The Hf isotopic composition of zircon reference material 91500

Ten new single zircon fragments, analyzed by solution chemistry and MC-ICP-MS, of the 91500 zircon standard show no evidence to support a recent claim based on in situ data that this reference material is heterogeneous in terms of its radiogenic Hf isotope composition and as a consequence should be abandoned as a reliable interlaboratory standard. Rather, the larger spread in ¹⁷⁶Hf/¹⁷⁷Hf among in situ data compared with solution chemistry data may reflect the uncertainties resulting from prominent isobaric interference corrections inherent to the in situ analytical protocol. The unweighted mean values of ¹⁷⁶Hf/¹⁷⁷Hf and ¹⁷⁶Lu/¹⁷⁷Hf measured for the ten zircon fragments of this study are 0.282313 ± 0.000008 (2σ) and 0.000311 ± 0.000136 (2σ), respectively. Pooling the mean ¹⁷⁶Hf/¹⁷⁷Hf of this work with those of published solution chemistry studies results in a value of 0.282308 ± 0.000006 (2σ; relative to ¹⁷⁶Hf/¹⁷⁷Hf = 0.282163 for JMC-475), which is recommended here as the currently best estimate of the Hf isotopic composition of this standard. All published studies agree on a value of ~ 0.0003 for the corresponding ¹⁷⁶Lu/¹⁷⁷Hf ratio.     

La-Ce法岩石标准物质和Ce同位素标准溶液研制

报道了La-Ce法岩石标准物质的研制结果。标准物质选自峨眉山玄武岩中的新鲜微晶玄武岩（编号EQB）,具有间隐结构,矿物组成相对均一。岩石经粉碎和均一化加工,成为粉末后分装成1000小瓶。经均匀性和稳定性检验合格后,对该岩石标准物质的Ce同位素比值和La、Ce元素含量进行了测定和定值统计,其结果分别表示为：138Ce／142Ce=0．0225755±0．0000003,Ce=（117．4±1．3）μg／g,La=（55．8±0．9）μg／g。对二氧化铈化学试剂进行了溶液制备,以用于Ce同位素分析仪器标准物质。标准溶液编号为CBRICeO2,其138Ce／142Ce比值的测定统计值为0．0225748±0．0000006。为检验所制标准物质分析数据的准确度,对国际标样进行了比对测量,其中JMC304标准溶液的138Ce／142Ce比值测定结果为0．0225762±0．0000015,USGS玄武岩标样BCR-2的La和Ce元素含量测定结果分别为（25．2±0．6）μg／g（2σ）和（54．2±0．8）μg／g（2σ）,所获数值与文献报道值或证书值在误差范围内相符。     

Evaluation of the sulfur isotopic composition and homogeneity of the Soufre de Lacq reference material

Sulfur isotopic analysis of the elemental sulfur reference material Soufre de Lacq, prepared as silver sulfide by chromous chloride reduction and as copper sulfide by sealed-tube synthesis, indicates that Soufre de Lacq is isotopically homogeneous across different size fractions to within analytical uncertainty (±0.15‰). The sulfur isotopic composition of aliquots of Soufre de Lacq prepared by these two techniques are identical to within analytical uncertainty. The mean sulfur isotopic composition for Soufre de Lacq prepared as silver sulfide and copper sulfide (relative to VCDT) is +16.20±0.15‰ (1σ).     

A comparison of two techniques for the isolation of adsorbed dissolved organic material from seawater

¹³C solid-phase NMR and pyrolysis-chemical ionization mass spectrometry were used to characterize adsorbed organic material isolated on an XAD-2 macroreticular resin. Pyrolysis-chemical ionization mass spectrometry was used directly to fingerprint the organics sorbed to a titanium foil exposed in the same marine environment. The XAD-2 isolate was shown to be fractionated relative to the native material and contaminated with the isolation resin.     

Application of chlorine dioxide for secondary effluent polishing

There are still many difficulties for developing the projects of using treated effluents. In this study, the efficiency of chlorine deoxide in the process of preparing the effluent of Sahebgharanieh Plant of Tehran for reuse purposes has been determind. Major results are as follows: Total COD reductions resulted from effluent treatment by ClO₂ solutions having concentrations equal to 1/4, 1/2 and 1/1 of COD samples at one hour contact time have been about 42%, 49% and 59% respectively. Total suspended solids were also reduced by treatment with ClO₂ solutions having the certain concentrations mentioned, and the reductions were about 37%,47% and 58% respectively. Besides total and fecal coliforms results indicated that ClO₂ apllied was quite efficient in effluent disinfection. The conclusion is that reasonable reductions would be expected in the amounts of remained major pollutants and so reuse applications for some non-potable purposes may become possible. The acidification of chlorite has been used for ClO₂ generation as it is better suited to small treatment systems.     

Diurnal variations in the isotopic composition of dissolved inorganic carbon in seawater from coral reef environments

The isotopic composition of total dissolved inorganic carbon in seawater was determined as a function of time of day in coral reef environments at Saipan, Abaiang Atoll, Tahiti, Florida and Heron Island on the Great Barrier Reef of Australia. At each locality water collected during the day was enriched in ¹³C with respect to water collected at night. The form and magnitude of the diurnal cycles is dependent upon the ratio of local biomass to local water mass and on the degree of exchange between local water mass and the open ocean reservoir. Comparison of open and closed system models is made using computer generated δ¹³C vs. time curves to illustrate modulation by the tidal cycle of the simple diurnal variation in a closed system. The results are of geochemical significance in that the δ¹³C of CaCO₃ precipitated in certain environments is dependent on the time of crystallization. This must be taken into account in isotope ratio studies of both plant and animal secreted carbonates which are preferentially precipitated during certain periods of the day.     

Characterisation of chlorinated hydrocarbons from chlorine and carbon isotopic compositions: scope of application to environmental problems

A set of chlorinated hydrocarbons (TCE, PCE, DCM, 1,1,1-TCA, chloroform) provided by four manufacturers has been isotopically characterised for both C and Cl, using a new sensitive method. A very large range of δ¹³C (from −51.66 to −24.07‰/PDB) associated with a very large range of δ³⁷Cl (from −2.7 to +3.4‰/SMOC) was obtained. This range of δ³⁷Cl is much larger than that of inorganic Cl (±1‰ SMOC) and most individual solvents show a very distinct δ³⁷Cl compared to inorganic Cl isotopic signatures. Moreover, δ³⁷Cl/δ¹³C pairs are distinct from one solvent/manufacturer to another. In a δ¹³C versus δ³⁷Cl diagram, δ³⁷Cl / δ¹³C pairs show different trends for the products of a single manufacturer compared to another. This suggests that Cl isotopic compositions are probably highly fractionated during organic synthesis. The δ³⁷Cl values can be interpreted in terms of the probable manufacturing processes. Unlike the data published previously, with one exception, all the new results for samples reported here have positive δ³⁷Cl values which might differentiate natural Cl from that derived from degradation. This method has significant potential as a tool for investigating environmental pollution problems; in particular, it offers the possibility for validating models of transport and fate of pollutants.     

Stable chlorine and carbon isotope measurements of selected chlorinated organic solvents

Stable Cl and C isotope ratio results for 3 selected chlorinated solvents, perchloroethylene (PCE), trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA) provided by 4 different manufacturers are presented. The isotope ratio for all compounds range between −3.5 and +6.0‰ forδ³⁷Cl and from −37.2 to −23.3%. forδ¹³C. The greatest³⁷Cl difference between manufacturers is observed in the TCE samples which showδ³⁷CI values of −2.5%o for PPG, +2.43‰ for ICI and +4.4‰ for DOW. TCAs show a smaller range (−2.4 to +2.0‰), while the TCEs have slightly different³⁷Cl contents. The¹³C data show the most distinctδ¹³C values for PCEs (−23.3 for DOW, −24.1 for Vulcan, −33.8 for PPG and −37.2‰ for ICI) while both TCEs and TCAs show a smallerδ¹³C range, but still distinct differences. These preliminary data suggest that each manufacturer and solvent type may have distinctiveδ⁶³⁷Cl andδ¹³C values. These results show that by using a combination of³⁷Cl and¹³C, there is a potential to indicate a specific source of chlorinated solvents, as well as an ability to delineate contamination episodes caused by these compounds in groundwaters.     

Stable chlorine isotopic signatures and fractionation mechanism of groundwater in Anyang,China

The present work provides an online Bench II-IRMS technique for the measurement of stable chlorine isotope ratio, which is used to measure the δ³⁷Cl of 38 groundwater samples from the Karst and Quaternary aquifers in Anyang area. The regional distribution and signature of δ³⁷Cl value are characterized on the base of isotopic data. The results suggest that the δ³⁷Cl value of Quaternary groundwater decreases with increasing Cl^? concentration, and has no correlation with δ¹⁸O and δD values, but closely correlates with the depth to water table. The fractionation mechanism of the chlorine isotope is expounded according to the type of groundwater. The δ³⁷Cl value of karst water is generally positive, which is relevant to the dissolution of evaporite (gypsum mine), and may be caused by the mixing of groundwater and precipitation. The groundwater of Quaternary unconfined aquifer is mainly recharged by precipitation, and the δ³⁷Cl value of groundwater is generally negative. The δ³⁷Cl value of groundwater in Quaternary confined aquifer is more negative with increasing the depth to water level and elevated Cl^? concentration, which is possible to result from the isotope fractionation of ion filtration. The groundwater with inorganic pollutants in Quaternary unconfined aquifer has generally a positive δ³⁷Cl value.     

Deep-sea coral aragonite as a recorder for the neodymium isotopic composition of seawater

Deep-sea corals have been shown to be useful archives of rapid changes in ocean chemistry during the last glacial cycle. Their aragonitic skeleton can be absolutely dated by U-Th data, freeing radiocarbon to be used as a water-mass proxy. For certain species of deep-sea corals, the growth rate allows time resolution that is comparable to ice cores. An additional proxy is needed to exploit this opportunity and turn radiocarbon data into rates of ocean overturning in the past.Neodymium isotopes in seawater can serve as a quasi-conservative water-mass tracer and initial results indicate that deep-sea corals may be reliable archives of seawater Nd isotopes. Here we present a systematic study exploring Nd isotopes as a water-mass proxy in deep-sea coral aragonite. We investigated five different genera of modern deep-sea corals (Caryophyllia, Desmophyllum, Enallopsamia, Flabellum, Lophelia), from global locations covering a large potential range of Nd isotopic compositions. Comparison with ambient seawater measurements yields excellent agreement and suggests that deep-sea corals are reliable archives for seawater Nd isotopes.A parallel study of Nd concentrations in these corals yields distribution coefficients for Nd between seawater and coral aragonite of 1-10, omitting one particular genus (Enallopsamia). The corals and seawater did however not come from exactly the same location, and further investigations are needed to reach robust conclusions on the incorporation of Nd into deep-sea coral aragonite.Lastly, we studied the viability of extracting the Nd isotope signal from fossil deep-sea corals by carrying out stepwise cleaning experiments. Our results show that physical removal of the ferromanganese coating and chemical pre-cleaning have the highest impact on Nd concentrations, but that oxidative/reductive cleaning is also needed to acquire a seawater Nd isotope signal.     

Molecular-scale mechanisms of distribution and isotopic fractionation of molybdenum between seawater and ferromanganese oxides

The distribution of Mo between seawater and marine ferromanganese oxides has great impacts on concentration and isotopic composition of Mo in modern oxic seawater. To reveal the adsorption chemistry of Mo to ferromanganese oxides, we performed (i) detailed structural analyses of Mo surface complexes on δ-MnO₂, ferrihydrite, and hydrogenetic ferromanganese oxides by L₃- and K-edge XAFS, and (ii) adsorption experiments of Mo to δ-MnO₂ and ferrihydrite over a wide range of pHs, ionic strengths, and Mo concentrations. XAFS analyses revealed that Mo forms distorted octahedral (Oh) inner-sphere complexes on δ-MnO₂ whereas it forms a tetrahedral (Td) outer-sphere complex on ferrihydrite. In the hydrogenetic ferromanganese oxides, the dominant host phase of Mo was revealed to be δ-MnO₂. These structural information are consistent with the macroscopic behaviors of Mo in adsorption experiments, and Mo concentration in modern oxic seawater can be explained by the equilibrium adsorption reaction on δ-MnO₂. In addition, the large isotopic fractionation of Mo between seawater and ferromanganese oxides detected in previous studies can be explained by the structural difference between and adsorbed species on the δ-MnO₂ phase in ferromanganese oxides. In contrast, smaller fractionation of Mo isotopes on ferrihydrite is due to little change in the Mo local structures during its adsorption to ferrihydrite.The structures of Mo species adsorbed on crystalline Fe (oxyhydr)oxides, goethite, and hematite were also investigated at pH 8 and I = 0.70 M (NaNO₃). Our XAFS analyses revealed that Mo forms inner-sphere complexes on both minerals: Td edge-sharing (46%) and Oh double corner-sharing (54%) for goethite, and Td double corner-sharing (14%) and Oh edge-sharing (86%) for hematite. These structural information, combined with those for amorphous ferrihydrite and δ-MnO₂, show the excellent correlation with the magnitude of adsorptive isotopic fractionation of Mo reported in previous studies: the proportion of Oh species or their magnitude of distortion in Mo surface complexes become larger in the order of ferrihydrite < goethite < hematite < δ-MnO₂, a trend identical to the magnitude of isotopic fractionation.Based on the comparison with previous reports for Mo surface species on various oxides, the chemical factors that affect Mo surface complex structures were also discussed. The hydrolysis constant of cation in oxides, log K_OH (or the acidity of the oxide surfaces, PZC) is well correlated with the mode of attachment (inner- or outer-sphere) of Mo surface complexes. Furthermore, the symmetric change in Mo species from Td to Oh is suggested to be driven by the formation of inner-sphere complexes on specific sites of the oxide surfaces.     

原油运移过程中的氮同位素分馏作用

辽河高升油田和塔里木轮南14井为实例，探索了原油横向和纵向运移过程中氮同位素的分馏作用，初步探讨了原油中含氮有机化合物的运移机制。在莲花油层中，原油沿横向运移约10km后，δ^15N值由12．80‰逐渐变化为11．07‰，下降了1.73‰。在轮南14井由下至上753m厚的五个油层中，原油δ^15N值由0.24‰逐渐变化到－2．92‰，下降了3．19‰。两个实例均表明，原油的运移过程会引起δ^15N值下降。     

Instability of seawater pH in the South China Sea during the mid-late Holocene: Evidence from boron isotopic composition of corals

We used positive thermal ionization mass spectrometry (PTIMS) to generate high precision δ¹¹B records in Porites corals of the mid-late Holocene from the South China Sea (SCS). The δ¹¹B values of the Holocene corals vary significantly, ranging from 22.2‰ to 25.5‰. The paleo-pH records of the SCS, reconstructed from the δ¹¹B data, were not stable as previously thought but show a gradual increase from the Holocene thermal optimal and a sharp decrease to modern values. The latter is likely caused by the large amount of anthropogenic CO₂ emissions since the Industrial Revolution but variations of atmospheric pCO₂ cannot explain the pH change of the SCS before the Industrial Revolution. We suggest that variations of monsoon intensity during the mid-late Holocene may have driven the sea surface pH increase from the mid to late Holocene. Results of this study indicate that the impact of anthropogenic atmospheric CO₂ emissions may have reversed the natural pH trend in the SCS since the mid-Holocene. Such ocean pH records in the current interglacial period can help us better understand the physical and biological controls on ocean pH and possibly predict the long-term impact of climate change on future ocean acidification.     

Nd and Sr isotopic compositions of tektite material from Barbados and their relationship to North American tektites

Isotopic analyses of Nd and Sr on individual microtektites and a bulk microtektite sample from Barbados show them to have a very well defined isotopic composition. These data plot on an ε_Srε_Nd diagram precisely within the narrow field determined by North American tektites (ε_Sr ≈ 111; ε_Nd ≈ ?6.2). They yield an Nd model age of 0.6 AE. These results show that the microtektites from the Oceanic beds of late Eocene age are derived from the same target as the North American tektites and should be associated with the same event. Samples of the deep sea sediments in which the Barbados microtektites occur are found to have isotopic signatures which appear to reflect ambient sea water and detrital sediments. They cannot be the source of Sr or Nd in the tektites. Following the arguments of Shaw and Wasserburg (1982) we conclude that the target area which produced the North American tektite field was composed of sediments (Eocambrian or younger) derived from very late Precambrian crust. Glass beads from Lake Wanapitei Crater are isotopically different from all other tektites (ε_Sr ≈ 960; ε_Nd ≈ ?31.4) and cannot be related to the North American tektites.     

Hydrogen isotopic composition of NBS and IAEA stable isotope water reference samples

The hydrogen isotopic compositions of several isotope water reference samples have been determined on a cycloidal double-collecting isotope ratio mass spectrometer that can resolve HD⁺ from the ‘contaminant’ H₃⁺ ion beam.     

南海北部珊瑚高分辨率硼同位素组成及其对珊瑚礁海水pH变化的指示意义

造礁珊瑚是研究热带海洋高分辨率气候环境演变的重要载体。对采自海南岛南部三亚湾的活体滨珊瑚SY10进行了约为月分辨率的碳、氧、硼同位素组成分析,并利用珊瑚δ11B重建了海水pH。结果显示,所测量样品的δ13C变化范围为–3.32‰~–1.76‰,δ18O为–6.13‰~–4.78‰,δ11B为23.51‰~26.23‰,且这些珊瑚样品的碳、氧、硼同位素组成均存在明显的季节性周期波动。其中pH与δ18O之间存在明显的正相关关系,高的pH值更倾向于在低温的季节出现,这意味着短时间尺度该处珊瑚礁海水pH可能主要不是受海水CO2溶解度控制,而是与生物活动有密切的关系。利用SY10珊瑚样品硼同位素组成重建的海水pH值变化范围为7.77~8.37,并呈季节性周期波动,这种大幅度的周期波动与我们对三亚珊瑚礁海水pH进行现场观测所得到的结果以及前人的研究成果相符,说明了利用珊瑚δ11B重建海水pH记录是可靠的。     

The isotopic composition of strontium and sulfur in seawater of Late Permian (Zechstein) age

The Paleozoic minima of ⁸⁷Sr/⁸⁶Sr ratios and δ³⁴S values in seawater are observed in anhydrite layers of the Stassfurt (A-2) and Aller (A-4) cycles of evaporation of Late Permian age in Germany. These minima were probably caused by extremely low rates of continental runoff and bacterial sulfate reduction. Thereafter conditions changed suddenly, with a steeply increasing supply of radiogenic Sr and of nutrients into seawater. The latter induced a large growth in the production of organic material, in bacterial activity in sediments, and in the flow of isotopically heavy sulfur back into the oceans. This large change in the cycles of S and Sr (as well as of C and O) within the relatively short Zechstein period (2–5 Ma) reflects a considerable modification of the plate tectonic and environmental conditions shortly before the beginning of the Mesozoic era. The Ochoan deposition in the USA is probably of the same age as the Stassfurt-Leine evaporation in W Europe.     

盐湖硼、锂、锶、氯同位素地球化学研究进展

盐湖作为盐矿资源的重要载体和富集区,探讨其矿物质来源及富集规律,不仅为盐湖的形成、演化及成盐成矿规律研究奠定了基础,也为盐湖资源评价及合理的开发利用提供了科学依据,具有重要的理论和现实意义。近年来,随着同位素地球化学的发展,同位素在盐湖领域的研究成果也日益丰富,使盐湖研究的深度和广度也得到快速发展。文章简要概述了硼、锂、锶、氯同位素的分馏机理及其在盐湖研究领域的发展历程,重点介绍了国内外取得的主要成果和最新进展,探讨了存在的问题,以促进硼、锂、锶、氯同位素地球化学研究在中国盐湖领域的进一步发展。     

中国海及大陆架沉积物标准物质系列评介

自20世纪90年代末以来,在有关国家专项的支持下,中国先后研制了分别取自黄海、东海和南海的共9个大陆架沉积物地球化学标准物质,基本构成了一个比较有代表性的中国海及大陆架沉积物标准物质系列,为中国海洋国土及专属经济区调查研究工作提供了有力技术支撑.本文简介了这些标准的研制背景、概况,着重评介了这些标准物质的特点,特别说明了该标准物质系列在海洋地质调查与研究中应用及在地质分析技术发展上的意义.