Isotope Ratio Values Research Articles

Anion-Exchange Fibers for Improved Sample Loading in Ultra-Trace Analysis of Plutonium by Thermal Ionization Mass Spectrometry.

A new sample loading procedure was developed for isotope ratio measurements of ultratrace amounts of plutonium with thermal ionization mass spectrometry (TIMS). The goal was to determine the efficacy of a polymer fiber architecture for TIMS sample loading by following similar sample loading procedures as those used in bead loading. Fibers with diameter of approximately 100 μm were prepared from triethylamine-quaternized-poly(vinylbenzyl chloride) cross-linked with diazabicyclo[2.2.2]octane. Fiber sections (2.5 mm) were loaded with 10 pg of New Brunswick Laboratory certified reference material (NBL CRM) 128 from an 8 M HNO3 matrix and affixed to rhenium filaments with collodion. A single filament assembly was used for these analyses. Total ion counts (239Pu + 242Pu) and isotope ratios obtained from fiber-loaded filaments were compared to those measured by depositing Pu amended resin beads on the filament. Fiber loading was found to improve sensitivity, accuracy, and precision of isotope ratio measurements of plutonium when compared to the established resin bead loading method, while maintaining its simplicity. The average number of detected Pu+ counts was 180% greater, and there was a 72% reduction in standard deviation of ratio measurements when using fiber loading. An average deviation of 0.0012 (0.117%) from the certified isotope ratio value of NBL CRM Pu128 was measured when fiber loading versus a deviation of 0.0028 (0.284%) when bead loading. The fiber formation method presented in this study can be extended to other anion-exchange polymer chemistries and, therefore, offers a convenient platform to investigate the efficacy of novel polymer chemistries in sample loading for TIMS.

Profiling of heroin and assignment of provenance by 87Sr/86Sr isotope ratio analysis

Heroin manufacturing and distribution by criminal and terrorist organizations produce illicit economic benefits from the opium and heroin trade and result in devastating societal problems. Heroin chemical signatures provide important information to law enforcement and the intelligence community in order to combat the national and international heroin epidemic. Authentic (known origin) heroin samples from Southeast Asia (SEA), Southwest Asia (SWA), South America (SA) and SA-like heroin manufactured in Mexico (MEX-SA), were prepared for chemical analysis by microwave-assisted acid digestion. Strontium concentration data were acquired using inductively-coupled plasma mass spectrometry (ICP-MS). The samples having sufficient [88Sr] (1.25µg/g in the solid sample) were purified by ion exchange resin and strontium isotope ratio (87Sr/86Sr) values were measured using multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS).South American and MEX-SA heroin samples are presently the most challenging regions to differentiate by analysis of their organic compositions. The SA and MEX-SA heroin samples were correctly classified 82% and 77% of the time, respectively, when the 87Sr/86Sr values of individual authentic samples were compared to the overall mean values from the four regions. This is the first reporting on the use of 87Sr/86Sr analysis of heroin for the profiling of samples from specific geographic regions. In addition, a value of 87Sr/86Sr for the National Institute of Standards and Testing’s standard reference material NIST SRM 1570a (spinach leaves) of 0.70905±0.00002 (95% confidence interval, n=3) is also reported for the first time.

Water source of typical plants in rocky mountain area of Beijing, China

Water is the key factor limiting plant growth in seasonal arid area. In order to analyze the water sources of community plant (Platycladus orientalis, Vitex negundo var. heterophylla, Broussonetia papyrifera and Lespedeza bicolor) in Beijing mountainous area, we measured hydrogen and oxygen stable isotope ratio (δD and δ18O) values of their xylem water and potential water sources. The results showed the four species had different water sources. P. orientalis mainly absorbed water from 40-60, 60-80 and 80-100 cm soil layers, and the utilization ratio of the three layers was 23.3%-25.9%. It still grabbed water from 0-20 and 20-40 cm soil layers with the utilization ratio of 12.3% and 13.0%, respectively. V. negundo var. heterophylla mainly absorbed 60-80 and 80-100 cm depth soil water, and the utilization rate was 51.9% and 25.2%, respectively, while it barely absorbed water in other soil layers. B. papyrifera mainly absorbed 0-20 and 20-40 cm depth soil water, and the utilization rate was 47.5% and 36.8%, respectively. L. bicolor used the water from five layers, and the utilization ratio of 0-20, 20-40 and 40-60 cm layer was 21.4%-22.8%, and that of 60-80 and 80-100 cm layer was 15.2%-18.3%, respectively. The competition was higher in mixed forest of P. orientalis and L. bicolor because they had similar water sources. It was better to mix V. negundo var. heterophylla and B. papyrifera because their water sources were complementary. The results could provide reference for the best combination of plant species to restore the damaged ecological environment.

Ammonite biostratigraphy and organic carbon isotope chemostratigraphy of the early Aptian oceanic anoxic event (OAE 1a) in the Tethyan Himalaya of southern Tibet

The early Aptian oceanic anoxic event (OAE 1a) is well known in the western Tethys, the North Atlantic and the Pacific Ocean, but has not been reported in the eastern Tethys to date. In this paper, we present bulk organic carbon isotope data and ammonite biostratigraphy of a lower Aptian succession from the Gucuo area (southern Tibet). These findings document the occurrence of the OAE 1a for the first time from the eastern Tethys. The studied sequence can be attributed to the D. forbesi and D. deshayesi ammonite zones of the lower Aptian. The δ13Corg data can be correlated with published early Aptian carbon isotope records from the western Tethys and the Pacific. A distinctive negative carbon isotope excursion of 2.4‰ in the upper part of the section corresponds to segment C3 of the OAE 1a, and the following positive excursion correlates to segment C4. The absolute values of the carbon isotope ratio in the Gucuo area are higher than those of known sections in the western Tethys and equatorial Pacific. We suggest that diagenetic alteration is the major cause of the higher absolute values in the Gucuo area.

The influence of oxygen isotope exchange between CO2 and H2O in natural CO2-rich spring waters: Implications for geothermometry

Oxygen isotope ratio (δ18O) value deviations from the Meteoric Water Line with no significant change in the hydrogen isotope (δ2H) composition have been reported in naturally occurring CO2-rich waters from around the world. Here we review the effects of oxygen isotope exchange with CO2, high temperature equilibration with bedrock minerals and mineral dissolution and precipitation reactions on the CO2-rich water isotopic composition. We present two case studies from Daylesford (Australia) and Pah Tempe (Utah, USA) mineral springs, where we use a numerical geochemical modelling approach to resolve the influence of low temperature water-rock interactions and CO2 equilibration to the oxygen isotope ranges observed in the mineral waters. In both cases, we find that mineral dissolution – precipitation reactions are unlikely to have a significant effect on the groundwater isotopic compositions, and that the observed δ18O values in natural CO2 springs can be simply explained by equilibrium fractionation between water and free phase CO2. Traditionally, the interaction of CO2 and water in a natural CO2-rich groundwater setting has only been associated with water 18O depletion and this is the first study to consider 18O enrichment. We establish that in a natural setting, CO2 and water equilibration can result in water 18O depletion or enrichment, and that the change in the oxygen isotope composition ultimately depends on the initial CO2 and water δ18O values. Our new conceptual model therefore provides a mechanism to explain water 18O enrichment at ambient temperatures. This finding is critical for the use of δ18O in groundwater geothermometry and for the interpretation of natural water circulation depths: we argue that in some cases, natural waters previously interpreted as geothermal based on their oxygen isotope composition may actually have acquired their isotopic signature through interaction with CO2 at ambient temperatures.

Isotopic analysis of epidermal mucus in freshwater fishes can reveal short‐time diet variations

AbstractAlthough stable isotope analysis is a powerful tool for determining animal diets, migration patterns, and the structure of food webs in aquatic systems, the slow response of isotopic ratios in the traditionally used muscle tissue of fishes often hampers this approach. By analyzing tissues with more rapid isotopic change, this technique can be used over a finer time scale than traditional isotopic analyses. We conducted a diet‐switch experiment to compare changes in the stable carbon and nitrogen isotope ratio values (δ13C and δ15N, respectively) in epidermal mucus, fin and muscle tissues of three species of freshwater cyprinid fishes. The half‐life of the isotopic change ranged from 62 to 144 days in mucus, 57 to 202 days in fin, and 196 to 680 days in the muscle tissue. The isotope ratios in mucus changed more rapidly than those in muscle tissues in the three species examined, similarly to the previously studied three species (catfish, steelhead, freshwater goby), whereas fin showed relatively variable trends in isotopic change. Interspecific variation in the trophic discrimination factor (TDF) was particularly large in the δ13C values of fin tissue compared with those in the other two tissues. With generally rapid change and relatively invariable TDF, the use of epidermal mucus in isotope analysis instead of the widely used fin and muscle tissues is advantageous for studying short‐term changes in food habits of fishes and food web structures.

Data reduction framework for standard atomic weights and isotopic compositions of the elements

We outline a general framework to compute consensus reference values of standard atomic weights, isotope ratios, and isotopic abundances, and to evaluate associated uncertainties using modern statistical methods for consensus building that can handle mutually inconsistent measurement results. The multivariate meta-regression approach presented here is directly relevant to the work of the IUPAC Commission on Isotopic Abundances and atomic weights (CIAAW), and we illustrate the proposed method in meta-analyses of the isotopic abundances and atomic weights of zinc, platinum, antimony, and iridium.

Investigations into Pb isotope signatures in groundwater and sediments in a uranium-mineralized area

ABSTRACT: This work presents the investigation in an environment that contains uranium deposits by using Pb isotope signatures. The study area, southeast of Brazil, is characterized by the lack of surface water and, as a consequence, the groundwater plays an important role in the economy of the region, such as the supply to the uranium industry and, above all serving the needs of the local population. The objective of the present investigation is the determination of the signatures of Pb in groundwater and sediments as well as the identification of environments under influences of geogenic and/or anthropogenic sources. It was determined that the Pb in the majority of sediments was geogenic in origin. Although data from the literature, related to the environmental studies, consider 206Pb/207Pb isotopic ratio values below or close to 1.2 as an indicative of anthropogenic Pb, the 206Pb/ 207Pb determined for the majority of groundwater samples ranged from 1.14 to 1.19, and are similar to the data reported for rocks samples (1.09 to 1.96) from area with U mineralization. It was also determined that the anthropogenic influence of the uranium was restricted to a single sampling point within the mining area.

Monitoring Lead (Pb) Pollution and Identifying Pb Pollution Sources in Japan Using Stable Pb Isotope Analysis with Kidneys of Wild Rats.

Although Japan has been considered to have little lead (Pb) pollution in modern times, the actual pollution situation is unclear. The present study aims to investigate the extent of Pb pollution and to identify the pollution sources in Japan using stable Pb isotope analysis with kidneys of wild rats. Wild brown (Rattus norvegicus, n = 43) and black (R. rattus, n = 98) rats were trapped from various sites in Japan. Mean Pb concentrations in the kidneys of rats from Okinawa (15.58 mg/kg, dry weight), Aichi (10.83), Niigata (10.62), Fukuoka (8.09), Ibaraki (5.06), Kyoto (4.58), Osaka (4.57), Kanagawa (3.42), and Tokyo (3.40) were above the threshold (2.50) for histological kidney changes. Similarly, compared with the previous report, it was regarded that even structural and functional kidney damage as well as neurotoxicity have spread among rats in Japan. Additionally, the possibility of human exposure to a high level of Pb was assumed. In regard to stable Pb isotope analysis, distinctive values of stable Pb isotope ratios (Pb-IRs) were detected in some kidney samples with Pb levels above 5.0 mg/kg. This result indicated that composite factors are involved in Pb pollution. However, the identification of a concrete pollution source has not been accomplished due to limited differences among previously reported values of Pb isotope composition in circulating Pb products. Namely, the current study established the limit of Pb isotope analysis for source identification. Further detailed research about monitoring Pb pollution in Japan and the demonstration of a novel method to identify Pb sources are needed.

New data on the composition and age of rocks from the Bathymetrists Seamounts (Eastern margin of the equatorial Atlantic)

The petrology, geochemistry, and isotope ratios of volcanics dredged during the 43rd cruise of R/V Academik Ioffe on the Bathymetrists Seamounts in the eastern equatorial Atlantic have been studied. These are alkaline volcanics of basic and ultramafic compositions. Spider diagrams of the trace elements of volcanic rocks demonstrate strong fractionation, indicating formation of their primary melts from an enriched mantle source at garnet depth facies. Considering the isotope ratio values of 143Nd/144Nd, 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, and 87Sr/86Sr and the character of their variations, the volcanic mantle source was chemically heterogeneous: for various volcanic rocks it was a mixture of the mantle components HIMU with EM–1 or EM–2. Limestones dredged together with the volcanics yielded microfossils suggesting a Middle Eocene age of their formation in a carbonate platform environment.

Production and Certification of the Reference Material GSB 04‐3258‐2015 as a 143Nd/144Nd Isotope Ratio Reference

A new certified reference material, labelled GSB 04‐3258‐2015, for use as a 143Nd/144Nd isotope ratio reference has been prepared by the Institute of Geology, Chinese Academy of Geological Sciences, Beijing. Standardization Administration of the People's Republic of China provided the certification for this reference material. This report presents the reference 143Nd/144Nd isotope ratio and supporting production and certification procedures. The reference value was determined by an interlaboratory comparison of results from eleven participating laboratories using MC‐TIMS or MC‐ICP‐MS. The calibration of mass fractionation was conducted by using the exponential law, and the 143Nd/144Nd isotope ratios were normalised to the 146Nd/144Nd isotope ratio value of 0.7219. Isobaric interference of 144Sm on 144Nd was corrected using an interference‐free 147Sm/149Sm isotope ratio value for mass fractionation. GSB 04‐3258‐2015 shows sufficient homogeneity and stability for use as an international isotopic reference material. The certified value was calculated from the unweighted means of the results submitted by the participating laboratories. The 143Nd/144Nd isotope ratio value for GSB 04‐3258‐2015 is 0.512438, with a combined expanded uncertainty (k = 2) of 5 × 10−6. Reference material GSB 04‐3258‐2015 is available upon request from the Institute of Geology, Chinese Academy of Geological Sciences, and may be used for accurate interlaboratory calibration of Nd isotope analysis.

Molecular and Carbon Isotopic Compositions of n-Alkanoic Acids in Smoke from Maize Straw Combustion

Four cultivars of maize straw were burned under flaming and smoldering conditions. Smoke samples were colleted and analyzed by GC/MS and GC/C/IRMS to determine molecular and stable carbon isotopic compositions of n-alkanoic acids in them. The results showed that n-alkanoic acids in flaming smoke were composed of C7 to C34, with a mean total content of 13895.0 mg·kg-1. The average ratio values of the content for homologues with lower carbon number (≤C16) to that for ones with higher carbon number (>C16) (L/H), C18/C16, C24/C16, C24/C18, and C24/(C22+C26) (CAR) were 1.1, 0.33, 0.17, 0.50, and 1.2, respectively. Moreover, the acids exhibited a bimodal profile with peaks at C16 and C24, respectively. They had evident even to odd carbon number predominance (mean CPI: 4.5). In smoldering smoke the acids were consisted of C6 to C34, with an average total content of 50183.7 mg·kg-1. The mean ratios of L/H, C18/C16, C24/C16, C24/C18, and CAR were 1.3, 0.33, 0.20, 0.60, and 1.6, respectively. In addition, the homologues had the same distribution pattern as in flaming smoke and even to odd carbon number predominance (mean CPI=6.1). The mean carbon isotopic ratio (δ13 C) values for individual n-alkanoic acids (C14 to C26) in flaming smoke ranged from -21.0‰ to -24.8‰, the overall average of which was -23.5‰. The difference between mean δ13 C values of n-fatty acids in flaming smoke and the straw (Δ13 C) was -0.7‰. In smoldering smoke, the mean δ13 C values for the compounds varied from -21.8‰ to -25.4‰, with an overall average of -23.3‰. The Δ13 C value was up to -0.5‰. The molecular and carbon isotopic compositions of n-alkanoic acids in smoke were significantly different from those in straw matter. L/H, C24/C16, C24/C18, CAR, and δ13 C might be useful proxies to discriminate the organic pollutants in atmospheric aerosols derived from maize straw combustion.

Exploring imperial expansion using an isotopic analysis of paleodietary and paleomobility indicators in Chachapoyas, Peru.

Inca imperial strategies of political and territorial expansion varied across conquered regions depending on local ecology and cultural resistance, and Chachapoya peoples in Peru's forested northeastern Andes were renowned for their rebellions against the invaders. The cliff tombs of Los Pinchudos (AD 1470-1535) present opportunities to use stable isotopes to: (1) explore dietary and mobility patterns from a mortuary community interred at a site attributed to the poorly-known Chachapoya culture during the period of Inca domination, and (2) explore the origins of the individuals as either local or foreign (Inca). Using biochemical tracers, we can help resolve the impact of foreign influence and changes in population and social structure during imperial occupation. While it is difficult to reconstruct individual life histories from incomplete skeletons, stable isotopic analysis of multiple skeletal tissues provides a direct means of characterizing diet and residential mobility. Values of stable carbon (δ13 C), nitrogen (δ15 N), and oxygen isotope (δ18 O) ratios were determined in bone and dentine collagen and bone and enamel carbonate from 28 samples (11 paired tissues) from males, females, and juveniles from Los Pinchudos. Dietary signatures are consistent with a mixed but more C3 -based plant and protein-based diet with moderate proportions of terrestrial animals. Oxygen isotopic values demonstrate limited variation between paired tissues, with a few possible nonlocal individuals buried in one particular tomb at the site. Compared to other Andean areas that underwent imperial domination, these data do not demonstrate expected dietary shifts. These are the first isotopic data from a Chachapoya site and our research shows evidence for minimal non-local presence in this commingled burial assemblage. The regional diet reconstructed at Los Pinchudos (2850 masl) focused on resources of higher altitude tuber crops, beans, and grains (C3 ) and terrestrial protein rather than on lower elevation grasses such as maize (C4 ) as in other highland Andean regions under Inca control. During imperial domination, inhabitants of this region appropriated Inca materials goods but continued to construct tombs in the local manner even though a potentially diverse population was occupying them.

Lead isotope ratio measurements as indicators for the source of lead poisoning in Mute swans (Cygnus olor) wintering in Puck Bay (northern Poland)

Lead (Pb) poisoning is most commonly linked amongst anthropogenically-caused deaths in waterfowl and this is often associated with hunting and fishing activities. However, the exact identification of the source may be difficult with commonly-used techniques. We have studied isotope ratios using Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) to investigate the source of Pb in the blood of Mute swans (n = 49) wintering in northern Poland. We compared the values of isotopic ratios from blood and ammunition pellets available on the Polish market. The mean Pb concentrations found was 0.241 μg/g (w/w) and nearly half of the blood specimens had elevated Pb levels (higher than the cited 0.23 μg/g w/w threshold of poisoning). Only the mean 208/206 Pb isotope ratio was similar in blood and pellet samples. Mean ratios of isotopes 206/204, 206/207 and 208/207 in swans' blood and in pellets differed significantly. Moreover, coefficients of variation were higher in blood samples than in pellets. These discrepancies and significant differences in abundance of 204Pb and 207Pb isotopes in both materials indicated that pellets available today on the Polish market were not the source of Pb in the blood of Mute swans wintering in northern Poland.

Microbial degradation of the brominated flame retardant TBNPA by groundwater bacteria: laboratory and field study

In the present study, the biodegradation of the brominated flame retardant tribromoneopentylalcohol (TBNPA) by a groundwater enrichment culture was investigated using a dual carbon (13C/12C)- bromine (81Br/79Br) stable isotope analysis. An indigenous aerobic bacterial consortium was enriched from the polluted groundwater underlying an industrial site in the northern Negev Desert, Israel, where TBNPA is an abundant pollutant. Aerobic biodegradation was shown to be rapid, with complete debromination within a few days, whereas anaerobic biodegradation was not observed. Biodegradation under aerobic conditions was accompanied by a significant carbon isotope effect with an isotopic enrichment factor of ɛCbulk = −8.8‰ ± 1.5‰, without any detectable bromine isotope fractionation. It was found that molecular oxygen is necessary for biodegradation to occur, suggesting an initial oxidative step. Based on these results, it was proposed that H abstraction from the C-H bond is the first step of TBNPA biodegradation under aerobic conditions, and that the C-H bond cleavage results in the formation of unstable intermediates, which are rapidly debrominated. A preliminary isotopic analysis of TBNPA in the groundwater underlying the industrial area revealed that there are no changes in the carbon and bromine isotope ratio values downstream of the contamination source. Considering that anoxic conditions prevail in the groundwater of the contaminated site, the lack of isotope shifts in TBNPA indicates the lack of TBNPA biodegradation in the groundwater, in accordance with our findings.

Biogenic, anthropogenic and sea salt sulfate size-segregated aerosols in the Arctic summer

Abstract. Size-segregated aerosol sulfate concentrations were measured on board the Canadian Coast Guard Ship (CCGS) Amundsen in the Arctic during July 2014. The objective of this study was to utilize the isotopic composition of sulfate to address the contribution of anthropogenic and biogenic sources of aerosols to the growth of the different aerosol size fractions in the Arctic atmosphere. Non-sea-salt sulfate is divided into biogenic and anthropogenic sulfate using stable isotope apportionment techniques. A considerable amount of the average sulfate concentration in the fine aerosols with a diameter < 0.49 µm was from biogenic sources (> 63 %), which is higher than in previous Arctic studies measuring above the ocean during fall (< 15 %) (Rempillo et al., 2011) and total aerosol sulfate at higher latitudes at Alert in summer (> 30 %) (Norman et al., 1999). The anthropogenic sulfate concentration was less than that of biogenic sulfate, with potential sources being long-range transport and, more locally, the Amundsen's emissions. Despite attempts to minimize the influence of ship stack emissions, evidence from larger-sized particles demonstrates a contribution from local pollution. A comparison of δ34S values for SO2 and fine aerosols was used to show that gas-to-particle conversion likely occurred during most sampling periods. δ34S values for SO2 and fine aerosols were similar, suggesting the same source for SO2 and aerosol sulfate, except for two samples with a relatively high anthropogenic fraction in particles < 0.49 µm in diameter (15–17 and 17–19 July). The high biogenic fraction of sulfate fine aerosol and similar isotope ratio values of these particles and SO2 emphasize the role of marine organisms (e.g., phytoplankton, algae, bacteria) in the formation of fine particles above the Arctic Ocean during the productive summer months.

Prey use by three deep-sea fishes in the Emperor Seamount waters, North Pacific Ocean, as revealed by stomach contents and stable isotope analyses

We analyzed the stomach contents and nitrogen and carbon stable isotope ratios of three deep-sea fishes Pentaceros wheeleri (North Pacific armorhead), Beryx splendens (splendid alfonsino), and Allocyttus folletti (oxeye oreo)—to elucidate interspecific and intraspecific differences in prey use among demersal fishes in the Emperor Seamount waters (North Pacific Ocean). Principal component analysis using an index of relative importance revealed interspecific differences in prey use: P. wheeleri preyed on plankton and benthos; B. splendens on micronekton and plankton, and A. folletti on micronekton. The relationship between the index of relative importance in B. splendens and body length also indicated ontogenetic shifts in prey use. High percentage of empty stomachs and low stomach fullness index in P. wheeleri indicated this species’ limited feeding ability during its demersal life on seamount. Nitrogen isotope ratio analysis suggested that the trophic level of A. folletti was the highest, followed by large B. splendens, small B. splendens, and P.wheeleri. Variation in carbon isotope ratio values were small, indicating that primary producers were similar. Differences in nitrogen isotope ratio (trophic level) coincided with differences in prey use by the three fishes. Thus, these species are likely able to coexist in seamount waters by partitioning their use of benthos, plankton, and micronekton food resources. They might be supported by food supplied from the surrounding water columns by horizontal flux of plankton or vertical migration of micronekton in the deep scattering layer because except for the benthic prey of P. wheeleri they consumed plankton and micronekton.

Linkages between the circulation and distribution of dissolved organic matter in the White Sea, Arctic Ocean

The White Sea is a semi-enclosed Arctic marginal sea receiving a significant loading of freshwater (225–231km3yr−1 equaling an annual runoff yield of 2.5m) and dissolved organic matter (DOM) from river run-off. We report discharge weighed values of stable oxygen isotope ratios (δ18O) of −14.0‰ in Northern Dvina river for the period 10 May–12 October 2012. We found a significant linear relationship between salinity (S) and δ18O (δ18O=−17.66±0.58+0.52±0.02×S; R2=0.96, N=162), which indicates a dominant contribution of river water to the freshwater budget and little influence of sea ice formation or melt. No apparent brine additions from sea-ice formation is evident in the White Sea deep waters as seen from a joint analysis of temperature (T), S, δ18O and aCDOM(350) data, confirming previous suggestions about strong tidal induced vertical mixing in winter being the likely source of the deep waters. We investigated properties and distribution of colored dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in the White Sea basin and coastal areas in summer. We found contrasting DOM properties in the inflowing Barents Sea waters and White Sea waters influenced by terrestrial runoff. Values of absorption by CDOM at 350nm (aCDOM(350)) and DOC (exceeding 10m−1 and 550µmoll−1, respectively) in surface waters of the White Sea basin are higher compared to other river-influenced coastal Arctic domains. Linear relationship between S and CDOM absorption, and S and DOC (DOC=959.21±52.99–25.80±1.79×S; R2=0.85; N=154) concentrations suggests conservative mixing of DOM in the White Sea. The strongest linear correlation between CDOM absorption and DOC was found in the ultraviolet (DOC=56.31±2.76+9.13±0.15×aCDOM(254); R2=0.99; N=155), which provides an easy and robust tool to trace DOC using CDOM absorption measurements as well as remote sensing algorithms. Deviations from this linear relationship in surface waters likely indicate contribution from different rivers along the coast of the White Sea. Characteristics of CDOM further indicate that there is limited removal or change in the DOM pool before it exits to the Barents Sea.

Geochemical comparison between the gas in bulk fluid inclusions and reservoir gas produced in Paleozoic formation, Ordos Basin, China

Taking the reservoir sandstones of natural gas pools in the Upper Paleozoic and the calcite veins in Ordovician carbonate collected in the Ordos Basin, China, as samples, a unique method for geochemical analysis of gases captured in fluid inclusions (FIs) is presented in this study. Geochemical comparison between FI gases and reservoir gases in this basin is conducted. The results show that the gases from FIs developed in Upper Paleozoic reservoir sandstones and from the corresponding reservoirs share similar geochemistry in hydrocarbon gaseous compositions, although there is a high concentration of non-hydrocarbon gases (e.g. CO2) in FIs. The occurrence of FIs in sandstones and the value of the carbon isotopic ratio of carbon dioxide (δ13CCO2>−8‰) suggest that non-hydrocarbon gas in FIs originated from primary FIs formed during hosted mineral (quartz) crystallization from magma. Similar geochemistry in hydrocarbon gases from FIs and from reservoirs indicates that the gases pooled in Upper Paleozoic sandstones represent the original state charging from the source rocks and thus experienced a weak or no secondary alteration. Dominating hydrocarbon gaseous components, such as wells Lt1 and Yu9, in FI gases at a secondary formation in calcite veins of Ordovician carbonate imply that the FIs are related to oil and gas charging. The gases originated from the Lower Paleozoic source rock is characterized by δ13C1<−38‰, although there is a great difference in geochemistry of gases from FIs of different samples and from FIs and reservoirs. The heavier δ13C2 value of reservoir gas in the Lower Paleozoic reservoir compared with that of FI gases might be attributed to thermochemical sulfate reduction (TSR) after oil and gas charging into the reservoir.

The performance of single and multi-collector ICP-MS instruments for fast and reliable 34S/32S isotope ratio measurements.

The performance and validation characteristics of different single collector inductively coupled plasma mass spectrometers based on different technical principles (ICP-SFMS, ICP-QMS in reaction and collision modes, and ICP-MS/MS) were evaluated in comparison to the performance of MC ICP-MS for fast and reliable S isotope ratio measurements. The validation included the determination of LOD, BEC, measurement repeatability, within-lab reproducibility and deviation from certified values as well as a study on instrumental isotopic fractionation (IIF) and the calculation of the combined standard measurement uncertainty. Different approaches of correction for IIF applying external intra-elemental IIF correction (aka standard-sample bracketing) using certified S reference materials and internal inter-elemental IIF (aka internal standardization) correction using Si isotope ratios in MC ICP-MS are explained and compared. The resulting combined standard uncertainties of examined ICP-QMS systems were not better than 0.3–0.5% (uc,rel), which is in general insufficient to differentiate natural S isotope variations. Although the performance of the single collector ICP-SFMS is better (single measurement uc,rel = 0.08%), the measurement reproducibility (>0.2%) is the major limit of this system and leaves room for improvement. MC ICP-MS operated in the edge mass resolution mode, applying bracketing for correction of IIF, provided isotope ratio values with the highest quality (relative combined measurement uncertainty: 0.02%; deviation from the certified value: <0.002%).