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Summary Background & aims Leveraging prokinetics to facilitate trans-pyloric migration is a conventional strategy. However, due to restrictions on the use of domperidone suspension, oral prokinetics is relatively modest. The study aims to assess the effectiveness of simo decoction as an alternative to domperidone suspension in facilitating post-pyloric placement of spiral nasoenteric tubes. Methods A prospective, open-label, parallel, and non-inferiority randomized controlled trial was performed involving critically ill adults in 6 university hospitals in China between September 2017 and May 2019. Patients were randomly assigned to receive either simo decoction 20 ml q8h, or domperidone suspension 20 mg/20 ml q6h for 24 h. The primary outcome was procedure success defined as post-pyloric placement (spiral nasoenteric tubes reached the first portion of the duodenum or beyond confirmed by abdominal X-ray 24 h after tube insertion). Results Of 268 patients assessed for eligibility, 224 patients were enrolled and randomly assigned to the simo decoction group or the domperidone suspension group (n = 112 per group). The success rate of post-pyloric placement was 41.1% (46/112) in the simo decoction group, as compared with 47.3% (53/112) in the domperidone suspension group (a risk difference of −6.3%, 95% CI, −19.2% to 6.7%, adjusted risk difference −3.7%, 95% CI −16.3% to 9.0%), in the intention-to-treat analysis, crossing the prespecified margin of −10% for non-inferiority. There were no differences between groups in the success rates of post-D1 (reaching the second portion of the duodenum or beyond), post-D2 (reaching the third portion of the duodenum or beyond), post-D3 (reaching the fourth portion of the duodenum or beyond) and proximal jejunum placement, the incidences of any adverse events, length of ICU stay or mortality in ICU. Conclusions Non-inferiority of simo decoction to domperidone suspension was not confirmed in facilitating post-pyloric placement of spiral nasoenteric tubes. Registration: The trial was registered with the Chinese Clinical Trial Registry at http://www.chictr.org.cn (registration number ChiCTR-INR-17011311).

A water circulation system with the almost same element composition and socket type was adopted in coral Acropora culture under different seawater pH value conditions and the data of the relationship between boron isotopic compositions of coral and seawater pH value by thermoelectric ionization mass spectrometer were obtained. According to the correlations between αcarb-3 of coral and the pH value of cultured seawater, αcarb-3 was not a constant but related to pH value, indicating that B(OH)3 also incorporated carbonate. Therefore, the theoretical formula could not be used to calculate the seawater pH value from the δ11Bcarb value of the measured marine biological carbonate. The empirical equations obtained experimentally would be an alternative method to calculate the seawater pH value. In addition, the mixed precipitation of CaCO3 and Mg(OH)2 was found in aquaculture tanks with high pH value, and the δ11B of the solid was significantly higher than that of cultured seawater. The result indicated that the presence of Mg(OH)2 had a significant effect on the boron isotope fractionation, which deserved our attention.

This study presents chlorine isotopic composition of salt deposits recovered in a core from the Qarhan Saline Lake in the Qinghai Province of China. The δ 37 Cl trend has three stages, and they correspond to the upper, middle, and lower salt-bearing groups of the entire evaporite system. The δ 37 Cl values are between −0.22‰ and 0.13‰ with an average value of −0.02‰ in the lower salt-bearing group. It ranges between 0.14‰ and 0.76‰ ( x ¯ = 0.36‰) in the middle salt-bearing group, and varies between −0.35‰ to 0.35‰ ( x ¯ = −0.04‰) in the upper salt-bearing group. This work indicates that stratification of δ 37 Cl values is accompanied by stratigraphic variations in Mg/Cl and K/Cl in halite. We suggest a “evaporation cycles model” and it indicates the potential of Cl isotope as a geochemical tracer in order to understand paleoclimatic conditions during different stages of evaporite deposition.

Experiments involving boron incorporation into brucite (Mg(OH)2) from magnesium-free artificial seawater with pH values ranging from 9.5 to 13.0 were carried out to better understand the incorporation behavior of boron into brucite and the influence of it on Mg/Ca-SST proxy and δ11B-pH proxy. The results show that both the concentration of boron in deposited brucite ([B]d) and its boron partition coefficient (Kd) between deposited brucite and final seawater are controlled by the pH of the solution. The incorporation capacity of boron into brucite is almost the same as that into corals, but much stronger than that into oxides and clay minerals. The isotopic compositions of boron in deposited brucite (δ11Bd) are higher than those in the associated artificial seawater (δ11Bisw) with fractionation factors ranging between 1.0177 and 1.0569, resulting from the preferential incorporation of B(OH)3 into brucite. Both boron adsorptions onto brucite and the precipitation reaction of H3BO3 with brucite exist during deposition of brucite from artificial seawater. The simultaneous occurrence of both processes determines the boron concentration and isotopic fractionation of brucite. The isotopic fractionation behaviors and mechanisms of boron incorporated into brucite are different from those into corals. The existence of brucite in corals can affect the δ11B and Mg/Ca in corals and influences the Mg/Ca-SST proxy and δ11B-pH proxy negatively. The relationship between δ11B and Mg/Ca in corals can be used to judge the existence of brucite in corals, which should provide a reliable method for better use of δ11B and Mg/Ca in corals to reconstruct paleo-marine environment.

We investigated the boron isotopic composition in loess–paleosol sequences in five different profiles in the Chinese Loess Plateau. Three possible boron sources are identified: atmospheric input, carbonates, and weathered silicate rocks. Variations of [Sr], [B], δ11B and the magnetic susceptibility correlate well with the pedogenetic intensity in three out of the five studied profiles, where pedogenesis under a cold–dry climate indicates lower δ11B, lower [B], lower magnetic susceptibility and higher [Sr] values. Exceptions to the variations between the δ11B and other known proxies were observed in arenaceous soils and the Red Clay sequence: the former suggested that vertical redistribution probably occurred with the boron migration, and the latter indicated an unknown mechanism of susceptibility enhancement. A better correlation between the δ11B and magnetic susceptibility and the quantitative estimation of boron budget from each source confirms the influence of paleoenvironmental changes on boron geochemical cycle. Significant positive correlations in Sr/Ca vs. B/Ca and Mg/Ca vs. B/Ca reflect consistent enrichment behavior of those mobile elements into calcium carbonate. The preliminary results imply that boron isotopic compositions in soils can be a potential geochemical proxy to reconstruct the paleoenvironmental changes in loess–paleosol sequences.

As a stable isotope, boron plays an important role in hydrogeology, environmental geochemistry, ore deposit geochemistry and marine paleoclimatology. However, there is no report of boron isotopic composition in gypsum. This is mainly confined to complete dissolution of Gypsum by water or acid. In this study, gypsum was converted to calcium carbonate (CaCO 3 ) with ammonium bicarbonate(NH 4 HCO 3 ) by two steps at 50 °C. In every step, the mass ratio of NH 4 HCO 3 /CaSO 4 ·2H 2 O was twice, and conversion rate reached more than 98%. Converted CaCO 3 was totally dissolved with hydrochloric acid (the dissolution rate was over 99%). In order to overcome the difficulties of the matrix interference and the detection limit of Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), we use Amberlite IRA 743 resin to purify and enrichment the boron at first, then eluting boron from the resin with 10 mL 0.1 mol/L hydrochloric acid at 75 °C. The boron isotopic composition of natural gypsum samples was determined using positive thermal ionization mass spectrometry (P-TIMS). The boron isotopic composition of gypsum may be an excellent indicator for the formation environment.

In order to better understand chlorine isotopic variations during brine evolution, experiments were designed to determine the changes in the chlorine isotope composition (δ37Cl value) during evaporations of solutions containing NaCl, KCl and MgCl2⋅6H2O at 28 ± 2 °C. Three evaporation experiments were conducted in a clean environment. The precipitate and brine samples were collected during the evaporation, and the chlorine isotopic ratios of the samples were determined using an improved thermal ionisation mass spectrometry procedure based on Cs2Cl+ ion measurement. The results are as follows: the mean fractionation factors of the three solutions are αNa = 1.00055, αK = 1.00025, and αMg = 1.00012, respectively, where αNa, αK and αMg are the fractionation factors between salts (NaCl, KCl and MgCl2⋅6H2O) and saturated solutions. The results showed that the δ37Cl values of precipitate and coexisting brine samples decrease during the precipitation of single chloride minerals. The residual brine was a 35Cl reservoir for different single chloride solutions. New chlorine isotopic evolution curve during seawater evaporation were also calculated. The results indicated that during the primary precipitation stage of halite, δ37Cl decreased continuously, and the most important thing is that this trend continues during the final stages when Mg–salts begin to precipitate.

The boron isotope paleo-pH proxy has been extensively studied due to its potential for understanding past climate change, and further calibrations were considered for accurate applications of the proxy because of significant variability related to biocarbonate microstructure. In this work, we studied the boron isotopic fractionation between modern marine corals and their coexisting seawater collected along shallow area in Sanya Bay, South China Sea. The apparent partition coefficient of boron (KD) ranged from 0.83×10−3 to 1.69×10−3, which are in good agreement with previous studies. As the analyzed coral skeleton (∼5 g) spanned the growth time period of 1–2 years, we discussed the boron isotopic fractionation between pristine corals and modern seawater using the annual mean seawater pH of 8.12 in this sea area. Without taking the vital effect into account, (11B/10B)coral values of all living corals spread over the curves of (11B/10B)borate vs. (11B/10B)sw with the α4−3 values ranging from 0.974 to 0.982. After calibrating the biological effect on the calcifying fluid pH, the field-based calcification on calcifying fluid pH (i.e., Δ(pHbiol-pHsw)) for coral species of Acropora, Pavona, Pocillopora, Faviidae, and others including Proites are 0.42, 0.33, 0.36, 0.19, respectively, and it is necessary to be validated by coral culturing experiment in the future. Correlations in B/Ca vs. Sr/Ca and B/Ca vs. pHbiol approve temperature and calcifying fluid pH influence on skeletal B/Ca. Fundamental understanding of the thermodynamic basis of the boron isotopes in marine carbonates and seawater will strengthen the confidence in the use of paleo-pH proxy as a powerful tool to monitor atmospheric CO2 variations in the past.

About a third of the approximately 30 known deposits in the Furnace Creek, California, borate district reveal mineralogical zoning of borates. The deposits feature an Na-Ca borate (ulexite and/or probertite) inner zone (or zones) surrounded by Ca borate (colemanite). The remaining deposits consist essentially of colemanite. Investigators have debated the origin of the mineralogical zoning and the relationship, if any, between the zoned and colemanite-only deposits. The Ca and Na-Ca borate zoning has been characterized as either primary or formed by postdepositional alteration. Boron isotope analysis was applied to drill core samples from two zoned deposits, one non-zoned deposit, and selected samples from six other deposits accessed from surface and subsurface mine workings. Probertite samples from the inner regions of two zoned deposits yield δ 11B values near 5‰, whereas most colemanite samples from both zoned and non-zoned deposits yield results near −1‰. The small δ 11B range of most of the colemanite samples and their distribution from a grouping near 0‰ to isotopically lighter values suggest a pattern formed by alteration from a common initial value. Based on the new isotopic data and existing sedimentologic and stratigraphic knowledge of the Furnace Creek borate deposits, it is proposed that the isotopically heavier boron of probertite in the inner zone of zoned deposits reflects the composition of the ancestral lake and its springs during an early stage of deposition of the laminated series of the Furnace Creek Formation. Furthermore, the isotopically lighter B of colemanite in zoned deposits reflects the alteration of earlier formed Na-Ca borate deposits by downward migrating lake water at a later stage of deposition of the laminated series. Some non-zoned Ca borate deposits may have been precipitated directly during the later stages.

Boron is a common element in vent fluids of seafloor hydrothermal fields, and it has been used to understand the hydrothermal flux and water-rock interaction in hydrothermal systems. We have measured the boron concentration and isotope composition of seawater, andesite, hydrothermal fluid and plume samples from the Kueishantao hydrothermal field. The delta B-11 value of ambient seawater near the field is 40.05 +/- 0.01 parts per thousand, and the boron concentration is 3.81 mg/L Andesite rocks from the hydrothermal field have an average boron content of 153 ppm. The hydrothermal fluids from the yellow spring and white spring span a small range of delta B-11 values, from 3327 +/- 022 to 36.84 +/- 0.11 parts per thousand, and plumes from both springs also cover a small range, from 37.56 +/- 0.01 to 40.37 +/- 0.21 parts per thousand. Hydrothermal fluids from both springs in the Kueishantao hydrothermal field have variable B enrichments relative to seawater between 7 and 21%. They have B concentrations (4.10-4.64 mg/L) that are slightly higher and delta B-11 values (3327-36.84 parts per thousand) that are lower than those of the hydrothermal plumes (3.94-4.17 mg/L, 37.56-40.37 parts per thousand). Hydrothermal fluids and plumes display a very regular array of data points in a delta B-11-B diagram, suggesting that the boron of hydrothermal fluids and plumes is mainly from seawater and that little of it is, from andesite. This implies that the interaction of subseafloor fluid and -andesite at the Kueishantao hydrothermal field is of short duration. In all the fluids, from springs to hydrothermal plumes, the pH values, B concentrations and B isotopic compositions show significant correlations with each other suggesting that the delta B-11/B and pH/B ratios of hydrothermal plumes have stable values over the small distance form vent to plume (

A static double-collector system for accurate, precise, and rapid boron isotope analysis has been established by employing a newly fixed Faraday H3 and H4 cup enabling simultaneously collected Cs2BO2(+) ion beams (m/z = 308 and 309) on a Finnigan-MAT Triton thermal ionization mass spectrometer of boron (Triton B). The experimental result indicated that Cs2BO2(+) ion beams (m/z = 308 and 309) were simultaneously collected using a fixed Faraday H3 and H4 cup without using the "Zoom Quad" function and reduced accelerating voltage. Furthermore, the method enabled the measurement of samples containing as little as 20 ng of boron. An analysis of the National Institute of Standards and Technology standard reference material (NIST SRM) 951 standard showed external reproducibility (2RSD) of ±0.013‰, ± 0.013‰, and ±0.019‰ for 100, 50, and 20 ng of boron, respectively. The present method of static multicollection of Cs2BO2(+) ions is applicable to a wide field of boron isotopic research that requires high precision and accuracy to analyze samples with low boron concentrations, including pore fluids, foraminifera, rivers, rainwater, and other natural samples.

Significant boron isotope fractionation occurs in nature (−70 ‰ to +75 ‰) due to the high geochemical reactivity of boron and the large relative mass difference between 10B and 11B. Since the 1990s, reconstruction of ancient seawater pH using the isotopic composition of boron in bio-carbonates (δ 11Bcarb), and then calculation of the past pCO2 have become important issues for the international isotope geochemistry community, and are called the δ 11B-pH proxy. Although many achievements have been made by this proxy, various aspects of boron systematics require rigorous evaluation. Based on the previous researches, mechanism of boron isotope fractionation, variation of boron isotope (δ 11B) in nature (especially in bio-carbonates) and controlling factors of the δ 11B-pH proxy, such as the dissociation constant of B(OH)3 in seawater (pKa), the δ 11B of seawater (δ 11BSW), the boron isotopic fractionation factor between B(OH) 4 − and B(OH)3 (α 4–3), and the incorporated species of boron into bio-carbonates, are reviewed in detail and the research directions of this proxy are proposed. Generally, the controversy about pKa, δ 11Bsw, and α 4–3 is relatively less, but whether boron incorporated into bio-carbonates only in the form of B(OH) 4 − remains doubtful. In the future, it is required that the physicochemical processes that control boron incorporation into carbonates be rigorously characterized and that the related chemical and isotopic fractionation be quantified. It is also necessary and important to establish a “best-fit empirically equation” between δ 11Bcarb and pH of seawater based on the precipitation experiments of inorganic or culture experiments of corals or foraminifera. In addition, extended application of the δ 11B-pH proxy to the earlier part of the Phanerozoic relying on the Brachiopods is worthy of studying. Like other geochemical indicators, there are limiting factors of δ 11B; however, it remains a very powerful tool in the reconstruction of past seawater pH at present.

The procedures of sample preparation for isotopic determination of boron in clay sediments is very cumbersome, by far, there haven’t been relevant reports on that. In order to establish an effective method for sample preparation, a series of experiments were carried out. In this paper, boron in clay sediments was extracted with HCl solution and purified by two-step ion exchange method. Extracted HCl solution should be adjusted to alkalescency before passing through the Amberlite IRA 743 resin column due to the fact that Amberlite IRA 743 resin absorbs boron only from alkalescent solution. However, a mass of hydroxides of Al and Fe will be precipitated when the extracted HCl solution becomes alkalescent. Hydroxides of Al and Fe have a strong adsorption capacity for boron, which can cause boron isotope fractionation. To treat precipitated hydroxides of Al and Fe, four procedures, namely direct ion exchange (DRIE), decationizing ion exchange (DCIE), once sedimentation ion exchange (OSIE) and repeated sedimentation ion exchange (RSIE) were used and assessed. The influences of the four procedures on separation and extraction and isotopic composition of boron in experimental solutions and clay sediments were also discussed. According to the results, the DRIE, DCIE and OSIE are improper. The result of sample determination indicates that when extracting boron via RSIE, with the increase of precipitation times, there’s an obvious decrease in boron content in the precipitated hydroxides while a sharp increase in recovery of boron and it is favorable for weakening the influence of boron isotope fractionation. But the process of RSIE is time consuming and it may introduce boron. It needs further research to establish a more effective sample preparation method for isotopic determination of boron in clay sediments.

In order to determine incorporation of boron species, boron isotopic fractionation, and influence of trace elements on isotopic compositions of boron in corals (δ11Bcoral), concentrations of Mg, Sr, Na, B and δ11Bcoral in growing corals from the South China Sea were measured. Relative to seawater, Sr enriched while Mg depleted in corals in the South China Sea. Although the δ11Bcoral values were different from various species and were not closely correlated with the element concentrations in corals in the South China Sea, Mg(OH)2 existed in corals can result in high δ11Bcoral. Thus, it is necessary to examine the existence of Mg(OH)2 and to choose the same species when δ11Bcoral is used in the δ11B-pH proxy. Based on the measured δ11B values of corals and coexisting seawater as well as the seawater pH in the South China Sea, a new isotopic fractionation factor a4-3 between B ( OH ) 4 - and B(OH)3 was determined to be 0.979. Besides B ( OH ) 4 - into corals, our results showed that B(OH)3 may also be incorporated into corals with variable proportions. The incorporation of B(OH)3 into corals may challenge the hypothesis of δ11Bcoral = δ11B4, resulting in increasing uncertainty to the calculated seawater pH values to the δ11B-pH proxy. We suggested that a best-fit empirical equation between δ11B of bio-carbonates and seawater pH needs to be established by the precipitation experiments of inorganic carbonates or culture experiments of corals or foraminifera.

Due to the greater thermodynamic stability of CaCO3 relative to Li2CO3, synthetic CaCO3 was precipitated from artificial seawater by the release of CO32 − from Li2CO3 and Ca2 + under different pH conditions. The pH of the solution was controlled by slowly bubbling high-purity NH3 or CO2 gas at 25 ± 0.5 °C, assuming that the pH at which nucleation takes place is the same as the average pH of the solution. This method is referred to as the “differential solubility technique”. The precipitated CaCO3 is dominated by crystalline calcite, as identified by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry. The boron concentrations in the precipitated calcite increased from 29.30 μg/g to 285.39 μg/g when the artificial solution pH values increased from 7.40 ± 0.03 to 8.80 ± 0.03, indicating that pH has a significant effect on the incorporation of boron into synthetic calcite. Our results support the hypothesis that boron uptake in carbonates takes place predominantly by incorporation of the charged borate species B(OH)4−. The partition coefficient KD (defined as [B/Ca]CaCO3/[B(OH)4−/HCO3−]seawater) shows a general decrease with pH, and KD × 1000 ranges from 2.13 to 1.27.

Because the variation in chlorine isotopic abundances of naturally occurring chlorine bearing substances is significant, the IUPAC Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights (CIAAW-IUPAC) decided that the uncertainty of atomic weight of chlorine (A(r)(Cl)) should be increased so that the implied range was related to terrestrial variability in 1999 (Coplen, T. B. Atomic weights of the elements 1999 (IUPAC Technical Report), Pure Appl. Chem.2001, 73(4), 667-683; and then, it emphasized that the standard atomic weights of ten elements including chlorine were not constants of nature but depend upon the physical, chemical, and nuclear history of the materials in 2009 (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396). According to the agreement by CIAAW that an atomic weight could be defined for one specified sample of terrestrial origin (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396), the absolute isotope ratios and atomic weight of chlorine in standard reference materials (NIST 975, NIST 975a, ISL 354) were accurately determined using the high-precision positive thermal ionization mass spectrometer (PTIMS)-Cs(2)Cl(+)-graphite method. After eliminating the weighing error caused from evaporation by designing a special weighing container and accurately determining the chlorine contents in two highly enriched Na(37)Cl and Na(35)Cl salts by the current constant coulometric titration, one series of gravimetric synthetic mixtures prepared from two highly enriched Na(37)Cl and Na(35)Cl salts was used to calibrate two thermal ionization mass spectrometers in two individual laboratories. The correction factors (i.e., K(37/35) = R(37/35meas)/R(37/35calc)) were obtained from five cycles of iterative calculations on the basis of calculated and determined R((37)Cl/(35)Cl) values in gravimetric synthetic mixtures. The absolute R((37)Cl/(35)Cl) ratios for NIST SRM 975, NIST 975a, and ISL 354 by the precise calibrated isotopic composition measurements are 0.319876 ± 0.000067, 0.319768 ± 0.000187, and 0.319549 ± 0.000044, respectively. As a result, the atomic weights of chlorine in NIST 975, NIST 975a, and ISL 354 are derived as 35.45284(8), 35.45272(21), and 35.45252(2) individually, which are consistent with the issued values of 35.453(2) by IUPAC in 1999.

Brine from the saline Qarhan Lake was evaporated at 28±2°C in a clean environment. Two groups of experiments were conducted; one with complete separation of precipitate and brine at different stages of evaporation, and the other with continuous precipitation during the evaporation. Seventy-nine precipitate and brine samples were collected during the experiments, and the δ 37Cl values were determined using an improved thermal ionization mass spectrometry procedure for precise measurement of chlorine isotopes based on Cs2Cl+ ions. Based on the concentrations of Na+, K+, and Mg2+, evaporation was divided into three main precipitation stages as follows: halite dominant, carnallite dominant, and bischofite dominant. The δ 37Clsolid and δ 37Clliquid values of the precipitate and coexisting brine samples at different stages showed the following characteristics. The precipitates were enriched with 37Cl relative to the coexisting brine samples, and the δ 37Cl of both the precipitate and brine samples decreased gradually during evaporation. The fractionation factors (α h) between halite and brine were the highest, followed by that (α c) between carnallite and brine, and then that (α b) between bischofite and brine. The α c and α b values of less than one, which indicate the precipitate is enriched in 35Cl, were found when the evaporation process entered a new stage. However, the δ 37Cl values of carnallite, bischofite, and the coexisting brine samples decreased during evaporation. The residual brine is a 35Cl reservoir. The experimental phenomena were consistent with the δ 37Cl values in saline deposits in the literature. δ 37Cl can be used as an indicator of brine evaporation processes, which is important in the exploration of sylvinite deposits.

From the point of growth units, the growth mechanism of hydrotalcite (HT) crystal is investigated in this paper. Results show that the growth morphology of HT is consistent with the model of anion coordination polyhedron growth units. The Raman shift of growth solutions of HT, Cu-HTlc, and Cu-Zn-HTlc are monitored using Raman spectroscopy. In the experiment, the growth units of Mg-Al-hydrotalcite are [Mg-(OH)6]4− and [Al-(OH)6]3−, and the growth units of Cu-Htlc and Cu-Zn-HTlc are [Mg-(OH)6]4− and [Al-(OH)6]3−, respectively. The growth process of hydrotalcite is as follows: growth units first incorporate into metal layers, then metal layers adsorb An− and H2O, and the growth units incorporate into layer compounds according to this rule. Growth units will have different incorporations and growth morphologies caused by different growth surroundings. Furthermore, the reason why Cu-HTlc is difficult to synthesize is also interpreted in this paper.

Boron isotope values in Paleozoic brachiopods and corals, collected from the Yunnan-Guizhou Plateau, China, can be used to constrain the boron isotope compositions of past oceans. All brachiopod shells and coral samples were screened for diagenetic recrystallization by cathodoluminescence microscopy, trace element geochemistry of B, Fe, Mn, Sr, and scanning electron microscopy. The boron isotope ratios for brachiopods in Silurian, Devonian, Carboniferous, and Triassic calcites are in the ranges 8.9‰–14.0‰, 8.8‰–13.8‰, 10.3‰–16.3‰, and 6.7‰–12.4‰, respectively. The boron isotope ratios of coral calcites in the Silurian, Devonian, and Permian are 9.1‰–12.2‰, 6.1%–13.8‰, and 9.2‰–16.1‰, respectively. The δ 11B values for both brachiopods and corals are significantly lower than those for modern biogenic carbonates, indicating that the Paleozoic oceans were depleted of δ 11B by up to 10‰. Our results are consistent with previous published studies. The boron isotope compositions of corals and brachiopods show the consistent trends. The low δ 11B values may be explained by an enhanced riverine flux of boron from the continents.

In order to better estimate the effectiveness of micro-sublimation technology on the elimination of organic matter interference during boron isotopic analysis, a series of improved experiments was carried out using simple apparatus. Recovery rates after micro-sublimation were measured for boric acid solutions with different B contents or different B/organic matter ratios. The improved micro-sublimation procedure combined with ion-exchange technology was then used to test natural samples (coral and foraminifera) for the separation of boron. Our results show that the time taken for 100% recovery of different amounts of B differed and that the proportions of B/organic matter within the natural organic matter have little effect on the relationship between the recovery rates of B and the micro-sublimation times. The experiments further confirm that the organic matter does indeed have an effect on boron isotope analyses by positive thermal ionization mass spectrometry and that the use of micro-sublimation can effectively remove interferences from the organic matter during boron isotopic analysis. Copyright (C) 2011 John Wiley & Sons, Ltd. In order to better estimate the effectiveness of micro-sublimation technology on the elimination of organic matter interference during boron isotopic analysis, a series of improved experiments was carried out using simple apparatus. Recovery rates after micro-sublimation were measured for boric acid solutions with different B contents or different B/organic matter ratios. The improved micro-sublimation procedure combined with ion-exchange technology was then used to test natural samples (coral and foraminifera) for the separation of boron. Our results show that the time taken for 100% recovery of different amounts of B differed and that the proportions of B/organic matter within the natural organic matter have little effect on the relationship between the recovery rates of B and the micro-sublimation times. The experiments further confirm that the organic matter does indeed have an effect on boron isotope analyses by positive thermal ionization mass spectrometry and that the use of micro-sublimation can effectively remove interferences from the organic matter during boron isotopic analysis. Copyright (C) 2011 John Wiley & Sons, Ltd.

Based on the theoretical model of anion coordination polyhedron growth units, the growth mechanism of the basic magnesium chloride whisker was discussed in this paper. It was found that the basic magnesium chloride whisker habits were related to the different environments in which anion coordination polyhedra grew. The growth units of basic magnesium chloride whiskers are [Mg − (OH)4]2− and [Mg − Cl4]−2. The growth process is the incorporation process of growth units. Growth units will have different incorporations and orientations caused by different system characters or heating. Furthermore, the formation mechanism of basic magnesium chloride whiskers was also interpreted using anion coordination polyhedron growth units.

Since 1990's,it has become a hotspot to use theδ11B-pH technique to reconstruct the pH of seawater throughδ11B in marine biogenetic carbonates.Although plenty of papers have been devoted to this topic,there are still a lot of technical problems due to the incompletion in theory,that constrain the further application of the method.We discussed in this paper some uncertain factors of theδ11B-PH technique,including the pKa,ionization constant of B(OH)3,δ11 Bsw of the seawater,δ11 B in B(OH)4-,and the fractionation factorαbetween B(OH)4-and B(OH)3.Suggestions are made for future studies to improve the method for paleoceangraphic investigations.

There are two main methods to determine boron isotopic composition. One is the solution method, in which boron is purified after the samples are dissolved in solution and the boron isotope ratios are determined by thermal ionization mass spectrometry (P-TIMS and N-TIMS) or multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). The other is an in-situ analysis method, in which the in-situ boron isotopic ratios in minerals are analyzed directly using secondary ion mass spectrometry (SIMS) or laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). In the in-situ analysis method for boron isotopes, the multifarious chemical purification and separation processes of the solution method are avoided, with increased work efficiency. In addition, the microzones and microbeddings of minerals can be analyzed in-situ to reveal the fine processes and conditions of mineral formation. In this study, using the standard-sample-bracketing (SSB) method, mass bias of the instrument and the fractionation of isotopes were calibrated, and the in-situ determination method of LA-MC-ICP-MS for boron isotopes was established. Through detailed analyses on a series of boron isotope standards and samples, a matrix effect was assessed but not detected, and the analysis results were in accordance with the formerly reported values or P-TIMS determined values, within the error range. The analytical results for IAEA B4 and IMR RB1 with relatively high boron contents were δ11B = −(8.36±0.58)‰ (2σ, n=50) and δ11B = −(12.96±0.97)‰ (2σ, n=57), respectively; the analytical result for IAEA B6 with relatively low boron content was δ11B = −(3.29±1.12)‰ (2σ, n=35). In-situ measurements for B isotopes were performed on geological samples such as tourmaline, ulexite, ludwigite, inyoite and ascharite, with the results consistent with those determined by P-TIMS, within the error range.

Since 2006, we have conducted a geological exploration of the Khammuane area in southeastern Laos. Several thick sequences of potash deposits containing sylvite and carnallite were discovered from drilling Paleocene strata of the Thangon Formation (E1 tg). To constrain the origin of the brine that formed thick sequences of salt mineral deposits, we measured the strontium and boron isotope composition of some salt minerals in the potash deposit. Boron isotope composition of halite- and potash-associated minerals in the Khammuane potash deposit varied from 19.91% to 31.01‰, which differs significantly from continental evaporates (−6.83‰–−5.79‰) but is very close to that of salts precipitated from evapo-concentrated seawater (10‰–36‰). The 87Sr/86Sr ratios (0.707542 to 0.709461) of salts were also close to the values of Paleocene seawater (0.70772 to 0.707830). The content of Br− (0.01%–0.25%) and Br×103/Cl ratios (0.10–0.52) of halite were >10 times higher than that of common continental salts. These characteristics indicate clearly that the Laos potash deposits were deposited from seawater. The small variation in boron and strontium isotopes in all salt sedimentary sequences (gypsum-halite-potash-halite) also suggests that the recharge source should be stable and the effects of other continental water mixing are negligible. Large-scale potash deposits are commonly precipitated from seawater. Hence, the results of recent regional drilling work and geochemical research suggest extensive potash resources could occur in the Thangon Formation of southeastern Laos.

An improved procedure for extraction and purification of boron from natural samples is presented. The separation and purification of boron was carried out using a boron-specific resin, Amberlite IRA743, and a mixed ion exchange resin, Dowex 50W × 8 and Ion Exchanger II resin. Using the mixed ion exchange resin which adsorbs all cations and anions except boron, the HCl and other cations and anions left in eluant from the Amberlite IRA 743 were removed effectively. In this case, boron loss can be avoided because the boron-bearing solution does not have to be evaporated to reach dryness to dislodge HCl. The boron recovery ranged from 97.6% to 102% in this study. The isotopic fractionation of boron can be negligible within the precision of the isotopic measurement. The results show that boron separation for the isotopic measurement by using both Amberlite IRA 743 resin and the mixed resin is more effective than that using Amberlite IRA 743 resin alone. The boron in samples of brine, seawater, rock, coral and foraminifer were separated by this procedure. Boron isotopic compositions of these samples were measured by thermal ionization mass spectrometry in this study.

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.

A laboratory inorganic carbonate precipitation experiment at high pH of 8.96 to 9.34 was conducted, and the boron isotopic fractionations of the precipitated carbonate were measured. The data show that boron isotopic fractionation factors (αcarb-3) between carbonate and B(OH)3 in seawater range 0.937 and 0.965, with an average value of 0.953. Our results together with those reported by Sanyal and collaborators show that the αcarb-3 values between carbonate and B(OH)3 in solution are not constant but are negatively correlated with the pH of seawater. The measured boron isotopic compositions of carbonate precipitation (δ11Bcarb) do not exactly lie on the best-fit theoretical δ11B4-pH curves and neither do they exactly parallel any theoretical δ11B4-pH curves. Therefore, it is reasonable to argue that a changeable proportion of B(OH)3 with pH of seawater should also be incorporated into carbonate except for the dominant incorporation of B(OH)4− in carbonate. Hence, in the reconstruction of the paleo-pH of seawater from boron isotopes in marine biogenic carbonates, the use of theoretical boron isotopic fractionation factor (α4−3) between B(OH)4− and B(OH)3 is not suitable. Instead, an empirical equation should be established.

The concentrations and isotopic compositions of boron and strontium of Quaternary foraminifers and bivalve fossils collected in the Yanghuzhuang section of Yanqing, Beijing and of modern gastropods living in the Guishui River and of river water were measured. The concentrations and isotopic compositions of Quaternary foraminifers and bivalve fossils differed from those of modern marine foraminifers and were similar to those of modern terrestrial gastropods from the Guishui River. These results indicate that early Quaternary foraminifers in the Yanghuzhuang section inhabited a nonmarine environment and that these foraminifers were not the result of a transgression or sea flooding. The foraminifers were not special halobios and can survive in the terrestrial condition that resembled those of the ocean.

The isotopic composition of dissolved boron, in combination with the elemental concentrations of B, Cl and salinities in freshwater-seawater mixed samples taken from the estuary of the Changjiang River, the largest one in China, was investigated in detail in this study. Brackish water and seawater samples from the estuary of the Changjiang River were collected during low water season in November, 1998. Boron isotopic compositions were determined by the Cs2BO2 +-graphite technique with a analytical uncertainty of 0.2‰ for NIST SRM 951 and an average analytical uncertainty of 0.8‰ for the samples. The isotopic compositions of boron, expressed in δ11B, and boron concentrations in the Changjiang River at Nanjing and seawater from the open marine East Sea, China, are characterized by δ11B values of −5.4‰ and 40.0‰, as well as 0.0272 and 4.43 mg B/L, respectively. Well-defined correlations between δ11B values, B concentrations and Cl concentrations are interpreted in terms of binary mixing between river input water and East Sea seawater by a process of straightforward dilution. The offsets of δ11B values are not related to the contents of clastic sediment and to the addition of boron. These relationships favor a conservative behavior of boron at the estuarine of the Changjiang River.

A new method for the removal SO42-, reacted with BaCO3, for isotopic measurement of chlorine is described in this study. The sample solution was first taken through a W form resin and a small excess of high-purity BaCO3 powder was added into the effluent. The released Ba2+ by the dissolution of BaCO3 reacts with SO42- to form a BaSO4 precipitate. Comparison with the traditional method based on ion exchange of a Ba2+ form resin showed that the new method has a much higher efficiency in removing SO42- and is suitable for the isotopic measurement of chlorine in sample with low Cl- and high SP42-. (c) 2006 Elsevier B.V All rights reserved. A new method for the removal SO42-, reacted with BaCO3, for isotopic measurement of chlorine is described in this study. The sample solution was first taken through a W form resin and a small excess of high-purity BaCO3 powder was added into the effluent. The released Ba2+ by the dissolution of BaCO3 reacts with SO42- to form a BaSO4 precipitate. Comparison with the traditional method based on ion exchange of a Ba2+ form resin showed that the new method has a much higher efficiency in removing SO42- and is suitable for the isotopic measurement of chlorine in sample with low Cl- and high SP42-. (c) 2006 Elsevier B.V All rights reserved.

Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally. The results show the clear positive relationships between boron concentration and δ 11 B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic fractionation between inorganic calcite and seawater/saline water with pH are inconsistent with the hypothesis that B(OH) 4 - is the dominant spe-cies incorporated into the biogenic calcite structure. The isotopic fractionation factors a between synthetic calcium carbonate precipitate and parent solutions increase systematically as pH increases, from 0.9884 at pH 7.60 to 1.0072 at pH 8.60 for seawater and from 0.9826 at pH 7.60 to 1.0178 at pH 8.75 for saline water. An unusual boron isotopic fractionation factor of larger than 1 in synthetic calcium carbonate precipitated from seawater/saline water at higher pH is observed, which implies that a substantial amount of the isotopically heavier B(OH) 3 species must be incorporated preferentially into synthetic inorganic carbonate. The results propose that the incorporation of B(OH) 3 is attributed to the formation of Mg(OH) 2 at higher pH of calcifying microenvironment during the synthetic calcium carbonate precipitation. The preliminary experiment of Mg(OH) 2 precipitated from artificial seawater shows that heavier 11 B is enriched in Mg(OH) 2 precipitation, which suggests that isotopically heavier B(OH) 3 species incorporated preferentially into Mg(OH) 2 precipitation. This result cannot be applied to explain the boron isotopic fractionation of marine bio-carbonate because of the possibility that the unusual environment in this study appears in formation of marine bio-carbonate is infinitesimal. We, however, must pay more attention to this phenomenon observed in this study, which accidentally appears in especially natural environment.

An ionization depressor, 1% H3PO4 was used to eliminate the isobaric interference that has been of a great concern during the procedure of boron isotopic ratio analysis by thermal ionization mass spectrometer (TIMS). Our experiments have shown that it appears to be an effective method to completely restrain the formation of isobaric ions of CNO− and Cs2CNO+ in the ionization source of mass spectrometer. We have also discussed the optimum proportion of depressor to nitrite for precise analysis of boron isotopes in natural samples based on a conditional experiment. In this case, the pretreatment of boron extraction from natural samples is greatly simplified since it is not necessary to remove nitrite and organic matter completely. In virtue of the method, we determined boron isotope in different types of natural samples, and our results are consistent with previous reports.

The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories - virtually all those performing geochemical boron isotope analyses in the world -which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ11B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution. L'Istituto di Geoscienze e Georisorse (IGG), pour le compte et avec le soutien de l'Agence Internationale de l'Energie Atomique (AIEA), a prepare huit materiaux geologiques (trois eaux naturelles et cinq roches et mineraux) destines a la conduite d'une comparaison en aveugle des mesures de composition isotopique et de concentration du bore entre differents laboratoires. Vingt-sept laboratoires -pratiquement tous ceux qui travaillent sur les isotopes du bore en geochimie - ont accepte de participer a cette intercomparaison, mais quinze seulement ont finalement envoye leurs donnees de composition isotopique et/ou de concentration du bore. Les resultats demontrent que la precision des valeurs indiquee par les laboratoires reflete mal la reproductibilite entre laboratoires des mesures de composition isotopique comme de concentration du bore. Les raisons de ces discordances peuvent comprendre l'existence de fractionnements isotopiques dus aux matrices chimiques des materiaux, un deplacement relatif du zero de l'echelle de δ11B, ainsi que le manque de materiaux bien caracterises pour calibrer les mesures de concentration du bore. Les materiaux utilises pour l'intercomparaison des mesures sont maintenant a disposition a l'AIEA (materiaux solides) et l'IGG (eaux) pour etre distribues.

The emission of M2X+ cluster ions in thermal ionization mass spectrometry when graphite is loaded on the heating filaments was studied. The emission model of non-reductive thermal ionization of graphite was preliminarily discussed and factors influencing the thermal emission of M2X+ ions were investigated. The results show that the intensities of M2X+ cluster ions are related to ionic radius and crystal lattice energy, and possibly also to the solvation energies of ions. The intensities of M2Cl+ (M stands for K, Rb, and Cs) cluster ions, the M2Cl+/M+ ratios, and the 37Cl/35Cl ratios determined from M2Cl+ ion measurement usually increase with measurement time. The variation of the 37Cl/35Cl ratios determined from Cs2Cl+ ion measurement is lower than those based on K2Cl+ and Rb2Cl+ ion measurement, indicating the lowest isotopic fractionation.

Springs and seeps in the Tecopa basin were sampled and analyzed for their major ion chemistry and oxygen, hydrogen, and boron isotope compositions in order to assess the possible origins of the waters. The Tecopa basin is a groundwater discharge area along the Amargosa River drainage basin south of the Nevada Test Site and proposed high-level nuclear waste repository at Yucca Mountain, NV. The spring waters are categorized into three end-member hydrochemical facies: (1) pH-neutral, Na+Ca+Mg+SO4+HCO3 water with moderate to high total-dissolved solids; (2) mildly alkaline, Na+Cl+SO4+HCO3 water with high total dissolved solids; and (3) alkaline, Na+HCO3+CO3 water with high total dissolved solids. The temperatures of most of the springs range from 17°C to 32°C; however, waters in the Tecopa Hot Spring area range from 9°C to 47°C. The oxygen and hydrogen isotope compositions (normalized to SMOW) of the waters are as follows. The facies 1 springs have a mean δ18O of −12.77±0.14‰ (1σ) and δD of−94.9±0.5‰ (1σ). The facies 2 springs have a mean δ18O of −12.73±0.19‰ (1σ) and δD of −97.7±0.9‰ (1σ). The facies 3 spring has a mean δ18O of −13.09±0.17‰ (1σ) and δD of −103.5±0.7‰ (1σ). The mean boron concentrations and isotope compositions range from 2.4 mg/l and δ11B of +2.5‰ for facies 1 springs to 72.8 mg/l and δ11B of −3.8‰ for the facies 3 spring. The facies 1 waters have chemical and isotope compositions consistent with meteoric recharge in the Spring Mountains, NV, groundwater flow through the regional carbonate aquifer, and minor mixing with more concentrated water. The thermal, facies 2 waters are isotopically and chemically distinct from waters in the regional basin-fill and carbonate aquifer systems. These waters are interpreted to originate from fractured water-bearing strata beneath the regional carbonate aquifer that discharge only in the southernmost part of the Great Basin. The facies 3 spring is isotopically and chemically similar to basin-fill aquifer waters in the Amargosa Desert, but has higher sodium, alkalinity, and boron contents due to interaction with saline, alkaline-lake deposits of the Plio-Pleistocene Lake Tecopa beds. Geologic, geochemical, and isotope data suggest that these three distinct water types flow through hydrogeologic compartments in the Tecopa basin. The compartments are interpreted to have been created by the impermeable Lake Tecopa beds and geologic structures within the basin.

A distinct difference in boron isotopes between seawater and terrestrial water is emphasized of δ11B values reported for seawater and groundwater, with an average of 38.8‰ and in the range of −8.9‰ to 9.8‰, respectively. The isotopic composition of boron in groundwater can be used to quantify seawater intrusion and identify intrusion types, e.g. seawater or brine intrusions with different chemical and isotopic characteristics, by using the relation of δ11B and chloride concentration. The feasibility of utilizing boron isotope in groundwater for studying seawater intrusion in Laizhou Bay Region, China, is reported in this study, which shows that boron isotope is a useful and excellent tool for the study of seawater intrusion.

The characteristics of non-reductive thermal ion emission in thermal ionization mass spectrometry for six kinds of graphite with different origins, purity and crystal structure and one high pure carbon powder are studied. The results show that the efficacy of non-reductive thermal ion emission of graphite is weakly related to the purity and particle size of graphite while dependent on the crystal microstructure of graphite. Graphite with a perfect crystal structure has a higher efficiency of non-reductive thermal ion emission.

The effect of NO 3 − on the isotopic measurements of boron based on the Cs 2 BO 2 + ion with graphite loading was investigated. The measured 309/308 ratio was considerably reduced by the presence of NO 3 − ion, especially in the presence of mannitol, due to the formation of the Cs 2 CNO + ion producing ion peaks at masses of 308 and 309. The procedure of ion exchange using Amberlite IAR 743 resin, a boron-specific resin, and OH-Dowex 1 resin for extracting boron from sample solution was developed. The NO 3 − ion could be removed from sample solution during sample preparation by using this procedure.

The isotopic compositions of chlorine in salt lake brine coexisting with halite, oil-field water and river water from the Qaidam Basin (Qinghai, China) have been examined using high-precision measurement of chlorine isotopes based on thermal ionization mass spectrometry of the Cs2Cl+ ion. δ 37Cl values vary from −2.05 to +2.94‰, with average values of +2.94‰ for hot spring water, +1.35‰ for river water, −0.38‰ for oil-field brine, −0.40‰ for saline water and −0.63‰ for salt lake brine. The preliminary results show isotopic fractionation of chlorine in salt lake brine during salt precipitation. The variation of the δ 37Cl value in these salt lakes is mainly associated with brine evaporation and halite precipitation and with the hydrochemistry of the input water. The chlorine isotopic composition may reflect the degree of evaporation of the salt lake brine and may be used to distinguish brines that are in equilibrium with precipitating salts and brines that have dissolved earlier evaporates.

The above results indicate that37Cl/35 C1 ratios in saline minerals are higher than those in brine due to chlorine isotopic fractionation during evaporation.37Cl/35 C1 ratios of salt lakes brine reflect the change in hydrochemical condition. The chlorine isotopic composition of saline mineral is associated with environment. Therefore, chlorine isotope may be used to trace evolution of salt lakes and the environment.

An improved procedure for precise measurement of chlorine isotope ratios in geological samples based on Cs2Cl+ ion by thermal ionization mass spectrometry is reported. Using this procedure the 37Cl/35Cl ratio of NIST SRM 975 is determined to be 0.318929±0.000028(1[sgrave]) with a precision of 0.009%(1 [sgrave]). The procedure has been successfully applied to study the variation of chlorine isotopic compositions in seawater and to determine atomic weight of chlorine.

The emission behavior of polyatomic ions in the ionization source of thermal ionization mass spectrometry (TIMS) was investigated. The results suggest that the presence of a graphite promoter plays a key role for the formation and stable emission of polyatomic ions, such as M(2)X(+), M(2)BO(2)(+), Cs(2)NO(2)(+), and Cs(2)CNO(+). Our data further implied that the intensity of M(2)X(+) and M(2)BO(2)(+) increases and the emission temperature decreases with increasing cationic and anionic radius. During the boron isotopic measurement using the Cs(2)BO(2)(+)-graphite-PTIMS method, the isobaric interference ion Cs(2)CNO(+) cannot be transformed from nitrate or organic compounds containing an amide group but can be induced by the existence of trace amounts of boron because of its special electron-deficiency property (B(3+)). Characterization on the planar crystalline structure of various graphite samples with SEM, TEM, and Raman spectroscopy confirmed the relationship of the emission capacity of polyatomic ions and the crystal microstructure of graphite and provides direct evidence that graphite with a perfect parallel and equidistant layer orientation shows a beneficial effect on the emission of polyatomic ions in TIMS. The mechanism study on the formation of polyatomic ions opens the possibility to establish high precision methods for isotopic composition analysis of more nonmetal elements with the TIMS technique.