Distribution Coefficients For Sr Research Articles

Microbially formed Mn(IV) oxide as a novel adsorbent for removal of Radium

Radioactivity of Ra isotopes in natural waters is of serious concern. Control of 226Ra concentrations in tailings ponds, which store waste from U ore extraction processes, is an important issue in mill tailings management. In this study, we tested microbially formed Mn(IV) oxide as an adsorbent for removal of Ra in water treatment. Biogenic Mn(IV) oxide (BMO) was prepared using a Mn(II)-oxidizing fungus, Coprinopsis urticicola strain Mn-2. First, adsorption experiments of Sr and Ba, as surrogates for Ra, onto BMO were conducted in aqueous NaCl solution at pH 7. Distribution coefficients for Ba and Sr were estimated to be ∼106.5 and ∼104.3 mL/g, respectively. EXAFS analysis indicated that both Sr and Ba adsorbed in inner-sphere complexes on BMO, suggesting that Ra would adsorb in a similar way. From these findings, we expected that BMO would work effectively in removal of Ra from water. Then, BMO was applied to remove Ra from mine water collected from a U mill tailings pond. Just 7.6 mg of BMO removed >98% of the 226Ra from 3 L of mine water, corresponding to a distribution coefficient of 107.4 mL/g for Ra at pH ∼7. The obtained value was convincingly high for practical application of BMO in water treatment. At the same time, the high distribution coefficient indicates that Mn(IV) oxide can be an important carrier and host phase of Ra in the environment.

Adsorption behavior of trace elements of 90Sr on MnO2–ZrO2 loaded with polyacrylonitrile polymer from aqueous solutions

A MnO2–ZrO2-polyacrylonitrile (MnO2–ZrO2-PAN) composite ion exchanger was produced and its properties were examined by Fourier-transformed infrared spectroscopy, scanning electron microscopy, The BET (Brunauer, Emmett and Teller) surface area, X-Ray diffraction analysis and thermogravimetric analysis. The adsorption of Strontium (Sr) from solutions by MnO2–ZrO2-PAN composite was studied thru batch experiments. The distribution Coefficient of Sr (II) on the composite sorbent was investigated against pH, interaction time, and primary concentration ion. To study the kinetics of adsorption, Pseudo-first-order and Pseudo second-order adsorption kinetics were studied and the results revealed that adsorption kinetics better fit to the pseudo-second-order model. Three iso-temperature models, Langmuir, Freundlich, and Temkin were applied to fit the experimental results. Among those models, Langmuir revealed the most suitable one with minimum deviation. The created composite exhibited strong compatibility to the elimination of Y (III), Ni (II), Pb (II), and Co (II) from radioactive waste streams. On the other, it is evident from the data that the quantifiable extraction of Sr (II) ions from Zr (IV), Mo (VI), and La (III) is feasible. MnO2–ZrO2 Loaded with (PAN) Polymer was figured out to have high ion exchange capacity and thermal stability and selectivity for strontium.

Experimental and theoretical investigations of stable Sr isotope fractionation during its incorporation in aragonite

Strontium partitioning and isotope fractionation between aragonite and fluid have been determined experimentally at low values of the fluid saturation state (Ω) with respect to this mineral (1.1 ≤ Ωaragonite ≤ 2.2), and the measured isotope fractionation has been compared with the results of first-principles simulations. For the latter, Density Functional Theory (DFT) was used for estimation of the equilibrium Sr isotope fractionation between aragonite and Sr2+(aq). The obtained results suggest that, for values of Ωaragonite close to unity, the apparent distribution coefficient of Sr in aragonite (DSr,aragonite=XSrCO3XCaCO3(CaSr)fluid) exhibits values higher than one that rapidly decrease at increasing aragonite growth rate. Under equilibrium conditions (i.e. Ωaragonite=1) a DSr,aragoinite value of 2.7 can be extrapolated. Additionally, for aragonite growth rates rp ≤ 10−8.0±0.2 (mol/m2/s) the Sr isotope fractionation between aragonite and the fluid (i.e. Δ88/86Sraragonite-fluid) shows a constant value of −0.1±0.05‰, whereas it decreases to −0.40‰ when the growth rate increases to 10−7.7(mol/m2/s). The surface reaction kinetic model (SRKM) developed by DePaolo (2011) has been used to describe the dependence of DSr,aragonite and Δ88/86Sraragonite-fluid on mineral growth rate. In this model the best fit for DSr,aragonite and Δ88/86Sraragonite-fluid were 4 and −0.01‰, respectively, whereas the kinetic isotope fractionation factor for Δ88/86Sraragonite-fluid was −0.6‰. The results of first-principles calculations yield an equilibrium Sr isotope fractionation factor of −0.04‰ which is in excellent agreement with the experimental value of the present study. These results are the first experimental measurements of Sr isotope fractionation during inorganic aragonite precipitation as a function of growth rate and the first DFT calculations of Sr equilibrium fractionation in the aragonite-fluid system. The results of this study provide new insight into the mechanisms controlling stable Sr isotope composition in aragonite, which has implications for using Sr isotopes for paleo-reconstructions of natural archives, particularly those of abiogenic origin.

Solid-liquid distribution coefficients of Sr(II) at a proposed nuclear power plant site in China and their relations to cation exchange capacity and pH

Solid-liquid distribution coefficients of Sr(II) at a proposed nuclear power plant site in China and their relations to cation exchange capacity and pH

Magnesium isotope fractionation between calcite and aqueous solutions under elevated temperatures of 98–170 °C

The incomplete understanding of Mg isotope fractionation behavior between calcite and aqueous solutions has limited the interpretation and application of Mg isotope data in natural carbonates. In this study, we performed a series of aragonite-to-calcite conversion experiments under hydrothermal conditions to investigate the effects of temperature and organic ligands on elemental and isotopic partitioning of Mg between calcite and aqueous solutions. The experiments produced magnesian calcite via a dissolution-and-precipitation process. The Mg distribution coefficients between solid and aqueous solution (DMg, 0.08 to 0.21) showed negative correlations with Sr distribution coefficients (DSr, 0.04 to 0.48), as well as the proportion of calcite in the bulk solid, which indicates mixing of calcite (Mg-rich and Sr-poor) and aragonite (Sr-rich and Mg-poor) in the solid phases. The apparent Mg isotope fractionation factors between solid and aqueous solutions (Δ26Mgsolid-soln) show a positive correlation with reaction temperatures, where Δ26Mgsolid-soln increases from ca. −1.84 ‰ at 98 °C to −1.35 ‰ at 170 °C. In addition, the presence of oxalate contributed to slightly lower Δ26Mgsolid-soln values, which is interpreted to be related to the isotopic effect of Mg-oxalate speciation. Based on the experimental results, we propose a temperature-dependent function for Mg isotope fractionation between calcite and free Mg-aquo ions (i.e., Mg(H2O)62+): Δ26Mgcal-Mg(aq) = (−0.17 ± 0.01) × 106/T2- (0.52 ± 0.08). This equation is applicable to a wide range of temperatures, especially at hydrothermal conditions, thus enabling interpretations of Mg isotope data from calcite of hydrothermal and burial origin.

Effects of the Sr/Ca ratio on the bioremediation of strontium based on microbially-induced carbonate precipitation

90Sr is a radionuclide that poses a potential threat to ecosystem security, and Sr bioremediation based on microbially-induced carbonate precipitation (MICP) usually affected by Ca. Experiments of carbonate mineralization induced by Enterobacter sp. JC-1 in solution with different Sr/Ca molar ratios were performed to explore the effect of Sr/Ca ratio on microbially-induced carbonate precipitation. X-ray diffraction patterns indicated that strain JC-1 induced the formation of calcite (Sr/Ca < 1) and strontianite (Sr/Ca = 1), and the increase in the d(104) and d(012) of calcite indicated that Sr entered the calcite lattice. The normalized distribution coefficient of Sr (DSr) in the minerals indicated that a higher Sr/Ca ratio promoted Sr incorporation into minerals. Sr2+ removal showed a V-shape (initial decrease and subsequent increase) with an increase in Sr/Ca ratio, which had no correlation with the DSr, but was positively correlated with the mass of CO32- (r = 0.779, p < 0.01) in the mineral. However, mineralization experiments induced by chemicals showed that Sr2+ removal was positively correlated with DSr (r = 0.785, p < 0.01), which suggested that MICP was not simple chemical process. The moles of carbonate in minerals revealed that a higher Sr/Ca ratio influenced the ability of bacteria to generate carbonate. The Sr2+ removal was due to the combined effect of microbial growth and the DSr. In conclusion, this study revealed the relationship of Sr/Ca ratios between the solution and minerals, which has reference value for the explanation of the formation mechanism of carbonate mineral and Sr bioremediation.

Experimental investigation on buffer/backfill materials for radioactive waste repository downward facing sorption additivity of cesium, strontium and cobalt with different concentrations

Abstract Buffer/backfill materials for radioactive waste disposal sites consist of pure bentonite or bentonite-rock mixtures. In this study, the batch test method was used to obtain the sorption characteristics of important radionuclides such as Cs, Sr and Co on buffer/backfill materials; i. e., mixing Wyoming MX-80 bentonite or local Taiwanese Zhi-Shin bentonite with possible host rock (argillite and granite) in different proportions (0∼100%). The distribution coefficients (Kd) for Cs, Sr and Co were obtained from the experiments. The distribution coefficient for the bentonite-rock mixtures were found, with more than 50% of mixing proportion of bentonite to argillite or granite, to have very similar values to that of pure bentonite. Furthermore, it was clearly found that the sorption of Cs, Sr and Co to bentonite-rock mixtures is decreased as ionic strength of the liquid phase is increased from 0.001M to 1M for NaCl solutions. According to the experimental results, in synthetic groundwater, it is quite convenient and helpful to assess the distribution coefficients (Kd) of Cs, Sr and Co for buffer/backfill materials using batch sorption experiments with bentonite-rock mixtures of fixed mixing proportions.

Incorporation of minor and trace elements into cultured brachiopods: Implications for proxy application with new insights from a biomineralisation model

Brachiopods present a key fossil group for Phanerozoic palaeo-environmental and palaeo-oceanographical reconstructions, owing to their good preservation and abundance in the geological record. Yet to date, hardly any geochemical proxies have been calibrated in cultured brachiopods and only little is known on the mechanisms that control the incorporation of various key elements into brachiopod calcite. To evaluate the feasibility and robustness of multiple Element/Ca ratios as proxies in brachiopods, specifically Li/Ca, B/Ca, Na/Ca, Mg/Ca, Sr/Ca, Ba/Ca, as well as Li/Mg, we cultured Magellania venosa, Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years with closely monitored ambient conditions, carbonate system parameters and elemental composition of the culture medium. The experimental setup comprised of two control aquariums (pH0 = 8.0 and 8.15, T = 10 °C) and treatments where pCO2 − pH (pH1 = 7.6 and pH2 = 7.35), temperature (T = 16 °C) and chemical composition of the culture medium were manipulated. Our results indicate that the incorporation of Li and Mg is strongly influenced by temperature, growth effects as well as carbonate chemistry, complicating the use of Li/Ca, Mg/Ca and Li/Mg ratios as straightforward reliable proxies. Boron partitioning varied greatly between the treatments, however without a clear link to carbonate system parameters or other environmental factors. The partitioning of both Ba and Na varied between individuals, but was not systematically affected by changes in the ambient conditions. We highlight Sr as a potential proxy for DIC, based on a positive trend between Sr partitioning and carbonate chemistry in the culture medium. To explain the observed dependency and provide a quantitative framework for exploring elemental variations, we devise the first biomineralisation model for brachiopods, which results in a close agreement between modelled and measured Sr distribution coefficients. We propose that in order to sustain shell growth under increased DIC, a decreased influx of Ca2+ to the calcifying fluid is necessary, driving the preferential substitution of Sr2+ for Ca2+ in the crystal lattice. Finally, we conducted micro-computed tomography analyses of the shells grown in the different experimental treatments. We present pore space – punctae – content quantification that indicates that shells built under increased environmental stress, and in particular elevated temperature, contain relatively more pore space than calcite, suggesting this parameter as a potential novel proxy for physiological stress and even environmental conditions.

Calcite Mg and Sr partition coefficients in cave environments: Implications for interpreting prior calcite precipitation in speleothems

Trace element to Ca ratios in speleothems have emerged as important proxies that reflect local environmental conditions. However, interpretations of speleothem trace element records can be challenging due to various processes. Positive correlations between speleothem Mg/Ca and Sr/Ca have often been interpreted to reflect prior calcite precipitation (PCP), a process potentially modulated by rainfall variability. For quantitative interpretation of PCP, the distribution coefficients for Mg and Sr (DMg and DSr) are required. Here, we use ten cave monitoring calcite and drip water datasets to investigate the influence of temperature and drip water and calcite Mg/Ca and Sr/Ca ratios on speleothem calcite DMg and DSr. The datasets cover a large range of climatic and geological settings resulting in a large range of drip water Mg/Ca ratios. Speleothem calcite DSr shows a positive correlation with the calcite Mg/Ca ratio. Furthermore, DMg shows a clear temperature dependence (DMg = 0.013*e0.035*T).Previous work proposed that the slope of a trend line through a plot of ln(Sr/Ca) versus ln(Mg/Ca) of a speleothem trace element dataset is between 0.709 and 1.003 if dominated by PCP. However, this only holds true if the initial drip water Mg/Ca and Sr/Ca ratios as well as DSr and DMg are constant for the whole dataset. We use an excel-based PCP model (see Electronic Annex) to assess the potential influence of PCP on drip water and speleothem Mg/Ca and Sr/Ca ratios and simulate different initial drip water Ca, Mg, and Sr concentrations corresponding to limestone, dolostone, and mixed host rock compositions. In the case of enhanced PCP and high Mg/Ca ratios, calcite DSr increases progressively with the mean Mg/Ca ratio of the speleothem time series resulting in steeper slopes of ln(Sr/Ca) versus ln(Mg/Ca) of up to 1.45.We show that PCP can induce slopes ranging from 0.709 (or even shallower) up to 1.45. This large range suggests that the previously applied criteria to detect PCP in speleothem records were too strict and may lead to unjustified exclusion of PCP as a potential interpretation of speleothem and drip water trace element ratios. Thus, the number of speleothem Mg/Ca and Sr/Ca datasets that potentially reflect past changes in effective rainfall may be larger than previously suggested.

Batch sorption experiments of cesium and strontium on crushed rock and biotite for the estimation of distribution coefficients on intact crystalline rock

The distribution coefficient (Kd) of radionuclides on bedrock is one of the key parameters used in the safety analysis of spent nuclear fuel repositories. Typically, distribution coefficients have been determined using crushed rock. However, recent studies have shown that crushing of the rock increases considerably the distribution coefficient compared with the values of intact rock. This study aimed to test if batch sorption experiments using different grain sizes (i.e. mean diameter of grains) can be used to evaluate the Kd of strontium (Sr) and cesium (Cs) on intact crystalline rock, which would decrease the needed experimental time compared with transport experiments. Here we report the results of the batch sorption experiments with crushed rocks and compare the results with those from a recent study performed using electromigration experiments with intact drill core samples (Puukko et al., 2018). The batch sorption experiments were done for rock samples from Olkiluoto, Finland, as a function of grain size and of Cs and Sr concentration. Furthermore, the specific surface areas of the same rock samples with different grain sizes were determined. It was shown that Cs distribution coefficients correlate with specific surface areas of the studied rocks and biotite, the correlation coefficient being 0.95. The Cs distribution coefficient was highest for biotite at about 0.1 m3/kg at 10−4 M cesium concentration and increased systematically to about 1 m3/kg at 10−8 M. Distribution coefficients for rocks were up to about two orders of magnitude lower, being lowest with the rock with the lowest biotite content (3.3%). The distribution coefficient of Sr varied from 0.04 m3/kg to 0.007 m3/kg and behaved in a different manner: it remained constant in two out of three studied rocks in the concentration range of 10−8-10−4 M and only in the case of one rock a decreasing trend was seen at the higher concentration range. It was also shown that batch sorption experiments overestimate the distribution coefficient in respect to intact rock. The decrease of the distribution coefficient as a function of grain size can be estimated using a power law function. It was also shown that estimation of distribution coefficients of Cs and Sr for intact rock by extrapolation of distribution coefficients determined for different grain sizes is not possible without increasing grain size, but in that case diffusion into the grains would also affect the results. A new method was developed for estimating the fraction of the inner surface area of the total surface area of crushed grains. For the mean grain sizes of 0.25 mm and 0.75 mm the fraction of the inner surface was found to be 35–70% and 60–90%, respectively. The inner specific surface area was highest with biotite at 1.2 m2/g and lowest with the rock with lowest biotite content (3.3%) at 0.07 m2/g. The surface area analysis revealed that crushing creates and/or allows access to additional inner surface area that is not measured in intact rock. Furthermore, it was demonstrated that sorption of Cs on crushed rock was dominated by mica minerals in multiple concentrations while the effect of mica minerals on the Kd of Sr was not as straightforward.

New observations of Tin Mineralization Potential Vis-à-Vis Ore Petrographic, Alteration and Geochemistry in the Southeastern part of Bastar Craton, Central India

The Tin mineralizations occur around the Katekalyan area, hosted in the acid magmatic rocks. The evolution differentiating granitic magma shows residual melt enrichment where end products intruded as pegmatites into the rocks. The different kind of pegmatite occur as simple unzoned, recrystallized (granitic pegmatite), and metasomatic greisenised and albitised pegmatites which emplaced within the pre-existing rocks of metabasic intrusive, granite (KG), granite gneiss (KGG). Sometimes it also found in metasediments as mineralised and non-mineralised characters along the fractures and foliation planes trending N-S, E-W and more frequently are observed NNW-SSE trends. Cassiterite is most important Tin-ore mineral and associated with pegmatites. Some cassiterite samples exhibit colourless to brown shades zoning which indicate multi stage growth. The cassiterite samples contain significant amounts of Sn, Nb, Ta with minor W.&#x0D; The partial melting model shows that the variation 5 to 50% partial melting of bulk continental crust for KG as well as KGG rocks but bulk distribution coefficient for Sr (DSr) shows low i.e. &lt;&lt;10. The upper limit of partial melting of bulk crust estimates ~50 % for KG and KGG rocks are consistent with required rheological, critical melt percentage to leave the source region has decreased granite melt which were capable to mineralised tin ore elements. It is interesting to note that the SnF4 and SnCl4 probably not stable in presence of water under geologically reasonable conditions.

Sorption and desorption studies of Cs and Sr in contaminated soil samples around Fukushima Daiichi Nuclear Power Plant

Huge amounts of radiocesium, radiostrontium, and fission products were released into the atmosphere during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Therefore, it is necessary to determine the distribution coefficient of Cs and Sr in the soil-water system around FDNPP from the viewpoint of their migration. The determination of sorption coefficient Kd(S) as well as desorption coefficient Kd(D) for Cs and Sr has been carried out in the present study using the laboratory batch method. In this experiment, stable Cs and Sr were used for sorption on contaminated Fukushima soil samples and groundwater collected in proximity to the soil sample sites. Different soil parameters were measured to understand their effect on the sorption and desorption processes. Desorption experiments were carried out on some selected contaminated soil samples. Kd(S)-Cs and Kd(S)-Sr varied from 65 to 2100 L/kg and 15 to 130 L/kg, respectively. Kd(D)-Cs and Kd(D)-Sr varied between 75–2500 and 10–120 L/kg, respectively. High values of sorption coefficients for Cs indicate sorption capacity of soils for Cs is more than Sr. For Cs, Kd(D) was higher than Kd(S) whereas for Sr, Kd(S) was either equal to or higher than Kd(D). A moderate Pearson’s correlation of (Kd) Cs and Sr with exchangeable cations (Al, K, Mg, and Na) supported that ion exchange sorption mechanism is significant. There is enhanced Cs sorption compared to Sr due to the presence of biotite, kaolinite and smectite minerals resulting in high mobility of Sr in the Fukushima environment. We concluded retention capacity of Fukushima soils for Cs is moderately stronger than Sr, which supports Sr is more mobile in the environment.

Stable isotopes and trace elements of drip waters at DeSoto Caverns during rainfall-contrasting years

A monitoring study at DeSoto Caverns during two years (2012−2013) of rainfall-contrasting variability presents the opportunity to test the response of the hydroclimate proxies in drips and active speleothems to forcing factors on intrannual and interannual time scales.The weighted monthly mean rainwater δ18O and δ2H range from −1.2 to −6.4 (‰ V-SMOW) and −4 to −41.6 (‰ V-SMOW), respectively, and show modest interannual variation. D-excess values exhibit a large intrannual contrast suggesting a primary control by sub-cloud evaporation processes. Coeval drip-water δ18O and δ2H vary from −3.1 to −5.3 (‰ V-SMOW) and −9.9 to −30.5 (‰ V-SMOW), respectively, and exhibit interannual negative trends from the 2012 dry/warm year to the 2013 relatively wet/cool year. Substantial attenuation of drip-water isotope amplitudes, relative to its rainwater source, is likely caused by mixing of fresh with residual evaporated-water in the epikarst zone.Drip-water Ca, Mg, Sr and Mg/Ca and Sr/Ca ratios exhibit an inverse relation with respect to the contrasting hydroclimate years such that lower values and higher ratios occur during the dry/warm year and higher values and lower ratios occur during the wet/cool year. We assert that interannual rainfall variability exerts a dominant control on the elemental concentrations and their ratios of the drips through changes of biomass productivity in the soils overlying the cave, and prior aragonite precipitation in the epikarst. The distribution coefficients of Mg (DMg = 3.49 × 10−3 ± 1.06 × 10−3) and Sr (DSr = 1.12 ± 0.041) between drips and aragonite speleothems estimated in this study are in broad agreement with aragonite-solute experimental values. Coeval changes of trace elements and δ18O in response to interannual rainfall variability confirm their usefulness to better constrain the controlling hydroclimate drivers.

The effect of changing seawater Ca and Mg concentrations upon the distribution coefficients of Mg and Sr in the skeletons of the scleractinian coral Pocillopora damicornis

The skeletal composition of calcifying organisms, in particular Mg/Ca and Sr/Ca ratios, have been widely used to understand fluctuations in seawater chemistry throughout the Phanerozoic. While the success of applying these data to the geologic record depends on a knowledge of the distribution coefficients for these elements (DMg and DSr), there are scarcely any studies which have described how these values vary as a result of changing seawater Mg/Ca ratios. To address this, we have cultured the scleractinian coral, Pocillopora damicornis, in seawater with ranges of Mg and Ca concentrations. Here, we demonstrate that Mg/Ca and Sr/Ca ratios of coral skeletons correlate with total seawater Mg/Ca and Sr/Ca molar ratios, but that apparent DMg and DSr values do not remain constant across the range of experimental seawater treatments, with DMg values significantly increasing with seawater Mg/Ca ratios and DSr values significantly increasing with seawater Ca concentrations. These trends are not rate dependent and may be best explained by a Rayleigh distillation model, in which the calcifying space is semi-isolated from seawater during skeletogenesis (i.e. leaky). As there is a slight increase in DMg and decrease in DSr values between our “Jurassic” and “Modern” seawater treatments, the application of a constant distribution coefficient to estimate changes in ancient seawater chemistry may underestimate seawater Mg/Ca ratios and overestimate Sr/Ca throughout the Mesozoic and Cenozoic. We suggest that interpretations of seawater chemistry from fossil corals may be improved by using the relationships derived for skeletal and seawater Mg/Ca and Sr/Ca ratios established by our experiments, as they incorporate the effect of seawater Mg/Ca ratios on skeletal Mg/Ca and Sr/Ca ratios.

Sorption of strontium ions onto mesoporous manganese oxide of OMS-2 type

Sorption of stable and radioactive strontium ions onto mesoporous manganese oxide of OMS-2 type, prepared by the sol–gel method via reduction of potassium permanganate with polyvinyl alcohol in aqueous medium, was studied. The influence exerted by the pore structure parameters and by the phase and chemical composition of manganese oxide on its sorption properties and selectivity to Sr ions was examined. Manganese oxide samples prepared using a 0.1 wt % KMnO4 solution exhibit the highest values of the sorption capacity for Sr, about 100–150 mg g–1, and of the Sr distribution coefficient, K d = (11.5–19.5) × 103 cm3 g–1. Introduction of 0.1 M NaCl into this solution considerably decreases the sorption of stable Sr ions, and for all the samples the sorption capacity is 25–35 mg g–1. On the other hand, for the most active sorbents the distribution coefficient in the presence of 0.1 M NaCl increases by a factor of approximately 8–10 relative to distilled water and reaches (91–208) × 103 cm3 g–1. Introduction of 0.05 M CaCl2 also decreases the Sr uptake, and the sorption capacity of the most active sorbents for stable Sr ions is 25–35 mg g–1 at K d (85Sr) equal to (0.14–0.35) × 103 cm3 g–1.

Comparison of coastal area sediment-seawater distribution coefficients (Kd) of stable and radioactive Sr and Cs

Values of the sediment-seawater distribution coefficient (Kd) in Japanese coastal areas were compared for stable and radioactive Sr and Cs, respectively, in order to clarify whether or not the constant exchangeable fraction in sediment of 20% for the ocean margin (the IAEA recommended method) for all elements was reasonable. Global fallout origin 90Sr and 137Cs concentrations in sediment and seawater were obtained from open data sources as collected in 1964–2010 and 319 and 1506 Kd values were calculated, respectively. When the values were classified into about 10 y intervals from the 1960's to 2000's, Kd values of the two most recent decades did not show any difference for 90Sr and 137Cs. The geometric means of the most recent Kd values in 2000–2010 were 1.2 × 102 L kg−1 for 90Sr and 5.8 × 102 L kg−1 for 137Cs. The stable Sr and Cs concentration data in sediment and seawater samples collected in 2000–2011 were used to calculate stable Sr and Cs Kd values based on the IAEA's recommended method and values were compared. It was found that the stable Sr Kd (geometric mean = 5.3) was much less than that of Kd-90Sr, while stable Cs Kd (geometric mean = 1.7 × 103) was higher than that of Kd-137Cs. Thus, it was judged to be unsuitable to estimate the Kds of these radionuclides by apply a factor of 0.2 to the total concentration of Sr and Cs in Japanese coastal sediment, assuming 20% was the exchangeable fraction. It is likely that applying the constant exchangeable fraction percentage to all elements will sometimes lead to overestimated or underestimated values.

Adsorption of Eu(III) ions on silicas with noncovalently immobilized thiacalix[4]arene derivatives

Using the noncovalent immobilization of some thiacalix[4]arene derivatives on the surface of silanized silica, we obtained efficient adsorption materials for the extraction of Eu(III) ions from aqueous solutions of medium mineralization. The specific surface area of the adsorbents is 200–370 m2/g. It is shown that adsorbents containing thiacalix[4]arenes with phosphoryl groups selectively extract up to 99% of europium ions from aqueous solutions at pH 5.5–6; they are characterized by adsorption capacity of 7.5–14.5 mg/g and high distribution coefficients. The studied adsorbents exhibit high selectivity with respect to Eu(III) ions, wherein the distribution coefficients for Cs, Sr, Tb(III), Sm(III), Gd(III), La(III), and UO 2 2+ are five times or more smaller.

Study on sorption and diffusion of Sr in crushed and intact basalt and granite investigated in through-diffusion experiments

This study investigates sorption and diffusion of strontium (Sr) in two potential host rocks (granite from Kingman Island and basalt from Penghu Island) by using batch and column methods. According to solid-phase analysis, the sorption component primarily contained iron–magnesium (Fe–Mg) minerals in basalt and granite. Moreover, the distribution coefficient (K d) of Sr in various concentrations obtained from batch tests indicated a higher sorption capacity in basalt than that in granite because of the 10 % Fe–Mg mineral content. According to the diffusive results in crushed and intact rocks, it showed that major retardation of Sr depended on the micro-porous structure of tested media, such as decreases of constrictivity and increases of tortuosity.

Stable strontium isotope fractionation in synthetic barite

The mineral barite (BaSO4) accommodates strontium (Sr) in its crystal structure, providing an archive of Sr-isotopes (87Sr/86Sr and δ88/86Sr) in the highly stable sulfate mineral. We investigated mass dependent stable Sr-isotope fractionation (Δ88/86Sr=δ88/86Srsolid−δ88/86Srsolution) during inorganic precipitation of barite from a barium-rich solution by addition of sulfate under controlled conditions and compared this to equilibrium isotopic fractionation calculated using Density Functional Theory modeling. Sr-substituted barite is predicted to have lower 88Sr/86Sr than any other studied species, and at 25°C will be about 0.6–0.7‰ lower than the two modeled Sr(H2O)82+-bearing salts that could approximate aqueous Sr2+. This agrees in direction and order of magnitude with experimental results that estimate equilibrium Sr-isotope fractionation in barite to be 0.3‰ lower than aqueous Sr2+ at ∼20°C. The high ionic strength of some of the precipitating solutions (up to 1M) and potential differences in the average coordination number of aqueous Sr2+ add to uncertainty in a direct comparison of the calculated equilibrium isotopic fractionation values with the experimental results.Stable Sr-isotope fractionation varied along with the distribution coefficient of Sr [Kd(Sr)=[Sr/Ba]barite/[Sr/Ba]solution], which is a function of both temperature and barite saturation state. However the relationship between mass dependent isotopic fractionation and Kd(Sr) is different for conditions of changing temperature versus barite saturation state. With increasing temperature (from 5 to 40°C), the barite phase became isotopically lighter (Δ88/86Sr=−0.29‰ to −0.41‰). Conversely, with increasing saturation state (saturation index of barite=3.0–4.3) the barite phase became isotopically heavier (Δ88/86Sr=−0.25‰ to −0.10‰). These observations suggest chemical kinetic effects control isotopic fractionation rather than equilibrium temperature effects. The relationship with saturation state indicates the potential presence of a diffusive boundary layer. Barite crystal morphology appears to be affected by the diffusion rate of solute (sulfate) to the growing crystal surface relative to the overall growth rate of barite crystals during precipitation.

Composition and origin of the dolostones of Um Bogma Formation, Lower Carboniferous, West Central Sinai, Egypt

Dolostones of Um Bogma Formation, Lower Carboniferous, have been possibly originated due to two different fluids. The main fluid source is related to meteoric water. The second fluid originated from deeper hydrothermal sources ascended through faults. The diagenetic features of Um Bogma Formation show many processes with conspicuous effects, including dolomitization, neomorphism, mechanical and chemical compaction, as well as it characteristics with stylolites, sutured and concave–convex contacts between grains. Based on mineralogical composition and petrography, the diagenetic environments are distinguished into shallow marine, near surface meteoric and burial environments. Dolostones in the studied area are possibly subjected to chemical and biochemical weathering. Um Bogma dolostones are nearly stoichiometric and ordered. Mineralogical and geochemical studies indicated that dolomite crystals were deposited in mixing zone of marine and meteoric water. In addition, it is formed in the near-surface oxidizing environment. The Sr distribution coefficient and Y content of the studied dolostones indicated that they are formed in temperature >110 and <150 °C. The CF (Contamination factor) and Igeo (Geo-accumulation index) have doubtlessly indicated that the Um Bogma dolomite rocks are polluted especially for Fe, Rb, Co, Cu, W, S, Ba, Zn, Zr and As. The studied dolomites of Area 45 and Um Bogma Mine sections are characterized by enrichment of Co and Cu, which indicated their deposition in marine environment. The studied dolomite of Um Bogma Mine is characterized by the enrichment of Zn, W, Ba, Mn, Ti and As which derived from hydrothermal solution. Consequently, the dolostones of the Um Bogma Formation are similar to those in Cayman Formation, Indies.