Extraterrestrial3 He in marine polymetallic nodules: A potential method for measuring growth rate of nodules

The comparative measurements of helium isotope compositions between marine polymetallic nodules and their surrounding sediments, their magnetic fractions and bulk from C-C Zone of the East Pacific Basin are reported. The⁴He content and³He/⁴He ratio of polymetallic nodules and their surrounding sediments are extremely high; the³He,⁴ He concentrations and most³He/⁴He ratios of magnetic fractions in nodules and sediments are apparently higher than those in bulk. The helium isotope data points of nodules and sediments are all distributed along or closely to the mixing curve of the interplanetary dust particles (IDPs) and the terrigenous sediments in the chart of³He-³He/⁴He. In the same sampling site, the³He/⁴He ratios of nodules and their surrounding sediments are very similar, and the changes of both ratios are synchronous. It shows that the high³He/⁴He ratios in nodules and sediments may all result from IDPs. So, if the flux of extraterrestrial³He into the nodules and sediments is constant, the growth rate of polymetallic nodules and the sedimentation rate of sediments can be independently calculated according to the concentra-tion of extraterrestrial³He in nodules and sediments.

     

Extraterrestrial ~3He in marine polymetallic nodules: a potential method for measuring growth rate of nodules

The comparative measurements of helium isotope compositions between marine poly-metallic nodules and their surrounding sediments, their magnetic fractions and bulk from C-C Zoneof the East Pacific Basin are reported. The ~4He content and ~3He/~4He ratio of polymetallic nodulesand their surrounding sediments are extremely high; the ~3He, ~4He concentrations and most~3He/~4He ratios of magnetic fractions in nodules and sediments are apparently higher than those inbulk. The helium isotope data points of nodules and sediments are all distributed along or closelyto the mixing curve of the interplanetary dust particles (IDPs) and the terrigenous sediments in thechart of ~3He-~3He/~4He. In the same sampling site, the ~3He/~4He ratios of nodules and their surround-ing sediments are very similar, and the changes of both ratios are synchronous. It shows that thehigh ~3He/~4He ratios in nodules and sediments may all result from IDPs. So, if the flux of extrater-restrial ~3He into the nodules and sediments is constant, the growth rate of polymetallic nodules andthe sedimentation rate of sediments can be independently calculated according to the concentra-tion of extraterrestrial ~3He in nodules and sediments.     

Detection of tritium and alpha decaying radionuclides in L/ILW by measurements of helium isotopes

As decay products, helium isotopes can clearly indicate the presence of tritium and alpha decaying isotopes in a closed system. This study presents the helium and neon measurements and their interpretation of long-term headspace gas investigations in L/ILW waste drums from Paks Nuclear Power Plant and closed vaults of the Radioactive Waste Treatment and Disposal Facility, Püspökszilágy, Hungary. Development of special sampling methods and preparation lines as well as isotope-analytical measurements of the headspace gas samples were done in the Hertelendi Laboratory of Environmental Studies in the ATOMKI. In the gas samples helium isotopes as well as neon isotopes have been determined mass spectrometrically. While neon content can be of atmospheric origin only, helium can be produced either by alpha decay (⁴He) or decay of tritium (³He). ³H/⁴He and He/Ne ratios have been used to determine the different origin of the helium isotopes. Helium isotope ratios always represented ³He enrichment in the headspace gases produced by the decay of the tritium in the waste. Using the recent ³He concentration in headspace gas the total amount of ³H restored in L/ILW vaults was estimated. The investigated seven different vaults were closed between 1979 and 1995 when they had been full with L/ILW. The calculated tritium activities based on the He measurements showed good agreement with the documented isotope inventory of the vaults. Typical tritium activity concentrations were between 0.1 and 10 Bq/L gas in the drums and between 10 and 1000 Bq/L gas in the vaults. Additionally, one drum showed a higher He/Ne ratio compared to air, which clearly indicates ⁴He excess, thus the presence an alpha source in the waste.     

Intrinsic ratios of glucose,fructose, glycerol and ethanol <Superscript>13</Superscript>C/<Superscript>12</Superscript>C isotopic ratio determined by HPLC-<Emphasis Type="Italic">co</Emphasis>-IRMS: toward determining constants for wine authentication

High-performance liquid chromatography linked to isotope ratio mass spectrometry (HPLC-co-IRMS) via a Liquiface© interface has been used to simultaneously determine ¹³C isotope ratios of glucose (G), fructose (F), glycerol (Gly) and ethanol (Eth) in sweet and semi-sweet wines. The data has been used the study of wine authenticity. For this purpose, 20 authentic wines from various French production areas and various vintages have been analyzed after dilution in pure water from 20 to 200 times according to sugar content. If the ¹³C isotope ratios vary according to the production area and the vintage, it appears that internal ratios of ¹³C isotope ratios \(\left( {R_{^{13} C} } \right)\) of the four compounds studied can be considered as a constant. Thus, ratios of isotope ratios are found to be 1.00?±?0.04 and 1.02?±?0.08 for \(R_{^{13} C_{G/F} }\) and \(R_{^{13} C_{Gly/Eth} }\), respectively. Moreover, \(R_{^{13} C_{Eth/Sugar} }\) is found to be 1.15?±?0.10 and 1.16?±?0.08 for \(R_{^{13} C_{Gly/Sugar} }\). Additions of glucose, fructose and glycerol to a reference wine show a variation of the \(R_{^{13} C}\) value for a single product addition as low as 2.5 g/L^?1. Eighteen commercial wines and 17 concentrated musts have been analyzed. Three wine samples are suspicious as the \(R_{^{13} C}\) values are out of range indicating a sweetening treatment. Moreover, concentrated must analysis shows that ¹³C isotope ratio can be also used directly to determine the authenticity of the matrix.

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Figure HPLC-co-IRMS chromatogram of a diluted sweet wine.

     

Determination of <Superscript>241</Superscript>Am/<Superscript>243</Superscript>Am ratios

Determination of ²⁴¹Am/²⁴³Am ratios is required for vanous purposes including assay of Am by isotope dilution techniques. Alpha-spectrometry on electrodeposited sources is a preferred technique for this determination. However, there is an inherent problem of tail contribution which necessitates the use of suitable algorithms to account for the same. Recently, in the frame of a Coordinated Research Program (CRP) of the International Atomic Energy Agency (IAEA), WinALPHA software has been developed which is a combination of an asymmetrical Gaussian for the main part of the peak and a low energy function. Therefore, it was of interest to compare the use of this algorithm with the routinely used method, in our laboratory, based on geometric progression (G. P.) decrease. Since, there are no reference materials available commercially for ²⁴¹Am/²⁴³Am ratios, synthetic mixtures covening a wide range (0.3 to 2.0) of ²⁴¹Am/²⁴³Am α-activity ratios were used and un-ignited electrodeposited sources were prepared for α-spectrometry. The α-spectra obtained using PIPS detector, were evaluated using the two algonthms The ²⁴¹Am/²⁴³Am α-activity ratios obtained were also compared with those determined by thermal ionization mass spectrometry (TIMS). An agreement of about 1% was obtained in the ²⁴¹Am/²⁴³Am ratios determined by the two methods and also by using the two algorithms for α-spectrum evaluation.     

Finite size effects in the evaporation rate of3He clusters

We have computed the density of states and the evaporation rate of³He clusters, paying special attention to finite size effects which modify the³He level density parameter and chemical potential from their bulk values. Ready-to-use liquid-drop expansions of these quantities are given.     

Depth-profiling of deuterium in steels: Preparation of calibration standards

The preparation of a set of standards for the calibration of the analysis of deuterium using the²H/³He, p/⁴He reaction is described. Important considerations in the selection of a suitable standard are that it should be stable under irradiation and be simple to prepare with ready control of the amount of analyte. These requirements were met by Ca/OH/₂ which was prepared by the replacement of hydrogen with its isotope in known proportions in the reaction of CaO with water.     

<Superscript>234</Superscript>U/<Superscript>238</Superscript>U and <Superscript>235</Superscript>U/<Superscript>238</Superscript>U ratios in domestic water from the environs of Obuasi mine in Ghana

Activity concentrations of ²³⁸U, ²³⁵U and ²³⁴U were determined in different sources of drinking water at the Obuasi gold mines and its surrounding areas in Ghana. Water samples collected from the mines and its surrounding areas were analyzed using direct gamma-ray spectrometry and neutron activation analysis. The ²³⁴U/²³⁸U and ²³⁵U/²³⁸U ratios were calculated and the mean values range from 1.27 to 1.38 and from 0.044 to 0.045 respectively. The average ²³⁴U/²³⁸U ratio was from 1.27 for groundwater to 1.38 for treated water, demonstrating the lack of equilibrium. The average ²³⁵U/²³⁸U activity ratio is 0.045, indicating that only natural uranium was detected in the samples investigated.     

Hyperfine structure of the 33 P state of3He and isotope shift for the 23 S-33 P 0 transition

The hyperfine structure of the³He 1s 3p ³ P state and the³He-⁴He isotope shift is determined by high precision measurements of the 1s2s ³ S ₁-1s 3p ³ p ³ P _J transition frequencies near 389 nm. A direct frequency measurement is made without the need for wavelength calibration by tuning a single laser to the atomic frequency, and using a novel heterodyne method to observe beat frequencies with a stable reference laser. A fit to a theoretical model of hyperfine structure is used to determine the hyperfine shifts. Additional off-diagonal mixing effects are investigated to resolve a possible systematic discrepancy in the hyperfine intervals. The final isotope shift without hyperfine structure of 42184308±165 kHz is used to deduce an rms nuclear charge radius for³He of 1.956±0.042 fm. This is in good agreement with other values obtained from atomic isotope shift measurements, and a recent theoretical value of 1.958±0.006 fm. The present result helps to resolve substantial differences in the³He nuclear radius derived from electron-nuclear scattering measurements, and it provides a significant test of the nuclear three-body problem.     

Determination of <Superscript>226</Superscript>Ra in sediments by ICP-MS: A comparative study of three sample preparation approaches

Three protocols (Method I: ion chromatography (IC) and extraction chromatography (EC), Method II: precipitation followed by IC, and Method III: adsorption onto MnO₂ followed by IC-EC) were investigated to determine their applicability for the separation and pre-concentration of ²²⁶Ra in sediments. ²²⁶Ra recoveries, measured using the isotope dilution method with ²²⁸Ra as yield tracer, and the removal of spectral and non-spectral interferences were evaluated. The formation of polyatomic interferences at m/z = 226 from elements found in the matrix of sediments was also investigated to assess the level of separation required. Methods I and III were found to be the most effective with respect to recoveries and interference removal. The efficiency of a rapid microwave based protocol for the complete digestion of 1 g of sediment is also described. The method was tested and ²²⁶Ra concentrations in the millibecquerel range (fg) were determined in a standard reference material and sediment cores collected from Lake Baikal.     

Study on distribution of elements in deep-sea Pacific polymetallic nodules via two-dimensional mapping laser ionization orthogonal time-of-flight mass spectrometry

A newly developed two-dimensional mapping high irradiance laser ionization orthogonal time-of-flight mass spectrometer (LI-O-TOFMS) has been applied for the elemental mapping of polymetallic nodules. Two polymetallic nodule standards were used to demonstrate the efficacy of LI-O-TOFMS for the standardless semiquantitative analysis and the spatial distribution of elements in a deep-sea Pacific polymetallic nodule was mapped. It was found that the two groups of elements, Mn–Ni–Cu–Fe and Co–Si–Al, show clear element-dependent spatial relationships. It is hypothesized that these spatial distributions reflect the environmental and physico-chemical conditions during the nodule formation. LI-O-TOFMS is shown to be a powerful tool in elemental analysis of polymetallic nodules, with the detection limits down to 10^− 7 g/g and a dynamic range of 7 orders of magnitude. Based on the images acquired, the contents of elements and their relationships can be revealed visually.     

Analysis of lanthanides and actinides in sea sediments from the Gulf of Tehuantepec

Seawater contains trace elements in solution, such as lanthanides and uranium, which can act as natural tracers when they flocculate to form the sediments of the seabed. Uranium is a special case because it is a radioactive element with isotopic ratio close to 1.14 (²³⁴U/²³⁸U) in sea water. Uranium is also present in all fractions of sediments, although the isotopic ratio in each fraction takes a specific value depending on its origin and surrounding environment. This work has been conducted in order to analyze lanthanides and uranium in a core of sea sediments. It is focused on separating the fractions forming the layers along the depth profile of the core sample so as to determine the ²³⁴U/²³⁸U activity ratios in fractions of organic matter, aquatic life skeletons and dissolved minerals. The Neutron Activation Analysis showed the presence of U, Lu, Hf, Eu, Ce and Yb ranging up to 50 ppm while alpha spectrometry gave a series of ²³⁴U/²³⁸U activity ratios which are discussed on the basis of statistical analysis.     

3He NMR studies on helium–pyrrole,helium–indole,and helium–carbazole systems: a new tool for following chemistry of heterocyclic compounds

The ³He nuclear magnetic shieldings were calculated for free helium atom and He–pyrrole, He–indole, and He–carbazole complexes. Several levels of theory, including Hartree–Fock (HF), Second‐order Møller‐Plesset Perturbation Theory (MP2), and Density Functional Theory (DFT) (VSXC, M062X, APFD, BHandHLYP, and mPW1PW91), combined with polarization‐consistent pcS‐2 and aug‐pcS‐2 basis sets were employed. Gauge‐including atomic orbital (GIAO) calculated ³He nuclear magnetic shieldings reproduced accurately previously reported theoretical values for helium gas. ³He nuclear magnetic shieldings and energy changes as result of single helium atom approaching to the five‐membered ring of pyrrole, indole, and carbazole were tested. It was observed that ³He NMR parameters of single helium atom, calculated at various levels of theory (HF, MP2, and DFT) are sensitive to the presence of heteroatomic rings. The helium atom was insensitive to the studied molecules at distances above 5 Å. Our results, obtained with BHandHLYP method, predicted fairly accurately the He–pyrrole plane separation of 3.15 Å (close to 3.24 Å, calculated by MP2) and yielded a sizable ³He NMR chemical shift (about ?1.5 ppm). The changes of calculated nucleus‐independent chemical shifts (NICS) with the distance above the rings showed a very similar pattern to helium‐3 NMR chemical shift. The ring currents above the five‐membered rings were seen by helium magnetic probe to about 5 Å above the ring planes verified by the calculated NICS index. Copyright © 2014 John Wiley & Sons, Ltd.     

<Superscript>206</Superscript>Pb/<Superscript>207</Superscript>Pb ratios in dry deposit samples from the Metropolitan Zone of Mexico Valley

²⁰⁶Pb/²⁰⁷Pb isotope ratios of dry deposit samples in the Metropolitan Zone of Mexico Valley (MZMV) were determined and correlated with some contemporary environmental material such as gasoline, urban dust, etc., as possibile pollution sources, the latter presenting different signatures ²⁰⁶Pb/²⁰⁷Pb ratios were determined in samples “as is” by ICP-MS, using an Elan-6100. A standard material NIST-981 was used to monitor accuracy and to correct mass fractionation. The calculated enrichment factors of lead (taking rubidium as a conservative endogenous element) show its anthropogenic origin with percentages higher than 97.65%. ²⁰⁶Pb/²⁰⁷Pb ratio in dry deposit samples ranges from 0.816 to a maximum of 1.154, following a normal distribution. Arithmetic mean was 0.9967±0.0864 lower than those of possible pollution sources: 1.1395±0.0165 for gasoline, 1.071±0.008 for industrially derived lead and, for the more radiogenic natural soil and urban dust values ranging from 1.2082±0.022 to 1.211±0.108. The possible origin of lead in gasoline used prior to 1960 is discussed.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Application of AMS <Superscript>14</Superscript>C measurements to criminal investigations

¹⁴C variations of atmospheric CO₂ as well as carbonaceous fraction of living materials, such as collagen from tooth and bone, tissue, skin, hair, nail, etc., of modern humans are influenced by ¹⁴C produced artificially by nuclear bomb tests in the atmosphere from late 1950s to early 1960s. By careful investigation of ¹⁴C concentration of tree rings and human body samples formed in this time intervals, we can establish a relationship of their ¹⁴C concentrations with calendar year. By applying this relation to a sample whose ¹⁴C concentration can be measured, we can estimate the formation age of the sample. In addition, sources of the chemicals that were used in some criminal cases can be possibly identified, by their carbon isotope ratios (¹³C/¹²C and ¹⁴C/¹²C). This method of age determination has been applied to a forensic study, i.e., two criminal cases of murder. For each case, by comparing the measured ¹⁴C abundances of several pieces of hair and one tooth (the third molar) from the body with the annual change on concentrations of bomb-produced ¹⁴C, the time of death of the body and the age of the victim were estimated. The estimated values were consistent with the real ones that were revealed by the confession of the real murderers.     

Global fallout levels of <Superscript>99</Superscript>Tc and activity ratio of <Superscript>99</Superscript>Tc/<Superscript>137</Superscript>Cs in the Pacific Ocean

Summary Global fallout levels of ⁹⁹Tc and ¹³⁷Cs of surface seawater in the Pacific Ocean were measured. The ⁹⁹Tc concentrations ranged from 0.62 to 3.33 mBq^. m^-3and 5 of 6 samples showed less than 1 mBq^. m^-3except one sample taken in the Great Barrier Reef, Australia. The ¹³⁷Cs concentrations ranged from 2.13 to 3.14 Bq^. m^-3, showing a gradual decrease in the North Pacific toward the equator and a constant level in the South Pacific. The ⁹⁹Tc/¹³⁷Cs activity ratios ranged from 2.5^. 10^-4to 2.9^. 10^-4, which is very close to that calculated theoretically from the fission yield.     

Distribution characteristics of <Superscript>14</Superscript>C and <Superscript>3</Superscript>H in spent resins from the Canada deuterium uranium-pressurized heavy water reactors (CANDU-PHWRs) of Korea

It is regarded that the spent resins from the water purification systems of moderator (MOD) and the primary coolant of the Canada deuterium uranium-pressurized heavy water reactor (CANDU-PHWR) are a unique waste, owing to their high ¹⁴C and gamma-emitting nuclides. In this work, ¹⁴C and ³H contents, anion and cation fractions and the predominant gamma-emitting nuclides of the spent resins from 4 units of CANDUPHWRs, were investigated. Also the chemical species of ¹⁴C of the spent resins were determined. For a simultaneous separation of ¹⁴C and ³H from the spent resins, the wet oxidation-16 wt% H₂SO₄ stripping process was utilized. The ¹⁴C and ³H activity concentration range of the spent resins of the nuclear power plant (NPP), 4 units of all CANDU-PHWR types, was 2.48E5 Bq/g ∼5.33E6 Bq/g, 1.29E5 Bq/g and ∼2.33E5 Bq/g, respectively. Among the analyzed spent resins, the highest ¹⁴C and ³H activity concentration was detected in units 4 and 3, respectively. It was found that more than 92% of the ¹⁴C activity concentration was retained on the anion resin and the predominant chemical species was inorganic ¹⁴C. It was revealed that the anion resin fraction of the spent resins from unit 1 and unit 2, was about 40% and that of unit 3 and unit 4 was around 60%. More than 80% of the total gamma-radioactivity concentration was associated with the cation fraction of the spent resin. The predominant gamma-emitting nuclide of the spent resin for unit 2 was ¹³⁷Cs, a fission product, and that for unit 4 was ⁶⁰Co, a corrosion product.     

Electron impact ionization of CCl4 and SF6 embedded in superfluid helium droplets

Electron impact ionization of helium nano-droplets containing several 10⁴ He atoms and doped with CCl₄ or SF₆ molecules is studied with high-mass resolution. The mass spectra show significant clustering of CCl₄ molecules, less so for SF₆ under our experimental conditions. Positive ion efficiency curves as a function of electron energy indicate complete immersion of the molecules inside the helium droplets in both cases. For CCl₄ we observe the molecular parent cation CCl₄⁺ that preferentially is formed via Penning ionization upon collisions with He*. In contrast, no parent cation SF₆⁺ is seen for He droplets doped with SF₆. The fragmentation patterns for both molecules embedded in He are compared with gas phase studies. Ionization via electron transfer to He⁺ forms highly excited ions that cannot be stabilized by the surrounding He droplet. Besides the atomic fragments F⁺ and Cl⁺ several molecular fragment cations are observed with He atoms attached.     

Complex formation of maleic acid with the Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> in aqueous solution

The process of complex formation of maleic acid (H₂L) with the ions Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ was studied by potentiometric titration in a wide range of concentration ratios at 298 K and I = 0.1 mol/l (NaNO₃). The moieties ZnL, CoL, NiL, NiL ₂ ^2? , CuL, and CuL ₂ ^2? were detected and their stability constants were determined.