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824 Ergebnisse:

Mid-twentieth century increases in anthropogenic Pb, Cd and Cu in central Asia set in hemispheric perspective using Tien Shan ice core
Atmospheric Environment (2016)
B. Grigholm, P.A. Mayewski, V. Aizen, K. Kreutz, C.P. Wake, E. Aizen, S. Kang, K.A. Maasch, M.J. Handley, S.B. Sneed

High-resolution major and trace element (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Li, Mn, Na, Pb, S, Ti, and V) ice core records from Inilchek glacier (5120 m above sea level) on the northwestern margin of the Tibetan Plateau provide the first multi-decadal ice core record spanning the period 1908–1995 AD in central Tien Shan. The trace element records reveal pronounced temporal baseline trends and concentration maxima characteristic of post-1950 anthropogenic emissions. Examination of Pb, Cd and Cu concentrations, along with non-crustal calculation estimates (i.e. excess (ex) and enrichment factor (EF)), reveal that discernable anthropogenic inputs began during the 1950s and rapidly increased to the late-1970s and early 1980s, by factors up to of 5, 6 and 3, respectively, relative to a 1910–1950 means. Pb, Cd and Cu concentrations between the 1950s-1980s are reflective of large-scale Soviet industrial and agricultural development, including the growth of production and/or consumption of the non-ferrous metals, coal and phosphate fertilizers. NOAA HYSPLIT back-trajectory frequency analysis suggests pollutant sources originating primarily from southern Kazakhstan (e.g. Shymkent and Balkhash) and the Fergana Valley (located in Kazakhstan, Uzbekistan and Kyrgyzstan). Inilchek ice core Pb, Cd and Cu reveals declines during the 1980s concurrent with Soviet economic declines, however, due to the rapid industrial and agricultural growth of western China, Pb, Cd and Cu trends increase during the 1990s reflecting a transition from primarily central Asian sources to emission sources from western China (e.g. Xinjiang Province).

PRELIMINARY INVESTIGATION OF SEASONAL PATTERNS RECORDED IN THE OXYGEN ISOTOPE COMPOSITIONS OF THEROPOD DINOSAUR TOOTH ENAMEL
PALAIOS (2016)
JEAN GOEDERT, ROMAIN AMIOT, LARBI BOUDAD, ERIC BUFFETAUT, FRANÇOIS FOUREL, PASCAL GODEFROIT, NAO KUSUHASHI, VARAVUDH SUTEETHORN, HAIYAN TONG, MAHITO WATABE, CHRISTOPHE LÉCUYER

Oxygen isotope compositions of tooth enamel increments in theropod dinosaurs are investigated as potential proxies of climate seasonality. Six teeth of large carnivorous theropods collected from four Cretaceous formations deposited under contrasted climates have been sampled. These teeth have been analyzed for the oxygen isotope compositions of their apatite phosphate ({delta}18Op) through incremental sampling performed along the major growth axis. Significant fluctuations in oxygen isotope compositions along the growth axis of each tooth are observed and interpreted as reflecting seasonality in ingested local surface water {delta}18Ow values. Fluctuations in {delta}18Op values of theropod teeth from the Aptian of Thailand and Cenomanian of Morocco vary similarly to meteoric water {delta}18Omw values occurring today in sub-tropical regions subjected to large seasonal amounts of precipitations. A dinosaur tooth recovered from the more inland and mid-latitude Nemegt Formation of Mongolia shows a seasonal pattern similar to present-day cold temperate and continental climate. Finally, the high latitude and coastal Kakanaut Formation (Russia) experienced strongly dampened seasonal variations, most likely due to the influence of warm Pacific oceanic currents. Such conditions occur today in high latitude regions submitted to marine influence. These results further highlight the potential of using the oxygen isotope compositions of large theropod teeth to reconstruct past seasonal variations of terrestrial climates. Increased knowledge of past seasonality may help to better understand the complex interactions between climate and the dynamics of land biodiversity in terms of ecological adaptations, biogeography and the evolutionary history of organisms.
Schlagworte: O , ge , ec , cc , EA

Isotope-based partitioning of streamflow in the oil sands region, northern Alberta: Towards a monitoring strategy for assessing flow sources and water quality controls
Journal of Hydrology: Regional Studies (2016)
J.J. Gibson, Y. Yi, S.J. Birks

STUDY REGION This study is based on the rapidly developing Athabasca Oil Sands region, northeastern Alberta. STUDY FOCUS Hydrograph separation using stable isotopes of water is applied to partition streamflow sources in the Athabasca River and its tributaries. Distinct isotopic labelling of snow, rain, groundwater and surface water are applied to estimate the contribution of these sources to streamflow from analysis of multi-year records of isotopes in streamflow. NEW HYDROLOGICAL INSIGHTS FOR THE REGION The results provide new insight into runoff generation mechanisms operating in six tributaries and at four stations along the Athabasca River. Groundwater, found to be an important flow source at all stations, is the dominant component of the hydrograph in three tributaries (Steepbank R., Muskeg R., Firebag R.), accounting for 39–50% of annual streamflow. Surface water, mainly drainage from peatlands, is also found to be widely important, and dominant in three tributaries (Clearwater R., Mackay R., Ells R.), accounting for 45–81% of annual streamflow. Fairly limited contributions from direct precipitation illustrate that most snow and rain events result in indirect displacement of pre-event water by fill and spill mechanisms. Systematic shifts in regional groundwater to surface-water ratios are expected to be an important control on spatial and temporal distribution of water quality parameters and useful for evaluating the susceptibility of rivers to climate and development impacts.

Bitumen in potsherds from two Apulian Bronze Age settlements, Monopoli and Torre Santa Sabina: Composition and origin
Organic Geochemistry (2016)
Marianna Faraco, Antonio Pennetta, Daniela Fico, Giacomo Eramo, Enkeleida Beqiraj, Italo Maria Muntoni, Giuseppe Egidio De Benedetto

Bitumen was found to occur on archaeological potsherds collected from two Apulia Middle Bronze Age sites, Monopoli and Torre Santa Sabina (Italy). Bitumen from two different areas, Majella (Italy) and Selenicë (Albania), were analyzed as potential reference samples to assess the geographic origin of the archaeological bitumen using geochemical analytical techniques. Analysis of the archaeological samples from different layers at both sites showed that the bitumen possesses the same gross composition and biomarker distribution patterns. Sterane and terpane profiles from the archaeological samples were very similar to some of the geological samples collected from Selenicë. In both archeological and selected Selenicë samples, sterane distributions were dominated by the C29 homologues (46–54%), followed by the C27 (26–33%) and C28 homologues (ca. 21%). Other biomarkers, such as gammacerane and oleanane, as well as the stable carbon isotopic composition of the asphaltene fraction, also suggest that the bitumen from the two archaeological sites was imported from Albania during Middle Bronze Age.

Preliminary analysis of beak stable isotopes (δ13C and δ15N) stock variation of neon flying squid, Ommastrephes bartramii, in the North Pacific Ocean
Fisheries Research (2016)
Zhou Fang, Katherine Thompson, Yue Jin, Xinjun Chen, Yong Chen

Stable isotopes (13C and 15N) have been confirmed as a useful tool for understanding trophic position and related dietary variation in squid. In this study, we performed isotopic analysis on Ommastrephes bartramii beaks to examine differences between the eastern and western stocks in the North Pacific Ocean. Isotopic values of the upper beak (UB) and the lower beak (LB) were also compared. A generalized additive model (GAM) was used to select variables that explain stock variation. Isotopic signatures (δ13C and δ15N) were significantly different between the two stocks whereas there was no difference in C/N ratios. All isotopic values were significantly different between the UB and LB. Trophic niche width was distinct between two stocks with little overlap. The δ13C signature increased with latitude and mantle length (ML) with greater variability in the eastern stock. None of the variables could explain the variation in δ13C values for the western stock. The δ15N signature increased rapidly with ML in the eastern stock, whereas δ15N gradually increased with latitude and ML in the western stock. The isotopic variations can be successfully explained by different migration patterns and feeding behaviors of the two stocks. The δ13C and δ15N values of the UB were lower than those of the LB, possibly due to variable chitin/protein ratios at different developmental stages. Future studies should account for a greater sample size and the functionality of the UB.

GEOCHEMICAL CHARACTERIZATION OF THE PERMIAN-TRIASSIC TRANSITION AT OUTCROP, CENTRAL SAUDI ARABIA
Journal of Petroleum Geology (2016)
H. A. Eltom, O. M. Abdullatif, L. O. Babalola, M. A. Bashari, M. Yassin, M. S. Osman, A. M. Abdulraziq

This study presents the results of chemostratigraphic analyses and spectral gamma-ray logging integrated with sedimentological data across the Permian-Triassic boundary at a measured outcrop section in central Saudi Arabia. The studied section encompasses the uppermost part of the Midhnab Member and the Lower and Upper Khartam Members of the Khuff Formation. Lithofacies were interpreted to have been deposited in subtidal, tidal to supratidal, lacustrine and meandering fluvial / flood plain, marginal marine and lagoonal depositional environments. Integration of bulk geochemical and carbon isotope (δ13C) data allowed the identification of a stratigraphic interval with a negative shift in δ13C ratio values, which was interpreted to correspond to the end-Permian mass extinction event. The end of this “first negative shift in δ13C values” is taken to mark the Permian-Triassic boundary. Above this boundary and just below an interval containing scattered thrombolites, a second negative shift in δ13C ratios was observed, and corresponds to an interval with long-term uranium depletion as indicated by the bulk sediment geochemical and spectral gamma-ray uranium data. The Permian-Triassic boundary (PTrB) was placed at the transition between marginal-marine and subtidal deposits. This stratigraphic position corresponds to the end of the “first negative δ13C shift” and the point of greatest uranium depletion. Although previous studies on outcrops of the Khuff Formation in Saudi Arabia identified a major sequence boundary between the Lower and Upper Khartam Members and interpreted it as the P TrB, no evidence is presented in this study for exposure and dissolution at this surface. Accordingly, the Permian-Triassic transition is placed in the transgressive portion of the Upper Khartam Member, while the sequence boundary below is interpreted to correspond to the end-Permian extinction. Correlation of Khuff time-equivalent units in the Arabian Plate is challenging, and this study will contribute to an improved understanding of this important stratigraphic unit, which contains prolific non-associated gas reservoirs. The identification of the Permian-Triassic boundary in central Saudi Arabia will help in the construction of a sequence-stratigraphic scheme for the Khuff, and with the correlation of lithofacies within this heterogeneous reservoir unit.
Schlagworte: C , ge , oi , MC

Origin and availability of organic matter leading to arsenic mobilisation in aquifers of the Red River Delta, Vietnam
Applied Geochemistry (2016)
Elisabeth Eiche, Michael Berg, Sarah-Madeleine Hönig, Thomas Neumann, Vi Mai Lan, Thi Kim Trang Pham, Hung Viet Pham

Groundwater arsenic (As) concentrations in the Red River Delta (Vietnam) are often patchy and related to the microbially induced reduction of Fe oxy-hydroxides. In this study, we explored the influence of the origin, composition and availability of natural organic matter on the hydrochemical variability in the aquifers of Van Phuc. Carbon isotope signatures (δ13Corg) and C/N ratios were assessed in combination with lithology, geochemistry, hydrochemistry, hydrology and the distribution of specific biomarkers. The elationship of C/N ratios and δ13Corg distinguished four groups of sediment types that differ in their organic carbon sources. This includes organic carbon originating predominantly from vascular C3 plants (C/N: 15.4–21.0, δ13Corg: −28.6 to −26.7‰), C4 plants (C/N: 10.6; δ13Corg: −14.8‰), freshwater derived particulate organic carbon (C/N: ≤8; δ13Corg:≤−24‰) as well as mixtures incorporating both sources. At the high As sites, we found particulate organic carbon (POC) being 1–2‰ less depleted in δ13Corg than at low As sites. More importantly, however, our assessment shows that, the availability of organic matter has to be considered decisive with regard to groundwater As contamination. Fine-grained clayey sediments overlaying sands generally protect organic matter from substantial degradation and its leaching into an adjacent aquifer. However, at the sites that are high in dissolved As in Van Phuc, sediment layers rich in organic matter are hydraulically connected to the underlying aquifer. Here, soluble organic matter seeping into the aquifer can induce and/or enhance reducing conditions, thereby mobilising As from Fe oxy-hydroxides. Our study shows that both the clay content as well as the origin of organic matter are largely controlled by the depositional environment of the sediments.

Exercise performed immediately after fructose ingestion enhances fructose oxidation and suppresses fructose storage.
The American journal of clinical nutrition (2016)
Léonie Egli, Virgile Lecoultre, Jérémy Cros, Robin Rosset, Anne-Sophie Marques, Philippe Schneiter, Leanne Hodson, Laure Gabert, Martine Laville, Luc Tappy

BACKGROUND: Exercise prevents the adverse effects of a high-fructose diet through mechanisms that remain unknown. OBJECTIVE: We assessed the hypothesis that exercise prevents fructose-induced increases in very-low-density lipoprotein (VLDL) triglycerides by decreasing the fructose conversion into glucose and VLDL-triglyceride and fructose carbon storage into hepatic glycogen and lipids. DESIGN: Eight healthy men were studied on 3 occasions after 4 d consuming a weight-maintenance, high-fructose diet. On the fifth day, the men ingested an oral (13)C-labeled fructose load (0.75 g/kg), and their total fructose oxidation ((13)CO2 production), fructose storage (fructose ingestion minus (13)C-fructose oxidation), fructose conversion into blood (13)C glucose (gluconeogenesis from fructose), blood VLDL-(13)C palmitate (a marker of hepatic de novo lipogenesis), and lactate concentrations were monitored over 7 postprandial h. On one occasion, participants remained lying down throughout the experiment [fructose treatment alone with no exercise condition (NoEx)], and on the other 2 occasions, they performed a 60-min exercise either 75 min before fructose ingestion [exercise, then fructose condition (ExFru)] or 90 min after fructose ingestion [fructose, then exercise condition (FruEx)]. RESULTS: Fructose oxidation was significantly (P < 0.001) higher in the FruEx (80% ± 3% of ingested fructose) than in the ExFru (46% ± 1%) and NoEx (49% ± 1%). Consequently, fructose storage was lower in the FruEx than in the other 2 conditions (P < 0.001). Fructose conversion into blood (13)C glucose, VLDL-(13)C palmitate, and postprandial plasma lactate concentrations was not significantly different between conditions. CONCLUSIONS: Compared with sedentary conditions, exercise performed immediately after fructose ingestion increases fructose oxidation and decreases fructose storage. In contrast, exercise performed before fructose ingestion does not significantly alter fructose oxidation and storage. In both conditions, exercise did not abolish fructose conversion into glucose or its incorporation into VLDL triglycerides. This trial was registered at clinicaltrials.gov as NCT01866215.

Relict soil evidence for profound quaternary aridification of the Atacama Desert, Chile
Geoderma (2016)
Angela Ebeling, Erik Oerter, J.W. Valley, Ronald Amundson

A relict soil on a late Tertiary/early Quaternary gravelly alluvial fan in the southern Atacama Desert was studied to determine if evidence of Quaternary climate change was evident in the profile. Stratigraphic relations of soil morphological features indicated that the initial phase of soil development was extensive chemical weathering with the loss of Si, Na, etc. and the formation of secondary clay. This was then followed by a prolonged period of carbonate accumulation that has discontinuously impregnated the earlier formed argillic horizons. The carbonate accumulation occurred both as fine-grained accumulations that engulfed and expanded the gravelly soil matrix, and as carbonate that formed dense and continuous coatings on gravel bottoms. Overlying the carbonate is a Holocene calcareous sand unit. Stable C and O isotope profiles of the disseminated carbonate show that this material appears to have formed under conditions of low to modest plant cover and significant soil water evaporation, very similar to soils presently found at higher latitudes and altitudes in modern Argentina. Seven transects of the carbonate laminations on the gravels at 10-μm scale reveal that all show a nearly 4‰ increase in δ13C values with time over distances of approximately 150mm, and variable δ18O values. The shift in C isotope values, which is unlikely to be due to significant changes in C3 vs. C4 vegetation, reflects a profound and prolonged aridification with a corresponding lowering of plant density and soil respiration. The precise beginning of the aridification is unknown due to a lack of carbonate dating methods amenable to the time frame involved. When all changes are considered, this remarkable soil indicates that local rainfall declined from somewhere between 500 to 1000mm y−1 in the late Tertiary/early Quaternary, to the present climate of about 25mm y−1. Future work will focus on developing more precise geochronological controls, but this initial study reveals the enormous potential that carbonate-bearing relict soils have for understanding climate change.

Contrasted accumulation patterns of persistent organic pollutants and mercury in sympatric tropical dolphins from the south-western Indian Ocean
Environmental Research (2016)
Alin C. Dirtu, Govindan Malarvannan, Krishna Das, Violaine Dulau-Drouot, Jeremy J. Kiszka, Gilles Lepoint, Philippe Mongin, Adrian Covaci

Due to their high trophic position and long life span, small cetaceans are considered as suitable bioindicators to monitor the presence of contaminants in marine ecosystems. Here, we document the contamination with persistent organic pollutants (POPs) and total mercury (T-Hg) of spinner (Stenella longirostris, n =21) and Indo-Pacific bottlenose dolphins (Tursiops aduncus, n=32) sampled from the coastal waters of La Réunion (south-western Indian Ocean). In addition, seven co-occurring teleost fish species were sampled and analyzed as well. Blubber samples from living dolphins and muscle from teleosts were analyzed for polychlorinated biphenyls (PCBs), DDT and metabolites (DDTs), chlordanes (CHLs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), and polybrominated diphenyl ethers (PBDEs). Methoxylated PBDEs (MeO-PBDEs), reported as having a natural origin, were also analyzed. T-Hg levels were measured in blubber and skin biopsies of the two dolphin species. Stable isotopes δ13C and δ15N values were determined in skin of the dolphins and in the muscle of teleosts. For PCBs, HCHs and T-Hg, concentrations were significantly higher in T. aduncus than in S. longirostris. For other POP levels, intra-species variability was high. MeO-PBDEs were the dominant compounds (55% of the total POPs) in S. longirostris, while PCBs dominated (50% contribution) in T. aduncus. Other contaminants showed similar profiles between the two species. Given the different patterns of POPs and T-Hg contamination and the δ15N values observed among analyzed teleosts, dietary and foraging habitat preferences most likely explain the contrasted contaminant profiles observed in the two dolphin species. Levels of each class of contaminants were significantly higher in males than females. Despite their spatial and temporal overlap in the waters of La Réunion, S. longirostris and T. aduncus are differently exposed to contaminant accumulation.