Isotope Ratio Mass Spectrometer Research Articles

Carbonate clumped isotope analysis using isotope dilution

The large sample size requirement is a major obstacle while conducting the measurement of isotopic abundances in carbonates for clumped isotope thermometry using MAT 253 isotope ratio mass spectrometer employing McCrea type setup or improved break-seal method at a reaction temperature of 25 °C. A long integration time at high (∼10000 mV) major ion beam intensity permits the highest analytical precision but requires a large sample size for CO2. However, in several instances, carbonate availability is restricted in the natural environment like foraminifera, otoliths, ostracods, etc., in sediment cores, prohibiting the application of the thermometry. Here we introduce a new isotope dilution method for stable and clumped isotope analysis for small size carbonates at a precision of ±0.005‰. In this method, two reference carbonate materials (MAR J1 and OMC) are quantitatively mixed with known proportions or weight fractions. The high-temperature reference carbonate (MAR J1) is treated as a spike end member, whereas the low-temperature carbonate reference is considered as unknown. The spike is identified based on similarity in mineralogy with the sample and well-defined isotopic composition as constrained by its formation temperature. These two carbonates used here are internal laboratory standards and are homogeneous, independently ascertained based on long-term reproducibility of δ13CVPDB and δ18OVPDB values lying within 0.002‰ and 0.003‰ respectively. These two reference carbonate powders have δ13CVPDB and δ18OVPDB values, which differ from each other by ∼6.3‰. The Δ47 values of these carbonates are 0.395‰ and 0.587‰, respectively. In our experiment, we observe a linear relationship governing δ13CVPDB and δ18OVPDB values of a mixture with a known weight fraction; however, Δ47 values follow a non-linear mixing trend upon exceeding the weight fraction ≥0.4 of the low-temperature carbonate (OMC). The linear trend allows the prediction of the Δ47 value of the unknown carbonate powders using a binary mixing model within an acceptable precision of 0.01–0.02‰ necessary for clumped isotope measurement. This new approach provides an alternative method of analyzing small size (∼3 mg) carbonate powder extending the application of the break-seal method for analysis at major ion beam intensity of 10000 mV. Here we demonstrate the application of this method for accurate determination of both stable and clumped isotopic composition of various low-temperature carbonates, including a deep-sea coral, an otolith, and ETH-3 reference carbonate.

Evaluation of longitudinal 13 C isotope ratio mass spectrometric data in antidoping analysis.

The detection of testosterone and its precursors' abuse in antidoping sports analysis is based on the longitudinal evaluation of markers of the urinary endogenous steroid profile. A Bayesian statistical approach is applied, allowing the establishment of credible intervals of the selected parameters for every athlete. Samples showing values outside the acceptable boundaries are selected for additional confirmation by isotope ratio mass spectrometric (IRMS) analysis. The alterations of the IRMS values last longer than the alterations of the steroid profile. Then the application of IRMS to a larger number of samples, at a screening level, would presumably allow detection of additional positive cases. The steroid profile and IRMS data can be treated using the same Bayesian inference procedure. In nonsports population, we have demonstrated the stability of IRMS data. In this work, we studied the variability of these data in real conditions, in samples collected on athletes subjected to antidoping analyses over the years. The data obtained confirmed previous observations and the applicability of the proposed approach. The results of cases where confounding factors of the steroid profile were reported are discussed, showing that in most of the cases no significant changes are observed over the absolute delta values. Changes in diet may significantly change the absolute delta values but not the ones relative to endogenous reference compounds. Finally, a case that could have been evaluated as normal with the current approach without a thorough review of the data was detected as positive by the proposed approach, demonstrating the benefit of its application.

Isotope Fingerprints of Common and Tartary Buckwheat Grains and Milling Fractions: A Preliminary Study.

The grains and milling fractions of common buckwheat (Fagopyrum esculentum Moench) and Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) are widely used for both industrial and small-scale food and non-food products. This paper represents a preliminary study of the isotopic signature (δ13C, δ15N, and δ34S) to differentiate between buckwheat species (common vs. Tartary), organic and conventional cultivation farming, and different buckwheat fractions (light flour, semolina, and hulls) obtained by a traditional cereal stone-mill. Stable isotope ratios were analyzed using an elemental analyzer coupled to an isotope ratio mass spectrometer (EA/IRMS). The results indicated that δ13C, δ15N, and δ34S values could be used to verify the origin and production practices of buckwheat and even its products.

A unified method for measuring noble gas isotope ratios in air, water, and volcanic gases via dynamic mass spectrometry

We describe a new method for the purification, transfer, and analysis of heavy noble gas isotope ratios in water, air, or volcanic gas samples using a dynamic dual-inlet isotope-ratio mass spectrometer (IRMS). IRMS noble gas analysis offers the potential for orders-of-magnitude higher precision than traditional (static) noble gas mass spectrometry. However, due to both inherent IRMS requirements and challenges associated with sample collection and purification, measuring noble gases via IRMS has typically been limited to samples with an air-like elemental composition. Our new method allows for highly accurate and precise measurements of Ar, Kr, and Xe isotope ratios via IRMS, independent of sample composition, thereby opening the door to air, water, or volcanic gas analyses all made with the same technique. This approach exploits the fact that purified heavy noble gas samples are dominated by 40Ar, such that matching 40Ar ion beams between sample and reference gas streams results in pressure balancing. We further introduce new techniques for precisely quantifying and correcting for (i) Kr and Xe isotope non-linearity and matrix effects, (ii) interference of the low energy 40Ar tail on 36Ar and 38Ar ion beams, and (iii) the impact of short-term background fluctuations on trace Xe isotope measurements. We also present results from adsorption-desorption experiments with multiple adsorbent materials across a range of temperatures. For adsorption on silica gel, we find small equilibrium isotopic fractionation of Kr (εeq = −0.37 ± 0.04‰ amu−1, ±2 SE) and Xe (εeq = −0.06 ± 0.02‰ amu−1, ±2 SE) that may be relevant to studies of terrestrial Xe isotope signatures. We demonstrate that adsorption and desorption of heavy noble gases on silica gel at 77 K and 303 K, respectively, is highly reproducible and thus constitutes a viable and efficient method for transferring gases without reliance on cryostats or liquid helium.

Isotope ratio dual-comb spectrometer

We demonstrate the use of dual-comb spectroscopy for isotope ratio measurements. We show that the analysis spectral range of a free-running near-infrared dual-comb spectrometer can be extended to the mid-infrared by difference frequency generation to target specific spectral regions suitable for such measurements, and especially the relative isotopic ratio $\delta {}^{13}$C. The measurements performed present a very good repeatability over several days with a standard deviation below 2$\unicode{x2030}$ for a recording time of a few tens of seconds, and the results are compatible with measurements obtained using an isotope ratio mass spectrometer. Our setup also shows the possibility to target several chemical species without any major modification, which can be used to measure other isotopic ratios. Further improvements could decrease the uncertainties of the measurements, and the spectrometer could thus compete with isotope ratio spectrometers currently available on the market.

Stable isotopes analysis and heavy metal contamination in the rocky shore intertidal food web on the east coast of South Africa

Using a short food web, i.e. from prey (macro-algae) to predator (limpet), this study investigated the concentrations and biomagnification of heavy metals from macro-algae (Ralfsia verrucosa, Ulva lactuca and Gelidium pristoides) to limpet (Scutellastra cochlear, S. longicosta, S. granularis and Cellana capensis) species. Samples were collected from four sites (Mbhashe; Mthatha; Hluleka; Silaka Mouth) in four seasons (winter 2019; spring 2019; summer 2020; spring 2020). In the laboratory samples were digested with the normal protocols, subsequently analysed for heavy metals using inductively coupled plasma optical emission spectrometry (ICP-OES), while δ15N and δ13C isotopes were analysed with Isotope Ratio Mass Spectrometer (IRMS). There were significant differences of heavy metals concentration between species of macro-algae and limpet, and metal concentration was species-specific. Spatio-temporal differences of (δ13C) isotope was evident, indicating a wide source of energy. Using (δ15N) as a proxy for biomagnification (BMF) of metals, As did not show any sign of biomagnification (BMF<1) among all seasons and sites. Though mercury and Ni had BMF >1, negative regression slope showed biodilution of these metals to the next trophic level. The toxic Cd, Pb, and essential metals Zn and Cu indicated possible biomagnification (BMF >1) between sites and seasons respectively. This study showed that the selected limpet species are notable accumulators of heavy metals and these contaminants have the potential to biomagnify in the next trophic level suggesting that they are possibly unfit for human consumption in these study sites.

Geochemistry Acidic Water of Banyupait River Effect Seepage of Crater Water Ijen Volcano, Asembagus, Indonesia

The Ijen volcano has the Pleistocene age, and this stratovolcano was very acidic crater water with a pH of 0-1. The acidic water seeps into the Banyupait River. Asembagus is a research area located on the northern slope of the Ijen volcano, and the Banyupait River drains this. This study used several different analytic methodologies with some previous researchers, namely geological mapping, pH measurement, spectrophotometry, IRMS (Isotope Ratio Mass Spectrometer), and the technique of Induced Coupled Mass Spectrometry (ICP-MS). Besides, the petrographic analysis is used to determine rock minerals' composition due to rocks interacting with acidic water. Banyupait River water in the Asembagus area has a pH of river water around 3-7.3, SO4 (220-683 ppm), and the type of water is meteoric water. Also, Ca, K, and Mg concentrations in the west Banyupait river irrigation water flow showed higher levels than the eastern. Likewise, REE elements from the Asembagus region showed lower concentrations compared to Ijen Crater water. This change in the level of chemical elements is caused by the Banyupait River's acidity being diluted or mixed with water from other water. The process of acidic water interaction with rocks can also be observed from rocks traversed by the Banyupait River flow. Chalcedony and hematite replace the primary minerals of basaltic rocks. This research is expected to improve the quality of water needed by the Asembagus community to live healthily.

Contribution of Spring Snowmelt Water to Soil Water in Northeast China and Its Dynamic Changes

Snowmelt water in spring is an important source of soil water, which is critical to supporting crop growth. Quantifying the contribution of snowmelt water to soil water and its dynamic changes is essential for evaluating soil moisture and allocating agricultural water resources. In this paper, through controlled outdoor experiments, different snow depths and soil depth gradients were set; and snow, precipitation, and soil samples were collected regularly. To analyze the contribution of snowmelt water to soil water and its dynamic changes, the MAT-253 stable isotope ratio mass spectrometer was adopted for hydrogen and oxygen isotope analyses. The results showed that the snowmelt water for snow depths of 10 cm, 30 cm, and 50 cm all contributed to the 0–30 cm soil layer. The contribution increased with soil depth, contributing 8.13%, 8.55%, and 11.24%, respectively. The contribution of the snow cover at the same depth to the soil moisture at different depths also varied, i.e., the contribution increased with increasing soil depth. The snowmelt water retention time at depths of 10 cm, 30 cm, and 50 cm was inconsistent, i.e., it was the longest at 0–10 cm (average of 69 days), followed by 20–30 cm (average of 59 days), and the shortest at 10–20 cm (average of 54 days). The greater the snow depth, the shorter the retention time of the snowmelt water in the different soil layers. For surface soil, the contribution of the snowmelt water at greater depths was significantly different; while for deep soil, the contribution was more sensitive to the snow depth. Regardless of snow depth, soil contributions at different depths were significantly different. Precipitation also affected the contribution of the snowmelt water to the soil water, exhibiting different effects at different depths.

Performance evaluations and applications of a δ13C-DIC analyzer in seawater and estuarine waters

Dissolved inorganic carbon (DIC) and its stable isotope (δ13C-DIC) are important parameters for studying carbon cycling in aquatic environments. Traditional methods based on isotope-ratio mass spectrometers are labor-intensive and not easily deployable at field sites. Here we report the performance of a method that simultaneously measures DIC concentration and its stable isotope by using a CO2 extraction device and a Cavity Ring-Down Spectroscopy (CRDS) detector. A multi-port valve is used to increase sample throughput and improve precision. The instrument achieves average precisions of better than ±1.95 μmol kg−1 and ±0.06‰, respectively, for DIC and δ13C-DIC in seawater based on three injections for each sample. We also provide recommendations on how to precisely determine δ13C-DIC samples with a wide range of DIC content in different types of waters by examining injection volume and concentration effects. This technique was applied to study carbon cycling in the Delaware Estuary. It demonstrates that a simultaneous and precise determination of both DIC and δ13C-DIC is a powerful and effective approach for constraining the processes controlling aquatic carbon cycling and CO2 fluxes. Both laboratory tests and field applications confirmed that this system can be used with high precision to study carbon cycling in various aquatic environments.

Carbon isotope composition for agronomic diagnostic: Predicting yield and yield response to nitrogen in wheat

Rainfed crops rely on two sources of water: stored soil water at sowing and seasonal rain. In strongly seasonal winter-rainfall environments, stored soil water at sowing is minor, and uncertain seasonal rainfall is a source of risk. In south-eastern Australia, under-fertilisation is a common outcome of nitrogen risk management with implications for wheat yield and mining of soil organic matter. Here we explore the use of carbon isotope composition (δ 13 C) to capture the effects of crop water status on grain yield in a context of nitrogen top dressing. In the sampled environments, crops receive at least 50% of seasonal rainfall by stem elongation, and at least 70% of seasonal rainfall by flowering. In a sample of 1518 plots, yield varied from 0.07 to 9.96 t ha -1 and correlated with δ 13 C measured with isotope ratio mass spectrometer (IRMS) at flowering (r = −0.76, p < 0.0001); this is consistent with the rainfall pattern and the physiology of the crop featuring a critical period for yield from 300 °Cd before to 100 °Cd after anthesis. In a sample of 135 plots, yield varied from 1.2 to 8.4 t ha -1 and correlated with δ 13 C measured with IRMS at stem elongation (r = −0.56, p < 0.0001). Yield response to nitrogen, defined as the difference between yield in fertilised crops (50–200 kg N ha -1 ) and unfertilised controls, correlated with δ 13 C measured with IRMS at stem elongation, except for late-sown crops. Mid-infrared spectroscopy (MIR) returned estimates of δ 13 C that agreed with δ 13 C measured with IRMS (calibration: R 2 = 0.82, RMSE = 0.53‰, n = 833; validation: R 2 = 0.70, RMSE = 0.75‰, n = 364). We conclude that a MIR based, high-throughput, affordable measurement of δ 13 C could be scaled to guide nitrogen management of wheat in winter-rainfall environments. • In a sample of 1518 plots, yield varied from 0.07 to 9.96 tha -1 and correlated with δ 13 C at flowering. • Yield response to nitrogen correlated with δ 13 C at stem elongation, except for late-sown crops. • Mid-infrared spectroscopy is a cost-effective, high-throughput approach to estimate δ 13 C for agronomic applications.

Isotope fractionation during capillary leaking in an isotope ratio mass spectrometer.

When isotope composition is measured in dual-inlet mode with an isotope ratio mass spectrometer (IRMS), reference gas may be gradually enriched in heavy isotopes due to preferential loss of light ones from the bellows over time. Quantifying the degree of isotopic enrichment of the reference gas is imperative for high-precision isotopic analysis (i.e. at per meg level). O2 and CO2 leaking experiments were performed with the dual-inlet system of an IRMS (Thermo Fisher® MAT 253 Plus). During each experiment, the drop of gas pressure in the bellows with time was recorded and isotope ratios of residual gas at various time intervals were analyzed. Isotopic enrichment of residual O2 gas could be as large as 1‰ for δ18 O when a large fraction (>75%) of initial gas was lost. The evolution of isotope compositions of the remaining gas can be well described by a pressure-dependent Rayleigh fractionation equation. When the pressure in the bellows is within 10-50 mBar, the isotope fractionation factor (α18 O) for O2 leaking ranges from 0.99911 to 0.99982 and the characteristic relationship of α17 O and α18 O is from 0.5123 to 0.5124. Isotope fractionation associated with capillary leaking from bellows is pressure-dependent. We recommend that the reference gas should be reloaded frequently, especially after a measurement with a low analyzing pressure for the analysis of small amounts of sample.

Isotopic analysis of otolith carbonates using laser heating: A fast method for obtaining high-resolution climate signal.

The stable isotopic compositions of biogenic carbonates like fish otoliths (ear bones) are widely used for palaeoclimatic reconstruction. The conventional method using acid-digestion of micro-milled samples is a multi-step time-consuming process. Here we report a fast method based on laser heating of otolith carbonates to obtain accurate and high-resolution stable isotopic compositions. Otoliths of catfish from the Gulf of Kutch were analysed to check the precision, accuracy and time-resolution of the isotope ratios. The CO2 , generated by heating otoliths with a 50 W CO2 laser, was analysed for its oxygen and carbon isotope ratio [δ18 O and δ13 C, with precision: 0.12 and 0.17‰ (1σ), accuracy: 0.13 and 0.25‰, respectively] using a continuous-flow isotope ratio mass spectrometer. The effect of laser power (0.7-2W) was assessed for reproducible data. Samples were roasted and analysed to account for the effect of the inherent organic matter on the isotopic values. Roasting did not alter the δ18 O of the otoliths but increased the δ13 C slightly. High-resolution (125 μm) analysis of the right and left otolith of a fish yielded similar δ18 O and δ13 C values, suggesting the suitability of either of them for deriving the climate signal. An increase in δ18 O values from ~ -2‰ to ~ -1‰, observed across the ontogeny, is consistent with the known migratory behaviour of the catfish between freshwater and the sea. The otolith δ18 O value of an adult fish records the sea surface temperature (with ~3°C uncertainty) on a monthly scale. The otolith δ13 C values, with the knowledge of dietary δ13 C, provide the mean annual δ13 C value of dissolved inorganic carbon. The study provides a rapid method for retrieving high-resolution seasonal climate data from otoliths found aplenty in geological/archaeological records.

ISOTOPE 18O OF ALTERATION ROCKS AT WELL C-1 KAMOJANG GEOTHERMAL FIELD, WEST JAVA, INDONESIA

The purpose of this study is to determine the reservoir condition system of Well C-1. Kamojang geothermal field located in the Quaternary volcanic complex caldera system (0.452 to 1.2 Ma). The volcanic complex contributes to the formation of vapor-dominated high-temperature geothermal systems (250oC). The potential of the electricity produced from this field was 260 MWe. This study describes a new method, namely the 18O isotope of alteration rock, to determine reservoir conditions. Another approach is to use a petrographic analytical form, X-ray diffraction, and isotope 18O and D on some core and cutting samples. Isotope abundances are measured using an isotope ratio mass spectrometer (IRMS). Zoning mineral alteration in Well C-1 comprises the cristobalite-montmorillonite zone, illite-montmorillonite zone, and chlorite-epidote zone. Hydrothermal fluids that generate steam in geothermal systems were derived from meteoric water. These fluids interact with rocks based on the ratio of reservoir water-rock interaction, Well C-1. The research shows that the value of the fraction of oxygen atoms of rocks in the system (1-x) was 0.16. That indicated that the reservoir containing fluid 16% or reservoir is rock-dominated. This research on 18O isotope is a novelty because it differs from what has been done by previous researchers who studied reservoir characteristics using water 18O isotope. Meanwhile, this study uses the 18O isotope of alteration rock to identify reservoir conditions. It is hoped that this method can be used in other geothermal fields.

Helium-flushed sheathed nickel tube reactor for continuous flow oxygen stable isotope compound-specific analysis.

Compound-specific oxygen stable isotope analysis has been commercially available for about 20 years but the technique has been infrequently applied and practical operating knowledge is limited. Existing reactor designs and chemistry fail to fully exclude contaminating oxygen, are chromatographically flawed, and are generally fabricated from expensive platinum tubing. As a new interface between the gas chromatograph and isotope ratio mass spectrometer, we used a nickel tube reactor (containing no platinum wires) in a ceramic sheath with countercurrent helium flushing, operated at 1250°C. We analyzed suites of four long-chain alcohols (LCAs), defining the least and most 18 O-enriched LCAs as internal standards. The other two LCAs, co-injected in varying amounts, were treated as unknowns and amplitude-corrected during data reduction. With this design, signals from non-oxygenated compounds are minimized with a hydrogen trickle, while excessive graphitization is counterproductive. A balance of hydrogen and graphite is required to maintain a proper, stable redox state in the reactor. With low extraneous oxygen, the exact hydrogen flow has little effect on final δ18 O data quality. Overall average δ18 O values precisions and errors for the unknowns were better than 0.4‰ for injections between 2 and 7nmol per component. Our actively flushed sheath reduces oxygen infiltration to negligible levels and results in a chromatographic flow devoid of dead or poorly swept volumes. The improved design allows measurement of LCAs with accuracy and precision sufficient to enable investigating real processes, and may also have wider applications to other isotopes.

Maturity and depositional controls on compound-specific sulfur isotope values of saline lacustrine source rocks in the north Dongpu Depression, Bohai Bay Basin

Source rocks and oil sands from the northern Dongpu Depression have been analyzed by gas chromatography multicollector inductively coupled plasma mass spectrometry (GC-MC-ICP MS) to investigate the compound-specific sulfur isotope (δ34S) values of saline lacustrine source rocks. The samples were also subject to more traditional organic geochemical analyses including hydrocarbon biomarker detection by gas chromatography/mass spectrometry (GC/MS), carbon and oxygen isotopic analysis by isotope ratio mass spectrometer, and major and trace inorganic element analysis. δ34SOSCs values measured for a limited number of organic sulfur compounds (OSCs) showed a quite large range (5.16‰–44.73‰). The source rocks and oil sands could be separated into two groups with δ34S values above or below 25.00‰. The first group with δ34S > 25.00‰, were primarily the Weicheng source rocks, which also typically showed an increase in δ34S values with increasing alkylation. The second group had δ34S < 25.00, the δ34S of dibenzothiophenes showed a positive correlation with the concentration of the saturated hydrocarbon fraction of rocks, and a negative correlation with the polar (resin + asphaltene) fraction. The δ34SOSCs show obvious positive correlation with gammacerane/C31 hopane and C35/C34 hopanes and excellent correlation with contents of minerals and ratios of trace elements, reflecting a 34S enrichment in closed evaporative environment (conducive to the sulfurisation of organic matter) and relative 34S depletion in terrestrial environments. These trends identify the depositional environment of the source rocks as one of controls on δ34SOSCs values. Thermal maturity was also observed to influence δ34SOSCs values, becoming heavier with increasing maturity. There was a good result of oil-source rock correlation by δ34SOSC in this study. This study demonstrates the contribution δ34SOSCs data can make to oil-oil and oil-source rock correlations as well as providing further evidence of their sensitivity to depositional environments and thermal maturity.

A simple CO2 equilibration method for measuring blood oxygen isotope compositions.

Blood water oxygen isotope compositions can provide valuable insights into physiological processes and ecological patterns. While blood samples are commonly drawn for medical or scientific purposes, blood fractions are infrequently measured for oxygen isotopic compositions (δ18 O) because such measurements are time consuming and expensive. We sampled blood from sheep, goats, and iguanas raised in field and animal laboratories into serum, EDTA, heparin, and uncoated plastic vials commonly used in medical and scientific research, then separated red blood cell (RBC) and plasma or serum blood fractions. These were injected into helium-flushed Exetainer tubes where they naturally outgassed endogenous CO2 (goat blood), or into He- and CO2 -flushed tubes (iguana blood). The CO2 gas was sampled on a GasBench II system, and δ18 O was measured by an isotope ratio mass spectrometer (IRMS). Repeated δ18 O measurements were stable over multiple days. The addition of desiccated blood solids to water standards had little impact on their δ18 O measurements, suggesting that organic molecular constituents within blood serum and plasma do not interfere with blood water δ18 O values. We observed slight but statistically significant δ18 O offsets between plasma, serum and RBC fractions. Mass-dependent body water turnover times for iguanas were derived from the data. We demonstrate that a simple blood-CO2 equilibration method using the GasBench can quickly, reliably and accurately characterize water δ18 O in the plasma, RBC, and whole blood fractions of mammalian and reptilian blood samples (precision ≤ 0.1‰). This method will expand the application of blood stable isotope analysis in physiological and medical research.

The Effect of Cultivation Practices on Agronomic Performance, Elemental Composition and Isotopic Signature of Spring Oat (Avena sativa L.).

The present study investigated the effects of cultivation practices on grain (oats) yield and yield components, such as straw yield, harvest index, thousand kernel weight, and plant lodging. In addition, multi-element composition and isotopic signature (δ13C, δ15N) of the oat grains were studied. The spring oat cultivar ‘Noni’ was grown in a long-term field experiment during 2015–2020, using three management practices: control without organic amendment, incorporation of manure every third year and incorporation of crop residues/cover crop in the rotation. Synthetic nitrogen (N) (0, 55, 110 and 165 kg/ha) was applied during oat development in each system. Multi-element analysis of mature grains from two consecutive years (2016 and 2017) was performed using EDXRF spectroscopy, while stable isotope ratios of carbon (C) and nitrogen (N) were obtained using an elemental analyzer coupled to an isotope ratio mass spectrometer (EA/IRMS). The results show how cultivation practices affect yield components and isotopic and elemental signatures. Increasing the N rate improved both the oat grain and straw yields and increased susceptibility to lodging. The results show how the elemental content (Si, Ca, Zn, Fe, Ti, Br and Rb) in the oat grains were influenced by intensification, and a noticeable decrease in elemental content at higher N rates was the result of a dilution effect of increased dry matter production. The mean δ15N values in oat grains ranged from 2.5‰ to 6.4‰ and decreased with increasing N rate, while δ13C values ranged from −29.9‰ to –28.9‰. Based on the δ15N values, it was possible to detect the addition of synthetic N above an N rate of 55 kg/ha, although it was impossible to differentiate between different management practices using stable isotopes.

Application of chromium catalysis technology to compound-specific hydrogen isotope analysis of natural gas samples

An easy-to-use and efficient approach for the catalytic pyrolysis of hydrocarbon gas here is proposed and tested, which allowed the precise measurement of δ2H. This method requires the reaction tube filled with twisted chromium wire, establishing a gas chromatography–Chromium wire/high temperature conversion–isotope ratio mass spectrometer (GC‒Cr/HTC‒IRMS) system. The approach described here has many remarkable advantages over other techniques. In comparison to traditional carbon-coating pyrolysis technique, this proposed method greatly reduces the pyrolysis temperature of the hydrocarbon gas, especially methane, with temperatures reduced from 1450 to 1250 °C, while still ensuring excellent analytical precision. Therefore, hydrogen isotope analysis of natural gas can be carried out at a lower cracking temperature for a longer time, with the advantage of increasing the service life of the HTC furnace. Meanwhile, no pretreatment or activation is required while putting the Cr/HTC system to use. Further, the accuracy of δ2H values obtained using this new method is better than using the traditional method. Our experiments demonstrate that the test errors of this novel method and the conventional method are within ±5.5‰ and ±6.5‰, respectively.

Rate and Efficiency of Organic Carbon Assimiliation by Aquacultured Juvenile Sandfish Holothuria scabra

Diet assimilation rate is crucial to the growth and survival of Holothuria scabra juveniles during culture. To understand the assimilation rate and efficiency we assess organic carbon assimilation, which is closely related to the growth and source of variations in diet. We conducted a two-factor experiment, i.e., juvenile origin (cultured and wild H. scabra juveniles), and diet treatment (one control with no additional diet, and three additional diets, i.e., rice bran, dried cow manure, and seagrass Enhalus acoroides extract). We monitored the amounts of each diet that the juveniles consumed and the fecal pellets they egested. The diet, sediment, body walls, and organic carbon content of the fecal pellets were measured using an elemental analyzer combined with an isotope ratio mass spectrometer. Exponential growth was seen in the juveniles fed with rice bran, which had a fecal pellet egestion of 0.12–0.21 gC/d. Stable isotope analysis showed that the contribution of the diet proportion to the growth of the sandfish did not exceed 30%. The range of the assimilation rate was 35.3–62.4 gC/d. The average assimilation efficiency of organic carbon was 43.6 ± 27.7% (max 57.9%). Considering the assimilation rate and efficiency, we suggest a feeding interval of once every two days or twice per week at a rate of 3–5% of the total H. scabra biomass for a juvenile culture system.

Seasonal variation of trace elements and stable isotope (δ13C and δ15N) values of commercial marine fish from the black sea and human health risk assessment

The purpose of this study is to examine changes in stable carbon and nitrogen isotope ratios, to determine the levels of metals (aluminum, copper, iron, manganese, lead, and zinc), and to assess the health risks associated with consumption of the most consumed pelagic and demersal fish species in Turkey. Trachurus mediterraneus, Mullus barbatus, and Merlangius merlangus were seasonally caught from the Eastern Black Sea in 2020. Concentrations of heavy metals in fish muscle tissues were measured using Inductively Coupled Plasma-Optical Emission Spectroscopy whereas stable isotope analysis was performed using Isotope Ratio Mass Spectrometer. The detected levels of metals studied in all fish species except lead were below the determined limits of national and international standards. In addition, the carcinogenic risk index was considered significant in all fish species. Considering the principal components analysis results, Cu and Pb may have originated from similar sources. No significant difference in metal content and stable isotope rates was observed between different species of fish. Also, target hazard quotient values were found below 1 in all species, which means that the consumption of the studied fish species does not pose a health risk.