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.
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.
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.
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.
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Characterizing the isotopic composition of atmospheric ammonia emission sources using passive samplers and a combined oxidation-bacterial denitrifier approach. Rapid communications in mass spectrometry : RCM (2013)
J David Felix, Emily M Elliott, Timothy J Gish, Laura L McConnell, Stephanie L Shaw
RATIONALE: Ammonia (NH3) emissions are a substantial source of nitrogen pollution to sensitive terrestrial, aquatic, and marine ecosystems and dependable quantification of NH3 sources is of growing importance due to recently observed increases in ammonium (NH4(+)) deposition rates. While determination of the nitrogen isotopic composition of NH3 (δ(15)N-NH3) can aid in the quantification of NH3 emission sources, existing methods have precluded a comprehensive assessment of δ(15)N-NH3 values from major emission sources. METHODS: We report an approach for the δ(15)N-NH4(+) analysis of low concentration NH4(+) samples that couples the bromate oxidation of NH4(+) to NO2(-) and the microbial denitrifier method for δ(15)N-NO2(-) analysis. This approach reduces the required sample mass by 50-fold relative to standard elemental analysis (EA) procedures, is capable of high throughput, and eliminates toxic chemicals used in a prior method for the analysis of low concentration samples. Using this approach, we report a comprehensive inventory of δ(15)N-NH3 values from major emission sources (including livestock operations, marine sources, vehicles, fertilized cornfields) collected using passive sampling devices. RESULTS: The δ(15)N-NH4(+) analysis approach developed has a standard deviation of ±0.7‰ and was used to analyze passively collected NH3 emissions with a wide range of ambient NH3 concentrations (0.2 to 165.6 µg/m(3)). The δ(15)N-NH3 values reveal that the NH3 emitted from volatilized livestock waste and fertilizer has relatively low δ(15)N values (-56 to -23‰), allowing it to be differentiated from NH3 emitted from fossil fuel sources that are characterized by relatively high δ(15)N values (-15 to +2‰). CONCLUSIONS: The isotopic source signatures presented in this emission inventory can be used as an additional tool in identifying NH3 emission sources and tracing their transport across localized landscapes and regions. The insight into the transport of NH3 emissions provided by isotopic investigation is an important step in devising strategies to reduce future NH3 emissions, a mounting concern for air quality scientists, epidemiologists, and policy-makers.
Saithe (Pollachius virens) stocks in the Northeast Atlantic intermingle as a result of migration among stock areas. The extent of mi- gration has been poorly quantified. Here, we estimate measures of the migration based on existing tagging data from Icelandic, Faroese and Continental (Scotland, North Sea and Norway) waters. Saithe tagged in Icelandic waters were seldom caught outside Icelandic waters (,1% of tag returns), whereas 42% of adult saithe tagged in Faroese waters were recaptured outside Faroese waters. Of adult saithe tagged in Norwegian waters 6.6% were recaptured outside Continental waters. In broad terms, there was a net migra- tion of saithe towards Icelandic waters. The distance between tagging and recapture increased with increasing size and age, with saithe tagged in Norwegian waters moving the longest distances. The results demonstrate significant, but variable, migration rates of adult saithe in the Northeast Atlantic. More detailed studies are needed to clarify the mechanisms behind the migration and what causes the differences among the areas.
Turnover of organic carbon and nitrogen in soil assessed from ??13C and ??15N changes under pasture and cropping practices and estimates of greenhouse gas emissions Science of the Total Environment (2013)
Ram C. Dalal, Craig M. Thornton, Bruce a. Cowie
The continuing clearance of native vegetation for pasture, and especially cropping, is a concern due to declines in soil organic C (SOC) and N, deteriorating soil health, and adverse environment impact such as increased emissions of major greenhouse gases (CO2, N2O and CH4). There is a need to quantify the rates of SOC and N budget changes, and the impact on greenhouse gas emissions from land use change in semi-arid subtropical regions where such data are scarce, so as to assist in developing appropriate management practices. We quantified the turnover rate of SOC from changes in ??13C following the conversion of C3 native vegetation to C4 perennial pasture and mixed C3/C4 cereal cropping (wheat/sorghum), as well as ??15N changes following the conversion of legume native vegetation to non-legume systems over 23years. Perennial pasture (Cenchrus ciliaris cv. Biloela) maintained SOC but lost total N by more than 20% in the top 0-0.3m depth of soil, resulting in reduced animal productivity from the grazed pasture. Annual cropping depleted both SOC and total soil N by 34% and 38%, respectively, and resulted in decreasing cereal crop yields. Most of these losses of SOC and total N occurred from the >250??m fraction of soil. Moreover, this fraction had almost a magnitude higher turnover rates than the 250-53??m and <53??m fractions. Loss of SOC during the cropping period contributed two-orders of magnitude more CO2-e to the atmosphere than the pasture system. Even then, the pasture system is not considered as a benchmark of agricultural sustainability because of its decreasing productivity in this semi-arid subtropical environment. Introduction of legumes (for N2 fixation) into perennial pastures may arrest the productivity decline of this system. Restoration of SOC in the cropped system will require land use change to perennial ecosystems such as legume-grass pastures or native vegetation. ?? 2013 Elsevier B.V.
As an indicator for terrestrial paleovegetation, the stable isotopic composition of total organic matter (d13Corg) in loess sediments has been widely used for paleoclimatic reconstruction in western Europe, the Great Plains of North America and the Chinese Loess Plateau (CLP). However, little is known about the variation and paleoclimatic significance of the loess d13Corg in arid Central Asia (ACA). We report d13Corg data from an Axike (AXK) loess/paleosol profile from the eastern Ili Basin, eastern Central Asia. Along the profile, the d13Corg values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic car- bon (TOC), consistent with results for western Europe and the northwestern CLP. Our results demonstrate that the loess d13Corg in this region documents mainly the response of d13C of locally predominant C3 plants to paleoclimatic variation, especially paleoprecipitation. Our results also suggest that the loess d13Corg values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed d13Corg results from modern plants and surface soils in the future
Bulk and isotopic characterization of biogenic CO2 sources and variability in the weyburn injection area International Journal of Greenhouse Gas Control (2013)
David Risk, Gordon McArthur, Nicholas Nickerson, Claire Phillips, Christian Hart, Jocelyn Egan, Martin Lavoie
To help evaluate surface monitoring tools for Weyburn, it is important to establish ranges of natural variation, and signal to noise ratio (SNR) of MMV tools in their intended setting. This study took place at three sites, two of which were in the injection field. For six months, we measured parameters at various temporal scales from half-hourly (CO2 surface flux and meteorology), to monthly (soil gas CO2 and ??13CO2), to bi-monthly (soil gas CO142), to compare SNRs of promising MMV techniques for Weyburn. Our summary of findings is as follows:1.All observed data fell within the range of values considered normal for Weyburn and for proximal control sites such as the Minard farm.2.High temporal variation in CO2 surface fluxes were observed. Lower atmospheric CO2 concentrations were also highly variant, and coupled with abiotic factors. A modelling strategy was able to reduce observed variability by 80-95%. When used together, soil CO2 surface flux + modelling methods can produce high SNRs for leak detection.3.Temporal variability in soil profile CO2 concentration was controlled by soil gas diffusivity (soil wetting/drying) and not biological production. Despite various sources of noise, we conclude that soil gas bulk CO2 investigations can still be useful for MMV.4.There were many possible influences on ??13CO2, including biological variation, normal steady and non-steady state physical transport (several ???), spatial differences (0-3???), and temporal fluctuations (0-3???). The effects of these influences are cumulative. Relative to this background variation, the Cenovus-source ??13CO2 is not highly differentiated, and ??13CO2 is not a robust tracer.5.High precision radiocarbon soil profile data indicates that CO2 produced within the soil profile is modern and its average age is less than decades old. This age is consistent with other studies, and recent Kerr investigations (Trium, 2011). There was a tendency towards older CO142 production with increasing depth. There is a marked differentiation in CO142 signature from deep gases, and low variation. Radiocarbon is a very promising tracer for Weyburn with high SNR. ?? 2013 Elsevier Ltd.
Paleoproductivity during the middle Miocene carbon isotope events: A data-model approach Paleoceanography (2013)
Liselotte Diester-Haass, Katharina Billups, Ingrid Jacquemin, Kay C. Emeis, Vincent Lefebvre, Louis Fran??ois
To what extent are individual middle Miocene eccentricity-scale benthic foraminiferal carbon isotope maxima (the so-called CM events) related to changes in marine export productivity? Here we use benthic foraminiferal accumulation rates from three sites in the Pacific and Southern Oceans and a geochemical box model to assess relationships between benthic foraminiferal δ13Crecords, export productivity, and the global carbon cycle. Results from Deep Sea Drilling Project Hole 588 and Ocean Drilling Program Site 747 show a distinct productivity maximum during CM 6 at 13.8 Ma, the time of major expansion of ice on Antarctica. Productivity maxima during other CM events are only recorded at high-latitude Site 747. A set of numerical experiments tests whether changes in foraminiferal δ13C records (CM events) and export productivity can be simulated solely by sea level fluctuations and the associated changes in global weathering-deposition cycles, by sea level fluctuations plus global climatic cooling, and by sea level fluctuations plus invigorated ocean circulation. Consistent with data, the periodic forcing of sea level and albedo (and associated weathering cycles) produces δ13C variations of the correct temporal spacing, albeit with a reduced amplitude. A productivity response of the correct magnitude is achieved by enhancing ocean circulation during cold periods. We suggest that the pacing of middle Miocene δ13C fluctuations is associated with cyclical sea level variations. The amplitude, however, is muted perhaps due to the competing effects of a time-lagged response to sea level lowstands but an immediate response to invigorated ocean circulation during cold phases.
Stable carbon isotope ratios of toluene in the boundary layer and the lower free troposphere Atmospheric Chemistry and Physics (2013)
J. Wintel, E. Hösen, R. Koppmann, M. Krebsbach, A. Hofzumahaus, F. Rohrer
During the field campaign ZEPTER-2 in autumn 2008 whole air samples were collected on board a Zeppelin NT airship in the planetary boundary layer (PBL) and the lower free troposphere (LFT) over south-west Germany using the ZEppelin Based Isotope Sampler (ZEBIS). These samples were analysed with respect to volatile organic compound (VOC) mixing ratios and stable carbon isotope ratios using a gas chromatograph combustion isotope ratio mass spectrometer (GC-C-IRMS). In this study we present results for toluene, one of the major anthropogenic pollutants, which emphasise the viability of isotope ratio measurements in VOC for atmospheric research, especially to study VOC sources or to track both dynamical and chemical processes. In situ measurements of CO mixing ratios on board the Zeppelin NT were used to allocate the air samples either to the PBL or the LFT. In the PBL we observed rather fresh emissions mixing into the background air. We estimated a toluene source isotope ratio of δ13C = −28.2 ± 0.5‰. Samples from the PBL and the LFT were clearly distinguishable by means of their mixing ratio and isotope ratio signatures. Using the concept of the effective kinetic isotope effect, we were able to separate the effects of dilution processes and photochemical degradation in the free troposphere. We calculated the photochemical age of toluene in the atmosphere in two different ways using isotope ratios and mixing ratios. The results differ strongly in the PBL, probably due to mixing processes, but are compatible with each other in the LFT. Here, they correlate with a slope of 0.90±0.31.
Isotopic and palynological evidence for a new Early Jurassic environmental perturbation Palaeogeography, Palaeoclimatology, Palaeoecology (2013)
James B. Riding, Melanie J. Leng, Sev Kender, Stephen P. Hesselbo, Susanne Feist-Burkhardt
The Early Jurassic Epoch was a predominantly greenhouse phase of Earth history, but a comprehensive understanding of its climate dynamics is hampered by a lack of high resolution multi-proxy environmental records. Here we report a geologically brief (approximately several hundred thousand years) negative carbon isotope excursion (CIE) of 2-3??? in both marine and terrestrial materials, recognised for the first time for the Late Sinemurian Substage (Early Jurassic, ~. 194. Ma) of eastern England. The Late Sinemurian carbon isotope excursion, which is termed the S-CIE herein, is accompanied by peaks in the abundance of the pollen grain Classopollis classoides and the dinoflagellate cyst Liasidium variabile. Classopollis classoides was thermophilic and is a reliable proxy for hot/warm climatic conditions. Liasidium variabile is interpreted as thermophilic and eutrophic using multivariate statistics, its fluorescence properties being similar to living heterotrophic dinoflagellate cysts, and its association with C. classoides. Moreover, the morphological and ecological similarities of L. variabile to the Cenozoic genus Apectodinium are noteworthy. The co-occurrence of the acmes of C. classoides and L. variabile with a negative CIE is interpreted here as having wide geographical significance due to the marine and terrestrial carbon isotope signals being precisely in phase within an open marine setting. This is consistent with an oceanic-atmospheric injection of isotopically-light carbon, coupled with global warming and increased marginal marine nutrient supply, possibly the result of increased precipitation due to an enhanced hydrological cycle or a seasonally-stratified water column. A probable sea level rise of at least regional extent has been identified at the L. variabile event in other records, which supports this putative phase of global warming. All these features are common to the Paleocene/Eocene thermal maximum (PETM, ~. 56. Ma), and there are also similarities with the Early Toarcian oceanic anoxic event (T-OAE, ~. 182. Ma). ?? 2012 Natural Environment Research Council.
The influence of kinetics on the oxygen isotope composition of calcium carbonate Earth and Planetary Science Letters (2013)
James M. Watkins, Laura C. Nielsen, Frederick J. Ryerson, Donald J. DePaolo
Paleotemperature reconstructions rely on knowledge of the equilibrium separation of oxygen isotopes between aqueous solution and calcium carbonate. Although oxygen isotope separation is expected on theoretical grounds, the temperature-dependence remains uncertain because other factors, such as slow exchange of isotopes between dissolved CO2-species and water, can obscure the temperature signal. This is problematic for crystal growth experiments on laboratory timescales and for interpreting the oxygen isotope composition of crystals formed in natural settings. We present results from experiments in which inorganic calcite is precipitated in the presence of 0.25??M dissolved bovine carbonic anhydrase (CA). The presence of dissolved CA accelerates oxygen isotope equilibration between the dissolved carbon species CO2, H2CO3, HCO3-, CO32- and water, thereby eliminating this source of isotopic disequilibrium during calcite growth. The experimental results allow us to isolate, for the first time, kinetic oxygen isotope effects occurring at the calcite-water interface. We present a framework of ion-by-ion growth of calcite that reconciles our new measurements with measurements of natural cave calcites that are the best candidate for having precipitated under near-equilibrium conditions. Our findings suggest that isotopic equilibrium between calcite and water is unlikely to have been established in laboratory experiments or in many natural settings. The use of CA in carbonate precipitation experiments offers new opportunities to refine oxygen isotope-based geothermometers and to interrogate environmental variables other than temperature that influence calcite growth rates. ?? 2013.