Sequential radiochemical separations from Alpine Wetland soils (Boréon, France) with emphasis on 90Sr measurement

A radiochemical procedure to extract plutonium, americium and strontium from soils is presented. Strontium was separated from americium and plutonium fraction at the beginning of the method to increase the Sr recovery. The studied soils coming from an Alpine wetland site contain a big amount of iron which was eliminated by an oxalate precipitation before the column step. The hydroxide precipitation should be made by adding iron of known quantity to avoid interference. The procedure was validated by reference soils from IAEA. Plutonium-238, 239, 240, ²⁴¹Am, ⁹⁰Sr and ¹³⁷Cs activities are given and some isotopic ratios are calculated in order to know the origin of the radionuclides.     

汤湖热矿泥中微量元素的分析及其作用

用原子吸收分光光度法测定了汤湖热矿泥中锌、铅、铁、钙、镁、锰、．硒、铜、 砷的含量,并对其在泥疗中的作用进行了探讨。     

Preferential solvation in urea solutions at different concentrations: properties from simulation studies

We performed molecular dynamics simulations of urea solutions at different concentrations with two urea models (OPLS and KBFF) to examine the structures responsible for the thermodynamic solution properties. Our simulation results showed that hydrogen-bonding properties such as the average number of hydrogen bonds and their lifetime distributions were nearly constant at all concentrations between infinite dilution and the solubility limit. This implies that the characterization of urea-water solutions in the molarity concentration scale as nearly ideal is a result of facile local hydrogen bonding rather than a global property. Thus, urea concentration does not influence the local propensity for hydrogen bonds, only how they are satisfied. By comparison, the KBFF model of urea donated fewer hydrogen bonds than OPLS. We found that the KBFF urea model in TIP3P water better reproduced the experimental density and diffusion constant data. Preferential solvation analysis showed that there were weak urea-urea and water-water associations in OPLS solution at short distances, but there were no strong associations. We divided urea molecules into large, medium, and small clusters to examine fluctuation properties and found that any particular urea molecule did not stay in the same cluster for a long time. We found neither persistent nor large clusters.     

Plutonium, 137Cs and U in some pond and lake sediments from areas surrounding the Semipalatinsk Nuclear Test Site: With emphasis on anomalously high U accumulation

Sediment core samples were collected up to a depth of 25–40 cm from three ponds (P. Korosteli, P. Mihairov and P. Alkat) and two lakes (L. Kanoneruka and L. Semanaika) located in widely separated regions outside the former Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan. The ¹³⁷Cs, Pu and U concentrations with depth were determined in samples divided at 1 cm intervals from the top of each core. These sediment cores were dated by the excess ²¹⁰Pb method. The reservoirs with low sedimentation rates of 0.038–0.41 g·cm^–2·y^–1 permitted, but not in detail, the estimation of the depositional history of close-in fallout of ¹³⁷Cs and Pu within these regions. The sediments accumulating an anomalously high ²³⁸U concentration of 250–400 Bq/kg were also found for two of the five reservoirs, in which their ²³⁴U/²³⁸U and ²³⁵U/²³⁸U activity ratios were 1.3–2.0 and around 0.047 (nearly the same as that of natural U), respectively. Such U enrichment at the subsurface with a thin layer of lower-U sediment at the surface is mainly due to infiltration of lake water containing U from the ground water flowing into the lake or pond, followed by reduction of U(VI) to U(IV) at the redox boundary.The authors would like to express their gratitude to research staff of the Kazakh Scientific Research Institute for Radiation Medicine and Ecology for sediment and soil sampling. This work was supported by a Grant in Aid for Scientific Research from the Ministry of Education and Culture of Japan, Monbusuo International Scientific Research Program during the period of 1995–2003, represented by Profs. M. Hoshi and M. Yamamoto.     

Laboratory studies of organic peroxy radical chemistry: an overview with emphasis on recent issues of atmospheric significance

Organic peroxy radicals (often abbreviated RO(2)) play a central role in the chemistry of the Earth's lower atmosphere. Formed in the atmospheric oxidation of essentially every organic species emitted, their chemistry is part of the radical cycles that control the oxidative capacity of the atmosphere and lead to the formation of ozone, organic nitrates, organic acids, particulate matter and other so-called secondary pollutants. In this review, laboratory studies of this peroxy radical chemistry are detailed, as they pertain to the chemistry of the atmosphere. First, a brief discussion of methods used to detect the peroxy radicals in the laboratory is presented. Then, the basic reaction pathways - involving RO(2) unimolecular reactions and bimolecular reactions with atmospheric constituents such as NO, NO(2), NO(3), O(3), halogen oxides, HO(2), and other RO(2) species - are discussed. For each of these reaction pathways, basic reaction rates are presented, along with trends in reactivity with radical structure. Focus is placed on recent advances in detection methods and on recent advances in our understanding of radical cycling processes, particularly pertaining to the complex chemistry associated with the atmospheric oxidation of biogenic hydrocarbons.     

Plutonium, 137Cs and U in some pond and lake sediments from areas surrounding the Semipalatinsk Nuclear Test Site: With emphasis on anomalously high U accumulation

Sediment core samples were collected up to a depth of 25–40 cm from three ponds (P. Korosteli, P. Mihairov and P. Alkat) and two lakes (L. Kanoneruka and L. Semanaika) located in widely separated regions outside the former Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan. The ¹³⁷Cs, Pu and U concentrations with depth were determined in samples divided at 1 cm intervals from the top of each core. These sediment cores were dated by the excess ²¹⁰Pb method. The reservoirs with low sedimentation rates of 0.038–0.41 g·cm^–2·y^–1 permitted, but not in detail, the estimation of the depositional history of close-in fallout of ¹³⁷Cs and Pu within these regions. The sediments accumulating an anomalously high ²³⁸U concentration of 250–400 Bq/kg were also found for two of the five reservoirs, in which their ²³⁴U/²³⁸U and ²³⁵U/²³⁸U activity ratios were 1.3–2.0 and around 0.047 (nearly the same as that of natural U), respectively. Such U enrichment at the subsurface with a thin layer of lower-U sediment at the surface is mainly due to infiltration of lake water containing U from the ground water flowing into the lake or pond, followed by reduction of U(VI) to U(IV) at the redox boundary.The authors would like to express their gratitude to research staff of the Kazakh Scientific Research Institute for Radiation Medicine and Ecology for sediment and soil sampling. This work was supported by a Grant in Aid for Scientific Research from the Ministry of Education and Culture of Japan, Monbusuo International Scientific Research Program during the period of 1995–2003, represented by Profs. M. Hoshi and M. Yamamoto.     

An upper limit to interstellar 244Pu abundance as deduced from radiochemical search in deep-sea sediment: An account

We report here a search for the “live” ²⁴⁴Pu in 1 kg deep-sea dry sediment collected in 1992 in the North Pacific. After a 546 day alpha-counting of a Pu fraction chemically separated from the alkaline-fused sediment sample at Kanazawa University, AMS analysis was performed at Hebrew University and Weizmann Institute. Only one count of ²⁴⁴Pu with no background ions was detected, indicating no excess over the expected stratospheric man-made fallout. A limit of 0.2 atoms of ²⁴⁴Pu cm⁻²·y⁻¹ for extra terrestrial deposition was set under reasonable assumptions and it was then concluded from this result and the available data on interstellar medium (ISM) that the abundance of ²⁴⁴Pu in the ISM is less than 2·10⁻¹¹ g ²⁴⁴Pu (g·ISM)⁻¹. Implications of the present result are discussed.     

Improvements on radiochemical method for the determination of Am and Cm in typical waste streams from nuclear power plants

The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates.     

Neutron activation determination of noble metals in rocks: A rapid radiochemical separation based on tellurium coprecipitation

A procedure is described for the determination of Pd, Au, Ir, and Pt in rocks at the ppb concentration level. After irradiation with thermal neutrons, powdered rock samples are fused with carriers and Na₂O₂−NaOH. The fusion cake is dissolved in dilute HCl, and the activated noble metals and carriers are coprecipitated as a group with Te, using Sn²⁺ as a reductant. Gamma and X-rays are counted on semi-conductor Ge deterctors. Yields are determined by reirradiation. Results are given for several rocks, including U.S.G.S. standards PCC-1 and W-1.     

The need for external validation in machine olfaction: emphasis on health-related applications

Over the last two decades, electronic nose research has produced thousands of research works. Many of them were describing the ability of the e-nose technology to solve diverse applications in domains ranging from food technology to safety, security, or health. It is, in fact, in the biomedical field where e-nose technology is finding a research niche in the last years. Although few success stories exist, most described applications never found the road to industrial or clinical exploitation. Most described methodologies were not reliable and were plagued by numerous problems that prevented practical application beyond the lab. This work emphasizes the need of external validation in machine olfaction. I describe some statistical and methodological pitfalls of the e-nose practice and I give some best practice recommendations for researchers in the field.

INAA at the top of the world: Elemental characterization and analysis of airborne particulate matter collected in the Himalayas at 5,100 m high

A magnetic filter — continuous electrodeionization (CEDI) hybrid separation system was investigated for the purification of the primary coolant in a nuclear power plant. A magnetic filter system with a 3000 Gauss magnetic field and a CEDI system with a cell consisting of 3 compartments were used for the removal of magnetite and nickel ions, respectively. The hybrid separation system achieved removal rates of 98% for magnetite and 99% for the nickel ions demonstrating its feasibility for the purification of primary coolant.The authors gratefully acknowledge the Basic Atomic Energy Research Institute (BAERI) program at the Korea Institute of Science and Technology Evaluation and Planning (KISTEP) for the financial support to carry out this work.     

Speciation analysis of arsenic in groundwater from Inner Mongolia with an emphasis on acid-leachable particulate arsenic

Arsenic in drinking water affects millions of people around the world. While soluble arsenic is commonly measured, the amount of particulate arsenic in drinking water has often been overlooked. We report here determination of the acid-leachable particulate arsenic and soluble arsenicals in well water from an arsenic-poisoning endemic area in Inner Mongolia, China. Water samples (583) were collected from 120 wells in Ba Men, Inner Mongolia, where well water was the primary drinking water source. Two methods were demonstrated for the determination of soluble arsenic species (primarily inorganic arsenate and arsenite) and total particulate arsenic. The first method used solid phase extraction cartridges and membrane filters to separate arsenic species on-site, followed by analysis of the individual arsenic species eluted from the cartridges and filters. The other method uses liquid chromatography separation with hydride generation atomic fluorescence detection to determine soluble arsenic species. Analysis of acidified water samples using inductively coupled plasma mass spectrometry provided the total arsenic concentration. Arsenic concentrations in water samples from the 120 wells ranged from <1 to ∼1000 μg L⁻¹. On average, particulate arsenic accounted for 39 ± 38% (median 36%) of the total arsenic. In some wells, particulate arsenic was six times higher than the soluble arsenic concentration. Particulate arsenic can be effectively removed using membrane filtration. The information on particulate and soluble arsenic in water is useful for optimizing treatment options and for understanding the geochemical behavior of arsenic in groundwater.     

A simple radiochemical method for determining bone-seeking radionuclides in bone and teeth: 90Sr in teeth of children from Ukraine and Germany

Bone is a critical organ for the accumulation of ⁹⁰Sr but also of other “bone-seeking” radionuclides such as Ra, Pb, Th, U and Pu. That's why a simple radiochemical procedure to separate ⁹⁰Sr, ²¹⁰Pb, ²²⁶Ra, Th_nat. U_nat., ²³⁸Pu and ^239/240Pu from bone and teeth was developed. The separation scheme is based on extraction chromatography. Deciduous teeth, extracted from children born in 1982-1991 were collected in various regions of Germany and in Northwest Ukraine and analyzed for ⁹⁰Sr concentrations with regard to the Chernobyl accident in 1986. The teeth were grouped into samples according to the year of birth and the residence of the donors. The ⁹⁰Sr content in teeth from the Ukraine (mean = 63.8 mBq/g Ca) averaged more than twice as much as that found in teeth from Germany (mean = 28.4 mBq/g Ca). The obvious explanation for this effect is that the concentration of ⁹⁰Sr decreased with increasing distance from the damaged Chernobyl nuclear power plant. The measured levels of ⁹⁰Sr concentrations, however, were much lower than ⁹⁰Sr concentrations determined in the mid-60s and mid-70s. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of NAA to air particulate matter collected at thirteen sampling sites in eight Asian countries: A collaborative study

Air particulate matter (APM) samples (PM_2.5 and PM_10–2.5) were collected at 13 sampling points in 8 Asian countries and their chemical compositions were determined by using neutron activation analysis (NAA) with the k ₀-standardization method in addition to conventional comparative method of NAA. Analytical data showed that mass concentration and elemental composition of the APM collected are variable in terms of time and space, and are related to the characteristics of the sampling sites concerned. NAA was proved to be highly effective for the regional characterization of APM in chemical composition.     

Evidence of surface charge at the air/water interface from thin-film studies on polyelectrolyte-coated substrates

The stability of thin water films on silicon substrates coated with cationic and anionic polyelectrolytes was investigated by the thin film pressure balance technique. Depending on the surface charge of the substrate, the water films are either stable (on negatively charged wafers) or rupture rapidly (on positively charged wafers). It is supposed that this behavior is due to a negative surface charge of the free water surface. The underlying assumption that the films' stability is due to electrostatic interactions is supported by measurements of the disjoining pressure on silicon wafers with a native oxide layer, which indicates a decrease of the film thickness, and thus decreasing repulsive interaction between the two film interfaces, with increasing ionic strength.     

Thermodynamic studies on thin liquid films. III: Miscibility in adsorbed films at film interfaces

Thermodynamic treatment of surfactant mixture was developed for the adsorption at interfaces of thin liquid films and applied to the study of the foam film stabilized by decyl methyl sulfoxide (DeMS) in the presence of NaCl. The total surface density of NaCl and DeMS and the mole fraction of DeMS in the adsorbed film at the film surface were numerically evaluated by applying thermodynamic equations to the film tension as a function of the total molality of NaCl and DeMS and the mole fraction of DeMS in the mixture. Miscibility of NaCl and DeMS at the film surface was clarified by a phase diagram of adsorption and compared with that at the meniscus adjacent to the foam film. Judging from a phase diagram of phase transition, the transition in the DeMS foam film between common black and Newton black films, observed in part II, is a negative azeotropic transformation caused by the attractive interaction between the head group of DeMS molecule and Na⁺ or Cl^– in the adsorbed film.     

Model studies in heterogeneous catalysis at the microscopic level: from the structure and composition of surfaces to reaction kinetics

Heterogeneous catalysis is one of the fields of modern technology, in which a characterization of structural and chemical properties of solid surfaces at the microscopic level is of enormous importance. For a long time, such insights have been precluded by the complexity of most catalytically active materials. Recently, substantial progress has been made, however, toward a microscopic-level understanding of complex catalyst surfaces. We discuss the driving factors for these advancements, which are based on the development of new well-defined model systems as well as on advances in experimental technology and theory. Scrutinizing the example of planar model catalysts, we identify the process of linking structural and chemical information to microscopic reaction kinetics as a particular challenging aspect of today’s work. We review the kinetic effects which may have an influence on the reaction kinetics on complex surfaces. As an example how structural and kinetic information can be correlated at the microscopic level we discuss the case of surface oxidation and oxygen induced restructuring of Pd nanoparticles as studied by molecular beam methods.     

Pressurized Hot Water Extraction of anthocyanins from red onion: A study on extraction and degradation rates

Pressurized Hot Water Extraction (PHWE) is a quick, efficient and environmentally friendly technique for extractions. However, when using PHWE to extract thermally unstable analytes, extraction and degradation effects occur at the same time, and thereby compete. At first, the extraction effect dominates, but degradation effects soon take over. In this paper, extraction and degradation rates of anthocyanins from red onion were studied with experiments in a static batch reactor at 110 °C. A total extraction curve was calculated with data from the actual extraction and degradation curves, showing that more anthocyanins, 21-36% depending on the species, could be extracted if no degradation occurred, but then longer extraction times would be required than those needed to reach the peak level in the apparent extraction curves. The results give information about the different kinetic processes competing during an extraction procedure.