Oxygen and Carbon Isotope Variations of Carbonates and Silicates from the Carbonatite Massif Tiksheozero (Northern Karelia)

Abstract

Carbon and oxygen isotope compositions have been determined for carbonate minerals from different types of carbonatites (large carbonatite bodies, veins, eruptive breccia), as well as from different temperature classes of carbonatites (according to Samoilov [1]). It could be shown, that only high temperature carbonatites exhibit small variations of δ¹⁸O and δ¹³C falling in the range of “high temperature mantle carbonates”, whereas low temperature calcites and dolomites show wide variations in δ¹⁸O. These changes in both isotope and mineral compositions of low temperature carbonatites are interpreted as a result of repeated interaction with fluids. The oxygen isotope ratios in most of the eruptive breccia have been changed by secondary processes. The primary deep-seated isotope record has been preserved only in samples, in which carbonate occurs as fine-grained calcite groundmass.

Preliminary results on oxygen isotope composition of different silicate minerals (amphibole, magnetite, biotite, albite, apatite) indicate isotope equilibrium for the mineral pair calcite-amphibole with isotope temperatures representing superimposed processes.     

Natural and anthropogenic variations in the Po river waters (northern Italy): insights from a multi-isotope approach

Po is the main Italian river and the δ¹⁸O and δ²H of its water reveal a similarity between the current meteoric fingerprint and that of the past represented by groundwater. As concerns the hydrochemisty, the Ca–HCO₃ facies remained constant over the last 50 year, and only nitrate significantly increased from less than 1?mg/L to more than 10?mg/L in the 1980s, and then attenuated to a value of 9?mg/L. Coherently, δ¹³C_DIC and δ³⁴S_SO4 are compatible with the weathering of the lithologies outcropping in the basin, while extremely variable δ¹⁵N_NO3 indicates contribution from pollutants released by urban, agricultural and zootechnical activities. This suggests that although the origin of the main constituents of the Po river water is geogenic, anthropogenic contributions are locally significant. Noteworthy, the associated aquifers have the same nitrogen isotopic signature of the Po river, but are characterized by significantly higher NO^– ₃ concentration. This implies that aquifers’ pollution is not ascribed to inflow of current river water, and that the attenuation of the nitrogen load recorded in the river is not occurring in the aquifers, due to their longer water residence time and delayed recovery from anthropogenic contamination.     

Sulphur and Oxygen Isotopes in Sulphates in Natural Waters: (2) Deep-Waters from Horizons Below Baltic Sea Floor

Abstract

In this paper we consider deep waters from horizons located under the Baltic-Sea bottom. The samples were taken twice from wells bored in Hel peninsula. The δ¹⁸O and δD values of these waters show their glacial origin since they have significantly low values (δ¹⁸O from ?14 to ?11 whereas the modern groundwaters in Gdańsk area have ?10%₀). In contrast to surface waters the sulphates dissolved in these deep waters have rather high and uniform δ¹⁸O values which are correlated with δ¹⁸O of H₂O but not correlated with δ³⁴S. The isotope patterns may be explained assuming that the waters are very old, in which the slow process of oxygen isotope exchange at low temperatures, but extended in time, could enrich the sulphate in heavier oxygen isotopes.     

Study of isotopes of carbon,thorium, and uranium in travertine and thermal spring samples: implications for effects of changes in geochemical environment and processes

Data on modern radiocarbon activity in the old travertine formations of the Pymvashor hydrothermal system were used, in combination with ²³⁰Th/U dating of the travertine, to estimate the ¹⁴C contents of the total dissolved inorganic carbon in the ancient thermal water at the time of precipitation of the travertine (¹⁴C_calc). With the known values of ¹⁴C_calc and average age of the thermal water, and under the assumption that the residence time of the water in aquifer was constant over the last 13.9?±?1.5 ka, the initial ¹⁴C contents (¹⁴C₀) in the ancient thermal water were estimated. The findings in this study are that (1) both ¹⁴C₀ and δ¹³С have decreased in young waters compared to the ancient waters; (2) although atmospheric ¹⁴C activity (¹⁴C_atm) has also decreased in the same time, the decrease in ¹⁴C₀ is faster than the decrease in ¹⁴C_atm. Under certain assumptions, one could link changes in ¹⁴C₀ and δ¹³C to climate change. Decrease in δ¹³С of soil CO₂ and decrease in ¹⁴C₀ was caused predominantly by warmer and wetter climate, decomposition of fossil organic matter, and decrease in ¹⁴C_atm. There could be also increased dissolution of solid carbonate and increased carbon exchange between DIC and soil CO₂, caused by thawing permafrost.     

Barium isotope fractionation during the experimental transformation of aragonite to witherite and of gypsum to barite,and the effect of ion (de)solvation

In this study, we present the experimental results for stable barium (Ba) isotope fractionation (¹³⁷Ba/¹³⁴Ba) during the transformation of aragonite (CaCO₃) and gypsum (CaSO₄·2H₂O) in Ba-bearing aqueous solution to witherite (BaCO₃) and barite (BaSO₄), respectively. The process was studied at three temperatures between 4 and 60?°C. In all cases, the transformation leads to a relative enrichment of the lighter ¹³⁴Ba isotope in the solid compared to the aqueous solution, with ^137/134Ba enrichment factors between –0.11 and ?0.17?‰ for BaCO₃, and –0.21 and –0.26?‰ for BaSO₄. The corresponding mass-dependent ^138/134Ba enrichment factors are ?0.15 to –0.23?‰ for BaCO₃, and –0.28 to –0.35?‰ for BaSO₄. The magnitude of isotope fractionation is within the range of recent reports for witherite and barite formation, as well as trace Ba incorporation into orthorhombic aragonite, and no substantial impact of temperature can be found between 4 and 80?°C. In previous studies, ion (de)solvation has been suggested to impact both the crystallization process of Ba-bearing solids and associated Ba isotope fractionation. Precipitation experiments of BaSO₄ and BaCO₃ using an methanol-containing aqueous solution indicate only a minor effect of ion and crystal surface (de)solvation on the overall Ba isotope fractionation process.     

Nd∶KY(WO4)2和Nd∶KG(WO4)2晶体吸收光谱性能分析

通过研究分析钨酸盐晶体Nd∶KY(WO₄)₂和Nd∶KG(WO₄)₂在室温下的吸收光谱，发现这2种晶体具有作为激光晶体的优良特性。根据Judd-Ofelt理论和测试所得的吸收光谱及数据，用VC++编程计算出晶体的谱线强度、振子强度、吸收截面等，拟合得Nd³⁺离子的3个晶场调节参数Ω_λ(λ=2，4，6)的值，并从理论上计算了自发跃迁几率、能级寿命、荧光分支比和积分发射截面。从计算得出的荧光分支比β可以看出，Nd∶KY(WO₄)₂(β_1060nm=0.4380)和Nd∶KG(WO₄)₂(β_1060nm=0.4618)晶体荧光分支比都较大，计算了该晶体的X=Ω₄/Ω₆，并将其X值与其他晶体的X值加以比较，Nd∶KY(WO₄)₂和Nd∶KG(WO₄)₂均易于实现1.06μm激光输出，适合作为LD泵浦的钨酸盐晶体激光器。     

Electronic structure and fluorescence of the Mg(II) complex of 1,4-diazepinotribenzoporphyrazine

Spectral and luminescent properties of a new phthalocyanine analog, the magnesium complex of diphenyl substituted mono(1,4-diazepino)tribenzoporphyrazine, have been studied at 293 and 77 K. The results have been explained on the basis of quantum-chemical calculations for both this molecule and its simpler analogs with respect to 6H/1H-isomerism of the 1,4-diazepine ring. The small difference between the ground-state energies for the 6H and 1H isomers makes tautomerism between them possible. It is shown that the electronic transitions with intramolecular charge transfer from the diazepine fragment to the macrocycle have relatively low energy, especially for the 1H isomers. These states can be of considerable importance for photophysical and photochemical processes. A comparison of the theoretical and experimental electronic absorption spectra has confirmed that the diazepine ring in the substituted Mg-diazepinoporphyrazine is present in the 6H-form. It is established that substitution of one benzene ring by a diazepine fragment leads to quenching of fluorescence, decreasing its quantum yield to 27% (for Mg-phthalocyanine 76%). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 365–375, May–June, 2009.     

Sulphur and Oxygen Isotopes in Sulphates in Natural Waters: (1) Surface Waters of Relatively Unpolluted Terrains

Abstract

The paper presents a whole-year study (1990) of an unique area in S-E Poland with numerous small rivers and streams carrying clean waters. We report the results of δ¹⁸O of waters and δ³⁴S of the sulphates sampled 4 times in 1990 from 20 rivers of the study area. The observations clearly show the impact of biological activity on the oxygen and sulphur isotopic compositions in sulphates. Attempts have been made to interpret the correlation between δ³⁴S and δ¹⁸O in sulphates. The highest correlation coefficient has been noticed for samples collected in April, whereas the lowest in August. The conclusion of this study is that the river sulphates are predominantly produced outside the river environment. We have distinguished three major sources of sulphates: (1) ones produced in the aquifer from which waters are discharged, (2) those produced in soils and marshes of forest environment, and (3) ones on anthropogenic origin.     

Geochemical and isotopic evidences from groundwater and surface water for understanding of natural contamination in chronic kidney disease of unknown etiology (CKDu) endemic zones in Sri Lanka

Chronic kidney disease of unknown etiology (CKDu) is the main health issue in the dry zone of Sri Lanka. Despite many studies carried out, causative factors have not been identified yet clearly. According to the multidisciplinary researches carried out so far, potable water is considered as the main causative factor for CKDu. Hence, the present study was carried out with combined isotopic and chemical methods to understand possible relationships between groundwater; the main drinking water source, and CKDu in four endemic areas in the dry zone. Different water sources were evaluated isotopically (²H, ³H and ¹⁸O) and chemically from 2013 to 2015. Results revealed that prevalence of CKDu is significantly low with the groundwater replenished by surface water inputs. It is significantly high with the groundwater stagnated as well as groundwater recharged from regional flow paths. Thus, the origin, recharge mechanism and flow pattern of groundwater, as well as geological conditions which would be responsible for natural contamination of groundwater appear as the main causative factors for CKDu. Therefore, detailed investigations should be made in order to identify the element(s) in groundwater contributing to CKDu. The study recommends providing drinking water to the affected zones using water sources associated with surface waters.     

Isotope Anomalies of Carbon,Hydrogen and Nitrogen in Peat from the Area of the Tunguska Cosmic Body Explosion (1908)

Abstract

Peat profiles from the area of the Tunguska explosion epicentre indicate significant carbon and hydrogen isotopic effects which are clearly associated with the zone of the 1908 “catastrophe”, and which cannot be attributed to any known terrestrial processes. We explain them with the presence of extraterrestrial matter similar to carbonaceous chondrites or, more probably, to cometary matter. Initial data on nitrogen content and its isotope composition are consistent with the assumption of acid rainfall following the passage and explosion of the Tunguska cosmic body, as is known to have occurred during the Cretaceous-Tertiary boundary.     

Preparation of Naturally 13C-Rich Free Fatty Acids (FFA) from Corn Oil and their Application in Metabolic Studies of Lactating Cows

Abstract

When the ¹³C/¹²C ratios in lactose and milk fat of normally fed healthy cows are compared to ¹³C/¹²C in feed a metabolic depletion of ¹³C in the milk constituents becomes obvious.

Due to a carbon isotope effect in the decarboxylation step of pyruvate to Acetyl-Co-A resulting in a ¹³C depleted acetate, depot fat and milk fat are especially reduced in ¹³C relative to ¹²C.

Under pathophysiological conditions after longer fasting periods or in ketosis, long chain fatty acids from depot fat are metabolized and their ¹³C depleted carbon atoms enter the citric acid cycle via Acetyl-Co-A. Then the intermediary products of this cycle become ¹³C depleted too and with a drain on the oxalacetate pool by gluconeogenesis ¹³C depleted carbon atoms are channeled into lactose.

This hypothesis is apt to explain a ¹³C/¹²C decrease in lactose of ketotic cows relative to healthy controls. It is supported by the observation that ¹³C-rich fatty acids from corn oil dosed orally to a ketotic cow increase the ¹³C/¹²C ratios in lactose. So a crossing-over of carbon atoms from long chain fatty acids into glucose and lactose seems highly probable.     

Analysis of the Tautomeric Properties of 2-Formylcyclopentane-1,3-Dione Using the Data of IR Spectroscopy and Nonempirical (ab initio and DFT) Quantum-Chemical Calculations

The tautomerism, spectral properties, and properties of intramolecular hydrogen bonds in 2-formylcyclopentane-1,3-dione (FCPD) have been investigated by the methods of nonempirical quantum chemistry (calculations by the ab initio and DFT methods) and IR and ¹³C NMR spectroscopy. It is shown that FCPD in a crystalline form, as also does malonic dialdehyde, exists as self-associated enolized molecules with an open chelate ring. It is found that in solutions in CCl₄ the compound investigated exists as an equilibrium mixture of its exo- and endoenolic forms, with predominance of the former. The IR spectra of the solutions of FCPD in CCl₄ fix the presence of small amounts of the associate formed from the anionic and protonated forms of the substance. For the first time, the energies of the intramolecular H bonds of the endo- and exoenolic tautomeric forms in FCPD have been estimated theoretically. They appeared to be equal to 3.69 and 4.91 kcal·mole^–1, respectively. The possible mechanisms of enol-enolic interconversions of FCPD have been discussed.     

FTIR光谱的海水入侵区水-岩(土)间氟迁移机理分析

滨海地区饮水型氟中毒和海水入侵十分普遍。海水入侵引起地下水性质的改变对岩（土）氟迁移具有潜在影响,但尚未有直接模拟实验证实,其氟迁移机理也不明确。用淡水和海（卤）水混合及配制溶液模拟海水入侵过程,对含水砂层沉积物进行静态水-岩（土）氟迁移模拟实验,对比分析沉积物FTIR特征,探讨海水入侵对岩（土）氟迁移影响规律及机理。结果表明,含水砂层沉积物氟迁移量大小顺序为：海水＞1∶1淡海＞淡水;卤水＞1∶1淡卤＞淡水,随海（卤）水混入程度增加,含水砂层沉积物岩（土）氟迁移能力增强。氟迁移能力随NaCl和NaHCO₃浓度增加而增加,随CaCl₂浓度增加而降低。对含水砂层沉积物傅里叶红外吸收光谱（FTIR）分析表明,随NaCl和NaHCO₃浓度增加,NaCl溶液中沉积物Si-O-Si键伸缩振动峰强度明显增强,氟磷灰石弯曲振动峰减弱,O-H键特征峰变化不明显,而NaHCO₃溶液中沉积物羟基磷灰石弯曲振动峰和Si-O-Si键伸缩振动峰强度变化不明显,O-H键特征峰强度变化明显,表明NaHCO₃溶液主要通过OH-与F-离子交换,而NaCl溶液是通过Si-O-Si键中Si-O置换来影响岩（土）氟迁移。随CaCl₂浓度增加,Si-O-Si键伸缩振动峰强度明显减弱,氟磷灰石弯曲振动峰强度增强,表明Ca2+强烈地抑制岩（土）氟析出。同时,随NaCl和NaHCO₃浓度增加和CaCl₂浓度减少,Si-F特征峰强度减弱,Si-O-Si键弯曲振动峰向低波数偏移。由于大气CO₂混入,1 mol·L-1 CaCl₂作用沉积物出现1 460和1 420 cm-1碳酸根特征峰。由于碳酸根沉积作用,1 mol·L-1的NaHCO₃作用的沉积物在1 460 cm-1处峰强度增强,且在875 cm-1出现新峰,但是在淡海卤水和NaCl溶液作用的沉积物中无碳酸根特征峰,表明含水砂层中无萤石（CaF₂）溶解作用。海水入侵引起的偏碱性、高钠低钙的环境促进岩（土）氟迁移释放,是滨海地区高氟地下水重要动力。     

Efficient and accurate determination of the overall rotational diffusion tensor of a molecule from (15)N relaxation data using computer program ROTDIF

We present a computer program ROTDIF for efficient determination of a complete rotational diffusion tensor of a molecule from NMR relaxation data. The derivation of the rotational diffusion tensor in the case of a fully anisotropic model is based on a six-dimensional search, which could be very time consuming, particularly if a grid search in the Euler angle space is involved. Here, we use an efficient Levenberg-Marquardt algorithm combined with Monte Carlo generation of initial guesses. The result is a dramatic, up to 50-fold improvement in the computational efficiency over the previous approaches. This method is demonstrated on a computer-generated and real protein systems. We also address the issue of sensitivity of the diffusion tensor determination from (15)N relaxation measurements to experimental errors in the relaxation rates and discuss possible artifacts from applying higher-symmetry tensor model and how to recognize them.     

Nd:Ca4ReO(BO3)3(Re=Gd,Y)晶体最佳激光、最佳倍频及最佳自倍频方向的确定

介绍了Nd:Ca4ReO(BO3)3(Re=Gd,Y)晶体最佳激光方向、最佳倍频方向的确定.综合考虑激光受激发射截面、抽运光吸收系数、有效非线性系数的各向异性,分析了自倍频性质的空间分布,并就此确定出最佳自倍频方向 关键词： Nd:Ca4ReO(BO3)3(Re=Gd Y)晶体 激光发射 倍频 自倍频     

The electronic and chemical structure of the a-B(3)CO(0.5):H(y)-to-metal interface from photoemission spectroscopy: implications for Schottky barrier heights

The electronic and chemical structure of the metal-to-semiconductor interface was studied by photoemission spectroscopy for evaporated Cr, Ti, Al and Cu overlayers on sputter-cleaned as-deposited and thermally treated thin films of amorphous hydrogenated boron carbide (a-B(x)C:H(y)) grown by plasma-enhanced chemical vapor deposition. The films were found to contain ～10% oxygen in the bulk and to have approximate bulk stoichiometries of a-B(3)CO(0.5):H(y). Measured work functions of 4.7/4.5?eV and valence band maxima to Fermi level energy gaps of 0.80/0.66?eV for the films (as-deposited/thermally treated) led to predicted Schottky barrier heights of 1.0/0.7?eV for Cr, 1.2/0.9?eV for Ti, 1.2/0.9?eV for Al, and 0.9/0.6?eV for Cu. The Cr interface was found to contain a thick partial metal oxide layer, dominated by the wide-bandgap semiconductor Cr(2)O(3), expected to lead to an increased Schottky barrier at the junction and the formation of a space-charge region in the a-B(3)CO(0.5):H (y) layer. Analysis of the Ti interface revealed a thick layer of metal oxide, comprising metallic TiO and Ti (2)O (3), expected to decrease the barrier height. A thinner, insulating Al(2)O(3) layer was observed at the Al-to-a-B(3)CO(0.5):H(y) interface, expected to lead to tunnel junction behavior. Finally, no metal oxides or other new chemical species were evident at the Cu-to-a-B(3)CO(0.5):H(y) interface in either the core level or valence band photoemission spectra, wherein characteristic metallic Cu features were observed at very thin overlayer coverages. These results highlight the importance of thin-film bulk oxygen content on the metal-to-semiconductor junction character as well as the use of Cu as a potential Ohmic contact material for amorphous hydrogenated boron carbide semiconductor devices such as high-efficiency direct-conversion solid-state neutron detectors.     

Novel synthesis of nanocomposite for the extraction of Sildenafil Citrate (Viagra) from water and urine samples: Process screening and optimization

A sensitive analytical method is investigated to concentrate and determine trace level of Sildenafil Citrate (SLC) present in water and urine samples. The method is based on a sample treatment using dispersive solid-phase micro-extraction (DSPME) with laboratory-made Mn@ CuS/ZnS nanocomposite loaded on activated carbon (Mn@ CuS/ZnS-NCs-AC) as a sorbent for the target analyte. The efficiency was enhanced by ultrasound-assisted (UA) with dispersive nanocomposite solid-phase micro-extraction (UA-DNSPME). Four significant variables affecting SLC recovery like; pH, eluent volume, sonication time and adsorbent mass were selected by the Plackett-Burman design (PBD) experiments. These selected factors were optimized by the central composite design (CCD) to maximize extraction of SLC. The results exhibited that the optimum conditions for maximizing extraction of SLC were 6.0 pH, 300 μL eluent (acetonitrile) volume, 10 mg of adsorbent and 6 min sonication time. Under optimized conditions, virtuous linearity of SLC was ranged from 30 to 4000 ng mL⁻¹ with R² of 0.99. The limit of detection (LOD) was 2.50 ng mL⁻¹ and the recoveries at two spiked levels were ranged from 97.37 to 103.21% with the relative standard deviation (RSD) less than 4.50% (n = 15). The enhancement factor (EF) was 81.91. The results show that the combination UAE with DNSPME is a suitable method for the determination of SLC in water and urine samples.