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Klimaforschung

Der Klimawandel ist eine der größten Bedrohungen der menschlichen Zivilisation. Klimaszenarien der Zukunft können nur auf Basis dessen berechnet werden, was wir über die Vergangenheit wissen. Durch das Verständnis der Variabilität des Klimas und der Mechanismen, welche die globalen Klimakreisläufe beeinflussen, sind Wissenschaftler in der Lage, anspruchsvolle Modelle unseres zukünftigen Klimas zu entwickeln und liefern entscheidende Informationen für die Öffentlichkeit und Regierungen über mögliche Konsequenzen anthropogener Aktivitäten.

Die Stabilisotopenanalyse fungiert als ein virtuelles Paläothermometer, an dem vergangene Temperaturen von einer Vielzahl von Materialien wie Mikrofossilien, Eisbohrkernen und Baumringen abgelesen werden können. Durch das Kombinieren dieser Temperaturinformationen und der Extrapolation der Daten in die Zukunft sind wir in der Lage, die schlimmsten Auswirkungen des Klimawandels zu verhindern. Die Stabilisotopenanalyse wird eine entscheidene Rolle spielen, uns dabei zu helfen.

Carbonate

Klimasignale liegen am Meeresgrund in Form von sedimentierten Carbonaten altertümlicher Biota vor. Die 13C and 18O Isotopenverhältnisse dieser Materialien stehen in direktem Zusammenhang mit der Meerestemperatur und dem Zeitraum ihrer Existenz. Unser Dual Inlet System, ausgestattet mit MultiCarb, ist in der Lage, 13C and 18O Analysen von extrem kleinen Proben mit der höchsten Präzision durchzuführen, und ermöglicht die aufregend neue "clumped isotope" Analysenmethode.

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Wasseranalyse aus Eisbohrkernen

Das Isotopenverhältnis des Niederschlags ist abhängig von der Temperatur der Ozeane, aus denen das Wasser verdunstet. Eisbohrkerne aus den arktischen und antarktischen Polarregionen haben die Variation der Isotope über Jahrtausende aufgezeichnet und ermöglichen es, die Temperatur zu dem Zeitpunkt zu rekonstruieren, als das Eis entstand. Verglichen mit anderen Techniken ist unser AquaPrep ist in der Lage, höchste 18O und 2H Analysen durchzuführen, was Unsicherheiten in Ihren Temperaturproxyberechnungen reduziert.

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Treibhausgase

Treibhausgase in der Atmosphäre sind die Haupttreiber des Klimawandels. Um die Mechanismen des Klimawandels zu verstehen, ist die Entkopplung des anthropogenen Beitrags dieser Gase in die Atmosphäre von solchen, die das Ergebnis natürlicher Prozesse sind, entscheidend. Mit iso FLOW können die Isotopenverhältnisse der wichtigsten Treibhausgase CO2, N2O und CH4 in atmosphärischen Gasproben untersucht werden. Die Ergebnisse dieser Analysen können dabei helfen, Strategien zum Umgang mit dem Klimawandel zu entwickeln.

Publikationen zum Thema Klimawandel mit unseren Geräten

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115 Ergebnisse:

Improving process-based estimates of N2O emissions from soil using temporally extensive chamber techniques and stable isotopes
Nutrient Cycling in Agroecosystems (2011)
Kurt a. Smemo, Nathaniel E. Ostrom, Matthew R. Opdyke, Peggy H. Ostrom, Sven Bohm, G. Philip Robertson

Nitrous oxide (N2O) is an important greenhouse gas that is emitted from soil, but obtaining precise N2O source and sink strength estimates has been difficult due to high spatial and temporal flux variability and a poor understanding of the mechanisms controlling fluxes. Tools that improve our ability to quantify trace gas fluxes from soil and constrain annual budgets are therefore needed. Here we describe an improved chamber-based sampling system that continuously traps evolving soil gases onto molecular sieve thereby obtaining a single sample that integrates fluxes over extended periods (several weeks or more) and the use of stable isotopic methods to study microbial origins of N2O. We demonstrate that N2O can be trapped on molecular sieve within our chamber system with near 100% recovery and without isotopic fractionation. In field trials the site preference of N2O (the difference in δ15N between the central and outer N atoms) varied between −6 and 14.4‰, indicating that the majority of flux was derived from bacterial denitrification. Further development with automation would improve flux estimates by providing a system capable of capturing episodic flux events owing to long-term deployment. Further, an automated trapping chamber approach will also provide process-based understanding of N2O dynamics via stable isotopes and a new and affordable tool for evaluating the response of trace gas fluxes to land management practices.
Schlagworte: nitrogen , oxygen , soil , clim , gashead

Pervasive oxygenation along late Archaean ocean margins
Nature Geoscience (2010)
Brian Kendall, Christopher T. Reinhard, Timothy W. Lyons, Alan J. Kaufman, Simon W. Poulton, Ariel D. Anbar

The photosynthetic production of oxygen in the oceans is thought to have begun by 2.7 billion years ago, several hundred million years before appreciable accumulation of oxygen in the atmosphere. However, the abundance and distribution of dissolved oxygen in the late Archaean oceans is poorly constrained. Herewe present geochemical profiles from2.6- to 2.5-billion-year-old black shales from the Campbellrand–Malmani carbonate platform in South Africa.We find a high abundance of rhenium and a low abundance of molybdenum, which, together with the speciation of sedimentary iron, points to the presence of dissolved oxygen in the bottom waters on the platform slope. The water depth on the slope probably reached several hundred metres, implying the export ofO2 belowthe photic zone. Our data also indicate that the mildly oxygenated surface ocean gaveway to an anoxic deep ocean.We therefore suggest that the production of oxygen in the surface oceanwas vigorous at this time, butwas not sufficient to fully consume the deep-sea reductants.Onthe basis of our results and observations fromthe Hamersley basin inWestern Australia, we conclude that the productive regions along ocean margins during the late Archaean eon were sites of substantialO2 accumulation, at least 100million years before the first significant increase in atmosphericO2 concentration.
Schlagworte: sulfur , geol , clim , elem

Oxygen isotope fractionation between apatite-bound carbonate and water determined from controlled experiments with synthetic apatites precipitated at 10-37 ??C
Geochimica et Cosmochimica Acta (2010)
Christophe Lecuyer, Vincent Balter, Fran??ois Martineau, Fran??ois Fourel, Aur??lien Bernard, Romain Amiot, V??ronique Gardien, Olga Otero, Serge Legendre, G??rard Panczer, Laurent Simon, Rossana Martini

The oxygen isotope fractionation between the structural carbonate of inorganically precipitated hydroxyapatite (HAP) and water was determined in the range 10-37 ??C. Values of 1000 ln ??(CO3 2 - s(-) H2 O) are linearly correlated with inverse temperature (K) according to the following equation: 1000 ln ??(CO3 2 - s(-) H2 O) = 25.19 (??0.53)??T-1 - 56.47 (??1.81) (R2 = 0.998). This fractionation equation has a slightly steeper slope than those already established between calcite and water (O'Neil et al., 1969; Kim and O'Neil, 1997) even though measured fractionations are of comparable amplitude in the temperature range of these experimental studies. It is consequently observed that the oxygen isotope fractionation between apatite carbonate and phosphate increases from about 7.5??? up to 9.1??? with decreasing temperature from 37 ??C to 10 ??C. A compilation of ??18O values of both phosphate and carbonate from modern mammal teeth and bones confirms that both variables are linearly correlated, despite a significant scattering up to 3.5???, with a slope close to 1 and an intercept corresponding to a 1000 ln ??(CO3 2 - s(-) PO4 3 -) value of 8.1???. This apparent fractionation factor is slightly higher or close to the fractionation factor expected to be in the range 7-8??? at the body temperature of mammals. ?? 2009 Elsevier Ltd. All rights reserved.
Schlagworte: oxygen , geol , ocea , clim , mulitcarb

A gas chromatography / pyrolysis / isotope ratio mass spectrometry system for high-precision dD measurements of atmospheric methane extracted from ice cores
Rapid Communications in Mass Spectrometry (2010)
Robert Schneider, Michael Bock, Jochen Schmitt, Melanie Behrens, Lars Mo, Celia Sapart, Hubertus Fischer

Air enclosures in polar ice cores represent the only direct paleoatmospheric archive. Analysis of the entrapped air provides clues to the climate system of the past in decadal to centennial resolution. A wealth of information has been gained from measurements of concentrations of greenhouse gases; however, little is known about their isotopic composition. In particular, stable isotopologues (dDand d13C) of methane (CH4) record valuable information on its global cycle as the different sources exhibit distinct carbon and hydrogen isotopic composition. However, CH4 isotope analysis is limited by the large sample size required and the demanding analysis as high precision is required. Herewepresent a highly automated, high-precision online gas chromatography/pyrolysis/isotope ratio monitoring mass spectrometry (GC/P/irmMS) technique for the analysis of dD(CH4). It includes gas extraction from ice, preconcentration, gas chromatographic separation and pyrolysis of CH4 from roughly 500g of ice withCH4 concentrations as low as 350 ppbv. Ice samples with approximately 40mLair and only ?1nmol CH4 can be measured with a precision of 3.4%. The precision for 65mL air samples with recent atmospheric concentration is 1.5%. TheCH4 concentration can be obtained along with isotope data which is crucial for reporting ice core data on matched time scales and enables us to detect flaws in the measurement procedure. Custom-made script-based processing of MS raw and peak data enhance the system’s performance with respect to stability, peak size dependency, hence precision and accuracy and last but not least time requirement
Schlagworte: hydrogen , clim , gaschrom

15N/14N and 18O/16O stable isotope ratios of nitrous oxide produced during denitrification in temperate forest soils
Geochimica et Cosmochimica Acta (2009)
David M. Snider, Sherry L. Schiff, John Spoelstra

Anaerobic incubations of upland and wetland temperate forest soils from the same watershed were conducted under different moisture and temperature conditions. Rates of nitrous oxide (N2O) production by denitrification of nitrate (NO3 -) and the stable isotopic composition of the N2O (??15N, ??18O) were measured. In all soils, N2O production increased with elevated temperature and soil moisture. At each temperature and moisture level, the rate of N2O production in the wetland soil was greater than in the upland soil. The 15N isotope effect (??) (product - substrate) ranged from -20??? to -29???. These results are consistent with other published estimates of 15N fractionation from both single species culture experiments and soil incubation studies from different ecosystems. A series of incubations were conducted with 18O-enriched water (H2O) to determine if significant oxygen exchange (O-exchange) occurred between H2O and N2O precursors during denitrification. The exchange of H2O-O with nitrite (NO2 -) and/or nitric oxide (NO) oxygen has been documented in single organism culture studies but has not been demonstrated in soils prior to this study. The fraction of N2O-O derived from H2O-O was confined to a strikingly narrow range that differed between soil types. H2O-O incorporation into N2O produced from upland and wetland soils was 86% to 94% and 64% to 70%, respectively. Neither the temperature, soil moisture, nor the rate of N2O production influenced the magnitude of O-exchange. With the exception of one treatment, the net 18O isotope effect (??net) (product-substrate) ranged from +37??? to +43???. Most previous studies that have reported 18O isotope effects for denitrification of NO3 - to N2O have failed to account for the effect of oxygen exchange with H2O. When high amounts of O-exchange occur after fractionation during reductive O-loss, the 18O-enrichment is effectively lost or diminished and ??18O-N2O values will be largely dictated by ??18O-H2O values and subsequent fractionation. The process and extent of O-exchange, combined with the magnitude of oxygen isotope fractionation at each reduction step, appear to be the dominant controls on the observed oxygen isotope effect. In these experiments, significant oxygen isotope fractionation was observed to occur after the majority of water O-exchange. Due to the importance of O-exchange, the net oxygen isotope effect for N2O production in soils can only be determined using ??18O-H2O addition experiments with ??18O-H2O close to natural abundance. The results of this study support the continued use of ??15N-N2O analysis to fingerprint N2O produced from the denitrification of NO3 -. The utilization of 18O/16O ratios of N2O to study N2O production pathways in soil environments is complicated by oxygen exchange with water, which is not usually quantified in field studies. The oxygen isotope fractionation observed in this study was confined to a narrow range, and there was a clear difference in water O-exchange between soil types regardless of temperature, soil moisture, and N2O production rate. This suggests that 18O/16O ratios of N2O may be useful in characterizing the actively denitrifying microbial community. Crown Copyright ?? 2008.
Schlagworte: nitrogen , oxygen , clim , gashead

Multiproxy reconstruction of the palaeoclimate and palaeoenvironment of the Middle Miocene Somosaguas site (Madrid, Spain) using herbivore dental enamel
Palaeogeography, Palaeoclimatology, Palaeoecology (2009)
Laura Domingo, Jaime Cuevas-González, Stephen T. Grimes, Manuel Hernández Fernández, Nieves López-Martínez

Profound palaeoclimatic changes took place during the Middle Miocene. The Miocene Climatic Optimum (∼20 to 14–13.5 Ma) was followed by a sudden (∼200 ka) decrease in temperature and an increase in aridity around the world as a consequence of the reestablishment of the ice cap in Antarctica. Somosaguas palaeontological site (Madrid Basin, Spain) has provided a rich record of mammal remains coincident with this global event (Middle Miocene Biozone E,14.1–13.8 Ma). It contains four fossiliferous levels (T1, T3-1, T3-2 and T3-3, with T1 being the oldest) that span an estimated time of ∼105–125 ka. Scanning Electron Microscope (SEM) and Rare Earth Element (REE) analyses performed on herbivore tooth enamel (Gomphotherium angustidens, Anchitherium cf. A. cursor, Conohyus simorrensis, Prosantorhinus douvillei and ruminants) indicate that diagenetic processes have not been intense enough as to obscure the original geochemical signal. Stable isotope (δ18OCO3, δ13CCO3 and δ18OPO4) analyses have been measured on the herbivore tooth enamel across these levels with the aim of determining to what extent the global cooling and aridity pattern is recorded at this site. A decrease in δ18OCO3 and δ18OPO4 has been detected from T1 to T3-3 and T3-1 to T3-3 respectively indicating a progressive drop of about 6 °C (from around 18 °C to 12 °C) in mean annual temperatures within T3. Tooth enamel δ13C values experience an increase from T3-1 to T3-3 suggesting an increase in aridity. Ba/Ca analyses have also been performed on the tooth enamel in order to detect changes in the palaeoecology of the studied taxa. This ratio allows the establishment of particular feeding patterns such as a more browsing habit in the case of Gomphotherium angustidens compared to Anchitherium cf. A. cursor as suggested by higher Ba/Ca values in the latter. Trace elements do not support any significant change across the succession in the dietary behaviour of the species analyzed, despite the stable isotopes evidence of an important palaeoclimatic shift from T1 to T3-3
Schlagworte: carbon , oxygen , arch , ecol , clim , gashead

12C/13C kinetic isotope effects of the gas-phase reactions of isoprene, methacrolein, and methyl vinyl ketone with OH radicals
Atmospheric Environment (2009)
Richard Iannone, Ralf Koppmann, Jochen Rudolph

The stable-carbonkinetic isotopeeffects (KIEs) for thegas-phase reactionsof isoprene,methacrolein(MACR), and methyl vinyl ketone (MVK) withOHradicalswere studied in a 25 L reaction chamber at (298?2) K and ambient pressure. The timedependence of both the stable-carbon isotope ratios and the concentrationswas determined using a gas-chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The volatile organic compounds (VOCs) used in the KIE experiments had natural-abundance isotopic compositionthus KIE dataobtained fromthese experiments canbe directlyappliedto atmospheric studies of isoprene chemistry. All 12C/13/C KIE values are reported as 3 values, where 3 ¼ (KIE ? 1) ? 1000&, and KIE ¼ k12/k13. The following average stable-carbon KIEs were obtained: (6.56 ? 0.12)& (isoprene), (6.47 ? 0.27)& (MACR), and (7.58 ? 0.47)& (MVK). The measured KIEs all agree within uncertainty to an inverse molecular mass (MM) dependence of OH3(&) ¼ (487 ? 18)MM?1, which was derived from two previous studies [J. Geophys. Res. 2000, 105, 29329–29346; J. Phys. Chem. A 2004, 108, 11537–11544]. Upon adding the isoprene,MACR, andMVK OH3 values from this study, the inverseMMdependence changes only marginally toOH3(&)¼(485?14)MM?1. The additionof these isoprene OH3 values toa recentlymeasuredset of O3 3 values in an analogous study [Atmos. Environ. 2008, 42, 8728–8737] allows for estimates of the average change in the 12C/13C ratio due to processing in the troposphere

A gas chromatography/combustion/isotope ratio mass spectrometry system for high-precision d13C measurements of atmospheric methane extracted from ice core samples
Rapid Communications in Mass Spectrometry (2008)
Melanie Behrens, Jochen Schmitt, Klaus-uwe Richter, Michael Bock, Ulrike C Richter, Ingeborg Levin, Hubertus Fischer

Past atmospheric composition can be reconstructed by the analysis of air enclosures in polar ice cores which archive ancient air in decadal to centennial resolution. Due to the different carbon isotopic signatures of different methane sources high-precision measurements of d13CH4 in ice cores provide clues about the global methane cycle in the past.Wedeveloped a highly automated (continuous-flow) gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) technique for ice core samples of?200 g. The methane is melt-extracted using a purge-and-trap method, then separated from the main air constituents, combusted and measured asCO2 by a conventional isotope ratio mass spectrometer. One CO2 working standard, one CH4 and two air reference gases are used to identify potential sources of isotope fractionation within the entire sample preparation process and to enhance the stability, reproducibility and accuracy of the measurement. After correction for gravita- tional fractionation, pre-industrial air samples from Greenland ice (1831W40 years) show a d13CVPDB ofS49.54W0.13%and Antarctic samples (1530W25 years) show a d13CVPDB ofS48.00W0.12%in good agreement with published data
Schlagworte: clim , gaschrom

Nitrogen isotopes as indicators of NO(x) source contributions to atmospheric nitrate deposition across the midwestern and northeastern United States.
Environmental science & technology (2007)
E M Elliott, C Kendall, S D Wankel, D a Burns, E W Boyer, K Harlin, D J Bain, T J Butler

Global inputs of NO(x) are dominated by fossil fuel combustion from both stationary and vehicular sources and far exceed natural NO(x) sources. However, elucidating NO(x) sources to any given location remains a difficult challenge, despite the need for this information to develop sound regulatory and mitigation strategies. We present results from a regional-scale study of nitrogen isotopes (delta15N) in wet nitrate deposition across 33 sites in the midwestern and northeastern U.S. We demonstrate that spatial variations in delta15N are strongly correlated with NO(x) emissions from surrounding stationary sources and additionally that delta15N is more strongly correlated with surrounding stationary source NO(x) emissions than pH, SO4(2-), or NO3- concentrations. Although emission inventories indicate that vehicle emissions are the dominant NO(x) source in the eastern U.S., our results suggest that wet NO3- deposition at sites in this study is strongly associated with NO(x) emissions from stationary sources. This suggests that large areas of the landscape potentially receive atmospheric NO(y) deposition inputs in excess of what one would infer from existing monitoring data alone. Moreover, we determined that spatial patterns in delta15N values are a robust indicator of stationary NO(x) contributions to wet NO3- deposition and hence a valuable complement to existing tools for assessing relationships between NO3- deposition, regional emission inventories, and for evaluating progress toward NO(x) reduction goals.
Schlagworte: nitrogen , oxygen , clim , gashead

Oxygen isotope ratios of cellulose-derived phenylglucosazone: An improved paleoclimate indicator of environmental water and relative humidity
Geochimica et Cosmochimica Acta (2007)
Leonel Da S L Sternberg, Maria C. Pinzon, Patricia F. Vendramini, William T. Anderson, a. Hope Jahren, Kristina Beuning

Oxygen atoms within fossil wood provide high-resolution records of climate change, particularly for the Quaternary. However, current analysis methods of fossil cellulose do not differentiate between different positions of the oxygen atoms. Here, we propose a refinement to tree-cellulose paleoclimatology modeling, using the cellulose-derived compound phenylglucosazone as the isotopic substrate. Stem samples from trees were collected at northern latitudes as low as 24??37???N and as high as 69??00???N. We extracted stem water and cellulose from each stem sample and analyzed them for their 18O content. In addition, we derived the cellulose to phenylglucosazone, a compound which lacks the oxygen attached to the second carbon of the cellulose-glucose moieties. Oxygen isotope analysis of phenylglucosazone allowed us to calculate the 18O content of the oxygen attached to the second carbon of the cellulose-glucose moieties. By way of these analyses, we tested two hypotheses: first, that the 18O content of the oxygen attached to second carbon will more closely reflect the 18O content of the stem water, and will not resemble the 18O content of either cellulose or its derivative phenylglucosazone. Second, tree-ring models that incorporate the variable oxygen isotope fractionation shown here and elsewhere are more accurate than those that do not. Our first hypothesis was rejected on the basis that the oxygen isotope ratios of the oxygen attached to the second carbon of the glucose moieties had a noisy isotopic signal with a large standard deviation and gave the poorest correlation with the oxygen isotope ratios of stem water. Related to this isotopic noise, we observed that the correlation between oxygen isotope ratios of phenylglucosazone with both stem water and relative humidity were higher than those observed for cellulose. Our hypothesis about tree-ring models which account for changes in the oxygen isotopic fractionation during cellulose synthesis was consistent only for the 18O content of phenylglucosazone. We showed that the tree-ring model based on the 18O content of phenylglucosazone was an improvement over existing models that are based on whole cellulose. Additionally, this approach may be used in other cellulose based archives such as peat deposits and lacustrine sediments. ?? 2007 Elsevier Ltd. All rights reserved.
Schlagworte: oxygen , soil , clim , gashead