Isotope Ratio Mass Spectrometer Research Articles

Distribution of stable Н, О and С isotopes in natural waters in the area of the Taz oil and gas condensate field (Yamalo-Nenets autonomous region)

Relevance. The study of isotopic composition of water and dissolved substances makes it possible to determine not only their genesis, but also the fractionation processes occurring in the “water–rock–gas–organic matter” system over time, i. e. as different stages of the evolution of water composition pass through. Interest in the groundwater of the Arctic regions of Western Siberia is additionally associated with the widespread occurrence of oil deposits at the depths of formation waters and the possible influence of cryogenic metamorphization processes on composition of near-surface waters. Aim. To study and compare the isotopic composition of oxygen, hydrogen and carbon in natural waters of the Yamalo-Nenets autonomous region to identify conditional isotopic markers, as well as to be able to trace the evolution of the isotopic composition of waters along a vertical section in the area of the Taz oil and gas condensate field. Objects. Surface (river, soil and lake), underground waters of the active water exchange zone of the Yamalo-Nenets autonomous region and formation waters of oil and gas deposits of the Taz field. Methods. The study of the isotopic composition of oxygen, hydrogen, and carbon of water-dissolved carbon dioxide was carried out in the Research Equipment Sharing Center at the Institute of Geology and Mineralogy SB RAS using Isotope Ratio Mass Spectrometer FinniganTM MAT 253 equipped with H/Device and GasBench II for sample preparation. Results and conclusions. The paper introduces the data on isotopic composition of O, H and C for natural waters of the Yamalo-Nenets autonomous region. The authors have determined the characteristic trends in changes in the isotopic composition of water and dissolved carbon dioxide for various water bodies. Surface and underground waters with active water exchange in terms of isotopic composition (δD and δ18О) are infiltration. As water moves down the section, with an increase in the time of interaction of the “water–rock” system and increase in temperatures, the isotopic composition becomes significantly heavier with a slope from the GMWL to the right. The authors compiled the diagram of the evolution of water-dissolved carbon isotopic composition in the region according to the obtained and some literature data. Despite the wide range of δ13C values from –30.4 to 23.6 ‰, there are, obviously, only two sources of carbon dioxide in the region: biogenic and atmospheric, with biogenic being predominant for groundwater.

Structures and contributions of active substances in the latent oxidation of coal based on the oxygen isotope tracer method

The oxygen isotope tracer method was used to determine the structures and contributions of the active substances that trigger coal spontaneous combustion (CSC). After artificially changing the oxygen isotope ratio, the coal samples were subjected to isothermal oxidation under different conditions (different temperatures, different oxidation times and different coal types) in an 18O2 atmosphere. First, the oxidation gases were obtained with cyclic oxidation experiments. The basic parameters were provided for tests of the gas isotopes. The oxidation products labeled with 18O were then analyzed with an isotope ratio mass spectrometer. The original active substances in the coal were determined. Evolution of the functional groups in the coal was determined by XPS. The transformation paths of the active substance were analyzed. The results showed that during the oxidation process, more than 70 % of the CO was generated from the original hydroxyl and aldehyde groups in the coal, and more than 99 % of the CO2 was generated from the original carboxyl groups in the coal. Inhibition of oxidative decomposition of hydroxyl, aldehyde and carboxyl groups can effectively control CSC and solve the problem of CO overflow caused by low-rank coal oxidation.

Authentication of Tonka beans extracts (Dipteryx odorata) using LC-UV/MS, GC-MS and multi element (13C, 2H and 18O) bulk specific isotope analysis

Tonka bean extract, prepared from Tonka beans, is mainly composed of Coumarin. However, due to alternative industrial procedure of production, different solvents and mixtures of solvents were tested for extraction. Investigation using HPLC-DAD-MS indicates influence of extraction procedure on compositions of main constituents. New polyphenols structures have also been found in extracts and improve the chemical analysis knowledge of these products. Waxes compositions using fatty acids methyl esters gas chromatography analysis have been determined and indicate important amounts of behenic and lignoceric acids. High polar constituents (sugars) were also pointed out with trimethyl silanization. As synthetic Coumarin addition represents the main adulteration, isotopic values of Tonka coumarin, isolated by crystallization, have also been determined using an elemental analyzer connected to an isotope ratio mass spectrometer (EA-IRMS). The δ13C values of authentic coumarin range from − 32.88 to − 31.38‰ for δ13C, between − 113‰ and − 83‰ for δ2H, and between 23.0 and 28.0‰ for δ18O. No isotopic effect was observed with different solvents extraction procedures, indicating that IRMS investigation of Coumarin is a powerful tool applied for naturalness control.

Hybrid pathways of denitrification drive N2O but not N2 emissions from an acid-sulphate sugarcane soil

AbstractAcid-sulphate sugarcane soils in the subtropics are known hot-spots for nitrous oxide (N2O) emissions, yet the reduction of reactive N2O to non-reactive dinitrogen (N2) via specific pathways remains a major uncertainty for nitrogen (N) cycling and loss from these soils. This study investigated the magnitude and the N2O:N2 partitioning of N2O and N2 losses from a subtropical acid-sulphate soil under sugarcane production using the 15N gas flux method, establishing the contribution of hybrid (co- and chemo-denitrification) and heterotrophic denitrification to N2O and N2 losses. Soils were fertilised with potassium nitrate, equivalent to 25 and 50 kg N ha−1, watered close to saturation then incubated over 30 days. An innovative, fully automated incubation system coupled to an isotope-ratio mass-spectrometer enabled real time analysis of 15N2O and 15N2 at sub-diel resolution. Peak losses of N2O and N2 reached 6.5 kg N ha−1 day−1, totalling > 50 kg of N2O+N2-N ha−1. Emissions were dominated by N2, accounting for more than 57% of N2O+N2 losses, demonstrating that the reduction of N2O to N2 proceeded even under highly acidic conditions. Over 40% of N2O, but only 2% of N2 emissions, were produced via hybrid pathways. These findings demonstrate hybrid pathways are generally limited to N2O production, likely driven by high organic matter content and low soil pH, promoting both biotic, and abiotic nitrosation. Regardless of the underlying process, the magnitude of the N2O emissions demonstrates the environmental, but also the potential agronomic significance, of hybrid pathways of N2O formation for N loss from fertilised acid-sulphate soils.

A new working reference material for cassiterite oxygen isotope microanalysis

Cassiterite is the principal ore mineral for tin, and its oxygen isotope is a promising proxy to trace the origin and evolution of ore‐forming fluids, which requires precise and accurate oxygen isotopic analysis. Secondary ion mass spectrometry (SIMS) is a powerful tool for oxygen isotope analysis, especially when samples bear complicated textures, but matrix‐matched reference materials are critical for accurate microanalysis. The only available matrix‐matched reference material for cassiterite oxygen isotope analysis is Yongde‐Cst, and more reference materials are required. Here, we report Piaotang‐Cst as a potential working reference material for cassiterite oxygen isotope microanalysis. Our extensive SIMS microanalysis confirmed that Piaotang‐Cst is relatively homogeneous, with an average two standard deviations (2SD) of 0.49‰ (n = 626). The δ18OVSMOW value of Piaotang‐Cst is 5.33 ± 0.07‰ (2SD, n = 5) as determined by a conventional fluorination isotope ratio mass spectrometer. We also demonstrated that there is no measurable matrix effect caused by the variable contents of trace elements for cassiterite oxygen isotope microanalysis. We proposed that the Piaotang‐Cst can be used as a working reference material for monitoring the external reproducibility and accuracy of SIMS analysis.

Turning a 3D Printer into a HPLC Fraction Collector: A Tool for Compound-Specific Stable Isotope Measurements

Compound-specific isotope analysis (CSIA) can provide unique insights into the cycling of elements including carbon and nitrogen. One approach for CSIA is the use of high-performance liquid chromatography (HPLC) to separate compounds of interest, followed by analysis of these compounds using an elemental analyser coupled to an isotope ratio mass spectrometer. A key component of this technique is the fraction collector, which automatically collects compounds as they are separated by HPLC. Here, we present a fraction collector that is a simple adaptation of a 3D printer, and, thus, can be easily adopted by any laboratory already equipped for HPLC. In addition to the much lower cost compared to commercial alternatives, this adaptation has the advantage for CSIA that the 3D printer is able to heat the collected fractions, which is not true for many commercial fraction collectors. Heating allows faster evaporation of the solvent, so that the dried compounds can be measured by EA–IRMS immediately. The procedure can be repeated consecutively so that diluted solutions can have the compounds concentrated for analysis. Any computer-controlled HPLC can be integrated to the fraction collector used here by means of AutoIt.

Studies of Isotopic Fractionation of D/H Water Ice in Lunar Regolith

In order to study the processes related to the origin and retention of water on the surface of the Moon, an experimental setup has been created at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences (GEOKHI RAS), for the analysis of (re)sublimation processes of water ice in a vacuum at low temperatures. The temperature range for (re)sublimation varies from –100 to 0°C. The setup is connected to an Isotope Ratio Mass Spectrometer (IRMS), which allows for measuring the isotopic composition of the vapor of the evaporating substance and providing an estimation of the (re)sublimation rate under specific physicochemical conditions. The direct introduction of gases into the mass spectrometer in real-time mode sets the developed setup apart from foreign counterparts. The setup is equipped with a transparent quartz window through which the surface of the studied substance can be heated using a halogen lamp, simulating the movement of solar rays on the surface of mineral grain compositions under conditions similar to those on the lunar surface. In addition to studying gas (de)sorption on the surfaces of mineral grains of various compositions, the setup can also be used for researching the (re)sublimation of gas hydrates and CO2.

Impacts of chemical pre-treatments on the hydrogen isotope composition of clay minerals: Determining potential effects in the absence of impurities

The structural hydroxyl hydrogen (H)-isotope compositions of clay minerals are frequently used as tracers of alteration or change in paleoenvironmental and material science studies. Dissolution pre-treatments are commonly used to remove cements and H-bearing impurities prior to isotopic analysis. These pre-treatments commonly include reactions respectively with: HCl or acetic-acetate buffer, H2O2 or NaClO, and a Na-dithionite-Na-citrate-bicarbonate (DCB) solution in order to remove carbonates, organic matter, and iron (oxy)hydroxides. However, there has been inconsistent data regarding to what extent the structural hydroxyl H-isotope composition of a clay mineral is altered during exposure to these chemical pre-treatments.This study examined the “most extreme” impacts of each pre-treatment on the structural H-isotope composition of reference nontronite, montmorillonite, saponite, and kaolinite samples obtained from the Clay Minerals Society Source Clay Repository. All chemical reagents were isotopically labeled to a δ2H value ≈ +200 or +570‰, to sharply contrast the average clay starting material δ2H value ≈ –120‰. H-isotope compositions were measured before and after pre-treatments by High Temperature Elemental Conversion (TCEA) coupled with an Isotope Ratio Mass Spectrometer (IRMS). TCEA-IRMS measurements were done on potassium (K)-exchanged samples pre-dried under active vacuum at 220 °C to mitigate isotopic contamination by adsorbed water vapor.The results showed that only the H-isotope composition of kaolinite was unaffected by all pre-treatments. NaClO and DCB treatments affected the H-isotope compositions of saponite and nontronite, respectively, with the remaining pre-treatments not causing measurable changes for these two clay minerals. The HCl and H2O2 pre-treatments caused massive alteration to the H-isotope compositions for montmorillonite and are considered unadvisable for use with this clay mineral, with respect to H-isotope analysis. The study confirms the possibility of altering the H-isotope composition of clays when using common selective dissolution procedures. The choice of applied pre-treatments before H-isotope measurements for clay-bearing materials should be based on the specific properties and mineralogy of the investigated samples and the amount and type of impurities they contain.

Comparison of δ13 C analyses of individual foraminifer (Orbulina universa) shells by secondary ion mass spectrometry and gas source mass spectrometry.

The use of secondary ion mass spectrometry (SIMS) to perform micrometer-scale in situ carbon isotope (δ13 C) analyses of shells of marine microfossils called planktic foraminifers holds promise to explore calcification and ecological processes. The potential of this technique, however, cannot be realized without comparison to traditional whole-shell δ13 C values measured by gas source mass spectrometry (GSMS). Paired SIMS and GSMS δ13 C values measured from final chamber fragments of the same shell of the planktic foraminifer Orbulina universa are compared. The SIMS-GSMS δ13 C differences (Δ13 CSIMS-GSMS ) were determined via paired analysis of hydrogen peroxide-cleaned fragments of modern cultured specimens and of fossil specimens from deep-sea sediments that were either untreated, sonicated, and cleaned with hydrogen peroxide or vacuum roasted. After treatment, fragments were analyzed by a CAMECA IMS 1280 SIMS instrument and either a ThermoScientific MAT-253 or a Fisons Optima isotope ratio mass spectrometer (GSMS). Paired analyses of cleaned fragments of cultured specimens (n = 7) yield no SIMS-GSMS δ13 C difference. However, paired analyses of untreated (n = 18) and cleaned (n = 12) fragments of fossil shells yield average Δ13 CSIMS-GSMS values of 0.8‰ and 0.6‰ (±0.2‰, 2 SE), respectively, while vacuum roasting of fossil shell fragments (n = 11) removes the SIMS-GSMS δ13 C difference. The noted Δ13 CSIMS-GSMS values are most likely due to matrix effects causing sample-standard mismatch for SIMS analyses but may also be a combination of other factors such as SIMS measurement of chemically bound water. The volume of material analyzed via SIMS is ~105 times smaller than that analyzed by GSMS; hence, the extent to which these Δ13 CSIMS-GSMS values represent differences in analyte or instrument factors remains unclear.

Sample pretreatment effects on isotopic compositions of oxygen and sulfur in BaSO4 derived from atmospheric sulfate.

Preparation of BaSO4 from samples of atmospheric rain, snow, and aerosols has been used for δ18 O and δ34 S analyses. In the present study, we investigated the effect of various sample pretreatments on δ18 O and δ34 S values determined from a Na2 SO4 reagent solution and samples of atmospheric precipitation to improve assay time and cost efficiency. BaSO4 was prepared from a Na2 SO4 solution by (a) evaporative concentration, (b) evaporation to dryness, (c) evaporation to dryness after adding HCl, and (d) evaporation to concentration after adding HCl, followed by cooling and then precipitation using a BaCl2 solution. To analyze the atmospheric precipitation samples for δ18 O, BaSO4 prepared from the samples was treated with diethylenetriaminepentaacetic acid (DTPA) and SO4 2- and separated chromatographically. The values of δ18 O and δ34 S were measured using a continuous-flow elemental analyzer coupled to an isotope-ratio mass spectrometer. The δ34 S values in BaSO4 precipitated from Na2 SO4 solution determined by methods (a)-(c) were consistent within precisions of ±0.5‰. The δ18 O values of methods (a) and (b) were consistent within ±0.2‰, whereas the δ18 O values of methods (c) and (d) increased with increasing HCl concentrations. Similar results were obtained from samples of atmospheric precipitations. The δ18 O values from DTPA-treated BaSO4 were consistent with those obtained by chromatographic separation within ±0.5‰. We found no significant differences in the effects of various pretreatments (acidification, heating, concentration, and drying) on δ18 O and δ34 S values in sulfate from samples of atmospheric precipitation and aerosols extracted as BaSO4 if HCl was not added to the sample before heating and BaSO4 was treated with DTPA for the δ18 O analysis.

Studies of Isotopic Fractionation of D/H Water Ice in Lunar Regolith

In order to study the processes related to the origin and retention of water on the surface of the Moon, an experimental setup has been created at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences (GEOKHI RAS), for the analysis of (re)sublimation processes of water ice in a vacuum at low temperatures. The temperature range for (re)sublimation varies from –100 to 0°C. The setup is connected to an Isotope Ratio Mass Spectrometer (IRMS), which allows for measuring the isotopic composition of the vapor of the evaporating substance and providing an estimation of the (re)sublimation rate under specific physicochemical conditions. The direct introduction of gases into the mass spectrometer in real-time mode sets the developed setup apart from foreign counterparts. The setup is equipped with a transparent quartz window through which the surface of the studied substance can be heated using a halogen lamp, simulating the movement of solar rays on the surface of mineral grain compositions under conditions similar to those on the lunar surface. In addition to studying gas (de)sorption on the surfaces of mineral grains of various compositions, the setup can also be used for researching the (re)sublimation of gas hydrates and CO2.

Revision of an open-split-based dual-inlet system for elemental and isotope ratio mass spectrometers with a focus on clumped-isotope measurements

Abstract. In this work, we present a revision of an open-split-based dual-inlet system for elemental and isotope ratio mass spectrometers (IRMSs), which was developed by the division of Climate and Environmental Physics of the University of Bern 2 decades ago. Besides discussing the corresponding improvements we show that with this inlet system (NIS-II, New Inlet System II) external precisions can be achieved that are high enough to perform measurements of multiply substituted isotopologues (clumped isotopes) on pure gases. For clumped-isotope ratios 35/32 and 36/32 of oxygen, we achieved standard deviations of 3.4×10-9 and 4.9×10-9, respectively, that we calculated from 60 interval means (20 s integration) of pure-oxygen gas measurements. Moreover, we report various performance tests and show that delta values of various air components can be measured with precisions of the order of tens of per meg and higher with the NIS-II. In addition, we demonstrate that our new open-split-based dual-inlet system allows us to measure some of these delta values with significantly higher precisions than an NIS-I (precursor of the NIS-II) and conventional changeover-valve-based dual-inlet systems (tests performed with two dual-inlet systems built by Elementar and Thermo Finnigan). Especially, our measurements point out that our inlet system provides reliable results at short idle times (20 s) and that the corresponding data do not need to be corrected for non-linearity. However, the sample consumption of our open-split-based dual-inlet system is several orders of magnitude higher than that of changeover-valve-based ones (0.33 sccm versus 0.005 sccm; standard cubic centimetres per minute). Due to the successful preliminary tests regarding measurements of clumped-isotope ratios, we will continue our work in this area to perform clumped-isotope studies according to common practices.

Triple oxygen stable isotope analysis of nitrite measured using continuous flow isotope ratio mass spectrometry

Oxygen stable isotopes (i.e., 16O, 17O, 18O) of nitrite (NO2−) are useful for investigating chemical processes and sources contributing to this important environmental contaminant and nutrient. However, it remains difficult to quantify the oxygen isotope compositions of NO2− due to the lack of internationally recognized NO2− reference materials with a well-known Δ(17O) value. Here we have adopted a combination of methodologies to develop a technique for measuring Δ(17O) of NO2− by reducing nitrate (NO3−) materials with internationally recognized Δ(17O) values to NO2− using activated cadmium catalyzed by chloride in a basic solution while conserving Δ(17O). The NO3− reference materials reduced to NO2− and sample NO2− unknowns are converted to N2O using sodium azide/acetic acid reagent and decomposed to O2 by passing through a heated gold tube and introduced into a continuous flow isotope ratio mass spectrometer for analysis at m/z 32, 33, and 34 for Δ(17O) quantification.The adapted method involves the following main points:•NO3− reference materials with internationally recognized oxygen isotope composition are reduced to NO2− under high pH conditions that conserve Δ(17O) values.•The NO3− reference materials reduced to NO2− and sample NO2− with unknown Δ(17O) values are reduced to N2O using chemical methods involving sodium azide/acetic acid.•The product N2O is extracted, purified, decomposed to O2, and analyzed for its isotope composition using a continuous flow isotope ratio mass spectrometer for Δ(17O) quantification. The Δ(17O) of NO2− samples are calibrated with respect to the NO3− reference materials with known Δ(17O) values.

Understanding trophic transference role in mercury biomagnification and bioaccumulation in the Atlantic spotted dolphin (Stenella frontalis)

Mercury is a metal of toxicological importance that occurs naturally. However, its concentration can be affected by anthropogenic activities and has the potential to bioaccumulate and biomagnify in food webs. Thus, knowing how its concentration varies along the trophic levels allows us to understand its potential risks to the biota. The present study aimed to investigate mercury transfer through the Stenella frontalis food web in Ilha Grande Bay (IGB), Rio de Janeiro state, Brazil. Samples of muscle and liver of S. frontalis were obtained from carcasses (n = 8) found stranded in the IGB, and its potential prey species were collected in fishing landings in the same Bay (n = 145). Total mercury (THg) concentrations were determined by atomic absorption spectrometry, and the δ15N was determined by an isotope ratio mass spectrometer. To investigate how trophic transfer affects mercury contamination in biota, six linear models were applied between THg logarithmic concentrations and δ15N or trophic position (TP). The trophic magnification factor (TMF) was calculated from each model to estimate the trophic transfer. Mean THg concentration in S. frontalis was higher in the liver than in muscle, but no correlation was found with age and δ15N values. Instead, the hepatic and muscular THg concentrations positively correlated with the trophic position. In the summer, THg concentration, TP, and δ15N values in prey species varied significantly, as well as in the winter, except for THg concentration. All trophic transfer models were significant in both seasons, and the TMF >1. The present study showed that trophic transfer is an essential factor in mercury biomagnification in both seasons but is not the unique driver. Both δ15N and TP could explain mercury trophic transfer, but TP better integrates metabolic diversity and seasonality.

Quantification of methane emissions in Hamburg using a network of FTIR spectrometers and an inverse modeling approach

Abstract. Methane (CH4) is a potent greenhouse gas, and anthropogenic CH4 emissions contribute significantly to global warming. In this study, the CH4 emissions of the second most populated city in Germany, Hamburg, were quantified with measurements from four solar-viewing Fourier transform infrared (FTIR) spectrometers, mobile in situ measurements, and an inversion framework. For source type attribution, an isotope ratio mass spectrometer was deployed in the city. The urban district hosts an extensive industrial and port area in the south as well as a large conglomerate of residential areas north of the Elbe River. For emission modeling, the TNO GHGco (Netherlands Organisation for Applied Scientific Research greenhouse gas and co-emitted species emission database) inventory was used as a prior for the inversion. In order to improve the inventory, two approaches were followed: (1) the addition of a large natural CH4 source, the Elbe River, which was previously not included in the inventory, and (2) mobile measurements were carried out to update the spatial distribution of emissions in the TNO GHGco gridded inventory and derive two updated versions of the inventory. The addition of the river emissions improved model performance, whereas the correction of the spatial distribution with mobile measurements did not have a significant effect on the total emission estimates for the campaign period. A comparison of the updated inventories with emission estimates from a Gaussian plume model (GPM) showed that the updated versions of the inventory match the GPM emissions estimates well in several cases, revealing the potential of mobile measurements to update the spatial distribution of emission inventories. The mobile measurement survey also revealed a large and, at the time of the study, unknown point source of thermogenic origin with a magnitude of 7.9 ± 5.3 kg h−1 located in a refinery. The isotopic measurements show strong indications that there is a large biogenic CH4 source in Hamburg that produced repeated enhancements of over 1 ppm which correlated with the rising tide of the river estuary. The CH4 emissions (anthropogenic and natural) of the city of Hamburg were quantified as 1600 ± 920 kg h−1, 900 ± 510 kg h−1 of which is of anthropogenic origin. This study reveals that mobile street-level measurements may miss the majority of total methane emissions, potentially due to sources located within buildings, including stoves and boilers operating on natural gas. Similarly, the CH4 enhancements recorded during the mobile survey from large-area sources, such as the Alster lakes, were too small to generate GPM emission estimates with confidence, but they could nevertheless influence the emission estimates based on total column measurements.

Status report of the first AMS laboratory in the Czech Republic at the Nuclear Physics Institute, Řež

The first accelerator mass spectrometry (AMS) laboratory in the Czech Republic has been established and put into routine operation in February 2022. Here we briefly describe the facilities available, namely a 300 kV multi-isotope low-energy AMS system (MILEA) capable of determination 10Be, 14C, 26Al, 41Ca, 129I, isotopes of U, especially 236U, Pu and other actinoids, and accessories for 14C measurements, which include a gas interface system, a preparative gas chromatography system for compound-specific radiocarbon dating analysis, and an isotope-ratio mass spectrometer. The first results achieved for separation and measurement of the above radionuclides (except for 41Ca) are also reported, with the main focus on 14C measurements. A specimen breakdown of 729 graphitised samples analysed for 14C so far is presented, as well as a proof of measurement stability of the MILEA system obtained by analysis of radiocarbon standards and analytical blanks. For the other radionuclides, well proven or novel procedures for sample preparation and measurement are presented.

Temporal and Seasonal Variations of Silicate Svratka River and Sediment Characterization, Czech Republic: Geochemical and Stable Isotopic Approach

This study investigated weathering and hydrobiogeochemical processes in a silicate dominated watershed (Svratka river) in the Czech Republic in comparison with nearby carbonate dominated catchments. Elemental and isotopic analysis of river waters, particulates and sediments provided a more holistic view of weathering contributions, anthropogenic contamination, biological activity and evasion or sinks of CO2 to the atmosphere. In water samples, we determined total alkalinity after Gran 1974, and cations and anions were determined with inductively coupled plasma–optical emission spectrometer and ion chromatograph. δ13CDIC in water samples was determined with isotope ratio mass spectrometer. pCO2 and saturation indexes of calcite and dolomite were calculated with PHREEQC speciation program. Evasion fluxes were calculated after Broecker, 1974. Isotopic composition of carbon and nitrogen in particulate matter and sediments were determined with isotope ratio mass spectrometer. Mineral composition of sediments was determined with XRD method and elements with XRF method. Further enrichment factors of elements were calculated. The Svratka river, which is the major tributary of the Dyje river, is dominated by Ca2+ > Na+ > Mg2+ > K+ and HCO3− (as total alkalinity). Partial pressure (pCO2) concentrations range from close to 0–572-fold of atmospheric pressure. Isotopic composition of carbon in dissolved inorganic carbon (δ13CDIC) value ranged from − 13.3 to − 8.0‰ reflecting degradation of organic matter and exchange with the atmosphere. Bicarbonate weathering intensity for the Svratka river at its mouth is 11.8 mol/(l⋅km2⋅s), more on par with silicate terrains and lower than nearby carbonate watersheds. Isotopic composition of carbon (δ13C) and isotopic composition of nitrogen (δ15N) values of river sediment reflect soil and temperate plant (C3 plant) values, while higher δ15N values could be attributed to application of organic fertilizers in lower reaches. The river sediments, which came from weathering of crystalline rocks, are dominated by silt size, geochemically less mature quartz, feldspar and muscovite particles. All the stream sediments examined revealed slightly increased amounts of Zn, Cu and Pb. However, using Al as the normalization element to calculate enrichment factors, Zn, Cu and Pb are only elevated downstream, related to industrial contamination. This study is important for local and global level since it deals with contribution of weathering rates and contribution of CO2 to the atmosphere in silicate watershed.

Seasonal variation in trophic niches and niche overlap between native and introduced cyprinid fishes

It is critical to understand the potential effects of non-native species, especially on ecologically similar native species, and to reveal their trophic relationships. Cyprinid invasive fishes, Carassius gibelio, and translocated fish Cyprinus carpio has been introduced to the Karacaören I reservoir located in the upstream reach of the Aksu River basin. Karacaören reservoir is also an important local habitat for native Cyprinid fishes, Capoeta antalyensis and Squalius fellowesii. In this study, we evaluated the trophic structure and interspecies trophic interactions (as isotopic niches and niche overlaps) of these Cyprinid fish using stable C and N isotopes analysis as measured by Isotope Ratio Mass Spectrometer. While equally all food sources contributed to the biomass of all fish species in the summer, their biomass is supported by more specialized sources in the winter season. Our results revealed increased niche breadth with increased niche overlap between C. antalyensis and C. gibelio, and C. carpio, and among C. gibelio and C. carpio in the summer, while decreased niche breadth with decreased niche overlap in the winter season. Interspecific competition has led to trophic niche divergence, which may facilitate the coexistence of native species with introduced fishes. Non-native fish were determined to have larger niche widths, which may contribute to their invasion success.

δ13C as a tool for iron and phosphorus deficiency prediction in crops.

Many studies proposed the use of stable carbon isotope ratio (δ13C) as a predictor of abiotic stresses in plants, considering only drought and nitrogen deficiency without further investigating the impact of other nutrient deficiencies, that is, phosphorus (P) and/or iron (Fe) deficiencies. To fill this knowledge gap, we assessed the δ13C of barley (Hordeum vulgare L.), cucumber (Cucumis sativus L.), maize (Zea mays L.), and tomato (Solanum lycopersicon L.) plants suffering from P, Fe, and combined P/Fe deficiencies during a two-week period using an isotope-ratio mass spectrometer. Simultaneously, plant physiological status was monitored with an infra-red gas analyzer. Results show clear contrasting time-, treatment-, species-, and tissue-specific variations. Furthermore, physiological parameters showed limited correlation with δ13C shifts, highlighting that the plants' δ13C, does not depend solely on photosynthetic carbon isotope fractionation/discrimination (Δ). Hence, the use of δ13C as a predictor is highly discouraged due to its inability to detect and discern different nutrient stresses, especially when combined stresses are present.

Isotopic comparison and correlation of δ<sup>13</sup>C between bulk wood and cellulose of <i>Vitis vinifera</i> L.

This study aims to compare the δ13C isotopic signal between bulk wood and α-cellulose in wood samples from the main trunk of Vitis vinifera L. to verify whether α-cellulose extraction is necessary for ecophysiological studies in this species. A pool of samples from different cultivars and provenances was analysed. The wood samples were obtained from cross sections of the main trunk of the plants, from where the annual growth rings were anatomically recognised, dated to the year of formation, and then separated. Each ring comprised both early- and latewood portions. For each sample, a part was saved as bulk wood and another part was destined for α-cellulose extraction. The δ13C isotopic signal in both types of samples was performed on a Vario Micro Cube elemental analyser coupled to a continuous flow mode to an isotope ratio mass spectrometer. A least squares regression was used to verify the correlation between the two variables. The results showed that the correlation coefficient of the isotopic signal for both types of samples was 0.86, and the slope of the regression line was not significantly different from one. Those results indicated that it is acceptable to use bulk wood instead of α-cellulose for δ13C isotopic studies in Vitis vinifera. This study is the first to compare isotopic δ13C signals between bulk wood and α-cellulose in grapevines. Therefore, this study constitutes a starting point to explore dendrochemical techniques based on the analysis of the δ13C content in Vitis vinifera wood, with the aim of deepening the ecophysiological knowledge of the grapevine in relation to water economy strategies and the links with climate variability and change.