. (author)

  8. RADIATION STABILITY OF NAFION MEMBRANES USED FOR ISOTOPE SEPARATION BY PROTON EXCHANGE MEMBRANE ELECTROLYSIS

    Energy Technology Data Exchange (ETDEWEB)

    Fox, E

    2009-05-15

    Proton Exchange Membrane Electrolyzers have potential interest for use for hydrogen isotope separation from water. In order for PEME to be fully utilized, more information is needed on the stability of Nafion when exposed to radiation. This work examines Nafion 117 under varying exposure conditions, including dose rate, total dosage and atmospheric condition. Analytical tools, such as FT-IR, ion exchange capacity, DMA and TIC-TOC were used to characterize the exposed membranes. Analysis of the water from saturated membranes can provide important data on the stability of the membranes during radiation exposure. It was found that the dose rate of exposure plays an important role in membrane degradation. Potential mechanisms for membrane degradation include peroxide formation by free radicals.

  9. Adenosine triphosphate-pyrophosphate isotopic exchange reaction: a tool for determination of tryptophan

    International Nuclear Information System (INIS)

    Quantitative determination of tryptophan at the picomole level is described, using the ATP-[32P]PPi isotopic exchange reaction catalyzed by tryptophanyl-tRNA synthetase. Sensitivity limits of 500 fmol were obtained. The presence of other amino acids at a 1000-fold excess over tryptophan did not interfere significantly with the quantitative determination of tryptophan. The specificity of the reaction was checked using five tryptophan analogs. These analogs did not prevent the determination of tryptophan when present in the same concentration range as tryptophan. When sensitive determination of a single amino acid is needed, the ATP-[32P]PPi exchange reaction catalyzed by aminoacyl-tRNA synthetases is suggested as a general method and as an alternative to HPLC procedures

  10. [Net CO2 exchange and carbon isotope flux in Acacia mangium plantation].

    Science.gov (United States)

    Zou, Lu-Liu; Sun, Gu-Chou; Zhao, Ping; Cai, Xi-An; Zeng, Xiao-Ping; Wang, Quan

    2009-11-01

    By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment. PMID:20135988

  11. Isotopic study of water exchange between atmosphere and biosphere at different sites in Pakistan

    International Nuclear Information System (INIS)

    Study of Isotopic behavior of water exchange between atmosphere and biosphere was initiated to understand the ties between these two spheres. This report presents the isotopic data of delta/sup 18/O and delta /sup 2/H in the water contents of leaves and stems in different plant species along with soil moisture. Non woody plants of wheat and grass along with soil from the surface and from the depth of 7 cm were collected during January 2005 to April 2005. Woody plants of many species were sampled from two sites near Islamabad and Lahore. Air moisture was also collected in the field. Moisture contents from these samples were extracted using the vacuum distillation method and analyzed for /sup 18/O and /sup 2/H Data depicts that the /sup 18/O and /sup 2/H of moisture in the leaves of non- woody and woody plants are much more enriched than their respective stems. This behavior is due to the evaporative enrichment trend originating from the soil moisture in the active root zone and also from the surface of the leaf. Degree of enrichment depends on the size of leaves, temperature, wind speed, stomatal resistance, soil chemistry and humidity. Significant evaporation effects in the moisture of grass stems are due to photosynthesis. Reflection of typical isotopic values of individual rain events is also observed in soil, plant water and atmospheric moisture, which can be used for studying water-use efficiency. Leaves of woody plants have relatively depleted/sup 18/O values during wet (monsoon) period mainly due to retardation of fractionation resulting from higher humidity. The stem samples do not show any significant variation in delta/sup 18/O indicating no evaporation from stems of big trees. Degree of enrichment of leave samples of woody plants also indicates the species- specific effects in oxygen and hydrogen isotopes during transpiration. Pine and Eucalyptus leaves show more variation in the isotopic contents as compared to other species. (author)

  12. Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis.

    Science.gov (United States)

    Larsen, K K; Wielandt, D; Schiller, M; Bizzarro, M

    2016-04-22

    Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of these species can result in incomplete Cr recovery during chromatographic purification. Because of large mass-dependent inter-species isotope fractionation, incomplete recovery can affect the accuracy of high-precision Cr isotope analysis. Here, we demonstrate widely differing cation distribution coefficients of Cr(III)-species (Cr(3+), CrCl(2+) and CrCl2(+)) with equilibrium mass-dependent isotope fractionation spanning a range of ∼1‰/amu and consistent with theory. The heaviest isotopes partition into Cr(3+), intermediates in CrCl(2+) and the lightest in CrCl2(+)/CrCl3°. Thus, for a typical reported loss of ∼25% Cr (in the form of Cr(3+)) through chromatographic purification, this translates into 185ppm/amu offset in the stable Cr isotope ratio of the residual sample. Depending on the validity of the mass-bias correction during isotope analysis, this further results in artificial mass-independent effects in the mass-bias corrected (53)Cr/(52)Cr (μ(53)Cr* of 5.2ppm) and (54)Cr/(52)Cr (μ(54)Cr* of 13.5ppm) components used to infer chronometric and nucleosynthetic information in meteorites. To mitigate these fractionation effects, we developed strategic chemical sample pre-treatment procedures that ensure high and reproducible Cr recovery. This is achieved either through 1) effective promotion of Cr(3+) by >5 days exposure to HNO3H2O2 solutions at room temperature, resulting in >∼98% Cr recovery for most types of sample matrices tested using a cationic chromatographic retention strategy, or 2) formation of Cr(III)-Cl complexes through exposure to concentrated HCl at high temperature (>120°C) for several hours, resulting in >97.5% Cr recovery using a

  13. Determination of plutonium, uranium and americium/curium isotopes in environmental samples with anion exchange, UTEVA, Sr and DGA resin

    International Nuclear Information System (INIS)

    This study presents a quantitative sequential radiochemical separation method for the Pu, U, Sr and Am/Cm isotopes with an anion exchange resin, UTEVA resin, Sr resin and DGA resin in environmental samples. After the radionuclides were leached from samples with 8M HNO3, the Pu, U, Sr and Am/Cm isotopes were sequentially adsorbed on the anion exchange column, UTEVA column connected with Sr Spec column and DGA column. The Pu isotopes were purified from other nuclides through the anion exchange column, and the uranium isotopes were separated from other nuclides through the UTEVA column. Also, 90Sr was separated from other hindrance elements such as Ca2+, Ba2+ and Y3+ with the Sr Spec column. Finally, Am/Cm fractions were purified with the DGA and anion exchange resins. After α source preparation for the purified Pu, U and Am/Cm isotopes with the micro-coprecipitation method, the Pu, U and Am/Cm isotopes were measured by an alpha spectrometry. Strontium-90 was measured by a low level liquid scintillation counter. The radiochemical procedure for Pu, U and Am nuclides investigated in this study has been validated by application to IAEA Reference soils. (orig.)

  14. Kinetic Isotope Effect on Transport Mediated by Clc-Type H+/CL- Exchangers

    Science.gov (United States)

    Picollo, Alessandra; Malvezzi, Mattia; Accardi, Alessio

    2013-01-01

    CLC transporters mediate the stoichiometric exchange of 2 Cl- ions for 1 H+ across the membranes of cellular compartments, mostly endosomes and lysosomes. Despite intense biophysical, structural and electrophysiological scrutiny the H+ transfer mechanism of these exchangers remains largely unknown. Previous work showed that two conserved Glutamates define the extremities of the H+ pathway in CLC exchangers. However, we don't know whether H+ transfer between these residues takes place along a series of protonatable moieties, via a Grotthuss mechanism and by diffusion of an H3+O cation and if at any step H+ tunneling plays a role. To differentiate between these possible mechanisms we measured the deuterium kinetic isotope effect on the transport rate of CLC-ec1 and CLC-5, respectively a prokaryotic and a eukaryotic CLC exchanger. We found that transport mediated by both proteins is slowed by ˜20-40% when H2O is replaced by D2O. This result suggests that the rate limiting step for H+ transport takes place along a hydrogen-bonded pathway, possibly formed by water molecules. However, we found that the voltage dependence of CLC-5 inhibition by extracellular H+ is eliminated by this substitution. This suggests that the voltage dependence of this process arises from a mechanism that is exquisitely sensitive to particle mass such as proton tunneling.

  15. Control factors of chemical and isotopic composition of groundwater in Varadero- Cardenas region, Matanzas, Cuba

    International Nuclear Information System (INIS)

    Multivariate analysis was performed to isotopic and chemical composition of groundwater from the karstic aquifer of Varadero- Cardenas in order to define those factor controlling or influencing its variations in time and space. The research was part of a project sponsored by International of Atomic Energy aimed to improve aquifer management applying isotopic techniques

  16. Deactivation of a hydrophobic Pt/SDBC catalyst by nitrogen compounds for hydrogen isotopic exchange reaction

    International Nuclear Information System (INIS)

    In order to evaluate the deactivation of a hydrophobic Pt/SDBC catalyst used for a hydrogen isotopic exchange reaction, changes over time in the reaction rate of H2/HDO(v) isotopic exchange over the catalyst induced by the addition of nitric acid, nitrates and nitrogen oxides were studied experimentally. Deactivation was discussed in terms of the balance of the active sites. The catalyst was poisoned by HNO3 reversibly and the poisoning was well explained in terms of the competitive adsorption of HNO3 with H2 or HDO onto the catalytic active sites. The poisoning kinetics were explained by the Zeldovich rate equation. Neutral nitrates of fission products such as Sr(NO3)2 showed negligible poisoning effect on the catalyst. ZrO(NO3)2 showed very similar poisoning behavior with HNO3, and this was considered to result from hydrolysis reactions which produced HNO3. No deactivation was observed by the introduction of NO, NO2 or NH3 into the reactor. Instead of poisoning, the reaction rate was accelerated by NO or NO2 and this was considered to be due to local heating of the catalyst surface by exothermic reactions between nitrogen oxides and hydrogen. (author)

  17. Fundamental study of practical separation of boron isotopes by means of anion exchange resin, (1)

    International Nuclear Information System (INIS)

    Separation of boron isotopes was carried out using a weak base anion exchange column (in free base form). After boric acid solution was passed through the column, the boric acid band formed on the column was eluted with pure water. The authors discuss the effects on boron isotope separation caused by variations of the concentration of feed solution charged to the column, of the amount of boric acid charged and of the flow rate of feed and eluent solutions. Results were as follows: (1) As the concentration of boric acid charged to the column increased and the amount of boric acid charged became large, the amount of enriched 10B(D sup(γ)) increased. (2) The optimum flow rate was 10 -- 20 ml/cm2.hr. (3) The atomic fraction of 10B in the plateau region of the isotope enrichment curve was nearly 0.190, compared with 0.198 for the feed solution. (4) In cases where the boric acid concentration in the effluent never exceeded 0.3 mol/l, no significant tailling was observed at the end of the chromatographic band. (auth.)

  18. Fundamental study of practical separation of boron isotopes by means of anion exchange resin, (2)

    International Nuclear Information System (INIS)

    As we reported earlier, a boric acid band formed in a column of weak base anion exchange resin Diaion WA21 can be eluted with pure water, resulting in good isotope fractionation. In the present research, we carried out various experiments using this process in order to find the necessary conditions for producing a displacement chromatogram at the end of the boric acid band, where 10B is enriched. Suitable conditions were found to be as follows: the concentration of boric acid was 0.1 mol/l, the operating temperature was 400C and the flow rate was 20 ml/hr.cm2. Under these conditions, four experimental runs having different migration lengths (1, 2, 4, 8 m) were carried out by a new method which we named ''Isotopic Plateau Holding Displacement Chromatography''. In these experiments, the enriched part of band was always preceded by the isotopic plateau part, in which the atomic fraction of 10B was maintained at its original value. The results of these experiments carried out by this method showed that the concentration of 10B at the end of the chromatogram increased with the migration length, and in the case of 8 m migration, 10B was enriched from an original value of 19.84 to 33.26%. The separation factor S was found to be constant, 1.0097+-0.0002, irrespective of migration length. (auth.)

  19. Investigation of the kinetics of acyl group exchange Pt. 8. Intramolecular general base catalysis of isotopic acyl exchange between 8-acetoquinolines and acetic-1-/sup 14/C acid

    Energy Technology Data Exchange (ETDEWEB)

    Dutka, F.; Marton, A.F. (Hungarian Academy of Sciences, Budapest. Central Research Inst. for Physics)

    1982-11-03

    8-acetoxyquinolines undergo isotopic acyl group exchange with acetic-1-/sup 14/C acid by the effect of ring nitrogen atom acting as an intramolecular general base catalytic function. Rate constants and activation parameters suggest a reaction mechanism intracomplex in nature.

  20. Analysis of 235U enrichment by chemical exchange in U(IV) - U(VI) system on anionite

    International Nuclear Information System (INIS)

    Full text: A theoretical study about the 235U enrichment by chemical exchange method in U(IV)-U(VI) system on anion-exchange resins is presented. The 235U isotope concentration profiles along the band were numerically calculated using an accurate mathematical model and simulations were carried out for the situation of product and waste withdrawal and feed supply. By means of numerical simulation, an estimation of the migration time, necessary for a desired enrichment degree, was obtained. The required migration distance, the production of uranium 3 at.% 235U per year and the plant configuration are calculated for different operating conditions. An analysis of the process scale for various experimental conditions is also presented. (authors)

  1. Chemical and Isotopic Compositions of the Euphrates River Water, Syria

    International Nuclear Information System (INIS)

    Stable isotope (18O and 2H) ratios, were measured together with tritium content and major ion concentrations on a monthly basis at 12 stations along the Syrian portion of the Euphrates River during the period January 2004-December 2006. Spatial variations of stable isotope ratios are moderated compared with other large rivers in the world. The concentrations of major ions and environmental isotopes systematically increased with distance downstream, with the sharpest enrichment at Al-Assad Lake. This systematic increase could be explained by: 1. direct evaporation from the river and its tributaries; and 2. drainage return flows of irrigation water via the groundwater system. The isotopic properties of the Euphrates water suggest negligible roles of precipitation and local runoff, compared with evaporation. (author)

  2. Isotopic and chemical characterization of coal in Pakistan

    International Nuclear Information System (INIS)

    Stable carbon isotope ratios (delta/sup 13/C PDB) and toxic/trace element concentration levels are determined for Tertiary coal samples collected from seven coal fields in Pakistan. No systematic isotope effects are found in the process of coal liquefaction from peat to Tertiary lignites and sub bituminous coal. Similarly, no age effects are observed during the Tertiary regime. The observed variations in the carbon isotopic composition of coal obtained from 'Sharigh coal field' and the 'Sor-Range/Degari coal field' in Baluchistan are attributed to the depositional environments. More sampling of stable carbon isotope analysis are required to validate these observations. Significant concentrations of toxic elements such as S, Cr, Cd and Pb in Makarwal coal may pose environmental and engineering/operational problems for thermal power plants. (author)

  3. Isotopic and chemical characterization of coal in Pakistan

    International Nuclear Information System (INIS)

    Stable carbon isotope ratios (delta /sup 13/C % PDB) and toxic/trace element concentration levels are determined for tertiary coal samples collected from seven coal fields in Pakistan. No systematic isotope effects are found in the process of coalification from peat to tertiary lignites and sub-bituminous coal. Similarly, no age effects are observed during the Tertiary regime. The observed variations in the carbon isotopic composition of coal obtained from 'Sharigh coal field' and the 'Sor-range/Degarl coalfield'. In Balochistan are attributes to the depositional environments. More sampling/stable carbon isotope analysis are required to validate these observations. Significant concentrations of toxic elements such as S, Cr, Cd and Pb in Makarwal coal may pose environmental and engineering/operational problems for thermal power plants. (author)

  4. Quality control of chemical and isotopic analyses of geothermal water samples

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Marshall J.; Mariner, Robert H.

    1991-01-01

    Chemical and isotopic analyses of geothermal water samples must meet certain levels of accuracy and reliability to be useful for identifying geochemical processes in hydrothermal systems. Quality control is largely a concern for the analytical laboratory, but the geochemist or reservoir engineer using the chemical data must also be concerned with analytical quality. To test accuracy and reliability of analyses available from laboratories, splits of seven water samples were sent to four stable-isotope laboratories, and splits of five water samples were sent to four chemical laboratories. The analyses of each sample were compared among laboratories, and the differences in analyses were evaluated using criteria developed for this comparison. Isotopic compositions were considered reliable if they deviated from mean values by less than 2{per_thousand}, for hydrogen and by less than 0.15{per_thousand}, for oxygen. Concentrations of each chemical component were considered reliable if they differed from mean values by less than 10%. Chemical analyses were examined for internal consistency by calculating the error in ionic charge balance and the error between ionic charge and electrical conductivity. To be considered internally consistent, chemical analyses must have less than 5% error in charge balance and less than 10% error in conductivity balance. Three isotope laboratories gave consistent compositions of all samples. No chemical laboratory gave consistent analyses of all samples. Recommendations are made that provide the user of isotopic and chemical data with the ability to better evaluate the quality of analyses.

  5. Analysis of heavy water production plant using bithermal and monothermal H2/H2O isotopic exchange processes

    International Nuclear Information System (INIS)

    The analysis of the heavy water production rate was carried out numerically for a heavy water production plant composed of the 3 stages bithermal H2/H2O-isotopic exchange columns of multisection separated-bed type and monothermal H2/H2O-isotopic exchange EXEL-finisher of the same type. The production rate was influenced by the isotopic exchange efficiency in the hydrophobic Pt-catalyst bed, ηc, and in the scrubbing bed, ηb, and by the water stream cut, θ1, from the first to the second stage and θ2 from the second to the third stage and θ3 from the third to the EXEL-finisher. Finally, the D-concentration profile in the EXEL-finisher was calculated under the standard conditions. (author)

  6. Isotopic study of the water exchange between atmosphere and biosphere at selected sites in Pakistan

    International Nuclear Information System (INIS)

    Study of water exchange between atmosphere and biosphere was initiated to understand the ties between these two spheres. Main objective of this study is to acquire sufficient environmental isotopic data for the exploration of water cycle dynamics in selected areas of Pakistan, in order to contribute to the IAEA global network for the development of regional scale model on ecosystems. Isotope investigations (18O, 2H) help evaluate the major processes such as photosynthesis, respiration and evapotranspiration. From January 2005 to April 2005 non woody plants (wheat, grass) and soil samples from wheat and grass fields (from the surface and 7cm below the surface) were collected. Moisture contents from these samples were extracted using the vacuum distillation method and analysed for hydrogen and oxygen isotope contents. Air moisture was also collected in the field. Woody plants consisting of eucalyptus, pine, delbergia sisso, melia azedarch were sampled from Islamabad. Seventeen more species of woody plants are included in the study, from another site, located near Lahore. Data depicts that the leaves of the wheat plant are more enriched in 18O and 2H than other parts of the same plant and grass. It may be due to the process of evapotranspiration which is more rapid from the wider leaves as compared to the small ones. Rain effect was also observed on δ18O and δ2H of the samples collected just two days after the rain event. Isotopic values of this rainwater were more negative as compared to other rain events that took place during this season. This depletion may be due to the 'continental effect' in precipitation. More than 200 samples from woody plants of different species and soil were collected. Isotopic data of the moisture extracted from leaves and stems of the plants of different species indicate that leaves of all the plants are more enriched in 2H and 18O than that of the respective stems. There also seem some considerable species-specific effects transforming

  7. An integrated chemical and stable-isotope model of the origin of Midocean Ridge Hot Spring Systems

    Science.gov (United States)

    Bowers, Teresa Suter; Taylor, Hugh P., Jr.

    1985-12-01

    Chemical and isotopic changes accompanying seawater-basalt interaction in axial midocean ridge hydrothermal systems are modeled with the aid of chemical equilibria and mass transfer computer programs, incorporating provision for addition and subtraction of a wide-range of reactant and product minerals, as well as cation and oxygen and hydrogen isotopic exchange equilibria. The models involve stepwise introduction of fresh basalt into progressively modified seawater at discrete temperature intervals from 100° to 350°C, with an overall water-rock ratio of about 0.5 being constrained by an assumed δ18OH2O at 350°C of +2.0 per mil (H. Craig, personal communication, 1984). This is a realistic model because: (1) the grade of hydrothermal metamorphism increases sharply downward in the oceanic crust; (2) the water-rock ratio is high (>50) at low temperatures and low (demand that the major portion of the water-rock interaction occur at temperatures of 300°-350°C. Interaction at temperatures below approximately 250°C results in negative δ18OH2O shifts, contrary to the observed positive δ18O values of the fluids exiting at midocean ridge vents. Hydrogen isotope fractionation curves by Suzuoki and Epstein (1976), Lambert and Epstein (1980), and Liu and Epstein (1984), among others, are compatible with the model, and require δDH2O to increase at all temperatures as a result of seawater-basalt interaction.

  8. Two stages of isotopic exchanges experienced by the Ertaibei granite pluton, northern Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    刘伟

    2000-01-01

    18O/16O and D/H of coexisting feldspar, quartz, and biotite separates of twenty samples collected from the Ertaibei granite pluton, northern Xinjiang, China are determined. It is shown that the Ertaibei pluton experienced two stages of isotopic exchanges. The second stage of 18O/16O and D/H exchanges with meteoric water brought about a marked decrease in the δ18O values of feldspar and biotite from the second group of samples. The D/H of biotite exhibits a higher sensitivity to the meteoric water alteration than its 18O/16O. However, the first stage of 18O/16O exchange with the 18O-rich aqueous fluid derived from the dehydration within the deep crust caused the Δ18OQuariz-Feidspar reversal. It is inferred that the dehydration-melting may have been an important mechanism for anatexis. It is shown that the deep fluid encircled the Ertaibei pluton like an envelope which serves as an effective screen to the surface waters.

  9. Two stages of isotopic exchanges experienced by the Ertaibei granite pluton, northern Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    18O/16O and D/H of coexisting feldspar, quartz, and biotite separates of twenty samples collected from the Ertaibei granite pluton, northern Xinjiang, China are determined. It is shown that the Ertaibei pluton experienced two stages of isotopic exchanges. The second stage of 18O/16O and D/H exchanges with meteoric water brought about a marked decrease in the δ18O values of feldspar and biotite from the second group of samples. The D/H of biotite exhibits a higher sensitivity to the meteoric water alteration than its 18O/16O. However, the first stage of 18O/16O exchange with the 18O-rich aqueous fluid derived from the dehydration within the deep crust caused the δ18OQuartz-Feldspar reversal. It is inferred that the dehydration-melting may have been an important mechanism for anatexis. It is shown that the deep fluid encircled the Ertaibei pluton like an envelope which serves as an effective screen to the surface waters.

  10. Radium isotopes as a tracer of sediment-water column exchange in the North Sea

    Science.gov (United States)

    Burt, W. J.; Thomas, H.; Pätsch, J.; Omar, A. M.; Schrum, C.; Daewel, U.; Brenner, H.; Baar, H. J. W.

    2014-08-01

    Sediment-water column exchange plays an important role in coastal biogeochemistry. We utilize short-lived radium isotopes (224Ra and 223Ra) to understand and quantify the dominant processes governing sediment-water column exchange throughout the North Sea. Our comprehensive survey, conducted in September 2011, represents the first of its kind conducted in the North Sea. We find that two main sources regulate surface Ra distributions: minor coastal input from rivers and shallow mudflats and North Sea sediments as the dominant source. Pore waters show 100-fold larger activities than the water column. North Sea sediment characteristics such as porosity and mean grain size, as well as turbulence at the sediment-water interface, are the dominant factors contributing to variability of Ra efflux. Ra inventory and mass balance approaches consistently yield high benthic Ra effluxes in the southern North Sea, driven by strong tidal and wind mixing, which in turn cause high sediment irrigation rates. These results exceed incubation-based Ra flux estimates and the majority of previously reported Ra flux estimates for other regions. Ra-based estimates of benthic alkalinity fluxes compare well to observed values, and the high rates of Ra efflux imply a potentially significant exchange of other products of sedimentary reactions, including carbon and nutrient species. Passive tracer simulations lend strong support to the Ra source attribution and imply seasonal variation in the surface water Ra distribution depending on stratification conditions.

  11. Influence of packing material and method on the efficiency of liquid phase water-hydrogen isotope exchange

    International Nuclear Information System (INIS)

    The influence of packing material in the countercurrent catalytic column on the efficiency of liquid phase water-hydrogen isotope exchange is studied. Stainless steel triangle spring packing demonstrates best performance among the tested three hydrophilic packing materials. Pretreatment of the stainless steel packing lowers the height of a mass transfer unit (HTU) by about 50%. The effectiveness of a catalytic column for water-hydrogen isotope exchange is proved to be higher when the column is packed in layers with hydrophilic packing and hydrophobic catalyst in the volume ratio 1:4

  12. Study of T-H isotope exchange between H2-H2O by Pt-C-PTFE hydrophobic catalyst

    International Nuclear Information System (INIS)

    The preparation of Pt-C-PTFE hydrophobic catalyst is described. The experiments of T-H isotope exchange between H2/H2O by Pt-C-PTFE hydrophobic catalyst were carried out at 30 deg C, 50 deg C and 75 deg C respectively. Within the limits (9.65-38.22) cm/s, catalystic activity increases with the increase of hydrogen flow rate. The catalystic activity at 50 deg C is optimum. The catalystic activity of this catalyst between gas-liquid is larger than that between gas-vapour. Mixture of the hydrophobic catalyst with hydrophilic filler in the bed can improve hydrogen isotope exchange

  13. Process for the exchange of hydrogen isotopes between streams of liquid water and gaseous halohydrocarbon and an apparatus therefor

    International Nuclear Information System (INIS)

    This invention provides a process for the exchange of hydrogen isotopes between streams of liquid water and gaseous halohydrocarbons comprising: (a) bringing into contact a water stream, a halohydrocarbon stream, and a catalytic porous anion exchange resin so that the isotope-deficient halohydrocarbon stream is enriched; (b) decomposing the halohydrocarbon stream photolytically into two gaseous streams, one enriched and the other deficient; (c) removing as a product the first, enriched stream; and (d) recycling the second stream for enrichment. An apparatus is also provided

  14. Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds

    DEFF Research Database (Denmark)

    Hansen, Poul Erik

    2015-01-01

    The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between “static......” and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N−. The paper will be deal with both secondary...... and primary isotope effects on chemical shifts. These two types of isotope effects monitor the same hydrogen bond, but from different angles...

  15. New chemical and original isotopic data on waters from El Tatio geothermal field, Northern Chile

    International Nuclear Information System (INIS)

    The El Tatio geothermal field is located at an height of 4200-4300 m on the Cordillera de los Andes (Altiplano). Geysers, hot pools and mudpots in the geothermal field and local meteoric waters were sampled in April 2002 and analyzed for major and trace elements, δ2H, δ18O and 3H of water, δ34S and δ18O of dissolved sulfate, δ13C of dissolved total carbonate, and 87Sr/86Sr ratio of aqueous strontium. There are two different types of thermal springs that field, that are chloride-rich water and sulfate-rich water. The chemical composition of chloride springs is controlled by magma degassing and by water-rock interaction processes. Sulfate springs are fed by shallow meteoric water heated by ascending gases. In keeping with the geodynamic setting and nature of the reservoir rocks, chloride water is rich in As, B, Cs, Li; on the other hand, sulfate waste is enriched only in B relative to local meteoric water. Alternatively to a merely meteoric model, chloride waters can be interpreted as admixtures of meteoric and magmatic (circa andesitic) water, which moderately exchanges oxygen isotopes with rocks at a chemical Na/K temperature of about 270degC in the main reservoir, and then undergoes loss of vapor (and eventually mixing with shallow water) and related isotopic effects ascent to the surface. These chloride waters do not present tritium and can be classified as submodern (pre-1952). A chloride content of 5,400 mg/l is estimated in the main reservoir, for which δ2H and δ18O values, respectively of -78 per mille and -6.9 per mille, are calculated applying the multistage-steam separation isotopic effects between liquid and vapor. From these data, the meteoric recharge (Cl≅0 mg/l) of the main reservoir should approach a composition of -107 per mille in δ2H and -14.6 per mille in δ18O, when a magmatic water of δ2H=-20 per mille, δ18O=+10 per mille and Cl=17,500 mg/l is assumed. The 87Sr/86 ratios of the hot springs are quite uniform (0.70876 to 0.70896), with

  16. Study application of the chemical cleaning in heat exchanger in RSG-GAS

    International Nuclear Information System (INIS)

    Chemical cleaning in heat exchanger of RSG-GAS can be carried out, this process is aimed at removing any dirts, slugs on the wall or shell with certain chemical in order to improve the performance of the heat exchanger. The performance of the heat exchanger can be determinated from the increase of global heat transfer coefficient or U global (Ug). In this paper is presented the method of evaluation of heat exchanger that can be carried out periodically when the system is operation. From the distinction result that the chemical cleaning can be to do in RSG-GAS. After chemical cleaning to do the heat exchanger of RSG-GAS performance must be obtained better U global values compared to the previous values

  17. Application of expert systems to heat exchanger control at the 100-megawatt high-flux isotope reactor

    International Nuclear Information System (INIS)

    The High-Flux Isotope Reactor (HFIR) is a 100-MW pressurized water reactor at the Oak Ridge National Laboratory. It is used to produce isotopes and as a source of high neutron flux for research. Three heat exchangers are used to remove heat from the reactor to the cooling towers. A fourth heat exchanger is available as a spare in case one of the operating heat exchangers malfunctions. It is desirable to maintain the reactor at full power while replacing the failed heat exchanger with the spare. The existing procedures used by the operators form the initial knowledge base for design of an expert system to perform the switchover. To verify performance of the expert system, a dynamic simulation of the system was developed in the MACLISP programming language. 2 refs., 3 figs

  18. Search for new chemical elements and possibilities to synthesize transactinide isotopes for chemical studies

    International Nuclear Information System (INIS)

    Elements up to Z=112 as well as 114 and 116 are officially recognized as discovered and have been named. The current literature contains reports about the synthesis of all elements up to Z=118, meaning that more than 10% of all elements are members of the transactinide series with Z=104-118. Therefore, search experiments for the new elements with Z=119 and Z=120 have been performed. An important question for such experiments concerns the optimum choice of the nuclear reaction. While only one experiment has been conducted so far with the aim of discovering Z=119, already four experiments on the synthesis of Z=120 have been performed, all employing different reactions. Still, Z=119 and 120 are not yet announced as discovered. The situation using the TASCA experiments as an example and the perspectives for the discovery of new elements are studied. The optimum reactions leading to the relatively long-lived isotopes of the transactinides as they are frequently used in chemical studies of these elements, including elements which were not studied chemically to date are discussed

  19. Ion exchange chromatographic separation and MS analysis of isotopes of boron

    International Nuclear Information System (INIS)

    Using electrochemical techniques of pH-metry and conductimetry, the choice of a suitable complexing reagent was made amongst ethylene glycol, propylene glycol, dextrose and mannitol for cost-effective separation of isotopes of boron by ion exchange chromatography. Quantitative relationships between pH and concentration; pKa and concentration of each of these complexing reagents were determined by least square polynomial curve fitting and an attempt was made to determine the formation constants of mannitol-borate complex. The results of experiments carried out for selection; regeneration of a resin; separation factor determinations using batch as well as column techniques and monitoring of band movements using these electrochemical techniques are discussed. (author)

  20. Carbon mass-balance modeling and carbon isotope exchange processes in the Curonian Lagoon

    Science.gov (United States)

    Barisevičiūtė, Rūta; Žilius, Mindaugas; Ertürk, Ali; Petkuvienė, Jolita

    2016-04-01

    The Curonian lagoon one of the largest coastal lagoons in Europe is located in the southeastern part of the Baltic Sea and lies along the Baltic coast of Lithuania and the Kaliningrad region of Russia. It is influenced by a discharge of the Nemunas and other smaller rivers and saline water of the Baltic Sea. The narrow (width 0.4 km, deep 8-14 m) Klaipėda Strait is the only way for fresh water run-off and brackish water intrusions. This research is focused on carbon isotope fractionations related with air - water exchange, primary production and organic carbon sedimentation, mineralization and uptake from both marine and terrestrial sources.

  1. Direct calculation of equilibrium constants for isotopic exchange reactions by ab initio molecular orbital theory

    International Nuclear Information System (INIS)

    The ability of simple levels of ab initio molecular orbital theory to describe with reasonable accuracy the energetics of isotopic exchange processes is demonstrated. Three levels of ab initio molecular orbital theory have been surveyed. The first two levels are single-determinant Hartree-Foch methods utilizing the 3-21G split-valence and 6-31G* polarization basis sets. The third level, which is computationally the most complex, uses the 6-31G* basis set but allows for partial account of electron correlation by way of Moller-Plesset perturbation theory terminated at second order. Theoretical and spectroscopic equilibrium constants for reactions XH + XD reversible XD + H2 where XD is a hydride of the first row of the periodic table are tabulated

  2. Hydrogen isotope exchange and conditioning in graphite limiters used in TFTR

    International Nuclear Information System (INIS)

    Isotopic exchange experiments performed in TFTR are used to examine the outgassing and diffusive properties of graphite used as the plasma limiter. Changeover from hydrogen to deuterium for different periods ranges from approx.600 to 60 plasma discharges, which appears to be correlated to the limiter temperature. We present a simple analytical model that predicts a fast transient (approx.10 plasma discharges) changeover where the deuterium fueling dilutes the adsorbed and near-surface hydrogen, and a slowly changing term where bulk hydrogen diffuses to the surface. Using this model we can extract an activation energy for diffusion of 0.15 +- 0.02 eV. We hypothesize that interpore diffusion for this porous (approx.15%) material is consistent with our observations. 19 refs

  3. A theoretical consideration on uranium isotope effects observed in chemical uranium-235 enrichment processes

    International Nuclear Information System (INIS)

    Theoretical consideration on the uranium isotope effects in chemical chromatographic uranium isotope enrichment processes are presented, making use of up-to-date spectroscopic, solution chemical and separation factor data. It is shown that hydration of the uranyl (UO22+) and uranous (U4+) ions has a profound effect on the reduced partition function ratios (RPFR's) of these ions and that, in accordance with experiment, the RPFR of the uranous ion is larger than that of the uranyl ion. Future prospects concerning the separation factors in chemical processes are mentioned. (orig.)

  4. Models for calculating the effects of isotopic exchange, radioactive decay, and of recycle in removing iodine from gas and liquid streams

    International Nuclear Information System (INIS)

    Different decontamination factors for 129I and 131I are frequently invoked in environmental impact reports concerned with nuclear fuel recycle. Selected differences, or ratios, have not been justified on the basis of mathematical models or experimental data. A description is given of the origins of these differences in terms of isotopic exchange and material balance equations for the short- and long-lived (or stable) isotopes. The ratios of decontamination factors can be calculated when there is complete attainment of isotopic exchange between gas- or liquid-phase iodine and iodine sorbed by a solid or liquid. If there is no exchange, decontamination factors are isotope-independent unless material recycle occurs within the system. Between these extremes, there can be decontamination factors whose explanation requires experimental determination of the extent of exchange. The model applies to other radioactive isotopes of iodine as well as to other elements with short- and long-lived (or stable) isotopes. (auth)

  5. Isotope effect and isotope separation. A chemist's view

    International Nuclear Information System (INIS)

    What causes the isotope effects (IE)? This presentation will be centered around the equilibrium isotope effects due to the differences in the nuclear masses. The occurrence of the equilibrium constant, K, of isotope exchange reactions which differ from the values predicted by the classical theory of statistical mechanics, Kcl, is explored. The non-classical K corresponds to the unit-stage separation factor, α, that is different from unity and forms a basis of an isotope separation process involving the chemical exchange reaction. Here, the word 'chemical exchange' includes not only the isotope exchange chemical reactions between two or more chemical species but also the isotope exchanges involving the equilibria between liquid and vapor phases and liquid-gas, liquid solution-gas, liquid-liquid, and solid-liquid phases. In Section I, origins of the isotope effect phenomena will be explored and, in the process, various quantities used in discussions of isotope effect that have often caused confusions will be unambiguously defined. This Section will also correlate equilibrium constant with separation factor. In Section II, various forms of temperature-dependence of IE and separation factor will be discussed. (author)

  6. An experimental investigation of the process of isotope exchange that takes place when heavy water is exposed to the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Deeney, F A; O' Leary, J P [Physics Department, National University of Ireland, Cork (Ireland)], E-mail: f.a.deeney@ucc.ie

    2009-07-15

    We have used the recently developed method for rapid measurement of maximum density temperature to determine the rate at which hydrogen and deuterium isotope exchange takes place when a sample of heavy water is exposed to the atmosphere. We also provide a simple explanation for the observed linear rate of transition.

  7. An Experimental Investigation of the Process of Isotope Exchange that Takes Place when Heavy Water Is Exposed to the Atmosphere

    Science.gov (United States)

    Deeney, F. A.; O'Leary, J. P.

    2009-01-01

    We have used the recently developed method for rapid measurement of maximum density temperature to determine the rate at which hydrogen and deuterium isotope exchange takes place when a sample of heavy water is exposed to the atmosphere. We also provide a simple explanation for the observed linear rate of transition. (Contains 2 figures.)

  8. Chemical and environmental isotopic characteristics of deep aquifers systems in Jabal Al-Hass (Aleppo area)

    International Nuclear Information System (INIS)

    Chemical and environmental isotopes have been used for studying the deep aquifer systems in Aleppo area. Salinity of deep groundwater ranges between 3 to 6 g/1. Study of salinity reveals that the dissolution of marine evaporate rocks is the main source of high salinity. Major part of salinity is basically attributed to SO4-- (1400 to 2000mg/1). Origin of sulfate is confirmed by the relationship between δ34Sso4 and δ18Oso4 which indicate that the source of sulfate is gypsum dissolution, and the enrichment of 34Sso4 and 18O2o4 are related to the reduction of sulfate. Spatial variation degree of salinity is related to flow direction of deep groundwater. The salinity increases from north and northeast towards south and southwest. High values are recorded in the Al-Mouth area. Stable isotopes composition of deep groundwater (δ18O=-8.05±0.24%o, δ2H=-53.0±1.72%o) show a similar pattern of depletion with low deuterium excess (d=10-13%o), and negligible standard deviation. These values are very close to the values of isotopic composition measured in Euphrates river at Jrablus station on the Syrian-Turkish border. The relationship between δ18O and δ2H of deep groundwater show polar distribution pattern at the WMWL emphasize the unique origin of recharge from the Turkish ranges and Euphrates fault system. Deep groundwater is mostly 3H-Free. Estimates of their mean subsurface residence times have been constrained on the basis of 14CDIC. Low values of 14C (13C=-1.7%o indicate the advanced stages of geochemical evolution. Significant corrections have been made for 14C-dilution processes comprising: Carbonate dissolution, sulfate reduction and matrix exchange. All dilution processes were quantified on the basis of geochemical and 13C mass balance equations. Results of this model show increase of water age in accordance with groundwater flow direction pattern, and the main age range between 8 to 11ka BP. (author)

  9. Preparation of [3H]sulfobromophthalein and related with it problems of tritium label introduction by the method of solid-phase isotopic exchange

    International Nuclear Information System (INIS)

    Sulfobromophthalein labelled with tritium with molar radioactivity 0.5-0.6 pBq/mol is prepared. Different aspects of the process of label introduction into organic compounds with the use of solid-phase catalytic isotopic exchange are considered. A row of arguments are represented for that the isotopic exchange degree depends predominantly on efficiency of tritium spillover in the volume of organic substance applied on catalyst. The fact that isotopic exchange at temperatures up to 180-200 Deg C is realized in solid-phase exchange manly by reaction with tritium cations is the most proved currently

  10. Isotopic exchange during derivatization of platelet activating factor for gas chromatography-mass spectrometry

    International Nuclear Information System (INIS)

    One approach to the quantitative analysis of platelet activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycerol-3-phosphocholine; also referred to as AGEPC, alkyl glyceryl ether phosphocholine) is hydrolytic removal of the phosphocholine group and conversion to an electron-capturing derivative for gas chromatography-negative ion mass spectrometry. [2H3]Acetyl-AGEPC has been commonly employed as an internal standard. When 1-hexadecyl-2-[2H3]acetyl glycerol (obtained by enzymatic hydrolysis of [2H3]-C16:0 AGEPC) is treated with pentafluorobenzoyl chloride at 120 degrees C, the resulting 3-pentafluorobenzoate derivative shows extensive loss of the deuterium label. This exchange is evidently acid-catalyzed since derivatization of 1-hexadecyl-2-acetyl glycerol under the same conditions in the presence of a trace of 2HCl results in the incorporation of up to three deuterium atoms. Isotope exchange can be avoided if the reaction is carried out at low temperature in the presence of base. Direct derivatization of [2H3]-C16:0 AGEPC by treatment with pentafluorobenzoyl chloride or heptafluorobutyric anhydride also results in loss of the deuterium label. The use of [13C2]-C16:0 AGEPC as an internal standard is recommended for rigorous quantitative analysis

  11. Electropholic Transition Metal Complexes: Catalysis of Isotope Exchange. April 1, 1992 - December 3, 1996. Final Report

    International Nuclear Information System (INIS)

    The central aim of this project is to exploit transition metal dihydrogen complexes to develop catalysts for isotope exchange reactions between hydrogen and substrates such as water. The authors have partially met this goal by the synthesis of novel cationic rhenium complexes of the form [Re(CO)3(PR3)2(H2)]+. These complexes bind hydrogen somehwat more strongly than the neutral tungsten analogs but also activate the bound H2 to heterolytic cleavage. Thus rapid proton (deuteron) exchange between hydrogen and water can be achieved. An example of this reaction is the rapid formation of bound HD from the complex [Re(CO)3(PR3)2(H2)]+ and deuterium gas. Rapid incorporation of deuterium from D2O has also been observed. In these systems, the competitive binding of water to the metal center is a drawback. The affinity of the Re center for water depends upon the nature of the phosphine ligands, with the presumably more electrophilic PPh3 complex binding water strongly and irreversibly, while the PCy3 complex binds water reversibly. These results have been published in J.Am.Chem.Soc 1994, 116, 4515 and J.Am.Chem.Soc 1997, 119, 4172

  12. Isotopic and chemical composition of submarine geothermal gases from the Bay of Plenty, New Zealand

    International Nuclear Information System (INIS)

    Gas samples collected from the ocean floor near Whale Island, Bay of Plenty, New Zealand, are composed of carbon dioxide, methane, hydrogen, and air. The methane has an isotopic composition of delta13C(PDB) = -280/00 and deltaD(SMOW) = -1250/00. The isotopic and chemical composition show that the gases are of geothermal origin and similar to gas evolved from Whale Island hot springs

  13. Treatment of radioactive wastewaters by chemical precipitation and ion exchange

    International Nuclear Information System (INIS)

    Precipitation and ion exchange methods are being developed at Oak Ridge National Laboratory to decontaminate wastewaters containing small amounts of 90Sr and 137Cs while minimizing waste generation. Distribution coefficients have been determined for strontium and cesium as functions of Ca, Na, and Mg concentrations from bench- and pilot-scale data for ion exchange resins and zeolites using actual wastewaters. Models have been used to estimate the total amount of waste that would be generated at full-scale operation. Based on these data, four process flowsheets are being tested at full-scale. 14 refs., 8 figs., 7 tabs

  14. Measurement of Ecosystem-Atmosphere Exchange of Isotopic CO2 Using Fourier Transform Infrared (FTIR) Spectroscopy

    Science.gov (United States)

    Cambaliza, M. O.; Mount, G.; Lamb, B.; Westberg, H.; Gibson, R.

    2005-12-01

    Analysis of the isotopic content of atmospheric carbon dioxide provides a wealth of information about the complex interaction between the biosphere and the atmosphere. Traditionally, the isotopic content of atmospheric CO2 has been determined by taking grab samples from field sites followed by laboratory mass spectrometry analysis. This procedure severely limits the duration and frequency of measurements. In this work, we investigate the performance of a measurement method that is based on Fourier Transform Infrared (FTIR) spectroscopy. The FTIR separately measures the concentrations of the 12CO2 and 13CO2 isotopomers of carbon dioxide at approximately one minute intervals with very high signal-to-noise ratio using molecular absorption in a 1-meter cell in the 2100 to 2600 cm-1 region of the isotopic vibration-rotation bands. δ13C values are determined with a precision of approximately 0.7‰ every minute, with higher precision obtained by averaging the short integrations. The FTIR system also measures CO2 flux using the disjunct eddy covariance technique, so the net ecosystem exchange (NEE) and isoflux can also be measured, potentially allowing for the partitioning of the NEE into its photosynthetic and respiratory components. First scientific results from this new instrument are presented from two field campaigns conducted in summer 2005 in a poplar forest near Boardman, Oregon. A 25-m tower was used with air inlets at 0.3, 4.1, 7.5, 10.8, 14.0, and 20.6 meters above the ground. These were switched sequentially into the instrument to achieve height resolution in the canopy, or were kept at constant height. Canopy height was 13 meters. Carbon dioxide concentrations are measured to a precision of about 0.7 ppmv from a one-minute integration with higher precisions obtained from time averaging. CO2 isotopic concentrations were measured with a precision of about 2 ppmv/minute. In this work, we present results of temporal and vertical variations of CO2 concentrations

  15. Influence of organic carbon sources and isotope exchange processes between water and nitrate on the fractionation of the stable isotopes 15N/14N and 18O/16O in dissolved nitrate during microbial dentrification in groundwater

    International Nuclear Information System (INIS)

    Stable isotopes of nitrate are commonly used to determine sources and degradation of nitrate. In this study, nitrite oxidizing bacteria were found to promote an oxygen isotope exchange between water and nitrate under anoxic conditions. Also, different carbon sources were found to influence the enrichment of stable isotopes in nitrate during microbial denitrification. Both results refine the stable isotope model of nitrate in respect to nitrate source determination and microbial nitrate reduction.

  16. The isotopic and chemical evolution of Mount St. Helens

    Science.gov (United States)

    Halliday, A.N.; Fallick, A.E.; Dickin, A.P.; Mackenzie, A.B.; Stephens, W.E.; Hildreth, W.

    1983-01-01

    Isotopic and major and trace element analysis of nine samples of eruptive products spanning the history of the Mt. St. Helens volcano suggest three different episodes; (1) 40,000-2500 years ago: eruptions of dacite with ??{lunate}Nd = +5, ??{lunate}Sr = -10, variable ??18O, 206Pb/204Pb ??? 18.76, Ca/Sr ??? 60, Rb/Ba ??? 0.1, La/Yb ??? 18, (2) 2500-1000 years ago: eruptions of basalt, andesite and dacite with ??{lunate}Nd = +4 to +8, ??{lunate}Sr = -7 to -22, variable ??18O (thought to represent melting of differing mantle-crust reservoirs), 206Pb/204Pb = 18.81-18.87, variable Ca/Sr, Rb/Ba, La/Yb and high Zr, (3) 1000 years ago to present day: eruptions of andesite and dacite with ??{lunate}Nd = +6, ??{lunate}Sr = -13, ??18O ???6???, variable 206Pb/204Pb, Ca/Sr ??? 77, Rb/Ba = 0.1, La/Yb ??? 11. None of the products exhibit Eu anomalies and all are LREE enriched. There is a strong correlation between 87Sr/86Sr and differentiation indices. These data are interpreted in terms of a mantle heat source melting young crust bearing zircon and garnet, but not feldspar, followed by intrusion of this crustal reservoir by mantle-derived magma which caused further crustal melting and contaminated the crustal magma system with mafic components. Since 1000 years ago all the eruptions have been from the same reservoir which has displayed a much more gradual re-equilibration of Pb isotopic compositions than other components suggesting that Pb is being transported via a fluid phase. The Nd and Sr isotopic compositions lie along the mantle array and suggest that the mantle underneath Mt. St. Helens is not as depleted as MORB sources. There is no indication of seawater involvement in the source region. ?? 1983.

  17. Survey of knowledge of hazards of chemicals potentially associated with the advanced isotope separation processes

    International Nuclear Information System (INIS)

    Hazards of chemical potentially associated with the advanced isotope separation processes are estimated based on open literature references. The tentative quantity of each chemical associated with the processes and the toxicity of the chemical are used to estimate this hazard. The chemicals thus estimated to be the most potentially hazardous to health are fluorine, nitric acid, uranium metal, uranium hexafluoride, and uranium dust. The estimated next most hazardous chemicals are bromine, hydrobromic acid, hydrochloric acid, and hydrofluoric acid. For each of these chemicals and for a number of other process-associated chemicals the following information is presented: (1) any applicable standards, recommended standards and their basis; (2) a brief discussion to toxic effects including short exposure tolerance, atmospheric concentration immediately hazardous to life, evaluation of exposures, recommended control procedures, chemical properties, and a list of any toxicology reviews; and (3) recommendations for future research

  18. Characterizing the origins of bottled water on the South Korean market using chemical and isotopic compositions

    International Nuclear Information System (INIS)

    We analyzed the major elements and stable isotopes of oxygen, hydrogen, and carbon (dissolved inorganic carbon: DIC) in various types of bottled water (domestic and foreign) commercially available in South Korea to classify the water types and to identify their origins. Only marine waters and some sparkling waters could be discriminated by their physicochemical compositions. Oxygen and hydrogen isotopes made marine waters more distinguishable from other water types. The determination of the carbon isotope composition of DIC was clearly useful for distinguishing between naturally and artificially sparkling waters. In addition, statistical analysis also appeared to aid in the discrimination of bottled water types. Our results indicate that a method that combines chemical and stable isotope composition analysis with statistical analysis is the most useful for discriminating water types and characterizing the origins of bottled water

  19. Assessing chromate availability in tropical ultramafic soils using isotopic exchange kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, Jeremie; Quantin, Cecile [Univ. Paris Sud CNRS, Orsay (France); Echevarria, Guillaume [ENSAIA-INPL-INRA, Vandoeuvre-les-Nancy (France); Becquer, Thierry [IRD - Univ. Paris VI and XII, Montpellier (France)

    2009-10-15

    Background, aim, and scope The presence of labile chromate in the soils is an environmental problem because of its high toxicity. The isotopic exchange kinetics (IEK) methods have been shown to be a useful tool to measure the phytoavailability of major (P, K) and trace elements (Cd, Zn, Ni, Pb) in soils. This study focused on the potential of applying IEK for chromate to characterize its availability in two tropical ultramafic Ferralsols. Materials and methods Two Ferralsols (NIQ II and NIQ III) of the ultramafic complex of Niquelandia (Goias, Brazil), known to have a high content of extractable chromate, were investigated. We adapted IEK for chromate in order to distinguish different pools of available chromate according to their rate of exchange kinetic. Results The extractable Cr(III) ranged from 9 to 132 mg kg{sup -1}, whereas extractable Cr(VI) ranged from 64 to 1,014 mg kg{sup -1}. The intensity factor, i.e., concentration of soluble Cr, ranged from 78 to 231 {mu}g L{sup -1} in profile NIQ II and from 6 to 141 {mu}g L{sup -1} in profile NIQ III. The highest concentrations were found in both topsoils and in the NIQ II-5 horizon. Most of the Cr(VI) was labile in short (E{sub 0-1} {sub min}) or medium-term (E{sub 1} {sub min-24} {sub h}) in both soils. The E{sub 0-1} {sub min} and E{sub 1} {sub min-24} {sub h} represented 39 to 83% of labile Cr (VI) in NIQ II and 69 to 80% in NIQ III. A high quantity of Cr(VI) was thus extremely labile and highly available, particularly in NIQ II. Moreover, both soils had a high buffering capacity of soluble Cr(VI) by labile pools. (orig.)

  20. Identifying Stereoisomers by ab-initio Calculation of Secondary Isotope Shifts on NMR Chemical Shieldings

    Directory of Open Access Journals (Sweden)

    Karl-Heinz Böhm

    2014-04-01

    Full Text Available We present ab-initio calculations of secondary isotope effects on NMR chemical shieldings. The change of the NMR chemical shift of a certain nucleus that is observed if another nucleus is replaced by a different isotope can be calculated by computing vibrational corrections on the NMR parameters using electronic structure methods. We demonstrate that the accuracy of the computational results is sufficient to even distinguish different conformers. For this purpose, benchmark calculations for fluoro(2-2Hethane in gauche and antiperiplanar conformation are carried out at the HF, MP2 and CCSD(T level of theory using basis sets ranging from double- to quadruple-zeta quality. The methodology is applied to the secondary isotope shifts for 2-fluoronorbornane in order to resolve an ambiguity in the literature on the assignment of endo- and exo-2-fluoronorbornanes with deuterium substituents in endo-3 and exo-3 positions, also yielding insight into mechanistic details of the corresponding synthesis.

  1. Charge-exchange and charge-conserving reactions on Mg, Ar, Zr, and Sn isotopes

    International Nuclear Information System (INIS)

    We investigate charge-exchange reactions (CEXRs) and charge-conserving reactions (CCORs) on Mg, Ar, Zr, and Sn isotopes by comparing our theoretical results to relevant experimental data on stable nuclei. As for CEXRs, first, we discuss nuclear beta decay because it may give more convincing input data on the network calculations for successive capture reactions by protons and neutrons. Second, we address the importance of the Gamow Teller (GT) states that are low-lying excited states well known in the conventional nuclear physics while high-lying excited states still remain to be studied. The third topic, which is viable through the CCORs, is the symmetry energy associated with the equation of state of nuclear matter. By using the CCORs, we can study the isoscalar giant dipole resonance (ISGDR) and the pigmy dipole resonance (PDR). We discuss theoretical results regarding these CEXRs and CCORs on 26Mg, 40Ar, 90,92Zr, and 112∼124Sn and compare them with available experimental data. Our calculations are carried out by using the proton-neutron quasi-particle random phase approximation (pnQRPA), the QRPA, the deformed QRPA (DQRPA), the shell model and a hybrid model. Our results are shown to agree with the data available. These nuclear reactions considered in this report will complement capture reactions by protons and neutrons which are of vital importance for understanding the element abundances in the cosmos.

  2. Method of making hydrophobic industrial catalyst for water-hydrogen isotope exchange

    International Nuclear Information System (INIS)

    The authors have performed the research centering around the development of platinum catalyst carried by styrene divinylbenzene copolymer as the hydrophobic catalyst for water-hydrogen isotope exchange for the purpose of heavy water concentration and especially tritium removal. In this paper, the method of industrial production of this catalyst, the results of catalytic performance test by trickle bed and the problems are reported. It was found that only chloroplatinic acid was suitable as the practical raw material of the catalyst. The ethanol solution of chloroplatinic acid is practically most desirable. Generally, the catalytic activity increases by the aging of SDB in pure hydrogen flow. For the impregnation of chloroplatinic acid into SDB, the column method is suitable. The impregnated carriers are dried with an air drier. Then the carriers carrying chloroplatinic acid are reduced in a reaction tube with highly pure hydrogen. The catalytic performance test was performed in a packed tower, and the effects of the shape of catalysts, flow mode, oxygen, scale-up, pressure and impurities are reported. (Kako, I.)

  3. Isotopic and chemical survey of two thermal manifestations in the Serchio River valley, northern Tuscany, Italy

    International Nuclear Information System (INIS)

    A detailed study of isotopic (18O, 2H, 3H) composition of springs in the Larderello geothermal field, Italy, was started in 1992 with the aim to bring to light the existence of local and/or temporal fluctuations. Some measurements of chemical composition of the associated gas were also made

  4. Ab Initio Calculations of Deuterium Isotope Effects on Chemical Shifts of Salt-Bridged Lysines

    DEFF Research Database (Denmark)

    Ullah, Saif; Ishimoto, Takayoshi; Williamson, Mike P.;

    2011-01-01

    Deuterium isotope effects measure the change in chemical shift on substitution of a proton by deuterium. They have been calculated by direct treatment of the H/D nuclear quantum effect using a multicomponent ab initio molecular orbital method based on a non-Born−Oppenheimer approximation. This me...

  5. Thermal, chemical and isotopic homogenization of syn-extensional I-type plutons and mafic microgranular enclaves

    Science.gov (United States)

    Tatar Erkül, Sibel; Erkül, Fuat; Uysal, İbrahim

    2015-04-01

    Magma mixing and mingling processes are common phenomenon in the evolution of granitoid magmas. This study deals with examination of mineral chemical, geochemical and isotopic characteristics of enclaves and enclosing syn-extensional granite bodies in western Turkey to make an attempt to solve problems regarding their origin. Mafic microgranular enclaves have granodiorite, quartz monzonite, monzonite and monzodiorite compositions, are subalkaline/calc-alkaline and high-K in character and display typical mixing/mingling textures. Mafic enclaves have partially overlapping geochemical characteristics onto their host rocks in terms of mobile elements and their isotopes while distinct immobile element patterns occur within host rocks and enclaves. Contrasting geochemistry of enclaves is mainly defined by their low SiO2 and high MgO, Mg# and high Fe2O3 contents. Chondrite-normalized spidergrams of enclaves also reveal two contrasting patterns. One is relatively enriched in rare earth element content and the other is slightly enriched and displays relatively flat pattern. 87Sr/86Sr and 143Nd/144Nd contents of enclaves imply considerable amount of crustal input. Crustally derived felsic magma coeval with mafic magma have been chemically, thermally and mechanically exchanged with each other and resulting homogenization led to compositional and isotopic equilibration of mafic and felsic magmas. Fractional crystallization, mixing and the following crustal contamination were responsible for the final composition of syn-extensional granitoids. Such processes appear to have been widely occurred in continental extensional regime that caused melting and mixing of crustal and mantle sources at MOHO depth.

  6. Characterization of the available soil Ni by the isotopic exchange kinetics; Mesure de la fraction assimilable des elements en traces du sol par la methode des cinetiques d`echange isotopique: cas du nickel

    Energy Technology Data Exchange (ETDEWEB)

    Echevarria, G.; Klein, S.; Morel, J.L. [Laboratoire INRA, Ecole nationale superieure d`agronomie et des industries alimentaires, 54 - Vandoeuvre-les-Nancy (France); Fardeau, J.C. [CEA Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Direction des Sciences du Vivant

    1997-12-31

    The aim of this study was to demonstrate that soil Ni available for plants can be characterized by the isotopic exchange kinetics method. Therefore, isotopic exchange kinetics were performed in soil-solution systems to quantify the pool of soil isotopically exchangeable Ni (E value). Another isotopic exchange method in soil-plant was designed to measure the pool of soil available Ni (L value). Results clearly demonstrated that the pool of isotopically exchangeable soil Ni for a given time is the pool of available soil Ni. (author)

  7. Deactivation of hydrophobic catalysts for a hydrogen isotope exchange: Application of the time-on-stream theory

    International Nuclear Information System (INIS)

    A recycle reactor was built for the purpose of characterizing newly developed hydrophobic catalysts for a hydrogen isotope exchange. The catalytic rate constants of two types of hydrophobic catalysts were measured at a 100% relative humidity. The catalytic rate constants were measured at 60 deg C for 28 days and both the catalysts showed very high initial catalytic rate constants. The measured deactivation profile showed that the catalytic rate constants of both the catalysts were almost identical for 28 days. The deactivation of the catalysts was modelled based upon the time-on-stream theory. The deactivation profiles of the catalysts were estimated by using the model for a period of three years. The results showed that both the catalysts had a good exchange capacity for hydrogen isotopes and they could be applicable to a tritium removal facility that will be built at the Wolsong nuclear power plants in the near future

  8. Isotopic and chemical characteristics of groundwater in Beijing city

    International Nuclear Information System (INIS)

    The characteristics of the alluvial-diluvial aquifer of the Beijing area were studied by means of environmental isotopes, especially tritium, which may be considered as a useful natural tracer to demonstrate the pollutant behavior in groundwater aquifer. The results of tritium monitoring indicate that the natural regime of the groundwater system of the Quaternary aquifer has been destroyed due to intensive exploitation. Two subsystems could be divided based on tritium data. Subsystem A with active circulation was formed in the course of exploitation. Subsystem B is of slow circulation. The δ2H and δ18O values of the groundwater are higher in the western suburb than that in eastern suburb. The sketch maps os δ2H and δ18O isolines reflect a mixing between ground waters from the base rock and from the local vertical recharge. The trace elements Sr, Ru and Rh have a very special distribution in groundwater system with very high concentrations in the north-eastern part of the old Beijing city. The results of 87Sr/86Sr measurement show that Sr in groundwater of the Quaternary aquifer is from the groundwater of the basement rock. High concentrations of Sr in groundwater of the Quaternary aquifer are not related to any special pollution source. (author)

  9. Evaluation of the determination of iodine in drinking well water by neutron activation analysis and separation by isotope exchange

    International Nuclear Information System (INIS)

    The determination of total iodine in drinking and well water by neutron activation analysis and separation of 128I(T=25.0 min) by isotope exchange has been examined at the 5-15 ng.ml-1 level. Using the Lazy Suzan of a Triga Mark-II reactor, the capacity is ≤5 samples per hour at a precision of 15-20% per aliquot and no apparent systematic bias. (author) 6 refs.; 1 tab

  10. Partitioning net ecosystem exchange of CO2: A comparison of a Bayesian/isotope approach to environmental regression methods

    Science.gov (United States)

    Zobitz, J. M.; Burns, S. P.; OgéE, J.; Reichstein, M.; Bowling, D. R.

    2007-09-01

    Separation of the net ecosystem exchange of CO2 (F) into its component fluxes of net photosynthesis (FA) and nonfoliar respiration (FR) is important in understanding the physical and environmental controls on these fluxes, and how these fluxes may respond to environmental change. In this paper, we evaluate a partitioning method based on a combination of stable isotopes of CO2 and Bayesian optimization in the context of partitioning methods based on regressions with environmental variables. We combined high-resolution measurements of stable carbon isotopes of CO2, ecosystem fluxes, and meteorological variables with a Bayesian parameter optimization approach to estimate FA and FR in a subalpine forest in Colorado, United States, over the course of 104 days during summer 2003. Results were generally in agreement with the independent environmental regression methods of Reichstein et al. (2005a) and Yi et al. (2004). Half-hourly posterior parameter estimates of FA and FR derived from the Bayesian/isotopic method showed a strong diurnal pattern in both, consistent with established gross photosynthesis (GEE) and total ecosystem respiration (TER) relationships. Isotope-derived FA was functionally dependent on light, but FR exhibited the expected temperature dependence only when the prior estimates for FR were temperature-based. Examination of the posterior correlation matrix revealed that the available data were insufficient to independently resolve all the Bayesian-estimated parameters in our model. This could be due to a small isotopic disequilibrium (?) between FA and FR, poor characterization of whole-canopy photosynthetic discrimination or the isotopic flux (isoflux, analogous to net ecosystem exchange of 13CO2). The positive sign of ? indicates that FA was more enriched in 13C than FR. Possible reasons for this are discussed in the context of recent literature.

  11. The D2O effect on catalysis by triose phosphate isomerase requires isotope exchange on the enzyme

    International Nuclear Information System (INIS)

    The present work shows the value of measuring the rate of onset or loss of a D2O effect to distinguish between enzyme-bound protons and protons of the medium as the cause of the effect. This alternative was examined in the important studies of Bender on deacylation of chymotrypsin and papain in which the isotope effect in D2O was lost within 10 s of dilution into H2O and therefore was concluded to result from D2O rather than from a deuterium-substituted enzyme. However, 10 s is a long interval for all but the hydrogen-bonded backbone hydrogens. With the ususal rapid mixing device this interval can be shortened by a least 103, putting it in the range of many group ionizations. The results suggest that H/D exchange on the enzyme, occurring more slowly than catalysis, is required for the isotope effect to be seen. Because the isotope effect implies that a proton transfer within the enzyme occurs at some step of the reaction and because exchange is much slower than catalysis, the transfer must be reversed without exchange with the medium during product formation. It is proposed that a conformational change of E-G3P prior to the enolization is the step requiring such a proton transfer

  12. Chemical and Isotopic Thresholds in Charring: Implications for the Interpretation of Charcoal Mass and Isotopic Data

    Science.gov (United States)

    Pyle, L.; Hockaday, W. C.; Boutton, T. W.; Zygourakis, K.; Kinney, T.; Masiello, C. A.

    2014-12-01

    Charcoal plays a significant role in the long-term carbon cycle and its use as a soil amendment is becoming a viable carbon sequestration strategy (biochar). One challenge in this research area has been comparing results between studies in part due to the diversity of lab and field production conditions. Although the highest treatment temperature (HTT) is often used to describe pyrolysis conditions, several studies have shown that length of time at the highest temperature can also cause changes to the physicochemical qualities of charcoal and ignoring this effect may introduce inter-comparison problems. Addressing this issue becomes especially important in the discussion of optimizing biochar for soil remediation and carbon sequestration, and in discussions of charcoal use in reconstructing past fire regimes, as increasing time at temperature may cause changes in charcoal properties similar to the changes caused by increasing HTT. Here we introduce a formal definition of charring intensity (CI) to more accurately characterize pyrolysis, and we document variation in this property with pyrolysis temperature and reaction duration. We found two types of responses to CI: either a linear or a threshold relationship. We show that a threshold exists where %C, %N and δ15N begin exhibiting large changes, and this CI threshold co-occurred with an increase in charcoal aromaticity. Mass yield decreased linearly with charring intensity and carbon isotopes did not change from original biomass values in our controlled laboratory experiments. Analysis of these data shows that pyrolysis parameters should be defined in the literature as a combination of temperature and duration conditions, and that biomass that has undergone pyrolysis may be influencing soil organic nitrogen. Additionally, the lack of alteration in carbon isotopes across our matrix supports the efficacy of using pyrolyzed material for archaeological reconstructions.

  13. Monitoring of chemical and isotopic composition of the Euphrates river in Syria

    International Nuclear Information System (INIS)

    The ratios of stable isotopes (18O and 2H), tritium content, together with the chemical composition of major ions of the Euphrates and Balikh (Euphrates tributary) Rivers, and the groundwaters of four wells drilled close to the Euphrates River course, were measured on a monthly basis. The Euphrates River water was monitored at twelve stations along its course in Syria during the period from January 2004 to December 2006, whereas those of the Balikh and groundwaters were only investigated during 2005. Although, the spatial variations of heavy stable isotope concentrations are moderated with respect to other large rivers in the world, the concentrations of these isotopes increase generally downstream the Euphrates River, with a sharp enrichment at Al-Assad Lake. This sharp increase could be explained by the effect of direct evaporation from the river and its tributaries; and the effect of drainage return flows of irrigation waters, isotopically more enriched. Enrichment of stable isotopes in the Euphrates River water was used as a direct indicator of evaporation. Based on an experimental evaporation result of a Euphrates water sample and the integral enrichment of heavy stable isotopes in the Euphrates River system, the amount of water losses by evaporation from Al-Assad Lake was estimated to be about 1.26 to 1.62 billion m''3, according to 18O and deuterium (2H), respectively. This amount represents about 12-16% of the renewable surface water resources in the country. (author)

  14. Isotopic and geochemical studies of fluid-rock interactions and the chemical evolution of the oceans

    Energy Technology Data Exchange (ETDEWEB)

    Derry, L.A.

    1989-01-01

    The isotopic compositions of Sr and Nd, and the abundances of rare earth elements (REE) are used to study various types of fluid-rock interactions in the Earth's crust. The isotopic compositions of Sr and Nd and REE patterns in marine chemical sediments of Precambrian age are used to estimate the relative importance of continental weathering versus submarine hydrothermal activity in determining the chemical mass balance of the Precambrian oceans. Major and trace element abundances and Sr and Nd isotopes are used to quantify the degree of interaction of a carbonatite fluid-magmatic system with felsic crust, and to constrain the isotopic characteristics of the mantle source region. The isotopic composition of Sr is reported from a well characterized sequence of Upper Proterozoic carbonates from Svalbard and east Greenland. A simple model of carbonate recycling and isotopic mass balance calculations illustrate that sedimentary recycling can have a strong influence on Sr in the oceans. REE patterns from Precambrian banded iron formations (BIFs) are very similar to modern metalliferous sediments, and imply that the overall REE pattern of Precambrian seawater was similar to today. The mantle-like {var epsilon}{sub Nd} values and positive Eu anomalies imply that the source of the REE in the BIFs was submarine hydrothermal activity. The implications of a large hydrothermal flux of reduced Fe on the redox controls of the Precambrian atmosphere are explored, and a testable hypothesis is developed. The mass balance of Eu in the oceans is affected by preferential scavenging at hydrothermal sites. Data from the Cherry Hill, CA mineralizing system imply a complex plumbing system and a long residence time for the water. Isotopic data from the Fen alkaline complex, Norway, define mixing trends between mantle derived magmas or magmatic fluids and old crust.

  15. Chemical, crystallographic and stable isotopic properties of alunite and jarosite from acid-Hypersaline Australian lakes

    Science.gov (United States)

    Alpers, C.N.; Rye, R.O.; Nordstrom, D.K.; White, L.D.; King, B.-S.

    1992-01-01

    Chemical, crystallographic and isotopic analyses were made on samples containing alunite and jarosite from the sediments of four acid, hypersaline lakes in southeastern and southwestern Australia. The alunite and jarosite are K-rich with relatively low Na contents based on chemical analysis and determination of unit cell dimensions by powder X-ray diffraction. Correcting the chemical analyses of fine-grained mineral concentrates from Lake Tyrrell, Victoria, for the presence of halite, silica and poorly crystalline aluminosilicates, the following formulas indicate best estimates for solid-solution compositions: for alunite, K0.87Na0.04(H3O)0.09(Al 0.92Fe0.08)3(SO4)2(OH) 6 and for jarosite, K0.89Na0.07(H3O)0.04(Fe 0.80Al0.20)3(SO4)2(OH) 6. The ??D-values of alunite are notably larger than those for jarosite from Lake Tyrrell and it appears that the minerals have closely approached hydrogen isotope equilibrium with the acidic regional groundwaters. The ??D results are consistent with a fractionation ???60-70??? between alunite and jarosite observed in other areas. However, interpretation of ??D results is complicated by large variability in fluid ??DH2O from evaporation, mixing and possible ion hydration effects in the brine. ??D-values of water derived from jarosite by step-wise heating tend to be smaller at 250??C, at which temperature hydronium and other non-hydroxyl water is liberated, than at 550??C, where water is derived from the hydroxyl site, but the differences are not sufficiently different to invalidate measurements of total ??D obtained by conventional, single-step heating methods. ??34S-values for alunite and jarosite from the four lakes (+19.7 to +21.2??? CDT) and for aqueous sulfate from Lake Tyrrell (+18.3 to +19.8???) are close to the values for modern evaporites (+21.5 ??0.3???) and seawater (+20??0.5???) and are probably typical of seawater-derived aerosols in arid coastal environments. ??34-S-values slightly smaller than that for seawater may

  16. Investigation of hydrogen isotope exchange reaction rate in mixed gas (H2 and D2) at pressure up to 200 MPa using Raman spectroscopy

    International Nuclear Information System (INIS)

    Raman spectroscopy is a relevant method for obtaining objective data on isotopic exchange rate in a gaseous mix of hydrogen isotopes, since it allows one to determine a gaseous mix composition in real time without sampling. We have developed a high-pressure fiber-optic probe to be used for obtaining protium Raman spectra under pressures up to 400 MPa and we have recorded spectral line broadening induced by molecule collisions starting from ∼ 40 MPa. Using this fiber-optic probe we have performed experiments to study isotopic exchange kinetics in a gaseous mix of hydrogen isotopes (protium-deuterium) at pressures up to 200 MPa. Preliminary results show that the dependence of the average isotopic exchange rate related to pressure take unexpected values at the very beginning of the time evolution. More work is required to understand this inconsistency

  17. Peach Bottom 2 and 3 regenerative heat exchangers: chemical decontamination and solidification

    International Nuclear Information System (INIS)

    In 1977, Dow Nuclear Services, under contract to Philadelphia Electric Company, chemically decontaminated the regenerative heat exchangers at the Peach Bottom 2 and 3 Atomic Power Station. The purpose of the decontamination was to reduce the radiation levels associated with the subsequent heat exchanger repairs to be performed by PECO maintenance. Samples of piping from the regenerative heat exchangers were analyzed at Dow Chemical, Midland, Michigan, and solvent testing and selection was performed. Nuclear Solvent-1 was selected. Temporary equipment, piping and radiation shielding was installed to perform all necessary functions safely. All designs and procedures were approved by the Peach Bottom Plant Operations Review Committee. The chemical decontamination removed 10.6 curies of radioactive material in the case of Peach Bottom 3 and similarly at Peach Bottom 2, 6.3 curies of material was removed. Radioactive waste generated by decontamination that could not be treated by existing facilities was successfully solidified by the Dow Solidification process

  18. Isotopic and chemical studies of geothermal waters of Northern Areas in Pakistan

    International Nuclear Information System (INIS)

    Northern Areas is one of the major thermal fields of Pakistan with more than two dozen known hot springs having discharge temperature ranging from 35 deg. C to 94 deg. C. Isotopic and chemical techniques applied to study the geothermal fields show that thermal waters are of meteoric origin and can be classified as Na-HCO3, Na-SO4 and mixed type on the basis of their chemical contents. At some places cooling of thermal waters seems to be due to steam separation whereas mixing with fresh cold water is prominent at the remaining sites. The temperatures estimated by isotopic and chemical geothermometers for the two major fields i.e. Tatta Pani and Murtazabad are 83-257 deg. C and 65-296 deg. C respectively. (author). 24 refs, 11 figs, 3 tabs

  19. Calculation of reduced partition function ratios of isotopically substituted molecules on a quantum chemical base

    International Nuclear Information System (INIS)

    By means of the semiempirical quantum chemical MINDO/3- and MNDO-MO-methods it is possible to perform calculations for use in evaluation or interpretation of isotope effects to such an extent that would not be rationally fossible by corresponding experiments. But only the calculated reduced partition function ratios of isotopically substituted molecules can be applied with sufficient reliability for discussions. The temperature dependence of the reduced partition function ratios of over 100 molecules, ions, and radicals regarding the H/D, 12C/13C-, 14N/15N-, 16O/18O-, 28Si/30Si-, 32S/34S-, and 35Cl/37Cl-substitution has been calculated. From these results general conclusions concerning the dependence of isotope effects from the chemical structure of the corresponding molecules have been drawn. In particular, a relationship between the reduced partition function ratio and the electronic charge of the substituted atom has been found. In addition, examples are given for the application of the calculation algorithm used above in connection with combined isotopic substitutions, radical cations, and transition states of chemical reactions. (author)

  20. Isotopic and chemical techniques in geothermal exploration, development and use. Sampling methods, data handling, interpretation

    International Nuclear Information System (INIS)

    This book is designed as an instructional manual of essential nuclear and complementary methodologies for a multidisciplinary approach to geothermal exploration development and monitoring. It provides comprehensive procedures for carrying out isotope and geochemical investigations of geothermal systems. It focuses on the three stages of geothermal studies of geothermal fluids, i.e. sampling, analysis and data interpretation. Specific chapters of the book provide some background information on the generally adopted strategy and on the behaviour of chemical and isotopic components in the geothermal environment; deal with the nature of surface thermal manifestations and sampling techniques; present analytical data handling and presentation; and concentrate on data interpretation

  1. Peach Bottom 2 and 3 regenerative heat exchangers: chemical decontamination and seal ring repairs

    International Nuclear Information System (INIS)

    In 1977 and early 1978, Philadelphia Electric Company chemically decontaminated and installed seal rings into the shell to channel joints of all Reactor Water Clean-up Regenerative Heat Exchangers located in Units 2 and 3 at Peach Bottom Station. The cost to perform this work was approximately $900,000. The radiation exposure accumulated during chemical decontamination and repairs of all heat exchangers was approximately 215 man-rem. This exposure was spread among approximately 300 individuals with individual exposures ranging from 0.5 to 7 rem over a one year period

  2. Impact of Atmosphere-sea Exchange on the Isotopic Expression of Carbon Excursions: Observations and Modeling of OAE-1a

    Science.gov (United States)

    Finkelstein, D. B.; Pratt, L. M.; Brassell, S. C.; Montañez, I. P.

    2005-12-01

    Negative carbon isotope excursions are a recurring phenomenon in earth history (e.g., Permo-Triassic boundary, Jurassic and Cretaceous oceanic anoxic events, and the Paleocene-Eocene Thermal Maximum) variously attributed to destabilization of methane clathrates, a decrease in primary productivity, intensified volcanism, and more recently to widespread peat fires. Each forcing mechanism invoked accounts for both the magnitude of the negative isotopic shift and the reservoir required to drive the shift as observed at one to several locales. Studies rarely consider the effect of latitudinal temperature changes on the excursion. Here, we explore the early Aptian oceanic anoxic event as an example of a negative isotopic shift whose magnitude varies with paleolatitude in terrestrial settings. It increases (from -2.0 to -8.2 ‰) with paleolatitude (5° to 33°N) and is greater than that expected for changes in plant C isotope discrimination driven by environmental stresses (~3 ‰). Conceptually, an isotopic shift of terrestrial vegetation across paleolatitudes represents a response to its forcing mechanism and temperature. A closed system carbon cycle model constructed of five reservoirs (atmosphere, vegetation, soil, and shallow and deep oceans), and five fluxes (productivity, respiration, litter fall, atmosphere-ocean exchange, and surface-deep ocean exchange) was employed is assessment of a negative isotopic shift at 2x pre-industrial atmospheric levels (P.A.L.) for pCO2 keeping all variables constant with the exception of temperature. The model was run at 5°C increments from 5° to 40°C to simulate the effect of temperature gradients on isotopic shifts at variable latitudes, with the appropriate temperature dependent fractionations for atmosphere - sea exchange. The magnitude of the negative isotopic shift at each temperature was calculated for both terrestrial and marine organic matter. In terrestrial vegetation it changed from -4 to -5.8 ‰ with decreasing

  3. Lithium isotope separation

    International Nuclear Information System (INIS)

    Published methods for 6Li-7Li lithium isotope separation have been reviewed. Future demand for 6Li, whose main use will be as a tritium breeder in blankets surrounding the core of DT fusion power reactors, is likely to exceed 5 Mg/a in the next century. The applicability of the various available methods to such a large scale production rate has been assessed. Research on improving the effectiveness of current lithium isotope separation processes has been carried out worldwide in several major areas during the past decade; these include two-phase chemical exchange systems, ion exchange resin chromatography, highly isotope-selective techniques like laser photoactivation and radiofrequency spectroscopy. Chemical exchange systems appear to offer good potential in the near term for 6Li enrichment

  4. Contribution to chlorine cycle: a Cl stable isotope approach on Mantle-Ocean exchanges

    Science.gov (United States)

    Bonifacie, M.; Jendrzejewski, N.; Pineau, F.; Agrinier, P.

    2003-04-01

    The stable isotope composition of chlorine (37Cl/35Cl) can be used to trace its geochemical cycle and is a powerfull tool to constrain the origin of high chlorine contents found for some fresh MORB glasses. Despite the fact that chlorine is a volatile element of primary importance, its cycle and isotopic fractionation factors during exchange processes between Earth's reservoirs or phases are poorly known. Furthermore, the scarcity of data for solid samples (rocks or minerals) reflects the analytical difficulty to extract chlorine from silicate structure. The classical methods of pyrohydrolysis followed by isotope-ratio mass spectrometric measurements on CH_3Cl gas have been optimised. Our technique represents the most quantitative and precise method of chlorine extraction for δ37Cl determination on solids published to date. Mean extraction yields are 100 ± 3%, δ37Cl values on duplicate extractions show reproducibility better than 0.2 ppm and the blanks represent less than 5% of the sample size. To characterise chlorine behaviour during the oceanic crust alteration, we have analysed fresh MORB glasses (from SWIR and EPR), altered basalts from leg 504B site (EPR), serpentinized peridotites (from SWIR and MAR) and an altered gabbro from the Hess Deep site (EPR). All samples (n=9) are depleted in 37Cl (δ37Cl from -1.4 to 0 ppm) relative to seawater (δ37Cl =0 ppm); Cl concentrations are between 200 and 2200 ppm. Our results on fresh MORBs: δ37Cl = -1.4 ppm and -0.6 ppm are in the lower range already published (-3 to +11 ppm, e.g. Magenheim et al., 95; Stewart, 2000). However, our δ37Cl range of altered samples: δ37Cl = -1.3 to -0.2 ppm (basalts, serpentinised peridotites and gabbro) is outside the range observed by Magenheim et al., 95 (+0.4 to +7.5 ppm in amphibole-rich rocks and smectite veins) despite the fact that in both study amphibole-rich rocks from the same site (i.e. leg 504B) have been analysed. On this site, our δ37Cl results are very homogeneous

  5. Kinetics of isotopic exchange reaction between hydrogen and water vapor over hydrophobic catalyst in a Co-current bed

    International Nuclear Information System (INIS)

    The kinetics of isotopic exchange reaction between hydrogen and water vapor over Pt- SDB as a hydrophobic catalyst was investigated in a fixed co-current bed. The influence of vari- ous factors on the rate constant of water vapor-hydrogen co-current exchange reaction were studied, including rate equation, order of reaction, temperature dependence of reaction and the species of catalysts. The results show that the overall reaction is first order. The relation of apparent rate constant with temperature accorded with Arrhenius and the apparent rate constant increases with temperature rising. The apparent activation energy of Pt-SDB is lower than Pt-C-PTFE and the rate constant of water vapor-hydrogen co-current exchange reaction increases when the apparent activation energy of the hydrophobic catalyst decreases. (authors)

  6. Stable isotope and chemical compositions of European and Australasian ciders as a guide to authenticity.

    Science.gov (United States)

    Carter, James F; Yates, Hans S A; Tinggi, Ujang

    2015-01-28

    This paper presents a data set derived from the analysis of bottled and canned ciders that may be used for comparison with suspected counterfeit or substitute products. Isotopic analysis of the solid residues from ciders (predominantly sugar) provided a means to determine the addition of C4 plant sugars. The added sugars were found to comprise cane sugar, high-fructose corn syrup, glucose, or combinations. The majority of ciders from Australia and New Zealand were found to contain significant amounts of added sugar, which provided a limited means to distinguish these ciders from European ciders. The hydrogen and oxygen isotopic compositions of the whole ciders (predominantly water) were shown to be controlled by two factors, the water available to the parent plant and evaporation. Analysis of data derived from both isotopic and chemical analysis of ciders provided a means to discriminate between regions and countries of manufacture. PMID:25536876

  7. Determination of plutonium isotopes in freshwater lake sediments by sector-field ICP-MS after separation using ion-exchange chromatography

    International Nuclear Information System (INIS)

    The determination of Pu isotopes in lake sediments is important for many studies, such as Pu pollution source identification, sediment mixing estimation, erosion evaluation and establishment of deposition chronology in lakes. In this paper, a simple analytical method using sector field inductively coupled plasma mass spectrometry (ICP-MS) combined with two-stage chromatographic separation and purification of Pu was developed based on the optimization and adaptation of the previously published method for marine samples with an emphasis on the study of the elimination of interferences for the analysis of freshwater lake sediments. A strong base anion-exchange resin (AG MP-1M) was used to purify Pu isotopes with concentrated HBr as the final eluent for Pu elution. The chemical yields were ca. 64% and the decontamination factor for U was ca. 105. The developed method was validated using a freshwater lake sediment reference material (SRM-4354) and a marine sediment reference material (IAEA-368), and applied to the determination of Pu isotopes in sediment samples of Lake Poyang, East China. For the analysis of certified reference materials, both 239+240Pu activity of 31.6 mBq g-1 and 240Pu/239Pu atom ratio of 0.033 for IAEA-368 were comparable to the certified value and/or literature values. As for SRM-4354, 239+240Pu activity of 3.90 mBq g-1 agreed well with the certified value. However, the mean 240Pu/239Pu atom ratio of 0.144 was lower than those reported by other laboratories. This difference suggested that this material may be isotopically inhomogeneous. 240Pu/239Pu atom ratios of Poyang Lake sediment samples ranged from 0.185 to 0.192 with a mean value of 0.187±0.004, indicating that plutonium pollution originated from global fallout

  8. Studying the Permian cross-section (Volga region) using chemical and isotopic investigations

    Science.gov (United States)

    Gareev, Bulat; Georgii, Batalin; Nurgaliev, Danis; Nurgalieva, Nuriya

    2016-04-01

    This paper presents a study of international important site: the cross-section of Permian system's Urzhumian Stage in the ravine "Pechischy". Outcrop is located on the right bank of the Volga River (about 10 km West of Kazan). It has local, regional and planetary correlation features and also footprints of different geographical scale events. The main objective in the research is the deep study of sediments using chemical and isotopic investigations. XRF spectrometer was used for chemical investigations of samples. Chemistry of carbonates and clastic rocks includes the analysis of chemical elements, compounds, petrochemical (lithogeochemical) modules for the interpretation of the genesis of lithotypes. For the review of the geochemistry of stable isotopes of carbon (oxygen) we used IRMS. The main objective is the nature of the isotope fractionation issues, to addressing the issues of stratigraphy and paleogeography. The measurements have shown the variability of chemical parameters in cross-section. It gives us opportunity to see small changes in sedimentation and recognize the factors that influence to the process. The work was carried out according to the Russian Government's Program of Competitive Growth of Kazan Federal University, supported by the grant provided to the Kazan State University for performing the state program in the field of scientific research.

  9. Phosphorus Use Efficiency for Symbiotic Fixation Nitrogen in Voandzou (Vigna Subterranea) Using Isotopic Exchange Method in Rhizotron

    International Nuclear Information System (INIS)

    Low bioavailability of nitrogen and phosphorus is one of the main constraints in the acid soils with high P-fixing capacity. Plants adapt to low nutrient availability through various biological and physico-chemical mechanisms. Since genetic variation of N2 fixation exists in numerous legume species, optimization of symbiotic nitrogen fixation (SNF) under P deficiency could be a way to the replenishment of soil fertility in tropical soils. As the genetic potential of crops like Vigna subterranea (Bambara groundnut or voandzou) is little studied, although its agronomic potential is interesting for the farmers of Africa, a physiological study through legume screening for N2 fixation was performed with 54 cultivars from Madagascar, Niger and Mali, inoculated with the reference strain of Bradyrhizobium sp. Vigna CB756 in hydroponic culture under P deficiency and sufficiency (30 and 75 μmol KH2PO4 plant-1 week -1, respectively), corresponding respectively to 28 and 70 mg P kg-1 of soil. Large variability of nodulation and plant biomass was found among cultivars. These two parameters were generally correlated and the slope of the plant biomass regression as a function of nodulation was considered as an indicator of the efficiency in use of the rhizobial symbiosis. For the two cultivars most tolerant to P deficiency, V1 and V4 from Madagascar, the increase in use efficiency of the rhizobial symbiosis under P deficiency was linked with an increase in nodulated root O2 consumption linked to N2 fixation, and in phytase gene expression observed on the nodule sections by in situ RT- PCR. As the complexity of P compartments makes it difficult to assess the P bioavailability in the plant rhizosphere, an isotopic 32P exchange method was carried out in a rhizotron in order to assess the direct effect of the roots on P mobilization in rhizosphere soil, comparing V1 and V4 with 28 or 70 mg P kg-1 of soil. Throughout this study, the various rhizospheric mechanisms involved in the P

  10. Features of adsorbed radioactive chemical elements and their isotopes distribution in iodine air filters AU-1500 at nuclear power plants

    CERN Document Server

    Neklyudov, I M; Dikiy, N P; Ledenyov, O P; Lyashko, Yu V

    2013-01-01

    The main aim of research is to investigate the physical features of spatial distribution of the adsorbed radioactive chemical elements and their isotopes in the granular filtering medium in the iodine air filters of the type of AU1500 in the forced exhaust ventilation systems at the nuclear power plant. The gamma activation analysis method is applied to accurately characterize the distribution of the adsorbed radioactive chemical elements and their isotopes in the granular filtering medium in the AU1500 iodine air filter after its long term operation at the nuclear power plant. The typical spectrum of the detected chemical elements and their isotopes in the AU1500 iodine air filter, which was exposed to the bremsstrahlung gamma quantum irradiation, produced by the accelerating electrons in the tantalum target, are obtained. The spatial distributions of the detected chemical element 127I and some other chemical elements and their isotopes in the layer of absorber, which was made of the cylindrical coal granule...

  11. What are the instrumentation requirements for measuring isotopic composition of net ecosystem exchange of CO2 via eddy covariance methods?

    Science.gov (United States)

    Shorter, J.; Saleska, S.; Herndon, S.; Jimenez-Pizarro, R.; McManus, J. B.; Munger, J. W.; Nelson, D. D.; Zahniser, M.

    2005-12-01

    Better quantification of isotope ratios of atmosphere-ecosystem exchange of CO2 could substantially improve our ability to probe underlying physiological and ecological mechanisms controlling ecosystem carbon exchange, but the ability to make long-term continuous measurements of isotope ratios of exchange fluxes has been limited by measurement difficulties. In particular, direct eddy covariance methods have not yet been used for measuring the isotopic composition of ecosystem fluxes. Here we explore the feasibility of such measurements by: (a) proposing a general criterion for judging whether a sensor's performance is sufficient for making such measurements (the criterion is met when the contribution of sensor error to the flux measurement error is comparable to or less than the contribution of meteorological noise inherently associated with turbulence flux measurements); (b) using data-based numerical simulations to quantify the level of sensor precision and stability required to meet this criterion for making direct eddy covariance measurements of the 13C/12C ratio of CO2 fluxes above a specific ecosystem (a mid-latitude temperate forest in central Massachusetts, USA); and (c) testing whether the performance of a new sensor -- a prototype pulsed quantum cascade laser-based isotope-ratio absorption spectrometer (and plausible improvements thereon) -- is sufficient for meeting the criterion in this ecosystem. We found that the error contribution from a prototype sensor (0.2 per mil, 1 SD of 10-sec integrations) to total isoflux measurement error was comparable to (1.5 to 2X) the irreducible meteorological noise inherently associated with turbulent flux measurements above this ecosystem (daytime measurement error SD of 60 percent of flux versus meteorological noise of 30-40 percent for instantaneous half-hour fluxes). Our analysis also shows that plausible instrument improvements (increase of sensor precision to 0.1 per mil, 1 SD of 10-sec integrations, and

  12. Application of isotopic and chemical methods to the study of hydrological problems in Brazilian northeastern areas

    International Nuclear Information System (INIS)

    Hydrological studies are reported with samples of ground water from several region of northern - and northeastern Brazil: Marajo Island (State of Para), State of Piaui, Ceara and Rio Grande do Norte. A description is given of the utilization of chemical and isotopic methods, in particular measurements of tritium concentration and 14C- counting techniques for the determination of the origin and residence time of water. (I.C.R.)

  13. Mass-independent isotope effect in the earliest processed solids in the solar system: a possible chemical mechanism.

    Science.gov (United States)

    Marcus, R A

    2004-11-01

    (ads) and other adsorbed metal atoms or metallic monoxides to form CAIs. The latter are thereby mass-independently poor in (17)O and (18)O. Some O (ads) used to form the minerals are necessarily in excess of the XO (ads), because of the stoichiometry of the mineral, and modify the fractionation pattern. This effect is incorporated into the mechanistic and mathematical scheme. A merit of this chemical mechanism for the oxygen isotope anomaly is that only one oxygen reservoir is required in the solar nebula. It also does not require a sequestering of intermediate products which could undergo isotopic exchange, hence undoing the original isotopic fractionations. The gas phase source of adsorbed O atoms in this environment is either O or H(2)O. As inferred from data on the evaporation of Mg(2)SiO(4) taken as an example, the source of O (ads) is primarily H(2)O rather than O and is accompanied by the evolution of H(2). Nonisotopic kinetic experiments can determine more sharply the mechanism of condensed phase growth of these minerals. Laboratory tests are proposed to test the existence of a surface eta effect on the growing CAI surfaces at these high temperatures. PMID:15511139

  14. Isotope separation of carbon-13 by counter-current column with exchange reaction between carbon dioxide and carbamic acid

    International Nuclear Information System (INIS)

    The isotope separation performance of carbon-13 with exchange reaction between CO2 and carbamic acid was studied and some factors for the counter-current column were studied for improving the overall performance. The working fluid for the experiments was a solution of DNBA, (C4H9)2NH, and n-octane mixture. The rate-controlling step of 13C transfer at temperatures higher than 10 deg C was the exchange reaction between carbamic acid and CO2 dissolved by physical absorption. The capacity coefficient of 13C transfer between gas and liquid in the counter-current column was successfully related to the product of three factors: the concentration of carbamic acid, the concentration of CO2 dissolved by physical absorption and the liquid holdup of the column. The liquid holdup was also an important factor. As the holdup increased, the isotope exchange rate and the overall separation factor of the column increased. However, the transient time to equilibrium was much longer. (author)

  15. Reactions on solid supports. Part-3. Hydrogen isotope exchange reactions catalysed by montmorillonite clay

    International Nuclear Information System (INIS)

    'Deuteriated clay' in which the interlammelar water has been replaced by deuterium oxide can be used for exchange of acidic protons in a variety of organic substrates. β-Keto esters and β-diketones undergo rapid exchange of the methylene protons in chloroform solutions in presence of deuterated clay; pyrrole undergoes exchange of all protons, whereas indoles preferentially undergo exchange at the 3-position as expected, although prolonged exposure to the reagent leads to exchange at other positions. (author). 8 refs. 1 tab

  16. Isotopic and chemical investigation of water samples from Arno and Tiber rivers (Central Italy)

    International Nuclear Information System (INIS)

    Full text: The δ18O and δ2H isotope signature in the main rivers Tiber and Arno and principal tributaries, in Central Italy, were investigated along with major ion chemistry in order to evaluate the relative impact of natural processes and pollution on superficial water quality of related catchments. The Tiber Basin extends over an area of about 17156 km2 between the Apennine and Anti-Apennine Ridges to the Tyrrhenian Sea, in the Umbria and Latium regions. The main direction of fluid flow is NE-SW. Along its 402 km length, the Tiber River undergoes a vertical fall of about 1300 meters and crosses the town of Rome. With a surface area of about 8228 km2, northwest to Tiber Basin, the Arno Basin is located in Tuscany between the Apennine Ridge and the Tyrrhenian Sea. The Arno River flows westward crossing the tows of Florence and Pise. Along its 241 km length, the Arno River undergoes a vertical fall of about 1360 meters. Repeated surveys were carried out from 1996 to 2001 as to obtain water samples representative of high and low flow hydrologic conditions. The chemical and isotopic compositions of waters from both the systems were compared in order to assess the impact of local environmental factors on surface chemistry. Despite very similar climatic conditions, i.e. monthly precipitation amounts, average ambient temperature, temporal duration of dry, wet and intermediate seasons, the geochemical signature of surface waters results in different patterns in the two catchments. The Arno River shows a fairly homogeneous geochemical behaviour, characterised by a progressive enrichment of solute contents and 18O and 2H concentrations moving away from source to mouth, essentially due to the evaporation processes of the surface/soil waters. Both the chemical and isotopic data suggest that runoff control the chemical behaviour of river waters, according with the low average permeability of outcropping formations. In contrast, the Tiber River is characterised by a more

  17. Stereo-dynamics of the exchange reaction Ha+LiHb→LiHa+Hb and its isotopic variants

    Institute of Scientific and Technical Information of China (English)

    Zhai Hong-Sheng; Yin Shu-Hui

    2012-01-01

    The quasi-classical trajectory (QCT) method is used to calculate the stereo-dynamics of the exchange reaction Ha+LiHb→LiHa+Hb and its isotopic variants based on an accurate potential energy surface reported by Prudente et al.[Prudente F V,Marques J M C and Maniero A M 2009 Chem.Phys.Lett.474 18].The reactive probability of the title reaction is computed.The vector correlations and four polarization-dependent generalized differential cross sections (PDDCSs) at different collision energies are presented.The influences of the collision energy and the reagent rotation on the product polarization are studied in the present work.The results indicate that the product rotational angular momentum j' is not only aligned,but also oriented along the direction perpendicular to the scattering plane.The product polarization distributions of the title reaction and its isotopic variants exhibit distinct differences which may arise from different mass combinations.

  18. Oxygen isotope exchange in rocks and minerals from the Cerro Prieto geothermal system: indicators of temperature distribution and fluid flow

    Energy Technology Data Exchange (ETDEWEB)

    Williams, A.E.; Elders, W.A.

    1981-01-01

    Oxygen isotopic compositions have been measured in drill cuttings and core samples from more than 40 wells ranging in depth to more than 3.5 km in the Cerro Prieto geothermal field. Oxygen isotopic profiles of pore-filling calcites in sandstones appear to be a reliable measure of the recent equilibrium temperature distribution in the field before production began. From these data, a detailed, three-dimensional map has been developed, showing the equilibrium temperatures in the geothermal field. A mass balance calculation has been performed using measured /sup 18/O enrichment of the geothermal brine. This calculation implies an overall water; rock volume ratio of approximately 3:1 during the history of the Cerro Prieto system. Paleotemperatures different from the present thermal regime have been studied by examining coexisting mineral systems which exchanged their oxygen with the geothermal brines at different rates.

  19. A study on the deactivation and stability of hydrophobic catalyst for hydrogen isotope exchange

    International Nuclear Information System (INIS)

    The hydrophobic catalyst has been prepared by deposition of platinum on porous styrene divinylbenzene copolymers(Pt/SDBC) and at the same time a separated type catalytic reactor has been developed for the Wolsong tritium removal facility(WTRF). Several tests carried out to obtain the experimental performance data of the Pt/SDBC with a recycle reactor system. The long-term stability was also measured with the Pt/SDBC catalyst immersed in water for a long time. The long-term deactivations of the Pt/SDBC catalyst were evaluated quantitatively by mathematical models. The simple mathematical models were presented to evaluate the uniform poisoning and shell progressive poisoning to be occurred simultaneously during the hydrogen isotope exchange between hydrogen gas and liquid water in the Liquid Phase Catalytic Exchange(LPCE) column. The uniform poisoning was well characterized by a time on stream theory and then the deactivation parameters were determined from the experimental performance data. The impurity poisoning was derived by a shell progressive model with two-layer mass transfer. The water vapor condensation was a main cause of the reversible uniform poisoning for the Pt/SDBC catalyst. The values of the decay rate constant (Kd) and order of the decay reaction(m) were of 2 and 4, respectively, based on the experimental data. It indicated that the decay might be attributable to pore mouth poisoning. From the long-term stability of the catalyst immersed in water, there was no intrinsic decay of catalyst activity due to water logging to the catalyst. The activity decreased by only 7% over 18 months, which was equivalent to a catalyst half-life longer than 15 years. On the basis of the above deactivation parameters, the values for kc/kco with Thiele modulus=20 after 3 years and 10 years of operation were expected about 19% and 15% of the initial activity, respectively, while the values for kc/kco with Thiele modulus=100 were of about 22% and 18%, respectively. However

  20. Capture and isotopic exchange method for water and hydrogen isotopes on zeolite catalysts up to technical scale for pre-study of processing highly tritiated water

    International Nuclear Information System (INIS)

    Highly tritiated water (HTW) may be generated at ITER by various processes and, due to the excessive radio toxicity, the self-radiolysis and the exceedingly corrosive property of HTW, a potential hazard is associated with its storage and process. Therefore, the capture and exchange method for HTW utilizing Molecular Sieve Beds (MSB) was investigated in view of adsorption capacity, isotopic exchange performance and process parameters. For the MSB, different types of zeolite were selected. All zeolite materials were additionally coated with platinum. The following work comprised the selection of the most efficient zeolite candidate based on detailed parametric studies during the H2/D2O laboratory scale exchange experiments (about 25 g zeolite per bed) at the Tritium Laboratory Karlsruhe (TLK). For the zeolite, characterization analytical techniques such as Infrared Spectroscopy, Thermogravimetry and online mass spectrometry were implemented. Followed by further investigation of the selected zeolite catalyst under full technical operation, a MSB (about 22 kg zeolite) was processed with hydrogen flow rates up to 60 mol*h-1 and deuterated water loads up to 1.6 kg in view of later ITER processing of arising HTW. (authors)

  1. A New Class of Contrast Agents for MRI Based on Proton Chemical Exchange Dependent Saturation Transfer (CEST)

    Science.gov (United States)

    Ward, K. M.; Aletras, A. H.; Balaban, R. S.

    2000-03-01

    It has been previously shown that intrinsic metabolites can be imaged based on their water proton exchange rates using saturation transfer techniques. The goal of this study was to identify an appropriate chemical exchange site that could be developed for use as an exogenous chemical exchange dependent saturation transfer (CEST) contrast agent under physiological conditions. These agents would function by reducing the water proton signal through a chemical exchange site on the agent via saturation transfer. The ideal chemical exchange site would have a large chemical shift from water. This permits a high exchange rate without approaching the fast exchange limit at physiological pH (6.5-7.6) and temperature (37°C), as well as minimizing problems associated with magnetic field susceptibility. Numerous candidate chemicals (amino acids, sugars, nucleotides, heterocyclic ring chemicals) were evaluated in this preliminary study. Of these, barbituric acid and 5,6-dihydrouracil were more fully characterized with regard to pH, temperature, and concentration CEST effects. The best chemical exchange site found was the 5.33-ppm indole ring -NH site of 5-hydroxytryptophan. These data demonstrate that a CEST-based exogenous contrast agent for MRI is feasible.

  2. Isotopic and chemical studies of geothermal waters of northern areas of Pakistan

    International Nuclear Information System (INIS)

    Northern Area is one of the major thermal fields of Pakistan. It has more than two dozen known hot springs having discharge temperature ranging from 350 deg. C to 940 deg. C. The area is characterized by U-shaped glaciated valleys among high mountain ranges. Tectonically the area is still active and has two major thrust faults viz. main mantle thrust (MMT) and Main Karakoram Thrust (MKT). Most of the hot springs are lying along these faults. Chemical and isotopic investigation was undertaken to get he information about the origin and composition of hot water, age and reservoir temperatures. Samples of water, gas and chemical precipitates were collected in four field trips and analyzed for various chemical ions and isotopes. The results show that the geothermal waters are of meteoric origin which have acquired their heat during circulation in fault system. Thermal waters are classified into Na-HCO/sub 3/, Na-SO/sub 4/ and mixed type on the basis of their chemical contents. In Murtazabad, Budelas, Sassi and Chutran areas, thermal waters are being mixed with cold fresh waters while in the remaining areas occurrence of mixing process is not evident. Tritium contents suggest that hot waters of Tatta Pani and Tato springs have not been recharged within last 40 to 50 years. The hot waters of remaining areas are relatively younger in age. Different isotopic and chemical geothermometers have been applied to estimate the reservoir temperatures at different locations. These temperature estimates for the two major fields i.e., Tatta Pani and Murtazabad are in the range of 130 to 239 deg. C and 114 to 296 deg. C respectively. Sulphate water and Silica thermometers yield close estimates where as Na-K-Ca temperatures are relatively high. (author) 19 figs

  3. Isotopic enrichment of diamond using microwave plasma-assisted chemical vapor deposition with high carbon conversion efficiency

    International Nuclear Information System (INIS)

    Isotopically-controlled diamond crystals were grown using microwave plasma-assisted chemical vapor deposition. First, the highest carbon isotopic enrichment and their controllability were examined. Although the highest 12C isotopic ratio of 99.998% was achieved using methane with an isotopic ratio of 99.999%, the memory effect of an unintended carbon isotope was found to be considerable when the carbon isotopic ratio of feeding methane was tuned for isotopic multilayer formation. Secondly, a unique gas feeding sequence was proposed for increasing the carbon conversion efficiency from methane to diamond. Increasing the conversion efficiency is done by finding a suitable balance between the methane feeding rate and the carbon consumption rate for diamond growth. A high conversion efficiency of 70% was obtained for a polycrystalline diamond with a high 12C isotopic ratio of 99.997%. - Highlights: • Isotopic control of diamond films was investigated. • A high microwave power density condition was applied for diamond growth. • The controllable range of the carbon isotopic ratio was demonstrated. • Diamond films having the highest 12C carbon isotopic enrichment were grown. • High carbon conversion efficiency of 70% was achieved

  4. Chemical and environmental isotope study of the basaltic aquifer systems of Yarmouk Basin (Syria)

    International Nuclear Information System (INIS)

    The water in the fissured basalt aquifer system, the Upper Jurassic aquifer of the Yarmouk Basin and the atmospheric precipitation have been investigated using chemical and environmental isotope techniques. The groundwaters flowing through the different aquifers are differentiated by their chemical ratios and their isotopic compositions. The evolution of chemical facies of groundwater from the recharge area towards the basin outlet is characterized by increasing of sodium and magnesium contents as a result of silicate leaching. The stable isotope compositions of precipitation and mountainous spring waters match the Mediterranean Meteoric Water Line, while the groundwaters from the central zone and from the major springs of the Yarmouk Basin are mixtures of freshwater, which is isotopically depleted and salty groundwater of Laja plateau area. The interpretations of tritium and radiocarbon (14 C) data indicate that the recharge zones of the groundwater in the Yarmouk Basin occur on the high-land of more than 1000 m of altitude. The residence time of the mountainous springs is short (of about 40 years or less). However, water ages corrected by Vogel's concept and Gonfiantini's Model show, in general, a range from 1000 to 11000 years for the central zone groundwater. The groundwater moves from the Mt. Hermon and Mt. Arab towards the central zone and from the north-east (i.e. the Laja plateau) towards south-west (i.e. the major springs). The radiometric flow velocities range from 20 to 60 m/year within the central zone, while the flow velocities from both sides of Mt. Hermon and Mt. Arab are lower (1-7 m/year). (author). 43 refs., 37 figs., 6 tabs

  5. Ruthenium(0) nanoparticle-catalyzed isotope exchange between 10B and 11B nuclei in decaborane(14).

    Science.gov (United States)

    Yinghuai, Zhu; Widjaja, Effendi; Sia, Shirley Lo Pei; Zhan, Wang; Carpenter, Keith; Maguire, John A; Hosmane, Narayan S; Hawthorne, M Frederick

    2007-05-23

    Well dispersed ruthenium(0) nanoparticles, stabilized in the ionic liquid agent, trihexyltetradecylphosphonium dodecylbenzenesulfonate, have been successfully prepared via a reduction reaction of the precursor [CpRuCp*RuCp*]PF6 (Cp* = C5Me5). The ruthenium(0) nanoparticles were shown to catalyze the isotope exchange reaction between 10B enriched diborane and natural abundant B10H14 to produce highly 10B enriched (approximately 90%) decaborane(14) products. The ruthenium(0) nanoparticles were characterized by TEM, XRD, and XPS. The 10B enriched decaborane(14) has been analyzed by Raman spectroscopy, NMR, and high-resolution MS. PMID:17472379

  6. Data acquisition and quantitative analysis of stable hydrogen isotope in liquid and gas in the liquid phase catalytic exchange process

    International Nuclear Information System (INIS)

    A pilot plant for the Liquid Phase Catalytic Exchange process was built and has been operating to test the hydrophobic catalyst developed to remove the tritium generated at the CANDU nuclear power plants. The methods of quantitative analysis of hydrogen stable isotope were compared. Infrared spectroscopy was used for the liquid samples, and gas chromatography with hydrogen carrier gas showed the best result for gas samples. Also, a data acquisition system was developed to record the operation parameters. This record was very useful to investigate the causes of the system trip

  7. Preparation of Pt-SDB hydrophobic catalyst used in H2-H2O isotope exchange reaction

    International Nuclear Information System (INIS)

    The preparation of Pt-SDB hydrophobic catalyst is studied, in which platinum as active metal and polystyrene divinylbenzene (SDB) as the carrier. Hydrogen isotope exchange reaction is carried out with Pt-SDB catalyst in counter-current in the trickle bed. The effect of preparing condition on the activity of catalyst is discussed. The results show that the excellent catalyst is obtained by reduced at the temperature of 200 degree C over 8 hours. Hydrophobic catalyst is high activity and stability as the amount of platinum content is 3%, the platinum can reach the economic use with the content of (1-2)%

  8. Treatment and disposal of steam generator and heat exchanger chemical cleaning wastes

    International Nuclear Information System (INIS)

    Wet air oxidation was effective in reducing the organic loading of Ontario Hydro's EDTA-based steam generator cleaning wastes and the organic acid formulation used for heat exchanger chemical cleaning. Destruction of the complexing agents resulted in direct precipitation of iron from the waste steam generator magnetite solvent and from the heat exchanger cleaning waste. The oxidized liquors contain lower molecular weight organic acids, ammonia and amines, suitable for secondary biological treatment. The oxidized copper waste requires further treatment to reduce dissolved copper levels prior to biological digestion. A preliminary evaluation of UV and ozone degradation of these wastes showed less promise than wet air oxidation. 24 refs., 1 fig., 4 tabs

  9. Exchange reaction of hydrogen isotopes on proton conductor ceramic of hydrogen pump for blanket tritium recovery system

    International Nuclear Information System (INIS)

    Electrochemical hydrogen pump using ceramic proton conductor has been investigated to discuss its application for the blanket tritium recovery system of the nuclear fusion reactor. As the series of those work, the transportation experiments of H2-D2 mixture via ceramic proton conductor membrane have been carried out. Then, the phenomenon that was caused by the exchange reaction between the deuterium in the ceramic and the hydrogen in the gas phase has been observed. So, the ceramic proton conductor which doped deuterium was exposed to hydrogen under the control of zero current, and the effluent gas was analyzed. It is considered that the hydrogen in the gas phase is taken as proton to the ceramic by isotope exchange reaction, and penetrates to the ceramic by diffusion with replacement of deuteron. (author)

  10. Study of Pt/SDB hydrophobic catalyst for T-H isotopic exchange between water and hydrogen

    International Nuclear Information System (INIS)

    A methods of preparing platinum/polystyrene divinyl benzene (Pt/SDB) hydrophobic catalyst for hydrogen isotopic exchange between water and hydrogen is presented. Specific surface of the support is more than 400 m2/g. Two approaches of reduction are used for platimum dispersion and comparison is made with each other. Platinum particles obtained by reduction of hydrazine hydrate are smaller. Particles obtained by reduction of hydrogen are larger and their shapes of boundary are unclear. Dispersion of platinum on the support decreases with increasing the amount of platinum. When the amount of platinum is increased to 4 percent, granules of platinum exist as colony. The T-H catalytic exchange at 30 deg C, 50 deg C and 70 deg C has been measured. The activity at 50 deg C is the best. Optimum amount of platinum on the SDB is between 0.5% to 1.5%

  11. Chemical and isotopic study to define the origin of acidity in the Los Humeros geothermal reservoir

    International Nuclear Information System (INIS)

    Chemical and isotopic analyses of geothermal fluids were carried out at the Los Humeros, Mexico, geothermal field in order to establish the water-rock equilibrium state and to determine the origin of the acidity in the reservoir. From the perspective of water-rock equilibrium, the Los Humeros geothermal reservoir is out of equilibrium. This is probably the case since it is associated with recent volcanism, with magmatic components in the geothermal fluids that are not neutralized by reaction with feldspar and mica. Superheated magmatic steam contains HCl gas, which condenses or mixes with liquid at moderate temperature (2/Ar of 270 to 340 deg. C. The isotopic composition of the Los Humeros wells shows anδ18O shift which is characteristic of fluids of geothermal origin that have reached equilibrium with the rock at high temperatures. The isotopic compositions of cold spring waters in the area are mostly located on the meteoric line. The sample from Alchichica lagoon has an isotopic composition typical of evaporated water. (author)

  12. Chemical and isotopic studies of fluids in the Bacon-Manito geothermal field, Philippines

    International Nuclear Information System (INIS)

    Chemical and isotopic data from springs rainfall and wells have been used to characterize the fluids and to identify the major reservoir processes at Bacon-Manito geothermal field, Philippines. The deep reservoir fluid is postulated to be heated to about 325 deg. C and have 7500-8500 mg/kg chloride. Its chemical and isotopic composition is best characterized by wells OP-3D and OP-4D. Spring isotopic data show that their discharges are predominantly meteoric in origin, with a few following a simple evaporation trend. Chloride-enthalpy and chlorid-δ18O relations reveal that the upflowing geothermal reservoir fluid undergoes: (1) dilution with meteroic water, (2) conductive cooling as these move away, (3) mixing with steam condensate, and (4) vapor gain. Well gas chemistry points to the absence of direct magmatic contributions while it is shown that the equilibrium reaction CH4 + 2H2O = CO2 + 4H2 is likely to be established. The observed positive 18O shifts of well waters relative to the local water meteoric line were considered to be due primarily to mixing of deeply-seated ''andesitic'' and meteoric waters while water-rock interaction could not be ruled out. Finally, a conceptual geochemical model of the geothermal system is proposed. (author). 21 refs, 12 figs, 5 tabs

  13. Isotopic and chemical investigations of springs from different karst zones in the Swiss Jura

    International Nuclear Information System (INIS)

    The karst hydrology of a region in the Jura of Neuchatel has been studied by means of a large number of isotopic, chemical and bacteriological analyses. Three springs are considered which represent different karst zones: saturated phreatic karst, confined karst and unsaturated karst. Runoff component analysis by means of tritium and oxygen-18 reveals that in all three springs aged reservoir water contributes the major part to discharge peaks, quick runoff of precipitation water being less important. The discharge of fresh water, as identified by isotopic composition and also by dilution of ionic concentrations and increased bacteria content, reaches its maximum for some springs considerably after the hydrograph peak. Under favourable conditions, a component separation is also possible using chemical analyses. The result that pre-event reservoir water is so important for peak discharge points to the existence of water reserves situated in large-volume, highly permeable karst channels. The mean age and volume of this reservoir water have been estimated. Discharge as well as isotopic composition of springs draining unsaturated karst exhibit regular oscillations. Four different characteristic times can be defined for karst springs: the hydraulic response time, the flow time of fast fresh water, the recession time constant and the mean age of reservoir water. (author)

  14. Chemical analyses and calculation of isotopic compositions of high-burnup UO2 fuels and MOX fuels

    International Nuclear Information System (INIS)

    Chemical analysis activities of isotopic compositions of high-burnup UO2 fuels and MOX fuels in CRIEPI and calculation evaluation are reviewed briefly. C/E values of ORIGEN2, in which original libraries and JENDL-3.2 libraries are used, and other codes with chemical analysis data are reviewed and evaluated. Isotopic compositions of main U and Pu in fuels can be evaluated within 10% relative errors by suitable libraries and codes. Void ratio is effective parameter for C/E values in BWR fuels. JENDL-3.2 library shows remarkable improvement compared with original libraries in isotopic composition evaluations of FP nuclides. (author)

  15. Evaluating the mobile heavy metal pool in soak-away sediment, road dust and soil through sequential extraction and isotopic exchange.

    Science.gov (United States)

    Kumar, Manish; Furumai, Hiroaki; Kurisu, Futoshi; Kasuga, Ikuro

    2010-01-01

    Selective sequential dissolution (SSD) and isotopic dilution are two most commonly applied techniques for the measurement of mobile fraction of heavy metal present in the urban environment. This work examined the compliance between SSD proposed by the Community Bureau of Reference (BCR) and isotopic dilution technique (IDT) for determination of mobile pool of heavy metal contained in soakaway sediment, road dust, and soil sample. Heavy metals (Cu, Zn, Cd and Pb) were fractionated using the three-stage BCR protocol, while isotopically exchangeable metal concentrations (E-value) were investigated through isotopic tracers (¹¹¹Cd, ⁶⁵Cu, ²⁰⁷Pb and ⁶⁶Zn). In general, total contamination level, E-value and BCR exchangeable fractions of different samples followed the similar order of road dust > soakaway sediment > soil. Results revealed that the E-value exceeded the BCR exchangeable fraction in all samples. In addition, the first three fractions of BCR which have potential to become mobile under certain environmental conditions were collectively termed as "potential mobile pool" and compared with E-value. It was concluded that metal extracted by weak acid underestimates the exchangeable fraction while the potential mobile pool extracted by three reagents overestimates the real mobile forms of heavy metals. However, better mobility characteristics of heavy metals can be assessed by coupling information obtained through sequential extraction and isotopic exchange. PMID:20729597

  16. Numerical comparison among water distillation column process, monothermal and bithermal. H2/H2 O - isotopic exchange column process producing D-depleted water

    International Nuclear Information System (INIS)

    Full text: Deuterium-depleted (D-depleted) water is said to be a new anti-tumor veterinary medicine for treating cats and dogs. G. Somlyai reported the biological effect of D-depleted water which is a new possibility in cancer therapy. The authors tried to estimate numerically the size of plants producing D-depleted water, namely: (1) Water distillation column process, (2) Monothermal H2/H2O- isotopic exchange column process, (3)Bithermal H2/H2O-isotopic exchange column process, excluding H2 or H2O/NH3-isotopic exchange and H2O/H2S- isotopic exchange process from a sanitary point of view of drink water. D-depleted water, as a by-product of heavy water production by means of bithermal H2/H2O-isotopic exchange process, may be considered to be the cheapest, but in this paper the authors tried to estimate an independent and non-parasite producing D-depleted water. As the result, the water distillation column process was found to be a favourable process for the production of a cheaper D-depleted water. (authors)

  17. Chemical and carbon isotopic composition of dissolved organic carbon in a regional confined methanogenic aquifer

    Science.gov (United States)

    Aravena, R.; Wassenaar, L.I.; Spiker, E. C.

    2004-01-01

    This study demonstrates the advantage of a combined use of chemical and isotopic tools to understand the dissolved organic carbon (DOC) cycle in a regional confined methanogenic aquifer. DOC concentration and carbon isotopic data demonstrate that the soil zone is a primary carbon source of groundwater DOC in areas close to recharge zones. An in-situ DOC source linked to organic rich sediments present in the aquifer matrix is controlling the DOC pool in the central part of the groundwater flow system. DOC fractions, 13C-NMR on fulvic acids and 14C data on DOC and CH4 support the hypothesis that the in-situ DOC source is a terrestrial organic matter and discard the Ordovician bedrock as a source of DOC. ?? 2004 Taylor and Francis Ltd.

  18. Chemical investigations of isotope separation on line target units for carbon and nitrogen beams

    CERN Document Server

    Franberg, H; Gäggeler, H W; Köster, U

    2006-01-01

    Radioactive ion beams (RIBs) are of significant interest in a number of applications. Isotope separation on line (ISOL) facilities provide RIB with high beam intensities and good beam quality. An atom that is produced within the ISOL target will first diffuse out from the target material. During the effusion towards the transfer line and into the ion source the many contacts with the surrounding surfaces may cause unacceptable delays in the transport and, hence, losses of the shorter-lived isotopes. We performed systematic chemical investigations of adsorption in a temperature and concentration regime relevant for ISOL targets and ion source units, with regard to CO/sub x/ and NOmaterials are potential construction materials for the above-mentioned areas. Off-line and on-line tests have been performed using a gas thermochromatography setup with radioactive tracers. The experiments were performed at the production of tracers for atmospheric chemistry (PROTRAC) facility at the Paul Schener Institute in Villigen...

  19. Carbon isotopic analysis of dissolved organic carbon in produced water brines by wet chemical oxidation and cavity ring-down spectroscopy

    Science.gov (United States)

    Thomas, B.; Conaway, C.; Kharaka, Y. K.; Saad, N.

    2012-12-01

    We have adapted the Picarro iTOC CRDS isotope analyzer for analysis of produced water brines via wet chemical persulfate oxidation. In particular, we developed strategies and techniques for overcoming the limitation imposed by low oxidation efficiencies due to the chloride ion interference with persulfate oxidation. These techniques are important for understanding the origin of dissolved organic carbon in subsurface fluids from oilfields, as a tracer of fracking fluids in groundwater, and in interpreting changes in groundwater DOC as a result of microbial activity including oil biodegradation or microbially enhanced oil recovery. We describe the limitations of this new instrument for the analysis of DOC in brines including sample requirements, matrix effects, and the effect of DOC composition on reaction efficiency and isotopic measurements. We compare strategies including anion exchange cartridges, persulfate reactant concentrations, and reaction time. The CRDS analysis of DOC in brines is a useful tool for understanding the origin and fate of DOC and is a potentially powerful tool to identifiy evidence of contamination due to hydrofracturing chemicals that have a distinctive carbon isotopic signature relative to natural brine.

  20. Inferring global and regional methane sources and sinks using isotopic observations and atmospheric chemical transport models

    Science.gov (United States)

    Rigby, M. L.; Wenger, A.; O'Doherty, S.; Lunt, M. F.; Ganesan, A.; Manning, A.; Prinn, R. G.

    2015-12-01

    Measurements of the major isotopologues of atmospheric methane have the potential to improve our understanding of the methane budget at the global and regional scale. Using global and regional chemical transport models, we can predict the atmospheric variations in 13C-CH4 and D-CH4, for given assumptions about source isotope ratios and fractionation due to methane sinks. This information can then be used to test the impact that various measurement techniques, technologies and sampling strategies have on our knowledge of the methane budget. We show that, at the global scale, an extensive and accurate network of isotopic measurements can lead to a reduction in the uncertainties in the major global sources. Furthermore, measurements of the D/H ratio in methane may provide some level of uncertainty reduction in the magnitude of the OH sink. Uncertainties can be reduced with improved precision and accuracy of the atmospheric observations. However, to make the most of an atmospheric methane isotope network, we show that the characterisation of source isotope ratios must also be improved. Finally, we put the theory into practice by deriving sector-specific methane sources at the national scale using 13C-CH4 samples collected as part of the Greenhouse gAs Uk and Global Emissions (GAUGE) project. GAUGE measurements are made from a tall tower site to the east of the UK, a background station on the west coast of Ireland and during intensive aircraft sampling campaigns. We will discuss the challenges and benefits associated with adding isotopic information to a national greenhouse gas sampling network and outline a strategy for improvements in the future.

  1. Climatic factors controlling chemical and isotopic characteristics of precipitation in Syria

    International Nuclear Information System (INIS)

    The chemical and isotopic composition of monthly composite rain samples collected at thirteen meteoric stations in Syria during two hydrological cycles from 1991 to 1993, have been measured. The chemical analysis of the samples revealed at a number of stations pollution due to industry and sand storms. The temporal and spatial variation of the isotopic composition has been found to be comparable with the one of neighboring countries such as Jordan and others. The average weighted oxygen-18 and deuterium values are -7.5 and -39.11 %, respectively, and the deuterium excess is 21%. The individual isotope values can be divided into two groups. One group is represented by winter precipitation and fits closely the Mediterranean Meteorological Water Line (MMWL). Thus, for winter precipitation condensation of Mediterranean water vapor appears to be the dominating isotope fractionation process. The other group represents spring precipitation and is spread along an evaporation line below the MMWL, thus indicating the influence of sub-cloud evaporation. The d-excess has been found to be lower in the north of Syria (19.9% at Tartous, 18.1% at Jarablous) than in the south of the country (23.4% at Sweida, 24.1% at Izra) where Mediterranean air mass dominates. The d-excess of precipitation in neighboring countries is also close to the average value of the eastern Mediterranean basin of 22%, e.g. for Jordan the value is 23%, which signifies that Mediterranean water vapor is for all these countries the dominant source of precipitation. The tritium content of precipitation was found to increase with distance form the coast (5.3 TU at coastal station Tartous, 8.8 TU at continental station Palmyra). Low tritium content and high d-excess at coastal stations clearly indicate a Mediterranean air moisture source. (author)

  2. Polymerization dependence of the reactivity of polyacrylamide observed with hydrogen-isotope exchange reaction in a liquid-solid system

    International Nuclear Information System (INIS)

    The tritium (T) labeled polyacrylamide (abbreviated PAAm(T) below) was synthesized using the hydrogen-isotope exchange reaction (gas-solid reaction) between HTO vapor and PAAm. The degree of the polymerization of PAAm used was 2800 (and 80000) (abbreviated PAAm2800 (and PAAm80000) below). Using the PAAm(T) thus obtained, the hydrogen-isotope exchange reaction (liquid-solid reaction) between PAAm(T) and each liquid organic material has been observed at the temperature range of 50 to 90degC. Applying the A''-McKay plot method to the data thus obtained, the rate constant (k) for the reaction was obtained. Including k obtained previously, the value of k thus obtained were compared with each other. The following six items have consequently been confirmed. The reactivity of PAAm80000 is larger than that of PAAm2800. PAAm2800 is about 0.4 times PVA2900 in reactivity. The temperature dependence of the reactivity of PAAm2800 is about 6 times that of PVA-2900. The reactivity of these three compounds for several liquid organic materials can roughly be expressed as follows: (PVA2900):(PAAm80000):(PAAm2800)=1:1:0.3. It is possible to use PAAm as a solid material in the liquid-solid reaction (instead of PVA). The method used in this work can be useful to clarify the reactivity of a certain material, and to obtain the data for the prevention of tritium-contamination. (author)

  3. Numerical analysis of hydrogen isotope separation characteristics in improved dual temperature exchange reaction system between water and hydrogen gas

    International Nuclear Information System (INIS)

    A dual temperature hydrogen isotopic exchange reaction system between water and hydrogen gas is numerically analyzed. The system has two features; high efficiency of isotope exchange reaction and operation under atmospheric pressure. To achieve them, the low temperature section of the system is composed of water mist and hydrogen gas co-current reactor units. For the high temperature section, a multistage-type reactor, in which a bubble plate, superheater and catalyst bed are alternatively arranged, is applied. From a material balance between these reactors, enrichment and decontamination factors for the system are expressed as functions of seven parameters: unit number of the low temperature co-current reactor (X); stage number of the high temperature section (Y); flow ratio of tritium enriched water to decontaminated water (P/W), flow ratio of feed water to hydrogen gas (F/G); reaction temperatures of the low and high temperature sections (Tsub(c), Tsub(h)); and bubble plate temperature (Tsub(b)). Numerical calculations show that enrichment factor depends remarkably on F/G and Tsub(b) as well as X and Y. In order to understand the separation characteristics visually, the McCabe-Thiele diagrams for the present system are drawn and compared with the results calculated. (author)

  4. Intramolecular (18O) isotopic exchange in the gas phase observed during the tandem mass spectrometric analysis of peptides

    International Nuclear Information System (INIS)

    Fast atom bombardment/tandem mass spectrometry of protonated and metal cationized peptides has revealed evidence for novel intramolecular rearrangements in the gas phase. Second generation product ion scanning (MS/MS/MS) analyses of the protonated (18O2) analogues established that both isotope labels are located at the new C-terminus formed via the rearrangement. The kinetic energies released during the formation of the (18O1)-and (18O2)-labeled rearrangement products are indistinguishable, consistent with the involvement of a common intermediate. First generation product ion spectra (MS/MS) of protonated (18O2)-peptides include fragments arising from simple peptide bond cleavage which show isotope enrichments consistent with immediate precursor ions which incorporate (18O) at the peptide bond between the penultimate and C-terminal amino acid residues. Several lines of evidence eliminate the possibility of such incorporation of label during solution-phase preparation of the (18O2)-labeled analogues. Thus, the combined data are in accord with an isotope exchange process occurring in the gas phase, most likely through a mechanism involving the reversible formation of a cyclic intermediate. These studies, combined with previous data, emphasize the importance of the conformations adopted by gas-phase peptide ions in influencing fragmentation pathways. 30 refs., 8 figs

  5. Size-Induced Enhancement of Chemical Exchange Saturation Transfer (CEST) Contrast in Liposomes

    OpenAIRE

    Zhao, Jason M.; Har-el, Yah-el; McMahon, Michael T.; Zhou, Jinyuan; Sherry, A. Dean; Sgouros, George; Bulte, Jeff W. M.; van Zijl, Peter C.M.

    2008-01-01

    Liposome-based chemical exchange saturation transfer (lipoCEST) agents have shown great sensitivity and potential for molecular magnetic resonance imaging (MRI). Here we demonstrate that the size of liposomes can be exploited to enhance the lipoCEST contrast. A concise analytical model is developed to describe the contrast dependence on size for an ensemble of liposomes. The model attributes the increased lipoCEST contrast in smaller liposomes to their larger surface-to-volume ratio, causing ...

  6. The application of isotope and chemical analyses in managing transboundary groundwater resources

    International Nuclear Information System (INIS)

    Highlights: ► Chemical analyses, D, O and C isotopes were used to correlate cross border aquifers. ► Water of transboundary thermal GWB Mura-Zala is of meteoric origin. ► δD (−87‰ to −75‰), δ18O (−11.9‰ to −10.4‰) and 14C (less than 6.1 pmC). ► δ13C values are shifted significantly, cannot be used for radiocarbon age corrections. ► Environmental isotopes can act as an early warning in the thermal water management. - Abstract: Managing transboundary groundwater resources requires accurate and detailed knowledge of aquifers and groundwater bodies. The Pannonian Basin is the largest intracontinental basin in Europe with a continuous succession of more than 7 km of Miocene to Quaternary sediments and with an average geothermal gradient of about 5 °C/100 m. Geographically the Pannonian basin overlaps eight countries (Hungary, Romania, Serbia, Croatia, Slovenia, Austria, Slovakia and Ukraine), so the issue of transboundary cold and thermal water resources is regionally very important. The T-JAM bilateral Hungarian–Slovenian (HU–SLO) project is the first to apply modern isotopic and chemical analyses in the characterization and correlation of a number of shared groundwater resources in the Mura-Zala Sub-basin of the Pannonian. The aims of this work were the identification of groundwater flow paths, the delineation of transboundary aquifers based on thermal and cold groundwater geochemical and isotope properties in the Mura-Zala Basin, and providing input to calibrate a hydraulic numerical model. Following a common groundwater sampling campaign, 24 cold and thermal groundwater samples from seven aquifers were collected for chemical, isotope, gas and noble gas analyses. Chemical analyses, and D, O and C isotopes were used to correlate cross border aquifers. A regional groundwater flow is hydrogeologically possible in some aquifers in the Mura-Zala Basin, and has been confirmed by hydrogeochemistry. The Újfalu (HU) and Mura (SLO) Formations

  7. Measuring the Effect of Fuel Chemical Structure on Particulate and Gaseous Emissions using Isotope Tracing

    International Nuclear Information System (INIS)

    Using accelerator mass spectrometry (AMS), a technique initially developed for radiocarbon dating and recently applied to internal combustion engines, carbon atoms within specific fuel molecules can be labeled and followed in particulate or gaseous emissions. In addition to examining the effect of fuel chemical structure on emissions, the specific source of carbon for PM can be identified if an isotope label exists in the appropriate fuel source. Existing work has focused on diesel engines, but the samples (soot collected on quartz filters or combustion gases captured in bombs or bags) are readily collected from large industrial combustors as well

  8. Lithospheric evolution of the Northern Arabian Shield: Chemical and isotopic evidence from basalts, xenoliths and granites

    Science.gov (United States)

    Stein, M.

    1988-01-01

    The evolution of the upper-mantle and the lower-crust (the conteinental lithosphere), is the area of Israel and Sinai was studied, using the chemical composition and the Nd-Sr isotopic systematics from mantle and crustal nodules, their host basalts, and granites. The magmatism and the metasomatism making the lithosphere are related to uprise of mantle diapirs in the uppermost mantle of the area. These diapirs heated the base of the lithosphere, eroded, and replaced it with new hot material. It caused a domal uplift of the lithosphere (and the crust). The doming resulted in tensional stresses that in turn might develop transport channels for the basalt.

  9. Isotopic and chemical investigation of ground water salinization in upper part of Chaj Doab

    International Nuclear Information System (INIS)

    Environmental isotopes and chemical composition of water have been used to study the origin of groundwater salts in upper part of Chaj Doab. Three important possible processes of salinization i.e. enrichment of salt content of water by evaporation, mixing with connate marine water and dissolution of salts from soil sediments have been investigated. no evidence for mixing with connate marine water could be found. The dissolution of salts from soil sediments appears as the dominant mechanism for increasing the salt content of water in this area. (author)

  10. Absence of oxygen isotope fractionation/exchange of (hemi-) cellulose derived sugars during litter decomposition

    NARCIS (Netherlands)

    M. Zech; R. A. Werner; D. Juchelka; K. Kalbitz; B. Buggle; B. Glaser

    2011-01-01

    Aiming at developing a novel tool for palaeoclimate research, we recently proposed a new method for determining the oxygen isotope composition of monosaccharides (Zech, M., Glaser, B., 2009. Compound-specific δ18O analyses of neutral sugars in soils using GC-Py-IRMS: problems, possible solutions and

  11. Associated chemical and carbon isotopic composition variations in diamonds from Finsch and Premier kimberlite, South Africa

    International Nuclear Information System (INIS)

    The carbon isotopic composition of 66 inclusion-containing diamonds from the Premier kimberlite, South Africa, 93 inclusion-containing diamonds and four diamonds of two diamond-bearing peridotite xenoliths from the Finsch kimberlite, South Africa was measured. The data suggest a relationship between the carbon isotopic composition of the diamonds and the chemical composition of the associated silicates. For both kimberlites similar trends are noted for diamonds containing peridotite-suite inclusions (P-type) and for diamonds containing eclogite-suite inclusions (E-type): Higher delta13C P-type diamonds tend to have inclusions lower in SiO2, Al2O3, Cr2O3, MgO, Mg/(Mg + Fe) and higher in FeO and CaO. Higher delta13C E-type diamonds tend to have inclusions lower in SiO2, Al2O3, MgO, Mg/(Mg + Fe), Na2O, K2O, TiO2 and higher in CaO, Ca/(Ca + Mg). Consideration of a number of different models that have been proposed for the genesis of kimberlites, their zenoliths and diamonds shows that they are all consistent with the conclusion that in the mantle, regions exist that are characterized by different mean carbon isotopic compositions. (author)

  12. On-line investigation of short-lived Os and Re isotopes as a test for chemical studies of 108 (Hs) and 107 (Bh) elements in HCl solutions by continuous chromatography

    International Nuclear Information System (INIS)

    On-line chemistry studies of short-lived isotopes of Os and Re, as homologs of 108 (Hs) and 107 (Bh), respectively, produced in the nuclear reactions at the (LNR, Dubna) cyclotron have been carried out. It was shown, that Os and Re are not sorbed on cation exchangers, but very strongly sorbed on anion exchangers from diluted HCl solutions. Re is also retained by a TOPO containing sorbent and may be separated from Os. The possibilities of chemical species and oxidation states investigation of short-lived transactinide elements by continuous chromatography have been shown. (author)

  13. Impact of sediment-seawater cation exchange on Himalayan chemical weathering fluxes

    Science.gov (United States)

    Lupker, Maarten; France-Lanord, Christian; Lartiges, Bruno

    2016-08-01

    Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga-Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga-Brahmaputra is estimated ca. 6.5 meq 100 g-1. The cationic charge of sediments in the river is dominated by bivalent ions Ca2+ (76 %) and Mg2+ (16 %) followed by monovalent K+ (6 %) and Na+ (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca2+ for marine Na+ yields a maximal additional Ca2+ flux of 28 × 109 mol yr-1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga-Brahmaputra is responsible for an additional Ca2+ flux of 23 × 109 mol yr-1, while ca. 27 × 109 mol yr-1 of Na+, 8 × 109 mol yr-1 of Mg2+ and 4 × 109 mol yr-1 of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na+ flux, 8 % of the dissolved K+ flux and 4 % of the Mg2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment-seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and

  14. Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization

    Science.gov (United States)

    Vaikkinen, Anu; Kauppila, Tiina J.; Kostiainen, Risto

    2016-04-01

    The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M+. decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques.

  15. Separation of 15N by chemical exchange in NO, NO2 - HNO3 system under pressure

    International Nuclear Information System (INIS)

    The basic isotopic exchange reaction is responsible for the separation of 15N in the Nitrox system that between gaseous nitrogen oxides and aqueous nitric acid with a single stage separation factor α = 1.055 for 10M nitric acid, at 25 deg C and atmospheric pressure takes place. In order to know what happens in 15N separation at higher pressure, when the isotopic transport between two phases is improved, a stainless steel laboratory experimental plant with a 1000 mm long x 18 mm i.d. column, packed with triangular wire springs 1.8 x 1.8 x 0.2 mm2, was utilised. At 1.5 atm (absolute), and 2.36 ml x cm-2 x min-1 flow rate HETP was 7% smaller than at atmospheric pressure and 1.5 times smaller flow rate. HETP at 3.14 ml x cm-2 x min-1 flow rate and 1.8 atm is practically equal with that obtained at atmospheric pressure and 2 times smaller flow rate. The operation of the 15N separation plant at 1.8 atm (absolute), instead of atmospheric pressure, will permit doubling of the 10M nitric acid flow rate and of 15N production of the given column. (author)

  16. The influence of leaf-atmosphere NH3(g ) exchange on the isotopic composition of nitrogen in plants and the atmosphere.

    Science.gov (United States)

    Johnson, Jennifer E; Berry, Joseph A

    2013-10-01

    The distribution of nitrogen isotopes in the biosphere has the potential to offer insights into the past, present and future of the nitrogen cycle, but it is challenging to unravel the processes controlling patterns of mixing and fractionation. We present a mathematical model describing a previously overlooked process: nitrogen isotope fractionation during leaf-atmosphere NH3(g ) exchange. The model predicts that when leaf-atmosphere exchange of NH3(g ) occurs in a closed system, the atmospheric reservoir of NH3(g ) equilibrates at a concentration equal to the ammonia compensation point and an isotopic composition 8.1‰ lighter than nitrogen in protein. In an open system, when atmospheric concentrations of NH3(g ) fall below or rise above the compensation point, protein can be isotopically enriched by net efflux of NH3(g ) or depleted by net uptake. Comparison of model output with existing measurements in the literature suggests that this process contributes to variation in the isotopic composition of nitrogen in plants as well as NH3(g ) in the atmosphere, and should be considered in future analyses of nitrogen isotope circulation. The matrix-based modelling approach that is introduced may be useful for quantifying isotope dynamics in other complex systems that can be described by first-order kinetics. PMID:23452149

  17. Isotopic exchange between 2,2-dimethylbutane and deuterium on rhodium/silica gel catalysts

    International Nuclear Information System (INIS)

    Isotropic exchange between 2.2-dimethylbutane and deuterium has been investigated at 75 C on 10 rhodium on wide-pore silica gel catalysts with H(chemisorbed)/Rh(Dh) ranging from 11 to 108% and subjected to a variety of pretreatment conditions. Some catalysts were prepared by ion exchange with Rh(NH3)5(H2O)3- and some by impregnation to incipient wetness with Rh4(CO)12 or Rh6(CO)16. The turnover frequency (Nt) is affected both by Dh and by the conditions of pretreatment. The extreme variation was a factor of 330. Exchange into the ethyl group was about 10 times faster than into the t-butyl group. In general, the catalysts of largest Dh gave the largest Nt and the smallest degree of multiple exchange in the ethyl group. The pretreatment, H2, 450 C gave the largest Nt. Mere removal of H* from catalysts so treated by He, 300 C had little effect, but He, 450 C led to a substantial decrease in Nt except for 11-Rh/SiO2. The various coupled values of Nt and selectivity resulting from variations in Dh and pretreatment require a minimum of eight different sites. Nt's and selectivities in the hydrogenolysis of methylcyclopropane on these same catalysts parallel those in the exchange of neohexane

  18. Tracing sources of nitrate in groundwater by using hydro-chemical and isotopic methods: Beirut region and its suburbs

    International Nuclear Information System (INIS)

    Analyses of hydrochemical and stable isotopes of 2H and 18O were conducted on groundwater samples collected in Beirut city and its suburbs and tapped in a limestone aquifer. The analyses were done to document the chemical and isotopic characters of the natural groundwater and to determine its origin. Hydrochemical data are classified on the basis of dominant anions. Mineral groundwater quality was found affected by different pollution sources in the southern suburb of Beirut. Isotopic analyses delineate two major groups of groundwater. The first group is directly influenced by direct recharge into the aquifer from precipitation. The second group, showing elevated mineral characteristics, is influenced by a secondary evaporation process reflecting an isotopic enrichment in groundwater. δ15N investigation of the isotopically enriched samples determines the origin of nitrate pollution from either infiltration of animal waste or septic systems to groundwater. (author)

  19. Hydrological modeling of the Lahore aquifer, using isotopic, chemical and numerical techniques

    International Nuclear Information System (INIS)

    Lahore, the capital city of Punjab Province, has about 6 million population. The only water supply to the public is groundwater, pumped through tube wells. With the increase in population, the demand of water is also increasing accordingly. Radiation and Isotope Application Division of (Pakistan Institute of Nuclear Science and Technology) PINSTECH is carrying out hydrological investigations of Lahore aquifer, sponsored by IAEA. For the last three years, 7 samplings have been performed on groundwater of Lahore city area. Natural isotopes of water, such as O/sup 18/, deuterium and tritium, have been analyzed from the collected water samples. Major and important chemical ions, such as Ca, Mg, Na, K, CO/sub 3/, HCO/sub 3/ SO/sub 4/ and Cl, have also been analyzed. Hydrological data on pumping wells and soil characteristics has been gathered from different agencies. A conceptual flow model was developed on Lahore aquifer and was calibrated with Visual Modflow. Hydrochemical interpretations were made with the locally developed innovative techniques and diagrams, as well. The groundwater have been identified as calcium bicarbonate, magnesium bicarbonate and sodium bicarbonate, with the help of Multi-Rectangular Diagram (MRD). A spatial variation of groundwater quality map has been constructed. Recharge mechanism is addressed by chemical and isotopic techniques. Both shallow and deep aquifers get significant recharge from river Ravi. Simulations have been run on dynamic depression cone, which has emerged as a result of daily abstractions of groundwater after 1960. In the vicinity of Governor House, the water level was 191 m above mean sea level (amsl) in 1989. It has been observed to have gone down to 185 m in 1998. Preliminary numerical simulations predict that the water table will further lower to 174 m and 171 m in the years 2009 and 2019, respectively. (author)

  20. Chemical and isotopic characterisation of bulk deposition in the Louros basin (Epirus, Greece)

    Science.gov (United States)

    D'Alessandro, W.; Katsanou, K.; Lambrakis, N.; Bellomo, S.; Brusca, L.; Liotta, M.

    2013-10-01

    About 120 rainwater samples were collected through a network of five bulk collectors in the area of the Louros basin (Epirus, Greece) during the wet season from October 2008 to August 2009. They were analysed for their isotopic (δD and δ18O) and chemical (H+, Na+, K+, Mg2 +, Ca2 +, NH4+, F-, Cl-, Br-, NO3-, SO42 -) composition. A local meteoric water line (δD‰ = 5.80 ± 0.02 δ18O‰ + 0.02 ± 0.12) and a local isotopic lapse rate (- 0.18 δ18O‰/100 m) were obtained considering the volume-weighted means of the five sampling sites. These results agree well with those obtained in nearby areas. The chemical composition of the samples allows to identify an almost entirely marine origin for chloride and sodium with decreasing deposition values at increasing distance from the coast. Nitrate and ammonium are almost completely of anthropogenic origin, calcium and potassium are overwhelmingly geogenic, sulphate has a prevailingly anthropogenic origin with a significant marine contribution and magnesium has a mixed marine and soil dust origin. Finally, as for most of the Mediterranean area, rainwater acidity is buffered by the dissolution of the abundant geogenic carbonate aerosol.

  1. Sr isotope evolution during chemical weathering of granites -- impact of relative weathering rates of minerals

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Sr isotopic systematics in the weathering profiles of biotite granite and granite porphyry in southern Jiangxi Province were investigated. The results showed that during the chemical weathering of granites, remarked fractionation occurred between Rb and Sr. During the early stages of chemical weathering of granites, the released Sr/Si and Sr/Ca ratios are larger than those of the parent rocks, and the leaching rate of Sr is higher than those of Si, Ca, K, Rb, etc. Dynamic variations in relative weathering rates of the main Sr-contributing minerals led to fluctuation with time in 87Sr/86Sr ratios of inherent and released Sr in the weathering crust of granite. Successive weathering of biotite, plagioclase and K-feldspar made 87Sr/86Sr ratios in the weathering residues show such a fluctuation trend as to decrease first, increase, and then decrease again till they maintain stable. This work further indicates that when Sr isotopes are used to trace biogeochemical processes on both the catchment and global scales, one must seriously take account of the prefer-ential release of Sr from dissolving solid phase and the fluctuation of 87Sr/86Sr ratios caused by the variations of relative weathering rates of Sr-contributing minerals.

  2. Research on the hydrogen-water isotope exchange reaction by Pt-SDB hydrophobic catalyst

    International Nuclear Information System (INIS)

    The authors study the Pt-SDB hydrophobic catalyst used in the hydrogen-water exchange reaction. Platinum is as active metal and the polystyrene divinylbenzene (SDB) is as hydrophobic carrier in the Pt-SDB hydrophobic catalyst. The experimental results show that the efficiency of catalytic exchange reaction is higher in random bed with a packing ratio of 1:1 mixture of catalyst and hydrophilic or 1:4 in order bed. The volume transfer coefficient increases with increasing temperature, but the trend is slow down when the temperature is above 60 degree C

  3. Variability of pesticides and nitrates concentrations along a river transect: chemical and isotopic evidence of groundwater - surface water interconnections

    Science.gov (United States)

    Baran, Nicole; Petelet-Giraud, Emmanuelle; Saplairoles, Maritxu

    2015-04-01

    Groundwater quality is increasingly monitored in Europe where various levels of nitrate and pesticide and/or metabolite contamination have been demonstrated (Loos et al., 2010, Stuart et al., 2012). The Groundwater Daughter Directive (2006/118/EC) to Water Framework Directive (WFD) particularly requires measures to prevent or limit inputs of pollutants into groundwater and compliance with good chemical status criteria (based on EU standards of nitrate and pesticides). The WFD mentioned the need to protect groundwater but also to have a particular regard to its impact and interrelationship with associated surface waters and directly dependent terrestrial Ecosystems. The Ariège river basin (SW France - 538 km²) is an alluvial plain under high agricultural pressure leading to a contamination of the aquifer by several pesticides and metabolites (Amalric et al., 2013). The Crieu is an allochtone river, crossing the plain (~ 10 km length) before joining the Ariège River. The Crieu is often dry in its middle section suggesting water leakage from surface water towards groundwater. At the opposite, the permanent flow observed downstream suggests an input of groundwater into surface water. In May 2014, while the Crieu flow was continuous through the plain, 7 river samples were collected and analyzed for pesticides, major ions, strontium concentration and isotopes. In situ measurements of electric conductivity were also performed as well as flow gauging. Two groundwaters close to the river were also sampled. The flow gauging measurements show a decreasing river discharge in the central area of the Crieu River, suggesting surface water leakage towards groundwater. Nevertheless, the electric conductivity increases along the river flow as well as some pesticides and nitrates concentrations. This chemical evolution of the river water is thus inconsistent with a simple water infiltration and another source of dissolved solutes is required to explain the increased of

  4. Ceramic Heat Exchangers and Chemical Reactors with Micro-Scale Features for In-Situ Resource Processing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — It is proposed to develop compact and lightweight ceramic heat exchangers and chemical reactors suitable for high temperature processes. These devices will have...

  5. Influence of helium on hydrogen isotope exchange in tungsten at sequential exposures to deuterium and helium–protium plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Bobyr, N.P., E-mail: NPBobyr@gmail.com [NRC “Kurcharov Institute”, Ac. Kurcharov sq., 1/1, Moscow 123182 (Russian Federation); Alimov, V.Kh. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany); Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555 (Japan); Khripunov, B.I.; Spitsyn, A.V. [NRC “Kurcharov Institute”, Ac. Kurcharov sq., 1/1, Moscow 123182 (Russian Federation); Mayer, M. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany); Hatano, Y. [Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555 (Japan); Golubeva, A.V.; Petrov, V.B. [NRC “Kurcharov Institute”, Ac. Kurcharov sq., 1/1, Moscow 123182 (Russian Federation)

    2015-08-15

    Hydrogen isotopes exchange in tungsten was investigated after sequential exposures to low energy deuterium (D) and helium–seeded protium (He–seeded H) plasmas at sample temperatures of 403 and 533 K. Deuterium depth profiles were measured by the D({sup 3}He, p){sup 4}He nuclear reaction with {sup 3}He{sup +} energies between 0.69 and 4.5 MeV allowing determination of the D concentration up to a depth of 8 μm. It was found that a significant part of the deuterium initially retained in tungsten after D plasma exposure was released during sequential exposure to a protium plasma. However, exposure of the D-plasma-exposed W samples to the He–seeded H plasma reduces the amount of released deuterium as compared to pure H plasma exposure.

  6. Influence of helium on hydrogen isotope exchange in tungsten at sequential exposures to deuterium and helium–protium plasmas

    International Nuclear Information System (INIS)

    Hydrogen isotopes exchange in tungsten was investigated after sequential exposures to low energy deuterium (D) and helium–seeded protium (He–seeded H) plasmas at sample temperatures of 403 and 533 K. Deuterium depth profiles were measured by the D(3He, p)4He nuclear reaction with 3He+ energies between 0.69 and 4.5 MeV allowing determination of the D concentration up to a depth of 8 μm. It was found that a significant part of the deuterium initially retained in tungsten after D plasma exposure was released during sequential exposure to a protium plasma. However, exposure of the D-plasma-exposed W samples to the He–seeded H plasma reduces the amount of released deuterium as compared to pure H plasma exposure

  7. Contribution to the study of proteins and peptides structure by hydrogen isotopic exchange

    International Nuclear Information System (INIS)

    Development of hydrogen exchange measurement methods to study the structure and the molecular interaction of globular protein molecules in aqueous solution (ribonuclease A, cytochrome c, coupling factors of chloroplasts), in peptide hormones in trifluoroethanol solution (angiotensin II, corticotropin) and in proteins of membranes (rhodopsin)

  8. Kinetics of isotopic oxygen exchange between water and vanadium(V) in basic media

    International Nuclear Information System (INIS)

    The exchange between 18O-labeled solvent water and vanadium(V) in basic media ([OH-] greater than or equal to 0.1 M) has a half-time of approximately 20 s at 00C and is measurable by conventional sampling methods. Under selected conditions it has been shown that there are 4.0 +- 0.1 equivalent oxygens associated with aqueous vanadium(V) with half-times of exchange as great as 30 s at 00C. This supports the orthovanadate (VO3-4) structure as the predominant species in water at high pH. The rate of exchange follows the equation R = k[VO3-4] and is essentially independent of [OH-] and of the nature of other ions in the medium. The rate is an inverse function of ionic strength and has activation parameters of ΔH = 22.0 +- 0.8 kcal/mole and ΔS = 14.4 +- 1 cal deg-1 mole-1 (μ = 1.4). The reaction mechanism for water exchange is discussed

  9. Isotopic exchange between alkanes and deuterium on rhodium/silica gel catalysts

    International Nuclear Information System (INIS)

    Isotropic exchange between deuterium and cyclopentane and between pentane and ethane on the Rh/SiO2 catalysts of the preceding paper has been investigated after several different pretreatments. Although a more restricted number of catalysts was examined, as with 2,2-dimethylbutane, increased percentage exposed (Dh) appears to lead to increased turnover frequency (Nt). After the standard pretreatment, H2, 300 C; He, 450 C, the rates in alkane(g) rightleftharpoons alkane(ads) increase only slowly as Dh increases, but the rates in monoadsorbed alkane rightleftharpoons diadsorbed alkane decline relatively rapidly. As with 2,2-dimethylbutane, the pretreatment H2, 450 C leads to the largest values of Nt. He, 450 C following H2, 450 C removes surface hydrogen atoms and leads to reconstruction to a surface of much lower activity for exchange. Cyclopentane exchanges much faster than pentane on these catalysts. It appears that adsorption and desorption of cyclopentane involve single-step processes to and from diadsorbed cyclopentane + 2H*. Adsorption is faster than that with pentane because cyclopentane is essentially in the eclipsed conformation needed for this process. The rate of monoadsorbed rightleftharpoons diadsorbed cyclopentane is similarly augmented. Adsorbate-surface strain reduces the rate constant for adsorption of 2,2-dimethylbutane and increases rate of exchange of the hindered hydrocarbon vs that of the unhindered hydrocarbon will be larger than one would conclude merely from the relative rate constants of adsorption

  10. The effect of chemical and organic amendments on sodium exchange equilibria in a calcareous sodic soil.

    Science.gov (United States)

    Ranjbar, Faranak; Jalali, Mohsen

    2015-11-01

    In this study, the reclamation of a calcareous sodic soil with the exchangeable sodium percentage (ESP) value of 26.6% was investigated using the cheap and readily available chemical and organic materials including natural bentonite and zeolite saturated with calcium (Ca2+), waste calcite, three metal oxide nanoparticles functionalized with an acidic extract of potato residues, and potato residues. Chemical amendments were added to the soil at a rate of 2%, while potato residues were applied at the rates of 2 and 4% by weight. The ESP in the amended soils was reduced in the range of 0.9-4.9% compared to the control soil, and the smallest and the largest decline was respectively observed in treatments containing waste calcite and 4% of potato residues. Despite the reduction in ESP, the values of this parameter were not below 15% at the end of a 40-day incubation period. So, the effect of solutions of varying sodium adsorption ratio (SAR) values of 0, 5, 10, 20, 30, 40, and 50 on sodium (Na+) exchange equilibria was evaluated in batch systems. The empirical models (simple linear, Temkin, and Dubinin-Radushkevich) fitted well to experimental data. The relations of quantity to intensity (Q/I) revealed that the potential buffering capacity for Na+ (PBCNa) varied from 0.275 to 0.337 ((cmolc kg(-1)) (mmol L(-1))(-1/2)) in the control soil and amended soils. The relationship between exchangeable sodium ratio (ESR) and SAR was individually determined for the control soil and amended soils. The values of Gapon selectivity coefficient (KG) of Na+ differed from the value suggested by U.S. Salinity Laboratory (USSL). The PHREEQC, a geochemical computer program, was applied to simulate Na+ exchange isotherms by using the mechanistic cation exchange model (CEM) along with Gaines-Thomas selectivity coefficients. The simulation results indicated that Na+ exchange isotherms and Q/I and ESR-SAR relations were influenced by the type of counter anions. The values of K G increased in

  11. Assessing river-groundwater exchange in the regulated Rhone River (Switzerland) using stable isotopes and geochemical tracers

    International Nuclear Information System (INIS)

    Modern flood protection projects are often combined with measures for river restoration, which enlarge the river bed to improve the flow capacity during peak discharge. For the planning of such projects it is essential to quantify the river-groundwater exchange. To address this question in the highly regulated upper Rhone River basin, a combination of stable isotope techniques with geochemical and transient tracers has been used. The δ18O signal in precipitation decreases towards more negative values with a slope of 0.34%% per 100 m altitude, precipitation during winter was about 5.5%% more negative than in summer. Since in winter about 55% of the water in the River Rhone comes from high alpine hydropower reservoirs with a known δ18O value, this isotopic signature provides direct information of the source region and the seasonality in samples from groundwater wells. On a spatial scale SO42- measurements help to constrain groundwater components, because the tributaries and groundwater sources south of the Rhone are rich in SO42- with concentrations of more than 12 mM in spring water. In winter the Rhone water reaches concentrations of up to 1.5 mM, and during snowmelt in summer, this value drops below 0.5 mM. Finally the transient tracer 3H/3He is used to estimate groundwater inflow in deep gravel pits and to calculate an average travel velocity in the alluvial aquifer of about 1.7 kma-1

  12. Installation for study on photoinduced chemical exchange on the basis of NMR spectrometer and laser

    International Nuclear Information System (INIS)

    The facility for studying the kinetics of reversible photochemical processes is described. It contains the Tesla BS-567 NMR-spectrometer, the IBM PC Pentium personal computer and the LG-106M argon laser. The facility makes it possible to measure the flow rate constants from 0.01 up to 100 s-1 and the chemical exchange quantum yield. The example of using the above facility for determination of the reversible cis-trans photo-isomerization of the platinum molecules complexes is considered

  13. Design and optimization of pulsed Chemical Exchange Saturation Transfer MRI using a multiobjective genetic algorithm

    Science.gov (United States)

    Yoshimaru, Eriko S.; Randtke, Edward A.; Pagel, Mark D.; Cárdenas-Rodríguez, Julio

    2016-02-01

    Pulsed Chemical Exchange Saturation Transfer (CEST) MRI experimental parameters and RF saturation pulse shapes were optimized using a multiobjective genetic algorithm. The optimization was carried out for RF saturation duty cycles of 50% and 90%, and results were compared to continuous wave saturation and Gaussian waveform. In both simulation and phantom experiments, continuous wave saturation performed the best, followed by parameters and shapes optimized by the genetic algorithm and then followed by Gaussian waveform. We have successfully demonstrated that the genetic algorithm is able to optimize pulse CEST parameters and that the results are translatable to clinical scanners.

  14. Nitrogen isotope exchange between NO and NO2 and its implications for δ15N variations in tropospheric NOx and atmospheric nitrate

    Science.gov (United States)

    Walters, Wendell W.; Simonini, Damian S.; Michalski, Greg

    2016-01-01

    The nitrogen (N) isotope exchange between nitric oxide (NO) and nitrogen dioxide (NO2) has been previously suggested to influence N stable isotope compositions (δ15N) of these molecules. However, there is disagreement in the magnitude of the N isotopic fractionation (αNO2>/NO) resulting from this exchange process between previous experimental and theoretical studies. To this end, we measured αNO2>/NO associated with this exchange reaction at various temperatures. Our results indicate αNO2>/NO to be 1.0403 ± 0.0015, 1.0356 ± 0.0015, and 1.0336 ± 0.0014 at 278 K, 297 K, and 310 K, respectively. These measured values are within experimental error of the values we calculated using a modified version of the Bigeleisen-Mayer equation corrected for accurate zero-point energies, indicating an agreement between experiment and theory. Modeling of this exchange reaction demonstrates that δ15N-NO2 may exhibit a diurnal and seasonal profile if N isotopic equilibrium is achieved.

  15. Chemically selective polymer substrate based direct isotope dilution alpha spectrometry of Pu

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Sumana, E-mail: sumana@barc.gov.in [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Pandey, Ashok K. [Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Shah, R.V. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Aggarwal, S.K., E-mail: skaggr2002@gmail.com [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2015-06-09

    Highlights: • Membrane based alpha spectrometry was developed for plutonium. • A thin bifunctional layer was grafted on a porous membrane. • UV method used for grafting is simple and highly reproducible. • This method does not require preconcentration and source preparation steps. • Isotope dilution was used to enhance analytical performance. - Abstract: Quantification of actinides in the complex environmental, biological, process and waste streams samples requires multiple steps like selective preconcentration and matrix elimination, solid source preparations generally by evaporation or electrodeposition, and finally alpha spectrometry. To minimize the sample manipulation steps, a membrane based isotope dilution alpha spectrometry method was developed for the determination of plutonium concentrations in the complex aqueous solutions. The advantages of this method are that it is Pu(IV) selective at 3 M HNO{sub 3}, high preconcentration factor can be achieved, and obviates the need of solid source preparation. For this, a thin phosphate–sulfate bifunctional polymer layer was anchored on the surface of microporous poly(ethersulfone) membrane by UV induced surface grafting. The thickness of the bifunctional layer on one surface of the poly(ethersulfone) membrane was optimized. The thickness, physical and chemical structures of the bifunctional layer were studied by secondary ionization mass spectrometry (SIMS), scanning electron microscopy (SEM) and SEM–EDS (energy-dispersive spectroscopy). The optimized membrane was used for preconcentration of Pu(IV) from aqueous solutions having 3–4 M HNO{sub 3}, followed by direct quantification of the preconcentrated Pu(IV) by isotope dilution alpha spectrometry using {sup 238}Pu spike. The chemical recovery efficiency of Pu(IV) was found to be 86 ± 3% below Pu(IV) loading capacity (1.08 μg in 2 × 1 cm{sup 2}) of the membrane sample. The experiments with single representative actinides indicated that Am

  16. Chemically selective polymer substrate based direct isotope dilution alpha spectrometry of Pu

    International Nuclear Information System (INIS)

    Highlights: • Membrane based alpha spectrometry was developed for plutonium. • A thin bifunctional layer was grafted on a porous membrane. • UV method used for grafting is simple and highly reproducible. • This method does not require preconcentration and source preparation steps. • Isotope dilution was used to enhance analytical performance. - Abstract: Quantification of actinides in the complex environmental, biological, process and waste streams samples requires multiple steps like selective preconcentration and matrix elimination, solid source preparations generally by evaporation or electrodeposition, and finally alpha spectrometry. To minimize the sample manipulation steps, a membrane based isotope dilution alpha spectrometry method was developed for the determination of plutonium concentrations in the complex aqueous solutions. The advantages of this method are that it is Pu(IV) selective at 3 M HNO3, high preconcentration factor can be achieved, and obviates the need of solid source preparation. For this, a thin phosphate–sulfate bifunctional polymer layer was anchored on the surface of microporous poly(ethersulfone) membrane by UV induced surface grafting. The thickness of the bifunctional layer on one surface of the poly(ethersulfone) membrane was optimized. The thickness, physical and chemical structures of the bifunctional layer were studied by secondary ionization mass spectrometry (SIMS), scanning electron microscopy (SEM) and SEM–EDS (energy-dispersive spectroscopy). The optimized membrane was used for preconcentration of Pu(IV) from aqueous solutions having 3–4 M HNO3, followed by direct quantification of the preconcentrated Pu(IV) by isotope dilution alpha spectrometry using 238Pu spike. The chemical recovery efficiency of Pu(IV) was found to be 86 ± 3% below Pu(IV) loading capacity (1.08 μg in 2 × 1 cm2) of the membrane sample. The experiments with single representative actinides indicated that Am(III) did not sorb to

  17. Determination of plutonium isotopes in urine samples from radiation workers using 236Pu tracer, anion exchange resin and alpha spectrometry

    International Nuclear Information System (INIS)

    Bioassay technique is used for the estimation of actinides present in the body based on their excretion rate through body fluids. For occupational radiation workers urine assay is the preferred method for monitoring of chronic internal exposure. Determination of low concentrations of actinides such as plutonium, americium and uranium at low level of mBq in urine by alpha spectrometry requires pre-concentration of large volumes of urine. This paper deals with standardization of analytical method for the determination of Pu-isotopes in urine samples using anion exchange resin and 236Pu tracer for radiochemical recovery. The method involves oxidation of urine followed by co-precipitation of plutonium along with calcium phosphate. Separation of Pu was carried out by Amberlite, IRA-400, anion exchange resin. Pu-fraction was electrodeposited and activity estimated using tracer recovery by alpha spectrometer. Twenty routine urine samples of radiation workers were analyzed and consistent radiochemical tracer recovery was obtained in the range 74-96% with a mean and standard deviation of 85 and 6% respectively. (author)

  18. Chemical and Isotope Compositions of Neogene Hippopotamidae Teeth From Lake Albert (Uganda): Implications for Environmental Change

    Science.gov (United States)

    Brugmann, G. E.; Brachert, T. C.; Ssemmanda, I.; Mertz, D. F.

    2008-12-01

    lake, and is therefore a powerful tool for tracing ancient hydrological networks. The large variation of the Sr isotope composition can be explained if the lake is fed by different sources: water draining Cenozoic volcanic terrains have low 87Sr/86Sr (~ 0.704), whereas Proterozoic-Achaean terrains of the rift flanks have high 87Sr/86Sr (>0.718). Thus, the increasing 87Sr/86Sr from 5.2 to 2.3 Ma, suggests that water supply from volcanic terrains ceases and the local, Achaean run-off dominated the lake water chemistry. Consistent with the concurrent increase of ?18O, this suggests that increasing aridity and evaporation of lake water on a regional scale, interrupts the axial river network and local river discharge becomes dominant. The decrease of 87Sr/86Sr starting at about 2 Ma indicates new water supply from volcanic rock dominated terrains, which could reflect a tectonic restructuring of the rift valley or the initiation of the young Toro-Ankole igneous province. Palaeoclimate records from rift systems are governed by global climate forcing mechanisms and interacting geodynamics. Our study of the chemical and isotope record of tooth enamel from mammals permits the identification of these local and global environmental changes, in the western EARS on geological time scales. investigation.

  19. Application of a chemical ion exchange model to transport cask surface decontamination

    International Nuclear Information System (INIS)

    Radionuclide contamination of stainless steel surfaces occurs during submersion in a spent fuel storage pool, Subsequent release or desorption of these contaminants from a nuclear fuel transportation cask surface under varying environmental conditions occasionally results in the phenomenon known as contamination 'weeping'. Experiments have been conducted to determine the applicability of a chemical ion exchange model to characterise the problem of cask contamination and release. Surface charge characteristics of Cr2O3 and stainless steel (304) powders have been measured to determine the potential for ion exchange at metal oxide-aqueous interfaces. The solubility of Co and Cs electrolytes at varying pH and the absorption characteristics of these ions on Cr2O3 and stainless steel powders in aqueous slurries have been studied. Experiments show that Co ions do reversibly absorb on these powder surfaces and, more specifically, that absorption occurs in the nominal pH range (pH = 4-6) of a boric acid moderated spent fuel pool. Desorption has been demonstrated to occur at pH≤3. Cs+ ions also have been shown to have an affinity for these surfaces although the reversibility of Cs+ bonding by H+ ion exchange has not been fully demonstrated. These results have significant implications for effective decontamination and coating processes used on nuclear fuel transportation casks. (author)

  20. Application of a chemical ion exchange model to transport cask surface decontamination

    International Nuclear Information System (INIS)

    Radionuclide contamination of stainless steel surfaces occur during submersion in a spent fuel storage pool. Subsequent release or desorption of these contaminants from a nuclear fuel transportation cask surface under varying environmental conditions occasionally results in the phenomenon known as contamination ''weeping.'' Experiments have been conducted to determine the applicability of a chemical ion-exchange model to characterize the problem of cask contamination and release. Surface charge characteristics of Cr2O3 and stainless steel (304) powders have been measured to determine the potential for ion exchange at metal oxide -- aqueous interfaces. The solubility of Co and Cs electrolytes at varying pH and the absorption characteristics of these ions on Cr2O3 and stainless steel powders in aqueous slurries have been studied. Experiments show that Co ions do reversibly adsorb on these powder surfaces and, more specifically, that adsorption occurs in the nominal pH range (pH = 4--6) of a boric acid-moderated spent fuel pool. Desorption has been demonstrated to occur at pH ≤ 3. Cs ions also have been shown to have an affinity for these surfaces although the reversibility of Cs+ bonding by H+ ion exchange has not been fully demonstrated. These results have significant implications for effective decontamination and coating processes used on nuclear fuel transportation casks. 8 refs., 5 figs

  1. Chemical and isotopic methods for characterization of pollutant sources in rain water

    International Nuclear Information System (INIS)

    The acid rain formation is related with industrial pollution. An isotopic and chemical study of the spatial and temporary distribution of the acidity in the rain gives information about the acidity source. The predominant species in the acid rain are nitrates and sulfates. For the rain monitoring is required the determination of the anion species such as HCO3, Cl, SO4, NO3 and p H. So it was analyzed the cations Na+ , K+ , Ca2+ and Mg2+ to determine the quality analysis. All of them species can be determined with enough accuracy, except HCO3 by modern equipment such as, liquid chromatograph, atomic absorption, etc. The HCO3 concentration is determined by traditional methods like acid-base titration. This work presents the fundamental concepts of the titration method for samples with low alkalinity (carbonic species), for rain water. There is presented a general overview over the isotopic methods for the characterization of the origin of pollutant sources in the rain. (Author)

  2. Chemical and isotopic compositions of natural gases from the Japanese major oil and gas fields

    International Nuclear Information System (INIS)

    Carbon isotopic ratios (13C/12C) and chemical compositions of methane (C1), ethane (C2), propane (C3), i-butane (i-C4) and n-butane (n-C4) were measured for natural gases from the Japanese major oil and gas fields. The C1/(C2+C3) vs. δ13C(C1) plot suggests that most samples analyzed in the present study are of thermogenic origin with a minor contribution of biogenic gases. Some gases show unusually high ratios of C2/C3 and i-C4/n-C4, and low ratios cf C3/i-C4 (Unusual-Hydrocarbon-Ratio gases: UHR gases). The carbon isotopic ratios and hydrocarbon compositions strongly suggest that these unusual ratios were caused by the chromatographic effect of sediments during migration of the gases. By comparing hydrocarbon ratios (C1/C2, C2/C3, C2/i-C4, C2/n-C4, C3/i-C4, C3/n-C4 and i-C4/n-C4) of the UHR and normal gases, it was found that the natural gases tend to lose their hydrocarbons during migration in the order: n-C4 ≅ C3 > C2 ≅ i-C4 > C1. (author)

  3. Use of isotope techniques in order to evaluate the efficiency of Chemical fertilizers in rice

    International Nuclear Information System (INIS)

    Rice crop (Oryza sativa L.) in the areas with engineers systems, characterized by potentials elevated yields, receive high rates of chemical fertilizers that they not always have a good use by the plant. In present work, 15 N isotope was used in order to evaluate different forms to increase the efficiency of nitrogen fertilizer (urea), while by means of 32 P isotope, of the triple superphosphate (TSP). The investigations were carried out in areas of a sandy texture soil classified like Ferric Luvisol of the Agroindustrial Complex Los Palacios, Cubanacan Farm, province of Pinar del Rio. Results indicate that, in the first case, the rice plants hardly take advantage of the first of the three fractions of urea usually applied during the crop cycle (10 days after germination) due to the poor nutrient demand of the plant in that moment and that the application of a dose of 6 t.ha -1 of zeolite, allows during at least three consecutive rice crops to increase the urea efficiency significantly. On the order hand, split application of TSP (50% after soil preparation and 50% in active tillering) increased phosphorus uptake by the plant from the fertilizer as well as the soil, thus rice yield increases in comparison to their total application before planting

  4. Lithium distribution and isotopic fractionation during chemical weathering and soil formation in a loess profile

    Science.gov (United States)

    Tsai, Pei-Hsuan; You, Chen-Feng; Huang, Kuo-Fang; Chung, Chuan-Hisung; Sun, You-Bin

    2014-06-01

    Lithium (Li) is a fluid-mobile element and δ7Li in secondary deposits represents an excellent proxy for silicate weathering and authigenic mineral formation. The soil samples from 1205 to 1295 cm in the Weinan profile, one of the best developed loess-paleosol sequences covering the last glacial-interglacial climatic cycle, were collected and chemically separated into detritus and carbonate fractions for subsequent analyses of Li, δ7Li, major and trace elements. Other desert specimens (i.e., Qaidam Desert, Tengger Desert, Badain Juran Desert and Taklimakan Desert) near the Chinese Loess Plateau (CLP) and various standard clays were analyzed for assisting provenance determination. The Li and δ7Li distributions in the detritus are rather homogeneous, 1.4-2.0 μg/g and +2.5‰ to +4.7‰, respectively, compared with the carbonate fraction. The detrital δ7Li varies systematically with magnetic susceptibility and grain size changes, reflecting significant Li isotopic variation associated with sources and mineralogy of detrital material. On the other hand, Li and δ7Li in carbonates show large changes, 781-963 ng/g and -4.1‰ to +10.2‰, respectively. These carbonate δ7Li correlated well with the estimated index of chemical weathering, as a result of Li mobilization and soil formation during chemical weathering.

  5. Coordinated Chemical and Isotopic Imaging of Bells (CM2) Meteorite Matrix

    Science.gov (United States)

    Clemett, S. J.; Messenger, S.; Naklamura-Messenger, K.; Thomas-Keprta, K. L.

    2014-01-01

    Meteoritic organic matter is a complex conglomeration of species formed in distinct environments and processes in circumstellar space, the interstellar medium, the Solar Nebula and asteroids. Consequently meteorites constitute a unique record of primordial organic chemical evolution. While bulk chemical analysis has provided a detailed description of the range and diversity of organic species present in carbonaceous chondrites, there is little information as to how these species are spatially distributed and their relationship to the host mineral matrix. The distribution of organic phases is nevertheless critical to understanding parent body processes. The CM and CI chondrites all display evidence of low temperature (< 350K) aqueous alteration that may have led to aqueous geochromatographic separation of organics and synthesis of new organics coupled to aqueous mineral alteration. Here we present the results of the first coordinated in situ isotopic and chemical mapping study of the Bells meteorite using a newly developed two-step laser mass spectrometer (mu-L(sup 2)MS) capable of measuring a broad range of organic compounds.

  6. Chemical and isotopic investigations of runoff in a mountainous watershed, Venezuelan Andes (Rio Bocono)

    International Nuclear Information System (INIS)

    The Rio Bocono watershed, located in the Western part of Venezuela on the South western side of Andes is considered by the 'Ministerio de1 Ambiente y de los Recursos Naturales Renovables' (MARN) as a priority zone for environmental management. The studies of relation between flow, dissolved elements and solid transport are essential to estimate soil degradation and sediment deposition which provokes loss of depth in the dam reservoir at the Southern margin of the basin. Because of the large surface which reach 1540 km2, the lack of equipment and the flash flood character of the river do not enable the flow mechanisms and transit times to be determined using usual hydrologic methods; therefore this problem has been approached by the way of chemical and isotopic investigation

  7. Chemical and isotopic compositions of gases in geothermal fluids in Iceland

    International Nuclear Information System (INIS)

    We have measured chemical compositions (CO2, CH4, N2, O2, H2S, H2, He, Ne and Ar), and isotopic compositions of light elements (delta13C, delta15N and deltaD) and of rare gases (He, Ne, Ar, Kr, and Xe) in seven gaseous and four fluid samples collected in Icelandic geothermal areas. Major chemical constituents of the gas samples are CO2, N2, H2 and H2S. Isotopic compositions of Ne, Kr and Xe are indistinguishable from those of the atmosphere within the experimental accuracy of this study. There are slightly lower 40Ar/36Ar ratios than in the air for samples with extremely high 3He/4He ratios. No positive evidence for excess 129Xe is found. The measured 3He/4He ratios in the samples can be explained in terms of mixing among three end members: MORB-type He with a 3He/4He ratio of 1.1 x 10-5, plume-type He of 5.0 x 10-5, and atmospheric He of 1.4 x 10-6. Samples obtained from the northeastern part of the island contain typical MORB-type He, whereas significant contributions (up to 33 %) of plume-type He are apparent in samples from the southern region. Based on the 13C/12C ratios, CO2 in Icelandic gases is considered to be directly derived from magma, whereas CH4 may be formed by reaction of reduced carbon with water in the source magma. There is an inverse correlation between the 3He/4He ratios and delta15N values in Icelandic gases, suggesting co-genetic origin of He and N2. (author)

  8. Sulphur isotopic and chemical compositions of the natural waters in the Chuncheon area, Korea

    International Nuclear Information System (INIS)

    The contribution of Chinese sources to the acid deposition in neighbouring countries in Far East Asia has been disputed. This study is to examine the isotopic composition of the S in the natural waters in the Chuncheon area to see if the isotopic composition can be an indicator of the pollution sources in the area. Meteoric water sampled between September 2000 and July 2001 and surface water sampled in December 2000 and April 2001 in the area were collected to examine their chemical and isotopic compositions. The pH values of the meteoric water lie between 4.02 and 6.89, but mostly lower than 5.6, indicating considerable acid deposition. The pH of the surface water is generally higher than that of the atmospheric water. Factor analysis on the concentrations of the dissolved components suggests that the surface water chemistry depends principally on the chemistry of the atmospheric water. The dissolution of carbonate minerals and silicate-water interaction plays a rather minor role in affecting the water chemistry. δ18O and δD of all the natural water samples align fairly well along the global meteoric water line. The δ34S of the dissolved SO4 in the meteoric water has values ranging from 3.4 to 8.2 per mille, showing little seasonal difference. The contribution from sea-salt to the total atmospheric S is estimated to be less than 10%. The δ34S of the anthropogenic S in the Chuncheon atmosphere is calculated to be 2.5 to 7.2 per mille, which partly overlaps the reported values of S in Chinese coal, Chinese rainfall, and Japanese fallout. Appropriate tracking and quantitative estimation of the contribution from possible pollution sources to the local S concentrations requires more information on the isotopic compositions of the potential pollution sources. The δ34S of the dissolved SO4 in the surface water has values ranging from 3.2 to 6.2 per mille, which is a little narrower than that of the meteoric water. The δ34S and the concentration range of the

  9. Possibilities of chemical isolation of element 106 from aqueous solutions according to the model experiments with short lived tungsten isotopes

    International Nuclear Information System (INIS)

    A rapid method for continuous separation of short-lived tungsten isotopes from the lanthanides has been developed. It consists in transforming nuclear reaction products from the target by an aerosol jet to an absorber where the KCl particulates are dissolved in 0.2 M HF and percolating the product solution through three successively linked columns filled with ion exchange resins Dowex 50X8 (cationite), Dowex 1X8 (anionite) and again Dowex 50X8. 3 refs

  10. Chemical and isotopic techniques for development of groundwater management strategies in a coastal aquifer: Krishna river delta, South India

    International Nuclear Information System (INIS)

    The Krishna and Godavari districts of the Andhra Pradesh in India have a flourishing agricultural production and the farmers of these areas make use of the mineral rich alluvium of the Krishna river delta more effectively for the purpose. The delta comprises sediments of both fluvial and marine origin. The groundwater quality vary widely both laterally and vertically in the alluvial formations. By and large, the most potential fresh water aquifers occur as isolated pockets and their extent is more in upper deltaic plain, whereas in the coastal tracts the fresh water occurrence is limited to sand dunes and beach ridges at shallow depth up to 14 m. The quality of deeper aquifers down to about 200m is generally brackish to saline water in the deltaic region except in some pockets (Rao, 1999). The irrigation demand is met through the extensive canal network that offtake from Prakasam Barrage located across the river Krishna in Vijayawada. In recent years it has been reported that groundwater is being extensively used in addition to the surface water supplied through the canal systems. The groundwater is also used to meet the domestic needs. Several tube wells have been installed in the northern part of the delta region. Identification of the origin of groundwater salinity and design of measures to control the salinisation process are the problems usually faced by a hydrogeologist. The conventional chemical data on groundwater allow formulation of hypothesis regarding chemical evolution and origin of salinity. Generally the ionic ratios such as Na+/Cl-, Ca2+/Mg2+, Cl-/I- are used for the purpose. However, in many cases the chemistry of water may undergo further secondary changes such as precipitation, ion exchange etc., which may make it difficult to identify the salinisation mechanism precisely. Environmental isotopes 3H, 14C, 2H and 18O could help in knowing the source of the salinity. Age evaluations using radio-isotopic techniques confirm the chemical

  11. Isotope and chemical studies of the thermal waters in the Busan area, Republic of Korea

    International Nuclear Information System (INIS)

    The geochemical and isotopic studies on thermal waters in the Busan city, on the southeastern tip of Korea, were carried out. The Haeundae and Dongrae geothermal areas are located in the Busan city. Both of the areas have been recorded as hot spring areas in the historical archives and characterized by high Cl content compared to other geothermal waters in Korea. All available δ18D and δD data for the study area are plotted to the worldwide meteoric water line, indicating that all waters are of a local meteoric origin. Although the isotopic data are plotted in the narrow range without a deviation to the seawater mixing line, the δ18O-Cl diagram clearly show that the Haeundae water lies on a mixing line between a meteoric end member and the seawater from off-shore of Busan. The carbon isotope result shows very depleted values, indicating that the organic carbon was contributed to both thermal waters. The 14C data indicate large contribution of modern carbon. It indicates that the salinities of the Dongrae and the Haeundae water might be derived from the present seawater intruded beneath the Busan area. The overall hydrochemical features indicate that the sulfate in thermal waters is contributed by seawater. The δ 34S values of dissolved sulfate of the thermal water support the mixing with seawater. However, the lower SO4/Cl ratio compared with seawater should be explained. The multicomponent mineral equilibrium approach to the Dongrae water are applied to estimate the reservoir temperature at depth. This approach to determine equilibrium conditions can be limited by a lack of reliable Al analyses and dilution of thermal water through mixing with fresh water. The hypothetical Al concentration can be determined for each temperature by applying the FixAl method and considering mixing ratio with fresh water. The mineral equilibrium geothermometer temperatures and therefore the probable reservoir temperatures are estimated to be about 110 deg. C to 130 deg. C. It is

  12. Re-Os Isotopic Constraints on the Chemical Evolution and Differentiation of the Martian Mantle

    Science.gov (United States)

    Brandon, Alan D.; Walker, Richard J.

    2002-01-01

    The (187)Re-187Os isotopic systematics of SNC meteorites, thought to be from Mars, provide valuable information regarding the chemical processes that affected the Martian mantle, particularly with regard to the relative abundances of highly siderophile elements (HSE). Previously published data (Birck and Allegre 1994, Brandon et al. 2000), and new data obtained since these studies, indicate that the HSE and Os isotopic composition of the Martian mantle was primarily set in its earliest differentiation history. If so, then these meteorites provide key constraints on the processes that lead to variation in HSE observed in not only Mars, but also Earth, the Moon and other rocky bodies in the Solar System. Processes that likely have an effect on the HSE budgets of terrestrial mantles include core formation, magma ocean crystallization, development of juvenile crust, and the addition of a late veneer. Each of these processes will result in different HSE variation and the isotopic composition of mantle materials and mantle derived lavas. Two observations on the SNC data to present provide a framework for which to test the importance of each of these processes. First, the concentrations of Re and Os in SNC meteorites indicate that they are derived from a mantle that has similar concentrations to the Earth's mantle. Such an observation is consistent with a model where a chondritic late veneer replenished the Earth and Martian mantles subsequent to core formation on each planet. Alternative models to explain this observation do exist, but will require additional data to test the limitations of each. Second, Re-Os isotopic results from Brandon et al. (2000) and new data presented here, show that initial yos correlates with variations in the short-lived systems of (182)Hf- (182)W and (142)Sm-142Nd in the SNC meteorites (epsilon(sub W) and epsilon(sub 142Nd)). These systematics require an isolation of mantle reservoirs during the earliest differentiation history of Mars, and

  13. Study of multi-site chemical exchange in solution state by NMR: 1D experiments with multiply selective excitation

    Indian Academy of Sciences (India)

    Samanwita Pal

    2010-07-01

    Chemical exchange in solution state has been investigated traditionally by both 1D and 2D NMR, permitting the extraction of kinetic parameters (e.g. the spin-lattice relaxation time 1, the exchange rate constant and the activation parameters). This work demonstrates a simple 1D NMR approach employing multiply selective excitation to study multi-site exchange processes in solution, applying it to systems that exhibit three-site exchange. This approach involves simultaneous excitation of all - or a chosen subset of - the exchanging sites by using an appropriately modulated shaped radiofrequency pulse. The pulse sequence, as well as analysis is summarized. Significant features of the experiment, which relies on sign labelling of the exchanging sites, include considerably shorter experiment time compared to standard 2D exchange work, clear definition of the exchange time window and uniform pulse non-ideality effects for all the exchanging sites. Complete kinetic information is reported in the study of dynamic processes in superacid solutions of two weak bases, studied by 1H NMR. An analytical solution, leading to the determination of four rate parameters, is presented for proton exchange studies on these systems, which involve a mixture of two weak bases in arbitrary concentration ratio, and stoichiometric excess of the superacid.

  14. A counter-intuitive approach to calculating non-exchangeable 2H isotopic composition of hair: treating the molar exchange fraction fE as a process-related rather than compound-specific variable

    Science.gov (United States)

    Landwehr, J.M.; Meier-Augenstein, W.; Kemp, H.F.

    2011-01-01

    Hair is a keratinous tissue that incorporates hydrogen from material that an animal consumes but it is metabolically inert following synthesis. The stable hydrogen isotope composition of hair has been used in ecological studies to track migrations of mammals as well as for forensic and archaeological purposes to determine the provenance of human remains or the recent geographic life trajectory of living people. Measurement of the total hydrogen isotopic composition of a hair sample yields a composite value comprised of both metabolically informative, non-exchangeable hydrogen and exchangeable hydrogen, with the latter reflecting ambient or sample preparation conditions. Neither of these attributes is directly measurable, and the non-exchangeable hydrogen composition is obtained by estimation using a commonly applied mathematical expression incorporating sample measurements obtained from two distinct equilibration procedures. This commonly used approach treats the fraction of exchangeable hydrogen as a mixing ratio, with a minimal procedural fractionation factor assumed to be close or equal to 1. Instead, we propose to use full molar ratios to derive an expression for the non-exchangeable hydrogen composition explicitly as a function of both the procedural fractionation factor α and the molar hydrogen exchange fraction fE. We apply these derivations in a longitudinal study of a hair sample and demonstrate that the molar hydrogen exchange fraction fE should, like the procedural fractionation factor α, be treated as a process-dependent parameter, i.e. a reaction-specific constant. This is a counter-intuitive notion given that maximum theoretical values for the molar hydrogen exchange fraction fE can be calculated that are arguably protein-type specific and, as such, fE could be regarded as a compound-specific constant. We also make some additional suggestions for future approaches to determine the non-exchangeable hydrogen composition of hair and the use of

  15. Chemical, physical and isotopic characterization of U3Si2, for nuclear forensics purposes

    International Nuclear Information System (INIS)

    In the early 1990's, the first illicit trafficking of nuclear and radioactive materials was observed mainly in Europe. A decade marked by numerous cases of seizures of these materials. As a result, these events have become the subject of criminal forensic investigations and develop from there, nuclear forensics. In Brazil there are no illicit trafficking official records of nuclear material, however, is widely known the extraction and illegal transportation of radioactive geological materials, and the materials pieces attachment used as shielding for radioactive sources. One of the main tools used in nuclear forensics is the nuclear materials databases establishment. These documents must contain the most information as possible about the physical, chemical and nuclear material seized, allowing the identification of their origin, manufacturing process or age. Thus, it sets characteristic composition standards of each material, called 'chemical signatures' (chemical finger print). In this work nuclear forensic protocol was adopted as well as the three stages of assessment suggested by International Atomic Energy Agency (IAEA) in identifying the origin of uranium silicide (U3Si2). Assays were performed in order to make physical, chemical and isotopic characterization of the studied materials and compared the data with those obtained for other uranium compounds (Uranium tetrafluoride, UF4; uranium oxide, UO2 and U3O8; Yellow cake) by establishing a characteristic signature for each one. Through the assays the uranium compounds were classify by origin groups, as far as they are from different manufactured process and/ or origin. It was also possible to show the importance of a nuclear forensic database during an investigation of a nuclear forensic event. (author)

  16. Chemical and isotopic characteristics of a glacier-derived naled in front of Austre Grønfjordbreen, Svalbard

    OpenAIRE

    Jacob C. Yde; Andy J. Hodson; Solovjanova, Irina; Steffensen, Jørgen P.; Nørnberg, Per; Heinemeier, Jan; Olsen, Jesper

    2012-01-01

    The chemical and stable isotope composition of a glacier-derived naled in front of the glacier Austre Grønfjordbreen, Svalbard, is examined to elucidate how secondary processes such as preferential retention and leaching affect naled chemistry. Internal candle ice layers have a chemical composition almost similar to that of the lower stratified granular ice layer, whereas the upper granular ice layer has a significantly different composition, which resembles the composition found in glacier m...

  17. A physical-chemical modeling of strontium isotopes behavior in Chernobyl Exclusion zone fresh water

    International Nuclear Information System (INIS)

    Radiogeochemical models for dissolution and sedimentation of isotopic forms of strontium compounds in the exclusion zone's freshwater environments were created and verified. It was established that isotope effects shall be observed both during dissolution and deposition of strontium isotopic forms. For both models, solid phase (with respect to the solution) is depleted by light isotopes of strontium (84SR, 86Sr and 87Sr) and enriched by 90Sr. Isotopic composition of strontium in the solution is governed by isotopic composition of ion mSr2+

  18. Kinetic isotope effects in the reactions of hydrogen exchange of CH aromatic bonds of benzene, fluorobenzene, and nitrogen-containing heterocycles with alkali metal amide solution in liquid ammonia

    International Nuclear Information System (INIS)

    Kinetic isotope effects during deutero- and tritium exchange of benzene, fluorobenzene, pyridine, N-oxide of pyridine and quinoline with solution of potassium or sodium amide in liquid ammonia were determined experimentally. The character of rate constant change of tritium exchange in benzene, when passing from light-weight to deutero-substituted ammonia, was ascertained. Reasons for reduction in the secondary isotope effect of the solvent in reference to theoretic maximum equal to 2.4, as well as the change in the primary kinetic isotope effect resulting from hydrogen isotopic exchange in CH aromatic bonds, depending on substrates CH-acidity, are discussed. The conclusion on applicability of the Eigen theory for explaining the mechanism of hydrogen isotopic exchange reactions in CH aromatic binds was confirmed

  19. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Science.gov (United States)

    2010-01-01

    ... as: (i) Equipment for contacting chlorine and oxygen with the aqueous effluent from the isotope... control, and pumps or other transfer devices for feeding to the electrochemical reduction cells. A major... adjustment and control, and pumps or other transfer devices for feeding to the electrochemical...

  20. The measurement of the chemically mobile fraction of lead in soil using isotopic dilution analysis

    International Nuclear Information System (INIS)

    The chemically available fraction of lead in eight soils measured by isotopic dilution analysis using 212Pb ranged from 7 to 16% of the total content of lead in soil. The soluble fractions achieved values up to 63% of the total content in 1 M NH4NO3, 1 M MgCl2 and 0.05 M DTPA solutions. Increasing the contact time between water and soil, the water-soil ratio from 1:1 to 5:1 and increasing the temperature of the soil-water suspension raised the chemically available fraction in soil. Comparing various soil parameters and the mobile fraction of lead, only pH shows a significant correlation. The amphoteric character of lead causes a minimum of mobility about pH 6; pH-values below are responsible for the higher mobility of lead as Pb2+, at pH-values above 6 soluble hydroxy and humic acid complexes are formed. (orig.)

  1. On-line stable isotope gas exchange reveals an inducible but leaky carbon concentrating mechanism in Nannochloropsis salina.

    Science.gov (United States)

    Hanson, David T; Collins, Aaron M; Jones, Howland D T; Roesgen, John; Lopez-Nieves, Samuel; Timlin, Jerilyn A

    2014-09-01

    Carbon concentrating mechanisms (CCMs) are common among microalgae, but their regulation and even existence in some of the most promising biofuel production strains is poorly understood. This is partly because screening for new strains does not commonly include assessment of CCM function or regulation despite its fundamental role in primary carbon metabolism. In addition, the inducible nature of many microalgal CCMs means that environmental conditions should be considered when assessing CCM function and its potential impact on biofuels. In this study, we address the effect of environmental conditions by combining novel, high frequency, on-line (13)CO2 gas exchange screen with microscope-based lipid characterization to assess CCM function in Nannochloropsis salina and its interaction with lipid production. Regulation of CCM function was explored by changing the concentration of CO2 provided to continuous cultures in airlift bioreactors where cell density was kept constant across conditions by controlling the rate of media supply. Our isotopic gas exchange results were consistent with N. salina having an inducible "pump-leak" style CCM similar to that of Nannochloropsis gaditana. Though cells grew faster at high CO2 and had higher rates of net CO2 uptake, we did not observe significant differences in lipid content between conditions. Since the rate of CO2 supply was much higher for the high CO2 conditions, we calculated that growing cells bubbled with low CO2 is about 40 % more efficient for carbon capture than bubbling with high CO2. We attribute this higher efficiency to the activity of a CCM under low CO2 conditions. PMID:24844569

  2. Kinetic and equilibrium isotope effects of proton exchange and autoprotolysis of pure methanol studied by dynamic NMR spectroscopy

    International Nuclear Information System (INIS)

    The rate constants of the intermolecular proton exchange in pure methanol, i.e. the reciprocal proton lifetimes, tau0-1, have been determined as a function of the temperature by total lineshape analysis of the 1H-NMR spectra. Since CH3OH is an AB3 spin system of high order the quantum mechanical density matrix formalism was employed for the simulation of the spectra. The neglect of high order effects as well as the presence of impurities had led to inconsistencies in previous studies. For the first time, the primary kinetic isotope effects were determined indirectly by simulation of the 1H-NMR spectra of CH3OD samples containing 1 vol-% CH3OH. The data cannot be explained by a cyclic exchange mechanism. However, they can be quantitatively related to the autoprotolysis constant of methanol and to Grunwald's kinetic data on proton transfer in buffered methanol solutions. It is concluded that the proton lifetimes in pure methanol are determined by the natural amount of free solvated CH3OH2+ and CH3O- ion generated by autoprotolysis. The observed energy of activation is then the sum of two terms, namely the energy of activation of the proton jumps between the ions and a methanol molecule, and half the enthalpy of methanol selfdissociation. In the presence of acid or basic impurities the second term becomes negligible. We propose a method for the quantitative determination of these impurities in the 10-9 to 10-7 mol l-1 range. From our results we derive an equilibrium isotrope effect of (Ksup(H)/Ksup(D))sub(298 K)=6 +- 3 for the autoprotolysis of pure methanol. (orig./HK)

  3. Towards multi-tracer data-assimilation: biomass burning and carbon isotope exchange in SiBCASA

    Directory of Open Access Journals (Sweden)

    I. R. van der Velde

    2014-01-01

    Full Text Available We present an enhanced version of the SiBCASA photosynthetic/biogeochemical model for a future integration with a multi-tracer data-assimilation system. We extended the model with (a biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from Global Fire Emissions Database (GFED version 3.1, (b a new set of 13C pools that cycle consistently through the biosphere, and (c, a modified isotopic discrimination scheme to estimate variations in 13C exchange as a~response to stomatal conductance. Previous studies suggest that the observed variations of atmospheric 13C/12C are driven by processes specifically in the terrestrial biosphere rather than in the oceans. Therefore, we quantify in this study the terrestrial exchange of CO2 and 13CO2 as a function of environmental changes in humidity and biomass burning. Based on an assessment of observed respiration signatures we conclude that SiBCASA does well in simulating global to regional plant discrimination. The global mean discrimination value is 15.2‰, and ranges between 4 and 20‰ depending on the regional plant phenology. The biomass burning emissions (annually and seasonally compare favorably to other published values. However, the observed short-term changes in discrimination and the respiration 13C signature are more difficult to capture. We see a too weak drought response in SiBCASA and too slow return of anomalies in respiration. We demonstrate possible ways to improve this, and discuss the implications for our current capacity to interpret atmospheric 13C observations.

  4. Investigation of Chemical and Physical Changes to Bioapatite During Fossilization Using Trace Element Geochemistry, Infrared Spectroscopy and Stable Isotopes

    Science.gov (United States)

    Suarez, C. A.; Kohn, M. J.

    2013-12-01

    Bioapatite in the form of vertebrate bone can be used for a wide variety of paleo-proxies, from determination of ancient diet to the isotopic composition of meteoric water. Bioapatite alteration during diagenesis is a constant barrier to the use of fossil bone as a paleo-proxy. To elucidate the physical and chemical alteration of bone apatite during fossilization, we analyzed an assortment of fossil bones of different ages for trace elements, using LA-ICP-MS, stable isotopes, and reflected IR spectroscopy. One set of fossil bones from the Pleistocene of Idaho show a diffusion recrystallization profile, however, rare earth element (REE) profiles indicate diffusion adsorption. This suggests that REE diffusion is controlled by changing (namely decreasing) boundary conditions (i.e. decreasing concentration of REE in surrounding pore fluids). Reflected IR analysis along this concentration profile reveal that areas high in U have lost type A carbonate from the crystal structure in addition to water and organics. Stable isotopic analysis of carbon and oxygen will determine what, if any, change in the isotopic composition of the carbonate component of apatite has occurred do to the diffusion and recrystallization process. Analysis of much older bone from the Cretaceous of China reveal shallow REE and U concentration profiles and very uniform reflected IR spectra with a significant loss of type A carbonate throughout the entire bone cortex. Analysis of stable isotopes through the bone cortex will be compared to the stable isotopes collected from the Pleistocene of Idaho.

  5. Chemical and Isotopes study of pollutants transport through unsaturated zone in Damascus oasis (Syria)

    International Nuclear Information System (INIS)

    The primary objectives of this study were to determine the hydrochemical and isotopic characteristics of groundwater and to study vertical transport processes for trace elements through the unsaturated zone, from the surface water into the groundwater system. A third objective is to identifying the importance of the unsaturated zone in protecting groundwater from contamination. Distribution of trace elements, including Cu, Pb, Cr, Cd, Zn and As in the soil with depth were studied. Mineralogy was investigated using X-Ray diffraction techniques and granulometry in three drilled soil profile (KA, KB and KS) in Damascus Oasis, which indicated that the soil consists mainly of calcite, a mineral that has the ability to bind some of the trace elements. Measurement of nitrate concentrations in groundwater permitted an investigation of the urban, industrial and agricultural pollution in the Oasis, in particular, in the eastern part of Damascus city and in the north of Oasis where the irrigation by treated wastewater is applied. Depending on the chemical characteristics of the studied trace elements and soil conditions, these elements have high concentrations in the upper part of the soil (20-30 cm depth), due to absorption by clay minerals and organic matter. These high concentrations represent pollution by leather industries (tannery) in the area. The trace element concentrations decrease towards the east in parallel with river flow direction. The lower part of profiles show low trace element concentrations, below the international permitted limit. The low concentrations of trace elements in groundwater which are also below the international limit, indicates no pollution is presented. The isotopic composition of shallow groundwater indicates the underground recharge, originated from the Anti-Lebanon Mountain, is more significant than the direct recharge through unsaturated zone. It is concluded the unsaturated zone and the decrease of groundwater levels have played an

  6. Chemical and isotopic study of pollutant transport through unsaturated zone in Damascus Oasis (Syrian Arab Republic)

    International Nuclear Information System (INIS)

    The primary objectives of this study were to determine the hydrochemical and isotopic characteristics of groundwater and to study vertical transport processes for trace elements through the unsaturated zone, from the surface water into the groundwater system. A third objective was to identifying the importance of the unsaturated zone in protecting groundwater from contamination. Distribution of trace elements, including Cu, Pb, Cr, Cd, Zn and As in the soil with depth were measured. Mineralogy was investigated using X ray diffraction techniques and grain size distribution in three drilled soil profile (KA, KB and KS) in Damascus Oasis, which indicated that the soil consists mainly of calcite, a mineral that has the ability to bind some of the trace elements. Measurement of nitrate concentrations in groundwater permitted an investigation of the urban, industrial and agricultural pollution in the Oasis, in particular, in the eastern part of Damascus city and in the north of the Oasis where the irrigation by treated wastewater is applied. Depending on the chemical characteristics of the studied trace elements and soil conditions, these elements can have high concentrations in the upper part of the soil (20-30 cm depth), due to absorption by clay minerals and organic matter. The high concentrations represent pollution by leather industries (tannery) in the area. The trace element concentrations decrease towards the east in parallel with river flow direction. The lower part of profiles show low trace element concentrations below the international permitted limit. The low concentrations of trace elements in groundwater are also below the international limit, indicating significant concentrations of contaminants are not presently entering the water table. The isotopic composition of shallow groundwater indicates the underground recharge, originated from the Anti-Lebanon Mountain, is more significant than the direct recharge through unsaturated zone. It is concluded the

  7. Fast simulation and optimization of pulse-train chemical exchange saturation transfer (CEST) imaging

    International Nuclear Information System (INIS)

    Chemical exchange saturation transfer (CEST) MRI has been increasingly applied to detect dilute solutes and physicochemical properties, with promising in vivo applications. Whereas CEST imaging has been implemented with continuous wave (CW) radio-frequency irradiation on preclinical scanners, pulse-train irradiation is often chosen on clinical systems. Therefore, it is necessary to optimize pulse-train CEST imaging, particularly important for translational studies. Because conventional Bloch–McConnell formulas are not in the form of homogeneous differential equations, the routine simulation approach simulates the evolving magnetization step by step, which is time consuming. Herein we developed a computationally efficient numerical solution using matrix iterative analysis of homogeneous Bloch–McConnell equations. The proposed algorithm requires simulation of pulse-train CEST MRI magnetization within one irradiation repeat, with 99% computation time reduction from that of conventional approach under typical experimental conditions. The proposed solution enables determination of labile proton ratio and exchange rate from pulse-train CEST MRI experiment, within 5% from those determined from quantitative CW-CEST MRI. In addition, the structural similarity index analysis shows that the dependence of CEST contrast on saturation pulse flip angle and duration between simulation and experiment was 0.98  ±  0.01, indicating that the proposed simulation algorithm permits fast optimization and quantification of pulse-train CEST MRI. (paper)

  8. Radiolytic and chemical degradation of strong acidic ion-exchange resins: Study of ligands formed

    International Nuclear Information System (INIS)

    The formation of water-soluble organic ligands by radiolytic and chemical degradation of several strong acidic ion-exchange resins was investigated under conditions close to those of the near field of a cementitious repository. The most important degradation products were studied and their complexing properties evaluated. Irradiation of strong acidic cation exchange resins (Powder PCH and Lewatite S-100) resulted in the formation of mainly sulfate and dissolved organic carbon. High-performance liquid chromatography analysis indicated the presence of oxalate, contributing to 10 to 20% of the organic carbon. The identity of the remainder is unknown. The presence of oxalate as a complexant is consistent with results from earlier work. Complexation studies with Cu2+ and Ni2+ showed the presence of two ligands: oxalate and ligand X. Although ligand X could not be identified, it could be characterized by its concentration ([X]T ∼ 10-5 to 10-6 M), a deprotonation constant (pKH approximately 7.4 at I = 0.1 M), and a complexation constant for the NiX complex (log KNiXapproximately 7.0 at I = 0.1 M). In the absence of irradiation, no evidence for the formation of ligands was found

  9. Isotopic and chemical characterization of coastal and submarine karstic groundwater discharges in southern Turkey

    International Nuclear Information System (INIS)

    This study aims to determine the sites of SGD and their physical, chemical and isotopic properties along a 100 km long coastal zone in southwestern Turkey. The aquifer feeding coastal and submarine SGDs comprises of well karstified Mesozoic carbonate massifs that extends from coast to more than 100 km inland. The carbonate massif forms a rugged topography stretching from sea level to over 3000 m. Systematic search dives for every metre of coastal zone down to 30 m below sea level were carried out for precise determination of SGDs. Majority of karstic SGDs were found to be point wise outflows through cracks and submarine caves rather than being spatially dispersed discharges. Comparison of SGD locations detected by means of search dives with those inferred from thermal/infrared satellite images and lineament analyses revealed that systematic screening of coastal zone by divers is essential to determine all existing SGDs. Visual disturbance caused by halocline and temperature gradient felt by diver's skin were the most effective tools to locate SGDs. Stable isotope (18O and 2H) and specific electrical conductivity (SEC) data gathered from SGDs in summer and autumn revealed a freshwater contribution rate ranging from 20% to 80%. Autumn samples which had more depleted stable isotopic signal were found to have relatively high freshwater contribution based on SEC. This suggests apparently higher SGD rate in autumn while precipitation to meet such increase has not occurred. Samples from fresh groundwater indicated a local deuterium excess value of +14 which is typical of research area and neighboring coastal zone. SGDs are located fairly well along a freshwater-seawater mixing line that intersects meteoric line around -6 per mille and -30 per mille for O-18 and H-2, respectively. Tritium composition of SGDs ranges between 0 TU and 4.5 TU and is not correlated with mixing ratio. This implies that freshwater components of different SGDs have different residence times. High

  10. Chemical and isotopic study of extraterrestrial particles from the ocean floor

    International Nuclear Information System (INIS)

    We report chemical, mineralogic and Rb-Sr data on deep-sea spherules and on particles from an Antarctic Ocean core in which an excess Ir content has been identified. 87Sr/86Sr compositions in the deep-sea spherules are determined to 1-2% and are in the range 0.730-0.757. The 87Sr/86Sr compositions and the Sr concentrations are in the range observed for the majority of chondritic meteorites. 84Sr/88Sr ratios are normal to within 1%. Extreme depletion of Rb relative to the chondritic abundance is found in the deep-sea spherules. These data support the inference based on chemical composition and mineralogy that the deep-sea spherules are produced by the ablation or heating of meteroroids in the Earth's atmosphere with substantial loss of Rb by volatilization. Most terrestrial sources for the deep-sea spherules can be excluded, based on the chemical composition and on the Sr isotopic composition. The results on vesicular, Ir-rich particles from the Antarctic Ocean core give 87Sr/86Sr in the range 0.703-0.705 and within the range observed for ocean island basalts but significantly above mid-ocean ridge basalts (MORB). A crystalline basaltic particle from this core shows non-radiogenic 87Sr/86Sr=0.701 +- 0.001, in the range observed for MORB and basaltic achondrites. The Sr data on the vesicular particles do not provide positive support for an extraterrestrial provenance for these materials. The basaltic particles cannot be reasonably be the primary source of high Ir concentration and some other lithic component remains to be identified. (orig.)

  11. Kinetic bottlenecks to chemical exchange rates for deep-sea animals – Part 1: Oxygen

    Directory of Open Access Journals (Sweden)

    E. T. Peltzer

    2012-10-01

    Full Text Available Ocean warming will reduce dissolved oxygen concentrations which can pose challenges to marine life. Oxygen limits are traditionally reported simply as a static concentration thresholds with no temperature, pressure or flow rate dependency. Here we treat the oceanic oxygen supply potential for heterotrophic consumption as a dynamic molecular exchange problem analogous to familiar gas exchange processes at the sea surface. A combination of the purely physico-chemical oceanic properties temperature, hydrostatic pressure, and oxygen concentration defines the ability of the ocean to supply oxygen to any given animal. This general oceanic oxygen supply potential is modulated by animal specific properties such as the diffusive boundary layer thickness to define and limit maximal oxygen supply rates. Here we combine all these properties into formal, mechanistic equations defining novel oceanic properties that subsume various relevant classical oceanographic parameters to better visualize, map, comprehend, and predict the impact of ocean deoxygenation on aerobic life. By explicitly including temperature and hydrostatic pressure into our quantities, various ocean regions ranging from the cold deep-sea to warm, coastal seas can be compared. We define purely physico-chemical quantities to describe the oceanic oxygen supply potential, but also quantities that contain organism-specific properties which in a most generalized way describe general concepts and dependencies. We apply these novel quantities to example oceanic profiles around the world and find that temperature and pressure dependencies of diffusion and partial pressure create zones of greatest physical constriction on oxygen supply typically at around 1000 m depth, which coincides with oxygen concentration minimum zones. In these zones, which comprise the bulk of the world ocean, ocean warming and deoxygenation have a clear negative effect for aerobic life. In some shallow and warm waters the

  12. Short and long term chemical and isotopic variations of Lake Trasimeno (Italy)

    Science.gov (United States)

    Frondini, Francesco; Dragoni, Walter; Chiodini, Giovanni; Caliro, Stefano; Cardellini, Carlo; Donnini, Marco; Morgantini, Nicola

    2016-04-01

    Lake Trasimeno, located in Umbria (central Italy), is a shallow lake of a remarkable naturalistic interest and a significant resource for the economy of the region (Ludovisi and Gaino, 2010; Dragoni, 2004). The Lake Trasimeno has an average area of about 124 km2 with a maximum depth of approximately 5.5 m, has no natural outlet and the volume of water stored is strictly linked to rainfall. In order to limit water level variations in 1898 an efficient outlet was built. At present the water exits from the Lake only when the level reaches a fixed threshold above the outlet channel, so during periods with low precipitation the evaporation becomes the most relevant output from the lake. For instance, between 1989 and 2013 the outlet did not work, and the maximum depth of the lake was reduced to little more than three meters. In the framework of climate change, it is important to understand the changes that could affect Lake Trasimeno in the near future. To this aim it is necessary to individuate the long term trends of the hydrologic, chemical and physical characteristics of the Trasimeno water and distinguish them from the short term variations. At the present it is available a long record of hydrologic data allowing reliable studies on quantitative variations at Lake Trasimeno (Dragoni et al., 2015; Dragoni et al., 2012; Ludovisi and Gaino, 2010), but the definition of the chemical and isotopic trends of lake water it is still a problematic task. On the basis of new chemical and isotopic data, collected from 2006 to 2015, it is possible to observe (i) short term and/or very short (seasonal) variations in temperature, salinity and saturation state with respect to carbonate minerals and a long term trends in isotopic composition of water and total load of mobile species (Cl, Na). The short term variations readily respond to the precipitation regime and are strongly related to lake level; the long term trend is probably related to the progressive increase of near

  13. Tracing amino acid exchange during host-pathogen interaction by combined stable-isotope time-resolved Raman spectral imaging

    Science.gov (United States)

    Naemat, Abida; Elsheikha, Hany M.; Boitor, Radu A.; Notingher, Ioan

    2016-02-01

    This study investigates the temporal and spatial interchange of the aromatic amino acid phenylalanine (Phe) between human retinal pigment epithelial cell line (ARPE-19) and tachyzoites of the apicomplexan protozoan parasite Toxoplasma gondii (T. gondii). Stable isotope labelling by amino acids in cell culture (SILAC) is combined with Raman micro-spectroscopy to selectively monitor the incorporation of deuterium-labelled Phe into proteins in individual live tachyzoites. Our results show a very rapid uptake of L-Phe(D8) by the intracellular growing parasite. T. gondii tachyzoites are capable of extracting L-Phe(D8) from host cells as soon as it invades the cell. L-Phe(D8) from the host cell completely replaces the L-Phe within T. gondii tachyzoites 7-9 hours after infection. A quantitative model based on Raman spectra allowed an estimation of the exchange rate of Phe as 0.5-1.6 × 104 molecules/s. On the other hand, extracellular tachyzoites were not able to consume L-Phe(D8) after 24 hours of infection. These findings further our understanding of the amino acid trafficking between host cells and this strictly intracellular parasite. In particular, this study highlights new aspects of the metabolism of amino acid Phe operative during the interaction between T. gondii and its host cell.

  14. Contribution to the study of isotopic exchange of oxygen between nickel oxide and the gases arising from the oxidation reaction of carbon monoxide

    International Nuclear Information System (INIS)

    The 3 isotopic reactions of oxygen: C18O + Ni16O ↔ C16O + Ni18O, 16O18O + Ni16O ↔ 16O2 + Ni18O, and C16O18O + Ni16O ↔ C16O2 + Ni18O between CO, CO2, O2 and NiO are studied using a mass spectrometer. The isotopic gaseous mixtures are prepared from oxygen-18 enriched water. A first order kinetic law has been found for these reactions in the gaseous phase, and the activation energies have been determined. Only CO and CO2 exchange oxygen, at room temperature, but only with part of the oxide surface. Gaseous O2 reacts with the whole surface at 250 C, the slow step of the exchange process, in the gaseous phase, being certainly the mobility of oxygen ions on the surface of NiO. (author)

  15. On the basic substances used in the separation process by isotope exchange H2S - H2O, at two temperatures, in view of producing heavy water

    International Nuclear Information System (INIS)

    In view of producing heavy water, the influence of the deuterium proportion in the basic substances, on the efficiency of the isotope exchange process H2S - H2O for two temperatures was studied. Heavy water is extracted from ordinary water and concentrated from 0.014 per cent to 5-15 per cent D2O by isotope bithermal exchange with the hydrogen sulphite. Theoretical and experimental research was carried out in laboratories and then applied on a pilot plant by designing and testing a drying equipment for hydrogen sulphite. The maximum H2S concentration rose to 99.84 per cent. The purity of the hydrogen sulphite resulting from the pilot plant, as well as the optimization of the installation for producing H2S depending on the deuterium distribution, make sure that the two methods for the preparation of sodium sulphite and hydrogen sulphite can be applied in industry. (author)

  16. Sm isotope composition and Sm/Eu ratio determination in an irradiated 153Eu sample by ion exchange chromatography-quadrupole inductively coupled plasma mass spectrometry combined with double spike isotope dilution technique

    International Nuclear Information System (INIS)

    Within the framework of the research undertaken by the French Atomic Energy Commission on transmutation of long-lived radionuclides, targets of highly enriched actinides and fission products were irradiated in the fast neutron reactor Phenix. Precise and accurate measurements of the isotopic and elemental composition of the enriched elements are therefore required. In order to obtain the uncertainties of several per mil and to reduce handling time and exposure to analyst on radioactive material, the on-line coupling of ion exchange chromatography with quadrupole inductively coupled plasma mass spectrometry has been associated with the technique of the double spike isotope dilution. We present in this paper the results obtained on an irradiated sample of Europium oxide powder (enriched at 99.13% in 153Eu). After irradiation of around 5 mg of Eu2O3 powder the theoretical calculations predict the formation of several micrograms of gadolinium and samarium isotopes. In relation to the very high activity of the sample after irradiation and the very low quantity of Sm formed, the on-line ion exchange chromatography separation of Gd, Sm and Eu before Sm isotope ratio measurements has been developed for the quantification of the 152Sm/153Eu ratio. These on-line measurements were associated with the double spike isotope dilution technique after calibration of a 147Sm/151Eu spike solution. The external reproducibility of Sm isotopic ratios was determined to be around 0.5% (2 σ) resulting in a final uncertainty on the 152Sm/153Eu ratio of around 1% (2 σ). These on-line measurements present therefore a robust and high-throughput alternative to the thermal-ionisation mass spectrometry technique used so far in combination with off-line chromatographic separation, particularly in nuclear applications where characterisation of high activity sample solutions is required. (authors)

  17. The radiometric analysis of non-radioactive materials by chemical exchange

    International Nuclear Information System (INIS)

    The use of radioisotopes to measure the composition of different materials via chemical exchange within an instrument is described. The product of the reaction is a radioactive gas which is counted and serves as the indicator of measurement. This method has been applied to a number of different liquids and gases for their specific and sensitive determination. The chief limiting condition on sensitivity is imposed by the specific activity of the radiochemical component. Where high specific activities are available, sensitivity in terms of chemical quantity will be very great. The recent development of quinol- Kr85 clathrate compounds has provided a basic radiochemical source which not only provides high specific activities at low cost but also excellent half-life and energy characteristics. These clathrate compounds can be oxidized only by very strong oxidizing agents, such as ozone to release Kr85. When coupled with a salt, such as sodium chlorite, the sensing of reducing materials such as SO2 may be accomplished. Two applications of the radiometric technique employing clathrates are described. The first is the development of a balloon-borne sonde for the meteorological analysis of ozone in the upper atmosphere. The other is its use in air pollution and process control work in the form of a portable analyser. Different gases may be analysed by this device by merely changing the radiochemical reaction cell. (author)

  18. A new experimental facility for the investigation of hydrogen isotopes permeation through heat exchanger tubes with sweep gas intermediate circuit under nuclear conditions

    International Nuclear Information System (INIS)

    In this work a new experimental facility is presented to study the permeation of hydrogen isotopes (tritium and protium) through heat exchanger tubes with sweep gas intermediate circuit under process gas conditions. Beside temperature and pressure dependant measurements to determine the permeation data of Incoloy 800 H double wall tubes further parameter investigations have been made to study the action of a sweep gas circuit against hydrogen permeation. The experimental results show that the obtained impending factor could be destinctly increased. (orig.)

  19. Processes affecting the stable isotope composition of calcite during precipitation on the surface of stalagmites: Laboratory experiments investigating the isotope exchange between DIC in the solution layer on top of a speleothem and the CO2 of the cave atmosphere

    Science.gov (United States)

    Dreybrodt, Wolfgang; Hansen, Maximilian; Scholz, Denis

    2016-02-01

    We present a theoretical derivation of the exchange time, τex, needed to establish isotopic equilibrium between atmospheric CO2 in a cave and HCO3- dissolved in a thin water film covering the surface of a speleothem. The result is τex = τredex · [HCO3-]/ (KH · pCO2 cave) , where τredex depends on the depth, a, of the water film and on temperature. [HCO3-] is the concentration of bicarbonate, pCO2 cave the partial pressure of CO2, and KH is Henry's constant. To test the theory we prepared stagnant or flowing thin films of a NaHCO3 solution and exposed them at 20 °C to an CO2 containing atmosphere of pCO2 500, 12,500, or 25,000 ppmV and defined isotope composition. The δ13C and δ18O values of the DIC in the solution were measured as a function of the exposure time. For stagnant films with depths between 0.06 and 0.2 cm the δ13C values exhibit an exponential approach towards isotope equilibrium with the atmospheric CO2 with exchange time, τex. The δ18O values first evolve towards isotopic equilibrium with atmospheric CO2, reach a minimum value and then drift away from the isotopic equilibrium with atmospheric CO2 approaching a steady state caused by isotopic exchange of oxygen with water. The experimental findings are in satisfactory agreement with the theoretical predictions. To further investigate isotope evolution in cave analogue conditions, a water film containing 5 mmol/L of NaHCO3 with a depth of 0.013 cm flowing down an inclined borosilicate glass plate was exposed to an atmosphere with pCO2 = 500 ppmV at a temperature of 20 °C. The δ13C and δ18O values were measured as a function of flow (exposure) time, t. The isotope compositions in the DIC of the water film decrease linear in time by δDIC (t) =δDIC (0) - (δDIC (0) -δDIC (∞)) · t /τex where δDIC (0) is the initial isotope composition of dissolved inorganic carbon (DIC) in the water film and δDIC (∞) its final value. From these data an exchange time τex of ca. 7000 s was obtained

  20. Isotopic and chemical studies of groundwater in the Llanura Tucumana geothermal area; Tucuman, Argentina

    International Nuclear Information System (INIS)

    The Llanura Tucumana extends along the eastern Andean margin, between 27oS-28oS and 64o50'W- 65o40'W. It is a structural depression infilled by a thick sedimentary sequence, as shown by the preliminary geophysical studies (Pomposiello, et al., 1991, 2000; Favetto et al. 2000). It is bounded to the west by the Nevados del Aconquija (5500m) and the Sierra de Guasayan (600m) at east. Both ranges are part of the Sierras Pampeanas System. The southern part of this plain is an important thermal area, which is known through surface manifestations and drilled wells. There are a great quantity of artesian wells with discharge water at temperatures that oscillate between 30oC and 50oC. The Aconquija System is a climatic barrier for the humid east winds. The precipitation is torrential with intense and short time storms, mainly in summer. The rain amount decreases gradually to the SE, from 1200 to 800mm and it is 600mm near the Rio Hondo Dam area. The mean January temperature is 26.7oC and the coldest month is July with 12.9oC. This paper presents the isotopic and chemical results and a first approach for the origin and circulation pattern of water (au)

  1. Gases in Taiwan mud volcanoes: Chemical composition, methane carbon isotopes, and gas fluxes

    International Nuclear Information System (INIS)

    Mud volcanoes are important pathways for CH4 emission from deep buried sediments; however, the importance of gas fluxes have hitherto been neglected in atmospheric source budget considerations. In this study, gas fluxes have been monitored to examine the stability of their chemical compositions and fluxes spatially, and stable C isotopic ratios of CH4 were determined, for several mud volcanoes on land in Taiwan. The major gas components are CH4 (>90%), 'air' (i.e. N2 + O2 + Ar, 1-5%) and CO2 (1-5%) and these associated gas fluxes varied slightly at different mud volcanoes in southwestern Taiwan. The Hsiao-kun-shui (HKS) mud volcano emits the highest CH4 concentration (CH4 > 97%). On the other hand, the Chung-lun mud volcano (CL) shows CO2 up to 85%, and much lower CH4 content (4 content (>90%) with low CO2 (1 (methane)/C2 (ethane) + C3 (propane) and δ13CCH4 results, with the exception of mud volcanoes situated along the Gu-ting-keng (GTK) anticline axis showing unique biogenic characteristics. Only small CH4 concentration variations, 4 emission fluxes for mud volcanoes on land in Taiwan fall in a range between 980 and 2010 tons annually. If soil diffusion were taken into account, the total amount of mud volcano CH4 could contribute up to 10% of total natural CH4 emissions in Taiwan.

  2. Isotopic exchange on the diurnal scale between near-surface snow and lower atmospheric water vapor at Kohnen station, East Antarctica

    Science.gov (United States)

    Ritter, François; Steen-Larsen, Hans Christian; Werner, Martin; Masson-Delmotte, Valérie; Orsi, Anais; Behrens, Melanie; Birnbaum, Gerit; Freitag, Johannes; Risi, Camille; Kipfstuhl, Sepp

    2016-07-01

    Quantifying the magnitude of post-depositional processes affecting the isotopic composition of surface snow is essential for a more accurate interpretation of ice core data. To achieve this, high temporal resolution measurements of both lower atmospheric water vapor and surface snow isotopic composition are required. This study presents continuous measurements of water vapor isotopes performed in East Antarctica (Kohnen station) from December 2013 to January 2014 using a laser spectrometer. Observations have been compared with the outputs of two atmospheric general circulation models (AGCMs) equipped with water vapor isotopes: ECHAM5-wiso and LMDZ5Aiso. During our monitoring period, the signals in the 2 m air temperature T, humidity mixing ratio q and both water vapor isotopes δD and δ18O are dominated by the presence of diurnal cycles. Both AGCMs simulate similar diurnal cycles with a mean amplitude 30 to 70 % lower than observed, possibly due to an incorrect simulation of the surface energy balance and the boundary layer dynamics. In parallel, snow surface samples were collected each hour over 35 h, with a sampling depth of 2-5 mm. A diurnal cycle in the isotopic composition of the snow surface is observed in phase with the water vapor, reaching a peak-to-peak amplitude of 3 ‰ for δD over 24 h (compared to 36 ‰ for δD in the water vapor). A simple box model treated as a closed system has been developed to study the exchange of water molecules between an air and a snow reservoir. In the vapor, the box model simulations show too much isotopic depletion compared to the observations. Mixing with other sources (advection, free troposphere) has to be included in order to fit the observations. At the snow surface, the simulated isotopic values are close to the observations with a snow reservoir of ˜ 5 mm depth (range of the snow sample depth). Our analysis suggests that fractionation occurs during sublimation and that vapor-snow exchanges can no longer be

  3. NMR stratagems for the study of multiple kinetic hydrogen/deuterium isotope effects of proton exchange. Example: Di-p-fluorophenylformamidine/THF

    International Nuclear Information System (INIS)

    Stratagems are presented for the determination of kinetic isotope effects of proton exchange reactions by dynamic NMR spectroscopy. In such experiments, lineshape analyses and/or polarization transfer experiments are performed on the exchanging protons or deuterons as well as on remote spins, as a function of the deuterium fraction in the mobile proton sites. These methods are NMR analogs of previous proton inventory techniques involving classical kinetic methods. A theory is developed in order to derive the kinetic isotope effects as well as the number of transferred protons from the experimental NMR spectra. The technique is then applied to the problem of proton exchange in the system 15N, 15N'-di-p-fluorophenylformamidine, a nitrogen analog of formic acid, dissolved in tetrahydrofuran-d8 (THF). DFFA forms two conformers in THF to which s-trans and s-cis structures have been assigned. Only the s-trans conformer is able to dimerize and exchange protons. Lineshape simulations and magnetization transfer experiments were carried out at 189,2 K, at a concentration of 0.02 mol l-1, as a function of the deuterium fraction D in the 1H-15N sites. Using 1H NMR spectroscopy, a linear dependence of the inverse proton lifetimes on D was observed. From this it was concluded that two protons are transported in the rate limiting step of the proton exchange. This result is expected for a double proton transfer in an s-trans dimer with a cyclic structure. The full kinetic HH/HD/DD isotope effects of 233:11:1 at 189 K were determined through 19F NMR experiments on the same samples. The deviation from the rule of geometric mean, although substantial, is much smaller than found in previous studies of intramolecular HH transfer reactions. Possible causes of this effect are discussed. (orig.)

  4. The chemical composition of red giants in 47 Tucanae. II. Magnesium isotopes and pollution scenarios

    CERN Document Server

    Thygesen, A O; Ludwig, H -G; Ventura, P; Yong, D; Collet, R; Christlieb, N; Melendez, J; Zaggia, S

    2016-01-01

    The phenomenon of multiple populations in globular clusters is still far from understood, with several proposed mechanisms to explain the observed behaviour. The study of elemental and isotopic abundance patterns are crucial for investigating the differences among candidate pollution mechanisms. We derive magnesium isotopic ratios for 13 stars in the globular cluster 47 Tucanae (NGC 104) to provide new, detailed information about the nucleosynthesis that has occurred within the cluster. For the first time, the impact of 3D model stellar atmospheres on the derived Mg isotopic ratios is investigated. Using both tailored 1D atmospheric models and 3D hydrodynamical models, we derive magnesium isotopic ratios from four features of MgH near 5135{\\AA} in 13 giants near the tip of the RGB, using high signal-to-noise, high-resolution spectra. We derive the magnesium isotopic ratios for all stars and find no significant offset of the isotopic distribution between the pristine and the polluted populations. Furthermore, ...

  5. Chemical and isotopic evolution of a layered eastern U.S. snowpack and its relation to stream-water composition

    Science.gov (United States)

    Shanley, J.B.; Kendall, C.; Albert, M.R.; Hardy, J.P.

    1995-01-01

    The chemical, isotopic, and morphologic evolution of a layered snowpack was investigated during the winter of 1993-94 at Sleepers River Research Watershed in Danville, Vermont. The snowpack was monitored at two small basins: a forested basin at 525 m elevation, and an agricultural basin at 292 m elevation. At each site, the snowpack morphology was characterized and individual layers were sampled seven times during the season. Nitrate and 8d18O profiles in the snowpack remained relatively stable until peak accumulation in mid-March, except near the snow surface, where rain-on-snow events caused water and nitrate movement down to impeding ice layers. Subsequently, water and nitrate moved more readily through the ripening snowpack. As the snowpack evolved, combined processes of preferential ion elution, isotopic fractionation, and infiltration of isotopically heavy rainfall caused the pack to become depleted in solutes and isotopically enriched. The release of nitrate and isotopically depleted water was reflected in patterns of nitrate concentrations and ??18O of meltwater and stream water. Results supported data from the previous year which suggested that streamflow in the forested basin during snowmelt was dominated by groundwater discharge.

  6. Efficient Total Chemical Synthesis of (13) C=(18) O Isotopomers of Human Insulin for Isotope-Edited FTIR.

    Science.gov (United States)

    Dhayalan, Balamurugan; Fitzpatrick, Ann; Mandal, Kalyaneswar; Whittaker, Jonathan; Weiss, Michael A; Tokmakoff, Andrei; Kent, Stephen B H

    2016-03-01

    Isotope-edited two-dimensional Fourier transform infrared spectroscopy (2 D FTIR) can potentially provide a unique probe of protein structure and dynamics. However, general methods for the site-specific incorporation of stable (13) C=(18) O labels into the polypeptide backbone of the protein molecule have not yet been established. Here we describe, as a prototype for the incorporation of specific arrays of isotope labels, the total chemical synthesis-via a key ester insulin intermediate-of 97 % enriched [(1-(13) C=(18) O)Phe(B24) ] human insulin: stable-isotope labeled at a single backbone amide carbonyl. The amino acid sequence as well as the positions of the disulfide bonds and the correctly folded structure were unambiguously confirmed by the X-ray crystal structure of the synthetic protein molecule. In vitro assays of the isotope labeled [(1-(13) C=(18) O)Phe(B24) ] human insulin showed that it had full insulin receptor binding activity. Linear and 2 D IR spectra revealed a distinct red-shifted amide I carbonyl band peak at 1595 cm(-1) resulting from the (1-(13) C=(18) O)Phe(B24) backbone label. This work illustrates the utility of chemical synthesis to enable the application of advanced physical methods for the elucidation of the molecular basis of protein function. PMID:26715336

  7. Chemical and isotopic properties and origin of coarse airborne particles collected by passive samplers in industrial, urban, and rural environments

    Science.gov (United States)

    Guéguen, Florence; Stille, Peter; Dietze, Volke; Gieré, Reto

    2012-12-01

    Passive air samplers have been installed in industrial, urban, rural and remote forested environments in order to collect coarse airborne particles for subsequent chemical characterization. To identify principal polluting sources, isotopic tracers, such as Sr, Nd and Pb isotopic ratios, have been used. The mass deposition rates (MDRs) of trace metals, determined for each of the studied environments, clearly indicate that industrial and traffic sites are especially affected by air pollution. Elements such as V, Pb, Fe, Cr, Co, Mo, Cd, Ni, As, Sb and Zn are notably enriched in samples from industrial zones, whereas V, Mn, Ba, Sr, Al, U, Th, rare earth elements (REE), Zr, Y, Cs, Rb, Sb, Sn and Cu are principal components of the airborne particles collected close to areas influenced by heavy traffic. The chemical/isotopic baseline composition derived from the airborne particles is the result of mixing of particles from different industrial sources, traffic and fertilizers. The monthly analysis of trace-metal MDRs of the collected airborne particle samples from different stations around the industrial zone allows for the detection of distinct atmospheric dust-deposition events during the year, characterized by high MDRs. "Natural" dusts from regional soil re-suspension, including from more distant regions like the Sahara desert, might overprint the regional atmospheric baseline composition, as suggested by trace metal trajectories in ternary diagrams and by Sr, Nd and Pb isotope data.

  8. Investigation of geothermal fields in himalayan range in pakistan using isotope and chemical techniques

    International Nuclear Information System (INIS)

    /sub 4/-H/sub 2/O) geothermometer indicates equilibrium temperatures around 150 degree C. For the Tato springs, the isotope and chemical geothermometers (except for the K-Mg) agree on equilibrium temperature of about 170-200 degree C. Thermal waters of Kotli are immature having meteoric origin. They are of sodium bicarbonate type. The thermal water seems to be young or significant component of fresh water is mixing. Reservoir temperatures estimated by K-Mg and Na-K-Ca-Mg thermometers have similar range (122-l25 degree C). Geothermometer based on dissolved silica gives reservoir temperature about 100 degree C. (author)

  9. Carbon and oxygen isotope separation by plasma chemical reactions in carbon monoxide glow discharge

    International Nuclear Information System (INIS)

    The separation of carbon and oxygen isotopes in CO glow discharge has been studied. The isotope enrichment in the products was measured by quadru-pole mass spectrometer. The reaction yield and empirical formula of solid phase products were determined by the gas-volumetric analysis. The stable products obtained in our experiment are CO2 and solid polymers formed on the discharge wall. The polymer consists of both carbon and oxygen and the oxygen/carbon mole ratio in the polymer is 0.35±0.05. Thi isotope enrichment coefficients show a strong negative dependence on discharge current though the relative reaction yields have an opposite tendency. Consequently, the maximum isotope enrichment coefficients for 13C in wall deposit of 2.31 and for 18O in CO2 of 1.37 are obtained when the discharge current and the reaction yields are minimum in our experimental range. The experimental results of isotope enrichment have been compared with theoretical values estimated by an analytical model of literature. The dilution mechanism of the isotope enrichment of stable products is inferred from the isotopic distributions of 13C and 18O in products and theoretical predictions for isotope enrichment. (author)

  10. Chemical weathering of granitic rocks: an experimental approach and Pb-Li isotope tracing

    International Nuclear Information System (INIS)

    In order to characterize water-rock interactions in granite, we performed laboratory experiments and Pb-Li isotope tracing. The aim of the present work is to better constrain the processes of water-rock interactions, both in terms of source and extent of weathering, by measuring major and trace elements, as well as Pb and Li isotope signatures. (authors)

  11. Chemical exchange saturation transfer MR imaging of Parkinson's disease at 3 Tesla

    International Nuclear Information System (INIS)

    To demonstrate the feasibility of using chemical exchange saturation transfer (CEST) imaging to detect Parkinson's disease (PD) in patients at 3 Tesla. Twenty-seven PD patients (17 men and 10 women; age range, 54-77 years) and 22 age-matched normal controls (13 men and 9 women; age range, 55-73 years) were examined on a 3-Tesla MRI system. Magnetization transfer spectra with 31 different frequency offsets (-6 to 6 ppm) were acquired at two transverse slices of the head, including the basal ganglia and midbrain. One-way analysis of variance tests was used to compare the differences in CEST imaging signals between PD patients and normal controls. Total CEST signal between the offsets of 0 and 4 ppm in the substantia nigra was significantly lower in PD patients than in normal controls (P = 0.006), which could be associated with the loss of dopaminergic neurons. Protein-based CEST imaging signals at the offset of 3.5 ppm in the globus pallidus, putamen and caudate were significantly increased in PD patients, compared to normal controls (P < 0.001, P = 0.003, P < 0.001, respectively). CEST imaging signals could potentially serve as imaging biomarkers to aid in the non-invasive molecular diagnosis of PD. (orig.)

  12. Exchange repulsive potential adaptable for electronic structure changes during chemical reactions

    International Nuclear Information System (INIS)

    Hybrid methods combining quantum mechanical (QM) and classical calculations are becoming important tools in chemistry. The popular approach to calculate the interaction between QM and classical calculations employs interatomic potentials. In most cases, the interatomic potential is constructed of an electrostatic (ES) potential and a non-ES potential. Because QM treatment is employed in the calculation of the ES potential, the electronic change can be considered in this ES potential. However, QM treatment of the non-ES potential is difficult because of high computational cost. To overcome this difficulty of evaluating the non-ES potential, we proposed an exchange repulsive potential as the main part of the non-ES potential on the basis of a QM approach. This potential is independent of empirical parameters and adaptable for electronic structure. We combined this potential with the reference interaction site model self-consistent field explicitly including spatial electron density distribution and successfully applied it to the chemical reactions in aqueous phase

  13. Chemical exchange saturation transfer MR imaging of Parkinson's disease at 3 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chunmei; Peng, Shuai; Wang, Rui; Chen, Min [Beijing Hospital, Department of Radiology, Beijing (China); Chen, Haibo; Su, Wen [Beijing Hospital, Department of Neurology, Beijing (China); Zhao, Xuna [Peking University, Center for MRI Research and Beijing City Key Lab for Medical Physics and Engineering, Beijing (China); Zhou, Jinyuan [Johns Hopkins University, Department of Radiology, Baltimore, MD (United States)

    2014-10-15

    To demonstrate the feasibility of using chemical exchange saturation transfer (CEST) imaging to detect Parkinson's disease (PD) in patients at 3 Tesla. Twenty-seven PD patients (17 men and 10 women; age range, 54-77 years) and 22 age-matched normal controls (13 men and 9 women; age range, 55-73 years) were examined on a 3-Tesla MRI system. Magnetization transfer spectra with 31 different frequency offsets (-6 to 6 ppm) were acquired at two transverse slices of the head, including the basal ganglia and midbrain. One-way analysis of variance tests was used to compare the differences in CEST imaging signals between PD patients and normal controls. Total CEST signal between the offsets of 0 and 4 ppm in the substantia nigra was significantly lower in PD patients than in normal controls (P = 0.006), which could be associated with the loss of dopaminergic neurons. Protein-based CEST imaging signals at the offset of 3.5 ppm in the globus pallidus, putamen and caudate were significantly increased in PD patients, compared to normal controls (P < 0.001, P = 0.003, P < 0.001, respectively). CEST imaging signals could potentially serve as imaging biomarkers to aid in the non-invasive molecular diagnosis of PD. (orig.)

  14. Isotopic and chemical composition of waters and gases from the east coast accretionary prism, New Zealand

    International Nuclear Information System (INIS)

    Gases and saline waters discharges from springs and mud volcanoes along the east coast of the North Island of New Zealand provide a unique opportunity to study the evolution of fluids within an active accretionary prism. The waters show intermediate (5000 mg Cl/kg) to high (26,000 mg Cl/kg) salinities and are enriched in both deuterium (δ 2H from -20 to -2 per mille) and oxygen-18 (δ18O from +3 to 7 per mille) with respect to local groundwater. Cl/Br ratios are with 250±50 close to those of seawater (285), B/Cl ratios are higher than those of seawater (0.0003) and range from 0.003 to 0.03 at comparatively uniform Li/B ratios of 0.05 ± 0.03. Relative Na, K and Mg contents suggest close attainment of water-rock equilibrium at temperatures of 85 ± 25 deg. C. Gas geothermometers (CO2, CH4, Ar) indicate equilibration in the liquid phase at somewhat higher temperatures of 100 ± 20 deg. C. Ratios of 3He/4He in gases from the central sector reach values of 3.35 RA indicating the presence of about 40% of mantle He. Significant amounts of N2 appear to be added from other than atmospheric sources. Formation of the highest Cl water (26,000 mg Cl/kg) is explained in terms of the hydration of basalt of a subducted seamount to form chlorite or serpentine. The isotopic and chemical compositions of the waters in the subducting sediments are compatible with the assumption that they form the main source for the magmatic components of waters discharged from andesitic volcanoes and associated geothermal systems. (author). 37 refs, 9 figs, 3 tabs

  15. U-Sr isotopic speedometer: Fluid flow and chemical weatheringrates inaquifers

    Energy Technology Data Exchange (ETDEWEB)

    Maher, Kate; DePaolo, Donald J.; Christensen, John N.

    2005-12-27

    Both chemical weathering rates and fluid flow are difficultto measure in natural systems. However, these parameters are critical forunderstanding the hydrochemical evolution of aquifers, predicting thefate and transport of contaminants, and for water resources/water qualityconsiderations. 87Sr/86Sr and (234U/238U) activity ratios are sensitiveindicators of water-rock interaction, and thus provide a means ofquantifying both flow and reactivity. The 87Sr/86Sr values in groundwaters are controlled by the ratio of the dissolution rate to the flowrate. Similarly, the (234U/238U) ratio of natural ground waters is abalance between the flow rate and the dissolution of solids, andalpha-recoil loss of 234U from the solids. By coupling these two isotopesystems it is possible to constrain both the long-term (ca. 100's to1000's of years) flow rate and bulk dissolution rate along the flow path.Previous estimates of the ratio of the dissolution rate to theinfiltration flux from Sr isotopes (87Sr/86Sr) are combined with a modelfor (234U/238U) to constrain the infiltration flux and dissolution ratefor a 70-m deep vadose zone core from Hanford, Washington. The coupledmodel for both (234U/238U) ratios and the 87Sr/86Sr data suggests aninfiltration flux of 5+-2 mm/yr, and bulk silicate dissolution ratesbetween 10-15.7 and 10-16.5 mol/m2/s. The process of alpha-recoilenrichment, while primarily responsible for the observed variation in(234U/238U) of natural systems, is difficult to quantify. However, therate of this process in natural systems affects the interpretation ofmost U-series data. Models for quantifying the alpha-recoil loss fractionbased on geometric predictions, surface area constraints, and chemicalmethods are also presented. The agreement between the chemical andtheoretical methods, such as direct measurement of (234U/238U) of thesmall grain size fraction and geometric calculations for that sizefraction, is quite good.

  16. POPs and stable isotopes in killer whales and their prey (Use of chemical tracers to infer the winter diet of southern resident killer whales.)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to assess the chemical tracers (e.g., stable isotopes, patterns and ratios of persistent organic pollutants, and fatty acid profiles)...

  17. Estimating ground-water exchange with lakes using water-budget and chemical mass-balance approaches for ten lakes in ridge areas of Polk and Highlands counties, Florida

    Science.gov (United States)

    Sacks, L.A.; Swancar, Amy; Lee, T.M.

    1998-01-01

    Water budget and chemical mass-balance approaches were used to estimate ground-water exchange with 10 lakes in ridge areas of Polk and Highlands Counties, Florida. At each lake, heads were monitored in the surficial aquifer system and deeper Upper Floridan aquifer, lake stage and rainfall were measured continuously, and lakes and wells were sampled three times between October 1995 and December 1996. The water-budget approach computes net ground-water flow (ground-water inflow minus outflow) as the residual of the monthly waterbudget equation. Net ground-water flow varied seasonally at each of the 10 lakes, and was notably different between lakes, illustrating short-term differences in ground-water fluxes. Monthly patterns in net ground-water flow were related to monthly patterns of other hydrologic variables such as rainfall, ground-water flow patterns, and head differences between the lake and the Upper Floridan aquifer. The chemical mass-balance approach combines the water budget and solute or isotope mass-balance equations, and assumes steady-state conditions. Naturally occurring tracers that were analyzed for include calcium, magnesium, sodium, potassium, chloride, and bromide, the isotopes deuterium and oxygen-18. Chloride and sodium were the most successful solute tracers; however, their concentrations in ground water typically varied spatially, and in places were similar to that in lake water, limiting their sensitivity as tracers. In contrast, the isotopes were more robust tracers because the isotopic composition of ground water was relatively uniform and was distinctly different from the lake water. Groundwater inflow computed using the chemical massbalance method varied significantly between lakes, and ranged from less than 10 to more than 150 inches per year. Both water-budget and chemical mass-balance approaches had limitations, but the multiple lines of evidence gained using both approaches improved the understanding of the role of ground water in the

  18. Carbamoyl-phosphate synthetase II of the mammalian CAD protein: kinetic mechanism and elucidation of reaction intermediates by positional isotope exchange

    International Nuclear Information System (INIS)

    The kinetic mechanism of carbamoyl-phosphate synthetase II from Syrian hamster kidney cells has been determined at pH 7.2 and 37 degrees C. Initial velocity, product inhibition, and dead-end inhibition studies of both the biosynthetic and bicarbonate-dependent adenosinetriphosphatase (ATPase) reactions are consistent with a partially random sequential mechanism in which the ordered addition of MgATP, HCO3-, and glutamine is followed by the ordered release of glutamate and Pi. Subsequently, the binding of a second MgATP is followed by the release of MgADP, which precedes the random release of carbamoyl phosphate and a second MgADP. Carbamoyl-phosphate synthetase II catalyzes beta gamma-bridge:beta-nonbridge positional oxygen exchange of [gamma-18O]ATP in both the ATPase and biosynthetic reactions. Negligible exchange is observed in the strict absence of HCO3- (and glutamine or NH4+). The ratio of moles of MgATP exchanged to moles of MgATP hydrolyzed (nu ex/nu cat) is 0.62 for the ATPase reaction, and it is 0.39 and 0.16 for the biosynthetic reaction in the presence of high levels of glutamine and NH4+, respectively. The observed positional isotope exchange is suppressed but not eliminated at nearly saturating concentrations of either glutamine or NH4+, suggesting that this residual exchange results from either the facile reversal of an E-MgADP-carboxyphosphate-Gln(NH4+) complex or exchange within an E-MgADP-carbamoyl phosphate-MgADP complex, or both. In the 31P NMR spectra of the exchanged [gamma-18O]ATP, the distribution patterns of 16O in the gamma-phosphorus resonances in all samples reflect an exchange mechanism in which a rotationally unhindered molecule of [18O, 16O]Pi does not readily participate

  19. What are the instrumentation requirements for measuring the isotopic composition of net ecosystem exchange of CO2 using eddy covariance methods?

    Science.gov (United States)

    Saleska, Scott R; Shorter, Joanne H; Herndon, Scott; Jiménez, Rodrigo; McManus, J Barry; Munger, J William; Nelson, David D; Zahniser, Mark S

    2006-06-01

    Better quantification of isotope ratios of atmosphere-ecosystem exchange of CO2 could substantially improve our ability to probe underlying physiological and ecological mechanisms controlling ecosystem carbon exchange, but the ability to make long-term continuous measurements of isotope ratios of exchange fluxes has been limited by measurement difficulties. In particular, direct eddy covariance methods have not yet been used for measuring the isotopic composition of ecosystem fluxes. In this article, we explore the feasibility of such measurements by (a) proposing a general criterion for judging whether a sensor's performance is sufficient for making such measurements (the criterion is met when the contribution of sensor error to the flux measurement error is comparable to or less than the contribution of meteorological noise inherently associated with turbulence flux measurements); (b) using data-based numerical simulations to quantify the level of sensor precision and stability required to meet this criterion for making direct eddy covariance measurements of the 13C/12C ratio of CO2 fluxes above a specific ecosystem (a mid-latitude temperate forest in central Massachusetts, USA); (c) testing whether the performance of a new sensor-a prototype pulsed quantum cascade laser (QCL) based isotope-ratio absorption spectrometer (and plausible improvements thereon)-is sufficient for meeting the criterion in this ecosystem. We found that the error contribution from a prototype sensor (approximately 0.2 per thousand, 1 SD of 10 s integrations) to total isoflux measurement error was comparable to (1.5 to 2x) the irreducible 'meteorological' noise inherently associated with turbulent flux measurements above this ecosystem (daytime measurement error SD of approximately 60% of flux versus meteorological noise of 30-40% for instantaneous half-hour fluxes). Our analysis also shows that plausible instrument improvements (increase of sensor precision to approximately 0.1 per

  20. Nuclear overhauser enhancement mediated chemical exchange saturation transfer imaging at 7 Tesla in glioblastoma patients.

    Directory of Open Access Journals (Sweden)

    Daniel Paech

    Full Text Available BACKGROUND AND PURPOSE: Nuclear Overhauser Enhancement (NOE mediated chemical exchange saturation transfer (CEST is a novel magnetic resonance imaging (MRI technique on the basis of saturation transfer between exchanging protons of tissue proteins and bulk water. The purpose of this study was to evaluate and compare the information provided by three dimensional NOE mediated CEST at 7 Tesla (7T and standard MRI in glioblastoma patients. PATIENTS AND METHODS: Twelve patients with newly diagnosed histologically proven glioblastoma were enrolled in this prospective ethics committee-approved study. NOE mediated CEST contrast was acquired with a modified three-dimensional gradient-echo sequence and asymmetry analysis was conducted at 3.3 ppm (B1 = 0.7 µT to calculate the magnetization transfer ratio asymmetry (MTR(asym. Contrast enhanced T1 (CE-T1 and T2-weighted images were acquired at 3T and used for data co-registration and comparison. RESULTS: Mean NOE mediated CEST signal based on MTR(asym values over all patients was significantly increased (p<0.001 in CE-T1 tumor (-1.99 ± 1.22%, tumor necrosis (-1.36 ± 1.30% and peritumoral CEST hyperintensities (PTCH within T2 edema margins (-3.56 ± 1.24% compared to contralateral normal appearing white matter (-8.38 ± 1.19%. In CE-T1 tumor (p = 0.015 and tumor necrosis (p<0.001 mean MTR(asym values were significantly higher than in PTCH. Extent of the surrounding tumor hyperintensity was smaller in eight out of 12 patients on CEST than on T2-weighted images, while four displayed at equal size. In all patients, isolated high intensity regions (0.40 ± 2.21% displayed on CEST within the CE-T1 tumor that were not discernible on CE-T1 or T2-weighted images. CONCLUSION: NOE mediated CEST Imaging at 7 T provides additional information on the structure of peritumoral hyperintensities in glioblastoma and displays isolated high intensity regions within the CE-T1 tumor that cannot be acquired on CE-T1 or T2

  1. Preliminary geothermal model of volcanic areas in Ecuador based on chemical and isotopic investigation of thermal indicators

    International Nuclear Information System (INIS)

    Since 1986, the waters and gases of eight geothermal areas have been sampled and analysed to establish their chemical and isotopic composition. In Chachimbiro and Cuicocha 18O enrichment up to 5% and deuterium enrichment up to 20% have been observed. The isotopic variations seen in Chachimbiro could be explained by hypothetical deep geothermal water with a temperature range from 240 deg. C to surface temperature. The values observed in Cuicocha, on the other hand, are due to mixing of hot groundwater with fresh lagoon water. In other areas, the isotopic composition of the thermal waters basically corresponds to that of meteoric water falling from various altitudes ranging from 2500 to 4200 m above sea level. The Na/K ratios indicate reservoir temperatures for the chloride waters emerging in the Chachimbiro, Cuenca and Papallacta geothermal areas of approximately 240 deg. C, 210 deg. C and 200 deg. C, respectively. From the data on the Chalupas caldera it is impossible to construct any reasonable theory regarding the presence of a deep, high-temperature aquifer. Tungurahua volcano samples consist of sulphuric acid water with an isotopic composition similar to waters evaporating at about 200 deg. C. The number of samples from the Chimborazo area was too low to justify any assumptions about the thermal characteristics of the water. The waters in Tufino originate in surface aquifers modified by hot gases registering 230 deg. C on the geothermometers. (author). 24 refs, 12 figs, 1 tab

  2. Application of H2/HTO isotopic exchange method to recovery of tritium from waste water generated in spent nuclear fuel reprocessing plant

    International Nuclear Information System (INIS)

    The application of H2/HTO isotopic exchange method to the tritium recovery at reprocessing plants was investigated. The size of multiunit exchange column was evaluated numerically for the recovery of tritium from the waste water containing a main impurity, HNO3. The Pt-catalyst packed in the exchange column undergoes weak poisoning by HNO3. However, the exchange efficiency of catalyst bed η c is maintained at 0.75 even in the presence of 0.1 mol/l HNO3. As the HNO3 concentration in the waste water is estimated as the order of 10-2 mol/l, the column size is little affected by the HNO3 poisoning. The height and diameter of exchange column required for recovering 99% of tritium generated in a 4 t/d reprocessing plant (recovery efficiency ε =0.99) are evaluated as about 6m and 0.63m, respectively. When the tritium concentration in the waste gas is depleted below the environmental protection standard (ε =0.9999996), they are evaluated as about 19m and 0.57m, respectively. 9 refs., 3 figs., 3 tabs

  3. Tree-Ring Carbon Isotopic Constraints on Carbon-Water Exchanges between Atmosphere and Biosphere in Drought Regions in Northwestern China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The comparison between the carbon isotope and the index of ring width of a pine disc from the Tuomuer Peak region in Xinjiang shows that the effects of climate changes on the tree-ring growth and carbon isotopic fractionation varies with time. The reason is probably relative to the characters of climate changes and adaptability of the tree-ring growth to climate changes. The relationships between the atmospheric CO2 level and the revised d 13Cair by the tree-ring carbon isotope indicate that the carbon cycle is not in a steady state, but under a stage-change condition in this area. It also can be concluded that the ratio of CO2 from the terrestrial eco-system has increased, and the flux of CO2 exchange between the atmosphere and the biosphere was gradually increasing over the past century. In addition, the results also confirm the validity and superiority of the carbon isotope to the research of the water-use efficiency.

  4. Isotope and chemical techniques in assessing groundwater contamination from Metro Manila landfill

    International Nuclear Information System (INIS)

    The first objective of the investigations is establishing benchmark isotopic characteristics of water sources and baseline concentrations of main environmental parameters related to contamination from the landfill. Water samples were collected from the production wells and surface water in the municipalities in proximity of the landfill, in Rodriguez and in San Mateo. Stable isotope characterization of the deep groundwater and rivers shows isotopic values clustering along the LMWL with ae 18O ranging from -7.5 promille to -6.5 promille and ae 2H ranging from - 53.59 promille to -42.91. The shallow groundwater are more isotopically enriched trending towards the evaporation line, with mean ae18O and aeD values of -6.46 promille and -44.14 promille, respectively. The mean isotopic signatures of surface water, with mean ae18O of -7.19 promille and deep groundwater, with mean ae18O of -6.67 promille, in Rodriguez are significantly distinct. San Mateo groundwater appear to be more isotopically enriched, indicating recharge different from that of Rodriguez groundwater. Leachate from the landfill exhibits a distinct isotopic composition from the freshwaters, with ae18O and aeD values of -5.58 promille and -31.66 promille. The significant differences in the isotopic signatures of the different water sources in the study area would facilitate detection of contamination from leachate run-off to the surface water, and eventually, to the groundwater. Trace metals in the water samples collected, generally, were below the regulatory limits for drinking water and surface water. Results of elemental determination in the sediment samples obtained from rivers showed that aside from the major crustal elements, Zn, Cu, and Ni were also present in significant amount. (author)

  5. Isotope and chemical techniques in assessing groundwater contamination from Metro Manila landfill

    International Nuclear Information System (INIS)

    Investigations were conducted to establish benchmark isotopic characteristics of water sources and baseline concentrations of trace elements related to contamination from the Montalban landfill. Water samples were collected from the production wells and surface water in Rodriguez and in San Mateo, both in the province of Rizal. These municipalities are nearest to the Montalban landfill. Stable isotope characterization of the deep groundwater and rivers shows isotopic values clustering along the LMWL with δ18O ranging from -7.5 per mille to -6.5 per mille and δ2H ranging from -53.59 per mille to -42.91. The shallow groundwater are more isotopically enriched trending towards the evaporation line, with mean δ18O and δD values of -6.46 per mille and -44.14 per mille, respectively. The mean isotopic signatures of surface water, with mean δ18O of -7.19 per mille, and deep groundwater, with mean δ18O of -6.67 per mile, in Rodriguez are significantly distinct. San Mateo groundwater appear to be more isotopically enriched, indicating recharge different from that of Rodriguez groundwater. Leachate from the landfill exhibits a distinct isotopic composition from the freshwaters, with most enriched δD values of +5.84 per mille for the leachate run-off and +16.55 per mille in the leachate pond. The significant differences in the isotopic signatures of the different water sources in the study area facilitates detection of contamination from leachate run-off to the surface water, and eventually, to the groundwater. Trace metals in the water samples collected, generally, were below the regulatory limits for drinking water and surface water. (author)

  6. Isotope and chemical techniques in assessing groundwater contamination from Metro Manila landfill

    International Nuclear Information System (INIS)

    Investigations were conducted to establish benchmark isotopic characteristics of water sources and baseline concentrations of trace elements related to contamination from the Montalban landfill. Water samples were collected from the production wells and surface water in Rodriguez and in San Mateo, both in the province of Rizal. These municipalities are nearest to the Montalban landfill. Stable isotope characterization of the deep ground water and rivers shows isotopic values clustering along the LMWL with δ18O ranging from -7.5 per mille to -6.5 per mille and δ2H ranging from -53.59 per mille to -42.91. Shallow groundwater is isotopically enriched, trending towards the evaporation line, with mean δ18O and δD values of -6.46 per mille and -44.14 per mille, respectively, The mean isotopic signatures of surface water, with mean δ18O of -7.19 per mille, and deep groundwater, with mean δ18O of -6.67 per mille, in Rodriguez are significantly distinct. San Mateo groundwater appear to be more isotopically enriched, indicating recharge different from that of Rodriguez groundwater. Leachate from the landfill exhibits a distinct isotopic composition from the freshwaters, with most enriched δD values of +5.84 per mille for the leachate run-off and + 16.55 per mille in the leachate pond. The significant differences in the isotopic signatures of the different water sources in the study area facilitates detection of contamination from leachate run-off to surface water, and eventually, to groundwater. Trace metals in the water samples collected, generally, were below the regulatory limits for drinking water and surface water. (author)

  7. Human immunodeficiency virus-1 protease. 1. Initial velocity studies and kinetic characterization of reaction intermediates by 18O isotope exchange

    International Nuclear Information System (INIS)

    The peptidolytic reaction HIV-1 protease has been investigated by using four oligopeptide substrates, Ac-Ser-Gln-Asn-Pro-Val-Val-NH2, Ac-Arg-Ala-Ser-Gln-Asn-Tyr-Pro-Val-Val-NH2, Ac-Ser-Gln-Ser-Tyr-Pro-Val-Val-NH2, and Ac-Arg-Lys-Ile-Leu-Phe-Leu-Asp-Gly-NH2 that resemble two cleavage sites found within the naturally occurring polyprotein substrates Pr55gag and Pr160gag-pol. By use of a variety of inorganic salts, it was concluded that the peptidolytic reaction is nonspecifically activated by increasing ionic strength. V/K increased in an apparently parabolic fashion with increasing ionic strength, while V was either increased or decreased slightly. From product inhibition studies, the kinetic mechanism of the protease is either random or ordered uni-bi, depending on the substrate studied. The protease-catalyzed exchange of an atom of 18O from H218O into the re-formed substrates occurred at a rate which was 0.01-0.12 times that the forward peptidolytic reaction. The results of these studies are in accord with the formation of a kinetically competent enzyme-bound amide hydrate intermediate, the collapse of which is the rate-limiting chemical step in the reaction pathway

  8. Isotopic partitioning of net ecosystem CO2 exchange reveals the importance of methane oxidation in a boreal peatland

    Science.gov (United States)

    Hasselquist, Niles; Peichl, Matthias; Öquist, Mats; Crill, Patrick; Nilsson, Mats

    2016-04-01

    Partitioning net ecosystem CO2 exchange (NEE) into its different flux components is crucial as it provides a mechanistic framework to better assess how the terrestrial carbon cycle may respond to projected environmental change. This is especially important for northern boreal peatlands, which store approximately one-quarter of the world's soil carbon and yet at the same time are projected to experience some of the greatest environmental changes in the future. Using an experimental setup with automated chambers for measuring NEE (transparent chambers), ecosystem respiration (Reco; opaque chambers) and heterotrophic respiration (Rh; opaque chambers on vegetation-free trenched plots) in combination with continuous measurements of δ13C using near-infrared, diode-laser-based cavity-ring down spectroscopy (Picarro G1101-i analyzer), we partitioned NEE of CO2 into gross primary productivity (GPP), ecosystem respiration (Reco), heterotrophic respiration (Rh) and autotrophic respiration (Ra) using two different approaches (i.e., chamber- and isotope-based methods) in a boreal peatland in northern Sweden (Degerö). Given that δ13C was continuously measured in each chamber, we were also able to further partition Rh into soil organic matter (SOM) mineralization by saprotrophic microbes and the oxidation of methane (CH4) by methanotrophic bacteria. During the ten day measurement period (in late July 2014), the average daily NEE flux at the mire was -0.6 g C m-2 d-1. Overall, the two partitioning approaches yielded similar estimates for the different NEE component fluxes. Average daily fluxes of Rh and Ra were similar in magnitude, yet these two flux components showed contrasting diurnal responses: Ra was greatest during the day whereas there was little diurnal variation in Rh. In general, average 13C signature of CO2 efflux from the Rh chambers (-41.1 ± 0.6 ‰) was between the 13C signature of SOM (-25.8 ± 0.6 ‰) and CH4 in pore water (-69.0 ± 0.8 ‰). Assuming that

  9. Studies on thermal stability of type I and type II anion exchange resins used for separation of isotopes of boron by ion exchange chromatography

    International Nuclear Information System (INIS)

    Thermal stability of indigenously available type I and type II anion exchange resins were studied in chloride and hydroxyl forms. The results of the study indicated that the resins under study were thermally stable up to 50 deg C even when heated in an oven for 180 days and there was no appreciable loss in ion exchange capacity of the resins for boric acid. (author)

  10. Comparison of acetate turnover in methanogenic and sulfate- reducing sediments by radiolabeling and stable isotope labeling and by use of specific inhibitors: Evidence for isotopic exchange

    NARCIS (Netherlands)

    De Graaf, W.; Wellsbury, P.; Parkes, R.J.; Cappenberg, T.E.

    1996-01-01

    Acetate turnover in the methanogenic freshwater anoxic sediments of Lake Vechten, The Netherlands, and in anoxic sediments from the Tamar Estuary, United Kingdom, and the Grosser Jasmunder Bodden, Germany, the latter two dominated by sulfate reduction, was determined, Stable isotopes and radioisotop

  11. Isotopic geology

    International Nuclear Information System (INIS)

    Born from the application to geology of nuclear physics techniques, the isotopic geology has revolutionized the Earth's sciences. Beyond the dating of rocks, the tracer techniques have permitted to reconstruct the Earth's dynamics, to measure the temperatures of the past (giving birth to paleoclimatology) and to understand the history of chemical elements thanks to the analysis of meteorites. Today, all domains of Earth sciences appeal more or less to the methods of isotopic geology. In this book, the author explains the principles, methods and recent advances of this science: 1 - isotopes and radioactivity; 2 - principles of isotope dating; 3 - radio-chronological methods; 4 - cosmogenic isotope chronologies; 5 - uncertainties and radio-chronological results; 6 - geochemistry of radiogenic isotopes; 7 - geochemistry of stable isotopes; 8 - isotopic geology and dynamical analysis of reservoirs. (J.S.)

  12. Activity of the La1-xSrxMnO3 and La1-xSrxCrO3 phases in oxygen isotope exchange and oxidation of CO and CH4

    International Nuclear Information System (INIS)

    Perovskite-like manganites La1-xSrxMnO3 (x = 0, 0.3, 1) and La1-xSrxCrO3 (x = 0, 0.2) were obtained by crystallochemical method. Using dynamic-thermal method of isotopic exchange the temperature intervals of the preferred scheme of different processes in oxygen exchange on the complex oxide - gas phase interface are determined. The effect of composition of manganites and chromites on their catalytic activity in the reactions of isotopic exchange of oxygen, oxidation of carbon monoxide and methane is discussed. Manganites were shown to be more active, than chromites as in the isotopic exchange of oxygen, so in the oxidation of CO and CH4

  13. Novel Chemically Stable Er3+-Yb3+ Codopded Phosphate Glass for Ion-Exchanged Active Waveguide Devices

    Institute of Scientific and Technical Information of China (English)

    陈宝玉; 赵士龙; 胡丽丽

    2003-01-01

    A novel Er3+-Yb3+ codoped phosphate glass,which combines good chemical durability with good spectroscopic properties,is developed for the ion-exchange process.The relevant properties of this glass are presented for reference in the design and modelling of ion-exchanged active waveguide devices.The weight-loss rate of this glass is 1.45 × 10-5 g.cm-2.h-1 in boiling water,which is comparable to that of Kigre's Q-246 silicate glass.The emission cross section of Er3+ in this glass is calculated to be 0.72 × 10-20 cm2 using the McCumber theory.It is found that a planar waveguide with three modes at 632.8 nm is readily realized in this glass from our primary ion-exchange experiments.

  14. The chemical composition of red giants in 47 Tucanae. II. Magnesium isotopes and pollution scenarios

    Science.gov (United States)

    Thygesen, A. O.; Sbordone, L.; Ludwig, H.-G.; Ventura, P.; Yong, D.; Collet, R.; Christlieb, N.; Melendez, J.; Zaggia, S.

    2016-04-01

    Context. The phenomenon of multiple populations in globular clusters is still far from understood, with several proposed mechanisms to explain the observed behaviour. The study of elemental and isotopic abundance patterns are crucial for investigating the differences among candidate pollution mechanisms. Aims: We derive magnesium isotopic ratios for 13 stars in the globular cluster 47 Tucanae (NGC 104) to provide new, detailed information about the nucleosynthesis that has occurred within the cluster. For the first time, the impact of 3D model stellar atmospheres on the derived Mg isotopic ratios is investigated. Methods: Using both tailored 1D atmospheric models and 3D hydrodynamical models, we derive magnesium isotopic ratios from four features of MgH near 5135 Å in 13 giants near the tip of the red giant branch, using high signal-to-noise, high-resolution spectra. Results: We derive the magnesium isotopic ratios for all stars and find no significant offset of the isotopic distribution between the pristine and the polluted populations. Furthermore, we do not detect any statistically significant differences in the spread in the Mg isotopes in either population. No trends were found between the Mg isotopes and [Al/Fe]. The inclusion of 3D atmospheres has a significant impact on the derived 25Mg/24Mg ratio, increasing it by a factor of up to 2.5, compared to 1D. The 26Mg/24Mg ratio, on the other hand, essentially remains unchanged. Conclusions: We confirm the results seen from other globular clusters, where no strong variation in the isotopic ratios is observed between stellar populations, for observed ranges in [Al/Fe]. We see no evidence for any significant activation of the Mg-Al burning chain. The use of 3D atmospheres causes an increase of a factor of up to 2.5 in the fraction of 25Mg, resolving part of the discrepancy between the observed isotopic fraction and the predictions from pollution models. Based on observations made with the ESO Very Large Telescope

  15. Origin of the thermal waters of Stabio (Switzerland) and Sirmione (Italy) based on isotope and chemical investigations

    International Nuclear Information System (INIS)

    The study area is located in Southern Switzerland near the Swiss boundary and in Northern Italy, at the Garda Lake. The thermal waters of Stabio and Sirmione as well as the mineral water of Salo were investigated with hydrochemical and isotope methods as tritium, stable isotopes and also 36Cl, radon and uranium. The results of these investigations clearly indicate that the waters of Stabio and Sirmione have a different origin than the normal shallow groundwater of the today's meteoric water cycle. They may be linked to the deep tectonic fault zones and induced flow systems. Also its chemical composition reflects a strong influence of water rock interaction processes or of a mixing component of an original deep sedimentary brine (author)

  16. Origin of the thermal waters of Stabio (Switzerland) and Sirmione (Italy) based on isotope and chemical investigations

    International Nuclear Information System (INIS)

    The study areas are located in Southern Switzerland near the Swiss boundary to Italy and in Northern Italy, at Garda Lake. The thermal waters of Stabio and Sirmione as well as the mineral water of Salo were investigated with hydrochemical and isotopic methods in which tritium, stable isotopes as well as 36C1, Radon and Uranium were measured. The results of these investigations clearly indicate that the waters of Stabio and Sirmione have a different origin than the normal shallow groundwater arising from the present day meteoric water cycle. Both areas may be linked to deep tectonic fault zones and induced flow systems. Furthermore, its chemical composition reflects a strong influence of water rock interaction processes and/or of mixing components of original deep sedimentary brine with a shallow groundwater. Interaction with the uprising CO2 also takes place. (author)

  17. Inorganic anion exchangers for the treatment of radioactive wastes

    International Nuclear Information System (INIS)

    Inorganic anion exchangers are evaluated for Tc, I and S isotope removal from aqueous nuclear waste streams. Chemical, thermal, and radiation stabilities were examined. Selected exchangers were examined in detail for their selectivities, kinetics and mechanism of the sorption process (especially in NO3-, OH- and BO3- environments). Cement encapsulation and leaching experiments were made on the exchangers showing most promise for 'radwaste' treatment. (author)

  18. Gases in Taiwan mud volcanoes: Chemical composition, methane carbon isotopes, and gas fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Hung-Chun [Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan (China)] [Earth Dynamic System Research Center, National Cheng Kung University, Tainan, Taiwan (China); You, Chen-Feng, E-mail: cfy20@mail.ncku.edu.tw [Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan (China)] [Earth Dynamic System Research Center, National Cheng Kung University, Tainan, Taiwan (China); Sun, Chih-Hsien [Exploration and Production Research Institute, Chinese Petroleum Corporation, Taiwan (China)

    2010-03-15

    Mud volcanoes are important pathways for CH{sub 4} emission from deep buried sediments; however, the importance of gas fluxes have hitherto been neglected in atmospheric source budget considerations. In this study, gas fluxes have been monitored to examine the stability of their chemical compositions and fluxes spatially, and stable C isotopic ratios of CH{sub 4} were determined, for several mud volcanoes on land in Taiwan. The major gas components are CH{sub 4} (>90%), 'air' (i.e. N{sub 2} + O{sub 2} + Ar, 1-5%) and CO{sub 2} (1-5%) and these associated gas fluxes varied slightly at different mud volcanoes in southwestern Taiwan. The Hsiao-kun-shui (HKS) mud volcano emits the highest CH{sub 4} concentration (CH{sub 4} > 97%). On the other hand, the Chung-lun mud volcano (CL) shows CO{sub 2} up to 85%, and much lower CH{sub 4} content (<37%). High CH{sub 4} content (>90%) with low CO{sub 2} (<0.2%) are detected in the mud volcano gases collected in eastern Taiwan. It is suggestive that these gases are mostly of thermogenic origin based on C{sub 1} (methane)/C{sub 2} (ethane) + C{sub 3} (propane) and {delta}{sup 13}C{sub CH4} results, with the exception of mud volcanoes situated along the Gu-ting-keng (GTK) anticline axis showing unique biogenic characteristics. Only small CH{sub 4} concentration variations, <2%, were detected in four on-site short term field-monitoring experiments, at Yue-shi-jie A, B, Kun-shui-ping and Lo-shan A. Preliminary estimation of CH{sub 4} emission fluxes for mud volcanoes on land in Taiwan fall in a range between 980 and 2010 tons annually. If soil diffusion were taken into account, the total amount of mud volcano CH{sub 4} could contribute up to 10% of total natural CH{sub 4} emissions in Taiwan.

  19. High-capacity, selective solid sequestrants for innovative chemical separation: Inorganic ion exchange approach

    International Nuclear Information System (INIS)

    The approach of this task is to develop high-capacity, selective solid inorganic ion exchangers for the recovery of cesium and strontium from nuclear alkaline and acid wastes. To achieve this goal, Pacific Northwest Laboratories (PNL) is collaborating with industry and university participants to develop high capacity, selective, solid ion exchangers for the removal of specific contaminants from nuclear waste streams

  20. Partitioning Net Ecosystem Carbon Exchange Into net Assimilation and Respiration With Canopy-scale Isotopic Measurements: an Error Propagation Analysis With Both 13C and 18O Data

    Science.gov (United States)

    Peylin, P.; Ogee, J.; Cuntz, M.; Bariac, T.; Ciais, P.; Brunet, Y.

    2003-12-01

    Stable CO2 isotope measurements are increasingly used to partition the net CO2 exchange between terrestrial ecosystems and the atmosphere in terms of non-foliar respiration (FR) and gross photosynthesis (FA). However the accuracy of the partitioning strongly depends on the isotopic disequilibrium between these two gross fluxes and a rigorous estimation of the errors on FA and FR is needed. In this study we account and propagate uncertainties on all terms in the mass balance equations for total and "labeled" CO2 in order to get precise estimates of the errors on FA and FR. We applied our method to a maritime pine forest in the Southwest of France. Using the δ 13C-CO2 and CO2 measurements, we show that the resulting uncertainty associated to the gross fluxes can be as large as 4 æmol m-2 s-1. In addition, even if we could get more precise estimates of the isoflux and the isotopic signature of FA we show that this error would not be significantly reduced. This is because the isotopic disequilibrium between FA and FR is around 2-3‰ , i.e. the order of magnitude of the uncertainty on the isotopic signature of FR (δ R). With δ 18O-CO2 and CO2 measurements, the uncertainty associated to the gross fluxes lies also around 4 æmol m-2 s-1. On the other hand, it could be dramatically reduced if we were able to get more precise estimates of the CO18O isoflux and the associated discrimination during photosynthesis. This is because the isotopic disequilibrium between FA and FR is large, of the order of 10-15‰ , i.e. much larger than the uncertainty on δ R. The isotopic disequilibrium between FA and FR or the uncertainty on δ R vary among ecosystems and over the year. Our approach may help to choose the best strategy to study the carbon budget of a given ecosystem using stable isotopes.

  1. Radiosynthesis of [18F]fluorophenyl-L-amino acids by isotopic exchange on carbonyl-activated precursors

    International Nuclear Information System (INIS)

    Aromatic [18F]fluoroamino acids have earlier been developed as promising probes for diagnostics using PET. However, a wider use of these radiofluorinated compounds has been limited due to radiosynthetic constraints. The work here presents an amenable three-step radiosynthesis pathway for the preparation of 2-[18F]fluoro-L-phenylalanine (2-[18F]Fphe), 2-[18F]fluoro-L-tyrosine (2-[18F]Ftyr), 6-[18F]fuoro-L-m-tyrosine (6-[18F]Fmtyr) and 6-[18F]fluoro-L-DOPA (6-[18F]FDOPA). For this, corresponding precursors were 18F-fluorinated by nucleophilic isotopic exchange, followed by either removal of an activating formyl group with Rh(PPh3)3Cl or its conversion by Baeyer-Villiger oxidation, respectively, and subsequent hydrolysis of protecting groups in acidic medium. Two efficient synthetic approaches were developed for the preparation of highly functionalized fluoro-benzaldehydes and -ketones which were used as labeling precursors. The compounds (2S,5S)-tert-butyl 2-tert-butyl-5-(2-fluoro-5-formylbenzyl)-3-methyl-4-oxoimidazolidine-1 -carboxylate (1a), (2S,5S)-tert-butyl 5-(5-acetyl-2-fluorobenzyl)-2-tert-butyl-3-methyl-4-oxoimidazolidine-1 -carboxylate (1c), (2S,5S)-benzyl 2-tert-butyl-5-(2-fluoro-5-formylbenzyl)-3-methyl-4-oxoimidazolidine-1 -carbo-xylate (1d), 4-fluoro-3-(((2S,5R)-5-isopropyl-3,6-dimethoxy-2,5-dihydropyrazin-2-yl) me-thyl)b enzal-dehyde (1e) and 1-(4-fluoro-3-(((2S,5R)-5-isopropyl-3,6-dimethoxy-2,5-dihydropyrazin-2-yl) me-thy l)phenyl)ethanone (1f), could be prepared in six steps and overall yields of 41%, 48%, 37%, 27%, and 32%, respectively. (2S,5S)-tert-Butyl 5-(4-(benzyloxy)-2-fluoro-5-formylbenzyl)-2-tert-butyl-3-methyl-4 -oxoimidazolidi ne-1-carboxylate (1b) was prepared in ten steps with an overall yield of 19% while compounds (2S,5S)-tert-butyl 5-(5-(3,5-bis(trifluoromethyl)-benzoyl)-2-fluorobenzyl)-2-tert-butyl-3 -methyl-4-oxoimidazolidine-1-carboxylate (1g) and (2S,5S)-tert-butyl 2-tert-butyl-5-(2-fluoro-5-(2,2,2-trifluoroacetyl)benzyl)-3-methyl

  2. Radiosynthesis of [{sup 18}F]fluorophenyl-L-amino acids by isotopic exchange on carbonyl-activated precursors

    Energy Technology Data Exchange (ETDEWEB)

    Castillo Melean, Johnny

    2011-02-01

    Aromatic [{sup 18}F]fluoroamino acids have earlier been developed as promising probes for diagnostics using PET. However, a wider use of these radiofluorinated compounds has been limited due to radiosynthetic constraints. The work here presents an amenable three-step radiosynthesis pathway for the preparation of 2-[{sup 18}F]fluoro-L-phenylalanine (2-[{sup 18}F]Fphe), 2-[{sup 18}F]fluoro-L-tyrosine (2-[{sup 18}F]Ftyr), 6-[{sup 18}F]fuoro-L-m-tyrosine (6-[{sup 18}F]Fmtyr) and 6-[{sup 18}F]fluoro-L-DOPA (6-[{sup 18}F]FDOPA). For this, corresponding precursors were {sup 18}F-fluorinated by nucleophilic isotopic exchange, followed by either removal of an activating formyl group with Rh(PPh{sub 3}){sub 3}Cl or its conversion by Baeyer-Villiger oxidation, respectively, and subsequent hydrolysis of protecting groups in acidic medium. Two efficient synthetic approaches were developed for the preparation of highly functionalized fluoro-benzaldehydes and -ketones which were used as labeling precursors. The compounds (2S,5S)-tert-butyl 2-tert-butyl-5-(2-fluoro-5-formylbenzyl)-3-methyl-4-oxoimidazolidine-1 -carboxylate (1a), (2S,5S)-tert-butyl 5-(5-acetyl-2-fluorobenzyl)-2-tert-butyl-3-methyl-4-oxoimidazolidine-1 -carboxylate (1c), (2S,5S)-benzyl 2-tert-butyl-5-(2-fluoro-5-formylbenzyl)-3-methyl-4-oxoimidazolidine-1 -carbo-xylate (1d), 4-fluoro-3-(((2S,5R)-5-isopropyl-3,6-dimethoxy-2,5-dihydropyrazin-2-yl) me-thyl)b enzal-dehyde (1e) and 1-(4-fluoro-3-(((2S,5R)-5-isopropyl-3,6-dimethoxy-2,5-dihydropyrazin-2-yl) me-thy l)phenyl)ethanone (1f), could be prepared in six steps and overall yields of 41%, 48%, 37%, 27%, and 32%, respectively. (2S,5S)-tert-Butyl 5-(4-(benzyloxy)-2-fluoro-5-formylbenzyl)-2-tert-butyl-3-methyl-4 -oxoimidazolidi ne-1-carboxylate (1b) was prepared in ten steps with an overall yield of 19% while compounds (2S,5S)-tert-butyl 5-(5-(3,5-bis(trifluoromethyl)-benzoyl)-2-fluorobenzyl)-2-tert-butyl-3 -methyl-4-oxoimidazolidine-1-carboxylate (1g) and (2S,5S

  3. Auto-FACE: an NMR based binding site mapping program for fast chemical exchange protein-ligand systems.

    Directory of Open Access Journals (Sweden)

    Janarthanan Krishnamoorthy

    Full Text Available BACKGROUND: Nuclear Magnetic Resonance (NMR spectroscopy offers a variety of experiments to study protein-ligand interactions at atomic resolution. Among these experiments, 15N Heteronuclear Single Quantum Correlation (HSQCexperiment is simple, less time consuming and highly informative in mapping the binding site of the ligand. The interpretation of 15N HSQC becomes ambiguous when the chemical shift perturbations are caused by non-specific interactions like allosteric changes and local structural rearrangement. Under such cases, detailed chemical exchange analysis based on chemical shift perturbation will assist in locating the binding site accurately. METHODOLOGY/PRINCIPAL FINDINGS: We have automated the mapping of binding sites for fast chemical exchange systems using information obtained from 15N HSQC spectra of protein serially titrated with ligand of increasing concentrations. The automated program Auto-FACE (Auto-FAst Chemical Exchange analyzer determines the parameters, e.g. rate of change of perturbation, binding equilibrium constant and magnitude of chemical shift perturbation to map the binding site residues.Interestingly, the rate of change of perturbation at lower ligand concentration is highly sensitive in differentiating the binding site residues from the non-binding site residues. To validate this program, the interaction between the protein hBcl(XL and the ligand BH3I-1 was studied. Residues in the hydrophobic BH3 binding groove of hBcl(XL were easily identified to be crucial for interaction with BH3I-1 from other residues that also exhibited perturbation. The geometrically averaged equilibrium constant (3.0 x 10(4 calculated for the residues present at the identified binding site is consistent with the values obtained by other techniques like isothermal calorimetry and fluorescence polarization assays (12.8 x 10(4. Adjacent to the primary site, an additional binding site was identified which had an affinity of 3.8 times weaker

  4. Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

    Science.gov (United States)

    Patchett, P. J.

    1983-01-01

    The Lu-176-Hf-176 isotope method and its applications in earth sciences are discussed with regard to planetary-evolution studies. From new data on basalts from oceanic islands, Hf-176/Hf-177 and Nd-143/Nd-144 are found to display a single linear isotopic variation in the suboceanic mantle, whereas considerable divergences occur in Hf-176/Hf-177-Sr-87/Sr-86 and Nd-143/Nd-144-Sr87/Sr-86 diagrams. With the acquisition of further Hf-Sr-Nd isotopic data, these discordant Sr-87/Sr-86 relationships may allow a distinction between processes such as mantle metasomatism, influence of sea-water altered material in the magma source, or recycling of sediments into the mantle. The best quality Hf isotope data are obtained from granitoid or zircons, and are most suitable for studying ancient terrestrial Hf isotopic variations. Lu-Hf is shown to be a viable method for dating ancient terrestrial and extraterrestrial samples, but is unlikely to find wide application in pure chronological studies because it offers little advantage over existing methods.

  5. A study on the isotopic exchange between hydrogen and water on a catalyst in the liquid phase

    International Nuclear Information System (INIS)

    It is well known that catalytic exchange in the liquid phase offers many advantages over exchange in the gaseous phase; however the rate of reaction is much smaller in the former case. The object of the following work is to study the influence of the various parameters on which the reaction rate depends (pressure, temperature, concentration, agitation), to classify catalysts according to their activity and to determine the economic possibility of liquid phase exchange. (author)

  6. Oxygen isotope exchange in rocks and minerals from the Cerro Prieto geothermal system: Indicators of temperature distribution and fluid flow

    Energy Technology Data Exchange (ETDEWEB)

    Williams, A.E.; Elders, W.A.

    1981-01-01

    Oxygen isotopic compositions have been measured in drill cuttings and core samples from more than 40 wells ranging in depth to more than 3.5 km in the Cerro Prieto geothermal field. Profiles of isotopic ratios versus sampling depths provide information on the three-dimensional distribution of temperature and fluid flow. These parameters also indicate variations in the history of hydrothermal processes in different areas of the geothermal field.

  7. Temporal variability in Chemical and Stable isotopic characteristics of ambient bulk aerosols over a coastal environment of India

    Science.gov (United States)

    Agnihotri, R.; Karapurkar, S. G.; Sarma, V. V.; Praveen, P.; Kumar, M. D.

    2012-12-01

    Atmospheric carbonaceous aerosols are known to influence regional biogeochemical cycles of carbon (C) and nitrogen (N) in addition to regional radiation budgets. Owing to multiplicity of primary sources of natural and anthropogenic origin, their detailed chemical and isotopic characterization can greatly help in source apportionment and identifying secondary processes. From the roof of NIO-Goa (India) [15.46οN, 73.8oE; at ~55.8 MASL], atmospheric bulk aerosols (n=22) were collected on Quartz filters, from 2009 December to January 2011 covering entire 2010 (except monsoon period) to investigate temporal variability in their chemical and isotopic characteristics of the carbonaceous fraction i.e. TC, TOC and TN mass concentrations and their stable isotopic ratios (δ13CTC, δ13CTOC and δ15NTN). Both δ13CTC and δ13CTOC varied in narrow ranges (-24.9±1.1‰, -25.7±0.9‰ respectively), but significant differences were observed between the two during pre-monsoon months (as high as 2.3‰), possibly due to mixing of inorganic mineral dust. δ15NTN values showed a wide range of variability (average = 13.6±7.2‰), with significantly lower values (~2-5‰; as reported earlier by Agnihotri et al. 2011) during pre-monsoon period compared to those during winter (as high as ~26‰). Using δ13CTC values and two end-member mixing model (assuming δ13C of marine and continental carbon as -21 and -27‰ respectively), the average marine carbon fraction for Goa aerosols was estimated as 36±18.5%, significantly higher than reported for Chennai aerosols (~19%) (Pavuluri et al., 2011), but close to the reported average for marine aerosols at Bermuda (38%) (Turekian et al., 2003). Chemical and isotopic characteristics of ambient aerosols over Goa along with contemporaneous meteorological data indicate that winter aerosols contain significant proportion of carbonaceous fraction originated from biomass burning and other anthropogenic activities carried out in northern parts of

  8. Chemical evolution of Mg isotopes versus the time variation of the fine structure constant

    International Nuclear Information System (INIS)

    We show that the synthesis of Mg25,26 at the base of the convective envelope in low-metallicity asymptotic giant branch stars can produce the isotopic ratios needed to explain the low-z subset (with z<1.8) of the many-multiplet data from quasar absorption systems without invoking a time variation of the fine structure constant. This is supported by observations of high abundances of the neutron-rich Mg isotopes in metal-poor globular-cluster stars. We conclude that the quasar absorption spectra may be providing interesting information on the nucleosynthetic history of such systems

  9. Ageing and structural effects on the sorption characteristics of Cd2+ by clinoptilolite and Y-type zeolite studied using isotope exchange technique

    International Nuclear Information System (INIS)

    This research investigates the long-term kinetics of Cd2+ sorption and desorption by calcium-exchanged clinoptilolite (CaCpt) and Y-type (CaY) zeolite using isotopic exchange with 109Cd while maintaining pH at circumneutral values. The effects of Si/Al ratio and crystal structure of these zeolitic materials on intracrystalline transport of Cd are discussed. A first-order kinetic model was developed to describe the progressive transfer of Cd2+ to a less reactive form within the zeolite structure, following initial sorption and subsequent desorption of Cd subject to different initial contact times. The kinetic model differentiates between two forms of sorbed Cd2+ designated 'labile' and 'non-labile' in which the labile form is in immediate equilibrium with the free Cd2+ ion activity in solution. A model combining diffusion and first-order kinetics for cation exchange was also employed to determine Cd2+ diffusivity and intracrystalline exchange rates in CaY and CaCpt. The efficiency of Permeable Reactive Barriers (PRBs) containing zeolitic materials in protecting water systems against lateral flow of metal-contaminated leachate was simulated for three contrasting zeolites. The slow transfer of Cd between labile and non-labile forms was particularly important in moderating high concentration pulses of Cd traversing the PRB. In addition, the reversibility of Cd fixation effectively restored the sorption capability of the zeolite through slow leakage to drainage water.

  10. Chemical exchange saturation transfer of the cervical spinal cord at 7 T.

    Science.gov (United States)

    Dula, Adrienne N; Pawate, Siddharama; Dethrage, Lindsey M; Conrad, Benjamin N; Dewey, Blake E; Barry, Robert L; Smith, Seth A

    2016-09-01

    High-magnetic-field (7 T) chemical exchange saturation transfer (CEST) MRI provides information on the tissue biochemical environment. Multiple sclerosis (MS) affects the entire central nervous system, including the spinal cord. Optimal CEST saturation parameters found via simulation were implemented for CEST MRI in 10 healthy controls and 10 patients with MS, and the results were examined using traditional asymmetry analysis and a Lorentzian fitting method. In addition, T1 - and T2 *-weighted images were acquired for lesion localization and the transmitted B1 (+) field was evaluated to guide imaging parameters. Distinct spectral features for all tissue types studied were found both up- and downfield from the water resonance. The z spectra in healthy subjects had the expected z spectral shape with CEST effects apparent from 2.0 to 4.5 ppm. The z spectra from patients with MS demonstrated deviations from this expected normal shape, indicating this method's sensitivity to known pathology as well as to tissues appearing normal on conventional MRI. Examination of the calculated CESTasym revealed increased asymmetry around the amide proton resonance (Δω = 3.5 ppm), but it was apparent that this measure is complicated by detail in the CEST spectrum upfield from water, which is expected to result from the nuclear Overhauser effect. The z spectra upfield (negative ppm range) were also distinct between healthy and diseased tissue, and could not be ignored, particularly when considering the conventional asymmetry analysis used to quantify the CEST effect. For all frequencies greater than +1 ppm, the Lorentzian differences (and z spectra) for lesions and normal-appearing white matter were distinct from those for healthy white matter. The increased frequency separation and signal-to-noise ratio, in concert with prolonged T1 at 7 T, resulted in signal enhancements necessary to detect subtle tissue changes not possible at lower field strengths. This study

  11. Inorganic ion exchangers and adsorbents for chemical processing in the nuclear fuel cycle

    International Nuclear Information System (INIS)

    The application of inorganic ion exchangers and adsorbents to both waste treatment and the recovery of fission products and actinides were of primary concern at this meeting. The meeting covered the two major fields of fundamental studies and industrial applications

  12. Kinetic isotope effect of the 16O + 36O2 and 18O + 32O2 isotope exchange reactions: Dominant role of reactive resonances revealed by an accurate time-dependent quantum wavepacket study

    International Nuclear Information System (INIS)

    The O + O2 isotope exchange reactions play an important role in determining the oxygen isotopic composition of a number of trace gases in the atmosphere, and their temperature dependence and kinetic isotope effects (KIEs) provide important constraints on our understanding of the origin and mechanism of these and other unusual oxygen KIEs important in the atmosphere. This work reports a quantum dynamics study of the title reactions on the newly constructed Dawes-Lolur-Li-Jiang-Guo (DLLJG) potential energy surface (PES). The thermal reaction rate coefficients of both the 18O + 32O2 and 16O + 36O2 reactions obtained using the DLLJG PES exhibit a clear negative temperature dependence, in sharp contrast with the positive temperature dependence obtained using the earlier modified Siebert-Schinke-Bittererova (mSSB) PES. In addition, the calculated KIE shows an improved agreement with the experiment. These results strongly support the absence of the “reef” structure in the entrance/exit channels of the DLLJG PES, which is present in the mSSB PES. The quantum dynamics results on both PESs attribute the marked KIE to strong near-threshold reactive resonances, presumably stemming from the mass differences and/or zero point energy difference between the diatomic reactant and product. The accurate characterization of the reactivity for these near-thermoneutral reactions immediately above the reaction threshold is important for correct characterization of the thermal reaction rate coefficients

  13. Chemical and isotopic constrains on the origin of brine and saline groundwater in Hetao plain, Inner Mongolia.

    Science.gov (United States)

    Liu, Jun; Chen, Zongyu; Wang, Lijuan; Zhang, Yilong; Li, Zhenghong; Xu, Jiaming; Peng, Yurong

    2016-08-01

    The origin and evolution of brine and saline groundwater have always been a challenged work for geochemists and hydrogeologists. Chemical and isotopic data of brine and saline waters were used to trace the sources of salinity and therefore to understand the transport mechanisms of groundwater in Xishanzui, Inner Mongolia. Both Cl/Br (molar) versus Na/Br (molar) and Cl (meq/L) versus Na (meq/L) indicated that salinity was from halite dissolution or at least a significant impact by halite dissolution. The logarithmic plot of the concentration trends of Cl (mg/L) versus Br (mg/L) for the evaporation of seawater and the Qinghai Salt Lake showed that the terrestrial halite dissolution was the dominated contribution for the salinity of this brine. The stable isotope ratios of hydrogen and oxygen suggested that the origin of brine was from paleorecharge water which experienced mixing of modern water in shallow aquifer. δ(37)Cl values ranged from -0.02 to 3.43 ‰ (SMOC), and reflecting mixing of different sources. The Cl isotopic compositions suggest that the dissolution of halite by paleometeoric water had a great contribution to the salinity of brine, and the contributions of the residual seawater and the dissolution of halite by the Yellow River water could be excluded. PMID:27080408

  14. Assessment of chemical exchange in tryptophan–albumin solution through 19F multicomponent transverse relaxation dispersion analysis

    International Nuclear Information System (INIS)

    A number of NMR methods possess the capability of probing chemical exchange dynamics in solution. However, certain drawbacks limit the applications of these NMR approaches, particularly, to a complex system. Here, we propose a procedure that integrates the regularized nonnegative least squares (NNLS) analysis of multiexponential T2 relaxation into Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion experiments to probe chemical exchange in a multicompartmental system. The proposed procedure was validated through analysis of 19F T2 relaxation data of 6-fluoro-DL-tryptophan in a two-compartment solution with and without bovine serum albumin. Given the regularized NNLS analysis of a T2 relaxation curve acquired, for example, at the CPMG frequency υCPMG = 125, the nature of two distinct peaks in the associated T2 distribution spectrum indicated 6-fluoro-DL-tryptophan either retaining the free state, with geometric mean */multiplicative standard deviation (MSD) = 1851.2 ms */1.51, or undergoing free/albumin-bound interconversion, with geometric mean */MSD = 236.8 ms */1.54, in the two-compartment system. Quantities of the individual tryptophan species were accurately reflected by the associated T2 peak areas, with an interconversion state-to-free state ratio of 0.45 ± 0.11. Furthermore, the CPMG relaxation dispersion analysis estimated the exchange rate between the free and albumin-bound states in this fluorinated tryptophan analog and the corresponding dissociation constant of the fluorinated tryptophan–albumin complex in the chemical-exchanging, two-compartment system

  15. Assessment of chemical exchange in tryptophan–albumin solution through {sup 19}F multicomponent transverse relaxation dispersion analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Ping-Chang, E-mail: pingchang.lin@howard.edu [Howard University, Department of Radiology, College of Medicine (United States)

    2015-06-15

    A number of NMR methods possess the capability of probing chemical exchange dynamics in solution. However, certain drawbacks limit the applications of these NMR approaches, particularly, to a complex system. Here, we propose a procedure that integrates the regularized nonnegative least squares (NNLS) analysis of multiexponential T{sub 2} relaxation into Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion experiments to probe chemical exchange in a multicompartmental system. The proposed procedure was validated through analysis of {sup 19}F T{sub 2} relaxation data of 6-fluoro-DL-tryptophan in a two-compartment solution with and without bovine serum albumin. Given the regularized NNLS analysis of a T{sub 2} relaxation curve acquired, for example, at the CPMG frequency υ{sub CPMG} = 125, the nature of two distinct peaks in the associated T{sub 2} distribution spectrum indicated 6-fluoro-DL-tryptophan either retaining the free state, with geometric mean */multiplicative standard deviation (MSD) = 1851.2 ms */1.51, or undergoing free/albumin-bound interconversion, with geometric mean */MSD = 236.8 ms */1.54, in the two-compartment system. Quantities of the individual tryptophan species were accurately reflected by the associated T{sub 2} peak areas, with an interconversion state-to-free state ratio of 0.45 ± 0.11. Furthermore, the CPMG relaxation dispersion analysis estimated the exchange rate between the free and albumin-bound states in this fluorinated tryptophan analog and the corresponding dissociation constant of the fluorinated tryptophan–albumin complex in the chemical-exchanging, two-compartment system.

  16. Quasiclassical trajectory studies of 18O(3P) + NO2 isotope exchange and reaction to O2 + NO on D0 and D1 potentials

    Science.gov (United States)

    Fu, Bina; Zhang, Dong H.; Bowman, Joel M.

    2013-07-01

    We report quasiclassical trajectory calculations for the bimolecular reaction 18O(3P) + NO2 on the recent potential energy surfaces of the ground (D0) and first excited (D1) states of NO3 [B. Fu, J. M. Bowman, H. Xiao, S. Maeda, and K. Morokuma, J. Chem. Theory. Comput. 9, 893 (2013)], 10.1021/ct3009792. The branching ratio of isotope exchange versus O2 + NO formation, as well as the product angular distributions and energy and rovibrational state distributions are presented. The calculations are done at the collision energy of relevance to recent crossed beam experiments [K. A. Mar, A. L. Van Wyngarden, C.-W. Liang, Y. T. Lee, J. J. Lin, and K. A. Boering, J. Chem. Phys. 137, 044302 (2012)], 10.1063/1.4736567. Very good agreement is achieved between the current calculations and these experiments for the branching ratio and final translational energy and angular distributions of isotope exchange products 16O(3P) + NO2 and O2 + NO formation products. The reactant 18O atom results in 18O16O but not N18O for the O2 + NO formation product channel, consistent with the experiment. In addition, the detailed vibrational and rotational state information of diatomic molecules calculated currently for the 34O2 + NO formation channel on D0 and D1 states are in qualitative agreement with the previous experimental and theoretical results of the photodissociation of NO3 and are consistent with older thermal bimolecular kinetics measurements.

  17. Optimization of the direct utilization of irradiated *TeO2 for meta-iodo-benzyl guanidine (M-IBG) radioiodination via gas-solid isotopic exchange

    International Nuclear Information System (INIS)

    The technical parameters and thermodynamic characteristics of the direct radioiodination of meta-iodo benzyl-guanidine 0.5 sulphate (M-IBG. 0.5 H2SO4) by technique basically depends on a heterogeneous isotopic exchange reaction between M-IBG. 0.5 H2SO4 molecule and radioiodine gas produced by heating *TeO2 up to 550 c degree - c degree via dry Al2O3 column previously deactivated by 0.1 N H2SO4 (ph approx= 1.2) in a relation of 3 mg/97 mg Al2O3. A radiochemical yield over 95% has been obtained with 20-30 min by performing the isotopic exchange at 140-160 c degree. The technique allows the possible utilization of *TeO2 irradiated from either nuclear reactors or cyclotrons using neutron gamma or protons (i.e. 134TeO2) and deuterons (i.e. 132TeO2) respectively. Different radio chromatographic analysis has already been used to determine the radiochemical yields % and the radionuclidic purity as well as the radiochemical purity

  18. Synthesis and radioiodination of di-iodo-Evan's blue via isotopic exchange reaction in the molten state and evaluation of the kinetics

    Energy Technology Data Exchange (ETDEWEB)

    El-Azony, K.M. [Research Center Juelich (Germany). Inst. of Nuclear Chemistry]|[Hot Lab. Center, Cairo (Egypt). Radioactive Isotopes and Generators Dept.; Bier, D.; Coenen, H.H. [Research Center Juelich (Germany). Inst. of Nuclear Chemistry

    2004-07-01

    Many aryl halides were synthesized from aryl amines such as iodo-trypan, iodo-methylene blue and iodo-toluidine. Methylene blue and toludine blue are phenothiazinium dyes and were used to localize parathyroid glands visually during surgery. Radioiodination of these compounds by using iodine-123 analogues for scintgraphic localization of parathyroids was reported. Radiolabelled dyes administered may also localize in tumor tissues. Evan's blue dye was used to study altered sarcolemmal permeability in dystrophic muscle fibers, and in animals to study muscular dystrophy. In this work Diiodo-Evan's blue was synthesized via Sandmeyer reaction and characterized by mass spectrum analysis. A procedure for labelling DIEB with Na{sup 131}I via isotopic exchange in molten medium was developed. The labelling conditions studied for the isotopic exchange of {sup 131}I-for-I in DIEB included the effect of temperature and solvents (melt of acetamide, benzoic and pivalic acid). Kinetic studies were performed to obtain [{sup 131}I] DIEB with more reliable reaction conditions. Quality control for the final product ([{sup 131}I] DIEB) was performed by HPLC. (orig.)

  19. Synthesis and radioiodination of di-iodo-Evan's blue via isotopic exchange reaction in the molten state and evaluation of the kinetics

    International Nuclear Information System (INIS)

    Many aryl halides were synthesized from aryl amines such as iodo-trypan, iodo-methylene blue and iodo-toluidine. Methylene blue and toludine blue are phenothiazinium dyes and were used to localize parathyroid glands visually during surgery. Radioiodination of these compounds by using iodine-123 analogues for scintgraphic localization of parathyroids was reported. Radiolabelled dyes administered may also localize in tumor tissues. Evan's blue dye was used to study altered sarcolemmal permeability in dystrophic muscle fibers, and in animals to study muscular dystrophy. In this work Diiodo-Evan's blue was synthesized via Sandmeyer reaction and characterized by mass spectrum analysis. A procedure for labelling DIEB with Na131I via isotopic exchange in molten medium was developed. The labelling conditions studied for the isotopic exchange of 131I-for-I in DIEB included the effect of temperature and solvents (melt of acetamide, benzoic and pivalic acid). Kinetic studies were performed to obtain [131I] DIEB with more reliable reaction conditions. Quality control for the final product ([131I] DIEB) was performed by HPLC. (orig.)

  20. Chemical and isotopic analysis of hydrocarbon traces degassed out of Callovo-Oxfordian argilites from Bure (France): methodology and results

    International Nuclear Information System (INIS)

    Isotopic mass spectrometry online with gas chromatography (GC-C-IRMS) allows the measurement of the carbon isotopic ratios of hydrocarbon gases (C1 to C4) after complete combustion to CO2. The method also permits to measure proportions of the different hydrocarbon gases and CO2. Such data provide valuable information about the source and genesis of a gas sample, as well as the post-formation physicochemical processes which might affect it in the geological environment. In particular, it is possible to distinguish hydrocarbon gases of bacterial or thermogenic origin based on the proportion of methane and the carbon isotope ratio as measured by GC-C-IRMS. However, if the relative concentrations of carbon molecules are very small (from 1 ppm to 1000 ppm), the isotopic information cannot be obtained directly with GC-C-IRMS. An additional step allowing the pre-concentration of hydrocarbons must be introduced in the analytical procedure. Indeed, in order to obtain an adequate accuracy, several operating conditions are of prime importance: sufficient signal intensity, good quality peak shape, low signal/noise ratio. We present here a pre-concentration system based on the removal of major gas compounds (N2, O2, Ar, etc...) and trapping of carbon molecules. The purified carbon molecules are released in an inert carrier gas, focussed through a tiny capillary, and introduced in the chromatograph for separation, combustion of each compound and final analysis in the mass spectrometer. This technique provides the chemical concentration in the initial gas and the carbon isotope composition of each individual carbon molecular compound. Its high sensitivity allows measurement of isotopic ratios for concentrations as low as 1 ppm of methane, 0,5 ppm of ethane and 0,3 ppm of propane, for bulk gas samples of 10 cc in standard conditions. Total analytical uncertainty on δ13C measurements is ± 1 0/00 or better. The results of a first application of this technique to the Callovo

  1. Chemical and isotopic study of thermal springs and gas discharges from Sierra de Chiapas, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Nencetti, A; Tassi, F; Vaselli, O [Department of Earth Sciences, Florence (Italy); Macias, J. L [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, D.F. (Mexico); Magro, G [CNR-Institute of Geosciences and Earth Resources, Pisa (Italy); Capaccioni, B [Institute of Volcanology and Geochemistry, Urbino (Italy); Minissale, A [CNR-Institute of Geosciences and Earth Resources, Florence (Italy); Mora, J. C [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, D.F. (Mexico)

    2005-01-15

    Thermal water and gas discharges south-east of El Chichon volcano, Mexico are associated mainly with NW-SE oriented fault systems. Spring discharges include i) waters with Na-Cl composition and TDS>3000 mg/L; ii) waters with Ca-SO{sub 4} composition and TDS values between 1400 and 2300 mg/L; iii) waters with Na-Cl composition and TDS of 800 to 2400 mg/L and sulphate content up to 650 mg/L and iv) waters with Ca-HCO{sub 3} composition and low salinity (TDS <250mg/L). Most of these waters are associated with free-gas discharges of N{sub 2} (up to 93 % by vol.), CO{sub 2} (2.4 to 31.2 % by vol.) and Ar (up to 1.25 % by vol.) with a predominant meteoric origin. H{sub 2}S is present only in gas samplers collected at El Azufre (up to 1.1 % by vol.). The {delta}13C CO{sub 2} values are always below -9.7% (PDB) and suggest a partially biogenic origin for CO{sub 2}. Chemical and isotopic features of spring discharges indicate that fluid circulation in the Sierra de Chiapas is mainly regulated by meteoric waters that tend to infiltrate the upper and middle-Cretaceous carbonate units up to the lower Cretaceous-upper Jurassic evaporitic formations (by Lopez-Ramos, 1982). The latter provide the main source of the species in solution. No evidence for high-to-medium enthalpy systems at depth beneath the Sierra de Chiapas has been found. [Spanish] La Sierra de Chiapas localizada en el Sureste de Mexico, se caracteriza por la presencia de descargas de gas y agua. La mayoria de los manantiales termales se asocian a rocas volcanicas Terciarias a lo largo de fallas regionales con orientacion NOSE. Las descargas termales se dividen en cuatro grupos: i) aguas con composicion Na-Cl y Solidos Disueltos Totales (SDT) >3000 mg/L; ii) aguas con composicion Ca-SO{sub 4} y valores de SDT entre 1400 y 2300 mg/L; iii) aguas con composicion Na-Cl, bajos contenidos de SDT (800 2400 mg/L) y un contenido de sulfato alto (hasta 650 mg/L) y iv) aguas con una composicion Ca-HCO{sub 3} y salinidad baja

  2. Biology and air-sea gas exchange controls on the distribution of carbon isotope ratios (δ13C) in the ocean

    Science.gov (United States)

    Schmittner, A.; Gruber, N.; Mix, A. C.; Key, R. M.; Tagliabue, A.; Westberry, T. K.

    2013-09-01

    Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate processes that control the distribution of δ13C of dissolved inorganic carbon (DIC) in the contemporary and preindustrial ocean. Biological fractionation and the sinking of isotopically light δ13C organic matter from the surface into the interior ocean leads to low δ13CDIC values at depths and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air-sea gas exchange has two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature-dependent fractionation tends to increase (decrease) δ13CDIC values of colder (warmer) water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, since air-sea gas exchange is slow in the modern ocean, the biological effect dominates spatial δ13CDIC gradients both in the interior and at the surface, in contrast to conclusions from some previous studies. Calcium carbonate cycling, pH dependency of fractionation during air-sea gas exchange, and kinetic fractionation have minor effects on δ13CDIC. Accumulation of isotopically light carbon from anthropogenic fossil fuel burning has decreased the spatial variability of surface and deep δ13CDIC since the industrial revolution in our model simulations. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed and remineralized contributions as well as the effects of biology and air-sea gas exchange. The model reproduces major features of the observed large-scale distribution of δ13CDIC as well as the individual contributions and effects. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by

  3. Biology and air–sea gas exchange controls on the distribution of carbon isotope ratios (δ13C in the ocean

    Directory of Open Access Journals (Sweden)

    A. Schmittner

    2013-09-01

    Full Text Available Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate processes that control the distribution of δ13C of dissolved inorganic carbon (DIC in the contemporary and preindustrial ocean. Biological fractionation and the sinking of isotopically light δ13C organic matter from the surface into the interior ocean leads to low δ13CDIC values at depths and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air–sea gas exchange has two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature-dependent fractionation tends to increase (decrease δ13CDIC values of colder (warmer water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, since air–sea gas exchange is slow in the modern ocean, the biological effect dominates spatial δ13CDIC gradients both in the interior and at the surface, in contrast to conclusions from some previous studies. Calcium carbonate cycling, pH dependency of fractionation during air–sea gas exchange, and kinetic fractionation have minor effects on δ13CDIC. Accumulation of isotopically light carbon from anthropogenic fossil fuel burning has decreased the spatial variability of surface and deep δ13CDIC since the industrial revolution in our model simulations. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed and remineralized contributions as well as the effects of biology and air–sea gas exchange. The model reproduces major features of the observed large-scale distribution of δ13CDIC as well as the individual contributions and effects. Residual misfits are documented and analyzed. Simulated surface and subsurface

  4. Chemical and isotopic characteristics of a glacier-derived naled in front of Austre Grønfjordbreen, Svalbard

    Directory of Open Access Journals (Sweden)

    Jacob C. Yde

    2012-03-01

    Full Text Available The chemical and stable isotope composition of a glacier-derived naled in front of the glacier Austre Grønfjordbreen, Svalbard, is examined to elucidate how secondary processes such as preferential retention and leaching affect naled chemistry. Internal candle ice layers have a chemical composition almost similar to that of the lower stratified granular ice layer, whereas the upper granular ice layer has a significantly different composition, which resembles the composition found in glacier meltwater. Grey, platy cryogenic calcite precipitates are found in clusters on the surface of the naled assemblage, indicating preferential retention of Ca2 +  and HCO3 −. This process is particular pronounced in the distal part of the naled. The isotopic composition in the naled is in accordance with the local meteoric water line and without indications of kinetic fractionation during freezing. The ability to form ice-marginal naled indicates that Austre Grønfjordbreen has the high meltwater storage potential required for triggering a glacier surge event.

  5. A Novel Ion Exchange System to Purify Mixed ISS Waste Water Brines for Chemical Production and Enhanced Water Recovery

    Science.gov (United States)

    Lunn, Griffin; Spencer, LaShelle; Ruby, Anna-Maria; McCaskill, Andrew

    2014-01-01

    Current International Space Station water recovery regimes produce a sizable portion of waste water brine. This brine is highly toxic and water recovery is poor: a highly wasteful proposition. With new biological techniques that do not require waste water chemical pretreatment, the resulting brine would be chromium-free and nitrate rich which can allow possible fertilizer recovery for future plant systems. Using a system of ion exchange resins we can remove hardness, sulfate, phosphate and nitrate from these brines to leave only sodium and potassium chloride. At this point modern chlor-alkali cells can be utilized to produce a low salt stream as well as an acid and base stream. The first stream can be used to gain higher water recovery through recycle to the water separation stage while the last two streams can be used to regenerate the ion exchange beds used here, as well as other ion exchange beds in the ISS. Conveniently these waste products from ion exchange regeneration would be suitable as plant fertilizer. In this report we go over the performance of state of the art resins designed for high selectivity of target ions under brine conditions. Using ersatz ISS waste water we can evaluate the performance of specific resins and calculate mass balances to determine resin effectiveness and process viability. If this system is feasible then we will be one step closer to closed loop environmental control and life support systems (ECLSS) for current or future applications.

  6. Isotopic, chemical and dissolved gas constraints on spring water from Popocatepetl volcano (Mexico): evidence of gas–water interaction between magmatic component and shallow fluids

    OpenAIRE

    Inguaggiato, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Martin-Del Pozzo, A.L.; Instituto de Geofisica UNAM, Ciudad Universitaria, Mexico DF, 04510 Mexico; Aguayo, A.; Instituto de Geofisica UNAM, México D.F., México; Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Favara, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia

    2005-01-01

    Geochemical research was carried out on cold and hot springs at Popocatepetl (Popo) volcano (Mexico) in 1999 to identify a possible relationship with magmatic activity. The chemical and isotopic composition of the fluids is compatible with strong gas–water interaction between deep and shallow fluids. In fact, the isotopic composition of He and dissolved carbon species is consistent with a magmatic origin. The presence of a geothermal system having a temperature of 80–1008 C was estimated o...

  7. Isotopic and chemical characteristics of water in the basin of Gafsa,Tunisia

    International Nuclear Information System (INIS)

    Water in the basin of Gafsa in characterized by a very negative 18O contens (-0.7 to -0.76% vs SMOW). These contents differ from the average recorded for precipitation in Tunis-Carthage (-0.5% vs SMOW). The dating with 14C demonstrated that the recharge of the water table dates back to a period relatively ancient probably the humid Holocen. These isotopic analysis (18O, 2H, 14C) permitted to better specify the origin of the underground water, the communications between the different levels of aquifers, the refill and the age of waters. However, additional isotopic analysis are necessary for a better appraisal of these interpretations (author)

  8. Isotopic and Chemical Analysis of Nitrate Source and Cycling in the San Joaquin River, California

    Science.gov (United States)

    Silva, S. R.; Kendall, C.; Bemis, B.; Bergamaschi, B.; Kratzer, C.; Dileanis, P.; Erickson, D.; Avery, E.; Paxton, K.

    2001-12-01

    The sources and cycling of nitrate was investigated during a pilot study at four sites along the San Joaquin River using carbon and nitrogen isotopes of total dissolved and particulate organic matter along with hydrological measurements and various concentration data including chlorophyll-a. The nitrate source, its relationship to phytoplankton, and the effect of the nitrate source and cycling on the isotopic composition of dissolved and particulate organic matter were the primary concerns of the study. Samples were collected between July and October 2000 at (1) Crow's Landing, (2) Laird Park, (3) Vernalis, and (4) upstream of the Merced River. Particulate organic matter samples (POM) were collected on pre-combusted glass fiber filters. Combined dissolved organic and inorganic samples were prepared by roto-evaporating filtered waters (RV samples). Both the RV and the POM samples were acidified to eliminate inorganic carbon. Stable carbon and nitrogen isotopes and C:N ratios of POM in addition to chlorophyll-a concentrations were consistent with POM derived primarily from plankton at all sites and sampling times except in late October during a dam release event. The late October samples showed a shift toward isotopically heavier carbon and lighter nitrogen isotopes and higher C:N ratios reflecting a significant input from non-planktonic (probably terrestrial) sources. About 90 percent of the nitrogen in the RV samples was inorganic, 97 percent of which was in the form of nitrate. Assuming that the nitrogen isotopic composition of the minor organic fraction fell within the range of common organic samples (0 to 25 per mil), the delta 15N value of the RV samples was a close representation of the nitrogen isotopic composition of the nitrate. The POM and RV samples therefore appear to be reasonable proxies for the nitrogen isotopic compositions of plankton and nitrate, respectively. By comparison with other dissolved species, most of the variation in nitrate

  9. Identification of methanotrophic lipid biomarkers in cold-seep mussel gills: chemical and isotopic analysis.

    OpenAIRE

    Jahnke, L L; Summons, R E; Dowling, L M; Zahiralis, K D

    1995-01-01

    A lipid analysis of the tissues of a cold-seep mytilid mussel collected from the Louisiana slope of the Gulf of Mexico was used in conjunction with a compound-specific isotope analysis to demonstrate the presence of methanotrophic symbionts in the mussel gill tissue and to demonstrate the host's dependence on bacterially synthesized metabolic intermediates. The gill tissue contained large amounts of group-specific methanotrophic biomarkers, bacteriohopanoids, 4-methylsterols, lipopolysacchar...

  10. The oxygen transfer process on solid oxide/noble metal electrodes, studies with impedance spectroscopy, polarization and isotope exchange

    OpenAIRE

    Boukamp, B.A.; Hassel, van, E Edwin; Vinke, I.C.; De, Vries, J.A.; Burggraaf, A.J.

    1993-01-01

    The electrochemical oxygen transfer process at the yttria stabilized zirconia (YSZ) and Fe-implanted YSZ, and at the erbia stabilized bismuth oxide (BE25) surface is studied with dc polarization and impedance spectroscopy using gold electrodes, and with 18O gas phase exchange. The surface modification by Fe-implantation increases the exchange current density up to a factor of 50, but analysis of the impedance spectra at different polarization levels indicates that the type of electrode reacti...

  11. Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

    International Nuclear Information System (INIS)

    The 176Lu-176Hf isotope method and its applications in earth sciences are discussed. Greater fractionation of Lu/Hf than Sm/Nd in planetary magmatic processes makes 176Hf/177Hf a powerful geochemical tracer. In general, proportional variations of 176Hf/177Hf exceed those of 143Nd/144Nd by factors of 1.5 to 3 in terrestrial and lunar materials. Lu-Hf studies therefore have a major contribution to make in understanding of terrestrial and other planetary evolution through time, and this is the principal importance of Lu-Hf. New data on basalts from oceanic islands show unequivocally that whereas considerable divergences occur in 176Hf/177Hf-87Sr/ 86Sr and 143Nd/144Nd-87Sr/86Sr diagrams, 176Hf/ 177Hf and 143Nd/144Nd display a single, linear isotopic variation in the suboceanic mantle. These discordant 87Sr/86Sr relationships may allow, with the acquisition of further Hf-Nd-Sr isotopic data, a distinction between processes such as mantle metasomatism, influence of seawater-altered material in the magma source, or recycling of sediments into the mantle. Further applications of the method are discussed. (author)

  12. Chemical reduction and sulfur-isotope effects of sulfate by organic matter under hydrothermal conditions

    International Nuclear Information System (INIS)

    Under hydrothermal conditions sulfuric acid, sodium bisulfate and sodium sulfate solutions were reduced by dextrose to hydrogen sulfide in order to clarify the origin of sulfide species in hot-springs, geothermal water and ore-forming fluids. At temperatures above 2500C, reduction of sulfuric acid and at above 3000C of sodium bisulfate and sodium sulfate was observed. The reduction rate depends fairly well on the temperatures, pH and sulfate species. The reduction of sulfate seems to be a first-order reaction. Sulfur-isotope compositions of sulfate and hydrogen sulfide were measured in order to disclose isotope effects in the reduction of sulfate. The reduction of sulfuric acid and sodium bisulfate solution results in enrichment of 32S in the hydrogen sulfide and of the heavy isotope into residual sulfate. The fractionation factor in the reduction is independent of the temperature and is seen to be 1.007 to 1.009, in agreement with previously published values. (Auth.)

  13. Chemical and isotopic fingerprinting of small ungauged watershed: How far the hydrological functioning can be understood?

    Science.gov (United States)

    Petelet-Giraud, Emmanuelle; Luck, Jean-Marc; Ben Othman, Dalila; Joseph, Christian; Négrel, Philippe

    2016-05-01

    This study presents the ability of major/trace elements together with strontium isotopes to trace water origins at small scale at the outlet of a small watershed (Peyne, Hérault, France). Two small sub-basins draining distinct lithologies in their headwater (Plio-Villafranchian conglomerate versus Triassic gypsum-rich marls and dolomites) and the Miocene formations downstream are investigated. The Ca/Na vs. Mg/Na ratios and Ca/Sr vs. 87Sr/86Sr ratios allow the different facies that imprint the water signature to be identified, according to the hydrological conditions (low/high flows). Moreover, Sr isotopes evidence the two distinct Miocene facies, the sandy marls and the marine carbonates. The variation of the signature at the outlet of the basin allows identifying the main contributing compartments according to the hydrological conditions. This approach, based on a limited number of samples, highlights the potential of geochemical and isotopic tracers to define the contributing compartments to the runoff at the outlet of a basin. It thus could be considered as a potential alternative way to classical hydrological monitoring to delineate the main contributing areas during floods, especially in small ungauged river basins, where most of the devastating flash floods are recorded.

  14. Chemically modified glasses for analysis of hydrogen isotopes by gas chromatography

    International Nuclear Information System (INIS)

    An extensive experimental research has been carried out by gas chromatographic runs in order to identify the most suitable adsorbents and define the best operated conditions for selective separation and analysis of hydrogen isotopes in near real-time (i.e. less than 10 min.). Preparation and operation procedures of chromatographic column for hydrogen isotope separation have been examined. This is one of the main requirements of the tritium separation from heavy water of CANDU reactor and of the tritium fuel cycle in D-T fusion reactors. This paper describes the preparation of absorbent materials utilised as stationary phase in the gas-chromatographic column for hydrogen isotope separation and treatment (activation) of stationary phase. Modified thermoresisting glass with Fe(NH4)2(SO4)2 6H2O and Cr2O3, respectively, have been experimentally investigated at 77 K for H2, HD, and D2 separation and the results of chromatographic runs are also reported and discussed. The hydrogen operating conditions of the adsorbent column Fe (III)/glass and Cr2O3/glass, i.e. granulometry, column length, pressure-drop along the column, carrier gas flow rate, sample volume have been study by means of the analysis of the retention times, separation factors and HETP. (authors)

  15. Heat recovery from a spray dryer using a glass tube heat exchanger. A demonstration at ABM Chemicals, Gloucester

    Energy Technology Data Exchange (ETDEWEB)

    1986-01-01

    This project at ABM Chemicals demonstrates the use of a glass tube heat exchanger to recover heat directly from a spray dryer exhaust to pre-heat the inlet air. It was originally envisaged that this would reduce the energy consumption of the dryer by around 20%. The background to the project, the results to date, corrosive nature of exhaust and expected savings are discussed. Reduced performance, believed to be due to a higher-than-anticipated level of fines in the exhaust, leading to fouling of the heat transfer surfaces, and eventually to the failure of a number of the glass tubes is described. Measures are currently in hand to reduce the carryover and further monitoring of the replacement exchanger is planned.

  16. Isotope exchange reactions of the hydrogen H-5 of selected pyrimidine derivatives and the preparation of tritium-labeled pyrimidines

    Czech Academy of Sciences Publication Activity Database

    Dračínský, Martin; Jansa, Petr; Elbert, Tomáš

    2011-01-01

    Roč. 76, č. 12 (2011), s. 1567-1577. ISSN 0010-0765 R&D Projects: GA AV ČR KJB400550903; GA MŠk 1M0508 Institutional research plan: CEZ:AV0Z40550506 Keywords : isotopic labeling * NMR spectroscopy * nucleobases * pyrimidines Subject RIV: CC - Organic Chemistry Impact factor: 1.283, year: 2011

  17. Chlorine isotope enrichment on a strong alkaline anion exchanger in dependence of type and concentration of the strange electrolytic solution

    International Nuclear Information System (INIS)

    Chlorine isotope enrichment for heterogenous ionexchange equilibria was studied. The dependence of element separation effects on the anion of the strange electrolyte (for same cation), on the cation of the strange electrolyte (for same anion), on the concentration of the strange electrolyte and also on the acetone: water ratio of the solvent was investigated. (orig./HBR)

  18. Oxygen isotopes in nitrite: Analysis, calibration, and equilibration

    Science.gov (United States)

    Casciotti, K.L.; Böhlke, J.K.; McIlvin, M.R.; Mroczkowski, S.J.; Hannon, J.E.

    2007-01-01

    Nitrite is a central intermediate in the nitrogen cycle and can persist in significant concentrations in ocean waters, sediment pore waters, and terrestrial groundwaters. To fully interpret the effect of microbial processes on nitrate (NO3-), nitrite (NO2-), and nitrous oxide (N2O) cycling in these systems, the nitrite pool must be accessible to isotopic analysis. Furthermore, because nitrite interferes with most methods of nitrate isotopic analysis, accurate isotopic analysis of nitrite is essential for correct measurement of nitrate isotopes in a sample that contains nitrite. In this study, nitrite salts with varying oxygen isotopic compositions were prepared and calibrated and then used to test the denitrifier method for nitrite oxygen isotopic analysis. The oxygen isotopic fractionation during nitrite reduction to N2O by Pseudomonas aureofaciens was lower than for nitrate conversion to N2O, while oxygen isotopic exchange between nitrite and water during the reaction was similar. These results enable the extension of the denitrifier method to oxygen isotopic analysis of nitrite (in the absence of nitrate) and correction of nitrate isotopes for the presence of nitrite in "mixed" samples. We tested storage conditions for seawater and freshwater samples that contain nitrite and provide recommendations for accurate oxygen isotopic analysis of nitrite by any method. Finally, we report preliminary results on the equilibrium isotope effect between nitrite and water, which can play an important role in determining the oxygen isotopic value of nitrite where equilibration with water is significant. ?? 2007 American Chemical Society.

  19. Delineating sources of sulfate and nitrate in rivers and streams by combining hydrological, chemical and isotopic techniques

    International Nuclear Information System (INIS)

    Full text: There is an increasing number of studies published in the literature, which report on the isotopic compositions of sulfate (δ34S and δ18O) and nitrate (δ15N and δ18O) in headwater creeks, rivers, and streams. Many of these studies are, however, characterized by infrequent sampling and by a scarcity of accompanying hydrological or chemical data. This severely hampers the ability to relate the obtained isotope data to potential sources of sulfate and nitrate, or to processes which these solutes may have undergone in aquatic systems. We present a number of case studies, in which sulfate and nitrate from surface water systems were sampled repeatedly and the obtained δ34S, δ15N and δ18O values were interpreted in conjunction with hydrological and chemical data. Using this approach in selected forested headwater catchments in New Hampshire and Vermont (USA), we were able to show that a significant portion of stream water sulfate during base flow may be derived from weathering of bedrock, particularly in catchments with sulfur-rich lithology. During storm events at the Archer Creek sub-catchments in the Arbutus Lake Watershed in the central Adirondack Mountains of New York State (USA) in the fall of 2002, sulfate concentrations in stream water increased significantly and δ34Ssulfate decreased to minimum values. This suggested that sulfate derived from oxidation of sulfide minerals, possibly in wetland areas or the hyporheic zone, contributed to the increased sulfate load in the streams following the storm events. Monitoring of stream water during spring snowmelt events in the Sleepers River Research Watershed (Vermont, USA) revealed elevated contributions of sulfate from pedospheric sources, but little direct contribution of sulfate from the melting snowpack. Also, nitrate was not derived from atmospheric inputs but primarily from nitrification processes in the soils. In agriculturally used portions of a large watershed in southern Alberta (Canada

  20. Constraints on continental crustal mass loss via chemical weathering using lithium and its isotopes

    OpenAIRE

    Liu, Xiao-ming; Rudnick, Roberta L.

    2011-01-01

    Chemical weathering, as well as physical erosion, changes the composition and shapes the surface of the continental crust. However, the amount of continental material that has been lost over Earth’s history due to chemical weathering is poorly constrained. Using a mass balance model for lithium inputs and outputs from the continental crust, we find that the mass of continental crust that has been lost due to chemical weathering is at least 15% of the original mass of the juvenile continental ...

  1. The isotopic and chemical composition of natural gases from the South Island, New Zealand

    International Nuclear Information System (INIS)

    Analyses of seep gases from the prospective petroleum areas of Marlborough, Westland and Southland and of gases associated with other warm and cold springs in the South Island are presented and compared with those from Taranaki and elsewhere. Isotopic analyses of gases from the sedimentary basins show that CH4 from southern Marlborough is derived from mature sources, that from Wharf Stream being the most mature of the South Island hydrocarbon-rich gases. Three gases from the Murchison Basin show increasing maturity from W to E, with isotopic values similar to those for the McKee field. Gases from Kotuku (Westland) appear to be derived from thermogenesis at low maturity levels. Gas from the Hindley Burn (Western Southland) is probably derived from a source similar to that of the gas collected from a well drilled into the Ohai coal deposit. Gases from three areas, Marlborough, the Murchison Basin and Kotuku, have high (>5%) ethane contents and high N2/Ar ratios confirming formation from mature sources and their potential for hydrocarbon production. Gas from an alluvial delta in Lake Te Anau is produced through microbial reduction of CO2 from decomposition of buried vegetation. In contrast an unusual H2 rich gas from Fiordland contains CH4, similar in C isotopic composition to gases from greywacke, but with very depleted H isotopic composition probably due to abiogenic reduction. Several warm spring gases from fault zones are CO2 rich or N2 rich and some have microbially oxidised, isotopically enriched CH4.CH4 from Hanmer Springs and some of the other fault springs have thermogenic compositions resembling those of gases from greywackes of the axial ranges of the North Island. Ratios of 3He/4He for most gases are generally above crustal values (>O.1 RA) implying addition of mantle fluids. High values >2.5 RA are observed in CH4 rich gases discharged in the Murchison and Grey Valley basins, in Fiordland (H2 rich) and in East Otago (CO2 rich). (author). 36 refs., 2 tabs

  2. I. Nuclear Production Reaction and Chemical Isolation Procedure for Americium-240 II. New Superheavy Element Isotopes: Plutonium-242(Calcium-48,5n)(285)114

    Science.gov (United States)

    Ellison, Paul Andrew

    2011-12-01

    Part I discusses the study of a new nuclear reaction and chemical separation procedure for the production of 240Am. Thin 242Pu, natTi, and natNi targets were coincidently activated with protons from the 88-Inch Cyclotron, producing 240Am, 48V, and 57Ni, respectively. The radioactive decay of these isotopes was monitored using high-purity Ge gamma ray detectors in the weeks following irradiation. The excitation function for the 242 Pu(p, 3n)240Am nuclear reaction was measured to be lower than theoretical predictions, but high enough to be the most viable nuclear reaction for the large-scale production of 240 Am. Details of the development of a chemical separation procedure for isolating 240Am from proton-irradiated 242Pu are discussed. The separation procedure, which includes two anion exchange columns and two extraction chromatography columns, was experimentally investi- gated using tracer-level 241Am, 239Pu, and model proton-induced fission products 95Zr, 95Nb, 125Sb, and 152Eu. The separation procedure was shown to have an Am/Pu separation factor of >2x10 7 and an Am yield of ˜70%. The separation procedure was found to purify the Am sample from >99.9% of Eu, Zr, Nb, and Sb. The procedure is well suited for the processing of ˜1 gram of proton-irradiated 242Pu to produce a neutron-induced fission target consisting of tens of nanograms of 240Am. Part II describes the use of the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron for the study of the 242Pu(48Ca,5n)285114 nuclear re- action. The new, neutron-deficient, superheavy element isotope 285114 was produced in 48Ca irradiations of 242Pu targets at a center-of-target beam energy of 256 MeV ( E* = 50 MeV). The alpha decay of 285114 was followed by the sequential alpha decay of four daughter nuclides, 281Cn, 277Ds, 273Hs, and 269 Sg. 265Rf was observed to decay by spontaneous fission. The measured alpha-decay Q-values were compared with those from a macroscopic

  3. Chemical bond as a test of density-gradient expansions for kinetic and exchange energies

    International Nuclear Information System (INIS)

    Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al. and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N2 and F2, which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules

  4. Production waters associated with the Ferron coalbed methane fields, central Utah: Chemical and isotopic composition and volumes

    Science.gov (United States)

    Rice, C.A.

    2003-01-01

    This study investigated the composition of water co-produced with coalbed methane (CBM) from the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale in east-central Utah to better understand coalbed methane reservoirs. The Ferron coalbed methane play currently has more than 600 wells producing an average of 240 bbl/day/well water. Water samples collected from 28 wellheads in three fields (Buzzards Bench, Drunkards Wash, and Helper State) of the northeast-southwest trending play were analyzed for chemical and stable isotopic composition.Water produced from coalbed methane wells is a Na-Cl-HCO3 type. Water from the Drunkards Wash field has the lowest total dissolved solids (TDS) (6300 mg/l) increasing in value to the southeast and northeast. In the Helper State field, about 6 miles northeast, water has the highest total dissolved solids (43,000 mg/l), and major ion abundance indicates the possible influence of evaporite dissolution or mixing with a saline brine. In the southern Buzzards Bench field, water has variable total dissolved solids that are not correlated with depth or spatial distance. Significant differences in the relative compositions are present between the three fields implying varying origins of solutes and/or different water-rock interactions along multiple flow paths.Stable isotopic values of water from the Ferron range from +0.9??? to -11.4??? ?? 18O and -32??? to -90??? ?? 2H and plot below the global meteoric water line (GMWL) on a line near, but above values of present-day meteoric water. Isotopic values of Ferron water are consistent with modification of meteoric water along a flow path by mixing with an evolved seawater brine and/or interaction with carbonate minerals. Analysis of isotopic values versus chloride (conservative element) and total dissolved solids concentrations indicates that recharge water in the Buzzards Bench area is distinct from recharge water in Drunkards Wash and is about 3 ??C warmer. These variations in

  5. Principles of stable isotope distribution

    CERN Document Server

    Criss, Robert E

    1999-01-01

    1. Abundance and Measurement of Stable Isotopes 1.1. Discovery of Isotopes 1.2. Nuclide Types, Abundances, and Atomic Weights 1.3. Properties and Fractionation of Isotopic Molecules 1.4. Material Balance Relationships 1.5. Mass Spectrometers 1.6. Notation and Standards 1.7. Summary 1.8. Problems References 2. Isotopic Exchange and Equilibrium Fractionation 2.1. Isotopic Exchange Reactions 2.2. Basic Equations 2.3. Molecular Models 2.4. Theory of Isotopic Fractionation 2.5. Temperature Dependence of Isotopic Fractionation Factors 2.6. Rule of the Mean 2.7. Isotopic Thermometers

  6. PH dependence of deuterium isotope effects and tritium exchange in the bovine plasma amine oxidase reaction: a role for single-base catalysis in amine oxidation and imine exchange

    International Nuclear Information System (INIS)

    The pH dependence of steady-state parameters for [1,1-1H2]- and [1,1-2H2]benzylamine oxidation and of tritium exchange from [2-3H]dopamine has been measured in the bovine plasma amine oxidase reaction. Deuterium isotope effects on kcat/Km for benzylamine are observed to be constant, near the intrinsic value of 13.5, over the experimental pH range, indicating that C-H bond cleavage is fully rate limiting for this parameter. As a consequence, pKa values derived from kcat/Km profiles, 8.0 +/- 0.1 (pK1) and 9.0 +/- 0.16 (pKs), can be ascribed to microscopic pKa values for the ionization of an essential active site residue (EB1) and substrate, respectively. Profiles for kcat and Dkcat show that EB1 undergoes a perturbation from 8.0 to 5.6 +/- 0.3 (pK1') in the presence of substrate; additionally, a second ionization, pK2 = 7.25 +/- 0.25, is observed to mediate but not be essential for enzyme reoxidation. The pH dependence of the ratio of tritium exchange to product formation for dopamine also indicates base catalysis with a pKexch = 5.5 +/- 0.01, which is within experimental error of pK1'. We conclude that the data presented herein support a single residue catalyzing both substrate oxidation and exchange, consistent with recent stereochemical results that implicate a syn relationship between these processes [Farnum, M., and Klinman, J.P. (1985) Fed. Proc., Fed. Am. Soc. Exp. Biol. 44, 1055]. This conclusion contrasts with earlier kinetic data in support of a large rate differential for the exchange of hydrogen from C-1 vs. C-2 of phenethylamine derivatives

  7. Backbone dynamics of a model membrane protein: measurement of individual amide hydrogen-exchange rates in detergent-solubilized M13 coat protein using 13C NMR hydrogen/deuterium isotope shifts

    International Nuclear Information System (INIS)

    Hydrogen-exchange rates have been measured for individual assigned amide protons in M13 coat protein, a 50-residue integral membrane protein, using a 13C nuclear magnetic resonance (NMR) equilibrium isotope shift technique. The locations of the more rapidly exchanging amides have been determined. In D2O solutions, a peptide carbonyl resonance undergoes a small upfield isotope shift (0.08-0.09 ppm) from its position in H2O solutions; in 1:1 H2O/D2O mixtures, the carbonyl line shape is determined by the exchange rate at the adjacent nitrogen atom. M13 coat protein was labeled biosynthetically with 13C at the peptide carbonyls of alanine, glycine, phenylalanine, proline, and lysine, and the exchange rates of 12 assigned amide protons in the hydrophilic regions were measured as a function of pH by using the isotope shift method. This equilibrium technique is sensitive to the more rapidly exchanging protons which are difficult to measure by classical exchange-out experiments. In proteins, structural factors, notably H bonding, can decrease the exchange rate of an amide proton by many orders of magnitude from that observed in the freely exposed amides of model peptides such as poly(DL-alanine). With corrections for sequence-related inductive effects, the retardation of amide exchange in sodium dodecyl sulfate solubilized coat protein has been calculated with respect to poly(DL-alanine). The most rapidly exchanging protons, which are retarded very little or not at all, are shown to occur at the N- and C-termini of the molecule. A model of the detergent-solubilized coat protein is constructed from these H-exchange data which is consistent with circular dichroism and other NMR results

  8. Identification of Methanotrophic Lipid Biomarkers in Cold-Seep Mussel Gills: Chemical and Isotopic Analysis

    Science.gov (United States)

    Jahnke, Linda L.; Summons, Roger E.; Dowling, Lesley M.; Zahiralis, Karen D.

    1995-01-01

    A lipid analysis of the tissues of a cold-seep mytilid mussel collected from the Louisiana slope of the Gulf of Mexico was used in conjunction with a compound-specific isotope analysis to demonstrate the presence of methanotrophic symbionts in the mussel gill tissue and to demonstrate the host's dependence on bacterially synthesized metabolic intermediates. The gill tissue contained large amounts of group-specific methanotrophic biomarkers, bacteriohopanoids, 4-methylsterols, lipopolysaccharide-associated hydroxy fatty acids, and type I-specific 16:1 fatty acid isomers with bond positions at delta-8, delta-10, and delta-ll. Only small amounts of these compounds were detected in the mantle or other tissues of the host animal. A variety of cholesterol and 4-methylsterol isomers were identified as both free and steryl esters, and the sterol double bond positions suggested that the major bacterially derived gill sterol(11.0% 4(alpha)-methyl-cholesta-8(14), 24-dien-3(beta)-ol) was converted to host cholesterol (64.2% of the gill sterol was cholest-5-en-3(beta)-ol). The stable carbon isotope values for gill and mantle preparations were, respectively, -59.0 and -60.4 per thousand for total tissue, -60.6 and -62.4 per thousand for total lipids, -60.2 and -63.9 per thousand for phospholipid fatty acids, and -71.8 and -73.8 per thousand for sterols. These stable carbon isotope values revealed that the relative fractionation pattern was similar to the patterns obtained in pure culture experiments with methanotrophic bacteria further supporting the conversion of the bacterial methyl-sterol pool.

  9. Development of hydrophobic catalyst for hydrogen isotope exchange between hydrogen gas and liquid water (Preprint No. CI-2)

    International Nuclear Information System (INIS)

    The exchange of deuterium between hydrogen and water is important for heavy water production. The exchange reaction is too slow and requires a catalyst for any practicability. However usual catalysts lose their catalytic activity in contact with liquid water probably because of water engulfing all the catalytic sites and preventing hydrogen from reaching them. This problem has been overcome by imparting hydrophobicity to these catalysts. A brief account of the development of a hydrophobic catalyst Pt-C-PTFE is given. (author). 16 refs., 4 tabs., 6 figs

  10. Chemical and Isotopic Composition of Rain water in Coastal and Highland Regions in Lebanon

    International Nuclear Information System (INIS)

    Rain water samples were collected from six stations at coasted and highland regions in Lebanon and analyzed for the major species Ca2+ , K+ , Na+, Mg2+ ,NO3, NH-4, pH , Cl-, and SO2-4. Absolute concentration and element-to sodium ratios show clear variation with higher levels found in coastal stations and lower levels found in continental sites for most of the species Levels of major species from coastal areas can be twice as high those of the highland in terms of both absolute concentration and element-to-sodium ratio. The contrast between low and high altitudes can be explained by proximity to the Mediterranean Sea and local agricultural pollution sources. Isotopic composition of rainwater in coastal sites presents high values of δ18O and δD, whereas rainwater in continental areas is characterized by low values of δ18O and δD. The altitude effect influences the isotopic fractionation in precipitation, including Water Line was defined as δD = 7.13 δ18O + 15.98. This relation is close to the Regional Meteoric water Line in the eastern Mediterranean with a lower d-excess indicating a relatively less pronounced secondary evaporation effect in Lebanon. From a series of 3H data of monthly precipitation from six stations within the small country of Lebanon, we concluded that between stations there are significant differences in altitude effect. However , a small continental effect is apparent at the Baalbak station. (author)

  11. Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed – Lake exchange

    International Nuclear Information System (INIS)

    Highlights: • Trace element concentrations and lead isotopic ratios were measured in sediment. • Increased element fluxes driven by increased erosion rates linked to land use changes. • Lead isotopic ratios suggest the two sites received lead input from different sources. - Abstract: Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815–1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements – likely caused by changes in land use – over that period. For example, the flux of Pb increased by ∼300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r = 0.77–0.99, p < 0.05) between the fluxes of Co, Cu, Mn, Ni, Pb, and Zn and those of iron (Fe) at both sites, (ii) positive correlations (r = 0.82–0.98, p < 0.01, n = 9) between the fluxes of elements (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) and the mass accumulation rates at the offshore site, (iii) the low enrichment factors (EF < 5) of those trace elements, and (iv) the temporal consistencies of the isotopic composition of Pb in the sediment. These measurements indicate that accelerated weathering, rather than industrialization, accounts for most of the increases in trace element fluxes to Lake Tanganyika in spite

  12. Chemical maintenance of heat exchangers and condensers for prevention of corrosion and fouling [Paper No.: VI B-6

    International Nuclear Information System (INIS)

    The present paper describes the various types of corrosion, viz., inlet local and malignant impingement attacks, biofouling, sand erosion, etc. to which condenser tubes of the heat exchangers of the nuclear power plants are susceptible. Mention is also made to the effects of under deposit differential oxygen cell attack, leading to general wastage/pitting corrosion of heat exchanger shells and tubes outer surfaces because of stagnant conditions. Regular and systematic monitoring of water chemistry parameters helps in formulation of remedial measures whenever necessary; the data obtained from the improved maintenance methods serve as useful feed back. In the present paper these aspects of chemical maintenance are illustrated by reference to two methods commonly employed in pre-treatment of condenser cooling water/process water used in heat exchangers. Ferrous sulphate is added to condenser cooling water for promoting the formation of protective coating on inside surfaces of condenser tubes. In addition, inhibitors are also employed for corrosion prevention. Chlorine is injected as biocide in the process water/condenser cooling water to remove biogrowth which would seriously interfere with the efficiency of heat transfer. In both instances treatment schedules and treatment levels are constantly kept under review for efficient management. (author)

  13. Chemical exchange saturation transfer (CEST) and MR Z-spectroscopy in vivo: a review of theoretical approaches and methods

    International Nuclear Information System (INIS)

    Chemical exchange saturation transfer (CEST) of metabolite protons that undergo exchange processes with the abundant water pool enables a specific contrast for magnetic resonance imaging (MRI). The CEST image contrast depends on physical and physiological parameters that characterize the microenvironment such as temperature, pH, and metabolite concentration. However, CEST imaging in vivo is a complex technique because of interferences with direct water saturation (spillover effect), the involvement of other exchanging pools, in particular macromolecular systems (magnetization transfer, MT), and nuclear Overhauser effects (NOEs). Moreover, there is a strong dependence of the diverse effects on the employed parameters of radiofrequency irradiation for selective saturation which makes interpretation of acquired signals difficult. This review considers analytical solutions of the Bloch–McConnell (BM) equation system which enable deep insight and theoretical description of CEST and the equivalent off-resonant spinlock (SL) experiments. We derive and discuss proposed theoretical treatments in detail to understand the influence of saturation parameters on the acquired Z-spectrum and how the different effects interfere and can be isolated in MR Z-spectroscopy. Finally, we provide an overview of reported CEST effects in vivo and discuss proposed methods and technical approaches applicable to in vivo CEST studies on clinical MRI systems. (topical review)

  14. The application of Dow Chemical's perfluorinated membranes in proton-exchange membrane fuel cells

    Science.gov (United States)

    Eisman, G. A.

    1990-02-01

    Dow Chemical's research activities in fuel cells revolve around the development of perfluorosulfonic acid membranes, useful as the proton transport medium and separator. The following work will outline some of the performance characteristics which are typical for such membranes.

  15. Lithium isotope separation by 6Li/7Li countercurrent exchange between lithium-amalgam and aqueous LiOH in a spray column

    International Nuclear Information System (INIS)

    Lithium isotope separation by 6Li/7Li exchange between lithium-amalgam and aqueous LiOH has been investigated by using a column consisting of a vertical Pyrex glass tube in which aqueous LiOH flows up and a fine spray of lithium-amalgam falls down. As the number of theoretical plates, a value of 48 was obtained on a single column while the amalgam stability was η = 0.74, where η is the ratio between Li concentration in amalgam at the column bottom and that at the column top. That is, a large separation may be obtained in a single column in spite of amalgam decomposition which takes place as a side reaction. (author)

  16. Szilard-Chalmers effect and isotopic exchange reactions in a mixed valency compound Tl3(I) (Tl(III)Cl6)

    International Nuclear Information System (INIS)

    Transfer annealing has been studied in solid 204Tl(I) or 204Tl(III) labelled Tl2Cl6. Three steps are evidenced, and the annealing is not influenced by pre-irradiating with gamma-rays, nor by the presence or not of oxygen. Grinding of the samples leads to an important increase of the weight of the step of lowest activation energy, without modifying significantly the activation energy of each step. Isotopic exchange is invoked for explaining the results. Reactor irradiation of the compound leads to a 1/5 proportion for 204Tl(III)/204Tl(I). The evolution of these species on heating is identical to that observed for the labelled samples, which imply a common mechanism. It is therefore suggested the recoil species rapidly stabilize in the lattice in the form of stable chlorinated ions, such as are well known in aqueous solutions

  17. Positive-pion double-charge-exchange reaction: experiments on the isotopic pairs oxygen-16,18 and magnesium-24,26

    International Nuclear Information System (INIS)

    The (π+,π-) double-charge-exchange (DCX) reaction has been performed on targets of T = 0,1 isospin (and isotopic) pairs 1618O and 2426Mg. Energy excitation functions of d sigma/d Ω, across the (3,3) π-N resonance, are presented for transitions to double-isobaric analog state (DIAS) and non-DIAS ground-state residual nuclei. Angular distributions in the region of 50 to 330 are presented for the DIAS from the T = 1 nuclei. The similarities and differences of DIAS and non-DIAS distributions are discussed in relation to reaction-mechanism and nuclear-structure effects. Also, a simple, two-amplitude model for the 18O excitation function, consistent with the data, is presented. The utility of DCX in nuclear mass measurements is discussed, with some examples

  18. Positive-pion double-charge-exchange reaction: experiments on the isotopic pairs oxygen-16,18 and magnesium-24,26

    Energy Technology Data Exchange (ETDEWEB)

    Greene, S.J.

    1981-06-01

    The (..pi../sup +/,..pi../sup -/) double-charge-exchange (DCX) reaction has been performed on targets of T = 0,1 isospin (and isotopic) pairs /sup 16/ /sup 18/O and /sup 24/ /sup 26/Mg. Energy excitation functions of d sigma/d ..cap omega.., across the (3,3) ..pi..-N resonance, are presented for transitions to double-isobaric analog state (DIAS) and non-DIAS ground-state residual nuclei. Angular distributions in the region of 5/sup 0/ to 33/sup 0/ are presented for the DIAS from the T = 1 nuclei. The similarities and differences of DIAS and non-DIAS distributions are discussed in relation to reaction-mechanism and nuclear-structure effects. Also, a simple, two-amplitude model for the /sup 18/O excitation function, consistent with the data, is presented. The utility of DCX in nuclear mass measurements is discussed, with some examples.

  19. Effect of isotopic hydrogen exchange on thermochemistry of solution of ammonium halides and deuteroammonium in water, heavy water and their mixtures with dimethylsulfoxide

    International Nuclear Information System (INIS)

    Standard dissolution enthalpies of ammonium and deuteroammonium bromides and iodides in water, heavy water and their mixtures with dimethylsulfoxide (DMSO) at 298.15 K and compositions up to X=0.4 (X-mole part of DMSO) are presented. The influence of isotopic hydrogen exchange on the values of the standard dissolution enthalpies of NH4Cl, ND4Cl, NH4Br, ND4BR and NH4I in H2O, D2O and H2O (D2O)-DMSO mixture at 298.15 K, as well as of NH4Cl and ND4Cl in the same solvents at 323.15 K has been discussed. The values of NH4Cl and ND4Cl crystal lattice enthalpies have been compared. 15 refs., 3 tabs

  20. A preserving procedure for the anti-corrosive shielding in the H2O-H2S isotopic exchange installations

    International Nuclear Information System (INIS)

    The anti-corrosive protection of the H2O-H2S isotopic exchange installations consisting of an adherent deposition of iron sulfides, particularly pyrite and pyrotite, undergo at the contact with atmospheric air degrading processes which impair their protective role against the operation environment. Consequently, for long period of interruption, preserving measures should be provided. The procedure achieved and applied in the pilot installation of ICIS - Rm.Valcea consists in pressurization at 0.5 - 2 bar with nitrogen or hydrogen sulfide of the equipment, while the oxygen containing gases should not exceed a 0.1% volume. The experimental testing have determined that after an 1 year period the anti-corrosive protection do not undergo modifications in what concerns the morpho-structural characteristics of the passivating layers. This procedure is recommended for conserving the GS ROMAG installations over long periods

  1. Paleoceanographic environment of Japan Sea deduced from chemical and isotopic features of Miocene-Pliocene sedimentary rocks

    International Nuclear Information System (INIS)

    Chemical and isotopic analyses (Sr isotopic ratio, major element, trace element, rare earth element, total carbon, nitrogen, and sulfur contents) of rock samples collected from middle Miocene to early Pliocene sedimentary rocks, Oga Peninsula, northern Japan were performed to elucidate the paleoceanographic environment of Japan Sea. The rocks studied include shale from Nishikurosawa, Onnagawa, and Funakawa formations in stratigraphically ascending order. The Onnagawa sedimentary rocks in the lower (ca. 12.6-11.4 Ma), middle (ca. 10.5-9.0 Ma), and upper (ca. 8.3-7.0 Ma) horizons are characterized by high Mo/Al, P/Al, and Ba/Al ratios and total organic carbon content. Positive Eu anomaly, K/Ti ratio and 87Sr/86Sr ratio are also high in the same horizons. These geochemical variations imply that high primary productivity, and reducing condition of deep paleoocean, and formation of petroleum source rocks were caused by an upwelling of deep seawater. The upwelling of deep seawater is considered to have been influenced by strong winds from the Asian continent, which was related to the uplift of Himalayan and Tibetan regions. (author)

  2. Process and Control Design for a Novel Chemical Heat Exchange Reactor

    OpenAIRE

    Haugwitz, Staffan; Hagander, Per; Norén, Tommy

    2006-01-01

    A new chemical reactor, the Open Plate Reactor (OPR), is being developed by Alfa Laval AB. It has a very flexible configuration with distributed inlet ports, cooling zones and internal sensors. This gives the OPR improved control capabilities compared to standard chemical reactors in addition to better heat transfer capacity. In this paper, we address the relationship between the process design, the number of actuators used and how to use these actuators in feedback contro...

  3. Determination of wine authenticity and geographical origin by measuring non-exchangeable hydrogen stable isotopes in wine ethanol with EIM-IRMS® methodology in combination with δ18O values obtained from wine water.

    Science.gov (United States)

    Smajlovic, Ivan; Glavanovic, Mirko; Sparks, Kimberlee L.; Sparks, Jed P.; Jovic, Slobodan

    2014-05-01

    Wine consumption has grown significantly in the last two decades, with the United States being the leading consumer of wine in the world. It is also the second largest wine producer and importer after the European Union, which consists of 27 European countries. The world has seen a significant increase in production from new world countries, especially the United States, Australia and Chile, and wine imports have grown significantly with this globalization. The quality and authenticity of products have become critical concerns. With the amount of wine being imported the need for verifying wine authenticity and understanding procedures used in wine making has become more important than ever. Understanding the origin of consumed wine in rapidly expanding global economy has become fundamental in order to control quality and protect consumers. In our previous scientific work we have shown that EIM-IRMS®, Ethanol Isotope Measurement - Isotope Ratio Mass Spectrometry (EIM-IRMS®), is capable of providing unique molecular fingerprint that cannot be reproduced or counterfeited. Today we know that δ18O value from the wine water is one of the most important parameters which can give information about wine geographical origin. Earlier we have suggested that grape juice or grape pulp is a closed biochemical system in which all chemical compounds stand in dynamic equilibrium and are in direct connection with each other. Taking that into consideration we have concluded that if system is genuine and if no water, or no sugar has been added to the grape must or grape juice prior to alcoholic fermentation, then ethanol which is made in process of alcoholic fermentation will have specific δD value of non-exchangeable hydrogen stable isotopes which will be in range from -205 to -215 ‰ vs. V-SMOW. In this work we will show that this value, which we named δDn (non-exchangeable hydrogen stable isotopes in ethanol), is very important because it can support or refute conclusions

  4. MRI nanoprobes based on chemical exchange saturation transfer: LnIII chelates anchored on the surface of mesoporous silica nanoparticles

    Science.gov (United States)

    Ferrauto, Giuseppe; Carniato, Fabio; Tei, Lorenzo; Hu, He; Aime, Silvio; Botta, Mauro

    2014-07-01

    The formation of ternary complexes between neutral LnIII-DO3A chelates anchored on MCM-41 mesoporous silica nanoparticles (MSNs) and silanol groups on the surface allows obtaining highly efficient chemical exchange saturation transfer (CEST) MRI nanoprobes. These new probes achieve excellent sensitivity in the μM range (per LnIII ion), significantly greater than that of other paramagnetic CEST nanosystems such as dendrimers or micelles and three orders of magnitude higher than that of the corresponding molecular agents.The formation of ternary complexes between neutral LnIII-DO3A chelates anchored on MCM-41 mesoporous silica nanoparticles (MSNs) and silanol groups on the surface allows obtaining highly efficient chemical exchange saturation transfer (CEST) MRI nanoprobes. These new probes achieve excellent sensitivity in the μM range (per LnIII ion), significantly greater than that of other paramagnetic CEST nanosystems such as dendrimers or micelles and three orders of magnitude higher than that of the corresponding molecular agents. Electronic supplementary information (ESI) available: Synthesis and characterization of the materials; Z- and ST-spectra of all materials; sensitivity threshold for TmDO3A-MCM-41 and EuDO3A-MCM-41 pH and temperature dependence of ST% for TbDO3A-MCM-41. See DOI: 10.1039/c4nr02753a

  5. The role of rock in chemical and isotopic composition of groundwater in the vicinity of radioactive waste disposal site

    International Nuclear Information System (INIS)

    The research results of the hydrodynamic situation, as well as the chemical and isotopic compositions of target aquifers in the vicinity of radioactive waste storage are considered. The surpassing of water quality standards for Ra- 226, α-activity, Si, Fe, F, and some heavy metals was detected in target Upper Carboniferous aquifers. It was ascertained that the main reason for these changes was disturbance of hydrodynamic conditions as a result of withdrawal enhancement. Intensification of water-rock interactions caused the values of Ra-226 and a-activity to increase in target aquifers, because the main natural sources of Ra-226 are water-bearing rocks containing flints with natural radioactivity and overlying Jurassic layers containing phosphorite. Descending or ascending groundwater leakage caused contaminant incursion from the adjacent aquifers. (authors)

  6. The Strontium Isotope Record of Zavkhan Terrane Carbonates: Strontium Isotope Stability Through the Ediacaran-Cambrian Transition

    OpenAIRE

    Petach, Tanya N.

    2015-01-01

    First order trends in the strontium isotopic (87Sr/86Sr) composition of seawater are controlled by radiogenic inputs from the continent and non-radiogenic inputs from exchange at mid-ocean ridges. Carbonates precipitated in seawater preserve trace amounts of strontium that record this isotope ratio and therefore record the relative importance of mid-ocean ridge and weathering chemical inputs to sea water composition. It has been proposed that environmental changes during the Ediacaran-Cambria...

  7. Estimates of regional surface carbon dioxide exchange and carbon and oxygen isotope discrimination during photosynthesis from concentration profiles in the atmospheric boundary layer

    International Nuclear Information System (INIS)

    The integrating properties of the atmospheric boundary layer allow the influence of surface exchange processes on the atmosphere to be quantified and estimates of large-scale fluxes of trace gases and plant isotopic discrimination to be made. Five flights were undertaken over two days in and above the convective boundary layer (CBL) in a vegetated region in central Siberia. Vertical profiles of CO2 and H2O concentrations, temperature and pressure were obtained during each flight. Air flask samples were taken at various heights for carbon and oxygen isotopic analysis of CO2. Two CBL budget methods were compared to estimate regional surface fluxes of CO2 and plant isotopic discrimination against 13CO2 and C18O16O. Flux estimates were compared to ground-based eddy covariance measurements. The fluxes obtained for CO2 using the first method agreed to within 10% of fluxes measured in the forest at the study site by eddy covariance. Those obtained from the second method agreed to within 35% when a correction was applied for air loss out of the integrating column and for subsidence. The values for 13C discrimination were within the range expected from knowledge of C3 plant discriminations during photosynthesis, while the inferred 18O discrimination varied considerably over the two-day period. This variation may in part be explained by the enrichment of chloroplast water during the day due to evaporation from an initial signature in the morning close to source water. Additional potential complications arising from the heterogeneous nature of the landscape are discussed

  8. Pollutant removal from industrial discharge water using individual and combined effects of adsorption and ion-exchange processes: Chemical abatement

    Directory of Open Access Journals (Sweden)

    Jérémie Charles

    2016-03-01

    Full Text Available In this study, adsorption-oriented processes for pollutant removal from metal polycontaminated surface-finishing discharge water were applied individually as well as in combination with ion-exchange treatment to remove the remaining metal ions and organic load. Several materials were compared using batch experiments, namely an activated carbon, three ion-exchange resins (IRA 402Cl, IR 120H and TP 207, and two non-conventional cross-linked polysaccharide-based biosorbents (starch and cyclodextrin. This article presents the abatements obtained in chemical pollution as monitored by complete chemical analysis. For the same experimental conditions (similar discharge water, pollutant concentrations, stirring rate, contact time, and initial pH, the highest levels of pollutant removal were attained with the combined use of two materials, an activated carbon and a mixture of two ion-exchange resins. This physicochemical treatment effectively lowered the main pollutants present in the discharge water such as Cu, Ni and COD, by more than 96%, 79% and 74% respectively (average values for three samples, while the treatment with carbon alone lowered them by 58%, 9% and 70%, and resins alone by 85%, 61% and 16%. Similar interesting results were obtained with the cyclodextrin-based adsorbent and its use alone was sufficient to obtain decreases in Cu, Ni and COD of more than 94%, 77% and 67% respectively. The adsorption-oriented process using cyclodextrin polymer could be an advantageous approach for removing organic and metallic pollutants from metal surface-finishing discharge water due to the non-toxic character of CD to humans and the environment.

  9. Prominent features in isotopic, chemical and dust stratigraphies from GV7, a drilling site in East Antarctica

    Science.gov (United States)

    Caiazzo, Laura

    2016-04-01

    In the framework of the new project "The IPICS 2k Array: a network of ice core climate and climate forcing records for the last two millennia", which represents a thematic research line of International Partnerships in Ice Core Sciences (IPICS), a 250 m deep ice core was retrieved (spanning roughly the last millennium) at GV7 site, together with several shallow firn cores and snow pits. The PNRA (Programma Nazionale di Ricerche in Antartide) project "IPICS-2kyr-It" represents the Italian contribution to IPICS "The 2k Array" and it is being accomplished in collaboration with KOPRI (Korean Polar Reasearch Institute). The availability of various records from the same site all spanning a temporal period ranging from the last decades to the last centuries will allow achieving a stacked record of chemical and isotopic markers and accumulation rate that is basic for a reliable climatic reconstruction. Previous surveys in the area of GV7 (70°41' S - 158°51' E, 1950 m a.s.l., East Antarctica) showed that this site is characterized by a relatively high snow accumulation (about 240 mm water eq./year), allowing a high resolution study of the climatic variability in the last millennium. Here we present the isotopic, chemical and dust stratigraphies of the snow pits sampled at GV7 during the 2013/14 field season and analysed in Italy and in Korea. Reversibly deposited components such as nitrate and methansulphonic acid (MSA) appear to be well preserved and show a clear seasonal profiles, as one can observe from the records achieved both by Italian and Korean labs. Such a feature, together with the high accumulation rate, allowed obtaining an accurate dating of the snow pits, based on the counting of annual layers. At this purpose, a multi-parametric approach was chosen by using MSA, non-sea-salt sulphate, and d18O as seasonal markers. The dating confirmed the value of the accumulation rate found during previous samplings.

  10. Identification of Groundwater Nitrate Contamination from Explosives Used in Road Construction: Isotopic, Chemical, and Hydrologic Evidence.

    Science.gov (United States)

    Degnan, James R; Böhlke, J K; Pelham, Krystle; Langlais, David M; Walsh, Gregory J

    2016-01-19

    Explosives used in construction have been implicated as sources of NO3(-) contamination in groundwater, but direct forensic evidence is limited. Identification of blasting-related NO3(-) can be complicated by other NO3(-) sources, including agriculture and wastewater disposal, and by hydrogeologic factors affecting NO3(-) transport and stability. Here we describe a study that used hydrogeology, chemistry, stable isotopes, and mass balance calculations to evaluate groundwater NO3(-) sources and transport in areas surrounding a highway construction site with documented blasting in New Hampshire. Results indicate various groundwater responses to contamination: (1) rapid breakthrough and flushing of synthetic NO3(-) (low δ(15)N, high δ(18)O) from dissolution of unexploded NH4NO3 blasting agents in oxic groundwater; (2) delayed and reduced breakthrough of synthetic NO3(-) subjected to partial denitrification (high δ(15)N, high δ(18)O); (3) relatively persistent concentrations of blasting-related biogenic NO3(-) derived from nitrification of NH4(+) (low δ(15)N, low δ(18)O); and (4) stable but spatially variable biogenic NO3(-) concentrations, consistent with recharge from septic systems (high δ(15)N, low δ(18)O), variably affected by denitrification. Source characteristics of denitrified samples were reconstructed from dissolved-gas data (Ar, N2) and isotopic fractionation trends associated with denitrification (Δδ(15)N/Δδ(18)O ≈ 1.31). Methods and data from this study are expected to be applicable in studies of other aquifers affected by explosives used in construction. PMID:26709616

  11. Deposition of carbon nanotubes by a marine suspension feeder revealed by chemical and isotopic tracers

    Energy Technology Data Exchange (ETDEWEB)

    Hanna, Shannon K., E-mail: hanna.shannonk@gmail.com [Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106 (United States); Miller, Robert J. [Marine Science Institute, University of California, Santa Barbara, CA 93106 (United States); Lenihan, Hunter S. [Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106 (United States)

    2014-08-30

    Highlights: • CNTs decrease the filtration rate of mussels by as much as 24%. • Metals in CNTs and their δ{sup 13}C can be used to quantify CNTs in biological samples. • Mussels exposed to CNTs deposit high concentrations of them in biodeposits. • CNTs accumulate mainly in gut tissue of mussels during exposure. - Abstract: Carbon nanotubes (CNTs) are one of the few truly novel nanomaterials and are being incorporated into a wide range of products, which will lead to environmental release and potential ecological impacts. We examined the toxicity of CNTs to marine mussels and the effect of mussels on CNT fate and transport by exposing mussels to 1, 2, or 3 mg CNTs l{sup −1} for four weeks and measuring mussel clearance rate, shell growth, and CNT accumulation in tissues and deposition in biodeposits. We used metal impurities and carbon stable isotope ratios of the CNTs as tracers of CNT accumulation. Mussels decreased clearance rate of phytoplankton by 24% compared with control animals when exposed to CNTs. However, mussel growth rate was unaffected by CNT concentrations up to 3 mg l{sup −1}. Based on metal concentrations and carbon stable isotope values, mussels deposited most CNTs in biodeposits, which contained >110 mg CNTs g{sup −1} dry weight, and accumulated about 1 mg CNTs g{sup −1} dry weight of tissue. We conclude that extremely high concentrations of CNTs are needed to illicit a toxic response in mussels but the ability of mussels to concentrate and deposit CNTs in feces and pseudofeces may impact infaunal organisms living in and around mussel beds.

  12. Arrhenius' law in turbulent media and an equivalent tunnel effect. [in binary exchange chemical reactions

    Science.gov (United States)

    Tsuge, S.; Sagara, K.

    1978-01-01

    The indeterminacy inherent to the formal extension of Arrhenius' law to reactions in turbulent flows is shown to be surmountable in the case of a binary exchange reaction with a sufficiently high activation energy. A preliminary calculation predicts that the turbulent reaction rate is invariant in the Arrhenius form except for an equivalently lowered activation energy. This is a reflection of turbulence-augmented molecular vigor, and causes an appreciable increase in the reaction rate. A similarity to the tunnel effect in quantum mechanics is indicated. The anomaly associated with the mild ignition of oxy-hydrogen mixtures is discussed in this light.

  13. The distribution of neodymium isotopes and concentrations in the Eastern Equatorial Pacific: Water mass advection versus particle exchange

    Science.gov (United States)

    Grasse, Patricia; Stichel, Torben; Stumpf, Roland; Stramma, Lothar; Frank, Martin

    2012-11-01

    The radiogenic isotope composition of the Rare Earth Element (REE) neodymium (Nd) is a powerful water mass proxy for present and past ocean circulation. The processes controlling the Nd budget of the global ocean are not quantitatively understood and in particular source and sink mechanisms are still under debate. In this study we present the first full water column data set of dissolved Nd isotope compositions and Nd concentrations for the Eastern Equatorial Pacific (EEP), where one of the globally largest Oxygen Minimum Zones (OMZ) is located. This region is of particular interest for understanding the biogeochemical cycling of REEs because anoxic conditions may lead to release of REEs from the shelf, whereas high particle densities and fluxes potentially remove the REEs from the water column. Data were obtained between 1°40‧N and 16°S along a nearshore and an offshore transect. Near surface zonal current bands, such as the Equatorial Undercurrent (EUC) and the Subsurface Countercurrent (SSCC), which are supplying oxygen-rich water to the OMZ are characterized by radiogenic Nd isotope signatures (εNd=-2). Surface waters in the northernmost part of the study area are even more radiogenic (εNd=+3), most likely due to release of Nd from volcanogenic material. Deep and bottom waters at the southernmost offshore station (14°S) are clearly controlled by advection of water masses with less radiogenic signatures (εNd=-7) originating from the Southern Ocean. Towards the equator, however, the deep waters show a clear trend towards more radiogenic values of up to εNd=-2. The northernmost station located in the Panama basin shows highly radiogenic Nd isotope signatures in the entire water column, which indicates that particle scavenging, downward transport and release processes play an important role. This is supported by relatively low Nd concentrations in deep waters (3000-6000 m) in the EEP (20 pmol/kg) compared to locations in the Northern and Central Pacific

  14. Determination of uranium isotopes in urine samples from radiation workers using 232U tracer, anion-exchange resin and alpha-spectrometry

    International Nuclear Information System (INIS)

    Bioassay technique is used for the estimation of actinides present in the body based on the excretion rate of body fluids. For occupational radiation workers urine assay is the preferred method for monitoring of chronic internal exposure. Determination of low concentrations of actinides such as plutonium, americium and uranium at low level of mBq in urine by alpha-spectrometry requires pre-concentration of large volumes of urine. This paper deals with standardization of analytical method for the determination of U-isotopes in urine samples using anion-exchange resin and 232U tracer for radiochemical recovery. The method involves oxidation of urine followed by co-precipitation of uranium along with calcium phosphate. Separation of U was carried out by Amberlite, IRA-400, anion-exchange resin. U-fraction was electrodeposited and activity estimated using tracer recovery by alpha-spectrometer. Eight routine urine samples of radiation workers were analyzed and consistent radiochemical tracer recovery was obtained in the range of 51% to 67% with a mean and standard deviation of 60% and 5.4%, respectively. (author)

  15. Kinetic estimation of hydrogen isotope exchange reaction between tritiated-water (HTO) vapor and each amino acid in a heterogeneous system

    International Nuclear Information System (INIS)

    The hydrogen isotope exchange reaction between HTO vapor and each amino acid has been observed in order to establish a method of estimation of the internal exposure of organically bound tritium in a heterogeneous system at 25-70degC. Rate constants (k) for the amino acids have been obtained by applying the A''-McKay plot method. Using these k values, Arrhenius plots for both the COOH and NH2 groups are drawn, and linearity was obtained over the range of 25-70degC. Comparing the rate constants, the following four statements can be made regarding the T-for-H exchange reaction. (1) The reactivity of the functional groups in amino acids increases with increasing temperature. (2) Applying Taft's equation, the ratio of polar effect to steric effect is 2:8 in the COOH group and 9:1 in the NH2 group at 25degC. (3) The A''-McKay plot method is useful for studying the reactivity of materials, not only with one (or the same kind of) functional group(s) but also with two different kinds of functional groups. (4) The method used in this work may be useful to investigate the behavior of organically bound tritium, quantitatively. (author)

  16. Nondestructive radio isotopic technique for performance evaluation of industrial grade anion exchange resins Amberlite IRN78 and Indion NSSR

    International Nuclear Information System (INIS)

    The present study deals with the application of radiotracers 131I and 82Br as a non-destructive tool to evaluate the performance of Amberlite IRN78 (nuclear grade) and Indion NSSR (non-nuclear grade) anion exchange resins. In general based on radiotracer applications it was observed that Amberlite IRN78 resins show superior performance over Indion NSSR resins under identical operational parameters.

  17. Nondestructive radio isotopic technique for performance evaluation of industrial grade anion exchange resins Amberlite IRN78 and Indion NSSR

    Energy Technology Data Exchange (ETDEWEB)

    Singare, Pravin U. [Bhavan' s College, Mumbai (India). Dept. of Chemistry

    2016-01-15

    The present study deals with the application of radiotracers 131I and 82Br as a non-destructive tool to evaluate the performance of Amberlite IRN78 (nuclear grade) and Indion NSSR (non-nuclear grade) anion exchange resins. In general based on radiotracer applications it was observed that Amberlite IRN78 resins show superior performance over Indion NSSR resins under identical operational parameters.

  18. Chemical, multi-isotopic (Li-B-Sr-U-H-O) and thermal characterization of Triassic formation waters from the Paris Basin

    OpenAIRE

    Millot, Romain; Guerrot, Catherine; Innocent, Christophe; Négrel, Philippe; Sanjuan, Bernard

    2011-01-01

    International audience This work reports chemical and isotope data and temperature estimates for seven water samples collected from Triassic formations in the Paris Basin in France. Four samples were collected in the central part of the Basin (saline waters) and three were collected at the edge of the Basin near the recharge zone (dilute waters). The saline waters collected from the Chaunoy and Champotran boreholes have high salinities (around 120 g/L) and very similar chemical and isotopi...

  19. Biology and air–sea gas exchange controls on the distribution of carbon isotope ratios (δ13C in the ocean

    Directory of Open Access Journals (Sweden)

    A. Schmittner

    2013-05-01

    Full Text Available Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate the processes that control the distribution of δ13C in the contemporary and preindustrial ocean. Biological fractionation dominates the distribution of δ13CDIC of dissolved inorganic carbon (DIC due to the sinking of isotopically light δ13C organic matter from the surface into the interior ocean. This process leads to low δ13CDIC values at dephs and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air–sea gas exchange provides an important secondary influence due to two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature dependent fractionation tends to increase (decrease δ13CDIC values of colder (warmer water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, air-sea gas exchange is slow, so biological effect dominate spatial δ13CDIC gradients both in the interior and at the surface, in constrast to conclusions from some previous studies. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed (δ13Cpre and remineralized (δ13Crem contributions as well as the effects of biology (Δδ13Cbio and air–sea gas exchange (δ13C*. The model reproduces major features of the observed large-scale distribution of δ13CDIC, δ13Cpre, δ13Crem, δ13C*, and Δδ13Cbio. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by details of the ecosystem model formulation. For example, inclusion of a simple parameterization of iron limitation of phytoplankton growth rates and temperature-dependent zooplankton grazing rates improves the agreement

  20. Long-term fertilization alters chemically-separated soil organic carbon pools: Based on stable C isotope analyses

    Science.gov (United States)

    Dou, Xiaolin; He, Ping; Cheng, Xiaoli; Zhou, Wei

    2016-01-01

    Quantification of dynamics of soil organic carbon (SOC) pools under the influence of long-term fertilization is essential for predicting carbon (C) sequestration. We combined soil chemical fractionation with stable C isotope analyses to investigate the C dynamics of the various SOC pools after 25 years of fertilization. Five types of soil samples (0-20, 20-40 cm) including the initial level (CK) and four fertilization treatments (inorganic nitrogen fertilizer, IN; balanced inorganic fertilizer, NPK; inorganic fertilizer plus farmyard manure, MNPK; inorganic fertilizer plus corn straw residue, SNPK) were separated into recalcitrant and labile fractions, and the fractions were analysed for C content, C:N ratios, δ13C values, soil C and N recalcitrance indexes (RIC and RIN). Chemical fractionation showed long-term MNPK fertilization strongly increased the SOC storage in both soil layers (0-20 cm = 1492.4 gC m2 and 20-40 cm = 1770.6 gC m2) because of enhanced recalcitrant C (RC) and labile C (LC). The 25 years of inorganic fertilizer treatment did not increase the SOC storage mainly because of the offsetting effects of enhanced RC and decreased LC, whereas no clear SOC increases under the SNPK fertilization resulted from the fast decay rates of soil C.